基于子模块电容电压允许值的MMC均压控制策略

A Voltage Balancing Control Strategy for Modular Multilevel Converter Based on Allowable Capacitance Voltage of Sub-modules

针对模块化多电平变换器(modular multilevel converter,MMC)传统子模块(sub-module,SM)均压策略存在的开关频率高、开关损耗量多、计算量大等问题,提出基于子模块电容电压允许值的均压控制策略。通过引入电容电压允许值变量,使得SM电压始终在规定的范围内运行,降低了功率器件损耗。与此同时,由于不需要每个控制周期对全部SM进行排序,进一步减少了控制策略的计算量。通过仿真结果验证了所提策略的有效性,可以显著减少单位时间内功率器件的开关次数。

Aiming at the problems of high switching frequency, large switching loss and large amount of computation in traditional voltage balancing strategy for modular multilevel converter(MMC), an improved capacitor voltage balancing control strategy is proposed. The sub-module(SM) voltage is constantly kept in the specified range through introducing the allowable value variable of capacitor voltage, consequently reducing the loss of power devices. In the meantime, all the sub-modules need not to be sorted in each control cycle, thus further reducing the amount of computation of the control strategy. Finally, the Matlab/Simulink-based simulation is carried out and the results show that the proposed strategy can significantly reduce the switching times of power devices per unit time.