CONTROLLER FOR RESONANCE TYPE ACTIVE FILTER

PURPOSE:To obtain the current commands of each phase by simple arithmetic operation from delay load currents generated from sinusoidal two-phase voltage, load currents and a current storage circuit by utilizing two-phase coordinate transformation in a controller for an active filter. CONSTITUTION:A voltage generating circuit 1 generates the two phase sinusoidal voltage of sinusoidal voltage ealpha having the same frequency as a three-phase AC system power supply and sinusoidal voltage ebeta having phase delayed at 90 deg., and outputs the voltage to the p, q arithmetic circuits of each phase and current command-value arithmetic circuits 6. Current storage circuits successively store currents at every 90 deg., and output the currents of 90 deg. lagging as lagging currents and send the currents to the arithmetic circuits. Instantaneous actual power and virtual power are computed by special formula, and inverted and sent to the circuits 6. The circuits 6 arithmetically operate current command signals by special formula, and transmit the signals over a current control circuit 7. A compensation current command signal and the detecting value of compensation currents are compared, and a trigger signal VG turning SW elements S1-S6 ON-OFF is output.