一种改进的PV-AF系统最大功率点跟踪方法

An Improved Method of MPPT for PV-AF System

在具有有源滤波功能的光伏并网(Photovoltaic Power Generation and Active Filter,PV-AF)系统中,光伏电池的最大功率点跟踪(Maximum Power Point Tracking,MPPT)方法是其关键技术之一,针对常用的MPPT方法存在的问题,提出了一种改进的MPPT方法。该方法利用扰动观察法在最大功率点附近扰动的正向步数和反向步数基本相同的特点,判断系统工作点是否处于最大功率点(Maximum Power Point,MPP)附近。在此基础上利用变步长的扰动观察法,在远离最大功率点时采用大步长扰动,在最大功率点附近采用小步长扰动。在确定系统工作在最大功率点附近后,采用恒定电压法跟踪。扰动观察法的最大跟踪误差为1.5个电压扰动步长,提出的改进MPPT方法将最大跟踪误差降低为0.5个电压扰动步长。仿真和实验结果表明,该方法兼顾了跟踪的快速性、准确性和稳定性。

In the photovohaic power generation and active filter （PV -AF） system, Maximum Power Point Tracking （MPPT） of photovoltaic cells method is one of the key technologies. Aiming at the problems existed in common control types of constant voltage methods in MPPT, an improved method of MPPT is proposed in this paper. Using the characteristic that the numbers of positive steps and reverse steps are basically the same, it will judge whether the system is near the maximum power point or not. Based on this, a kind of variable step perturbation and observation method is presented, in which a large step will be adopted to perturb when it lies far from the Maximum Power Point （MPP） , , and a small step will be adopted to perturb when it is near the maximum power point. After confirming the system working near the maximum power point, the constant voltage method will be taken instead. The maximum tracking error of perturbation and observation method is 1.5 voltage perturbation step, while the new MPPT method put forward reduce the error to 0.5 voltage perturbation step . Simulation and experiment results show that the improved method gives consideration to rapidity, accuracy and stability.