Optimal Conditions Under Partial Shade Photovoltaic System Control

PV array palys a key role in a photovoltaic system, photovoltaic (PV) array modelling and maximum power point tracking (MPPT) algorithm are significant for optimizing the efficiency of the entire system. So the focus of this paper is PV array modeling and multi-peak MPPT technology under partial shading conditions.Firstly, a dual-mode MPPT method which combined the Perturb and Observe (P&O) method with the incremental conductance (INC) method together is proposed in this paper. It uses the golden section point (0.618) to improve the control precision and has good effect on reducing oscillations around the Maximum Power Point (MPP) and reducing the tracking speed.Secondly, an improved two-diode model is established on MATLAB/Simulink using component librarys and embedded functions, not only avoided the complexity and poor readability of using components only in modeling, but also overcoming drawbacks of the one-diode model at high temperature and low irradiance.Thirdly, characteristics of the PV array is analysised in depth, verifying that the good effect of by-pass diodes in avoiding hot spots, the overlapping and non-overlapping connection have different effects and several PV cells shared a by-pass diode reduce peaks effectively; Besides, shadows in overlap area make the maximum output current increase.Forth, ways in solving hot spots problem is summaried and a new method is proposed. The irradiance balance of the equivalent series module could eliminate partial shading effects mostly, the higher the equivalent series arrays of light balance is, the smaller the impact of partial shading of the PV array.In addition, a dule-direction multimodal MPPT algorithm based on P&O is designed to solve multiple peaks maximum power point tracking problems.