JP2013174223A - Speed governing controller for steam turbine, method for controlling the same and steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a speed governing controller for a steam turbine which can satisfy both of suppression of valve body vibration of an intercept valve and turbine output control of high response.SOLUTION: A speed governing controller for a steam turbine includes: a control valve opening calculation part that calculates an opening of a control valve 6 according to a system frequency f of a system grid 21 and a CV reduction ratio; an intercept valve opening degree calculation part that calculates an opening degree of an intercept valve 7 according to the system frequency f and the ICV reduction ratio; a timer 46 that measures a passing time after the opening of the intercept valve 7 is reduced; and a control part that controls the intercept valve 7 depending on a calculated opening when the passing time is less than a setting time, and controls the intercept valve 7 into a fully opened state when the passing time reaches the setting time.

Description

  Embodiments described herein relate generally to a speed control device for a steam turbine, a control method thereof, and a steam turbine.

  Power plants such as thermal power plants and nuclear power plants include a steam turbine, and the steam turbine is used to generate power with a generator. The generator generates electric power by being driven by a steam turbine. Electric power is supplied to the grid via a generator breaker.

  For example, a steam turbine of a thermal power plant has a high pressure turbine, a medium pressure turbine, and a low pressure turbine. The main steam generated from the boiler is adjusted by a control valve (Control Valve, CV) to drive a high-pressure turbine. The main steam is exhausted at a reduced temperature and pressure after working in the high-pressure turbine. The main steam is guided to a reheater in the boiler via a cold heat pipe.

  The steam is heated again by the reheater to become reheated steam. The reheat steam is led to an intercept valve (ICV) via a hot reheat pipe, and drives an intermediate pressure turbine. After the reheated steam works in the medium pressure turbine, the temperature and pressure are lowered and exhausted as medium pressure exhaust steam. The medium pressure exhaust steam is guided to the low pressure turbine via the crossover pipe.

  The generator rotates in synchronization with the power system. As a result, the frequency of the power system (hereinafter referred to as “system frequency”) and the turbine speed coincide. The situation where the system frequency rises above the rated value (generally 50 Hz or 60 Hz) is a state where the amount of power generation is excessive with respect to the load of the power system. On the other hand, the situation where the system frequency falls below the rated value is a state where the amount of power generation is insufficient.

  Such a steam turbine includes a control device that controls the steam turbine. This control device adjusts the turbine output (power generation amount) by performing the governor-free operation. In governor-free operation, when the system frequency of the power system rises above the rated value, control is performed so as to reduce the opening of the control valve. On the contrary, when the system frequency falls below the rated value, control is performed so as to increase the opening of the adjusting valve. In this way, the adjusting valve always adjusts the turbine output in an intermediate opening state.

  On the other hand, the control device keeps the intercept valve fully open (100%) even if the system frequency rises in the normal range. After the control valve is fully closed, the control device reduces the opening degree of the intercept valve from full opening (sets to an intermediate opening degree).

  Conventionally, inventions that provide effective governor-free operation have been proposed. For example, even when the control valve (CV) is in the open state, speed control is known in which the intercept valve is reduced to an intermediate opening according to the system frequency.

JP-A-5-33606

  Regulating valves will not interfere even if the intermediate opening is maintained under governor-free operation. However, when the intercept valve is controlled to an intermediate opening and the intermediate opening reaches a long time, there is a possibility that a new problem of suppressing valve body vibration may occur.

  This is due to the difference in structure between the adjusting valve and the intercept valve. Since the intercept valve is a combination valve with an RSV valve (Reheat Stop Valve), if the intermediate opening degree is maintained for a long time, the valve body has a natural vibration. As a result, the intercept valve can be damaged or have significant lifetime consumption.

  The present invention has been made in consideration of such circumstances, and a steam turbine speed control device capable of achieving both suppression of valve vibration of the intercept valve and turbine output control with good responsiveness, a control method therefor, And it aims to provide a steam turbine.

  In order to solve the above-described problem, a speed control device for a steam turbine according to an embodiment of the present invention adjusts a main steam supplied to a first turbine, and adjusts and discharges from the first turbine. An intercept valve for regulating steam guided to a second turbine having a lower pressure than the first turbine, and a steam turbine including a generator driven by the first and second turbines to generate electric power and supply electric power to an electric power system In the speed control device, an adjusting valve opening calculation unit that calculates the opening of the adjusting valve according to the system frequency and the adjusting valve adjustment rate of the power system, and the intercept valve according to the system frequency and the intercept valve adjusting rate. An intercept valve opening calculation unit for calculating the opening, a timer for measuring an elapsed time since the opening of the intercept valve was reduced, and the elapsed time A control unit that controls the intercept valve according to the opening calculated by the intercept valve opening calculation unit when the time is less than the time, and that controls the intercept valve to be fully opened when the elapsed time reaches a set time; It is characterized by having.

The lineblock diagram showing the thermal power plant provided with the steam turbine in a 1st embodiment. The circuit block diagram of the speed control apparatus as a reference example for demonstrating governor free driving | operation. FIG. 3 is an opening characteristic graph of an adjusting valve and an intercept valve controlled by the speed control device of FIG. 2. The time chart which shows the behavior of the steam turbine accompanying control of the speed control apparatus of FIG. 2, and control. The circuit block diagram of the speed control apparatus of the steam turbine in 1st Embodiment. The opening / closing characteristic graph of the control valve and intercept valve controlled by the speed control apparatus in 1st Embodiment. The 1st time chart which shows the behavior of the steam turbine accompanying control of the speed control apparatus in 1st Embodiment, and control. The time chart as a comparative example with respect to the time chart of FIG. The 2nd time chart which shows the behavior of the steam turbine accompanying control of the speed control apparatus in 1st Embodiment, and control. The circuit block diagram of the speed control apparatus of the steam turbine in 2nd Embodiment. The opening / closing characteristic graph of the control valve and intercept valve controlled by the speed control apparatus in 2nd Embodiment.

  The steam turbine speed control device, the control method thereof, and the steam turbine in each embodiment can be applied to various power plants including a steam turbine such as a thermal power plant and a nuclear power plant. In each embodiment, an example in which the present invention is applied to a steam turbine of a thermal power plant will be described.

