Research On Active Disturbance Rejection Current Control Of LCL Grid-connected Inverter

With the increasing proportion of bio-energy in the energy system of today's society and the enhancement of human awareness of environmental protection,the distributed generation technology of renewable energy,mainly solar energy and wind energy,has developed rapidly.Grid-connected inverter is the key equipment for applying renewable energy,and the electric energy generated by solar power generation and wind power generation is fed into the Grid.This paper studies the current control technology of grid-connected inverter.First,taking the LCL grid-connected inverter as the research object,the generation mechanism of the resonance of LCL grid-connected inverter,grid voltage disturbance and digital control delay are described.And the common solutions to these problems are analyzed,and the advantages and disadvantages of various methods are compared.Then,for the problems of resonance damping,grid voltage disturbance and digital control delay of LCL grid-connected inverter,the current control method of LCL grid-connected inverter based on ADRC is proposed.Based on the analysis of the principle of ADRC control technology,the ADRC current controller is designed to realize resonance damping and disturbance suppression,and the output current tracks the given reference current.The effectiveness of the ADRC control is verified by simulation.Compared with the control method based on PI and capacitive current feedback active damping,the current control and harmonic suppression capabilities of the LCL grid-connected inverter based on ADRC are better,and no additional capacitive current sensor is required.Finally,this paper proposes an online frequency response measurement method that can be used to verify the effectiveness of the control algorithm in practical applications.Compared with the traditional method of frequency response measurement using a spectrum analyzer and other equipment,the online frequency response measurement method proposed in this paper does not require external measurement equipment.The inverter control system processor only injects a small-signal sinusoidal signal at the steady-state operating point of the grid-connected inverter to achieve the grid-connected inverter system frequency response measurement.The method not only has a simple measurement process,but also can measure and analyze the frequency response of the system in real time during the operation of the system to achieve real-time monitoring of the system's operating status.