JP2006161566A - Frequency bias control device for thermal electric power plant and method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain plant stability and exert allowable maximum frequency fluctuation suppressing effect regardless of a state of load operation, by multiplying an output setting correction amount 33 by proper upper and lower limits cooperated with a frequency compensation amount 31. <P>SOLUTION: The frequency bias control device suppressing the frequency deviation in a thermal electric power plant comprises a control circuit, in addition to a frequency compensation circuit correcting a load request signal (MWD) 22 depending on frequency deviation. The control circuit has an output setting correction function generating an output setting correction signal depending on the frequency deviation and adding the signal to the MWD 22 to acquire a control target value of a power generation control, and a means for multiplying the output setting correction signal 33 by upper and lower limit values. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to frequency compensation control that suppresses frequency fluctuation when the frequency fluctuates in a thermal power plant, and in particular, correction of a load request signal (hereinafter sometimes referred to as MWD) 22 that is a control target of a unit master. In addition, since the target value of the generator output, which is the control target of the turbine master, can be corrected and the amount of each correction can be limited according to the plant capacity, a thermal power plant suitable for active frequency compensation operation) It relates to the control device.

The configuration of a conventional thermal power plant is shown in FIG.
The thermal power plant shown here is a boiler 1, a steam turbine 2 that converts steam energy generated in the boiler 1 into kinetic energy (rotational torque) (hereinafter sometimes simply referred to as a turbine), and rotates coaxially with the turbine 2. A generator 3 that converts kinetic energy into electrical energy, a turbine control valve 4 that adjusts the amount of power 7 generated by the generator 3 by adjusting the amount of steam flowing from the boiler 1 into the turbine 2, and the amount of power generated 7 A plant control device (hereinafter also referred to as APC) 6 that controls the entire thermal power plant including the power generator, each of the elements 13 to 19 of the speed control function for correcting the rotational speed of the turbine, and a power generation amount detector 8 as a related measuring device, a frequency The detector 10 and the turbine rotational speed detector 12 are included.

FIG. 10 shows frequency bias control of a conventional plant control apparatus for a thermal power plant.
The frequency of the power transmission system varies depending on the supply and demand balance of the power transmission system. That is, the frequency increases when the amount of power generation is larger than the demand amount, and conversely, the frequency decreases when the amount of power generation is small. In general, thermal power plants have an operation mode function that suppresses frequency fluctuations, which is called governor-free operation. This is because the power generation amount is increased and corrected when the frequency decreases due to insufficient power generation amount. This is an operation mode that improves the supply and demand balance and suppresses fluctuations in the frequency by correcting the power generation amount to decrease when the frequency increases.

  In the conventional thermal power plant, the frequency compensation operation of the thermal power plant when the frequency of the generator fluctuates due to the fluctuation of the system frequency (the generator rotation speed may be considered the same fluctuation) will be described below. .

  Since the present invention largely involves control (hereinafter referred to as “generator output control” or simply “output control”) that matches the power generation amount 7 with the power generation target value MWD22, the output control function will be described first.

  In order to make the explanation of the operation easy to understand, the transient movement is omitted. In the present invention, the power generation amount 7, the power generation amount detection value 9, and the generator output signal 43 may be handled as the same, and therefore are treated as the same.

  The configuration and function of the output control circuit will be described with reference to FIG. The output command 21 is a basic signal for plant control, and the frequency compensation signal 31 is added to the basic signal to form the MWD 22 to set the load state of the plant. The MWD 22 is a boiler input basic signal such as a water supply amount, a fuel amount, and an air amount for the boiler 1 and a generator output target signal. The boiler 1 on the steam generation side and the turbine 2 on the steam consumption side This is a common basic signal for the generator 3.

  When there is a difference between the MWD 22 and the generator output signal 43 (the same signal value is called the generator output 43), a difference signal is generated in the generator output deviation signal 44 (the same signal value is called the generator output deviation 44), The PI controller 46 increases or decreases the load command 45 until the generator output signal 43 matches the MWD 22 (= the generator output deviation 44 becomes 0).

  As shown in FIG. 3, the load command 45 is added with the turbine speed correction signal 17 to become the turbine control valve opening command 18, and the opening of the turbine control valve 4 is changed to the turbine control valve opening command 18 by the servo 19. Adjusted. When the opening of the turbine control valve 4 increases or decreases, the amount of steam 5 flowing from the boiler 1 to the turbine 2 changes, and according to the increase or decrease of the amount of steam 5, the amount of conversion to electrical energy changes and the power generation amount 7 changes. This is the basis of output control.

  This will be described below assuming specific numerical values. For the sake of simplicity, it is assumed that the output command 21, MWD 22, load command 45, turbine control valve opening command 18 and turbine control valve 4 are all 70% as initial states. Here, when the generator output 43 is adjusted to a constant 70%, the plant shifts to a stable operating state with a constant output.

  For example, assume an initial state in which the power generation amount 7 (= generator output 43) is 69% lower than the MWD 22 by 1%. The generator output deviation 44 becomes 70% −69% = + 1%, and the value of the load command 45 starts to increase from 70% by the PI controller 46. Here, when the turbine speed correction signal 17 = 0, the turbine control valve opening command 18 has the same value as the load command 45, and the opening of the turbine control valve 4 is increased from 70% according to the value of the load command 45 by the servo 19 ( Start opening). By opening the turbine control valve 4, the steam flow rate of the steam 5 supplied from the boiler 1 to the turbine 2 increases, and the power generation amount 7 starts to increase from 69%. For example, when the load command 45 increases from 70% to 71% and the turbine control valve 4 opens from 70% to 71%, if the generator output 43 increases from 69% to 70%, then the generator output is The deviation 44 becomes 0, the control operation stops, and the state is stabilized in this state.

  On the other hand, assuming that the generator output signal 43 is 71% which is 1% higher than the MWD 22 in the initial state, the generator output deviation 44 is 70% -71% =-1%, and the load command 45 is the PI controller 46. Is controlled in a decreasing direction from 70%. When the load command 45 is reduced from 70% to 69% and the turbine control valve 4 is also reduced from 70% to 69%, the generator output 43 is reduced from 71% to 70%. The deviation 44 becomes 0, the control operation stops, and the state is stabilized in this state.

Next, the behavior of the prior art when frequency fluctuations occur will be described sequentially by function.
First, as a case 1, let us consider a case where the frequency correction function is only the speed control function of the turbine shown in FIG. 3 and there is no frequency compensation signal 31 shown in FIG. 10, and therefore the MWD 22 is not corrected by the frequency deviation.

  When the system frequency varies, the rotational speed of the turbine 2, the rotational speed of the generator 3, and the generator frequency are affected. When the turbine rotational speed fluctuates, the rotational speed signal 13 detected by the turbine rotational speed detector 12 fluctuates, and a difference from the reference rotational speed signal 14 is generated, resulting in a rotational speed deviation signal 15 (the same signal value as the rotational speed deviation 15). May be called). The settling rate function 16 outputs a rotation speed correction signal 17 (the signal value may be referred to as a rotation speed correction amount 17) proportional to the rotation speed deviation 15, and is added to the load command 45 to be a turbine adjustment valve opening command. 18 is corrected, the opening degree of the turbine control valve 4 is adjusted, and the power generation amount 7 is controlled. The output control PI controller 46 has a proportional-integral control function, whereas the settling rate function 16 has only a proportional control function.

  Similar to the output control, description will be made assuming specific numerical values. In a state where the output command 21, MWD 22, generator output 43, load command 45, turbine control valve opening command 18 and turbine control valve 4 are all 70% constant and stable, for example, power in a 50 Hz region The prior art case 1 in the case where the frequency deviation increases from 0 Hz to +0.2 Hz due to excessive supply amount will be described.

