基于坐标变换的单相光伏并网控制策略的研究

Research on control strategy of single-phase photovoltaic grid-connected system based on frame transformation

一种单相两级式光伏并网发电控制系统的仿真研究。根据硅型光伏电池的特性,研究设计了光伏电池的仿真模型,该模型可以模拟任意日照和温度下光伏电池的输出特性。在最大功率点跟踪的算法方面,基于传统电导增量法的进行改进,提出了一种变步长的跟踪算法。逆变环节采用全桥逆变电路,根据瞬时无功理论,虚拟出一个与单相交流电流分量正交的交流量,基于旋转坐标变换并利用PI调节控制来实现逆变电流的无静差并网控制,同时实现了有功、无功功率的解耦控制。详细分析了所提出的系统的工作原理和控制策略,采用Matlab/Simulink对系统进行了仿真验证,仿真结果表明该系统能实现光伏阵列最大功率点的快速、准确跟踪,逆变输出电流控制精度高、谐波含量低,能实现单位功率因数并网发电。

A simulation system for single-phase grid-connected photovoltaic （PV） system was proposed. The electrical model and nonlinear characteristics of the silicon PV cell were analyzed. The Simulink simulation model was built based on the output characteristics of single PV cell. An improved maximum power point tracking （MPPT） method based on the traditional incremental conductance method was simulated and studied. DC-AC link, using the full-bridge inverter circuit, according to the instantaneous reactive power theory, imaginary component was built and processed by Park transformation. The AC component into DC component was changed. The steady-state error of the grid current could be eliminated by the simple PI control. Then the inverter active and reactive power control were allowed. Experimental results show that when the high stability and high efficiency of this modified strategy is applied in single- phase grid-connected PV system, the output current has high control precision, low harmonic and unit power factor operation are realized.