AU2019205015B2

AU2019205015B2 - Power generation plan developing apparatus, power generation plan developing method, and recording medium

Info

Publication number: AU2019205015B2
Application number: AU2019205015A
Authority: AU
Inventors: Atsushi Hashimoto; Jin Murata; Tomoshi Otsuki; Shotaro Yamane
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2016-10-14
Filing date: 2019-07-12
Publication date: 2020-09-24
Anticipated expiration: 2037-10-03
Also published as: AU2019205015A1; AU2017239489A1; JP2018064423A; TW201814564A; JP6716420B2; TWI660282B

Abstract

In one embodiment, a calculator calculates amounts of power generation of first to X-th (X is at least two) generators at first to M-th (M is at least two) times in an order of the first 5 to M-th times, and calculates the amounts of power generation of the first to X-th generators at an N-th (N ranges from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time. A creator creates a power generation plan for the first to X-th generators, based on 10 the amounts of power generation of the first to X-th generators at the first to M-th times. The calculator determines whether to activate (to stop), at the N-th time, the generator being stopped (in operation) at the (N-1)-th time, in an order from the first to X-th (from the X-th to first) generators. 15 (Fig. 1) 1120 LL. LU Lu CjCD , C LU LunU L-U CD C-9 LUU 0F- C/D LU W> C'C) ZD~

Description

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POWER GENERATION PLAN DEVELOPING APPARATUS, POWER GENERATION PLAN DEVELOPING METHOD, AND RECORDING MEDIUM

FIELD Embodiments described herein relate to a power generation plan developing apparatus, a power generation plan developing method, and a recording medium.

BACKGROUND Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field. In a power generation department in an electric utility corporation, an operation that predicts a power demand in the future and develops a power generation plan for generators so as to satisfy the predicted power demand is one of important operations. For example, in a case where LNG (liquefied natural gas) is used as a fuel for generators, reservation of LNG has more limitations than reservation of oil or coal because LNG is reserved in special tanks. Consequently, an accurate power generation plan for appropriately consume and replenishes LNG according to the power demand is required. In a case where power that satisfies the power demand is supplied by multiple generators, it is desirable to reduce the power generation cost by stopping some generators when the power demand decreases. However, if the generator is once stopped, reactivation requires a long time. Consequently, there is a case where the generator cannot be stopped. When the power demand gradually decreases, the generator cannot be stopped in some cases with the amount of reduction in power demand being smaller than the minimum amount of power generation of the stop target generator. Consequently, activation and stop control for the generator to reduce the power generation cost cannot be sufficiently performed in some cases.

SUMMARY One embodiment provides a power generation plan developing apparatus comprising: a power generation amount calculator configured to calculate amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time, and calculate the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time; and a power generation plan creator configured to create a power generation plan for the first to X-th generators, based on the amounts of power generation of the first to X-th generators at the first to M-th times, wherein the power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs, and the power generation amount calculator determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs. One embodiment provides a power generation plan developing method comprising: calculating, by a power generation amount calculator, amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time and calculating, by the power generation amount calculator, the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time; and creating, by a power generation plan creator, a power generation plan for the first to X-th generators, based on the amounts of power generation of the first to X-th generators at the first to M-th times, wherein the power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs, and the power generation amount calculator determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs. One embodiment provides a non-transitory computer-readable recording medium containing a power generation plan developing program which causes a computer to perform a power generation plan developing method, the method comprising: calculating, by a power generation amount calculator, amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time and calculating, by the power generation amount calculator, the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time; and creating, by a power generation plan creator, a power generation plan for the first to X-th generators, based on the amounts of power generation of the first to X-th generators at the first to M-th times, wherein the power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs, and the power generation amount calculator determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs. One embodiment provides a power generation plan developing apparatus comprising: a power generation amount calculator configured to calculate amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time, and calculate the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time; and a power generation plan creator configured to create a power generation plan for the first to X-th generators, based on the amounts of power generation of the first to X-th generators at the first to M-th times, wherein the power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs, when a total amount of power generation of the first to X-th generators at the N-th time increases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the power generation amount calculator determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs, when the total amount of power generation of the first to X-th generators at the N-th time decreases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the apparatus further comprises an increase determiner configured to determine, in a case where the total amount of power generation at the N-th time decreases by a first value from the total amount of power generation at the (N-1)-th time and the first value is lower than a minimum amount of power generation of a Y-th (Y is an integer ranging from two to X) generator, whether or not the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by a second value so as to allow a total of the first value and the second value to reach the minimum amount of power generation of the Y-th generator, and when it is determined that the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by the second value, the power generation amount calculator stops the Y-th generator at the N-th time, and increases the amount of power generation of the (Y-1)-th generator at the N-th time by the second value from the amount of power generation of the (Y-1)-th generator at the (N-1)-th time. One embodiement provides a power generation plan developing method comprising: calculating, by a power generation amount calculator, amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time and calculating, by the power generation amount calculator, the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time; and creating, by a power generation plan creator, a power generation plan for the first to X-th generators, based on the amounts of power generation of the first to X-th generators at the first to M-th times, wherein the power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs, when a total amount of power generation of the first to X-th generators at the N-th time increases from the total amount of power generation of the first to the X-th generators at the (N-1)-th time, the power generation amount calculator determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs, when the total amount of power generation of the first to X-th generators at the N-th time decreases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the method further comprises determining, by an increase determiner, in a case where the total amount of power generation at the N-th time decreases by a first value from the total amount of power generation at the (N-1)-th time and the first value is lower than a minimum amount of power generation of a Y-th (Y is an integer ranging from two to X) generator, whether or not the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by a second value so as to allow a total of the first value and the second value to reach the minimum amount of power generation of the Y-th generator, and when it is determined that the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by the second value, the power generation amount calculator stops the Y-th generator at the N-th time, and increases the amount of power generation of the (Y-1)-th generator at the N-th time by the second value from the amount of power generation of the (Y-1)-th generator at the (N-1)-th time. One embodiment provides a non-transitory computer-readable recording medium containing a power generation plan developing program which causes a computer to perform a power generation plan developing method, the method comprising: calculating, by a power generation amount calculator, amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time and calculating, by the power generation amount calculator, the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time; and creating, by a power generation plan creator, a power generation plan for the first to X-th generators, based on the amounts of power generation of the first to X-th generators at the first to M-th times, wherein the power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs, when a total amount of power generation of the first to X-th generators at the N-th time increases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the power generation amount calculator determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs, when the total amount of power generation of the first to X-th generators at the N-th time decreases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the method further comprises determining, by an increase determiner, in a case where the total amount of power generation at the N-th time decreases by a first value from the total amount of power generation at the (N-1)-th time and the first value is lower than a minimum amount of power generation of a Y-th (Y is an integer ranging from two to X) generator, whether or not the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by a second value so as to allow a total of the first value and the second value to reach the minimum amount of power generation of the Y-th generator, and when it is determined that the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by the second value, the power generation amount calculator stops the Y-th generator at the N-th time, and increases the amount of power generation of the (Y-1)-th generator at the N-th time by the second value from the amount of power generation of the (Y-1)-th generator at the (N-1)-th time. A further embodiment provides a power generation plan developing apparatus comprising: a demand data storage to store demand data that is time-series data regarding a prediction of power demand; a condition storage to store a power generation creation condition that is input from a user interface; a power generation amount calculator configured to calculate amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time, and calculate the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time; a power generation plan creator configured to create a power generation plan for the first to X-th generators, based on the demand data, the power generation creation condition, and the amounts of power generation of the first to X-th generators at the first to M-th times; and a power generation plan storage to store the power generation plan to be output to the user interface, wherein the power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs, when a total amount of power generation of the first to X-th generators at the N-th time increases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the power generation amount calculator determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs, when the total amount of power generation of the first to X-th generators at the N-th time decreases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the apparatus further comprises an increase determiner configured to determine, in a case where the total amount of power generation at the N-th time decreases by a first value from the total amount of power generation at the (N-1)-th time and the first value is lower than a minimum amount of power generation of a Y-th (Y is an integer ranging from two to X) generator, whether or not the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by a second value so as to allow a total of the first value and the second value to reach the minimum amount of power generation of the Y-th generator, and when it is determined that the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by the second value, the power generation amount calculator stops the Y-th generator at the N-th time, and increases the amount of power generation of the (Y-1)-th generator at the N-th time by the second value from the amount of power generation of the (Y-1)-th generator at the (N-1)-th time. A further embodiment provides a power generation plan developing method comprising: storing, in a demand data storage, demand data that is time-series data regarding a prediction of power demand; storing, in a condition storage, a power generation creation that is input from a user interface; calculating, by a power generation amount calculator, amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time and calculating, by the power generation amount calculator, the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time; creating, by a power generation plan creator, a power generation plan for the first to X-th generators, based on the demand data, the power generation creation condition, and the amounts of power generation of the first to X-th generators at the first to M-th times; and storing, in a power generation plan storage, the power generation plan to be output to the user interface, wherein the power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs, when a total amount of power generation of the first to X-th generators at the N-th time increases from the total amount of power generation of the first to the X-th generators at the (N-1)-th time, the power generation amount calculator determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs, when the total amount of power generation of the first to X-th generators at the N-th time decreases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the method further comprises determining, by an increase determiner, in a case where the total amount of power generation at the N-th time decreases by a first value from the total amount of power generation at the (N-1)-th time and the first value is lower than a minimum amount of power generation of a Y-th (Y is an integer ranging from two to X) generator, whether or not the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by a second value so as to allow a total of the first value and the second value to reach the minimum amount of power generation of the Y-th generator, and when it is determined that the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by the second value, the power generation amount calculator stops the Y-th generator at the N-th time, and increases the amount of power generation of the (Y-1)-th generator at the N-th time by the second value from the amount of power generation of the (Y-1)-th generator at the (N-1)-th time. A further embodiment provides a non-transitory computer-readable recording medium containing a power generation plan developing program which causes a computer to perform a power generation plan developing method, the method comprising: storing, in a demand data storage, demand data that is time-series data regarding a prediction of power demand; storing, in a condition storage, a power generation creation condition that is input from a user interface; calculating, by a power generation amount calculator, amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time and calculating, by the power generation amount calculator, the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time; creating, by a power generation plan creator, a power generation plan for the first to X-th generators, based on the demand data, the power generation creation condition, and the amounts of power generation of the first to X-th generators at the first to M-th times; and storing, in a power generation plan storage, the power generation plan to be output to the user interface, wherein the power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs, when a total amount of power generation of the first to X-th generators at the N-th time increases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the power generation amount calculator determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs, when the total amount of power generation of the first to X-th generators at the N-th time decreases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the method further comprises determining, by an increase determiner, in a case where the total amount of power generation at the N-th time decreases by a first value from the total amount of power generation at the (N-1)-th time and the first value is lower than a minimum amount of power generation of a Y-th (Y is an integer ranging from two to X) generator, whether or not the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by a second value so as to allow a total of the first value and the second value to reach the minimum amount of power generation of the Y-th generator, and when it is determined that the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by the second value, the power generation amount calculator stops the Y-th generator at the N-th time, and increases the amount of power generation of the (Y-1)-th generator at the N-th time by the second value from the amount of power generation of the (Y-1)-th generator at the (N-1)-th time.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of a power generation plan developing apparatus of a first embodiment; FIG. 2 is a graph for illustrating a stop permissibility determining process in a first embodiment; FIGS. 3A to 3D are diagrams for illustrating the amount of power generation of a generator in the first embodiment; FIGS. 4A to 4C are graphs for illustrating the amount of power generation of the generator in the first embodiment; FIGS. 5A to 5C are graphs for illustrating a stop priority calculating process in a comparative example of the first embodiment; FIGS. 6A to 6C are graphs for illustrating a stop priority calculating process in the first embodiment; FIGS. 7A and 7B are diagrams for comparing the stop priority calculating processes in the first embodiment and its comparative example; FIG. 8 is a flowchart showing a power generation plan developing method in the first embodiment; FIG. 9 is a flowchart showing the details of step S3 in the first embodiment; FIG. 10 is a flowchart showing the details of step S17 in the comparative example of the first embodiment; FIG. 11 is a flowchart showing the details of step S24 in the comparative example of the first embodiment; FIG. 12 is a flowchart showing the details of step S17 in the first embodiment; FIG. 13 is a flowchart showing the details of step S45 in the first embodiment; FIG. 14 is a flowchart showing the details of step S43 in the first embodiment; FIG. 15 is a flowchart showing the details of step S46 in the first embodiment; FIG. 16 is a flowchart showing the details of step S43 in a second embodiment; FIG. 17 is a flowchart showing a power generation plan developing method in the second embodiment; FIG. 18 is a flowchart showing the details of step S15 in a third embodiment; FIG. 19 is a diagram for illustrating a configuration example of a pipe network in a fourth embodiment; and FIG. 20 is a flowchart showing the details of a power generation plan developing method in the fourth embodiment.