First, as the operation of the turbine speed control function, the frequency increases by 0.2 Hz (corresponding to the fact that the rotational speed increases by 12 rpm as the turbine standard rotational speed of 3000 rpm), so that the rotational speed signal 13 increases from 3000 to 3012 rpm. -12 rpm is generated in the rotational speed deviation signal 15 which is a difference from the value 3000 rpm of the reference speed signal 14. Assuming that the settling rate is 4% (4% frequency fluctuation (50 Hz × 0.04 = 2 Hz or 3000 rpm × 0.04 = 120 rpm, the ratio at which the output correction amount becomes 100%)) 16 −12 rpm ÷ (3000 rpm × 4/100) × 100% = − 10%
Is added as the rotational speed correction signal 17 and added to the value 70% of the load command 45 output from the APC 6, so that the turbine control valve opening command 18 becomes 70% -10% = 60%.

  In accordance with the turbine control valve opening command 18, the servo 19 throttles the opening of the turbine control valve 4 from 70% to 60%, and reduces the amount of steam 5 supplied to the turbine 2 by an amount corresponding to 10% output. As a result, the power generation amount 7 decreases from 70% to 60%. As a result, the output is reduced by 10% in the supply and demand balance state where the power supply is excessive. It acts in the direction to do.

  However, 70% of the MWD 22 does not change even if the frequency fluctuates. When the power generation amount 7 decreases by 10% to 60%, the generator output deviation 44 becomes + 10%, and the PI controller 46 controls the load command. 45 begins to increase from 70%. Specifically, when the load command 45 increases to 80%, the turbine control valve opening command 18 becomes load command (80%) + turbine speed correction amount 17 (−10%) = 70%, and the turbine control valve 4 Is adjusted to the original 70% by the servo 19, the power generation amount 7 also returns to the original 70% output, the generator output deviation 44 becomes 0, the plant is stabilized, and the effect of suppressing the frequency fluctuation is lost.

  That is, when the frequency fluctuation occurs, the power generation amount 7 is temporarily adjusted by the speed control function of the turbine 2 so as to suppress the frequency fluctuation. When the power generation amount 7 is adjusted, the output target value of the output control is adjusted. Since there is a difference from a certain MWD 22, the PI controller 46 pulls it back to the original power generation amount and cancels out the frequency fluctuation suppressing effect by the turbine speed control function.

Next, as case 2 of the prior art, a case will be described in which a frequency compensation function 24 (FIG. 10) is provided in order to eliminate the canceling action of the frequency fluctuation suppression effect by the output control.
Since the output is controlled with the MWD 22 as a target, when the frequency is increased, the MWD 22 is corrected to be decreased, and when the frequency is decreased, the MWD 22 is increased to be corrected, as in the case 2 of the conventional technique. It is possible to eliminate the canceling effect of the frequency fluctuation suppressing effect by the simple output control.

  Therefore, it can be considered that the frequency compensation function 24 generates the frequency compensation signal 25 according to the frequency deviation and adds it to the output command 21 to obtain the MWD 22. However, if the MWD 22 fluctuates due to the frequency deviation, the operation amount, control target, and state quantity of the entire plant are directly affected by the frequency deviation. Therefore, in order to ensure the stability of the plant, the following considerations are generally taken on the circuit. Has been.

(1) For the purpose of ensuring the plant stability, the compensation amount exceeding the allowable range of the plant is limited. For this purpose, a frequency compensation lower limit function 26 and a frequency compensation upper limit function 29 are provided as shown in FIG. Since the amount of fluctuation that can be tolerated by the plant varies depending on the plant load state, the upper and lower limit functions 26 and 29 are functions that have the output command 21 as an input.
The lower limit of the frequency compensation signal 25 is selected by selecting a high value with the output signal 27 of the lower limit function 26, and the upper and lower limits of the frequency compensation signal 25 are further selected by selecting a lower value of the frequency compensation signal 28 with the lower limit limited as the output signal 30 of the upper limit function 29. The frequency compensation signal 31 is limited. The frequency compensation signal 31 is added to the output command 21 to obtain the MWD 22.

(2) The frequency compensation function 24 is set to a dead zone so that the frequency compensation signal 25 is output 0 for frequency fluctuations that are not highly important for suppressing frequency fluctuations and are not preferable in terms of plant stability and are small and have a fast cycle. Provide.
As shown in the frequency compensation amount curve of FIG. 4, there is a dead zone in the setting of the frequency compensation function 24, and the frequency compensation signal 25 is not set to be output when there is a small frequency fluctuation (there is often a fluctuation period is fast). The width of the dead band is generally about ± 0.1 Hz to ± 0.2 Hz, but the frequency after an arbitrary frequency fluctuation (for example, ± 0.25 Hz) beyond the dead band is generated separately from the dead band of the frequency compensation function. The interlock of the switch 47 may be set so that the compensation signal 31 is added to the output command 21.

(3) If the frequency compensation signal 31 changes suddenly, a thermal power plant with a slow response speed cannot be considered. Therefore, a LAG or a change rate limiter is provided in the frequency compensation circuit for the purpose of maintaining the stability of the plant.

  By the way, in Japan, frequency fluctuations exceeding ± 0.2 Hz are rare, and normal frequency fluctuations are often ± 0.15 Hz or less. On the other hand, since the dead zone is set in the frequency compensation amount 31 as described above, the frequency compensation signal 25 is generated at a low rate, and even if the frequency compensation signal 25 is produced due to frequency fluctuations beyond the dead zone, it is shown in FIG. The correction amount is smaller than the correction amount by the turbine speed control function. Therefore, the frequency fluctuation suppression effect by the turbine speed control function is largely canceled by the output control.

  Therefore, as case 3 of the prior art, in order to set the generator output corrected by the speed adjusting function of the turbine as the output target value of the generator output control, the turbine rotation speed correction signal 17 and the frequency compensation signal 31 as shown in FIG. The output setting correction function 32 generates a correction amount corresponding to the difference between the output setting correction function 32 and the output setting correction signal 33 (the signal value may be referred to as the output setting correction amount 33) as the output. There is a circuit that is newly added to the generator output setting signal 42.

  In case 2, the generator output 43 is output controlled with the MWD 22 as a target, but in case 3, the generator output 43 is controlled with the generator output setting signal 42 as a target.

Here, the setting of the output setting correction function 32 is as shown in the characteristics of FIGS.
Frequency compensation amount 31 + output setting correction amount 33 = rotation speed correction amount 17
It is to do. As a result, the effect of suppressing the frequency fluctuation obtained by the speed control function of the turbine is canceled or reduced by the output control, or is reduced.

  FIG. 5 is a setting that focuses on the normal frequency fluctuation range and particularly improves the dead band of the frequency compensation function 24. When the frequency fluctuation is large, correction by the output setting correction function 32 is not performed, and plant stability is achieved. This setting is mainly adopted. FIG. 6 shows a setting for improving the entire frequency fluctuation, and setting the highest priority on frequency fluctuation suppression.

  A feature of the output setting correction circuit including the output setting correction function 32 shown in FIG. 3 is that the MWD 22 is not directly corrected. The MWD 22 is a signal that directly affects the operation amount and behavior of the entire plant, whereas the output setting signal 42 directly affects the load command 45, the turbine regulator 4 to the power generation amount 7, and particularly the plant stability. The boiler 1, which is an important main machine, has an effect as a result of fluctuations in the amount of steam 5. Therefore, it is generally considered more advantageous in terms of plant stability than directly correcting the MWD 22.

  The difference in control operation depending on the presence or absence of the output setting correction circuit including the output setting correction function 32, which is the difference between the case 2 and the case 3, will be described assuming specific numerical values as in the case 1.

  As shown in FIG. 4, the frequency compensation function 24 has a dead band of ± 0.15 Hz, and the slope of the function is set to 4% (the slope at which the output is corrected by 100% with a fluctuation of 2 Hz) in accordance with the slope of the turbine speed control function. . The MWD 22, the load command 45, the turbine control valve 4, and the generator output signal 43 are set to a constant state of 70%. As in the case 1, the frequency condition is assumed to change from +0 Hz to +0.2 Hz. Also, transient behavior and subtle response time deviations are not considered.

