System and method of power demand limiting and temperature control

• US 4,228,511 A
• Filed: 10/06/1978
• Issued: 10/14/1980
• Est. Priority Date: 10/06/1978
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Simcoe, Robert J., Finch, David C.
• Primary Examiner(s): Wise, Edward J.
• Application Number:
  US05/949,306
• Time in Patent Office: 739 Days
• Field of Search: 364/506, 364/557, 364/493, 364/494, 165/11-14, 165/24-29, 307/31, 307/35, 307/39, 307/117
• US Class Current: 700/278
• CPC Class Codes: G05D 23/1905 associated with tele control

Abstract

A room thermostatic control providing for automatic power defer, i.e. modification of load consumption of electrically energized heating and cooling systems during intervals when there is a peak load demand on the electrical supply system. During power defer ambient indoor temperature is controlled by set point adjustment to minimize discomfort, e.g. by pre-boosting, by ramped temperature deferral at controlled rates, and thereafter by ramped recovery at controlled rates to the reference, i.e. desired, temperature. The preferred embodiment has normal and night set back reference temperature potentiometers and ambient indoor temperature sensing circuits providing, respectively, analog reference and analog indoor signals. Digital set point signals are derived and compared with the analog indoor signal to actuate relays controlling operation of the heating and cooling means, e.g. compressor and auxiliary resistance heating. A circuit sensing external conditions, e.g. outdoor temperature, indicative of power defer, is utilized to generate a power defer signal for enabling modification of the set point. In the preferred embodiment digital signals are stored for each of a plurality of consecutive real time intervals for heating and cooling modes. A real time clock is utilized to access the digital signals for the current time interval. During presence of a power defer signal set point variation is controlled in accordance to the relevant digital signals for each current time interval.

Claims

1. A thermostatic control for use in controlling indoor temperature within a structure and for selectively reducing electrical energy consumption of ambient temperature conditioning means during intervals of peak load demand on the electrical system, comprising:

(a) user adjustable reference temperature selection means for selecting a desired reference temperature and first means for deriving therefrom a temperature set point value;

(b) second means responsive to a signal condition indicative of an imminent electric power peak demand for generating a power defer signal;

(c) third means responsive to said power defer signal for automatically ramping said temperature set point value during actual peak load demand in a defer direction at a predetermined rate to increase electrical energization of the ambient temperature conditioning means to ramp indoor ambient temperature in a defer direction from the desired reference temperature;

(d) means responsive to termination of actual peak load demand for automatically ramping said temperature set point value at a predetermined rate to increase energization of the ambient temperature conditioning means until said temperature set point value returns to the value of the temperature set point derived from said reference temperature selection means;

(e) fourth means for deriving a signal representative of indoor ambient temperature value;

(f) fifth means responsive to signals representative of said indoor ambient temperature value and said temperature set point value of generating a control signal; and

(g) sixth means responsive to said control signal and adapted for connection to the ambient temperature conditioning means to modify operation of the last named means.

5. The arrangement of claims 3 or 1 wherein said thermostatic control is utilized for controlling ambient heating means and wherein said third means provides for automatically ramping said temperature set point value in said boost direction to increase indoor ambient temperature in respect to the desired reference temperature and during an interval of actual peak demand to ramp said indoor ambient temperature from said increased ambient temperature to a value below the desired reference temperature so as to defer power consumption.

6. The arrangement of claim 5 for controlling ambient heating means incorporating a heat pump and auxiliary heating means, means for generating a second temperature set point value offset from the temperature set point value by a predetermined value in a first direction, representative of a higher set point temperature;

said sixth means comprising a first control output adapted for connection to the heat pump and providing a first signal for actuating the heat pump responsive to the indoor ambient temperature being reduced to the temperature set point value and for deactivating the heat pump responsive to said indoor ambient temperature increasing to the second temperature set point value;

further means for generating a third temperature set point value offset from the temperature set point value in a second direction by a predetermined value representative of a lower set point temperature, said sixth means further comprising a second control output adapted for connection to the auxiliary heating means and providing a second signal for actuating the auxiliary heating means responsive to the indoor ambient temperature being reduced to the third temperature set point value.

