JPS61190205A - Controller for turbine for driving feed water pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a device for controlling a turbine that drives a feed water pump used in a steam motor plant of a thermal power plant or the like.

[Background of the invention]

The control technology for this type of water pump drive turbine is as follows:
JP-A-58-133505 is known.

The above-mentioned known technology calculates the rotation speed equivalent to the water supply starting point based on the differential pressure between the system header pressure and the feed water pump system (RFP) outlet pressure to control the feed water pump of a power generation plant, etc. The configuration is configured to control speed increase,
When the speed has been increased to the water supply starting point Osho rotation speed, the water supply target rotation speed is switched to the water supply command from the water supply control device, and the water supply is stabilized.
This will lead to smooth water supply control. According to this known technology, when the target water supply rotation speed is switched to the water supply command of the water supply control device after completing the speed increase of the turbine for driving the water supply pump, a smooth transition to water supply control can be performed, but the water supply control device Fluctuations in system header pressure and water supply flow rate due to plant load fluctuations in manual operation, especially for plant operation in low flow ranges, are controlled manually by the operator. Stable control is difficult because the system must rely on operations or higher-level control devices such as computers and water supply control devices.

[Purpose of the invention]

The purpose of the present invention is to prevent B from changing the system head of the water supply system and fluctuations in the water supply flow rate due to plant load fluctuations, even if the water supply control device, which is a host control device, is in a manual state.
It is an object of the present invention to provide a BFP-T control device that can automatically follow the rotational speed of FP-'I' and perform stable water supply operation.

[Summary of the invention]

Next, the basic principle of the present invention will be briefly described.

The device of the present invention has a differential pressure/
A correction circuit on the water supply side is added, and when the plant load fluctuates while the water supply control device is under manual control, it detects the deviation between the system header pressure and the RFP outlet pressure and the fluctuation in the water supply flow rate, and corrects the RFP.

-The BFP-T can be adjusted by variable setting of the T target rotation speed.
Performs rotation speed tracking control.

In order to achieve the above object (automatic tracking of BFP-T during manual control of the feedwater control device) based on the above-mentioned principle, the turbine control device of the present invention has the following advantages: In the device for controlling the water supply, a means for detecting the system header pressure and a means for detecting the water supply pump outlet pressure is provided, an automatic calculator is provided for calculating the deviation between the two pressures, and a means for detecting the flow rate of the water supply is provided. 1. a circuit for controlling a feed water pump drive turbine based on the pressure deviation;
The present invention is characterized in that a circuit for controlling the water supply pump driving turbine based on the water supply pump flow rate is provided, and a circuit for switching between both of the control circuits is provided.

[Embodiments of the invention]

FIG. 2 is a piping system diagram of a water supply pump circuit for explaining a state in which a water supply system header pressure detection means and a water supply pump outlet pressure detection means are provided in an embodiment of the present invention.

The feedwater pump circuit of this example includes two turbine-driven feedwater pump series RFP-TI and RFP-T2, each of which includes a water supply pump 2 driven by a steam turbine 1, a check valve 50, and a stop valve 6o. A pressure detector 22 is provided.

BFP-M is a motor-driven water supply pump series, with motor 4
A water supply pump 2/1 check valve 70 and a stop valve 80 are provided.

The system header pressure detector 21 is used to supply boiler water to the water supply pump system header H that connects the above three systems in total, and after reaching the specified load, RFP-TI is activated and the water supply load is transferred to the BFP-T side. and then turn on the second B
Start up PP-T2 and take the water supply load (water supply amount) with the two BFPs.

FIG. 1 is a control block diagram in one embodiment of the present invention, and 21 and 22 shown in the lower right of this figure are the system header pressure detector and water pump outlet pressure detector explained in FIG. 2. It is.

The steam turbine 1 is directly connected to a water supply pump 2 to drive a shaft, and a gear 5 is provided at the end of the shaft. Steam flows into the steam turbine 1 through the high pressure regulating valve 3 and the low pressure regulating valve 4, rotates the turbine, and drives a directly connected pump. The rotational speed of the turbine is detected as a pulse train by speed detectors 6 and 7, and converted into a calculation signal by speed signal converters 8 and 9. In the true value selection 10, a value that is considered to be the true value is selected from the two speed signals. In true value selection, if the difference between the '2 signals is within a tolerance value, the higher value is determined to be the true value, and if the difference is greater than or equal to the tolerance value, the one with the smaller rate of change is selected as the true value. A selector like B is publicly known.

When the steam turbine 1 is started, the speed increase rate of the steam turbine is set by the speed increase rate setting circuit 20, and the deviation detection circuit 25 (hereinafter abbreviated as differential pressure or differential pressure detection circuit) between the BFP output pressure 32 and the stem header pressure 31. At , the turbine speed is increased until the differential pressure reaches the set tolerance value, and turbine rotational speed control is shifted to water supply control.

