System and method for optimizing power shed/restore operations

• US 4,464,724 A
• Filed: 06/17/1981
• Issued: 08/07/1984
• Est. Priority Date: 06/17/1981
• Status: Expired due to Fees

• Current Assignee: Cyborex Laboratories Incorporated
• Original Assignee: Cyborex Laboratories Incorporated
• Inventors: Matheson, Frederick A., Gurr, George P.
• Primary Examiner(s): Wise, Edward J.
• Application Number:
  US06/274,488
• Time in Patent Office: 1,147 Days
• Field of Search: 364/492, 364/493, 364/494, 307/39, 307/35, 307/41, 307/33, 307/34, 307/38
• US Class Current: 700/291
• CPC Class Codes: H02J 2310/12 The local stationary network supplying a household or a building
• 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 power shedding-restoring system for controlling delivery of electrical energy from a power line to a residence having a plurality of controlled loads with predetermined priorities includes a plurality of load relays, a circuit for measuring total power delivered to the residence, a computer for computing and storing a shed value for each controlled load as it is shed, a minor average equal to the average power delivered to the residence over the past minute, and a major average equal to the average power delivered to the residence over the past hour. The computer also stores a power limit preset by the residence owner, and compares the minor average and the major average to the power limit. If the minor average and the major average both exceed the power limit, the system sheds the lowest priority controlled load that is presently electrically connected to the power line. If the minor average and the major average both are less than the power limit, the system restores the highest priority controlled load that is presently not electrically connected to the power lines. If either the minor average or the major average exceeds the power limit and the other is less than the power limit, the system postpones any decision to shed or restore a load until both the minor average and the major average either exceed or are less than the power limit.

Claims

1. A method for controlling delivery of electrical energy from a power line to an establishment having a plurality of electrical loads in order to maintain the total power delivered to the electrical loads close to a selected power limit, the electrical loads including a plurality of controlled loads which can be electrically connected to and disconnected from the power line in accordance with priorities of the controlled loads by means of a control system, the control system including a plurality of load switching means for controllably connecting the controlled loads to and disconnecting the controlled loads from the power line, the control system also including power measuring means for measuring power delivered from the power line to the electrical loads, said method comprising operating a processor to effect the steps of:

(a) computing and storing a power consumption number for any one of the controlled loads when that controlled load is electrically disconnected from the power line or is electrically connected to the power line;

(b) computing a minor average that represents the average power consumption of the establishment during a first period of time prior to the present time;

(c) computing a major average that represents the average power consumption of the establishment during a second period of time prior to the present time, said second period of time being substantially greater than said first period of time;

(d) comparing said major average to said selected power limit, and comparing said minor average to said selected power limit;

(e) electrically disconnecting the lowest priority controlled load presently electrically connected to the power line, if both said major average and said minor average are greater than said selected power limit;

(f) repeating steps (b), (c), (d) and (e) until either said major average or said minor average is less than said selected power limit;

(g) computing a first power availability number representative of the difference between the selected power limit and said major average;

(h) comparing a stored power consumption number of a first highest-priority one of the controlled loads not presently electrically connected to the power line with said first power availability number and electrically connecting said first highest-priority controlled load to the power line if the power consumption of that controlled load is less than said first power availability number and both said major average and said minor average are less than said selected power limit; and

(i) repeating steps (b), (c), (d), (g) and (h) until the highest priority remaining controlled load not presently electrically connected to the power line has a power consumption that is greater than the power availability number computed in step (g).

2. The method of claim 1 including the step of using the processor to defer any decision to shed any of the controlled loads until both said major average and said minor average exceed the selected power limit, and using the processor to defer any decision to restore any of the controlled loads until both said major average and said minor average are less than the selected power limit.

3. The method of claim 2 including the step of causing each controlled load of a particular group of the controlled loads to remain shed for at least a first predetermined amount of time each time that controlled load is shed, and causing each controlled load of the group to remain restored for at least a second predetermined amount of time each time that controlled load is restored, in order to avoid rapid on and off cycling of the controlled loads of the groups.

4. The method of claim 1 including the steps of storing a first number of consecutively computed minor averages in a table in a memory, and wherein said computing of said major average includes the steps of computing the total of all of said minor averages stored in said table and dividing said total by said first number to obtain an updated value of said major average.

5. The method of claim 4 including the steps of deleting the oldest minor average from said table each time a new minor average is entered into said table.

