Design and Control of Single-Phase Grid-Connected Photovoltaic Microinverter with Reactive Power Support Capability

Abstract

This paper proposes a single-phase photovoltaic (PV) microinverter capable of supplying reactive power to the grid. In the past, researchers mainly focused on obtaining high efficiency, low cost, and high boost ratio. However, as the solar power generation has increased in recent years, the grid regulations have been changed so that PV inverters provide reactive power for the grid stability. Therefore, the proposed PV microinverter is constructed by the bidirectional boost/buck dc-dc converter for reactive power support and achieving high step-up ratio by using coupled inductors. In addition to the design guideline, this paper presents the control strategy of the proposed microinverter. Unlike traditional two-stage microinverters, the dc-link voltage is shaped like the rectified grid voltage. The experimental results verify that the 320-W laboratory prototype can supply reactive power and reaches 96.5% California Energy Commission (CEC) efficiency at unity power factor operation.