JPH0244107A - Automatic switching device for water feeding pump - Google Patents

Abstract

PURPOSE:To enable automatic switching of a feed pump in a short time in a state that a fluctuation in a flow rate of feed is suppressed to a minimum by a method wherein a switching change factor is corrected according to a feed flow rate deviation between an increase amount of water fed with the aid of a turbine-driven feed pump and a decrease amount of water fed with the aid of a motor-driven feed pump. CONSTITUTION:A deviation between an actual feed flow rate signal 20 and a feed demand set signal 21 from a boiler master system is determined by an adder 25, and a proportional and integrating computation is effected by a feed controller 26 to determine a flow rate demand value. In the case of a turbine-driven feed pump, a deviation between a flow rate demand value and a pump outlet flow rate (check valve flow rate) signal 27 is determined by an adder 28, and proportional and integrating computation is effected by a flow rate control device 29. This controller output is inputted to a turbine controller 30. An output from the turbine controller 30 is provided as a signal by means of which a steam regulating valve 32 to control a flow rate of low pressure steam extracted from a main turbine 3 is opened and closed, and the number of revolutions of a turbine 31 for driving a feed pump is controlled. Meanwhile, in the case of a motor-driven feed pump, a feed regulating valve 9 is directly controlled by a means of an output from a flow rate controller 33.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic water pump switching device, and particularly to an automatic water pump switching device that is most suitable for use in a steam generator in a thermal power plant or the like.

[Conventional technology]

In a conventional system, as described in Japanese Patent Publication No. 63-685, a water supply pump for a steam generator (for example, a boiler) is composed of a plurality of pumps with different drive systems such as turbine drive and motor drive. When the output of the steam generator is low, the motor-driven feed water pump (M-RFP) is mainly used, and in the process of increasing the output, the turbine-driven feed water pump (T-RFP) is used.
RFP). Conventionally, this switching operation was performed manually by an operator. A turbine-driven water pump controls the water pump flow rate based on the turbine rotation speed.

When the rate of increase in the turbine rotational speed is increased, the flow rate increases rapidly and the boiler feed water flow rate increases. Fluctuations in water supply to boilers are strictly limited due to requirements for protecting the boiler and turbine main engines, and an interlock is activated that trips the boiler and turbine when the deviation exceeds a specified value. Boiler trip interlocks are activated due to dry firing protection requirements. Therefore, the switching operation of the water supply pump was performed carefully and over a long period of time by experienced operators.

In response to this, in recent years, devices have been proposed that automatically switch the water supply pump regardless of its availability; for example, there is a system shown in FIG. 2.

Steam generated in the boiler 1 is introduced into the turbine 3 through the main steam pipe 2, drives a generator (not shown), and is then sent to the condenser 4 and returned to water. This condensate is pumped by low pressure condensate pump 5. The pressure is increased by the high-pressure condensate pump 6 , the pressure is further increased by the turbine-driven water pump (T-BFP) 7 and the motor-driven water pump (M-BFP) 8 , and water is supplied to the boiler 1 via the water supply pipe 10 . Typically, water pumps include
2 turbine-driven water pumps and 1 motor-driven water pump
A total of three machines are used. When starting the turbine,
The motor-driven water pump 8 is operated and the turbine is at 20%
When the output level is reached, the turbine-driven water supply pump 7 is operated. Adder 2 subtracts the boiler feed water flow rate from the set value. This output becomes a control signal for the main controller 13.

At the start of startup, the computer 14 turns off the controller 15 and turns on the controller 16, so the main controller 13 only controls the water supply adjustment valve 9.

When the generator output increases as described above, the computer 14 turns on the controller 15, transfers water supply control from the water supply control valve 9 to the turbine controller 18, and then turns off the controller 6.

Therefore, the output of the main controller 13 is sent to a function generator 17 to generate a control pattern. The output of the function generator, 17, is sent to a turbine control 18 to control the turbine steam rate for the feed water pump 7.

