Aiming at the problem that the traditional maximum power point tracking ( MPPT ) algorithm has slow response and is easy to fall into local optimum when the PV array presents multi-peak power-voltage characteristics due to local shadows, a hybrid control strategy ( LGWO-ZVINC ) combining improved gray wolf optimization algorithm ( LGWO ) and partitioned variable step size incremental conductance method ( ZVINC ) is proposed. The strategy uses a linear increasing function to initialize the wolves to ensure the individual diversity of the wolves. A nonlinear adjustable factor is introduced to balance the local and global search ability. Combined with Levy algorithm and greedy selection mechanism, the wolf pack is avoided to fall into local optimum. The partition variable step size conductance increment method is used for local search to accelerate convergence and improve accuracy. Simulation experiments and experimental results show that under static and dynamic multi-peak conditions, the LGWO-ZVINC algorithm has the fastest tracking speed and accuracy of more than 99.90% compared with the three comparison algorithms. The research conclusions provide a reference for photovoltaic MPPT control under partial shading conditions.
灰狼优化(grey wolf optimization,GWO)算法参数少,控制过程简单,但在收敛速度、收敛精度等方面还有待改进。文献[9]引入Levy飞行策略,增强全局搜索能力,但收敛速度有待提升。文献[10]将灰狼算法和定步长电导增量法相结合,加快了收敛速度,但是后期局部振荡问题未得到改善。文献[11]将樽海鞘群优化算法和GWO算法相结合,利用SSA算法的自适应机制,跳出局部最优解,降低功率损耗,但跟踪速度较慢。文献[12]将粒子群搜索机制与GWO算法相结合,但参数设置复杂。
由图4可知,当Bp处于[a,b]和[e, f ]时,采用大步长策略,可以快速接近最大功率点A;当Bp输出功率在[b,c]和[d,e]时,切换为小步长,避免大步长导致的功率振荡,提升跟踪精度;当Bp点处于[c,d]时,如果继续保持固定步长,可能导致B在A点附近振荡,无法继续接近点A,则此时采用变步长策略。由式(21)和式(22)可知,距离点A越近,越小,步长也就越小,当步长为0时,此时B点与A点重合。
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