Thermal power generating unit AGC performance online detection and optimization method

Abstract

The invention discloses a thermal power generating unit AGC performance online detection and optimization method. A programmable logic controller is arranged outside a distributed control system of each thermal power generating unit; the distributed control system transmits an AGC instruction target value, an AGC input signal, a unit variable load rate set value and a unit load of the thermal power unit to the programmable logic controller in real time; and the programmable logic controller calculates the real-time variable load rate of the unit, transmits the real-time variable load rate of the unit to the decentralized control system to correct the set value of the variable load rate of the unit, obtains key data points and AGC real-time performance indexes, and transmits the key data points and the AGC real-time performance indexes to the decentralized control system. According to the invention, the real-time variable load rate of the unit and the set variable load rate of the unit are calculated on line to obtain the variable load rate correction coefficient, the variable load rate of the unit can be corrected on line in real time, the adjustment performance of the unit is optimal, and power plant engineers can accurately master the AGC performance of a single unit.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of thermal power generation technology, in particular to an online detection and optimization method for AGC performance of a thermal power unit. BACKGROUND

[0002] With the development of the power system, the proportion of intermittent new energy such as wind power and photovoltaic power is increasing, regional power grid ultra-high voltage interconnection and unit generator capacity are gradually increasing, and the operation characteristics of the power grid are becoming increasingly complex. In order to maintain the safe and stable operation of the power system and ensure the power quality, the State Electricity Regulatory Commission and regional electricity regulatory bureaus have formulated and promulgated relevant rules, and put forward higher requirements for the AGC (Automatic Generation Control) capability of thermal power units. Taking the "two rules" of the Southern Power Grid, namely the "Implementation Rules for the Operation and Management of the Southern Regional Power Grid" and the "Implementation Rules for the Management of the Southern Regional Power Grid Auxiliary Service", as an example, the thirty-fifth rule stipulates that the automatic generation control provided by the power generation side grid connection main body should meet three standards (regulation rate, response time, and regulation accuracy). When all three standards are met, the qualified rate is 100%; when the regulation rate is not met, the qualified rate is reduced by 50%, when the response time is not met, the qualified rate is reduced by 25%, and when the regulation accuracy is not met, the qualified rate is reduced by 25%. When the AGC operation performance examination is unqualified, the AGC compensation for the corresponding period is zero, and the corresponding power examination is generated for the thermal power plant. The plant-level AGC examination power = [1 - (plant-level AGC regulation rate qualified rate x 0.5 + response time qualified rate x 0.25 + regulation accuracy qualified rate x 0.25)] x monthly equivalent open capacity x 0.5 hours. The monthly equivalent open capacity of the whole plant = Σ single machine capacity x (grid-connected operation hours ÷ total monthly hours). It can be seen from the "two rules" of the Southern Power Grid that the regulation rate index of the thermal power unit occupies the largest proportion in the AGC performance qualified rate, and the regulation rate of the thermal power unit is determined by the unit variable load rate set value, so it is necessary to adjust the unit variable load rate set value in real time according to the unit performance in order to make the unit regulation rate meet the requirements of the power grid.

[0003] At present, there are many problems in the evaluation of AGC performance of thermal power generating units: 1) The thermal power generating unit adopts a plant-level AGC mode, and multiple units are combined as a whole. The plant-level AGC data are calculated by the power grid, and the calculation result is the comprehensive performance of the multiple units under the plant-level AGC. The engineering personnel of the power plant cannot accurately master the AGC performance of a single unit. The parameters of a single unit cannot be optimized and adjusted. 2) The existing AGC performance evaluation method usually relies on offline calculation and periodic inquiry. For example, the plant-level AGC performance calculation result of the Southern Power Grid needs to be inquired on the website of the Southern Regional Power Spot Market Technical Support System (updated daily). The data have serious lag, and can only be used as a post-reference value. Due to the lack of effective online monitoring and evaluation means, the engineering personnel cannot timely find the frequency modulation problems of the unit. The power examination and compensation generated by the unit due to the substandard AGC performance of the previous day cannot be recovered. 3) The current AGC online evaluation system only has the function of evaluating the AGC performance of the unit. For example, the authorized announcement No. CN2118965123B discloses a "thermal power plant unit AGC performance online evaluation method and system", which realizes the online evaluation of the state performance of the AGC system of the thermal power plant unit, but cannot use the evaluation result for real-time adjustment of the unit parameters. Therefore, it is of great practical significance to develop a method capable of real-time online detection of the AGC performance indicators of the thermal power generating unit and using the detection results for real-time adjustment of the unit parameters. SUMMARY

[0004] The present application solves the problems of poor timeliness, weak pertinence and inability to use AGC performance indicators for unit parameter adjustment in existing AGC performance calculation, and provides a thermal power generating unit AGC performance online detection and optimization method, which can accurately calculate and adjust the unit variable load rate in real time, and improve the operation stability and adaptability of the thermal power generating unit in the power grid.