[First Embodiment]
A steam turbine speed control apparatus, a control method thereof, and a steam turbine according to a first embodiment of the present invention will be described with reference to the accompanying drawings.

  Drawing 1 is a lineblock diagram showing a thermal power plant provided with a steam turbine in a 1st embodiment.

  The power plant 1 mainly includes a steam turbine 2, a boiler 3, a generator 4, a condenser 5, an adjusting valve 6, and an intercept valve 7.

  The steam turbine 2 includes a high pressure turbine 10, an intermediate pressure turbine 11, and a low pressure turbine 12. In the first embodiment, the high-pressure turbine 10 is a first turbine, and the intermediate-pressure turbine 11 is a second turbine having a lower pressure than the first turbine.

  The boiler 3 has a superheater 13 and a reheater 14. The superheater 13 generates main steam y that is high-temperature and high-pressure steam. The superheater 13 and the high-pressure turbine 10 are connected by a main steam pipe 15, and the main steam y is supplied to the high-pressure turbine 10. The main steam pipe 15 has an adjusting valve 6 (Control Valve, CV) for adjusting the main steam y.

  The reheater 14 is connected to the high-pressure turbine 10 via a cold reheat pipe 16 and is connected to the intermediate pressure turbine 11 via a hot reheat pipe 17. The reheater 14 reheats steam (main steam y) whose temperature and pressure are reduced by working in the high-pressure turbine 10. The reheater 14 supplies reheated reheat steam z to the intermediate pressure turbine 11. The hot reheat pipe 17 has a reheat stop valve 18 (Reheat Stop Valve, RSV) for adjusting the reheat steam z and an intercept valve 7 (Intercept Valve, ICV).

  The crossover pipe 19 connects the intermediate-pressure turbine 11 and the low-pressure turbine 12, and guides the intermediate-pressure exhaust steam whose temperature and pressure are reduced by working in the intermediate-pressure turbine 11 to the low-pressure turbine 12.

  The generator 4 is driven by the steam turbine 2 to generate electric power. The generator 4 supplies electric power to the grid (electric power system) 21 via the generator breaker 20. The generator 4 rotates in synchronization with the system grid 21. As a result, the frequency of the system grid 21 (hereinafter referred to as “system frequency”) and the turbine speed coincide.

  The condenser 5 cools the exhaust steam of the low-pressure turbine 12 with seawater. The condenser 5 supplies cooled and condensed condensate (hot well) 22 to the boiler 3 via a condensate pump 23 and a boiler feed pump 24. The main steam pipe 15 and the condenser 5 are connected by a bypass pipe 25. The condenser 5 cools the bypass steam x discharged through the turbine bypass valve 26.

  Next, a general speed control device provided in the steam turbine 2 of FIG. 1 will be described. FIG. 2 is a circuit configuration diagram of a speed control device 30 as a reference example for explaining governor-free operation.

  The speed control device 30 is a device that controls the speed of the steam turbine 2 and is proportional to the deviation of the turbine rotation speed (system frequency) with respect to a reference rated value (generally 50 Hz or 60 Hz). Thus, the opening / closing of the adjusting valve 6 and the intercept valve 7 is controlled.

  When the system frequency f rises above the reference rated value, the amount of power generation is excessive with respect to the load on the system grid 21. On the contrary, when the system frequency f falls below the reference rated value, the power generation amount is insufficient with respect to the load. The speed control device 30 pays attention to such an event and adjusts the turbine output (power generation amount) by performing control called governor-free operation. Specifically, the speed control device 30 reduces the opening degree of the control valve 6 when the system frequency f rises above the reference rated value. Further, the speed control device 30 increases the opening degree of the control valve 6 when the system frequency f drops below the reference rated value. The speed control device 30 adjusts the turbine output by constantly opening and closing the adjusting valve 6 minutely (with an intermediate opening state).

  The speed control device 30 acquires the system frequency f, and the subtracter 32 generates a deviation e from the set value of the rated frequency setter 33. For example, when the system frequency f is 101%, the subtractor 32 generates a deviation e = −1%. In each embodiment, for convenience of explanation, the fluctuation value (for example, 101%) of the system frequency f is described using a value larger than the system frequency f that is actually fluctuated and observed.

  The speed control device 30 inputs the deviation e to the multiplier 34 and multiplies the deviation e by the reciprocal of the CV adjustment rate (here, 5%) to generate an output g. The speed control device 30 inputs the output g to the adder 35 and adds the output g to the governor set value (100%) of the governor setter 36. The speed control device 30 controls the opening degree of the regulating valve 6 using the output a generated by the adder 35 as the regulating valve command a. For example, when the deviation e = −1%, the control valve command a = 80%.

  On the other hand, the speed control device 30 performs control so that the intercept valve 7 is fully opened (100%) even if the system frequency f rises in the normal range. That is, the speed control device 30 inputs the output a to the multiplier 37 and multiplies the output a by CV adjustment rate / ICV adjustment rate (here, 5% / 2%). The speed control device 30 inputs the output of the multiplier 37 to the adder 38 and adds the bias value (here, 100%) set in the setting device 39. The speed control device 30 controls the opening degree of the intercept valve 7 using the output c generated by the adder 35 as the intercept valve command c.

  As a result, when the system frequency f is extremely increased, the speed control device 30 changes the intercept valve 7 from a fully open position to an intermediate opening degree (an opening degree other than a fully opened and fully closed position) after the adjusting valve 6 is fully closed. By subtracting, the reheater blockage which is the state in which the regulating valve 6 is opened and the intercept valve 7 is closed is avoided.

  FIG. 3 is an opening characteristic graph of the control valve 6 and the intercept valve 7 controlled by the speed control device 30 of FIG. As shown in FIG. 3, according to the system frequency f, the regulating valve 6 is a straight line with a downward slope to the right with a slope of CV regulation rate = 5%. The adjusting valve 6 is 80% open at the system frequency f = 101% and is fully closed at the system frequency f = 105%. On the other hand, the intercept valve 7 starts closing after the adjusting valve 6 is fully closed in order to avoid reheater blockage.

