Control of a GaN-Based High-Power-Density Single-Phase Online Uninterruptible Power Supply

摘要

This paper presents a GaN based high-power-density high-frequency single-phase online uninterruptible power supply (UPS) with a common neutral between the input and output. The proposed online UPS utilizes GaN half-bridge structures that operate with zero-voltage switching (ZVS) throughout the line cycle, thus maintaining high efficiency while operating at MHz frequencies. A novel control strategy for the proposed online UPS is also presented. The proposed control scheme utilizes a dual-mode operation for the input power factor correction (PFC) rectification stage of the UPS, enabling soft-switching by operating in boundary conduction mode. The inversion (dc-ac) stage is also operated in dual mode, wherein a digital controller regulates the output voltage of the converter across both resistive and reactive loads. A GaN based 1-kVA prototype online UPS, utilizing the proposed UPS topology and control technique, is designed, built, and tested. The prototype UPS operates up to 2 MHz switching frequency achieving a power density of 26.4W/in³.