Design of a novel MPPT algorithm based on the two stage searching method for PV systems under partial shading

When photovoltaic panels are non-uniformly irradiated, they experience shadowing effect and the power against voltage curve will demonstrate multiple peaks which cause maximum power point tracking method to become challenging. A method often used to track the real peak is the two stage searching method which uses a ratio of the open circuit voltage. However, this method has some shortcomings especially at heavy shadowing condition where it can easily miss the real peak and demonstrate a slow tracking speed. Hence, a novel method to track the GMPP based on the two stage open circuit voltage method was proposed in this paper with the aim of improving the speed and accuracy of the tracker. The Simulink/SimPowerSystems environment is used to model a photovoltaic system with bypass diodes which can take both temperature and irradiance as inputs to be able to simulate different shading patterns for the implementation of the tracking algorithm. The response of the system was compared with other models proposed in previous papers to validate the system and it was found that the system could most accurately model the characteristic of the panel. Afterwards, the maximum power point tracking algorithm was tested and compared with the above-mentioned two stage searching method. It was observed that the new method was able to reach the real peak faster.

I. Introduction

In a partially shaded photovoltaic (PV) system, commonly used maximum power point tracking methods such as perturb and observe cannot track the global maximum power point but will instead get stucked at a local maximum power point. This was reported in many papers where different methods for global maximum power point tracking (GMPPT) were proposed. A comprehensive review of the methods used for GMPPT can be found in [1].