  FIG. 4 is a time chart showing the control of the speed control device 30 of FIG. 2 and the behavior of the steam turbine 2 accompanying the control.

  When the system frequency f increases from the reference rated value 100% to 101% at time t = 0 seconds, the control valve command a (CV) becomes 80%, and the control valve 6 closes to 80%. Along with this, the speed control device 30 reduces the turbine output (load) to 80%. However, by the time the turbine output (load) settles to 80%, a response with a slow response waveform such as curve α is exhibited. During this time, the intercept valve command c (ICV) remains fully open (opening degree 100%), and the intercept valve 7 remains fully open.

  As shown in FIG. 4, it takes about 10 seconds for the turbine output (load) to settle to 80%. The reason for the delay of about 10 seconds will be described with reference to FIG. At time t = 0 seconds, the main steam y that has already passed through the control valve 6 when the control valve 6 is fully open passes to the high-pressure turbine 10, the cold reheat pipe 16, the reheater 14, and the hot reheat pipe 17. It remains (hereinafter, the remaining steam is referred to as “residual excess steam”). This residual excess steam drives the intermediate pressure turbine 11 and the low pressure turbine 12 via the fully opened intercept valve 7. Therefore, it takes about 10 seconds until the residual excess steam finishes driving the turbine 2 and the turbine output (load) settles to 80%.

  For convenience of explanation, the time until the main steam y that has passed through the control valve 6 becomes the reheat steam z through the reheater 14 and passes through the intercept valve 7 (that is, the time until the residual excess steam is removed). Hereinafter, simply referred to as “vapor transit time”) is 10 seconds. In general, the steam transit time is about 5 seconds for a relatively small power plant and about 15 seconds for a large power plant.

  In order to improve this response delay, it is conceivable to control the intercept valve 7 to an intermediate opening even when the adjusting valve 6 is in the open state. However, when the intermediate opening of the intercept valve 7 extends for a long time, the valve body vibration of the intercept valve 7 may occur. The holding time of the intermediate opening for generating valve body vibration (that is, the above-mentioned “long time”) comprehensively considers a wide range of technical factors such as the valve body material, vibration intensity, amplitude, and natural frequency. Need to be identified. For this reason, it is difficult to specify the holding time of the intermediate opening for all the intercept valves 7.

  As described above, it is difficult for the speed control device 30 as the reference example to simultaneously improve the response delay and suppress the vibration of the valve body of the intercept valve 7.

  On the other hand, FIG. 5 is a circuit configuration diagram of the speed control device 40 of the steam turbine 2 in the first embodiment. In addition, the same code | symbol is attached | subjected about the structure and part corresponding to the speed control apparatus 30 of FIG. 2, and the overlapping description is abbreviate | omitted. The speed control device 40 according to the first embodiment can simultaneously improve the response delay and suppress the valve body vibration of the intercept valve 7 by suitably controlling the opening degree of the intercept valve 7.

  Specifically, after the time t = 10 seconds in FIG. 4 (after the steam passage time), the governing control device 40 is after the residual excess steam has passed through the intercept valve 7, and the adjusting valve 6 is opened. If 80% is maintained, the fact that the turbine valve (load) can maintain 80% even when the intercept valve 7 is fully opened is utilized. After the residual excess steam has passed through the intercept valve 7, the governing control device 40 returns the intercept valve 7 to a fully open state so that the state in which the intercept valve 7 is at an intermediate opening does not extend for a long time. did. Hereinafter, the speed control device 40 in 1st Embodiment is demonstrated concretely.

  The speed control device 40 generates the control valve command a by a circuit substantially similar to the speed control device 30 as a reference example.

  The speed control device 40 is built in a digital arithmetic control device in which a program is executed (computed) every predetermined sampling period. In the embodiment, this sampling period is assumed to be 50 milliseconds. The digital arithmetic and control unit stores a data amount value in the past of an integral multiple of the sampling period. It is assumed that the digital arithmetic and control unit uses a sampling delay unit configured to output the stored value at the current time.

The speed control device 40 includes sampling delay units 5001, 5002, 5003... 5200 (in the case where the sampling delay units 5001, 5002, 5003... 5200 are not distinguished, they are simply referred to as “sampling delay units 50”). The speed control device 40 stores the system frequency f for a predetermined time (here, 10 seconds) with a relatively simple circuit configuration by using the sampling delay unit 50 in the storage unit that stores the past system frequency f. The function of selecting the maximum value f _MAX is realized.

The speed control device 40 inputs the system frequency f to the sampling delay unit 50. The sampling delay unit 5001 functions as a storage unit that stores the system frequency f ₁ that is one sampling period (50 milliseconds) past the current time point (the time point when the system frequency f ₀ is obtained). The sampling delay unit 5002 stores a system frequency f ₂ that is two sampling periods (100 milliseconds) past the current time point. Similarly, the sampling delay units 5003 to 5200 store the past system frequency f _n for n sampling periods (3 ≦ n ≦ 200, 150 msec to 10 sec). That is, the sampling delay unit 50 stores the system frequency f of the past 10 seconds (50 milliseconds × 200), which is a period corresponding to the steam passage time.

The maximum value selector 43 receives the past 200 system frequencies f _{1 to} f ₂₀₀ from the sampling delay unit 50 and compares them. The maximum value selector 43 selects and outputs the maximum value f _MAX from the system frequencies f _{1 to} f ₂₀₀ .

The comparator 44 inputs the current system frequency f ₀ and the maximum value f _MAX and compares the magnitude relationship between the two. The comparator 44 outputs an output j = 1 when the system frequency f ₀ ≦ maximum value f _MAX . The comparator 44 outputs an output j = 0 when the system frequency f ₀ > f _MAX .

  The timer 46 keeps counting the elapsed time when the output j = 1 is input from the comparator 44. When the output j = 0 is input from the comparator 44, the timer 46 resets the elapsed time (sets to 0 seconds) and newly starts timing. The timer 46 holds a set time consisting of a predetermined value. The set time is set to a time longer than the steam passage time. For example, when the steam passage time is 10 seconds, the set time is 12 seconds with a 2 second margin added to the steam passage time. When the elapsed time is less than the set time (12 seconds), the timer 46 outputs the SW output d = 0. On the other hand, when the elapsed time reaches the set time, the timer 46 outputs the SW output d = 1.

