Composite filter for suppressing harmonic frequencies on electric power transmission lines
First Claim
1. A composite filter for suppressing harmonics produced by a converter in an AC to DC power line transmission system comprising first and second filter sections, said first section passing current having a given harmonic frequency and also passing current having harmonic frequencies thereabove which are multiples of the system frequency, means connecting said first and second sections in series between one line of the AC portion of said power system and a second line thereof, said serially connected first and second filter sections together being substantially series-resonant at said given harmonic frequency, and means connected to the junction of said first and second filter sections for injecting current into said filter sections at said junction which injected current is sufficient to cause substantially complete filtration at said given harmonic frequency.
0 Assignments
0 Petitions
Accused Products
Abstract
AC to DC converters used in high-voltage direct-current power transmission lines produce objectionable harmonics. The composite filter herein described is actively tuned for the eleventh and thirteenth harmonics in addition to providing a low impedance path for the higher order harmonics, thereby eliminating such undesired harmonics so that they will not be transmitted over power lines where they can cause telephone interference, undesired heating of electrical equipment and other difficulties.
-
Citations
8 Claims
- 1. A composite filter for suppressing harmonics produced by a converter in an AC to DC power line transmission system comprising first and second filter sections, said first section passing current having a given harmonic frequency and also passing current having harmonic frequencies thereabove which are multiples of the system frequency, means connecting said first and second sections in series between one line of the AC portion of said power system and a second line thereof, said serially connected first and second filter sections together being substantially series-resonant at said given harmonic frequency, and means connected to the junction of said first and second filter sections for injecting current into said filter sections at said junction which injected current is sufficient to cause substantially complete filtration at said given harmonic frequency.
- 5. A composite filter for suppressing harmonics produced by a converter in an AC to DC power line transmission system comprising first and second filter sections, said first section including a capacitor, resistor and inductor, said resistor and inductor being in parallel with each other and in series with said capacitor for passing current through said filter section having a given harmonic frequency and also passing current having harmonic frequencies thereabove which are multiples of the system frequency, said second filter section including a capacitor and inductor in parallel with each other, means connecting said first and second sections in series between one line of the AC portion of said power system and a second line thereof, said capacitor and inductor of said second filter section having component values for causing said serially connected first and second filter sections to be substantially series-resonant at said given harmonic frequency, and means connected to the junction of said first and second filter sections for injecting a relatively small current into said filter sections at said junction which injected current is only sufficient to cause substantially complete filtration at said harmonic frequency.
- 7. A method of suppressing harmonics in an AC to DC power line transmission including therein at least two power lines, one of which may be ground, comprising the steps of providing a first filter section containing components capable of passing current having frequencies above a given harmonic frequency, connecting a second filter section in series with said first filter section between said two power lines, said second filter section containing components capable of providing a combined series-resonant condition of said first and second filter sections, and injecting current in said first and second filter sections at a location between said first and second filter sections which is sufficient to cause substantially complete filtration at said given harmonic frequency.
Specification