JPH08200155A - Operation plan setting method in cogeneration system - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] Regarding the method of setting the operation plan of the cogeneration system, perform energy simulation of the operation method at each point of the year and set it to the minimum cost. [Structure] A method of simulating the operating method of the prime mover for the estimated annual electric power load and heat load, calculating the energy consumption of each operating method, and comparing the operating methods based on this to minimize the objective function. In the operation plan setting method that selects the method at each time point and selects the method for the year, the objective function is the running cost, and multiple operation methods include the power load following operation, the heat load following operation, and an appropriate number of units. Rated operation, one unit partial load operation, and prime mover stop operation. In single-unit partial load operation, the influence of non-linear factors, in electric power load following operation, the effect of the difference between the purchased electric power price and the sold electric power charge, and in the thermal load following operation, the operation of the auxiliary heat source or the discard of excess heat. Can be considered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation plan setting method in a cogeneration system.

[0002]

2. Description of the Related Art A cogeneration system is an energy-saving system that drives a generator with a prime mover to supply electric power, and also uses the exhaust heat of the prime mover to supply heat. The power load following operation is generally used in which the prime mover is always operated to follow the power load.

However, for example, the power load following operation in a time zone when the heat load is smaller than that in the power load is an operation for discarding the exhaust heat, so that the energy saving effect obtained in other time zones is offset. However, it is not possible to exert the original energy-saving, economic merit, etc. effectiveness only by the power load following operation.

Therefore, in order to improve energy saving and economic efficiency, a plurality of operating methods such as a power load following operation method and a heat load following operation method are used as the operation method of the prime mover in response to the electric power load, the heat load and the like. Attempts are being made to select and operate from among these. As an attempt of such an operation policy, the operation rules such as the power load following operation, the heat load following operation, or the rated output operation are set in advance throughout the year, and then the energy simulation is performed through the year to perform economic simulation. The performance characteristics of each equipment composing the cogeneration system are described in a simple linear form, and a linear programming problem with energy consumption as the objective function is formulated, and the energy is solved by solving this. There are things such as determining the optimal operation that minimizes the amount of consumption. (Koichi Ito, Ryohei Yokoyama, "Optimal Planning of Cogeneration",
(See Sangyo Tosho Co., Ltd. in 1990)

[0005]

However, the above-mentioned problems have the following problems. However, since the operation method is constant throughout the year, it is impossible to request operation that minimizes energy consumption. In the case of solving a linear programming problem such as, it is necessary to express all the system characteristics in a simple linear form, so in the operating region where non-linear elements such as partial load characteristics of the prime mover strongly appear,
There is a risk that the formulation will not match the actual situation, and depending on the results to be obtained, there may be problems in terms of reliability.
In addition, if you formalize even the finer parts such as changes in prime mover efficiency due to outside air temperature and changes in exhaust heat temperature level, the size of the problem will increase, and a solution will be required due to the nature of linear programming that iterates the matrix. The number of calculations (time) required for is extremely large, which is not practical. Therefore, in practice, the above-mentioned non-linear factors must be omitted, and there is a problem in accuracy. The present invention is intended to solve the above problems.

[0006]

In order to solve the above-mentioned problems, the present invention provides an energy simulation for each of a plurality of operating modes of a prime mover with respect to an estimated power load and heat load at each time point throughout the year. And calculate the energy consumption of each operating method from the result, and select the operating method that minimizes the objective function by comparing each operating method based on the calculated energy consumption at each time, In the operation plan setting method that selects the operation method at each time point over the year, the objective function is the running cost, and multiple operation methods include the power load following operation that generates the power equal to the estimated power load and the estimated demand. Heat load follow-up operation that generates electric power that generates the same amount of heat, rated operation of a suitable number of units, partial load operation of one unit, and motor stop operation Proposed operational plan setting how to.

