EP1764486A1 - Method for determining the actual peak load of a power plant and device for regulating - Google Patents

Abstract

The method involves measuring a measuring value (x i) that affects the maximum power (P max). A conversion factor (f(x i)) is determined from the measured measuring value, which represents the changes of an actual maximum power concerning a reference power (P ref), based on a conversion curve or power plant model. The reference power is converted into the actual maximum power by the conversion factor. An actual gas turbine power and the actual value of the measuring value are measured for calibrating the reference power. Independent claims are also included for the following: (1) a method for regulating a gas turbine plant (2) a regulation device for regulating a power plant such as gas turbine plant or a gas or steam turbine plant (3) a power plant including a regulation device.

Description

The present invention relates to a method for determining the current maximum power of a power plant, in particular a gas turbine plant or a gas and steam turbine plant. In addition, the present invention relates to a control device for controlling a power plant, in particular a gas turbine plant or a gas and steam turbine plant.

In a power grid, the network operator must ensure the balance between the load, ie the requested power, and the power provided. Differences between the load on the one hand and the available power on the other hand lead to a change in the network frequency, which adversely affects the network operation and worst case can lead to the complete collapse of the network.

In order to be able to react quickly in the event of sudden imbalances between the load and the available power, the grid operators purchase reserve power from the generators, the so-called control reserve. A power plant participating in the control reserve must be able to provide a given power within a certain period of time. A power plant participating, for example, in the so-called minute reserve must be able to provide a certain power after a few minutes (in Germany 15 minutes). Other backup modes require power to be delivered within a few seconds.

In particular, those control reserves that must be available within seconds, are important for the frequency support operation of the network. For deviations of the mains frequency From the nominal frequency, a power plant participating in the frequency support operation must be able to quickly make available the agreed reserve power, for example 5% of the maximum power, in the event of a frequency decline. For this purpose, power plant operators must know at all times how large the currently possible maximum power of the power plant is, and adjust the power setpoint of the system on the basis of the maximum power taking into account the reserve power. The maximum output mainly depends on the compressor inlet conditions, in particular on the temperature, the humidity and the pressure of the ambient air entering the compressor, as well as on the degree of contamination of the compressor and on the mains frequency. The power setpoint for the current driving style of the power plant then results from the maximum power minus the agreed reserve throttle.

So far, the maximum power is estimated by the power plant operator and entered the power setpoint manually. If the boundary conditions change, for example the compressor inlet conditions or the degree of contamination of the compressor, the power setpoint must be readjusted manually. The frequency of readjustment depends both on the stability of the compressor entry conditions and on the desired reliability of the control reserve to be observed.

Object of the present invention is to provide a suitable for automation method for determining the current maximum power of a power plant available. A further object of the invention is to provide a control device for controlling a power plant on the basis of a reference variable representing a power setpoint. Finally, it is an object of the present invention to provide an improved power plant.

The first object is achieved by a method according to claim 1, the second object by a control device according to claim 12 solved. The third object is achieved by a power plant, in particular a gas turbine plant or a gas and steam turbine plant according to claim 15. The dependent claims contain advantageous embodiments of the invention.

• Erfassen mindestens einer die Maximalleistung beeinflussenden Messgröße. Im Falle einer Gasturbinenanlage oder einer Gas- Und Dampfturbinenanlage kann als Messgröße mindestens eine der folgenden Größen gemessen werden: Verdichter-Eintrittstemperatur der Gasturbine, Verdichter-Eintrittsdruck der Gasturbine, Verdichter-Eintrittsfeuchte der Gasturbine, die Netzfrequenz oder die Betriebsstunden seit der letzten Reinigung des Verdichters (Verdichterwäsche).
• Ermitteln einer Umrechnungsgröße aus der mindestens einen erfassten Messgröße, welche die Änderung der aktuellen Maximalleistung bezogen auf eine Referenzleistung repräsentiert. Das Ermitteln der Umrechnungsgröße kann hierbei beispielsweise anhand eines Kraftwerksmodells oder anhand mindestens einer vorab ermittelten Umrechnungskurve, in der Umrechnungsgrößen in Abhängigkeit von den Messgrößen gegeben sind, ermittelt werden.
• Umrechnen der Referenzleistung, die insbesondere eine Referenz-Maximalleistung darstellen kann, in die aktuelle Maximalleistung mit Hilfe der Umrechnungsgröße.

