JPS63205406A - Control device for turbine bypass valve - Google Patents

Abstract

PURPOSE:To make it possible to maintain pressure in a factory steam system stably, by memorizing the total flow of main steam in the normal operation and controlling a turbine bypass valve to make that total flow of main steam to flow into a turbine bypass line in the case of a turbine trip. CONSTITUTION:When a trip of a back pressure turbine 3 occurs in a steady operation of the back pressure turbine 3, an adjusting valve 2 is wholly closed by a control device which is not indicated in the illustration, a timer 74 is started and a switch 72 is changed over to (b) side during a certain time. In this time, a flow detector 8 detects zero of a steam flow and an output of an adder 752 which adds this detected signal to a signal which indicates a flow of turbine bypass steam and comes from an opening/flow converter 751, goes down drastically, but the above output is output to a turbine bypass valve 5 by the function of a delay unit 753 after being delayed a preset time. Thus the total flow of steam before the occasion of the turbine trip is allowed to flow into the turbine bypass line and a flow of steam to a factory steam system is maintained at a constant flow level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application) The present invention relates to a device for controlling a turbine bypass valve disposed in a bypass line of a back pressure turbine in a private power generation facility.

(Conventional technology) Figure 3 shows the configuration of a conventional private power generation facility.

In the figure, main steam taken out from a boiler 1 is supplied to a back pressure turbine 3 via a regulating valve 2.
After passing through the reheater 4, the exhaust steam is supplied to the factory steam system. The regulating valve 2 is gradually opened to a predetermined opening degree when the back pressure turbine 3 is started up, and the speed of the back pressure turbine 3 is increased. Opening/closing is controlled by a control valve control device (not shown).

By the way, the steam pressure supplied to the factory system must always be maintained at a constant pressure. For this reason, a turbine bypass line is provided with a turbine bypass valve 5 that allows the main steam from the boiler 1 to flow to the reheater 4 so as to keep the steam pressure constant especially when the back pressure turbine 3 is started up or tripped. provided. A pressure detector 6 is attached to the main steam side of the turbine bypass valve 5 to detect pressure.

When the back pressure turbine 3 is started, the turbine bypass valve control device 7 controls the opening and closing of the turbine bypass valve 5 by the arithmetic control circuit 71 so that the main steam pressure detected by the pressure detector 6 matches a set value. Boiler 1 is adjusted to supply the necessary amount of main steam to the factory steam system, so by controlling the main steam pressure to a constant value according to the set value, the steam pressure to the factory system can be kept constant. Retained.

On the other hand, after the back pressure turbine 3 is started, the turbine bypass valve 5 is fully open, so the main steam pressure is controlled by adjusting the opening degree of the regulating valve 2 by a control device (not shown). That is, if the amount of steam used in the factory decreases, the regulator valve 2 is adjusted in the closing direction, and if it increases, it is adjusted in the open direction to keep the factory steam pressure constant. At this time,
The output of the backpressure turbine fluctuates, but this is unavoidable, and in private power generation equipment, the main objective is to maintain a constant steam pressure on the factory side, and power generation is a secondary issue.

(Problems to be Solved by the Invention) However, according to the above conventional configuration, the back pressure turbine 3
When a trip occurs, the following problems occur. That is, the control valve 2 is fully opened by the lip to the back pressure turbine 1. The steam flow rate from the reheater 4 to the factory steam system decreases, and the steam pressure of the factory steam system tends to decrease. In order to prevent this, the turbine bypass valve 5 is opened by the turbine bypass valve control device 7 when the turbine trips. Pressure fluctuations occur. Therefore, in order to quickly open the turbine bypass valve 5, the switch 72 is switched to the opening setting device 73 side. At this time, the opening degree setting device 73 is fixedly set to an opening degree corresponding to the full opening of the turbine bypass valve 5.
As a result, the turbine bypass valve 5 is suddenly opened until it is fully open.

By fully opening this turbine bypass valve 5, main steam is supplied to the reheater 4 via the turbine bypass line, and normally, the pressure rise of the boiler main steam and the steam pressure drop to the factory steam system are prevented. become.

However, at this time, since the opening degree setting device 73 is set to a constant opening degree, for example, fully open, the turbine bypass valve 5 always opens from the fully closed state to that opening degree. As a result, if a turbine trip occurs during normal operating conditions, that is, when the turbine bypass valve 5 is fully open, the amount of steam used in the factory is low, and the steam flow rate of the back pressure turbine 3 is low, the factory system There is a problem in that increasing the steam flow rate of the steam increases the steam pressure.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a turbine bypass valve control device that does not cause pressure fluctuations in a factory system during a turbine trip.

[Structure of the Invention] (Means for Solving the Problems) Therefore, the present invention determines and stores the main steam flow rate flowing to the factory side during normal times, and when a back pressure turbine trip occurs, the main steam flow rate is changed to the main steam flow rate when a back pressure turbine trip occurs. Based on this, the opening degree of the turbine bypass valve is controlled, and the control of the turbine bypass valve is returned to feedback control after a certain period of time has elapsed.

