JPS6039846B2 - Setting method of regulating valve opening for variable pressure operating thermal power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for setting a regulator valve relationship for a variable pressure operation system that corrects main steam pressure control using the opening degree of the main turbine regulator valve, and particularly relates to a method for setting a regulator valve relationship in a variable pressure operation system that corrects main steam pressure control using the main turbine regulator valve opening. The present invention relates to a method for setting a regulating valve function suitable for use in a load Punto.

With the increase in system capacity and nuclear power generation capacity,
Thermal power generation, which used to operate at base load, is now being forced to operate at intermediate load.

For this reason, improving efficiency and improving load followability in intermediate load bands have become particularly important issues, but conventional control systems have two important problems. One is that conventional thermal power was for base load use, so the main focus was on improving efficiency at rated output, and the design was such that the main steam pressure remained constant. Therefore, in order to keep the main steam pressure constant even in a low load zone, the power loss of the feed water pump is large, which causes a problem of lowering plant efficiency. Second, because the main steam pressure was kept constant, the main steam flow rate was small in the low load zone, and the plant characteristics were highly nonlinear. For this reason, load followability deteriorates, and
The problem is that stable low-load operation is becoming difficult. Against this background, so-called variable pressure operation, in which the main steam pressure is varied according to the load, has been introduced in order to solve these problems. The characteristics of this variable pressure operation are: 1) Efficiency is good in a low load zone.In other words, the main steam pressure is lower in a low load zone, so the required pump power is reduced, and the plant efficiency is improved accordingly.

'2} It has good load followability in the low load range, and can be expected to reduce the minimum load and start/stop time. That is, since the main steam pressure is low in a low load zone, even if the load decreases, the decrease in the main steam flow rate is small.

This reduces nonlinearity compared to constant pressure operation, making load control easier and improving load followability.
'3' Relaxation of thermal stress in turbine metal can be expected.
That is, variable pressure operation reduces the variation in steam flow rate between high and low loads, so the change in steam temperature after the first stage of the turbine becomes small, and thermal stress is less likely to occur in the metal. For the above reasons, variable voltage operation has been adopted in recent intermediate load thermal power plants.

Conventional variable pressure operation methods for boiler and turbine plants include a variable pressure operation method in which the main steam pressure demand is determined directly from the load demand, and a preset value for the main turbine control valve (hereinafter referred to as control valve). For example, all the valves in the turbine are fixed at 2 valves fully open or 3 valves are fully open, and the load demand is corrected using the proportional control output based on the deviation between the regulator valve set value and the actual regulator valve (regulator valve relationship detection). There is a variable pressure operation method that determines the pressure demand, but in the former, if the process characteristics change due to aging etc. during plant operation, the control valve may not necessarily settle to the desired state when the load is stabilized. do not have.

Therefore, there is a drawback that the control valve cannot be set to the highest point of plant efficiency. Furthermore, the latter has the disadvantage that since the relationship setting value of the control valve is fixed, it is impossible to operate at the highest efficiency point in response to load changes. It is an object of the present invention to eliminate the drawbacks of the prior art, to obtain the relationship setting value of the regulator valve as a function of load demand, to make the regulator valve opening setting value the highest efficiency point in response to load changes, and to improve the efficiency. An object of the present invention is to provide a control valve opening setting method that allows a plant to be operated at the maximum efficiency at all times by modifying the main steam pressure demand until the control valve relation matches the control valve opening set value.

The present invention focuses on the fact that the total efficiency of the boiler/turbine during variable pressure operation shifts from 4 valves fully open to 3 valves fully open to 2 valves fully open depending on the load, and the regulator valve relationship setting value is changed to The main steam pressure demand is determined as a function of load demand when the demand rises and when it falls, and the main steam pressure demand is modified until the actual control valve relation matches the set value of the control valve relation. It is something.

FIG. 1 shows a control system diagram of a boiler automatic control device showing one embodiment of the present invention.