6. The method of claim 1 wherein step (j) includes the steps of electrically disconnecting, in order of increasing priority, as many of the controlled loads that are presently electrically connected to the power line and have lower priority than the highest priority controlled load presently not electrically connected to the power line as is necessary for the sum of their respective stored power consumption numbers to exceed the most recently computed power available number computed in accordance with step (g).

7. The method of claim 1 wherein said first period of time in step (b) is immediately prior to the present time, and said second period of time in step (c) is immediately prior to the present time.

8. The method of claim 1 further including the step of electrically disconnecting a second, lowest-priority one of the controlled loads presently electrically connected to the power line from the power line if said stored power consumption number of said first controlled load is greater than said first power availability number and the priority of said second controlled load is lower than the priority of said first controlled load.

9. A method for controlling delivery of electrical energy from a power line to an establishment having a plurality of electrical loads in order to maintain the total power delivered to the electrical loads close to a selected power limit, the electrical loads including a plurality of controlled loads which can be electrically connected to and disconnected from the power line in accordance with priorities of the controlled loads by means of a control system, the control system including a plurality of load switching means for controllably connecting the controlled loads to and disconnecting the controlled loads from the power line, the control system also including power measuring means for measuring power delivered from the power line to the electrical loads, said method comprising operating a processor to effect the steps of:

(a) computing and storing a power consumption number for any one of the controlled loads when that controlled load is electrically disconnected from the power line or is electrically connected to the power line;

(b) computing a minor average that represents the average power consumption of the establishment during a first period of time prior to the present time;

(c) computing a major average that represents the average power consumption of the establishment during a second period of time prior to the present time, said second period of time being substantially greater than said first period of time;

(d) comparing said major average to said selected power limit, and comparing said minor average to said selected power limit;

(e) computing a first power availability number representative of a difference between the selected power limit and said major average;

(f) comparing a power consumption number of a first highest-priority one of the controlled loads not presently electrically connected to the power line with said first power availability number, and electrically connecting said first highest-priority controlled load to the power line if the power consumption of that controlled load is less than said first power availability number and both said major average and said minor average are less than said selected power limit;

(g) repeating steps (b), (c), (d), (e) and (f) until the highest priority remaining controlled load not presently electrically connected to the power line has a power consumption that is greater than the power availability number computed in step (f).

10. A method for controlling delivery of electrical energy from a power line to an establishment having a plurality of electrical loads in order to maintain the total power delivered to the electrical loads close to a selected power limit, the electrical loads including a plurality of controlled loads which can be electrically connected to and disconnected from the power line in accordance with priorities of the controlled loads by means of a control system, the control system including a plurality of load switching means for controllably connecting the controlled loads to and disconnecting the controlled loads from the power line, the control system also including power measuring means for measuring power delivered from the power line to the electrical loads, said method comprising operating a processor to effect the steps of:

(a) computing and storing a power consumption number for any one of the controlled loads when that controlled load is electrically disconnected from the power line or is electrically connected to the power line;

(b) computing a minor average that represents the average power consumption of the establishment during a first period of time prior to the present time;

(c) computing a major average that represents the average power consumption of the establishment during a second period of time prior to the present time, said second period of time being substantially greater than said first period of time;

(d) comparing said major average to said selected power limit, and comparing said minor average to said selected power limit;

(e) electrically disconnecting the highest priority controlled load presently electrically connected to the power line, if both said major average and said minor average are greater than said selected power limit; and

(f) repeating steps (b), (c), (d) and (e) until either said major average or said minor average is less than said selected power limit.

11. A system for controlling delivery of electrical energy from a power line to an establishment having a plurality of electrical loads in order to maintain the total energy consumption of the electrical loads close to a selected power limit, the electrical loads including a plurality of controlled loads that can be electrically connected to and disconnected from the power line in accordance with priorities of the controlled loads by means of said system, said system comprising in combination:

(a) a plurality of load switching means for controllably electrically connecting the controlled loads to and electrically disconnecting the controlled loads from the power line;

(b) power measuring means for measuring instantaneous power delivered from the power line to the electrical loads;

(c) computing and storing means for computing and storing a power consumption number for any one of the controlled loads when that controlled load is electrically disconnected from the power line or electrically connected to the power line;

(d) means for computing a minor average that represents the average power consumption of the establishment measured by said power measuring means during a first period of time prior to the present time;

