Three-phase On-board Integrated Battery Chargers For Electric Vehicles

The integration of electric vehicles(EVs)drivetrain circuit like,electrical machine,inverter and DC-DC converter into three-phase EV battery-charger-circuit has attracted the attention of many industries and academia in the last decades,thus resulting in a number of published papers and patents in this domain.This category of EV battery charger has advantages of gaining spare space,reducing weight and cost of EVs over off-board and on-board independent chargers counterparts.However,depending on the system topology,many reported solutions of three-phase integrated battery chargers have problems.Majority of them suffered from torque production of machine during charging,high ripple of grid current and low fault tolerant capability.And some of them require additional extra elements(like relay,mechanical rotor blocking device,clutch,etc.)that degrade the system performance,occupy space and increase weight and cost of EVs.In this thesis,multi-winding machine and multi-leg inverter are employed in order to solve the problems faced by the three-phase integrated battery chargers.So,three novel solutions of three-phase integrated battery charger with vehicle-to-grid(V2G)mode function are proposed.The first proposed solution is based on segmented three-phase machine with nine windings and nine-leg inverter which is the main focus study in this doctoral thesis.The second and third proposed solutions,supplementary solutions briefly introduced in this thesis,are based on the dual three-phase open-end winding machine and dual six-leg inverter,and based on six-phase open-end winding machine and twelve-leg inverter.In the first proposed charger,an optimization of stator winding inductance is proposed in order to get an optimum leakage inductance capable of achieving acceptable ripple during charging and does not degrade the traction mode performance.In charging/V2 G mode,the three-phase grid is directly connected to the three machine's neutral points without intervention of mechanical switches;thus the proposed machine becomes grid side filter and the nine-leg bidirectional inverter becomes three-phase nine-leg rectifier without adding any new elements.During charging/V2 G,grid currents flowing through the proposed configuration machine's windings produce zero average total magnetic field inside the machine;thus resulting zero average torque and small torque fluctuation compared with the nine-phase integrated charger.Through proper three-phase control strategies(with unity power factor(UPF)control,harmonic current control like resonant vector proportional integral(VPI)and interleaved PWMs,and torque ripple control),the proposed system operates under UPF with total harmonic distortion(THD)below 5 % in charging/V2 G mode,and low torque ripple in traction mode.In the second and third proposed battery chargers,the three-phase grid is directly connected to middle points of machine's phase windings without intervention of mechanical switches;thus the open-end winding machine becomes grid side filter and the twelve-leg bidirectional inverter becomes three-phase twelve-leg rectifier without additional extra elements.During charging/V2 G,the grid currents flowing through the machine windings are split in equal portions and flow in opposite directions;thus canceling torque in this mode.Regarding the topology of proposed multi-winding and multi-leg chargers,proposed open-end winding integrated chargers have large grid-side filter inductance and high fault tolerant capability.And they are capable to produce high charging/V2 G power,which is more than two times of the traction power.Moreover,through the proper control strategy like UPF control and resonant VPI controller,the proposed systems operate under UPF with THD below 5 %.Topology of integrated battery charger using segmented three-phase machine with nine windings is presented in detail in chapter 2.Mathematical models of segmented three-phase machine,nine-leg bidirectional inverter and bidirectional DCDC converter performed in charging/V2 G mode and traction mode are presented and explained.In chapter 3 and chapter 4,system operations in three-phase charging/V2 G and traction mode are discussed.And supplementary solutions of three-phase integrated battery charger based on open-end winding machine are introduced in chapter 5.Mathematical models of open-end winding machine,twelve-leg bidirectional inverter and bidirectional DC-DC converter performed in charging/V2 G mode are presented and explained.Simulation and experimental results of proposed three-phase integrated battery chargers presented in chapter 2 to chapter 5 are provided to verify the proper operations of fast,robust,low harmonic current,as well as the high fault tolerant capability and high-power integrated battery chargers.