DC ripple current rejection in a bidirectional SiC single-phase AC-DC converter for V2G application

Single phase electric vehicle battery charging converters are bulky due to electrolytic capacitors. These capacitors are used to reduce the voltage ripple in the dc bus. These electrolytic capacitors occupy significant volume and suffer from reliability issues. The required capacitance can be greatly reduced by rejecting the ripple current in the dc bus. The ripple current in the dc bus is rejected at the cost of an additional half-bridge inverter. The half-bridge inverter injects a current out of phase in reference to the dc bus ripple current. The current is injected by applying a voltage across an energy storage element (Inductor). The voltage across the energy storage element is controlled by the dutycyle of the half-bridge. A mathematical relationship between the voltage applied across the energy storage element and the ripple current in the dc bus is derived. Analysis of the ripple current rejection is performed on a Dual Active Bridge (DAB) based SiC single phase AC-DC converter capable of sinking or sourcing real and reactive power. Simulation results are presented verifying ripple current rejection in the dc bus for various operating conditions. Average modeling of the inverter leg currents over a switching cycle is also presented to highlight distinct inverter leg current profiles.