In the present invention, the energy simulation of the power load following operation of the prime mover in the above method is
A step of obtaining a prime mover load factor corresponding to the power load with the estimated power load as an initial value, a step of calculating power generation and exhaust heat recovery efficiency according to the obtained load factor, a step of calculating an exhaust heat amount of the prime mover, A step of determining excess or deficiency by comparing the heat quantity with the heat demand amount, and a step of setting an excess or deficiency elimination operation of heat supply by other equipment without changing the power generation amount of the prime mover when the excess or deficiency occurs , The step of calculating the power load of the auxiliary machine when performing the excess / deficiency elimination operation, the step of calculating the total power load of the prime mover by adding the power load of the auxiliary machine and the power load, and the convergence of the power load of the prime mover If it is not converged, the difference between the power load of the previous auxiliary machine when it has not converged is added to the entire power load, and the process proceeds to the step of obtaining the prime mover load factor again. The rolling state save proposes that shall have the step of terminating the simulation.

Further, according to the present invention, in the above method, a step of obtaining a prime mover load factor corresponding to the estimated power load as an initial value, and a step of calculating power generation and exhaust heat recovery efficiency according to the obtained load factor , A step of calculating the exhaust heat amount of the prime mover, a step of determining excess or deficiency by comparing the exhaust heat amount and the demand heat amount, when the excess or deficiency occurs,
Within the range of capacity, the step of setting the excess and deficiency elimination operation by changing the amount of power generated by the prime mover, and when performing the excess and deficiency elimination operation, purchase or sale of the entire electric load including auxiliary equipment power load and commercial power The step of calculating the amount of electric power, the step of judging the convergence of the electric power load to be generated, the step of returning to the step of obtaining the prime mover load factor again when it has not converged, and the operating state is saved when it converges. It is proposed to have a step of ending the simulation.

Further, in the present invention, the energy simulation of the appropriate number of prime mover rated operations in the above method is performed in the rated operation of the number of operating units set according to the estimated power load, for the estimated power load and the required heat quantity of each device. It is proposed to have a step of deriving operating conditions.

Further, in the present invention, in the above method, the energy simulation of the single load operation of the prime mover sets a plurality of operating points in the range from the minimum output of the prime mover to the rated operation, and generates power at each operating point. For exhaust heat recovery efficiency, in each partial load operation,
It is proposed to have a step of deriving the operating state of each device that covers the estimated power load and the heat demand.

Further, in the present invention, it is proposed in the above method that the energy simulation of the stop operation of the prime mover has a step of deriving an operating state of each device that covers the estimated electric load and the heat demand when the prime mover is stopped. To do.

[0012]

[Operation] Energy simulation is performed for a plurality of operating methods based on the estimated load at each point in the year, and the operating method with the running cost as the objective function is selected to select the operating method with the minimum cost at each point in the year. The annual operation plan can be set.

During multiple energy simulations,
The influence of the non-linear element can be considered by including an appropriate number of simulations of partial load operation, which is the operating region of the prime mover in which the non-linear element appears strongly. In addition, since the power load following operation during a plurality of energy simulations simulates the point that both the purchased power amount and the sold power amount are 0, the current situation is different from other operating methods in which these power amounts are not 0. It is possible to consider the impact on costs due to the large difference between the purchased and sold electric power charges. Furthermore, since the heat load following operation simulates the point where a heat quantity equal to the demand heat quantity is generated, it can be used as a supplement to other operation methods in which the generated heat quantity is insufficient or the surplus must be discarded. It is possible to consider the balance between the cost due to the operation of the heat source or the discard of the surplus heat amount and the cost due to the purchase and sale of power.

[0014]

The present invention will now be described in detail with reference to the accompanying drawings showing an embodiment. FIG. 1 is a flow chart schematically showing the operation of the operation plan setting method of the present invention. First, in step S1, data of power load and heat load estimated at each time of the year, configuration of cogeneration equipment, characteristics Enter data such as data, electricity charges (basic charges, metered charges), fuel gas charges for prime movers, etc. Thus, in this embodiment, each time point in the year corresponds to each time point. Next, in step S2, the target time of the simulation at each time is set, that is, the first time of the year.

