The Research And Design Of On-Board Charging Power For New Energy Electric Vehicles

With the development of electric vehicles,the research on their key technologies is of vital importance.Battery charging technology is the key to promote the development and popularization of new energy electric vehicles.For the on-board charging power in low-power applications,the grid-side power factor,overall machine efficiency and power density are the research focuses.Firstly,this paper studies the front-end single-stage Boost-PFC circuit with power level of 1.3kw.Three operating modes,namely continuous,discontinuous and critical continuous,are analyzed in detail,and three control methods,namely average current,peak current and hysteresis current,are compared and analyzed.The analysis shows that the inductance current pulse is the least in the continuous conduction mode,and the average current control has better current following characteristics.Through simulation analysis under half-load and full-load conditions,it can be known that CCM Boost-PFC circuit with average current control can realize unit power factor operation,the harmonic content of network side current is 2.24% and 3.15%,and the ripple coefficient of output voltage is ±1.75% and ±3.25%respectively.At the same time,this paper also analyzes the front-end interleaved and parallel topology with a power grade of 3.3kw.The working principle,current ripple property and inductance size are analyzed.Compared with single-stage topology,this topology has smaller input current ripple and higher power density.By analyzing the current sharing characteristics of the circuit,the undisturbed duty cycle compensation ring is added to the current loop to improve the traditional control method,so that it can achieve better current sharing effect.Simulation analysis shows that the improved control method can achieve better current equalization effect,the current stress of the switch tube can reach equal,at the same time,the output voltage is stable,meet the input requirements of the back-end circuit,the input current ripple is small,verify the superiority of this circuit compared with the single-stage circuit.In addition,the synchronous rectifier resonance circuit is studied as the back-stage DC-DC conversion circuit.The working principle and driving mode of synchronous rectifier are analyzed in detail,the working conditions of zero-voltage on and zero-current off of resonant circuit are analyzed,and the resonance parameters are calculated,the simulation analysis shows that the system can realize zero-voltage on and zero-current off on the premise of meeting the requirements of output voltage and current.Finally,this paper builds a two-stage circuit test platform for vehicle charging power supply with a power level of 1.3kW.The experimental results show that the charging powersupply can realize the operation of unit power factor,meanwhile,the back-end circuit can realize the ZVS operation and the synchronous MOS tube can be driven accurately,which verifies the correctness of the control method and design scheme adopted in this paper.