The inventive method for determining the current maximum power of a power plant includes the following steps:

• Detecting at least one of the maximum power influencing measure. In the case of a gas turbine plant or a gas and steam turbine plant, at least one of the following variables can be measured: Compressor inlet temperature of the gas turbine, compressor inlet pressure of the gas turbine, gas turbine compressor inlet moisture, the mains frequency or the operating hours since the last time the compressor was cleaned (compressor wash).
• Determining a conversion quantity from the at least one detected measured variable, which represents the change of the current maximum power relative to a reference power. The determination of the conversion quantity can be determined, for example, by means of a power plant model or by means of at least one previously determined conversion curve, in which conversion variables are given as a function of the measured variables.
• Converting the reference power, which may in particular represent a reference maximum power, in the current maximum power using the conversion size.

The method according to the invention can replace the estimation of the maximum power of the power plant operator and makes it possible to regulate a power plant on the basis of a reference variable representing a power setpoint. The power setpoint then results from the current maximum power value determined by the method according to the invention minus the required control reserve and, if necessary, less a safety reserve.

The method according to the invention therefore makes it possible to automatically track the power setpoint when the boundary conditions change. The agreed control reserve can thus be met automatically and precisely. Furthermore, it can be ensured that the power plant can be operated while maintaining this control reserve at maximum power and maximum efficiency.

By means of a calibration, which is advantageously carried out regularly, the reference power can be redetermined, whereby in particular the degree of contamination of the compressor can be taken into account when determining the current maximum power. For calibrating the reference power, the current gas turbine power and the current value of the at least one measured variable can be measured, for example, during base load conditions, and the reference power can be newly determined on the basis of the power plant model or the at least one conversion curve. Since in the calibration the compressor entry conditions are included as measured variables, and the result of the calibration depends on the state of the contamination of the air inlet filter, the filter contamination in the reference power is taken into account.

The conversion quantity, with the help of which the current maximum power is determined, may in particular be a conversion factor with which the reference power is to be multiplied.

In the application of the method according to the invention in a control method in which the power setpoint is tracked automatically with changes in the boundary conditions, the measured variables are measured continuously or repeatedly and the current maximum power is determined continuously or repeatedly.

As already mentioned, the method according to the invention can be used in particular for determining the current desired power value of a power plant, in particular a turbine plant, from the current maximum power of the power plant. The current power setpoint is then determined based on the current maximum power determined by the method according to the invention. This can be done in particular continuously or repeatedly.

• Mindestens einen zum Erfassen einer die Maximalleistung der Kraftwerksanlage beeinflussenden Messgröße und zum Ausgeben einer diese Messgröße repräsentierenden Sensorgröße ausgebildeten Messgrößensensor. Der Messgrößensensor kann insbesondere zum Messen einer der nachfolgenden Größen ausgebildet sein: Verdichter-Eintrittstemperatur, Verdichter-Eintrittsdruck, Verdichter-Eintrittsfeuchte, Netzfrequenz.
• Einen Speicher mit einer darin gespeicherten Referenzleistung.
• Eine mit dem mindestens einen Messgrößensensor zum Empfang der Sensorgröße und mit dem Speicher zum Empfang der Referenzleistung verbundene Umrechnungseinheit. Die Umrechnungseinheit umfasst ein Kraftwerksmodell oder mindestens eine Umrechnungskurve und ist zum Umrechnen der Referenzleistung in die aktuelle Maximalleistung sowie zum Ausgeben einer die Maximalleistung repräsentierenden Maximalleistungsgröße ausgebildet.
• Außerdem umfasst die erfindungsgemäße Regelungsvorrichtung eine Leistungssollwert-Berechnungseinheit, die zum Empfang der Maximalleistungsgröße mit der Umrechnungseinheit verbunden ist und die zum Berechnen des Leistungssollwerts auf der Basis der Maximalleistungsgröße und mindestens einer vorgegebenen Regelreservegröße sowie zum Ausgeben einer Leistungssollwertgröße als Führungsgröße ausgestaltet ist. Mit der erfindungsgemäßen Regelungsvorrichtung kann der Leistungssollwert aus vorhanden Messgrößen berechnet und bei einer Änderung der Randbedingungen automatisch nachgeführt werden.

