A control system and method for improving the primary frequency regulation performance index of a thermal power unit

Abstract

This invention discloses a control system and method for improving the primary frequency regulation performance of thermal power units. The system includes a turbine speed or grid frequency signal acquisition device F1, which processes the acquired signals and sends them to a primary frequency regulation optimization control system. Simultaneously, an additional high-precision grid frequency co-source acquisition device sends the acquired grid frequency co-source signal (co-source with the PMU) to the primary frequency regulation optimization control system. The primary frequency regulation optimization control system then sends the processed primary frequency regulation load command to the turbine main control system. The output of the turbine main control system is sent to the turbine control system, which also receives the primary frequency regulation valve command output from the primary frequency regulation optimization control system, jointly controlling the turbine valve operation. This invention ensures the accuracy of primary frequency regulation operation, employs rapid response, increases the primary frequency regulation contribution, reduces the frequency of turbine valve operation, and improves the unit's primary frequency regulation performance.

Description

Technical Field

[0001] This invention relates to the field of automatic control technology for thermal power plants, specifically to a control system and method for improving the primary frequency regulation performance of thermal power units. Background Technology

[0002] With the continuous increase in installed capacity of new energy sources such as wind power, hydropower, and photovoltaic power generation, the proportion of new energy power generation is constantly increasing, the rotational inertia of the power system is constantly decreasing, and the frequency fluctuations of the power grid caused by various sudden power disturbances are more frequent, which puts forward higher requirements for the primary frequency regulation control performance of thermal power units.

[0003] As the main force of frequency regulation in the power system, thermal power units typically employ a primary frequency regulation control strategy that uses frequency or speed deviations to directly apply to the turbine control valves after passing through a unequal law function. Simultaneously, the primary frequency regulation load command is superimposed on the unit load command to form the final turbine main control setpoint, thereby performing closed-loop control of the unit power to prevent the turbine main control from reverse-regulating the primary frequency regulation power and achieving precise primary frequency regulation control.

[0004] When the unit performs a primary frequency regulation operation, the turbine control valve command on the DEH side responds immediately, that is, the turbine control valve opens or closes rapidly. This process inevitably causes changes in the unit's main steam pressure. The turbine main control setpoint circuit generally includes a main steam pressure deviation correction circuit, which has an adverse effect on the primary frequency regulation and leads to a decrease in the primary frequency regulation performance indicators.

[0005] In the primary frequency control loop of thermal power units, many units use turbine speed signals acquired by the DEH system to replace the grid frequency signals for primary frequency regulation. However, due to the low measurement accuracy and large measurement errors of the turbine speed signals, and their non-locality with the grid frequency, it is difficult for the unit's primary frequency regulation performance to meet grid requirements.

[0006] Meanwhile, the primary frequency control is simply set as a static function of frequency difference-frequency load in the control logic according to relevant regulations, without fully considering the dynamic characteristics of the unit during actual operation. At the same time, the installation and adjustment of the turbine control valve during long-term operation and overhaul will cause the actual flow characteristic curve of the turbine control valve to deviate from the DEH set flow curve, resulting in poor primary frequency control performance of the unit, and even power oscillation problems in a certain load range.

[0007] Furthermore, with the rapid changes in grid frequency, the unit power will also experience large and rapid fluctuations, which is detrimental to grid stability; at the same time, it will increase the wear of the turbine control valves, and in severe cases, it may even cause equipment damage, affecting the safe operation of the unit. Summary of the Invention

[0008] The purpose of this invention is to overcome the above-mentioned problems by providing a control system and method for improving the primary frequency regulation performance of thermal power units. Through dynamic predictive control technology, the accuracy of primary frequency regulation is ensured. By adopting a fast response and slow regression approach, the power contribution of primary frequency regulation is increased, the frequency of turbine regulating valve operation is reduced, and the primary frequency regulation performance index of the unit is improved.

