Abstract

Electric vehicles (EVs) have recently garnered popularity in the consumer market due to its environment friendly nature as it uses clean energy to power vehicles. The EVs that are on road majorly comprise of two-wheeler, E-rickshaw, intralogistics equipment, trio, golf carts, short range mobility vehicle, which come under the category of low power EVs and passenger buses, loading trucks, electric trucks, which fall under the category of high power EVs. Batteries are the primary source of energy to power these EVs. Therefore, to recharge these batteries a battery charger is required. The conventional battery chargers have the merit of easy implementation but have higher component count, lower efficiency, complex control, low input power quality, and inflexible charging options. In order to achieve unity power factor (UPF), low THD, and high power quality; a power factor correction (PFC) unit becomes a crucial part of the AC-DC converters of the battery charger. The DCM design proves advantageous due to its inherent PFC operation at the input side, reduction of switching losses due to zero turn-on losses as well as zero reverse recovery diode losses. Also, the control circuit becomes simple as it requires only a single control loop and a single sensor. Thereby, making the converter reliable and robust towards high frequency noise. Further, to make the EV battery chargers flexible and to combat range anxiety, vehicle-to-vehicle power transfer aids in solving the issue.

This thesis analyses and designs a single-phase bridgeless Cuk-derived converter as onboard EV charger for AC and DC charging systems. At first, a single sensor based Cuk derived PFC AC-DC converter has been analyzed and studied which has the advantages of lower component count, improved efficiency, high power quality, and low cost. The converter is designed in DCM to accomplish PFC naturally on the input side. The voltage stress is lower compared to the conventional Cuk converter thereby, reducing the switching losses and enhancing the overall system efficiency. The converter control is simple requiring only one voltage loop and sensor. The detailed small-signal modelling using the current injected equivalent circuit approach and controller design has been presented. Further, to enhance the charging flexibility to mitigate the range anxiety, the same topology has been analyzed and designed for V2V charge transfer. A novel charge transfer technique has been implemented using the same topology. The loss analysis for both configurations has been reported in detail. The steady-state analysis and converter design for both configurations has been provided. Simulation results from PSIM 11 as well as proof-of-concept hardware prototype results are discussed extensively to validate the converter analysis, design and high performance.