KR20010026628A - Control System for water level of drum in a HRSG of power plant - Google Patents

Abstract

PURPOSE: An apparatus for adjusting water level of drum for heat recovery steam generator is provided to achieve a stabilized control and enhance control efficiency by eliminating instability caused by swelling and shrink of fluid. CONSTITUTION: An apparatus comprises a fluid change compensation unit for taking, as an input, control elements for a drum and a generator, and a fluid ingredient comparing element, and calculating the fluid change compensation value for controlling water level of the drum; and a PID control unit for taking, as an input, control elements for the drum and the generator and the fluid ingredient compensation value, and performing PID control for controlling flow rate of water being supplied to the generator. The fluid change compensation unit includes fluid change detectors(352,356) for taking as an input control elements and fluid ingredient change element, and detecting fluid change ingredient; function generators(354,358,372) for generating function based on the output from the fluid change detector; a correction signal generator(360) for taking as an input the output from function generators and generating correction signal for correcting the fluid change ingredient; a discriminator(364) for adjusting correction signal based on the maximum limit value of the fluid changed state and the reference value preset in the control unit; a correction adder(368) for adding the output value from the discriminator and the PID control ingredient fed back from the PID control unit, and outputting the added result to the PID control unit; and a rate-of-change computing unit(370) for computing the rate-of-change of output value of the correction adder, generating function for the computed rate-of-change, and outputting the result to the PID control unit.

Description

Control system for water level of drum in a HRSG of power plant

The present invention relates to a power generation recovery boiler of a power plant, and to actively control the fluid expansion and contraction in the drum by performing a control operation by further receiving the drum pressure as an input element in addition to the conventional input elements to control the level of the drum. The present invention relates to a drum level control device of a heat recovery boiler for improving operation stability and improving operation efficiency.

In general, the power generation equipment takes the principle of generating electricity by driving a steam turbine with steam generated from a heat recovery boiler using the exhaust gas of the gas turbine as a heat source. In such a power plant, maintaining a constant level of the drum constituting the heat recovery boiler is an important requirement for stable operation of the boiler. With reference to Figure 1 will be described in detail with reference to Figure 1 of the conventional power generation facilities installed with the conventional heat recovery boiler.

As shown in FIG. 1, the combined cycle power generation system of FIG. 1 includes a gas turbine 100, a heat recovery boiler 120, a boiler feed water pump 140, and a steam turbine 160.

The gas turbine 100 rotates a turbine by using a gas of high temperature and high pressure generated by burning fuel, and the gas discharged from the gas turbine 100 is supplied to the heat recovery boiler 120. The boiler feed water pump 140 supplies water to the heat recovery boiler 120, and the heat recovery boiler 120 absorbs heat of the gas discharged from the gas turbine 100 to supply water from the boiler feed water pump 140. Is converted to steam and the generated steam is supplied to the steam turbine 160. The steam turbine 160 generates electricity by rotating the turbine with the supplied steam.

The heat recovery boiler 120 includes the first and second economizers 121a and 121b, the drum level control valves 122a and 122b, the drum 123, the first and second superheaters 124a and 124b, and the superheat reducer. (125) and steam temperature control valve (126).

The boiler feed water pump 140 supplies water to the first blower 121a, which is caused by the heat of the gas discharged from the gas turbine 100 while flowing through the first and second blowers 121a and 121b. After it warms up, it flows to the 1st and 2nd water supply control valves 123a and 123b. The heated water is controlled by the first and second water supply control valves 123a and 123b and flows into the drum 124 under high pressure. The water introduced into the drum 124 descends through the downcomer 127a, absorbs heat from the evaporator 127, turns into steam, and enters the drum 124 again through the upcomer 127b. The high-pressure drum 123 supplies this steam to the first superheater 124a, which is converted back to the superheated steam state by the heat of the gas discharged from the gas turbine 100, and then to the superheat reducer 125. Supplied. In the superheat reducer 125, the water flowing from the boiler feed pump 140 and controlled by the steam temperature control valve 126 controls the heat of steam passing through the first superheater 124a to a predetermined temperature. Supply to superheater 124b. The second superheater 124b superheats the steam and supplies the steam to the steam turbine 160. The supplied superheated steam rotates the steam turbine 160 to generate electricity, that is, generate additional electricity.

