JPS62236397A - Controlling method for preparation of paralleling generator off - Google Patents

Abstract

PURPOSE:To stably reduce a generator load by decreasing the output signal of a load limiter of a turbine controller to a minimum level in a preparation of paralleling the generator off. CONSTITUTION:When a load is reduced as a preparation of paralleling a generator off, a computer 1 outputs a load limiter (LL) drop command 3 to a LL 2 when a load is reduced to approx. 10% of a rated value. When an LL signal 5 decreases to become smaller than a pressure error signal 11, a steam control valve (CV) flow rate signal 10 from a low value priority circuit 4 is switched from the signal 11 to the LL signal 5, and the load starts reducing when the signal 5 reduces. A CV opening request signal 9 does not reduce the signal 5 by the small variation in a turbine speed due to the variation in a system frequency since a load set signal 8 is tracked at a level higher by 10% than the signal 10 in an automatic tracking mode.

Description

[Detailed Description of the Invention] [Purpose of the invention] (Industrial Application Field) The present invention provides, as one of the shutdown operation processes of a power plant,
When the generator load is reduced and the generator load drops to the front row load, the generator circuit breaker is released and the grid is disconnected.In the generator disconnection operation, the generator load lowering operation can be performed stably as a preparation operation. 1 to the generator disconnection preparation control method.

(Prior art) Control of generator drive turbines in thermal power plants, nuclear power plants, etc. is usually performed using an electro-hydraulic turbine control device (
(hereinafter referred to as EHC). In other words, EH
C is the steam control valve (hereinafter referred to as CV) located in the turbine
and an intermediate control valve (IV) and a turbine bypass valve (B
By controlling the opening of the PV), the steam pressure from the boiler or reactor is kept constant (pressure control), and the turbine speed is adjusted by changing the opening of the Cv to adjust the amount of steam flowing into the turbine. (speed control) to control the load current of the generator (load current 1ll). Hereinafter, an overview of conventional E tl C turbine control will be explained with reference to the control block diagram shown in FIG.

The pressure control system (2) uses a gain (pressure The pressure error signal 11 multiplied by 27 (reciprocal of a constant called adjustment rate) is output as a CV opening degree request signal.

The speed control system (2) uses a speed 1 vertical deviation signal 36, which is the deviation between the turbine speed signal 29 detected by the turbine speed sensor 28 and the speed setting signal from the speed setting device 30, and the turbine speed signal 29, to a differentiator 31. Acceleration signal 3 obtained through
3 and the acceleration setting from the acceleration setting device 32 (acceleration deviation value @ 35, which is obtained by integrating the deviation from No. H with the integrator 34),
lfi priority circuit ′□“′ (hereinafter referred to as LVG) 3
7 manually selects the one with the lower level of the two signals 35°36 and applies a gain (reciprocal of a constant called speed regulation rate) 39 to this LVG output signal 38. is multiplied by , and output as the speed error signal 7.

In addition, the load control system (■) sets the load to the speed error signal 7 above! (hereinafter referred to as LR) 6 is added to the negative part setting signal (hereinafter referred to as LR signal) 8, and this signal is output as a Cv interval request signal @9.

The pressure error signal 11 as the CV opening request signal from the pressure control system (2) and the CV opening request signal 9 from the speed control system (2) and the load control system m are the low value I destination circuit (hereinafter referred to as LV
G) 4.

Furthermore, the LVG4 includes a load limit signal 5 from the load limiter 2 and a maximum flow limit signal 4 from the maximum flow limiter 40.
1 is input. The sum of these input signals to the LVG 4 and the lower level signal are selected and used as the CV flow 1fl signal 10 to control the opening degree of the CV 14.

Before the generator is connected in parallel, that is, connected to the grid to supply power, the turbine bypass valve is being heard, and in this state, the levels of the pressure error signal 11 and the CV opening request signal 9 are compared. Then, since the Cv opening request signal 9 is lower, the opening of the CV 14 is controlled by fluctuations in the turbine speed and the LR signal 8. When generators are connected in parallel,
Since the turbine speed is determined by the system frequency, only LR
When the signal 8 rises, the CV 14 is opened and a load control state is entered in which the generator load increases. Furthermore, the LR signal 8 is
Then, the Cv opening request signal 9 becomes larger than the pressure error signal 11, the turbine bypass valve becomes fully open, and the state shifts to the pressure control state in which only the pressure control system (2) acts. During normal operation, this pressure control state is maintained, and even if there is a slight fluctuation in the turbine speed, the opening degree will not be affected.

Next, when a blank/shutdown operation is started, the output of the boiler or reactor is reduced, and the generator load is accordingly reduced. During this time, the LR signal 8 is automatically tracked (: racking) at a position slightly higher than the actual load, for example at 10%, and the load limit signal 5 is at a position at, for example, 110% of the rated load. is the rated outflow, for example 11
It is held at the 5% position.