[0009] A control system and method for improving the primary frequency regulation performance of thermal power units includes a turbine speed or grid frequency signal acquisition device F1. The turbine speed or grid frequency signal acquisition device F1 acquires the signal and sends it to the primary frequency regulation optimization control system 3 after passing through a signal processing system 2. At the same time, an additional high-precision grid frequency homogeneous acquisition device 6 acquires the grid frequency homogeneous signal (homogeneous with the PMU) and sends it to the primary frequency regulation optimization control system 3. The primary frequency regulation optimization control system 3 sends the processed primary frequency regulation load command to the turbine main control system 4. The output of the turbine main control system 4 is sent to the turbine control system 5. The turbine control system 5 also receives the primary frequency regulation control valve command output by the primary frequency regulation optimization control system 3, and jointly controls the turbine control valve action.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A control system for improving the primary frequency regulation performance of thermal power units includes a turbine speed signal or grid frequency input. The turbine speed or grid frequency signal input is connected to the input of an inertial link. The output of the inertial link is connected to the input N of a first analog switch. The input Y of the first analog switch is connected to a high-precision grid frequency signal input. The switching condition of the first analog switch is connected to the primary frequency regulation index boosting switch input. The output of the first analog switch is connected to the input of a first function converter. The output of the first function converter is connected to the input N of a second analog switch, the input of a second function converter, the input of a third function converter, the input of a fourth function converter, and the input of a fifth function converter, respectively. The input of the first function converter is connected to the input of the second function converter. The output of the second function converter is connected to the input of the first rate limiter. The output of the third function converter is connected to the negative rate limit input NL of the first rate limiter. The positive rate limit input PL of the first rate limiter is a fixed value of 100. The output of the first rate limiter is connected to the input of the multiplier. The input of the multiplier is connected to the output of the multiplier. The input of the multiplier is connected to the output of the multiplier. The input of the multiplier is connected to the output of the sixth function converter. The input of the sixth function converter is connected to the unit load command input. The input of the multiplier is connected to the output of the seventh function converter. The seventh function converter... The input of the multiplier is connected to the turbine control valve command input; the input of the multiplier is connected to the output of the eighth function converter, the input of the eighth function converter is connected to the main steam pressure deviation input, the input of the multiplier is connected to the output of the ninth function converter, and the input of the ninth function converter is connected to the main steam pressure input; the output of the multiplier is connected to the input of the adder, the input of the adder is connected to the output of the multiplier, the input of the multiplier is connected to the output of the second rate limiter, the input of the second rate limiter is connected to the output of the fourth function converter, the positive rate limit input PL of the second rate limiter is connected to the output of the fifth function converter, and the negative rate limit input NL of the second rate limiter is constant. Value 100; The input of the multiplier is connected to the output of the multiplier; The input of the multiplier is connected to the output of the multiplier; The input of the multiplier is connected to the output of the eleventh function converter; The input of the eleventh function converter is connected to the turbine control valve command input; The input of the multiplier is connected to the output of the twelfth function converter; The input of the twelfth function converter is connected to the main steam pressure deviation input; The input of the multiplier is connected to the output of the thirteenth function converter; The input of the thirteenth function converter is connected to the main steam pressure input.The adder's output is connected to the input Y of the second analog switch. The switching condition of the second analog switch is connected to the primary frequency regulation index boosting switch input. The output of the second analog switch is connected to both the primary frequency regulation load command output and the input of the fourteenth function converter. The output of the fourteenth function converter is connected to the primary frequency regulation gate command output.

[0012] The load command input is connected to the input of the adder. The input of the adder is connected to the output of the third analog switch. The input Y of the third analog switch is connected to the output of the third analog switch. The input N of the third analog switch is connected to the output of the fifteenth function converter. The input of the fifteenth function converter is connected to the main steam pressure deviation input. The switching condition of the third analog switch is connected to the primary frequency regulation action input. The primary frequency regulation load command input is connected to the input of the adder. The output of the adder is connected to the input SP of the first PID controller. The actual load input is connected to the input PV of the first PID controller. The output of the first PID controller is connected to the input of the first manual controller. The output of the first manual controller is connected to the input of the adder. The input of the adder is connected to the primary frequency regulation valve command input. The output of the adder is connected to the turbine valve command output.

[0013] The control system and method for improving the primary frequency regulation performance of thermal power units include the following steps:

[0014] Step 1: Set the primary frequency regulation index boosting switch to the active state, that is, convert the primary frequency regulation signal from the selected turbine speed or grid frequency signal to a high-precision grid frequency homogeneous signal;

[0015] Step 2: Set the parameters of the first function converter according to the rotational speed inequality function;

[0016] Step 3: Set the parameters of the second and fourth function converters according to the direction of the first frequency modulation operation;

[0017] When a frequency modulation operation requires an increase in load, the output of the second function converter is the same as the output of the first function converter, and the output of the fourth function converter is 0;

[0018] When a frequency modulation action requires load reduction, the output of the second function converter is 0, and the output of the fourth function converter is the same as the output of the first function converter.

