EP3301267A1 - Method and device for operating a turbo set - Google Patents

Abstract

The invention relates to a method for operating a turbine set (1) with a turbine (3) and a generator (2) coupled to the turbine (3), the generator (2) for feeding electrical rotary or alternating current with a grid frequency ( NF) is formed in a network, wherein the turbine (3) has a live steam valve (7) and an overload valve (8), with the steps: Monitoring the line frequency (NF) for a frequency drop (FA) against a frequency reference, Detecting a state of the live steam valve (7) to an open state (ZU), and Opening the overload valve (8) to a detection of a frequency drop (FA) and a detected open state (ZU) of the live steam valve (7) out.

Description

The invention relates to a method for operating a turbo set.

A turbine set is understood to mean an assembly which has at least one turbine, such as a turbine. a steam turbine, and a generator, such as e.g. a rotary or alternator, wherein the turbine drives the generator and this generates electrical rotary or alternating current, which is fed into a network, such as a supply network.

The turbine may have an overload valve that increases the ability of the turbine to absorb moisture. Thus, the performance of the turbine can be increased with unchanged pressure. However, the efficiency of the turbine decreases when the overload valve is open. Thus, the overload valve should open only in special, selected operating cases. Such operating cases are a drop in frequency or a high electricity price.

Therefore, the overload valve is opened with a fixed allocation to the opening of a live steam valve. In other words, the overload valve and the main steam valve are rigidly positively coupled. However, this rigid positive coupling of the overload valve and the main steam valve entails efficiency losses if the overload valve would not have to be opened.

It is therefore an object of the invention to show ways in which the efficiency of a turbine can be improved.

• Überwachen der Netzfrequenz auf einen Frequenzabfall gegenüber einem Frequenz-Sollwert hin,
• Erfassen eines Zustands des Frischdampfventils auf einen geöffneten Zustand hin, und
• Öffnen des Überlastventils auf ein Erfassen eines Frequenzabfalls und auf einen erfassten geöffneten Zustand des Frischdampfventils hin.

According to the invention, in a method of operating a turbine set with a turbine and a generator coupled to the turbine, wherein the generator for feeding electrical rotary or alternating current with a grid frequency is formed in a network and wherein the turbine is a live steam valve and having an overload valve, the steps performed:

• Monitoring the grid frequency for a frequency drop versus a frequency reference,
• Detecting a state of the live steam valve toward an open state, and
• Opening the overload valve to detect a drop in frequency and a detected open state of the live steam valve out.

This ensures that the overload valve is opened only when the main steam valve is fully open and there is a drop in frequency. Thus, the efficiency can be increased in nominal operation and with the overload valve, the performance of the turbine can be dynamically increased in the case of frequency drops.

Preferably, upon detection of a frequency drop, an indicative binary signal is generated, upon detection of an open state of the live steam valve, another indicative binary signal is generated, and the two signals are combined with an AND gate to generate a drive signal to open the overload valve , So it is ensured with simple means that the overload valve is opened only when the main steam valve is fully open and there is a drop in frequency.

Preferably, for example, based on the drive signal, at least one power setpoint is compared with a power actual value to determine a control deviation and the overload valve is opened in dependence on the specific control deviation. For example, the control deviation can be fed to a PI controller. Thus, a particularly fast and deviation-free adjustment of the power of the turbine in the case of a frequency drop can be achieved. Additionally or also Alternatively it can be provided to compare the mains frequency with the frequency setpoint and to determine a further value for determining the control deviation. The further value may be, for example, a measure of the power required to stabilize the grid frequency. Thus, the scheme can be further improved.

It is preferred, e.g. to the drive signal, a power setpoint compared to a power actual value to determine a control deviation and the main steam valve is opened in dependence on the specific control deviation. For example, The control deviation can be fed to a PI controller. Thus, a particularly fast and deviation-free adjustment of the steam supply to the turbine can be achieved.

Preferably, the mains frequency is compared to the frequency setpoint to lock for the presence of a frequency drop. The mains frequency is the frequency of the rotary or alternating current of the network. So even a simple way a frequency drop can be detected.

Preferably, by evaluating at least the mains frequency and the desired frequency value, a value is indicatively determined for a frequency drop and is closed to a frequency drop, if the value is greater than a limit value. This ensures that there is no erroneous conclusion about a drop in frequency and that the overload valve is not opened unnecessarily, which would otherwise lead to losses of efficiency.

Preferably, a live steam sensor signal is compared with a threshold value and closed to the open state when the main steam sensor signal is greater than the threshold value. This ensures that it is not incorrectly closed on an open steam main valve and the overload valve is not opened unnecessarily, which would otherwise lead to loss of efficiency.

Furthermore, the invention includes a computer program product and an apparatus for carrying out such a method.