[0005] To solve the above problems, the present application is realized by the following technical scheme:

[0006] A thermal power generating unit AGC performance online detection and optimization method, comprising the following steps:

[0007] Step 1, an external programmable logic controller is arranged in the distributed control system of each thermal power generating unit, and the programmable logic controller is connected with the distributed control system in communication;

[0008] Step 2, the distributed control system transmits the AGC instruction target value, the AGC input signal, the unit variable load rate set value and the unit load in real time to the programmable logic controller;

[0009] Step 3, the programmable logic controller continuously monitors the unit load when the AGC input signal is input and the AGC instruction target value changes, and calculates the unit real-time variable load rate in real time within the time period from when the unit load exceeds the action dead zone of the last AGC instruction to when the unit load enters the target dead zone of the current AGC instruction, and transmits the unit real-time variable load rate to the distributed control system;

[0010] Step 4, the distributed control system corrects the unit variable load rate set value based on the unit real-time variable load rate;

[0011] Step 4.1, the distributed control system inputs the real-time variable load rate and the unit variable load rate set value into the PID controller to obtain the current correction coefficient, and if the current correction coefficient is greater than 1, the current correction coefficient remains unchanged; otherwise, the current correction coefficient is set to 1;

[0012] Step 4.2, when the unit is in the AGC instruction load increasing process, the main steam pressure is greater than the set value and the turbine valve opening is less than the upper limit set value of the valve, or the unit is in the AGC instruction load decreasing process, the main steam pressure is less than the set value and the turbine valve opening is greater than the lower limit set value of the valve, then the current correction coefficient remains unchanged; otherwise, the current correction coefficient is set to 1;

[0013] Step 4.3, multiply the current correction coefficient by the unit variable load rate set value to obtain the corrected unit variable load rate set value;

[0014] Step 5, the programmable logic controller temporarily stores and analyzes the real-time transmitted AGC instruction and unit load, extracts the key data points in the unit load increasing and decreasing process, and transmits the key data points to the distributed control system;

[0015] Step 6, the programmable logic controller merges the AGC instructions based on the AGC instruction target value and the unit load;

[0016] Step 7, the programmable logic controller calculates the unit AGC real-time performance index based on the merged AGC instruction, and transmits the unit AGC real-time performance index to the distributed control system; wherein the AGC real-time performance index includes the unit actual regulation rate, the regulation rate, the response time, the regulation accuracy and the comprehensive performance;

[0017] Step 8, the distributed control system presents the unit real-time variable load rate, the key data points and the unit AGC real-time performance index through its display interface.

[0018] In the above step 1, the programmable logic controller and the distributed control system use the modbus communication protocol to establish communication connection.

[0019] In the above step 3:

[0020] The unit load exceeding the action dead zone of the last AGC instruction includes two cases:

[0021] When the unit is in the process of AGC instruction load increase (i.e. the current AGC instruction target value is greater than the last AGC instruction target value), if the unit load is greater than the last AGC instruction target value plus the action dead zone threshold value , it indicates that the unit load exceeds the action dead zone;

[0022] When the unit is in the process of AGC instruction load decrease (i.e. the current AGC instruction target value is less than the last AGC instruction target value), if the unit load is less than the last AGC instruction target value minus the action dead zone threshold value , it indicates that the unit load exceeds the action dead zone;

[0023] The unit load entering the target dead zone of the current AGC instruction includes two cases:

[0024] When the unit is in the process of AGC instruction load increase (i.e. the current AGC instruction target value is greater than the last AGC instruction target value), if the unit load is greater than the current AGC instruction target value minus the target dead zone threshold value , it indicates that the unit load exceeds the action dead zone;

[0025] When the unit is in the process of AGC instruction load decrease (i.e. the current AGC instruction target value is less than the last AGC instruction target value), if the unit load is less than the current AGC instruction target value plus the target dead zone threshold value , it indicates that the unit load exceeds the action dead zone.

