极大似然模糊控制器在光伏MPPT中的应用

Maximum Likelihood Algorithm Based on Fuzzy Controller Used in Photovoltaic MPPT

针对光伏电池的非线性输出特点,其最大功率点具有时变性,提出了基于极大似然估计的模糊PID控制算法。该算法根据最大功率阻抗匹配原则,建立了基于Boost结构的光伏电路系统,通过调节电路的占空比实现最大功率点跟踪,当外部环境变化时,根据光伏阵列的P—U非线性曲线,得出功率预测原理,将功率预测原理应用到模糊PID控制器,通过对模糊PID控制器中模糊规则的参数进行极大似然估计,从而更快、更准地找到最大功率点。仿真结果与传统扰动法进行比较,表明系统运行动态响应速度快、跟踪效率高,验证了算法的正确性,具有一定的推广应用价值。

The maximum power point of photovoltaic(PV)cell varies all the time for its output nonlinear features.Therefore,a fuzzy proportional integral derivative(PID)controller optimized with maximum likelihood estimation algorithm based on power prediction was proposed.In the algorithm,according to the principle of the maximum power impedance matching,the photovoltaic circuit system based on Boost structure was established,and then the maximum power point tracking(MPPT)was fulfilled by adjusting the duty cycle of the circuit.Principle of power prediction was obtained in line with the P-U nonlinear curve of the PV arrays,which changed with the external environment.The power prediction principle was applied to the fuzzy PID controller,and the membership functions of the input and output variables of the fuzzy PID controller were optimized by maximum likelihood estimation,so that the maximum power point could be found more quickly and accurately.From the above,the simulation results,by comparing with the traditional perturbation and observation method,show that the system runs with fast dynamic response and high tracking efficiency,which verifies the correctness of the algorithm.The algorithm has a certain value of popularization and application.