Research On Ripple Current Elimination Method For Electric Vehicle On-board Charger

With the rapid development and widely application of electric vehicles,it is necessary to propose further research on the energy interaction technology between the electric vehicles and the grid.The idea of typical on-board charger system for electric vehicles implement energy flow between batteries and grid by converter.There is growing interest in harmonic current elimination method for on-board charger.For a high power density single-phase PWM rectifier with harmonic current elimination in electric vehicles applications,the detailed work has been carried out:The single-phase voltage source PWM rectifier mathematical model has been set up based on Kirchhoff law and the circuit topology,modulation and operation modes have been analysed accordingly.The main circuit parameters of the single-phase PWM rectifier have been designed.A control strategy based on conventional proportion integral controller for single-phase PWM rectifier has been established.An integrated on-board battery charger test platform has been set up to verify the proposed control method.Impact on grid current harmonic caused by dc-link voltage ripple,grid current predictive error and voltage harmonic have been described in detail.The topology and operational principle have been explained based on parallel active power filter to eliminate harmonic current pollution from the application of nonlinear converter.The second-order harmonic current and corresponding ripple voltage on the dc bus can be filtered by active ripple energy storage method.The low-frequency harmonic current can be filtered using compensation current generated by capacitive active filter,which results in high power density.To eliminate the second-order harmonic current on the dc bus,a resonant controller has been designed.The magnitude characteristic and phase characteristic with different resonant controller coefficients have been discussed.The resonant controller has been design based on root-locus method.Direct two-order filter has been chose to discretize the transfer function.To eliminate the low-frequency harmonic generated by single-phase PWM rectifier phase lock loop,a modified phase lock loop model based on second order generalized integrator has been proposed.A band-stop filter has been used to filter second-order frequency ripple and a trapezoidal discretization method has been given to discretize phase lock loop integrity component.A model predictive direct power control of single-phase PWM rectifier based on modulation function optimization has been proposed.The expression of rotational voltage and rotational current have been achieved based on a second-order generalized integrator.The instantaneous active power and reactive power have been discussed.The modulation function optimization has been presented based on cost function.The input inductance mismatch has been discussed.A model predictive control scheme with input inductance on line estimation has been described in details.It has achieved accurate the instanteous reactive power estimation.The thesis propose a high power density single-phase PWM rectifier with active power filter,a grid current harmonic elimination method based on resonant controller and a model predictive direct power control based on modulation function optimization to solve single-phase PWM rectifier current harmonic problem,which possesses important applicable value in theory research and practical engineering.