A control device according to the invention for controlling a power plant installation, in particular a gas turbine installation or a gas and steam turbine installation on the basis of a reference variable representing a power setpoint includes:

• At least one for detecting a maximum power of the power plant conditioning measuring variable and for outputting a sensor size representing this measured variable formed Meßgrößenensensor. The measured variable sensor can be designed, in particular, for measuring one of the following variables: compressor inlet temperature, compressor inlet pressure, compressor inlet moisture, mains frequency.
• A memory with a reference power stored in it.
• A conversion unit connected to the at least one measured-quantity sensor for receiving the sensor size and to the memory for receiving the reference power. The conversion unit comprises a power plant model or at least one conversion curve and is designed to convert the reference power into the current maximum power and to output a maximum power size representing the maximum power.
• In addition, the control device according to the invention comprises a power setpoint calculation unit which is connected to the conversion unit for receiving the maximum power quantity and which is designed to calculate the power setpoint value on the basis of the maximum power size and at least one predetermined control reserve size and for outputting a power setpoint value as a reference variable. With the control device according to the invention, the power setpoint can be calculated from existing measured variables and tracked automatically when the boundary conditions change.

The power setpoint calculation unit can be designed, in particular, for calculating the power setpoint value on the basis of the maximum power size, a predetermined control reserve size and a predetermined safety variable. The safety variable can serve to ensure that the control reserve is reliably maintained. For example, if calibration of the reference maximum power occurs at certain intervals, the safety margin may be used, for example, to absorb shifts in the reference maximum power that occur between two calibrations.

To perform a calibration, the control device may include, for example, a power sensor that is designed to detect the current power of the power plant and to output a performance variable representing the current power. Furthermore, in this embodiment there is an updating unit which is connected to the power sensor for receiving the power quantity, for receiving the sensor size with the at least one measured variable sensor and for outputting a reference power to the memory. The updating unit is designed to determine the reference power from the received power quantity and the at least one received sensor size.

A power plant according to the invention, which can be configured in particular as a gas turbine plant or as a gas and steam turbine plant, is equipped with a control device according to the invention. In such a power plant, the power setpoint can be tracked automatically with changes in the boundary conditions.

FIG 1

zeigt den prinzipiellen Aufbau eines Gas- und Dampfturbinenkraftwerks in einer stark vereinfachten schematischen Darstellung.

FIG 2

zeigt die erfindungsgemäße Regelvorrichtung in einem Blockschaltbild.

FIG 3

zeigt in einer schematischen Darstellung einen Regelkreis für den Gasturbinenteil der in FIG 1 dargestellten Gas- und Dampfturbinenanlage.

Further features, properties and advantages of the present invention will become apparent from the following description of a Embodiment with reference to the accompanying figures.

FIG. 1

shows the basic structure of a gas and steam turbine power plant in a highly simplified schematic representation.

FIG. 2

shows the control device according to the invention in a block diagram.

FIG. 3

shows a schematic representation of a control loop for the gas turbine part of the gas and steam turbine plant shown in FIG.

The invention will be described below by way of example with reference to determining the maximum power of a gas and steam turbine plant. However, the invention is not limited to use in gas and steam turbine plants. In particular, it can also be used in gas turbine plants without a downstream steam turbine.