First, a case 2 where there is no output setting correction circuit including the output setting correction function 32 as shown in FIG. 10 will be described below.
When the frequency deviation increases from +0 Hz to +0.2 Hz in this state, the turbine rotation speed signal 13 increases from 3000 rpm to 3012 rpm, the rotation speed deviation signal 15 becomes −12 rpm, and the rotation speed correction signal 17 is
−12 rpm ÷ (3000 rpm × 4/100) × 100% = − 10%
Is output, the turbine control valve opening command 18 becomes 70% -10% = 60%, and the servo 19 reduces the opening of the turbine control valve 4 from 70% to 60%. For this reason, the power generation amount 7 is also reduced from 70% to 60%. Up to this point, the operation is the same as the operation of the turbine speed control function in case 1.

On the other hand, the output of the frequency compensation function 24 is a compensation amount for the frequency fluctuation of +0.05 Hz excluding the dead band +0.15 Hz. That is, the frequency compensation signal 25 is +0.05 Hz / (50 Hz × 4/100) × (−100%) = − 2.5%
It becomes the value of. Here, the upper and lower limits of the frequency compensation signal 25 are omitted, and the MWD 22 is 70% −2.5% = 67.5%. Therefore, the generator output deviation 44 is 67.5% -60% = + 7.5%, and the PI controller 46 increases the load command 45 until the power generation output 43 increases to 67.5%, which is the same as the MWD 22.

  As a result, the load command 45 is 70% → 77.5%, the turbine control valve opening command 18 is 70% → 60% → 67.5%, and the power generation amount 7 is 70% → 60% → 67.5%. It fluctuates and stabilizes at a power generation amount of 67.5%. For this reason, the power generation amount 7 is essentially -10% by the turbine speed control function and contributes to the suppression of the frequency rise. However, the power generation amount 7 is only -2.5% because of the canceling action by the output control. The suppression effect has been reduced to ¼.

  Next, the case where the output setting correction circuit for generating the output setting correction signal 33 is provided as shown in FIG. 11 and the function of FIG. 6 is adopted as the output setting correction function 32 will be described under the same conditions. .

  In the case 3, if the frequency fluctuation amount increases from +0 Hz to +0.2 Hz as in the cases 1 and 2, the rotational speed correction amount 17 is −10 as in the case 2 due to the turbine speed control function. %, The turbine control valve opening command 18 becomes 70% -10% = 60%, and the servo 19 reduces the opening of the turbine control valve 4 from 70% to 60%. For this reason, the power generation amount 7 is also reduced from 70% to 60%. Similarly to the case 2, the frequency compensation amount 25 of the frequency compensation circuit is −2.5%, and the MWD 22 is 70% −2.5% = 67.5%. The process up to this point is the same as Case 2.

On the other hand, the output setting correction function 32 is a correction amount equivalent to +0.15 Hz.
+0.15 Hz ÷ (50 Hz × 4/100) × (−100%) = − 7.5%
Is output as the output setting correction signal 33. Therefore, the generator output setting signal 44 is MWD22 (67.5%) + output setting correction amount 33 (−7.5%) = 60%, which is the same value as the generator output 43 adjusted by the rotational speed correction amount 17. Become.

  Therefore, the generator output deviation signal 44 is 0, the PI controller 46 does not work, and the load command 45 does not change. The MWD 22 is 70% → 67.5%, and the generator output setting signal 42 is 70%. → 60%, load command 45 remains 70%, turbine opening / closing valve opening command 18 and turbine opening / closing valve 4 opening change from 70% to 60%, and power generation amount 7 changes from 70% to 60% and stable. To do. Therefore, the 10% reduction of the power generation amount 7, which is the frequency fluctuation suppressing effect obtained by the turbine speed control function, can be maintained as it is and is not canceled out. As described above, the point is that the generator output deviation signal 44 is maintained at 0, the load command 44 is not changed, and the speed control function of the turbine 2 is utilized as it is.

  From another point of view, since the power generation amount 7 is finally controlled by the generator output setting signal 42, the frequency fluctuation suppression effect is finally the frequency compensation amount 31 and the output setting correction, apart from the transient response. It can be said that it is determined by the total correction amount of the amount 33.

  Further, in the invention disclosed in Japanese Patent Application Laid-Open No. 11-223105, when the frequency fluctuates beyond a certain range, the output ΔMW of the subtracter (36), which is an output deviation, is blocked by the limiting circuit (38). Then, by setting the input ΔMW ′ to the proportional / integral calculator (40) for controlling the output to 0, the output control is temporarily stopped, and the frequency control function by the turbine speed control function can be exhibited.

  The output setting correction circuit for generating the output setting correction signal 33 in case 3 of the prior art, the invention disclosed in Japanese Patent Laid-Open No. 11-223105, the PI controller 46 or the proportional / integral calculator 40 (Japanese Patent Laid-Open No. No. 223105) is set to 0, the load command 45 is not changed, and the frequency fluctuation suppression function by the turbine speed control function is exhibited as it is. It is aimed at effect.

  However, in the case shown in FIG. 11, the output setting correction amount 33 is limited only by the setting of the output setting correction function 32, and cannot be limited by parameters other than the frequency deviation.

  Similarly, the invention disclosed in Japanese Patent Application Laid-Open No. 11-223105 cannot be limited by parameters other than the frequency deviation.

Thermal power plants are generally less stable in low-power operation than in high-power operation, and are less susceptible to external disturbances. Therefore, the maximum effect is achieved at high loads, and plant stability in low-load operation. Consideration was not made in terms of ensuring.
JP-A-11-223105 IEEJ Technical Report No. 869 “Regular and Emergency Load Frequency Control in Power Systems” P43-45, IEEJ, March 2002

  The output setting correction circuit including the output setting correction function 32 of the prior art, in particular, when the frequency deviation is small, makes it possible to maximize the frequency fluctuation suppression effect by adjusting the power generation amount 7 by the turbine speed control function. In this control method, the output setting correction signal 33 is generated so that the power generation amount 7 adjusted by the correction signal 17 and the generator output setting value 42 coincide with each other. However, the output setting correction has an adverse effect on the plant stability with respect to the frequency compensation. In the past, the output setting correction signal 33 is conventionally provided with a limiting circuit, for example, because it is determined that the amount of correction is small, or because it is determined that the correction amount itself is a small value and there is no concern of having a significant impact on plant stability. It wasn't. In practice, however, the output setting correction signal has a greater influence on the plant stability than the frequency compensation signal.

  Therefore, the correction can be fully utilized in the high load operation state to achieve the maximum effect, and in the low load operation state where the plant stability is poor, the correction amount is limited to achieve both the frequency fluctuation suppression effect and the plant stability. Therefore, it cannot be said that sufficient consideration has been made so that optimum control can be performed.

  An example of the output setting correction amount range allowable by the plant is shown in FIG. Generally, the lower the load, the smaller the allowable range. The combined output correction limit amount on the vertical axis indicates the upper and lower limit limit ranges for keeping the plant stable with respect to the combined correction amount of frequency compensation and output setting correction. A specific example will be described. If the output setting correction function 32 is set as shown in FIG. 5 or FIG. 6, the value of the output setting correction signal 33 becomes ± 7.5% when a frequency variation of ± 0.15 Hz occurs. On the other hand, as shown in FIG. 7, if the output command 21 is 75% or more, the upper and lower limit range is ± 7.5% or more, which is within the allowable range, but if the output command 21 is less than 75%, the upper and lower limits The limit range is less than ± 7.5%, and the output setting correction amount 33 exceeds the limit range, and the plant may become unstable. Further, when the set value of the output setting correction function 32 is set to the minimum value ± 3% of the upper and lower limit limit range shown in FIG. 7 so as not to exceed the limit range, a maximum correction amount of 10% is obtained in the high load operation state. Despite being allowed, if the correction amount is limited to ± 3%, the function of suppressing the frequency fluctuation cannot be sufficiently exhibited.

