电网电压不平衡下三相电压型变流器直流侧脉动电压的消除策略

在电力系统运行过程中,电压不平衡导致三相电压型变流器(VSC)直流侧产生二次脉动电压,映射到VSC输出端电压形成三次谐波和基波负序电压,影响输出电压品质,并有可能造成变流器过电流。对此,提出在电压环中加入带阻滤波器来滤除二次谐波电压的方法。但受电磁暂态过程影响,输出电压品质仍不理想,通过优化开关函数的办法,达到彻底消除三次谐波的效果。根据瞬时功率平衡原理,设计基波负序电压前馈控制,使电网负序电压全部降落在自耦变压器漏感和滤波器阻抗上,提高了变流器的运行性能。通过仿真试验验证了该方法的正确性。

Eliminating Strategy of VSC DC Side Fluctuation Voltage Under Unbalanced Grid Voltage

In power system operation,power quality will be affected by network voltage unbalance,which makes three-phase VSC put out a secondary ripple,and it will generate three-time harmonic and negative voltage in three-phase VSC output place.The factors mentioned above had a bad effect on the output voltage quality and caused converter over current.For those reasons,the article put forward using band filter to filter out second harmonic in voltage loop.While the influence of electromagnetic transient would affect the quality.Using optimization switch function could eliminate the effect.Considering the instantaneous power balance principle,designing feed-forward control of base negative voltage would make grid negative be used in transformer and filter,in that case,the performance of system would be improved,which was also proved by computer simulation.