Optimal Control of a Grid Connected Photovoltaic System with Constant Switching Frequency

This paper presents maximum power point tracking (MPPT) algorithms for grid connected photovoltaic system. Due to the instantaneous changing of solar irradiance and temperature, it is desirable to determine the optimal voltage that ensures maximum energy yield. In order to optimize the photovoltaic energy generation, the MPPT is integrated in the inverter control. Perturb & Observ (P&O), Incremental Conductance (Inc Cond) techniques and fuzzy logic controller (FLC) are applied. A comparison shows the effectiveness of the FLC. The maximum power generated by the photovoltaic system is sent to the power grid to be consumed by the nearest customers. A constant switching frequency is used for the current controlled inverter. The main idea of this method is to superpose an adequate triangular signal having the desired switching frequency to the reference current. The new modulated reference current is then compared to the calculated current in hysteresis controller. Simulation results and some experimental ones are presented to prove the feasibility of the studied system.