When the turbine rotation speed control shifts to water supply control, the turbine rotation speed is controlled by the water supply command 26 from the water supply control device 11, and the water supply command 26 is converted into a turbine speed signal by the signal conversion 12. The conversion characteristic includes a nonlinear function that corrects the nonlinear characteristic between the water supply signal and the turbine rotation speed. In the deviation calculation 13, a speed deviation is determined by comparing the speed signal and the speed true value from the true value selection 10. The speed deviation signal is calculated by the PI calculation 14, and as a result, the turbine drive steam control valve position command X is obtained by the control valve opening position conversion 28.

The turbine-driven steam control valve position command X is power amplified by an amplifier 16 and further converted into hydraulic pressure by an electro-hydraulic converter 17 to drive a hydraulic servo 18 .

Corresponding to the position of the hydraulic servo 18, the link mechanism 19 opens and closes the high pressure regulating valve 3 and the low pressure regulating valve 4.

The apparatus of this embodiment is provided with a correction circuit 15 shown at the left end of FIG. The detailed configuration of this correction circuit 15 will be described later with reference to FIG.

In FIG. 1, the above-mentioned correction circuit 15 and two types of signals input to the correction circuit 15 (broken line 23, solid line 24) are shown.
The components other than ) have a similar configuration to the control device in the prior art. In the prior art, the steam turbine 1 is
After increasing the turbine speed, water supply command 26 from water supply control device 11
However, when the water supply control device 11 is manually operated in the water supply control area] and the water supply flow rate fluctuates. For this reason, stable operation was particularly difficult near the water supply start point, near the water supply end point, and in low flow areas.

The above-mentioned correction circuit 15 installed in this embodiment focuses on the above-mentioned system header pressure fluctuations and water supply flow rate fluctuations, and even in the manual state of the water supply control device 11, regardless of plant load fluctuations, the correction circuit 15 The system is configured so that the deviation between the header pressure and the BFP outlet pressure or the water supply flow rate is kept constant at an arbitrary value, and the detailed configuration is shown in FIG.

Header pressure 31 and pump outlet pressure 32 shown in Fig. 3
are the signal outputs emitted from the pressure detectors 21 and 22 of FIG. 1, respectively. The differential pressure ΔP is calculated based on both of these signals.

11 shown in Fig. 3 is the water supply control device 1 shown in Fig. 1.
1, a manual operation command signal 23 for the correction circuit 15, a signal 23 representing the water supply flow rate Q, water supply: This correction circuit 15
11, PI calculation elements 103 and 104, and a differential pressure/water supply control switching circuit 105 are provided to satisfy both the differential pressure correction and water supply correction functions.

This correction circuit 15 is used only when the water supply control device 11 is in manual operation, and the changeover switch 203 is set to 0-1, and the rotation speed command is obtained by adding the correction amount to the water supply command.

Differential pressure correction is performed after RFP-T startup is completed until water supply starts, using water supply commands from the water supply control device 11 to keep the differential pressure ΔP constant against fluctuations in system header pressure due to increases (and decreases) in plant load. 26 is corrected and Lj
), the differential pressure setting device 101 sets ΔP at the completion of RFP-T startup.
If ΔP changes and becomes ΔP, then (Δ
By calculating the deviation of P-Δpt) by the PI calculator 103, the correction amount ΔS is added to the water supply command to control the turbine rotation speed. For differential pressure correction control, selector switch 200°2
02 is 0-1, and 201 is O-2.

The water supply flow rate correction is performed by setting the value of the water supply flow rate 24Q in the water supply flow rate setting device 102 during water supply operation using the BFP-T, and when the water supply flow rate changes to Q due to plant load fluctuations,
By calculating the deviation of (Q-Qi) in the PI calculator 201, the correction amount ΔQ is added to the water supply command and the turbine rotation speed is controlled. In the water supply correction control, the changeover switch 201 is set to the 0-2 state at O-1°200.202.

The differential pressure/water supply side setting device shall have a setting value variable function by manual operation 23, and in particular, the switching of the differential pressure/water supply correction function shall be performed smoothly near the water supply start and end points and in the low flow area. For the purpose of table control, by adding a differential pressure/water supply correction switching circuit 105 with differential pressure ΔP and water supply flow rate Q as parameters, and operating the changeover switches 200, 201, 202,
It is assumed that this can be done automatically by the BFP-T-EHG device alone. To switch from the differential pressure correction area to the water supply correction area,
Aiming at the water supply start point, the setting of the differential pressure setting device 101 is gradually brought closer to O, and when a predetermined amount of water or more is supplied, the system moves to the water supply correction region. To switch from the water supply correction area to the differential pressure correction area, the setting of the water supply setting device 102 is gradually brought closer to 0 (or minus), and when the differential pressure exceeds a preset certain amount, the transition is made to the differential pressure correction area. .

The above switching logic is configured by a differential pressure/water supply correction switching circuit.

In addition, in order to prevent a sudden change in the turbine rotation speed when switching the differential pressure/water supply correction circuit, the changeover switches 200 and 201 are used to tie each other's correction amount to the PI calculator (track it as an initial value), so that it is bumpless. The structure allows for shock-free switching.

