JPS6149487B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a gas turbine device, an exhaust heat recovery boiler that generates steam using the heat of the gas turbine exhaust gas, and a steam turbine device that is driven by the steam emitted from the boiler. This relates to initial pressure control switching for a steam turbine in a combined cycle plant.

First, the general configuration of a combined cycle plant will be explained with reference to FIG.

A combined cycle plant generally includes one or more gas turbine devices 1, the same number of exhaust heat recovery boilers 11 as the gas turbine devices, and one steam turbine device 40. The gas turbine device 1 includes a compressor 2, a combustor 3 that generates high-temperature, high-pressure combustion gas by burning fuel sent from a fuel pipe 4 using air pressurized by the compressor 2, and a combustor 3 that is driven by the combustion gas. and a gas turbine 5 that rotates a gas turbine generator 6. Combustion gas discharged from this gas turbine device 1 is guided to an exhaust heat recovery boiler 11 through an exhaust gas duct 7. Further, the exhaust gas duct 7 is provided with a bypass duct 10 that bypasses the exhaust heat recovery boiler 11, and the exhaust gas duct 7 and the bypass duct 10 are provided with a boiler inlet damper 8 and a boiler bypass tamper 9, respectively, that adjust the flow of exhaust gas. It is provided. The exhaust heat recovery boiler 11 is a drum-type boiler, and is composed of an economizer 15 that heats feed water introduced through the water supply pipe 14, a drum 16 and an evaporator 17 for steam generation, and a superheater 18. Vessel 1
The steam coming out from the steam pipe 19 and the boiler outlet valve 2
0 to the steam header 21, and from the steam header 21 to the steam turbine 2 through the control valve 22.
3 to drive the generator 24, and the condenser 3
The water is condensed in 2. The condensed water is supplied to the water supply pump 1
2, the water supply pipe 14 equipped with the water supply regulating valve 13
is returned to the exhaust heat recovery boiler 11 through the exhaust heat recovery boiler 11. Also,
The steam pipe 19 includes a bypass steam pipe 26 equipped with a turbine bypass valve 25 on the upstream side of the boiler outlet valve 20.
The steam header 21 is branched and communicates with the condenser 32 via the desuperheater 27, but when the exhaust heat recovery boiler is started, the steam pressure in the steam header 21 and the generation of the exhaust heat recovery boiler 11 are Steam is introduced into the condenser 22 to match the steam pressure, and is not used during normal operation. 28 is a spray pipe branched from the water supply pipe downstream of the water supply pump 12 and connected to the desuperheater 27;
29 is a spray regulating valve.