7. The arrangement of claim 6 comprising timing means, means for activating said timing means responsive to commencing production of said first signal for actuating the heat pump and for inhibiting deactivation of the heat pump for a predetermined time interval.

8. The arrangement of claims 3 or 1 wherein said thermostatic control is utilized for controlling air conditioning means and wherein said third means automatically ramps said temperature set point value in said boost direction to decrease the indoor ambient temperature in respect to the desired reference temperature, and during actual peak demand ramps said indoor ambient temperature from said decreased ambient temperature value to a value above the desired reference temperature so as to defer power consumption.

9. The room thermostatic control of claims 3 or 1 wherein said fifth means, comprises:

(a) means for generating a second set point signal representative of the algebraic sum of said set point signal and a set off signal;

(b) and comparison means for sequentially comparing said set point signal and said second set point signal with a signal representative of indoor ambient temperature;

(c) means responsive to conincidence between one of the aforesaid set point signals with said indoor ambient temperature signal for producing a first control signal for actuating operation of said ambient temperature conditioning means and responsive to coincidence between the other one of the aforesaid set point signals with said indoor ambient temperature signal for producing a second control signal for deactivating operation of said ambient temperature conditioning means.

10. The arrangement of claim 9 further comprising first and second timing means, means for activating said first timing means responsive to commencing production of said first control signal and for inhibiting termination of said first control signal for a predetermined first time interval, and means for activating said second timing means responsive to commencing production of said second control signal and for inhibiting termination of said second control signal for a predetermined second time interval, whereby the ambient temperature conditioning means has minimum time periods of activation and deactivation.

11. The arrangement of claim 10 wherein the ambient temperature conditioning means is adapted to be actuated from the commencement of production of said first control signal for at least said predetermined first time interval until said ambient indoor temperature attains the value of said second set point signal, and wherein said set off signal has a predetermined value, further comprising:

(a) means for generating a second set off signal of predetermined value greater than the value of said set off signal;

(b) means for generating a third set point signal representative of the algebraic sum of said set point signal and of said second set off signal;

(c) said comparison means being adapted to sequentially compare said set point, second set point and third set point signals with a signal representative of indoor temperature;

(d) means responsive to said signal representative of indoor ambient temperature attaining the value of said third set point signal for modifying said control signals to deactivate the ambient temperature conditioning means so that the conditioning means may be deactivated prior to lapse of said predetermined time interval in the event of an excessive deviation of indoor ambient temperature.

12. The arrangements of claims 3, 4, 9, 10 or 1 further comprising means for preventing modification of the temperature set point by user adjustment of said control during intervals of peak load demand to prevent defeat of power deferral.

13. The arrangement of claim 12 comprising:

(a) first digital storage means for storing said desired reference temperature value;

(b) second digital storage means for storing said temperature set point;

(c) means for periodically transferring said desired reference temperature value from said first to said second digital storage means; and

(d) means for disabling such transfer during intervals of peak load demand.

20. The indoor thermostatic control assembly of claims 13, 14 or 15 wherein said power defer signal means is adapted to be coupled to outdoor temperature sensing means and said power defer signal means produces a power defer signal when the temperature outdoors of the structure is in a predetermined range.

2. In a thermostatic control for selective energization of ambient heating means responsive to comparison of a signal representative of actual indoor ambient temperature and a signal representative of a set point value for controlling indoor temperature within a structure at a first user selected temperature value during a first predetermined time interval and at a second lower temperature value during a second predetermined time interval, the combination comprising:

(a) first means for deriving a first digital signal having a value representative of first selected temperature value;

(b) second means for deriving a second digital signal having a value representative of second lower temperature value;

(c) digital storage means for storing a set point value;

(d) means operative during the second predetermined time interval for storing said second digital signal as a set point value in said digital storage means;

(e) digital ramping means adapted to consecutively modify the value of a signal by a predetermined magnitude upon the lapse of predetermined time intervals;

(f) means responsive to termination of said second predetermined time interval for enabling said ramping means to ramp the set point value stored in said digital storage means at a rate established by said predetermined magnitude and preselected time interval to increase the set point from a value representative of the second lower temperature value to a value representative of the first selected temperature value, whereby the rate of temperature increase is limited to a desired value.

