Research On Grid-connected Current Control Strategy Of Three-phase Inverter System In Micro-grid

With the rapid development of the renewable energy industry in the world,the microgrid as a controllable network unit composed of various new energy sources is an indispensable and effective way to develop into a smart grid.The microgrid has the characteristics of multi-functional complementary energy supply,which not only improves the natural environment but also has good social and economic benefits.At the same time,the access of the microgrid will increase the distribution network planning problem caused by the inaccuracy of load forecasting.The impact on the energy distribution and reactive voltage distribution of the original distribution network caused by the undetermined or intermittent new energy production capacity and its impact on the grid and the grid.Based on the characteristics of microgrid grid-connected inverters,the paper analyzes the circuit topology of three-phase grid-connected inverters with different isolation types.The LCL type filter is used to establish the three-phase static coordinate system of the LCL grid-connected inverter and the mathematical model of the two-phase stationary coordinate system and the two-phase rotating coordinate system,and theoretical analysis is carried out.The paper studies the control methods of active and passive damping.The filter parameter feedforward decoupling scheme is designed.And in the rotating coordinate system,the power controller is designed according to the Park transformation.The inverter system simulation model is established in Matlab/Simulink environment,and the space vector(SVPWM)modulation algorithm is implemented.The simulation results of different filtering parameters and grid-connected current control strategies are verified.The simulation results and experimental data show that the current control strategy can effectively suppress the resonance phenomenon of LCL filter.The current inner loop steady-state error is effectively reduced,so that the power factor of the grid-connected system is further improved,and the quality of the grid-connected current is effectively improved.