Microcomputer controlled power regulator system and method

• US 4,695,737 A
• Filed: 03/19/1986
• Issued: 09/22/1987
• Est. Priority Date: 03/19/1986
• Status: Expired due to Fees

• Current Assignee: Southern California Edison Company (Edison International)
• Original Assignee: Southern California Edison Company (Edison International)
• Inventors: Rabon, Joe D., Haro, Rudy
• Primary Examiner(s): BEHA JR, WILLIAM
• Application Number:
  US06/841,317
• Time in Patent Office: 552 Days
• Field of Search: 323/256, 323/257, 323/260, 323/264, 307/17, 307/31, 307/147, 364/493
• US Class Current: 307/31
• CPC Class Codes: G05F 1/468 characterised by reference voltage circuitry, e.g. soft start, remote shutdown
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks

Abstract

A load-compensating power distribution regulator system includes a plurality of circuit regulators interfaced to a single microcomputer, the microcomputer sensing for each circuit a regulator voltage and an output current. The microcomputer compares a computer line-drop compensated actual circuit voltage with a dynamically determined desired circuit voltage using a variably offset deadband for controlling regulator action depending on whether the output current is changing favorably for bringing the actual circuit voltage toward the desired circuit voltage. The number of regulator actions in a time period is also monitored for adjusting the magnitude of the deadband to limit wear-and-tear of the regulator.

Claims

1. A method for operating an A.C. power distribution substation for centralized control of a plurality of distribution circuits, each circuit having regulator means and associated control means for connecting a common voltage to first and second sides of drive means for selectively raising and lowering a regulator voltage of the circuit, the method comprising the steps of:

(b) sensing the regulator voltage;

(c) sensing an output current of the regulator means;

(d) repetitively producing digital voltage and current data corresponding to the sensed regulator voltage and output current;

(e) determining, based on the voltage and current data, and actual circuit voltage and a change in the output current;

(f) detecting whether the actual circuit voltage is within a deadband about a desired circuit voltage, the deadband being variably offset with respect to the desired circuit voltage in response to the change in the output current for selectively producing a raise command and a lower command; and

(g) selectively driving the first and second sides of the drive means to the common voltage in response to the raise command and the lower command for regulating the actual circuit voltage at approximately the desired circuit voltage.

2. A method for controlling an A.C. power distribution substation for centralized control of a plurality of distribution circuits, each circuit having regulator means and associated control means for connecting a common voltage to first and second sides of drive means for selectively raising and lowering a regulator voltage of the circuit, the method comprising the steps of:

(a) sensing the regulator voltage of the regulator means;

(b) sensing an output current of the regulator means;

feeding the sensed voltage and current to a digital computer for repetitively producing in the computer digital voltage and current data corresponding to the sensed regulator voltage and output current;

(d) determining, based on the voltage and current data, an actual circuit voltage and a change in the output current;

(e) detecting whether the actual circuit voltage is within a predetermined deadband about a desired circuit voltage, the deadband being variably offset with respect to the desired circuit voltage in response to the change in the output current for selectively producing a raise command and a lower command; and

first

(f) selectively connecting the first and second sides of the drive means to the common voltage in response to the raise command and the for regulating the actual circuit voltage at approximately the desired circuit voltage.

3. A load compensating power regulator system for a plurality of A.C. power distribution circuits, each circuit being connected to a source of power at a source voltage, each circuit having a feedpoint and a customer point located thereon, the regulator comprising:

(a) regulator means connected between the source and the circuit for varying a regulator voltage of the circuit;

(b) control means for the regulator means for changing the regulator voltage in response to a control signal;

(c) means for sensing the regulator voltage;

(d) means for sensing an output current of the regulator means;

(e) means for sensing a phase relationship between the regulator voltage and the output current;

(f) a digital computer;

(g) interface means for repetitively producing in the computer digital voltage, current, and phase data corresponding respectively to the sensed regulator voltage, output current, and phase relationship;

(h) means in the computer for calculating a desired feedpoint voltage at the feedpoint as a function of the digital regualtor voltage, output current, and phase data;

(i) means in the computer for referencing digital deadband data with respect to the desired feedpoint voltage; and

(j) means for generating the control signal for the control means for changing the output voltage for conforming the output voltage with the desired feedpoint voltage when the output voltage corresponds to a voltage outside of the deadband.

4. The system of claim 3 further comprising means in the computer for determining, based upon the digital output current data, changes in the output current.

5. The system of claim 4 wherein the regulator means include at least a first regulator having a slow response characteristic and a second regulator having a fast response characteristic, the detecting means being programmed for selectively overdriving the first regualtor for avoiding unnecessary regulation activity when the change in the output current is in a direction tending to move the actual circuit voltage away from the desired circuit voltage, the detecting means being programmed for selectively underdriving the second regulator when the change in the output current is in a direction tending to move the actual circuit voltage toward the desired circuit voltage.

6. The system of claim 4 wherein the regulator means include at least a first regulator having a slow response characteristic and a second regulator having a fast response characteristic, the generating means being programmed for continuously generating for the first regulator the control signals for up to a predetermined period of time, the generating means being programmed for pulsing for the second regulator the control signal for up to the predetermined period of time.

7. The system of claim 3 wherein the digital computer comprises a microprocessor and at least five of the regulator means are controlled by the microprocessor.

8. The system of claim 7 in which the microprocessor is capable of controlling up to ten of the regulator means.

9. The system of claim 7 wherein the interface means, the calculating means, and the generating means cooperate in a repetitive control cycle, the control cycle operating in a high-level interpretive program language wherein successive program elements are interpreted by the microprocessor and translated into directly executable instruction codes as the cycle progresses.

