Secondary magnetic excitation generator-motor device

Patent metadata

Field	Value
Publication number	US-11942873-B2
Application number	US-201917611100-A
Country	US
Kind code	B2
Filing date	Aug 8, 2019
Priority date	May 16, 2019
Publication date	Mar 26, 2024
Grant date	Mar 26, 2024

Abstract

A secondary magnetic excitation generator-motor device that inputs a first ignition pulse command to a three-level NPC power converter such that a detected excitation current value corresponds with an excitation current command value, the secondary magnetic excitation generator-motor device having a function of identifying a first phase, a second phase, or a third phase in descending order of a current absolute value, wherein a pulse switch to output an ignition pulse command to the three-level NPC power converter switches the ignition pulse command to the second ignition pulse command when a current absolute value exceeds a set overcurrent level 1, and switches the ignition pulse command to the first ignition pulse command when current absolute values for three phases are all equal to or smaller than a set overcurrent level 2.

First claim

The invention claimed is:

1. A secondary magnetic excitation generator-motor device comprising:
a winding induction machine with a stator-side armature winding being connected to an AC system;
a three-level NPC power converter to which a rotor-side excitation winding of the winding induction machine is connected;
a first DC capacitor connected between a positive DC terminal and a neutral point of the three-level NPC power converter;
a second DC capacitor connected between the neutral point and a negative DC terminal of the three-level NPC power converter;
a DC voltage source to supply a DC voltage to the first DC capacitor and the second DC capacitor;
an excitation current detector to detect an excitation winding current of the winding induction machine; and
an excitation current command device to compute an excitation current command value with a slip frequency equal to a difference between a frequency of the AC system and a rotational frequency of the winding induction machine, and to output a first ignition pulse command such that a detected excitation current value from the excitation current detector corresponds with the excitation current command value,
wherein the secondary magnetic excitation generator-motor device is configured to input the first ignition pulse command to a self-arc-extinguishing semiconductor element of the three-level NPC power converter,
wherein the secondary magnetic excitation generator-motor device has a function of identifying a first phase, a second phase, or a third phase in descending order of a current absolute value from the excitation current detector,
wherein the secondary magnetic excitation generator-motor device further comprises a pulse command device configured to:
separate four series-connected self-arc-extinguishing semiconductor elements formed of a self-arc-extinguishing semiconductor element P 1 C between the first phase and a positive-side clamp diode, a self-arc-extinguishing semiconductor element P 1 between the self-arc-extinguishing semiconductor element P 1 C and a positive electrode, a self-arc-extinguishing semiconductor element N 1 C between the first phase and a negative-side clamp diode, and a self-arc-extinguishing semiconductor element N 1 between the self-arc-extinguishing semiconductor element N 1 C and a negative electrode into a first-phase P group formed of the self-arc-extinguishing semiconductor element P 1 and the self-arc-extinguishing semiconductor element PIC, and a first-phase N group formed of the self-arc-extinguishing semiconductor element N 1 and the self-arc-extinguishing semiconductor element N 1 C;
determine a polarity of a detected current value for the first phase;
fix an ignition pulse in either the first-phase P group or the first-phase N group to an on-side, while fixing an ignition pulse in the other group to an off-side in a direction in which the first and second DC capacitors are charged;
separate four series-connected self-arc-extinguishing semiconductor elements formed of a self-arc-extinguishing semiconductor element P 2 C between the second phase and a positive-side clamp diode, a self-arc-extinguishing semiconductor element P 2 between the self-arc-extinguishing semiconductor element P 2 C and a positive electrode, a self-arc-extinguishing semiconductor element N 2 C between the second phase and a negative-side clamp diode, and a self-arc-extinguishing semiconductor element N 2 between the self-arc-extinguishing semiconductor element N 2 C and a negative electrode into a second-phase P group formed of the self-arc-extinguishing semiconductor element P 2 and the self-arc-extinguishing semiconductor element P 2 C, and a second-phase N group formed of the self-arc-extinguishing semiconductor element N 2 and the self-arc-extinguishing semiconductor element N 2 C;
fix an ignition pulse in the second-phase P group to a same side as the first-phase N group, while fixing an ignition pulse in the second-phase N group to a same side as the first-phase P group;
to separate four series-connected self-arc-extinguishing semiconductor elements formed of a self-arc-extinguishing semiconductor element P 3 C between the third phase and a positive-side clamp diode, a self-arc-extinguishing semiconductor element P 3 between the self-arc-extinguishing semiconductor element P 3 C and a positive electrode, a self-arc-extinguishing semiconductor element N 3 C between the third phase and a negative-side clamp diode, and a self-arc-extinguishing semiconductor element N 3 between the self-arc-extinguishing semiconductor element N 3 C and a negative electrode into a third-phase first group formed of the self-arc-extinguishing semiconductor element P 3 C and the self-arc-extinguishing semiconductor element N 3 C, and a third-phase second group formed of the self-arc-extinguishing semiconductor element P 3 and the self-arc-extinguishing semiconductor element N 3 ;
fix an ignition pulse in the third-phase first group to on, while fixing an ignition pulse in the third-phase second group to off;
output the ignition pulses as a second ignition pulse command, and