  The speed control device 40 includes a switch 47 that generates an intercept valve command c for controlling the intermediate opening of the intercept valve 7. The switch 47 selects either the control valve command a (output a) for the intercept valve command c or the setting device 48 for commanding the fully open value b (opening degree 100%), and sets the value of the intercept valve command c. Switch. The switch 47 selects the intercept valve command c based on the value of the SW output d.

  Specifically, the switch 47 selects the intercept valve command c = full open value b when the SW output d = 1. On the other hand, when the SW output d = 0, the switching unit 47 selects the intercept valve command c = the increasing / decreasing valve command a. Briefly explaining this action, the switch 47 fully opens the intercept valve 7 when the elapsed time of the timer 46 reaches the set time (12 seconds), and adjusts the intercept valve 7 when the elapsed time is less than the set time. The same intermediate opening as the valve 6 is used. The switch 47 functions as a control unit that returns the intercept valve 7 to the fully opened state when the elapsed time reaches the set time.

  Note that at least the circuit from the subtractor 32 to which the system frequency f is input to the adder 35 that generates the control valve command a is an intermediate opening of the control valve 6 according to the system frequency f and the CV regulation rate of the system grid 21. It functions as an adjusting valve opening calculation unit that calculates the degree. The circuit from the subtractor 32 to which the system frequency f is input to the adder 35 that generates the control valve command a calculates the opening of the intercept valve 7 according to the system frequency f and the ICV regulation rate. It functions as a degree calculation unit. At this time, the ICV adjustment rate is the same value as the CV adjustment rate of 5%.

  Further, as a specific circuit configuration that can be taken by the speed control device 40 that generates the intercept valve command c, the setting value of the setting device 39 of the speed control device 30 of FIG. A basic configuration is obtained by changing the gain of the multiplier 37 to 1 by changing the constant rate value to 5% which is the same as the CV adjustment rate.

  Next, the operation of the speed control device 40 in the first embodiment will be described.

  First, the operation of the speed control device 40 when the system frequency f continues to be a constant value of 101% will be described.

  FIG. 6 is an opening characteristic graph of the adjusting valve 6 and the intercept valve 7 controlled by the speed control device 40 in the first embodiment.

  FIG. 7 is a first time chart showing the control of the speed control device 40 in the first embodiment and the behavior of the steam turbine 2 accompanying the control.

  FIG. 8 is a time chart as a comparative example with respect to the time chart of FIG.

  As shown in FIG. 6, according to the system frequency f, the adjusting valve 6 is a straight line with a downward slope to the CV regulation rate = 5%. The adjusting valve 6 is 80% open at the system frequency f = 101% and is fully closed at the system frequency f = 105%. The intercept valve 7 decreases its opening degree with a slope substantially equal to that of the control valve 6 while the switch 47 selects the control valve a.

Further, as shown in FIG. 7, the system frequency f = 100% before time t = 0 seconds (past 10 seconds), the outputs of all the sampling delay devices 50 are 100%, and the maximum value f of the sampling delay devices 50. _MAX = 100%.

When the system frequency f ₀ increases from the reference rated value 100% to 101% at time t = 0 seconds, the control valve command a (CV) becomes 80%, and the control valve 6 closes to 80%. The maximum value selector 43 obtains the maximum value f _MAX = 100% of the past system frequency f. Since the current system frequency f ₀ = 101%, the comparator 44 obtains a relationship of system frequency f ₀ > maximum value f _MAX . The comparator 44 outputs an output j = 0, and based on the output j, the timer 46 starts timing from 0 seconds and outputs an SW output d = 0. That is, the timer 46 measures the elapsed time after the opening degree of the intercept valve 7 is reduced.

  The switching device 47 switches the intercept valve command value c based on the value of the SW output d so that the intercept valve command c = the control valve command a (80%). As a result, the turbine output (load) quickly settles to 80% compared to the turbine output (load) of FIG.

At time t = 50 ms, the sampling delay unit 5001 outputs the system frequency f ₁ = 101% at time t = 0 seconds (one sampling period before) to the maximum value selector 43. The maximum value selector 43 obtains the maximum value f _MAX = 101% of the past system frequency f. Since the current system frequency f ₀ = 101%, the comparator 44 obtains the relationship of system frequency f ₀ = maximum value f _MAX . The comparator 44 outputs an output j = 1, and based on this output j, the timer 46 continues to measure time and obtains an elapsed time of 50 milliseconds. Since the set time has not yet elapsed, the timer 46 outputs the SW output d = 0. Based on the value of the SW output d, the switching unit 47 holds the intercept valve command c = the increasing / decreasing valve command a (80%).

At time t = 12 seconds, the sampling delay unit 50 outputs the system frequency f _{1 to} f ₂₀₀ = 101% at time t = 0 seconds to 12 seconds to the maximum value selector 43. The maximum value selector 43 obtains the maximum value f _MAX = 101% of the past system frequency. Since the current system frequency f ₀ = 101%, the comparator 44 obtains the relationship of the system frequency f ₀ = f _MAX . The comparator 44 outputs an output j = 1, and based on this output j, the timer 46 continues to measure time and obtains an elapsed time of 12 seconds. The timer 46 outputs SW output d = 1 since the set time has elapsed.

  The switch 47 switches based on the value of the SW output d so that the intercept valve command c = the full open value b (100%). At this time, residual excess steam remaining in the path from the control valve 6 to the intercept valve 7 after the control valve 6 reaches the intermediate opening has already passed through the intercept valve 7. For this reason, even if the intercept valve 7 returns to full open, the turbine output is maintained at 80%.

  That is, the speed control device 40 can achieve both effective governor-free operation and vibration avoidance of the intercept valve 7.

  Here, as shown in FIG. 8, when the set time of the timer 46 is set to 5 seconds and the intercept valve 7 is fully opened at time t = 5 seconds, the steam passage time has not elapsed and the remaining time Excess steam has not passed through the intercept valve 7. Therefore, the turbine output (load) rises once under the influence of the residual steam as the intercept valve 7 opens, and then settles to 80%.

