三相并网变流器的无锁相环控制策略研究

Study on the Control Strategy for Three-phase Grid-connected Converter without Phase-Locked Loop

基于同步旋转的dq坐标系可将三相并网变流器中的工频交流量映射为直流量,此时采用经典PI调节器便可实现对交流参量的跟踪控制。dq变换需要的电网电压矢量角通常情况下需要锁相环的支持,增加了控制系统复杂性。通过导出电网电压矢量角的正余弦值与电网电压在两相静止坐标系下分量之间的关系,提出了三相并网变流器在dq坐标系下的无锁相环控制策略。该算法仅以电网电压瞬时值为输入变量,大大简化了控制系统的复杂性。最后,搭建了系统仿真模型,仿真结果证明了文中理论分析的正确性和所提控制策略的有效性。

The signal with power frequency in the three-phase grid-connected converter system can be mapped to DC signal by the dq synchronous rotating reference frame.Therefore,the classic PI controller can be used for tracking the AC signal.However,the angle of the grid-voltage vector used for dq transformation usually provided by the phase-locked loop(PLL),and this will increase the complexity of the control system.Firstly,the relation among the sine and cosine values of the grid-voltage vector angle and the grid voltage components in the two-phase static coordinate is derived in this paper,and then the PLLless control strategy in dq coordinates for three-phase grid-connected converter is proposed.The input variables of the proposed method are the momentary values of the grid voltage only,which reduces the complexity of the control system greatly.Finally,the simulation model of the system is built,and the simulation results confirm the validity of the analysis and the proposed strategy in this paper.