MMC型STATCOM子模块电容电压的自适应优化平衡控制

Self-Adaptive Control of the Sub-Module Voltage for STATCOM Based on Modular Multilevel Converter

对模块化多电平变换器(Modular Multilevel Converter,MMC)子单元模块电容电压的谐波特性进行理论分析,并给出电容值选型的计算方法。针对传统的基于CSPWM分级电容电压平衡控制和基于NLM排序电容电压平衡控制,提出了一种适合MMC型STATCOM的自适应电容电压优化平衡控制策略,将平衡控制的重点放在如何选择最优控制器上。使用Matlab/Simulink对自适应优化控制策略进行仿真,同时搭建3kvar的实验平台,仿真及实验结果一致,结果均表明该优化平衡控制策略与传统方法相比,可以在不增加电容电压波动的前提下,降低器件的开关频率,并显著提高电容电压的响应速度。

The harmonic characteristic of sub-module capacitor voltage in modular multilevel converter is analyzed. Based on the result of theoretical analysis, the principle and calculation method for the selection of sub-module capacitance are given. In order to solve the problem of hierarch ical control strategy based on carrier shifted PWM modulation and the capacitor voltage sorting control based on nearest level modulation, a novel self-adaptive capacitor voltage balancing algorithm for STATCOM have been presented. The proposed control strategy is verified by simulation Matlab/Simulink, and the results show that this balancing algorithm can achieve low switching losses, fast DC voltage response speed and good dynamic performance.