  On the other hand, the speed control device 40 improves the response of the turbine output (load) by fully opening the intercept valve 7 after the residual excess steam passes through the intercept valve 7, and the intercept valve 7 is in the middle. The valve body vibration accompanying the opening degree can be suppressed.

  Next, the operation of the speed control device 40 when the system frequency f fluctuates with a random value and the intermediate opening of the adjusting valve 6 fluctuates accordingly will be described.

  In general, the system frequency f always varies with a random value, and the intermediate opening of the intercept valve 7 also varies accordingly. If each time the intercept valve 7 reaches a new intermediate opening, the opening is held for 12 seconds, the elapsed time does not reach 12 seconds, and the intercept valve 7 always has an intermediate opening.

  Therefore, the speed control device 40 in the first embodiment compares the past system frequency f with the current system frequency f and controls the intercept valve 7, whereby the intermediate opening of the intercept valve 7 becomes a long time, Suppresses occurrence of valve body vibration.

  That is, in the time chart of FIG. 7, at time t = 0 seconds, the system frequency f becomes 101%, the opening degree of the intercept valve 7 is reduced to 80%, and the system frequency f thereafter maintains a constant value of 101%. In this case, the intercept valve 7 is fully opened at time t = 12 seconds, and thereafter, it is not necessary to set the intermediate opening.

  If this is laid down, as an assumed case, the system frequency f becomes 101% at time t = 0 seconds, the opening degree of the intercept valve 7 is reduced to 80%, and all the system frequencies f thereafter are values of 101% or less. Therefore, it is not necessary to set the intercept valve 7 to the intermediate opening after time t = 12 seconds (can be returned to full open). This is because even when the constant value of the system frequency f = 101% is maintained (the case of controlling as shown in FIG. 7), the opening degree of the intercept valve 7 does not need to be an intermediate opening degree after 12 seconds. Therefore, in the assumed case where the system frequency f does not increase, this is not necessary.

  Based on the above, the operation of the speed control device 40 when the system frequency f fluctuates with a random value will be described.

  FIG. 9 is a second time chart showing the control of the speed control device 40 in the first embodiment and the behavior of the steam turbine 2 accompanying the control.

When the system frequency f rises from the standard rated value 100% to 101% at time t = 0 seconds, the time t = when the adjusting valve 6 and the intercept valve 7 are closed to 80% as in the time chart of FIG. When the system frequency f rises to 101.5% in 4 seconds, the control valve command a becomes 70%. For example, the sampling delay unit 5020 outputs the system frequency f ₂₀ = 101% at time t = 3 seconds (4 seconds−50 milliseconds × 20) to the maximum value selector 43. The maximum value selector 43 obtains the maximum value f _MAX = 101%. Here, since the current system frequency f ₀ = 101.5%, the comparator 44 obtains a relationship of system frequency f ₀ > maximum value f _MAX . The comparator 44 outputs an output j = 0, and based on the output j, the timer 46 resets the elapsed time to zero. That is, since the newly acquired system frequency f ₀ = 101.5% is larger than the past maximum value f _MAX = 101%, the timer 46 is affected by the reset, and the elapsed time is reset, from the time t = 4 seconds. Start timing again.

  Since the set time (12 seconds) has not yet elapsed, the timer 46 outputs the SW output d = 0. Based on the value of the SW output d, the switching unit 47 outputs an intercept valve command c = an increasing / decreasing valve command a (70%). Accordingly, the intercept valve 7 has an intermediate opening degree of 70% according to the calculated opening degree, and the turbine output (load) also rapidly decreases to 70%.

When the system frequency f is reduced to 100.5% at time t = 9 seconds, the control valve command a is 90%. For example, the sampling delay unit 5120 outputs the system frequency f ₁₂₀ = 101% when the time t = 3 seconds (9 seconds−50 milliseconds × 120) to the maximum value selector 43. Further, the sampling delay unit 5040 outputs the system frequency f ₄₀ = 101.5% at time t = 7 seconds (9 seconds−50 milliseconds × 40) to the maximum value selector 43. The maximum value selector 43 obtains the maximum value f _MAX = 101.5%.

Since the current system frequency f ₀ = 100.5%, the comparator 44 obtains a relationship of system frequency f ₀ <maximum value f _MAX . The comparator 44 outputs an output j = 1, and based on this output j, the timer 46 continues counting time and obtains an elapsed time of 5 seconds. Since the set time has not yet elapsed, the timer 46 outputs the SW output d = 0. Based on the value of the SW output d, the switch 47 outputs an intercept valve command c = adjustment valve command a (90%). The intercept valve 7 has an intermediate opening degree of 90%, and the turbine output (load) gradually increases toward 90%.

That is, at time t = 9 seconds, the system frequency f ₀ fluctuated to 100.5%, but the fluctuation is in a direction smaller than the past maximum value f _MAX = 101.5%. Continue timing without receiving it. This differs from the control at time t = 4 seconds, this difference is based on the magnitude relationship between the current system frequency f ₀ and the maximum value f _MAX.

At time t = 12 seconds, the elapsed time of the timer 46 is 8 seconds. The turbine output (load) is in a transient state increasing towards 90%. The control valve 6 and the intercept valve 7 maintain an intermediate opening of 90%. Since 12 seconds have passed since the intercept valve 7 started the intermediate opening (from time t = 0 seconds), the maximum value f _MAX = 101.5% was obtained at time t = 4 seconds. In FIG. 5, the set time of 12 seconds has not elapsed, and the intercept valve 7 does not return to full open.

  At time t = 16 seconds, the timer 46 outputs SW output d = 1 since the elapsed time has reached 12 seconds. Based on the SW output d, the switching unit 47 switches the intercept valve command c to a fully open value b (100%) and controls the intercept valve 7 to be fully open. Based on this, the intercept valve 7 is fully opened again. That is, at time t = 9 seconds, the system frequency f has changed to 100.5%, and 7 seconds (<set time 12 seconds) has elapsed. Without intercepting, the intercept valve 7 is controlled to be fully opened. As a result, the intercept valve 7 always eliminates (or reduces) the occurrence of valve body vibration due to the intermediate opening without affecting the responsiveness of the turbine output (load).

