JPH08200095A - Combined cycle power plant load control system - Google Patents

Abstract

(57) [Summary] [Structure] Combined cycle power plant load control system 1
000 includes required unit determining means 100, unit target load calculating means 200, operating unit instantaneous target load commanding means 300, optimum timing calculating means 400, and start / stop timing correcting means 700. [Effect] Since the combined cycle power plant can be economically operated and CO ₂ and NOx emitted from the plant are reduced, a power plant with high environmental compatibility can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load control system for a combined cycle power generation plant, and more particularly, it minimizes start-stop loss when a load consisting of a plurality of units is changed while changing the number of operating units. Load control system for.

[0002]

2. Description of the Related Art A gas turbine, an exhaust heat recovery boiler for recovering the exhaust gas energy and generating steam, a steam turbine driven by the generated steam, and a generator driven by the gas turbine and the steam turbine When the combined cycle power plant composed of a plurality of units is used as the external power generator, and the load is controlled in response to the load command from the outside, for example, the central power supply command station, the plant total output satisfies the load command value. Therefore, it is necessary to start and stop some units so that the required number of operating units is reached. In addition, the thermal efficiency characteristics of the unit generally increase as the unit load factor increases, so it is desirable to operate with the minimum number of units required to maintain high overall plant thermal efficiency in all load zones. Be done. Therefore, when there is a notice of load change (hereinafter referred to as a notice load command value) from the central power supply command center, a specific unit is started and stopped according to a unit start / stop schedule prepared in advance, and other units are Equal load control. In this case, when the load increases that requires additional startup of the units, load equalization is controlled for all units when the load of the additional unit matches the operating unit load. Load control is performed. Here, when the unit start / stop schedule is executed, in the conventional method, the unit is started so that the reference point (hereinafter referred to as the reference time) in the start / stop schedule is aligned with the timing when the plant load command value actually changes. It had been stopped. The reference time is generally the start time of gas turbine acceleration, the time of gas turbine load admission or the time of gas turbine load increase at start-up, and the time of stop when gas turbine load starts to fall or gas turbine breaks. Is generally used. In the conventional method, this reference time is fixed and any load change is dealt with. That is, the start / stop schedule is always executed at the same timing regardless of the number of operating units, the load change width, and the number of start / stop units.

[0003]

However, if the reference time in the start-stop schedule is focused on the energy loss associated with unit start-stop (hereinafter referred to as start-stop loss), the optimum start-stop timing is always given. Not necessarily. That is, when the unit is additionally started when the load rises, if the start timing is too early, the load per unit will be low, that is, the start loss will be large because the operating state with low efficiency continues, and conversely the start timing will be delayed. Even if it passes, the plant has the characteristic that the start-up loss increases because the start-up of the additional unit is delayed, and this characteristic varies depending on the number of operating units, the load change width, and the number of starting units. The same applies when the load drops,
If the stop timing is too early, it takes time from the start to the end of the stop, and even if it is too late, the low load operation per unit is prolonged and the stop loss becomes large. Therefore, the conventional method, which fixed the reference time and always executed the start / stop schedule at the same timing to cope with any load change, had a problem that the start / stop loss due to the load change became large. .

An object of the present invention is to provide a load control system having a unit start / stop timing determining means that minimizes start / stop loss under any load change regardless of the number of units in operation, the load change width, and the number of start / stop units. To provide. Further, it is intended to reduce the CO ₂ and NOx emitted from the plant, thereby providing a highly environmentally friendly control system.

[0005]

The combined cycle power plant load control system of the present invention is, in order to achieve the above-mentioned problems, required unit determining means, unit target load calculating means, operating unit instantaneous target load commanding means, and optimum unit. A timing calculation means and a start / stop timing correction means are provided.

[0006]

The required unit number determining means determines the number of units that need to be operated based on the advance notice plant load command value given from the central power supply command station, and the unit target load calculating means calculates the final target load per unit. Then
The operating unit instantaneous target load command means calculates the instantaneous target load per unit, and the optimum timing calculation means sets the start / stop timing for executing the unit start / stop schedule created in advance to the operating unit initial load and unit load change. Width, determined as a function of a predefined unit load change rate. As a result, regardless of the number of operating units, load change range, and number of start / stop units,
The unit start / stop timing that minimizes the start / stop loss under any load change can be determined.

