An Isolated Grid-Connected Charger with Reduced DC-Link Capacitor and Grid Filter Requirement

This paper proposes a grid-tied isolated low-voltage battery charging system. The ac-dc conversion stage is line frequency switched with ZVS capability and reduced grid filter requirement. The rectification is done by a three-level T-type neutral point clamped converter followed by a balancer circuit for power-factor correction. The dc-dc stage is a phase-shifted full-bridge converter which ensures high-frequency galvanic isolation. The rectification is done in such a way that pulsed dc voltage is obtained at the output of the T-type converter that reduces dc link capacitor requirement significantly. A new high-voltage polymer aluminium electrolytic capacitor technology has been proposed instead of conventional metalized film capacitors which leads to a more compact design. The switches in the ac-dc stage and dc-dc stage undergo zero-voltage-switching which improves the system efficiency. The control strategy of different stages and the simulation results for a 2 kW system is discussed here.