Global Flexible Power Control of Photovoltaic Systems under Partial Shading Conditions Based on Direct Multipeak P-V Curve-Fitting

Accurately and flexibly tracking the operating point of photovoltaic (PV) system under partial shading condition (PSC) is challenging due to the multipeak feature of power-voltage (P-V) curve, especially with the aim of flexible power control (FPC). This article proposes a global FPC (GFPC) method based on a direct multipeak curve-fitting of PV system under PSC. First, an optimized search skip and judgment-global maximum power point tracking (GMPPT) method is applied to accurately and quickly track the maximum power point. During the GMPPT process, the key points on the P-V curve, e.g., local MPPs and stationary points, are recorded, which are then applied for direct fitting of the multipeak P-V curve. Subsequently, a pseudomonotonic P-V curve is developed as a reference for locating the flexible power point according to the GFPC demands. The directly obtained pseudomonoatomic P-V curve enables fast and flexible power adjustments without redundant perturbation and tracking processes. The results of simulations on MATLAB/Simulink and experiments on StarSim platform demonstrate that the proposed GFPC method can quickly and accurately adjust the PV power adapting to flexible control demands and grid support requirements. Then, the flexibility and adaptability of PV systems as well as the stability of power grid are enhanced.