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Research Of The Power Converter And Its Control Strategies Used In On-Board Bi-Directional Charger Of Electric Vehicle

Posted on:2013-09-03Degree:MasterType:Thesis
Country:ChinaCandidate:Q C HeFull Text:PDF
GTID:2232330362973788Subject:Electrical engineering
Abstract/Summary:PDF Full Text Request
In recent years, along with the proposal and development of smart gridtechnologies, a technology of electric vehicles (EVs) to smart grid two-way interactionsimplified as V2G technology also emerged. In V2G technology, EVs are acted asdistributed energy storage units interacting of energy and information with smart gridbi-directionally. It is of great significance to grid secure, stable, economical operationand the development of EV industry itself. In order to achieve the V2G technology,on-board bi-directional charger is one of the key equipment, and its performance willdirectly affect the efficient, reliable and large-scale implementation of V2G technology.For the present study of on-board bi-directional charger is still less, this thesis will takethe on-board bi-directional charger of EV for research object, and focuses on its powerconverter topology and control strategies to improve performance. The research workcompleted and the main results achieved by this thesis are as follows:①According to the key technical requirements of bi-directional power flow andhigh efficiency and high power density for on-board bi-directional charger, a two-stagetopology constituted with the front single-phase reversible PWM rectifier and the backtwo-phase interleaved parallel Buck/Boost converter is proposed. The methods toimprove the efficiency and power density for the front and back converter topology arestudied respectively.②Based on the proposed two-stage topology of on-board bi-directional charger,the system performance optimized and function diversified control strategies areresearched. For the front single-phase reversible PWM rectifier, a control strategy basedon the virtual dq coordinates is introduced, which compared to the traditional controlstrategies can achieve zero error of inner current loop and most importantly independentcontrol of active and reactive current so that the on-board bi-directional charger can alsohave the function of the reactive power compensation. According to the equivalentcircuit model of battery and the needs of charge and discharge mode, a dual-modevoltage and current unified control strategy which can simplify the controller for thetwo-phase interleaved parallel Buck/Boost converter is proposed. In order to beunsusceptible to the input voltage fluctuation and reduce the influence of the integralcompensation to system dynamics and stability, a voltage feedforward control strategy based on the steady state duty cycle is proposed. By appling this proposed controlstrategy, an improved dual-mode unified control strategy based on input voltagefeedforward is formulated, and the theoretical analysis shows that the influence of theDC bus voltage fluctuation can effectively be reduced and so the DC bus capacitorvalue can be reduced.③Based on the theoretical analysis, the main circuit and conrtroller parameters ofa3.5kW on-board bi-directional charger system are designed and also verified on thesimulation model in Matlab/Simulink. The feasibility of the design and correctness ofthe theoretical analysis are verified by the steady and dynamic simulation results. At last,an experimental prototype of the single-phase reversible PWM rectifier close to theengineering application condition is built and the rectifier experiment is carried out toverify the correctness of front stage theory and simulation analysis, on which thefollowing research work is well based.
Keywords/Search Tags:V2G technology, On-board bi-directional charger, Virtual dq coordinates, Dual-mode unified control, Input voltage feedforward
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