JPS6157921B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a turbine pressure control system, and in particular,
The present invention relates to a turbine pressure control method suitable for improving control valve control characteristics during variable pressure operation of a combined cycle power plant.

Figure 1 is a system diagram of a combined cycle power plant.

As shown in FIG. 1, a combined cycle power plant consists of a gas turbine and a steam turbine that generates steam using the exhaust gas heat and is driven by the generated steam. That is, gas turbine 1
The main engines are a gas turbine generator 2, an exhaust heat recovery boiler 5 using gas turbine exhaust gas 4, a steam turbine 6 using steam generated by the exhaust heat recovery boiler, and a steam turbine generator 7. As in a general steam turbine cycle, the steam system starts with a condenser 8, a condensate pump 9, a deaerator 10, a feed water pump 11, an exhaust heat recovery boiler 5, and then passes through a main steam pipe and a steam turbine control valve 12. This leads to turbine 6. There may be a plurality of gas turbines and exhaust heat recovery boilers 5, and in that case, a plurality of systems from the outlet header of the feed water pump 11 to the header in front of the steam turbine control valve are arranged in parallel.

There is also a configuration in which the gas turbine generator and the steam turbine are directly connected through one shaft.

A load control method in a plant as shown in FIG. 1 will be explained in the case of two gas turbines.

Load detectors 14 and 15 are provided in each of the generators 2 and 7, and the detection signals are sent to the load control device 16 by GT.
(Gas turbine) Load signal 20a (No.1GT is 2
0a, No. 2GT (20b) and ST (steam turbine) load signal 21, and this load control device 16 operates the gas turbine fuel pump 3 or fuel valve. In addition, the steam turbine control valve 12
is controlled by a turbine front pressure control device 17 based on a steam turbine front pressure signal 13.

FIG. 2 is a detailed block diagram of the load control device 16.

A target load signal is created for the target load setting 18 via the change rate limiter 19, and each gas turbine load 20
A subtracter 23 calculates the deviation between a, 20b and the total steam turbine load 21, and a demand load signal for each gas turbine is created via a regulator 24. The demand load signal may also be compared to each gas turbine load 20a or 20b via regulator 26 to provide a gas turbine fuel operating signal.

On the other hand, the steam turbine adopts a steam turbine control valve front pressure control system, which accepts all the steam generated by the exhaust heat recovery boiler in order to effectively utilize it. As shown in FIG. 3, this method of setting the pressure in front of the regulating valve is such that the pressure setting is low at low loads with respect to the steam turbine load, and the pressure setting is high at high loads, with a straight line connecting the two. Setting function 28 is desirable both for improving steam turbine efficiency and for reducing turbine wetting.

FIG. 3 is a block diagram showing a conventional pressure control system.

As a function of the gas turbine load command value 27, the front pressure setting function shown in FIG.
, and is subtracted from the steam turbine front pressure signal 13 by a subtractor 29 to create an adjustment valve opening signal 31 via a regulator 30.

However, in this method, a phenomenon as shown in FIG. 5 occurs.

In FIG. 5, Lsr, Ar, and Pr are reference values for the steam turbine load, control valve opening, and pressure, respectively. Here, the reference value means a value when the state quantities of the entire plant are statically balanced. Also,
Lsa ₁ , Aa ₁ , and Pa ₁ are the load of the steam turbine, the opening degree of the regulating valve, and the pressure, respectively, when considering changes in the dynamic characteristics (transient changes) of the plant.

Further, Gr and Ga ₁ are the reference value and actual value of the amount of steam generated by the boiler, respectively. Further, L _G is a gas turbine load command or load.

The characteristics of the actual values shown in Fig. 5 are obtained when the control system shown in Fig. 3 is adopted for the front pressure control of the steam turbine regulator, and when the gas turbine load L _G is increased from time _t0 to _t1 , the boiler Since the generated steam amount has a dynamic delay, it becomes Ga ₁ with respect to the reference value Gr, and the steam turbine load Lsa ₁ is also constant at the front pressure P ₁ , so
It rises slightly later than Lr. But from time t ₁ to t ₂
The front pressure is set according to the gas turbine load.
When increasing from P ₁ to P ₂ , the regulating valve opening degree Aa ₁ decreases, and the steam turbine load Lsa ₁ also decreases to a primary degree.

This is because although the boiler generated steam amount Ga ₁ increases later than the reference value Gr, since only the front pressure is controlled, it becomes the same as the reference value (Pa ₁ =Pr) and the control valve is closed.

For this reason, the increase in load on the steam turbine is delayed beyond the delay in the amount of steam generated by the boiler.

