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In order to maintain grid-forming converter (GFM) voltage source behaviour under current limiting mode, a threshold virtual impedance (TVI) current limiting control is proposed, which is controlled in the positive and negative sequence synchronous reference frames for symmetrical and asymmetrical fault conditions. The converter current is strictly limited within the maximum limit without the need for current saturation limiters. Since the TVI control is based on 3-phase sinusoidal currents, it is shown that using the measured current instead of the existing current reference for the TVI control may cause oscillatory behaviour when a large switching delay is considered. Since sequence extraction control is necessary, the paper also compares GFM dynamic stability under the three well-known sequence extraction methods (i.e. delay cancellation, dual second order generalized integrator, and decoupled double synchronous reference frame). It is shown that the differences are small when GFM is not in current limiting mode, but they are large when GFM is in current limiting mode or switching delays are considered.

Many engineering systems can be described by using differential models whose solutions, generally obtained after discretization, can exhibit a noticeable deviation with respect to the response of the physical systems that those models are expected to represent. In those circumstances, one possibility consists of enriching the model in order to reproduce the physical system behavior. The present paper considers a dynamical system and proposes enriching the model solution by learning the dynamical model of the gap between the system response and the model-based prediction while ensuring that the time integration of the learned model remains stable. The proposed methodology was applied in the simulation of the top-oil temperature evolution of a power transformer, for which experimental data provided by the RTE, the French electricity transmission system operator, were used to construct the model enrichment with the hybrid rationale, ensuring more accurate predictions.

Greater numbers of power electronics (PEs) converters are being connected to energy systems due to the development of renewable energy sources, high-voltage transmission, and PE-interfaced loads. Given that power electronics-based devices and synchronous machines have very different dynamic behaviours, some modelling approximations, which may commonly be applied to run transient simulations of transmission systems, may not be optimal for future grids. Indeed, the systematic utilisation of the phasor approximation for power lines, implemented in most transient simulation programs, is increasingly not appropriate anymore. In order to avoid the requirement for full electromagnetic transient simulations, which can be resource-demanding and time-consuming, this paper proposes a combination of an event-based state residualisation approximation and the Kron reduction technique. The proposed technique has the advantage of allowing accurate transient simulations based on the optimal reduction of the number of state variables, depending on the observed variables, the considered events, and the tolerated approximation error, along with simplifying power systems equations for accelerated simulations.

The fast development of renewable energies leads to an increase in the power electronics penetration in transmission systems. This is particularly true if one considers a 100% renewable energies power system, where wind and solar photovoltaic energies, which make most of the renewable energies connections today, are connected to the grid through power electronics converters. Because power electronics-based generators and synchronous machines-based generators have very different dynamic behaviours, some approximations usually used to run transient simulations of transmission systems might not be optimal for future grids. The systematic use of the phasor approximation applied to the power lines, implemented in most of the Transient Simulation Programs, is indeed not relevant any more. To avoid the use of Electromagnetic Transient simulations, that are resource-demanding and time-consuming, this paper presents a novel Model Order Reduction technique for large grids with a high penetration of power electronic devices. Compared to the classical phasor approximation, this event-based state residualization approximation allows accurate transient simulations and at the same time an optimal reduction of the number of the system's state variables depending on the observed variables, the considered events and the tolerated approximation error.

The inclusion of higher-order terms in small-signal (modal) analysis augments the information provided by linear analysis and enables better dynamic characteristic studies on the power system. This can be done by applying Normal Form theory to simplify the higher order terms. However, it requires the preliminary expansion of the nonlinear system on the normal mode basis, which is impracticable with standard methods when considering large scale systems. In this paper, we present an efficient numerical method for accelerating those computations, by avoiding the usual Taylor expansion. Our computations are based on prescribing the linear eigenvectors as unknown field in the initial nonlinear system, which leads to solving linear-only equations to obtain the coefficients of the nonlinear modal model. In this way, actual Taylor expansion and associated higher order Hessian matrices are avoided, making the computation of the nonlinear model up to third order and nonlinear modal analysis fast and achievable in a convenient computational time. The proposed method is demonstrated on a single-machine-infinite-bus (SMIB) system and applied to IEEE 3-Machine, IEEE 16- Machine and IEEE 50-Machine systems.

Increasing nonlinearity in today’s grid challenges the conventional small-signal (modal) analysis (SSA) tools. For instance, the interactions among modes, which are not captured by SSA, may play significant roles in a stressed power system. Consequently, alternative nonlinear modal analysis tools, notably Normal Form (NF) and Modal Series (MS) methods are being explored. However, they are computation-intensive due to numerous polynomial coefficients required. This paper proposes a fast NF technique for power system modal interaction investigation, which uses characteristics of system modes to carefully select relevant terms to be considered in the analysis. The Coefficients related to these terms are selectively computed and the resulting approximate model is computationally reduced compared to the one in which all the coefficients are computed. This leads to a very rapid nonlinear modal analysis of the power systems. The reduced model is used to study interactions of modes in a two-area power system where the tested scenarios give same results as the full model, with about 70% reduction in computation time.

The modern control of power drives involves the consideration of electrical constraints in the regulator strategy, including voltage/current limits imposed by the power converter and the electrical machine, or magnetic saturation due to the iron core. This issue has been extensively analysed in conventional three-phase drives but rarely studied in multiphase ones, despite the current interest of the multiphase technology in high-power density, wide speed range or fault-tolerant applications. In this paper, a generalised controller using model-based predictive control techniques is introduced. The proposal is based on two cascaded predictive stages. First, a continuous stage generates the optimal stator current reference complying with the electrical limits of the drive to exploit its maximum performance characteristic. Then, a finite-control-set predictive controller regulates the stator current and generates the switching state in the power converter. A five-phase induction machine with concentrated windings is used as modern high-performance drive case example. This is a common multiphase drive that can be considered as a system with two frequency-domain control subspaces, where fundamental and third harmonic currents are orthogonal components involved in the torque production. Experimental results are provided to analyse the proposed controller, where optimal reference currents are generated and steady/transient states are studied.

Multiphase machines have recently gained interest in the research community for their use in applications where high power density, wide speed range and fault-tolerant capabilities are required. The optimal control of such drives requires the consideration of voltage and current limits imposed by the power converter and the machine. While conventional three-phase drives have been extensively analyzed taking into account such limits, the same cannot be said in the multiphase drives’ case. This paper deals with this issue, where a novel two-stage Model Predictive optimal Control (2S-MPC) technique is presented, and a five-phase permanent magnet synchronous multiphase machine (PMSM) is used as a case example. The proposed method first applies a Continuous-Control-Set Model Predictive Control (CCS-MPC) stage to obtain the optimal real-time stator current reference for given DC-link voltage and stator current limits, exploiting the maximum performance characteristics of the multiphase drive. Then, a Finite-Control-Set Model Predictive Control (FCS-MPC) stage is utilized to generate the switching state in the power converter and force the stator current tracking. An experimental validation of the proposed controller is finally provided using a real-time simulation environment based on OPAL-RT technologies.

The high quality of electrical power in high power and high reliability applications is a crucial necessity even under fault mode function. However, in these conditions, the quality of the torque is a key feature. To overcome this problem, the multiphase permanent magnet (PM) motors seems to be a very attractive choice. In order to highlight the robustness and reliability of this technology, this paper investigates the control of a five-phase PM motor under an open circuited phase fault conditions. Moreover, a High Order Sliding Mode (HOSM) controller combined to an optimal reference current generation is tested and compared to a PID controller under fault mode conditions. This original control strategy is proposed for faulted conditions. Compared to classical fault tolerant control, this strategy allows a better dynamic tracking of the non-sinusoidal reference currents and leads to a smooth torque with minimal losses even in severe fault conditions. To validate the proposed control strategy, simulation, and experimental results are presented and discussed.