3. A room thermostatic control for use in controlling indoor temperature within a structure and for selectively reducing electrical energy consumption of ambient temperature conditioning means during intervals of peak load demand on the electrical system, comprising:

(a) user adjustable reference temperature selection means for selecting a desired reference temperature and first means for deriving therefrom a temperature set point value;

(b) second means for generating a power defer signal responsive to a signal condition, indicative of an imminent electric power peak demand and supplied from a location external of the thermostatic control and the structure being conditioned by ambient temperature conditioning means;

(c) third means responsive to said power defer signal for automatically ramping said temperature set point value in a first boosting direction to increase energization of the ambient temperature conditioning means, and subsequently ramping said temperature set point value in a second defer direction to decrease electrical energization of the ambient temperature conditioning means, whereby indoor ambient temperature is offset in a boost direction from the desired reference temperature and during actual peak load demand is ramped in a defer direction from the desired reference temperature;

(d) fourth means for deriving a signal representative of indoor ambient temperature value;

(e) fifth means responsive to signals representative of said indoor ambient temperature value and said temperature set point value for generating a control signal; and

(f) sixth means responsive to said control signal and adapted for connection to the ambient temperature conditioning means to modify operation of the last named means.

4. The arrangement of claim 3 further comprising means for automatically ramping said temperature set point value in said first direction subsequent to ramping in said defer direction until said temperature set point value returns to the value of the temperature set point derived from said reference temperature selection means.

14. An indoor thermostatic control arrangement for controlling ambient indoor temperature conditioning means to condition ambient indoor temperature within a structure and providing power defer operation for reducing electrical energy consumption of said conditioning means during intervals of peak demand on the electrical supply system energizing said conditioning means, comprising:

(a) indoor temperature sensing means providing a first electrical signal having a value representative of actual ambient indoor temperature;

(b) temperature reference means for user selection of a selected ambient temperature reference value and providing a second signal of value representative of said selected ambient temperature;

(c) means to derive a temperature set point signal from said second signal;

(d) digital ramping means adapted to consecutively modify the value of a signal by a predetermined magnitude upon the lapse of preselected time intervals;

(e) means responsive to a signal condition, indicative of an imminent peak demand on the electrical supply system for enabling said ramping means to ramp said set point signal at a rate established by said predetermined magnitude and preselected time interval;

(f) means responsive to said first electrical signal attaining the value of said set point signal for providing a control signal; and

(g) means responsive to said control signal and adapted for connection to said ambient temperature conditioning means to modify operation of the latter means, whereby during periods of peak demand ambient indoor temperature is modified from the selected ambient temperature value at a rate defined by said ramping means.

15. An indoor thermostatic control assembly adapted for location in a building for controlling electrically energized ambient temperature conditioning means, such as heat pump systems, to maintain ambient indoor temperature within a building and power defer operation for selectively reducing electrical energy consumption of said conditioning means during time intervals of peak demand on the electrical supply system energizing said conditioning means, comprising:

(a) indoor temperature sensing means providing a first electrical signal having a value representative of actual ambient indoor temperature;

(b) temperature reference means for user selection of a desired ambient temperature and providing a second electrical signal of value representative of said desired ambient temperature;

(c) set point selection means for deriving a temperature set point signal from said second signal;

(d) signal storage means storing a block of digital signals for each of a plurality of contiguous time intervals, the block for each time interval defining any ramping of said set point signal desired to be performed during power defer operation occurring during such interval;

(e) power defer signal means for producing a power defer signal responsive to a signal condition occurring external of the building which condition is indicative of the need for power defer operation;

(f) digital real time clock means for consecutively selecting the block of digital signal applicable to the current real time increment;

(g) digital ramping means for incrementally ramping the digital value of said temperature set point signal in accordance to said selected block of digital signals upon occurrence of said power defer signal;

(h) comparison means for comparing the thus modified set point signal and said first electrical signal;

(i) means responsive to said comparison for producing a control signal adapted to actuate ambient temperature condition means, whereby during power defer operation the ambient temperature is gradually variable in respect to the desired ambient temperature at rates controlled by said outdoor thermostatic control assembly.

