This study presents a multi-fault tolerant strategy for a cascaded H-bridge (CHB) based static synchronous compensator (STATCOM) with star configuration. A new method for post-fault operation of CHB-STATCOM is proposed, where after switch failures, the full-bridge (FB) submodules are used as two different types of half-bridge submodules named as positive half-bridge (P-HB) and negative half-bridge (N-HB). Using a modified level shift pulse-width modulation technique, a combination of FB, P-HB and N-HB submodules is employed in three legs of the converter to generate the maximum attainable ac side voltage in post-fault condition. In order to restore the nominal capacity of CHB-STATCOM, the capacitor voltage of submodules is increased based on the type and number of switch failures. Furthermore, by utilising a voltage balancing strategy, the voltages of submodules’ capacitors are kept balanced and regulated at the desired value in post-fault condition. The feasibility and effectiveness of the proposed strategy is validated on a scaled-down 9-level CHB-STATCOM laboratory prototype.

中文翻译：

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基于STATCOM的级联H桥的改进的故障后操作策略。

这项研究提出了星形配置基于级联H桥（CHB）的静态同步补偿器（STATCOM）的多容错策略。提出了一种CHB-STATCOM故障后操作的新方法，其中在开关故障后，全桥（FB）子模块用作两种不同类型的半桥子模块，称为正半桥（P-HB）负半桥（N-HB）。使用改进的电平移位脉冲宽度调制技术，在转换器的三个支路中采用了FB，P-HB和N-HB子模块的组合，以在故障后条件下产生最大可获得的交流侧电压。为了恢复CHB-STATCOM的标称容量，将根据开关故障的类型和数量来增加子模块的电容器电压。此外，利用电压平衡策略，故障后条件下，子模块电容器的电压保持平衡并调节到所需值。在按比例缩小的9级CHB-STATCOM实验室原型上验证了所提出策略的可行性和有效性。