[0019] Step 4: When the load increases during a primary frequency modulation operation, set the parameters of the first rate limiter: the positive rate limiter has no limiting effect, allowing the primary frequency modulation load command to rise rapidly to the target value; when the load increase during a primary frequency modulation operation ends or the primary frequency modulation load command decreases, the negative rate limiter of the first rate limiter takes effect, that is, the primary frequency modulation load command slowly decreases to 0, and the negative rate of decrease of the primary frequency modulation load is given by the third function converter according to the current primary frequency modulation load command;

[0020] Then, based on the unit load command input, turbine valve command input, main steam pressure offset input, and main steam pressure input, the sixth, seventh, eighth, and ninth function converters are set respectively to obtain the output of the primary frequency regulation load command multiplier after positive processing, so as to ensure the accuracy and response speed of the primary frequency regulation under different load commands, different turbine valve openings, different main steam pressures, and different main steam pressure deviations.

[0021] Step 5: When a primary frequency modulation operation requires load reduction, set the parameters of the second rate limiter: the negative rate limit has no limiting effect, which allows the primary frequency modulation load command to be quickly reduced to the target value; when the primary frequency modulation operation ends or the primary frequency modulation load command increases, the positive rate limit of the second rate limiter takes effect, that is, the primary frequency modulation load command slowly rises to 0, and the positive rate of increase of the primary frequency modulation load is given by the fifth function converter according to the current primary frequency modulation load command;

[0022] Then, based on the unit load command input, turbine valve command input, main steam pressure offset input, and main steam pressure input, the tenth, eleventh, twelfth, and thirteenth function converters are set respectively to obtain the output of the primary frequency regulation load command multiplier after negative processing, so as to ensure the accuracy and response speed of the primary frequency regulation under different load commands, different turbine valve openings, different main steam pressures, and different main steam pressure deviations;

[0023] Step 6: The primary frequency modulation load command after positive processing and the primary frequency modulation load command after negative processing are summed to form the optimized primary frequency modulation load command, which is the primary frequency modulation load command output.

[0024] Step 7: Based on the actual flow curve of the steam turbine, set the fourteenth function generator to obtain the final frequency regulation valve command output;

[0025] Step 8: The load command, main steam pressure deviation correction value, and primary frequency regulation load command together constitute the setpoint of the turbine main control regulator;

[0026] When a frequency regulation operation is performed, the main steam pressure deviation correction value is increased with a hold function to improve the accuracy of the primary frequency regulation and prevent changes in the main steam pressure deviation from causing load reversal.

[0027] The deviation between the setpoint of the turbine main control regulator and the actual load is calculated using PID control to control the output of the turbine main control handheld device;

[0028] Step 10: The output of the turbine main control handheld device, superimposed with the previous frequency regulation valve command, acts together on the turbine valve to control it, ensuring the speed and accuracy of the primary frequency regulation response.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1) Based on the study of the turbine control valve and unit load response characteristics, dynamic feedforward prediction technology is adopted to correct the positive and negative load commands of primary frequency regulation by using main steam pressure, main steam pressure deviation, unit load command, and turbine control valve opening command, respectively, so as to ensure the speed and accuracy of primary frequency regulation response under various operating conditions.

[0031] 2) Use high-precision grid frequency signals to replace the original speed signals or low-precision grid frequency signals to ensure that the primary frequency regulation source signal of the unit is the same as the signal of the grid-tested unit, thereby ensuring the correctness of the primary frequency regulation action and the accuracy of the primary frequency regulation response.

[0032] 3) During the primary frequency regulation operation, the interlocking principle is adopted to maintain the main steam pressure deviation correction circuit in the turbine main control setpoint, so as to prevent the main steam pressure deviation correction circuit from adjusting the primary frequency regulation load, thereby ensuring the accuracy of the primary frequency regulation.

[0033] 4) During a primary frequency regulation operation, the primary frequency regulation load command is responded to quickly; when the primary frequency regulation operation ends or the primary frequency regulation load positive command decreases, the primary frequency regulation load command is slowly returned to zero, which increases the primary frequency regulation integral power to a certain extent, while reducing the oscillation frequency of the turbine control valve and extending the service life of the turbine control valve.

[0034] 5) Wide range of applications: This control system and method are applicable to the control logic design of primary frequency regulation in all coal-fired power plants. It can effectively improve the primary frequency regulation index, meet the requirements of the "two detailed rules" for the primary frequency regulation index, obtain additional electricity revenue, and have predictable benefits for power plants. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the control system for improving the primary frequency regulation performance of thermal power units according to the present invention.

[0036] Figure 2 The present invention provides a logic diagram of a primary frequency regulation optimization system for improving the primary frequency regulation performance of thermal power units.

[0037] Figure 3The present invention provides a logic diagram of a steam turbine control system for improving the primary frequency regulation performance of thermal power units.