wherein a pulse switch is provided to switch between the first ignition pulse command and the second ignition pulse command bidirectionally to be output to the three-level NPC power converter, so that on conditions including a condition that any of absolute values of detected current values from the excitation current detector exceeds a set overcurrent level 1, the pulse switch switches from a first ignition pulse command to a second ignition pulse command, and on conditions including a condition that detected current values for three phases from the excitation current detector are all equal to or smaller than a set overcurrent level 2, the pulse switch switches from the second ignition pulse command to the first ignition pulse command.

2. The secondary magnetic excitation generator-motor device according to claim 1 , wherein the DC voltage source is constituted by an excitation voltage transformer insulated from the AC system to supply two sets of AC voltages, a first two-level power converter connected at an AC terminal thereof to one of the two sets of AC voltages, and connected at a DC terminal thereof to the first DC capacitor to execute voltage control, and a second two-level power converter connected at an AC terminal thereof to the other of the two sets of AC voltages, and connected at a DC terminal thereof to the second DC capacitor to execute DC voltage control.

3. The secondary magnetic excitation generator-motor device according to claim 1 , wherein a current bypass circuit is provided between a rotor-side excitation winding of the winding induction machine and the excitation current detector, and when any of absolute values of detected current values from the excitation current detector exceeds a set overcurrent level 3, the current bypass circuit is closed, and ignition commands for self-arc-extinguishing semiconductor elements of the three-level NPC power converter are all off, where a value of the set overcurrent level 3 is larger than that of the set overcurrent level 1.

4. The secondary magnetic excitation generator-motor device according to claim 1 , wherein a current bypass circuit is provided between a rotor-side excitation winding of the winding induction machine and the excitation current detector, and when a current absolute value for the third phase exceeds a set overcurrent level 4, the current bypass circuit is closed, and ignition commands for self-arc-extinguishing semiconductor elements of the three-level NPC power converter are all off, where a value of the set overcurrent level 4 is smaller than that of the set overcurrent level 1.

5. The secondary magnetic excitation generator-motor device according to claim 1 , wherein a first DC voltage sensor and a

Assignees

• Hitachi Mitsubishi Hydro Corporation
• Hitachi Ltd

Inventors

• Bando Akira
• Kawazoe Hironari
• Kikuchi Akira

Classifications

• H02M7/487 Primary

  Neutral point clamped inverters · CPC title

• H02K21/04

  Windings on magnets for additional excitation {; Windings and magnets for additional excitation} · CPC title

• H02M7/5395

  by pulse-width modulation · CPC title

• H02P9/007 Primary

  Control circuits for doubly fed generators · CPC title

• H02P9/38

  Self-excitation by current derived from rectification of both output voltage and output current of generator · CPC title