A dual-active-bridge based bi-directional micro-inverter with integrated short-term Li-Ion ultra-capacitor storage and active power smoothing for modular PV systems

This work targets modular nanogrids for remote locations, where photovoltaic modules can be gradually introduced to grow the renewable energy capacity at minimal capital cost, while reducing diesel fuel consumption. Today's grid-tied micro-inverters provide a modular solution for ac power generation in nanogrids but battery storage remains centralized, requiring an additional ac-dc converter. The main contribution of this work is a new micro-inverter platform and control scheme with bidirectional power flow between the nanogrid, the photovoltaic module and integrated short-term storage, using new high energy-density Lithium-Ion Capacitor technology. A real-time power smoothing algorithm is also proposed and the performance of the new 100 W micro-inverter is experimentally verified under various closed-loop dynamic conditions.