This combined cycle plant first starts the gas turbine device 1 and transfers the exhaust gas to the exhaust heat recovery boiler 1.
1, and until the steam condition generated in the drum 16 reaches a specified value, the boiler outlet valve 20 is closed and the turbine bypass valve 25 is controlled to increase the steam pressure. Steam temperature for steam turbine ventilation,
When the steam pressure is reached, the boiler outlet valve 20 is opened and air is sent from the steam header 21 through the control valve 22 to speed up the steam turbine 23. When the rated speed is reached, synchronization adjustment is made to match the voltage, frequency, and phase difference of the grid, and the generator 24 and disconnector are closed to perform synchronization. The steam turbine in a combined cycle plant does not perform load control on its own, but rather controls the amount of steam generated from the exhaust heat recovery boiler 11, since the amount of steam generated by the exhaust heat recovery boiler 11 is uniquely determined by the output of the gas turbine device 1. Pressure governor operation is performed using an initial pressure control device 51 that controls the front pressure of the regulating valve 22 to a constant value so as to efficiently recover steam. However, during the startup process, the gas turbine device 1 completes startup quickly, and therefore the exhaust heat recovery boiler 11 generates more steam than is required by the steam turbine device 40, so the turbine bypass valve 25 is activated as described above. Excess steam is dumped into the condenser 32 via the attemperator 27 while maintaining the steam pressure at a specified value. If the initial pressure control device 51 controls the front pressure of the regulator valve 22 while the turbine bypass valve 25 is controlling the steam pressure, the pressures will be controlled mutually and favorable control results will not be obtained. While the steam pressure is being controlled at 25, the load of the steam turbine is controlled by the speed governor control device 54. That is, until the turbine bypass valve 25 is fully closed, the exhaust heat recovery boiler 11
This means that sufficient steam is generated to take up the load on the steam turbine device 40. When the load on the steam turbine increases by controlling the regulating valve 22 by the speed governor control device 54, the turbine bypass valve 25
is controlled in the closing direction to maintain steam pressure, and eventually becomes fully closed. On the other hand, while the speed governor control device 54 is controlling the adjustment valve 22, the set value of the initial pressure control device 51 is maintained at the lower limit and is in an excluded state.
Since the turbine bypass valve 25 is fully closed, steam pressure control must be performed by the initial pressure control device 51. For this purpose, the setting value of the initial pressure control device 51 is increased from the lower limit to the pressure setting value of the turbine bypass valve 25, and when they match, the setting value of the turbine bypass control device 57 is increased by a certain value to control the steam pressure to the initial pressure. Transferred to the control device 51. At this stage, since there is no deviation in steam pressure, the output signal of the initial pressure control device 51 remains at the upper limit, that is, equivalent to fully open with respect to the control valve 22, and this signal is not selected by the low selector 55 and is on standby. In this state, the low selector 55 selects the output of the speed governor control device 54. Here, when the set value of the speed governor control device 54 is increased, the opening degree of the regulating valve 22 is increased, and therefore the steam pressure is reduced, and the output signal of the initial pressure control device 51 becomes lower than the output signal of the speed governor control device 54. At this point, the output signal of the initial pressure control device 51 is selected by the low selector 55 to control the regulating valve 22.
However, in this switching, the initial pressure control device 51 starts control from an opening command equivalent to full opening, so the setting value of the speed governor control device 54 is increased, the opening degree of the regulating valve 22 is increased, and the steam pressure is lowered. Pressure control device 5
1, the steam pressure decreases until the switch is made, and after the switch is made, the control valve 22 is suddenly controlled in the closing direction, making it impossible to obtain stable control results.

An object of the present invention is to provide a combined cycle plant control device that can perform stable switching of the initial pressure control device 51 without the above-described fluctuations in steam pressure or sudden changes in the opening degree of the regulating valve 22.