[0007]

FIG. 1 shows the overall configuration of a combined cycle power plant load control system 1000 according to an embodiment of the present invention, a load command from a central power feed command station 2000, a unit start / stop schedule creating means 3000, and a power plant. It shows the relationship with 4000. First, the central power feeding command station 2000 gives a notice plant load command (L ₁ , t ₀ ) “Change the plant target load to L ₁ at time t ₀ ” to the load control system.
Next, the required unit number determination means 100 determines the number N _R of units that must be operated in order to satisfy the notice plant load command value L ₁ . In response to this, the unit target load calculation means 200 receives the final target load L _1U per unit.
To calculate. Instantaneous target load command means 30 for operating unit
At 0, the instantaneous target load command L _UNR per unit is calculated from the operating unit load L _RUNA , the unit load change rates L ′ and L _1U defined in advance, and this is calculated as the operating unit gas turbine load command means (hereinafter, Unit G in operation
T load command means 500) and the operating unit load L _OU (= L) at time t ₀ .
_RUNA (t ₀ )) and the load change width ΔL per unit are calculated, and these are given to the optimum timing calculation means 400.
The optimum timing calculation means 400 calculates the optimum timing ΔT _OPT as a function of L _OU , ΔL and L ′.
The characteristic coefficient a _i of the function used at this time is given from the characteristic coefficient selecting means 600 using N _R and the number of operating units N _RUN . Unit start / stop schedule creation means 3
Start about speed and load of the gas turbine provided 000 a shutdown schedule N _GTSRO and L _GTSRO
Is shifted in time by ΔT _OPT by the start / stop timing correction means 700 to become N _GTSR and L _GTSR , which are used for actual unit start / stop. That is, N
_GTSR is _given to the start / stop unit control means 850, and L _GTSR is given to the start / stop unit GT load command means 800.
The start / stop unit control means 850 receives the N _GTSR to control the gas turbine speed of the start / stop unit 4100, and also receives the gas turbine load command L _GT2R from the start / stop unit GT load command means 800 to similarly start / stop the unit 4200. Control gas turbine load. In addition, the operating unit control means 550 controls the operating unit G
Gas turbine load command from the T load command means 500 L _GT1R
In response to this, the gas turbine load of the operating unit 4100 is controlled.

Before specifically explaining the load control system of the present invention, start-stop timing and start-stop loss will be defined here. FIG. 2 shows the definition of the start timing Δt and the start loss integration section by taking the case of additionally starting the unit as an example. First, the start timing Δt is defined as the time difference between the start time t _{0 of the} change in the plant target load and the gas turbine load combined time, which is the reference time of the additional unit start schedule. Next, the start-up loss is defined as the sum of the additional unit start-up loss due to the load change and the integrated value regarding the operating unit loss. Specifically, the additional unit startup loss is defined as the integrated value of energy loss from the start of gas turbine acceleration of the additional unit to the completion of plant load change (defined as completion of load change when 97% of the target load change amount of the plant is reached). Then, the unit loss during operation is defined by the integrated value of energy loss from the point of time when the gas turbine load is added to the additional unit to the completion of plant load change (same as above). Here, energy loss is defined as an amount obtained by subtracting effective energy obtained as electric power from energy consumed as gas turbine fuel. Although not shown in the figure, the stop timing and stop loss are defined as follows. First, stop timing Δ
t is defined as a time difference between the time point t ₀ at which the target plant load changes and the gas turbine disconnection time, which is the reference time of the stop schedule of the stop unit. Stop loss is defined as the sum of unit stop loss due to load change and integrated value for continuous operation unit loss. Specifically, the stop loss of the stop unit is defined by the integrated value of energy loss from the start of the gas turbine descent to the completion of the plant load change (defined as the load change completion when 97% of the target load change amount of the plant is reached), and continues. The operating unit loss is defined as the integrated value of energy loss from the start of gas turbine load drop of the stop unit to the completion of plant load change (same as above). The energy loss in this case is also defined as the amount obtained by subtracting the effective energy obtained as electric power from the energy consumed as gas turbine fuel, as in the case of load increase.

Next, the load control method of the present invention will be specifically described. 3 and 4 show specific processing contents in each means of the control system. FIG. 3 shows the processing contents for calculating the instantaneous target load command signal of the operating unit, and FIG.
Shows the processing contents for calculating the GT load control command signals of the operating unit and the start / stop unit. First, in FIG. 3, first, the notice plant load command value L ₁ from the central power supply command station 2000 is the required unit number determining means 100.
Given to a predetermined load L and the number of operating units N
From the above relationship, the number N _R of units that need to be operated to satisfy the notice plant load command value L ₁ is determined. In response to this, the unit target load calculating means 200 causes the final target load per unit L _1U (= L ₁ /
N _R) is calculated in advance. In the operating unit instantaneous target load command means 300, in order to calculate the instantaneous target load command L _UNR per unit, the operating unit load L _0U and the load change width per unit Δ at the load change start time t ₀ .
L is obtained, and the unit load change rate L'specified in advance is used. That is, the operating unit load L _{0U at} the load change start time t ₀ is the actual value of the operating unit load L _RUNA
Obtained by feeding back the load change width Δ
L is represented by the difference between the final target loads L _1U and L _0U . Further, the instantaneous target load command L _UNR can be defined by obtaining the load change period Δt _L (= ΔL / L ′) from the load change width ΔL and the unit load change rate L ′. The operating unit instantaneous target load command means 300 gives an instantaneous target load command L _UNR to the operating unit GT load command means 500, and L _0U and ΔL are optimum timing calculation means 40.
Give to 0. The optimum timing calculation means 400 calculates the optimum timing ΔT _OPT as a function of L _0U and ΔL and L ′, the details of which will be described later.