[0026] The action dead zone threshold value is:

[0027]

[0028] The target dead zone threshold value is:

[0029]

[0030] In the formula, min represents the minimum value function, is the unit capacity, is the unit capacity proportion corresponding to the action dead zone of the last AGC instruction, is the bottom line value corresponding to the action dead zone of the last AGC instruction, is the unit capacity proportion corresponding to the target dead zone of the current AGC instruction, is the bottom line value corresponding to the target dead zone of the current AGC instruction.

[0031] In step 3 above, the unit real-time variable load rate is:

[0032]

[0033] wherein, is the current time, is the unit load at the current time, is the unit load at the time when the unit load enters the action dead zone of the previous AGC instruction, is the unit load at the time when the unit load enters the action dead zone of the previous AGC instruction, is the unit load at the time when the unit load enters the action dead zone of the previous AGC instruction.

[0034] In step 3 above, the programmable logic controller needs to smooth the unit load transmitted by the distributed control system.

[0035] In step 3 above, when the distributed control system does not receive the unit real-time variable load rate returned by the programmable logic controller, the unit variable load rate set value is taken as the unit real-time variable load rate.

[0036] In step 5 above, the key data points extracted by the programmable logic controller include key time points and key load points; the key time points include: the AGC instruction change time, the time when the unit load enters the action dead zone of the previous AGC instruction, the time when the unit load enters the action dead zone of the previous AGC instruction and delays for a predetermined length of time, the time when the unit load change reaches a predetermined proportion of the AGC instruction target value change, and the time when the unit load enters the target dead zone of the current AGC instruction; the key load points include: the unit load at the AGC instruction change time, the unit load at the time when the unit load enters the action dead zone of the previous AGC instruction, the unit load at the time when the unit load enters the action dead zone of the previous AGC instruction and delays for a predetermined length of time, the unit load at the time when the unit load change reaches a predetermined proportion of the AGC instruction target value change, and the unit load at the time when the unit load enters the target dead zone of the current AGC instruction.

[0037] In step 6 above, the merging principle of the AGC instruction is as follows:

[0038] Step 6.1, determine whether the adjustment direction of the current AGC instruction target value and the previous AGC instruction target value is the same: if yes, go to step 6.2; otherwise, the current AGC instruction and the previous AGC instruction are not merged;

[0039] Step 6.2, determine whether the interval between the issuing time of the current AGC instruction target value and the issuing time of the previous AGC instruction target value is less than a preset value ​If yes, proceed to step 6.3; otherwise, the current AGC instruction and the previous AGC instruction will not be merged.

[0040] Step 6.3: Determine whether the duration of the unit load entering the target dead zone of the previous AGC command is less than the preset value. If yes, then the current AGC instruction will be merged with the previous AGC instruction; otherwise, the current AGC instruction will not be merged with the previous AGC instruction.

[0041] In step 7 above:

[0042] For each AGC instruction in the merged AGC instructions, calculate its actual unit regulation rate. for:

[0043]

[0044] In the formula, The moment when the unit load enters the action dead zone of the previous AGC command. To achieve a predetermined proportion of the change in unit load to the target value of the AGC command. time, This refers to the unit load at the moment when the unit load enters the dead zone of the previous AGC command. To achieve a predetermined proportion of the change in unit load to the target value of the AGC command. Unit load at any given time;

[0045] For each AGC instruction in the merged AGC instructions, calculate its adjustment rate. for:

[0046]

[0047] In the formula, This represents the actual adjustment rate of the unit under the current AGC command. For unit capacity, The average standard regulation rate of power generation units within the frequency regulation resource distribution area;

[0048] Calculate the response time for the merged AGC command. for:

[0049]

[0050] In the formula, The action dead zone of the first AGC instruction after the unit load enters the merged AGC instruction is delayed for a predetermined duration. time, This refers to the moment when the first AGC instruction changes after the AGC instruction is merged.

[0051] Calculate the adjustment accuracy of the combined AGC instruction For:

[0052]

[0053] In the formula, is the time when the unit load enters the target dead zone of the last AGC instruction of the combined AGC instruction, is the sampling time step, the total number of sampling times, is the unit load at time is the target value of the last AGC instruction of the combined AGC instruction, is the allowable error of the power generation unit adjustment;

[0054] Calculate the comprehensive performance of the combined AGC instruction For:

[0055]

[0056] In the formula, is the adjustment rate, is the response time, is the adjustment accuracy, is the weight of the adjustment rate, is the weight of the response time, is the weight of the adjustment accuracy.

