Fast global flexible power point tracking of photovoltaic systems under partial shading condition with tracking-affiliated environmental parameter estimation

In the modern power system with increasing uncertainties and risks, grid-supporting services are required for photovoltaic (PV) systems, thus requiring flexible power point tracking (FPPT) to achieve high-quality grid-supporting performance. The PV systems usually suffer partial shading condition (PSC), stimulating the demand of global FPPT (GFPPT) method. However, keeping the speed and accuracy of power point tracking accuracy at the same time are challenging due to the uncertainty of environmental condition. This paper proposes a fast GFPPT (F-GFPPT) method based on a modified search-skip-judge global maximum power point tracking (SSJ-GMPPT) algorithm, where a tracking-affiliated environmental parameter estimation (EPE) is developed for the multi-peak power-voltage (P-V) curve fitting. Firstly, the modified SSJ-GMPPT is applied to collect the key information points of the P-V curve of PV system under PSC, including the section-dividing points and the maximum power points. Then, the key information points collected in the tracking process are utilized to sequentially identify the voltage of each PV panel and estimate the environmental parameters, which is then utilized in the model-based multi-peak P-V curve fitting. With the identified P-V curve, the flexible power point (FPP) of PV system can be accurately and rapidly located, and the F-GFPPT is realized. Simulations and hardware-in-the-loop experimental case studies validate the performance of the proposed method, which facilitates fast and accurate flexible active power control of PV system under PSC. Compared with previous methods, the proposed method eliminates the redundant searching process and steady-state oscillation, while achieving higher power regulation accuracy.