Research On Grid-connected Control Strategy Of Microgrid With Photovoitaic And Storage System

Firstly, the model of the microgrid distributed power had been studied. The theoretical analysis and simulation study of photovoltaic MPPT algorithm and the charge and discharge control algorithm for energy storage system had been done. The efficiency of the microgrid photovoltaic systems had been improved adopting the variable interference method and voltage control optimization for MPPT algorithm. The buck-boost bidirectional DC-DC converter had been used of the battery charge and discharge control to achieve three-stage charge method, including constant current-constant voltage-floating charge.On this basis, two typical microgrid control strategies including the master-slave control and drooping control had been studied, and the microgrid control strategy for this paper constructed had been confirmed. The closed-loop control algorithm for power quality had been studied, to solve the microgrid voltage jump change and unstable amplitude. Islanding detection method and the PCC structure and control strategies had been analyzed to determine the PCC thyristor anti-parallel topology. Islanding detection had been realized through detecting port voltage and frequency of the large power grid in the normal scope or on. The connection status between microgrid and main grid, and the PCC control strategy of the switch from off-grid to grid-connected or from grid-connected to off-grid had been realized.Finally, combined with Hebei electric power science and technology park microgrid demonstration projects, according to the distribution of natural resources conditions and selection of equipment, microgrid with photovoltaic and storage system had been designed. The microgrid control method of grid-connected and off-grid operating status and the communications structure had been confirmed. Based on Matlab-Simulink, the model had been done, and the operating status had been simulated from off-grid to grid-connected or from grid-connected to off-grid. The simulated data results show that the microgrid with photovoltaic and storage system using the proposed control strategy can be achieved seamlessly switch from off-grid to grid-connected or from grid-connected to off-grid, and the system operation is stable and reliable.