Research On Resonance Suppression Technology Of Photovoltaic Grid-Connected Power Generation System

With the proposal of the "Double Carbon" plan,the photovoltaic industry has shown a rapid development trend,and the grid-connected power generation of photovoltaic systems has become more and more widely used.The photovoltaic grid-connected power generation system often has resonance problems.The LCL filter in the system has a natural resonance frequency.The interaction between the photovoltaic systems and the grid impedance form a complex high-order coupling system,which will lead to the existence of a resonance point in the overall system.If the external resonance source just matches the resonant frequency of the system,it is easy to cause resonance of the photovoltaic grid-connected power generation system.There have been many cases of photovoltaic projects causing losses or unsuccessful grid connection due to resonance problems.Therefore,system resonance has become a problem that cannot be ignored in the development of photovoltaic industry.This thesis takes the photovoltaic grid-connected power generation system as the research object.First,the system structure is analyzed,and the physical model and mathematical model of a single photovoltaic system are constructed.The photovoltaic grid-connected power generation system model is constructed according to the grid-connected form of the photovoltaic system,and the transfer function of the input and output of the system is deduced through the mathematical model,and the spectrum analysis is carried out to study the resonance characteristics of the photovoltaic grid-connected power generation system.Aiming at the self-resonance problem of photovoltaic system,the mechanism and implementation of various passive damping resonance suppression methods and active damping resonance suppression methods are analyzed.Aiming at the problem that the feedback depth of the traditional active damping method is insufficient,an active damping notch control method is applied in this thesis,and a notch controller is introduced into the active damping feedback link to improve the resonance suppression effect.Aiming at the coupled resonance problem of photovoltaic grid-connected power generation system,a compound resonance suppression strategy is proposed in this thesis.According to the resonance characteristics of photovoltaic grid-connected power generation system,combined with the idea of external centralized resonance suppression,an active damper device is introduced and its structure,control strategy and main circuit parameter design are analyzed.The active damping notch control method has a good suppression effect on the self-resonance of the photovoltaic system,and the active damper device can significantly suppress the coupled resonance of the photovoltaic grid-connected power generation system,thereby realizing the suppression of various resonance conditions of the photovoltaic grid-connected power generation system.Finally,the effectiveness of the method is verified by simulation.