Power distribution control system

Abstract: The present invention relates to a power distribution control system which includes a center communication terminal (S) and a plurality of customer's communication terminals (C1,...,Cn) operatively connected to the center communication terminal through communication lines. Each of the customer's communication terminals is responsive to a presentation signal from the center communication terminal for outputting a response signal to the center communication terminal. The center communication terminal also provides a response signal to the respective one of the customer's communication terminals.

Description: BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates to a power distribution control system for distributing an electric power by transmitting and receiving signals between the terminal of an electric power company and the terminals of houses, factories and the like. Description of the Related Art: Energy produced in the power plant of an electric power company is mainly distributed to houses, factories and others. In recent years, the power consumption has greatly changed throughout the year. In general, the power consumption is on peak in the summer daytime while it is off peak in the winter nighttime. The power installation is constructed to cope with the on-peak power consumption. As the power demand in typical houses increases with the spread of air conditioner, the difference between on-peak and off-peak energy consumption increases. As a result, the annually averaged load or annual load factor for the service capability gradually decreases. The production cost is also increasing. Therefore, the leveling of loads is urgently required. In order to accomplish the leveling, there has been proposed a system wherein the power supply to loads such as air conditioners is forcedly shut off depending on the need of the energy supplier, irrespective of the customers' needs. Instead incentive payments are paid back to the customers. For example, in U.S.A., the electric power company computes a tariff from an expected power consumption based on a predicted energy factor for a customer before one day. The computed tariff is one-sidedly reported from the electric power company to the customer. Such a system is called "spot tariff system". Literature "Actual Proof and Test for concentrically Controlling Loads (Control of Air Conditioners)" in JEC, Convention of Electric Power and Energy Department, 1991 proposed a method for intermittently stopping the power supply to the air conditioners. Although such a method is effective to reduce the on-peak energy consumption, circumstances on the side of houses, factories and others will be completely ignored. Furthermore, the spot tariff system cannot provide a remarkably improved advantage since the predicted demand will not accurately reflect variations in demand due to variable weather. When the air conditioners are intermittently shut off, the levelinig of all the leads cannot be effectively accomplished since the instruments to be controlled are limited to the air conditioners. WO 8912342 A1 discloses a process for reducing power peaks of supply and/or consumption of power, wherein a power cost signal, giving the momentary costs of the corresponding power, is delivered at the power supply end, said signal is received at the consumer's end and compared with a power cost-value predetermined by the consumer. Depending on the result of the comparison, the consumer can decide whether or not to avail himself of the power offered. Further, EP 265342A2 describes a load management electrical energy distribution system, wherein a distribution network establishes bidirectional data communications between a system operations center and a plurality of load terminals. The distribution network comprises independent processor controlled, primary communication interface units in communication with the center over a primary bidirectional communication network. A plurality of independent processor controlled, secondary communications interface units is in communication with each primary interface unit over a second bidirectional communications network including electrical utility primary distribution power lines, and load terminals are in communication with each secondary interface unit over a third bidirectional communications network. Finally, from EP 445448A1 a control supervisory system for power distribution equipment is known which includes a plurality of terminal control and/or supervisory devices each capable of controlling and/or supervising a plurality of power distribution devices in an extremely simple, high-speed and efficient manner without requiring any central control and/or supervisory unit. Each of the terminal control devices comprises a control and/or supervisory instruction section operable to output a control or supervisory command for controlling or supervising a plurality of power distribution devices, and a control and/or supervisory section operable to receive the control or supervisory command from the control and/or supervisory instruction section for generating a control or supervisory signal suited to control or supervise a corresponding one of the power distribution devices, and outputting it to the corresponding power distribution device. SUMMARY OF THE INVENTION It is therefore the object of the present invention to provide a power distribution system which can properly distribute the electric energy and level the loads depending on variations of demand through time and circumstances of houses, factories and other customers. This object according to the invention is solved by a power distribution control system comprising the features of claim 1. Preferred embodiments of this control system are defined in the subclaims. In a power distribution control system comprising a center side communication terminal and customer side communication terminals, the electric power can be distributed to houses, factories and other customers to level the loads while considering the variable demand through time and the circumstances of the house, factories and other customers. Particularly, since a customer makes a bid for the presentation from the center side which in turn makes a successful bid for the customer's bid, the optimum distribution can be made considering circumstances on both the center and customer sides. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of an electric power distribution system. Fig. 2 is a view illustrating the operation of the power distribution system of Fig. 1. Fig. 3 is a block diagram of another electric power distribution system. Fig. 4 is a view illustrating the operation of the electric power distribution system of Fig. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. 1, the power distribution control system, which is the first embodiment of the present invention, comprises an electric power company's communication terminal S or center communication terminal and a plurality of customer's communication terminals C1 to Cn connected to the center communication terminal through the respective communication lines. Each of the customer's communication terminals is connected to a corresponding load which has been installed in a house, factory or the like. The center communication terminal S comprises a predicted demand calculating section S1 which is adapted to receive input signals relating to, for example, present demand (X1), season (X2), day of the week (X3), time (X4), air temperature (X5), event schedule (X6), possible audience rating (X7) and so on. Thus, a predicted demand U1 will be computed from a function U1=F1 (X1, X2, X3, X4, X5, X6, ...). The computation of the predicted demand may be carried out for periods of every thirty minutes. The predicted demand is then compared with a power supply capacity to judge whether or not it should be considered to reduce the number of loads. Even if the predicted demand does not exceed the power supply capacity, there may be a case when it is desired to reduce the demand in place of the incentive payment without increase of the electric power generation having its critical cost. The critical cost may be computed from the predicted demand to judge whether or not it should be considered to reduce the number of loads. The incentive payment is a compensation returned back to a customer in place of the reduction of electric power level and proportional to the reduced quantity of electric power. The center communication terminal S also comprises a computing section S2. When it should be considered to reduce the number of loads, the computing section S2 determines a time zone through which the predicted demand computed exceeds the power supply capacity to compute a load reduction time period and to determine the incentive payment level. The incentive payment depends on the critical cost, the past response from the customer and so on. The center communication terminal further comprises a presentation signal outputting section or means S3 which outputs and sends a presentation signal including the load reduction time period and incentive payment to the respective one of the customer's communication terminals C1 to Cn, as shown in Fig. 2 . When each of the customer's communication terminals C1 to Cn receives a presentation signal, its computing section 101 checks a potential of reduction resulting in a reduction factor considering the load reduction request time and the incentive payment. It is now judged whether or not the reduction of the supplied power is possible. If it is possible, the computing section 101 computes the quantity and time period of power to be reduced. The potential for reduction includes event and operation schedule (Xc1), reduction of air conditioner load (Xc2), running time shift in water heater (Xc3), partial stoppage of elevator (Xc4). partial lights-out (Xc5), partial stoppage of computer (Xc6), amount of loss due to partial shutdown of operations in a factory (Xc7) and so on. The potential of reduction Xc is computed from the above factors. If there is a reduction of electric power, the reduced quantity of power U2 and the reduction time period U3 are computed from functions, U2=F2 (Xa, Xb and Xc) and U3=F3 (Xa, Xb and Xc), considering the load reduction request time period (Xa) and incentive payment (Xb) in the presentation signal and the computed potential of reduction (Xc). When the computing section 101 in each of the customer's communication terminals C1 to Cn computes the reduced amount of power and reduction time period, a response signal outputting section or means 102 outputs a tender signal functioning as a response signal containing the reduced amount of power U2 and reduction time period U3 to the center communication terminal S. A customer's communication terminal may decide not to output a tender signal depending on the contents of a presentation signal from the center communication terminal S. When the center communication terminal S receives the tender signal, its selecting section S4 selects customers from the functions including parameters such as the reduction time period and reduced amount of power. For example, the selected customers may be any number of customers in the higher rank which has an increased product of the reduced amount of power times the reduction time period in each of the tender signals. Namely, a successful bid is made. After selection of the customers, a selection signal outputting section or means S5 in the center communication terminal S sends a successful bid signal as a selection signal including the reduced amount of power, the reduction time period and the incentive payment to each of the customer's communication terminals selected. As shown in Fig. 2 , for example, if the second customer's communication terminal C2 is selected, a successful bid signal is provided thereto. The reduced amount of power, the reduction time period and the incentive payment in the successful bid signal sent are computed from the reduced amount of power and reduction time period in the tender signal from each of the customer's communication terminals. A non-selection signal may be provided to the other customer's communication terminals which are not selected. The aforementioned successful bid signal may be a simple selection signal which does not include the reduced amount of power, the reduction time period and the incentive payment. When each of the customer's communication terminals receives a successful bid signal, its power reducing section or means 103 reduces the power supply to the group of connected loads, in accordance with the reduced amount of power and reduction time period in the successful bid signal. In the second embodiment of the present invention shown in Fig. 3, a plurality of customer's communication terminals C1 to Cn are connected to an electric power company's communication terminal or center communication terminal R, as in the first embodiment. The center communication terminal R comprises a predicted demand computing section S1 for computing a predicted demand U1 