[0057] Compared with the prior art, the present application has the following characteristics:

[0058] 1. Strong pertinence: can be deployed alone in a single thermal power unit, and can perform real-time detection and online analysis on the unit AGC performance, so that the power plant engineers can accurately master the AGC performance of the single unit.

[0059] 2. Realize online parameter adjustment: through online calculation of the unit real-time variable load rate and the unit set variable load rate to obtain the variable load rate correction coefficient, the unit variable load rate can be corrected in real time, and the unit adjustment performance can be optimized.

[0060] 3. Strong real-time performance: by directly collecting data from DCS in real time and quickly calculating and analyzing, the dynamic changes of the unit AGC performance can be reflected in time, greatly improving the real-time performance of AGC performance calculation, so that the operating personnel and engineers can intuitively and timely understand the unit operating condition. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 is a DCS and PLC communication schematic. ​

[0062] Figure 2 A flow chart for real-time variable load rate of the unit.

[0063] Figure 3 A logic diagram for real-time optimization of the unit variable load rate.

[0064] Figure 4 A schematic diagram for key data points.

[0065] Figure 5 A schematic diagram for single AGC instruction merging rule. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application is further described in detail below with reference to specific examples and the accompanying drawings.

[0067] An online detection and optimization method for AGC performance of a thermal power unit, comprising the following steps:

[0068] Step 1, a PLC is externally connected to the DCS of each thermal power unit, and the PLC is connected to the DCS.

[0069] Considering that the DCS (Distributed Control System) of the thermal power unit does not have a data temporary storage function, the present application externally connects a PLC (Programmable Logic Controller) to the DCS of each thermal power unit, as shown in the figure. Figure 1 In the embodiment, the PLC and the DCS communicate with each other by using a modbus communication protocol. Through the PLC, real-time data such as the AGC instruction and the unit load of the DCS of a single thermal power unit can be analyzed and judged, the real-time variable load rate of the unit is obtained, and the variable load rate set for the unit is corrected in real time based on the real-time variable load rate of the unit, so as to achieve the purpose of optimizing the AGC performance. The added PLC is aimed at the DCS of a single thermal power unit, and is more targeted than other online detection systems for the plant-level AGC system.

[0070] Step 2, the DCS transmits the AGC instruction target value, the AGC input signal, the unit variable load rate set value and the unit load of the thermal power unit to the PLC in real time.

[0071] The AGC instruction target value is calculated by the power grid dispatching system according to the frequency and the tie-line power deviation, and is sent to the DCS through the power dispatching data network.

[0072] The AGC input signal is sent by an operator clicking the "AGC input" button on the DCS special operation system, which triggers the DCS to switch the unit control to the automatic adjustment mode, so that the unit receives and responds to the AGC instruction target value issued by the power grid dispatching, and realizes the automatic adjustment of the load.

[0073] The unit variable load rate set value is the load change amount (usually in MW / min) per unit time that needs to be reached, which is input by the operator on the DCS special operation system.

[0074] The unit load is collected by the current transformer and voltage transformer to collect the current and voltage signals of the generator, and then converted into standard signals by the power transmitter or merging unit, and then transmitted to the DCS through shielded cable or optical fiber.

[0075] Step 3, the PLC continuously monitors the unit load when the AGC input signal is input and the AGC instruction target value changes, and calculates the real-time unit real-time variable load rate in the time period from when the unit load exceeds the action dead zone of the last AGC instruction to when the unit load enters the target dead zone of the current AGC instruction, and transmits the unit real-time variable load rate to the DCS.

[0076] The unit load exceeding the action dead zone of the last AGC instruction includes two cases:

[0077] When the unit is in the process of increasing the load according to the AGC instruction (i.e. the current AGC instruction target value is greater than the last AGC instruction target value), if the unit load is greater than the last AGC instruction target value plus the action dead zone threshold value , it indicates that the unit load exceeds the action dead zone;

[0078] When the unit is in the process of reducing the load according to the AGC instruction (i.e. the current AGC instruction target value is less than the last AGC instruction target value), if the unit load is less than the last AGC instruction target value minus the action dead zone threshold value , it indicates that the unit load exceeds the action dead zone;

[0079] The calculation formula of the action dead zone threshold value is as follows:

[0080]

[0081] In the formula, represents the minimum function, is the unit capacity, is the unit capacity proportion corresponding to the action dead zone of the last AGC instruction, is the bottom line value corresponding to the action dead zone of the last AGC instruction. According to the "South Regional AGC Power Unit Frequency Modulation Index Calculation Specification", for thermal power units, , .

