System and method of controlling power to a non-motor load

• US 7,932,693 B2
• Filed: 07/07/2005
• Issued: 04/26/2011
• Est. Priority Date: 07/07/2005
• Status: Active Grant

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Lee, Kevin, Ahlgren, Jyrki K., Doring, Thomas M., Wallace, Ian T.
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US11/176,820
• Publication Number:
  US 20070007929A1
• Time in Patent Office: 2,119 Days
• Field of Search: 318/139, 318/254, 318/439, 318/434, 318/800, 318/812, 318/727, 318/722, 318/801, 318/807, 318/805, 318/625, 318/569, 318/802, 318/701, 318/721, 363/40, 363/41, 363/131, 323/205, 388/811, 388/906
• US Class Current: 318/802
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 7/53875 with analogue control of three-phase output
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence
• CPC Class Codes: H02P 29/026 the fault being a power fluctuation

Abstract

A motor drive for conditioning power to be delivered to a non-motor load includes a voltage feedback circuit that monitors a DC bus voltage and, based on changes in the DC bus voltage, adjusts a power conditioning scheme such that near steady-state load conditions are maintained in response to a transient load condition. The voltage feedback circuit has a voltage sensor that provides voltage feedback to a controller that determines what changes in power conditioning are needed in response to a transient load condition that manifests itself in a change in DC bus voltage.

Claims

1. A motor drive comprising:

a power input;

a DC bus connected to the power input;

at least one switch connected to the DC bus;

a power output connectable to a load; and

a controller connected to the DC bus and configured to control switching of the at least one switch to maintain near steady-state at the load in response to changes in voltage at the DC bus.

2. The motor drive of claim 1 wherein the power output is connectable to a non-motor load.

3. The motor drive of claim 1 further comprising a rectifier configured to convert power received by the power input from AC to DC and supply DC power to the DC bus.

4. The motor drive of claim 1 further comprising a voltage sensor connected to measure voltage across the DC bus and provide voltage feedback to the controller.

5. The motor drive of claim 1 wherein the power input is configured to receive a 480VAC input.

6. The motor drive of claim 1 wherein the power output is connectable to a non-linear load.

7. The motor drive of claim 6 wherein the non-linear load includes a medical imaging device.

8. The motor drive of claim 1 wherein the controller is further configured to control switching of the at least switch to provide a load voltage regulation of ±

1% in steady-state with less than 3% total harmonic distortion and ±

0.1 Hz with fixed output frequency.

9. The motor drive of claim 1 wherein the controller includes a PID controller.

10. The motor drive of claim 1 wherein the at least one switch includes six IGBTs.

11. A power conditioner to supply conditioned power to a non-motor load, the power conditioner comprising:

a rectifier bridge to convert an AC power input to DC power and provide a DC bus voltage;

an inverter connected to receive the DC bus voltage;

a filter connected to the inverter to feed an output of the inverter to the non-motor load; and

a PID controller that receives feedback of the DC bus voltage and regulates the inverter to maintain near steady-state at the non-motor load in response to transient load conditions.

12. The power conditioner of claim 11 further comprising a step-up transformer connected to the filter and designed to step up a voltage of the modulated DC bus voltage and feed the stepped-up voltage to the non-motor load.

13. The power conditioner of claim 11 wherein the load is a non-linear load.

14. The power conditioner of claim 11 further comprising an RMS voltmeter designed to provide feedback to the PID controller regarding load voltage.

15. The power conditioner of claim 11 wherein the inverter includes a plurality of IGBTs and anti-parallel diodes.

16. The power conditioner of claim 11 wherein the PID controller is further configured to determine a transient load condition from changes in DC bus voltage.

17. The power conditioner of claim 11 further comprising a voltage sensor connected across a DC bus electrically present between the rectifier bridge and the switch array.

18. A method of regulating power to a load comprising the steps of:

detecting a change in voltage across a DC bus of a motor drive; and

dynamically controlling switching of a switch array of the motor drive in response to a detected change in voltage across the DC bus such that load voltage regulation is ±

1% in steady-state with less than 3% total harmonic distortion.

19. The method of claim 18 further comprising the step of monitoring DC bus voltage with a voltage sensor and detecting a change in DC bus voltage from feedback provided by the voltage sensor.

20. The method of claim 18 further comprising the step of detecting a transient load condition based on changes in DC bus voltage.

21. The method of claim 18 further comprising the step of dynamically controlling switching of the switch array with a PID controller.

22. The method of claim 18 wherein the motor drive is an ASD motor drive and the load is a non-linear load.

23. The method of claim 22 wherein the non-linear load is a medical imaging scanner.

24. The method of claim 23 wherein the medical imaging scanner is one of a CT scanner and an MR scanner.

25. The method of claim 18 further comprising the step of receiving feedback of load voltage from an RMS voltmeter.

26. A power conditioner comprising:

an adjustable speed drive (ASD) having an inverter configured to receive a DC bus voltage and deliver an output voltage;

a transformer configured to receive the output voltage of the inverter and provide a load voltage to a non-motor load;

a voltage sensor connected to sense the DC bus voltage and provide feedback thereof; and

a controller connected to control at least one switch of the inverter, the controller programmed to;

input the DC bus voltage feedback from the voltage sensor;

process the DC bus voltage feedback to provide a derivative term;

forecast changing load conditions from the derivative term; and

control the at least one switch of the inverter to maintain a near stead-state load condition.