JPH0231763B2 - JOKITAABINNOJOKIATSURYOKUSEIGYOSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a power generation plant system, and particularly to a power generation plant system, in which the steam pressure of a steam turbine can be controlled stably and quickly regardless of any changes in environmental conditions. It relates to a pressure control device.

[Technical background of the invention]

In recent large-scale plants such as thermal power plants, steam turbine pressure control has come to play an important role as generator capacity increases.
In particular, there is a need for accurate and responsive steam pressure control in response to system load fluctuations.

By the way, steam pressure control of a steam turbine in a conventional thermal power plant has mainly been performed by the following method. That is, if the load suddenly increases in a system in which a turbine generator is included, the turbine speed governor instantly detects this and opens the steam control valve wide.

On the other hand, in the case of a boiler, when a drop in steam pressure is detected, both the amount of fuel and water supplied are increased, but the response speed is far slower than that of the governor due to the heat capacity of the boiler. . For this reason, when the load suddenly changes, especially when the load increases, the main steam pressure decreases, causing condensate to occur and seriously damaging the turbine blades.In particular, if a breakage accident occurs, the life of the plant will be shortened. .

In addition, when the degree of vacuum in the condenser on the return flow side of the turbine decreases, wind loss increases near the final stage of decline where the long blades of the turbine rotate at high circumferential speed, and the generation of frictional heat causes damage to the turbine blades. The turbine blades will be exposed to high temperatures and the life span of the turbine blades will be shortened due to thermal stress.

Furthermore, in the case of a condenser, the pressure increases, resulting in unfavorable conditions in terms of strength. A steam pressure control device for a steam turbine that can cope with these phenomena detects the main steam pressure in front of the main steam stop valve and operates directly using the main steam pressure as a control signal in response to a drop in inlet steam pressure. or once converted into other media signals such as air pressure or electricity,
A control mechanism is used that moves a steam control valve lever via a feedback amplification mechanism such as a hydraulic pilot or relay to close the steam control valve to an arbitrary opening degree. In addition, in response to a decrease in the degree of vacuum, the pressure inside the condenser is detected and converted to oil pressure, amplified and feedback is applied, and the steam control valve lever is moved.
The valve is operated in the direction of opening the valve.

FIG. 1 is a system diagram in which such a steam pressure control device for a steam turbine is applied to a power generation plant.

In FIG. 1, 1 is a boiler, and 2 is a main steam stop valve that shuts off the steam supplied to the high-pressure turbine 4 in an emergency.

Reference numeral 3 denotes a steam control valve to be controlled, which adjusts the flow rate of steam supplied to the steam turbine (high-pressure turbine) 4. The superheated steam from the boiler 1 passes through the steam control valve 3 and flows into the high-pressure turbine 4, and after imparting part of the energy contained in the steam to the turbine, it returns to the boiler 1 and flows into the reheater 1A in the boiler 1. is reheated. The steam then passes through an intercept valve 5, an intermediate pressure turbine 6, and a low pressure turbine 7, where the thermal energy of the steam is converted into mechanical energy. The steam is then sucked by the vacuum in the condenser 8, condensed by heat exchange with the cooling water, compressed by the feed water pump 9, sent to the boiler 1, heated, and cycled in the same manner as above. Repeat. The steam pressure at the turbine inlet is normally detected midway through the steam line between the outlet of the boiler 1 and the steam stop valve 2, and the vacuum pressure is detected at the condenser 8.
It is detected by the pressure 11 in the room.

In FIG. 2, both the inlet steam pressure signal and the vacuum pressure signal in FIG. is given priority, and the lift of the steam control valve 3 is determined according to the control amount.

14A and 14B are inlet steam pressure signals, respectively;
This is a pressure displacement conversion device for converting the deviation between the vacuum pressure signal and each set value into a displacement amount, and the size is 15A,
15B is a displacement amplifier for amplifying each displacement amount.

16 is a high value priority device in which the displacement amplifiers 15A and 15B select and output the larger signal, and the displacement amplifiers 15A and 15B select the larger signal as the control signal based on the signal. . Further, 17 is a hydraulic cylinder to which the output signal selected by the high value priority device 16 is inputted as the hydraulic signal 16 _-1 .
is for controlling the lift of the steam control valve 3 based on the oil pressure signal 16 _-1 . That is, the hydraulic cylinder 17 determines the lift value of the steam control valve 3 based on the signal amount based on the displacement amplification value, and opens or closes the steam control valve 3 based on that value.
Therefore, the steam control valve 3 is controlled by adjusting its valve opening degree in accordance with the above-mentioned lift value.