  The object of the present invention is to apply an appropriate upper / lower limit limit that is coordinated with the frequency compensation amount 31 to the output setting correction amount 33, thereby maintaining the plant stability and the maximum allowable value regardless of the load operation state. The purpose is to achieve both the effect of suppressing the frequency fluctuation.

In order to solve the problem of the present invention, separately from the frequency compensation circuit that corrects the MWD 22 according to the frequency deviation, an output setting correction signal 33 is generated according to the frequency deviation and added to the MWD 22 to control the power generation amount control. In the case of having an output setting correction function serving as a target value, the output setting correction signal 33 also includes means for multiplying an upper / lower limit limit value different from the upper / lower limit limit value applied to the frequency compensation signal. Means for determining the frequency compensation lower limit tolerance signal 34 from the difference from the frequency compensation lower limit signal 27; means for determining the frequency compensation upper limit tolerance signal 37 from the difference between the frequency compensation signal 31 and the frequency compensation upper limit signal 30; A means for multiplying each of the signal 34 and the upper limit tolerance signal 37 by a coefficient to obtain an output setting correction lower limit signal 35 and an upper limit signal 38, and the output setting correction signal 33 A control circuit including means for limiting by upper and lower limit signals 35 and 38 and means for adding the output setting correction signal 39 limited by the upper and lower limit signals 35 and 38 to the MWD 22 to obtain a generator output setting signal 42. Or configure
As another means, apart from the frequency compensation lower limit signal 27 and the upper limit signal 30, a means for generating upper and lower limit restriction signals 35 and 38 dedicated for output setting correction, and the upper and lower limit restriction signal for the output setting correction signal 33. A control circuit including means for limiting upper and lower limits at 35 and 38, and means for adding the output setting correction signal 39 subjected to upper and lower limits to the MWD 22 to obtain a generator output setting signal 42;
Further, there may be a case where LAG is included between the frequency signal 23 or the output setting correction signals 33 to 39 which are inputs of the output setting correction function 32.

Further, for all frequency deviations, the total correction amount of the frequency compensation amount 31 and the output setting correction amount 39 is configured to fall within at least the range of the frequency compensation upper limit value 30 and the lower limit value 27.
Alternatively, in consideration of the case where the frequency compensation signal 31 and the output setting correction signal 39 are selectively used depending on the setting of the interlock circuit and the correction function, the frequency compensation amount upper and lower limit limitation and the output setting correction amount upper and lower limit limitation are individually provided, Configure the control circuit to ensure plant stability in function,
Further, in some cases, the control circuit is configured so that the output setting correction signal 39 is delayed by the LAG 40 and the phase of the change in the generator output 43 by the generator output setting value 42 and the rotation speed correction signal 17 is matched.

  By configuring the control device in this way, when the frequency deviation occurs, the frequency compensation amount 31 and the output setting correction amount 39 are set to the optimum settings so that the stability of the plant can be ensured and the maximum effect can be exhibited. Is possible.

  The invention described in claim 1 includes a boiler 1, a steam turbine 2 that converts thermal energy of steam 5 generated in the boiler 1 into electric energy, a generator 3 coaxial with the steam turbine 2, and the boiler 1. A turbine control valve 4 that adjusts the flow rate of steam 5 supplied to the steam turbine 2, a plant control device 6 that controls the operation of the boiler 1 and the operation of the steam turbine control valve 4, and a load that is output from the plant control device 6 In a frequency bias control device used in a thermal power plant having a turbine speed control function unit that adjusts the turbine control valve 4 by adding the turbine rotation speed correction signal 17 to the command signal 45, the plant control device 6 When the output command signal 21 is input, the frequency compensation signal 2 corresponding to the frequency deviation generated between the set frequency of the power transmission system and the output frequency signal 23. Is limited to a correction range acceptable by the plant, a frequency compensation signal 31 is obtained, and the frequency compensation signal 31 is added to the output command signal 21 to generate the load request signal 22, and according to the frequency deviation An output setting correction signal 33 of the generated power amount is generated, and the obtained output setting correction signal 33 is also limited to a correction range allowable by the plant to obtain an output setting correction signal 39, and the output setting correction signal 39 is set to the load. An output setting correction circuit that is added to the request signal 22 to obtain a control target value for power generation amount control, and the obtained frequency compensation signal 31 and output setting correction signal 39 are added to the load request signal 22 to generate a generator output setting signal 42. And a load command circuit for adding a generator output signal 43 to the turbine control valve 4 to output a load command signal 45 obtained by feedback control. It is the frequency bias control unit runt.

  According to the second aspect of the present invention, the frequency correction circuit of the plant control device 6 outputs the output command signal by the frequency compensation lower limit function 26 and the frequency compensation upper limit function 29 set based on the allowable variation amount of the load request command 22 that the plant can accept. The frequency compensation lower limit signal 27 and the frequency compensation upper limit signal 30 of 21 are obtained respectively, and the frequency compensation signal 31 in which the frequency compensation signal 25 is limited based on the upper and lower limit signals 27 and 30 is obtained. The output setting correction circuit calculates the upper and lower tolerances of the frequency compensation signal 31 with respect to the target value frequency compensation lower limit signal 27 and the frequency compensation upper limit signal 30 to calculate the frequency compensation amount lower limit margin signal 34 and the frequency compensation amount upper limit margin signal. 37, respectively, and signals obtained by multiplying the frequency compensation amount upper and lower limit margin signals 37 and 34 by predetermined coefficients K1 and K2, respectively. The output setting correction lower limit signal 35 and the output setting correction upper limit signal 38 are used, and the output setting correction upper / lower limit signals 38 and 35 are used to limit the output setting correction signal 33 of the power generation amount according to the frequency deviation. The frequency bias control device for a thermal power plant according to claim 1, wherein the output setting correction signal (39) is used.

  According to a third aspect of the present invention, the frequency correction circuit of the plant control device 6 is configured so that the frequency compensation lower limit function 26 and the frequency compensation upper limit function 29 set based on the fluctuation amount of the load request command 22 that the plant can tolerate are respectively set to the target value frequency. The compensation lower limit signal 27 and the frequency compensation upper limit signal 30 are obtained, and the frequency compensation signal 31 obtained by limiting the frequency compensation signal 25 based on the upper and lower limit signals 30 and 27 is obtained. The circuit obtains an output setting correction lower limit signal 35 and an output setting correction upper limit signal 38 by an output setting correction lower limit function 50 and an output setting correction upper limit function 53 set based on the output command 21, respectively, and outputs the output setting correction upper and lower limit signal 38. A configuration in which the output setting correction signal 33 according to the frequency deviation is limited by 38 and 35 to form an output setting correction signal 39; And a frequency bias control device for a thermal power plant of claim 1, wherein.

  The invention according to claim 4 adds a delay element 40 to at least one of the frequency signal 23, the output setting correction signal 33, and the output setting correction signal 39 in the output setting correction circuit of the plant control device 6. It is a frequency bias control apparatus of the described thermal power plant.

According to the fifth aspect of the invention, the plant control device 6 is configured such that the frequency compensation upper limit value 30, the frequency compensation lower limit value 27, the frequency compensation signal (= frequency compensation amount) 31, and the output setting correction signal (= output setting correction amount). The amount of power generation for performing plant operation in a state where both corrections of the frequency compensation signal 31 and the output setting correction signal 39 are applied by performing a control operation having the relationship of the following expressions (1) and (2) between 7. The frequency bias control device for a thermal power plant according to claim 2, wherein the control of 7 is performed.
(1) [Frequency compensation upper limit 30]
≧ [frequency compensation amount 31] + [output setting correction amount 39] / K1
(2) [Frequency compensation lower limit value 27]
≦ [frequency compensation amount 31] + [output setting correction amount 39] / K2
However, 0 ≦ K1 ≦ 2, 0 ≦ K2 ≦ 2.