Although the method of the present invention is preferably implemented as program processing using a computer, the following description will be made using blocks for convenience of explanation. As shown in the figure,
The poller automatic control system consists of [11 Load demand setting system,
■ Load control system, [3' Pressure demand determination system, 4...
Main steam pressure compensation system, Main steam temperature auxiliary system, [6' Water supply flow rate control system, '7' Fuel quantity control system, '8} Air flow rate control system, '9' 2-valve spray control system, (10) 1 It consists of 11 sub-control systems: a valve spray control system, and (11) a gas recirculation amount control system. The detailed configuration and operation of each sub-control system will be explained below in order. SI: Load demand setting system 200: A simple example of the load demand setting system is shown in the second example.
As shown in the figure. In the figure, first, the load request value sent from the central power dispatch center is combined with the load demand Ld currently applied to the boiler automatic control device by a subtracter 500.
The difference is taken. Next, the load change rate limiter 501 compares the upper and lower limits set in the rate of change upper limit value setter 502 and the rate of change lower limit value setting unit 503, and if the result of the subtractor 500 is equal to or greater than the upper limit value, the upper limit value is set. However, if it is below the lower limit, the lower limit is applied to the integrator 504, and if it is within the upper and lower limits, the result of the subtracter 500 itself is applied to the integrator 504. In the integrator 504,
The load demand W is determined by integrating the value according to the input. When applied to an actual plant, functions such as frequency correction, rapid loading, and shutoff are added, but these are omitted here because they are not directly related to the present invention. S2: Load control system: The load demand Ld indicated by SI and the load detector 10
The difference between the signals from 0 (subtractor 300) is taken, and based on the deviation, a control valve controller 301 performs control calculations such as proportional and integral operations to operate the control valve 400.

S3: Pressure demand determination system: Using the load demand Ld determined by SI, the main steam pressure setting device 207 determines the main steam pressure setting value. This main steam pressure set value is realized by storing it as a function of load demand, as shown in Figure. Also, the adjustment valve opening setting value is the adjustment valve relation setting device 2.
01 gives a function setting according to the load demand Ld.
FIG. 4 shows an embodiment of this control valve function setting device 201. This device is comprised of a load demand mode determiner 600 and a control valve opening setting device 603. The control valve opening setting device 603 includes a control valve setting device '1' 601 used in the load demand increase mode and a control valve setting device (2'602) used in the load demand decrease mode.Load demand determination device 600 includes a detection unit that detects an ascending mode when the load demand is increasing and a descending mode when the load demand is decreasing, and a selecting unit that selects which mode should be selected for the regulator valve relationship setting device 603. In the load demand mode determiner 600, the load demand signal Let detected at a certain time t and the load demand signal Let detected at a certain time t and
The load demand signal Wt+△t detected at 10△t is compared, and when L4<L40△t, the rising mode is selected, and LQ>Ld
When t+Δt, the descending mode is selected. Note that the smaller the sampling time Δt is, the better. The regulating valve relation setting device 201 receives a selected signal from the load demasor 600, and provides the regulating valve opening degree for the load demand Ld using a regulating valve relation setting device suitable for that mode. Note that when the load demand signal has not changed above L4=L4+Δ, the opening degree by the adjustment valve acceleration setter of the currently selected mode is given. Figure 5 shows the control valve function setting device m6.
01 and the adjustment valve opening setting value for the load of the adjustment valve opening setting device [21602]. It is actually better for the values of Q and 8 to be zero, but since an unfavorable phenomenon occurs due to plant characteristics, such as not knowing where the adjustment valve opening is for a certain load, these values should be changed for each plant. should be determined. In this way, as shown in FIG. 5, the regulating valve relation setting device 201 gives a relation setting according to the load demand Ld, and the deviation from the signal from the regulating valve opening detector 101 is calculated (the subtracter 202 ), the controller 203 performs proportionality and integration so that the deviation becomes 0.

