Design and Control of Power Converters for Electric Vehicle Battery Charging

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Name of the Speaker: Shubham Dhiman (EE18S039)
Name of the Guide: Dr. Krishna Vasudevan
Date/Time: September 5th (Monday), 5:00 PM

In the development of electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs), the battery charger plays an important part. The number of all-electric (EVs) and hybrid electric vehicles (HEVs) in India is expected to expand substantially in the next years. On-board batteries in EVs/HEVs require complete or partial recharging via a low voltage utility network that supplies home or light industrial customers. A battery charger is required for the utility connection, which is made up of a unidirectional or bidirectional power electronic converter that converts AC to DC or vice versa. Because of the smaller size of the high-frequency isolation transformer, a two-stage AC/DC and DC/DC power conversion is widely used in battery charging systems. This thesis is organized into seven chapters and focuses on the design and development of AC-DC and DC-DC converters for a 5 kW, 84V battery charger.

The battery charger scenario in India, as well as the topologies of AC-DC and DCDC converters that could be used in the battery charger, are presented in the thesis. The AC-DC converter uses a six-switch three-phase PWM rectifier design, which has advantages such as UPF operation, low grid line current distortion, and high efficiency. An energy efficiency approach takes into consideration the optimal DC-DC power converter topology, and a ZVS-PSFB (zero voltage switching-phase shift full-bridge) converter is chosen. It is demonstrated that, from the standpoint of total ownership cost, a converter topology for battery chargers selected based on the minimum energy consumption over a charging cycle would be more appropriate than a selection based on maximum efficiency at peak load of operation for battery charging applications.

In this work, AC-DC and DC-DC converters have been designed, built, and tested to satisfy the required specifications, as well as the necessary hardware. Several major aspects of design investigated using calculations and simulations. These were validated using the hardware built. The LCL filter is used to filter harmonics on the grid side, and a detailed analysis of magnetics design in DC-DC converters has been carried out. Testing was done, and the results closely matched the simulation. Both the converters designed demonstrate an efficiency of around 95%, which is in line with the design target.