The feature of the present invention is that while the steam turbine device 40 is being controlled by the speed governor control device 54, the output signal of the initial pressure control device 51 is made to follow the output signal of the speed governor control device 54, and when switching to the initial pressure control device 51, the adjustment valve is 22
The reason is that the opening degree can be changed without sudden changes.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. At start-up, the pressure setting value of the turbine bypass control device 57 is applied by the signal generator 80 to the subtractor 81 via the high selector 86 . The subtracter 81 compares the output signal of the steam pressure transmitter 56 and controls the turbine bypass valve 25 with the proportional/integral controller 82 so that the deviation is eliminated. The steam turbine device 40 compares the command given by the setter 77 of the speed governor control device 54 and the output signal of the speed detector 53 with a subtracter 76, and depending on the difference, the low selector 5 is changed by the proportional operation controller 79.
5, the control valve 22 is controlled to increase the load. In FIG. 3, the turbine bypass control device 57
Accordingly, the steam pressure is controlled to be constant like the curve 91. Setting value 7 of speed governor control device 54
As the command 7 increases, the opening degree of the regulator valve 22 increases as shown by a curve 94, and conversely, the opening degree of the regulator valve 22 increases as shown by the curve 94.
5 is 9 to maintain a constant value like 91 for steam pressure.
As shown in 3, the opening degree is reduced and eventually it becomes fully closed. on the other hand,
While the initial pressure control device 51 is controlling the adjustment valve 22 with the speed governor control device 54, the switch 73 switches from A to C side and gives a set value that follows the steam pressure transmitter 52 to the subtractor 71 so that the deviation is zero. Also, the switch 74 is switched from E to F side, and the output signal of the speed governor control device 54 is given to the proportional/integral controller 75 from the output side of the low selector 55 so that the same output signal is output. . The fact that the turbine bypass valve 25 is fully closed means that the exhaust heat recovery boiler 11
The entire amount of steam generated in the steam turbine equipment 4
0, and if the speed governor control device 54 increases the load on the steam turbine device 40 any further, the control valve 22 will open further and the steam pressure will fall below the specified value, which is favorable for the steam turbine device 40. Not. Here, it is necessary to quickly switch to the initial pressure control device 51. Under the condition that the turbine bypass valve 25 is fully closed, switch 73 is switched from A to C side to B.
→C side, switch 74 from E→F side to D→F side, switch 78 from G→K side to H→K side, switch 85 from M→N side to L→N side. . The function generator 72 determines the set value of the prepressure based on the steam flow rate to the steam turbine 23. That is, the output signal of the steam flow rate transmitter 58 is input to the function generator 72 and is given by the characteristic of the curve 91 in FIG. curve 9
1 is equal to the steam pressure setting value of the turbine bypass control device 57 until the turbine bypass valve 25 is fully closed, so the setting value of the switching subtractor 71 of the switching device 73 is the feedback value.The output of the steam pressure transmitter 52 It is equal to the signal and has zero deviation. Further, since the proportional/integral controller 75 follows the command of the speed governor control device 54 while controlling the adjustment valve 22, the same output signal remains even when the switch 74 is switched from the D to the F side. The steam pressure set value is transmitted from the initial pressure control device 51 to the turbine bypass control device 57, and this and the bias amount given by the signal generator 84 are added by an adder 83, and the value is transmitted to the switch 85 through the rate of change limiter 87. Passing through L → N, it is selected by the high selector 86 and becomes the curve 92 in Figure 3.
Change the pressure setting value of the turbine bypass control device 57 as follows. This completes the switching of steam pressure control from the turbine bypass control device 57 to the initial pressure control device 51, and thereafter the steam pressure is changed along the turbine 91 to cope with the increase in steam amount due to the increase in the load of the exhaust heat recovery boiler 11. It is controlled by a pressure control device 51.
On the other hand, in the speed governor control device 54, the switch 78 is set to H→
K and follows the opening command from the initial pressure control device 51. This is to immediately close the regulating valve 22 when the speed of the steam turbine 23 becomes excessive for some reason.

By causing the initial pressure control device 51 to follow the speed governor control device 54 as described above, stable control can be achieved by eliminating pressure fluctuations and sudden changes in the adjustment valve when switching the control system.

Although this embodiment has been explained based on an electric control circuit for simplicity, it is obvious that the same idea can be applied to a governor control device of a mechanical link mechanism.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a combined cycle plant, Figure 2
The figure shows an initial pressure control device according to the present invention, and FIG. 3 is a drawing showing initial pressure control switching characteristics according to the present invention. 1...Gas turbine device, 11...Exhaust heat recovery boiler, 16...Drum, 25...Turbine bypass valve, 22...Adjustment valve, 51...Initial pressure control device,
52... Steam pressure transmitter, 53... Speed transmitter,
54...Speed governor control device, 55...Low selector, 56...Steam pressure transmitter, 57...Turbine bypass control device, 58...Steam flow rate transmitter, 71...Subtractor, 72...Function generator , 73
...Switcher, 74...Switcher, 75...Proportional/integral controller, 76...Subtractor, 77...Setter, 78...Switcher, 79...Proportional action controller, 80...Signal generator , 81...subtractor, 8
2...Proportional/integral controller, 83...Adder, 84...Signal generator, 85...Switcher, 86
...High selector, 87... Rate of change limiter.

Claims (1)

[Claims] 1 one or more gas turbine devices,
In a combined cycle plant consisting of a combination of an exhaust heat recovery boiler device that generates steam using the exhaust gas of the gas turbine device as a heat source, and a steam turbine device that performs work using the steam generated by the exhaust heat recovery boiler, the control of the steam turbine is performed. A steam turbine control device is provided that has an initial pressure control device that controls the pre-valve pressure to a constant value and a speed governor control device that controls the load,
By automatically following the control commands of the initial pressure control device with the control commands of the speed governor control device, it is possible to switch from steam pressure control using the turbine bypass valve installed in the steam pipe of the exhaust heat recovery boiler to steam pressure control using the initial pressure control device. A combined cycle plant control device characterized by preventing sudden changes in control valve opening due to changes in steam pressure.