Energy sources and multi-input DC-DC converters used in hybrid electric vehicle applications - A review

With the drastic inclination towards reduction of atmospheric issues, hybrid electric vehicles are becoming the major alternative for internal combustion engine vehicles. Compared to internal combustion engine vehicles, hybrid electric vehicles are remarkable in terms of efficiency, durability and acceleration capability. However, the major drawback of hybrid electric vehicle is energy storage capability. An electric vehicle requires the energy sources with high specific power (W/kg) and high specific energy (Wh/kg) to reduce the charging time. Generally, fuel cells, batteries, ultracapacitors, flywheels and regenerative braking systems are used in hybrid electric vehicles as energy sources and energy storage devices. All these energy storage devices are connected to the different DC-DC converter topologies to increase the input source voltage. From the recent past, most of the hybrid electric vehicles are using multi-input converters to connect more than one energy source in order to improve the efficiency and reliability of the vehicle. This survey presents an assessment of present and future trend of energy storage devices and different multi-input DC-DC converter topologies that are being used in hybrid electric vehicles. In addition, different electric vehicle architectures are also discussed.