Research Of Integrated Control Strategy Of Microgrid Dual Mode Smooth Switching

Microgrid as a new operation mode of distributed generation, it can coordinate the contradiction between distributed power supply and power grid effectively, therefore it becomes an important branch of the smart grid, and has the important research significance and practical value. And the smooth transition is the key technology of microgrid, based on this, this paper studies based on energy storage of bi-directional inverter microgrid smooth dual mode switching control strategy to realize the switching process seamless.First, after reading a large number of domestic and foreign related to micro operation mode smooth switching literature, it designs the overall structure and control strategy of the master-slave control of microgrid, to use storage energy system as the core control unit of the Microgrid, to use photovoltaic power generation system as the slave unit. And PCS as the core control unit of storage energy system, we mainly analysis its topology structure, mathematical modeling, control strategy, We select V/f control as control strategy for PCS islanding operation and the PQ control as a control strategy for grid connected PCS the PQ control as a control strategy for grid connected PCS grid-connected operation.On the basis of the above research, the current more mature smooth switching control strategy is selected, and the new control strategy is added. In the island switched to grid connected operation process, the pre synchronization control algorithm is adopted. At the same time, the energy storage system control strategy by the V/f control conversion to PQ control; In the network switch to network operation process, the power adjustment and follow the state controller control strategy is adopted. At the same time, the energy storage system control strategy by PQ control into a V/f control. Finally building the simulation model in the SIMULINK platform, selected two groups of data to verify the proposed control method, when the power balance between the load power and the micro power, they can achieve the fast and reliable smooth switching, under micro power is less than the load power conditions, we have discovered voltage distortion,and the frequency of the fluctuations in a relatively short time, but it can basically realizes the smooth switching.In addition, we build a experimental platform, and carry out experimental verification on this platform. Firstly, the overall design scheme of Microgrid is presented, and the overall design framework of the core control unit-PCS is introduced in this paper. The hardware circuit design of PCS is given, including the main circuit topology and device selection, the design of main control circuit, the design of sampling circuit and the design of power drive circuit. And then gives the design flow chart of several key procedures of PCS, including the main program, the power driver protection subroutine, the control algorithm subroutine design. Finally four cases are tested on the experimental platform, including Island running experiments, grid connected operation experiment, switching Microgrid from grid-connected operation mode to island operation, switching Microgrid from island operation mode to grid-connected operation mode, and carries on the analysis to the corresponding experimental waveforms. The experimental results demonstrate the proposed control strategy is effective, it also ensures the operation mode of the smooth switching and stable operation mode of power supply system reliability.