采用载波移相技术的模块化多电平换流器电容电压平衡控制

Submodule Capacitance Voltage Balancing of Modular Multilevel Converter Based on Carrier Phase Shifted SPWM Technique

模块化多电平换流器(modular multilevel converter,MMC)是应用于电压源换流器直流输电(voltage sourceconverter-high voltage DC,VSC-HVDC)的新型多电平换流器拓扑。该文介绍了MMC的拓扑结构及相应的工作原理。针对该新型换流器拓扑的特点及其在高压直流输电领域中的应用,提出一种新颖的适用于模块化多电平换流器的载波移相调制策略(carrier phase-shifted SPWM,CPS-SPWM)。与其他调制策略相比,该策略动态调节能力强,且使MMC在较低开关频率的同时,亦具有良好的谐波特性。换流器中子模块的电容电压平衡问题,是MMC亟待解决的难点之一。该文根据子模块能量均分和电压均衡两种原则,结合换流器拓扑结构特点和调制策略,提出一种子模块电容电压平衡控制策略,有效确保各子模块电容电压处于相同的动态变化范围。仿真结果验证了所提策略的正确性与有效性。

Modular multilevel converter （MMC） was a new multilevel converter suitable for VSC-HVDC. The working principle of the submodules of MMC and converter topology were introduced in this paper. Considering the new topology and its application in the field of high voltage direct current transmission system, a novel carried phase shifted sinusoidal pulse width modulation（CPS-SPWM） scheme suitable for MMC was presented. Compared with other modulation schemes, the scheme proposed had superior dynamic regulation and excellent harmonic characteristics at lower switching frequency. Voltage balancing among the submodules was a crucial problem of MMC. Based on the equipartition of energy and voltage balance, a voltage-balancing scheme of submodules was presented in this paper with the topology of MMC and modulation. This scheme can effectively ensure each submodule at the same capacitance and voltage level. The correctness and effectiveness of the proposed schemes are verified by the simulation.