Bi-directional non-isolated impedance converter for extra low-voltage battery system safety

For bi-directional power converters, modularity, low leakage currents, low ripple, and a simple bi-directional control that utilizes storage effectively with low-voltage stress are required. This paper proposes a new configuration for converters that meet all of the above requirements to realize a robust converter for both vehicle to low-voltage DC microgrid (V2G) and low-voltage DC microgrid (LVDC-MG) to vehicle (G2V) technologies. The proposed power-dense modular-impedance source configuration employs coupled inductors, which ensures a power-dense modular architecture configuration with low current ripple and negligible leakage currents. The new auxiliary boost capability of the impedance source provides a wide operating range. A unified bi-directional control algorithm enables operation to/from battery stacks at customized rates, based on the state of charge (SoC). Based on the requirements of the control scheme, this automatically invokes the use of the impedance network to cater to the low charge conditions of the battery stack or the transient conditions on the LVDC microgrid. The proposed bi-directional converter is tested through both simulations and experimental studies on a developed prototype to confirm high efficiency operations over a wide range of duty cycles.