A combined cycle unit cold end optimization method considering unit operation state deviation

Abstract

The application discloses a kind of combined cycle unit cold end optimization methods considering unit operation state deviation, comprising the following steps: calculating the theoretical back pressure value and unit net power increase value under each cold end operating mode, and the system correction value obtained by calculating theoretical back pressure value;Based on system correction value, obtain the corrected theoretical back pressure value under each cold end operating mode, and then obtain the corrected theoretical optimal back pressure and corresponding optimal cold end operating mode and as initial optimization result;The rationality of initial optimization result is checked, and the final optimization result is determined based on the checking result.The application can obtain a higher accuracy calculation result by collecting system operating parameters to correct the system deviation caused by the change of unit operation state;And it also has good applicability to the operating conditions of extreme situations such as accident blowdown, condenser vacuum leakage, etc.

Description

Technical Field

[0001] This invention belongs to the field of combined cycle power generation technology, specifically relating to a method for optimizing the cold end of a combined cycle unit that takes into account deviations in the unit's operating state. Background Technology

[0002] In the field of combined cycle power generation, the main equipment in the cold end system includes circulating water pumps and mechanically ventilated cooling towers. Their operating economy is affected by the power consumption of the circulating water pumps and the power consumption of the mechanically ventilated cooling tower fans. Therefore, it is necessary to optimize the operation mode of the circulating water pumps and fans.

[0003] Current methods for optimizing the operation of cold-end equipment are mainly based on the power industry standard "DL / T 932-2019 Guidelines for the Operation and Maintenance of Condensers and Vacuum Systems". This method optimizes the operation with circulating water temperature as the boundary condition and has good accuracy in power plants using open-cycle systems. However, in combined cycle units, the circulating water temperature changes due to the operating mode of the mechanical draft cooling tower fans and the condenser heat load. This means that the calculated optimal cold-end operation mode is only applicable to the current moment and deviates from the true optimal operation mode under the current ambient temperature and thermal load. Therefore, it is necessary to use a cold-end optimization method with ambient temperature and humidity as boundary conditions. Currently, such optimization methods are usually based on experimental data and use thermal system simulation software to perform variable operating condition calculations. Because the unit's operating conditions, such as vacuum pump, condenser cleanliness, steam-water isolation, and aging correction, deviate from those during testing, the calculated optimal operating mode and corresponding optimal back pressure differ significantly from the actual back pressure value under the unit's cold-end operating mode. Furthermore, in extreme cases such as accidental condensate draining or condenser vacuum leakage, the theoretically calculated optimal back pressure is in an unattainable range, severely deviating from the actual operating conditions of the unit. Therefore, a new method for optimizing the cold end of a combined cycle unit that considers deviations in unit operating conditions is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to provide a combined cycle unit cold-end optimization method that considers deviations in unit operating conditions, in order to solve one or more of the aforementioned technical problems. The method provided by this invention corrects system deviations caused by changes in unit operating conditions by collecting system operating parameters, thereby obtaining highly accurate calculation results; and it also has good applicability to operating conditions with extreme situations such as accidental condensate drainage and condenser vacuum leakage.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for optimizing the cold end of a combined cycle power unit considering deviations in unit operating conditions, comprising the following steps:

[0007] Obtain the combined cycle unit operating parameters and all possible cold-end operating modes at a preset time, calculate the theoretical back pressure value and the increase in net power of the unit under each cold-end operating mode, and obtain the calculation results; among them, the operating condition with the largest increase in net power of the unit is the optimal cold-end operating mode;

[0008] Based on the calculation results, the theoretical back pressure value under the actual cold-end operation mode at the preset time is selected and denoted as P. cur_cal The actual back pressure value of the combined cycle unit at the preset time is collected and recorded as P. cur_act According to the calculation expression ΔP=P cur_cal -P cur_act The system correction value ΔP for the theoretical back pressure value is calculated.

[0009] Based on the system correction value ΔP, according to the calculation expression P i_cor =P i +ΔP is used to systematically correct the theoretical back pressure value under each cold-end operation mode, resulting in the corrected theoretical back pressure value P for each cold-end operation mode. i_cor Among them, P i This represents the actual back pressure value under the i-th cold-end operation mode;

[0010] Based on the corrected theoretical back pressure value P for each cold-end operation mode i_cor The corrected theoretical optimal back pressure and the corresponding optimal cold end operation mode are obtained and used as the initial optimization result. The rationality of the initial optimization result is verified based on the actual back pressure value, ambient temperature, and condenser inlet circulating water temperature of the combined cycle unit at the preset time. The final optimization result is determined based on the verification result.