DETAILED DESCRIPTION Embodiments will now be explained with reference to the accompanying drawings. In FIGS. 1 to 20, the same or similar components are denoted by the same reference numerals, and overlapping explanations thereof are omitted. In one embodiment, a power generation plan developing apparatus includes a power generation amount calculator configured to calculate amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time, and calculate the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time. The apparatus further includes a power generation plan creator configured to create a power generation plan for the first to X-th generators, based on the amounts of power generation of the first to X-th generators at the first to M-th times. The power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs. The power generation amount calculator further determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs. (First Embodiment) FIG. 1 is a block diagram showing a configuration of a power generation plan developing apparatus 1 of a first embodiment. The power generation plan developing apparatus 1 develops a power generation plan (operation plan) that defines when generators are activated and how much power generation outputs the generators operate to achieve. The generators can include various generators with different fuels and power generation schemes. The power generation plan developing apparatus 1 transmits and receives data to and from a demand predicting system 2, a power generation data obtaining system 3, and a user input and output I/F (interface) 4. The power generation plan developing apparatus 1 includes a demand data storage 11, a basic characteristic data storage 12, a stop permissibility determiner 13, a stop priority calculator 14, a sequential processor 15, a power generation plan creator 16, a power generation plan creation condition storage 17, and a power generation plan data storage 18. The stop priority calculator 14 is an example of an increase determiner. The sequential processor 15 is an example of a power generation amount calculator. The demand predicting system 2 supplies the power generation plan developing apparatus 1 with demand data that is time-series data regarding a prediction of power demand. The demanded power predicted from the demand data is also a supply power that the generators serving as power generation plan development target are required to satisfy. The demand data supplied from the demand predicting system 2 is stored in the demand data storage 11. The power generation data obtaining system 3 supplies the power generation plan developing apparatus 1 with the basic characteristic data that is data regarding the basic characteristics of generators. Examples of the basic characteristic data include the values of rated MW and minimum MW of each generator, and information and the like regarding limitations imposed on each generator. The basic characteristic data supplied from the power generation data obtaining system 3 is stored in the basic characteristic data storage 12. The basic characteristic data storage 12 stores limitation conditions that the power generation plan is required to satisfy, and various conditions regarding the power generation cost, for creating the power generation plan. A first example of the limitation conditions is a limitation (supply demand balance limitation) that the amount of power supply at each time should be at least the power demand prediction. A second example is a limitation (maximum and minimum limitations) regarding the maximum values and the minimum values of outputs of generators in operation. A third example is a limitation (output designating limitation) that fixes the outputs of certain generators at certain times to predetermined values. A fourth example is a limitation (must-run limitation) that "k" or more generators should be stopped or activated with respect to a certain generator or a certain combination of generators. A fifth example is a limitation (stop time period limitation) that stopping for a predetermined time period is required to activate a generator having once been stopped next time. A sixth example is a limitation (curve limitation) that when a certain generator is activated or stopped, a predetermined stop curve limitation or an activation curve limitation should be satisfied. A seventh example is a limitation (variation rate limitation) on the amount of variation from that at the immediately preceding time to that at the subsequent time. An eighth example is a limitation (activation and stop restriction limitation) that a certain combination of generators cannot be activated or stopped without a lapse of a certain time width. A ninth example is an upper and lower limit limitation (pipe limit) regarding the flow rate in a gas pipe through which gas passes. A tenth example is an upper and lower limit limitation (group output limitation) regarding the total amount of power generation of a certain combination of generators. Simply, the power generation cost is a cost required for power generation of 1 kWh, which varies according to the difference in fuel cost and the difference in power generation efficiency. Note that the power generation cost may be a cost to which 1) the fixed cost of the generators themselves, 2) a cost regarding an activation process and a stop process in a case where an activation determination or a stop determination is executed (e.g., also including a cost regarding heat loss related to activation and stop) and the like have been added. Such costs may be those having different values with respect to each generator, each time, or each immediately previous output of the generator. It is desirable that the power generation plan be a plan that satisfy the limitation conditions described above as much as possible and make the total amount of power generation costs small as much as possible. The user input and output I/F 4 is a user interface used by a user for inputting and outputting information. For example, the user input and output I/F 4 is used to receive the power generation plan creation condition on a screen of the power generation plan developing apparatus 1, and to output the details of the power generation plan data on the screen of the power generation plan developing apparatus 1. The power generation plan creation condition input through the user input and output I/F 4 is stored in the power generation plan creation condition storage 17. Meanwhile, the power generation plan data is read from the power generation plan data storage 18 and is output to the user input and output I/F 4. Examples of the power generation plan creation condition include the number of repetitions of a process for creating the power generation plan, the margins of variables and conditions, and the swing/stop ratios of the generators. The stop permissibility determiner 13 determines whether or not the generator can be stopped at the time when the amount of power generation of the generator at a predetermined time is calculated. The stop priority calculator 14 determines whether the amount of power generation of a generator other than a power generator whose amount of power generation at a predetermined time is intended to be calculated can be increased or not to stop the generator. The details of the stop permissibility determiner 13 and the stop priority calculator 14 are described later. The sequential processor 15 calculates the amounts of power generation of multiple generators at multiple times in an ascending order of time, and uses the amounts of power generation of the generators at a certain time to calculate the amount of power generation at the subsequent time. The sequential processor 15 determines whether to activate the generators at a certain time or not in an ascending order of power generation costs of the generators, and determines whether to stop the generators at a certain time or not in a descending order of power generation costs. Consequently, the power generation plan that suppresses the power generation cost to be low can be developed in a short time period with the logic of a simple sequential process. The details of the sequential processor 15 are described later. The power generation plan creator 16 obtains the demand data from the demand data storage 11, obtains the power generation plan creation condition from the power generation plan creation condition storage 17, and obtains the calculation result of the plan at each time from the sequential processor 15. The power generation plan creator 16 then creates (generates) the power generation plan on the multiple generators described above at the multiple times, on the basis of the obtained demand data, power generation plan creation condition, and plan. The power generation plan created by the power generation plan creator 16 is stored, as power generation plan data, in the power generation plan data storage 18 on the time-mesh basis. The processes of the stop permissibility determiner 13, the stop priority calculator 14, the sequential processor 15 and the power generation plan creator 16 can be achieved by causing the CPU (Central Processing Unit) of the power generation plan developing apparatus 1 to execute a power generation plan developing program stored in an HDD (Hard Disc Drive) of the power generation plan developing apparatus 1, for example. In this embodiment, a computer-readable recording medium stored with this program may be inserted into a memory interface of the power generation plan developing apparatus 1, and this program may be installed from the recording medium into the HDD. FIG. 2 is a graph for illustrating a stop permissibility determining process in the first embodiment. Curves a, a' and a" in FIG. 2 indicate examples of the temporal variation in power demand predicted from the demand data. These show examples where the power demand gradually decreases and subsequently gradually increases. Note that the power demand of the curve a' more gradually varies than the power demand of the curve a does, and the power demand of the curve a" more steeply varies than the power demand of the curve a does. The power demand of the curves c, cc' and c" have the same value at time ti. According to the curve a, the power demand starts to decrease at time ti, and the power demand returns to the value that is the value at time ti, at time t 4 after a lapse of a time period T after time ti. According to the curve ax', the power demand returns to the value that is the value at time ti, at time after a lapse of a time period T' (> T) after time ti. According to the curve a", the power demand returns to the value that is the value at time ti, at time after a lapse of a time period T" (< T) after time ti. The curve P in FIG. 2 shows an activation and stop control of a certain generator. According to the curve P, the stop process for the generator is started at time ti, the stop process for the generator is completed at time t 2 , the reactivation process for the generator is started at time t 3 , and the reactivation process for the generator is completed at time t4 .