In the next step S3, an operating state is derived by performing an energy simulation on the power load following operation with the estimated power load as an initial value in the data of the estimated load at each time of the year. Details of this energy simulation will be described later. Then, step S4
At, the energy consumption in the operating state derived in step S3 is calculated.

After step S4, the estimated power load is set as an initial value, and steps S5, S7, S9 and S1 are performed.
In S1, S13 and S15, thermal load following operation, appropriate number of units rated operation, one unit partial load operation (load: 75%), 1
Energy simulation is performed for each operation method of stand partial load operation (load: 50%), stand partial load operation (load: 25%) and prime mover stop operation, and the operating state is derived. Then, in steps S6, S8, S10, S12, S14, and S16 that follow these steps, the energy consumption amount in each derived operating state is calculated. In this example, in the one-unit partial load operation, the above-mentioned three operating points are set in the operating range where the nonlinear element strongly appears from 25% corresponding to the minimum output of the one-unit operation, but the number of operating points is It is appropriate.

After the energy simulation of each operating method and the calculation of their energy consumption including power purchase and power sale by the above steps S3 to S16, based on these data, at the next step S17. Select the operation method that matches the objective function to be minimized. In this case, the objective function is the running cost, and in this step S17, the driving method with the minimum cost is selected.

Next, at step S18, it is judged whether or not the selection of the driving method is completed at all times of the year,
If it is not completed, a loop is executed, and step S19
At step S3, the time is advanced and the process proceeds to step S3. Then, with respect to the stepped time, the same energy simulation, calculation of energy consumption, and selection operation of the minimum cost driving method are performed as described above. Further, when the operation mode selecting operation for all the times of the year is completed and it is determined in step S18, the operation plan setting operation is ended.

2 to 4 conceptually show the relationship between the amount of electric power generated and the cost in the cogeneration system. In these figures, the amount of electric power generated is represented by the operating state of the prime mover. First, Fig. 2 shows the generated power
It shows the relationship with the cost of fuel input to the prime mover after deducting the amount of heat that can be used as exhaust heat.
In one unit partial load operation from 5% to one unit rated load, a non-linear element appears strongly due to the reason that the power generation efficiency of the prime mover changes depending on the partial load factor. Therefore, as described above, for example, the operating point a (25%), b (50%), c
Energy simulation is performed every (75%). Reference numerals d and d'represent operating points for one-unit rated operation and two-unit rated operation, respectively. In the present invention, the operating points d and d for the number of prime movers thus set according to the estimated power load are set. ’…
An energy simulation of multiple unit rated operation in which rated operation is performed is performed as shown in.

Next, FIG. 3 shows the relationship between the power generation amount and the power purchase cost. The power purchase cost is equal to the estimated power load (in this case, the power between one and two unit ratings). Is gradually reduced until it occurs, and becomes 0 at the operating point e at which the power equivalent to the estimated power load is generated. Next, when the amount of generated electric power is further increased, if the surplus power is sold, the negative power purchase cost gradually increases as shown by the dotted line in the figure. At this time, since there is a large difference between the purchased power price and the sold power price, the operating point e is important in consideration of cost. Therefore, in the present invention, the energy simulation of the power load following operation corresponding to this operating point e is performed.

Next, FIG. 4 shows the relationship between the amount of electric power generation and the cost of fuel input to the boiler. The cost of fuel input to the boiler gradually decreases until it reaches the amount of electric power generation capable of generating heat equal to the heat demand. , Becomes 0 at the operating point f that generates a heat quantity equal to the demand heat quantity. However, even if the amount of generated electric power is further increased and the amount of generated heat is increased, it is only a surplus and no negative cost is generated. Therefore, the operating point f is important in consideration of cost. Therefore, in the present invention, the energy simulation of the thermal load following operation corresponding to this operating point f is performed.