[Problem to be solved by the invention]

In the conventional water pump switching method shown in FIG. 2 above, the computer 14 switches between the motor-driven water pump and the turbine-driven water pump instead of manual operation. As conditions related to various control characteristics such as turbine drive oil and air conditions change, it is necessary to suppress fluctuations in the water supply flow rate when switching. However, the second
As can be seen from the block diagram in Figure 3 and the operating characteristic diagram of each part of the conventional water pump switching device example in Figure 4, the water supply flow rate is It has the disadvantage that it cannot suppress fluctuations. Furthermore, the fourth
In the figure, the load (water supply) is assumed to be constant to make the figure easier to read.

In other words, in conventional switching control, after pressure equalization control, an increase signal with a predetermined rate of change and a limited upper limit is output to the turbine-driven water feed pump control system to increase the amount of water supplied from the turbine-driven water pump, and at the same time It is a switching control system that outputs a reduction signal corresponding to the signal to the motor-driven water supply pump system to reduce the amount of water supplied from the motor-driven water supply pump,
Efforts have been made to reduce fluctuations in the water supply flow rate, but fluctuations have not yet been sufficiently suppressed for the following reasons.

1) The control signal vs. flow rate characteristics are different between the turbine-driven water supply pump control system and the motor-driven water supply pump control system. If the decrease signal is output to the motor-driven water supply pump control system, fluctuations in the water supply flow rate will occur.

2) Adjust the 813 units of 2 turbine-driven water feed pumps and 1 motor-driven water feed pump to the required generator output value.・-The enthalpy of the oil vapor vapor 1 for driving the bottle-driven water supply pump is not determined, and as a result, the convection-diffusion characteristics of the 8 controllers differ for each switch, and from the principle 1102:' of 1) Fluctuations in the water supply flow rate will occur.

, '3) A water supply pump is usually equipped with a water recirculation valve to prevent the pump from overheating due to shut-off operation: 3/1. ．． 35 is provided to ensure that the water supply pump suction flow rate is above a certain value Σj1. I'm trying to do that. These valves 34.35 are the pump suction Jf
, 51.37, which is controlled by a recirculation flow controller 38.39 with on/off or continuous control function that takes in %36.37. During the switching control of the valve '0 (the recirculation flow rate suddenly changes due to opening/closing at -), the switching control is performed to promote this g-force. (This may increase fluctuations in the water supply flow rate.)

The purpose of the present invention is to provide a water supply pump switching capacity that suppresses water supply fluctuations at the time of switching and allows good switching under various switching conditions. ), [Tth means for solving the problem] In order to achieve the above object, the present invention has the following features: 1., 2.
Afterwards, the switching change rate is limited by the feedwater flow rate deviation, and a '/- rise signal is output to the turbine-driven feedwater pump control system. Has the amount of water supplied from the IJ water pump also increased? 5, at the same time, the switching change rate is limited by a feed water flow rate deviation different from this L increase signal, and the rate of change is reduced to 1.
Drive water pump control system 11. ``Decrease the amount of water supplied from the instant-acting water supply pump by outputting the output! 5. Controlling the amount of water leakage.

[Effect]

In the present invention, five evenings - Pino Kakeru! 1. 1. Limit the switching rate of change depending on the water supply flow rate deviation, such as increase in water supply by pump L and - to iJ supply♂ and motor-driven water supply decoupling. Operates to control switching. As a result, fluctuations in water supply flow rate.

This water supply flow rate deviation limits the switching rate of change, so fluctuations can be suppressed (a).

〔Example〕

An embodiment of the present invention will be explained with reference to FIG. 1. FIG. 1 is a block diagram showing an embodiment of the water pump automatic switching device according to the present invention. This is an example in which a boiler is adopted as the 5-distillation region 1 generator, and the configuration of its steam flow path and water supply system is the same as the system shown in Figure 2.7 The boiler feed water control system has an actual feed water flow of M An adder 25 calculates the deviation between the water supply request setting signal 21 and the boiler master system.
The water supply controller 2G (1) performs proportional and integral calculations to obtain the required flow rate value.