FIG. 4 is a chart showing the operating state of the control device of this embodiment, in which the horizontal axis shows time, and the vertical axis shows water supply amount, water supply pressure, and turbine rotation, respectively.

In this embodiment, by adding a differential pressure/water supply correction circuit and a differential pressure/water supply correction switching circuit, the differential pressure or water supply flow rate can be kept constant even when the plant load fluctuates when the water supply control device is operated manually. Turbine speed, ) rotation speed follow-up control can be performed.

The differential pressure/water supply correction amount is the differential pressure fluctuation amount (ΔP−ΔP1
) or (Q-Q, This enables rotational speed follow-up control.

According to the present invention, the differential pressure/water supply side correction circuit and the differential pressure/water supply correction switching circuit are installed to deal with plant load fluctuations when the water supply control device is in manual mode.
It is possible to control the turbine rotation speed to keep the water supply flow constant, and in particular, it has enabled smooth control at the start and end points of the water supply and in low flow range operation in variable pressure plants where the system header pressure constantly changes.

Furthermore, since the differential pressure/water supply control function of the RFP-T control device alone has been established, interfaces such as computers and water supply control devices can be simplified by representing the entire system. Furthermore, RFP-T startup and water supply start can be treated as independent operations, and the components that can realize the stop operation with high reliability are configured as shown in Figure 5,
In addition, the correction circuit 15 shown in FIGS. 1 and 3 of this embodiment
There are known examples that do not have this. The known device is configured to be applied to a voltage transformation plant. In a pressure transformer plant, the system header pressure changes as the load changes, so the pump operating range changes over 50 to 100% of the rated rotation speed of the BFP-T. and bypass valve 50
1, and performs comprehensive RFP-T control by combining the opening/closing control of these valves and the rotation speed control of the turbine.

Compared to the above-mentioned known technology (FIG. 5), this embodiment has a control valve 5.
Since there is no need to provide a bypass valve 501 and a bypass valve 501, the equipment cost is low.In addition, high efficiency can be maintained because no throttling loss occurs on the discharge side of the water supply pump 2.

〔Effect of the invention〕

A means for detecting the force and a means for detecting the water supply pump outlet pressure are provided, an automatic calculator is provided for calculating the deviation between the two pressures, and a means for detecting the flow rate of the water supply is provided,
and a circuit for controlling the water supply pump drive turbine based on the pressure deviation and a circuit for controlling the water supply pump drive turbine based on the water supply pump flow rate;
By providing a circuit that switches both of the control circuits mentioned above, even if the water supply control device, which is a higher-level control device, is in manual mode, it is possible to prevent changes in the system head of the water supply system due to plant load fluctuations and fluctuations in the water supply flow rate. This has an excellent practical effect in that the rotation speed of the BFP-T can be automatically followed and stable water supply operation can be performed.

[Brief explanation of the drawing]

Fig. 1 is a control block diagram showing one embodiment of the turbine control device of the present invention, Fig. 2 is a piping system diagram around the water supply pump in the above embodiment, and Fig. 3 is details of the first correction path in the above I embodiment. The configuration diagram and FIG. 4 are also diagrams for explaining the functions and effects. FIG. 5 is a piping system diagram around a water supply pump according to a known technique. 1...Steam turbine, 2...Water pump, 3...
High pressure lid 14...PI calculator, 28...Turbine steam control valve opening position conversion, 16...Amplifier, 17...Electrohydraulic converter, 18...Hydraulic servo, 19...Link Mechanism, 12... Signal conversion, 15... Differential pressure/water supply correction circuit, 20... Acceleration rate setting circuit, 25... Differential pressure detection circuit, 23... Manual operation signal, 24... Water supply flow rate (BF'PI unit), 26... Water supply command, 21... System header pressure detector, 22... BFP output pressure detector 1... System header pressure, 32... BF
P outlet pressure, 30...Motor-driven water supply pump, 40
...Motor, 50...BFP outlet check valve, 60...
・BFP outlet stop valve, 70... Motor-driven water supply pump outlet check valve, 80... Motor-driven water supply pump outlet stop valve,
lOO...Water supply control device automatic signal, 101...Differential pressure setting device, lO2...Water supply setting device, 105...Differential pressure/
Water supply correction switching circuit, 103゜104...PI calculator,
200, 201, 202゜203... changeover switch,
500...BFP outlet control valve, 501...BF'P
Output bypass valve.

Claims (1)

[Claims] 1. In a device for controlling the rotation speed of a turbine that drives a feedwater pump of a steam power plant, a means for detecting the water supply system header pressure and a means for detecting the feedwater pump outlet pressure are provided, and the deviation between the two pressures is detected. An automatic calculator is provided for calculating the feed water flow rate, a means for detecting the flow rate of the feed water is provided, a circuit is provided for controlling the feed water pump driving turbine based on the pressure deviation, and a circuit for controlling the feed water pump driving turbine based on the water feed pump flow rate. What is claimed is: 1. A control device for a turbine for driving a water supply pump, characterized in that a circuit is provided, and a circuit for switching between both control circuits is provided.