CN110617118A - System and method for optimizing speed regulation of steam turbine under FCB working condition - Google Patents

Abstract

The invention discloses a system and a method for optimizing the speed regulation of a steam turbine under the FCB working condition, wherein the system comprises a bias quantity calculation module, a bias switching quantity judgment module and a PID speed regulator connected with the bias quantity calculation module and the bias switching quantity judgment module; the offset calculation module comprises a first analog input module, a first division block, a second analog input module, a differential block, a second division block, a third division block, a subtraction block, a low comparison block, a switching block and an analog output end; the bias switching value judging module comprises a switching value input module, a first pulse block, a second pulse block, an RS trigger, a non-block and a switching value output module.

Description

System and method for optimizing speed regulation of steam turbine under FCB working condition

Technical Field

The invention relates to the technical field of steam turbines, in particular to a system and a method for optimizing the speed regulation of a steam turbine under an FCB (flux-cored bus) working condition.

Background

With the promotion of series policies such as national energy conservation and emission reduction, energy structure optimization and adjustment and the like, new requirements are put forward on a power plant control system under the new situation that the proportion of new energy is increased and the structures of power grids such as western and east power transmission, power grid interconnection and the like are increasingly complex, and the function normalization of the FCB tends to be great.

The inventor finds that the DEH rotating speed control scheme under the current FCB working condition has the following defects in the research and development process:

(1) after the FCB occurs, the load of the steam turbine is changed rapidly, the steam turbine is switched from a load control mode to a rotating speed control mode, and the rotating speed control mode adopts a PID control mode. Since the load change precedes the rotation speed change, the PID control method based on the amount of modulation as the rotation speed has a large lag, resulting in frequent oscillations of the control system.

(2) The original control scheme estimates the island load by using a frequency difference signal and a rotation speed unequal rate, and the estimated value is greatly different from the actual value due to the nonlinear relation between the frequency difference and the island load.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a system and a method for optimizing the speed regulation of a steam turbine under the FCB working condition.

The technical scheme of the steam turbine speed regulation optimizing system under the FCB working condition provided by the invention on the one hand is as follows:

a speed regulation optimization system of a steam turbine under an FCB working condition comprises a bias calculation module for calculating a bias and a bias switching value judgment module for outputting a bias switching value.

The offset calculation module comprises a first analog input module and a first division block;

the first analog quantity input module 1 receives the main steam pressure output by the DEH system and inputs the main steam pressure to the first division block, and the first division block divides the rated main steam pressure and the main steam pressure to obtain a main steam pressure correction coefficient.

Further, the offset calculation module further comprises a second analog input module, a differential block, a second division block and a third division block;

the second analog quantity input module receives the actual rotating speed output by the DEH system and inputs the actual rotating speed to the differential block, the differential block performs differential processing on the received actual rotating speed to obtain rotor acceleration and outputs the rotor acceleration to the second division block, and the second division block divides the rotor flying acceleration and the rotor acceleration to obtain island load and outputs the island load to the third division block; and the third division block receives the main steam pressure correction coefficient output by the first division block and divides the received main steam pressure correction coefficient and the island load to obtain an island load correction value.

Further, the offset calculation module further comprises a subtraction block, a low comparison block, a switching block and an analog output end;

the second analog quantity input module receives the actual rotating speed output by the DEH system and inputs the actual rotating speed to the subtraction block, the subtraction block subtracts the received actual rotating speed from the set OPC reset rotating speed and outputs the obtained difference value to the low comparison block, the low comparison block compares the received difference value with the set threshold value, when the difference value is smaller than the set threshold value, the actual rotating speed is judged to be higher than the OPC reset rotating speed, the selection switch quantity is output to the switching block, the switching block receives the island load correction value output by the third division block and outputs the island load correction value as the offset quantity to the analog quantity output module, and the analog quantity output module outputs the offset quantity to a tracking quantity input pin of the PID speed regulator.

