JPS6189910A - Steam turbine start-up circuit - Google Patents

Abstract

PURPOSE:To improve the follow-up performance at a time of a speed up operation by allowing a regulating valve to be kept open before the number of revolution reaches a value within the stated range of deviation at the early stage of a start-up operation of a steam turbine so that a PI blind controller is shifted to a control mode after the PI blind controller is permitted to track an actual valve opening. CONSTITUTION:A deviation signal C between the set number of revolution NR and an actual number of revolution N is inputted into a PI blind controller 13 allowing the control signal to be transmitted to a regulator valve drive device through a signal selector 27. A signal selector 26 determines the initial opening LGVI of a steam regulating valve as a function of steam pressure PL or PH in such a manner that the output from a function generator 23 is selected when low steam pressure PL exceeds the reference value PLT, and the output from a function generator 24 is selected when PL is lower than PLT. On start-up command St being inputted, a flip-flop 30 is set up, the PI blind controller 13 is in a tracking mode allowing a discriminator 28 to be initiated when both speed up and deviation in the number of revolution and become smaller. Subsequently, this allows the flip-flop 30 to be reset permitting the PI blind controller 13 to be shifted to a control mode.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a steam turbine startup circuit that improves speed increase follow-up performance during startup of a steam turbine.

Conventional technology steam turbine (taking as an example a boiler feed water pump turbine with low pressure steam and high pressure steam as the driving steam source)
An outline of the control is shown in FIG. 4, and an internal configuration of the control device is shown in FIG.

The steam turbine 1 has a low pressure steam source LPS and a high pressure steam source H.
It is driven using a PS as a driving steam source, and a boiler feed water pump, for example, is connected as a load 2.

The control device 4 compares the steam turbine rotation speed N detected by the detector 3 with the set rotation speed NR of the rotation speed setting device 11 using a comparator 12, and calculates the deviation NR−N using a PI controller 13. Opening degree finger 4L of steam control valve 7.9. V to electro-hydraulic converter 5
Output to. The electro-hydraulic converter 5 converts the opening degree indicator ◆LGV output from the control device 4 into a hydraulic signal and adjusts the opening degrees of the low-pressure steam regulating valve 7 and the high-pressure steam regulating valve 9 via the valve drive mechanism 6.8. to control the steam flow rate. As a result, steam turbine 1
Control is performed by increasing or decreasing the 0 rotation speed N and moving toward the set rotation speed NR.

Consider the case where the NR is raised on a ramp as shown in FIG. 6 in order to start the stopped steam turbine 1.

At the initial stage of starting the steam turbine, even if the steam control valve is opened, the incoming steam is used to fill the turbine with steam and does not contribute to the rotation of the turbine. Since the speed of the turbine is increased by the steam that flows in after the turbine is sufficiently filled with steam, the rise in the rotational speed N is delayed as shown in FIG. PI while the rise of the rotation speed N is delayed
The regulator 130 input deviation NR-N increases and the PI regulator output increases. Once the rotational speed N starts to rise, a large amount of driving steam flows in and is rapidly accelerated because the LGV is too large, exceeding NR and causing the PI to decrease in the direction of decreasing the GV. The regulator acts.When LGV decreases,
Since the driving steam decreases, the increase in the rotational speed N is restricted and falls below NR.

Thereafter, the above-mentioned phenomenon is repeated, and as shown in FIG. 6, the response becomes a curved line with respect to the ideal response curve a, which has the disadvantage of poor speedup followability.

Problems to be Solved by the Invention The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to obtain a starting circuit for a steam turbine that has excellent speed followability when starting a steam turbine.

Means for Solving the Problems According to the present invention, when the steam turbine is started, the steam control valve is opened at a constant opening until the input deviation to the PI controller of the governor becomes equal to or less than a predetermined set value. After filling with steam, switch the governor to control mode and set the governor's PI
By tracking the actual valve opening before switching the regulator to control mode, and setting the steam control valve opening at the initial stage of turbine startup using the driving steam pressure, deviation accumulation in the PI regulator is eliminated and speed increases are achieved. Improved followability. A steam turbine startup circuit is provided.

Embodiment FIG. 1 shows an outline of the control of a steam turbine according to the present invention, and FIG. 2 shows the internal configuration of a control device.

1 and 2, reference numeral l is a steam turbine, 2 is a load, 3 is a rotation speed detector, 5 is an electro-hydraulic converter, and 6
．． 8 is a valve drive mechanism, 7 is a low pressure steam control valve, 9 is a high pressure steam control valve, 11 is a rotation speed setting device, 12 is a comparator, 13 is P
I regulator, 21 and 22 are pressure detectors, 23 and 24 are function generators, 25 are low-pressure steam pressure determiners, 26 and 27 are signal switchers, 28 is a rotation speed deviation determiner, 29 is an OR element,
30 is the SFL flip-flop, 40 is the control device, N is the steam turbine rotation speed, LPS is the low pressure steam source, HPS is the high pressure steam source, NR is the set rotation speed, Lov is the opening index ◆, SL
indicates the starting finger +, and 'rr indicates a trip command.

