ACTIVE HARMONIC FILTER AND POWER FACTOR CORRECTOR

摘要

An active harmonic filter selectively sources current to or draws current from power lines. The active harmonic filter includes a controller which executes a predictor routine which predicts the current to be supplied to or drawn from the power line at a time t+.DELTA.t to reduce load induced phase differences between the line voltage and the line current. An integrating slow control routine integrates difference currents between actual line currents and desired line currents in equivalent segments of time in different cycles of the power line. The integrated differences may be combined with proportionally controlled difference currents to reduce or eliminate harmonic line currents. A current balancing routine enables the active harmonic filter to balance currents in two or more lines of a polyphase power line. The predictor, integrating slow control and current balancing routines, may be used singly or in combination to improve the condition of line currents on the power lines.