FIG. 2 shows an example of controlling the activation and stop of the generator as the curve P, in a case where the power demand is predicted to vary as the curve a. More specifically, the power demand begins to decrease at time ti. At time t 4 ,

the power demand returns to the value at time ti.

Consequently, it is planned to stop the generator from time ti to time t 4

. In this case, the relationship between the time period from time t 2 to time t4 (hereinafter called "stop time period") and the minimum stop time period S of the generator should be discussed. The minimum stop time period S is the minimum time period required from the completion of stopping the generator to the completion of reactivating the generator. The generator cannot be reactivated in a shorter time period than the minimum stop time period S. The minimum stop time period S may have a different value on a generator-by-generator basis, or a value common to some generators. When the power demand varies as the curve a, the stop time period is the same as the minimum stop time period S. Consequently, the generator can be stopped from time ti to time t 4 (= ti + T). That is, in a case where the stop process for the generator is started at time ti, the reactivation process for the generator can be completed at time t 4 (= ti + T) at which the power demand is restored. Likewise, when the power demand varies as the curve a', the stop time period is longer than the minimum stop time period S. Consequently, the generator can be stopped from time ti to time ti + T'. That is, in a case where the stop process for the generator is started at time ti, the reactivation process for the generator can be completed at time ti + T' at which the power demand is restored. On the other hand, in a case where the power demand varies as the curve a", the stop time period is shorter than the minimum stop time period S. Consequently, the generator cannot be stopped from time ti to time ti + T". That is, when the stop process for the generator is started at time ti, the reactivation process for the generator cannot be completed at time ti + T" at which the power demand is restored. When the stop permissibility determiner 13 (FIG. 1) determines whether the stop process for a certain generator is started at time ti or not, this determiner determines whether the generator can be stopped at time ti or not on the basis of the minimum stop time period S of the generator and the variation in power demand. More specifically, if the time at which the power demand is restored is time t 2 + S or thereafter as with the cases of the curve a or the curve a', it is determined that the generator can be stopped. On the other hand, if the time at which the power demand is restored is before time t 2