The inclusion of higher-order terms in Small-Signal (Modal) analysis has been an intensive research topic in nonlinear power system analysis. The inclusion of 2nd order terms with the Method of Normal Forms (MNF) has been well developed and investigated, overcoming the linear conventional small-signal methods used in the power system control and stability analysis. However, application of the MNF has not yet been extended to include 3rd order terms in a mathematically accurate form to account for nonlinear dynamic stability and dynamic modal interactions. Due to the emergence of larger networks and the long transmission line with high impedance, modern grids exhibit predominant nonlinear oscillations and existing tools have to be upgraded to cope with this new situation. In this paper, fundamentals of Normal Form Theory along with a review of existing tools based on this theory is firstly presented. Secondly, a new formulation of MNF based on a third-order transformation of the system's dynamic approximation is proposed and nonlinear indexes are proposed to make possible to give information on the contribution of nonlinearities to the system stability and on the presence of significant 3rd order modal interactions. The induced benefits of the proposed method are compared to those afforded by existing MNFs. Finally, the proposed method is applied to a standard test system, the IEEE 2-area 4-generator system, and results given by the conventional linear small-signal and existing MNFs are compared to the proposed approach. The applicability of the proposed MNF to larger networks with more complex models has been evaluated on the New England New York 16 machine 5 area system.

Direct torque control (DTC) has been recently used for the development of high performance five-phase induction motor (IM) drives, where normal operation of the system has been usually considered and the ability of DTC to manage the situation has been analyzed in comparison with different rotor field-oriented control (RFOC) strategies. The exploitation of fault-tolerant capabilities is also an interesting issue in multiphase machines, where the utility of RFOC controllers has been stated when the open-phase fault operation is considered. In this paper, the performance of DTC and RFOC controllers based on proportional resonant regulators and predictive control techniques is compared when an open-phase fault appears in a five-phase IM drive. Experimental tests are provided to compare the performance of the system using these control alternatives.

Model predictive control techniques have been recently proposed as a viable control alternative for power converters and electrical drives. The good current tracking, flexible control design or reduced switching losses are some of the benefits that explain the recently increased attention on finite-control-set model predictive control. The performance of the predictive model of the drive, which is the core of the predictive control, highly depends on the parameters of the real system. In this context, most research works assume good agreement between electrical parameters of the predictive model and the real machine, on the basis of nominal values. Nevertheless, this is far from being a real assumption, where non-modeled variables (i.e. the temperature, the magnetic saturation or the deep-bar effect) produce a detuning effect between the real system and its model, which can harm the control performance. The influence of parameter variations on the predictive control has barely been investigated in recent research works, where only conventional three-phase power converter configurations and permanent magnet drives have been taken into account. However, there is a lack of knowledge when different technologies like induction machines or multiphase drives are considered. It is worth highlighting the interest of the industry in induction motors as a mature technology or in multiphase drives as a promising alternative in applications where high overall system reliability and reduction in the total power per phase are required. This paper attempts to fill this gap by examining the impact of parameters mismatch on the finite-control-set predictive control performance of a five-phase induction motor drive, one of the multiphase electromechanical conversion systems with greatest impact in the research community. An exhaustive experimental sensitivity analysis of the close loop system performance based on more than three hundred trials in a test bench is presented.

Direct torque control (DTC) has been widely used as an alternative to traditional field-oriented control (FOC) methods for three-phase drives. The conventional DTC scheme has been successfully extended to multiphase drives in recent times, using hysteresis regulators to independently track the desired torque and flux in symmetrical five-phase induction machines (IM). The fault-tolerant capability of multiphase drives is an interesting intrinsic advantage for safety-critical applications, where recent research has demonstrated the effectiveness of FOC schemes to perform ripple-free post-fault operation. In spite of the utility of DTC methods in normal operation of the multiphase machine, no extension to manage the post-fault operation of the drive is found in the literature. In this paper, a novel fault-tolerant DTC scheme is presented. The performance of the proposed method is experimentally validated in a five-phase IM drive considering an open-phase fault condition. Provided tests analyze steady and transient states, including the transition from pre- to post-fault operation. Obtained results prove the interest of the proposal, which ensures the open-phase fault-tolerant capability of DTC controlled five-phase IM drives.

The performance of a dual energy storage electric vehicle system mainly depends on the quality of its power and energy managements. A real-time management strategy supported by a Model Predictive Control using the non-uniform sampling time concept is developed and fully addressed in this paper. First, the overall multiple energy storage powertrain model including its inner control layer is represented with the Energetic Macroscopic Representation and used to introduce the energy strategy level. The model of the system with its inner control layer is translated into the state space domain in order to develop a Model Predictive Control approach. The management algorithm based on mixed short- and long-term predictions is compared to rule-based and constant sampling time Model Predictive Control strategies in order to assess its performance and its ability to be used in a real vehicle. The real-time simulation results indicate that, compared to other strategies, the proposed Model Predictive Control strategy can balance the power and the energy of the dual energy storage system more effectively, and reduce the stress on batteries. Moreover, battery and supercapacitor key variables are kept within safety limits, increasing the lifetime of the overall system.

This paper proposes a novel variable speed control strategy of a particular 5-phase Permanent Magnet Synchronous Generator (PMSG) in healthy and faulty modes by taking into account the constraints on voltages and currents. These constraints are related to the converter and machine design. The considered faults are open-circuited phases (one phase, two adjacent phases and two non-adjacent phases). A variable speed control strategy is presented, including flux weakening operations. Based on analytical formulations, a numerical computation is proposed to bring out the torque-speed characteristics. This method allows the determination of the current references which ensure the functioning of a 5-phase PMSG at variable speed while keeping phase voltages and currents below their limits. Theoretical, numerical and experimental results are presented. These results are compared in order to validate the proposed approach.

Multiphase machines are more and more used in applications where a high power density, a low bus voltage, a wide speed range and possibilities to work in fault mode are required. Due to the high number of available degrees of freedom, multiphase machines are not easy to optimally control in the flux weakening region. This paper shows several strategies for the control of multiphase machines in flux weakening regions and compares them in terms of simplicity to implement and optimality in the use of available quantities. Proposed strategies are applied to a five-phase synchronous machine that has been developed for the MHYGALE project proposed by Valeo company.

Multi-phase machines are well-known for their fault tolerant capability. Star-connected multiphase machines have fault tolerance in open-circuit. For inverter switch short-circuit fault, it is possible to keep a smooth torque of Permanent Magnet Synchronous Machine (PMSM) if the currents of faulty phases are determined and their values are acceptable. This paper investigates fault-tolerant operations of an open-end five-phase drive, i.e. a multi-phase machine fed with a dual-inverter supply. Inverter switch short-circuit fault is considered and handled with a simple solution. Original theoretical developments are presented. Simulation and experimental results validate the proposed strategy.

This paper presents and compares control strategies for three-phase open-end winding drives operating in the flux-weakening region. A six-leg inverter with a single dc-link is associated with the machine in order to use a single energy source. With this topology, the zero-sequence circuit has to be considered since the zero-sequence current can circulate in the windings. Therefore, conventional over-modulation strategies are not appropriate when the machine enters in the flux-weakening region. A few solutions dealing with the zero-sequence circuit have been proposed in literature. They use a modified space vector modulation or a conventional modulation with additional voltage limitations. The paper describes the aforementioned strategies and then a new strategy is proposed. This new strategy takes into account the magnitudes and phase angles of the voltage harmonic components. This yields better voltage utilization in the dq frame. Furthermore, inverter saturation is avoided in the zero-sequence frame and therefore zero-sequence current control is maintained. Three methods are implemented on a test bed composed of a three-phase permanent-magnet synchronous machine, a six-leg inverter and a hybrid DSP/FPGA controller. Experimental results are presented and compared for all strategies. A performance analysis is conducted as regards the region of operation and the machine parameters.

This paper deals with an on-line method for turn-to-turn short-circuit fault detection in low-voltage permanent-magnet synchronous machine drives. Due to the closed-loop control, the fault effects are reflected in the voltage. Therefore, an appropriate diagnostic index is proposed, which is derived from the positive- and negative-sequences of the voltage references. These sequences are obtained in the time domain via adaptive filters, which require only a few calculations. To increase the sensitivity to the fault, the algorithm is only applied to a part of the voltage references, i.e. the output of the proportional-integral controllers. Further, the cumulative-sum algorithm is introduced to cope with changes of small magnitudes. This algorithm allows a change of a fault index to be detected and can be used as a decision system. The resulting fault detection scheme is computationally cheap and can be embedded in the control unit. Simulations and experimental results validate the proposed method in steady state and the performances under non-stationary operating conditions are also investigated.