The above operating points a, b, c, d (, d ',
...), e, and f, the energy simulation without the prime mover, that is, the energy simulation without cogeneration is performed, and the running costs are compared to obtain the lowest running cost at each time point throughout the year. The operation method can be selected.

FIG. 5 is a flow chart showing the basic operation of an example of energy simulation of power load following operation,
First, in step S20, the power load is set. The initial value of this electric power load is the estimated electric power load input in step S1 above, and the electric power load of the auxiliary machine is 0 during the first operation, but when the operation is continued, the electric power load does not change significantly at each time point. Assuming that, by using the value that has converged in the simulation at the previous time point, it is possible to accelerate the later-described convergence.

In step S21, a prime mover load factor is calculated based on the estimated power load. The prime mover load factor is obtained by allocating the electric power load to the n prime movers by, for example, capacity proportional distribution. In step S22, power generation and exhaust heat recovery efficiency are calculated from the prime mover load factor calculated in step S21, and then the amount of exhaust heat is calculated in step S23.

In step S24, the exhaust heat amount calculated in step S23 is compared with the demand heat amount to determine whether the amount is excessive or insufficient. As a result of the comparison, if the exhaust heat amount is excessive, step S
In 25, an operation is performed to discard the excess heat amount without collecting it, and if it is insufficient, in step S26, an auxiliary heat source such as a boiler is operated to cover the insufficient heat amount. After each step, the process proceeds to the next step S27.

In step S27, the electric power load of the auxiliary machine for performing the above operation is calculated, and then in step S28, the convergence of the entire electric power load including the auxiliary machine is determined. That is, in step S28, the value of the power load of the auxiliary machine calculated in step S27 is compared with the value calculated in step S27 in the previous loop, and the difference between them is set to the preset minimum fluctuating power load A, For example, when it is 0.5 kW or less, it is determined to be converged. The convergence of the electric power load means that the excess or deficiency of the amount of heat has been eliminated. Therefore, when the convergence is determined in step S27, the operating state at this time is saved and the energy simulation is ended in step S29. On the other hand, when the difference between the electric power loads is larger than the above A, it is determined that the electric power load has not converged, that is, whether the excess or deficiency of the amount of heat has not been resolved yet, or the electric power load of the auxiliary machine has not converged. Judgment and the next step S3
In step S30, the difference between the power loads of the auxiliary equipment and the power load of the auxiliary machine is added to make a new power load in step S30. Then, the process returns to step S20, and this value is set as the entire power load. Continue the simulation.

FIG. 6 is a flow chart showing the basic operation of an example of energy simulation of the heat load following operation, and steps S31 to S35 are the same as steps S20 to S24 in the power load following operation.

As a result of the comparison in step S35, if it is determined that the exhaust heat amount is excessive, operation is performed to reduce the prime mover load in step S36, and if it is determined to be insufficient, operation is performed to increase the prime mover load in step S37. To do. Of course, the load of the prime mover is changed within the capacity range, and when the capacity range is exceeded, the auxiliary heat source is used. In this way, after each step, the process proceeds to the next step S38.

In step S38, the electric power load for the above operation is calculated by adding the electric power load of the auxiliary equipment, and then in step S39, the electric power load converges, that is, the excess or deficiency of the heat quantity is eliminated as described above. It is determined whether or not. That is, in step S39, the value of the power load calculated in step S38 is set to the value in step S in the previous loop.
If the difference is less than or equal to a preset minimum fluctuating power load B, for example, 0.5 kW, it is determined to be converged, and the operation state at this time is saved in step S440. Then, the energy simulation is finished. On the other hand, when the difference between the power loads is larger than the above B, it is determined that the power load has not converged, the process returns to step S31, the value of the current power load is set as the power load in step S31, and the simulation is further performed. To continue.

