Compensation And Control Strategy For Dwpt System Applicated In Electric Vehicle Charging

In order to improve the energy supply structure,traditional fuel vehicles are gradually replaced by new energy electric vehicles.Compared with the traditional wired charging mode,the dynamic wireless power transfer(DWPT)technology,which supplies energy to the moving vehicles in a non-contact has attracted great attention for its high security,reliability,environmental adaptability and other advantages.However,in practical dynamic charging process,the equivalent resistance of battery packs in EVs varies significantly with respect to their charging profile.In addition,the horizontal and vertical misalignments between the transmitting coil and the receiving coil will cause the variation of the coupling coefficient to varying degrees.The above phenomenon will make the system operating parameters significantly deviate from the theoretical value.The resulting power transmission characteristics will deviate from the design expectations,and the active power transfer capacity and system efficiency will be reduced accordingly.Therefore,it is necessary to modulate the DWPT system through relevant control strategies to achieve stable and effective energy transmission under various conditions.In order to solve the problems of slow regulation speed,poor dynamic response and small regulation range of traditional DWPT system control strategy,a primary-side control strategy based on parameter identification method is proposed.Aiming at the limitation of basic compensation network in DWPT system,the transmission characteristics and configuration conditions of LCC-S compensation network is discussed.and the parameter identification model based on switched-controlled capacitor structure is established.By adjusting the equivalent capacitance of SCC,the system can switch between the steady-state operation mode and the non-steady-state operation mode.By deriving the operation equations of DWPT system under the two operation modes,the simultaneous identification of the coupling coefficient and the load resistance parameters is realized.Based on the real-time parameter information,this paper proposes the primary side closed-loop control strategy.The input voltage of the inverter is adjusted by controlling the front buck converter,so that the system can maintain constant voltage output performance even if the coupling coefficient and load resistance changes.To eliminate the parameter drift caused by component tolerance and ages,the dynamic impedance matching strategy is proposed.Theoretical analysis shows that the phase-difference between the induced voltage and the current in receiver side is determined by the equivalent capacitance of SCC.Thereby,by introducing the phase-difference closed-loop control strategy,the equivalent capacitance of SCC can be modulated dynamically to be consistent with the theoretical value in both two modes.To avoid sophisticated mistuning detection,the feasibility of introducing the auxiliary measurement coil is analyzed.Based on the theoretical derivation,the simulation analysis is carried out by using PSIM software,and the hardware experimental platform based on TMS320F28335 is built.The experimental and simulation results show that the detection accuracy with dynamic reactance regulation is much higher than the direct open-loop modulation of SCC.Based on the accurate parameter identification,the front-end buck converter is used to regulate the output voltage and the corresponding experimental results have demonstrated its validity.