FIG. 4 shows specific processing contents of the operating unit GT load control command means 500 and the start / stop unit GT load control means 800. As described above, the optimum start / stop schedule N obtained by shifting the time ΔT _OPT by the start / stop timing correction means 700.
_GTSR and L _GTSR are adopted for actual unit start / stop. In the operating unit GT load control command means 500,
First, from the number of units N _RUN currently in operation and its unit load L _RUNA to the unit total load L _{1AT in} operation, the number of units N _STRT to be started and stopped and its unit load L _{STRTA
Calculate the} start / stop unit total load L _2AT from
_{Calculate the} total plant load L _PA from _1AT and L _2AT . next,
From the instantaneous target load command L _UNR per unit and the number of units N _RUN currently in operation, the total instantaneous target load command L _PR for the operating units is obtained, and the load deviation DL from the plant total load L _PA is obtained. In order to convert the load deviation DL into a load deviation per unit, the first period load deviation calculating means 510 before unit start / stop and the second period load deviation calculating means 520 after unit start / stop are respectively used as the first period load deviation DL ₁ (= DL). / N _RUN ) and late load deviation DL ₂ (= D
L / (N _RUN + N _STRT )) is calculated. These two load deviations are adopted as the input value DL _X to the PI adjusting means 530 while being switched under the switching condition described later. Further, the output value L _GT1R from the PI adjusting means 530 is given to the operating unit control means 550 as a gas turbine load command value of the operating unit. According to this load command value, the gas turbine of the operating unit is load-controlled uniformly. In the start / stop unit GT load control means 800, first, the load on the unit is increased or decreased according to the start / stop schedule L _GTSR . That is, the load command value L _GT2R for the start / stop unit is L _GTSR at the start.
Deviation from the L _GT1R as load increases | DL _GT ｜
When (= | L _GT1R −L _GTSR |) is less than or equal to the specified value e, L
_{Set GT2R} = L _GT1R and DL _X = DL ₂ to shift to equal load operation for all units. At the time of load drop, on the contrary, L _GT2R = L _GTSR , DL _X = DL ₁ are set at the same time as the load start of the unit to be stopped, the operation continuation unit is controlled by the equal load, and the stop unit becomes the operation continuation unit according to the stop schedule L _GTSR. Are independently loaded.

Next, the plant start / stop loss and optimum timing calculation means 400 will be described in detail. Figure 5
FIG. 3 illustrates the starting loss characteristics of the plant and shows an example of calculating the optimum timing, taking the case of additionally starting the unit as an example. FIG. 11A generally shows the relationship between the start timing Δt and the start loss Q _LT . In this characteristic, the optimum timing is Δt _OPT, which is the minimum starting loss Q _LTMIN . Therefore, if the start timing is too early (for example, Δt = Δt ₁ ), the load per unit becomes low, and the operating loss remains low, resulting in a large start loss. Conversely, if the startup timing is too late (for example, Δ
(t = 0) The start-up loss increases because the start-up of the additional unit is delayed. The figure (b) shows a concrete example of calculation of the optimum timing, and the initial load L _0U per unit is 85%.
In the case of additionally starting 1 unit while operating 3 units with / u, when unit load change rate L '(% / min / u) is used as a parameter, unit load change width ΔL (% / u) and optimum timing Δt _OPT ( min) relationship is shown. This figure shows that the larger the unit load change width ΔL or the larger the unit load change rate L ′, the larger the optimum timing Δt _OPT . Therefore, in the embodiment of the optimum timing calculating means 400 of the present invention, the optimum timing characteristic is expressed by the following equation, that is, the optimum timing Δt _OPT is the initial load L _0U , the unit load change width ΔL, and the unit load change rate L ′ are variables. It was approximated by a quadratic equation.