Industrial motion control of dual–drive gantry stages is usually performed by position controllers acting independently on each actuator. This approach neglects the unbalance and the mechanical coupling between actuators, leading to poor positioning performances. To overcome this drawback, a model–based decoupling control is proposed. Initially, a dynamic model of the gantry stage is proposed. Once identified and validated, such model is written in terms of a decoupling basis. Then, by model inversion, a feedbackfeedforward decoupling control is presented. Experimental results show that, in comparison to the independent axis control approach, the proposed solution leads to improved motion control.

In this study, a three-phase drive with a six-leg voltage source inverter and an open-end winding interior permanent magnet synchronous machine designed for traction of an electric vehicle is studied in a flux-weakening operation. The topology allows the functionality of a high-power charger to be obtained, without adding any other supplementary power devices. On the other hand, since there are three independent currents, the control structure has to handle not only the two dq-current components but also a zero-sequence current. If neglected, in comparison with a wye-coupled three-phase drive, this zero-sequence component can cause a higher maximum peak value of the phase currents, additional stator Joule losses, torque ripple, inverter voltage saturation and insulated gate bipolar transistor (IGBT) oversizing. The proposed control strategy consists in adapting a conventional method used for wye-connected machines particularly in flux-weakening operation. This strategy allows the closed-loop control of the zero-sequence current to be maintained in the whole speed range and therefore inverter saturation is avoided. Simulations and experimental results are presented and analysed.

A general method for fault detection and isolation is proposed and applied to inverter faults in drives of electric vehicles. This method is based on a change-detection algorithm, which allows multiple fault indices to be combined for retrieving the most likely state of the drive. The considered drive topology is a six-leg inverter associated with a three-phase machine. Due to the inherent fault-tolerant topology, the conventional fault indices are no longer effective. Therefore, an analysis of simulations in faulty conditions leads to the derivation of suitable fault indices. These are based on the envelope of the phase currents as well as their instantaneous frequency. Specific operating conditions related to the electric vehicle environment are taken into account, such as the flux-weakening region and energy recovery. Finally, the performances of the fault detection and isolation scheme are evaluated under steady state and non-stationary conditions through simulations and experimental results.

Cet article est consacré à l’étude d’une méthode de commande d’une machine synchrone à aimant permanent à cinq phases associée à un onduleur de tension à MLI. On s’intéresse au cas de la commande en mode normal et en mode dégradé. Les défauts étudiés sont liés à la déconnexion d’une phase ou de plusieurs phases. Dans ce cas, la méthode étudiée est basée sur une approche vectorielle permettant la détermination en ligne des courants de référence optimaux adaptés au défaut. L’étude se propose de comparer l’utilisation de régulateurs PID avec des régulateurs non linéaire de type hystérésis à bande fixe et à bande adaptative. Cette comparaison est effectuée en mode normal et en mode de défaut. Les résultats de simulation effectués sur MATLAB / Simulink sont présentés et discutés afin de vérifier les performances de la stratégie et des régulateurs étudiés. Ils montrent en particulier que si la régulation de type PID est performante en mode normal, elle ne permet pas d’assurer un suivi correct des références en mode de défaut car celles ci présentent des variations dynamiques importantes. Dans ce dernier cas d’étude l’utilisation de commandes non linéaires comme la commande par hystérésis est nécessaire et permet de garder le même schéma de commande en mode normal et dégradé. L’utilisation d’une commande par hystérésis à bande adaptative est alors judicieuse car elle permet de bonnes performances de suivi et une maitrise de la fréquence de commutation de l’onduleur. The use of multiphase PM machines associated with VSI drives appears to be a very efficient solution. Presented work focus on the use of such a system in open circuited phase fault conditions. With this kind of system it is possible to determine optimal currents references which maximize the torque density of the system when one or two phases are open circuited. Classical linear controllers (as PID for example) cannot provide a correct tracking of these optimal reference currents because they have a highly dynamical behavior. We propose in this paper to combine this optimal reference current generation with hysteresis control. This kind of solution allows a good tracking of these unconventional reference currents with a fixed switching frequency for the VSI. In this case of adaptive hysteresis band control appears to be particularly efficient.

This paper deals with the generation of optimal current references for Multiphase Permanent Magnet Synchronous Machines in normal or fault mode (open-circuited phases). Current references are computed in order to keep a constant torque while minimizing instantaneous Joule losses. In comparison with commonly used scalar methods, a vectorial approach makes it possible to reduce the number of computations in order to generate optimal current references, in real-time. In addition to this, since current references are expressed in terms of physical parameters of the machine, this approach can be used to evaluate the influence of the machine parameters over the control performances. Finally, experimental results of a surface mounted permanent magnet five-phase synchronous machine are provided in order to demonstrate the proposed strategy.

Français RÉSUMÉ. Cet article établit un modèle causal unique pour les fonctionnements normal et dégradé d’un entraînement électromécanique à phases non couplées en s’appuyant sur un formalisme vectoriel et une Représentation Energétique Macroscopique (REM). L’inversion systématique du modèle permet de déduire une architecture de commande dans laquelle des correcteurs spécifiques sont utilisés pour assurer les deux modes de fonctionnement. Les validations en simulation, l’examen des performances en mode dégradé par rapport au mode normal et plusieurs validations expérimentales mettent en évidence la validité de la commande établie. Enfin, la méthode développée dans l’article pour les machines triphasées est adaptable aux machines polyphasées pour mettre en évidence la généralité de la méthode. MOTS-CLÉS : machines polyphasées, machines alternatives triphasées, filtrage de couple, commande auto adaptée, entraînements électromécaniques tolérants aux pannes. Anglais ABSTRACT. This paper deals with a unique causal model in normal and open-circuited phase operation of a electromechanical drive with independent supplied phases. This overall degraded system model is based on a vectorial formalism and the Energetic Macroscopic Representation (EMR). The systematic inversion of the model leads to a control structure using a dedicated controller available in the two operating modes. The simulating validation, the performances verifications in open-circuited mode versus normal mode and the experimental validations establish the validity of the control. Finally, this tree-phase method is adaptable to polyphase machines to bring to light the generality of the method. KEYWORDS: multiphase machines, alternative machines, torque filtering, auto adaptable control, fault tolerant drives.

Dual-drive gantry systems are commonly used in many industrial applications. However,as few papers are available in the literature, this kind of system is difficult to broach. Based on an energetic approach so-called Energetic Macroscopic Representation (EMR), this paper presents a graphical modelling based on lumped-parameters. The initial drive is decomposed into a set of decoupled fictitious systems using a mathematical transformation. Since the modelling respects the integral causality, inversion-based controls are thus deduced. More generally, this approach proposes a way to analyze and deduce models and controls of multi-drive mechatronic systems.

This paper deals with easy to implement control strategies when a seven-phase Axial Flux Permanent Magnet machine (AFPM) supplied by a seven-leg Voltage Source Inverter (VSI) is in fault operation mode. Using a vectorial multi-machine description, a seven-phase machine presenting a heightened ability to be controlled with one or two open-circuited phases has been designed. The machine is first presented and experimental results are provided when one or two phases are open-circuited. Based on a vectorial approach, new current references are calculated to avoid high torque ripples.

This paper deals with fault tolerant multiphase electrical drives. The quality of the torque of vector-controlled Permanent Magnet (PM) Synchronous Machine supplied by a multi-leg Voltage Source Inverter (VSI) is examined in normal operation and when one or two phases are open-circuited. It is then deduced that a seven-phase machine is a good compromise allowing high torque-to-volume density and easy control with smooth torque in fault operation. Experimental results confirm the predicted characteristics.

A Dual-Drive Moving Gantry Stage Robot can be modelled as a square MIMO system. However, it is usually considered as two independent SISO systems: classical industrial gantry control is achieved by two independent position controllers. This control structure does not take into account the mechanical coupling between the two actuators and leads to a reduction of the overall performances of the system. In this paper, a physical lumped parameters model of an industrial robot is proposed and experimentally identified. It is based on a structural, modal, and Finite Element Method analysis. Then, a physical model-based control structure is deduced. The solution is finally simulated and implemented on an experimental test bench. Results are compared to the performances of the initial industrial control and show an improvement of the overall performances.

In order to increase the power capability of direct-drive PM wind generators with respect to established quality criteria like the electromagnetic torque and the power transferred to the grid, a polyphased multi-star system is studied. The influence of the number of stars, their phase shift and the waveform of the electromotive force are investigated. The possible configurations, i.e. the numbers of magnets and slots, are found and compared.