[0038] Figure 1 middle:

[0039] F1 – Steam turbine speed or power grid frequency acquisition device; SIG – Signal processing system;

[0040] OPT – Primary Frequency Optimization Control System; DEM – Steam Turbine Main Control System;

[0041] THR – Steam Turbine Control System; F2 – High-Precision Power Grid Frequency Acquisition Device

[0042] Figures 2-3 middle:

[0043] LAG – Inertial element; T – Analog converter; F(x) – Function converter;

[0044] RATE – Rate limiter; ADD – Adder; MUL – Multiplier;

[0045] PID – PID controller; M / A – handheld controller; Detailed Implementation

[0046] A control system for improving the primary frequency regulation performance of thermal power units includes: a primary frequency regulation performance enhancement switching switch input 1, a turbine speed or grid frequency signal input 2, a high-precision grid frequency homogeneous signal input 3, a unit load command input 16, a turbine regulating valve command input 20, a main steam pressure deviation input 22, a main steam pressure input 25, a first inertial element 4, a first analog quantity switch 5, a first function converter 6, a second analog quantity switch 7, a second function converter 8, a first rate limiter 9, a third function converter 10, a fourth function converter 11, a second rate limiter 12, a fifth function converter 13, a multiplier 14, an adder 15, a sixth function converter 17, and a multiplier. 18. Multiplier 19. Seventh function converter 21. Eighth function converter 23. Multiplier 24. Ninth function converter 26. Tenth function converter 27. Multiplier 28. Eleventh function converter 31. Multiplier 29. Twelfth function converter 32. Multiplier 33. Thirteenth function converter 34. Multiplier 30. Fourteenth function converter 36. Primary frequency modulation command output 35. Primary frequency modulation control valve command output 37. Actual load input 38. Primary frequency modulation action input 39. Fifteenth function converter 40. Third analog quantity switcher 41. Adder 42. First PID controller 43. First manual control station 44. Adder 45. Steam turbine control valve command output 46.

[0047] The turbine speed or grid frequency signal input 2 is connected to the input of the inertial element 4. The output of the inertial element 4 is connected to the input N of the first analog switch 5. The input Y of the first analog switch 5 is connected to the high-precision grid frequency source signal input 3. The switching condition of the first analog switch 5 is connected to the primary frequency regulation index boosting switch input 1. The output of the first analog switch 5 is connected to the input of the first function converter 6. The output of the first function converter 6 is connected to the input N of the second analog switch 7, the input of the second function converter 8, the input of the third function converter 10, the input of the fourth function converter 11, and the input of the fifth function converter 13, respectively. The second function converter 8... The output of the first rate limiter 9 is connected to its input. The output of the third function converter 10 is connected to the negative rate limit input NL of the first rate limiter 9. The positive rate limit input PL of the first rate limiter 9 is a fixed value of 100. The output of the first rate limiter 9 is connected to input 1 of multiplier 14. Input 2 of multiplier 14 is connected to the output of multiplier 19. Input 1 of multiplier 19 is connected to the output of multiplier 18. Input 2 of multiplier 19 is connected to the output of multiplier 24. Input 1 of multiplier 18 is connected to the output of the sixth function converter 17. The input of the sixth function converter 17 is connected to the unit load command input 16. Input 2 of multiplier 18 is connected to the seventh function converter... The output of multiplier 21 is connected to the output of the seventh function converter 21, and the input of the seventh function converter 21 is connected to the turbine control valve command input 20; input 1 of multiplier 24 is connected to the output of the eighth function converter 23, and the input of the eighth function converter 23 is connected to the main steam pressure deviation input 22; input 2 of multiplier 24 is connected to the output of the ninth function converter 26, and the input of the ninth function converter 26 is connected to the main steam pressure input 25; the output of multiplier 14 is connected to input 1 of adder 15, input 2 of adder 15 is connected to the output of multiplier 30, input 1 of multiplier 30 is connected to the output of the second rate limiter 12, and the input of the second rate limiter 12 is connected to the output of the fourth function converter 11. The positive rate limit input PL of the second rate limiter 12 is connected to the output of the fifth function converter 13, and the negative rate limit input NL of the second rate limiter 12 is a fixed value of 100; the input 2 of the multiplier 30 is connected to the output of the multiplier 29, the input 1 of the multiplier 29 is connected to the output of the multiplier 28, the input 2 of the multiplier 29 is connected to the output of the multiplier 33, the input 1 of the multiplier 28 is connected to the output of the tenth function converter 27, the input of the tenth function converter 27 is connected to the unit load command input 16, the input 2 of the multiplier 28 is connected to the output of the eleventh function converter 31, and the input of the eleventh function converter 31 is connected to the turbine control valve command input 20;Input 1 of multiplier 33 is connected to the output of the twelfth function converter 32, and the input of the twelfth function converter 32 is connected to the main steam pressure deviation input 22. Input 2 of multiplier 33 is connected to the output of the thirteenth function converter 34, and the input of the thirteenth function converter 34 is connected to the main steam pressure input 25. The output of adder 15 is connected to the input Y of the second analog quantity switch 7. The switching condition of the second analog quantity switch 7 is connected to the input 1 of the primary frequency regulation index boosting switch. The output of the second analog quantity switch 7 is connected to the primary frequency regulation load command output 35 and the input of the fourteenth function converter 36, respectively. The output of the fourteenth function converter 36 is connected to the primary frequency regulation control gate command output 37. Load command input 16 is connected to input 1 of adder 42. Input 2 of adder 42 is connected to the output of the third analog switcher 41. Input Y of the third analog switcher 41 is connected to its output. Input N of the third analog switcher 41 is connected to the output of the fifteenth function converter 40. The input of the fifteenth function converter 40 is connected to the main steam pressure deviation input 22. The switching condition of the third analog switcher 41 is connected to the primary frequency regulation action input 39. Primary frequency regulation load command input 35 is connected to input 3 of adder 42. The output of adder 42 is connected to input SP of the first PID controller 43. Actual load input 38 is connected to input PV of the first PID controller 43. The output of the first PID controller 43 is connected to the input of the first manual controller 44. The output of the first manual controller 44 is connected to input 1 of adder 45. Input 2 of adder 45 is connected to the primary frequency regulation valve command input 37. The output of adder 45 is connected to the turbine valve command output 46.