[Background technology issues]

However, when these control safety devices such as main steam pressure and vacuum level reduction are used in a steam turbine, with the conventional method, only the detection part and control operation amount are different, and the control device up to the steam control valve lever is different. Since the control mechanisms used are completely similar, the control signals for both systems are subject to slow response of pressure signal amplification and play in the lever link, which may cause signal transmission problems before the high values are prioritized at the steam control valve lever. There will be a delay.
Therefore, in recent years, large-scale turbine generators are increasingly required to have quick response and rapid control, and correct operation is desired to extend the life of the turbine. It is necessary to improve the quick response of pressure control.

[Purpose of the invention]

An object of the present invention is to provide a highly reliable steam pressure control device for a steam turbine that can improve responsiveness to sudden changes in load and stably control valve opening by reducing rattling of lever links. It's about doing.

[Summary of the invention]

In order to achieve the above objects, the present invention detects the pressure at the inlet and outlet sides of a steam turbine, converts each pressure amount into an analog digital amount, compares it with each set pressure value, and calculates the deviation value. , and determine the larger deviation value among these deviation values, give priority to this larger deviation value and move the lever of the steam control valve using a signal with a faster response based on the calculation, thereby reducing the looseness of the lever link. It is characterized by controlling the valve opening degree by reducing the

[Embodiments of the invention] Examples of the present invention will be described below.

FIG. 3 shows a system diagram in which the device of the present invention is applied to a power generation plant.

In FIG. 3, the same parts as those in FIG. 1 are given the same reference numerals, and the explanation thereof will be omitted, and only the different parts will be described here.

18 is a conversion device that converts the vacuum pressure signal in the condenser 8 to a level required for calculation processing, and 21 is an analog-to-digital converter that converts the inlet steam from an analog quantity to a digital quantity and outputs a digital signal. , 22 is an analog-to-digital converter that converts the output signal of the converter 18 from an analog quantity to a digital quantity. Reference numeral 23 denotes a calculation/discrimination circuit, and as shown in _FIG .
a comparison calculation circuit 24, a second comparison calculation circuit 25 that detects the deviation between the vacuum pressure signal of the condenser and its set value _25-1 , and a comparison calculation circuit 24, 2 for both of them.
It is comprised of a high value determination circuit 26 which selectively outputs the larger one among the five deviation outputs preferentially. This is a signal amplifier that amplifies the output signal of the high value judgment circuit 26 as a signal of the lift value of the steam control valve. Based on the signal of this signal amplifier 27, the hydraulic cylinder 1
7 to control the lift of the steam control valve.

Next, we will discuss the effect. The inlet steam pressure signal and the vacuum pressure signal are converted from analog quantities to digital quantities by analog-to-digital converters 21 and 22, respectively, and are input to a calculation/discrimination circuit 23. When each of the signals converted into digital quantities is input to the calculation/discrimination circuit 23, the inlet steam pressure signal is combined with the digital signal from the setting circuit _24-1 that sets the relationship between the main steam flow rate and the pressure, and the vacuum The pressure signal is compared with a digital signal from the setting circuit _25-1 which sets the relationship between the condenser vacuum degree and the pressure in the comparison calculation circuits 24 and 25, respectively, as follows.

Figure 5 is a diagram to explain the comparison calculation with the setting value of the setting circuit 24 _-1 which sets the relationship between the main steam flow rate and pressure.The horizontal axis shows the main steam flow rate as a function of time, and the vertical axis shows the main steam flow rate as a function of time. Shows pressure. In Figure 5, A ₁₁
is a setting curve showing the main steam flow rate-pressure relationship set in the setting circuit _24-1 , and _A12 is an actual main steam flow rate-pressure relationship curve. Now, fix the main steam flow rate T ₁ , decide on this T ₁ and sampling points in a small range -ΔT ₂ and +ΔT ₁ .
Said setting curve A ₁₁ in the range of T ₁ −ΔT ₁ and T ₁ +ΔT ₁
Compare the areas of and the actual curve _A12 .

That is, the area of the curve A ₁₁ is expressed as S ₁₁ =∫ ^T1+ 〓 ^T1 _T1- 〓 _T1 (setting curve A ₁₁ from the setting device 23 _-1 ), and the curve
The area of A ₁₂ is expressed as S ₁₂ =∫ ^T1+ 〓 ^T1 _T1- 〓 _T1 (actual main steam flow rate and pressure curve A ₁₂ ). The comparison calculation circuit 24 compares these two areas S ₁₁ and S ₁₂ and calculates the amount of displacement from S ₁ =S ₁₁ -S ₁₂ . Then, the amount of displacement whose area value has been determined in the range of time T ₁ and sampling point ±ΔT ₁ is applied to the high value determination circuit 26 .

On the other hand, Figure 6 is a diagram for setting the comparison calculation with the set value of the setting circuit 25 _-1 which sets the relationship between the condenser vacuum degree and pressure.The horizontal axis shows the function of time with the condenser vacuum degree. The vertical axis shows pressure. In Fig. 6, _B11 is a setting curve showing the relationship between the condenser vacuum level and pressure set by the setting device _23-2 , and _B12 is the actual relationship between the condenser vacuum level and pressure. It shows a curve.