The gas and steam turbine plant 1 shown schematically in FIG. 1 comprises a gas turbine plant 1a and a steam turbine plant 1b. The gas turbine plant 1a is equipped with a gas turbine 2, a compressor 4 and at least one combustion chamber 6 connected between the compressor 4 and the gas turbine 2. By means of the compressor 4, fresh air L is sucked in, compressed and fed via the fresh air line 8 to one or more burners of the combustion chamber 6. The supplied air is mixed with supplied via a fuel power 10 liquid or gaseous fuel B and the mixture is then ignited. The resulting combustion exhaust gases form a working medium AM of the gas turbine plant 1a, which is fed to the gas turbine 2, where it performs work under relaxation and drives a shaft 14 coupled to the gas turbine 2. The shaft is coupled with the gas turbine 2 as well as with the compressor 4 and with a generator 12 to drive them. Depending on the design of the gas turbine plant 1a, a load transmission can still be connected between the compressor 4 and the generator 12 be. The expanded working medium AM 'is discharged via an exhaust pipe 15 to a heat recovery steam generator 30 of the steam turbine plant 1b.

In addition to the heat recovery steam generator 30, the steam turbine installation 1 b comprises a steam turbine 32, a condenser 34 and a feedwater pump 36. The waste heat steam generator 30 is connected to the steam turbine 32 via a steam line 31. This is in turn connected via a vapor line 33 to the capacitor 34. Finally, a condensate line 35 connects the condenser 34 to the heat recovery steam generator 30. The steam generator 30, the steam turbine 32, the condenser 34, the steam lines 31 and 33 and the condensate line 35 together form a water-steam cycle of the steam turbine plant. The circulation of the condensate or the steam is accomplished by the condensate pump 36. It should be noted at this point that the circuit diagram shown in FIG. 1 contains a greatly simplified representation, in particular of the steam turbine plant. In real steam turbine plants, the water-steam cycle is usually more complicated. Thus, the heat recovery steam generator 30 often includes a plurality of evaporators, reheater, preheater, etc. with which the steam can be further heated or the condensate can be preheated. Likewise, the steam turbine 32 may have a plurality of turbine stages, which are designed for different steam pressures and steam temperatures. These are usually connected in series and increase the efficiency of the steam turbine plant.

A control circuit for regulating the power of the gas turbine plant 1a of the gas and steam turbine plant 1 is shown schematically in FIG 2 as a block diagram. The control circuit is used in the present example for acting on the combustion chamber 6 supplied air mass flow and / or the combustion chamber 6 supplied fuel mass flow. The air supply and the fuel supply therefore form the controlled system 56 of the control circuit 50. To act on the controlled system 56, an actuator 54 is present, which control signals for a fuel supply valve and for the vanes of the first compressor vane row or rows. In addition to the fuel mass flow and the air mass flow, disturbances z, which act on the controlled system 56, also lead to changes in the gas turbine power. By means of a power sensor 58, the current power P of the gas turbine is measured and output in the form of a power quantity. The power quantity is subtracted from a power setpoint W in a subtracter 60 and the difference is forwarded to the controller 52. This determines a control signal REG, which is output to the actuator 54 and this causes to act by means of a manipulated variable U on the control system 56 such that the current power value is equalized to the power setpoint W.

