Method and system for local load control

• US 7,778,737 B2
• Filed: 09/06/2006
• Issued: 08/17/2010
• Est. Priority Date: 09/07/2005
• Status: Active Grant

• Current Assignee: Itron, Inc.
• Original Assignee: Comverge Incorporated (Itron, Inc.)
• Inventors: Ng, Howard, Rossi, John F.
• Primary Examiner(s): Masinick; Michael D
• Application Number:
  US11/470,549
• Publication Number:
  US 20070129851A1
• Time in Patent Office: 1,441 Days
• Field of Search: 700/276, 700/278, 700/286, 700/295
• US Class Current: 700/295
• CPC Class Codes: H02J 2310/60 Limiting power consumption in the network or in one section of the network, e.g. load shedding or peak shaving
• CPC Class Codes: H02J 3/14 by switching loads on to, or off from, network, e.g. progressively balanced loading
• 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 method and system for shedding loads based upon a power system characteristic, such as voltage or frequency, is provided. In one embodiment, a remote party, such as a power generator or utility, transmits a signal to a control device proximately located with a load device. Upon receipt of the signal, the control device measures the power system characteristic for a predetermined time to establish a baseline threshold. The control device then monitors the power system characteristic. When the power system characteristic falls outside the baseline threshold, the control device sheds load. In one embodiment, the loads are prioritized such that the load of least importance may be shed first.

Claims

1. A method of controlling a local electrical load across a power distribution grid, the method comprising the steps of:

a. receiving a one-way communication signal from a remote source having measurement indicia therein, the one-way communication signal being generated when line losses of the power distribution grid exceed a predetermined line loss threshold, the measurement indicia comprising an indication to begin a base-line measurement of line voltage;

b. in response receiving to the one-way communication signal, performing a base-line measurement by measuring the line voltage for at least a predetermined time;

c. averaging the line voltage across the at least a predetermined time to obtain an average base-line measurement;

d. retrieving a differential factor from a local memory, wherein the differential factor is received from the remote source by a communication signal;

e. reducing the average base-line measurement by the differential factor to obtain a threshold value;

f. monitoring the line voltage; and

g. upon the line voltage falling below the threshold value, shedding at least one local electrical load.

2. The method of claim 1, wherein the differential factor is at least 0.5 volts.

3. The method of claim 1, wherein the predetermined time is at least 0.1 seconds.

4. The method of claim 1, wherein the receiving the one-way communication signal occurs when another system operating conditions exceed a predetermined threshold of at least one predetermined criterion.

5. The method of claim 4, wherein the at least one predetermined criterion comprises load demand of an electrical distribution network coupled to the local electrical load.

6. The method of claim 4, wherein the at least one predetermined criterion comprises ambient temperature.

7. The method of claim 1, wherein the step of reducing the average base-line measurement by the differential factor comprises multiplying the average base-line measurement by the differential factor.

8. The method of claim 1, wherein the step of reducing the average base-line measurement by the differential factor comprises subtracting the differential factor from the average base-line measurement.

9. The method of claim 1, wherein the step of performing a base-line measurement by measuring the line voltage for at least the predetermined time occurs proximately with the electrical load.

10. The method of claim 1, wherein the step of performing the base-line measurement by measuring the line voltage for at least the predetermined time comprises taking at least five measurements of the line voltage.

11. The method of claim 1, wherein the step of shedding the at least one local electrical load comprises determining a prioritization of a plurality of loads, and removing a load having a highest priority from service.

12. The method of claim 1, further comprising the steps of:

a. monitoring again the line voltage; and

b. actuating the at least one electrical load when the line voltage exceeds the threshold value by at least a predetermined restart value.

13. The method of claim 1, further comprising the steps of:

a. monitoring again the line voltage; and

b. actuating the at least one electrical load when the line voltage exceeds the threshold value for at least a predetermined restart time.

14. A load controlling device disposed proximately with an electrical load, the load controlling device comprising:

a. a receiver in communication with an electrical services provider across a distribution grid;

b. a controller coupled to the transceiver;

c. a memory coupled to the controller;

d. a power system characteristic measurement module operable with the controller, the power system characteristic measurement module being configured to establish an averaged base-line measurement of a power system characteristic in response to the receiver receiving a communication signal from the electrical services provider having measurement indicia therein, wherein the power system characteristic comprises voltage, the one-way communication signal being generated when line losses of the power distribution grid exceed a predetermined line loss threshold;

e. a threshold module operable with the controller, the threshold module being configured to determine a threshold value by retrieving a differential factor from the memory, wherein the differential factor is received from the remote source by a communication signal, and reducing the averaged base-line measurement by the differential factor;

f. a comparator coupled to the controller, the comparator being configured to monitor the power system characteristic and determine when the power system characteristic falls below the threshold value; and

g. a load shedding module operable with the comparator, the load shedding module being configured to decouple power to at least one electrical load when the comparator indicates that the power system characteristic falls below the threshold value.

15. The load controlling device of claim 14, further comprising a restart module operable with the comparator, the restart module being configured to recouple power to the at least one electrical load when the comparator indicates that the power system characteristic exceeds the threshold value one of by at least a predetermined amount and for at least a predetermined time.

16. A system for controlling power delivery to an electrical load, the system comprising:

a. a power distribution grid having multiple nodes;

b. an electrical services provider coupled to a first node of the power distribution grid, the electrical services provider being capable of generating a one-way communication signal having measurement indicia therein;

c. at least one electrical load coupled to a second node of the power distribution grid; and

d. a load controlling device coupled to the second node of the power distribution grid, the load controlling device comprising;

i. a receiver in communication with an electrical services provider;

ii. a controller coupled to the transceiver;

iii. a memory coupled to the controller;

iv. a power system characteristic measurement module operable with the controller, the power system characteristic measurement module being configured to establish an averaged base-line measurement of a power system characteristic in response to the receiver receiving a communication signal from the electrical services provider having measurement indicia therein, wherein the power system characteristic comprises voltage;

v. a threshold module operable with the controller, the threshold module being configured to determine a threshold value by retrieving a differential factor from the memory, wherein the differential factor is received from the remote source by a communication signal, and reducing the averaged base-line measurement by the differential factor;

vi. a comparator coupled to the controller, the comparator being configured to monitor the power system characteristic and determine when the power system characteristic falls below the threshold value; and

vii. a load shedding module operable with the comparator, the load shedding module being configured to decouple power to at least one electrical load when the comparator indicates that the power system characteristic falls below the threshold value;

e. wherein the electrical services provider generates the one-way communication signal based upon losses at load of the power distribution grid exceeding a predetermined load loss threshold.