The bias switching value judging module comprises a switching value input module, a first pulse block, a second pulse block, an RS trigger and a switching value output module;

the switching value input module receives an FCB signal output by a DEH system and inputs the FCB signal to a set end of an RS trigger, when the actual rotating speed is less than an OPC reset rotating speed, the low comparison block outputs offset switching value to a first pulse block, the first pulse block inputs the offset switching value to a reset end of the RS trigger, the RS trigger outputs the offset switching value to a second pulse block, the second pulse block outputs the offset switching value to the switching value output module, and the switching value output module outputs the offset switching value to a tracking switch pin of a PID speed regulator.

Further, a non-block is connected between the RS flip-flop and the second pulse block.

The technical scheme of the method for optimizing the speed regulation of the steam turbine under the FCB working condition provided by the invention is as follows:

a speed regulation optimization method for a steam turbine under an FCB working condition comprises the following steps:

the main steam pressure output by the DEH system is input into a first division block through a first analog quantity input module, the first division block divides the rated main steam pressure and the main steam pressure to obtain a main steam pressure correction coefficient, and the main steam pressure correction coefficient is output to a third division block;

the actual rotating speed N output by the DEH system is input into a differential block through a second analog quantity input module, the differential block performs differential processing on the received actual rotating speed to obtain rotor acceleration and outputs the rotor acceleration to a second division block, the rotor flying acceleration and the rotor acceleration a are divided by the second division block to obtain island load, and the island load is output to a third division block;

the third division block divides the received main steam pressure correction coefficient and the island load to obtain an island load correction value, and outputs the island load correction value to the switching block;

and the actual rotating speed N output by the DEH system is input into a subtraction block through a second analog quantity input module, when the actual rotating speed is less than the OPC reset rotating speed, the low comparison block outputs offset switching quantity to a first pulse block, the first pulse block inputs the offset switching quantity into a reset end of an RS trigger, the RS trigger outputs the offset switching quantity to a second pulse block, the second pulse block outputs the offset switching quantity to a switching quantity output module, and the switching quantity output module outputs the offset switching quantity to a tracking switch pin of the PID speed regulator.

When the actual rotating speed is less than the OPC reset rotating speed, the bias switching value output by the low-comparison block is input into the reset end of the RS trigger through the first pulse block, the bias switching value output by the RS trigger is output to the second pulse block through the non-block, the second pulse block outputs the bias switching value to the switching value output module, and the switching value output module outputs the bias switching value to a tracking switch T pin of the PID speed regulator.

After receiving the offset switching value, the PID controller tracks the set pulse time and then starts to control the rotating speed by taking the received offset as an initial value.

Through the technical scheme, the invention has the beneficial effects that:

(1) the invention realizes the advanced control of the rotating speed of the steam turbine, and effectively avoids the phenomena of serious rotating speed overshoot, severe and frequent network frequency fluctuation and the like;

(2) the island load correction value is calculated by adopting the ratio of the rotor acceleration to the rotor flying acceleration, and the island load after the FCB occurs can be accurately calculated;

(3) the invention adopts a PID control plus offset control mode to control the rotating speed of the steam turbine under the FCB working condition, realizes the short-time tracking of the DEH rotating speed controller after OPC reset, enables the output of the DEH rotating speed controller to be directly stepped from zero to offset, ensures the quick balance of the power of the steam turbine and island load, realizes the advanced control of the rotating speed of the steam turbine, avoids the downward overshoot of the rotating speed and quickly stabilizes the island network frequency.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the application and not to limit the invention.

FIG. 1 is a block diagram of a turbine speed regulation optimization system under an FCB condition according to an embodiment;

the device comprises an analog quantity input module 1, a first analog quantity input module 2, a first division block 3, a second analog quantity input module 4, a differential block 5, a second division block 6, a third division block 7, a subtraction block 8, a low comparison block 9, a switching block 10, an analog quantity output end 11, a switching quantity input module 12, a first pulse block 13, an RS trigger 14, a non-block 15, a second pulse block 16, a switching quantity output module 17 and a PID speed regulator.

