电压波动情况下的模块化多电平换流器宽频环流抑制

Broadband Circulation Suppression of Modular Multilevel Converter under Voltage Fluctuation

随着电力行业的飞速发展,模块化多电平换流器(modular multilevel converter,MMC)越来越多地被用于直流输电、配电、新能源并网等情况。但是当MMC直流侧或交流侧发生电压波动时,都会在桥臂上产生环流。为了降低环流对MMC的影响,首先通过上、下桥臂电流和开关函数耦合推导子模块电容电压波动,得到环流在相序和频率上的传递规律。其次,基于准快速重复控制,结合准比例谐振控制器,设计环流抑制控制器,达到环流的宽频抑制和特定频率重点抑制的效果。最后在PSCAD仿真平台上针对直流侧母线电压波动、交流侧电压波动等2种异常工况进行仿真分析,验证了理论推导的正确性和所提抑制措施的有效性。

Along with the rapid development of power industry,modular multilevel converter(abbr.MMC)has been increasingly used in DC transmission,distribution,grid-connection of new energy,and so on.However,when voltage fluctuation occurs at the DC side or AC side of MMC,circulating current will be generated on the bridge arm.To reduce the influence of circulation on MMC,firstly,the capacitance voltage fluctuation of the sub-module was derived by coupling the upper and lower bridge arm currents with the switching function,and the transfer law of the circulating current in phase sequence and frequency was obtained.Secondly,based on quasi fast repetitive control(abbr.Q-FRC)and combining with quasi proportional resonance(abbr.QPR)controller,a circulating current suppression controller was designed to achieve the effects of wide-band suppression of circulating current and key suppression of specific frequency.Finally,the analysis on the PSCAD simulation platform for three abnormal conditions,i.e.DC side bus voltage fluctuation and AC side voltage fluctuation were simulated by the PSCAD simulation platform,thus,the correctness of the theoretical derivation and the effectiveness of the proposed suppression measure are verified.