bestimmt. Hierbei bezeichnet R die geforderte Regelreserve (in Prozent) und S eine Sicherheit (ebenfalls in Prozent), die dazu dient, die geforderte Regelreserve mit größtmöglicher Sicherheit einhalten zu können. Außer der geforderten Regelreserve R und der Sicherheit S geht in diese Formel auch die aktuell mögliche Maximalleistung P_max ein. Diese Maximalleistung ist jedoch keine konstante Größe, sondern hängt von Randbedingungen ab. Derartige Randbedingungen x_i sind insbesondere Verdichtereintrittsbedingungen wie etwa die Temperatur, die Feuchte und der Druck der in den Verdichter 4 eintretenden Luft L. Zudem wird die erzielbare Maximalleistung vom Verschmutzungsgrad des Verdichters 4, vom Verschmutzungsgrad des Luftansaugfilters, der Alterung der Kraftwerkskomponenten, der Netzfrequenz, etc. beeinflusst.The power setpoint W should take into account the control reserve, ie it must be smaller than the maximum power of the gas turbine system. It is calculated from the currently possible maximum power according to the formula $${\mathrm{P}}_{\mathrm{s}\mathrm{O}\mathrm{l}\mathrm{l}}\mathrm{=}{\mathrm{P}}_{\mathrm{m}\mathrm{a}\mathrm{x}}\mathrm{\times }\left(\mathrm{1}\mathrm{-}\left(\mathrm{R}\mathrm{+}\mathrm{S}\right)\mathrm{/}\mathrm{100}\mathrm{\%}\right)$$

certainly. Here, R denotes the required control reserve (in percent) and S a security (also in percent) which serves to be able to comply with the required control reserve with the greatest possible certainty. Apart from the required control reserve R and the safety S, the currently possible maximum power P _max also enters this formula. However, this maximum power is not a constant quantity, but depends on boundary conditions. Such boundary conditions x _i are in particular compressor entry conditions such as the temperature, humidity and pressure of entering the compressor 4 air L. In addition, the achievable maximum power from the degree of contamination of the compressor 4, the degree of contamination of the air intake filter, the aging of the power plant components, the grid frequency, etc. influenced.

Based on what has been said, the knowledge of the current maximum power P _{max is} necessary if the power setpoint P _{soll is to be} determined.

The determination of the desired power value P _soll is explained below with reference to the block diagram shown in FIG. The block diagram shows a device for determining the desired power value, which enters into the control circuit 50 shown in FIG.

The device 70 includes a number of measurement size sensors, shown as block 72. Measured variable sensors can be, for example, sensors which determine the compressor inlet temperature, the compressor inlet humidity, the compressor inlet pressure of the ambient air, the mains frequency, etc. In addition, the device 70 includes as a further sensor, a power sensor 73, with which the current gas turbine power can be detected. The device 70 further comprises a calculation unit 74, which includes a gas turbine model and outputs a conversion factor f (x _i ), a memory 75, in which a reference power P _{ref is} stored, and a multiplication unit 76, which is connected to the memory 75 for receiving the reference power P _ref and connected to the calculation unit 74 for receiving the conversion factor f (x _i ). The multiplication unit 76 is designed to calculate the maximum power by multiplying the reference power P _ref by the conversion factor f (x _i ) and outputting the value of the maximum power P _max . Furthermore, the device 70 comprises a power setpoint calculation unit 78 as well as two memories or memory locations 80, 82 in which the value R for the control reserve or the value S for the safety are stored. In addition, the device 70 may comprise an offset memory 84, in which offset values for the measured variables x _i measured by the measuring-quantity sensors 72 are stored. These offsets can be added to the determined measured variables x _i before they are input to the calculation unit 74. Furthermore, the device 70 includes one with the calculation unit 74 for receiving the conversion factor f (x _i ) and reference power calculation unit 86 connected to the memory 75 for outputting the reference power P _ref and a trigger unit 88 connected to the memory 75 for triggering a memory operation in the memory 75.

The determination of the power target value P _soll is carried out with the embodiment illustrated in FIG 3 device 70 by using the measured values detected by the measuring size sensors 72 are x _i transmitted to the calculation unit 74 that includes a model of the gas turbine plant and on the basis of the detected measured variables the conversion factor f (x _i ). Optionally, offsets can be added to the acquired measured variables before the measured variables x _{i are} entered into the calculation unit 74. The conversion factor is forwarded to the multiplication unit 76, where it is multiplied by a reference power P _ref related to the memory 75. The product of the reference power P _ref and the conversion factor f (x _i ) provides the maximum possible power P _{max of} the gas turbine plant. The calculation unit 74 and the multiplication unit 76 together form a conversion unit which converts the reference power P _ref into the current maximum power P _max on the basis of the measured values x _i . In the power setpoint calculation unit 78, the power setpoint P _soll is then calculated according to the formula 1 from the maximum power P _max , the required control reserve R and the safety S and forwarded as a reference variable to the control circuit 50 shown in FIG.