(e) means for computing a major average that represents the average power consumption of the establishment during a second period of time prior to the present time, said second period of time being substantially greater than said first period of time;

(f) first comparing means for comparing the selected power limit with said minor average;

(g) second comparing means for comparing the selected power limit with said major average;

(h) first means for electrically disconnecting in order of increasing priority, and if said major average and said minor average are both greater than said selected power limit, a sufficient number of the controlled loads from the power line to reduce the total power consumed by the controlled loads to a level such that the most recently computed minor average or the most recently computed major average is less than the selected power limit;

(i) computing means for computing a first power or energy availability number representing an amount of power or energy that additionally can be consumed by the electrical loads without causing a computed major average to exceed said selected power limit;

(j) third comparing means for comparing a power consumption number of a first, highest-priority one of the controlled loads that is not presently electrically connected to the power line with said first power availability number; and

(k) second means for electrically connecting said first highest priority controlled load to the power line if both said minor average and said major average are less than said selected power limit and said electrical connecting of said first controlled load will not cause the selected power limit to be exceeded by the most recently computed major average.

12. The system of claim 11 including third means for electrically disconnecting a second, lowest-priority one of the controlled loads that is presently electrically connected to the power line from the power line on the conditions that said stored power consumption number of said first controlled load is greater than said first power availability number and the priority of said second controlled load is lower than the priority of said first controlled load.

13. A system for controlling delivery of electrical energy from a power line to an establishment having a plurality of electrical loads in order to maintain the total energy consumption of the electrical loads close to a selected power limit, the electrical loads including a plurality of controlled loads that can be electrically connected to and disconnected from the power line in accordance with priorities of the controlled loads by means of said system, said system comprising in combination:

(a) a plurality of load switching means for controllably electrically connecting the controlled loads to and electrically disconnecting the controlled loads from the power line;

(b) computing and storing means for computing and storing a power consumption number for any one of the controlled loads when that controlled load is electrically disconnected from the power line or electrically connected to the power line;

(c) means for computing a minor average that represents the average power consumption of the establishment during a first period of time prior to the present time;

(d) means for computing a major average that represents the average power consumption of the establishment during a second period of time prior to the present time, said second period of time being substantially greater than said first period of time;

(e) first comparing means for comparing the selected power limit with said minor average;

(f) second comparing means for comparing the selected power limit with said major average; and

(g) first means for electrically disconnecting, in order of increasing priority, and if said major average and said minor average are both greater than said selected power limit, a sufficient number of the controlled loads from the power line, to reduce the total power consumed by the controlled loads to a level such that the most recently computed minor average or the most recently computed major average is less than the selected power limit.

14. A system for controlling delivery of electrical energy from a power line to an establishment having a plurality of electrical loads in order to maintain the total energy consumption of the electrical loads close to a selected power limit, the electrical loads including a plurality of controlled loads that can be electrically connected to and disconnected from the power line in accordance with priorities of the controlled loads by means of said system, said system comprising in combination:

(a) a plurality of load switching means for controllably electrically connecting the controlled loads to and electrically disconnecting the controlled loads from the power line;

(b) computing and storing means for computing and storing a power consumption number for any one of the controlled loads when that controlled load is electrically disconnected from the power line or electrically connected to the power line;

(c) means for computing a minor average that represents the average power consumption of the establishment measured by said power measuring means during a first period of time prior to the present time;

(d) means for computing a major average that represents the average power consumption of the establishment during a second period of time prior to the present time, said second period of time being substantially greater than said first period of time;

(e) first comparing means for comparing the selected power limit with said minor average;

(f) second comparing means for comparing the selected power limit with said major average; and

(g) second means for electrically connecting said first highest priority controlled load to the power line if both said minor average and said major average are less than said selected power limit and said electrical connecting of said first controlled load will not cause the selected power limit to be exceeded by the most recently computed major average.

