JP2012159024A - Method for controlling water level of steam turbine condenser - Google Patents

Abstract

The present invention provides a water level control method for a steam turbine condenser that can withstand sudden and sudden disturbance of steam load fluctuations.
A deviation signal between an inlet steam flow rate of a steam turbine measured by a turbine inlet steam flow meter and a condensate flow rate measured by a condensate flow meter in a condenser level control output correction circuit is obtained. The condenser level control valve is converted into a condenser level control correction amount mv corresponding to the opening amount of the condenser level control valve, and added to the output MV of PID control in which the steady-state circuit 22 performs constant value control. To control.
[Selection] Figure 2

Description

  The present invention relates to a water level level control method for a steam turbine condenser, and more particularly to a water level control method for a steam turbine condenser in a steam power plant or the like where a large steam load fluctuation is expected.

  In general, in the water level control of a steam turbine condenser, the water level of the condenser 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 the steam load is operating at a constant level. However, when a large steam load fluctuation occurs suddenly, the disturbance cannot be absorbed by the PID control alone. It is difficult to perform stable level control because the water level of the vessel needs to be adjusted.

  Moreover, as shown in Patent Document 1, the level of the condenser is constantly monitored, and after the level change amount per unit time becomes large, the output correction of the condenser level control is performed to cause sudden disturbance. There is also known a water level control method for a condenser that can withstand this.

JP 2002-129908 A

  As described above, with the conventional control method, there is no major problem when the steam load is operating at a constant level. However, when a large fluctuation in the steam load occurs suddenly, the condenser is manually operated by the operator. It is necessary to adjust the water level. Here, if such load fluctuations can be predicted in advance, it is possible to wait for the operator in advance and respond to the water level adjustment of the condenser by manual intervention, but the equipment connected to the system The operator's response is delayed for unpredictable load fluctuations such as trips, and the water level of the condenser falls, causing the vacuum of the condenser to break and tripping the steam turbine, greatly affecting operations. There was also a problem.

  In addition, the method disclosed in Patent Document 1 is superior in responsiveness to sudden disturbances compared to the conventional technique. However, after the condenser level changes, the condenser level control output correction is performed. For this reason, if the change rate of the disturbance is abrupt, the level control may not be in time and the steam turbine may be tripped.

  The present invention has been made in view of the above, and an object of the present invention is to provide a water level level control method for a steam turbine condenser that can withstand sudden and sudden disturbances in steam load fluctuations.

  In order to solve the above-described problems and achieve the object, a water level control method for a steam turbine condenser according to the present invention monitors a change in the water level of the steam turbine condenser by a water level transmitter. In a water level level control method for a steam turbine condenser that performs constant value control by PID control by calculating an opening amount of a condenser level control valve that supplies and drains water from a surge tank to a condenser based on a measured value, Condenser level control correction corresponding to the amount of opening of the condenser level control valve, based on the deviation signal between the steam flow rate measured by the steam flow meter and the condensate flow rate measured by the condensate flow meter The condenser level control valve is controlled by converting it into a quantity and adding it to the output of the PID control performing the constant value control.

  According to the present invention, the deviation signal between the steam flow rate and the condensate flow rate of the steam turbine is constantly monitored, and the condenser level control correction amount is obtained by multiplying the deviation signal by the capacity conversion coefficient of the condenser level control valve. The steam turbine condensate that can withstand sudden and sudden disturbances in steam load fluctuations because the condenser level control valve is controlled by adding to the output of PID control performing constant value control. A water level control method for the vessel can be provided.

FIG. 1 is a schematic system diagram showing a steam / water balance system of a steam turbine in the present embodiment. FIG. 2 is a schematic system diagram showing an extracted condenser level control circuit of the present embodiment.

  Hereinafter, an embodiment of a water level control method for a steam turbine condenser according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. FIG. 1 is a schematic system diagram showing a steam / water balance system of a steam turbine in the present embodiment. In this example, only one unit of the condensate steam turbine 3, the back pressure steam turbine 4 and the boiler 17 is depicted, but actually, a plurality of facilities are connected. The high pressure steam produced by the boiler 17 is distributed via a high pressure steam receiver 18 and supplied to the condensate 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 decompressed steam as factory steam to various places in the factory.

  On the other hand, after the steam from the high-pressure steam receiver 18 is supplied to the condensate steam turbine 3 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. The water in the condenser 1 is boosted by the condensate pump 10, the flow rate is adjusted by the condensate flow rate control valve 11, and supplied to the condensate mother pipe 12 while measuring the flow rate by the condensate flow meter 21. Further, the water supplied from the condensate mother pipe 12 to the deaerator 13, where the water is deaerated and the dissolved oxygen is removed, the water is boosted by the feed pump 15 through the low-pressure feed water pipe 14, and the high-pressure feed water is supplied. The mother pipe 16 is entered, and from there, the boiler 17 is again supplied with water to produce high-pressure steam.

