多电平变换器补偿不平衡负载的应用分析

Analysis of multilevel converters in compensating unbalanced load

为了准确分析级联H桥星型接法变换器、级联H桥角型接法变换器和模块化多电平变换器在电网故障情况补偿不平衡负载的能力,根据功率平衡原理分别建立了这三种多电平变换器的数学模型进行对比分析,并得出结论:基于级联H桥星型接法的STATCOM不适合补偿不平衡负载。基于级联H桥角型接法变换器的STATCOM在电网电压正常时能很好地补偿不平衡负载,但是当电网电压发生故障时补偿不平衡负载的性能迅速降低。基于模块化多电平变换器的STATCOM无论是在电网电压正常还是故障不对称的情况下都能很好地补偿无功电流和负序电流。最后,基于Matlab/Simulink仿真结果表明了理论分析的正确性和有效性。

In order to accurately analyze the performances of cascaded H-bridge with star connection, cascaded H-bridge with delta connection and modular multilevel converter in handling the unbalanced load under the asymmetrical grid fault condition, firstly, this paper builds mathematical models of these three multilevel converters based on the principle of power equilibrium. Then it gives contrastive analysis. The final analysis conclusion is that the STATCOM based on cascaded H-bridge with star connection converter is not suitable for compensating unbalanced load, while the STATCOM based on cascaded H-bridge with delta connection converter can work well to compensate unbalanced load when grid is normal. But the capability of compensating unbalanced load is greatly suppressed when asymmetrical grid fault happens. The the STATCOM based on modular multilevel converter works well to compensate reactive power and negative-sequence current even under serious asymmetrical grid fault condition. Finally, Matlab/simulink simulations verify the correctness and effectiveness of theoretical analysis.