Long life ups based on active filter and flywheel without electrolytic capacitor

This paper describes single-phase uninterruptible power supply (UPS) with active filter and flywheel. The UPS consists of a diode rectifier, a single-phase inverter, a flywheel energy storage unit with PM motor/generator and a three-phase inverter, not using a bulky electrolytic capacitor, battery and filter reactor. It contains many excellent characteristics: small size, lightweight and maintenance-free. The switching frequency of the single-phase inverter is more efficient with low frequency, which is synchronous with source voltage. However, it can supply stable power with the load. The unity input power factor control and the sinusoidal current waveform control of input side are realized by the active filter ability with quick energy charge/discharge control based on flywheel. The proposed system gives rise to sinusoidal output voltage waveform without LC filter. In this paper, the experiments are carried out under the structural conditions of using the pilot flywheel unit and the driving simulator of PM motor/generator connected to flywheel. The results indicate that the UPS has a desired active filter operation, and supplies the stable power with the load under any power condition.