中文摘要：

随着高压直流输电系统电压等级和输送容量的提升,对模块化多电平换流器的电容电压平衡控制提出了更高的要求。为了实现对高压大容量模块化多电平换流器电容电压的优化控制,基于桥臂子模块分段控制思想,采用分段电容电压排序控制方法。首先,分析了段内和段间电容电压平衡机理,提出了段间电压平衡控制策略;其次,将MMC开关频率分为两部分,分别分析了各部分开关频率的影响因素,提出了基于子模块电容电压预估的段内电容电压平衡优化控制策略,以降低器件的等效开关频率;最后,基于PSCAD/EMTDC的仿真结果表明,在有效保证电容电压平衡的条件下,等效开关频率降幅可达25%,从而验证了相关理论分析的正确性和控制策略的有效性。

英文摘要：

With the increase of voltage levels and transmission capacity of the modular multilevel converter based HVDC, the capacitor voltage balance control will become more difficult. To deal with the problem, segmented design for each ann is introduced. Combining the segmented design and capacitor voltage sorting based balance control strategy, we ana- lyzed the mechanisms of voltage balance among different sub-modules in each segment and among different segments. Then, we proposed a voltage balance control strategy among segments. The equivalent switching frequency of MMC is divided into two parts. Thereby, the influence factors for different switching frequency are then analyzed. Thereafter, an optimization control strategy for capacitor voltage balance is proposed to decrease the equivalent switching frequency. The simulation results, based on the PSCAD/EMTDC software environment, indicate that the capacitor voltage balancing is well guaranteed while the equivalent switching frequency reduce by more than 25%, verifying the correctness of the relative theory analysis and validity of the proposed control strategy.