Detailed Description

The invention is further described with reference to the following figures and examples.

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

Example one

Fig. 1 is a structural diagram of a turbine speed regulation optimization system under the FCB working condition according to the present embodiment. As shown in fig. 1, the system for optimizing speed regulation of a steam turbine includes a bias amount calculating module and a bias switching amount judging module.

Specifically, the offset calculation module comprises a first analog input module 1, a first division block 2, a second analog input module 3, a differential block 4, a second division block 5, a third division block 6, a subtraction block 7, a low comparison block 8, a switching block 9 and an analog output end 10.

One end of the first analog quantity input module 1 is connected with the analog output end of the DEH system, the other end is connected with the input end of the first division block 2, the output end of the first division block 2 is connected with a third division block 6, one end of the second analog quantity input module 3 is connected with the analog output end of the DEH system, the other end of the second analog quantity input module is connected with the input end of a differential block 4, the output end of the differential block 4 is connected with a third division block 6 through a second division block 5, the output end of the third division block 6 is connected with a switching block 9, the input end of the subtraction block 7 is connected with the output end of the second analog quantity input module 3, the output end of the subtraction block 7 is connected with the input end of the low comparison block 8, the output end of the low comparison block 8 is connected with a switching block 9, the output end of the switching block 9 is connected with an analog output module 10, the output end of the analog quantity output module 10 is connected with the analog input end of the PID speed regulator 17.

Main steam pressure P output by DEH system_TInputting a first division block 2 through a first analog quantity input module 1, wherein the first division block 2 divides the rated main steam pressure P_TeWith the received main steam pressure P_TAnd (4) dividing to obtain a main steam pressure correction coefficient K, and outputting to the third division block 6.

The actual rotating speed N output by the DEH system is input into the differential block 4 through the second analog quantity input module 3, the differential block 4 performs differential processing on the received actual rotating speed N to obtain rotor acceleration a, the differential block 4 outputs the rotor acceleration a to the second division block 5, the second division block 5 divides the rotor flying acceleration and the rotor acceleration a to obtain island load, and the island load is output to the third division block 6.

The third division block 6 divides the received main steam pressure correction coefficient K and the island load to obtain an island load correction value, and outputs the island load correction value to the switching block 9.

The actual rotating speed N output by the DEH system is input into a subtraction block 7 through a second analog quantity input module 3, and the subtraction block 7 combines the received actual rotating speed N with the set OPC reset rotating speed N_OPCSubtracting, outputting the obtained difference value to a low comparison block 8, comparing the received difference value with-0.1 by the low comparison block 8, and if the difference value is less than-0.1, judging that the actual rotating speed N is the actual rotating speed<OPC reset rotation speed N_OPCThe method comprises the steps of outputting a selection switch value 1 to a switching block 9, wherein the switching block 9 selects Y-path output, directly outputs an island load correction value at the moment to an analog quantity output module 10 as an offset, and the analog quantity output module 10 outputs the offset to a tracking quantity input pin TRIN of a PID (proportion integration differentiation) speed regulator 17; if the difference is not less than-0.1, the actual rotating speed N is judged to be not less than the OPC reset rotating speed N_OPCAnd outputting the selection switch value 0 to a switching block 9, wherein the switching block 9 selects N paths as output, outputs an island load correction value, and does not act on the analog quantity output module 10.

In this embodiment, the time constant T of the micro-segment 4₁Set to 1 second, time constant T for filtering out high frequency interference signals₂Set to 2 seconds. The rotor fly-lift acceleration is a constant and can be measured by a load shedding test, such as the rotor fly-lift acceleration of a million unitsThe speed was 350 r/min/s. The rated main steam pressure is a constant and can be obtained by checking a specification of a steam turbine, for example, the rated main steam pressure of a million units is 28 MPa. OPC reset rotation speed N_OPCIs constant, obtained by looking up the DEH configuration setting, typically set 3060.