This flow rate request value is the set value of the subloop control system that independently controls the flow rate of each pump. That is, in the case of a turbine-driven feed water pump, the deviation between this flow rate request value and the pump outlet flow Jt (check valve flow rate) signal 27 is determined by the W adder 28, and the flow rate controller "28" performs proportional/integral calculations. 8 This controller output is given to the turbine controller 30. The output of the turbine controller 30 is a signal to open and open the steam control valve 32 that controls the flow rate of the low pressure black gas from the turbine 3. On the other hand, in the case of a motor-driven water pump, the feed water regulating valve 9 is directly controlled by the output of the flow controller 33.

The flow rate control system and pump configuration of the turbine-driven feed water pump I3 (not shown) are the same as those of each pump A in FIG. Take in the values.

The turbine-driven feed water pump has a capacity of 55% of the rated feed water flow class, the motor-driven feed water pump has a capacity of 27.5%, and in the range of generator output 50''-100%, two turbine-driven feed water pumps are used. One motor-driven water pump is used.
I'll pack up my bag and wait.

On the other hand, during the boiler startup process, since turbine-driving steam is not available, a motor-driven water pump is used.

Zunawaji, generator output 0=20% 8M-BFP 20 units
-50%: 1-BFP 50-・-1,00
%: T-Rt'P2. It is driven like a machine.

Therefore, when the generator output is about 20% or more, it is necessary to switch from the motor-driven water feed pump to the turbine-driven water pump, and when the generator output is about 50% or more, it is necessary to start the second turbine-driven water feed pump. input is required.

The configuration that performs switching for this purpose is the control unit 1 shown in FIG.
00, and switching from a motor-driven water supply pump to a turbine-driven water supply pump can be divided into three types: (1) speed increase control, (2) pressure equalization control, and (3) switching control.

Here, each control stage is defined as follows.

(1) Speed-up control: Raising the speed of the turbine-driven water supply pump to a predetermined rotational speed at a predetermined speed-up rate.

The predetermined rotation speed is the rotation speed (approximately 1/2 of the rated speed) at which the pump discharge pressure is sufficient to prevent water from being supplied to the boiler through the pump outlet check valve, but is below the rated rotation speed. ) Pressure equalization control: After the end of speed increase control, bring the pump discharge pressure close to the pump discharge pressure. The process ends when the differential pressure between the two becomes 0.

(3) Switching control: Switching the share of the pump flow rate that contributes to the boiler feed water flow rate from one pump to another.

Next, each control stage will be explained in detail.

(1) Speed-up control The output of the speed-up control setter 101 is given to the integrator 103 via the switch 102S1 and integrated.

This integral output is limited within a predetermined integral value by a limiter 104, and a speed converter 40 provided in the turbine controller 30
is output to. The output of the limiter 104 becomes the speed-up signal C1. The turbine controller 30 adjusts the amount of steam supplied to the turbine 31 from the turbine-driven water supply pump 7 to increase the speed of the turbine-driven water supply pump 7 to a predetermined rotational speed at a predetermined rate of increase.

(2) Pressure equalization control After the speed increase control is completed, the differential pressure between the water supply pump outlet header pressure and the discharge pressure of the turbine-driven water supply pump 7 is detected by the differential pressure detector 105, and the switch 106S! , limiter switch 107. The signal converter 108 is input to the high value priority circuit 110 via the compensator 109. The output Cz' of the high value priority circuit 110 is added to the bias 111 in an adder 122 to form a (T-BEP)/(M-BFP) switching signal Cz, which is applied to an adder 28 of the turbine-driven feed water pump flow rate control system.

