MMC-STATCOM的不平衡补偿分析及控制

Analysis and Control of Unbalanced Load Compensation of MMC-STATCOM

基于模块化多电平的静止同步补偿器(MMC-STATCOM)在补偿不平衡负载时需要考虑装置组成器件的电流承受能力,为了衡量MMC-STATCOM的不平衡补偿能力,可以将桥臂电流最大值与待补偿负序电流幅值的比值来作为衡量标准,并且可经理论分析得出影响其补偿能力的关键因素。此外,针对MMC-STATCOM中存在的内部环流,其直流分量可在处理功率平衡和相间平衡控制时被加以利用,其二倍频分量则予以消除。电流控制策略基于准PR控制,可实现对待补偿电流的快速跟踪和对环流二倍频分量的实时抑制,然后通过电压前馈控制得到包含多谐振环的调制波方程。各子模块直流侧电压分三层控制,其中相间平衡控制可首先利用功率平衡来实施,然后再通过环流的直流分量进行修正。相关分析结果的正确性和控制策略的有效性在仿真实验中得到了验证。

Modular multilevel-based static synchronous compensator(MMC-STATCOM)needs,in case of compensating unbalanced load,considering the current bearing capacity of the components of the device.In order to measure the unbalanced compensation capability of MMC-STATCOM,the ratio of the maximum arm current to the negative sequence current amplitude to be compensated can be used as the measurement standard,and the key factors affecting its compensation ability can be obtained through theoretical analysis.In addition,as for the internal circulating current existed in MMC-STATCOM,its DC component can be used when processing power balance and the inter-phase balance control,and its double frequency component can be eliminated.The current control strategy is based on the quasi-PR control,which can realize the fast tracking of the current to be compensated and the real-time suppression of the double frequency component of the circulating current.And then,the modulated wave equation containing the multiple resonance ring can be obtained through the voltage feedforward control.The DC side voltage of each sub-module is controlled in three layers,in which the inter-phase balance control can be implemented by power balance firstly,and then corrected by the DC component of the circulating current.The correctness of related analysis and the effectiveness of control strategy are verified in the simulation experiment.