无冗余模块的故障环流分析及抑制策略研究

Analysis of Fault Circulating Current Without Redundant Sub-Module and Its Suppression Strategy

故障子模块的切除运行会使模块化多电平变换器系统输出不平衡。分析了故障运行期间,由于相与相之间模块的不对称投入,相间环流将明显增大,不及时处理易造成输出过流、子模块过压等的情况。针对无冗余模块的子模块故障问题,使用调制波重组方式的故障穿越策略后,证明了相桥臂间仍不对称运行。然后,通过理论推导故障期间以及调制波重组后的环流状态,证明奇次谐波明显增加,并设计了基于二阶广义积分器的多谐波提取控制器,通过准比例谐振调节器完成对环流的抑制。最终,通过Matlab仿真以及10 k W样机平台完成控制策略的验证。

MMC system Output will be unbalanced when sub-module（SM） fault happens. Because of unbalanced inserted SMs between different phase arms during SM fault period, circulating current, especially odd harmonic components, will increase. Overcurrent output and SM overvoltage will occur if the fault is left unsettled. To solve unbalanced output problem, modulation reconfiguration technology is adopted. However, the circulating current is still unbalanced. Thus, by analyzing circulating current during fault operation and modulation reconfiguration time, second-order generalized integrator based on multiple-harmonic filter is proposed. The circulating current will be suppressed with Quasi PR regulator. Finally, simulation and experiment results show validity of the model and control strategy.