The signal from the differential pressure detector 105 is positive when the flow rate passing through the check valve 41 is O, but becomes negative when a flow rate occurs, so it is used to cut the negative value and continue pressure equalization control. It will be done. The upper and lower limit values of the limiter 107 are both set to positive values.

That is, since the output signal of the differential pressure detector 105 is a value obtained by subtracting the pump discharge pressure from the discharge header pressure, the output signal approaches O from a positive value in the first half of pressure equalization control. When the pump discharge check valve 14 is opened and a flow rate passing therethrough is generated, the turbine pump discharge pressure becomes higher than the spout header pressure, and the differential pressure changes to a negative value. The reason why the lower limit value of the limiter 107 is set to a positive value is that if it becomes a negative value, the speed of the turbine-driven water supply pump will decrease.
This is a reverse operation of pressure equalization, and when the differential pressure approaches O, the switching signal Cx' also approaches O, the progress of pressure equalization control of the turbine-driven water pump becomes stagnant, and rapid operation cannot be achieved. This is to avoid the inconvenience of Note that the signal converter 108 determines a gain for converting a pressure signal into a control system signal.

(3) Switching Control As shown in FIG. 5, the switching change rate is programmatically limited by the water supply flow rate deviation signal 22. The signal from the switching rate of change setter 201 is sent to the switch 13S3° integrator 114. It passes through the limiter 115 and becomes the switching signal C3, which is added as a negative value to the input adder 116 of the motor-driven water supply pump flow rate control system, while the rate of change is limited by the individual limit program. The signal of the switching force setting device 202 is sent to the switch 135.
a.

Integrator 203. A switching signal C4 is generated through the limiter 204, and both pumps are switched.

The conditions for starting automatic water pump switching are that the water supply flow rate is 20% or more, one motor-driven water pump 8 is in operation, and the turbine 31 of the turbine-driven water pump 7 is ready for startup. . The water supply control system includes a water supply controller 26. All of the flow controllers 29.33 are automatic, and switches 81% and 321S3 are also open. The output of the water supply control 2G (water supply request value) 20 is input to the input adder 28 of the bottle-driven water supply pump flow rate controller 290.
There is a percentage, flow! Since signal 27 is 0, bias 11
1 is applied with -20%, the output of the adder 28 is 0, and the output of the flow rate controller 29 is also 0.7 On the other hand, the adder 1-161 on the motor-driven water supply pump side is the water supply control 2
There is a signal of 20% from 6, the flow rate signal 42 is 20%, and the water supply regulating valve 9 is controlled to a certain opening degree and is in a stable state.

The operating characteristics of each part (reactor water level, control No. 5, flow rate) of the embodiment shown in FIG. 1 are shown in FIG.

Referring to FIG. 6, the operation of the embodiment shown in FIG. 1 will be described in more detail.

Note that C2° is not shown in Figure 6 because C2 is 02'
Since this is the value added by the bias adder 122 to C2', it is a signal obtained by shifting C2', and the waveform itself is as follows.
This is to avoid complexity since there is no change in C2'.

(1) Speed-up control First, when the switch 102S1 is turned on manually or automatically, the speed-up signal C1 increases at a constant rate and becomes a limiter.
The pressure is increased to the upper limit value of 04, and pressure equalization control is performed. As a result, the rotation speed of the water supply pump driving turbine 31 increases and becomes constant.

The second rotational speed is about 60% of rated, and at this rotational speed the seven bomb discharge pressure is lower than the outlet header pressure and all pump discharge flow is flowing through the recirculation valve 34.

The Ku Bin control system 30 is configured such that when the output of the speed converter 40 reaches an upper limit value of a high speed limiter (not shown), it can be controlled by the hexagonal signal of the flow rate controller 29. The speed increase signal C1 should be set to a value slightly higher than the -J2 limit value of the high speed limiter.
The value of the speed increase rate setter 101 may be set to a desired turbine speed.

(2) Pressure equalization control When the turbine speed has settled to about 60%.