+ S as the case of the curve a", it is determined that the generator cannot be stopped. The determination result of the stop permissibility determiner 13 is output to the sequential processor 15. Before determination of whether the stop process for a certain generator is started at time ti or not, the sequential processor 15 refers to the determination result of the stop permissibility determiner 13. In a case where it has been determined that the generator can be stopped at time ti, the generator is stopped at time ti as required (i.e., the stop process is started at time ti). On the contrary, in a case where it has been determined that the generator cannot be stopped at time ti, the generator is not stopped at time ti. FIGS. 3A to 3D are diagrams for illustrating the amount of power generation of a generator in the first embodiment. FIGS. 3A to 3D show the amount of power generation of one generator. In FIG. 3A, the amount of power generation of the generator in operation is the maximum amount of power generation (max). In FIG. 3C, the amount of power generation of the generator in operation is the minimum amount of power generation (min). In FIG. 3B, the amount of power generation of the generator in operation is a value between the maximum amount of power generation and the minimum amount of power generation. In FIG. 3D, the amount of power generation of the stopped generator is zero. As described above, the amount of power generation of the generator in operation can be a value between the maximum amount of power generation and the minimum amount of power generation, but cannot be a value smaller than the minimum amount of power generation. Consequently, when the amount of power generation of the generator in operation is intended to be lower than the minimum amount of power generation, the generator should be stopped to make the amount of power generation zero. FIGS. 4A to 4C are graphs for illustrating the amount of power generation of the generator in the first embodiment. FIG. 4A shows the temporal variation in power demand and the total amount of power generation of multiple generators that operate to satisfy the power demand. The power generation plan developing apparatus 1 develops the power generation plan so that the total amount of power generation at each time can be at least the power demand. For example, the total amount of power generation at time TN is set to at least the power demand at time TN. Note that it is desirable that the total amount of power generation be close to the power demand as much as possible so as to avoid useless power generation. FIG. 4A shows an example that the total amount of power generation at each time approximately coincides with the power demand. In FIG. 4A, the total amount of power generation is set on a time-mesh basis. The width of one mesh in this embodiment is, for example, 30 minutes. In this case, the total amount of power generation at each time is provided as the total amount of power generation (mWh) for 30 minutes while the power demand at each time is provided as the amount of power demand (mWh) for 30 minutes. The power generation plan developing apparatus 1 calculates the amounts of power generation of multiple generators at multiple times, and creates the power generation plan on the basis of the calculation results. These times are examples of first to M-th ("M" is an integer of at least "2") times. These generators are examples of first to X-th ("X" is an integer of at least "2") generators. More specifically, the power generation plan developing apparatus 1 calculates the amounts of power generation of multiple generators at multiple times in an ascending order of time, and uses the amounts of power generation of the generators at a certain time to calculate the amounts of power generation at the subsequent time. For example, in FIG. 4A, the amounts of power generation of the generators at time TN are calculated on the basis of the amounts of power generation of the generators at time TN-1. Times TN and TN-i are examples of the N-th and (N-1)-th times ("N" is an integer ranging from "2" to "M"), respectively. Specific examples of these generators are first to third generators (U1 to U 3 ) described later. FIG. 4B shows the total amount of power generation at time TN-1 and the amounts of power generation of the first to third generators (U1 to U 3 ) at time TN-1 with hatching. At time TN-1, the amount of power generation of the first generator is the maximum amount of power generation, the amount of power generation of the second generator is a value between the maximum amount of power generation and the minimum amount of power generation, and the amount of power generation of the third generator is the minimum amount of power generation. The power generation costs of the first, second and third generators are 50, 60 and 70 yen, respectively. In this embodiment, a power generation plan is developed so that the generator having a low power generation cost as much as possible can be activated and the generator having the low power generation cost can have a large amount of power generation. Consequently, the amount of power generation of the first generator at time TN-1 is set to the maximum amount of power generation. However, the amount of power generation of the second generator is not set to the maximum amount of power generation. This is because setting of the second generator to the maximum amount of power generation requires the third generator to be set to have an amount of power generation smaller than the minimum amount of power generation but the setting is impossible as described with reference to FIG. 3. FIG. 4C shows the total amount of power generation at time TN and the amounts of power generation of the first to third generators at time TN with hatching. Furthermore, the amounts of power generation of the first to third generators at time TN-1 is also shown for the sake ofcomparison. In FIG. 4C, the power demand at time TN decreases by A1 from the power demand at time TN-1. Consequently, the total amount of power generation at time TN also decreases by A1 from the total amount of power generation at time TN-1.

Consequently, the amount of power generation of any of the first to third generators is required to be reduced, or any of the first to third generators is required to be stopped. When the total amount of power generation at time TN

increases from the total amount of power generation at time TN-1, the power generation plan developing apparatus 1 determines whether the stopped generators at time TN-i are activated at time TN or not in an ascending order of power generation costs (i.e., the order from the first to third generators). On the contrary, when the total amount of power generation at time TN decreases from the total amount of power generation at time TN-1, the power generation plan developing apparatus 1 determines whether the generators in operation at time TN-i are stopped at time TN or not in a descending order of power generation costs (i.e., the order from the third to first generators). Consequently, in FIG. 4C, it is determined whether to stop the third generator or not. At this time, the fact that the amount of reduction A1 in total amount of power generation is smaller than the minimum amount of power generation A of the third generator should be discussed (Ai < A). This is because stopping the third generator makes the total amount of power generation at time TN smaller than the power demand at time TN.

