METHOD FOR LOAD CONTROL USING TEMPORAL MEASUREMENTS OF ENERGY FOR INDIVIDUAL PIECES OF EQUIPMENT

• US 20100070103A1
• Filed: 09/11/2009
• Published: 03/18/2010
• Est. Priority Date: 09/15/2008
• Status: Active Grant

• Current Assignee: Aclara Technologies LLC (Hubbell, Inc.)
• Original Assignee: Aclara Power-Line Systems Incorporated (Hubbell, Inc.)
• Inventors: Kobeszka, Edward, Virkus, Mark, Fleck, Christopher K.
• Granted Patent: US 8,433,452 B2
• Time in Patent Office: Days
• US Class Current: 700/296
• CPC Class Codes: H02J 2310/54 according to a pre-established time schedule
• 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 for load control in an electrical distribution system using energy usage profiles based on temporal measurements. A load control unit (10) installed at a customer site profiles equipment (E1-En) directly connected to the load control unit and remotely located equipment (RE1-REn) wirelessly connected to the load control unit using measurements of time rather than energy usage. This reduces the cost and complexity of the load control unit. Profiling is done for individual pieces of load controlled equipment rather than for the site as a whole. This improves data resolution. The load control unit controls the load only when the equipment is powered, and adaptively synchronizes load shedding during this time, so to improve local load control performance. Termination of a load control event results in gradual reduction in load shedding so to control the inrush of demand seen by the distribution system. Performance metrics related to the load control are provided to the utility such that complexity of the system is reduced through decreased computations.

Claims

1. In an electrical distribution system by which a utility supplies electricity to one or more pieces of equipment at each utility'"'"'s customer'"'"'s location, each piece of equipment placing an electrical load on the system when it is operating, a method of shedding electrical load placed on the system comprising:

connecting at least one piece of equipment at a location to a load control apparatus;

profiling by the load control apparatus, on a temporal basis, the electricity usage of the piece of equipment, said profiling being characterized not by the amount of energy consumed by the piece of equipment during a defined interval of time, but rather by the duration of time during successive predetermined intervals of time the piece of equipment was energized or de-energized; and

,

when a load control event occurs in which load on the system must be shed, shedding load by the load control apparatus as a function of the profile created for the piece of equipment thereby to prevent system instability or overload, and to control operating costs of the system.

2. The method of claim 1 in which the profiling includes determining the amount of time during a predetermined time interval each piece of equipment uses electricity so to produce a separate energization profile for each piece of load controlled equipment, the amount of load shed by the piece of equipment during a load control event being based upon the energization profile for the piece of equipment for the time of the event, and in response to a command from the load control apparatus.

3. The method of claim 2 in which each energization profile includes cycling of the respective piece of equipment “

on” and

“

off”

during the predetermined time intervals, and all of the energization profiles together representing the aggregate usage of electricity by all the pieces of load controlled equipment at any time within the interval.

4. The method of claim 1 in which profiling by the load control apparatus includes sensing when electricity is being supplied to a piece of equipment and providing an indication thereof to the load control apparatus.

5. The method of claim 4 in which equipment is estimated during the period of a power outage so that the equipment'"'"'s energization profile is updated even without sensing of the equipment'"'"'s power usage.

6. The method of claim 2 including periodically updating the piece of equipment'"'"'s energization profile once it has been produced.

7. The method of claim 6 in which the piece of equipment'"'"'s energization profile is continuously updated.

8. The method of claim 6 in which the energization profile is updated upon a change in parameters affecting load energization including, but not limited to replacement of the piece of equipment, a change in the customer using the equipment, or a change in the season.

9. The method of claim 8 further including adjusting the energization profile as a function of changes in system time.

10. The method of claim 2 in which if the load control event extends across more than one interval within the time period over which the energization profile is established, the amount of energy shed by the piece of equipment will differ if the profile indicates that the energization of the piece of equipment varies from the current interval to a succeeding interval.

11. The method of claim 10 in which the time that load control cycling for load controlled pieces of equipment occurs is delayed so to extend the time when shedding occurs across the boundaries of time intervals.