At time t = 18 seconds, the power system frequency _{f 0} is raised to 101%. The control valve command a is 80%, and the control valve 6 is closed to 80%. For example, the sampling delay unit 5200 outputs the system frequency f ₂₀₀ at time t = 8 seconds (18 seconds−50 milliseconds × 200) to the maximum value selector 43. The maximum value selector 43 obtains the maximum value f _MAX = 101.5%. Since the current system frequency f ₀ = 101%, the comparator 44 obtains a relationship of system frequency f ₀ <maximum value f _MAX . The comparator 44 continues to output output j = 1, and based on this output j, the timer 46 continues to count time, and the elapsed time is 14 seconds. The timer 46 outputs the SW output d = 1 since the set time 12 seconds has already elapsed. The switch 47 maintains the intercept valve command c = full open value (100%) based on the value of the SW output d. The intercept valve 7 is kept fully open.

As described above with reference to FIG. 9, even when the system frequency f ₀ increases when the intercept valve 7 is in the fully open state, the speed control device 40 has an increase value that is less than the maximum value f _MAX for the past 10 seconds. In this case, the intercept valve 7 is kept fully open without being reduced to an intermediate opening. On the other hand, the governor control unit 40, if the system frequency f ₀ is greater than the maximum value f _MAX, until the elapse of the set time (12 seconds) maintains the intermediate opening corresponding to the system frequency f _0.

  The speed control device 40, the control method thereof, and the steam turbine 2 of the steam turbine 2 according to the first embodiment achieve both suppression of valve body vibration of the intercept valve 7 and responsive turbine output control. Can do.

[Second Embodiment]
A steam turbine speed control device, a control method therefor, and a steam turbine according to a second embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 10 is a circuit configuration diagram of the speed control device 60 for the steam turbine 2 in the second embodiment. The steam turbine 2 is substantially the same as that shown in FIG. Moreover, about the structure and part corresponding to the speed control apparatus 40 of FIG. 2, FIG. 5, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  The speed control device 60 generates an increase / decrease valve command a by a circuit substantially similar to the speed control device 40 of the first embodiment. The control valve command a is output to the switch 47.

  The speed control device 60 inputs the deviation e, which is the output of the subtractor 32, into the multiplier 61. The multiplier 61 multiplies the deviation e by the reciprocal of the ICV adjustment rate (here, 4%) to generate an output t. The speed control device 60 inputs the output t to the adder 62 and adds the output t to the governor set value (100%) of the governor setter 36. The speed control device 60 inputs the output u generated by the adder 62 to the switch 47. The subtractor 32, the multiplier 61, and the adder 62 function as an intercept valve opening calculator that calculates the opening of the intercept valve 7 in accordance with the system frequency f and the ICV valve regulation rate.

  The speed control device 60 includes sampling delay units 5001 to 5200, a maximum value selector 43, a comparator 44, and a timer 46. The timer 46 outputs k = 0 when the elapsed time is less than the set time (12 seconds). On the other hand, the timer 46 outputs k = 1 when the elapsed time reaches the set time.

The speed control device 60 inputs the system frequency f ₀ to the comparator 63. The comparator 63, the dead zone set value of the dead band setting unit 64 (100.5% in this case) and is compared with the system frequency _{f 0.} The dead band set value is the value of the upper limit system frequency f that maintains the intercept valve 7 fully open regardless of the change in turbine output. The comparator 63 outputs an output m = 1 when the system frequency f ₀ <the dead band set value 100.5%. On the other hand, the comparator 63 outputs m = 0 when the system frequency f ≧ the dead band set value 100.5%.

  The speed control device 60 inputs the reheat steam pressure n to the comparator 65. The comparator 65 compares the pressure set value α [MPa] of the setter 66 with the reheat steam pressure n. The pressure set value α is set to 110% of the reheat steam pressure n when the output of the power plant is a rated value, for example. The pressure set value α is a value for determining whether or not the reheater is blocked or that the opening degree of the intercept valve 7 is maintained regardless of the turbine output or the like. The comparator 65 outputs p = 1 when the reheat steam pressure n> the pressure set value α. On the other hand, the comparator 65 outputs p = 0 when the reheat steam pressure n ≦ the pressure set value α.

  Further, the speed control device 60 inputs the reheat steam pressure n to the comparator 67. The comparator 67 compares the pressure set value β [MPa] of the setter 68 with the reheat steam pressure n. The pressure set value β is a value for determining whether or not the reheater is blocked or that the intercept valve 7 is fully opened regardless of the turbine output or the like. The pressure set value β as the second pressure value is set to a value larger than the pressure set value α as the first pressure value (pressure set value α <β). The comparator 67 outputs an output q = 1 when the reheat steam pressure n> the pressure set value β. On the other hand, the comparator 67 outputs an output q = 0 when the reheat steam pressure n ≦ the pressure set value β.

  The OR gate 70 receives the output k of the timer 46, the output m of the comparator 63, and the output q of the comparator 67. The OR gate 70 outputs the SW output d = 1 when at least one signal of the output k = 1 of the timer 46, the output m = 1 of the comparator 63, and the output q = 1 of the comparator 67 is input. The OR gate 70 does not input any of the output k = 1, the output m = 1, and the output q = 1 (when the output k = 0, the output m = 0, and the output q = 0), and the SW output d = 0 is output.

  The switch 47 receives the SW output d from the OR gate 70. When the SW output d = 1, the switch 47 selects the output h = full open value b (100%). On the other hand, when the SW output d = 0, the switch 47 selects output h = output u.

  A sample hold 71 receives an output p from the comparator 65. The sample hold 71 is provided at the subsequent stage of the switch 47 and receives the output h from the switch 47. When the output p = 1 is input, the sample hold 71 stores the instantaneous value of the output h. The sample hold 71 outputs a hold value r while the output p = 1 is established.

  The high value selector 72 receives and compares the output h output from the switch 47 and the hold value r output from the sample hold 71. The high value selector 72 outputs a large value between the output h and the hold value r as the intercept valve command c.

  Next, the operation of the speed control device 60 in the second embodiment will be described.