[0082] There are two cases for the unit load entering the target dead zone of the current AGC instruction:

[0083] When the unit is in the process of AGC instruction load increase (i.e. the target value of the current AGC instruction is greater than the target value of the last AGC instruction), if the unit load is greater than the target value of the current AGC instruction minus the target dead zone threshold value , it indicates that the unit load exceeds the action dead zone;

[0084] When the unit is in the process of AGC instruction load decrease (i.e. the target value of the current AGC instruction is less than the target value of the last AGC instruction), if the unit load is less than the target value of the current AGC instruction plus the target dead zone threshold value , it indicates that the unit load exceeds the action dead zone.

[0085] The calculation formula of the target dead zone threshold value is:

[0086]

[0087] In the formula, represents the minimum value function, is the unit capacity, is the unit capacity ratio corresponding to the target dead zone of the current AGC instruction, is the bottom line value corresponding to the target dead zone of the current AGC instruction. According to the “South Regional AGC Power Generation Unit Frequency Modulation Index Calculation Specification”, for thermal power units, , .

[0088] The real-time variable load rate of the unit is:

[0089]

[0090] In the formula, is the current time, is the unit load at the current time , is the time when the unit load enters the action dead zone of the last AGC instruction, is the unit load at the time when the unit load enters the action dead zone of the last AGC instruction. The purpose of is to convert to a unified dimension MW / min.

[0091] ​The unit load collected in the PLC is smoothed before participating in the calculation to prevent the real-time load measurement value of the unit from shaking and affecting the calculation results.

[0092] The DCS receives the real-time variable load rate of the unit from the PLC using the T switch function block. As shown in Figure 2 the main purpose of using the T switch function block is:

[0093] When the AGC input signal is input and the AGC command target value changes, if the unit load exceeds the action dead zone of the last AGC command to the time period when the unit load enters the target dead zone of the current AGC command, the PLC calculates the real-time variable load rate of the unit. The DCS takes the calculated variable load rate of the unit as the real-time variable load rate of the unit in this stage.

[0094] When the PLC detects that the AGC input signal is not input and the AGC command does not change, if the unit load does not exceed the action dead zone of the last AGC command or the unit load enters the target dead zone of the current AGC command within the time period, the PLC does not calculate the real-time variable load rate of the unit. The DCS takes the variable load rate set value of the unit as the real-time variable load rate of the unit in this stage.

[0095] Step 4, the DCS corrects the variable load rate set value of the unit based on the real-time variable load rate of the unit. As shown in Figure 3 .

[0096] Step 4.1, the distributed control system sends the real-time variable load rate and the variable load rate set value of the unit into the PID controller to obtain the current correction coefficient, and linearly corrects the current correction coefficient. If the current correction coefficient is greater than 1, the current correction coefficient remains unchanged; otherwise, the current correction coefficient is set to 1.

[0097] Step 4.2, comprehensive judgment of the variable load capacity of the unit, that is, when the unit is in the AGC command load increasing process, the main steam pressure is greater than the set value and the turbine valve opening is less than the upper limit set value of the valve, or the unit is in the AGC command load decreasing process, the main steam pressure is less than the set value and the turbine valve opening is greater than the lower limit set value of the valve, then it is indicated that the unit has the margin to increase the variable load rate in the increasing direction or the decreasing direction, at this time the current correction coefficient remains unchanged; otherwise, the current correction coefficient is set to 1.

[0098] Step 4.3, multiply the current correction coefficient by the variable load rate set value of the unit to obtain the corrected variable load rate set value of the unit.

[0099] By real-time correcting the set variable load rate of the unit, the actual variable load rate of the unit is as close as possible to the set variable load rate of the unit, and finally the unit achieves the optimal regulation effect.

[0100] Step 5: The PLC temporarily stores and analyzes the real-time transmitted AGC instructions and unit load, extracts key data points during the unit load rise and fall process, and transmits the key data points during the unit load rise and fall process to the DCS.

[0101] The key data points extracted (identified) by the PLC fall into two categories: key time points and key load points, such as... Figure 4 As shown.

[0102] Key time points include: the moment when AGC instructions change. The unit load enters the action dead zone of the previous AGC command. The unit load enters the action dead zone of the previous AGC command and is delayed for the predetermined time. time The change in unit load reaches the predetermined proportion of the target value change in the AGC command. time The moment when the unit load enters the target dead zone of the current AGC command. .

