具有改进最大功率跟踪算法的光伏并网控制系统及其实现

光伏并网控制系统输送到电网的功率随着光照强度、环境温度以及光伏阵列输出电压的不同而变化，控制光伏阵列的工作点使其连续稳定地向电网输出最大功率非常必要。该文提出了基于同步旋转坐标变换实现光伏阵列最大功率跟踪与电流控制的电压源型逆变器相结合的三相光伏并网控制系统，该系统主要包括光伏阵列、直流母排电容、电压源型逆变器、滤波电感、数字信号控制器与电网。提出的改进最大功率跟踪方法，根据光伏阵列dP/dU-U的特性曲线，利用Newton-Raphson方法快速计算光伏阵列输出功率对电压的微分值，由此进一步形成光伏阵列工作在最大功率点的参考电压值。整个控制系统为双环控制，外环为电压控制环，利用一个PI调节器使光伏阵列输出电压工作在最大功率工作点；内环为电流控制环，利用2个PI调节器分别对d-q轴电流进行解耦控制，使逆变器输出电流与参考电流一致。根据所提出的控制算法，研制了一台三相光伏并网系统原理性样机，仿真与实验结果一致，系统具有良好的动稳态性能，说明了所提出的控制方案是非常有效的。

Implementation of a Photovoltaic Grid-connected System Based on Improved Maximum Power Point Tracking

As the power transmission from the photovoltaic (PV) array into the grid in the PV grid-connected system depends on the insolation, temperature, and array voltage, it is necessary to control the operating points to draw the maximum power of the solar array. In the paper, an improved maximum power point tracking (MPPT) method for PV array combined with current-controlled voltage source inverter based on the synchronous rotating coordinate transformation is presented, which mainly includes PV arrays, DC bus capacitors, voltage-source inverter, filter inductor, digital signal controller, and the grid. The improved MPPT method uses dP/dU as an index which is calculated quickly by using Newton-Raphson method to get the voltage reference of the maximum power point. The whole control system uses double loop control, the outer loop PI controller aims at controlling the output voltage of the PV array to track the voltage reference provided by the MPPT controller, and the inner loop controller has two synchronous vector PI controller to make the output current of the inverter consistent with the d-q reference currents separately. According to the proposed control algorithm, a three-phase PV grid-tied system prototype machine is developed. Simulation results are consistent with the experimental, which shows that the proposed system is validated and has good dynamic and steady-state performance.