Transformerless UPS System Based on the Half-Bridge Hybrid Switched-Capacitor Operating as AC–DC and DC–DC Converter

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Abstract
A single-phase transformerless online uninterruptible power supply (UPS) is proposed in this paper. This UPS is based on the new half-bridge doubler-boost with switchedcapacitor operation. It is capable of operating with AC and DC input sources. The proposed converter provides a high power factor and improves power efficiency for line voltage applications. The switched capacitor concept allows a natural balance of the DC bus capacitor voltages, both in the AC-DC mode and in the DC-DC mode. It presents a common point between line voltage source, load, and batteries. This characteristic makes it possible to eliminate the common mode current, reducing problems with EMI and allowing the use of a simple bypass system. The feasibility of the proposed UPS is verified by experimental results from a 2.5 kW prototype with an efficiency of up to 94.9% and unity power factor.
Funding Information
  • Brazilian company NHS Sistemas Eletrônicos

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