Soft-start of DC link capacitors for power electronics and drive systems

• US 6,744,644 B2
• Filed: 02/13/2002
• Issued: 06/01/2004
• Est. Priority Date: 10/02/2001
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Kojori, Hassan A.
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US10/075,880
• Publication Number:
  US 20030063481A1
• Time in Patent Office: 839 Days
• Field of Search: 363/49, 363/48, 363/47, 363/45, 363/53, 323/908
• US Class Current: 363/49
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: Y10S 323/908 Inrush current limiters

Abstract

A soft-start system and method for use in the soft-start of DC links for capacitor banks are disclosed. The soft-start system (200) includes a capacitor (230) connected to a first bus (282) of a DC link (280). A resistor (210) is connected a second bus (284) of the DC link (280). The resistor (210) and capacitor (230) are connected in series. A switching device (220) is connected in parallel with the resistor (210). A triggering circuit (240) measures a DC voltage on the DC link (280) and activates the switching device (220) to short circuit the resistor (210). The method includes charging the capacitor (230) of the DC link (280), measuring the charge on the capacitor (280) and activating the switching device (220) thereby short circuiting the resistor (210) when the charge on the capacitor reaches a predetermined value.

Claims

1. A soft-start system for electrical power systems comprising:

a capacitor connected to a first bus of a DC link;

a resistor connected to a second bus of the DC link, wherein the resistor and capacitor are connected in series between the first and second bus;

a switching device co-packaged with a front-end rectifier in an Intelligent Power Module (IPM), the switching device being electrically connected in parallel with the resistor; and

a triggering circuit for measuring a DC voltage on the DC link and activating the switching device to short circuit the resistor.

2. The soft-start system of claim 1, wherein the front-end rectifier is configured to receive AC power from a source and converts the AC power into DC power in the DC link.

3. The soft-start system of claim 2, wherein the switching device is an Insulated Gate Bipolar Transistor (IGBT).

4. The soft-start system of claim 3, wherein the rectifier has a configuration including six IGBTs co-packaged with the switching device in the IPM.

5. The soft-start system of claim 1, wherein the switching device is an Insulated Gate Bipolar Transistor (IGBT).

6. The soft-start system of claim 1, wherein the capacitor is a capacitor bank.

7. The soft-start system of claim 1, wherein the resistor is one of a plurality of resistors in a resistor bank.

8. The soft-start system of claim 1, wherein the first DC bus and second DC bus are coupled to an inverter.

9. The soft-start system of claim 1, wherein the triggering circuit is powered from the DC link.

10. A method for soft-starting a DC link in an electrical power system, the method comprising:

charging a capacitor connected to a first bus of the DC link,

wherein a resistor is connected to a second bus of the DC link, and

wherein the resistor and capacitor are connected in series;

measuring the charge of the capacitor; and

activating a switching device according to hysteresis control of the charge on the capacitor, the switching device being configured to short circuit the resistor and conduct a current flowing through the capacitor, when activated.

11. The method of claim 10, wherein the activating step activates the switching device occurs when the charge on the capacitor decreases below a first threshold, and the switching devices is deactivated when the charge on the capacitor rises above a second threshold, as determined by hysteresis control, the first threshold being lower than the second threshold.

12. The method of claim 10, wherein the charge on the capacitor is measured by measuring at least one voltage across the resistor, current through the resistor, a voltage between the first and second bus and voltage across the capacitor.

13. The method of claim 10, wherein the switching device includes at least one of:

a Bipolar Junction Transistor (BJT), a Field Effect Transistor (FET), a Metal Oxide Semiconductor FET (MOSFET), a Silicon Controlled Rectifier (SCR), and a switching diode.

14. The method of claim 10, wherein the switching device is co-packaged with a front-end rectifier in an Intelligent Power Module (IPM), the front-end rectifier being operable to convert AC power to DC power and supply the DC power to the DC link.

15. The method of claim 14, wherein the switching device is an Insulated Gate Bipolar Transistor (IGBT).

16. The method of claim 14, wherein the rectifier has a configuration including six Insulated Gate Bipolar Transistors (IGBTs), and the switching device is an IGBT co-packaged with the IGBTs of the front-end rectifier in the IPM.

17. The method of claim 10, wherein a triggering circuit measures the DC voltage on the DC link and activates the switching device to short circuit the resistor, and wherein the triggering circuit is powered from the DC link.

18. The method of claim 10, wherein the resistor and capacitor are connected in series between the first and second buses of the DC link.

19. The method of claim 10, wherein the switching device is electrically connected in parallel with the resistor.

20. A soft-start circuit for an electrical power system that utilizes first and second buses of a DC link to charge a capacitor bank including one or more capacitors, comprising:

a resistor connected in series with a capacitor bank;

a switching device co-packaged with a front-end rectifier in an Intelligent Power Module (IPM), the switching device being electrically connected in parallel with said resistor; and

a triggering device configured to activate the switching device in response to a DC voltage applied to the DC link,

wherein the switching device is configured not to carry the full current load of the DC link after activation.

21. The soft-start circuit of claim 20, wherein the switching device is configured to conduct the current flowing through the capacitor bank in response to being activated.

22. The soft-start circuit of claim 20, wherein

the resistor and capacitor bank are electrically connected in series between the first and second buses.

23. The soft-start circuit of claim 20, wherein

the switching device is configured to short out the resistor in response to being activated, thereby causing the switching device to be operably connected in series with the capacitor bank.

24. The soft-start circuit of claim 20, wherein the switching device is configured so that it does not share a high voltage potential as the DC link.

25. The soft-start circuit of claim 20, wherein

the triggering device is configured to activate the switching device in response to the DC voltage exceeding a first level, and

the triggering device is configured to deactivate the switching device in response to the DC voltage decreasing below a second level, the first level being higher than the second level.

26. The soft-start circuit of claim 20, wherein the switching device comprises an Insulated Gate Bipolar Transistor (IGBT).

27. The soft-start circuit of claim 26, wherein the front-end rectifier has a configuration including a plurality of IGBTs co-packaged with the switching device in the IPM.

28. The soft-start circuit of claim 27, wherein the front-end rectifier is configured to convert AC power to DC power and supply the DC power to the DC link.