HIGHLY STABLE POWER-SUPPLY USING DIGITALLY CONTROLLED PHASE-CONTROLLED RECTIFIER AND ACTIVE-FILTER

A design of a highly stable current-controlled power supply combining a phase-controlled rectifier (PCR), passive filter and active filter i s investigated. A digital phase-locked voltage control (PLVC) with a c apability of compensating the thyristor firing angles under an unbalan ced power source is proposed; otherwise the PCR output voltage has low -order subharmonics whose suppression requires a bulky passive filter. The digital PLVC has a fast dynamic characteristic as an inner contro l loop of the PCR. To suppress further the output ripple, an active fi lter using a transformer is introduced and its design is described thr ough a frequency-domain analysis. An optimal, proportional and measura ble-variable feedback (IPM) controller is designed using a time-weight ed performance index based on a time-domain analysis. The design metho d based on the time-weighted performance index gives a better response characteristic than that based on the conventional performance index. It is shown via experimental results that the proposed scheme gives g ood dynamic and static performance.