FIG. 7 is a flow chart showing the basic operation of an example of energy simulation of rated operation of a suitable number of prime movers. In step S41, the rated number of operated prime movers (including one) is determined according to the estimated power load. Set. An appropriate method can be used to set the rated number of operating machines according to the target cogeneration system. Next, in step S42, the operating state of each device that covers the estimated power load and the required heat amount is derived, the operating state is saved, and the simulation ends.

FIG. 8 is a flow chart showing the basic operation of an example of energy simulation of a single load operation of a prime mover. In step S51, the power generation and exhaust heat recovery efficiency of the prime mover at the selected operating point is set. That is, this flow chart corresponds to steps S9, S11, and S13 of FIG. 1, and the operating point corresponds to the minimum output of one unit operation.
%, The three points are set in the operating range where the non-linear element strongly appears, and the above efficiency of the prime mover at each operating point is stored as a data table, so that in each step S9, S11, S13, The efficiency can be derived and set according to the selected partial load of the prime mover. Then, in step S52,
Based on the set efficiency of the prime mover, the operating state of each device that covers the estimated power load and the required heat quantity is derived and saved, and the simulation ends.

FIG. 9 is a flow chart showing the basic operation of an example of energy simulation of a prime mover operation. In step S61, the operating state of each device that covers the estimated power load and the required heat quantity is derived when the prime mover is stopped. End the simulation.

As described above, there is no branch or loop in the simulation of the proper number of prime mover rated operation, one unit partial load operation, and the prime mover stopped operation, and in these methods preset in the target cogeneration system. The operating state can be derived according to the specific operating method and the estimated power load and the demanded heat amount.

Based on the operating state in each operating method derived from the above energy simulation, that is, the amount of power generation, the amount of power purchased or sold, the amount of exhaust heat, the amount of heat supplied to the auxiliary heat source, the power of auxiliary machinery, etc., the above-described step S4. , S6, S
The energy consumption amount can be calculated by an appropriate method in 8, S10, S12, S14, and S16. Further, in these steps, the objective function for selecting the operation plan setting method, in this case, the running cost can be calculated as described above.

[0035]

As described above, the present invention has the following effects. In the cogeneration system, it is possible to set the operation plan by selecting the optimum operation method at each time point of the year, that is, the operation method that minimizes the running cost in this case, from a plurality of operation methods. By including an appropriate number of simulations of partial load operation, which is an operating region of a prime mover in which a non-linear element strongly appears, the energy simulation can select the minimum cost operation method in consideration of the influence of the non-linear element. The energy simulation includes simulations of an electric power load following operation that generates electric power equal to the estimated electric power load and a thermal load following operation that generates electric power equal to the estimated demand heat amount It is possible to select the operation method with the minimum cost in consideration of the influence on the cost due to a large difference between the electric power selling price and the power sale price, and the influence on the cost due to the operation of the auxiliary heat source or the discard of the surplus heat amount. Since the selection is made by comparing all of the plurality of operating methods including the method described in, the accuracy equivalent to searching for all the optimum points can be obtained. Since the energy simulation is a simulation in which the operation method is set at each time point, it is relatively easy to perform precise energy calculation including fine parts such as efficiency change due to outside air temperature and change of exhaust heat temperature level. It can be executed in a short time.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example of a basic operation of an operation plan setting method of the present invention.

FIG. 2 is an explanatory diagram conceptually showing the relationship between the amount of electric power generated in the cogeneration system and the fuel cost of the prime mover from which the amount of usable exhaust heat is subtracted.

FIG. 3 is an explanatory diagram conceptually showing the relationship between the amount of power generated in the cogeneration system and the power purchase cost.

FIG. 4 is an explanatory diagram conceptually showing the relationship between the amount of electric power generated in the cogeneration system and the fuel input cost of the boiler.

FIG. 5 is a flowchart showing a basic operation of an example of energy simulation of power load following operation.