12. The method of claim 1 in which the method further includes selectively controlling each piece of load controlled equipment to stagger the shedding of load by the equipment at the beginning of a load control event and to stagger the restoring of the equipment load at the end of the event thereby facilitating a smooth transition into and out of load control during the event.

13. The method of claim 10 in which the shedding of load is further a function of when a load controlled piece of equipment is powered during the load control event.

14. The method of claim 13 further including dynamically modifying the pattern of load control as a function of when the piece of equipment is to be powered so to take into account any short cycle limits for the piece of equipment.

15. The method of claim 13 further shedding load by the piece of equipment as a function of short cycle limits for the piece of equipment, wherein the short cycle limits define a minimum run time and a minimum shed time for the piece of equipment so to protect the equipment if its operation requires an equalization of operational characteristics which, if not equalized, would result in damage to the equipment.

16. The method of claim 1 further including restoring load to the system when a load control event terminates, restoring of the load for each piece of load controlled equipment being in accordance with the energization profile for that piece of equipment.

17. The method of claim 16 in which restoring load to the system is controlled so to gradually reduce the amount of shed load over a predetermined time period, or number of load cycles, whereby as the pieces of load controlled equipment are fully brought back online, the electrical distribution system does not experience a spike in demand such as would initiate another load controlled event.

18. The method of claim 16 in which the load is brought back online by extending the period of control for each piece of load controlled equipment in accordance with the energization profile for that piece of equipment, the period being separately chosen for each piece of equipment, thereby to diversify the time for re-establishing the load.

19. The method of claim 17 further including cancelling a load control event and bringing the load back online in the controlled manner so to gradually reduce the amount of shed load over a predetermined time period, or number of load cycles,

20. The method of claim 19 in which, if the load control event is cancelled, the load is brought back online by extending the period of control for each piece of load controlled equipment, the period being separately chosen for each piece of equipment in accordance with the energization profile for that piece of equipment, thereby to diversify the time for re-establishing the load.

21. The method of claim 16 in which all load controlled pieces of equipment are fully brought back online at the same time, with the restoration of load for one piece of load controlled equipment not being staggered with respect to other pieces thereof.

22. The method of claim 1 in which pieces of equipment remote from the load control apparatus are energization profiled by load control logic units of the load control apparatus located in proximity to each respective piece of equipment, each load control logic unit storing the energization profile for its associated piece of equipment and controlling the shedding of load by the piece of equipment during a load control event.

23. The method of claim 22 in which the load control apparatus wirelessly communicates with the load control logic units for the remote pieces of equipment to command the shedding of load by these pieces of equipment during a load control event in accordance with the energization profile for each piece of equipment.

24. The method of claim 2 in which load shed commands are also issued directly by the utility in addition to load shed commands issued by the load control apparatus and the method further includes programming the load control apparatus with a pre-established priority scheme that determines with which particular command the load control apparatus must comply when conflicting commands occur.

25. The method of claim 1 further including the load control apparatus reporting to the utility, during and after a load control event, the performance of load control strategies and commands being issued so the performance of the load control strategies and commands can be determined as well as the load control unit modifying, if necessary, an algorithm employed thereby to execute a load control strategy during a load control event.

26. The method of claim 25 in which the load control unit computes the amount of time a piece of equipment is allowed to run, actually runs, and sheds load during the load control event and reports this information.

27. The method of claim 26 further including the load control apparatus utilizing information relating to the performance of load shed based on the energization profile for each piece of load controlled equipment involved in the event, so that patterns of load control and load control strategies can be modified based upon actual load control events.

28. The method of claim 7 in which energization profiling is suspended during, and for a period of time subsequent to termination of a load control event so the effects of load control during the event do not affect the energization profile.

29. The method of claim 1 further including shedding load using a capping protocol in which load shedding is based upon an assumed, rather than an actual, energization profile with the assumed profile representing the maximum dispatchable load for a given piece of equipment for a given interval.