The power generation plan developing apparatus 1 then considers possible increase in the amount of power generation of the second generator at time TN from the amount of power generation of the second generator at time TN-i by A2 (= A - A1). This is because if the amount of power generation of the second generator can be increased by A2, the amount of power generation of the third generator can be reduced by A1 + A2 (i.e., A). In this case, the third generator can be stopped while the total amount of power generation at time TN is set to be the same value as the power demand at time TN. A1 and A2 are examples of a first value and a second value, respectively. The second and third generators are examples of (Y-1)-th and Y-th generators ("Y" is an integer ranging from "2" to "X"), respectively. As described above, the power generation plan developing apparatus 1 determines whether or not the amount of power generation of the second generator at time TN-1 can be increased by A2 so that the total of A1 and A2 can reach the minimum amount of power generation A of the third generator. In FIG. 4C, even if the amount of power generation of the second generator at time TN-1 is increased by A2, the amount of power generation of the second generator does not exceed the maximum amount of power generation. Consequently, the increase in amount of power generation is determined to be "possible". In this case, the power generation plan developing apparatus 1 creates a plan for time TN so as to stop the third generator at time TN and to increase the amount of power generation of the second generator at time TN by A2 from the amount of power generation of the second generator at time TN-1. The possibility of the increase in amount of power generation is determined by the stop priority calculator 14 (FIG. 1). The determination result is output to the sequential processor 15. When the determination result is "possible", the sequential processor 15 creates a plan that stops the third generator and increases the amount of power generation of the second generator. On the contrary, when the determination result is "impossible", a plan is created that does not stop the third generator and reduces the amount of power generation of the second generator by A1. In this case, the sequential processor 15 refers not only to the determination result of the stop priority calculator 14 but also to the determination result of the stop permissibility determiner 13. More specifically, the determination result of whether the third generator can be stopped at time TN or not is referred to. When both the determination results of the stop permissibility determiner 13 and the stop priority calculator 14 are "possible", the sequential processor 15 creates a plan that stops the third generator and increases the amount of power generation of the second generator. On the contrary, when any of the determination results is "impossible", a plan is created that does not stop the third generator and reduces the amount of power generation of the second generator by A1. Note that this embodiment may adopt a configuration where the sequential processor 15 only refers to the determination result of the stop priority calculator 14. For example, in a case of application of this embodiment to situations where the variation in power demand is sufficiently gradual, the sequential processor 15 does not refer to the determination result of the stop permissibility determiner 13 and only refers to the determination result of the stop priority calculator 14 to create the plan at each time. Next, the stop priority calculating processes in the first embodiment and its comparative example are compared with each other. FIGS. 5A to 5C are graphs for illustrating a stop priority calculating process in a comparative example of the first embodiment. FIG. 5A shows reduction in total amount of power generation at time TN from the total amount of power generation at time TN-i by A1. FIG. 5B shows that A1 is smaller than the minimum amount of power generation A of the third generator (A1 < A). In this case, as described above, the amount of power generation of the third generator cannot be reduced by A1. Consequently, in this comparative example, the amount of power generation of the second generator at time TN is reduced by A1 from the amount of power generation of the second generator at time TN-i to maintain the amount of power generation of the third generator to be the minimum amount of power generation A (FIG. 5C). As a result, the second generator having the low power generation cost cannot be sufficiently utilized, and the third generator having the high power generation cost is needlessly operated. FIGS. 6A to 6C are graphs for illustrating a stop priority calculating process in the first embodiment. FIG. 6A shows reduction in total amount of power generation at time TN from the total amount of power generation at time TN-1 by A1. FIG. 6B shows that A1 is smaller than the minimum amount of power generation A of the third generator (A1 < A). Note that as shown in FIG. 6B, the amount of power generation of the second generator can be increased by A2 (= A - A1). In this case, according to this embodiment, the third generator is stopped at time TN, and the amount of power generation of the second generator at time TN is increased from the amount of power generation of the second generator at time TN-1 by A2 (FIG. 6C). Consequently, the third generator having the high power generation cost is stopped while the second generator having the low power generation cost can be sufficiently utilized. Before the process of FIG. 6C, the sequential processor 15 of this embodiment refers to the determination results of the stop permissibility determiner 13 and the stop priority calculator 14. That is, the determination result of whether the third generator can be stopped at time TN or not and the determination result of whether the amount of power generation of the second generator can be increased by A2 at time TN or not are referred to. When any of the determination results is "impossible", the processes in FIG. 5C are executed instead of the processes in FIG. 6C. FIGS. 7A and 7B are diagrams for comparing the stop priority calculating processes in the first embodiment and its comparative example. FIG. 7A pertains to the comparative example, and shows the amounts of power generation of the first to third generators at time TN. As show in FIG. 7A, application of this comparative example in situations where the power demand is gradually decreasing maintains the amount of power generation of the generator having the high power generation cost to the minimum amount of power generation, which is a cause of increase in power generation cost. In FIG. 7A, the amount of power generation of the second generator does not reach the maximum amount of power generation while the third generator operates at the minimum amount of power generation. On the other hand, FIG. 7B pertains to the first embodiment, and shows the amounts of power generation of the first to third generators at time TN. As shown in FIG. 7B, application of this embodiment in situations where the power demand is gradually decreasing can stop the generator having the high power generation cost, thereby allowing the power generation cost to be reduced. In FIG. 7B, the second generator operates at the maximum amount of power generation while the third generator is stopped. FIG. 8 is a flowchart showing a power generation plan developing method in the first embodiment. The power generation plan developing method is executed by the power generation plan developing apparatus 1 in FIG. 1. First, an input file for executing the power generation plan developing method is read (step Si) to obtain the required demand data, basic characteristic data, power generation plan creation condition and the like. Next, a preprocess before creation of the power generation plan is executed (step S2). Examples of the preprocess include a calculation process regarding the pipes (pipelines) provided between the generators, and a calculation process regarding the activation and stop curve of the generator. Next, a planning process according to a sequential method is executed (step S3). More specifically, processes by the stop permissibility determiner 13, stop priority calculator 14, sequential processor 15 and the power generation plan creator 16 are executed. The details of step S3 are described later. Next, a postprocess after creation of the power generation plan is executed (step S4). An example of the postprocess is a process of adding the activation and stop curve of the generator. Next, the created power generation plan is written into an output file (step S5) to store the plan as power generation plan data. FIG. 9 is a flowchart showing the details of step S3 in the first embodiment. First, the plan for time T1 is created (step S11), and subsequently the plan for times T 2 to T are created by a loop process (steps S12 to S19). Times T1 to T correspond to examples of the first to M-th times. Hereinafter, a process of creating the plan for time TN is described. First, a process regarding the generator in operation at time TN-1 is executed (step S13). More specifically, in a case where the amount of power generation of a certain generator in operation at time TN-1 can be maintained, the amount of power generation of the generator is maintained also at time TN. Here, in a case where the generator cannot be maintained to be activated at time TN owing to an output fixing limitation, must-run limitation, gas pipe lower limit limitation, group output lower limit limitation and the like, the generator is stopped. Next, a process regarding the stopped generator at time TN-1 is executed (step S14). More specifically, it is determined whether a certain stopped generator at time TN-1 is required to be activated at time TN or not. If required, the generator is activated at time TN. Here, in a case where the generator is required to be activated at time TN owing to the output fixing limitation, must-run limitation, gas pipe lower limit limitation, group output lower limit limitation and the like, the generator is activated. Next, a process of causing each generator to satisfy the upper and lower limit limitation is applied (step S15). Examples of the upper and lower limit limitation include limitations regarding the output of the generator, the output of a group of generators, the physical quantity related to the pipes, and the upper and lower limits of output variation rate and the like. The details of the upper and lower limit limitation are described later. Next, it is determined whether the limitation condition other than the supply demand balance limitation is satisfied or not (step S16). When it is determined that the limitation other than the supply demand balance limitation is satisfied in step S16, the processes of activation, stop and output change of each generator are executed (step S17). More specifically, the generator is activated or stopped, or the output (amount of power generation) of the generator is changed. The details of these processes are also described later. Next, it is determined whether creation of the plan for time TN has succeeded or not (step S18). If it is determined as success in step S18, the process at time TN is finished, the process at time TN+1 is started. In this manner, the plans at times T1 to TM are created, and the power generation plan is created by integrating these plans. In this embodiment, repetition of the processes in steps S12 to S19 without turning back can create the power generation plan. In this meaning, the process is called a sequential time process. If it is determined that the limitation is not satisfied in step S16, it is determined that the creation of the plan for time TN has failed. In this case, the process of creating the power generation plan may be stopped, or the result may be ignored and the processes thereafter may be continued. In the latter case, after completion of the power generation plan, it can be considered that the process of satisfying the limitation is performed automatically or manually. This is also applicable to the case of determination of failure in step S18. Hereinafter, as to the processes of activation, stop and output change in step S17, step S17 in the first embodiment and step S17 in its comparative example are described. FIG. 10 is a flowchart showing the details of step S17 in the comparative example of the first embodiment. In this comparative example, a demand prediction value (power demand) at time TN is calculated on the basis of the demand data (step S21). Next, it is determined whether the demand prediction value at time TN is at least the total amount of power generation at time TN-1 or not (step S22). When the demand prediction value at time TN is at least the total amount of power generation at time TN-1, the total amount of power generation at time TN is required to be increased to the demand prediction value at time TN to support increase in demand. An increase and activation process of increasing the amount of power generation of the generator in operation and activating the stopped generator is performed (step S23). On the contrary, when the demand prediction value at time TN is less than the total amount of power generation at time TN-1, the total amount of power generation at time TN is required to be reduced to the demand prediction value at time TN to support reduction in demand. A reduction and stop process of reducing the amount of power generation of the generator in operation and stopping the generator in operation is performed (step S24). This corresponds to the processes shown in FIGS. 5A to 5C. FIG. 11 is a flowchart showing the details of step S24 in the comparative example of the first embodiment. In step S24, first, the stop process for the generators ui to uMAX are performed according to a loop process (steps S31 to S34). This loop process is performed in the order of the generators uMAX to ui that is a descending order of power generation costs. Next, the reduction process for the generators ui to UMAX is performed according to a loop process (steps S35 to S38). This loop process is performed in the order of the generatorsUMAX to ui that is a descending order of power generation costs. The generators ui to UMAX correspond to examples of the first to X-th generators described above. Hereinafter, the stop process and the reduction process for the generator UK are described. First, the stop process determines whether or not the sum of the demand prediction value at time TN and the amount of power generation of the generator uK at time TN-1 is equal to or less than the total amount of power generation at time TN-1

(step S32). If the determination result is "YES", the generator uK is stopped at time TN because the demand can be satisfied even when the generator uK is stopped and the amount of power generation decreases by the amount of power generation of the generator uK (step S33). On the contrary, if the determination result is "NO", the generator uK is not stopped at time TN

because the demand cannot be satisfied when the generator uK is stopped and the total amount of power generation decreases by the amount of power generation of the generator uK. In step S33, the generator uK is stopped only when the stop permissibility determining process determines that the generator uK can be stopped. When a certain generator is stopped in step S33, the "total amount of power generation" described above is replaced with "the total amount of power generation - the amount of power generation of the generator" in the processes thereafter. That is, the total amount of power generation is decremented. The decremented total amount of power generation is also applied to the loop processes in steps S35 to S38. Next, if the amount of power generation of the generator uK can be reduced, the reduction process reduces this amount

(step S36). More specifically, it is determined whether the demand prediction value at time TN is equal to or less than the total amount of power generation or not, if reduction in the amount of power generation of the generator UK by a certain amount reduces the total amount of power generation by the amount of reduction (step S37). If the determination result is "NO", the reduction process is not performed because reduction in the amount of power generation prevents the demand from being satisfied. On the contrary, if the determination result is "YES", the reduction process is performed because reduction in the amount of power generation allows the demand to be satisfied, and the reduction process is finished. The final total amount of power generation becomes the total amount of power generation at time TN.