The array recovery boiler 120 includes three measuring devices T1 to T3. The superheat reducer temperature measuring device T1 measures the steam temperature at the outlet of the superheat reducer 125. The main steam temperature measuring instrument T2 and the main steam flow measuring instrument T3 measure the temperature and flow rate of steam finally set and discharged from the second superheater 124b. The temperature and flow rate of the steam measured by these measuring devices T1 to T3 are used to control the drum level.

The general method for controlling the drum level of a combined cycle power plant is a one-element control method for controlling the water supply flow into the drum using only the drum level as an input element, and the drum level control using the drum level, the water supply inflow, and the steam outflow as input elements. It is divided into three element control method. The three-element control method consists of a cascade method and a feed-forward method.

In general, since the feed water inflow and the steam generation amount are small at the initial start or low load of the turbine, the one-element control method is used to adjust the water supply only by the drum level considering the characteristics of the flowmeter. In normal operation, however, the drum level is controlled by a three-element control method.

Cascade method of the three-element control method described above is to control the water supply with fast response characteristics in the form of an inner loop by the water supply control valve, and the drum level with the slow response characteristics to the outer loopa. The PI (Proportional Integral) controller is used to control the feedforward (feedforward) method, which controls the flow rate of the steam flow acting as a disturbance component during the drum level control by applying the feed forward (feed forward) form.

Figure 2 shows a drum level control device of a conventional power plant arrangement recovery boiler. As described above, the drum level control is generally divided into one element control and three element control, and a separate selection control unit may be provided to select a desired control method. This section describes the drum level control process, focusing on the three-element control method.

The drum level control apparatus for three-element control includes a drum level meter 200, a steam flow meter 206, and a water supply flow meter 214 for measuring three input elements. When the three-element control is started, the drum level gauge 200 measures the drum level and outputs it to the first comparator 202 at the rear stage. The first comparator 202 receives and compares the received drum level with the drum level set value set in the operation switch 218 of the rear end of the drum level adjusting device. The first proportional integral controller 204 at the rear stage proportionally integrates the difference between the compared drum level and the drum level set value.

The steam flow meter 206 measures and outputs the steam flow rate, and the multiplier 208 of the rear stage multiplies a predetermined coefficient by the controller. The adder 210 receives the output values of the first proportional integral controller 204 and the multiplier 208 and adds the output values to the second comparator 212 at a later stage. The second comparator 212 receives and compares the output value of the adder 210 and the water supply flow rate measured by the water supply flow rate meter 214, and outputs the result. The second proportional integral controller 216 of the rear stage is an adder 212. After proportional integration of the output value of the output value and the water supply flow rate is output to the operation switch 218. The operation switch 218 of the rear stage can be operated by switching the operation automatically or manually. The drum level setting value of the operation switch 218 is input to the first comparator 202 and the output is output to control the water supply flow rate control valve 220.

The three-element control method is composed of a proportional integral control by performing a comparative operation on the three elements of the drum water level, steam flow rate and water supply flow rate, and other conventional three-element control method may be different in each configuration. The concept of the adjustment of the drum level is almost the same.

However, the drum level control apparatus of the conventional heat recovery equipment array recovery boiler has a problem that can not properly control the drum level during the start-up and rapid load rise. In other words, if the exhaust gas temperature of the gas turbine rises sharply, the fluid of the evaporator rapidly warms up, and the volume of the fluid rapidly expands, thereby failing to adequately cope with the phenomenon of swelling & shrinking in which the drum level rises rapidly.

Accordingly, an object of the present invention is to combine the devices for detecting and correcting the fluid expansion shrinkage phenomenon in the conventional control method to solve the above problems, thereby improving the stability of the drum level control and improve the control efficiency of the drum level In providing.

1 is a view showing a schematic configuration of a typical combined cycle power plant.

