基于单极性SPWM控制的并网逆变器的研究

Research on Grid-connected Inverter Based on Unipolar SPWM Control

光伏并网发电技术已经成为新能源利用的一个重要方向,并网逆变器是光伏系统的核心部件,因此高质量逆变电源成为研究的重点。单极性并网逆变器相对于双极性并网逆变器损耗低、谐波小、电磁干扰小,因此更适合用于并网逆变控制。这里分别介绍了两种单极性调制原理,并通过谐波关系图和仿真验证了单极性倍频控制下进网电流具有较小的THD,同时详细分析了普通单极性控制下进网电流过零畸变的原因。

PV grid-connected power generation is the trend at present in the world,and the grid-connected inverter is core part of PV power generation system,so high quality inverter is important.The unipolar spwm converter has lower loss,lower harmonics and lower EMI than bipolar spwm inverter.So unipolar spwm control is fit to be used in grid-connected control.Two control methods are studied.According to the harmonics graph and simulation,the grid-connect-ed current of unipolar SPWM control has lower THD.The oscillation reason of grid-connected current based on bipolar SPWM control occurring on the zero point of sine wave is analyzed in details.