一种改善三相不平衡下逆变器并网系统电能质量的新方法

针对典型的逆变器并网系统,研究三相不平衡度对公共并网点(PCC)电能质量的影响。三相不平衡电压经序分量分解后,由瞬时功率可推导其对并网逆变器直流侧二倍频波动量的影响,结合开关函数的傅里叶表达式,分析逆变器交直流侧交互影响机理,同时经过数学推导得出公共并网点的谐波特性。基于此谐波特性,建立由有源滤波器和无源滤波器组成的混合电力滤波器(HPF),达到改善并网电能质量的目的。利用Matlab/Simulink软件搭建三相不平衡并网系统,检测特定次谐波与理论推导值作对比,考虑并网系统具有的谐波特性,建立HPF滤波模块,验证了HPF在提高电网电压三相不平衡时并网系统的电能质量方面具有优越性。

A new method to improve power quality of inverter grid system under three-phase unbalance

This paper studies the influence of three?phase unbalance degree on the power quality at the point of common coupling ( PCC ) for typical grid?connected system. The unbalanced three?phase voltage is decomposed through sequence components. Then the effect on two times wave of the DC side is derived by the instantaneous power theory, which is combined with the switch function of Fourier expression to analyze the inverter AC/DC side interaction mechanism and to derive harmonic characteristic at PCC. The hybrid power filter ( HPF) composed of active filter ( APF) and passive filter ( PPF) is established on the basis of the harmonic characteristic, which im?proves the power quality effectively. On the three?phase unbalanced grid?connected system built by Matlab/Simu?link the correctness of mathematical derivation is verified in terms of comparison between the detection of specific harmonics and theoretical derivation. According to the harmonic characteristics of the grid?connected system, the HPF module is established to validate the superiority of HPF on improving the power quality of the grid?connected system when three?phase voltage is unbalanced.