光伏并网逆变器谐波特性分析与谐波电流抑制

Analysis of Harmonic Characteristics and Suppression of Harmonic Current for Photovoltaic Grid-connected Inverter

考虑光伏并网逆变器功率器件的死区效应和非理想开关特性,分析基于双极性正弦脉冲宽度调制三相逆变器输出电压的谐波特性,推导计及功率器件死区效应与开通关断延时的逆变器输出误差电压定量计算公式,建立包含逆变器输出误差电压的两相静止坐标系下三相LCL型并网逆变器的受控电流源等效电路模型,提出基于光伏并网逆变器功率控制的虚拟阻抗控制器设计方法,以抑制谐波电流并确保光伏逆变器最大功率输出。Matlab/Simulink仿真表明并联的虚拟阻抗控制可有效抑制谐波电流。

With the consideration of dead-zone effect and non-ideal switching characteristics of power devices in photovoltaic(PV)grid-connected inverters,the harmonic characteristics of output voltage from a three-phase inverter based on bipolar sinusoidal pulse width modulation(SPWM)are analyzed,and a quantitative calculation formula for inverter output error voltage is derived by taking into account the dead-zone effect and turn-on/off time delay of power devices.An equivalent circuit model of controlled current source for a three-phase LCL grid-connected inverter under a twophase static coordinate system including the inverter output error voltage is established,and a design method for virtual impedance controller based on the power control of PV grid-connected inverter is proposed to suppress harmonic current and ensure the maximum power output from the PV inverter.Simulation results based on Matlab/Simulink show that the harmonic current can be effectively suppressed by parallel virtual impedance control.