[0011] A further improvement to the method of the present invention lies in the step of obtaining the operating parameters of the combined cycle unit at a preset time and all possible cold-end operating modes, calculating the theoretical back pressure value and the net power increase value of the unit under each cold-end operating mode, and obtaining the calculation results.

[0012] The calculation expressions for the theoretical back pressure value and the net power increase of the unit are as follows:

[0013] ΔW i =ΔW Ti -ΔW Ci ΔW Ti =C0(P i -P cur_cal W T ;

[0014] In the formula, ΔW represents the net increase in unit power; ΔW T For a slight increase in output of the steam turbine; ΔW CC0 is the power consumption change of the cold-end system equipment; C0 is the incremental output coefficient determined by the condenser heat load; P cur_cal This is the theoretical back pressure value under actual cold-end operation; W T P represents the steam turbine shaft power; P represents the actual back pressure value under the actual cold-end operation mode; the subscript i represents the number of each cold-end operation mode, the value of i ranges from 1 to n, and n represents the total number of all possible cold-end operation modes.

[0015] A further improvement to the method of the present invention is that the step of verifying the rationality of the initial optimization result based on the actual back pressure value, ambient temperature, and condenser inlet circulating water temperature of the combined cycle unit at the preset time, and determining the final optimization result based on the verification result, includes:

[0016] If the actual back pressure value is greater than the maximum allowable back pressure, then the combination method that reduces the cold end operating power in the calculation results is eliminated; in the remaining operating conditions, ΔW i The cold-end operation mode under the maximum operating condition is taken as the optimal cold-end operation mode, corresponding to P. i_cor The theoretically optimal back pressure is obtained through optimization.

[0017] A further improvement to the method of the present invention is that the step of verifying the rationality of the initial optimization result based on the actual back pressure value, ambient temperature, and condenser inlet circulating water temperature of the combined cycle unit at the preset time, and determining the final optimization result based on the verification result, includes:

[0018] If the actual back pressure is less than the blocking back pressure, then the combination that reduces the cold-end operating power in the calculation results is eliminated; in the remaining operating conditions, ΔW i The cold-end operation mode under the maximum operating condition is taken as the optimal cold-end operation mode, corresponding to P. i_cor The theoretically optimal back pressure is obtained through optimization.

[0019] A further improvement to the method of the present invention is that the step of verifying the rationality of the initial optimization result based on the actual back pressure value, ambient temperature, and condenser inlet circulating water temperature of the combined cycle unit at the preset time, and determining the final optimization result based on the verification result, includes:

[0020] If the condenser inlet circulating water temperature is lower than the ambient temperature, then the operating condition of increasing the number of operating fans under the same pump is excluded; in the remaining operating conditions, ΔW i The cold-end operation mode under the maximum operating condition is taken as the optimal cold-end operation mode, corresponding to P. i_cor The theoretically optimal back pressure is obtained through optimization.

[0021] A further improvement to the method of the present invention is that, after determining the final optimization result based on the verification result, it further includes:

[0022] When the condenser heat load and ambient temperature change are less than the preset threshold, the optimized cold end operation mode maintains the optimization result of the previous moment.

[0023] When the condenser heat load and ambient temperature change are greater than or equal to the preset threshold, the optimal cold end operation mode and theoretical optimal back pressure are updated.

[0024] A further improvement to the method of the present invention is that, after determining the final optimization result based on the verification result, it further includes:

[0025] A gradual, incremental approach is adopted to recommend the optimal cold-end optimization method.

[0026] A further improvement of the method of the present invention is that the cold end system of the combined cycle unit includes a circulating water pump and a mechanically driven cooling tower fan.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The combined cycle unit cold end optimization method provided by this invention takes into account the system deviation caused by the difference between the unit's operating state in actual operation and the unit's operating state during the test. By collecting system operating parameters, the system deviation caused by the change in the unit's operating state is corrected, and calculation results with high accuracy can be obtained.

[0029] The method provided by this invention, based on the above, also considers extreme operating conditions in actual operation, ensuring that the cold end optimization results will not cause safety problems due to abnormal operating conditions such as accidental condensate draining or condenser vacuum leakage, and has good applicability to operating conditions with extreme situations such as accidental condensate draining or condenser vacuum leakage.

[0030] The method provided by this invention is applicable to combined circulation units in cold-end systems, including circulating water pumps and mechanically driven cooling tower fans. This invention optimizes by using ambient temperature as a boundary condition, avoiding the deviation problem of optimal results caused by optimizing by using circulating water temperature as a boundary condition. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art are briefly introduced below; obviously, the drawings described below are some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort;

[0032] Figure 1 This is a flowchart illustrating a combined cycle unit cold end optimization method considering unit operating state deviations provided in an embodiment of the present invention;

[0033] Figure 2This is a flowchart illustrating another method for optimizing the cold end of a combined cycle unit that considers deviations in unit operating status, provided by an embodiment of the present invention.