AC machines supplied in parallel by a common voltage source inverter are sometimes used in industrial drives and railway traction applications. This reduction of power and control electronics leads to a reduction of cost, weight and dimensions that is very useful for on-board systems. But this common supply imposes common voltages to all machines and the possibilities of independent behavior are reduced. In this paper a graphical modeling is suggested to model such parallel drives for a railway application. A weighted control is then systematically deduced from this modeling and different possibilities of control are highlighted. Experimental results are provided to compare two of the deduced controls.

The transient stability of a power system with both grid-forming converters (GFMs) and synchronous generators (SGs) under large faults is rarely reported. This paper finds out that even when a SG and GFM have the same frequency during a fault by setting the same inertia and damping coefficient for both, due to the impact of the dynamics of the SG field and amortisseur flux linkage, a parallel connected GFM with low capacity ratio between the GFM and SG outputs negative postfault active power. In other words, the GFM becomes synchronization unstable according to traditional definition. Since normally a GFM has much larger damping (to have strong robustness during small and large disturbances), this negative active power is even lower and lasts longer in practical cases. When conducting transient stability analysis, existing methods usually model a GFM in the same form as the classic SG model, and did not provide theoretical analysis. To simplify analysis and facilitate control design under large disturbances, this paper adopts a modal analysis-based model order reduction technique and finds out that while a GFM can be modelled as the classic form together with the virtual impedance current limiting control, the interacted SGs should not be modelled in the classic form, because the SG field and amortisseur flux linkage should also be included. Finally, this paper finds that for systems with only GFMs as voltage sources, reserving only the dynamics of the voltage angle control loop of GFMs is precise enough for representing the system low-frequency oscillations phenomenon.

Threshold virtual impedance (TVI) is a promising current limiting technology to ensure the hardware integrity of grid-forming converters (GFMs), as it maintains the voltage source characteristic behind an impedance. Existing TVI parameter design principles are based on limiting the GFM current to a maximum value when a bolted fault is applied at the point of common coupling (PCC). However, adopting existing TVI parameter design practices can cause the GFM current to exceed the maximum value after a fault is cleared, or under a large grid phase jump, since the angular difference between the GFM internal and PCC voltage vector can be large, causing the voltage across the virtual impedance and output transformer to exceed that assumed for TVI parameter design. Hence, the worst case design scenario is not during a fault, but during the subsequent recovery period, or under a large phase jump. Here, a new TVI parameter design process is proposed based on the GFM internal voltage vector being in anti-phase to the PCC voltage vector. However, the new approach should not be applied directly as the GFM current capacity may not be fully used. Hence, three alternative strategies are proposed, with a combined approach being recommended based on electromagnetic transient (EMT) simulations for a range of case studies.

The question of grid forming control is very different depending on the connection to a low voltage or high voltage grid. In case of higher power application, the low switching frequency may induce some stability issues. This question has been studied and some solutions have been proposed through new inner current and voltage control tuning methods. However, the possible interactions between the inner and the outer controls have not been discussed yet. Actually, in large power system, the phasor modeling approximation is used in order to ease the analysis and reduce the time computations. It assumes a good decoupling between the control loops, which allows neglecting the inner loop dynamics. This paper investigates the effectiveness of this assumption by taking some examples of tuning methods proposed in the literature and showing the ability of each method to guarantee the decoupling between controllers. In this paper, small-signal analysis tool, participation factors and parametric sensitivities are used.

Today’s power systems are strongly nonlinear and are becoming more complex with the large penetration of power-electronics interfaced generators. Conventional Linear Modal Analysis does not adequately study such a system with complex nonlinear behavior. Inclusion of higher-order terms in small-signal (modal) analysis, associated with the Normal Form theory proposes a nonlinear modal analysis as an efficient way to improve the analysis. However, heavy computations involved make Normal Form method tedious, and unamenable to large power system application. In this paper, we present a less rigorous and speedy approach for obtaining the required nonlinear coefficients of the nonlinear equations modelling of a power system, without actually going through all the usual high order differentiation involved in Taylor’s expansion. The method uses eigenvectors to excite the system modes independently which lead to formulation of linear equations whose solution gives the needed coefficients. The proposed method is demonstrated on the conventional IEEE 9-bus system and 68-bus New england/New York system.

Multiphase machines have recently gained importance in the research community for their use in applications where high power density, wide speed range and fault-tolerant capabilities are needed. The optimal control of such drives requires to consider voltage and current constraints imposed by the power converter and the machine itself. If classical three-phase drives have been optimally controlled under such limits for a long time, the same cannot be said in the case of multiphase drives. This paper deals with this issue, where an optimal control technique based on Cascaded Model Predictive Controls (MPC) is presented for a five-phase permanent magnet synchronous machine (PMSM). A Continuous-Control-Set MPC (CCS-MPC) numerically computes optimal current references in real-time in order to exploit the maximum performance for given DC bus voltage and current limits. Then, a Finite-Control-Set MPC (FCS-MPC) is used to carry out the current control in the machine, directly applying the switching state that minimizes a cost function related to the current tracking. Obtained mixed microprocessor-based and FPGA-based real-time simulations prove the interest of the proposal, which ensures the optimal control of the multiphase drive operating under current and voltage constraints.

This papers presents a sensorless control for fivephase PM synchronous machines. An adaptive method, based on a linear neural network called Adaline (Adaptive Linear Neural Networks), has been achieved to estimate the rotor position with a high precision even at low speed without high frequency signal injection. Non-sinusoidal three-phase PM machines require more complex algorithm for sensorless control because of harmonics in the back-EMF. This is not the case for multiphase PM machines thanks to the property of equivalent machines in the eigenspace. Some given simulation and experimental results in laboratory confirm the possibility of real-time implementation of Adaline networks and the good performance of sensorless control based on this.

Voltage Source Converter-based transmission grids might be the future of power system with the increasing share of interfaced electricity generation. These systems should be able to support the utility grid autonomously. The present paper focuses on the VSC output filter design and internal control of filter states. Nested AC current and voltage loops are the state of the art for power converters, controlled as voltage sources, in Microgrid or UPS applications. These internal controls are candidates for future industrial implementation at high power level. However, in a VSC based transmission system, those controls will face various topologies while requiring robustness against transient events (load changes, line tripping, etc.). The following development aims at providing keys for designing a versatile internal control suitable for VSC-based transmission system.

The multiplication of interfaced generation units connected to the utility grid might form VSC-based transmission grids in a near future. To support the utility grid autonomously, the converters must provide grid-forming capabilities and be connected in parallel. As the structure of a transmission grid is changing and unknown, these requirements presume a robust local voltage control for each highpower VSC, to face various network topologies. Indeed, the stability is challenged when voltagecontrolled VSCs are close to each other, namely, when the tie-impedance is low. The present contribution describes an impedance-based criterion method as a convenient and effective tool for assessing the stability of the voltage control of converters in a VSC-based transmission grid. The method is successfully applied to a typical two-VSC system to anticipate unstable situations

Power electronics have been widely used in the transmission systems due to its capability to control the power flows as well as the voltages and currents. However, in the renewable energy transmission system, the weak-grid will make the VSCs work under nonlinear domain, where their behavior are quite different from the linear case. What’s more, the interconnected VSCs are sometimes used to ensure more robust and flexible power transmission, leading to a multi-machine system, where the predominant nonlinear oscillations should be studied to suggest more information in designing the parameters of the system. This paper proposed a methodology to offer analytical results to predict nonlinear interaction for both oscillation amplitude and frequency-shift while avoiding numerical simulation of huge computational burden. Based on Normal Form theory, this methodology can be applied to large-scale power system that exhibits behavior of N coupled second-order oscillators. The nonlinear indices are then proposed to quantify the parameter impact on the nonlinear system dynamics

The increase of renewable energy sources and HVDC links lead to power systems composed of a large number of interconnected Voltage Source Converters, involving predominant nonlinear oscillations. The strong coupling effect in the severely stressed system obscures the characteristics of the nonlinear dynamics. To tackle this problem, a proposed Nonlinear Mode method based on Normal Form theory makes possible to decompose the system modeled by $N$ coupled nonlinear damped oscillators into a sum of decoupled nonlinear damped oscillators, keeping the physical meaning along with reducing the complexity of the problem. Mode decomposition and amplitude-dependent frequency-shift are then extracted, rendering a deeper insight of the system dynamics possible. The efficiency of the method is illustrated by a simple but didactic case-study.