[0048] A control method for improving the primary frequency regulation performance of thermal power units, based on the above, includes: increasing the primary frequency regulation performance boosting switch to ensure the original primary frequency regulation performance when the optimization logic is not engaged; issuing a primary frequency regulation reference load command based on the grid frequency signal; when the primary frequency regulation reference load is positively activated, the primary frequency regulation load command responds quickly in the positive direction; when the primary frequency regulation positive load command decreases, the primary frequency regulation command decreases slowly, thereby increasing the unit's primary frequency regulation integral power while reducing the frequency of turbine regulating valve operation; when the primary frequency regulation reference load is negatively activated, the primary frequency regulation load command responds quickly in the negative direction; when the primary frequency regulation negative load command increases... The primary frequency regulation command rises slowly, increasing the integral power of the unit's primary frequency regulation while reducing the frequency of turbine valve operation. Based on different load increases and decreases in primary frequency regulation, the unit load command, turbine valve command, main steam pressure deviation, and main steam pressure are used to correct the primary frequency regulation reference load command, ensuring the speed and accuracy of primary frequency regulation under different loads, turbine valve openings, main steam pressure deviations, and main steam pressures. A main steam pressure deviation correction unit load setting holding circuit is added during primary frequency regulation to improve the counter-adjustment of the primary frequency regulation command by the main steam pressure deviation, thereby improving the unit's primary frequency regulation performance.

[0049] Example

[0050] The steam turbine of a certain coal-fired power unit is a supercritical, single-shaft, three-cylinder, four-exhaust, double-back-pressure condensing steam turbine manufactured by Dongfang Turbine Co., Ltd., model N600-24.2 / 566 / 566. The digital electro-hydraulic control system (DEH) of the steam turbine is provided as a complete set by Dongfang Turbine, and its main task is to control the turbine speed and load.

[0051] The specific control methods for improving the primary frequency regulation performance of thermal power units include the following steps:

[0052] Step (1): Set the primary frequency regulation index boosting switch to the active state, that is, select a high-precision power grid frequency source signal for the primary frequency regulation signal, and at the same time perform primary frequency regulation command optimization processing.

[0053] Step (2): Set the parameters of the first function converter 6 according to the speed unequal rate function to ensure the accuracy of the primary frequency regulation reference load command (speed unequal rate is 5%).

[0054] The parameters for the first function converter are set as follows:

[0055]

[0056] Step (3): Set the parameters of the second function converter 8 and the fourth function converter 11;

[0057] When a frequency modulation operation increases the load, the output of the second function converter 8 is the same as the output of the first function converter 6, and the output of the fourth function converter 11 is 0; when a frequency modulation operation decreases the load, the output of the second function converter 8 is 0, and the output of the fourth function converter 11 is the same as the output of the first function converter 6.

