Research On Improved Linear Active Disturbance Rejection Control Strategy For DC Charging Pile Rectifie

The wide application of electric vehicles is an important way to realize energy saving and emission reduction.With the significant increase of the number of electric vehicles,the scale of charging piles is also expanding.DC charging pile consists of front-stage rectifier part and back-stage DC regulating part,where the rectifier part performs power factor correction and outputs stable and reliable DC power,which is the key part of DC charging pile.Due to the harsh working environment of DC charging pile,the frequent switching of working conditions will cause the fluctuation and large overshoot of rectifier DC side output voltage,which will affect the safe operation of charging system.Therefore,in this paper,the control strategy of DC charging pile rectifier is studied for the problems of unstable DC voltage,weak robustness and high harmonic content in DC charging pile rectifier.Firstly,the common topologies of DC charging pile rectifiers are introduced,and the three-phase voltage type pulse width modulation(PWM)converter structure is used as the system rectifier model,which has the advantages of unit power operation and easy control.The operating principle is analyzed,a mathematical model is established,and the model is coordinate transformed for further study In order to reduce the hardware cost and complexity of the system,and to avoid the impact of grid-side voltage sensor failure on the system control performance,a control algorithm without grid voltage sensor based on an improved virtual magnetic chain observer is studied,which can effectively eliminate the errors caused by the filter and improve the accuracy of virtual magnetic chain estimation,and this algorithm is simulated and verified in Matlab platform.Then,for the traditional dual closed-loop PI control of the three-phase voltage type PWM rectifier,the immunity performance of the voltage outer loop and current inner loop is poor and the response time is long.In this paper,active disturbance rejection control(ADRC)strategy is used to control its voltage and current double closed-loop,so as to improve the dynamic performance and anti-disturbance capability of the three-phase PWM rectifier output.Due to its complex parameters and cumbersome data,linear active disturbance rejection control(LADRC)strategy is proposed for the dual closed-loop control of the three-phase voltage-based PWM rectifier,and its linear expansion state observer part is improved according to the total disturbance error control.The improved control strategy is used to design the controller for rectifier voltage and current double closed loop,and the simulation model is established by Matlab platform to simulate the three strategies in steady-state and dynamically varying operation,and a comparative analysis is performed.Finally,the experimental platform of DC charging pile rectifier was built.The steady-state experimental verification and dynamic experimental verification were carried out by the experimental platform.Both simulation and experimental results show that the improved LADRC strategy proposed in this paper has better dynamic response than PI control and traditional LADRC strategy,and the DC-side voltage is more stable and robust.The grid-side currents are more sinusoidal and have less harmonic content,which creates better grid connection conditions.