An Improved Variable Step PO and Global Scanning MPPT Method for PV Systems under Partial Shading Condition

In the case of partially shading PV array would appear multi-peak characteristics of the P-U curve, and it is difficult to track the maximum power point with the conventional method. Therefore, this paper proposes an improved variable step PO (perturb and observe) and Global scanning method (VSPO&GS) to achieve the maximum power point tracking. This algorithm is guaranteed not to fall into local optimum, and to make the power oscillation less. This scheme is divided into two steps: 1) The improved variable step size PO is used to track the local optimum; 2) Then the global scanning is used to obtain the global optimum. Finally, the proposed algorithm is compared with a conventional fixed step size PO algorithm and validated for sudden changes in the irradiance. The simulation results show the proposed algorithm can accurately track the maximum power point (MPP) to avoid the power loss and improve the efficiency of PV array under partial shading condition.