JP2002129908A - Water level control method for steam turbine condenser - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a water level control method of a condenser which can withstand sudden disturbance of steam load fluctuation. SOLUTION: A water level change of a condenser 1 is constantly monitored, and when there is no large steam load fluctuation and a process value is within a normal control range, a water level level signal PV measured by a condenser level transmitter 6 is used. If the process value deviates from the steady-state control range based on the PID control based on the PID control, the condensate increase / decrease per unit time is calculated from the level change per unit time to compensate for the increase / decrease. The required increase / decrease of the opening of the condenser level control valves 7 and 8 is obtained, and this is corrected.
Add to the opening output value MV in constant value control as mv (MV + mv)
In addition, the water level control of the condenser which can endure sudden disturbance of steam load fluctuation is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a water level of a steam turbine condenser in a steam power plant, and more particularly to a level control of a steam turbine condenser in a steam power plant or the like where a large steam load fluctuation is expected to occur. It is about the method.

[0002]

2. Description of the Related Art In general, in water level control of a steam turbine condenser, a water level is measured by a transmitter, and constant value control is often performed by simple PID control. For this reason, there is no major problem when operating with a constant steam load, but if a sudden large load change occurs, the PID
The control alone could not absorb the disturbance, necessitating manual water level adjustment of the condenser by manual intervention of the operator, and it was difficult to perform stable level control.

FIG. 2 shows a steam / water balance system of a steam turbine. In this example, the condensing steam turbine 3,
Although only one back pressure steam turbine 4 and one boiler 17 are illustrated, a plurality of facilities are actually connected. In FIG. 2, the high-pressure steam produced by the boiler 17 is distributed through a high-pressure steam receiver 18 and supplied to the condensing steam turbine 3 and the back-pressure steam turbine 4. The steam supplied to the back-pressure steam turbine 4 drives a generator 5 to collect a part of the steam energy as a power generation amount, and sends the reduced pressure steam to various parts of the factory as factory steam.

On the other hand, after the steam from the high-pressure steam receiver 18 is supplied to the steam condensing turbine 3 and used while measuring the flow rate by the turbine inlet steam flow meter 19, the steam is supplied to the condenser 1 and condensed into water. Is done. The water in the condenser 1 is pressurized by the condensate pump 10 and the flow rate is adjusted by the condensate flow control valve 11.
The flow rate is supplied to the condensate mother pipe 12 while being measured by the condensate flow meter 21. Further, the water supplied from the condensate main pipe 12 to the deaerator 13 is subjected to a deaeration treatment of water, and the water from which dissolved oxygen has been removed passes through a low-pressure water supply pipe 14, and is pressurized by a water supply pump 15,
The high-pressure water supply pipe 16 enters the high-pressure water supply pipe 16, from which water is again supplied to the boiler 17 to produce high-pressure steam.

[0005] Here, when a load fluctuation occurs in the factory steam supplied to various parts of the factory, the amount of steam generated by the boiler 17 changes, and this is caused by the high-pressure water supply pipe 16 and the low-pressure water supply pipe 1 one after another.
4.Appears as a change in the pressure of the condensate main pipe 12, and the condensate flow control valve 1
Even if the opening degree of 1 is constant, the amount of water flowing into the condensate mother pipe 12 changes due to a change in the differential pressure before and after the valve. Condensing steam turbine 3
In order to keep the water level of the condenser 1 generated by the steam supplied from the condenser constant, the water level of the condenser 1 is measured by the condenser level transmitter 6. The obtained water level signal PV is input to the condenser level control controller 9, where the PID calculation is performed based on the deviation from the set water level SV, whereby the valve from the condenser level control controller 9 is opened. Make-up valve 7 (open when supplying water from condenser 2 to condenser 1) or spill valve 8 (collect water from condenser 1 to condenser 2) The opening amount MV of the condenser 1 is controlled to increase or decrease the water in the condenser 1 so as to maintain the steam balance.

[0006] In such a control method, when the operation is performed with a constant steam load, there is no major problem in operation even if the steam load is not adjusted by the operator with respect to the load fluctuation of the factory steam. However, when the high-pressure steam supplied to the high-pressure steam receiver 18 suddenly fluctuates greatly due to a trip of the boiler 17 or the like, it is necessary to increase or decrease the inlet steam flow rate of the recuperator 3 in order to compensate for the excess or deficiency of the steam. As a result, it is assumed that the water level control of the condenser 1 will be temporarily unstable, and in some cases, the water level of the condenser 1 will drop and the condensate vacuum will be broken, leading to a trip of the equipment. Is done.