Specifically, the offset switching value judging module comprises a switching value input module 11, a first pulse block 12, a second pulse block 15, an RS flip-flop 13, a non-block 14 and a switching value output module 16.

One end of the switching value input module 11 is connected with the switching value output end of the DEH system, the other end is connected with the position end S of the RS trigger 13, the input end of the first pulse block 12 is connected with the output end of the low comparison block 8, the output end of the first pulse block 12 is connected with the reset end R of the RS trigger 13, the output end of the RS trigger 13 is connected with the input end of the non-block 14, the output end of the non-block 14 is connected with the input end of the second pulse block 15, and the output end of the second pulse block 15 is connected with the T pin of the tracking switch of the PID speed regulator 17 through the switching value output module 16.

The FCB signal output by the DEH system is input to a setting end S of an RS trigger 13 through a switching value input module 11, and when the low comparison block 8 judges that the actual rotating speed N is<OPC reset rotation speed N_OPCThe offset switching value output by the low comparison block 8 is input to a reset end R of the RS flip-flop 13 through the first pulse block 12, the RS flip-flop 13 outputs the offset switching value to the second pulse block 15 through the non-block 14, the second pulse block 15 outputs the offset switching value to the switching value output module 16, and the switching value output module 16 outputs the offset switching value to a tracking switch T pin of the PID speed regulator 17.

In the steam turbine speed regulation optimization system under the FCB working condition provided by this embodiment, a steam turbine rotation speed signal, an FCB signal, and a main steam pressure signal of a DEH system are introduced into the steam turbine speed regulation optimization system, an island load percentage is determined by calculating a ratio of a rotor acceleration to a rotor flying acceleration, and then a rotation speed control offset is calculated by main steam pressure correction; the offset is output and then is connected to a DEH rotating speed controller tracking input pin, so that the tracking offset of the DEH rotating speed controller within two seconds of OPC resetting is realized, and the rotating speed controller performs PID automatic control by taking the offset as an initial value after the OPC resetting is performed for two seconds, thereby solving the problems of serious rotating speed overshoot and frequent fluctuation under the FCB working condition.

As shown in fig. 1, the operating principle of the steam turbine speed regulation optimizing system under the FCB working condition proposed in this embodiment is as follows:

under the FCB working condition, the rotating speed of the steam turbine rapidly rises, OPC acts, and the PID speed regulator rapidly reaches zero. The OPC is reset along with the reduction of the rotating speed, the offset switching value sends out 2-second pulses, because a tracking switch pin of the PID speed regulator is connected with an offset switching value judging module of the system, the PID speed regulator is in a tracking state at the moment, the tracking value is the offset, the offset switching value is the 2-second pulses, the PID speed regulator is released to be in a normal regulation state after tracking for 2 seconds, and the PID speed regulator starts to control the rotating speed by taking the offset as an initial value at the moment.

Example two

The embodiment provides a method for optimizing the speed regulation of a steam turbine under the FCB working condition, which is realized based on the system for optimizing the speed regulation of the steam turbine under the FCB working condition.

The method for optimizing the speed regulation of the steam turbine under the FCB working condition comprises the following steps:

main steam pressure P output by DEH system_TThe first analog quantity input module 1 inputs a first division block 2, and the first division block 2 converts the rated main steam pressure P_TeWith the received main steam pressure P_TAnd (5) dividing to obtain a main steam pressure correction coefficient K, and outputting to a third division block 6.

The actual rotating speed N output by the DEH system is input into a differential block 4 through a second analog quantity input module 3, the differential block 4 carries out differential processing on the received actual rotating speed N to obtain rotor acceleration a and outputs the rotor acceleration a to a second division block 5, and the second division block 5 divides the rotor flying acceleration a by the rotor acceleration a to obtain island load and outputs the island load to a third division block 6.

