Impact of Vehicle Requirements on Accessory Power Module Design for Ultium Electric Vehicle Platforms

Ultium is an electric vehicle platform built on a flexible battery architecture. It enables the production of EVs across different vehicle types by offering multiple power, range, and performance options. A successful implementation of this strategy requires an optimized high voltage (HV) DC bus architecture [1]. The HV bus systems for Ultium Platforms are mechanized with multiple inverters, converters and HV components depending on vehicle needs. A DC-DC converter, also known as Accessory Power Module (APM), plays a key role in efficiently converting power provided from the HV Rechargeable Energy Storage System (RESS) into power available to service standard 12V vehicle loads. The APM ensures bias power during different propulsion operating modes as well as HV battery charging. Therefore, to maintain a stable and reliable HV bus system, a well-regulated APM design is needed. APMs regulate the 12V output voltage across different HVDC input voltages and 12V bus conditions including transients. In this paper, we begin our discussion with the different vehicle system requirements which impact APM design. We then explore the impact of HV bus inverter ripple, operating modes and control techniques which impact APM design with supporting simulation results and experimental verification.