Research On Control Strategy Of Grid-connected Inverter Based On Capacitor Reference Voltage Feedforward Under Weak Grid

The renewable energy is converted into alternating current that can be incorporated into the grid through the distributed power generation system Grid-connected inverter is the core device of distributed generation system,and its control quality directly affects the power quality of the input grid.Duing to the long distance transmission and a large number of nonlinear loads,the power grid usually has weak grid characteristics,this puts forward higher requirements for grid-connected inverter control.Therefore,it is of great significance to study the control strategy of grid-connected inverters under weak power grid.This paper studies the control strategy of grid-connected inverter under weak power grid.First,the various types of inverters and filters are analyzed.According to the analysis,the voltage inverter and LCL filter are selected as the inverter and output filter of the grid-connected system,and the parameters of the LCL filter were selected.Secondly,the mathematical modeling of single-phase grid-connected inverter is carried out,and mathematical derivation is carried out according to the differential equation of grid-connected inverter system,and a grid-connected inverter control strategy based on capacitive reference voltage feedforward is preliminarily obtained.After that,the control strategy of the derived grid-connected inverter is further modified.Aiming at the disadvantage that a second-order differential in the capacitance reference voltage feedforward is easy to introduce noise to the grid-connected system,the low-pass filter1/(?s(10)1)is introduced in the capacitance reference voltage feedforward.Aiming at the disadvantage that a large number of harmonics in the power gridwill have a bad effect on the grid-connected current of the grid-connected system,the voltage feed-forward of the power grid is introduced in the control.Aiming at the shortcomings that the traditional power grid voltage feedforward will greatly reduce the phase margin with the increase of the inductive reactance,a resonance function is introduced in the grid voltage feedforward.Finally,the control parameters of the grid-connected system are analyzed and selected,and the performance of the grid-connected system under the weak power grid is analyzed.At the same time,the simulation model and experimental platform of the grid-connected system based on the capacitance reference voltage feedforward under weak power grid are built,and the effectiveness of the proposed control strategy is verified through simulation and experiment.