  The invention according to claim 6 is the thermal power plant according to claim 3, wherein the frequency compensation signal 31 obtained by the frequency correction circuit and the output setting correction signal 39 obtained by the output setting correction circuit are used separately or both. This is a method of operating the frequency bias control apparatus.

  In the seventh aspect of the invention, when frequency fluctuation occurs, the LAG 40 compensates for the delay of the power generation amount 7 with respect to the operation of the turbine control valve 4, and the phase of the generator output set value 42 and the generator output signal 43 is adjusted. The operation method of the frequency bias control device for a thermal power plant according to claim 4, wherein control disturbance is prevented by matching and stable plant control is performed.

  According to the first aspect of the present invention, by correcting the output setting for the frequency compensation, the correction is sufficiently performed in a high-load operation state so that the maximum effect is exhibited and the plant stability is deteriorated. In the load operation state, the correction amount is limited, and optimal control that can achieve both the effect of suppressing the frequency fluctuation and the stability of the plant can be performed. In other words, according to the first aspect of the invention, since the maximum frequency fluctuation suppressing effect can be obtained while ensuring the plant stability in the entire load range, the maximum contribution to the stability of the system frequency can be achieved. .

  According to the second and fifth aspects of the invention, in addition to the effect of the first aspect of the invention, the total correction amount of the frequency compensation and the output setting correction is managed on the circuit. Output setting correction is possible.

  According to the third and sixth aspects of the invention, in addition to the effect of the first aspect of the invention, since the total correction amount of the frequency compensation and the output setting correction is not managed on the circuit, the setting of the output setting correction function 32 is performed. Is suitable for a setting (see FIG. 5) that takes into account the segregation such that the frequency compensation dead band is complemented by the output setting correction.

  According to the inventions of claims 4 and 7, in addition to the effects of the inventions of claims 2 and 3, in addition to the high-pressure turbine 2, when using an intermediate-low pressure turbine using a reheater, the turbine adjustment When the LAG 40 corresponding to the time difference between the operation of the valve 4 and the power generation amount 7 is inserted into the output setting correction circuit, an excessive transient operation can be suppressed.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 3 is a configuration diagram of a thermal power plant that is the subject of the present invention as described in the section of the prior art, and FIG. 1 is a diagram of the plant showing an embodiment of the present invention applied to the thermal power plant of FIG. It is a control circuit diagram of a frequency bias control device.

  The control circuit shown in FIG. 1 is limited to the lower limit of the LAG 40 for adjusting the phase of the generator output 43 and the generator output set value 42, the frequency compensation lower limit signal 27, in addition to the control circuit of FIG. A subtractor 62 that performs subtraction with the frequency compensation signal 28, and a conversion signal 41 (0 ≦ K1 ≦ 2) obtained by converting the output command 21 into the output signal (frequency compensation lower limit tolerance) 34 of the subtractor 62 by the conversion function 63. Multiplying the multiplier 64, the lower limit limiter 65 for selecting the high value of the output signal 35 and the output setting correction signal 33 of the multiplier 64, the frequency compensation upper limit signal 30 and the upper and lower limit limited frequency compensation signal 31 are performed. A subtractor 66; and a multiplier 68 that multiplies the output signal (frequency compensation upper limit margin) 37 of the subtractor 66 by the conversion signal 41 (K1 = K2 in FIG. 1 and the common conversion signal 41 is used); Multiplier 8 is an upper limit limiter 69 for selecting a low value of the output signal 38 and the output setting correction signal 36, a conversion function 63 for converting the frequency compensation amount margin into an output setting correction upper / lower limit value, and a conversion signal that is an output signal thereof. 41 is comprised. The output frequency signal 23 of the generator output 43 phase-adjusted by the LAG 40 is corrected by the output setting correction function 32. The output setting correction signal 33 obtained by the lower limit limiter 65 sets the lower limit. The output setting correction signal 36 becomes an output setting correction signal 39 whose upper limit is set by the upper limiter 69 and is added to the load request signal (MWD) 22.

The behavior of the control circuit and the control signal of the present invention will be described with reference to FIG.
As described in case 3 of the prior art, specific numerical values are assumed. The frequency compensation function 24 and the output setting correction function 32 are set as shown in FIG. The following description will be made assuming that the output command 21 to the power generation amount 7 is stable at 70%.

  When the frequency signal 23 fluctuates during operation of the thermal power plant and the frequency deviation changes from +0 Hz to +0.2 Hz, the value of the frequency compensation signal 25 becomes −2.5% as shown in FIG. The frequency compensation lower limit signal 27 and the frequency compensation upper limit signal 30 at the output command 70% are ± 7% as shown in FIG. Therefore, the frequency compensation signal 25 is output as the frequency compensation signal 31 with -2.5% without being limited by the frequency compensation lower limit limiter 60 and the frequency compensation upper limit limiter 61.

  The output setting correction signal 33 is -7.5% as shown in FIG. Here, the output setting correction upper / lower limit operation works as follows. The frequency compensation lower limit margin 34 is the frequency compensation lower limit value (−7%) − the frequency compensation signal 28 (−2.5%) = − 4.5%, and the frequency compensation upper limit margin 37 is the frequency compensation upper limit margin ( +7%) − frequency compensation signal 31 (−2.5%) = + 9.5%. Here, as an example of the output signal 41 of the conversion function 63 taking a numerical value in the range of 0 to 2, K1 = 1, K2 = 1, the output setting correction lower limit signal 35 is −4.5%, and the upper limit signal 38 is + 9.5%.

The values of K1 and K2 are basically “1” in order to match the characteristics of the settling rate function 16 and the characteristics of the generator output setting signal 42. However, if the pressure fluctuation of the steam amount 5 is large as will be described later, it may be set to a value of 1 or less.
On the other hand, when the output setting correction function 32 has the characteristics shown in FIG. 5, K1 and K2 are set in the range of 1 to 2 under conditions where there is a margin for pressure fluctuation because of the operation in the small frequency fluctuation range, and a greater effect can be obtained. You can also.

  The output setting correction signal 33 (−7.5%) and the output setting correction lower limit signal 35 (−4.5%) are selected at a high value by the lower limit limiter 65 and limited to −4.5% as the output setting correction signal 36. Output. Further, the output setting correction signal 36 (−4.5%) and the output setting correction upper limit signal 38 (+ 9.5%) are selected by the upper limiter 69 as a low value, and the output setting correction signal 39 is −4.5%. Is output.

  The total compensation amount of the frequency compensation signal 25 before the upper / lower limit restriction and the output setting correction signal 33 −2.5% + (− 7.5%) = − 10%, and the frequency compensation signal 31 and the output after the upper / lower limit restriction The total correction amount of the setting correction signal 39 is −2.5% + (− 4.5%) = − 7%, and the total correction amount is limited to the frequency compensation lower limit value 27 (−7%). Incidentally, in the case of the prior art case 3, since the output setting correction signal is not limited, the total correction amount is -10% and exceeds the frequency compensation lower limit value.

As for output control, MWD 22 is output command 21 (70%) + frequency compensation amount 31 (−2.5%) = 67.5%, and generator output set value 42 is MWD 22 (67.5%) + output. The set correction amount 39 (−4.5%) = 63%, and the total correction is −7%. On the other hand, the rotational speed correction signal 17 by the speed control function of the turbine 2 is +0 as described in the related art. .2Hz corresponds to -12rpm deviation,
−12 rpm ÷ (3000 rpm × 4/100) × 100% = − 10%
It becomes.

