DESIGN AND ANALYSIS OF HYBRID INDUCTIVE AND CAPACITIVE WIRELESS BATTERY CHARGING SYSTEM FOR E-MOBILITY APPLICATIONS

Abstract

Growing environmental concerns and scarcity of fossil fuel resources make it possible to replace traditional vehicles with electric vehicles (EVs). However, higher capital cost, range anxiety, long charging time and requirement of battery charging infrastructure make hindrance for widespread of EVs. The charging of EV batteries are typically performed using on-board and off-board wired chargers. However, the issue with conductive/wired charging of EVs is that it necessitates the use of heavy gauge cables to connect to the vehicles, which are difficult to handle, pose tripping risks, and are vulnerable to vandalism. Wireless power transfer (WPT) can be either inductive power transfer (IPT) or capacitive power transfer (CPT) has been researched as an alternate method of charging the EVs. The salient features of WPT charging are aesthetics, safety, convenience, and a completely automated charging process. EV batteries are charged through the widely accepted IPT technology with remarkable efficiencies (>90%) for an air gap of 100 mm - 200 mm. On the other hand, the CPT-based charging have gained attention on low power (<100 W) with a small distance of <10 mm owing to inexpensive coupling link, no induced eddy current loss, low cost, and weight. This thesis aims to explore mutual benefits of IPT and CPT systems to transfer high power and efficiency under misalignment conditions. A new hybrid grid-connected WPT charger that combines inductive and capacitive couplers for EV battery charging applications is proposed in this thesis. It comprises a series-series compensated IPT system and the double-sided LC-LC compensated CPT system, which are connected in parallel configuration. A three-leg, mixed switching frequency inverter with incorporation of totem-pole based grid interactive systems is used to create a unique hybrid inductive and capacitive WPT system for the shared power transfer. In this topology, two legs are operated at 85 kHz for IPT operation, where one common leg and the third one will be switched at 1 MHz for CPT systems. The proposed HPT configuration is simulated for a power level of 3.3 kW on MATLAB/SIMULINK software. The proposed topology makes for an independent power flow and offers a modular structure at the coupler level. The couplers of HPT systems are designed analytically and then simulated using the ANSYS-MAXWELL platform and are used to assess the performance of these couplers in terms of mutual inductance/capacitance and magnetic/electric field intensity.