Direct Torque Control (DTC) technique has been applied in recent times in high performance five-phase induction motor drives during the normal operation of the system. The use of DTC in the multiphase area is far from becoming a reality because it has not been used in competitive multiphase applications where the fault operation needs to be considered. The authors have successfully tested the ability of DTC controllers to manage the open-phase fault operation in a five-phase induction motor drive. However, the conclusion of the mentioned study must be completed comparing the obtained results with other mature alternatives based on field oriented controllers. This paper focuses on the comparative analysis of DTC and Rotor Field Oriented Control (RFOC) when an open-phase fault appears in the five-phase induction motor drive. Simulation results are provided to compare the performance of the system using these control alternatives.

Direct torque control (DTC) is extensively used in conventional three-phase drives as an alternative to field-oriented control methods. The standard DTC technique was originally designed to regulate two independent variables using hysteresis controllers. Recent works have extended the procedure for five-phase drives in healthy operation accounting for the additional degrees of freedom. Although one of the main advantages of multiphase machines is the ability to continue the operation in faulty conditions, the utility of DTC after the appearance of a fault has not been covered in the literature yet. This paper analyses the operation of a five-phase induction motor drive in faulty situation using a DTC controller. An open-phase fault condition is considered, and simulation results are provided to study the performance of the drive, comparing with the behavior during healthy state.

In the near future, transmission grids will include an increasing share of directly connected voltage source converters. These systems should be able to support the utility grid autonomously. The present paper reviews the most popular approaches to address the challenge of proper load sharing amongst multiple parallel inverters applied to the utility grid case. Originally developed for Microgrid or UPS applications, these decentralized controls mimic a conventional synchronous generator based system steady-state behavior and showed suitable effectiveness to reach the desired operating point. However, the operations at the transmission grid level bring additional stress on the converters and require transient capabilities. Physical limitations of semi-conductor based converters fundamentally differ from a conventional synchronous generator. Therefore the paper illustrates how the usual real power controls may lead to undesirable behavior during transient events. This raises new issues for reliable operations of interconnected VSCs at transmission level.

The optimal control of electrical drives necessitates to take into account current and voltage limits that are imposed by the power electronics and the electrical machines. Let’s cite for example the flux-weakening operation of electrical drives or propulsion. If the control of classical three-phase drives under voltage and current limits are known for a long time, the specific characteristics of multiphase drives open the way to researches on their control under such constraints. This paper aims to explain what are the main differences between three-phase and multiphase drives when they run under voltage and current constraints and try to show what are the scientific and technical problems to be solved. Some first results are given in order to show that Model Predictive Control (MPC) is expected to be a good candidate to answer the proposed challenge.

An original analytical expression is presented in this paper to obtain optimal currents minimizing the copper losses of a multi-phase Permanent Magnet Synchronous Motor (PMSM) under fault conditions. Based on the existing solutions [i]opt1 (without zero sequence of current constraint) and [i]opt2 (with zero sequence constraint), this new expression of currents [i]opt3 is obtained by means of a geometrical representation and can be applied to open-circuit, defect of current regulation, current saturation and machine phase short-circuit fault. Simulation results are presented to validate the proposed approach.

All-electric vehicles should be made more reliable in such way one can continue driving even after the event of one or more faults in the electrical drive. For this, the use of multiphase (more than 3 phases) electrical machines is considered here due to its redundant feature. An additional technique to increase reliability is to replace sensors by observers. This paper studies the feasibility to control the torque in multi-phase permanent magnet synchronous drives without a position sensor, with the lowest Joule losses, and this for a healthy as well as for a faulty operation with one or more phases open-circuited.

Multi-phase machines are known for their fault-tolerant capability. However, star-connected machines have no fault tolerance to inverter switch short-circuit fault. This paper investigates the fault-tolerant operation of an open-end five-phase drive, i.e. a multi-phase machine fed with a dual-inverter supply. Open-circuit faults and inverter switch short-circuit faults are considered and handled with various degrees of reconfiguration. Theoretical developments and experimental results validate the proposed strategies.

This paper presents a specific control strategy of double-ended inverter system for wide-speed range of open-winding five phase PM machines. Different virtual stator winding configurations (star, pentagon, and pentacle) can be obtained by choosing the appropriated switching sequences of two inverters. The motor’s speed range is thus increased.

A method for fault detection and isolation is proposed and applied to inverter faults in multi-phase drives. An analysis of simulations in faulty conditions leads to the derivation of suitable fault indices. These are based on the unbalance of the phase currents and their instantaneous frequency. The method is applied to a five-phase permanent-magnet synchronous machine drive. Simulations and experiments validate the proposed method.

A general algorithm of a Space Vector approach is implemented on a 6-leg VSI controlling a PM synchronous machine with three independent phases. In this last case, the necessity of controlling the zero-sequence current motivates the choice of a special family of vectors, different of this one used in Pulse Width Modulation (PWM) intersective strategy and in common Space Vector PWM (SVPWM). To preserve the parallelism of the algorithm and fulfill the execution time constraints, the implementation is made on a Field Programmable Gate Array (FPGA). Comparisons with more classical 2-level and 3-level PWM are provided. Keywords – FPGA, Modulation strategies, Space vector, Multiphase machine, Multiphase, Multi-leg.

In order to get a low cost mild hybrid system, a global objective is to keep the actual thermal engine architecture as in Figure 1. As consequence, the current clawpole synchronous automotive generator must be replaced by a new more powerful electrical machine but with the same large speed range [0 -18000 rpm]. In the project, a power of 15 kW and a DC bus voltage of 60V have been chosen to provide a regenerative breaking at minimum cost. With this payload (250A for the DC bus current), a five-phase machine appears to be interesting because MOSFET transistors of the voltage source inverter (VSI) have not to be used in parallel configuration (only two rated 150A transistors per leg for the VSI). As the speed range is large, a flux weakening must be applied. As the five-phase drives [16] have more degrees of freedom than three-phase ones [13], different flux weakening strategies can be considered. The aim of this paper is to compare one of them.

This paper deals with on-line software fault detection and isolation method for a drive composed of a fourleg inverter and a three-phase permanent magnet synchronous machine. The considered faults are single-phase open-circuit and current sensor outage. The method is based on the monitoring of the abc currents with phase-locked loops and the `CUSUM’ algorithm for the decision system. The impact of the considered faults is examined: first, in case there is no modification of the control and then in case a control reconfiguration is performed taking into account the fault diagnosis. Closed-loop operation is performed before, during and after the fault. Experimental results show that the latter case allows maintaining the drive in safe operation.

For Electric Vehicles (EV), the charger is one of the main technical and economical weaknesses. This paper focuses on an original electric drive [1]-[3] dedicated to the vehicle traction and configurable as a battery charger without need of additional components. This cheap solution can outfit either electric or plug-in hybrid automotive vehicles, without needing additional mass and volume dedicated to the charger. Moreover, it allows a high charging power, for short duration charge cycles. However, this solution needs specific cares concerning the electrical machine control. This paper deals with the control of this drive [1], focusing on traction mode. In introduction, a review is done about topologies of combined on-board chargers. Then, the studied topology is introduced; using a 3-phase brushless machine supplied with a 6-leg Voltage Source Inverter (VSI). A model for its control is defined in the generalized Concordia frame, considering the traction mode. Then, an analysis of this model is established using a multimachine theory and a graphical formalism (the Energetic Macroscopic Representation denoted EMR). Using EMR, a description of energy flows shows specific control constraints. Indeed, numerical simulations illustrate the perturbations on the currents and the torque when controlling the machine with standard control methodologies. An improved control, deduced from the previous analysis, shows good performances, strongly reducing currents and torque ripples. Keywords- Electric Vehicle, Plug-in Hybrid Vehicle, On-board Battery Charger, H-bridge Voltage Source Inverter, Multiphase Drive, Control

Electrical marine propulsion systems are characterized by very high level requirements in terms of compactness, acoustic behavior and reliability. In this particular context, the use of multiphase PM machines associated with VSI drives appears to be a very efficient solution. Presented work focus on the use of such a system in open circuited phase fault conditions. With this kind of system it is possible to determine optimal currents references which maximize the torque density of the system when one or two phases are open circuited. Classical linear controllers (as PID for example) cannot provide a correct tracking of these optimal reference currents because they have a highly dynamical behavior. We propose in this paper to combine this optimal reference current generation with High Order Sliding Mode control. This kind of solution allows a good tracking of these unconventional reference currents with a fixed switching frequency for the VSI. This method is validated experimentally in laboratory low power experimental set-up which associates a 5-phase PM machine with a DSP controlled IGBT 5-leg VSI drive.