Now, fix the condenser vacuum degree to the same time T ₁ at which the main steam flow rate was sampled, and determine the sampling points -ΔT ₁ and +ΔT ₁ in this minute range,
Here, area comparison is performed between the set curve B ₁₁ and the actual curve B ₁₂ in the range of T ₁ -ΔT ₁ and T ₁ +ΔT ₁ .

That is, the area S ₂₁ of curve B ₁₁ is S ₂₁ =∫ ^T1+ 〓 ^T1 _T1- 〓 _T1
(Setting curve B ₁₁ from setting device 23 _-2 ), and the area S ₂₂ of curve B ₁₂ is S ₂₂ =∫ ^T1+ 〓 ^T1 _T1- 〓 _T1 (Actual condenser vacuum degree and pressure curve B ₁₂ ). The comparison calculation circuit 25 compares the two areas S ₂₁ and S ₂₂ and calculates the amount of displacement from S ₂ =S ₂₁ -S ₂₂ . Then, the amount of displacement determined from the area value in the range of time T ₁ and the sampling point ±ΔT ₁ is applied to the high value determination circuit 26 . These comparison calculation circuits 24, 2
When the displacement amounts S ₁ and S ₂ are input from 5 to the high value judgment circuit 26, this high value judgment circuit 26 calculates a comparison of the areas of S ₁ and S ₂ , and as a result of the calculation, the higher value is given priority, The signal is output to the signal amplifier 27. The signal amplifier 27 amplifies the output signal and sends it to the steam control valve 3.
Based on the lift value, the hydraulic cylinder 17 is driven to control the opening and closing of the steam control valve 3.

As described above, according to the present invention, two different types of steam pressure signals and vacuum pressure signals are converted from analog signals to digital signals, and the steam pressure signals are converted into settings that set the relationship between the main steam flow rate and the pressure. value and
In addition, the area of the vacuum pressure signal was compared with the set value that set the relationship between the degree of vacuum and pressure, and the area was compared at the same time and with the same sampling synchronization.
A value comparison calculation is performed to determine which value is given priority, and the valve opening is controlled by operating the steam control valve lever according to the displacement amount of the larger value. The operating time is therefore very quick,
In addition, since the high value priority judgment is made by calculating a more accurate amount by digital processing, the rattling of the lever link of the steam control valve can be reduced by the response of the hydraulic signal of the feed digital calculation. Improved reliability and more accurate steam pressure control.

This is also advantageous in adjusting the compressible vapor pressure.

Although the above-mentioned embodiment has been explained by taking the operation determination circuit as an example, the operation determination means can be controlled not only by a computer or a microcomputer, but also by a relay sequence. In addition, although we have described the comparison calculation of pressure control with two values of input steam pressure and vacuum pressure as control variables, it is also easy to detect many types of control conditions and compare multiple detected pressures with priority given to the highest value. It is possible to implement

〔Effect of the invention〕

As described above, according to the present invention, the response to sudden changes in load can be improved, and the valve opening degree can be stably controlled by reducing rattling of the lever link of the steam control valve. A steam pressure control device for a steam turbine can be provided.

[Brief explanation of drawings]

Figure 1 is a system diagram in which a conventional steam pressure control device for a condensing steam turbine is applied to a power generation plant.
The figure is a block diagram showing the pressure control device shown in FIG. 1, and FIG. Figure 4 is a block diagram showing the calculation/discrimination circuit in the device of the present invention, Figure 5 is a diagram showing the relationship between steam flow rate and pressure, and Figure 6 is a diagram showing the relationship between condenser vacuum degree and pressure. It is. 3...Steam control valve, 4...Steam turbine (high pressure), 21, 22...Analog-digital converter,
23... Calculation determination circuit, 24, 25... Comparison calculation circuit, 24 _-1 , 25 _-1 ... Setting circuit, 26... High value judgment circuit.

Claims (1)

[Claims] 1. In a steam pressure control device that controls the inlet steam pressure of a condensing steam turbine and the vacuum pressure of a condenser, which is the back pressure of the steam turbine, by operating a lever of a steam control valve, the steam pressure signal and The vacuum pressure signal was converted from an analog quantity to a digital quantity, and the steam pressure signal was used to set the relationship between the main steam flow rate and pressure, and the vacuum pressure signal was used to set the relationship between the degree of vacuum and pressure in the condenser. Perform a comparison operation with the set value at the same time and at the same sampling period to find the respective displacement amount,
Furthermore, these displacement amounts are compared and calculated, and the one having a larger value is selected and prioritized, and the valve opening degree of the steam control valve is controlled as the operation amount of the steam control valve lever. Steam pressure control device.