摘要
针对传统最近电平调制策略(NLM)在模块化多电平换流器(MMC)中造成的直流侧电压波动和二倍频环流等问题,提出改进最近电平的调制策略.充分考虑子模块电容电压的波动,采用优化的电容电压均衡策略.由于每个桥臂中各子模块的电压近似相等,用子模块平均电压代替每个子模块电压,通过分析系统的二倍频环流产生机理,建立数学模型,根据数学模型提出改进最近电平调制策略的控制策略.针对子模块电压波动带来的影响,改进的策略采取反馈实际电容电压,消除了实际桥臂电压与参考电压间的误差,抑制了直流侧电压波动和二倍频环流.通过PSCAD/EMTDC软件对系统进行仿真,结果表明,在系统稳态和动态运行情况下,提出的改进策略均能够有效抑制直流电压波动和二倍频环流,系统输出电流的毛刺显著减小,具有较高的稳定性.
In order to solve the fluctuations of DC voltages and circulating currents of modular multilevel converters by using traditional nearest level modulation(NLM),an improved NLM method for the modular multilevel converter was proposed.In the proposed method,full consideration to capacitance voltage of the sub-module was given and capacitance voltage balancing strategy of optimization was used.Instead of each module voltage,the module average voltage was used because the voltage of each module is approximately equal. Through the analysis of the circulating current's generation mechanism,mathematical model was established.According to the mathematical model,in view of the impact of the sub-modules' voltage fluctuations,the control strategy of NLM has been proposed,which is,feeding back actual capacitance voltage to curb circulating current.In this way,the improved NLM both eliminates the errors between actual arm voltage and reference voltage and inhibits the fluctuations of DC voltages and circulating currents.By the simulation in PSCAD/EMTDC,the results show that the improved NLM can suppress the fluctuation of DC voltage and circulating currents both in steady and dynamic state,which means that the system has a high reliability.
出处
《浙江大学学报（工学版）》
EI
CAS
CSCD
北大核心
2015年第8期1522-1528,共7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)
关键词
模块化多电平换流器
改进最近电平调制
直流电压波动
二倍频环流
modular multilevel converter
improved nearest level modulation
DC voltage fluctuation
circulating current.
