Method for controlling a gas turbine

Abstract

A method for controlling a gas turbine, wherein measurement signal values are measured at different times, namely at least a first time and a second time, wherein the first time lies before the second time and wherein attenuated signal values are generated from the measurement signal values by smoothing the measured measurement signal values by means of a attenuation factor, wherein a different attenuation factor is used depending on the difference of the measurement signal value at the second time and the attenuated signal value at the first time.

Claims

1. A method for controlling a gas turbine, comprising: operating the gas turbine; measuring a plurality of measurement signal values indicative of combustion oscillations that develop in a combustion chamber of the gas turbine during the operating of the gas turbine, the measurement signal values having peaks with amplitude and frequency variation during the operating of the gas turbine, the measurement signal values including a first measurement signal and a second measurement signal at different points in time, at least a first point in time and a second point in time wherein the first point in time is located before the second point in time; generating a plurality of attenuated signal values, a first attenuated signal and a second attenuated signal, from the plurality of measurement signal values, in that the measured measurement signal values undergo a smoothing with an attenuation factor, wherein depending on the difference between the second measurement signal value at the second point in time and the first attenuated signal value at the first point in time, a different attenuation factor is used for control of the combustion oscillations, wherein the smoothing is an exponential smoothing; and wherein the smoothing of the measured measurement signal values performed to generate the plurality of attenuated signal values used for control of the combustion oscillations is responsive to both the amplitude and the frequency variation of the peaks that occur in the measurement signal values during the operating of the gas turbine and thus conducive to efficient control of the combustion oscillations in the combustion chamber of the gas turbine.

2. The method according to claim 1, wherein the second attenuated signal value is formed from the sum of two products, wherein the first product is the multiplication of the attenuation factor the second measurement signal value measured at the second point in time, and wherein the second product is the multiplication of a differential value of one minus the attenuation factor and the first attenuated signal value at the first point in time.

3. The method according to claim 1, wherein a higher attenuation factor is used when the second measurement signal value measured at the second point in time is larger or the same as the first attenuated signal value at the first point in time, than when the second measurement signal value measured at the second point in time is smaller than the first attenuated signal value at the first point in time.

4. A method for controlling a gas turbine, comprising: operating the gas turbine; measuring a plurality of measurement signal values indicative of combustion oscillations that develop in a combustion chamber of the gas turbine during the operating of the gas turbine, the measurement signal values having peaks with amplitude and frequency variation during the operating of the gas turbine, the measurement signal values including a first measurement signal and a second measurement signal at different points in time, at least a first point in time and a second point in time wherein the first point in time is located before the second point in time; generating a plurality of attenuated signal values, a first attenuated signal and a second attenuated signal, from the plurality of measurement signal values, in that the measured measurement signal values undergo a smoothing with a respective attenuation factor, wherein depending on the difference between the second measurement signal value at the second point in time and the first attenuated signal value at the first point in time, a different attenuation factor is used for control of the combustion oscillations, wherein the smoothing is an exponential smoothing, wherein the exponential smoothing is characterized by the following relationships:
S.sub.n2=.sub.x*M.sub.n2+(1.sub.x)*S.sub.n1 where x=1.2 wherein, x=2 if M.sub.n2S.sub.n1 x=1 if M.sub.n2<S.sub.n1 .sub.2>.sub.1, .sub.x, x=1.2 represents the different attenuation factors, M.sub.n2 is the measured measurement signal value at the point in time n2, S.sub.n1 is the attenuated signal value at the point in time n1 and S.sub.n2 is the attenuated signal value at the point in time n2, and wherein the smoothing of the measured measurement signal values performed to generate the plurality of attenuated signal values used for control of the combustion oscillations is responsive to both the amplitude and frequency variation of the peaks that occur in the measurement signal values during the operating of the gas turbine and thus conducive to efficient control of the combustion oscillations in the combustion chamber of the gas turbine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features, characteristics and advantages of the present invention will become apparent from the following description of an exemplary embodiment with reference to the accompanying FIGURE.