If the load fluctuation can be predicted in advance, the operator is put on standby and the condenser 1 by manual intervention is put on standby.
It is possible to adjust the water level, but the operator's response to unpredictable load fluctuations such as trips of equipment connected to the system is delayed, and the water level of the condenser 1 drops, and the vacuum of the condenser 1 is reduced. There was also a problem that the steam turbine 3 was destroyed and tripped, which greatly affected the operation.

[0008]

As a countermeasure, all the balances of the condensate to the condenser 1 are measured, and the output of the condenser level control controller 9 is corrected in a feed-forward manner according to the deviation. (Refer to Japanese Patent Publication No. 62-61877), however, this method requires measuring all the flow related to the balance to the condenser 1, so the equipment cost of the transmitter etc. Is expensive.
Usually, the steam flow rate measured by the turbine inlet steam flow meter 19 and the condensate flow rate measured by the condensate flow meter 21 are often measured, but the make valve 7 for controlling the water level of the condenser 1 and The flow rate passing through the spill valve 8 and the extraction flow rate 20 extracted from the middle stage of the condensing steam turbine 3 are as follows:
Since the transmitter for measurement is expensive and the equipment cost increases, it is often omitted without measurement.

The present invention has been made in order to solve the above problems.
When high-pressure steam fluctuates significantly, the control level is corrected by calculating the correction amount of the level control from the change level of the water level of the condenser to improve controllability and controllability of the water level level without investing expensive equipment costs. It is an object of the present invention to provide a method for controlling a water level of a steam turbine condenser capable of improving the water level.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention monitors a water level change of a steam turbine condenser by a water level transmitter, and recovers water from a surge tank based on a measured value of the water level. In the water level control method of the steam turbine condenser that calculates the opening amount of the condenser level control valve that supplies and discharges water to the condenser and performs constant value control by PID control, when the water level deviates from the steady control range,
Calculate the condensate increase / decrease per unit time based on the level change per unit time obtained from the measured water level, and open the condenser level control valve required to compensate for this condensate increase / decrease Determining the amount of increase or decrease, adding this amount of increase or decrease to the amount of opening in the constant value control, and controlling the condenser level control valve by the obtained corrected amount of opening. It is a control method.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.
This will be described in detail with reference to FIG. Note that the steam / water balance system of the steam turbine according to the present invention is the same as that shown in FIG. The water level control circuit of the condenser according to the present invention,
There are two routes: a steady circuit route including a steady circuit 22 for performing simple PID control, and an abnormal circuit route including a condenser level monitoring circuit 23 and a condenser level control output correction circuit 24.

In the steady operation, the water level change of the condenser 1 is constantly monitored by the condenser level transmitter 6, and when there is no large steam load fluctuation, the condenser is controlled by the stationary circuit 22 which performs simple PID control. You. That is, the water level signal PV measured by the condenser level transmitter 6 is received by the condenser level control controller 9, where the calculation is performed based on the deviation between the water level signal PV and the set water level SV, An operation command signal is transmitted to a make valve 7 or a spill valve 8 (see FIG. 2) provided as a condenser level control valve. The opening degree of the make valve 7 or the spill valve 8 is proportionally, integrated and differentiated (PID) according to an operation command signal from the condenser level control controller 9, and constant value control is performed using the obtained steady-state opening amount MV. The steam balance is maintained by increasing or decreasing the water in the water dispenser 1.

On the other hand, if there is a large steam load fluctuation and the process value of the water level of the condenser 1 deviates up and down from the steady control range, the condenser 1 measured by the condenser level transmitter 6 Is subjected to moving average processing, and the level signal obtained by filtering the fine level fluctuation is input to the condenser level monitoring circuit 23. In the condenser level monitoring circuit 23, the received water level signal falls outside the steady-state control range deviating from the threshold set above and below the level control target value, that is, the upper limit control start line and the lower limit control start line of the water level. Detect the situation that occurred, and confirm that a large steam load fluctuation occurred. At this time, from the level change amount per unit time (mm), the condensate increase / decrease amount (m ³ ) flowing into and out of the condenser 1 per unit time is calculated, and the signal is converted to a condenser level control output correction circuit 24. Send to

For example, as shown in FIG. 1, when the filtered water level signal falls off the lower limit control start line, the condensate reduction amount per unit time is calculated from the level change amount per unit time. The signal is transmitted from the condenser level monitoring circuit 23 to the condenser level control output correction circuit 24. The conversion from the condenser level change per unit time (mm) to the condensate increase / decrease per unit time (m ³ ) is calculated in advance from the shape of the condenser 1 with the condenser water level. It is preferable to plot the relationship with the amount of condensed water and use it.

