Research On Resonant Feedforward Control Strategy Of PV Grid-connected Inverter Under Weak Grid

Recently,the search for new energy has led to the development of large amounts of wind energy and light energy.Distributed power generation systems have emerged.In the current distributed power generation system,improving the quality of gridconnected current is an important research direction.The existence of grid voltage background harmonics will distort the output grid-connected current.In the case of weak grids,the appearance of grid impedance will exacerbate this phenomenon.For these two problems,domestic and foreign scholars have done a lot of research.In this paper,the three-phase LCL photovoltaic grid-connected inverter system is taken as the research object.First,the mathematical models are established in the abc three-phase stationary coordinate system,the αβ two-phase stationary coordinate system and the dq two-phase rotating coordinate system.The independent control of the work selects the dq coordinate system and performs decoupling,and then gives the parameter design method of the LCL filter.Under the ideal grid,the capacitive current active damping feedback method is used to eliminate the resonance peak of the LCL filter.For the interference of the grid voltage background harmonics,the formula of the grid voltage full feedforward function is derived,and the specific function of each phase of the function is analyzed.Finally The effectiveness of the control method is verified by Matlab / Simulink simulation.In view of the shortcomings of the grid voltage proportional feedforward control method in the case of weak power grids,a resonant feedforward control method is proposed,the purpose of which is to attenuate the equivalent grid impedance in the middle and high frequency bands to increase the phase margin of the system to ensure efficient and stable operation of the system.Through simulation,the superiority of the resonant feedforward control strategy in the weak power grid is verified.