A novel reconfigurable induction machine drive for hybrid vehicles

With the growing concerns over global warming and depleting oil reserves, full and hybrid electric vehicles (EVs) are gaining significant attention from commercial bodies as well as government policymakers. Considering the high cost and range anxiety of full EVs, hybrid EVs are expected to be the immediate solution. The electric drive train of the hybrid vehicle needs to have four main functions, high torque low-speed motoring for engine starting,low torque high speed generating for charging the onboard battery as the vehicle alternator, medium torque medium speed motoring for torque boost, and medium torque medium speed generating for regenerative braking. Two electric machine drives are normally required to meet the above requirements, resulting in a complex system and higher cost. In this thesis, a novel induction machine drive, reconfigurable induction machine drive (RIMD) is proposed to achieve a modified torque-speed envelope, so the drive train of hybrid EVs can be replaced by one single machine drive. The reconfigurable induction machine drive is based on the principle of pole phase modulation. A novel concept of independent phase belt controlled pole-phase modulation is developed. The proposed pole-phase modulation technique offers higher reconfigurability compared to the previously reported literature. As an example, a toroidally wound machine with 36 stator slots can be reconfigured to 2/4/6/8/10 pole operation by using a 12-phase inverter. The proposed concept is analysed by using Finite Element Analysis (FEA) method and the equivalent circuit and parameters of the reconfigurable induction machine are obtained. To validate the proposed machine, a scaled-down 1.5 kW prototype has been developed which is capable of 2/4/6/8/10 pole operation. A 12-phase inverter has been developed as well to drive the machine. Results from open and short circuit tests have validated the design and equivalent circuit model of the machine. A circulating power test bench has been developed. The torque-speed characteristics of the developed machine have been obtained from the test bench. Finally, a dynamic model of the proposed RIMD has been developed based on the d-q model theory. The model has been then used to develop an online pole transition control scheme, which ensures there is no significant oscillation in speed and current. The scheme allows online pole transition in only 0.1 s. The dynamic model along with with the proposed control scheme has been simulated in Matlab – Simulink platform. Finally the online pole changing control scheme has been implemented in the hardware and the experimental results are reported.