Quad-active-bridge converter with flexible power flow based on LC series resonance decoupling for renewable energy charging stations

Integration of photovoltaic panels (PV) with electric vehicle (EV) charging stations could reduce the grid impact and carbon footprint from the extensive fast and ultra-fast charging. This paper introduces a decoupled quad-active-bridge converter (QAB) with multi-directional power flow capability, which can integrate PV, energy storage (ES), grid, and EV in a charging station and rule the power among them. As the number of ports increases in the multiple-active-bridge converter, the complexity of control increases exponentially because of power decoupling. For the QAB, by tuning one port in series with LC units, the decoupling is achieved between the other three ports, reducing the control difficulty significantly. Further, the resonance decoupling method is extended to the n-port converter. For different power flows, the system automatically switches between different resonance modes to form higher-efficiency power flow channels. Three operating modes with decoupled closed-loop control methods have been constructed for the QAB to be suitable for future charging stations: (1) Charging mode: PV, ES, and grid coordinate with each other to provide incessant and stable charging for EV. (2) Electricity sales mode: Gird is supplied by PV, ES, and EV flexibly. (3) Under no load, PV power is stored locally. Experimental waveforms were presented by a 1-kW prototype, verifying the effectiveness of power decoupling and the feasibility of the three operating modes.