Next, the multiplier 204 corrects the output of the controller 203, and the main steam pressure set value obtained by the main steam pressure setter 207 is corrected to become the main steam pressure demand Pd (adder 20
5). The main steam pressure demand determining method according to the present invention is characterized by a conventional regulator valve opening setting device (corresponding to 201 in Fig. 1).
In contrast, a constant value such as 2 valves fully open or 3 valves fully open was given, but a load demand peak is applied to the adjustment valve opening setting device 201, and the adjustment valve is adjusted according to the load as shown in Fig. 5. The purpose is to make it possible to change the relationship settings. This is because, as shown in Figure 6, the efficiency of the plant is determined by the control valve function that indicates the highest efficiency point depending on the load range, so the control valve function setting value is set to the valve opening degree that provides the highest efficiency depending on the load. It is. In FIG. 6, 1 and 2 are diagrams showing how much the efficiency improves as the load changes when three valves are fully opened during variable pressure operation, compared to constant pressure operation. Another feature is that in the past, the controller 203 could only perform proportional control compensation because the setting value of the regulator valve was constant and four valves had to be opened at high loads. Since it has become possible to change the temperature setting according to the load, it has become possible to add integral control compensation to the control 203. Due to this integral compensation, the regulator valve function always settles to the highest efficiency point at the final settling time. Furthermore, in the embodiment, the output of the controller 203 is corrected by the load demand Ld (the controller 203 is corrected by the multiplier 204), so that the control valve can be slowly stabilized at low loads where control is relatively unstable. It is considered a thing. S4: Main steam pressure compensation system discussion Using the main steam pressure demand Pd and the signal from the main steam pressure detector 102, the subtractor 206 takes the deviation and calculates the main steam pressure control.

controller 208 performs proportional/integral control. The output signal Pc of the main steam pressure controller 208 is used to correct the demands of a water supply flow rate control system, a fuel flow rate control system, and an air flow rate control system, which will be described later. S5: Main steam temperature compensation system First, using the output signal of the main steam temperature setter 209 and the output signal of the main steam temperature detector 103, the subtractor 210 takes the deviation, and then the main steam temperature controller 211 calculates the proportional - Integral control is implemented.

The output of the main steam temperature subtractor 210 is used to correct the demand signal of the primary and secondary spray control systems, which will be explained later. Used for correction. S
6: Water supply flow rate control system First, the water supply flow rate setting device 30 has a function as shown in Fig. 7.
2, determine the water supply amount setting value according to the load demand Ld,
Adding the output Pc of the main steam pressure controller 208 and the output Tc of the main steam pressure controller 211 to this, the water supply amount F
Determine d.

In this system, the secondary water supply amount setter 302 is not provided, and the output Pc of the main steam pressure control 208 provides the water supply amount setting, but the water supply amount setting device 302 is provided and the main Output Pc of steam pressure controller 208 and output Tc of main steam temperature controller 211
Since the control system is configured so that
Load operation can be continued with only the output of 02. Furthermore, using the water supply amount demand Fd determined in this manner and the output of the main water supply amount detector 104, a subtracter 304 calculates the deviation thereof, and a water supply amount controller 305 performs proportional/integral control. In addition, when there are multiple water supply pumps (two pumps are shown in the figure), the output of this water supply amount controller 305 becomes the demand for each water supply amount, and corresponds to the output signal of each water supply amount detector 111, 112. The deviation is taken by subtractors 306, 308, proportional/integral control is performed by water supply pump adjustment controllers 307, 309, and water supply amount control is realized by operating the water supply pump adjustment valves 401, 402. S7: Fuel quantity control system First, the fuel quantity set value corresponding to the load demand Ld is determined by the fuel quantity setter 212 having the function shown in FIG.
The deviation of the output of the main steam pressure controller 2 is taken, and
The adder 310 corrects the output Pc of 08 by the coefficient multiplied by the coefficient multiplier 225.

Next, using this corrected deviation, the fuel flow control valve controller 311 performs proportional/integral control, and the fuel flow control valve 4
Operate 03. Like the feed water flow rate control system, the fuel amount setting value is given as a function of the load, so even if the main steam pressure compensation system malfunctions, load operation can be continued using only the fuel amount setting device. S8: Air flow rate control system First, with the air amount setting device 214 having the function shown in FIG.
Subtractor 215 sets the air amount setting value according to the load demand Ld.
The difference between this and the output of the air amount detector 106 is calculated, and the output coefficient 226 of the main steam pressure controller 208 multiplies Pc by a coefficient, and the adder 312 corrects it.