This paper proposes an auto-adaptive current control that makes possible to reduce torque ripples of multi-phase machines in open-circuited phase conditions. Contrary to existing methods, current references are not recomputed and the control scheme used in normal mode is auto-adapted in order to run the machine with open-circuited phases. The number of degrees of freedom of the control scheme is adapted to the number of degrees of freedom of the drive and current controllers are auto-adaptive in order to reject the induced speed-dependent harmonic voltage disturbances that appear in fault-mode. Experimental results are presented to show the effectiveness of the proposed method.

dual–drive gantry stages are used for high–speed high–precision motion control applications such as flat panel display manufacturing and inspection. Industrially, they are usually controlled using independent axis control without taking into consideration the effect of inter–axis mechanical coupling over positioning accuracy and precision. To improve this and minimize the effect of mechanical coupling over synchronization and tracking errors, we propose to model and control the dual–drive gantry stage on a decoupling basis. This approach allows representing the highly coupled Multiple Input Multiple Output (MIMO) system as a set of independent Single Input Single Output (SISO) systems. Based on this representation, a model– based feedback–feedforward control scheme is deduced. Experimental results show that the proposed decoupling basis control scheme leads to an improved motion control of the point–tool in comparison to the present industrial control.

This paper proposes a simple way to control multi-phase drives in open-phase conditions. Contrary to existing methods, current references are not recomputed and the control scheme is kept the same to run in open-circuited phase condition. In order to work in fault-conditions, the number of degrees of freedom of the control scheme is adapted to the number of degrees of freedom of the drive. Since a particular attention has to be dedicated to the structure and controller tuning, harmonic content of induced perturbations in fault mode is exhibited. Simulation and experimental results are presented to show the effectiveness and the limitations of the proposed method.

Widely used for high-speed high-precision motion control in the electronics, nuclear and automotive industries, gantry stages are usually controlled using independent axis control. In order to avoid the effects of the mechanical coupling over synchronization and tracking errors, we propose a control on a modal reference frame. First, the system is modeled with respect to the center of mass of the moving beam and a modal transformation is applied to obtain the motion equations on a decoupling base. Next, a model-based control scheme is deduced with the minimization of synchronization and tracking errors as objectives. Finally, experimental results show that the proposed modal control scheme leads to an improved motion control of the point-tool in comparison with the present industrial control.

This paper deals with the generation of optimal current references for Multi-phase Permanent Magnet Machines with open-circuited phases. Compared to classical methods, the use of a vectorial approach makes it possible to generate optimal current references, from a copper losses point of view, on-line. This method is viable whatever the number of open-circuited phases. As an example, a five-phase machine is experimentally controlled.

This paper deals with the modelling and control of a three-phase induction machine supplied by three independent voltage sources when one phase is open-circuited. The modelling of the overall system leads to design a dedicated controller tuned with the generalised stability margin method in order to reduce the pulsating torque. The consequences of the new closed-loop control on the induction machine and the VSI are evaluated to quantify the currents, voltages and copper losses increasing. Finally, simulation and experimental results are achieved and show the global performances of this ripple torque reduction method.

Industrial control of Dual-Drive Moving Gantry Stage Robots is usually achieved by two independent position controllers. This control structure does not take into account the mechanical coupling between the two actuators that leads to a reduction of the overall performances. In this paper, a physical dynamic lumped parameters model of an industrial robot based on structural, modal, and Finite Element Method analysis is proposed, experimentally identified and validated. Then, using simple inversion rules of the Causal Ordering Graph formalism, a control structure is deduced in a systematic way. The solution is finally simulated and shows that it is possible to obtain better performances than the industrial control.

A Dual-Drive Moving Gantry Stage Robot can be modelled as a square MIMO system. However, it is usually considered as two independent SISO systems: classical industrial gantry control is achieved by two independent position controllers. This control structure does not take into account the mechanical coupling between the two actuators and leads to a reduction of the overall performances of the system. In this paper, a physical lumped parameters model of an industrial robot is proposed and experimentally identified. It is based on a structural, modal, and Finite Element Method analysis. Then, a physical model-based control structure is deduced. The solution is finally simulated and implemented on an experimental test bench. Results are compared to the performances of the initial industrial control and show an improvement of the overall performances.

This paper presents a physical dynamic modelling of a dual-drive gantry stage which takes into account the rigid body motion and the first flexion mode. It is used to study the influence of the mechanical coupling between the two parallel axes on the global positioning performances. Indeed, dual-drive mechanisms are commonly controlled with two independent and symmetrical position controllers while the mechanical structure is not symmetrical. This control strategy leads to an imperfect synchronism between the two axes and the mechanical coupling is submitted to huge levels of strain. In this paper, the influence of the stiffness of the joints and of the mass distribution is particularly discussed.

Dual-drive gantry systems are commonly used in many industrial applications. However, as few papers are available in the literature, this kind of system is difficult to broach. Based on an energetic approach so-called Energetic Macroscopic Representation (EMR), this paper presents a graphical modelling based on lumped-parameters. The initial drive is decomposed into a set of decoupled fictitious systems using a mathematical transformation. Since the modelling respects the integral causality, inversion-based controls are thus deduced. More generally, this approach proposes a way to analyze and deduce models and controls of multi-drive mechatronic systems.

In the context of high power low-voltage applications as starter-generator for automotive, multi-phase drives present the attractive characteristic of reducing the current per phase and per leg. A 5- or 7-phase machine is also more suitable for using concentrated windings, attractive for their short end-windings and subsequently for a higher expected torque-to-volume density. In this perspective, the 5- and 7-leg Voltage Source Inverters (VSI) are compared with the 3-leg VSI. In the first part, for the same set of resistances and inductances coupled in different wye-coupling configurations, we examined the DC-bus currents and the power recovered by the load for a square-wave VSI control: the 7-leg VSI is the more efficient because it makes best use of the harmonics. In the second part, the torque ripples of 3-, 5- and 7-phase drives are compared: the 7-phase drive torque ripples are the lowest ones because of the less sensitivity to the harmonics of the currents. In the last part, a Pulse Width Modulation control is studied, with almost the same voltage harmonics amount as this one obtained with the square-wave mode control. Experimental results are given for the 7-leg VSI either with a passive load or with a 7-phase permanent magnet synchronous motor.

More and more electrical systems need a high level of reliability. Among the potential solutions, multi-phase machines take a particular place to improve the reliability of AC drives. Efficient current controls lead to the use of the multiple d-q spaces concept. When one or several phases are short or open-circuited, ripples appearing in the d-q currents require a particular attention. Many authors have proposed a new model of the machine taking into account these asymmetrical connections. These models have made it possible to deduce efficient current controls. However, a new model is built for each new case. For machines with a high number of phases, this technique becomes rapidly cumbersome and time consuming. Moreover, some authors use the derivative operation to model voltages across open-circuited phases which can lead to problems of convergence, stability and long simulation time when using numerical simulations. This paper proposes a simple and easy-to-implement way of integral modelling which makes it possible to achieve numerical simulations of multi-phase drives under fault conditions with keeping the original model of the drive. Experimental measurements on a seven-leg seven-phase drive show the effectiveness of the proposed solution.

This paper deals with fault tolerant multiphase electrical drives. The quality of the torque of vector-controlled Permanent Magnet (PM) Synchronous Machine supplied by a multi-leg Voltage Source Inverter (VSI) is examined in normal operation and when one or two phases are open-circuited. It is then deduced that a seven-phase machine is a good compromise allowing high torque-to-volume density and easy control with smooth torque in fault operation. Experimental results confirm the predicted characteristics.

This paper deals with control in fault operation of a seven-phase Permanent Magnet Synchronous Machine supplied by a seven-leg Voltage Source Inverter (VSI). Using a Multi-Machine description, a seven-phase machine which presents a special ability to be controlled with only five phases supplied has been designed. The machine is presented and experimental results are provided when two phases are opened. In a first case of no change of classical control, high torque ripples are observed. In a second case, a specific control deduced from the Multi-Machine modelling is suggested for reducing torque ripples.