Switch 10eSz & manually or turn on. Switch 1-
When 06 is turned on, the discharge pressure of the turbine +Ei and the dynamic feed water pump is at a considerably lower level than the header pressure, so the differential pressure detector 1-05 outputs a differential pressure signal, and the L limit of the limiter 107 is activated. Signal converter that instantly rises above the value 1.
The output of 08 rises stepwise like C1oδ, but since the transfer function of compensation 9 and 09 is a first-order lag, the actual signal rises and falls slowly, resulting in a characteristic like C2'. This signal (Teng) is the high value priority cycle: the output C2,' of the Raku 110, that is, the output signal C2' of the limiter IJ-5 is selected as the high value signal. As the speed increases, the discharge pressure of the water supply pump driven by the turbine gradually increases, so the differential pressure signal that is the output of the differential pressure detector 105; and the c21 signal also decreases a little. .

, ′: Even if the differential pressure of
1) Is it necessary? - Already mentioned limiter]
, O7(7)-1' limit works effectively. In addition, increasing the F speed rate when the differential pressure at the discharge part of the bottle-driven water supply pump is large and decreasing the speed increase rate when the differential pressure is small will cause the opposite effect to occur as pressure equalization is completed. This is very effective in suppressing the increase in the flow passing through the stop valve and achieving pressure equalization control in a short time.

(3) At the point where the differential pressure at the discharge part of the switching control turbine-driven water supply pot becomes 0,
The check valve 41 opens and the flow rate is generated at 12.

At this point, it is assumed that the pressure equalization control has been completed, and the switch S3 is turned on manually or automatically when the differential pressure O or check valve flow rate occurs or when the φ stop valve opens.

The switching signal C4 integrates No. 111 of the switching change rate setter 202 and increases at a rate according to the water supply deviation up to the upper limit value of the limiter 204 (No. 'B').

On the other hand, for the motor instant water supply pump flow rate control system, the switching signal C8 integrates the signals of the switching change rate setters 1 and 12, and increases at a rate according to the water supply deviation until it reaches the upper limit of limiter 1 i-5. Since the input of the adder 1.3.6 becomes negative and the -CSS signal is applied, the flow rate of the motor-driven water supply pump immediately starts to decrease. On the other hand, for the turbine-driven feed water pump flow rate control system, the point 1 when the C4 signal becomes larger than the output signal C2' of the compensator 109. C8 is selected from , and Cz' becomes a ramp-like rising signal. During the time from when the switch S3 is closed until t,1, the flow rate of the check valve of the turbine-driven water supply pump begins to flow due to the acceleration of the pressure equalization control, so the water supply flow rate increases slightly. In consideration of the increase in the flow rate of the turbine-driven water supply pump due to this acceleration, the high value priority circuit 110 is useful for switching the pressure equalization control continuously and with little flow rate fluctuation, resulting in so-called bumpless switching.

After t1, the switching signal as shown in the middle part of FIG. 3 causes the motor-driven water feed pump flow rate to decrease and the turbine-driven water feed pump flow rate to increase, with almost no fluctuation in the water feed flow rate, and switching is executed. When the motor-driven water supply pump flow rate reaches O, a motor breaker (not shown) of the motor-driven water supply pump is shut off to complete the switching.

During this switching, as shown in FIG.
As a result of actually measuring the water supply fluctuation using means for programmatically limiting the switching rate, it was confirmed that it could be kept within ±2% (20 t/h). The switching rate of change is set for the turbine-driven water supply pump control system by limiting the rate of change from the predetermined rate of change R4 when the rate of change is above Pi when the feed water deviation is positive as shown in the rising rate of change signal C4, and setting it to zero when the rate of change is above Pz. By increasing the decreasing rate of change signal C3 of the motor-driven water supply pump control system from the predetermined rate of change Ra to Rat, the positive water supply deviation is corrected by the switching signal.

