The Study And Design Of Electric Vehicles Charger

Energy issues and environmental issues have contributed to the rapid development of electric vehicles.The battery charging technology,motor drive and control technology,vehicle technology and energy management technology are the key technologys of new electric vehicles.In this paper,a charger charging the lead-acid batterys of low-speed electric vehicles that consist of interleaved boost converter and LLC resonant half-bridge converter is designed.Firstly,interleaved Boost-PFC converter in the application of the single-phase Power Factor Correction(PFC)circuits is studied.Compared with traditional Boost-PFC converter,interleaved Boost-PFC circuit employed in the first-stage of the charger would enhance power density of the converter,minish input current ripple and total harmonic distortion(THD).The working principle of two-stage interleaved Boost-PFC converter is analyzed in detail and the small signal model under average current control is established,and the compensating network of current inner loop and voltage outer loop are designed.The stability of the control loop is analyzed by Bode diagram.The study rusults result shows that two-stage interleaved Boost-PFC converter can not only achieve PFC and the THD of the input current to comply with the IEC61000-3-2 class A standard,but also improve the power density of interleaved Boost-PFC converter and reduce the input current ripple.Secondly,half-bridge LLC resonant converter employed in the second-stage of the charger is studied.The working principle of half-bridge LLC resonant converter under Pulse Frequency Modulation(PFM)is analyzed in detail.At the same time,the steady-state model of LLC resonant circuit is established based on Fundamental Harmonic Analysis(FHA).DC gain characteristics and impedance characteristics of the LLC were studied to find out the operating conditions of Zero-Voltage Switching(ZVS)and Zero-Current Switching(ZCS).The study results show that the LLC resonant half bridge converter we designed in this paper can realize ZVS of the mosfets and the ZCS of the rectifiers when the load range from no load to full load,compared with the traditional DC-DC PWM converter.The lossness of converter is minished to improve efficiency.Finally,compered with three-phase voltage rectifier(VSR),the operating principle and application of three-phase current rectifier(CSR)are studied.A tri-logic PWM modulation and double closed-loop control method based on dq coordinate system were adopted.In view of the resonance of LC filter,the active damping is designed,which is based on the parallel resistance of capacitor.The study results show that dynamic response of the three-phase CSR is fast,the power factor on the network side is high and the output current ripple is small.The active damping control strategy can effectively suppress the resonance of the LC filter and reduce the THD.In order to verify the correctness of theoretical analysis and design,a mass of simulation are provided,and a corresponding prototype in lab is set up to present experimental result.A charger that interleaved Boost-PFC converter employed in the first stage and LLC resonant half-bridge converter employed in the second stage is designed,where the power up to 1.5kW.The test have a good agreement with the theoretical analysis and design.