JP2004023914A - Controller for cogeneration plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for a cogeneration plant capable of optimizing the total cost including contract charge. <P>SOLUTION: This cogeneration plant, provided with one or a plurality of cogeneration units 1 which performs power generation, operates the cogeneration units 1 by predicting the demand of electricity, using both of electricity reception from the outside and power generation by the cogeneration units 1, and planning the number of units and production volume of generation which make a total sum of specific tariff of electricity reception and power generation cost minimum. In this cogeneration plant, a plan correction part 4 is provided which corrects the plan so as to attain the production volume of generation corresponding to possible excess when electricity reception volume according to the plan almost exceeds its upper limit, by setting the upper limit. The upper limit is set so as not to exceed the contract tariff. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for a cogeneration plant using external power reception, and more particularly to a control device for a cogeneration plant that optimizes total cost including a contract fee.
[0002]
[Prior art]
A thermoelectric variable-type cogeneration unit (hereinafter, referred to as a gas turbine) having a steam injection gas turbine (hereinafter, referred to as a gas turbine) as a main engine and an exhaust heat recovery boiler for generating steam using the exhaust heat of the gas turbine. , A co-generation unit) can increase the power generation efficiency (power generation capacity) by inputting the steam from the exhaust heat recovery boiler to the gas turbine. Each output amount can be adjusted in a complex manner.
[0003]
As shown in FIG. 10, the cogeneration unit includes a steam injection type gas turbine 50 and an exhaust heat recovery boiler 51. In the steam injection type gas turbine 50, the supply air is compressed by a compressor 53 and is supplied to a combustion chamber 54. The turbine 55 is driven by burning the fuel supplied to the combustion chamber 54 to drive the turbine 55, power is generated by the generator G, and the combustion exhaust gas from the turbine 55 is supplied to the exhaust heat recovery boiler 51 to recover heat, and the exhaust heat is recovered. The steam obtained by supplying water to the recovery boiler 51 is sent to a pipe 58 connected to a demand destination, and a part of the steam is supplied to a combustion chamber 54 as injection steam, and is also sent to a turbine 55 together with compressed air via a nozzle 56. Supply.
[0004]
As described above, the cogeneration unit increases the power generation efficiency by injecting a part of the steam generated from the exhaust heat recovery boiler into the gas turbine, and the input condition that the same amount of fuel is consumed (for example, rated operation) The power amount and the steam amount can be adjusted by arbitrarily setting the power distribution between the electricity and the steam under the condition.
[0005]
The present applicant has previously proposed in Japanese Patent Application No. 2000-21820 a cogeneration plant having one or more cogeneration units (hereinafter referred to as a cogeneration plant). In this cogeneration plant, an integrated control device is provided above the individual control devices that control the individual cogeneration units, and commands are issued to the individual control devices. In detail, as described in the above-mentioned document, in summary, the general control device includes a demand forecasting unit (in the document, a demand planning unit) for forecasting demand for electricity and steam, and a minimum cost for the demand forecasting. And an operation planning unit (in the literature, an optimum operation calculation unit) that plans the number of operating units and the output distribution so as to satisfy the above.
[0006]
[Problems to be solved by the invention]
Incidentally, a cogeneration plant generally uses power reception from a commercial power supply in addition to the above-described power generation in the plant. In the case of using power reception together, there are various power reception modes and charging methods depending on the contract with the power company.
[0007]
There are two types of power reception, one in which so-called power sale for supplying surplus generated power to a commercial power source is approved, and the other in which power sale is not approved. In a cogeneration plant that has been approved to sell power, it is possible to contribute to reducing operating costs by selling surplus power if it generates more power than demand. It is important to make an operation plan.
[0008]
There are two types of billing methods: one related to a contract fee and one related to a usage fee.
[0009]
The usage fee (also called a metered fee) pays an amount that is proportional to the amount of received power or that is weighted in stages. In general, the usage fee is different in unit price per hour between daytime and nighttime. For example, in a certain power company, from 8:00 to 22:00 on a weekday in the morning (this time zone is called daytime), daytime rates and unit prices per hour are high, and weekday nights and holidays are nighttime rates and the unit price per hour is high. cheap. In a conventional cogeneration plant, an operation plan is made to minimize the operation cost that takes into account the usage fee of power reception in addition to the operation cost of the cogeneration unit such as fuel cost. The operation plan also takes into account the time zone.