  The first difference between the speed control device 60 in the second embodiment and the speed control device 40 in the first embodiment is that a dead zone is provided to hold the intercept valve 7 fully open when the fluctuation of the system frequency f is small. Is a point. The second point is that an ICV adjustment rate having a steeper change (good response) than the CV adjustment rate is set in order to improve the response delay associated with the dead zone. Further, in order to cope with reheater blockage due to a sharp closing of the intercept valve 7, the opening degree of the intercept valve 7 is controlled according to the reheat steam pressure n.

First, the first point will be described.
FIG. 11 is an opening characteristic graph of the control valve 6 and the intercept valve 7 controlled by the speed control device 60 in the second embodiment.

The speed control device 60 inputs the system frequency f ₀ to the comparator 63. The comparator 63 compares the set value 100.5% set in the dead zone setter 64 with the system frequency f. When the system frequency f ₀ is smaller than the set value 100.5%, the comparator 63 generates the output m = 1 in order to fully open the intercept valve 7 (in order to set the intercept valve command c to 100% opening). Output. As a result, as shown in FIG. 11, the speed control device 60 keeps the intercept valve 7 fully open while the system frequency f ₀ is smaller than 100.5%.

  Compared to the control by the speed control device 40 of the first embodiment (see FIG. 6), the speed control device 40 of the first embodiment opens the intercept valve 7 to the intermediate opening as soon as the system frequency f becomes 100% or more. To control. On the other hand, the speed control device 60 in the second embodiment is a dead zone when the system frequency f is between 100% and 100.5%, and the band keeps the intercept valve 7 fully open.

Thereby, the speed control device 60 contributes to a quick turbine output response by reducing the intercept valve 7 to the intermediate opening degree for a large fluctuation of the system frequency f. On the other hand, the speed control device 60 responds to a slight fluctuation with the system frequency f of 100.5% or less by the governor-free operation of only the adjusting valve 6 and keeps the intercept valve 7 in a stable fully open state. That is, the speed control device 60 can suppress the valve body vibration since the intercept valve 7 is not unnecessarily controlled to the intermediate opening degree under a situation where the system frequency f is unstable.
Next, the second point will be described.

  The speed control device 60 inputs the deviation e generated by the subtractor 32 to the multiplier 61. Since ICV regulation rate = 4% is set in the multiplier 61, the speed control device 60 reduces the intercept valve 7 to the intermediate opening more quickly than the adjusting valve 6 in which the CV regulation rate 5% is set. .

  As shown in FIG. 11, the intercept valve 7 is controlled to close with a steeper slope than the control valve 6, and is fully closed earlier than the control valve 6 when the system frequency f reaches 104%. Such a state is a “reheater blockage” state in which the adjusting valve 6 is opened and the intercept valve 7 is fully closed, and the reheat steam pressure n is abnormally increased.

  Specifically, with reference to FIG. 1, the main steam y that has passed through the control valve 6 flows into the reheater 14 through the high-pressure turbine 10 and the cold reheat pipe 16 in order. On the other hand, the reheat steam z generated by the reheater 14 has no destination because the intercept valve 7 is fully closed, and the reheat steam pressure n increases. If this is left unattended, the reheater 14 may be damaged.

  A typical case of reheater blockage is an operating state in which the regulator valve 6 is open and the intercept valve 7 is fully closed. However, the reheater blockage is not limited to the case where the intercept valve 7 is fully closed. In general, the opening degree of the intercept valve 7 is relatively very high relative to the opening degree of the adjusting valve 6. Can occur when small. Since the occurrence of the reheater blockage involves factors such as the passage flow rate and temperature of the main steam y, it is difficult to determine the reheater blockage from the opening states of the control valve 6 and the intercept valve 7.

  Therefore, the speed control device 60 is provided with means for inputting the pressure value of the reheat steam (reheat steam pressure n) and detecting the occurrence of the reheater blockage or the possibility thereof, and intercepts according to the detection result. The opening degree of the valve 7 is controlled.

  As shown in FIG. 10, the speed control device 60 inputs the reheat steam pressure n to the comparator 65. The comparator 65 compares the reheat steam pressure n with the pressure set value α [MPa]. The comparator 65 outputs p = 1 when the reheat steam pressure n> the pressure set value α. In other words, the speed control device 60 detects an abnormal pressure increase of the reheat steam, and determines that the reheater is blocked or possibly generated when the output p = 1.

  The sample hold 71 stores the instantaneous value of the output h when the output p = 1 is input. The sample hold 71 outputs the stored output h to the high value selector 72 as the hold value r while the output p = 1 is input. The high value selector 72 compares the hold value r with the current output h, and outputs a large value (a value with a large opening of the intercept valve 7) as the intercept valve command c.

  When the speed control device 60 detects the reheater blockage or its possibility (when it detects that the reheat steam pressure n is larger than the pressure set value α), the opening degree of the intercept valve 7 at almost the moment ( The output h = 1 or more at the moment when the output p = 1 is input to the sample hold 71 is held. That is, the speed control device 60 does not close the opening of the intercept valve 7 at the moment when the reheater blockage or the possibility is detected during the reheater blockage or the possibility that the reheater is closed. Wait for the device to be released from the blockage condition.

  If the reheat steam pressure n further increases even if the opening degree of the intercept valve 7 is maintained, the speed control device 60 returns the intercept valve 7 to full open.

  Specifically, the speed control device 60 inputs the reheat steam pressure n to the comparator 67. The comparator 67 compares the reheat steam pressure n with the pressure set value β [MPa]. The comparator 67 outputs an output q = 1 when the reheat steam pressure n> the pressure set value β. That is, if the governing control device 60 detects an increase in the reheat steam pressure n even though the opening degree of the intercept valve 7 is maintained, the reheater blockage or its possibility is not improved. to decide.

  When the output q = 1 is input, the OR gate 70 outputs the SW output d = 1. When the switch output d is input, the switch 47 selects output h = full open value b (100%). The high value selector 72 selects the fully open value b which is the output h having a large opening, and outputs the fully open value b as the intercept valve command c. As a result, the speed control device 60 can return the intercept valve 7 to the fully open state, thereby improving the reheater blockage or the possibility thereof.