SUMMARY OF THE INVENTION An object of the present invention is to provide a turbine pressure control method that prevents a reverse response of a steam turbine load that occurs at the start of pressure transformation of a prepressure controlled turbine.

As the gas turbine load increases, the present invention
When increasing the pressure in front of the steam turbine control valve, the front pressure control is interrupted and the control valve is kept at a constant starting point, and the pressure is increased.
By performing constant pressure control after reaching P ₂ ,
This is designed to prevent a drop in steam turbine load.

FIG. 6 is a diagram of various control states according to the present invention.

From time t ₀ to t ₁ , the steam turbine control valve is controlled at a constant front pressure (P ₁ ) as before, but when time t ₁
When the gas turbine load reaches L _G1 , the steam turbine regulating valve opening is maintained at the opening at that time.
The front pressure is maintained until it reaches P ₂ (time t ₃ ), and the front pressure is controlled to be constant as the gas turbine rises thereafter.

The same applies when lowering the gas turbine load, but in this case, after the gas turbine load falls below _the specified gas turbine _{load L} ) constant control.

FIG. 7 is a block diagram showing an embodiment of the present invention.

From time t ₀ to t ₁ , based on the load command 27, the adjustment valve opening signal is obtained from the regulator 30 (PI configuration) with the same configuration as shown in FIG. 3, and the front pressure is controlled to be constant. There is. At time _t1 to _t2 , comparators 41 and 4
At steps 2, 43, and 44, the gas turbine load L _G and the actual measured steam turbine front pressure are compared with the set values. That is, the comparator 41 holds L _G ≧L _G1 and the comparator 42 holds P
P ₂ , L _G L _G2 in comparator 43, P> in comparator 44
Compare P ₁ and set the AND condition of comparators 41 and 42.
Taken by AND circuit 45 and AND of comparators 43 and 44
The conditions are taken by the AND circuit 46, and the AND circuits 45 and 4
The OR circuit 47 takes the OR of 6. Comparators 41, 42
A load increase is determined by the comparators 43 and 44, and a load decrease is determined by the comparators 43 and 44. The output of either the AND circuit 45 or 46 drives the relay circuit 48, and the relay contacts 50a, 50b, 50c are turned off.
50b and 50c are switched on. As a result, the output of the regulator 30 at time t1 in FIG. ₆ is stored in the memory 32, and this stored value is output as a constant control valve opening signal until time _t2 . The output of the memory 32 is also sent to the regulator 30 as a tieback signal 33.

In addition, the OR output condition is gas turbine load L _G
However, the conditions _{shown in FIG} . This method completely prevents temporary increases (when the load drops).

Gas turbine loads L _G , L _G1 , in Fig. 7
A similar effect can be expected by using the gas turbine load command value, plant target load command value, or steam turbine load instead of L _G2 .

In the embodiments of the present invention, an example of a combined cycle turbine has been shown, but it is not limited to such a type; it may also be of a type that controls the front pressure at a constant level (such as a type in which all generated steam etc. is input to the turbine, or a type in which fuel cannot be controlled). Applicable to all items). Further, the turbine type can be widely applied to those using steam, gas, fluorocarbon, etc.

As is clear from the above, according to the present invention, it is possible to prevent a steam turbine load reversal phenomenon when a plant load changes, and to perform a smooth load change.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a combined cycle power plant.
FIG. 2 is a detailed block diagram of the load control device 16 shown in FIG. 1, and FIG. 3 is a block diagram of a conventional pressure control system.
FIG. 4 is a steam turbine front pressure setting characteristic diagram, FIG. 5 is a conventional control state diagram, FIG. 6 is a control state diagram of the present invention, and FIG. 7 is a block diagram of an embodiment of the present invention. 1... Gas turbine, 2, 7... Generator, 3...
...fuel pump, 5 ... heat recovery boiler, 6 ... steam turbine, 8 ... condenser, 10 ... deaerator, 1
4, 15...Load detector, 16...Load control device, 28...Prepressure setting function device, 29...Subtractor,
30...Adjuster, 32...Memory, 41, 42,
43, 44... Comparator, 45, 46... AND circuit, 47... OR circuit, 48... Relay circuit, 5
0a, 50b, 50c...Relay circuit.

Claims (1)

[Claims] 1. In a turbine pressure control method in which the front pressure setting of the regulating valve is set as a function of the load or a load equivalent signal when the fluidized medium generated from the heat exchanger whose generation amount is not controlled is taken into the turbine via the regulating valve. , a turbine characterized in that a front pressure constant control is executed in a load range where the front pressure set pressure is constant, and a control is executed to keep the opening degree of the regulating valve constant in a pressure changing range of the front pressure set pressure. Pressure control method.