Active snubber

Patent metadata

Field	Value
Publication number	US-10044258-B2
Application number	US-201515519084-A
Country	US
Kind code	B2
Filing date	Nov 16, 2015
Priority date	Nov 21, 2014
Publication date	Aug 7, 2018
Grant date	Aug 7, 2018

Abstract

The present invention generally relates to a switching cell for a phase leg of a power converter and a method of controlling a power converter to drive a load, and more particularly to a plurality of such switching cells, a phase arm for a power converter, a power converter phase leg, to a power converter for driving a load, and methods of making a power converter. A switching cell for a phase leg of a power converter may comprise: a power switch for conducting a current for driving a load; a commutation path coupled in parallel with the power switch, the commutation path comprising a cell capacitor and an auxiliary switch coupled in series, the auxiliary switch configured to allow control of a conduction state of the commutation path; and a cell inductor coupled to a coupling of the power switch and the commutation path, wherein the switching cell comprises at least one control input line for receiving a control signal, the at least one control input line configured to drive a control terminal of the power switch and a control terminal of the auxiliary switch.

First claim

The invention claimed is:

1. Switching cells for phase legs of a power converter, the switching cells comprising:
a power switch for conducting a current for driving a load;
a series connection comprising an auxiliary switch and a cell capacitor coupled in series, the series connection coupled in parallel with the power switch;
a cell inductor coupled to a coupling of the power switch and the series connection; and
a commutation loop to conduct a commutation current arising from turn-off of the power switch, the loop comprising:
a first bypass circuit for blocking current flow in a first direction and coupled in parallel with the power switch to conduct the commutation current in another, direction opposite the first direction;
a second bypass circuit for blocking current flow in a second direction and coupled in parallel with the auxiliary switch to conduct the commutation current in a direction opposite the second direction; and
the cell capacitor;

at least one control input line for receiving a control signal and configured to drive a control terminal of the power switch and a control terminal of the auxiliary switch; and
a series connection of the switching cells, each switching cell of the series connection being coupled to an adjacent one of the switching cells by a respective one of cell inductors.

2. The switching cells of claim 1 , wherein at least one of the first and second bypass circuits comprises an extrinsic diode.

3. The switching cells of claim 1 , wherein the first and second bypass circuits comprise an intrinsic diode of the power switch as the first bypass circuit or an intrinsic diode of the auxiliary switch as the second bypass circuit.

4. The switching cells of claim 1 , further comprising a control terminal drive input line configured to simultaneously turn either the power switch or the auxiliary switch ON and the other of the power switch and the auxiliary switch OFF.

5. The switching cells of claim 1 , further comprising:
at least one switching cell coupled in parallel with one of the switching cells of the series connection of switching cells.

6. The switching cells of claim 1 , wherein at least one of the power switches comprises a wide band-gap semiconductor device.

7. The switching cells of claim 1 , wherein an auxiliary switch of at least one of the switching cells is physically smaller than the power switch of another switching cell.

8. The switching cells of claim 1 , wherein an auxiliary switch of at least one of the switching cells has lower power rating than the power switch of another switching cell.

9. The switching cells of claim 1 , wherein at least one of the power switches comprises an IGBT, MOSFET, HEMT, BJT, JFET, GTO or GCT.

10. The switching cells of claim 1 , wherein each of at least some of the switching cells comprises a vertical FET device or a lateral HEMT as the power switch.

11. The switching cells of claim 1 , wherein at least one of the switching cells has a resistor in parallel with the cell inductor of respective switching cell.

12. The switching cells of claim 1 , comprising:
a drive circuit for driving a control terminal of the power switch or a control terminal of the auxiliary switch of one of the switching cells, the drive circuit configured to draw power from the one of the switching cells.

13. A phase arm for the power converter, the phase arm comprising the plurality of switching cells of claim 1 .

14. A power converter phase leg having arms coupled together to provide an output signal for driving the load, at least one of the arms according to claim 13 .

15. The power converter for driving the load, the power converter comprising at least one power converter phase leg of claim 14 , each of the phase legs having an output line for driving a phase input of a respective load, the power converter further comprising a link capacitor, the at least one power converter phase leg and the link capacitor being coupled between a first power rail and a second power rail.

16. The power converter according to claim 14 , wherein the power converter is a multilevel converter.

17. A method of making the power converter, the method comprising the steps of:
obtaining a second power converter comprising a phase arm having at least one IGBT and replacing a phase arm with the phase arm according to claim 13 , at least one of the switching cells of the phase arm according to claim 13 having wide band-gap semiconductor device as the power switch of the switching cell.

18. A method of making the power converter, the method comprising the steps of:
obtaining a second power converter comprising a phase arm having a turn-on snubber and a GTO module, and
replacing the turn-on snubber and at least one GTO module with the phase arm according to claim 13 .

19. A method of controlling a power converter to drive a load, the power converter having a phase leg coupled between two power rails and comprising two arms each having a switching cells and coupled at an output of the power converter, wherein each of the switching cells comprises:
a respective power switch for conducting a current for driving the load;
a respective series connection comprising an auxiliary switch and a cell capacitor coupled in series, the series connection coupled in parallel with the power switch;
a respective cell inductor coupled to a coupling of the power switch and the series connection; and
a commutation loop to conduct a commutation current arising from turn-off of the power switch, the loop comprising:
a first bypass circuit for blocking current flow in a first direction and coupled in parallel with the power switch to conduct a commutation current in a second direction, opposite to the first direction;
a second bypass circuit for blocking current flow in the second direction and coupled in parallel with the auxiliary switch to conduct a commutation current in the first direction; and
the cell capacitor,

the method comprising at least one step of:
switching a first number of switching cells of one of the arms ON and a second number of the switching cells of the other of the arms OFF to advance a voltage profile at the output of the converter and maintain a voltage across the phase leg, switching the first number of switching cells ON by turning the power switch of the switching cell ON and the auxiliary switch of the switching cell OFF, the first and second numbers being one or more.

20. The method of claim 19 , wherein at least two of the switching cells of an arm of the two arms are coupled in parallel, the method comprising switching the switching cells coupled in parallel at different times.

21. The method of claim 19 , wherein each of the arms comprises an array having a number (NS) of rows and a number (NP) of columns of the switching cells, wherein the numbers NS and NP are one or more,
each of the columns comprises a series connection of the switching cells coupled between a respective one of the power rails and the converter output, and
the method comprises less than or equal to NS×NP steps to generate the voltage profile.

22. The method of claim 19 , wherein the voltage profile varies between a voltage of one of the power rails and a voltage of the other of the power rails.

23. The method of claim 19 , further comprising the step of:
determining a switching firing pattern of the switching cells according to a derivative (dv/dt) value of a voltage profile transition.

Assignees

• Reinhausen Maschf Scheubeck

Inventors

• Bryant Angus

Classifications

• H02M7/53871

  with automatic control of output voltage or current · CPC title

• H02M7/487

  Neutral point clamped inverters · CPC title

• H02M1/34 Primary

  Snubber circuits · CPC title

• H02M5/04

  by static converters (controlling transformers, reactors or choke coils, e.g. by tap changing H02P13/00) · CPC title

• H02M3/04

  by static converters · CPC title