Power converter topologies for electric vehicle chargers: Future technology, challenges, and trends

An electric vehicle (EV) charger serves as a platform that connects EV batteries to the power supply network. Power electronic (PE) converters are a critical component of EV chargers, playing a vital role in the power conversion process. Therefore, selecting the appropriate converter and analyzing its design and performance are essential for the development of EV technology. PE converters are integrated within the vehicle as part of an onboard charger or externally as part of an offboard charger. These converters are categorized into single-stage, two-stage, and integrated chargers. An onboard charger is constructed using either a single converter or an integrated topology, which typically consists of a frontend AC-DC power converter and a DC-DC regulator. Conversely, offboard chargers are designed with two-stage power conversions for fast and ultra-fast charging. Depending on the requirements of EV battery cells, the converters used in chargers can be single-phase or three-phase. The primary function of a PE converter in an EV charger is to supply a DC output voltage to the battery packs, typically ranging from 250 to 800V, depending on the battery pack design. EV chargers must also handle high-power, high-energy capacity batteries. In recent years, wide bandgap (WBG) devices, such as silicon carbide (SiC) and gallium nitride (GaN), have offered advantages, including fast switching, low power losses, high switching frequency and high operating temperatures. To achieve higher charging efficiency, increased power density, reduced charger size, and lower weight, PE converters in EV chargers must incorporate WBG devices. These devices enable fast switching frequencies in the MHz range, leading to higher power density and reduced magnetic component sizes. WBG devices also benefit from lower on-state resistance and gate charge, which minimize switching and conduction losses. Three-phase power supply options can further enhance charging speed by delivering higher power. Multilevel and multiport converters can be stacked to achieve even greater power levels. Bidirectional PE converters in EV chargers allow two-way power flow between the battery and the electrical grid, facilitating applications such as vehicle-to-grid (V2G) system. Wireless charging is an innovative technology with advantages in safety, reliability, and convenience. In wireless charging, the PE converter plays a crucial role in power transfer at high frequency. The PE converters used in wireless charging work in accordance with the direction of power flow and the number of stages. This chapter explores various circuit configurations of PE converters used in low-power chargers, high-power chargers, WBG devices, and wireless chargers. It examines the roles and importance of various PE converters used for onboard, offboard, bidirectional, and wireless chargers. Finally, the chapter discusses the challenges of adapting chargers for future EV batteries, the impact of EV charging stations on the electrical grid, the sustainability of EVs, and the environmental impacts of manufacturing and disposing EVs and their charging systems.