基于双并联Boost电路的光伏系统最大功率点跟踪控制方法

Research on control method of MPPT for photovoltaic system based on double parallel Boost

光伏电池的输出功率取决于外界环境(温度和光照条件)和负载状况,需采用最大功率点跟踪(MPPT)电路,才能使光伏电池始终输出最大功率,从而充分发挥光伏器件的光电转换效能。在比较了常用光伏发电系统控制的优缺点后,依据MPPT控制算法的基本工作原理,主电路采用双并联Boost电路,具有电压提升功能,并且能够提高DCDC环节的额定功率和减小直流母线电压的纹波。针对传统扰动观察法存在的振荡和误判问题,提出了一种新型的基于双并联Boost电路的改进扰动观察法最大功率跟踪策略。在Matlab/Simulink下进行了建模与仿真,仿真结果表明,当外界环境发生变化时,系统能快速准确跟踪此变化,避免算法误判现象的发生,通过改变当前的负载阻抗,使之与光伏电池的输出阻抗等值相匹配来满足最大功率输出的要求,使系统始终工作在最大功率点处,并且在最大功率点处具有很好的稳态性能。最后通过实验验证了该算法的有效性。

The output power of PV module varies with module temperature, solar insolation and loads, so it is necessary to track MPP of the PV array all the time. So PV module can always output the maximum power and give full play to the photoelectric conversion efficiency of the photovohaic device. According to the mechanism and control methods of Maximum Power Point Tracking （MPPT）, the double parallel Boost topology , which can improve the rated power of the DC-DC link , increase the output voltage and reduce the ripple of the DC bus voltage, is used in the control circuit. Aiming at some questions of typical step perturbation and observation method, such as oscillation and misunderstanding, an improved perturbation and observation （P＆O） method MPPT algorithm based on double parallel Boost is introduced in this paper. Its model is established and simulated with Matlab/Simulink. Simulation results show that system can track the changes in the circumstances quickly and avoid tracking error. To satisfy maximum power output and make system work at the maximum power point, it changes the current load impedance to match with the output impedance of photovoltaic cells equivalently; and system has a good steady-state performance at the maximum power point. The experimental results prove the effectiveness of the proposed algorithm.