(Function) At the time of turbine trip, the memorized main steam flow rate flows to the turbine bypass line, so the steam flow rate supplied to the factory steam system is maintained at a constant value and its pressure fluctuation is prevented, and after a certain period of time, the turbine bypass valve is returned to control based on the main steam pressure, so the turbine bypass valve is controlled according to fluctuations in the main steam pressure, and the steam pressure in the factory steam system is stabilized.

(Example) Hereinafter, one embodiment of the present invention will be described in detail.

FIG. 1 is a configuration diagram of a turbine bypass valve control device according to an embodiment of the present invention. In the figure, the arithmetic control circuit 7
1 is a pressure setting device 711.1 for setting a constant main steam pressure.
Consists of a subtracter 712 and an integral control calculator 713,
Turbine bypass valve 5 to maintain constant main steam pressure
This is a circuit that outputs an opening signal to control opening and closing.

The arithmetic control circuit 75 includes an opening/flow rate converter 751. which converts an opening signal to the turbine bypass valve 5 into a steam flow rate signal.
Adder 752. Consists of a delay device 753 for storing signal values for a certain period of time and a flow rate/opening converter 754 for converting the flow rate signal into a valve opening signal, which controls the opening and closing of the turbine bypass valve 5 when the back pressure turbine 3 trips. This is a circuit that outputs a signal.

The switch 72 switches the opening signal output to the turbine bypass valve 5, and the one-shot tire 74 controls the switch 72 for a certain period of time when the back pressure turbine 3 trips.

The turbine bypass valve control device of this embodiment is configured as described above, and a fixed amount of main steam necessary for the factory steam system is supplied from the boiler 1.

When starting up the back pressure turbine 3, the regulating valve 2 is closed and the turbine bypass valve 5 is opened, and the steam necessary for the factory system is supplied from the turbine bypass line. Here, the control valve 2 is gradually opened to increase the speed of the back pressure turbine 3. The main steam pressure that changes due to this starting operation is detected by the steam pressure detector 6. The subtracter 712 inputs the main steam pressure and the main steam pressure set in the pressure setting device 711, and outputs the difference between the two. The computing unit 713 controls and computes the deviation,
If the deviation is +, that is, the detected pressure is greater than the set pressure, an operation signal is output in the direction of opening the turbine bypass valve 5, and when the deviation is +, that is, the detected pressure is equal to or smaller than the set pressure, the closing operation signal is normally connected to the a side. It is output to the turbine bypass valve 5 via the switching device 72 that is connected to the turbine bypass valve 5. As a result, when the regulating valve 2 is opened and the back pressure turbine 3 is completely started, the detected pressure becomes equal to or less than the set pressure, and the turbine bypass valve 5 is completely closed and enters steady operation.

After the back pressure turbine 3 reaches a predetermined speed and enters steady operation, the regulator valve 2 is controlled to maintain the pressure of the factory steam system at a constant level by a regulator valve control device (not shown).

is controlled to open and close. The main steam pressure set value of the pressure setting device 711 is set at a constant value somewhat higher than the main steam pressure during steady operation, so during steady operation the output of the calculator 713 becomes 0 and the turbine bypass valve 5 is fully closed.

On the other hand, the opening/flow rate converter 751 inputs the opening signal output from the computing unit 713 and outputs the flow rate of steam flowing into the turbine bypass line based on this opening signal. Therefore,
While the back pressure turbine 3 is in steady operation, the output of the converter 751 is 0.
It is. The adder 752 inputs the steam flow rate of the turbine bypass line and the steam flow rate on the back pressure turbine side detected by the steam flow rate detector 8, and outputs the sum of both steam flow rates. Now, assuming that the sum of the steam flow rates is output as shown by the dashed line in Figure 2, the delay device 753 inputs a signal indicating the sum of the steam flow rates, delays it by a certain time T1, and outputs the signal as shown by the solid line in the figure. Output this signal as shown. The flow rate/opening degree converter 754 inputs the delayed output steam flow rate and outputs an opening degree signal for causing the steam flow rate to flow through the turbine bypass line. In other words, this opening degree signal indicates the opening degree of the turbine bypass valve 5 necessary to cause the amount of air flowing into the back pressure turbine 3 and the turbine bypass line to flow only through the turbine bypass line.

By the way, if a trip occurs in the back pressure turbine 3 while the turbine is being started, at this time the regulator valve 2 is controlled to be fully open by a control device (not shown), and the single shot timer 74 is started. The single shot timer 74 switches the switch 72 to the b side for a predetermined time T2 (T2<TI) after activation.

Now, if a turbine trip occurs at time L+, the flow rate of steam to the back pressure turbine 3 becomes zero. For this reason, as shown by the dashed line in FIG. 2, the signal input to the delay device 753 that indicates the airflow rate suddenly decreases in its entirety. However, since the output signal is output for time T1 as shown by the solid line, the flow rate/opening converter 754 outputs an opening signal corresponding to the air flow rate for 11 hours, and this opening signal is now input to the turbine bypass valve 5. Therefore, the total main steam flow rate before the turbine trip is passed through the turbine bypass line. Thereby, the steam flow rate to the factory steam system is maintained constant, and its pressure is also maintained constant.