In addition to the compressor entry conditions mentioned, further measured variables influencing the maximum output of the gas turbine plant, for example the grid frequency or operating hours since the last compressor _wash (x _ΔOH , OH: operating hours), can be detected and taken into account in the conversion factor f (x _i ).

By means of the device 70 shown in FIG 3, a calibration is also performed at regular intervals.

As part of this calibration, a new reference power P _{ref is} calculated and stored in the memory 75. Calibration is possible, for example, during base load conditions of the gas turbine plant. In this case, the current gas turbine power is detected by means of the power sensor 73 and forwarded to the reference power calculation unit 86. It also receives from the calculation unit 74 the current conversion factor f (x _i ). The reference power P _ref then results from the quotient of the measured power, _hereinafter referred to P _kal , and the conversion factor determined on the basis of the simultaneously measured measured variables x _i , referred to _{below as} f _kal (x _i ). The thus determined new reference power P _ref is then stored in the memory 75 as a new, ie calibrated, reference power and is subsequently available to the conversion unit 76 as a reference power P _ref .

Calibration takes place when the system is started up and afterwards at regular intervals. A trigger unit 88 serves to trigger the storage of the new reference power. The calculation unit 74, the reference power calculation unit 86 and the trigger unit 88 together form an updating unit for updating or calibrating the reference power P _ref .

In the present embodiment, a model of the power plant was used in the calculation unit 74. Alternatively, it is also possible to use conversion curves which represent a relationship f _i for each detected measured variable x _i . The conversion factor f (x _i ) then results from the product of the individual factors f _i . For example, if there is ever a factor for the compressor inlet temperature (factor f _TV ), for the compressor inlet pressure (f _PV ), the compressor inlet temperature (f _V ) and for the mains frequency (f _N ), then the conversion factor results to $$\mathrm{f}\left({\mathrm{x}}_{\mathrm{i}}\right)\mathrm{=}{\mathrm{f}}_{\mathrm{T}\mathrm{V}}\left({\mathrm{x}}_{\mathrm{T}\mathrm{V}}\right)\mathrm{\times }{\mathrm{f}}_{\mathrm{p}\mathrm{v}}\left({\mathrm{x}}_{\mathrm{p}\mathrm{v}}\right)\mathrm{\times }{\mathrm{f}}_{\mathrm{v}}\left({\mathrm{x}}_{\mathrm{v}}\right)\mathrm{\times }{\mathrm{f}}_{\mathrm{N}}\left({\mathrm{x}}_{\mathrm{N}}\right)\mathrm{\times }{\mathrm{f}}_{\mathrm{\Delta }\mathrm{O}\mathrm{H}}\left({\mathrm{x}}_{\mathrm{\Delta }\mathrm{O}\mathrm{H}}\right)\mathrm{,}$$

The regular calibration of the reference power P _ref makes it possible to take account of changing contamination states of the compressor. For example, an increasing contamination with unchanged position of the compressor guide vanes leads to a reduction of the air mass flow to the combustion chamber. Since the maximum possible power at a given turbine exhaust gas temperature depends, inter alia, on the air mass flow, increasing pollution leads to a reduction in the maximum turbine output. The calibration can take into account the increasing reduction in maximum power. After cleaning the compressor is then again the largest possible air mass flow available. By means of a recalibration, the system can then be adapted to the cleaned compressor again.

If neither a calibration nor a compressor _{wash is} carried out for a (longer) period of time, the resulting reduction of the maximum power can be _taken into account by the factor f _ΔOH .