This paper deals with control in fault operation of a seven-phase Axial Flux Permanent Magnet (AFPM) supplied by a seven-leg Voltage Source Inverter (VSI). We present a seven-phase machine that has been designed with a special ability to be controlled with only five phases supplied. Experimental results are provided when two phases are opened in two cases. In the first case, the vector control is not changed when two phases are opened: high torque ripples are then observed. In the second case, a specific control allows to reduce the torque ripples.

This paper deals with modeling and control of a three-phase permanent magnet synchronous machine (PMSM) with sinusoidal back electromotive forces (emf) under supply fault conditions. The overall system is modeled thanks to the Energetic Macroscopic Representation (EMR) formalism considering that a fusible element opens the phase circuit. Using systematic inversion rules of the EMR, a Maximum Control Structure (MCS) is deduced. Based on the analysis of degrees of freedom (DOF) of the drive, two control strategies for constant-torque under supply fault conditions are inferred. One method balances generated perturbations caused by the supply fault and the other one consists in modifying current controller’s structure. These methods are validated through simulations with Matlab software.

Dresden , Germany, 11-14 september 2005, CD-ROM.

This paper deals with design constraints of a 7-phase Permanent Magnet Synchronous Machine (PMSM) supplied by a 7-leg Voltage Source Inverter. The optimum back electromotive force waveform is determined in order to get maximum torque for a given DC bus voltage.

IAS 2004, IEEE Industrial Application Society Annual Meeting, Seattle, Washington October 3-7, 2004, CD-ROM

PESC 2004, IEEE Power Electronics Specialists Conference, Aachen, Germany in June 20 - 25, 2004,CD-ROM.

With increase in the power electronic penetrations to power system, today’s grid exhibit complex nonlinear behaviour. It then becomes imperative to include higher-order terms in small-signal (modal) analysis to account for the nonlinear behaviour. This is often done in power systems by applying Normal Form theory or Modal Series method to simplify the higher order terms. However, heavy computations involved make these nonlinear tools tedious and inconvenient for large scale systems. If there is no strong resonance in the system, it is also possible to include only some specific terms in this higher order nonlinear analysis instead of using all the terms. In this paper, we present a technique for selectively obtaining any desired nonlinear coefficients when the dynamics are modelled as second order systems, by avoiding the higher order derivatives and Hessian matrices involved in Taylor expansion. The proposed method is demonstrated on an IEEE 9-bus system.

Nowadays, the industrial systems become more and more complex with a ot of variables to be controlled in order to ensure good performances both for each component and the global system. In this paper, a methodology is presented to analyze the dynamic properties of the system and to design the control strategy and tune the controller systematically. It introduces EMR and inversion-based control strategy to design the controller structure and tune the controller by Modal Analysis. It takes the elegantly developed control of grid-side VSC in D’Arco’s [14] paper as an example to illustrate and verify this methodology. This methodology is a universal methodology to systems which are linear or can be linearized at the equilibrium point. It can be applied to more complex systems and domains other than electrical network.

Dans le domaine des systèmes embarqués (avionique, marine, automobile), l’emploi d’entrainements électriques permet d’optimiser le rendement énergétique du système en apportant plus de souplesse dans la gestion énergétique. Une des facettes du rendement global d’un système est son taux de disponibilité que ce soit dans les systèmes de transport ou ceux de production de l’énergie à partir de sources renouvelable. Or, l’environnement des systèmes embarqués est souvent difficile (températures extrêmes, humidité,…). De ce fait, les entrainements électriques se doivent donc de présenter une aptitude la tolérance aux pannes : on cherche en fonctionnement dégradé à conserver la fonctionnalité de conversion électromécanique même si la puissance est réduire. De ce fait, les entrainements électriques polyphasés, naturellement à tolérance de pannes, font l’objet de nombreuses investigations tant du point de vue de la conception que de la commande, notamment en mode dégradé lorsqu’une ou plusieurs phases ne sont plus alimentées. Munis de contrôles vectoriels, ces entraînements nécessitent la présence de capteur de position (codeur optique ou synchro-résolver). L’objet du papier est de proposer une estimation de la position θ qui pourra se substituer à celle du capteur en cas de panne de celui-ci. Le contrôle vectoriel dans le repère de Park pourra ainsi être conservé. Dans le cas des entraînements triphasés de très nombreuses méthodes ont été proposées par contre très peu d’études existent sur les machines polyphasées. L’originalité de la méthode proposée repose sur l’exploitation de caractéristiques harmoniques particulières des machines polyphasées par rapport aux machines triphasées. En triphasé, l’harmonique de rang trois de force électromotrice d’une machine synchrone à p paires de pôles est utilisé, dans certaines méthodes sans capteur pour estimer les instants de commutation d’une commande en trapèze. Pour une machine à 5 phases vérifiant certaines hypothèses en termes de contenu spectral de force électromotrice, il est possible, non seulement de déterminer ces mêmes instants de commutation pour une commande trapèze, mais de plus d’estimer la position réelle θ, nécessaire pour réaliser la transformée de Park en commande vectorielle. Il est en effet possible dans ce cas d’obtenir non seulement comme en triphasé sin(3pθ), mais également cos (3pθ) et sin(5pθ) : ces trois grandeurs permettent de déterminer sans équivoque θ alors que sin(3pθ) donne au mieux pθ à 120° près.

Les moteurs linéaires sont indéniablement une avancée majeure pour les entraînements de systèmes à forte dynamique tels que les machines-outils à grande vitesse ou plus généralement les machines de production. Toutefois, malgré les nombreux avantages de ces actionneurs, le suivi de trajectoire et la précision du positionnement micrométrique dépend de la maîtrise de ces dispositifs électromagnétiques. Dans cet article, nous préciserons l’origine et l’influence des ondulations de force sur les performances d’un moteur linéaire synchrone à aimants permanents (PMLSM). L’utilisation de codes de calcul en éléments-finis 2D et 3D permet de montrer l’influence des courants sur les ondulations de force. Une validation expérimentale sur un système de type « Pick & Place » à moteurs linéaires est présentée. Dans une deuxième partie, nous préciserons les différentes techniques de commande permettant de compenser ces ondulations de force, et un bilan montrera les avantages et les limites de chaque méthode. Mots clés : Moteur linéaire, Force de détente, Commande, Machine de production. || Linear motors are a major improvement in system actuators with high dynamics, such as high-speed machine-tools, or more generally, production machines. Nevertheless, even with their numerous advantages, the tracking error and the high positioning accuracy are strongly linked with the perfect control of these electromagnetic devices. In this paper, we precise the origin and the influence of the force ripple on the performances of a permanent magnet linear synchronous motor (PMLSM). 2D- and 3D- Finite-Element Methods are used to spot the currents influence on the force ripple. An experimental validation on a “Pick & Place” system is presented. In a second part, different techniques to compensate the force ripple are explained. Advantages and limitations of each method are given. Keywords: Linear motor, Detent force, Control, Production machine

The rotary drive system comprises: - a DC voltage source (102) - An electric motor (104) having an axis of rotation (A), and having independent phases (a, b, c) having directions around the axis of rotation (A) - An inverter (106) for connecting each phase (a, b, c) to the DC voltage source (102) and - a control device (110) for providing a command to the inverter (106). The control device (110) comprises: - means (118) for selecting the formula, for selecting a formula from predetermined formulas, each predetermined formula being adapted to calculate an homopolar voltage set point or a zero sequence current setpoint - Means (124) set point determination, for applying the selected formula to determine, according to the selected formula, a zero sequence voltage set point or a zero sequence current setpoint, and - the means (126) for controlling the determining , for determining the order of the inverter (106) from the determined set.

L’invention se rapporte à un système de régulation d’un portique à plusieurs moyens d’entraînement linéaires et, plus particulièrement, un tel système comportant un dispositif de compensation prenant en compte toutes les forces perturbatrices dudit portique.

Mots clés : Systèmes électromécaniques à entrées multiples – Dynamiques couplées – Théorie des vecteurs d’espace multidimensionnels – Graphe Informationnel Causal (GIC) – Représentation Energétique Macroscopique (REM) La multiplication de sous-systèmes identiques décentralisés mais couplés, de puissance réduite, en lieu et place d’un système central de forte puissance, permet de doter les systèmes de degrés de libertés recherchés dans le développement de produits et processus compétitifs. Les entraînements électriques polyphasés et les systèmes de positionnement multi-actionnés sont des exemples de systèmes électromécaniques modernes et probants. Les travaux de recherche présentés dans ce mémoire portent sur la représentation et la commande de systèmes électromécaniques à entrées multiples et présentant des couplages énergétiques internes forts par une approche méthodologique basée sur les outils « Modélisation Physique Vectorielle » et « Représentation Graphique Causale et Energétique ». Un espace vectoriel associé au système permet de réaliser des modèles vectoriels à paramètres physiques, de complexités choisies différentes suivant les exigences. Le formalisme vectoriel permet à la fois des représentations géométriques synthétiques et une simplification des calculs à l’aide d’opérateurs tels que les produits scalaires, vectoriels ou mixtes. La représentation graphique du modèle, causale et énergétique, permet d’une part d’examiner les conditions permettant la commandablité du système et, d’autre part, d’en déduire des architectures de commande par inversion du modèle, autant en boucle fermée qu’en boucle ouverte. Un des points forts de l’approche réside dans le fait de représenter le système réel à entrées multiples et couplages énergétiques internes forts par un ensemble de systèmes fictifs mono-entrée découplés. L’architecture de commande déduite permet alors une gestion plus aisée des énergies stockées, une aide au fonctionnement en mode dégradé, ainsi que l’utilisation de correcteurs simples et faciles à régler, car chacun assigné à un objectif unique. De multiples applications de la méthodologie proposée ont été expérimentées sur des bancs prototypes équipés de systèmes électromécaniques à entrées multiples présentant des couplages magnétiques (machines synchrones polyphasées), électriques (onduleurs multi-bras) et mécaniques (systèmes de positionnement multi-actionnés configurés en gantry). Une perspective privilégiée des travaux proposés concerne le fonctionnement des systèmes électromécaniques à leurs limites, en particulier par la prise en compte et la gestion des saturations des grandeurs de réglage et des non-linéarités intrinsèques.

Ce chapitre est consacré à la modélisation et la commande de machines électriques comportant au moins deux courants statoriques indépendants. La machine triphasée couplée en étoile sans neutre sorti ou en triangle en constitue la plus élémentaire. Plus précisément, l’objectif de ce chapitre est de mettre en évidence les spécificités qu’induit un nombre de courants indépendants supérieur à deux par rapport à la machine triphasée classique.

This chapter discusses the modeling and control of voltage source inverters associated with multiphase loads of various topologies. Such inverters have mostly been developed for the supply of multiphase electrical machines, but we will focus on the inverters and will not discuss these machines in the current chapter. We will however note that present-day development of these machines is closely linked to the development of the voltage source inverters that supply them. As the number of phases is increased beyond three, specific problems are encountered in electrical drives where inverter/machine/control coupling becomes more complex. This coupling explains the specific interest in three-phase systems, particularly in terms of spatial and temporal interactions between harmonics. Although such multiphase systems have been developed since the 1960s in niche applications (high power applications requiring a high tolerance to power outages) using thyristor current source inverters, the advent of high speed computational aids such as DSPs and, more recently, powerful FPGA networks has led to a rapid expansion in the use of voltage source inverters since the turn of the century. As the number of phases and legs is increased, additional degrees of freedom become available in terms of both design and control. Although a unified consideration of the constraints on the machine and the inverter is necessary for the design of high performance systems, it is first important to understand the detailed operation of each component part. This chapter is dedicated to the type of static converter consisting of a two level n-leg voltage source inverter. We will discuss in detail the modeling and control of these inverters, attempting to avoid where possible discussing the characteristics of the multiphase loads themselves. We will begin by discussing vector modeling of an n-leg inverter without taking into account the constraints imposed by the load (modification of the number of degrees of freedom). We will demonstrate vector modeling using the specific case of modeling two-level voltage source inverters with two and three legs. This approach enables us to generalize various known results, obtained using a space vector approach, to multiphase systems. In the context of this vector model we will discuss the principle of controlling mean values using Pulse Width Modulation. The second part of the chapter focuses on studying the influence of connection topology between the load and the inverter. We will discuss various types of multiphase loads and examine their influence on the capabilities of the inverter in terms of control. The justification of a vector approach relies on the fact that it not only benefits from the generality offered by matrix-based approaches but also lends itself to visual representations such as the complex phasor approach developed for three-phase systems. Visual representations, widely used in electrical engineering since their introduction by Fresnel, make it possible to rapidly handle various problems such as the choice of modulation strategy, inverter saturation, harmonic injection, etc.

Cet ouvrage est une publication de la thèse du même auteur : Les machines polyphasées offrent de nombreux avantages par rapport à leurs homologues triphasées. Néanmoins, leur alimentation par onduleur de tension a montré qu’’il fallait apporter un soin particulier à leur modélisation. Dans cet ouvrage nous présentons un outil de modélisation des systèmes polyphasés, quel que soit le nombre de phases, basé sur une Représentation Énergétique Macroscopique (REM) associée au formalisme vectoriel (extension de la théorie des vecteurs d’’espace). Le formalisme, d’’abord appliqué à la modélisation des machines polyphasées synchrones à aimants permanents, montre l’’équivalence entre la machine réelle et un ensemble de machines mono et/ou diphasées fictives. Enfin, considérant l’’ensemble convertisseur-machine comme un Système Multimachines Multiconvertisseurs (SMM), on déduit des structures de commandes originales de l’’ensemble en mode normal comme dégradé (une ou plusieurs phases en défaut).

Ce chapitre est consacré à la modélisation et la commande d’onduleurs de tension associés à des charges polyphasées de topologies différentes. Ces onduleurs se développent principalement dans le cadre de l’alimentation de machines électriques polyphasées dont l’étude sort du cadre de ce chapitre. On notera néanmoins que le développement actuel de ces machines est étroitement lié à celui des onduleurs de tension qui les alimentent. L’augmentation du nombre de phases au-delà de trois pose des problèmes spécifiques d’entrainements électriques dans la mesure où les couplages onduleur/machine/commande deviennent plus complexes. Elles mettent en évidence la particularité des systèmes triphasés notamment en termes d’interactions entre harmoniques qu’ils soient spatiaux ou temporels. Bien que ces systèmes polyphasés se développent depuis les années 1960 dans des secteurs de niches (forte puissance nécessitant une tolérance aux pannes élevée) avec des commutateurs de courant à thyristors, l’avènement de moyens de calculs rapides de type DSP et plus récemment de puissants réseaux FPGA a permis à partir des années 2000 un fort développement de l’usage d’onduleurs de tension. L’augmentation du nombre de phases et de bras apporte des degrés de libertés tant au niveau de la conception que de la commande. Même si la prise en compte conjointe des contraintes existantes sur la machine et l’onduleur est un enjeu à la réalisation de systèmes performants, il est nécessaire dans une première étape de présenter les spécificités de chaque partie. Ce chapitre est consacré au convertisseur statique qu’est l’onduleur de tension n-bras deux niveaux. On s’attachera à présenter les spécificités en termes de modélisation et de commande de ces onduleurs en essayant de s’affranchir le plus possible des caractéristiques des charges polyphasées. Dans un premier temps la modélisation vectorielle d’un onduleur à n-bras est présentée sans tenir compte des contraintes imposées par la charge (modification du nombre de degrés de liberté). On aborde la modélisation vectorielle par l’exemple (modélisation d’onduleurs de tension à deux niveaux possédant deux et trois bras), approche permettant de généraliser aux systèmes polyphasés des résultats connus obtenus par l’approche des vecteurs d’espace. Dans le cadre de cette modélisation vectorielle, le principe de la commande aux valeurs moyennes par Modulation de la Largeur des Impulsions est explicité. La deuxième partie du chapitre est consacrée à l’étude de l’influence de la topologie des connexions entre la charge et l’onduleur. On détaille différents types de charges polyphasées et on examine leur influence sur les potentialités de l’onduleur en termes de commande. La justification de l’approche vectorielle tient dans le fait qu’elle bénéficie d’une part de la généralité procurée par les approches matricielles mais qu’elle permet également d’autre part des représentations visuelles du type de celles des phaseurs complexes développées pour les systèmes triphasés. La représentation visuelle, très développée en électrotechnique depuis Fresnel, permet rapidement de juger de différents problèmes comme le choix de la stratégie de modulation, la saturation de l’onduleur, l’injection d’harmoniques, etc…