[0103] Critical load points include: the moment when AGC commands change. Unit load The unit load enters the action dead zone of the previous AGC command. Unit load The unit load enters the action dead zone of the previous AGC command and is delayed for the predetermined time. time Unit load The change in unit load reaches the predetermined proportion of the target value change in the AGC command. time Unit load The moment when the unit load enters the target dead zone of the current AGC command. Unit load .

[0104] The change in the target value of the aforementioned AGC instruction is equal to the absolute value of the current AGC instruction target value minus the target value of the previous AGC instruction. According to the "Calculation Specification for Frequency Regulation Index of AGC Power Generation Units in Southern Region," for thermal power units, , .

[0105] Step 6: The PLC merges AGC instructions based on the target value of the AGC instruction and the unit load.

[0106] In actual operation, there is a situation of high density and multiple frequency of AGC instruction issuing. At this time, the power generation unit still has a responded but not completed AGC instruction when receiving a new instruction. At this time, in order to facilitate and accurately calculate the AGC real-time performance index, it is necessary to merge the continuous AGC instructions.

[0107] Referring to Figure 5 , the merging principle of AGC instructions is as follows:

[0108] Step 6.1, judge whether the adjustment direction of the target value of the current AGC instruction and the target value of the last AGC instruction is the same: if yes, go to step 6.2; otherwise, the current AGC instruction and the last AGC instruction are not merged;

[0109] Step 6.2, judge whether the interval between the issuing time of the target value of the current AGC instruction and the issuing time of the target value of the last AGC instruction is less than a preset value : if yes, go to step 6.3; otherwise, the current AGC instruction and the last AGC instruction are not merged;

[0110] Step 6.3, judge whether the duration of the unit load entering the target dead zone of the last AGC instruction is less than a preset value : if yes, merge the current AGC instruction and the last AGC instruction; otherwise, the current AGC instruction and the last AGC instruction are not merged.

[0111] According to the "South Regional AGC Power Generation Unit Frequency Modulation Index Calculation Specification", for thermal power units, , .

[0112] Step 7, the PLC calculates the unit AGC real-time performance index based on the merged AGC instruction, and transmits the unit AGC real-time performance index to the DCS.

[0113] The unit AGC real-time performance index includes the unit actual regulation rate , the regulation rate , the response time , the regulation accuracy and the comprehensive performance .

[0114] For each AGC instruction of the merged AGC instruction, the unit actual regulation rate is calculated as follows:

[0115]

[0116] In the formula, is the time when the unit load enters the action dead zone of the last AGC instruction, The unit load reaches a predetermined proportion of the AGC instruction target value change amount The time when The unit load when the unit load enters the action dead zone of the previous AGC instruction The unit load reaches a predetermined proportion of the AGC instruction target value change amount The time when.

[0117] The actual adjustment rate of the unit Satisfy the following conditions: And . The adjustment rate calculation threshold value is , The unit capacity is The on-line capacity proportion is The on-line bottom line value is. The adjustment rate calculation threshold time. According to the “South Regional AGC Power Generation Unit Frequency Modulation Index Calculation Specification”, for thermal power units, , , .

[0118] For each AGC instruction of the merged AGC instruction, calculate its adjustment rate Is:

[0119]

[0120] In the formula, The actual adjustment rate of the unit for the current AGC instruction is The unit capacity is The average standard adjustment rate of the frequency modulation resource distribution area within the power generation unit. According to the “South Regional AGC Power Generation Unit Frequency Modulation Index Calculation Specification”, for thermal power units, .

[0121] For the merged AGC instruction, calculate its response time Is:

[0122]

[0123] In the formula, The time when the unit load enters the action dead zone of the first AGC instruction of the merged AGC instruction and delays for a predetermined length of time The time when The first AGC instruction change time of the merged AGC instruction.

[0124] For the merged AGC instruction, calculate its adjustment accuracy Is:

[0125]

[0126] In the formula, is the target dead zone time of the last AGC instruction of the merged AGC instruction when the unit load enters, is the sampling time step, total number of sampling times, is the unit accuracy calculation time length, is the unit load at time , is the target value of the last AGC instruction of the merged AGC instruction, is the allowable error of the power generation unit adjustment. According to the “South Regional AGC Power Generation Unit Frequency Modulation Index Calculation Specification”, for thermal power units, , , .

[0127] For the merged AGC instruction, the comprehensive performance is calculated as:

[0128]

[0129] In the formula, is the adjustment rate, is the response time, is the adjustment accuracy, is the weight of the adjustment rate, is the weight of the response time, is the weight of the adjustment accuracy. According to the “South Regional AGC Power Generation Unit Frequency Modulation Index Calculation Specification”, for thermal power units, , , .