After that, when the load drops to about 10% of the rating, LR6
Switch to manual (or atn 11) mode and begin load lowering operation as generator disconnection quasi-association.

The situation is shown in Figure 4.

First, when the load 15 reaches 10% (the load indicated by 17 in the figure), the LR 6 is moved from the 1-racking mode to the manual mode, and the value of the LR signal 8 is changed manually (time 19). Since the LR signal 8 is at a position of +10% with respect to the actual load 15, even if it is lowered, the C■ opening degree will not be affected immediately. When the signal 8 gradually decreases, the level of the CV opening request signal 9 decreases and becomes lower than the pressure error signal 11, the CV flow rate 10 changes from the pressure error signal 11 to the CV opening. Instead of the request signal 9, the turbine bypass valve hears the request signal +15 (illustrated as bypass valve opening 16), and the load 15 begins to decrease (time 20).

After that, as the R signal 8 is lowered, the load 15 is also lowered,
At the same time, the bypass valve asks. This operation requires a load of 15
This is continued until the load reaches approximately 2 to 3% of the rated value (referred to as the parallel disconnection load 18). When the load 15 becomes the disconnected load 18, the drop of the LR signal 8 is stopped (at time 21), and the generator circuit breaker is then opened to disconnect the generator from the grid.
(Time point 22). During this time, the load lIl [limit signal 5 is at a high position of 110% of the rated value, so the Cv flow value signal 10
is not related at all.

(Problem to be solved by the invention) As explained above, in the pressure control state during normal operation, even if the turbine speed fluctuates slightly due to fluctuations in the system frequency, etc., it does not affect the CV 1m degree. . but,
Upon entering the generator disconnection preparation operation for plant shutdown, after the CV inter-connection request signal 9 becomes lower than the pressure deviation signal 11 due to the drop in the load setting signal 20 at time 20 in FIG. Speed control and load control instead of pressure control
Since it governs V tin/1 degree, fluctuations in system frequency etc. directly affect CV l! If it will affect the melon. In this case, there is not much of a problem while the load 15 is relatively large, but the risk increases as it approaches the disconnection load 18.

For example, if we assume that the system frequency drops due to some reason near the disconnection load 18, the turbine speed will drop accordingly, so the speed deviation signal 36 will be on the negative side (normally O), so the CV Opening degree request signal 9 decreases to 0
The distance is narrowed and the load is reduced. In the worst case, C
V14 has a total of 111, and is in the generator motoring state (
Is it generated by the system? Im is driven by an electric VJ machine), and there is a risk that the generator will trip. It is desirable to disconnect the generator normally, and disconnection due to trip circuit operation must be avoided as much as possible.

The present invention has been developed in view of such problems, and it is possible to avoid the influence of system frequency fluctuations, etc. by reducing the generator load, which is performed via the turbine control device, in the generator disassembly process of the power generation blunt. The purpose of the present invention is to provide a method for controlling the preparation of FE electrolysis in a stable manner.

[Structure of the invention]

(Means for Solving the Problems) Therefore, the present invention aims to reduce the output signal of the load limiter of the turbine IIJ III device so that it becomes the lowest level signal in the preparation operation for disconnection of the generator in the J3 power generation blunt. By lowering the generator load, the load limiter lowers the generator load.

(Operation) By lowering the output signal level of the load limiter so that it becomes the lowest level signal, the Kubin control device decreases the inflow steam PL of the turbine according to the load limiter only and lowers the load. It turns out. Therefore,
The speed control system of the turbine fIIJ III device does not have any effect on the load lowering operation, so a slight change in the turbine speed 6h due to system frequency fluctuation etc. has no effect on the load lowering.

(Example) The present invention will be explained below with reference to Examples.

FIG. 1I is an all+ control block diagram showing essential parts of an embodiment of the present invention, and shows an embodiment in which load reduction is performed by automatic computer control.

In this figure, the pressure error signal 11 and the speed error signal 7 are the same signals as those in FIG. Process meter r3 machine 1
is a load 1t111 limit lowering command (hereinafter referred to as LL lowering command) 3 for load limit 7S (hereinafter referred to as LL) 2
Output. Incidentally, in the conventional method described above, the lowering command was output to LR6. At the same time, the meter 1
A load limit feedback signal 13 is input from LL2 to monitor the tracking state of LL2, and a generator load feedback signal 12 is input to check the control state of the load. The LL2 outputs a load limiter @ (hereinafter referred to as LL signal) 5 at a level corresponding to the LL lowering command 3 to the LVG4.

