PSO based Direct Power Control of grid connected photovoltaic system

One of the most commonly used control methods for three phase converters is the so-called Direct Power Control (DPC), which is based on an appropriate selection of converter switching states via predefined switching table. One important feature of Direct Power Control strategy is the variable switching frequency due to the absence of Pulse Widths Modulation (PWM) block. However, a PWM generator can be included to improve the dynamic performance of traditional DPC scheme. In this paper, a simple DPC scheme for a grid connected photovoltaic system is established. Firstly, the mathematical model of the overall photovoltaic system is developed. Then, a DPC control scheme that assures a decoupled control of active and reactive powers is presented: two Proportional-Integral (PI) regulators control directly the instantaneous active and reactive power flow. While, the outer voltage loop acts on the amplitude of active power reference. The tuning of PI parameters of DC link voltage controller is achieved using the Particle Swarm Optimization (PSO) algorithm. The PSO algorithm performs offline search of the best PI parameters that give less overshoot and minimal steady state error. The simulation results, obtained in Matlab/Simulink environment, show fast transient response and good dynamic performance.