[0058] The parameters for the second function converter are set as follows:

[0059] Y 0 0 10

[0060] The parameters for the fourth function converter are set as follows:

[0061] Y -10 0 0

[0062] Step (4): Set the positive and negative rate limiting parameters of the first rate limiter 9; when the primary frequency regulation operation increases the load, the positive rate PL (set to 100) of the first rate limiter 9 does not have a limiting effect, and the primary frequency regulation positive load command quickly reaches the required value; when the primary frequency regulation positive load command decreases, the negative rate NL of the first rate limiter 9 has a limiting effect, and its effect makes the primary frequency regulation positive load command decrease slowly. The negative rate NL is determined by the third function converter to achieve the purpose of increasing the primary frequency regulation integral power and reducing the turbine regulating valve fluctuation.

[0063] The parameters for the third function converter are set as follows:

[0064]

[0065] Step (4): Set the positive and negative rate limiting parameters of the second rate limiter 12; when the primary frequency regulation action reduces the load, the negative rate NL (set to 100) of the second rate limiter 12 does not have a limiting effect, and the primary frequency regulation negative load command quickly reaches the required value; when the primary frequency regulation negative load command increases, the positive rate PL of the second rate limiter 12 has a limiting effect, and its effect makes the primary frequency regulation negative load command increase slowly. The positive rate PL is determined by the fifth function converter, so as to improve the primary frequency regulation integral power and reduce the turbine regulating valve fluctuation.

[0066] The parameters for the fifth function converter are set as follows:

[0067]

[0068] Step (5): When the load is increased by the primary frequency regulation action, the sixth function converter 17, the seventh function converter 21, the eighth function converter 23, and the ninth function converter 26 are set to ensure that the primary frequency regulation command meets the requirements of the regulations and the accuracy of the response when the load is increased by the primary frequency regulation action under different loads, different turbine valve openings, different main steam pressure deviations (PV-SP), and different main steam pressures.

[0069] The parameters for the sixth function converter are set as follows:

[0070] Correction coefficient 1 1 1 1 1 0.833 0.833

[0071] The parameters for the seventh function converter are set as follows:

[0072] Correction coefficient 1 1 0.94 0.94 1 1 1

[0073] The parameters for the eighth function converter are set as follows:

[0074] Correction coefficient 1.1 1.05 1.02 1 0.98 0.95 0.9

[0075] The parameters for the ninth function converter are set as follows:

[0076] Correction coefficient 1 1 1 1 1 0.9 0.85

[0077] Step (6): When the load is reduced by the primary frequency regulation action, the tenth function converter 27, the eleventh function converter 31, the twelfth function converter 32, and the thirteenth function converter 34 are set to ensure that the primary frequency regulation command meets the requirements of the regulations and the accuracy of the response when the load is reduced by the primary frequency regulation action under different loads, different turbine valve openings, different main steam pressure deviations (PV-SP), and different main steam pressures.

[0078] The parameters for the tenth function converter are set as follows:

[0079] Correction coefficient 0.8 0.8 1 1 1 1 1

[0080] The parameters for the eleventh function converter are set as follows:

[0081] Correction coefficient 1 1 0.94 0.94 1 1 1

[0082] The parameters for the twelfth function converter are set as follows:

[0083] Correction coefficient 0.9 0.95 0.98 1 1.02 1.05 1.1

[0084] The parameters for the thirteenth function converter are set as follows:

[0085] Correction coefficient 1 1 1 1 1 1.05 1.1

[0086] Step (7): After positive processing, the first frequency modulation command is added to the first frequency modulation command after negative processing to obtain a first frequency modulation load command. At the same time, the parameters of the fourteenth function converter 36 are set to obtain a first frequency modulation gate command.

[0087] The parameters for the fourteenth function converter are set as follows:

[0088]

[0089] Step (8), primary frequency regulation load command, load command, and main steam pressure deviation correction function (the fifteenth function converter) together constitute the turbine main control setpoint;

[0090] Add a primary frequency regulation operation hold logic to the main steam pressure deviation correction function to ensure the accuracy of the primary frequency regulation and prevent the main steam pressure deviation correction function from reverse adjustment during the primary frequency regulation operation.

[0091] The parameters for the fifteenth function converter are set as follows:

[0092]

[0093]

[0094] Step (8): The turbine main control regulator performs PID operation based on the deviation between the set value and the actual value, and controls the output of the turbine main control regulator.

[0095] Step (9): The main control handheld device command and the primary frequency control valve command together control the opening of the turbine valve, thereby achieving the speed and accuracy of the primary frequency control action.

