Research And Design Of High Performance On-Board Charger With Digital Control

With the increasing attention of the state to the environment,air quality and new energy source,electric vehicles(EV)have gradually become a major trend of automobile development in the future.China,as the largest consumer market of electric vehicles in the world,is leading the trend of global electric vehicles.The cumulative sales in the first seven months of 2018 have approached 500,000 vehicles,and in July there was an explosive growth with sales of about 84,000 units,an increase of 48%compared with last July.With the continuous expansion of the electric vehicle market,the challenges to the power electronics industry are also growing.As an important component of electric vehicles,on-board charger(OBC)is one of the research hotspots in the field of electric vehicles.The main function of OBC is to convert the AC input energy from the power grid into a stable and controllable DC output,and charge the power battery pack according to a certain charging mode.Because of the need for anti-seismic,heat dissipation conditions and volume limitation,it requires us to use car-grade devices and achieve high efficiency and high power-densityIn the first chapter of this paper,the main schemes and technologies at home and abroad are investigated,the performance of the circuit is evaluated,and the scheme of the circuit topology is determined.It includes a bridgeless Boost PFC converter followed by a full-bridge LLC resonant converter.In the second chapter,the operational principle of bridgeless Boost PFC converter is analyzed in detail.According to the requirement of project index,the power parameters are designed and devices are selected.Detailed loss analysis is carried out.The Boost PFC is modeled mathematically,and with the aim of controlling stability and rapidity,the current and voltage loops are designed and the PI parameters are optimized The simulation model of bridgeless Boost PFC is built by PSIM to verify the correctness of the analysis and the effectiveness of the design in this chapter.In Chapter Three,a detailed analysis of the operational principle of full-bridge LLC resonant converter is proposed.The characteristics of the circuit are analyzed by using first harmonic approximation method(FHA)and time domain analysis method,considering parasitic junctional capacitance od the secondary diode.Based on the voltage gain curve,the optimal design acheme of resonance parameters is proposed.The devices are selected.Detailed loss analysis is carried out.Finally,a 3.3kW experimental prototype is made and debugged according to the above research and design,and the experimental results of the prototype are given in the fourth chaper.The results show that the prototype can achieve a wide voltage range output within a wide load conditions,and under 220Vac input condition,the prototype can work on a peak efficiency up to 95.4%,full-load efficiency up to 95.1%,and PF on all conditions up to 0.99.The prototype has excellent characteristics in efficiency,power factor correction and output voltage range,which verifies the accuracy of the analysis and the validity of the design.