Claims (15)

Method for determining the current maximum power (P _max ) of a power plant, in particular a gas turbine plant or a gas and steam turbine plant, comprising the steps of: - Detecting at least one of the maximum power (P _max ) influencing the measured variable (x _i ); - Determining a conversion factor (f (x _i )) from the at least one detected measured variable (x _i ), which represents the change of the current maximum power (P _max ) with respect to a reference power (P _ref ); and - Converting the reference power (P _ref ) in the current maximum power (P _max ) using the conversion factor (f (x _i )). Method according to Claim 1, in which the conversion quantity (f (x _i )) is determined on the basis of a power plant model. Method according to Claim 1, in which the conversion quantity (f (x _i )) is determined on the basis of at least one previously determined conversion curve. Method according to one of the preceding claims, in which the reference power (P _ref ) is calibrated at least at one time. Method according to Claim 5, in which the current gas turbine power and the current value of the at least one measured variable (x _i ) are measured for calibrating the reference power (P _ref ) and from this the reference power (P _ref ) is determined on the basis of the power plant model or the at least one conversion _curve is determined. Method according to one of the preceding claims, in which the conversion variable (f (x _i )) is a conversion factor which depends on the measured variables (x _i ). Method according to one of the preceding claims, in which the current maximum power (P _max ) of a gas turbine plant or a gas and steam turbine plant is determined and measured (x _i ) at least one of the following sizes is measured: compressor inlet temperature of the gas turbine, compressor inlet pressure the gas turbine, compressor inlet humidity of the gas turbine, mains frequency, operating hours since the last compressor wash. Method according to one of the preceding claims, in which the measured quantities (x _i ) are measured continuously or repeatedly and the current maximum power (P _max ) is determined continuously or repeatedly. Method for determining the current desired power value (P _soll ) of a power plant, in particular a turbine plant, from the current maximum power (P _max ) of the power plant, wherein the current maximum power (P _max ) is determined according to one of the preceding claims. The method of claim 9, in which the power set value (P _soll) continuously or repeatedly from the current maximum power (P _max) is determined of the power plant and determining the maximum power (P _max) is carried out according to claim. 8 A method of controlling a gas turbine plant, in which the power set value (P _soll) as a command variable (W) is specified and the power set value (P _soll) is determined in accordance with claim 9 or 10 Control device (50, 70) for controlling a power plant, in particular a gas turbine plant or a gas and steam turbine plant, on the basis of a reference variable (P _soll ) representing a reference variable (W) with: - at least one influencing for detecting the maximum power (P _max) of the power plant measured variable (x _i) and outputting the measured variable (x _i) representing the sensor size formed measurand sensor (72), a memory (75) having a reference power (P _ref ) stored therein, a conversion unit (74, 76) connected to the at least one measured quantity sensor (72) for receiving the sensor size and to the memory (75) for receiving the reference power (P _ref ), which contains a power plant model or at least one conversion curve and which is used for converting the Reference power (P _ref ) in the current maximum power (P _max ) and for outputting a maximum power (P _max ) representing maximum power size is configured, and - formed a power target value calculation unit (78) which is connected to receive the Maximalleisungsgröße with the translation unit (74, 76) and for calculating the power reference value (P _soll) on the basis of Maximalleisungsgröße and at least one predetermined control reserve size (R) and for Issuing a Leistungssollwertgröße as a reference variable (W) is configured. The control device (50, 70) according to claim 12, wherein the power command calculation unit (78) is configured to calculate the target power value (P _soll ) on the basis of the maximum power amount, a predetermined command reserve size (R), and a predetermined margin size (S). Control device according to claim 12 or 13, additionally comprising: a power sensor (73) configured to detect the current power of the power plant and output a power amount representing the current power, and an updating unit (74, 86, 88) for receiving the power quantity with the power sensor (73), for receiving the sensor size with the at least one measured-quantity sensor (72) and for outputting a reference power (P _ref ) to the memory (75) and for determining the reference power (P _ref ) from the received power quantity and the at least one received sensor size is configured. Power plant, in particular gas turbine plant or gas and steam turbine plant, with a control device (50, 70) according to one of claims 12 to 14.

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