The LR signal 8 output from LR6 is the C from LVG4.
The V flow rate number 10 is compared with a signal obtained by adding a certain level, for example, 10% of the rated value, and the deviation signal is fed back into the LR6. LR6 changes the LR signal 8 to the Cv flow signal 10 by -1 so that the deviation signal becomes zero.
Control is performed to follow the 0% level. In this way, the L/R signal 8 is always controlled to a higher level than the CVV amount signal 10.
is added to the speed J) difference signal 7, and this added signal is input to the LVG 4 as the CVV degree request signal 9.

LVG4 selects the signal with the lowest level from among the input pressure error signal 11, LL signal 5, and CVV degree request signal 9, and uses this as the CV flow i11 signal 10 to output CV.
Used for opening control of 14. At that time, Cv opening request signal 9
Since L r< signal 8, which constitutes a part of it, is at a level 10% higher than C
Even if there is a slight variation within 0%, it will be kept at a level higher than the CV flow rate signal 10, and therefore will always be blocked by LVG/l, so that small speed variations will not affect the CV interval.

'1' Next, a load lowering operation as a train disconnection device with the above configuration will be explained with reference to FIG.

The process quantities such as the load and various set values at the start of this operation are the same as before and are the same as the state shown in FIG.

As in the conventional case, when the load 15 has decreased to about 10% of the rating (load not indicated by 17 in the figure), the load lowering operation by a total of nIfil is started (time 19).

First, the 51 G> machine 1 outputs the LL lowering command 3 to the LL2 to lower the LL signal 5 which has been shifted to the rated 110% position. At this starting point, the LL signal 5 is still at a sufficiently large position compared to the pressure error signal 11, so it does not affect the CV opening degree at all. Therefore, the kI calculator 1 lowers the LL signal 5 at a fairly large rate of change.

When the LL signal 5 approaches 0 load 15, the 510 aircraft 1 switches to a slightly slower rate of change (B, 1 point 42). L
When the L signal 5 further decreases and becomes smaller than the pressure error signal 11, the CV convoy signal 10 pressure error signal 11 to LL
Switches to signal 5, and as LL signal 5 falls to F, load 15
begins to fall (time point 20). At the same time, the turbine bypass valve is turned on (illustrated as bypass valve opening 16). On the other hand, since the LR signal 8 is tracking at a level 10% higher than the CV flow rate signal 10, that is, the LL signal 5, in the automatic 1-racking mode, the Cv opening request signal 9 is caused by changes in turbine speed due to fluctuations in system frequency, etc. Even with slight fluctuations, the LL signal will hardly fall below 5. Therefore, C
The v opening degree is controlled only by the LL signal 5, and the generator load 15 is stably lowered only according to the LL signal 5 without being affected by turbine speed fluctuations.

When fA 15 descends roughly and reaches uncoupling load 18 (2 to 3% of rated load), uncoupling rate ll? Operation a is completed and the falling of the LL signal 5 is stopped (time point 21).

Even in this state, since the load is controlled only by the Cv/opening LL signal 5, the load is maintained in a completely stable state. In this state, the generation circuit breaker is manually released, and the line-breaking operation is completed at time 22).

〔Effect of the invention〕

As explained above, according to the present invention, the output level of the load limiter of the turbine control device is lowered in J3 during the generator disconnection preparation operation, so that the generator load can be unintentionally operated only by the load limiter. I am trying to do this, so
The load can be lowered stably without being affected by turbine speed fluctuations caused by grid frequency fluctuations, etc., and the load can be stably maintained even after the disconnection load is reached. Machine trip accidents can be prevented and reliability of turbine control can be improved.

[Brief explanation of drawings]

Fig. 1 is a control block diagram showing the main parts of an embodiment of the present invention, Fig. 2 is a time chart showing changes in each process amount according to the embodiment, and Fig. 3 is an outline of a conventional line-disassembly preparation control method. FIG. 4 is a time chart showing changes in each process amount according to the conventional method. ■...Pressure control system, ■...Speed control system, ■...f
1 Load control system, 1... Process computer, 2... Load limiter (LL), 3... Load limit (LL) lowering command, 4
...Low value priority circuit (LVG), 5...Load limit (L
L) Signal, 6...Load setting device (LR), 7...Speed error signal, 8...Load setting (LR) signal, 9...C
V opening degree request signal, 10...Cv flow rate signal, 11...
Pressure error signal, 12... Generator load feedback signal, 13... Load limit feedback signal, 14...
・Steam control valve (CV), 15... Generator mouthpiece. Applicant's agent Sato -o f□' Figure 1 Figure 2 Figure S

Claims (1)

[Claims] The power plant is equipped with a speed control system for controlling the turbine speed, a load control system for controlling the generator load, and a load limiter for limiting the generator load. In a method for lowering the generator load as a generator disconnection preparation operation using a turbine control device configured to control the inflow steam amount according to the amount to be controlled the least, the load limiting The power generation device is characterized in that the load limiter lowers the load by lowering the output signal level of the load limiter so that the amount of inflow steam that the device is to control is minimized. Machine train preparation control method.