A Natural Bidirectional Isolated Single-Phase AC/DC Converter With Wide Output Voltage Range for Aging Test Application in Electric Vehicle

To ensure the safety and reliability, the aging test of on-board charger (OBC) and dc/dc auxiliary power module (dc/dc-APM) in electric vehicles are indispensable. However, a wide range of battery voltage levels and fast response to power conversion between forward and backward operations are still challenging aspects of the aging test power system. In this article, an improved ac/dc converter is proposed for the aging test application in electric vehicles. The converter consists of two identical topologies, which is made up of three cascaded converters. The first stage is a single-phase ac/dc rectifier, which realizes unity input power factor and power transmission between the ac grid and dc bus. The second stage is the LLC-dc/dc transformer (LLC-DCX) which provides electrical isolation and fixed voltage transfer ratio. Besides, the natural bidirectional power flow can be achieved by the proposed solution. The third stage is a synchronous buck converter (SBC) which guarantees the high dynamic performance and wide range voltage regulation. Experiments based on an 8-kW prototype are conducted to verify the feasibility and effectiveness of the proposed converter and the related control strategies.