A Single-Stage Isolated Bi-directional Micro-inverter Building Block for Off-grid Energy Access

Energy access to off-grid communities has been historically limited by the availability and cost of the bulk power system interconnection. Modern technologies with steep, sustained learning rates, e.g., solar and batteries, are capable of disrupting this trend and making energy available equitably across the population, especially if solar and storage are combined to create a dispatchable resource. Nonetheless, a cost-effective and scalable solution that integrates solar, storage, and output ac power remains the key roadblock toward distributed energy access. In this paper, a single single-stage, isolated, bi-directional micro-inverter design with reduced switch and sensor count, which interfaces with the battery, PV, and grid, is presented. It excludes large DC-link capacitors, which are commonly seen among prevailing PV converter options, and retains efficiency benefits from its design and operation. With a power rating of 1-kW, this converter can be stacked easily to scale up the total system power rating due to its current-source inverter nature. Throughout this paper, the operating principle, design, and control of the proposed micro-inverter are presented. Lastly, A 1-kVA/480-Vac hardware prototype is built to demonstrate the proposed microinverter.