Abstract
This paper develops a modulation based fault-tolerant (FT) strategy for restoring the operation of three-phase modular multilevel converters (MMCs) with faulty switches. This FT strategy is based on a proposed modified space vector modulation (SVM) technique that generates balanced line-to-line (line) voltages even in the case of a fault occurrence. In the postfault operation, the proposed strategy is able to restore the fundamental amplitude of the line to the neutral (load) voltages to that of the normal operation condition with a slightly increased voltage stress over the switches in the faulty phase. In this paper, first a brief background about MMCs and SVM technique is provided. Then, the proposed FT strategy and the modified SVM technique are presented. Finally, several simulation and experimental results are provided to validate operation of the proposed strategy.
Highlights
M ODULAR multilevel converters (MMCs) are an attractive solution for applications [1], [2]
The purpose of this paper is to propose a new control-based FT strategy for an modular multilevel converters (MMCs) with bypassed faulty SMs
The circuit topology of the MMC used in this paper is illustrated in [19, Fig. 1]
Summary
M ODULAR multilevel converters (MMCs) are an attractive solution for applications [1], [2]. In [23] and [24], FT methods based on the CB-PWM are reported In these papers, the references are modified to generate balanced phase voltages. The strategy proposed in [32], for instance, bypasses the faulty cell and utilizes the redundant switching states via SVM to generate balanced converter voltages. The purpose of this paper is to propose a new control-based FT strategy for an MMC with bypassed faulty SMs. The proposed FT strategy generates balanced line voltages without employing auxiliary SMs or bypassing any SMs in the healthy phases, makes better use of the converter capacity, and generates line to the neutral (load) voltages with the same fundamental amplitude of normal operation
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