[0010]
8 and 9 show actual examples of the operation status of the cogeneration plant on a weekday. Lines 81 and 91 indicate demand power, lines 82 and 92 indicate generated power of the first unit of the cogeneration unit, and line 83 indicates generated power of the second unit accumulated in the generated power of the first unit. The remaining value obtained by subtracting the vertical axis value of the line 83, which is the total generated power of both units, from the value is the received power. From FIG. 8, it can be seen that the entire demand is covered by power reception at midnight, the cogeneration units are sequentially started in accordance with the demand peak in the morning, and almost all the demand is covered by power generation at 8:00 when switching to daytime rates. This is based on the operation plan when the operation cost is higher than the nighttime charge and the daytime charge is higher than the operation cost. The reason why there is always a small amount of received power during the day is due to the minimum received power constant control described later. On the other hand, FIG. 9 shows a case where only one cogeneration unit is used, and the remaining power obtained by subtracting the vertical axis value of the line 92 from the vertical axis value of the line 91 is the received power. It can be seen that in the middle of the night, the entire demand is covered by power reception, and the cogeneration unit is rated at a constant operation from 10:00 to 22:00 when the demand is high. Since this is a holiday, the operation cost is higher than the daytime fee, so the operation plan is to operate only one cogeneration unit necessary to supply steam.
[0011]
In the conventional method taking into account the minimum power receiving amount constant control and the time zone, no limit is set for the larger power receiving amount. For example, at midnight 0, power receiving of about four and a half scales is performed.
[0012]
The contract fee (also referred to as a contract power fee) is different from the usage fee and is charged for being a user of the power company. The contract fee is set in accordance with the contract power. The contract power is determined by the maximum power (evaluated by an average value within a predetermined short time) in the actual power consumption throughout the year regardless of day or night. In the case of FIGS. 8 and 9, approximately four and a half steps of power reception are recorded at night, and the contract power is determined based on this. Even when the average power consumption is small and a large amount of power is received for a short time, the annual contract power is determined based on the large amount of power reception, and a large contract fee is charged. When receiving power exceeding the contract power, an excess fee is charged for the excess.
[0013]
As described above, in a cogeneration plant that also uses power from a commercial power source, there is a cost factor such as a contract fee in addition to a metered fee. It is possible that the contract fee cannot be suppressed even if the plan is executed only by itself and the total cost will increase.
[0014]
Therefore, an object of the present invention is to solve the above problems and provide a control device for a cogeneration plant that optimizes the total cost including the contract fee.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides one or more cogeneration units for generating power, predicts the demand for electricity, and uses both external power reception and power generation by the cogeneration unit to satisfy the prediction. In a cogeneration plant that operates the cogeneration unit by planning the number of operating units and the amount of power generation in which the sum of the usage fee and the power generation cost of the power reception is minimized, an upper limit value is set in advance for the amount of power reception, When the received power amount in the plan is likely to exceed the upper limit value, a plan correction unit is provided for correcting the plan so that the power generation amount corresponding to the excess amount is generated by the cogeneration unit.
[0016]
The plan correction unit may average the amount of received power from the present to a predetermined time in the past, and calculate the amount of power generation corresponding to the excess from the average value.
[0017]
A lower limit value is set in advance for the received power amount, and the plan may be designed to maintain the received power amount equal to or more than the lower limit value.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
[0019]
As shown in FIG. 1, a control device for a cogeneration plant according to the present invention includes a plurality of cogeneration units 1, a demand prediction unit 2 for predicting power demand, power reception from outside, and power generation by the cogeneration unit 1. And an operation planning unit 3 for planning the number of operating units and the amount of power generation to satisfy the prediction, and when the amount of received power in the plan is likely to exceed a preset upper limit, the cogeneration unit 1 generates the amount of power generation corresponding to the excess. A plan correction unit (also referred to as a power receiving constant control unit) 4 for correcting the plan so as to generate power. The sum of the power generation amount output from the cogeneration unit 1 and the power reception amount from the power company is the power supply amount to the supply destination (demand destination).
[0020]
The plan correction unit 4 controls the amount of power generation so that the amount of received power does not exceed a preset upper limit value. By setting the upper limit to a value equal to or slightly lower than the contracted power, the amount of received power becomes equal to the contracted power. Will have the function of controlling the amount of power generation so as not to exceed. This control will be referred to as maximum received power constant control.
[0021]
The plan correction unit 4 includes a power reception average value calculation unit 41 that averages the power reception amount from the current time to a past predetermined time, and a power generation amount calculation unit 42 that calculates a power generation amount corresponding to the excess from the average value, The power generation amount calculated by the power generation amount calculation unit 42 is instructed to the cogeneration unit 1.
