Highly Efficient HV boosting for xEV

The widespread electrification of transport demands increasingly efficient and reliable power management strategies, particularly in battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs). At the centre of this challenge is the effective regulation of the high-voltage (HV) DC bus - the primary energy distribution backbone linking the vehicle's power source to key subsystems such as the electric drive unit (EDU), charging systems, and auxiliaries.

Conventional approaches rely on DC-DC converters to buck (reduce) or boost (increase) voltage from the power source to maintain appropriate bus voltage levels. However, these converters typically incur power losses of 3-5%, which translate directly into reduced vehicle range or increased energy storage requirements. A 5% loss, for instance, necessitates a 5% increase in battery capacity or hydrogen storage for equivalent range - with direct implications for cost, weight, and packaging. Additionally, if HV bus voltage is not actively stabilised - and instead tracks the native output of the battery or fuel cell - system designers must engineer the EDU to operate reliably under low-voltage, high-current conditions. This 'worst-case' design constraint increases the current-handling demands, thermal load, and copper losses, thereby raising the cost and reducing the efficiency of the EDU under typical operating conditions.

This project investigates one such class of converter topologies - partial power processing architectures - wherein only a small proportion of the total power flow is processed to regulate the output. This approach substantially reduces converter power losses, component stress, and volume, enabling higher overall system efficiency.

A key focus is the Series-Connected Buck Converter (SCBC), a topology first proposed by NASA in the 1990s and subsequently applied in large-scale energy storage systems. SCBC enables tight voltage regulation by interleaving a high-efficiency buck (or buck/boost) stage in series with the main power path, thereby diverting only the voltage differential component through the converter. The result is a system capable of achieving efficiencies in the range of 99-99.8%, with minimal additional componentry. For FCEVs, such efficiency improvements correspond to a potential 9-10% increase in driving range - a significant advancement in the context of vehicle performance and commercial viability.
This research aims to evaluate the practical applicability of SCBC and related HV converter architectures in vehicular environments, including detailed modelling, simulation, and experimental validation. The outcomes are expected to inform next-generation drivetrain and power architecture design, enabling more compact, efficient, and cost-effective electric and hydrogen-powered vehicles.

By addressing fundamental inefficiencies in HV power management, this work contributes to the broader goal of accelerating the transition to net-zero transport - delivering tangible benefits in energy use, system integration, and range capability for zero-emission vehicles.