“AC Cube”: A Single-Stage PV/Battery/Grid Energy Router

This paper presents the AC Cube, a single-stage, 1 kW bidirectional energy router with integrated 1 kWh battery storage, based on an Inertia-less Isolated Converter (IIC) topology. This multi-port converter interfaces with low-voltage solar photovoltaic ($\mathbf{P V}$) panels and onboard battery storage to supply 120/240 VAC single-phase power for both off-grid and grid-tied applications. This system addresses key challenges with “plug-and-play” scalable hybrid power converter solutions for gridconnected PV and energy storage applications. In particular, this topology eliminates the intermediate DC bus capacitor, thus improving power density, reliability and cost. Additionally, the use of a simple pulse density modulation (PDM) scheme enables high bandwidth closed loop control of the output voltage without PWM dead-time and compensation loops. This scheme also mitigates the injection of DC flux in an ultra-low leakage transformer. A $1 \mathrm{~kW}, 48 \mathrm{VDC}$ to 120 VAC unit has been built and tested, validating zero voltage switching (ZVS) operation of the AC bridge and zero current switching (ZCS) operation of the DC bridge devices.