10. The system of claim 9 wherein the microprocessor is allocated up to about 30 seconds of time for each of the circuits for completing a single control cycle of all of the circuits.

11. A load compensating power regulator system for at least one A.C. power distribution circuit, the circuit being connected to the source of power at a source voltage, the circuit having a feedpoint and a customer point located thereon, the system comprising:

(a) regulator means connected between the source and the circuit for varying a regulator voltage of the circuit;

(b) control means for the regulator means for changing the regulator voltage in response to a control signal;

(c) means for sensing the regulator voltage;

(d) means for sensing an output current of the regulator means;

(e) a digital computer;

(f) interface means for repetitively producing in the computer digital voltage and current data corresponding respectively to the sensed regulator voltage and output current;

(g) means in the computer for determining, based on the digital voltage and current data, an actual circuit voltage;

(h) means in the computer for determining, based upon the digital current data, a change in the output current;

(i) means in the computer for detecting whether the actual circuit voltage is within a deadband about a desired circuit voltage, the deadband being variably offset with respect to the desired circuit voltage in response to the change in the output current; and

(j) means for generating the control signal for conforming the actual circuit voltage with the desired circuit voltage in response to the detecting means.

12. The system of claim 11 wherein the detecting means comprises:

(a) first comparison means for testing whether the desired circuit voltage reduced by the actual circuit voltage and multiplied by a function of the change in the output current is greater than a deadband value; and

(b) second comparison means for testing whether the desired circuit voltage reduced by the actual circuit voltage and multiplied by the function of output current change is less than a factor of the deadband value, the factor being greater than unity for increasing the deadband in a direction for avoiding regulator voltage changes when the change in output current is in a direction tending to change the actual circuit voltage toward the desired voltage.

13. The system of claim 12 wherein the function of the change in the output current is a constant, the constant having a polarity corresponding to the direction of the change.

14. The system of claim 11 further comprising:

(a) means for calculating a desired feedpoint voltage at the feedpoint as a function of a desired voltage at the customer point and the digital output current data; and

(b) means for calculating an actual feedpoint voltage at the feedpoint as a function of the digital regulator voltage and output current data,

wherein the circuit voltage is the feedpoint voltage.

16. The system of claim 11 further comprising:

(a) means for periodically accumulating a total number of regulator actions in response to the detecting means; and

(b) means for adjusting the deadband in response to the total number of actions.

17. The system of claim 16 including means for periodically comparing the total number of actions during the period with a desired range of the number, whereby the deadband is incremented when the total number of actions is less than the desired range, and the deadband is decremented when the total number of actions is greater than the desired range, the deadband being confined between a maximum deadband and a minimum deadband.

18. The system of claim 11 in which the means for determining a change in the output current maintains a moving average of the current data, and a filtered average of the moving average, periodically comparing the moving average with the filtered average.

19. The system of claim 11 in which the generating means includes means for repeatably measuring the regulator voltage and terminating the control signal after a predetermined change in the measured regulator voltage.

15. The system of claim further comprising means for sensing a phase relationship between the regulator voltage and the output current, wherein the interface means includes means for repetitively producing in the computer digital phase data corresponding to the sensed phase relationship, and the means for calculating the actual and desired feedpoint voltages include means for determining a power factor corresponding to the phase data.

20. A load compensating power regulator system for a plurality of A.C. power distribution circuits, each circuit being connected to a source of power at a source voltage, each circuit having a feedpoint and a customer point located thereon, the system comprising:

(a) regulator means connected between the source and the circuit for varying a regulator voltage of the circuit;

(b) control means for the regulator means for changing the regulator voltage in response to a control signal;

(c) means for sensing the regulator voltage;

(d) means for sensing an output current of the regulator means;

(e) means for sensing a phase relationship between the regulator voltage and the output current;

(f) a digital computer;

(g) interface means for repetitively producing in the computer digital voltage, current, and phase data corresponding respectively to the sensed regulator voltage, output current, and phase relationship;

(h) means in the computer for calculating a desired feedpoint voltage at the feedpoint as a function of the digital regulator voltage, output current, and phase data;

(i) means in the computer for referencing digital deadband data with respect to the desired feedpoint voltage;

(j) means in the computer for determining, based upon the digital output current data, changes in the output current;

(k) means in the computer for offsetting the digital deadband data with respect to the desired feedpoint voltage in response to the changes in the output current; and

(l) means for generating the control signal for the control means for changing the output voltage for conforming the output voltage with the desired feedpoint voltage when the output voltage corresponds to a voltage outside of the deadband.

21. The system of claim 20 wherein the digital computer is programmed for performing predetermined steps comprising the steps of FIG. 5.

22. The system of claim 20 wherein the regulator means include at least a first regulator having a slow response characteristic and a second regulator having a fast response characteristic, the detecting means being programmed for selectively overdriving the first regulator for avoiding unnecessary regulation activity when the change in the output current is in a direction tending to move the actual circuit voltage away from the desired circuit voltage, the detecting means being programmed for selectively underdriving the second regulator when the change in the output current is in a direction tending to move the actual circuit voltage toward the desired circuit voltage.

23. The system of claim 20 wherein the regulator means include at least a first regulator having a slow response characteristic and a second regulator having a fast response characteristic, the generating means being programmed for continuously generating for the first regulator the control signal for up to a predetermined period of time, the generating means being programmed for pulsing for the second regulator the control signal for up to the predetermined period of time.

24. The system of claim 20 wherein the digital computer comprises a microprocessor and at least five of the regulator means are controlled by the microprocessor.

25. The system of claim 24 in which the microprocessor is capable of controlling up to ten of the regulator means.