Figure 2 is a drum level control apparatus of a conventional power plant heat recovery boiler.

Figure 3 is a drum level control apparatus of the power plant heat recovery boiler according to the present invention.

<Explanation of symbols for the main parts of the drawings>

100: gas turbine 120: array recovery boiler

140: boiler feed pump 160: steam turbine

200, 300: Drum level measuring instrument 202, 302: First comparator

204, 304: first proportional integral controller 206, 306: steam flow meter

208, 308: Multiplier 210, 310: Adder

212, 312: second comparator 214, 314: water flow meter

216, 316: second proportional integral controller 218, 318: motion converter

220, 320: water supply flow control valve

350: Drum pressure measuring instrument 352: Fluid shrinkage detector

354: first function generator 356: fluid expansion detector

358: second function generator 360: correction signal generator

362: maximum limiter 364: discriminator

366: reference value 368: correction adder

370: change rate operator 372: third function generator

The drum level control apparatus of the heat recovery boiler of the power generation equipment according to the present invention for achieving the above object is to adjust the level of the drum provided in the heat recovery boiler of the power generation equipment,

A fluid change compensator for receiving the control elements for the drum and the boiler and a fluid component comparator within the drum and calculating and outputting a fluid change compensation value for adjusting the level of the drum;

And a general proportional integral control unit configured to receive a control element for the drum and the boiler, and to receive a fluid component compensation value from the fluid change compensation unit, and perform proportional integral control to control the flow rate of the water supply to the boiler. .

Hereinafter, with reference to the accompanying Figure 3 will be described a preferred embodiment of the present invention;

Figure 3 shows the drum level control apparatus of the power plant heat recovery boiler according to an embodiment of the present invention. As shown, the drum level control apparatus of the present invention is a three-element control configuration for controlling the level of the drum by using the drum level, steam flow rate and water supply flow rate, by receiving the drum pressure to detect the rapeseed expansion contraction in the drum to compensate The configuration for this is added.

The control flow for the components 302 to 322 of the conventional three element control shown on the right side of FIG. 3 is the same as in FIG. 2 described above, and therefore, the operation and description thereof will be replaced with the above description. The drum level control apparatus according to the present invention is a technique applied to both one-element control and three-element control, and improves the stability and control efficiency of the drum level control by actively controlling the unstable state caused by the expansion and contraction of the fluid according to the drum pressure. Will be improved.

As shown in Figure 3, the drum level control apparatus according to the present invention includes a drum pressure measuring device 350 for measuring the drum pressure in addition to the measured values of the drum level, steam flow rate and water supply flow rate. The measured drum pressure of the drum pressure measuring unit 350, the drum level of the drum level measuring unit 300, and the steam flow rate of the steam flow measuring unit 300 are input to the fluid shrink detector 352 and the fluid expansion detector 356 at the rear stage, respectively. do.

The fluid shrinkage detector 352 detects and outputs a fluid shrinkage phenomenon such as detecting a condition in which a fluid shrinkage occurs, that is, a decrease in the amount of steam and an increase in the drum pressure, a decrease in the amount of the steam, and a decrease in the level of the drum. The first function generator 354 at the rear end receives the input and outputs a result of calculating the function of the contraction phenomenon. On the contrary, the fluid expansion detector 356 detects and outputs a fluid expansion phenomenon such as detecting a condition in which a fluid expansion phenomenon occurs, that is, an increase in the amount of steam and a decrease in the drum pressure, and an increase in the amount of steam and an increase in the drum level. The second function generator 358 on the rear side receives the input and outputs a result of calculating the function of the expansion phenomenon.

The correction signal generator 360 receives a function calculation value regarding expansion and contraction of the fluid from the first and second function generators 354 and 358, and calculates and outputs a correction value according to the rapeseed expansion contraction. At the rear end of the correction signal generator 360, in order to ensure accuracy of the correction value, the highest and reference values of the fluid expansion and contraction phenomenon are compared and determined. That is, the maximum limiter 362 receives the drum pressure, the drum level, and the steam flow rate, which are input to the fluid shrink detector 352 and the fluid expansion detector 356, and calculates and outputs a threshold maximum value at which the fluid can be expanded and contracted. . A later stage discriminator 364 receives the correction value of the correction signal generator 360 and checks whether the correction value falls between the limit maximum value from the maximum limiter 362 and the reference value 366 from the control device. Control with the output.

