A low distortion inverter without low-frequency magnetics for UPS application

The increasing usage of digital data processing equipment has increased the demand for small capacity, compact, low-cost and energy-efficient UPS systems as a reliable power source. UPS systems utilise a power conversion stage from the battery backup to an output AC voltage compatible with the commercial supply, conventionally using a power frequency isolated step-up transformer. Recently, high frequency power conversion techniques have been used to replace the low frequency transformer by a high frequency power stage and transformer design reducing the size and weight of the overall equipment significantly. This paper presents an alternative approach to a compact inverter for UPS application by synthesizing a low distortion stepped waveform from a high voltage DC bus, without the need for output transformer or filter. A high frequency DC to DC power converter is used to generate the high voltage DC bus from the low voltage battery using a lightweight high frequency transformer. Thus, no low frequency magnetics are necessary