15. A control system for controlling delivery of electrical energy from a power line to an establishment having a plurality of electrical loads in order to maintain the total power delivered to the electrical loads close to a selected power limit, the electrical loads including a plurality of controlled loads which can be electrically connected to and disconnected from the power line in accordance with priorities of the controlled loads by means of a control system, said control system comprising:

(a) a plurality of load switching means for controllably connecting the controlled loads to and disconnecting the controlled loads from the power line;

(b) power measuring means for measuring power delivered from the power line to the electrical loads, said method comprising operating a processor to effect the steps of;

(c) means for computing and storing a power consumption number for any one of the controlled loads when that controlled load is electrically disconnected from the power line;

(d) means for computing a minor average power consumption number that represents the average power consumption of the establishment during a first period of time prior to the present time;

(e) means for computing a major average power consumption number that represents the average power consumption of the establishment during a second period of time prior to the present time, said second period of time being substantially greater than said first period of time;

(f) means for comparing said major average to said selected power limit and comparing said minor average to said selected power limit;

(g) means for electrically disconnecting the highest priority controlled load presently electrically connected to the power line, if both said major average power consumption number and said minor average power consumption number are greater than said selected power limit;

(h) means for computing a first power or energy availability number representative of a difference between the selected power limit and said major average power consumption number; and

(i) means for comparing a power consumption number of a first highest-priority one of the controlled loads not presently electrically connected to the power line with said first power availability number, and electrically connecting said first highest-priority controlled load to the power line if the power consumption of that controlled load is less than said first power availability number.

16. A method for controlling delivery of electrical energy from a power line to an establishment having a plurality of electrical loads in order to maintain the total power delivered to the electrical loads close to a selected power limit, the electrical loads including a plurality of controlled loads which can be electrically connected to and disconnected from the power line in accordance with priorities of the controlled loads by means of a control system, the control system including a plurality of load switching means for controllably connecting the controlled loads to and disconnecting the controlled loads from the power line, the control system also including power measuring means for measuring power delivered from the power line to the electrical loads, said method comprising operating a processor to effect the steps of:

(a) computing and storing a power consumption number for any one of the controlled loads when that controlled load is electrically disconnected from the power line or is electrically connected to the power line;

(b) computing a minor average that represents the average power consumption of the establishment during a first period of time prior to the present time;

(c) computing a major average that represents the average power consumption of the establishment during a second period of time prior to the present time, said second period of time being substantially greater than said first period of time;

(d) comparing said major average to the selected power limit, and comparing the minor average to said selected power limit;

(e) detecting a crossover time at which said major average falls below the selected power limit, said crossover time being the beginning of a computation period, if said major average and said minor average are less than the selected power limit;

(f) computing the sum of the differences between the present major average and the selected power limit since said crossover time;

(g) computing a projected number that is the product of the remaining time in said computation period and the power consumption number of the highest priority controlled load not presently electrically connected to the power line divided by the length of said computation period;

(h) comparing said sum to said projected number; and

(i) electrically connecting said highest priority controlled load to the power line if said summation exceeds said projected number; and

(j) repeating steps (b), (c), (d), (e), (f), (g) (h) and (i) if said summation is less than said projected number.

17. A method for controlling delivery of electrical energy from a power line to an establishment having a plurality of electrical loads in order to maintain the total power delivered to the electrical loads to a selected power limit, the electrical loads including a plurality of controlled loads which can be electrically connected to and disconnected from the power line in accordance with priorities of the controlled loads by means of control system, the control system including a plurality of load switching means for controllably connecting the controlled loads to and disconnecting the controlled loads from the power line, the control system also including power measuring means for measuring power delivered from the power line to the electrical loads, said method comprising operating a processor to effect the steps of:

(a) computing and storing a power consumption number for any one of the controlled loads when that controlled load is electrically disconnected from the power line or is electrically connected to the power line;

(b) computing a minor average that represents the average power consumption of the establishment during a first period of time prior to the present time;

(c) computing a major average that represents the average power consumption of the establishment during a second period of time prior to the present time, said second period of time being substantially greater than said first period of time;

(d) comparing said major average to the selected power limit, and comparing said minor average to the selected power limit;

(e) detecting a crossover time at which said major average falls above the selected power limit, said crossover time being the beginning of a computation period, if said major average and said minor average are greater than the selected power limit;

(f) computing the sum of the differences between the present major average and the selected power limit since said crossover time;

(g) computing a projected number that is the product of the remaining time in said computation period and the power consumption number of the lowest priority controlled load presently electrically connected to the power line divided by the length of said computation period;

(h) comparing said sum to said projected number; and

(i) electrically disconnecting said lowest priority controlled load from the power line if said summation exceeds said projected number; and

(j) repeating steps (b), (c), (d), (e), (f) (g), (h) and (i) if said summation is less than said projected number.