Active filter

Details Active filter Active filter

1976-01-29

1977-10-11

Shoop, William M.

Electric power conversion systems

Current conversion

With means to introduce or eliminate frequency components

367 3, 333 76, 363 48, H02M 112

Patent

active

040538206

ABSTRACT:
An active filtration system is described which may be particularly useful for filtering undesired harmonics of the fundamental AC frequency produced by AC to DC or DC to AC conversion. The filtration system of the invention produces currents of a phase, frequency and magnitude for injection into the AC system such that the undesired harmonic currents to be filtered sum with the injected currents giving a net zero current at the undesired harmonic frequency. The system can incorporate existing passive filtration elements and provides a high-impedance parallel-filtration network to prevent the filteration system from acting as a "sink" for the ambient harmonics generated elsewhere in the AC system. Because the frequency, phase and magnitude of the injected currents are controlled, the filter of the invention remains highly effective even when these quantities and the filter component values vary.

REFERENCES:
patent: 2008515 (1935-07-01), Plathner et al.
patent: 2008519 (1935-07-01), Smith
patent: 2236254 (1941-03-01), Willis
patent: 3229184 (1966-01-01), Churchill
patent: 3813593 (1974-05-01), Tice et al.

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