30. The method of claim 27 in which the method further includes reporting the information back to the utility, during and after the load control event,

31. In an electrical distribution system by which a utility supplies electricity to one or more pieces of equipment at each utility'"'"'s customer'"'"'s location, each piece of equipment placing an electrical load on the system when it is operating, a load control apparatus connected to the pieces of equipment and controlling the shedding of electrical load placed on the system by the respective pieces of equipment comprising:

a power sensor connected to each piece of equipment and sensing when electricity is being supplied to that piece of equipment;

a load control logic unit responsive to inputs from the sensor for profiling, on a temporal basis, the electricity usage of the piece of equipment, said profiling being characterized not by the amount of energy consumed by the piece of equipment during a defined interval of time, but rather by the duration of time during successive predetermined intervals of time the piece of equipment was energized or de-energized; and

,

a load control switch for shutting off electricity to each piece of equipment during occurrence of a load control event in which load on the system must be shed, the load control apparatus shedding load as a function of the energization profiles created for each piece of equipment thereby to prevent system instability or overload, and to control operating costs of the system.

32. The load control apparatus of claim 31 in which there is a separate load control logic unit for each piece of load controlled equipment and each load control logic unit produces an energization profile for its associated piece of equipment by identifying those periods of time during a predetermined time interval during which the piece of equipment uses electricity and the length of time of usage of electricity, the amount of load shed by each piece of equipment during a load control event being based upon the energization profile for the piece of equipment for the time of the event.

33. The load control apparatus of claim 31 in which each load control logic unit updates the energization profile for its associated piece of equipment except during, and for a period of time subsequent to termination of a load control event, so the effects of load control during the event do not affect the profile.

34. The load control apparatus of claim 31 in which some pieces of equipment are directly connected to the apparatus while other pieces of equipment are remote to the apparatus and the load control apparatus has a wireless communications link for communicating with the load control logic units associated with the remotely located equipment.

35. The load control apparatus of claim 31 for self-generating load control commands to shed load when a load control event occurs.

36. The load control apparatus of claim 35 which is further responsive to load shed commands issued directly by the utility, the apparatus further being programmed with a pre-established priority scheme that determines with which particular command the load control apparatus must comply when conflicting commands occur.

37. The load control apparatus of claim 31 which, once a load control event terminates, restores load to the electrical distribution system in a controlled manner based upon the energization profiles for the load controlled pieces of equipment so to gradually reduce the amount of shed load over a predetermined time period, or number of load cycles, whereby as the pieces of load controlled equipment are fully brought back online, the electrical distribution system does not experience a spike in demand such as would initiate another load controlled event.

38. The load control apparatus of claim 31 for reporting back to the utility, during and after a load control event, that a load control event occurred, and the performance of load shed based on the energization profile for each piece of load controlled equipment involved in the event.

39. The load control apparatus of claim 36 in which self-generated commands and commands issued by the utility are communicated to the apparatus using a two-way automatic communications system.

40. In an electrical distribution system by which a utility supplies electricity to one or more pieces of equipment at each utility'"'"'s customer'"'"'s location, each piece of equipment placing an electrical load on the system when it is operating, a method of controlling operation of the equipment throughout a load control event so to effectively manage the total load placed on the distribution system throughout the event comprising:

providing load control apparatus communicating load control commands to each piece of load control equipment, the apparatus being directly connected to a piece of equipment located proximate to the apparatus or communicating with a piece of equipment located remotely from the apparatus over a communications link;

profiling by the load control apparatus the electricity usage of the piece of equipment, the profile being temporally based and continuously updated to reflect recent usage of the equipment, said profiling being characterized not by the amount of energy consumed by the piece of equipment during a defined interval of time, but rather by the duration of time during successive predetermined intervals of time the piece of equipment was energized or de-energized; and

,

when a load control event occurs in which load on the distribution system must be shed, shedding load by the load control apparatus as a function of the energization profile created for the piece of equipment and restoring the load at the end of the event, the shedding and restoring of load including selectively controlling each piece of equipment to stagger the shedding of load by the equipment at the beginning of the event and to stagger the restoring of the equipment load at the end of the event thereby to facilitate a smooth transition into and out of load control so as to provide system stability throughout the event.