摘要
以单个子模块为出发点,分析死区对模块化多电平换流器(MMC)相单元总电压以及交流输出电压的影响.分析表明:在死区时间内,MMC相单元中实际处于投入状态的子模块总数与该相单元内部某一采样时刻发生投、切状态改变的子模块数相关,从而导致相单元总电压会出现短暂的过压(或欠压),不利于桥臂电抗器的运行,同时使MMC交流输出电压中出现不期望的电平数,增大了输出电压的总谐波畸变率.利用优化的均压算法减小了死区对MMC的影响,提高了输出电压的质量,研究最近电平逼近以及优化的均压算法在实现过程中面临的问题.设计一种适合于大规模MMC的控制系统硬件平台,研发了41电平三相MMC实验室样机.实验结果表明:所设计的控制系统是可行的;优化后的均压策略有效地降低了死区对MMC相单元总电压、交流输出电压以及桥臂电抗器的影响.
The total voltage of one phase unit and the output voltage in modular multilevel converter （MMC） were analyzed during the dead time based on a single sub-module （SM）. The analysis shows that during dead time, the real number of inserted SMs among one phase unit is related to the number of SM_ on/offs. Therefore, over-voltage or under-voltage may occur in the total voltage during the dead time, doing harmful to the arm inductors. Unexpected voltage levels in the output voltage of MMC appear, too. The widely-used traditional straightforward voltage balancing strategy （SVBS） was optimized to alleviate the dead time effect and improve the quality of output voltage. The implementation of nearest level modulation and the optimized SVBS was investigated. A controller for large-scale MMC was designed and a three-phase 41-level MMC prototype was developed to validate the theoretical analysis and the optimized SVBS. Experimental results demonstrate that the designed controller is feasible and the optimized SVBS can effectively reduce the dead time effect.
出处
《浙江大学学报（工学版）》
EI
CAS
CSCD
北大核心
2014年第4期561-567,574,共8页
Journal of Zhejiang University：Engineering Science
基金
浙江省重点科技创新团队资助项目(2010R50004)
