Semiconductor switching circuit

Patent metadata

Field	Value
Publication number	US-2016156344-A1
Application number	US-201414898098-A
Country	US
Kind code	A1
Filing date	Jun 10, 2014
Priority date	Jun 14, 2013
Publication date	Jun 2, 2016
Grant date	—

Abstract

A semiconductor switching circuit includes a main current branch which includes at least one main semiconductor switching element and through which current flows in a first direction when the or each main semiconductor switching element is switched on. The semiconductor switching circuit also includes an auxiliary current branch that is connected in parallel with the main current branch. The auxiliary current branch includes at least one auxiliary semiconductor switching element. One or more control units are configured to switch on the or each auxiliary semiconductor switching element as the or each main semiconductor switching element is switched on to selectively create an alternative current path via the auxiliary current branch whereby current flowing in the first direction through the main current branch is diverted instead to flow through the alternative current path to reduce the rate of change of current flowing through the or each main semiconductor switching element.

First claim

1 . A semiconductor switching circuit, for use in a HVDC power converter, comprising:
a main current branch including at least one main semiconductor switching element and through which current flows in a first direction when the or each main semiconductor switching element is switched on; and an auxiliary current branch connected in parallel with the main current branch and the or each main semiconductor switching element included therein, the auxiliary current branch including at least one auxiliary semiconductor switching element, the or each auxiliary semiconductor switching element having a control unit operatively connected therewith, the or each control unit being configured to switch on the or each auxiliary semiconductor switching element in the auxiliary current branch as the or each main semiconductor switching element is switched on to selectively create an alternative current path via the auxiliary current branch whereby stray capacitance discharge current flowing in the first direction through the main current branch is diverted to flow through the alternative current path to reduce the rate of change of discharge current flowing through the or each main semiconductor switching element when the or each said main semiconductor switching element is first switched on and exposed to a large change in current.

2 . A semiconductor switching circuit according to claim 1 wherein the or each control unit is configured to switch on the or each auxiliary semiconductor switching element in response to generation of a turn-on signal for the or each main semiconductor switching element.

3 . A semiconductor switching circuit according to claim 1 wherein the or each control unit is configured subsequently to switch the or each auxiliary semiconductor switching element off to control the amount of current diverted to flow through the alternative current path.

4 . A semiconductor switching circuit according to claim 1 wherein the or each auxiliary semiconductor switching element is or includes a transistor.

5 . A semiconductor switching circuit according to claim 1 wherein the or each auxiliary switching element is or includes a thyristor.

6 . A semiconductor switching circuit according to claim 1 wherein the auxiliary current branch includes a current limiting element connected in series with the or each auxiliary semiconductor switching element.

7 . A semiconductor switching circuit according to claim 1 wherein the or each control unit is configured to switch on the or each auxiliary semiconductor switching element to selectively create an alternative current path via the auxiliary current branch whereby current flowing in the first direction through the main current branch is diverted to flow through the alternative current path to reduce the rate of change of voltage appearing across the or each main semiconductor switching element.

8 . A semiconductor switching circuit according to claim 7 wherein the or each control unit is configured to switch on the or each auxiliary semiconductor switching element when the rate of change of voltage appearing across one or more main semiconductor switching elements exceeds a predetermined threshold to reduce the rate of change of voltage appearing across the or each main semiconductor switching element.

9 . A semiconductor switching circuit according to claim 1 wherein the or each control unit is configured to switch on the or each auxiliary semiconductor switching element in the auxiliary current branch at the same time as the or each main semiconductor switching element is switched on.

10 . A semiconductor switching circuit according to claim 1 wherein the or each control unit is configured to switch on the or each main semiconductor switching element in the auxiliary current branch just before the or each main semiconductor switching element is switched on.

11 . A semiconductor switching circuit according to claim 1 wherein the main current branch includes a single main semiconductor switching element having first and second connection terminals and the auxiliary current branch is connected between the first and second connection terminals whereby the main and auxiliary current branches together define a semiconductor switching assembly.

12 . A semiconductor switching circuit according to claim 11 wherein the auxiliary current branch includes a single auxiliary semiconductor switching element.

13 . A semiconductor switching circuit according to claim 11 wherein the auxiliary current branch includes a plurality of series-connected auxiliary semiconductor switching elements.

14 . A semiconductor switching circuit according to claim 1 wherein the main current branch includes a main string of series-connected main semiconductor switching elements, the main string having an upstream connection terminal at an upstream end thereof and a downstream connection terminal at a downstream end thereof, the auxiliary current branch is connected between the upstream and downstream connection terminals of the main string, and the auxiliary current branch includes an auxiliary string of series-connected auxiliary semiconductor switching elements.

15 . A semiconductor switching string, for use in a HVDC power converter, comprising:
a plurality of series-connected semiconductor switching assemblies, each of the plurality of series-connected semiconductor switching assemblies comprising:
a main current branch including at least one main semiconductor switching element and through which current flows in a first direction when the or each main semiconductor switching element is switched on and
an auxiliary current branch connected in parallel with the main current branch and the or each main semiconductor switching element included therein, the auxiliary current branch including at least one auxiliary semiconductor switching element, the or each auxiliary semiconductor switching element having a control unit operatively connected therewith, the or each control unit being configured to switch on the or each auxiliary semiconductor switching element in the auxiliary current branch as the or each main semiconductor switching element is switched on to selectively create an alternative current path via the auxiliary current branch whereby stray capacitance discharge current flowing in the first direction through the main current branch is diverted to flow through the alternative current path to reduce the rate of change of discharge current flowing through the or each main semiconductor switching element when the or each said main semiconductor switching element is first switched on and exposed to a large change in current
wherein, for each of the plurality of series-connected semiconductor switching assemblies, the main current branch includes a single main semiconductor switching element having first and second connection terminals and the auxiliary current branch is connected between the first and second connection terminals whereby the main and auxiliary current branches together define a semiconductor switching assembly.

16 . A semiconductor switching string according to claim 11 wherein, for each of the plurality of series-connected semiconductor switching assemblies, the auxiliary current branch includes a single auxiliary semiconductor switching element.

17 . A semiconductor switching string according to claim 11 wherein, for each of the plurality of series-connected semiconductor switching assemblies, the auxiliary current branch includes a plurality of series-connected auxiliary semiconductor switching elements.

Assignees

• Alstom Technology Ltd
• Gen Electric Technology Gmbh

Inventors

• Davidson Colin Charnock

Classifications

• H03K17/16

  Modifications for eliminating interference voltages or currents · CPC title

• H03K17/687

  the devices being field-effect transistors · CPC title

• H03K17/161 Primary

  in field-effect transistor switches · CPC title

• H03K17/66

  Switching arrangements for passing the current in either direction at will; Switching arrangements for reversing the current at will · CPC title

• H02M7/68

  by static converters · CPC title