When the demand prediction value at time TN does not become equal to or less than the total amount of power generation to the last in step S37 of the reduction process, the reduction and stop process fails. The reduction and stop process in this comparative example causes the problem described with reference to FIGS. 5A and 5C. More specifically, if stop of the generator uK prevents the demand from being satisfied even with the generator uK being stoppable, the generator uK cannot be stopped. In this case, the generator uK can sometimes be stopped if the amount of power generation of the generator uK-1 can be increased, but no step of performing such a process is prepared in this comparative example. On the contrary, the step of performing such a process is prepared in this embodiment. FIG. 12 is a flowchart showing the details of step S17 in the first embodiment. In this embodiment, a demand prediction value (power demand) at time TN is calculated on the basis of the demand data (step S41). Next, it is determined whether the demand prediction value at time TN is at least the total amount of power generation at time TN-1 or not (step S42). When the demand prediction value at time TN is less than the total amount of power generation at time TN-1, the total amount of power generation at time TN is required to be reduced to support the reduction in demand. The stop process of stopping the generator in operation is performed (step S43). This corresponds to the processes shown in FIGS. 6A to 6C. When a certain generator is stopped in step S43, the "total amount of power generation" described above is replaced with "the total amount of power generation - the amount of power generation of the generator" in the processes thereafter. That is, the total amount of power generation is decremented. The decremented total amount of power generation is also applied to the processes in steps S44 to S46. After execution of the stop process in step S43, the processing transitions to step S44. Also when the demand prediction value at time TN is at least the total amount of power generation at time TN-1 in step S42, the processing transitions to step S44. In step S44, it is determined whether the demand prediction value at time TN is at least the total amount of power generation described above or not. Here, if the result in step S42 is "YES", the total amount of power generation described above is the total amount of power generation at time TN-1. On the contrary, if the result in step S42 is "NO", the total amount of power generation described above is the total amount of power generation at time TN-1 or the total amount of power generation decremented in step S43. When the demand prediction value at time TN is at least the total amount of power generation described above, the total amount of power generation at time TN is required to be increased to support increase in demand. An increase and activation process of increasing the amount of power generation of the generator in operation and activating the stopped generator is performed (step S45). On the contrary, when the demand prediction value at time TN is less than the total amount of power generation described above, the total amount of power generation at time TN is required to be reduced to support reduction in demand.

The reduction process of reducing the amount of power generation of the generator in operation is performed (step S46). As described above, according to this embodiment, the stop process in step S43 and the reduction process in step S46 are separated from each other. The details of such steps are described later. FIG. 13 is a flowchart showing the details of step S45 in the first embodiment. In step S45, the increase and activation process for the generators ui to uMAX are performed according to a loop process (steps S51 to S55). This loop process is performed in the order of the generators ui touMAX that is an ascending order of power generation costs. Hereinafter, the increase and activation process for the generator uK is described. In the increase and activation process, the amount of power generation of the generator uK is increased if this amount can be increased (step S52), and the generator uK is activated if this generator can be activated (step S53). More specifically, the amount of power generation of the generator uK is increased by a certain amount through the activation or increase in amount of power generation of the generator uK to increase the total amount of power generation by the amount of increase, and the loop process is repeated until the total amount of power generation reaches or exceeds the demand prediction value at time TN (step S54). When the determination result in step S54 becomes "YES", the increase and activation process is finished. The final total amount of power generation becomes the total amount of power generation at time TN.

In a case where the total amount of power generation largely exceeds the demand prediction value (e.g., a case where the output of the generator generated at the last time is largely high) as a result of the increase and activation process, a modification may be made that causes the total amount of power generation to approach the demand prediction value by replacing the activation order with that of a generator having a high power generation cost. When the demand prediction value at time TN does not become equal to or less than the total amount of power generation to the last in step S54 of the increase and activation process, the increase and activation process fails. FIG. 14 is a flowchart showing the details of step S43 in the first embodiment. In step S43, first, the stop process for the generators ui to uMAX are performed according to a loop process (steps S61 to S64). This loop process is performed in the order of the generators uMAX to ui that is a descending order of power generation costs. Hereinafter, the stop process for the generator uK is described. First, the stop process determines whether or not the sum of the demand prediction value at time TN and the amount of power generation of the generator uK at time TN-1 is equal to or less than the total amount of power generation at time TN-1 (step S62). If the determination result is "YES", the generator uK is stopped at time TN because the demand can be satisfied even when the generator uK is stopped and the total amount of power generation decreases by the amount of power generation of the generator uK (step S63). On the contrary, if the determination result is "NO", the generator uK is not stopped at time TN because the demand cannot be satisfied when the generator uK is stopped and the total amount of power generation decreases by the amount of power generation of the generator uK. In step S63, the generator uK is stopped only when the stop permissibility determining process determines that the generator uK can be stopped. When a certain generator is stopped in step S63, the "total amount of power generation" described above is replaced with "the total amount of power generation - the amount of power generation of the generator" in the processes thereafter (decrement). The decremented total amount of power generation is also applied to the processes in steps S65 to S68. Subsequently, the next stoppable generator UA in the descending order of power generation costs is extracted (step S65). For example, in a case where the generators UMAX to UA+1 are stopped and the generators UA to ui are in operation and the generator UA satisfies the stop permissibility determination, the generator UA is extracted. Next, the amount of increase in power generation that can be achieved by the generator uB having a lower power generation cost than the generator uA has is calculated (step S66). A typical example of the generator uB is the generator uA-1. The generators uA and uA-1 correspond to the third and second generators U 2 and U1 described above, respectively. In a case where the amount of power generation of the generator uB is smaller than the maximum amount of power generation by a value P, the amount of increase in power generation that can be achieved by the generator uB is the value P at the maximum. Next, it is determined whether a value obtained by adding the amount of power generation of the generator uA at time TN-1 to and subtracting the amount of increase in power generation of the generator uB at time TN-1 from the demand prediction value at time TN is equal to or less than the total amount of power generation described above or not (step S67). If the determination result is "YES", the generator uA is stopped at time TN because the demand can be satisfied when the total amount of power generation decreases by the amount of power generation of the generator uA and increases by the amount of increase in power generation of the generator uB (step S68). On the contrary, if the determination result is "NO", the generator uA is not stopped at time TN because the demand cannot be satisfied when the total amount of power generation decreases by the amount of power generation of the generator uK and increases by the amount of increase in power generation of the generator uB. The total amount of power generation is also decremented in step S68, and the final total amount of power generation is also applicable to step S44.

The processes in steps S65 to S68 correspond to the processes shown in FIGS. 6A to 6C. More specifically, the process of increasing the amount of power generation of the generator UB and stopping the generator UA corresponds to the process of increasing the amount of power generation of the second generator U 2 and stopping the third generator U3. Note that steps S65 to S68 only determine increasing of the amount of power generation of the generator UB. The process of increasing the amount of power generation of the generator uB is performed by the increase and activation process. Such a process can be executed because the flow is adapted that the reduction process and the stop process are separated from each other and the increase and activation process is performed after the stop process. Information required for the increase and activation process for the generator uB is provided from the stop process for the increase and activation process. FIG. 15 is a flowchart showing the details of step S46 in the first embodiment. In step S46, the reduction process for the generators ui to uMAX are performed according to a loop process (steps S71 to S74). This loop process is performed in the order of the generators uMAX to ui that is a descending order of power generation costs. Hereinafter, the reduction process for the generator uK is described. If the amount of power generation of the generator uK can be reduced, the reduction process reduces this amount (step S72). More specifically, it is determined whether the demand prediction value at time TN can coincide with the total amount of power generation or not by reducing the amount of power generation of the generator uK by a certain amount and reducing the total amount of power generation by the amount of reduction (step S73). If the determination result is "NO", the total amount of power generation cannot be reduced to coincide with the demand. Consequently, the reduction process is not performed. On the contrary, if the determination result is

"YES", the total amount of power generation can be reduced to coincide with the demand. Consequently, the reduction process is performed, and the reduction process is finished. The final total amount of power generation becomes the total amount of power generation at time TN.

