Research Of Photovoltaic Grid-Connected Inverter Based On Particle Swarm Optimization Algorithms

With the increasing exhaustion of conventional fossil energy, solar energy, as a clean and non-pollution alternative energy, has been paid great attention to. A photovoltaic (PV) grid inverter, as a key equipment of energy conversion and real-time control, plays a vital role in improving the power quality and system security.Up to now, a great deal of research on solar photovoltaic inverter has been made, but there are still many problems to further research. On the basis of the study of photovoltaic grid inverter current control strategy, an investigation of the optimization of control parameters is performed. The main work is as follows:1. The PV grid inverter control strategy research is made. First, the system main circuit topology is determined by analyzing the topology structure of PV grid inverter; Second, the mathematical model is derived in terms of its operation principle and main circuit topology; Third, according to the mathematical model, the double loop space vector modulation algorithm based on voltage orientation is designed; Finally, an off-line optimization of PI parameters of the voltage outer loop for PV inverter by using an improved particle swarm algorithm.2. A simulation research of the control strategies is carried out. An off-line simulation of the double closed loop space vector control model and particle swarm optimization method is conducted by building MATLAB/Simulink simulation model and designing an offline PSO program. The effectiveness of the control strategy is verified by comparing the simulation results in the two cases with PI parameters optimized and un-optimized.3. The design of the hardware and software of the system is completed. Hardware system consists of main circuit, control circuit and the peripheral circuit, of which the intelligent power module is utilized in the main circuit, and the control circuit including DSP master control chip, which is the control center of the system, voltage and current sampling circuit and the zero-cross voltage comparison circuit. The auxiliary circuit mainly supplies power for the control system. The software design mainly includes the design of the main program, phase lock procedures, ADC sampling subroutine, interrupt subroutine and SVPWM control subprogram, etc.4. A20kW prototype based on DSP2812has been designed and made. The experimental platform based on the prototype has been set up, and1.9kW,3.5kW,15kW system experiment has been respectively conducted. The research results show that the designed inverter based on the presented control algorithm can convert DC power from the photovoltaic array output into AC power quickly and efficiently which satisfies the requirements of the grid, and can stably run under certain interference, thus verifying the effectiveness of the control strategy.