The third division block 6 divides the received main steam pressure correction coefficient K and the island load to obtain an island load correction value, and outputs the island load correction value to the switching block 9.

The actual rotating speed N output by the DEH system is output through a second analog quantity input module 3Go to the subtraction block 7, the subtraction block 7 compares the received actual rotation speed N with the set OPC reset rotation speed N_OPCSubtracting, outputting the obtained difference value to a low comparison block 8, comparing the received difference value with-0.1 by the low comparison block 8, and judging that the actual rotating speed N is the actual rotating speed N when the difference value is less than-0.1<OPC reset rotation speed N_OPCAnd outputting the selection switch quantity 1 to a switching block 9, wherein the switching block 9 outputs the island load correction value at the moment to an analog quantity output module 10 as an offset quantity, and the analog quantity output module 10 outputs the offset quantity to a tracking quantity input pin TRIN of a PID speed regulator 17.

The FCB signal output by the DEH system is input into a setting end S of the RS trigger 13, and when the actual rotating speed N is reached<OPC reset rotation speed N_OPCThe offset switching value output by the low comparison block 8 is input to a reset end R of an RS trigger 13 through a first pulse block 12, the offset switching value output by the RS trigger 13 is output to a second pulse block 15 through a non-block 14, the offset switching value output by the second pulse block 15 is output to a switching value output module 16, and the switching value output module 16 outputs the offset switching value to a tracking switch T pin of a PID speed regulator 17.

Upon receiving the offset switching value and following the set pulse time, the PID controller 17 starts the rotational speed control with the received offset as an initial value.

From the above description, it can be seen that the above-described embodiments achieve the following technical effects:

(1) the advanced control of the rotating speed of the steam turbine is realized, and the phenomena of serious rotating speed overshoot, severe and frequent network frequency fluctuation and the like are effectively avoided;

(2) the island load correction value is calculated by adopting the ratio of the rotor acceleration to the rotor flying acceleration, and the island load after the FCB occurs can be accurately calculated;

(3) the control mode of PID control plus offset is adopted to control the rotating speed of the steam turbine under the FCB working condition, short-time tracking of the DEH rotating speed controller after OPC reset is realized, the output of the DEH rotating speed controller is directly stepped to offset from zero, the rapid balance of the power of the steam turbine and island load is ensured, the advanced control of the rotating speed of the steam turbine is realized, the downward overshoot of the rotating speed is avoided, and the network frequency of the island is rapidly stabilized.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.

Claims (9)

1. A speed regulation optimization system of a steam turbine under an FCB working condition is characterized by comprising a bias calculation module for calculating a bias and a bias switching value judgment module for outputting a bias switching value.

2. The system for optimizing speed regulation of a steam turbine under an FCB operating condition of claim 1, wherein the offset calculation module comprises a first analog input module and a first division block;

the first analog quantity input module 1 receives the main steam pressure output by the DEH system and inputs the main steam pressure to the first division block, and the first division block divides the rated main steam pressure and the main steam pressure to obtain a main steam pressure correction coefficient.

3. The system for optimizing speed regulation of a steam turbine under the FCB working condition according to claim 2, wherein the offset calculation module further comprises a second analog input module, a differential block, a second division block and a third division block;

the second analog quantity input module receives the actual rotating speed output by the DEH system and inputs the actual rotating speed to the differential block, the differential block performs differential processing on the received actual rotating speed to obtain rotor acceleration and outputs the rotor acceleration to the second division block, and the second division block divides the rotor flying acceleration and the rotor acceleration to obtain island load and outputs the island load to the third division block; and the third division block receives the main steam pressure correction coefficient output by the first division block and divides the received main steam pressure correction coefficient and the island load to obtain an island load correction value.