When the demand prediction value at time TN does not coincide with the total amount of power generation to the last in step S73 of the reduction process, the reduction process fails. As described above, the power generation plan developing apparatus 1 of this embodiment calculates the amounts of power generation of multiple generators at multiple times in an ascending order of time, and uses the calculation result of the amount of power generation at a certain time to calculate the amount of power generation at the subsequent time. The power generation plan developing apparatus 1 of this embodiment determines whether to activate the generators at a certain time or not in an ascending order of power generation costs of the generators, and determines whether to stop the generators at a certain time or not in a descending order of power generation costs. Consequently, this embodiment can simply and appropriately reduce the power generation cost through the activation and stop control for these generators. For example, according to this embodiment, the power generation plan that suppresses the power generation cost to be low can be developed in a short time period with the logic of a simple sequential process. (Second Embodiment) FIG. 16 is a flowchart showing the details of step S43 in a second embodiment. According to this embodiment, the stop process in FIG. 14 in the first embodiment is replaced with the stop process in FIG. 16. In the stop process in FIG. 16, steps S62 and S67 are replaced with steps S62' and S67', respectively, and step S60 is added. In step S60, a target value through the stop process is set by an equation, target value= demand prediction value

+ (total amount of power generation- demand prediction value) x rate. In step S62', it is determined whether the sum of the target value and the amount of power generation of the generator uK is equal to or less than the total amount ofpower generation at time TN-1 or not. If the determination result is "YES", it is determined that the generator uK can be stopped. The generator uK is stopped if this generator uK can be stopped. On the contrary, if the determination result is "NO", the generator uK is not stopped because the target value cannot be reached when the total amount of power generation decreases by the amount of power generation of the generator uK. The processes in steps S65 and S66 are the same as those in FIG. 14. In step S67', it is determined whether or not a value obtained by subtracting the amount of power generation of the generator uB from the sum of the target value and the amount of power generation of the generator uA is equal to or less than the total amount of power generation at time TN-1. If the determination result is "YES", the generator uA is stopped. On the contrary, if the determination result is "NO", the generator uA is not stopped. The rate is a parameter that can be freely set. In a case where the rate is set to "0" (0%), the processes in FIG. 16 coincide with the processes in FIG. 14. In a case where the value of the rate is set to a value higher than "0", the total amount of power generation at each time can be set to the "target value" higher than the demand prediction value and the processes in steps S61 to S64 can be executed. For example, the value of the rate is changed in a case where the created power generation plan does not satisfy some of the conditions, steps S61 to S64 and the like are executed at the changed rate again, and the power generation plan is re-created. Repetition of such processes can create the power generation plan that satisfies as many conditions as possible. For example, this is effective in a case where when the demand prediction value rapidly increases at a time after the generator is stopped, the stopped generator cannot be activated and the supply demand balance limitation cannot be satisfied. FIG. 17 is a flowchart showing a power generation plan developing method in the second embodiment. FIG. 17 shows a flow of setting and changing the rate. This flow is executed by the sequential processor 15 in FIG. 1. First, the rate is set to a default value (step S81). An example of the default value is "0%". Next, processes in steps S82 to S86 are repeated four times at the maximum. The details of the processes are as follows. In step S83, the plan at times T1 to T is created using the set rate, as described above. Next, if the plan fails at a certain time TRES (step S84), the rate is increased from the current rate by "Z%" (e.g., "2 5%") with respect to time TRES

ATBEFORE to TRES + ATAFTER (step S85). The processes in steps S83 to S85 are re-executed. Accordingly, the plan with no or reduced failure can be created. According to this embodiment, the rate is changed and the power generation plan is re-created, which can create the power generation plan that satisfies a predetermined condition. In this embodiment, a parameter different from the rate may be adopted, and the flow of FIG. 17 may be executed. (Third Embodiment) FIG. 18 is a flowchart showing the details of step S15 in a third embodiment. As for step S15, see FIG. 9. In step S15, first, processes in steps S91 to S98 are executed for the generators in operation, and subsequently, processes in step S101 to S106 are executed for the generator in operation without any output designation. In the former processes, the upper limit limitation is applied to the linear sum of the outputs of the generators or some generators (hereinafter called "upper limit limitation satisfying process"). On the other hand, in the latter processes, the lower limit limitation is applied to the linear sum of the outputs of the generators or some generators (hereinafter called "lower limit limitation satisfying process"). Examples of the upper and lower limit limitation include the variation rate limitation, pipe limit, and group output limitation. In the upper limit limitation satisfying process, first, the amount of upper limit limitation violation (Deltal) of the generator uK is calculated (step S92), and, if the amount of violation is "0", the amount of upper limit limitation satisfying process for the generator uK is finished (step S93). On the contrary, if the amount of violation is larger than "0", it is determined whether the generator uK can be stopped or not (step S94). As a result, if the generator uK can be stopped, the generator uK is stopped and the upper limit limitation satisfying process for the generator uK is finished (step S95). On the contrary, if the generator uK cannot be stopped, the maximum amount capable of reducing the amount of power generation of the generator uK is calculated, and the amount of power generation of the generator uK is reduced by the maximum amount (steps S96 and S97). In this manner, the upper limit limitation satisfying process for the generator uK is finished. Subsequently, in the lower limit limitation satisfying process, the amount of lower limit limitation violation (Delta2) of the generator uK is calculated (step S102), and, if the amount of violation is "0", the amount of lower limit limitation satisfying process for the generator uK is finished (step S103). On the contrary, if the amount of violation is larger than "0", the maximum amount capable of increasing the amount of power generation of the generator uK is calculated, and the amount of power generation of the generator uK is increased by the maximum amount (step S104 and S105). In this manner, the lower limit limitation satisfying process for the generator uK is finished. As described above, steps S12 to S19 in FIG. 9 are executed by a loop process at times T 2 to TM. As a result, according to this embodiment, before the amount of power generation of the generator uK at time TN in step S17 is calculated, it is determined whether or not the generator UK satisfies the upper and lower limit limitation at time TN in step S16. Consequently, according to this embodiment, only in the case where the generator uK satisfies the predetermined upper and lower limit limitation at time TN, the generator uK at time TN can be adopted as an execution target of the sequential process. The power generation plan that satisfies the upper and lower limit limitation can therefore be developed. (Fourth Embodiment) FIG. 19 is a diagram for illustrating a configuration example of a pipe network in a fourth embodiment. Generators of this embodiment are thermal power generators that use LNG as fuel, and communicate with each other via pies (pipelines) for conveying LNG. These generators further communicate with fuel bases that are supply sources of LNG, via pipes. FIG. 19 topologically shows the relationship between these generators, fuel bases and pipes. More specifically, nodes ni to n4 indicate the generators, and nodes ns and n6 indicate the fuel bases. The nodes n3 and n4 indicate branching and joining. Arrows between the nodes ni to n6 indicate the pipes. The directions of the arrows indicate directions in which LNG flows. The nodes ni to n6 are classified into some types. The nodes ni and n2 are end nodes disposed at ends of the pipes. The nodes n3 and n4 are intermediate nodes disposed at positions other than the ends of the pipes. The intermediate nodes include a joining node disposed at a joining point of pipes (e.g., n4), and a branching node disposed at a branching point of pipes (e.g., n3). The node n4 communicates with the nodes ns and n6 that are parent nodes and with the node n3 that is a child node. The parent and child relationship between the nodes is defined with respect to an upstream side and a downstream side of the flow of LNG. FIG. 19 shows upper and lower limit limitations of LNG flow rate imposed on the respective pipes. For example, the upper limit value (pipe upper limit) and the lower limit value (pipe lower limit) of the LNG flow rate in the pipe between the nodes n4 and ns are 100 t/h and 10 t/h, respectively. As a result, the upper and lower limit limitation regarding fuel use per unit time period is imposed on each generator in this embodiment. The upper and lower limit limitation depends on the topological arrangement of the nodes ni to n6. For example, the upper and lower limit limitation on the fuel use of the generator disposed at the node ni depends on the upper and lower limit limitation on the LNG flow rate in the pipe between the nodes ni and n3 and on the upper and lower limit limitation on the fuel use of the generator disposed at the node n3. As described above, at the node ni, which is the end node, the relationship with the parent node (node n3) is considered. On the other hand, at the node n4, which is the intermediate node, relationship not only with the parent nodes (nodes ns and n6) but also with the child node (node n3) is considered. FIG. 20 is a flowchart showing the details of a power generation plan developing method in the fourth embodiment. This flow is processes for setting the upper and lower limit limitation on the fuel use of each generator. The process in step S15 is executed after the processes (see FIGS. 9 and 18). The nodes ni to n6 in FIG. 19 are sorted in an inverse order of that of the topological sort (step S111). That is, the nodes ni to n6 are sorted from the end. Next, the upper and lower limit setting process in steps S112 to S123 are executed as a loop process in the sorting order. Hereinafter, the upper and lower limit setting process for the node nA is described. In the upper and lower limit setting process, first, when the node nA is an end node (step S113), the fuel use f(u) is calculated when the amount of power generation of the generator u corresponding to the node nA is the maximum amount of power generation (step S114). Next, when the pipe upper limit to the node nA is lower than f(u), an upper limit limitation expression is added (step S115). When the pipe lower limit for the node nA is higher than "0", a lower limit limitation expression is added (step S116). Next, a continuation flag for the node nA is set, and information on the node nA is added to the parent node nB (step S117). For example, the upper limit "MAXB" on the parent node nB is replaced with MAXB + f(B). In a case where the node nA is an end node, the upper and lower limit setting process for the node nA is finished in this manner. On the contrary, in a case where the node nA is not an end node (step S113), it is determined whether the continuation flag is set for every child node nc of the node nA and the number of parent nodes nB of the node nA is only one or not (step S118). If the determination result of S118 is "NO", the upper and lower limit setting process for the node nA is finished. On the contrary, the determination result of S118 is "YES", information written as information on the node nA is referred to (step S119). Next, when the pipe upper limit to the node nA is lower than the upper limit "MAXA", the upper limit limitation expression is added (step S120). When the pipe lower limit for the node nA is higher than "0", the lower limit limitation expression is added (step S121). Next, the continuation flag for the node nA is set, and information on the node nA is added to the parent node nB (step S122). For example, the upper limit "MAXB" on the parent node nB is replaced with MAXB +