  Here, when a load fluctuation occurs in the factory steam supplied to each place in the factory, the amount of steam generated in the boiler 17 changes, which in turn changes to the high-pressure water supply mother pipe 16, the low-pressure water supply mother pipe 14, and the condensate mother. Even if the condensate flow rate control valve 11 has a constant opening, the amount of water flowing into the condensate mother pipe 12 changes due to the differential pressure change before and after the valve. In order to keep the water level of the condenser 1 generated by the steam supplied from the condenser steam turbine 3 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 PID calculation is performed based on the deviation from the set water level SV, thereby opening the valve from the condenser level control controller 9. Make valve 7 (opened when water is supplied from the surge tank 2 to the condenser 1) or a spill valve 8 (recovers water from the condenser 1 to the surge tank 2) as a condenser level control valve according to the operation command The opening amount MV of the condenser 1 is controlled to increase and decrease the water in the condenser 1 to maintain the steam balance.

  For this reason, when operating with a constant steam load, there is no major operational problem even if the operator does not adjust the steam load in response to fluctuations in the factory steam load. However, when the high-pressure steam supplied to the high-pressure steam receiver 18 suddenly changes 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 condensate steam turbine 3 in order to compensate for the excessive or insufficient steam. It is assumed that the water level control of the condenser 1 will become unstable temporarily, and in some cases, the water level of the condenser 1 will drop, the condensate vacuum will be broken, and the equipment will trip. Is done.

  Therefore, in this embodiment, a condenser level control circuit is provided. FIG. 2 is a schematic system diagram showing an extracted condenser level control circuit of the present embodiment. The condenser level control circuit of the present embodiment includes a steady circuit route including a steady circuit 22 that performs simple PID control, and an abnormal circuit route including a condenser level control output correction circuit 23.

  In the steady operation, the water level change of the condenser 1 is always monitored by the condenser level transmitter 6, and when there is no large steam load fluctuation, it is controlled by a steady circuit 22 that performs simple PID control. That is, the water level signal PV measured by the condenser level transmitter 6 is received by the condenser level control controller 9, where 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 the make valve 7 or the spill valve 8 arranged as a condenser level control valve. The opening of the make valve 7 or the spill valve 8 is proportionally, integrated and differentiated (PID) by the operation command signal from the condenser level control controller 9, and the constant value control is performed with the obtained steady opening MV, The steam balance is maintained by increasing or decreasing the water in the condenser 1.

  On the other hand, when there is a large steam load fluctuation, an abnormal circuit route including the condenser level control output correction circuit 23 is used together. In the condenser level control output correction circuit 23, the calculator 24 constantly monitors the deviation between 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. Then, referring to the conversion table 25, the deviation signal is converted into a condenser level control correction amount mv corresponding to the opening amount of the condenser level control valve (make valve 7 or spill valve 8). This condenser level control correction amount mv is based on the valve opening degree during normal operation of the condenser level control valve (make valve 7 or spill valve 8) as a reference, and the steam corresponding to the steam deviation signal is determined from that position. A condenser level control valve (make valve 7 or spill) necessary for eliminating the level change of the condenser 1 due to the change of the steam flow rate is obtained in advance by obtaining a valve opening amount necessary for varying the flow rate. It is calculated to be the operation amount of the valve 8). Therefore, a deviation-condenser level control correction amount conversion table 25 is created in advance, and is referred to in order to convert the deviation signal into a condenser level control correction amount.

  The condenser level control correction amount mv calculated in this way is added by the adder 26 to the output MV of the PID control performing the constant value control, and the condenser 1 of the condenser 1 when a large steam load fluctuation occurs. Controllability of level control is improved. As a result, the condensate steam turbine 3 feeds forward because the operation output of the water level control of the condenser 1 is controlled in a feed-forward manner even when a sudden and sudden large steam load fluctuation occurs. It is possible to continue operation without any problems. In addition to the stable operation of the equipment, there is an effect of reducing the workload by adjusting the operator.

1 Condenser 2 Surge Tank 3 Condensed Steam Turbine 6 Condenser Level Transmitter 7 Make Valve 8 Spill Valve 19 Turbine Inlet Steam Flow Meter 21 Condensate Flow Meter 23 Condenser Level Control Output Correction Circuit

Claims (1)

The water level change of the steam turbine condenser is monitored by a water level transmitter, and the opening amount of the condenser level control valve that supplies and drains water from the surge tank to the condenser is calculated based on the measured value of the water level. In a water level control method of a steam turbine condenser that performs constant value control by control,
The deviation signal between the steam flow rate at the inlet of the steam turbine measured by the turbine inlet steam flow meter and the condensate flow rate measured by the condensate flow meter is used as a condenser level corresponding to the opening amount of the condenser level control valve. A water level level control method for a steam turbine condenser, wherein the condenser level control valve is controlled by converting into a control correction amount and adding to the output of the PID control performing the constant value control.

Images