Next, using this corrected deviation, the air amount adjustment damper controller 313 performs proportional/integral control, and the damper 40
Operate 4. In this system, like the feed water flow rate control system and fuel amount control system, the air amount setting value is given as a function of load demand, so even if the main steam pressure compensation system malfunctions for some reason, the air amount Load operation can be continued using only the setting device. S9: Secondary spray control system First, the tertiary superheater inlet temperature setting value corresponding to the load demand W is determined using the tertiary weekly heating unit inlet temperature setter 216 having the function shown in FIG.
The deviation between this and the output of the tertiary weekly heater inlet temperature detector 107, that is, the next week's heater inlet temperature deviation is determined.

Next, the value obtained by multiplying the main steam temperature deviation obtained by the subtracter 210 by a coefficient by the coefficient unit 224 is added to the tertiary superheater inlet temperature deviation by an adder 315, and the value is proportionally Implement controls.

Furthermore, a secondary spray valve opening degree setter 314 having the function shown in FIG. Additionally, the secondary spray valve 406 is operated. In this system, the tertiary weekly heater inlet temperature set value is determined as a function of load demand, so even if the main steam temperature compensation system malfunctions for some reason, load operation can be continued. In addition, since the spray valve opening setting value is determined as a function of the load demand, the 3rd week heater inlet temperature controller 31
6 is just a correction, so even if the tertiary superheater inlet temperature controller becomes malfunctioning, load operation can be continued. S
IO: Primary spray control system First, the secondary superheater outlet temperature set value corresponding to the load demand W is determined using the secondary superheater outlet temperature setter 218 having the function shown in FIG. Chamber outlet temperature detector 1
A subtracter 219 calculates the deviation from the output of 08.

Next, an adder 319 adds a value obtained by correcting the main steam temperature deviation Tc using a coefficient unit 224, and a secondary weekly heater outlet temperature controller 320 performs proportional control. Next, the secondary superheater inlet temperature setting device 220 having the function shown in FIG. The subtracter 221 calculates the deviation from the output of .

Next, based on this deviation, the heater outlet temperature controller 320
The adder 321 adds the output of , and the secondary superheater inlet temperature controller 322 performs proportional control.
Primary spray valve function setting device 3 with the function shown in Fig. 14
The set value determined in step 18 is added, and the primary spray valve 406 is operated. In this system, the primary soubre valve function setting value is given as a negative p demand function, so the main steam temperature compensation system, the secondary weekly heater outlet temperature control system, and the secondary superheater inlet temperature control system are Even if any system malfunctions, load operation can be continued simply by disconnecting that system.

In addition, since the secondary superheater outlet temperature set value and the secondary superheater inlet temperature set value are given as a function of load, it is possible to compensate for nonlinear characteristics of the process depending on the load, and it works well over a wide range of load ranges. Moreover, stable control characteristics can be obtained.

SI1: Gas recirculation amount control system First, the load demand L is set using the reheater outlet temperature setting device 222 having the function shown in FIG.
Find the reheater outlet temperature set value according to d, and take the deviation between this and the reheater outlet temperature detector 110 with a subtractor 223,
A reheater outlet temperature controller 325 performs proportional and integral control.

Next, the load demand Ld is applied to this control output using a recirculation gas flow rate adjustment damper opening setting device 324 having a function shown in FIG.
The adder 326 adds the recirculation gas flow rate adjustment damper opening setting value obtained as a function of the recirculation gas flow rate adjustment damper 4.
Operate 06. In this system, the recirculation gas flow rate adjustment damper opening setting value is given as a function of the load demand W, so even if the reheater outlet temperature control system becomes malfunctioning, load operation can be continued.

