Standby power supply with active power filter ability using digital controller

This paper presents a standby power supply/active power filter (SPS/APF) system. This system provides combined functions of high efficiency power backup and harmful harmonics elimination. Based on the bilateral power converter using a current forced switching scheme, the line current can be sinusoidally regulated with unity power factor in APF mode and the voltage waveform distortion can be kept small in SPS mode by instantaneous voltage control. Introduction of the harmonic problems generated by the nonlinear loads, the calculation method of the instantaneous reactive current components achieving current distortion compensation and power factor correction, and the full digital control hardware and software schemes using a TMS320C25 digital signal processor are discussed in detail. Finally, the theoretical analysis is verified both by simulated and experimental results in a 3 kW laboratory prototype system