[0022]
This control device can be incorporated in the general control device of the cogeneration plant described in the aforementioned document; Japanese Patent Application No. 2000-21820. FIG. 2 is a configuration diagram of the cogeneration plant, in which the reference numerals of the respective units such as the general control device 8 are changed, but the functions of the respective units that have been conventionally used are as described in the literature.
[0023]
However, in the present embodiment, the target is a plant for which the sale of power is not approved. If the power generation exceeds the demand, the surplus power is completely wasted. Is appropriate. That is, instead of generating power exactly in accordance with predicted demand, power generation is always performed slightly less than demand, and the shortfall is received. As a result, even if the actual demand deviates from the predicted value and decreases, the amount of power generation does not become excessive by reducing the amount of power reception. As control, power generation is performed with a target smaller than the predicted demand by a certain value. Such control is referred to as minimum received power constant control. Specifically, the operation planning unit 3 plans the operation of the cogeneration unit so that the amount of power received from the outside is kept at a constant value.
[0024]
FIG. 3 shows a flowchart of the control of the number of cogeneration units operated by the operation planning unit 3. Since the number is generalized as n, this flowchart can be applied to any number of cogeneration units provided in the cogeneration plant. As shown in the figure, by executing the step 32 of the power generation plan following the step 31 of the demand prediction, the required power generation is obtained. Next, at step 33, the maximum output of each cogeneration unit is calculated. The maximum output is the amount of power generated by rated operation. However, since the steam plan is omitted here, the operation points are fixed at appropriate points.
[0025]
In the next step 34, using the necessary power generation amount obtained above and the maximum output of each cogeneration unit, the power generation amount is compared with the maximum output of the total number of currently operating n units, and the required power generation amount is satisfied. If not, the operation number is increased in step 35. If the required power generation amount is satisfied, the process proceeds to step 36, where the required power generation amount is compared with the total maximum output when one unit is reduced. If the required power generation amount is not satisfied when the number of operating units is reduced, the number of operating units is maintained as in step 37. If the required power generation amount is satisfied even if the number of operating units is reduced, the number of operating units is reduced in step 38.
[0026]
FIG. 4 shows a flowchart of the received power control executed by the operation planning unit 3 and the plan correcting unit 4. As shown in the figure, in step 41, a comparison is made between the power receiving price and the power generation price. That is, the cost when receiving power to obtain the same amount of power (use fee) and the cost when generating power (operating cost of the cogeneration unit) are compared. It goes without saying that the usage fee differs between the daytime time zone and the nighttime time zone. If the power receiving price is higher than the power generation price, increasing the amount of power generation will improve economic efficiency. Therefore, in step 42, it is compared whether or not a value obtained by subtracting the maximum amount that can be generated from the power demand is larger than the set minimum value. If YES, the power generation amount is maximized in step 43. As a result, the amount of power generation is maximum, and more power is received than the set minimum value, and the fluctuation in power demand is handled by increasing or decreasing the amount of received power. If “NO” in the step 42, the power generation amount is set to the power demand−set minimum value in a step 44. As a result, power reception is always performed for the set minimum value, and fluctuations in power demand are handled by increasing or decreasing the amount of power generation. Steps 43 and 44 correspond to the minimum power receiving amount constant control.
[0027]
If the power reception price is not higher than the power generation price in step 41, the economic efficiency is good if the power generation amount is reduced, but it is necessary to ensure that the power reception amount does not exceed the contracted power. Then, in step 45, it is compared whether the power demand is larger than the set maximum value. If YES, the power generation amount is set to the power demand-set maximum value in step 46. As a result, the power receiving at the set maximum value is always performed, and the fluctuation in the power demand corresponds to the increase or decrease in the power generation amount. If “NO” in the step 45, the power generation amount is set to 0 in a step 47. As a result, all of the power demand will be covered by the power reception. Steps 46 and 47 correspond to the maximum power receiving amount constant control.
[0028]
Next, a specific example of the power generation amount setting in the maximum power reception amount constant control performed by the plan correction unit 4 will be described. FIG. 5 shows a time waveform of the past received power amount. The power receiving average value calculation unit 41 of the plan correction unit 4 adds and averages the power reception amounts up to 30 minutes before the current time. The maximum received power is set in the power generation amount calculation unit 42. The set maximum received power is set to a value with a margin greater than the contract power (contract maximum received power). Therefore, the set maximum received power is set as the upper limit of the amount of received power. If the power generation is controlled so that the averaging value of the received power amount is lower than the set maximum received power, the received power can be prevented from exceeding the contract maximum received power.
