JPS5984004A - Method of controlling number of revolution of feed 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 The present invention relates to a water pump rotation speed control system with good control characteristics.

Boiler feed water pumps in thermal power generation facilities and reactor feed water pumps in nuclear power generation facilities are often driven by steam turbines.

As part of the control of the steam turbine ij% boiler or nuclear reactor in which these bongs fg:WA are operated, the rotational speed is controlled, thereby controlling the water supply flow. That is, the desired amount of water supply is obtained by changing the rotational speed of the steam turbine based on a signal from the water supply control device of the boiler or nuclear reactor.

However, the speed control range of the steam turbine is wide, and the steam source for steam turbine operation is the main turbine's extraction air and j
This is difficult to control due to changes in vapor pressure and non-linear discharge of the water pump (ft, ft).

In particular, as will be described later, there are restrictions in that control is unstable in a low flow range and operation using fast liver control is not possible.

For this reason, in low flow areas, control has been switched to a water supply regulating valve or a motor-driven pump.

Control using such a water supply regulating valve has the problem of reduced efficiency due to throttling loss of the valve, and the pump switching operation has the problem of restrictions on switching time.

In addition, in conventional mechanical hydraulic control devices, the dead zone is large due to play in the lever system, the detection range of the speed governor as a rotation speed detector is narrow, and its characteristics are nonlinear. There were drawbacks such as inability to perform boiler water supply control well.

The present invention achieves improved performance by replacing the conventional mechanical-hydraulic control device with an electro-hydraulic control device. In addition to correcting the pressure fluctuation of the 1iIII steam source and improving the control characteristics,
Improves the water supply vs. speed characteristic, which has a high gain in the low flow area,
It is an object of the present invention to provide a system for controlling the rotation speed of a water supply pump, which is equipped with a device suitable for controlling a turbine for driving the water supply pump.

The gist of the present invention is to accurately obtain the remote command value of the water supply pump in accordance with the water supply demand value and the pump discharge pressure, and, if necessary, to obtain a turbine drive command value. The main feature is that the 1υ steam condition is fed back and the turbine control valve opening degree is corrected.

By adopting such a configuration, the present invention can appropriately control the water supply pump over a wide speed range including the low 11rt and volume range, where speed control could not be performed conventionally, and achieve stable water supply control overall response. This was done so that it would be done well.

An embodiment of the present invention will be described below with reference to the drawings.

Figure 1 is a block diagram of an embodiment of the present invention.

In the figure, a steam turbine 1 is directly connected to and drives a water supply pump 2, and a pawl 5 is provided at the shaft end of the steam turbine 1. Steam flows into the steam turbine 1 through the high pressure regulating valve 3 and/or the low pressure regulating valve 4, rotates the turbine, and drives the directly connected feed water pump 2.

The rotational speed of the turbine I is detected as a pulse train by speed detectors 6 and 7 disposed opposite to the gear 5, and converted into signals by speed signal converters 8 and 9. True value selector 10
selects the true value from the two long-circuit signals.

In the aforementioned true value selector 10, if the difference between No. 2 and No. 2 is within the allowable value, the true value is set as the true value, and if the difference is greater than or equal to the FF capacity value, the one with the smaller rate of change is 'ff nearer (, 94). Processing is performed.

The water supply request signal from the water supply control device 11 is converted into a signal by bt
2. On the other hand, the signal converter 12 is also supplied with the discharge pressure t'1 and the discharge pressure k from the discharge pressure detector 22 of the water supply pump 2. The signal converter 12 has a function of generating a two-variable function that uses the water supply request signal and the discharge pressure signal as two variables (scan) and outputs a required turbine rotation speed signal.

Fig. 6 1, Feed water flow ffWQ (horizontal axis) and discharge pressure 11p (
It is a pump characteristic diagram showing the relationship of l to JfilJ axis) and turbine speed (rating.As is clear from the figure,
It can be seen that the required water supply flow rate and discharge pressure υ, the turbine speed, and therefore the rotation speed of the water supply pump are uniquely determined.

In other words, if the turbine speed is N (%) and [7, the discharge pressure is Hp, and the water supply flow rate is WQ, then the turbine speed ff[Na, N= g (Hp
, WQ ) can be obtained using the two-variable function generation function.

1 - Conventionally, the pump discharge pressure signal is not used,
The turbine speed was determined only from the required water supply flow rate WQ.

That is, conventionally, an operating state in which the discharge pressure of the water supply pump 2 is kept constant has been assumed.

Therefore, especially in the low flow region, the gain in feedwater flow rate vs. speed is high, so if changes in discharge pressure are ignored, the corresponding turbine speed cannot be determined accurately, leading to unstable control system operation. The problem was that there was no.

The present invention eliminates the above-mentioned instability factors and enables operation even in a low flow rate range by adding a discharge pressure signal to obtain accurate turbine speed and water pump rotation speed. .

The deviation calculator 13 compares the speed signal with the rounded true value from the true value selector 10 to obtain a speed difference. The speed deviation signal is calculated by a PI calculator 14, and as a result, turbine drive steam flows M and Q are obtained.

The steam flow rate Q of the drive #h is converted into the υ hydraulic servo position X by the pressure corrector 15, and then power amplified by the amplifier 16. The signal X is further converted into oil pressure by an electro-hydraulic converter 17 and drives a hydraulic servo 18. Corresponding to the position of the hydraulic servo 18, the linkage mechanism 19 opens and closes the υ high pressure regulating valve 3 and the low pressure regulating valve 4.