[0034] Figure 3 This is a schematic diagram of the optimal cold-end operation mode corresponding to the current operating state in an embodiment of the present invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0036] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0037] The present invention will now be described in further detail with reference to the accompanying drawings:

[0038] Please see Figure 1 The present invention provides a method for optimizing the cold end of a combined cycle power unit considering deviations in unit operating conditions, comprising the following steps:

[0039] Step 1: Obtain the combined cycle unit operating parameters and all possible cold-end operating modes at the preset time. Calculate the theoretical back pressure value and the increase in net power of the unit under each cold-end operating mode, and obtain the calculation results. Among them, the operating condition with the largest increase in net power of the unit is the optimal cold-end operating mode.

[0040] Step 2: Based on the calculation results, select the theoretical back pressure value under the actual cold-end operation mode at the preset time, denoted as P. cur_cal The actual back pressure value of the combined cycle unit at the preset time is collected and recorded as P. cur_act According to the calculation expression ΔP=P cur_cal -P cur_actThe system correction value ΔP for the theoretical back pressure value is calculated.

[0041] Step 3, based on the system correction value ΔP, calculate P according to the expression. i_cor =P i +ΔP is used to systematically correct the theoretical back pressure value under each cold-end operation mode, resulting in the corrected theoretical back pressure value P for each cold-end operation mode. i_cor Among them, P i This represents the actual back pressure value under the i-th cold-end operation mode;

[0042] Step 4, based on the corrected theoretical back pressure value P under each cold-end operation mode i_cor The corrected theoretical optimal back pressure and the corresponding optimal cold end operation mode are obtained and used as the initial optimization result. The rationality of the initial optimization result is verified based on the actual back pressure value, ambient temperature, and condenser inlet circulating water temperature of the combined cycle unit at the preset time. The final optimization result is determined based on the verification result.

[0043] The technical solution provided by the embodiments of the present invention corrects the system deviation caused by changes in the unit's operating status by collecting system operating parameters, and can obtain calculation results with high accuracy; it also has good applicability to operating conditions with extreme situations such as accidental drainage and condenser vacuum leakage.

[0044] Please see Figure 2 The present invention provides a combined cycle unit cold end optimization method considering unit operating state deviations, which specifically includes the following steps:

[0045] Step 1: Based on the current operating parameters and all possible cold-end operating modes, calculate the theoretical back pressure and net power increase of the unit under each cold-end operating mode, using the following formula:

[0046] ΔW i =ΔW Ti -ΔW Ci ;

[0047] ΔW Ti =C0(P i -P cur_cal W T ;

[0048] In the formula, the subscript i is the number of each cold-end operation mode, i = (1, 2, 3, ..., n), n is the number of all possible cold-end operation modes, and ΔW is the net power increase of the unit;

[0049] ΔW T This refers to the incremental output of the steam turbine; specifically, this value can be obtained by linear interpolation from the results of steam turbine incremental processing tests.

[0050] ΔW C This refers to the change in power consumption of the cold-end system equipment; for specific interpretation, it can be obtained through variable operating condition tests of the cold-end equipment. The power consumption of the cold-end system equipment of the combined cycle unit includes the power consumption of the circulating water pump and the mechanical ventilation cooling tower fan.

[0051] C0 is the incremental output coefficient determined by the condenser heat load; for more specific interpretation, it can be obtained by combining condenser variable operating condition tests and turbine incremental treatment tests.

[0052] P is the actual back pressure value under the current cold-end operation mode of the unit. cur_cal W represents the theoretical back pressure value under the current actual cold-end operation mode of the unit. T This refers to the shaft power of the steam turbine.

[0053] Step 2: Based on the calculation results of Step 1, sort all cold-end operating modes according to the increase in net power of the unit from largest to smallest. The operating mode with the largest increase in net power of the unit is the optimal operating mode, followed by the second-best operating mode, and so on.

[0054] Step 3: Based on the calculation results in Step 1, select the theoretical back pressure value P under the actual cold-end operation mode of the current unit. i , denoted as P cur_cal Simultaneously, the current actual back pressure value of the combined cycle unit is collected and denoted as P. cur_act The difference between the two is the system correction value ΔP for the theoretical back pressure value, that is: ΔP = P cur_cal -P cur_act ;

[0055] Step 4: Perform system correction on the theoretical back pressure value for each cold-end operation mode to obtain the corrected theoretical back pressure value P for each cold-end operation mode. i_cor That is: P i_cor =P i +ΔP;

[0056] Then the optimal working condition P obtained in step 2 i_cor (i = the number of the optimal operating condition) is the theoretically optimal back pressure obtained through optimization.

