Circulating Current Suppression Strategy Of Grid Connected Inverter Based On Active Disturbance Rejection Control

The problem of harmonic interaction is one of the main disturbances that affect the normal operation of microgrids,and the issues of harmonic resonance and harmonic circulation caused by this have attracted much attention.Circulation suppression is a key technology to ensure the reliable operation of microgrid systems.The general suppression method is to use PI control strategy,combined with the basic characteristics of circulation,to carry out droop control strategy and virtual impedance addition.In this paper,in order to deal with the poor effect of circulating current suppression when the double closed-loop PI control is disturbed,a circulating current suppression strategy based on auto disturbance rejection control for multi inverter parallel connection is proposed.The disturbance is estimated and feedback compensated by a linear expansion state observer,and the effect of current sharing control for multi inverter parallel connection is improved with the unique bandwidth method.The article mainly includes the following aspects:(1)The first chapter mainly introduces the research background and significance of power system disturbances,from smart grids to disturbances,and introduces the significance of circulating current research,which is the research center of this article.By summarizing a large number of research literature,describing the current research status of circulating currents,and introducing different parallel control strategies for inverters.(2)Chapter 2 starts with a simple circuit,obtains the definition of circulating current,and analyzes the physical meaning of circulating current based on actual operating conditions.On this basis,it is divided into two categories: active and reactive,and then the droop control theory is introduced.This is the theoretical basis of this article,which guides the construction of the simulation model in Chapter 4.(3)Chapter 3 first analyzes the inverter control framework based on dual closed-loop PI.And based on the ADRC theory,the control outer loop was redesigned,and the bandwidth method and system parameters were combined to simplify the parameter tuning of ADRC,reducing the difficulty of promoting this method.(4)In Chapter 4,a detailed parallel model of microgrid dual inverters was established on the MATLAB/Simulink platform.Highlight the difference between the dual closed-loop PI control and second-order linear ADRC control strategies from the perspectives of no-load circulation and load circulation(transient circulation),and verify each other with the theoretical derivation in Chapter 2 and Chapter 3.(5)Chapter 5 expands the parallel connection of dual inverters to parallel connection of multiple inverters,and re summarizes the expression of circulating current under multiple inverters.By analyzing the main body,the energy characteristics of the circulating current were described,and the impact of differences in control parameters and system parameters on the circulating current between various inverters was tested.And simulation of different control strategies under no-load and transient circulating currents was conducted based on a multi inverter model,verifying the suppression effect.