  As described above, since the power generation amount 7 is finally controlled by the generator output setting signal 42, the power generation amount 7 is corrected by -10% by the frequency fluctuation suppression effect of the speed control function. In order to ensure the stability of the plant during operation, the correction amount of the power generation amount 7 is suppressed to −7% in the output control.

An example in which the frequency variation condition is changed will be described.
When the fluctuation of the frequency 11 is changed from +0 Hz to −0.3 Hz, the value of the frequency compensation signal 25 is + 7.5% as shown in FIG. The frequency compensation lower limit signal 27 and the frequency compensation upper limit signal 30 at the output command 70% are ± 7% as shown in FIG. The frequency compensation signal 25 (+ 7.5%) and the frequency compensation lower limit signal 27 (−7%) are selected at a high value by the lower limit limiter 60, and + 7.5% is output as the frequency compensation signal 28. Further, the frequency compensation signal 28 (+ 7.5%) and the frequency compensation upper limit signal 30 (+ 7%) are selected by the upper limiter 61 to have a low value, and the frequency compensation signal 31 is limited to + 7% and output.

  As shown in FIG. 6, the output setting correction signal 33 is the same as the frequency compensation signal 25, + 7.5% is output. The frequency compensation lower limit margin 34 becomes the frequency compensation lower limit signal 27 (−7%) − frequency compensation signal 28 (+7.5%) = − 14.5% by the subtractor 62. Since the conversion coefficient 41 is 1, the output setting correction lower limit signal 35 is also -14.5%. Further, the frequency compensation upper limit margin 37 is set to 0% by the subtractor 66, so that the frequency compensation upper limit signal 30 (+7%) − frequency compensation signal 31 (+7%) = 0%, and the output setting correction upper limit signal 38 also becomes 0% of the same value.

  Next, the output setting correction signal 33 (+ 7.5%) and the output setting correction lower limit signal 35 (-14.5%) are selected to a high value by the lower limit limiter 65, and + 7.5% is output as the output setting correction signal 36. To do. Further, the output setting correction signal 36 (+ 7.5%) and the output setting correction upper limit signal 38 (+ 0%) are selected by the upper limiter 69 as a low value, and output as an output setting correction signal 39 limited to 0%. . The total correction amount of the frequency compensation signal 25 before the upper / lower limit restriction and the output setting correction signal 33 is + 7.5% + 7.5% = + 15%, whereas the frequency compensation signal 31 after the upper / lower limit restriction and the output setting correction signal 39 The total correction amount + 7% + 0% = + 7%, and the total correction amount is limited by the frequency compensation upper limit value + 7%. Also in this case, in the case of the prior art case 3, the total correction amount is + 7% + 7.5% = 14.5%, which greatly exceeds the limit value.

Regarding output control, MWD 22 is output command 21 (70%) + frequency compensation signal 31 (+7%) = 77%, and generator output setting signal 42 is MWD 22 (77%) + output setting correction signal 39 (0%). = 77%, which is a correction of a total of + 7%, but the rotation speed correction signal 17 by the speed adjusting function of the turbine corresponds to a deviation of +18 rpm because −0.3 Hz corresponds to +18 rpm deviation.
+18 rpm / (3000 rpm × 4/100) × 100% = + 15%
It becomes. When the power generation amount 7 is corrected by + 15% due to the frequency fluctuation suppression effect of the speed control function, the power generation amount 7 correction amount is + 7% in the output control in order to ensure the stability of the plant in operation with the output command 70%. To be suppressed.

An example of a low load operation state in which the output command 21 is 30% will be described.
When the variation of the frequency 23 is changed from +0 Hz to −0.1 Hz, the frequency compensation amount 25 is 0% because the frequency variation range of the dead zone is as shown in FIG. From FIG. 7, the frequency compensation lower limit signal 27 at the output command 30% is −0%, and the upper limit signal 30 is + 3%. The frequency compensation signal 25 (0%) and the frequency compensation lower limit signal 27 (0%) are selected at a high value by the lower limit limiter 60, and 0% is output as the frequency compensation signal 28. Further, the frequency compensation signal 28 (0%) and the frequency compensation upper limit signal 30 (+ 3%) are selected by the upper limiter 61 to have a low value, and 0% is output as the frequency compensation signal 31.

  As the output setting correction signal 33, + 5% is output as shown in FIG. For the frequency compensation lower limit margin 34, the frequency compensation lower limit signal 27 (0%) − frequency compensation signal 28 (0%) = 0% is output by the subtractor 62, and the output setting lower limit signal 35 is also 0% of the same value. Next, the output setting correction signal 33 (+ 5%) and the output setting correction lower limit signal 35 (0%) are selected to a high value by the lower limit limiter 65, and + 5% is output as the output setting correction signal 36. Further, the frequency compensation upper limit margin 37 becomes the frequency compensation upper limit signal 30 (+3%) − frequency compensation signal 31 (0%) = + 3% by the subtractor 66, and the output setting upper limit signal 38 also becomes + 3% of the same value. The output setting correction signal 36 (+ 5%) and the output setting correction upper limit signal 38 (+ 3%) are selected by the upper limiter 69 as a low value, and are output as the output setting correction signal 39 limited to + 3%. The total compensation amount 0% + 5% = + 5% of the frequency compensation amount 25 before the upper / lower limit restriction and the output setting correction amount 33, whereas the frequency compensation amount 31 and the output setting correction amount 39 after the upper / lower limit restriction are 0% + 3% = Thus, the total correction amount is limited to + 3% of the frequency compensation upper limit 30. Even under this condition, in the case of the prior art case 3, the total correction amount is 0% + 5% = 5%, which exceeds the limit value.

For output control, MWD22 = output command 21 (30%) + frequency compensation signal 31 (0%) = 30%, generator output setting signal 42 = MWD22 (30%) + output setting correction signal 39 (+ 3%) = 33% and the correction of the total + 3%, the rotation speed correction signal 17 by the turbine speed control function is −0.1 Hz corresponding to +6 rpm deviation.
+6 rpm / (3000 rpm × 4/100) × 100% = + 5%
It becomes. When the power generation amount 7 is corrected by + 5% due to the frequency fluctuation suppression effect of the speed control function, the power generation amount 7 correction amount is + 3% in the output control to ensure the stability of the plant in operation with the output command 30%. To be suppressed.

  By the way, the conversion coefficient 63 takes a value of 0-1. The reason for this is that even if the correction amount is the same, the output setting correction may cause greater fluctuations in the plant state amount than the frequency compensation, which may adversely affect the stability. In order to apply the functions 26 and 29 to the upper and lower limits of the output setting correction, it may be appropriate to use the functions 26 and 29 slightly reduced.

  It is the steam pressure fluctuation of the boiler 1 that is most concerned as the effect of frequency compensation and output setting correction on the plant. The steam pressure varies depending on the balance between the steam generation amount of the boiler 1 and the steam amount 5 passing through the turbine control valve 4. For example, if the steam control valve 4 is throttled in the stable state and the steam amount 5 is reduced, (evaporation amount of the boiler 1)> (steam amount 5), and since the steam supply amount exceeds the consumption amount, the steam pressure of the boiler 1 increases. At this time, it is necessary to reduce the amount of water supply and the amount of fuel by reducing the boiler control signal 73 (not shown) until the steam pressure of the boiler 1 returns. When the turbine adjusting valve 4 is opened, the pressure is decreased, so the amount of water supplied to the boiler 1 and the amount of fuel must be increased to increase the amount of evaporation, the steam pressure must be recovered and balanced with the amount of steam 5.