The condenser level control output correction circuit 24 uses the condensate increase / decrease amount per unit calculated by the condenser level monitoring circuit 23 to calculate the condenser per unit time required to operate the same amount. The amount of increase / decrease of the opening of the water level control valve, that is, the make valve 7 and the spill valve 8 is calculated. The conversion of the condensate increase / decrease amount to the opening / decrease amount of the make valve 7 and the spill valve 8 is performed by calculating the Cv value (capacity coefficient) of the condenser level control valve in advance and operating the make valve 7 and the spill valve 8 amount(%)
And the condensate increase / decrease (m ³ ) are plotted and obtained, and the condensate control valve (make valve) required to compensate for the condensate increase / decrease due to the water level change of the condenser 1 using this is obtained. 7. The amount of increase / decrease mv of the opening of the spill valve 8) can be obtained by inverse calculation.

The relationship between the valve operation amount (valve opening) and the condensate increase / decrease amount (flow rate) is based on the assumption that the differential pressure across the valve is constant.
The relationship between the Cv value and the flow rate passing through the valve is as follows:
The relationship between the Cv value and the valve opening can be determined in advance because it can be known from the characteristic table.

[0017]

(Equation 1)

The output of the opening degree increase / decrease amount mv is added to an adder 25.
Is added to the opening amount MV in the constant value control by simple PID calculation, and the make valve 7 or the spill valve 8 is controlled in accordance with the obtained corrected opening amount (MV + mv). Increase or decrease to maintain steam balance. As a result, the control of the condenser level is improved by correcting the increase or decrease of water only when a large steam load fluctuation occurs. Accordingly, in the condensing steam turbine 3, even when a large steam load fluctuation occurs, the operation output of the water level control is controlled in a feed-forward manner, so that no equipment trip occurs.

[0019]

As described above, according to the present invention, the change in the water level of the steam turbine condenser is constantly monitored, and if there is no large fluctuation in the steam load, the water level is measured by the condenser level transmitter. Normal PI
Performs constant value control by D. When the process value deviates up and down from the steady control range, the condensate increase / decrease amount per unit time is calculated from the level change amount per unit time, and the condenser level control required to compensate for the increase / decrease amount By calculating the amount of increase or decrease of the valve opening and adding that value as a correction amount to the output value of constant value control by PID control, low-level water level control that can withstand sudden disturbances due to steam load fluctuations can be constructed at low cost. It becomes possible. In addition to the stable operation of the equipment, there is also an effect of reducing the work load by adjusting the operator.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a condenser level control system of a steam turbine according to the present invention.

FIG. 2 shows steam and steam of a steam turbine according to the present invention and a conventional steam turbine.
It is explanatory drawing which shows a water balance system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Condenser 2 Surge tank 3 Condensing steam turbine 4 Back pressure steam turbine 5 Generator 6 Condenser level transmitter 7 Make valve 8 Spill valve 9 Condenser level control controller 10 Condensate pump 11 Condensate flow control valve 12 Condenser main pipe 13 Deaerator 14 Low-pressure water main pipe 15 Feed pump 16 High-pressure water main pipe 17 Boiler 18 High-pressure steam receiver 19 Turbine inlet steam flow meter 20 Bleed flow 21 Condensate flow meter 22 Steady-state circuit 23 Condenser level monitoring Circuit 24 Condenser level control output correction circuit 25 Adder

Claims (1)

[Claims] 1. A water level changer of a steam turbine is monitored by a water level transmitter, and a degree of opening of a condenser level control valve for supplying and discharging water from the surge tank to the condenser is calculated based on the measured value of the water level. When the water level deviates from the steady control range, the level change per unit time calculated from the measured water level when the water level deviates from the steady control range. The condensate increase / decrease amount per unit time is calculated based on the calculated condensate increase / decrease amount of the condenser level control valve necessary for compensating the condensate increase / decrease amount, and the opening degree increase / decrease amount in the constant value control is calculated. A method for controlling a water level of a steam turbine condenser, wherein the condenser level control valve is controlled by adding the corrected opening degree to the opening degree.