[0029]
FIGS. 6 and 7 show operating conditions in which the cogeneration plant of the present invention operates in response to the same change in demand power as in FIGS. 8 and 9 described above. Lines 61 and 71 indicate demand power, lines 62 and 72 indicate generated power of the first unit of the cogeneration unit, and line 63 indicates generated power of the second unit accumulated in the generated power of the first unit. The remainder obtained by subtracting the vertical axis value of the line 63, which is the total generated power of both units, from the value is the received power. In FIG. 6, the first unit is generating power from midnight to around 1:00. Also, after 22:00, Unit 2 is generating power. This is based on the operation plan when the operation cost is higher than the nighttime charge and the daytime charge is higher than the operation cost. However, when compared with FIG. Although the operation is similar to that of FIG. 8, when the demand power exceeds about 4 graduations at midnight and 22:00, it can be understood that the first or second unit is operated. Thus, the received power does not exceed four graduations. On the other hand, FIG. 7 shows a case where only one cogeneration unit is used, and the remaining power obtained by subtracting the vertical axis value of the line 72 from the vertical axis value of the line 71 is the received power. In contrast to FIG. 9, the cogeneration unit does not reach the rated operation even in the daytime, and the amount of received power is always large. This is based on the operation plan when the power reception price is not higher than the power generation price both at night and during the day. However, when the demand power exceeds about 4 divisions, the first unit is operated. Thus, the received power does not exceed four graduations. When the power reception price in the daytime is larger than the power generation price, the cogeneration unit is operated at the rated operation in the daytime as in FIG. 9, but the power generation is performed even when the demand power around 00:00 is large. The driving situation is different from that in FIG.
[0030]
In FIGS. 8 and 9, the received power reaches four and a half scales, so the annual contract power is determined on the basis of this. However, in FIGS. 6 and 7, the received power does not exceed the four scales, and therefore is lower. The contract power can be used, and the contract fee is reduced. In total, there is a trade-off between the cost of operating the cogeneration unit at night and the reduction in contract fees.
[0031]
【The invention's effect】
The present invention exhibits the following excellent effects.
[0032]
(1) Since the amount of received power does not exceed the upper limit, if the upper limit is set so as not to exceed the contract power, the contract fee can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram of a control device according to an embodiment of the present invention.
FIG. 2 is a configuration diagram of a cogeneration plant showing one embodiment of the present invention.
FIG. 3 is a flowchart of control of the number of operating units according to an embodiment of the present invention.
FIG. 4 is a flowchart of a received power control according to an embodiment of the present invention.
FIG. 5 is a conceptual diagram of power generation amount setting in the maximum power reception amount constant control of the present invention.
FIG. 6 is a time waveform chart showing an example of demand power and generated power for one day when the maximum received power constant control is performed.
FIG. 7 is a time waveform chart showing an example of demand power and generated power for one day when the maximum received power constant control is performed.
FIG. 8 is a time waveform chart showing an example of demand power and generated power for one day when the minimum received power constant control is performed.
FIG. 9 is a time waveform chart showing an example of demand power and generated power for one day when the minimum received power constant control is performed.
FIG. 10 is a configuration diagram of a cogeneration unit.
[Explanation of symbols]
1 Cogeneration unit 2 Demand forecasting section 3 Operation planning section 4 Planning correction section

Claims (3)

It is equipped with one or more cogeneration units for power generation, predicts the demand for electricity, uses external power reception and power generation by the cogeneration unit together to meet the prediction, and sums the usage-based fee for power reception and the power generation cost. In the cogeneration plant that operates the cogeneration unit by planning the number of operating units and the amount of power generation that minimizes, the upper limit is set in advance for the amount of received power, and the amount of received power in the above plan is likely to exceed the upper limit. A control unit for a cogeneration plant, comprising: a plan correction unit that corrects the plan so that the power generation amount corresponding to the excess amount is generated by the cogeneration unit. The control device for a cogeneration plant according to claim 1, wherein the plan correction unit averages the amount of power received from a current time to a predetermined time in the past, and calculates a power generation amount corresponding to the excess from the average value. . The control device for a cogeneration plant according to claim 1, wherein a lower limit is set in advance for the amount of received power, and the plan is to maintain the amount of received power equal to or more than the lower limit.

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