[0012]

## EQU1 ## Δt _OPT = a ₁ (L _0U ) ² + a ₂ L _0U + a ₃ (ΔL) ² + a ₄ ΔL + a ₅ (L ′) ² + A ₆ L ′ + a ₇ (Equation 1) The coefficient a _i (i = 1 to 7) of Equation 1 is prepared according to the operating unit number N _RUN and the required unit number N _R ,
It is appropriately selected by the characteristic coefficient selection means 600 and passed to the optimum timing calculation means 400. This allows the optimum timing Δt _OPT to be uniquely determined as a function of L _0U , ΔL and L ′.

Although the embodiments of the present invention have been described above in detail, it is not always necessary to reproduce the present invention in carrying out the present invention, and various modifications and alternatives described below are effective and applied. Also in this, the present invention can be applied without changing the essence.

First, the reference time of the unit start / stop schedule is the gas turbine load adjoining time in the embodiment, but the reference time is a convenience for executing the start schedule, and the reference time of the gas turbine rises. The essence of the present invention does not change even at the quick start time or the load increase start time. Further, when the unit is stopped, the gas turbine disconnection time is set, but the essence of the present invention does not change even at the gas turbine load drop start time.

The function used by the optimum timing calculating means in the embodiment is premised on using the characteristic coefficient selected in advance from the characteristic coefficient selecting means according to the number of operating units, but the number of operating units is also regarded as a variable. Prepare the function,
The method of calculating the optimum timing does not change the essence of the present invention.

In the optimum timing calculating means in the embodiment, the optimum timing is uniquely calculated as a function of the unit initial load, the unit load change width, and the unit load change rate.
An object of the present invention is also a method of determining a start / stop timing that minimizes a start / stop loss by using an optimum value search using a characteristic expression expressed as a function of a unit load change width, a unit load change rate and a start / stop timing. Can be achieved. Further, when the unit load change rate is also an adjustable parameter, this function is used to determine the optimum combination of both the unit load change rate and the start / stop timing by the optimum value search. The objective of minimization can be achieved. Furthermore, even when only the unit load change rate is an adjustable parameter, the function of this invention is used to determine the unit load change rate by the optimum value search, thereby achieving the object of minimizing the start-stop loss of the present invention. can do.

[0017]

The effect of the present invention is that, in a load control system for a combined cycle power plant, the entire system of the plant accompanying unit start / stop regardless of any load change, regardless of the number of operating units, the load change width, and the number of start / stop units. By enabling to determine the unit start / stop timing that minimizes the start / stop loss, it is possible to economically operate the combined cycle power plant, and this also reduces CO ₂ and NOx emitted from the plant. Therefore, a power plant with high environmental compatibility can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram of a combined cycle power plant load control system.

FIG. 2 is an explanatory diagram that defines a unit start timing and a start loss integration section.

FIG. 3 is an explanatory diagram showing the processing contents for calculating an operating unit instantaneous target load command signal.

FIG. 4 is an explanatory diagram showing the processing contents for calculating GT load control command signals for the operating unit and the start / stop unit.

FIG. 5 is an explanatory diagram showing a starting loss characteristic and an example of calculating an optimum timing.

[Explanation of symbols]

100 ... Necessary unit number calculation means, 200 ... Unit target load calculation means, 300 ... Operating unit instantaneous target load command means, 400 ... Optimal timing calculation means, 500 ... Operating unit gas turbine load command means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Akiyama 3-1-1 1-1 Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory

Claims (10)

