基于电流滞环控制的Z源光伏并网系统研究

Research on Z source based current hysteresis control used in photovoltaic grid-connected system

Z源光伏并网系统中,对于Z源的控制,必须在控制信号中加入直通时间,结合滞环的特点,提出一种适用于Z源光伏并网系统的定频电流滞环控制算法。设定滞环电流轨迹,固化零电压作用时间,开关周期固定插入直通时间。该算法保留了传统滞环控制动态响应速度快,跟踪精确度高,稳定性高等优点,克服了传统滞环控制开关频率不固定而带来的开关损耗大及滤波器设计困难的缺点。在该算法控制下,直流侧经Z源的升压后,使并网电流大大提升;直流侧电压波动得到有效的抑制;系统能有效地跟踪电网电压,保证并网电流与电网电压保持同相。通过仿真与传统滞环控制比较,并经过实验验证,证明了该算法的可行性。

In Z source based photovoltaic grid-connected system for the control of Z source,the shoot through time must be added in the control algorithm. A new kind of control algorithm based on fixed-frequency current hysteresis used in photovoltaic（PV） grid-connected system based on Z-source converter is presented in this pa-per. This algorithm comprehended benefits of direct current control,such as quick dynamic response,high tracking precision,high stability,ect. Overcoming the disadvantages such as high switch loss and difficulties of filter design which were caused by not fixed switch frequency. With the control of the algorithm,through the effect of Z source Boost,grid current was increased significantly,and there was no impact on grid current, when DC voltage was changed in some range,and the PV grid-connected system can track grid voltage effec-tively,so that grid current and grid voltage can be kept synchronous. Both comparison with the traditional hys-teresis control by simulation and grid connected experiment proved the feasibility of the algorithm.