Elements 21 to 26 are the initial opening degrees of the steam control valves. Elements 28 to 30, a circuit for setting the V mode, represent an operation mode control circuit, and the F/S mode and Trp are inputted from other devices not shown.

The function of the low pressure steam pressure device 25 to determine the low pressure steam pressure PL is as follows: When P < P, the output U1=1P@P
When , output U1=0.

L LT However, PIJ, r is the low pressure steam source LP as the driving steam source.
This is the criterion for determining whether or not to use S.

The function of the rotation speed deviation determiner 28 is as follows: When N8<NRo 0, output UΔ, = 0.

When NR>NRo and INR-Nl>ΔN, output U=0; When NR>NRo and INR-Nl<ΔN, output UJN"=1° However, NRo determines that the set rotation speed NR is not zero. The standard (direct, ΔN) is a reference value for determining whether the rotational speed deviation N9-N has become small and the rotational speed N has approached the target value NR.

Signal switch 26.270 function is When U is 20, Zi=Xi.

When Ui = 1, zi = Yi.

However, it is i21.2.

The PI regulator 13 adjusts the PI of the deviation input from terminal C when U8=00, and performs trunking manual power from terminal t when US=1. Track to VF.

When the working low pressure steam pressure PL exceeds the reference value PI, T (U
□=O) selects the output of the function generator 23, and when PL<PIIr (U□=1) selects the output of the function generator 24, and selects a signal that is a function of the low pressure steam pressure 9 or the high pressure steam pressure PH. Initial opening of the steam control valve. The signal is then sent to the signal switch 27 via the signal switch 26.

On the other hand, when the activation finger +5t (=1) is input, the output US of the SR flip-flop 30 is set to l. At this time, since the trip command Trp=O1UJN=O, the output of the OR element 29 is O, and the reset input of the SR Friso Dunlop 30 is O.

When U8=1, the PI controller 13 is in tracking mode, and the signal switch 27 is in signal mode. Select one of each. When the rotational speed N starts to rise and the deviation becomes smaller, the judge 28 operates and UJN'=: 0 → 1, so
The output of the disjunction element 29 becomes Q −+ l.

Therefore, the output US of the SR flip-flop 30 is reset, and US=1→0. As a result, the PI controller 13 shifts to the control mode, and the signal switch 27 switches to the signal mode.

Select VC.

Effects As described above, according to the startup circuit according to the present invention, at the beginning of steam turbine startup, the steam control valve is opened at a constant opening until the rotational speed deviation is within a predetermined number of rotations to supply steam to the turbine, and at the same time, the PI adjustment is performed. By moving the PI regulator to control mode after tracking the actual valve opening, the accumulation of deviation in the PI regulator due to the delay in the rise of the rotation speed is eliminated, and the followability during speed increase is improved. Ru.

By making the initial opening degree of the steam control valve a function of the driving steam pressure, it is possible to start the turbine in consideration of the conditions of the steam source.

Figure 3 shows the opening +L for the set rotational speed NR. It shows the changes in V and the actual steam turbine rotational speed N, where the solid line C shows the effect achieved by the present invention, and the broken line shows an example of the response achieved by the conventional method.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an overview of steam turbine control according to the present invention, Fig. 2 is a diagram showing its control device, Fig. 3 is a diagram showing response characteristics of a circuit according to the present invention, and Fig. 4 is a diagram showing a conventional control system. FIG. 5 is a diagram showing the control device thereof, and FIG. 6 is a diagram showing the response characteristics of the conventional circuit. 1... Steam turbine, 2... Load, 3... Rotation speed detector, 4... Control circuit, 5... Electro-hydraulic converter, 6.8... Valve drive mechanism, 7... Low pressure steam power Ω reduction Valve, 9... High pressure steam control valve, 11... Rotation speed setting device, 12... Comparator, 13...
PI regulator, 21.22...Pressure detector, 23.24.
・Function generator, 25 ・・Low pressure steam pressure gauge, 26, 2
7. Signal switch, 28. Rotation speed deviation determiner, 29.
・Order element, 30... SR flip frog, 40
--Control device, N...Steam turbine rotation speed, LPS...
Low pressure steam source, HPS...High pressure steam source, NA...Setting rotation speed, Lov...Opening◆, S...Start command, Tr,
・Book trip command. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A PI controller for the opening of the steam regulator of a steam turbine, an opening setting circuit that sets the opening of the steam regulator as a function of low-pressure steam pressure or high-pressure steam pressure, and a start command, trip command, set rotation speed, and rotation. A start command holding circuit holds the start command until the rotation speed deviation falls within a predetermined range by inputting the rotation speed deviation, and while the start command is held in this start command holding circuit, the opening command of the steam control valve is issued. and a signal selector that selects the signal of the opening degree setting circuit as the opening setting circuit, and selects the output of the PI regulator at other times, and selects the output of the PI adjuster when the starting command is held by the starting command holding circuit. A steam turbine starting circuit characterized in that the output of a steam turbine is tracked to the actual valve opening, and at other times, the rotation speed deviation is adjusted by PI.