Investigation of high efficient DC-DC converters for on-board battery charging system in electric vehicles

Due to the limited interior space in electric vehicles, two-stage battery chargers should meet some requirements such as high power density and high efficiency. The efficiency and power density of two-stage on-board battery chargers largely depend on isolated DC-DC converters. In this thesis, two different topologies are proposed for on-board battery charging systems in electric vehicles. A control method, based on artificial neural networks (ANN), is developed for soft switched (ZVS) LLC resonance converter in Topology-I and it was compared with the traditional method at different load conditions. Thanks to the proposed control method, improvement in steady state error and transient response time was observed. Both the grid and photovoltaic (PV) panel fed, two-stage battery charging unit proposed in the Topology-II. For the proposed topology, a maximum power point tracking (MPPT) method with high speed and high accuracy has been developed and compared to traditional methods. In addition, a LLC resonance DC-DC converter is designed to allow the high-power and low-power battery to be charged on a single circuit. Thus, the proposed Topology-II is intended to allow the electric vehicle to travel more miles with a single charge process. The proposed topologies have been analyzed at different load ranges to measure efficiency system according to European efficiency standards.