具有低入网电流谐波的组合光伏发电系统研究

Research on Combined Photovoltaic Power System with Low Network Current Harmonics

针对大功率并网逆变器在低负载率下并网电流总谐波畸变率(THD)普遍超过国家标准的问题,对并网发电系统结构进行改进,该系统由1台采用LCL型滤波器的三电平主逆变器和1台采用L型滤波器的电平辅助逆变器组成,输出并行通过隔离变压器连接主电网。根据光伏阵列功率大小,研究了2台逆变器的3种工作方式、参数设计方法和控制策略,使系统在宽输出功率范围内并网电流THD均满足国家标准要求。搭建了小功率等级的实验平台,实验结果验证了所研究改进型光伏并网发电系统的有效性和可行性。

When output power of photovoltaic(PV)array is low,the total harmonic distortion(THD)of the gridconnected current generally exceeds the national standard,so an improved grid-connected PV power generation system was proposed to solve this problem. The system included a larger capacity three-level master inverter with a LCL filter and a smaller capacity two-level slave inverter with an L-filter. Two inverters were connected in parallel with the utility grid via an isolated line-frequency transformer. Three operation modes,parameter design method and control strategy were discussed according to output power of the PV array and the THD of grid connected current was operated to meet the requirements of national standard in a wide range of output power. A low power experimental platform was built,and experimental results verify the effectiveness and feasibility of the improved grid-connected photoroltaic power generation system.