Here, the difference in behavior of the frequency compensation and the output setting correction with respect to the steam pressure will be described.
When there is a frequency variation and correction by the frequency compensation amount 31 occurs, the turbine control valve 4 is controlled by the turbine speed correction signal 17, and the MWD 22 is corrected by a considerable amount by the frequency compensation amount 31. As shown in FIG. 1, the MWD 22 simultaneously corrects the generator output setting signal 42 and the boiler control signal 73 by the same amount. Accordingly, the control of the turbine control valve 4 (adjustment of the amount of steam 5) and the control of the water supply amount and fuel supply amount (adjustment of the evaporation amount) of the boiler 1 by the boiler control signal 73 (not shown) are operated in the same phase. Therefore, although there is a response delay of the boiler 1, the difference between the amount of evaporation of the boiler 1 and the amount of steam 5 is relatively small, and therefore the pressure fluctuation is relatively small.

  On the other hand, when correction by the output setting correction amount 39 occurs, the turbine control valve 4 is controlled by the turbine rotation speed correction signal 17, and the generator output setting signal 42 is corrected by a considerable amount by the output setting correction amount 39. Although the power generation amount 7 balances with the generator output setting signal 42, the boiler control signal 73 is not directly corrected because the MWD 22 does not change. Therefore, even if the amount of steam 5 is adjusted, the amount of evaporation of the boiler 1 does not change, so the supply and demand balance of the amount of steam is disrupted and the steam pressure fluctuates. The fluctuation of the steam pressure is regarded as the pressure deviation 70, the PI controller 71 increases or decreases the boiler master signal 72, and the boiler control signal 73 is adjusted until the steam pressure returns. First, the turbine control valve 4 is controlled (adjustment of the amount of steam 5). As a result, an unbalanced amount of steam occurs and the steam pressure fluctuates, and then the water supply amount and fuel supply amount of the boiler 1 are controlled (adjustment of evaporation amount) Therefore, a time difference occurs in the operation, and the response of the boiler 1 is slower than the frequency compensation described above, and the supply / demand imbalance of the steam amount becomes large, so that the pressure fluctuation becomes relatively large.

  Examples of test results regarding the relationship between the frequency compensation amount, the output setting correction amount, and the pressure fluctuation amount are shown in FIGS. FIG. 8 shows the relationship between the frequency compensation amount and the pressure fluctuation, and FIG. 9 shows the relationship between the output setting correction amount and the pressure fluctuation. Comparing the pressure fluctuation characteristic of the frequency compensation amount and the pressure fluctuation characteristic of the output setting correction amount, the pressure fluctuation due to the frequency compensation amount is as small as about 60% of the pressure fluctuation due to the output setting correction amount. When the upper and lower limit functions 26 and 29 set for frequency compensation are used for the upper and lower limits of the output setting correction amount as in the above-described embodiment, the effects of the normal frequency compensation circuit and the output setting correction circuit are obtained. In order to make them equivalent, the conversion function 63 is set to “1”, but when it is necessary to suppress the pressure fluctuation due to the output setting correction amount to be equal to the pressure fluctuation due to the frequency compensation amount, the conversion function 63 is “0.6”. It is appropriate to set “degree”.

In this embodiment, the frequency compensation lower limit margin 34 is obtained by subtracting the frequency compensation amount 28 from the frequency compensation lower limit signal 27. For example, the frequency compensation lower limit margin 34 is obtained by subtracting the frequency compensation signal 25 from the frequency compensation lower limit signal 27. The same signal can be obtained by subtracting and selecting a low value of “0”. Expressed as a formula:
Frequency compensation lower limit margin 34 = frequency compensation lower limit value 27−frequency compensation amount 28
= Min. {(Frequency compensation lower limit value 27-frequency compensation amount 25), 0}
Similarly, for the frequency compensation upper limit margin 37, the following signals are the same.
Frequency compensation upper limit tolerance 37 = frequency compensation upper limit value 30−frequency compensation amount 31
= Max. {(Frequency compensation upper limit 30-frequency compensation amount 25), 0}
This means that there are a plurality of calculation methods by combining the frequency compensation signals 25, 28, 31 and the frequency compensation upper / lower limit signals 27, 30 as a circuit for obtaining the upper and lower limit tolerances 34, 37 of the frequency compensation signal. The embodiment of FIG. 1 is just one example.

  Although not shown in FIG. 3, a general thermal power plant has a reheater for improving efficiency. If the opening degree of the turbine control valve 4 is adjusted, the amount of steam 5 flowing into the high-pressure turbine 2 is controlled, and the power of the high-pressure turbine 2 follows without delay. However, even if the steam amount 5 is controlled by adjusting the opening degree of the turbine control valve 4, the volume effect until the steam discharged from the high pressure turbine 2 flows into the medium to low pressure turbine (not shown) via the reheater. The amount of steam flowing into the intermediate / low pressure turbine is slightly delayed with respect to the opening degree adjustment of the lower limit valve 4. Since the output of the medium / low pressure turbine occupies nearly 70% of the power generation amount, the power generation amount 7 actually lags behind the opening adjustment of the turbine control valve 4. Therefore, if the generator output setting signal 42 is corrected by the frequency compensation signal 31 or the output setting correction signal 39 in synchronization with the frequency fluctuation, the correction is made before the actual generator output 43, and the operation of the turbine control valve 4 is performed. It becomes over action. Therefore, if the LAG 40 corresponding to the time difference between the operation of the turbine control valve 4 and the power generation amount 7 is inserted into the output setting correction circuit, an excessive transient operation can be suppressed. The LAG of the frequency compensation circuit is preferably set to the same delay time.

  Another embodiment of the present invention is shown in FIG. In the embodiment shown in FIG. 1, the upper and lower limit values 35 and 38 for the output setting correction signal 33 are generated from the upper and lower limit margins 34 and 37 of the frequency compensation signal 25, whereas the feature of this embodiment is that The upper and lower limit values 35 and 38 for the output setting correction signal 33 are individually obtained by a function having the output command 21 as an input, and there is no correlation on the circuit with the tolerance of the frequency compensation circuit.

  In the circuit configuration of FIG. 2, first, an output setting correction lower limit signal 35 is generated by an output setting correction lower limit function 50 that receives an output command 21, and output setting correction is performed by an output setting correction upper limit function 53 that receives the same output command 21. An upper limit signal 38 is generated. The output setting correction signal 33 and the output setting correction lower limit signal 35 output from the output setting correction function 32 are selected to be high values by the lower limit limiter 65, and the output setting correction signal 36 is output. The output setting correction signal 36 and the output setting correction upper limit signal 38 are selected by the upper limiter 69 as a low value to obtain an output setting signal correction amount 39, which is added to the MWD 22 as a generator output setting signal 42.

  The operation is different only in the generation process of the output setting correction lower limit signal 35 and the output setting correction upper limit signal 38. The method of limiting the upper and lower limit limit values 35 and 38 with respect to the output setting correction signal 33, the operation of the output control, etc. are shown in FIG. It is the same as the form.

  As described in the description of the embodiment of FIG. 1, the setting values of the output setting upper and lower limit functions 50 and 53 are preferably set to be the same as or slightly smaller than the setting values of the frequency compensation upper and lower limit functions 26 and 29. . For example, in the case of the pressure response ratio difference as shown in FIGS. 8 and 12, the appropriate range is about 0.6 to 1 times the set value of the frequency compensation upper and lower limit functions 26 and 29. Further, in the present embodiment, the total correction amount of the frequency compensation and the output setting correction is not managed on the circuit, and therefore, regarding the setting of the output setting correction function 32, both the correction amounts as shown in FIG. Setting that mixes is not preferable, and it is appropriate to consider setting such that the frequency compensation dead band shown in FIG. 5 is complemented by output setting correction and / or divided within the range of the output command 21.

  The delay time of the LAG 40 is set to an appropriate value between 0 and 20 seconds in both the first and second embodiments.

  According to the present invention, the governor-free effect can be enhanced as much as possible, and it can be used as a thermal power plant having a stable governor-free frequency adjustment capability even at a low load.