[0057] Step 5: Based on the current actual back pressure value P of the combined cycle unit cur_act Ambient temperature t0, condenser inlet circulating water temperature t cyc Verify the reasonableness of the optimization results;

[0058] The main verification rules provided in this embodiment of the invention include:

[0059] Step 5-1: If the actual back pressure value P cur_act Exceeding the maximum permissible back pressure P for any reasonmax Then, combinations that reduce cold-end operating power in the calculation results are eliminated, i.e., ΔW Ci Cold-end operation mode with a value less than 0 prevents further increase in back pressure; in the remaining operating conditions, ΔW i The cold-end operation mode of the maximum operating condition (i.e., the suboptimal operating condition) is taken as the optimal cold-end operation mode, and the P of the suboptimal operating condition is... i_cor (i = the number of the suboptimal operating condition) is the theoretically optimal back pressure obtained through optimization; specifically, this verification step can prevent the safety risks caused by the back pressure further increasing when there are special circumstances such as accidental condensate draining or condenser vacuum leakage in the unit. The maximum permissible back pressure here is not the maximum permissible back pressure of the steam turbine. The maximum permissible back pressure mentioned in this invention is the limit value of the cold end optimization system, which is generally lower than the maximum permissible back pressure of the steam turbine.

[0060] Step 5-2: If the actual back pressure value P cur_act For any reason, the back pressure is less than the blocking back pressure P. min Then, combinations that reduce cold-end operating power in the calculation results are eliminated, i.e., ΔW Ci In cold-end operation mode with a value greater than 0, ΔW in the remaining operating conditions i The cold-end operation mode of the maximum operating condition (i.e., the suboptimal operating condition) is taken as the optimal cold-end operation mode, and the P of the suboptimal operating condition is... i_cor (i = the number of the suboptimal operating condition) is the theoretically optimal back pressure obtained through optimization; specifically, this method can solve the problem of low circulating water temperature caused by excessively low back pressure when the vacuum pump is running or under extremely low ambient temperature.

[0061] Step 5-3: If the condenser inlet circulating water temperature t cyc If the temperature is below the ambient temperature t0, then the operating condition of increasing the number of fans under the same pump is excluded; in the remaining operating conditions, ΔW i The cold-end operation mode of the maximum operating condition (i.e., the suboptimal operating condition) is taken as the optimal cold-end operation mode, and the P of the suboptimal operating condition is... i_cor (i = the number of the suboptimal operating condition) is the theoretically optimal back pressure obtained through optimization; because under the current cold end operation mode, the circulating water has already cooled to the ambient temperature, and restarting the forced ventilation cooling tower fan will not be able to further reduce the temperature of the circulating water.

[0062] Step 6: When the condenser heat load Q C When the ambient temperature t0 changes little, the optimized cold-end operation mode maintains the optimization result from the previous moment. This technical measure prevents the unit operating parameters from fluctuating near a critical point, which could lead to repeated switching of the cold-end operation mode and further cause repeated start-stop of the circulating water pump or mechanical ventilation cooling tower fan. When the condenser heat load Q... CWhen the ambient temperature t0 changes beyond a given threshold, update the optimal operating mode and theoretical optimal back pressure to the front-end interface of the cold-end optimization system, and record the cold-end operating mode update time T. update The current time;

[0063] Step 7: As long as the current time is within the cold end operation mode update time T update If the difference exceeds 20-30 minutes, the optimal result will be forcibly updated to the front-end interface; this ensures that the cold end operation mode tracks the optimal cold end operation mode as much as possible while preventing repeated switching of the cold end operation mode.

[0064] Step 8: If the calculated optimal cold-end operation mode differs too much from the actual cold-end operation mode of the current unit, then select the suboptimal cold-end operation mode that is closer to the actual cold-end operation mode of the current unit, and gradually recommend the optimal cold-end optimization mode.

