Internal Mode Control Method For Three Phase Voltage Source PWM Rectifier

In recent years,electric vehicles have enjoyed an unprecedented golden period of development with their great advantages of zero pollution and zero noise.But at the same time,there are a large amount of harmonic pollution during the charging process,which cannot be ignored.The three-phase voltage source PWM rectifier(VSR)is widely used in DC charging system for electric vehicle,which has smaller total harmonic distortion(THD),is easy to realize bidirectional energy transmission and can guarantee the operation of unity-power factor in a certain load range.Due to the existence of uncertain factors such as complex working environment and external disturbances,traditional control methods cannot meet the requirements,promoting the application of advanced control methods in PWM rectifier.This subject takes the three-phase VSR as the control object and introduces the principle of internal model control(IMC),improving the double closed-loop control strategy and the control performance of the system.Firstly,in view of the fact that traditional control methods easily lead to the problem of decoupling failure,inverted decouplers were designed to make up for this defect.The complete decoupled nominal system could be achieved by inserting its inverted decoupling matrix into the system before the controlled processes,and the complicated matrix inversion operation was avoided.What?s more,this approach allowed for more flexibility in choosing the transfer functions of the decoupled apparent process.According to the principle of IMC,the IMC-PI controllers were designed in the inner loop with only one tunable parameter.The simulation results show that the proposed method overcomes the shortcomings of the traditional feedforward decoupling,and the current inner loop has better tracking performance.Secondly,the IMC-PID controller was designed for the voltage outer loop.In addition,the simulation model of three-phase VSR was built by Matlab/Simulink simulation software,and the system simulation tests were carried out in rectification state,inverter state and load doubling state,showing the proposed method facilitates the improvement of system?s disturbance rejection problem.Finally,in order to further improve the system?s disturbance rejection response,the fractional order internal model(FOIMC)strategy was studied based on the simplified model of the voltage loop.The fractional order internal model controller was designed by combining the principle of IMC and FOC,and the parameters were obtained from the cut-off frequency and maximum sensitivity of the system.Through simulation and comparison of the system?s states of starting response,steady-state characteristic,load switching and grid side voltage perturbation,the results indicate that the proposed method can make the system acquire faster dynamic response and stronger robustness.