Electric power control system and efficiency optimization process for polyphase synchronous machine

• US 9,143,076 B2
• Filed: 12/23/2013
• Issued: 09/22/2015
• Est. Priority Date: 04/04/2006
• Status: Expired due to Fees

• Current Assignee: Utilidata, Inc.
• Original Assignee: Utilidata, Inc.
• Inventors: Bell, David Gordon
• Primary Examiner(s): Paul, Antony M
• Application Number:
  US14/139,602
• Publication Number:
  US 20140184134A1
• Time in Patent Office: 638 Days
• Field of Search: 318/400.01, 318/400.02, 318/400.14, 318/400.15, 318/700, 318/701, 318/713, 318/727, 318/799, 318/430, 318/432, 323/205, 322/43, 324/141, 388/800, 388/821
• US Class Current: 1/1
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks
• CPC Class Codes: H02P 2205/03 Power loop, i.e. comparison of the motor power with a power reference
• CPC Class Codes: H02P 2207/05 Synchronous machines, e.g. with permanent magnets or DC excitation
• CPC Class Codes: H02P 23/0004 Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control
• CPC Class Codes: H02P 25/024 controlled by supply frequency
• CPC Class Codes: Y02B 70/3225 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y04S 20/222 Demand response systems, e.g. load shedding, peak shaving

Abstract

A system and process includes continuously determining an applied armature voltage supplied to a polyphase synchronous machine for which a maximum mechanical load is characterized by a pull-out torque. The armature voltage is supplied from a power source via one of many taps of a regulating transformer. The armature voltage being supplied from the power source to the machine is changed by selecting one of the voltage levels from the taps of the regulating transformer. The tap voltage levels are selected based on the determined applied armature voltage to minimize power consumption of the machine while ensuring based on a predetermined confidence level that the pullout torque of the machine will not be exceeded.

Claims

1. A method comprising:

determining an applied armature voltage supplied to a polyphase synchronous machine having a pull-out torque, the armature voltage supplied from a power source via one of a plurality of taps of a regulating transformer, a first tap of the plurality of taps configured to supply a voltage at a different level than a second tap of the plurality of taps;

selecting the second tap to supply the armature voltage based on the determined applied armature voltage, power consumption of the machine, and a confidence level that the pull-out torque is not exceeded, wherein the confidence level corresponds to a probability distribution indicative of at least one operating characteristic of the polyphase synchronous machine; and

responsive to a slip of the polyphase synchronous machine, increasing a margin of the pull-out torque.

2. The method of claim 1, further comprising:

continuously determining the applied armature voltage supplied to the polyphase synchronous machine.

3. The method of claim 1, wherein the selected confidence level is applied to a statistic of the time varying mechanical load applied to the polyphase synchronous machine.

4. The method of claim 1, further comprising:

determining a slip of the polyphase synchronous machine.

5. The method of claim 1, further comprising:

determining a mechanical torque demand; and

comparing the mechanical torque demand against a predetermined torque.

6. The method of claim 5, further comprising:

determining an optimum armature voltage level corresponding to the predetermined torque.

7. The method of claim 5, wherein determining the mechanical torque demand is based on a measurement of the machine actual load.

8. The method of claim 7, further comprising:

determining the maximum mechanical torque demand in real time.

9. The method of claim 1, further comprising:

setting the armature voltage to be supplied to the machine to cause the pull-out torque of the machine to be greater than a maximum mechanical torque demand.

10. The method of claim 1, further comprising:

specifying a margin of the pull-out torque with an upper and a lower bound to decrease a frequency of armature voltage changes.

11. The method of claim 1, wherein the selecting the second tap comprises:

determining a suitably smooth estimate of the mechanical load torque using a real power demand signal observed at armature terminals of the polyphase synchronous machine;

determining a pull-out torque of the machine using physical parameters of the polyphase synchronous machine, a real and reactive power observed at the armature terminals, and the applied armature voltage; and

comparing a difference in the mechanical load torque and the pull-out torque against a pre-defined margin boundary.

12. A method comprising:

receiving, by a voltage signal processor, an indication of an armature voltage, real power and reactive power monitored at an armature of a synchronous machine;

determining a characteristic of the synchronous machine based on the received indication, the characteristic comprising a maximum mechanical torque demand; and

adjusting, based on the determined characteristic and a confidence level that a pull-out torque of the synchronous machine will not be exceeded, the armature voltage supplied to the synchronous machine.

13. The method of claim 12, wherein the characteristic comprises a slip of the synchronous machine.

14. The method of claim 13, further comprising:

responsive to determining the slip of the synchronous machine, increasing a margin of a pull-out torque.

15. The method of claim 12, further comprising:

specifying a margin of the pull-out torque with an upper and a lower bound to decrease a frequency of armature voltage changes.

16. The method of claim 12, further comprising:

determining a suitably smooth estimate of a mechanical load torque using a real power demand signal monitored at the armature of the synchronous machine;

determining an estimated pull-out torque of the machine using physical parameters of the synchronous machine, the real and reactive power monitored at the armature, and the applied armature voltage; and

comparing a difference in the estimate of the mechanical load torque and the estimated pull-out torque against a pre-defined margin boundary.

17. The method of claim 12, further comprising:

adjusting the armature voltage to be supplied to the machine to cause a pull-out torque of the machine is greater than a maximum mechanical torque demand.

18. The method of claim 12, wherein adjusting the armature voltage further comprises:

selecting a first tap of a regulating transformer supplying power from a power source.

19. The method of claim 18, further comprising:

selecting a second tap of the regulating transformer, the second tap configured to supply voltage at a different level than the first tap.

20. The method of claim 12, further comprising:

determining the characteristic based on a measurement of the machine actual mechanical load torque.