4. The system for optimizing speed regulation of a steam turbine under an FCB operating condition of claim 3, wherein the offset computation module further comprises a subtraction block, a low comparison block, a switching block, and an analog output;

the second analog quantity input module receives the actual rotating speed output by the DEH system and inputs the actual rotating speed to the subtraction block, the subtraction block subtracts the received actual rotating speed from the set OPC reset rotating speed and outputs the obtained difference value to the low comparison block, the low comparison block compares the received difference value with the set threshold value, when the difference value is smaller than the set threshold value, the actual rotating speed is judged to be higher than the OPC reset rotating speed, the selection switch quantity is output to the switching block, the switching block receives the island load correction value output by the third division block and outputs the island load correction value as the offset quantity to the analog quantity output module, and the analog quantity output module outputs the offset quantity to a tracking quantity input pin of the PID speed regulator.

5. The system for optimizing the speed regulation of the steam turbine under the FCB working condition according to claim 1, wherein the offset switching value judging module comprises a switching value input module, a first pulse block, a second pulse block, an RS trigger and a switching value output module;

the switching value input module receives an FCB signal output by a DEH system and inputs the FCB signal to a set end of an RS trigger, when the actual rotating speed is less than an OPC reset rotating speed, a low comparison block outputs offset switching value to a first pulse block, the first pulse block inputs the offset switching value to a reset end of the RS trigger, the RS trigger outputs the offset switching value to a second pulse block, the second pulse block outputs the offset switching value to a switching value output module, and the switching value output module outputs the offset switching value to a tracking switch pin of a PID speed regulator.

6. The system for optimizing speed regulation of a steam turbine under an FCB condition of claim 5, wherein a non-block is connected between the RS trigger and the second pulse block.

7. A method for optimizing the speed regulation of a steam turbine under an FCB condition, the method being implemented based on the system for optimizing the speed regulation of a steam turbine under an FCB condition according to any one of claims 1 to 6, the method comprising the steps of:

the main steam pressure output by the DEH system is input into a first division block through a first analog quantity input module, the first division block divides the rated main steam pressure and the main steam pressure to obtain a main steam pressure correction coefficient, and the main steam pressure correction coefficient is output to a third division block;

the actual rotating speed N output by the DEH system is input into a differential block through a second analog quantity input module, the differential block performs differential processing on the received actual rotating speed to obtain rotor acceleration and outputs the rotor acceleration to a second division block, the rotor flying acceleration and the rotor acceleration a are divided by the second division block to obtain island load, and the island load is output to a third division block;

the third division block divides the received main steam pressure correction coefficient and the island load to obtain an island load correction value, and outputs the island load correction value to the switching block;

and the actual rotating speed N output by the DEH system is input into a subtraction block through a second analog quantity input module, when the actual rotating speed is less than the OPC reset rotating speed, the low comparison block outputs offset switching quantity to a first pulse block, the first pulse block inputs the offset switching quantity into a reset end of an RS trigger, the RS trigger outputs the offset switching quantity to a second pulse block, the second pulse block outputs the offset switching quantity to a switching quantity output module, and the switching quantity output module outputs the offset switching quantity to a tracking switch pin of the PID speed regulator.

8. The method for optimizing the speed regulation of a steam turbine under the FCB condition according to claim 7, further comprising:

when the actual rotating speed is less than the OPC reset rotating speed, the bias switching value output by the low-comparison block is input into the reset end of the RS trigger through the first pulse block, the bias switching value output by the RS trigger is output to the second pulse block through the non-block, the second pulse block outputs the bias switching value to the switching value output module, and the switching value output module outputs the bias switching value to a tracking switch T pin of the PID speed regulator.

9. The method for optimizing the speed regulation of a steam turbine under the FCB condition according to claim 7, further comprising:

after receiving the offset switching value, the PID controller tracks the set pulse time and then starts to control the rotating speed by taking the received offset as an initial value.