from a function U1=F1 (X1, X2, X3, X4, X5, X6, ...) when the center communication terminal receives present demand (X1) season (X2), day of the week (X3), time (X4), air temperature (X5), event schedule (X6), possible audience rating (X7) and so on, and a price determining section or means T1 for comparing the predicted demand with the power supply capacity to determine an electric power price. More particularly, if the predicted demand exceeds the power supply capacity, the power price is set to be relatively high. This is because the demand is prevented from exceeding the power supply capacity and also because if the demand is too high, the rate of heating in a power plant using coal and petroleum having increased unit costs for power generation is increased. On the contrary, if the predicted demand is lower than the power supply capacity, the power price is set to be relatively low so that a proper profit can be obtained by the electric power company. The determination of power price may be carried out for every thirty minute period. When the power price is determined, a price signal outputting section or means T2 in the center communication terminal R outputs a power price signal containing the determined power price to each of the customer's communication terminals connected C1 to Cn to the center communication terminal. The second embodiment can be mainly applied to cases where the customers are provided with independent electric power plants. More particularly, each of the customer's communication terminals compares the power price contained in the power price signal sent from the center communication terminal R with the power generation cost of the independent power plant and for selecting any one of these which is advantageous for that customer. If the parameters in the above function include an additional parameter indicative of the amount of buying schedule on the customer side X8, this may have been previously reported to the center communication terminal through the customer's communication terminal of the customer to determine the demand schedule. This aspect of the second embodiment is advantageous in that it can provide the reduction of equipment and communication costs, in comparison with the first embodiment. The second embodiment of the present invention, however, also includes the features of the first embodiment. The second embodiment is adapted to execute the power distribution control cycles shown by the first embodiment and by the additional features alternately at given time intervals. More particularly, as shown in Fig. 3, the center communication terminal R comprises a predicted demand computing section S1, a computing section S2, a presentation signal outputting section S3, a selecting section S4, a selection signal outputting section S4, a price determining section T1 and a price signal outputting section T2. As shown in Fig.4, the center communication terminal R executes the outputs of a selection and price signals alternately to each of the customer's communication terminals. The second embodiment can more finely control the power distribution than the first embodiment.

Claims: A power distribution control system comprising center communication terminal (S) and a plurality of customer's communication terminals (C1... Cn) operatively connected to said center communication terminal (S) through communication lines and to a group of loads, said center communication terminal (S) comprising presentation signal outputting means (S3) for outputting a presentation signal containing a load reduction request time period (Xa) and an incentive payment (Xb) to each of said customer's communication terminals (C1...Cn), and selection signal outputting means (S5) responsive to response signals from said customer's communication terminals (C1...Cn) for outputting a selection signal or signals to one or more customer's communication terminals (C1...Cn) selected based on functions including parameters relating to the reduced quantity of power (U2) and reduction time period (U3), contained in the response signal from one or more customer's communication terminals (C1...Cn), each of said customer's communication terminals (C1...Cn) comprising response signal outputting means (102) for outputting a response signal to said center communication terminal (S), said response signal containing the reduced quantity of power (U2) and reduction time period (U3) which are computed from the load reduction request time period (Xa), incentive payment (Xb) contained in the presentation signal from said center communication terminal (S), and a potential of reduction (Xc), and power reduction means (103) for reducing the power supply to the group of connected loads for a given time period, based on the selection signal sent to the respective customer's communication terminal (C1 ... Cn) from said center communication terminal (S). A power distribution control system according to claim 1, wherein each of the selected customer's communication terminals (C1... Cn) has an increased product of the reduced quantity of power (U2) times the reduction time period (3). A power distribution control system as defined in claim 1 or 2 wherein said selection signal outputting means (S5) of the center communication terminal (S) is adapted to output a selection signal containing the reduction time period, reduced quantity of power and incentive payment which are computed from the reduced quantity of power and reduction time period in the response signal from each of said customer's communication terminals (C1 ... Cn). A power distribution control system as defined in any of claims 1 to 3 wherein said center communication terminal (T) further comprises predicted demand computing means (S1) for computing a predicted demand from a demand predicting potential, price determining means (T1) for comparing said predicted demand with a power supply capacity to determine an electric power price, and price signal outputting means (T2) for outputting a power price signal containing the determined power price to each of said customer's communication terminals (C1 ... Cn).

Inventors: INOUE MASAHIRO, IWATSUBO RIEKO, KUSHIRO NORIYUKI, MARUYAMA KAZUHIRO, INOUE, MASAHIRO, IWATSUBO, RIEKO, KUSHIRO, NORIYUKI, MARUYAMA, KAZUHIRO, Inoue, Masahiro, Mitsubishi Denki K.K., Iwatsubo, Rieko, Mitsubishi Denki K.K., Kushiro, Noriyuki, Mitsubishi Denki K.K., Maruyama, Kazuhiro, Mitsubishi Denki K.K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1993
Main classification: H02J13
IPC codes: H02J3, H02J13