• Fig. 1 eine schematische Darstellung eines Turbosatzes mit einer Turbine und einem mit der Turbine gekoppelten Generator, und
• Fig. 2 eine schematische Darstellung einer Vorrichtung zur Regelung der in Fig. 1 gezeigten Turbine.

In the following, a preferred embodiment of the method according to the invention will be explained with reference to the attached schematic drawings. Show it:

• Fig. 1 a schematic representation of a turbine set with a turbine and coupled to the turbine generator, and
• Fig. 2 a schematic representation of a device for controlling the in Fig. 1 shown turbine.

It is going on first Fig. 1 Referenced.

Fig. 1 shows a turbo set 1. In this case, a turbo set 1 is understood to mean a combination of rotating machines which serve to generate electricity. A turbo set 1 usually consists of a turbine 2, such as a steam or a gas turbine, and a generator 3, which is driven by the turbine 2.

In the present embodiment, the turbine 2 is designed as a steam turbine. Thus, the turbo set 1 in the present embodiment may also be referred to as a steam turbine set. The turbine 2 has a high-pressure stage 4, a medium-pressure stage 5 and a low-pressure stage 6.

Furthermore, in the Fig. 1 from the turbo set 1, a live steam valve 7 and an overload valve 8 are shown.

The main steam valve 7 may be a throttle valve, with which a steam supply to the turbine 3 and thus the speed of the turbine can be influenced. In this case, steam flows in succession through the high-pressure stage 4, the intermediate-pressure stage 5 and the low-pressure stage 6 of the turbine 3. The turbine 3 drives then the generator 2, the electrical rotary or alternating current with a grid frequency NF supplies.

The overload valve 8 is arranged parallel to the main steam valve 7, but allows in the present embodiment, a feed of steam in a central region of the high-pressure stage 4. In other words, with open overload valve 8 input stages of the high-pressure stage 4 are bridged and the remaining stages of the high-pressure stage 4 with a applied higher steam pressure in order to achieve an increase in performance of the turbine 3. Notwithstanding the present embodiment may also be provided that when the open overload valve 8 steam at the high-pressure stage 4 of the turbine 3 can be passed directly to the medium-pressure stage 5 in order to achieve an increase in performance if necessary.

It is now additionally on Fig. 2 Referenced.

Fig. 2 shows a device 9 for controlling the turbine 3 of the turbine set. 2

The device 9 has in the present embodiment, an AND gate 10, a characteristic element 11, a first PI controller 12, a second PI controller 13, a first comparator 14, a second comparator 15 and a subtractor 16 and a changeover switch 17th on.

The characteristic element 11 is designed to read in a value for the network frequency NF and to compare it with a frequency reference value.

On the basis of the result of this comparison of two frequency values, the characteristic element 11 determines a value WE. The value WE is representative of a difference of the two frequency values and, in the present embodiment, is a power offset, which is a value for the power required to stabilize the line frequency.

In the present exemplary embodiment, the first comparator 14 compares the value WE with a limit value GW. The limit value GW has a size of zero percent in the present exemplary embodiment. If there is a deviation between the network frequency NF and the frequency setpoint that is greater than zero percent, in the present exemplary embodiment, a frequency drop FA is concluded.

The frequency drop FA in the present embodiment is a binary signal which is logically one when there is a frequency drop FA. Otherwise the signal is logic zero. The frequency drop FA is supplied to the AND gate 10 as one of two input quantities.

In addition to the value WE as input variables, a power actual value LI and a power setpoint LS of the turbine 3 are fed to the subtracter 16 and a control deviation RA is determined.

The control deviation RA is supplied to the first PI controller 12 as an input variable, which provides a first valve control signal VS for actuating the live steam valve 7.

With a sensor (not shown), the opening degree OG of the main steam valve 7 is detected. The opening degree OG is supplied to the second comparator 15 as a first input. As a second input variable, a threshold value SW is supplied to the second comparator 15. The threshold SW has a size of 99 percent in the present embodiment. Thus, when the opening degree OG exceeds 99 percent, that is, the main steam valve 7 is fully opened, the second comparator 15 generates a logic one logical signal for an open state CLOSED. Otherwise, the logical signal is zero.

The open state ZU is supplied to the AND gate 10 as a second input.

If both a frequency drop FA and an open state ZU are present, the AND gate 10 supplies a drive signal AS in the form of a binary signal logic one, which drives the changeover switch 17. On the drive towards the changeover switch 17 switches the control deviation RA on the second PI controller 13. In other words, the second PI controller 13, the control deviation RA is supplied as an input variable, which provides a second valve control signal VS 'for driving the overload valve 8.

If, on the other hand, no drive signal AS logic one, but zero, is present, the second PI controller 13 is acted on by a predetermined reference value RW, which is selected so as to ensure that the second PI controller 13 does not generate the overload valve 8 opening signal , In the present embodiment, the reference value RW has a magnitude corresponding to a frequency excursion of 5 percent, i. a line frequency NF that is 5 percent greater than the frequency reference.