Claims

1. A control system for improving the primary frequency regulation performance of a thermal power unit, characterized in that, The input includes a turbine speed signal or grid frequency input (2), which is connected to the input of the inertial link (4). The output of the inertial link (4) is connected to the input N of the first analog switch (5). The input Y of the first analog switch (5) is connected to the high-precision grid frequency source signal input (3). The switching condition of the first analog switch (5) is connected to the primary frequency regulation index boosting switch input (1). The output of the first analog switch (5) is connected to the input of the first function converter (6). The output of the first function converter (6) is the original primary frequency regulation load command. When the primary frequency regulation index boosting switch input (1) is 0, the output of the first function converter (6) is the original primary frequency regulation load command. The unit load command input (16) is connected to the input of the sixth function converter (17), the output of the sixth function converter (17) is connected to the input of the first multiplier (18), the input of the first multiplier (18) is connected to the output of the seventh function converter (21), the input of the seventh function converter (21) is connected to the turbine control valve command input (20), the output of the first multiplier (18) is connected to the input of the second multiplier (19), the input of the second multiplier (19) is connected to the output of the third multiplier (24), the input of the third multiplier (24) is connected to the output of the eighth function converter (23), the input of the eighth function converter (23) is connected to the main steam pressure deviation input (22), and the input of the third multiplier (24) is connected to the ninth function converter (26). The output of the fourth multiplier (14) is connected to the input of the fifth multiplier (26), the input of the ninth multiplier (26) is connected to the main steam pressure input (25), the output of the second multiplier (19) is connected to the input of the fourth multiplier (14), the input of the fourth multiplier (14) is connected to the output of the first rate limiter (9), the positive rate limit input PL of the first rate limiter (9) is a fixed value of 100, the negative rate limit input NL of the first rate limiter (9) is connected to the output of the third multiplier (10), the input of the first rate limiter (9) is connected to the output of the second multiplier (8), the input of the second multiplier (8) and the input of the third multiplier (10) are both connected to the output of the first multiplier (6), and the output of the fourth multiplier (14) is the positive processing command of the optimized primary frequency regulation load. Using the same principle as the optimized primary frequency modulation load positive processing instruction, the optimized primary frequency modulation load negative processing instruction is designed. In the negative processing instruction loop, a second rate limiter (12) corresponding to the position of the first rate limiter (9) in the positive processing instruction loop is designed. The difference from the positive processing instruction loop is that the negative rate limit input NL of the second rate limiter (12) is a fixed value of 100, and the positive rate limit input PL is connected to the output of the corresponding function converter. The output of the eighth multiplier (30) is the optimized primary frequency modulation load negative processing instruction. The first input of the first adder (15) is connected to the output of the fourth multiplier (14), the second input of the first adder (15) is connected to the output of the eighth multiplier (30), and the output of the first adder (15) is the optimized first frequency modulation load command. The switching condition of the second analog switch (7) is connected to the input (1) of the primary frequency regulation index boosting switch. The input N of the second analog switch (7) is connected to the output of the first function converter (6). The input Y of the second analog switch (7) is connected to the output of the first adder (15). The output of the second analog switch (7) is connected to the input of the fourteenth function converter (36) and the primary frequency regulation load command output (35). The output of the fourteenth function converter (36) is connected to the primary frequency regulation gate command output (37). The unit load command input (16) is connected to input one of the second adder (42), input two of the second adder (42) is connected to the output of the third analog quantity switch (41), input Y of the third analog quantity switch (41) is connected to the output of the third analog quantity switch (41), input N of the third analog quantity switch (41) is connected to the output of the fifteenth function converter (40), input of the fifteenth function converter (40) is connected to the main steam pressure deviation input (22), and the switching condition of the third analog quantity switch (41) is connected to the primary frequency regulation action input (39); primary frequency regulation load command The output (35) is connected to the input three of the second adder (42), the output of the second adder (42) is connected to the input SP of the first PID controller (43), the actual load input (38) is connected to the input PV of the first PID controller (43), the output of the first PID controller (43) is connected to the input of the first handheld device (44), the output of the first handheld device (44) is connected to the input one of the third adder (45), the input two of the third adder (45) is connected to the primary frequency regulation valve command output (37), and the output of the third adder (45) is connected to the turbine valve command output (46).

2. The control system for improving the primary frequency regulation performance of a thermal power generating unit according to claim 1, characterized in that, The negative processing command loop includes the unit load command input (16), which is connected to the input of the tenth function converter (27). The output of the tenth function converter (27) is connected to the input of the fifth multiplier (28). The input of the fifth multiplier (28) is connected to the output of the eleventh function converter (31). The input of the eleventh function converter (31) is connected to the turbine regulating valve command input (20). The output of the fifth multiplier (28) is connected to the input of the sixth multiplier (29). The input of the sixth multiplier (29) is connected to the output of the seventh multiplier (33). The input of the seventh multiplier (33) is connected to the output of the twelfth function converter (32). The input of the twelfth function converter (32) is connected to the main steam pressure deviation input (22). The input of the seventh multiplier (33) is connected to the main steam pressure deviation input (22). The output of the thirteenth function converter (34) is connected, and the input of the thirteenth function converter (34) is connected to the main steam pressure input (25); the output of the sixth multiplier (29) is connected to the input of the eighth multiplier (30), the input of the eighth multiplier (30) is connected to the output of the second rate limiter (12), and the negative rate limit input NL of the second rate limiter (12) is a fixed value of 100; the positive rate limit input PL of the second rate limiter (12) is connected to the output of the fifth function converter (13), the input of the second rate limiter (12) is connected to the output of the fourth function converter (11), the input of the fourth function converter (11) and the input of the fifth function converter (13) are both connected to the output of the first function converter (6), and the output of the eighth multiplier (30) is the optimized primary frequency regulation load negative command.

