Z源逆变电路及其直通控制策略在光伏并网系统中的应用

Application of Directt-through State Control Strategy for Z-source Inverter in Grid-connected Photovoltaic Systems

针对传统的Z源逆变电路控制方式中需要独立分析升压电路控制因子和并网电路控制因子的问题,先在典型的Z源全桥逆变电路的拓扑结构中实现单桥臂上下管的直通相位控制方式下的开关时序,进而分析了Z源逆变电路的5种模态的工作原理,提出了一种适用于单相光伏逆变系统的Z源逆变电路直通控制方式,就是利用能量传递和傅里叶算法在直通零矢量和输出逆变电压之间建立直接联系。以一台3kW光伏并网逆变样机的测试结果表明,样机PV电压稳定,并网电压电流相位在50%输出功率下基本一致,其谐波含量和功率因数符合要求;同时,还具备一定的过压、欠压动态保护特性,反应时间迅速。结果表明,Z源逆变电路及其直通控制策略在光伏并网系统中的应用效果较好。

Aiming at the shortcomings of conventional Z-source inverter control methods,which include independent analysis of control factors in boost and grid-connected circuits,this paper firstly implements the switching sequence of single-bridge upper and lower transistors using direct-through state control strategy in the typical Z-source full-bridge inverter.Then a Z-source direct-through state control strategy is proposed for single-phase photovoltaic inverter power system based on five operational modes of Z-source inverter circuit.This enhanced control strategy,which utilizes energy transfer and Fourier algorithm,establishes the direct relations between shoot-through vector and inverter output voltage.The prototype test results of a 3-kW photovoltaic grid-connected inverter demonstrate that it has stable PV voltage with the approximately same phase between grid-connected voltage and current under the 50% maximum output,the harmonic distortion and power factor satisfy the requirement.Furthermore,it has some capabilities of dynamic voltage protection with short response time.The results show that the direct-through state control strategy for Z-source inverter has preferable performance in grid-connected photovoltaic system.