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Open AccessArticle

Research on an Asymmetric Fault Control Strategy for an AC/AC System Based on a Modular Multilevel Matrix Converter

1
College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China
2
School of automation, Beijing institute of technology, Beijing 100081, China
*
Authors to whom correspondence should be addressed.
Energies 2019, 12(16), 3137; https://doi.org/10.3390/en12163137
Received: 15 July 2019 / Revised: 2 August 2019 / Accepted: 13 August 2019 / Published: 15 August 2019
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Abstract

This paper studies control strategies for an AC/AC system based on a modular multilevel matrix converter (M3C) when an asymmetric fault occurs in the secondary side ac system. Firstly, the operating principle of M3C is briefly introduced and verified by simulation. Then, based on its mathematical model by double αβ0 transformation, the decoupled control strategies for the primary side and secondary side systems are designed. In view of the asymmetric fault condition of the secondary side system, the positive sequence and negative sequence components of voltages and currents are separated and extracted, and then a proportional resonant controller (PR) is used to regulate the positive and negative sequence currents at the same time to realize decoupled current control in the αβ reference frames. The capacitor voltage balancing control, which consists of an inter-subconverter balancing control and an inner-subconverter balancing control, is realized by adjusting four circulating currents. Finally, the proposed control strategy is validated by simulation in the PSCAD/EMTDC software (Manitoba HVDC Research Center, Canada). The result shows that during the period of the BC-phase short-circuit fault occurring in the secondary side system, the whole system can still operate stably and transmit a certain amount of active power, according to their set values. Furthermore, the capacitor voltages are balanced, with a slight increase during the fault period. The simulation results verify the effectiveness of the proposed control strategy. View Full-Text
Keywords: modular multilevel matrix converter; asymmetric fault; positive and negative sequence separation; capacitor voltage balancing; circulating current modular multilevel matrix converter; asymmetric fault; positive and negative sequence separation; capacitor voltage balancing; circulating current
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Zhang, C.; Jiang, D.; Zhang, X.; Liang, Y. Research on an Asymmetric Fault Control Strategy for an AC/AC System Based on a Modular Multilevel Matrix Converter. Energies 2019, 12, 3137.

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