考虑故障容错的双混合STATCOM研究

Research on dual-hybrid STATCOM considering fault tolerance

针对基于模块化多电平换流器的静止无功补偿器(MMC-STATCOM)所用子模块(submodule,SM)过多,导致系统复杂性上升等问题,文中提出一种双混合STATCOM,即在MMC-STATCOM基础上,用高耐压值GTO构成的H桥模块代替上桥臂,下桥臂采用半桥模块。首先对所提出的拓扑结构进行分析,并与其他方案的开关器件使用数量进行对比;然后提出针对该拓扑的载波移相、载波同相层叠两种调制方式,并考虑故障容错情况,形成两种三层电容电压均衡控制策略;最后在Simulink中搭建双混合STATCOM仿真模型对所提控制策略的有效性进行分析验证。结果表明:双混合STATCOM可明显降低开关器件使用数量;无故障时,两种控制策略下的双混合STATCOM均能稳定运行,保持良好的无功补偿能力;故障情况下,基于载波移相的控制策略具备更好的直流侧电容电压均衡能力。

There are too many submodules(SM)used for modular multilevel converter STATCOM(MMC-STATCOM),which lead to the increase of system complexity,a dual-hybrid STATCOM is proposed,that is,on the basis of MMC-STATCOM,the H-bridge module composed of GTO with high withstand voltage is used to replace the upper bridge arm,and the half bridge module is used at the lower bridge arm.The proposed topology is analyzed and compared with the number of switching devices used in other schemes.Two modulation methods,carrier phase shift and carrier in-phase cascade,are proposed for the topology,the fault tolerance is considered,and two three-layer capacitor voltage balancing control strategies are formed.The simulation model of dual-hybrid STATCOM is built in Simulink to analyze and verify the effectiveness of the proposed control strategy.The results show that the dual-hybrid STATCOM can significantly reduce the number of switching devices.When there is no fault,the dual-hybrid STATCOM under the two control strategies can run stably and keep good reactive power compensation ability.In the case of fault,the control strategy based on carrier phase shift has better capability of capacitor voltage equalization on DC side.