三电平逆变器滤波器元件电流应力分析

Analysis of Current Stress on Filter Component in Three-Level Inverter

三电平逆变器适用于光伏、储能并网系统,交流侧采用LCL滤波器。现有文献大都研究其对谐波的抑制能力或并网系统的稳定性。然而,对不同电压、功率因数、功率等级等工况下电感、电容器件的电流应力的分析不够全面,导致器件运行可靠性难以预测。以三电平逆变器及空间矢量调制为研究基础,推导了LCL滤波器3个元件的电流有效值及电流波形包络线的表达式,分析了功率因数、直流电压变化等对其电流应力的影响规律,据此能得出器件所受最大应力。通过电路仿真和实验,验证了解析式和分析结果的正确性。

Three-level inverter is suitable for photovoltaic and energy storage grid-connected system,with the AC side utilizing an LCL filter.Most of the existing literature studies on its ability to suppress harmonics or the stability of grid-connected systems.However,the analysis of the current stress of inductors and capacitors under different voltages,power factors,power levels,etc.is not comprehensive enough,which makes the reliability of the devices difficult to predict.This paper is based on the research of three-level inverter and space vector modulation to derive the expressions of current RMS and current waveform envelope of three components of LCL filter,and then analyzes the influence of power factor and DC voltage on current stress,on the basis of which the maximum stress on the device can be obtained.The correctness of the analytical formula and analysis results are verified by circuit simulation and experiments.