Abstract: Under partially shaded conditions, the reverse of avalanche effect occurs in the shadow of photovoltaic cells, resulting in multiple local maxima in the output power of photovoltaic array, then the conventional MPPT failures. This paper built the model of photovoltaic array under partially shaded conditions based on the perfect model of photovoltaic cells and verified the multipeak characteristics of the output power. The paper proposed a global MPPT control method based on PSO, and improved the tracking speed by accumulating search experience of individual particle. The simulations indicate the MPPT method can track the global maxima quickly when the external conditions change and make full use of energy in the end.

Key words: Photovoltaic cells, ⁺Maximum Power Point Tracking(MPPT), ⁺Particle Swarm Optimization(PSO) algorithm, ⁺Partially shaded condition