Research and Development of Traction-Drive-Integrated Onboard Charger for Electric Vehicles

At present, with the flexibility and convenice of charging, the onboard chargers have beenwidely applied in electric vehicles (EVs) and hybrid electric vehicles (HEVs) for theirbattery charging systems. However, the current onboard chargers suffer from thetechnical drawbacks of heavy weight, bulky size, high cost, low power (<6 kW), andadditional cooling system, which significantly limits the further development of onboardchargers.Since 2013 the integrated onboard chargers for EVs have developed fastly, whichpromotes the wide utilization of plug-in EVs. Thanks to the asynchronous working statusbetween the propulsion system and the charging system, the new technologyrestructures the machine inverters of the propulsion system into the rectifier for thebattery charging system. By this mean, the onboard charger effectively reduce theelectric components, which results in the optimal size, cost, and weight. Furthermore, thistechnology can use the windings of electric motor as the filtering inductors during thecharging, which significantly save the volume and the cost of the large inductors. Thus,this newly integrated onboard charger not only effectively save the system size and cost,but also significantly reduce the system weight and offer the surplus space for batteries.From the European market, Renault, an automobile company, has successfully launcheda supermini electric car “Renault ZOE” with the onboard charger in 2013. This EV adopts43kW charging system “Chameleon”, which can accomplish 80% of state-of-charge(SOC) within 30 minutes. By sharing one 3-phase power converter and functionalizing 3-phase induction motor windings with the drive and the charge, respectively, the adoptedcharging system successfully realize the high modularization and integration instead ofthe reduplicative accumulation of large electric components. Thus, it effectively reducethe system cost, size and weight. In 2015, the “Renault ZOE” reached 18.5 thousand carsales and became the best-selling EV in Europe.This project aims to develop a highly-compact and highly-integrated onboard charger forEVs, which is artfully integrating the advanced permanent magnetic drive system and thebattery charging system together. By this mean, the size, the cost, and the weigth of thewhole onboard charger can be reduced remarkably. We, Electrical Energy and PowerTechnology Laboratory (EEPTL) at City University of Hong Kong, will commit ourselves tothe research and development for this emerging integrated charging technique. Besides,by cooperating with the local APAS center, we strive to realize the technologycommercialization. Also, by cooperating with the Mainland automobile company, we planto built a matured product for the EV market. Undoubtfully, with the financial support ofInnovation and Technology Funding, the proposed integrated onboard charger techniquewill certainly impetus the development of relevant industries as well as promoting theinnovation and employment in Hong Kong.