模块化多电平换流器效率优化控制器设计

Efficiency Optimized Controller Designing for Modular Multilevel Converter

模块化多电平换流器每相投入模块的电压总和不平衡时,会导致三相桥臂之间出现以2倍频负序性质为主的环流。为此,设计了一种效率优化控制器。模块化多电平换流器模块化的特点使得电容电压排序算法成为一种非常好的均衡控制方法。在研究了模块化多电平换流器数学模型的基础上,利用2倍频负序dq旋转坐标变换,设计了环流解耦抑制控制器,并结合电容电压优化排序算法,得到对应的各个子模块的触发脉冲。仿真结果表明,所设计的控制系统不仅能够降低器件的开关频率,而且相间环流也得到了很好的抑制,因此降低了系统运行损耗,提高了系统运行效率。

in a modular multilevel converter （MMC）, unbalanced total voltage on inserted modules will lead to double-frequency negative-sequence phase-to-phase circulating current between the three phases. To deal with this problem, we proposed a design of efficiency optimized controller for MMC. The module characteristic of MMC makes the voltage-sorting algorithm to become an ideal balancing control method. After studying the mathematic model of MMC, we put forward the circulating-current suppressing/deeoupling controller by using double- frequency negative dq rotating coordinate transformation matrix. Moreover, combining the controller with capacitance voltage optimization-sorting algorithm, we obtained trigger pulses for each module. Further simulation shows that the developed control system can not only reduce the switch frequency of devices, but also suppress the phase--to--phase circulating current, i. e. , it reduces operation loss and promotes operation efficiency.