Research On RISE-LADRC Control Strategy For Off Grid Inverter

The conflict between traditional fossil energy reduction and environmental pollution is becoming critical.The valid measure to resolve the shortage of energy and resources is to adopt renewable energy and distributed generation,which can produce less pollution,acquire high reliability and energy conversion efficiency.At present,microgrid is proved to be a method of renewable energy and distributed generation.As the basic interface of microgrid,inverter is adopted to connect distributed generation and various loads,it is major to the stability of the system.This paper takes off-grid inverter as the research object to study the disturbance control strategy of inverter.The main contents of this paper are as follows:(1)The model of three-phase off grid inverter is built,and the voltage and current double loop operation is already analyzed;The basic principle of linear active disturbance rejection control(LADRC)and the design process of its main components are introduced systematically.(2)Second order LADRC is designed,and the influence of observation bandwidth on the tracking performance of the controller is analyzed.In order to improve the disturbance rejection ability of the inverter,a voltage control strategy based on the error sign robust integration control law and linear active disturbance rejection control(RISE-LADRC)is proposed.The linear state error feedback control law(LSEF)is replaced by RISE control law,which can reduce the dependence on the observation bandwidth.The disturbance in the system is effectively suppressed and the output voltage tracking accuracy is improved.By using Lyapunov theory,it is testified that the inverter system with second-order RISE-LADRC control is bounded stable.Simulation results show that the proposed strategy is effective to improve the anti-disturbance ability.(3)A first-order adaptive RISE-RLADRC control strategy is proposed to achieve the effect of asymptotic stability and further improve the anti-disturbance ability of the inverter system.Firstly,connect a resistor in series with the filter capacitor,then reconstruct the control input to abtain a first-order system,thereby reducing the order of the controlled object.Secondly,a reduced order state observer(RESO)is designed to reduce the phase delay and improve the accuracy of disturbance estimation,and the RISE control law is combined to suppress the disturbance.In addiction,to avoid the influence of observation bandwidth on the value of sign function gain,the sign function gain is adaptively controlled,the additional adaptive feedforward term is helpful to improve the tracking performance.Finally,it is proved that the first-order adaptive RISE-RLADRC controller is asymptotically stable,the simulation results verify the effectiveness of the proposed strategy.