FIG. 6 is a flowchart showing a basic operation of an example of energy simulation of heat load following operation.

FIG. 7 is a flowchart showing a basic operation of an example of energy simulation of a plurality of prime mover rated operations.

FIG. 8 is a flow chart showing a basic operation of an example of energy simulation of a partial load operation of one prime mover.

FIG. 9 is a flowchart showing a basic operation of an example of energy simulation of a prime mover stop operation.

Claims (6)

[Claims] 1. An energy simulation is performed for each of a plurality of operating modes of a prime mover with respect to an estimated electric power load and heat load at each time point throughout the year, and energy consumption of each operating mode is calculated from the result. In the operation plan setting method for selecting the operation method that minimizes the objective function by comparing the operation methods based on the calculated energy consumption at each time point and selecting the operation method at each time point for a year, The objective function is running cost, and multiple operation methods are suitable for power load follow-up operation that generates power equal to the estimated power load and heat load follow-up operation that generates power to generate heat equal to the estimated heat demand. In a cogeneration system characterized by several rated operation, one partial load operation and prime mover operation Operation plan setting method 2. An energy simulation of a power load following operation of a prime mover includes a step of obtaining a prime mover load factor corresponding to the power load with an estimated power load as an initial value, and power generation and exhaust heat recovery efficiency according to the obtained load factor. The step of calculating, the step of calculating the exhaust heat amount of the prime mover, the step of determining excess or deficiency by comparing the exhaust heat amount and the heat demand, and when the excess or deficiency occurs, without changing the power generation amount of the prime mover, Other than the equipment to set the excess and deficiency elimination operation of heat supply, the step of calculating the power load of the auxiliary machine when performing the excess and deficiency elimination operation, the power load of the auxiliary machine and the power load Add the difference between the step of calculating the total power load, the step of determining the convergence of the power load of the prime mover, and the power load of the previous auxiliary machine if it has not converged 2. The method of setting an operation plan in a cogeneration system according to claim 1, further comprising a step of shifting to a step of obtaining a prime mover load factor, and a step of saving the operating state and ending the simulation when converged. 3. The energy simulation of the heat load following operation of a prime mover includes a step of obtaining a prime mover load factor corresponding to the estimated power load as an initial value, and power generation and exhaust heat recovery efficiency according to the obtained load factor. A step of calculating the exhaust heat amount of the prime mover, a step of comparing the exhaust heat amount and the demand heat amount to determine excess or deficiency,
When excess or deficiency occurs, the step of setting the excess and deficiency elimination operation by changing the amount of power generation by the prime mover within the range of capacity, and the overall power load including the auxiliary equipment power load when performing the excess and deficiency elimination operation And a step of calculating the purchased or sold amount of commercial power, a step of determining the convergence of the power load to be generated, and again when the convergence does not occur,
A step of shifting to a step of obtaining a prime mover load factor,
The operation plan setting method in the cogeneration system according to claim 1, further comprising a step of saving the operation state and terminating the simulation when converged. 4. The energy simulation of a proper number of prime mover rated operations is a step of deriving an operating state of each device that covers the estimated power load and the required heat quantity in the rated operation of the number of operating units set according to the estimated power load. An operation plan setting method in a cogeneration system according to claim 1, characterized in that 5. The energy simulation of a single load operation of a prime mover sets a plurality of operating points in a range from the minimum output of the prime mover to a rated operation, and obtains power generation and exhaust heat recovery efficiency at each operating point. The operation plan setting method in the cogeneration system according to claim 1, further comprising the step of deriving an operating state of each device that covers the estimated electric power load and the demanded heat amount in each partial load operation. 6. The cogeneration system according to claim 1, wherein the energy simulation of the stop operation of the prime mover has a step of deriving an operating state of each device that covers the estimated electric power load and the heat demand when the prime mover is stopped. Operation plan setting method in the system