16. The indoor thermostatic control assembly of claim 15 wherein said digital ramping means is adapted to incrementally ramp the digital value of said temperature set point signal in a direction selected by a direction command in said selected block of digital signals, whereby during power defer operation said ambient temperature value may be gradually ramped in a plurality of directions so as to minimize discomforture.

17. The thermostatic control assembly of claim 16 wherein said block of digital signals comprises a digital signal representative of the time duration between intervals when said temperature set point signal is to be modified by a predetermined unit value, and said ramping means comprises:

(a) means for repetitively storing said signal representative of time duration;

(b) means for incrementally decrementing said time value; and

(c) means for modifying said control temperature value responsive to said stored time value being decremented.

18. The indoor thermostatic control assembly of claim 15 wherein said digital ramping means is adapted to incrementally ramp the digital value of said temperature set point signal at a rate specified by the block of digital signals.

19. The indoor thermostatic control assembly of claim 15 comprising mode selection switching means for selectively actuating heating or cooling mode operation, said digital signal storage means adapted to store a first series of blocks of digital signals for each of a plurality of contiguous time intervals for the heating mode, and to store a second series of blocks of digital signals for each of a plurality of contiguous time intervals for the cooling mode, means responsive to said digital real time clock means and to said mode selection means for consecutively selecting the block of digital signals applicable to the current time increment from the series of blocks for the mode selected by said mode selection switch.

21. In a room thermostatic control for mounting in a building and incorporating temperature sensing means providing an ambient indoor temperature signal, and operator adjustable means providing a reference temperature signal indicative of desired indoor temperature and output means responsive to comparison of signals derived therefrom to produce output signals for controlling electrical energization of ambient temperature conditioning means, first and second memory storage portions and a real time clock, a power deferral method of reducing electrical consumption of the conditioning means during intervals of peak load demand on the system supplying electrical energization, comprising the steps of:

(a) deriving a set point temperature value representative of the value of said reference temperature signal and storing said set point temperature value in a first memory storage portion;

(b) accessing a second memory storage portion containing stored digital signals for each of a plurality of consecutive real time increments, the stored digital signals for selected ones of said consecutive time increments containing an enabling signal for ramping said set point temperature signal during the presence of a power deferal signal;

(c) under control of a real time clock continuously selecting the stored digital signals of the currently effective time increment;

(d) responsive to the simultaneous presence of the power defer signal and of said enabling signal during the currently effective time increment, incrementally ramping the value of the stored set point signal in a first direction to gradually decrease energization of ambient temperature control means at the first predetermined rate;

(e) responsive to termination of either of said power defer signal or of said enabling signal during the currently effective time increment, terminating said incremental ramping in the first direction and commencing incremental ramping of the stored set point signal in an opposite, second, direction to gradually increase energization of the ambient temperature control means, whereby the ambient indoor temperature returns to the value representative of said reference temperature signal; and

(f) producing output signals responsive to comparison of the set point temperature signal and of the ambient indoor temperature signal for modifying the actuation of the ambient temperature conditioning means.

22. The method set forth in claim 21 wherein the value derived from said reference temperature in said signal is periodically stored as a set point temperature in said first memory portion, the further step of inhibiting such periodic storing during the simultaneous presence of said power defer and said enabling signals.

23. The method of claim 22 wherein the value of said ambient indoor temperature is transferred to said first memory portion at the commencement of ramping the value of said set point signal in said first direction to preclude defeat of power deferral by misadjustment of the operator adjustable means.

24. The method set forth in claim 21 comprising the further step of incrementally ramping the value of the stored set point signal in said direction prior to ramping in said first direction to boost ambient energy storage prior to decreasing energization of the ambient temperature conditioning means.

