Perturbation Observation Method Based on Fractional Order PID and Extended State Observer

In order to improve the conversion efficiency of photovoltaic cells and reduce the energy loss, the maximum power point tracking method needs to be studied. Aiming at the problem that the tracking accuracy and steady-state accuracy of the traditional perturbation observation (P & O) method cannot be balanced, and misjudgment occurs when the environment changes greatly, a variable-step P & O control strategy that can adapt to the environmental changes is proposed. Firstly, the short-circuit current under current illumination was obtained by using the characteristics of the photovoltaic cell similar to the constant current source when it was just started, and the reference voltage of the maximum power point was derived by the fixed current method. Secondly, when the illuminance changes abruptly, the power correction method is proposed, and the variable step size adjustment strategy is given. Finally, a fractional PID controller based on linear extended state observer is designed, which can further track and compensate the reference voltage output by the algorithm. Simulation results show that the proposed control strategy can improve the steady-state accuracy and tracking speed, and effectively improve the output power of photovoltaic cells.