Abstract:
Batteries of Electric Vehicles (EV) and Plugin Hybrid Electric Vehicle (PHEV) gain attention due to its vast usage as a source of energy in developed nations, as a result energy consumption is changing to electric power in automobile applications. Batteries of EV and PHEV participate in the regulation of power flow in microgrid or smart grid through battery charger, a sophisticated battery charger mainly constructed by rectifier followed by a DC-DC converter is a main module for battery charging setup. A 48-V, 1kW isolated bidirectional battery charger is proposed in this thesis. The proposed battery charger circuit worked in islanded mode, comprises of two-stage conversion i.e. AC-DC and DC-DC conversion. Neutral-point clamped converter is used for bidirectional AC-DC conversion while for DC-DC conversion High-frequency leg along with high-frequency Centered Tap Transformer followed be Half bridge is used. The proposed battery charger can convert three phase utility power to charge the vehicle battery by providing 48V and 20A. Similarly, the same battery charger can discharge back the connected battery to load when there is power demand of load in islanded mode of microgrid. In charging mode, the NPC act as universal diode-bridge rectifier to maintain the regulated DC-link voltage at DC-link Capacitor. The proper switching of only four switches of High-frequency leg across PI controller maintain the output 48V DC for the connected battery in charging mode of proposed battery charger. While in discharging mode, there are two controllers is used to discharge battery power to load of proposed battery charger circuit. One is open loop controller which maintain the regulated of DClink Bus voltage at DC-link Capacitor, while the second one closed loop PI controller work in a DQ frame of reference to control the output three-phases AC voltages for load through Neutral- Point Clamped converter. The Neutral-Point Clamped converter act as an inverted i.e. convert the DC voltage of DC-link Bus Capacitor Bus to three-phases AC voltages through closed loop PI controller for load.
