Enabling Rapid Charging of Large Vehicle Fleets

Electrifying large vehicle fleets, such as buses and delivery vehicles, will demand levels of on-site charging power ranging from hundreds of kilowatts to tens of Megawatts. Such power levels are simply too great for the existing Low Voltage Distribution network to handle and so additional sub stations and feeder cabling would be required to meet this demand. The costs of such an approach would prove prohibitive for fleet electrification, particularly in urban areas where fleet pools are typically located. The ESCAPE project has empowered Turbo Power Systems to realise unique Electric Vehicle charging equipment that can provide a viable alternative, which, enables vehicle charging from the Medium Voltage (MV) electricity distribution network where greater available electricity capacity can be accessed.

To achieve this solution, two major innovations have been realised. First, a modular solid state Medium Voltage to Low Voltage sub-station converter is being developed, at the heart of which is the ESCAPE Silicon Carbide power module which enables extremely high-power conversion efficiencies and an equipment footprint smaller than that of a traditional transformer. This novel converter uses thirty six 15 kW modules to achieve a 500 kW secondary sub-station transformer equivalent that converts the 11kV Medium Voltage supply to a Low Voltage DC network voltage on which multiple rapid chargers are connected. Modularising the system in such a way enables redundancy in the design to enable continued operation of the system in the event of equipment fault.

Second, a unique DC supplied rapid vehicle charger has been developed, again using Silicon Carbide technology to enable highly efficient, galvanically isolated, solution. The charger is capable of up to 120kW power delivery to the vehicle, hence up to four chargers can be connected to the sub station converter to complete the charging system. Solar PV generation and Battery storage are all DC technologies, and so can be easily connected to the DC micro network of the system to enable a greater number of charge points to be connected to the sub-station converter, whose cumulative charging power can be greater than that of the sub station converter itself. Using this smart approach to fleet charging avoids significant grid upgrade costs for the installer and greatly reduces electricity costs for the vehicle operator whilst ensuring that challenging timetabling requirements can still be met using electric fleets.