(2) The FIGURE shows a diagram in which the measurement signal, the attenuated signal value according to the prior art and the attenuated signal value according to the invention are plotted over time t.

DETAILED DESCRIPTION OF INVENTION

(3) The FIGURE shows a curve 1 with measurement signal values which were plotted over time t. The course of the measurement signal 1 has peaks 4 which initially occur every two to three seconds or so. Measurement signal values of above around 2.0 are seen here once as critical. If the repetition frequency of these peaks 4 is correspondingly high, a corrective action should take place. Between the time t=14 and the time t=19, the number of peaks 4 increases. At the time t=19 a change of the operating state was effected. The curve 1 along with the measurement signal values subsequently shows a sufficiently smooth course.

(4) In the curve 2 the attenuated signal values according to the prior art are generated from the measurement signal values of the curve 1 which are plotted over time t. The high-frequency components are avoided through the attenuation according to the prior art. The curve 2 does however drop off sharply over and over again between the peaks 4. For the signal values attenuated according to the prior art in curve 2, no value can be provided however which is decisively unambiguously critical or non-critical: Values between 0.95 and 1.15 occur in the critical phase up to the time t=19 as well as in the non-critical phase thereafter. Efficient regulation is therefore not possible.

(5) The curve 3 was generated by the inventive method. In this case, measurement signal values M.sub.n1, M.sub.n2 are measured at different points in time n1, n2, namely at at least a first point in time n1 and a second point in time n2, wherein the first point in time n1 is located before the second point in time n2. The measured measurement signal values M.sub.n1 and M.sub.n2 undergo an exponential smoothing with an attenuation factor . This allows the generation of signal values S.sub.n1 and S.sub.n2. In this case a higher attenuation factor is used if the measurement signal value M.sub.n2 measured at the second point in time n2 is larger or the same as the attenuated signal value S.sub.n1 at the first point in time n1, than if the measurement signal value M.sub.n2 measured at the second point n2 in time is smaller than the attenuated signal value S.sub.n1 at the first point in time n1.

(6) This exponential smoothing is indicated by the following formula:
S.sub.n2=.sub.x*M.sub.n2+(1.sub.x)*S.sub.n1 where x=1.2
wherein:
x=2 if M.sub.n2S.sub.n1
x=1 if M.sub.n2<S.sub.n1
where .sub.2>.sub.1

(7) Wherein .sub.x, x=1.2 is the attenuation factor, M.sub.n2 the measured measurement signal value at the point in time n2, M.sub.n1 the measured measurement signal value at the point in time n1, S.sub.n1 the attenuated signal value at the point in time n1 and S.sub.n2 the attenuated signal value at the point in time n1.

(8) In the inventive attenuated signal values in the exemplary embodiment, .sub.2=0.3 and .sub.1=0.05 are selected by way of example. Following a peak 4, an inventively attenuated signal value drops off in curve 3 significantly more slowly than is the case for a signal value in curve 2 attenuated according to a prior art method. This results in the inventively attenuated signal value reaching higher values in the chronologically subsequent peak 4 than the signal value attenuated according to the prior art. In terms of regulation, this is often a desired effect. Between the time t=14 and the time t=19, the frequency of the peaks 4 increases. Here it can be observed that the inventively attenuated signal values in the very critical time window remain above 1.5, while the signal values attenuated according to the prior art in curve 2 drop once again to almost 1.0. In the critical time between t=0 and t=19 on the other hand, the inventively attenuated signal values never drop below 1.3 and subsequently never rises above 1.16 in the non-critical time. A suddenly occurring peak 4 therefore provides in its ascent for a weak attenuation, i.e. the attenuation factor 2 is high and the attenuated signal values will therefore rapidly rise during the ascent of the peak. As the peak 4 drops, a switch to a strong attenuation is triggered, i.e. the attenuation factor 2 is low. The attenuated signal values therefore only drop off slowly. Efficient regulation of a gas turbine can therefore be accomplished with the inventive method which reacts quickly to a peak (by switching to weak attenuation) but also evaluates a rapid succession of peaks as more critical than individual peaks.