POWER LINE HARMONIC REDUCTION BY HYBRID PARALLEL ACTIVE/PASSIVE FILTER SYSTEM WITH SQUARE WAVE INVERTER AND DC BUS CONTROL

摘要

A hybrid parallel active/passive filter system is provided which provides line power harmonic isolation and compensation for power systems connected to high power non-linear loads. The hybrid filter includes a passive filter connected in series with an active filter inverter. The active filter inverter is controlled to generate inverter voltages such that the filter terminal voltage tracks the supply voltage harmonics at a selected dominant harmonic frequency to regulate the supply current harmonics to zero. A synchronous reference frame (SRF) based controller is used to generate harmonic inverter voltage commands based on measured supply current values. A feed forward command signal generator may be used to improve the response of the control system. The active filter inverter is preferably implemented as a square-wave inverter. The active filter inverter DC bus is controlled to achieve power balancing and to provide real power to compensate for losses of the inverter. Power balancing is achieved by exchanging energy at the fundamental and dominant harmonic frequency of the active filter inverter. Control of the active filter inverter to achieve DC bus control and harmonic isolation simultaneously is accomplished using DC bus control inverter voltage command signals generated at the fundamental frequency in combination with harmonic inverter voltage command carrier signals at the dominant harmonic frequency to form low frequency switching signals for the square-wave inverter switching devices.