In addition, in the case of O negative water supply deviation, this is the opposite.

Furthermore, the control signal versus flow rate characteristics of the motor-driven feedwater pump control system and the turbine-driven feedwater pump IIJ control system are different, and separate rate of change settings are required.

According to the embodiment shown in FIG. 1, the following effects can be obtained.

1) Fluctuations in the water supply flow rate can be suppressed when switching between a turbine-driven water supply pump control system and a motor-driven water supply pump control system, and when switching from one turbine-driven water supply pump control system to two turbine-driven water supply pump control systems.

2) Load change during switching in 1), enthalpy change of oil/steam for driving the turbine-driven water pump.

Even when the water supply fluctuates due to the opening and closing of the recirculation valve, the switching change rate can be easily automatically set (corrected) to suppress the fluctuation, so even in the case of unpredictable bad switching conditions, it is possible to smoothly switch in a short time.

3) Since the increase in flow rate passing through the check valve that occurs when pressure equalization is completed can be suppressed by this water supply flow rate deviation, switching control can be performed before pressure equalization is completed, and switching can be performed in a short time. be.

As another example 1, when the deviation between the flow rate supply request value and the water supply pump discharge flow rate is small, the water supply pump switching change rate is set higher than the normal water supply pump switching rate to accelerate the switching, thereby allowing the switching to be completed quickly.

As another example 2, fluctuations in the water supply flow rate are corrected by adding and correcting a correction signal set in a program to the water supply pump switching signal that changes at a predetermined rate of change, depending on the deviation between the flow rate supply request value and the water supply pump discharge flow rate. can be kept to a minimum.

〔Effect of the invention〕

According to the present invention, by correcting the rate of change in switching between the increase in water supply by the turbine-driven water supply pump and the decrease in water supply by the motor-driven water supply pump in accordance with the deviation in the supply water flow rate, fluctuations in the supply water flow rate are minimized. A water pump automatic switching device capable of automatically switching the water pump at different times can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an automatic water pump switching device according to the present invention, FIG. 2 is a block diagram showing a conventional water pump switching system, and FIG. 3 is a detailed block diagram of FIG. 2.
FIG. 4 is a diagram showing the operation characteristics of each part of the embodiment shown in FIG. show. 9...Motor-driven water supply pump water supply adjustment area, 22...
Water supply flow rate deviation, 26... Water supply mask controller, 29°3
0...Each water supply pump flow rate controller, 33...Turbine driven water supply pump steam control valve, 201...Turbine driven water supply pump flow rate control system switching change rate setting device, 202...
Motor-driven water supply pump flow rate control system switching change rate setting device. Yu 1 and 1 a), Figure 3

Claims (1)

[Scope of Claims] 1. The water supply amount is determined by a motor-driven water supply pump and a turbine-driven water supply pump for supplying condensate to the steam generator, a flow rate supply request value on the steam generator side, and a discharge flow rate of the water supply pump. In the feed water pump automatic switching device that switches both pumps according to the heat output of the steam generator consisting of a control system that adjusts After performing pressure equalization control to bring the pressure closer to the discharge pressure of the turbine-driven water supply pump, an increase (decrease) signal whose rate of change is limited by the deviation between the flow rate supply request value and the discharge flow rate of the water supply pump is applied to the turbine-driven water supply pump system. At the same time, the rate of change is limited by a feed water flow rate deviation different from the rise (fall) signal, and the rate of change is limited (
An automatic water pump switching device comprising: a switching controller that outputs an increase) signal to the motor-driven water pump control system to decrease (increase) the amount of water supplied from the motor-driven water pump. 2. The water pump automatic switching device according to item 1, characterized in that the water pump switching change rate is accelerated by the deviation between the flow rate supply request value and the water pump discharge flow rate. 3. The water pump automatic switching device according to item 1, wherein the water pump switching signal is corrected based on the deviation between the flow rate supply request value and the water pump discharge flow rate.