25. A room thermostatic control for use in controlling indoor temperature within a structure and for selectively reducing electrical energy consumption of ambient temperature conditioning means during intervals of peak load demand on the electrical system, comprising:

(a) means for selecting a desired indoor reference temperature, and deriving therefrom a set point temperature value;

(b) means for initiating a temperature control signal for actuating ambient temperature conditioning means when ambient indoor temperature attains said set point value;

(c) means for generating a power defer signal responsive to a signal condition indicative of an imminent power peak demand and supplied from a location external of said control and the structure being conditioned by the indoor ambient temperature conditioning means; and

(d) means responsive to said power defer signal for automatically shifting said set point value sequentially by different predetermined magnitudes whereby the electrical energization of the ambient temperature conditioning means and the indoor ambient temperature is variable in accordance to a desired profile during intervals of anticipated peak demand on the electrical system.

26. A room thermostatic control for use in controlling indoor temperature within a structure and for selectively reducing electrical energy consumption of ambient temperature conditioning means during intervals of anticipated peak load demand on the electrical system, comprising:

(a) user adjustable reference temperature selection means providing an analog reference temperature signal of value representative of desired indoor ambient temperature;

(b) indoor ambient temperature sensing means for providing an analog ambient indoor temperature signal;

(c) comparison means comprising a plurality of inputs and an output;

(d) analog control means comprising an output coupled to one input of the comparison means, and inputs connected for sequential coupling of said analog reference signal and of said analog ambient indoor temperature signal to said output;

(e) digital storage means for storing one of the aforesaid analog signals in digital form as a digital temperature signal;

(f) digital to analog conversion means comprising an input and an output coupled to another input of said comparison means;

(g) digital processing means for sequentially coupling the stored digital temperature signal to an input of said digital to analog conversion means and for controlling the simultaneous coupling of said one of the aforesaid analog signals to the one input of said comparison means;

(h) said digital processing means being responsive to the output of said comparison means for sequentially updating the value of said stored digital temperature signal to correspond to the current value of said one of the aforesaid analog signals;

(i) means for deriving a digital set point temperature value from said stored digital signal and for storing said digital set point value;

(j) means responsive to a signal condition indicative of an imminent electrical peak power demand for producing a power defer signal;

(k) means responsive to said power defer signal for modifying the stored digital set point value; and

(l) means responsive to comparison of the values of the other one of the aforesaid analog signals and of said stored digital set point value for producing a control signal adapted to modify actuation of the ambient temperature conditioning means.

27. The control of claim 26 wherein said analog control means supplies electrical energization to said indoor ambient temperature sensing means during intervals when said analog ambient indoor temperature signal is coupled to the output of the analaog control means so that said indoor ambient temperature sensing means is energized only periodically to minimize thermal drift.

28. The control of claim 27 wherein said digital processing means sequentially couples said digital set point value to an input of said digital to analog conversion means and simultaneously coupling said other one of the aforesaid analog signals to one input of said comparison means;

said digital processing means responsive to the resulting output of said comparison means for producing said control signal.

29. The control of claim 26 wherein said digital to analog conversion means comprises semiconductor resistance means connected across a source of potential, a plurality of taps being connected at displaced increments along said resistance means;

and semiconductor switching means coupling said taps to the output of said conversion means; and

means responsive to said digital processing means for gating a selected one of said switching means.

30. The digital to analog conversion means of claim 29 further comprising a plurality of tap points selected such that their respective output voltages correspond to the voltage values of said analog signals at one degree temperature increments.

31. The arrangement of claim 26 wherein said means responsive to a signal condition indicative of an imminent electrical peak power demand comprises ambient outdoor temperature sensing means for providing an analog ambient outdoor temperature signal.

32. The arrangement of claim 31 wherein said outdoor temperature sensing means sequentially provides a plurality of analog ambient outdoor temperature signals indicative of the relationship of the outdoor temperature in respect to preselected outdoor temperature values;

and means responsive thereto to generate said power defer signal.

33. The control of claim 32 wherein said means for modifying the stored digital set point value comprises means for modifying said set point value as a function of real time, and said control further comprises an adjustable real time clock, and means responsive to one or more of said analog ambient outdoor temperature signals for inhibiting user readjustment of said real time clock, responsive to ourdoor temperature indicative of anticipated peak load demand.