基于模块化多电平变换器（MMC）的UPFC新型环流抑制方法

A NEW CIRCULATING CURRENT SUPPRESSION STRATEGY OF UPFC BASED ON MODULAR MULTILEVEL CONVERTER（MMC）

在电力电子领域,针对模块化多电平变器(modular multilevel converter,MMC)在统一潮流控制器(unified power flow controller,UPFC)中应用时存在严重的环流谐波问题,分析平均电容电压控制模型,总结优缺点,给出数字控制改进方法。该方法在平均电容电压控制模型中加入环流直流电压提取环节以及准比例谐振的二倍频消除环节。针对改进部分,综合考虑稳定裕度和稳态精度后,在离散域中给出参数设计方法。最后,在MMC样机上分别对改进前后的控制方案进行实验。实验结果表明,改进后的方案具有良好的子模块电容电压均衡效果及环流中低频二次谐波抑制能力可验证方案的有效性以及参数设计的合理性。

In the field of power electronics,aiming at the serious circulant harmonic problem of the Modular Multilevel Converter(MMC)applied in the unified power flow controller(UPFC),analyzing advantages and disadvantages of average capacitor voltage control model,an improved digital control method is given.Average capacitor voltage control model is still used to balance arm voltage,but DC component extraction and quasi-proportional-resonant(quasi-PR)are added into the inner loop to eliminate second order circulating harmonic current.In this paper,the controller parameters of improved part are designed in discrete domain and stability analysis are also discussed.Finally,experiment results before and after improvement are analyzed and compared,which indicate that the improved control method has the merit of capacitor voltage balance and good performance in restraining circulating harmonic current.