[Claims] 1. A gas turbine, an exhaust heat recovery boiler for recovering exhaust gas energy of the gas turbine, a steam turbine driven by steam generated in the exhaust heat recovery boiler, the gas turbine and the steam turbine. A control system for a combined cycle power plant comprising a plurality of units of the power generation equipment, wherein the combined output of the combined cycle power generation plant is a plant load. In a load control system that performs start / stop and output control of each unit so that it matches the command value, when the load rises or falls, the start / stop timing for executing the unit start / stop schedule created in advance changes the load. Previous initial load, load change width from the initial load to the final load, and in between The load control system for a combined cycle power plant, characterized in that it is determined by an optimum timing calculating means for determining as a function of the load change rate. 2. A gas turbine, an exhaust heat recovery boiler for recovering exhaust gas energy of the gas turbine, a steam turbine driven by steam generated in the exhaust heat recovery boiler, the gas turbine and the steam turbine. A control system for a combined cycle power plant comprising a plurality of units of the power generation equipment, wherein the combined output of the combined cycle power generation plant is a plant load. In a load control system that performs start / stop and output control of each unit so as to match the command value, a necessary unit that determines the number of units that need to be operated based on the notice plant load command value given to the load control system Number determining means and unit target load calculator for calculating the final target load per unit Stage, operating unit instantaneous target load command means for calculating the unit initial load and unit load change width of the operating unit, and the unit instantaneous target load, and starting for executing the unit start / stop schedule created in advance A combined cycle power plant, characterized in that the stop timing is determined by an optimum timing calculation means for determining the initial load of the operating unit, the unit load change width, and a unit load change rate defined in advance. Load control system. 3. The combined cycle power plant load control system according to claim 1, wherein the start / stop timing is defined as a time difference between a reference time of the unit start / stop schedule and a plant load change start time. 4. The unit reference time of the unit start / stop schedule according to claim 3 is any one of a gas turbine acceleration start time, a gas turbine load combined time, and a gas turbine load increase start time of the unit at start-up. The load control system for a combined cycle power plant defined by the gas turbine load drop start time or the gas turbine disconnection time when it is stopped. 5. The function according to claim 1 or 2, wherein the function used by the optimum timing calculation means is an operating unit initial load, the unit load change width, and the unit load change rate as input parameters of the power plant. A combined cycle power plant load control system created to output optimum timing that minimizes start-stop loss. 6. The function according to claim 1 or 2, wherein the function used in the optimum timing calculating means is an initial load of a unit under operation, a width of change of the unit load, a rate of change of the unit load, the number of units under operation, A combined cycle power plant load control system created to output the optimum timing for minimizing the start / stop loss of the power plant by using the number of additional or stopped units as an input parameter. 7. A gas turbine, an exhaust heat recovery boiler for recovering exhaust gas energy of the gas turbine, a steam turbine driven by steam generated in the exhaust heat recovery boiler, the gas turbine and the steam turbine. A control system for a combined cycle power plant comprising a plurality of units of the power generation equipment, wherein the combined output of the combined cycle power generation plant is a plant load. In a load control system that performs start / stop and output control of each unit so as to match the command value, a necessary unit that determines the number of units that need to be operated based on the notice plant load command value given to the load control system Number determining means and unit target load calculator for calculating the final target load per unit Stage, operating unit instantaneous target load command means for calculating the unit initial load and unit load change width of the operating unit, and the unit instantaneous target load, and starting for executing the unit start / stop schedule created in advance For the stop timing, the operating unit initial load, the unit load change width, and a unit load change rate specified in advance are input, and an optimum value search function is provided so as to minimize the start-stop loss of the combined cycle power plant. A combined cycle power plant load control system characterized by being determined by an optimum timing calculation means included therein. 8. A gas turbine, an exhaust heat recovery boiler for recovering exhaust gas energy of the gas turbine, a steam turbine driven by steam generated in the exhaust heat recovery boiler, the gas turbine and the steam turbine. A control system for a combined cycle power plant comprising a plurality of units of the power generation equipment, wherein the combined output of the combined cycle power generation plant is a plant load. In a load control system that performs start / stop and output control of each unit so as to match the command value, a necessary unit that determines the number of units that need to be operated based on the notice plant load command value given to the load control system Number determining means and unit target load calculator for calculating the final target load per unit Stage, operating unit instantaneous target load command means for calculating the unit initial load and unit load change width of the operating unit, and the unit instantaneous target load, and starting for executing the unit start / stop schedule created in advance Optimum timing calculation means having an optimum value search function for inputting stop timing and unit load change rate, the operating unit initial load and the unit load change width, and minimizing the start-stop loss of the combined cycle power plant A combined cycle power plant load control system characterized by being determined by. 9. A gas turbine, an exhaust heat recovery boiler for recovering exhaust gas energy of the gas turbine, a steam turbine driven by steam generated in the exhaust heat recovery boiler, the gas turbine and the steam turbine. A control system for a combined cycle power plant comprising a plurality of units of the power generation equipment, wherein the combined output of the combined cycle power generation plant is a plant load. In a load control system that performs start / stop and output control of each unit so as to match the command value, a necessary unit that determines the number of units that need to be operated based on the notice plant load command value given to the load control system Number determining means and unit target load calculator for calculating the final target load per unit Unit, an operating unit instantaneous target load command means for calculating a unit initial load and a unit load change width of an operating unit, and a unit instantaneous target load, and a unit for executing a unit start / stop schedule created in advance The load change rate is input by the operating unit initial load and the unit load change width, and by the optimum unit load change rate calculating means having an optimum value search function so as to minimize the start-stop loss of the combined cycle power plant. A combined cycle power plant load control system characterized by determining. 10. A combined cycle power plant which is load-controlled by the combined cycle power plant load control system according to claim 1, 2, 7, 8 or 9.