[0130] Step 8, the DCS presents the unit real-time variable load rate, key data points and unit AGC real-time performance indicators through its display interface.

[0131] The DCS displays the unit real-time variable load rate, key data points and unit AGC real-time performance indicators through the DCS and configures a special display interface to display to the operation personnel and related engineering personnel through the picture configuration tool. The display interface can use charts, numbers and other forms to intuitively display real-time values, historical change trends and other information of various performance indicators, so that users can timely understand the unit AGC performance status. At the same time, the calculation results are stored in the database for subsequent query and analysis.

[0132] It should be noted that the above embodiments of the present application are illustrative, and not restrictive, of the present application, and thus the present application is not limited to the above specific embodiments. Other embodiments of the present application, which are within the scope of the present application, will be apparent to those skilled in the art from the disclosure herein.

Claims

1. An online detection and optimization method for AGC performance of a thermal power unit, characterized in that, The steps include the following: Step 1, externally connecting a programmable logic controller to the distributed control system of each thermal power unit, and establishing a communication connection between the programmable logic controller and the distributed control system; Step 2, the distributed control system transmits the AGC instruction target value, AGC input signal, unit variable load rate set value and unit load of the thermal power unit to the programmable logic controller in real time; Step 3, the programmable logic controller continuously monitors the unit load when the AGC input signal is input and the AGC instruction target value changes, and calculates the unit real-time variable load rate in the time period from when the unit load exceeds the action dead zone of the last AGC instruction to when the unit load enters the target dead zone of the current AGC instruction, and transmits the unit real-time variable load rate to the distributed control system; Step 4, the distributed control system corrects the unit variable load rate set value based on the unit real-time variable load rate; Step 4.1, the distributed control system inputs the real-time variable load rate and the unit variable load rate set value into a PID controller to obtain a current correction coefficient, if the current correction coefficient is greater than 1, the current correction coefficient remains unchanged; otherwise, the current correction coefficient is set to 1; Step 4.2, when the unit is in the AGC instruction load increasing process, the main steam pressure is greater than the set value and the turbine valve opening is less than the upper limit set value of the valve, or the unit is in the AGC instruction load decreasing process, the main steam pressure is less than the set value and the turbine valve opening is greater than the lower limit set value of the valve, then the current correction coefficient remains unchanged; otherwise, the current correction coefficient is set to 1; Step 4.3, multiply the current correction coefficient by the unit variable load rate set value to obtain the corrected unit variable load rate set value; Step 5, the programmable logic controller temporarily stores and analyzes the real-time transmitted AGC instruction and unit load, extracts the key data points in the unit load increasing and decreasing process, and transmits the key data points to the distributed control system; Step 6, the programmable logic controller merges the AGC instructions based on the AGC instruction target value and the unit load; Step 7, the programmable logic controller calculates the unit AGC real-time performance index based on the merged AGC instruction, and transmits the unit AGC real-time performance index to the distributed control system; wherein the AGC real-time performance index includes the unit actual regulation rate, the regulation rate, the response time, the regulation accuracy and the comprehensive performance; Step 8, the distributed control system presents the unit real-time variable load rate, the key data points and the unit AGC real-time performance index through its display interface.

2. The method according to claim 1, characterized in that, In step 1, the programmable logic controller and the distributed control system establish a communication connection using the modbus communication protocol.

3. The method according to claim 1, characterized in that, In step 3: The unit load exceeding the action dead zone of the last AGC instruction includes two cases: When the unit is in the process of AGC instruction load increase (i.e. the current AGC instruction target value is greater than the last AGC instruction target value), if the unit load is greater than the last AGC instruction target value plus the action dead zone threshold value , it indicates that the unit load exceeds the action dead zone; When the unit is in the process of AGC command load reduction (i.e. the current AGC command target value is less than the last AGC command target value), if the unit load is less than the last AGC command target value minus the action dead zone threshold value , it indicates that the unit load exceeds the action dead zone; The unit load entering the target dead zone of the current AGC instruction includes two cases: When the unit is in the process of AGC instruction load increase (i.e. the current AGC instruction target value is greater than the last AGC instruction target value), if the unit load is greater than the current AGC instruction target value minus the target dead zone threshold value , it indicates that the unit load exceeds the action dead zone; When the unit is in the process of AGC command load reduction (i.e. the current AGC command target value is less than the last AGC command target value), if the unit load is less than the current AGC command target value plus the target dead zone threshold value , it indicates that the unit load exceeds the action dead zone.