MAXA. In a case where the node nA is not an end node, the upper and lower limit setting process for the node nA is finished in this manner. Subsequently, in this embodiment, processes analogous to those in the third embodiment are executed. That is, steps S12 to S19 in FIG. 9 are executed by a loop process at times T 2 to TM. Consequently, in the process in step S15 for satisfying the upper and lower limit limitation, it is determined whether the upper and lower limit limitation on the fuel consumption is satisfied or not. Consequently, according to this embodiment, only in the case where the generator uK satisfies the upper and lower limit limitation on fuel consumption at time TN, the generator uK at time TN can be adopted as an execution target of the sequential process. The power generation plan that satisfies the upper and lower limit limitation on fuel consumption can therefore be developed. While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel apparatuses, methods and media described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the apparatuses, methods and media described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

Claims

CLAIMS 1. A power generation plan developing apparatus comprising: a demand data storage to store demand data that is time-series data regarding a prediction of power demand; a condition storage to store a power generation creation condition that is input from a user interface; a power generation amount calculator configured to calculate amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time, and calculate the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time; a power generation plan creator configured to create a power generation plan for the first to X-th generators, based on the demand data, the power generation creation condition, and the amounts of power generation of the first to X-th generators at the first to M-th times; and a power generation plan storage to store the power generation plan to be output to the user interface, wherein the power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs, when a total amount of power generation of the first to X-th generators at the N-th time increases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the power generation amount calculator determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs, when the total amount of power generation of the first to X-th generators at the N-th time decreases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the apparatus further comprises an increase determiner configured to determine, in a case where the total amount of power generation at the N-th time decreases by a first value from the total amount of power generation at the (N-1)-th time and the first value is lower than a minimum amount of power generation of a Y-th (Y is an integer ranging from two to X) generator, whether or not the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by a second value so as to allow a total of the first value and the second value to reach the minimum amount of power generation of the Y-th generator, and when it is determined that the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by the second value, the power generation amount calculator stops the Y-th generator at the N-th time, and increases the amount of power generation of the (Y-1)-th generator at the N-th time by the second value from the amount of power generation of the (Y-1)-th generator at the (N-1)-th time.
2. The apparatus of Claim 1, further comprising: a stop permissibility determiner configured to determine whether the Y-th generator can be stopped at the N-th time, based on a minimum stop time period of the Y-th generator and variation in power demand, wherein when it is determined that the Y-th generator can be stopped at the N-th time and it is determined that the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by the second value, the power generation amount calculator stops the Y-th generator at the N-th time, and increases the amount of power generation of the (Y-1)-th generator at the N-th time by the second value from the amount of power generation of the (Y-1)-th generator at the (N-1)-th time.
3. The apparatus of Claim 1 or 2, wherein when the power generation plan does not satisfy a predetermined condition, the power generation amount calculator changes values of parameters regarding the first to X-th generators and recalculates the amounts of power generation of the first to X-th generators so as to create the power generation plan that satisfies the predetermined condition.
4. The apparatus of any one of Claims 1 to 3, wherein after it is determined that a variable regarding a Y-th (Y is an integer ranging from two to X) generator satisfies a predetermined limitation at the N-th time, the power generation amount calculator calculates the amount of power generation of the Y-th generator at the N-th time.
5. The apparatus of Claim 4, wherein the limitation is provided as a limitation regarding a fuel conveying pipe provided between the first to X-th generators.
6. A power generation plan developing method comprising: storing, in a demand data storage, demand data that is time-series data regarding a prediction of power demand; storing, in a condition storage, a power generation creation that is input from a user interface; calculating, by a power generation amount calculator, amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time and calculating, by the power generation amount calculator, the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time; creating, by a power generation plan creator, a power generation plan for the first to X-th generators, based on the demand data, the power generation creation condition, and the amounts of power generation of the first to X-th generators at the first to M-th times; and storing, in a power generation plan storage, the power generation plan to be output to the user interface, wherein the power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs, when a total amount of power generation of the first to X-th generators at the N-th time increases from the total amount of power generation of the first to the X-th generators at the (N-1)-th time, the power generation amount calculator determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs, when the total amount of power generation of the first to X-th generators at the N-th time decreases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the method further comprises determining, by an increase determiner, in a case where the total amount of power generation at the N-th time decreases by a first value from the total amount of power generation at the (N-1)-th time and the first value is lower than a minimum amount of power generation of a Y-th (Y is an integer ranging from two to X) generator, whether or not the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by a second value so as to allow a total of the first value and the second value to reach the minimum amount of power generation of the Y-th generator, and when it is determined that the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by the second value, the power generation amount calculator stops the Y-th generator at the N-th time, and increases the amount of power generation of the (Y-1)-th generator at the N-th time by the second value from the amount of power generation of the (Y-1)-th generator at the (N-1)-th time.
7. A non-transitory computer-readable recording medium containing a power generation plan developing program which causes a computer to perform a power generation plan developing method, the method comprising: storing, in a demand data storage, demand data that is time-series data regarding a prediction of power demand; storing, in a condition storage, a power generation creation condition that is input from a user interface; calculating, by a power generation amount calculator, amounts of power generation of first to X-th (X is an integer of at least two) generators at first to M-th (M is an integer of at least two) times in an order of the first to M-th times that is an ascending order of time and calculating, by the power generation amount calculator, the amounts of power generation of the first to X-th generators at an N-th (N is an integer ranging from two to M) time, based on the amounts of power generation of the first to X-th generators at an (N-1)-th time; creating, by a power generation plan creator, a power generation plan for the first to X-th generators, based on the demand data, the power generation creation condition, and the amounts of power generation of the first to X-th generators at the first to M-th times; and storing, in a power generation plan storage, the power generation plan to be output to the user interface, wherein the power generation amount calculator determines whether to activate, at the N-th time, the generator being stopped at the (N-1)-th time, in an order from the first to X-th generators that is an ascending order of power generation costs, when a total amount of power generation of the first to X-th generators at the N-th time increases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the power generation amount calculator determines whether to stop, at the N-th time, the generator in operation at the (N-1)-th time, in an order from the X-th to first generators that is a descending order of the power generation costs, when the total amount of power generation of the first to X-th generators at the N-th time decreases from the total amount of power generation of the first to X-th generators at the (N-1)-th time, the method further comprises determining, by an increase determiner, in a case where the total amount of power generation at the N-th time decreases by a first value from the total amount of power generation at the (N-1)-th time and the first value is lower than a minimum amount of power generation of a Y-th (Y is an integer ranging from two to X) generator, whether or not the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by a second value so as to allow a total of the first value and the second value to reach the minimum amount of power generation of the Y-th generator, and when it is determined that the amount of power generation of the (Y-1)-th generator at the (N-1)-th time can be increased by the second value, the power generation amount calculator stops the Y-th generator at the N-th time, and increases the amount of power generation of the (Y-1)-th generator at the N-th time by the second value from the amount of power generation of the (Y-1)-th generator at the (N-1)-th time.