On the other hand, after the turbine trip, the main steam pressure temporarily increases during the time required for the turbine bypass valve 5 to reach the opening degree corresponding to the total steam flow rate as described above. This main steam pressure is detected by the steam pressure detector 6, and the arithmetic control circuit 71 performs the above-mentioned calculation based on this main steam pressure, and calculates the amount necessary to flow the lifetime steam flow rate to the turbine bypass valve 5. The opening signal will now be output. Note that this calculation is performed by the calculation unit 713.
Since this is performed by an integral operation, it takes a certain amount of time until this opening degree signal value is obtained. The single shot timer 74 returns the switch 72 to the a side when the time T2 has elapsed. At this time, if this time T2 is set longer than the calculation time, an opening signal of approximately the same level is input to the turbine bypass valve 5, and the steam flow rate is maintained approximately constant.

Next, assume that the back pressure turbine 3 trips during steady turbine operation. In this case, before the trip occurs, the arithmetic controller 71 outputs the opening signal at zero level in order to fully open the turbine bypass valve 5. However, in this case as well, after the turbine trip occurs, the switch 72 is switched to side b, and the turbine bypass valve 5 is opened to the opening corresponding to the lifetime steam flow rate before the turbine trip, and the factory steam system is opened. Steam flow rate is held constant. Further, after the predetermined time T2 has elapsed, the switch 72 is switched to the a side.

As a result, even if the main steam pressure from the boiler 1 changes thereafter, the turbine bypass valve 5 is controlled by the arithmetic control circuit 71 accordingly, so that the pressure in the factory steam system is maintained stably. Become.

As described above, in this embodiment, the steam flow rate detector 8 for detecting the steam flow rate of the back pressure turbine 3 is provided, and the lifetime steam The flow rate is calculated and the value is sent to the delay circuit 7.
53, the turbine bypass valve 5 is stored for a certain period of time T+, and at the time of turbine trip, the switch 72 is switched to control the turbine bypass valve 5 so as to flow the stored lifetime steam flow rate, during which a certain period of time T2 (T2<TI) has elapsed. After that, the control by the original arithmetic control circuit 71 is returned to by the single shot I--evening--11-timer 74.

As a result, even during a turbine trip, the previous main steam flow rate is maintained, thereby preventing pressure fluctuations in the factory steam system.

In this embodiment, the main steam total flow rate is determined based on the opening degree of the turbine bypass valve 5 and the steam flow rate of the back pressure turbine 3. Similar control can also be performed by providing a flow rate detector for detecting the total steam flow rate. Further, although the total flow rate of main steam is stored in the delay device 753, it is of course possible to use a memory circuit.

[Effects of the Invention] As described above, according to the present invention, the lifetime steam flow rate is stored during normal times, and the turbine bypass valve is controlled so that the lifetime steam flow rate flows through the turbine bypass line when the turbine trips. Since the amount of steam supplied to the factory steam system is always constant, its pressure fluctuations are reduced, and the control of the turbine bypass valve is returned to control based on the main steam pressure after a certain period of time, so it is less susceptible to fluctuations in the main steam pressure. However, the pressure in the factory steam system becomes stable.

[Brief explanation of the drawing]

Fig. 1 is a block configuration diagram of a private power generation facility to which a turbine bypass valve control device according to an embodiment of the present invention is applied, Fig. 2 is an explanatory diagram showing input and output signals of a delay device, and Fig. 3 is a conventional private power generation equipment. FIG. 2 is a block configuration diagram of power generation equipment. DESCRIPTION OF SYMBOLS 1... Boiler, 2... Control valve, 3... Back pressure turbine, 4... Reheater, 5... Turbine bypass valve, 6
... Steam pressure detector, 7... Turbine bypass valve control device, 8... Steam flow rate detector, 7], 75... Arithmetic control circuit, 72... Switch, 73... Open Degree setting device, 74... Single shot timer, 711... Pressure setting device, 712... Subtractor, 713... Arithmetic unit,
751...Opening degree/flow rate converter, 752...Adder,
753...Delay device, 754...Flow rate/opening converter. Agent Patent Attorney Crest 1) Makoto.

Claims (1)

[Claims] The deviation between the boiler main steam pressure set value set on the pressure setting device and the boiler main steam pressure detected value detected by the pressure detector is controlled and calculated by the calculation means, and the output is sent to the bypass line of the back pressure turbine. A turbine bypass valve control device that controls steam pressure to a factory steam system at a constant level by adjusting the opening degree of a provided turbine bypass valve includes a storage means for temporarily storing a boiler main steam flow rate, and a storage means for temporarily storing a boiler main steam flow rate; A flow rate/opening degree conversion means for converting the boiler main steam flow rate into a turbine bypass valve opening degree, and a switching means for switching an output for adjusting the turbine bypass valve opening degree from the calculation means to the flow rate/opening degree conversion means. A turbine bypass valve control device characterized by: