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This paper presents a diagnostic method of inverter open-switch and open-phase faults in multiphase PMSM drives. Adequate variables called “Virtual Current Vectors (VCVn)” are firstly defined. The projection of the zero-sequence current component (ZSCC) on these variables was used to define two simple fault indices. High sensitivity to fault is thus induced but with a good robustness to transient states and variation of machine parameters. The mathematical development of the proposed method is provided and supported by experimental tests conducted on two prototypes of multiphase machines in the laboratory, sinusoidal and bi-harmonic PMSMs. The experimental results confirm the effectiveness and the robustness of the proposed method and its capability to detect the single and multiple open-switches and open-phase faults in the electric drive.

This paper investigates a real-time fault diagnostic of a transportation system which needs two drives with fault-tolerance capabilities. Because of constraints on the mass of the system and on the cost of the Voltage Source Inverter (VSI), a drive with two Six-Phase Permanent Magnet Synchronous Machines (PMSM) in series-connection supplied by two six-leg inverters is chosen. Despite the serial -connection, independent control of the two machines and fault –tolerance to open-switch fault is ensured. Nevertheless, a Fault Detection Identification (FDI) process is required for analysis and/or control reconfiguration. The proposed FDI is based on the combination of different criteria obtained from the two zero-sequence currents and from the normalized currents mapped into two frames defined by the Concordia Transformation. Results obtained from simulation and experimental tests show the effectiveness of the proposal.

In the context of traction drives with required torque transient capabilities and a classically wide flux weakening speed range, this paper gives design considerations of a particular Double-Polarity (DP) five-phase machine. Beyond its intrinsic fault tolerance due its five phases, it specificity is the ability to develop torques of comparable values under three kinds of supply: with only first, third or both first and third sinusoidal currents. This property, due to first (E1) and third (E3) harmonic electromotive forces (emf) of comparable values, gives more degrees of freedom for the control of the machine. Unlike three-phase sinusoidal machine, flux weakening is no more the unique solution when maximum voltage is reached. Thanks to the extra degrees of freedom in this kind of machines, more possibilities for the control of the torque and current supply can be applied. At first, elements for the choice of slots/poles combination of such DP machines are given. Then, in case of an Interior Permanent Magnet Synchronous Machine (IPMSM), possible adaptations of the rotor are proposed in order to bring the double p/3p polarity property. The last design criterion considered is the level of eddy-current losses, important at high frequencies. For proof of the concept effectiveness, a prototype with a five-phase fractional-slot concentrated winding of 40 slots and 16/48 poles is presented with results from experimental set-up and Finite Element modeling. A comparison with equivalent no-fault-tolerant three-phase 24 slots /16 poles machines is also carried out

This paper proposes a procedure that is suitable for experimental investigation of real-time open-switch and open-phase faults diagnosis of a five-leg Voltage Source Inverter (VSI) feeding a five-phase bi-harmonic Permanent Magnet Synchronous Machine (5-Φ B-PMSM). The algorithm is based on the specific characteristics of multiphase machines, which allows inverter fault detection with sufficient robustness of the algorithm in the presence of fundamental and third harmonic components. Firstly, the inverter fault effects analysis is achieved in the characteristic subspaces of the five-phase PMSM. Specificities that are interesting for the elaboration of a real-time Fault Detection and Identification (FDI) process are highlighted. Original and particular algorithms are used for an accurate two-dimensional normalized fault vector extraction in a defined fault reference frame. This frame is dedicated only for fault detection and identification. To ensure the high immunity of the FDI process against transient states, a particular normalization procedure is applied. The normalized diagnostic signals are formulated from the defined frame and others variables derived from the reference and measured currents. Simulation and experimental results of open-switch and open-phase faults are provided to validate the proposed algorithm.

A novel centroid-based diagnostic method of the power switches in five-leg Voltage Source Inverter (VSI) is proposed in this paper. Using a vectorial multi-machine description, a five-phase drive presenting an opened switch or an opened phase faults has typical operating characteristics in comparison to classical three-phase drives. Based on such characteristics, this work aims to provide a simple and robust diagnostic process for switches fault regardless of the shape of the back-EMFs (harmonic components) and the transient states due to the load variation. Original theoretical developments are presented. Experimental results are shown to validate the proposed strategy.

This article presents the development of an algorithm which can be used at standstill and low speed for sensorless control of a five-phase Permanent Manget Synchronous Machines (PMSM) with non-salient poles. The estimation method is based on the machine’s torque. Two different strategies are investigated for the proposed method. The first one uses the torque measurement and the second one uses the estimated torque from the measured currents. Results for the implementation of both strategies are presented and analysed, together with possible improvements to explore.

Even if intrinsically a five-phase machine can work with one opened phase, thermal constraints (temperatures in windings and Permanent Magnets) impose to decrease the mean torque in faulty operation mode. In order to elaborate optimum control which ensures safety and maximum torque, it is necessary to estimate in real-time the temperatures induced by the currents imposed in the remaining healthy windings of the machine. For a five-phase prototype, a multi-nodal thermal modelling which can take into account irregular losses and flow distribution has been developed. It is based on Electromagnetic FEM results for the losses and CFD calculation analysis. Results are presented in normal and faulty operation modes.

