基于Park变换的单相光伏并网控制研究

Research on Controller of Single-phase PV Grid-connected System with Park Transformation

近年来,LCL滤波器由于体积小、滤波效果好等优点在光伏并网系统中获得了广泛应用。采用并网电流、电容电流双闭环控制能够有效抑制LCL滤波器振荡,提高并网系统稳定性,但传统PI控制无法实现对交流并网电流的无静差跟踪。因此,提出了一种基于Park变换的双电流闭环控制策略,它能够大大提高并网功率因数,减小入网电流的总谐波失真(THD)。该方法首先通过构造虚拟正交电流分量,将单相并网电流虚拟为α-β坐标系下两相正交电流,然后基于Park变换,在旋转坐标系下进行PI控制,从而实现无静差控制。最后,通过Matlab仿真验证了这种控制策略的正确性和有效性。

LCL filter is widely used in PV grid- connected system for its small volume and excellent filter characteristic in recent years. Dual-loop control strategy with grid current feedback and capacitor current feedback can inhibit resonance effectively and improve system stability. However, the traditional PI controller cannot track the AC grid-connected current without static error. Thus, a dual-loop control strategy based on Park transformation was proposed, which could improve the power factor and reduce the THD. Firstly, the virtual orthogonal component was created to constitute the ,β current while the grid-connected current constitutes the α current. After Park transformation, the static error was inhibited by PI control. Finally, the Matlab simulation results verify the correctness and availability of the designed control strategy.