It is a figure which shows the control circuit in connection with an example of embodiment of this invention. It is a figure which shows the control circuit in connection with other embodiment of this invention. It is a figure which shows the structure of a thermal power plant. It is the figure which showed an example of the frequency compensation function setting value. It is the figure which showed an example of the output setting correction function setting value. It is the figure which showed the other example of the output setting correction function setting value. It is the figure which showed an example of the frequency compensation upper-lower limit function. It is the figure which showed the relationship between a frequency compensation amount and a pressure fluctuation. It is the figure which showed the relationship between an output setting correction amount and a pressure fluctuation. It is a figure which shows the control circuit in connection with a prior art example. It is a figure which shows the control circuit in connection with a prior art example.

Explanation of symbols

1 Boiler 32 Output Setting Correction Function 2 Steam Turbine 33 Output Setting Correction Signal 3 Generator 34 Frequency Compensation Lower Limit Tolerance 4 Turbine Adjusting Valve 35 Output Setting Correction Lower Limit Signal 5 Steam Volume 36 Output Setting Correction Signal 6 APC (Plant Control Device) 37 Frequency compensation upper limit tolerance 7 Power generation amount 38 Output setting correction upper limit signal 8 Power generation amount detector 39 Output setting correction signal 9 Power generation amount signal 40 Delay element 10 Frequency detector 41 Conversion signal 11 Frequency signal 42 Generator output setting signal 12 Turbine rotation Number detector 43 Generator output signal 13 Rotational speed signal 44 Generator output deviation signal 14 Reference rotational speed signal 45 Load command 15 Rotational speed deviation signal 46 PI controller 16 Settling rate function 47 Switch 17 Rotational speed correction signal 50 Output setting Correction lower limit function 18 Turbine adjustment valve command 53 Output setting correction upper limit function 1 Turbine adjusting valve servo 60 Lower limit limiter 20 Output target value 61 Upper limit limiter 21 Output command 62 Subtractor 22 Load request signal (MWD) 63 Conversion function 23 Frequency signal 64 Multiplier 24 Frequency compensation function 65 Lower limit limiter 25 Frequency compensation signal 66 Subtractor 26 Frequency compensation lower limit function 68 Multiplier 27 Frequency compensation lower limit signal 69 Upper limit limiter 28 Frequency compensation signal 70 Main steam pressure deviation 29 Frequency compensation upper limit function 71 PI controller 30 Frequency compensation upper limit signal 72 Boiler master signal 31 Frequency compensation signal 73 Boiler control signal

Claims (7)

A boiler 1, a steam turbine 2 that converts thermal energy of steam 5 generated in the boiler 1 into electric energy, a generator 3 that is coaxial with the steam turbine 2, and steam 5 that is supplied from the boiler 1 to the steam turbine 2. Turbine adjusting valve 4 for adjusting the flow rate of the engine, plant controller 6 for controlling the operation of the boiler 1 and the operation of the steam turbine adjusting valve 4, respectively, and the turbine rotation speed correction to the load command signal 45 output from the plant controller 6 In a frequency bias control device used in a thermal power plant having a turbine speed regulation function unit that adjusts the turbine control valve 4 by adding a signal 17,
The plant control device 6
When the output command signal 21 of the power generation amount is input, the frequency compensation signal 25 corresponding to the frequency deviation generated between the frequency set by the power transmission system and the output frequency signal 23 is limited to a correction range that the plant can tolerate. A frequency correction circuit that obtains a compensation signal 31 and adds the frequency compensation signal 31 to the output command signal 21 to generate a load request signal 22;
An output setting correction signal 33 having a power generation amount corresponding to the frequency deviation is generated, and the obtained output setting correction signal 33 is also limited to a correction range acceptable by the plant to obtain an output setting correction signal 39. An output setting correction circuit that adds a signal 39 to the load request signal 22 to obtain a control target value for power generation amount control;
The obtained frequency compensation signal 31 and output setting correction signal 39 are added to the load request signal 22 to form a generator output setting signal 42, and a generator output signal 43 is added to this to generate a load command signal 45 obtained by feedback control. And a load command circuit for outputting to the turbine control valve 4 a frequency bias control device for a thermal power plant. The frequency correction circuit of the plant control apparatus 6 includes a frequency compensation lower limit function 26 set based on an allowable variation amount of the load request command 22 that can be accepted by the plant and a frequency compensation lower limit signal 27 of the output command signal 21 by a frequency compensation upper limit function 29. The frequency compensation upper limit signal 30 is obtained, and the frequency compensation signal 31 obtained by limiting the frequency compensation signal 25 based on the upper and lower limit signals 27 and 30 is obtained.
The output setting correction circuit of the plant control device 6 calculates the upper and lower limit tolerances of the frequency compensation signal 31 with respect to the target value frequency compensation lower limit signal 27 and the frequency compensation upper limit signal 30 to calculate the frequency compensation amount lower limit margin signal 34 and the frequency compensation. An amount upper limit margin signal 37 is obtained, and signals obtained by multiplying the frequency compensation amount upper and lower limit margin signals 37 and 34 by predetermined coefficients K1 and K2, respectively, are set as an output setting correction lower limit signal 35 and an output setting correction upper limit signal 38, respectively. The output setting correction upper / lower limit signals 38 and 35 are used to limit the power setting output setting correction signal 33 in accordance with the frequency deviation to obtain an output setting correction signal 39. The frequency bias control device for a thermal power plant according to claim 1. The frequency correction circuit of the plant control device 6 includes a target frequency compensation lower limit signal 27 and a frequency compensation upper limit by a frequency compensation lower limit function 26 and a frequency compensation upper limit function 29 which are set based on the variation amount of the load request command 22 that the plant can accept. A signal 30 is obtained, and a frequency compensation signal 31 obtained by limiting the frequency compensation signal 25 based on the upper and lower limit signals 30 and 27 is obtained.
The output setting correction circuit of the plant control device 6 obtains the output setting correction lower limit signal 35 and the output setting correction upper limit signal 38 by the output setting correction lower limit function 50 and the output setting correction upper limit function 53 set based on the output command 21, respectively. The output setting correction signal 33 according to claim 1, wherein the output setting correction upper and lower limit signals 38 and 35 are used to limit the output setting correction signal 33 according to the frequency deviation to form an output setting correction signal 39. Frequency bias control device for thermal power plant.   The thermal power according to claim 2 or 3, wherein a delay element 40 is added to at least one of the frequency signal 23, the output setting correction signal 33, and the output setting correction signal 39 in the output setting correction circuit of the plant control device 6. Power plant frequency bias controller. The plant control device 6 has the following (1) between the frequency compensation upper limit value 30, the frequency compensation lower limit value 27, the frequency compensation signal (= frequency compensation amount) 31, and the output setting correction signal (= output setting correction amount) 39. ) And (2) are controlled to control the power generation amount 7 for plant operation with both the frequency compensation signal 31 and the output setting correction signal 39 being corrected. The frequency bias control device for a thermal power plant according to claim 2.
(1) [Frequency compensation upper limit 30]
≧ [frequency compensation amount 31] + [output setting correction amount 39] / K1
(2) [Frequency compensation lower limit value 27]
≦ [frequency compensation amount 31] + [output setting correction amount 39] / K2
However, 0 ≦ K1 ≦ 2, 0 ≦ K2 ≦ 2.   4. The frequency bias of a thermal power plant according to claim 3, wherein the frequency compensation signal 31 obtained by the frequency correction circuit and the output setting correction signal 39 obtained by the output setting correction circuit are used separately or both. How to operate the control device.   When frequency fluctuation occurs, the delay of the power generation amount 7 with respect to the operation of the turbine control valve 4 is compensated by the LAG 40, and the phase of the generator output set value 42 and the generator output signal 43 is matched so that the control disturbance The operation method of the frequency bias control apparatus for a thermal power plant according to claim 4, wherein the plant is prevented and stable plant control is performed.

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