The use of stationary energy storage at fast electric vehicle charging stations can buffer the energy between the electricity grid and electric vehicles, thereby reducing the maximum required grid connection power and potentially mitigating the need for grid infrastructure upgrade. In this paper, a method is presented that sizes the stationary energy storage based on an acceptable average waiting time of drivers arriving at a fast charging station. The novelty of the paper is the focus on the relationship between size of stationary energy store and user waiting time. This relationship is often ignored, however is critical to obtaining the optimum capacity of stationary energy store. An example charging station location is chosen where there are currently eight chargers capable of 120kW charging and a 500kW grid connection. It is demonstrated that the method can be used at this location to design a charging station with stationary energy storage to support future 400kW charging without upgrading the current grid connection infrastructure. With future charging, using a stationary energy storage with a capacity of 1,000kWh reduces the maximum grid power from 1,800kW to 500kW.

High rate (<100kW) electric vehicle chargers (HREVCs) are crucial for achieving the benefits of reduced CO2 and particulate emissions promised by electric vehicles by enabling journey distances greater than the range of the vehicle. A method for predicting the expected demand pattern at these HREVCs is presented in this paper. This is critical to planning a network of chargers. This novel method uses freely available traffic flow data and travel patterns extracted from the open street map combined with a novel EV battery capacity prediction method, to find future HREVC usage patterns in the UK and their dependence on location and EV characteristics. This planning method can be replicated to find HREVC power demand for any location on the strategic road network in the UK and can be used in analysis of the role of high rate EV charging in the wider energy system.

A transformer-less Buck-Boost direct current–direct current (DC–DC) converter in use for the fast charge of electric vehicles, based on powerful high-voltage isolated gate bipolar transistor (IGBT) modules is analyzed, designed and experimentally verified. The main advantages of this topology are: simple structure on the converter’s power stage; a wide range of the output voltage, capable of supporting contemporary vehicles’ on-board battery packs; efficiency; and power density accepted to be high enough for such a class of hard-switched converters. A precise estimation of the loss, dissipated in the converter’s basic modes of operation Buck, Boost, and Buck-Boost is presented. The analysis shows an approach of loss minimization, based on switching frequency reduction during the Buck-Boost operation mode. Such a technique guarantees stable thermal characteristics during the entire operation, i.e., battery charge cycle. As the Buck-Boost mode takes place when Buck and Boost modes cannot support the output voltage, operating as a combination of them, it can be considered as critically dependent on the characteristics of the semiconductors. With this, the necessary duty cycle and voltage range, determined with respect to the input-output voltages and power losses, require an additional study to be conducted. Additionally, the tolerance of the applied switching frequencies for the most versatile silicon-based powerful IGBT modules is analyzed and experimentally verified. Finally, several important characteristics, such as transients during switch-on and switch-off, IGBTs’ voltage tails, critical duty cycles, etc., are depicted experimentally with oscillograms, obtained by an experimental model.

The purpose of the presented flyback converter is to equalise the voltage between the cells in a series string within a battery pack providing an active cell-balancing system. This would be an important part of a battery management system (BMS) for charging li-ion batteries in electric vehicles. The converter is based on primary side current sensing, where the conventional feedback circuit is omitted. The purpose of this converter is to improve efficiency by decreasing losses and to increase battery power density by decreasing the number of elements which constitute the power electronics; these are important factors for the future development of electric vehicle battery packs. Analysis of the circuit and the design procedure of the DC-DC flyback converter with primary current sensing is presented in this paper. Finally, several experimental converters have been built and tested to validate the authors’ approach.