In operation, the control deviation RA determined from the actual power value LI and the power setpoint LS and the value WE is supplied to the first PI controller 12 and then the second valve control signal VS 'is supplied to the main steam valve 7. The opening degree OG is detected and determined by means of the second comparator 15 of the open state ZU and the AND gate 10 is supplied.

Further, when a frequency drop FA has been detected with the first comparator 14, the AND gate 10 supplies the drive signal AS, whereupon the control deviation RA is switched to the first PI controller 12, which then supplies the first valve control signal VS to the overload valve 8. In contrast, if there is no frequency drop FA, the overload valve 8 is kept closed. In other words, the overload valve 8 is only opened when at the same time a frequency drop FA and the main steam valve 7 are fully open.

Thus, the efficiency can be increased in nominal operation and with the overload valve 8, the power of the turbine can be dynamically increased in the case of frequency drops.

Although the invention has been further illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims (15)

A method of operating a turbine set (1) having a turbine (3) and a generator (2) coupled to the turbine (3), the generator (2) for feeding electrical rotary or alternating current into a grid having a grid frequency (NF ), wherein the turbine has a main steam valve (7) and an overload valve (8), with the steps: Monitoring the line frequency (NF) for a frequency drop (FA) against a frequency reference, Detecting a state of the live steam valve (7) to an open state (ZU), and Opening the overload valve (8) to a detection of a frequency drop (FA) and a detected open state (ZU) of the live steam valve (7) out. Method according to claim 1,
wherein, upon detection of a frequency drop (FA), an indicative binary signal is generated, upon detection of an open state (ZU) of the live steam valve (7), another indicative binary signal is generated, and the two indicative signals are ANDed ( 10) to generate a drive signal (AS) for opening the overload valve (8). Method according to claim 2,
wherein at least one power setpoint (LS) is compared with an actual power value (LI) to determine a control deviation (RA), and the overload valve (8) is opened in dependence on the determined control deviation (RA). Method according to one of claims 1 to 3,
wherein at least one power setpoint (LS) is compared with a power actual value (LI) to determine a control deviation (RA), and the main steam valve (7) is opened in dependence on the determined control deviation (RA). Method according to one of claims 1 to 4,
wherein the mains frequency (NF) is compared with the frequency setpoint to infer the presence of a frequency drop (FA). Method according to one of claims 1 to 5,
wherein, by evaluating at least the line frequency (NF) and the frequency reference, a value (WE) is indicatively determined for a frequency drop (FA), and a frequency drop (FA) is inferred if the value (WE) is greater than a limit (GW) is. Method according to one of claims 1 to 6,
wherein a live steam sensor signal (FS) is compared with a threshold value (SW), and is closed to the open state (ZU) when the live steam sensor signal (FS) is greater than the threshold value (SW). Computer program product comprising software components for carrying out a method according to one of claims 1 to 7. Device (9) for controlling a turbine (3) of a turbine set (1) with the turbine (3) and a generator (2) coupled to the turbine (3), the generator (2) for feeding electrical rotary or alternating current in which the turbine (3) has a main steam valve (7) and an overload valve (8), the device (9) being designed to reduce the mains frequency (NF) to a frequency drop ( FA) toward a frequency command value, to detect an open state (ZU) of the live steam valve (7), and the overload valve (8) to detect a frequency drop (FA) and a detected open state (ZU) of the live steam valve (7) to open. Device (9) according to claim 9,
wherein the device (9) is adapted to generate an indicative binary signal and to generate upon detection of an open state (ZU) of the live steam valve (7) a further indicative binary signal, the device (9) being an AND gate (10) for logically combining the two signals, and the device (9) is adapted to generate a drive signal (AS) for opening the overload valve to (8). Device (9) according to claim 10,
wherein the device (9) is designed to compare to the drive signal (AS) at least one power setpoint (LS) with a power actual value (LI) to determine a control deviation (RA) and the overload valve (8) in Depending on the specific control deviation (RA) to open a frequency drop (FA). Device (9) according to one of claims 9 to 11,
wherein the device (9) is adapted to compare a power setpoint (LS) with a power actual value (LI) to determine a control deviation (RA) and in dependence on the specific control deviation (RA) the live steam valve (7) to open. Device (9) according to one of claims 9 to 12,
wherein the device (9) is adapted to compare the line frequency (NF) with the frequency set point to lock for the presence of a frequency drop (FA). Device (9) according to one of claims 9 to 13,
wherein the device (9) is adapted to determine a value (WE) indicative of a frequency drop (FA) by evaluating at least the line frequency (NF) and the frequency setpoint and to infer a frequency drop (FA) if the value (WE) is greater than a limit (GW). Device (9) according to one of claims 9 to 14,
wherein the device (9) is adapted to compare a live steam sensor signal (FS) with a threshold value (SW) and close it to the open state (ZU) when the live steam sensor signal (FS) is greater than the threshold value (SW).

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