The Research On The High-efficiency And Bi-directional Electric Vehicle Charger

As a kind of high efficient energy-saving and zero mission vehicle，electricvehicle will play a leading role in the future city life. The research of charger willhave a direct impact on the future development of the electric vehicle. Electric vehiclecharging system is an important foundation for electric vehicles support system，which provides energy for battery. It is also the important part of commercializationof electric vehicles and industrial processes. Because of the power qualitydeterioration caused by charging facilities, which interfere with the normal operationof electrical equipment and electrical loads， so this paper has put forward abi-directional、high power factor and low harmonic charger structure. This papermainly consists of the following parts:Firstly, the topology and working principle of the traditional electric vehiclecharging machine is analyzed. Its structure generally has two levels: the pre-stageuncontrolled rectifier circuit and the post-stage DC/DC converter circuit. Because ofthe low power factor and harmonic content higher problem, this paper presents anefficient bi-directional electric vehicle charging machine topology，which pre-stagecircuit is three-phase PWM converter and post-stage circuit is isolatedHalf-Bridge-Push DC/DC converter. The working principles of the pre-stage andpost-stage circuit are described in details.Secendly, by analyzing the characteristics of the electric vehicle battery charging,a multi-stage constant current charging mode is proposed on the basis of conventionalmethods of charging and fast charging. For the pre-stage, a power feed-forwarddead-beat control method is derived, which can realize quickly tracking. For thepost-stage, a double closed-loop control strategy of current out loop and voltage innerloop is proposed， which can achieve a high efficiency charge-discharge. Thesimulation results verified the correctness and effectiveness of the proposed controlmethod. The stability analysis of the proposed control strategy is also carried on inthis paper and the results show that the control strategy has good stability.Thirdly, DSP working principle and characteristics are briefly introduced, andEvent Management is described in detail, which including Purpose Timer, PWMsignal generation and Capture Unit. Electric vehicle charging control subsystem isdescribed in detail. To ensure the safe of entire system, a software protectionsubsystem is used. Finally, to verify the practicality of the proposed topology, a rated power of20kW high-efficiency bi-directional electric vehicle charger is developed, and themain circuit and control circuit design device are described in detail. The results ofthis experiment show that the high-efficiency bi-directional electric vehicle chargingmachine topologies and control methods are correct.The study of high-efficiency bi-directional electric vehicle charger makes thezero pollution and low noise electric vehicle possible, also makes it possible to adjustthe difference between peak and botten electricity.