The correction adder 368 at the rear stage receives and outputs the output value of the discriminator 364 and the drum level setting value of the operation switch 218 included for the three-element control. The output value of the correction adder 368 is input to the comparator 302, and the comparator 302 outputs the drum level from the drum level gauge 300 in comparison. The output of the correction adder 368 is also input to the change rate calculator 370. The change rate operator 370 calculates and outputs the change rate of the fluid expansion shrinkage correction value by differentiating the change rate of the output value of the correcting adder, and the third function generator 372 may change the change rate based on the change rate input from the change rate operator 370. Outputs the function calculation for The first proportional integral controller 304 adjusts the gain of the controller according to the output value of the third function generator 372, inputs the output value from the first comparator 302, proportionally integrates the output value, and then outputs it to the next stage. do.

The output value of the first proportional integral controller 304 is calculated from the steam flow rate from the steam flow rate meter 306 and the water flow rate from the water supply flow rate meter 314. Then, the normal drum level control is carried out so that the final calculation result is supplied. The drum level is controlled by controlling the flow control valve 320, and the control process and the calculation parts 300 to 320 are as described with reference to FIG.

Therefore, the drum level control apparatus according to the present invention controls the drum level stably by compensating for the unstable factors caused by the fluid expansion and contraction in the drum in the conventional three-element control process of the drum level, steam flow rate and feed water flow rate. Will be performed.

As described above, the present invention is not only applied to the one- and three-element control of the drum level, but also to the normal operation of the drum level due to fluid swelling & shrinkage occurring during start-up or excessive load fluctuations. Out of range can be prevented. In addition, by eliminating this instability, it has the effect of reducing the time to reach normal operation and increasing the stability of the operation to improve the operating efficiency.

Claims (5)

In the device for adjusting the water level of the drum provided in the heat recovery boiler of the power generation equipment, A fluid change compensator configured to receive control elements for the drum and the boiler and a fluid component comparator within the drum to calculate and output a fluid change compensation value for adjusting the level of the drum; And, And a general proportional integral control unit configured to receive a control element for the drum and the boiler, and receive a fluid component compensation value from the fluid change compensation unit, and perform proportional integral control to control the flow rate of the feed water supplied to the boiler. Drum level control device of power plant heat recovery boiler. According to claim 1, wherein the fluid change compensation unit At least one fluid change detector which receives the control elements for the drum and the boiler and the fluid change element in the drum and detects the change in fluid; At least one function generator for generating a function for a fluid change state based on an output of the fluid change detector corresponding to each of the at least one fluid change detector; A correction signal generator for receiving an output of the at least one function generator and generating a correction signal for correcting the fluid change component; A discriminator for adjusting a correction signal of the correction signal generator based on the highest limit value of the fluid change state and a reference value preset in the adjustment device; A correction adder for adding the output value of the discriminator and the proportional integral control component fed back from the general proportional integral controller and outputting the proportional integral control component to the general proportional integral controller; And, And a change rate function generator for calculating the rate of change of the output value of the correction adder and generating a function according to the rate of change and outputting it to the general proportional integral control unit. The method of claim 1 or 2, wherein the general proportional integral control unit A first proportional integral controller configured to receive the level of the drum, receive the output of the correction adder and the change rate function generator, and perform comparison and proportional integration with respect to the level of the drum; And a variable gain proportional integral controller for controlling the control gain of the first proportional integral controller according to the output of the change rate function generator. The apparatus of claim 1, wherein the fluid component comparing element is a drum pressure of the drum. The method of claim 1 or 2, wherein the at least one fluid change detector A fluid expansion detector for detecting an expansion component of the fluid in the drum; And, A drum level control apparatus of a power generation equipment array recovery boiler comprising a fluid reduction detector for detecting a reduced component of the fluid in the drum.