This paper analyses the copper losses due to the homopolar current of a five-phase open-end winding machine supplied by a 10-leg inverter and a single DC voltage source. This topology can have non-null high frequency homopolar current components that can increase the machine’s copper losses and result in overheating of the motor phase windings, a special concern for integrated drives. Accordingly, different modulation strategies are compared with the goal of reducing the homopolar current and, consequently the relative copper losses. The comparison study is achieved using Matlab/Simulink and a finite elements model in order to evaluate these losses.

Even if intrinsically a five-phase machine can work with one opened phase, thermal constraints (temperatures in windings and Permanent Magnets) impose to decrease the mean torque in faulty mode operation. In order to elaborate optimum control which ensures safety and maximum torque, it is necessary to estimate in real-time the temperatures induced by the currents imposed in the remaining healthy windings of the machine. For a five-phase prototype, a multi-nodal thermal modelling which can take into account irregular losses distribution has been developed. It is based on Electromagnetic FEM results for the losses and a thermal FEM analysis. Results are presented in normal and faulty operation modes.

A rotor position estimation for low speed and standstill applications in multiphase PMSMs with non-salient poles is presented in this paper. For this purpose, a comprehensive state of the art was performed. Then, an estimation method was proposed based on existing methods for surface three-phase PMSMs, and is finally adapted to a five-phase machine. Experimental results are illustrated and analysed.

This paper presents a comparative evaluation of fault tolerant control strategies for a five-phase Permanent Magnet Synchronous Machine (PMSM) under an opened-phase fault mode. Two main classical Fault Tolerant Control (FTC) methods and the no-reconfiguration strategy are compared with the normal mode operation considering peak current, peak voltage, average torque, torque ripples and measured temperatures of five windings of the five phases. The analysis of the temperature repartition shows that, in fault mode, at least in the particular studied case, the knowledge of the Joule losses is not sufficient for a correct control of the temperature.

In this paper we investigate the impact of the supply strategy on the peak voltage value for a five-phase bi-harmonic machine. In fact, this kind of machine is able to deliver significant equivalent torque from either the first, the third current harmonic due to the equivalent value of these harmonics in the back-emf. Since, different supply strategies are possible for this machine depending on the repartition of current between the two harmonics. Classically, the maximum torque per ampere strategy (MTPA) is used below the base speed, and it is achieved by setting a current in phase with the back-emf, with an optimal repartition of current density between the first and the third harmonic. However, it is not always possible practically to guarantee these features simultaneously, due to uncertainty in control. This uncertainty come out as a phase shift between back-emf and the current, or a modification in the optimal repartition of current density between the first and the third harmonic. Thus, this error can make the required voltage peak value more or less than the maximum voltage that can be delivered by the VSI. FE simulations and experimental are performed in order to test this phenomenon which can determine the sensitivity of the optimal control

This paper deals with the fault effects analysis and diagnosis in 6-Φ PMSM designed for aerospace applications. The addressed work aims to analyze the features offered by the space vector theory applied to these systems for fault detection and identification purposes. The paper starts with a presentation of the overall electric drive system structure and its control. Then, fault effects analysis under faulty operation mode of the 6-leg voltage source inverter is presented considering the space vector theory. Based on such analysis, an accurate FDI process is designed for these applications. All results are verified analytically and through simulation software using Matlab/Simulink

This paper deals with the real time Fault Detection and Identification (FDI) process of inverter Open Switch Fault (OSF) and Open Phase Fault (OPF) in five-phase PMSM designed for aerospace applications in which the electric drive system has particular operating characteristics either in healthy states or in the faulty ones. Two original contributions are considered in this paper. They consist in normalizing the input variables of the FDI process applied to multiphase system and compensating the noise (switching and sensors noises) and dc-component resulting from the fault occurrence. The proposed strategy uses multiple normalized criterias derived from the measured phase currents and the voltages obtained from the outputs of the current controllers. The FDI shows an independence with respect to the transient states and to the switching and measurement noises. Moreover, it can be easily included in an existing software without any additional sensors. The validity of the proposed method is verified by Matlab/Simulink simulation tests.

This paper describes analytical and simulation tools to analyze the effects of Open Switch Fault (OSF) and Open Phase Fault (OPF) on five-phase PMSM designed for aerospace applications. For such applications, the fault tolerance and the reliability of the drive (PMSM and the power converter) are important to take into account for design. The addressed work aims essentially to analyze the dynamic of the measured phase currents in post-fault operation with a real-time fault diagnostic purpose in the VSI. The paper starts with a presentation of the electric drive system structure and its control used in pre-fault and post-fault operation. Then, fault effects analysis (FEA) on the system will be considered. All results are verified analytically and through simulation software using Matlab/Simulink®. The theoretical development and the simulation results show that the five-phase PMSM under inverter faults presents typical characteristics which can be used as better input variables for designing a high performance real-time fault diagnostic and classification process