Furthermore, since the reheater outlet temperature setting value is given as a function of load, process nonlinearity during variable voltage operation can be compensated for, and good and stable control characteristics can be obtained over a wide range of load bands. As can be seen from the above embodiments, according to the present invention, even if the load demand changes, it is possible to always operate the plant at the maximum efficiency at full load.

[Brief explanation of the drawing]

Fig. 1 is a boiler automatic control system diagram showing one embodiment of the present invention, Fig. 2 is a principle diagram showing a load demand determination method, Fig. 3 is an explanatory diagram of the principle of main steam pressure setting, Fig. 4 is a schematic configuration diagram of the adjustment valve opening setting device, Fig. 5 is a diagram explaining the principle of adjustment valve opening setting, Fig. 6 is a diagram showing the relationship between load plant and efficiency, and Fig. 7 is a diagram showing the relationship between the load plant and efficiency. Figure 8 is a diagram explaining the principle of setting the fuel amount. Figure 9 is a diagram explaining the principle of setting the air quantity. Figure 10 is a diagram explaining the principle of setting the tertiary weekly heater inlet temperature. Fig. 11 is an explanatory diagram of the principle of setting the secondary spray valve function, Fig. 12 is an explanatory diagram of the principle of setting the secondary superheater outlet temperature, and Fig. 13 is an explanatory diagram of the principle of setting the secondary weekly heater inlet temperature. Fig. 14 is an explanatory diagram of the principle of setting the primary spray valve function, Fig. 15 is an explanatory diagram of the principle of setting the reheater outlet temperature, and Fig. 16 is an explanatory diagram of the principle of setting the recirculation gas flow rate adjustment damper opening. It is a diagram. 208... Main steam pressure controller, 209... Air temperature setting device, 210... Subtractor, 211... Main steam temperature controller, 212... Fuel amount setting device, 213
...Subtractor, 1214...Air amount setting device, 215.
...Subtractor, 216...Third superheater inlet temperature setter, 21
7... Subtractor, 218... Secondary heating unit outlet temperature setter, 219... Subtractor, 220... Secondary superheater inlet temperature setting unit, 221... Subtractor, 222... - Reheater outlet temperature setter, 223... subtractor, 224... coefficient unit, 225, 226... coefficient unit, 300... subtractor, 301... adjustment valve controller, 302... - Water supply amount setter, 303... Adder, 304... Subtractor, 305... Water supply amount controller, 306... Subtractor, 307... Water supply pump turbine control valve controller A, 308... - Subtractor, 309... Water pump turbine control valve controller B, 310... Adder, 311
...Fuel control valve controller, 312...Adder,
313... Air amount adjustment damper controller, 314...
Secondary spray valve opening setting device, 315... Adder, 316
...Third week heater inlet temperature controller, 317...
Adder, 318...Primary spray valve opening setting value, 319
...Adder, 320...Secondary superheater outlet temperature controller, 321...Adder, 322...Secondary heater inlet temperature controller, 323...Adder, 324...
・・Recirculation gas flow rate adjustment damper relationship setting device, 325・・
・Reheater outlet temperature controller, 326... adder,
400... Control valve (main turbine), 401... Water pump turbine control valve A, 402... Water pump turbine control valve B, 403... Fuel control valve, 404... Air amount control damper, 405.・Secondary spray valve, 406...
・Primary spray valve, 407...Recirculation gas flow rate adjustment Dan/L
OO Figure 1 Figure 2 Shigeru Figure 4 Figure 5 Tsutomu 6 Figure Inferior figure Figure 8 Figure q Figure Lot lo Figure 11 *'2 Figure 13 Figure Tsutomu' 4 Figure 15 Figure 16

Claims (1)

[Claims] 1. In a thermal power plant where the boiler and turbine are operated at variable pressure for intermediate load operation, the opening of the control valve at the inlet of the main turbine is required to make the efficiency of the boiler and turbine plant appropriate at this load based on the load demand. the main steam pressure demand set according to the load demand is corrected based on the deviation of the turbine inlet adjustment valve opening from the set actual opening. A method for setting the opening degree of a regulating valve in a variable pressure operating thermal power plant.