基于ESO和分数阶PID的改进P&O控制策略

Improved P&O control strategy based on extended state observer and fractional order PID

为了提高光伏电池转换效率、降低能量损失,有必要研究最大功率点跟踪(maximum power point tracking,MPPT)方法。针对传统扰动观察法(perturbation observation method,P&O)存在无法兼顾跟踪速度与稳态精度、在光照度发生较大变化时会产生误判现象的问题,文中提出一种能适应环境变化的变步长P&O控制策略。首先,利用光伏电池刚启动时类似恒流源的特性获取当前光照度下的短路电流,通过固定电流法推导出最大功率点(maximum power point,MPP)的参考电压;其次,当光照度突变时,提出功率修正方法,并给出突变时的变步长调整策略;最后,设计基于线性扩张状态观测器(linear extended state observer,LESO)的分数阶比例积分微分(fractional order proportion integration differentiation,FOPID)控制器,可以对算法输出的参考电压进一步进行跟踪补偿。仿真结果表明,所提控制策略可以提高稳态精度和跟踪速度,有效提高光伏电池的输出功率。

In order to improve the conversion efficiency of photovoltaic cells and reduce the energy loss,the maximum power point tracking(MPPT)method needs to be studied.Aiming at the problem that the tracking speed and steady-state accuracy of the traditional perturbation observation method(P&O)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 is obtained by using the characteristics of the photovoltaic cell similar to the constant current source when it first starts,and the reference voltage of the maximum power point(MPP)is 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 order proportion integration differentiation(FOPID)controller based on linear extended state observer(LESO)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.