  The speed control device 60, the control method thereof, and the steam turbine 2 according to the second embodiment, in addition to the effects exhibited by the first embodiment, unnecessarily close the intercept valve 7 by providing a dead zone. The valve body vibration can be suitably suppressed without causing the valve.

  Further, the speed control device 60 of the steam turbine 2, the control method thereof, and the steam turbine 2 can improve the response delay of the turbine output accompanying the provision of the dead zone by suitably setting the ICV regulation rate. it can.

  Further, the speed control device 60 of the steam turbine 2, the control method thereof, and the steam turbine 2 preferably control the opening degree of the intercept valve 7 when the reheater blockage or the possibility thereof is detected. Therefore, the reheater blockage can be improved, and the breakage of the reheater 14 can be avoided.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Power plant 2 Steam turbine 3 Boiler 4 Generator 6 Control valve 7 Intercept valve 10 High pressure turbine 11 Medium pressure turbine 12 Low pressure turbine 13 Superheater 14 Reheater 15 Main steam piping 16 Cold reheat pipe 17 Hot reheat pipe 21 System grid 30 , 40, 60 Speed control device 32 Subtractor 34, 37, 61 Multiplier 35, 38, 62 Adder 33, 36, 39, 48, 64, 66, 68 Setter 43 Maximum value selector 44, 63, 65 67 Comparator 46 Timer 47 Switch 50 (5001... 5200) Sampling delay 70 OR gate 71 Sample hold 72 High value selector

Claims (12)

An adjusting valve for adjusting main steam supplied to the first turbine; an intercept valve for adjusting steam discharged from the first turbine and guided to a second turbine having a lower pressure than the first turbine; In a steam turbine speed control device including a generator driven by the first and second turbines to supply electric power to an electric power system,
An adjusting valve opening calculating unit that calculates the opening of the adjusting valve according to the system frequency and the adjusting valve regulating rate of the power system;
An intercept valve opening calculation unit for calculating the opening of the intercept valve according to the system frequency and the intercept valve regulation rate;
A timer for measuring an elapsed time since the opening of the intercept valve is reduced;
When the elapsed time is less than the set time, the intercept valve is controlled according to the opening calculated by the intercept valve opening calculation unit, and when the elapsed time reaches the set time, the intercept valve is fully opened. A steam turbine speed control apparatus comprising: a control unit that controls the steam turbine.   The steam turbine speed control device according to claim 1, wherein the set time is longer than a time until the main steam that has passed through the control valve passes through the intercept valve. A storage unit for storing the system frequency in the past;
A maximum value selection unit for selecting a maximum value among the stored past system frequencies, and
The speed control device for a steam turbine according to claim 1 or 2, wherein the timer resets the elapsed time when a newly acquired system frequency is greater than a maximum value of the past system frequency.   The speed control device for a steam turbine according to claim 3, wherein the storage unit stores the system frequency in a period corresponding to a time until the main steam that has passed through the control valve passes through the intercept valve.   The said control part is a speed control apparatus of the steam turbine as described in any one of Claims 1-4 which hold | maintains the said intercept valve fully open, when the said system | strain frequency is below a predetermined value.   The steam turbine according to any one of claims 1 to 5, wherein the intercept valve opening degree calculation unit calculates an opening degree of the intercept valve according to the intercept valve regulation rate having a change rate larger than the adjustment valve regulation rate. Speed control device. The steam turbine includes a reheater that reheats steam that has worked in the high pressure turbine to generate reheat steam,
The said control part is a speed control apparatus of the steam turbine as described in any one of Claims 1-6 which controls the opening degree of the said intercept valve according to the pressure of the said reheated steam.   When the control unit detects that the pressure of the reheat steam is larger than a first value, the control unit detects the opening degree of the intercept valve and detects that the pressure of the reheat steam is larger than the first value. 8. The steam turbine speed control device according to claim 7, wherein the speed control device is maintained at a level equal to or greater than an opening of the intercept valve.   The speed control of the steam turbine according to claim 8, wherein when the pressure of the reheat steam is detected to be greater than a second value greater than the first value, the control unit controls the intercept valve to be fully opened. apparatus. The speed control device is built in a digital arithmetic control device in which a program is executed every predetermined sampling period,
The speed control device for a steam turbine according to claim 3, wherein the storage unit is a sampling delay device that stores and outputs a value of a past data amount of an integral multiple of the sampling period. An adjusting valve for adjusting main steam supplied to the first turbine; an intercept valve for adjusting steam discharged from the first turbine and guided to a second turbine having a lower pressure than the first turbine; In a speed control method for a steam turbine including a generator that is driven by a first turbine and a second turbine to generate electric power and supply electric power to an electric power system,
An adjusting valve opening degree calculating step for calculating the opening degree of the adjusting valve according to the system frequency and the adjusting valve regulating rate of the power system;
An intercept valve opening degree calculating step for calculating an opening degree of the intercept valve according to the system frequency and the intercept valve regulation rate;
A time measuring step for measuring an elapsed time since the opening of the intercept valve is reduced;
When the elapsed time is less than the set time, the intercept valve is controlled according to the opening calculated in the intercept valve opening calculating step, and when the elapsed time reaches the set time, the intercept valve is fully opened. And a control step for controlling the speed control method of the steam turbine. A first turbine and a second turbine having a lower pressure than the first turbine;
An adjusting valve for adjusting main steam supplied to the first turbine;
An intercept valve that regulates steam discharged from the first turbine and directed to the second turbine;
A generator driven by the first and second turbines to generate power and supply power to the power system;
A speed control device that performs speed control of the steam turbine,
The speed control device includes:
An adjusting valve opening calculating unit that calculates the opening of the adjusting valve according to the system frequency and the adjusting valve regulating rate of the power system;
An intercept valve opening calculation unit for calculating the opening of the intercept valve according to the system frequency and the intercept valve regulation rate;
A timer for measuring an elapsed time since the opening of the intercept valve is reduced;
When the elapsed time is less than the set time, the intercept valve is controlled according to the opening calculated by the intercept valve opening calculation unit, and when the elapsed time reaches the set time, the intercept valve is fully opened. A steam turbine comprising a control unit for controlling.

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