可用于光伏并网的双频逆变器控制策略

Control strategy of dual-frequency inverter suitable for photovoltaic grid-connection

研究了一种新型双频并网逆变器,其中一部分工作在低频,采用电流滞环控制,快速跟踪高频单元电流,传递大部分功率;另一部分工作在高频,采用单周控制,改善光伏并网电流的动态性能,使并网电流和电网电压同频同相。以双频逆变器A相为例分析了其在4种不同工作模态下电流、电压的变化,建立了高频单元平均电路模型,通过理论分析,推导出了单周控制策略。利用Matlab/Simulink建立了仿真模型,验证了双频光伏并网逆变器能够大幅降低开关损耗,使并网电流的总谐波畸变率减小,提高了并网效率。

A new-type photovoltaic grid-connected dual-frequency inverter is researched. Its low-frequency part adopts the hysteretic current-loop control to quickly follow the current of high-frequency cell and transit most of the power while its high-frequency part adopts the one-cycle control to improve the dynamic performance of photovoltaic current for grid-connection and make it in the same phase and frequency as the grid voltage. The voltage and current changes of dual-frequency inverter are analyzed in four working modes for phase A,the average circuit model of high-frequency cell is established and the one-cycle control strategy is derived through theoretical analysis. The simulation model is built with Simulink and the simulative result verifies that the proposed inverter reduces greatly the switching loss,decreases the total harmonic distortion rate and enhances the grid-connection efficiency.