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This paper presents an evolution of control systems of Modular Multilevel Converters (MMCs) focusing on the internal voltages and currents dynamics. MMCs have passive components that create extra dynamics compared to conventional VSCs. Some control schemes that do not consider these internal dynamics may still stabilize the system asymptotically thanks to the linearisation in the modulation step. However these control schemes are less robust because they are prone to poor damped oscillations on the dc side of the converter. The MMC circuit and energy relationships are presented in this paper. Along with a gradual development of the energy based control, the important roles of each internal dynamics are clearly demonstrated. Experimental results are presented to show the impacts of the linearisation in the modulation step on the system behaviour.

The Modular Multilevel Converter (MMC) is a power electronic structure used for high voltage adjustable speed drives applications as well as power transmission applications and high-voltage direct current (HVDC). MMC structure presents many advantages such as modularity, the absence of a high voltage DC bus and very low switching frequency. It presents also some disadvantages such as modeling complexity and control due to the large number of semiconductors to control. The objectives of this paper are to present the methodology to design a laboratory MMC converter and its control system. This methodology is based on an intensive used of real-time simulation, to develop and test the control algorithm is proposed. This MMC prototype must be as realistic as possible to a full scale MMC, with a large number of SM (i.e. 640kV on the DC side, a rated power of 1GW and 400 sub-modules). A control hardware integrating distributed processors (one for each arm) and a master control is presented. The protocols to validate sub-modules, arms and the converter are explained.

In this paper, the development of a high bandwidth power amplifier for power hardware-in-the-loop system is proposed. This amplifier consists of a multilevel interleaved converter, controlled by a real time model of a studied system that is implemented in a field programmable gate array. The accuracy of the proposed topology is illustrated with the design of a test bench for PV inverter testing. This topology is able to emulate both sides (AC and DC) of PV inverter. With this scheme it is possible to analyze the behavior of the complete photovoltaic system under special conditions like partial shading and disturbed grid voltage. The simulation and experimental results verify that the proposed topology exhibits good performance compared with classical topology.

The modular multilevel converter (MMC) is recognized for many advantages over conventional 2-level or 3-level voltage source converters (VSC). One of the features is that it is possible to control the stored energy in the distributed submodule (SM) capacitors. The aim of this paper is to propose a methodology to develop the control system implemented on a 21-level MMC mock-up. This control must be first validated in a real-time (RT) simulation environment with an accurate MMC model representing the behaviour of the physical MMC mock-up. Then it is performed in the hardware-in-the-loop (HIL) simulation before the implementation. The power system is emulated in a real time simulator from Opal-RT Technologies, which is connected to an external control system programmed in a dual-core microcontroller. The developed HIL platform facilitates the tests of the control and protection system in all possible scenarios.

This paper deals with the conception and the development of a detailed EMT Model for MMC based on experimental results obtained from a mock-up. The main purpose is to illustrate how to exploit the performances of EMT simulation tools to develop a detailed model that represents accurately the behaviour of a physical MMC. According to step-by-step identification of the MMC element parameters, the idea is to perform a systematic method, which allows expanding an accurate EMT model considering the behaviour of the prototype and its environment. The first part depicts the MMC topology and the modelling approach of the Half-bridge Sub-Module (SM) using a detailed IGBT-based model. The second part of the simulation model conception concerns both control levels such as high-level and low-level controllers. The last part of the EMT model conception involves the modelling of measurement process, ADC (Analogue Digital Converter), sensors dynamics, the communication delays and especially the quantization effect. Finally, the obtained results from the final detailed EMT model is compared to the experimental behaviour for different active and reactive powers operating points in order to prove the effectiveness and the capability of the EMT modelling to reach a detailed and accurate model.

Le Convertisseur Modulaire Multiniveaux (MMC) est une structure d’électronique de puissance utilisée dans des applications de variation de vitesse des machines électrique haute tension mais aussi des applications de transport de l’électricité à très haute tension et courant continu. La structure MMC présente beaucoup d’avantages tels que sa modularité, l’absence de bus DC haute tension et une fréquence de commutation très faible étant donnée le grand nombre de SM. Elle présente aussi des inconvénients comme la complexité de modélisation [2] et de contrôle [3] dû au grand nombre de semi-conducteurs à contrôler. Cet article a pour objectifs de présenter le dimensionnement d’un convertisseur MMC de laboratoire ainsi que son système de contrôle, le plus réaliste possible d’une structure échelle une, avec un grand nombre de SM. Le dimensionnement de ce dernier prendra en compte les contraintes et les caractéristiques son fonctionnement dans un réseau HVDC 640kV 1GW. Une architecture de contrôle, contraintes par le nombre de de sous module, sera présentée. Les protocoles de validation des sous modules, d’un demi-bras puis du convertisseur seront présentés.