3. The control method for improving the primary frequency regulation performance of a thermal power unit as described in claim 1, comprising the following steps: Step 1: Set the primary frequency regulation index boosting switch input (1) to the active state, that is, convert the primary frequency regulation signal from the selected turbine speed or grid frequency signal to a high-precision grid frequency source signal; Step 2: Set the parameters of the first function converter (6) according to the rotational speed inequality function; Step 3: Set the parameters of the second function converter (8) and the fourth function converter (11) according to the direction of the first frequency modulation operation; When a frequency modulation operation requires an increase in load, the output of the second function converter (8) is the same as the output of the first function converter (6), and the output of the fourth function converter (11) is 0; When a frequency modulation action requires a load reduction, the output of the second function converter (8) is 0, and the output of the fourth function converter (11) is the same as the output of the first function converter (6); Step 4: When the load increases during a primary frequency modulation operation, set the parameters of the first rate limiter (9): the positive rate limit does not have a limiting effect, so that the primary frequency modulation load command can quickly rise to the target value; when the load increase during a primary frequency modulation operation ends or the primary frequency modulation load command decreases, the negative rate limit of the first rate limiter (9) takes effect, that is, the primary frequency modulation load command slowly decreases to 0, and the negative rate of decrease of the primary frequency modulation load is given by the third function converter (10) according to the current primary frequency modulation load command; Then, based on the unit load command input (16), the turbine valve command input (20), the main steam pressure deviation input (22), and the main steam pressure input (25), the sixth function converter (17), the seventh function converter (21), the eighth function converter (23), and the ninth function converter (26) are set respectively to obtain the output of the fourth multiplier (14) of the primary frequency regulation load command after positive processing, so as to ensure the accuracy and response speed of the primary frequency regulation under different load commands, different turbine valve openings, different main steam pressures, and different main steam pressure deviations; Step 5: When the primary frequency regulation action requires load reduction, set the parameters of the second rate limiter (12): the negative rate does not have a limiting effect, so that the primary frequency regulation load command can be quickly reduced to the target value; when the primary frequency regulation action ends or the primary frequency regulation load command increases, the positive rate limit of the second rate limiter (12) takes effect, that is, the primary frequency regulation load command slowly rises to 0, and the positive rate of increase of the primary frequency regulation load is given by the fifth function converter (13) according to the current primary frequency regulation load command; Then, based on the unit load command input (16), the turbine valve command input (20), the main steam pressure deviation input (22), and the main steam pressure input (25), the tenth function converter (27), the eleventh function converter (31), the twelfth function converter (32), and the thirteenth function converter (34) are set respectively to obtain the output of the eighth multiplier (30) of the primary frequency regulation load command after negative processing, so as to ensure the accuracy and response speed of the primary frequency regulation under different load commands, different turbine valve openings, different main steam pressures, and different main steam pressure deviations; Step 6: The sum of the primary frequency modulation load command after positive processing and the primary frequency modulation load command after negative processing constitutes the optimized primary frequency modulation load command, i.e., the primary frequency modulation load command output (35). Step 7: Based on the actual flow curve of the steam turbine, set the fourteenth function converter (36) to obtain the final frequency regulation valve command output (37). Step 8: The unit load command, main steam pressure deviation correction value, and primary frequency regulation load command together constitute the setpoint of the turbine main control regulator; When a frequency regulation operation is performed, the main steam pressure deviation correction value is increased with a hold function to improve the accuracy of the primary frequency regulation and prevent changes in the main steam pressure deviation from causing load reversal. The deviation between the set value of the turbine main control regulator and the actual load is calculated using PID control to control the output of the turbine main control handheld device (44); Step 10: The output of the turbine main control handheld device (44) is superimposed with the output of the previous frequency regulation valve command (37) and together they act on the turbine valve to control the turbine valve, ensuring the speed and accuracy of the primary frequency regulation response.

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