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Line-commutated converter circuit

  • US 4,517,635 A
  • Filed: 09/24/1982
  • Issued: 05/14/1985
  • Est. Priority Date: 09/24/1982
  • Status: Expired due to Fees
First Claim
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1. In a line-commutated converter circuit that:

  • (i) normally operates with a power factor exceeding 0.3 when operating near full inversion or near full rectification, (ii) has two D.C. terminals, one positive and one negative, adapted to be connected to a D.C. system, (iii) has a pair of A.C. terminals adapted to be connected to an A.C. system, and (iv) during normal operating conditions has coupled between two predetermined nodes a normalized peak value V of the A.C. system voltage in the range of 1.85 to 3.5;

    (a) first, second, third, and fourth branches, each branch comprising the combination of a thyristor and a diode connected in inverse-parallel relationship and an inductor connected in series with the thyristor-diode combination;

    the first and third branches being connected to said positive D.C. terminal, and the second and fourth branches being connected to said negative D.C. terminal;

    (b) means for connecting said first and fourth branches in series across said D.C. terminals, with a first of said predetermined nodes located between said first and fourth branches, and means for connecting said second and third branches in series across said D.C. terminals, with a second of said predetermined nodes located between said second and third branches;

    the diodes of said four branches being connected in a blocking direction with respect to said D.C. terminals;

    (c) a transformer comprising two windings coupled together, means for connecting one of said windings between said nodes and means for connecting the other of said windings across said A.C. terminals;

    (d) gating means (i) for triggering the thyristors of said first and second branches into conduction substantially simultaneously to provide a conductive path between said D.C. terminals that extends through said first and second branches via said one winding and (ii) for triggering the thyristors of said third and fourth branches into conduction substantially simultaneously to provide a conductive path between said D.C. terminals that extends through said third and fourth branches via said one winding;

    (e) and means for controlling said gating means such that the thyristors of said first and second branches are triggered into conduction at a controlled phase angle with respect to the A.C. system voltage thereafter;

    (f) said triggering normally being repeated each cycle of the A.C. system voltage;

    (g) said means for controlling the gating means being adjustable over a range that provides for smooth adjustment through zero of the magnitude of the power flow between said A.C. and D.C. systems and for smooth reversal in the direction of said power flow between said A.C. and D.C. systems,(h) the phase angle φ

    of the triggering of the thyristors normally being confined to the following limits between a maximum value φ

    .sub.(max) and a minimum value φ

    .sub.(min) ;

    ##EQU13## where C is the ratio of the inductance of the branches of the converter in a conductive path to the total inductive path inductance.

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