On the other hand, a detector 20 detects the steam pressure at the inlet of the high pressure regulating valve 3.
Then, the low pressure steam pressure at the inlet of the low pressure regulating valve 4 is detected by the detector 2.
1 and sends the signal to the pressure correction 615 as a correction signal.

During normal operation, turbine 1 uses low-pressure steam extracted from the main turbine as driving steam, and only when the low-pressure steam pressure decreases and as a result, the driving force is insufficient, high-pressure steam from the main steam at the main turbine inlet is used as driving steam. υ11 steam is generated.

The high pressure regulating valve 3 and the low pressure regulating valve 4 correspond to the position X of the hydraulic servo 18 (7) and are opened and closed via link mechanisms 19. The structure is such that the high pressure regulating valve 3 is open.

The relationship of the steam flow MQ flowing into the turbine I with respect to the position X of the hydraulic servo 18 is shown in FIG.

As the position X of the oil pressure valve 18 increases from 0, the low pressure regulating valve 4 opens and the steam flow rate Q increases. At position X, the low pressure regulating valve is fully open and the maximum flow rate Q at the rated low steam pressure. is obtained.

When the position X of the hydraulic servo increases beyond X, the high pressure regulating valve 3 opens and the steam flow Stt further increases. When the high pressure regulating valve is also fully opened at the (~1) position of

Note that FIG. 2 shows the relationship when the inlet steam pressures of the high and low pressures are rated, and as is clear, when the pressures fluctuate, the ratio (PuL-r steam flow rate) to the pressure changes.

In addition, the method 1 to find with the digital controller used by the deceased
The bar is shown in Figure @5. Inside the controller, xa 'I and f are stored in advance as constants of the corner coordinates, and depending on the measured pressure py,,P)I, for each corner point, f, * Pt, / PLo + f * I) Pu/
By calculating Puo'Q', we can calculate the function form 'f:ii shown in Figure 3.This step was performed in parts 31 to 35 in Figure 4. It is the same as g-th γ.

Next e? , Ql with the turbine-driven steamship Q in between.

Q.? ++ ) + XI+H according to the hook type,
The hydraulic servo position layer jiH'I is set. This in-formula is a system called a linear complementary system II''1'.

This situation is shown in FIG. On the other hand, in order to correct the change in the steam flow rate in proportion to the pressure, a pressure corrector LSi (7) is installed in this embodiment. Turbine drive steam flow rate Q
From this, the hydraulic servo position X is calculated by g1.

*V3v,? :To do this, find the horizontal axis from the vertical axis in Figure 3, and this curve is the low pressure steam pressure PL,
Since the pressure vapor pressure changes with the vapor pressure, it cannot be determined using a -law function generator. FIG. 4 shows an example of a circuit obtained using an operational amplifier circuit.

The rated value (PLO+'Poo) shown in FIG. 3 is separated into two functions shown in FIG. 4(b), and the function generator 31
Have them calculate at ゜32. This value is the ratio of the actual pressure to the rated value Pt
, /pr,. , P+I/PHe to the power n, vessel 33.
By multiplying by 34 and adding by operational amplifier 35, the third
The function shown in the figure is found. In other words, Q can be found from %X, Pt, , Pn. By adding an operational amplifier 436 for calculating the inverse function to this circuit, 'Q + PL
tP) Assume that the circuit calculates X from I.

As described above, by adding all the various pressure corrections according to this embodiment, it is possible to obtain the accurate required rotation speed when the discharge pressure fluctuates, and at the same time, to calculate the required rotation speed completely before the result of steam pressure fluctuation appears in the rotation speed. By correcting the positions of ~ -, stable operation that is not affected by pressure fluctuations is realized.

In particular, when the load on the main turbine of a power plant is suddenly reduced due to a power transmission line accident, etc., and the plant is forced to run on its own, the power supply rotation speed in the low flow area is determined and the low pressure steam pressure σ) drop is detected. However, the high pressure control 1 (-) can be opened quickly. This makes it possible to secure the amount of water supply suitable for independent operation within the plant.

Note that it is naturally possible to use a normal servo mechanism or valve drive device in place of the above-mentioned hydraulic servo 18.

Further, the above-mentioned correction of the valve opening [1 target value] based on the turbine inflow steam pressure is not necessarily necessary, and may be omitted.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an embodiment of the present invention, Fig. 2 is a system diagram showing an embodiment of the present invention;
[An explanatory diagram showing the relationship between the servo position and the turbine inflow steam layer, FIG. 3 is an explanatory diagram showing the pressure correction characteristics in the embodiment of the present invention, and FIG. 4 (A). ←) is the pressure correction calculation hardware and its explanatory diagram in the implementation B-1 of the present invention, FIG. 5 ((), (b)
6 is an explanatory diagram of the pressure compensator, and FIG. 6 is an explanatory diagram showing the water supply distribution-discharge pressure characteristics of the water supply pump. ■...Turbine, 2...Water pump, 3...!
'jJFE control valve, Q 30 6th diagram→Continuation 1tiiovqノ

Claims (1)

[Claims] 1. The commanded speed of the water supply pump is determined based on the water supply demand value and the discharge pressure of the water supply pump, and the amount of steam supplied to the turbine that drives the water supply pump is adjusted and controlled based on the commanded speed. In the pump rotation speed control method, the turbine drive steam speed C is determined based on the deviation of the actual speed circle from the command speed, and
The rotational speed control of the water supply pump is characterized in that the steam flow rate is corrected by the turbine inflow steam pressure to determine the position of the steam control valve (e'Th), and the opening of the steam control valve (ff) is controlled based on the position of the steam control valve. Method.