4. The method of claim 3, wherein the step of In step 3: Action deadband threshold Is: ； Target deadband threshold is: ； In the formula, represents a minimum value function, is the unit capacity, is the unit capacity corresponding to the action dead zone of the last AGC instruction, is the bottom line value corresponding to the action dead zone of the last AGC instruction, is the unit capacity corresponding to the target dead zone of the current AGC instruction, is the bottom line value corresponding to the target dead zone of the current AGC instruction.

5. The method of claim 1, wherein the method further comprises: In step 3, the unit real-time variable load rate is: ； In the formula, is the current time, is the current time is the unit load, is the time when the unit load enters the action dead zone of the previous AGC instruction, is the unit load at the time when the unit load enters the action dead zone of the previous AGC instruction is the unit load at the time when the unit load enters the action dead zone of the previous AGC instruction.

6. The method of claim 1, wherein the method further comprises: In step 3, the programmable logic controller needs to smooth the unit load transmitted by the distributed control system.

7. The method according to claim 1, characterized in that, In step 3, when the distributed control system does not receive the unit real-time variable load rate returned by the programmable logic controller, the unit variable load rate set value is used as the unit real-time variable load rate.

8. The method according to claim 1, characterized in that, In step 5, the key data points extracted by the programmable logic controller include key time points and key load points; The key time points include: the time point when the AGC instruction changes, the time point when the unit load enters the action dead zone of the last AGC instruction, the time point when the unit load enters the action dead zone of the last AGC instruction and the delay is for a predetermined length of time, the time point when the unit load change reaches a predetermined proportion of the AGC instruction target value change, and the time point when the unit load enters the target dead zone of the current AGC instruction; The key load points include: the unit load at the time point when the AGC instruction changes, the unit load at the time point when the unit load enters the action dead zone of the last AGC instruction, the unit load at the time point when the unit load enters the action dead zone of the last AGC instruction and the delay is for a predetermined length of time, the unit load at the time point when the unit load change reaches a predetermined proportion of the AGC instruction target value change, and the unit load at the time point when the unit load enters the target dead zone of the current AGC instruction.

9. The method according to claim 1, characterized in that, In step 6, the merging principle of the AGC instruction is as follows: Step 6.1, determine whether the adjustment direction of the current AGC instruction target value and the last AGC instruction target value is the same: if yes, go to step 6.2; otherwise, the current AGC instruction and the last AGC instruction are not merged; Step 6.2, judging whether the interval between the time of issuing the current AGC instruction target value and the time of issuing the last AGC instruction target value is less than a preset value If yes, go to step 6.3; otherwise, the current AGC instruction is not merged with the last AGC instruction. Step 6.3, judging whether the unit load entering the target dead zone duration of the previous AGC instruction is less than a preset value If yes, the current AGC instruction is merged with the previous AGC instruction; otherwise, the current AGC instruction is not merged with the previous AGC instruction.

10. The method for online detection and optimization of AGC performance of thermal power units according to claim 1, characterized in that, In step 7: For each AGC instruction of the combined AGC instructions, calculate its actual adjusting speed of the unit group is: ； In the formula, is the time when the unit load enters the action dead zone of the previous AGC instruction, is the time when the unit load variation reaches a predetermined proportion of the AGC instruction target value variation , is the unit load at the time when the unit load enters the action dead zone of the previous AGC instruction, is the unit load at the time when the unit load variation reaches a predetermined proportion of the AGC instruction target value variation . For each AGC command of the combined AGC commands, calculate its adjustment rate is: ； In the formula, is the actual adjustment rate of the generating unit for the current AGC instruction, is the generating unit capacity, is the average standard adjustment rate of the generating unit in the frequency regulation resource distribution area; For the combined AGC command, calculate its response time is: ； In the formula, is the action dead zone and delay of the first AGC instruction of the combined AGC instruction for the unit load time, is the first AGC instruction change time of the combined AGC instruction For the combined AGC command, calculate its adjustment accuracy is: ； In the formula, is the target dead zone time of the last AGC instruction of the combined AGC instruction when the unit load enters, is the sampling time step, is the total number of sampling times, is the time is the unit load at the time is the target value of the last AGC instruction of the combined AGC instruction, is the adjustment allowable error of the power generation unit; For the combined AGC command, calculate its comprehensive performance is: ； wherein is the rate of adjustment, is the response time, is the accuracy of adjustment, is the weight of the rate of adjustment, is the weight of the response time, is the weight of the accuracy of adjustment.

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