[0065] In the method provided by this invention, the deviation between the theoretical back pressure value and the actual back pressure value under the current actual cold-end operation mode of the unit is due to the difference between the current operating state of the unit and the operating state during the test. The P calculated under different cold-end operation modes... i The difference is due to the different operating methods at the cold end, therefore P i The difference between the values ​​is a key focus for comprehensive energy-saving optimization of the cold-end system of a combined cycle unit. Therefore, in steps 3 and 4, the system deviation caused by the difference between the current operating state of the unit and the operating state during the test is corrected, so that the calculation results for each cold-end operating mode use the same deviation. Thus, the optimal cold-end operating mode will not change due to system deviation. The cold-end optimization method proposed in this embodiment of the invention is applicable to combined cycle units with circulating water pumps and mechanical ventilation cooling tower fans in the cold-end system, and it optimizes with ambient temperature as the boundary condition, avoiding the deviation problem of the best result caused by optimization with circulating water temperature as the boundary condition. At the same time, it considers the system deviation caused by the difference between the unit's operating state in actual operation and the unit's operating state during the test. On this basis, it further considers the extreme operating conditions in actual operation, ensuring that the cold-end optimization results will not cause safety problems due to abnormal operating conditions such as accidental drainage or condenser vacuum leakage.

[0066] This invention uses a power plant as an example to further illustrate the combined cycle unit cold-end optimization method considering unit operating state deviations. The power plant's cold-end system includes two constant-speed circulating water pumps (denoted as large pumps), two circulating water pumps that can be set to high-speed or low-speed operation (denoted as small pumps), and eight mechanically driven cooling tower fans. There are 10 circulating water pump operating modes and 9 fan operating modes, represented by letters A to I and X respectively. All pump operating modes are shown in Table 1.

[0067] Table 1. All operating modes of the pump

[0068]

[0069]

[0070] The cold end operation mode is represented by “[AX][0-8]”, where “[AX]” represents the operation mode of the circulating water pump and “[0-8]” represents the number of fans in operation. All cold end operation modes are shown in Table 2.

[0071] Table 2. All combinations of cold-end operation modes

[0072] A3 B3 C3 D3 E3 F1 G0 H0 I0 A4 B4 C4 D4 E4 F2 G1 H1 I1 A5 B5 C5 D5 E5 F3 G2 H2 I2 A6 B6 C6 D6 E6 F4 G3 H3 I3 A7 B7 C7 D7 E7 F5 G4 H4 I4 A8 B8 C8 D8 E8 F6 G5 H5 I5 F7 G6 H6 I6 F8 G7 H7 I7 G8 H8 I8

[0073] The operation method of the deep peak-shaving system based on thermal system coupling between units provided in this embodiment of the invention includes the following steps:

[0074] Step 1: Based on the current operating parameters and all possible cold-end operating modes, calculate the theoretical back pressure value and the net power increase of the unit under each cold-end operating mode. The calculation results are shown in Table 3.

[0075] Table 3. Calculation results for each cold-end operation mode

[0076]

[0077] Step 2: Based on the calculation results of Step 1, sort all cold-end operating modes according to the increase in net power of the unit from largest to smallest. The operating mode with the largest increase in net power of the unit is the optimal operating mode, followed by the second-best operating mode, and so on.

[0078] Step 3: Based on the calculation results of Step 1, select the theoretical back pressure value under the current actual cold-end operation mode of the unit. The current actual cold-end operation mode of the unit is G4, then P G4 =P cur_cal =6.01 kPa, and simultaneously, the actual back pressure value P of the combined cycle unit is collected. cur_act =5.56 kPa, and the difference between the two is the system correction value of the theoretical back pressure value. Therefore, the system correction value ΔP = (5.56-6.01) kPa = -0.46 kPa.

[0079] Step 4: Perform system correction on the theoretical back pressure value for each cold-end operation mode to obtain the corrected theoretical back pressure value P for each cold-end operation mode. i_cor The results, after sorting by the increase in net power of the units and making corrections, are shown in Table 4.

[0080] Table 4. Results after correction

[0081]

[0082] The optimal cold-end operation mode is G5, which is one large pump and five fans, with an optimal back pressure of 5.07 kPa.

[0083] Please see Figure 3 , Figure 3 This represents the optimal cold-end operation mode for the current running state, but whether this result is updated to the front-end interface of the cold-end optimization software requires further steps.

[0084] Step 5: Based on the current actual back pressure value P of the combined cycle unit cur_act Ambient temperature t0, condenser inlet circulating water temperature t cyc The rationality of the optimization results is verified. The verification results show that G5 meets all verification rules, and there is no need to remove this operating condition. If the verification results show that G5 does not meet any verification rule, then G5 is removed, and the second-best operating condition, namely H4 in this calculation, is selected, and H4 is further verified.

[0085] Step 6: When the condenser heat load Q c When the ambient temperature t0 changes little, the optimized cold-end operation mode maintains the optimization results from the previous moment. When the condenser heat load Q... c When the ambient temperature t0 changes beyond a given threshold, update the optimal operating mode and theoretical optimal back pressure to the front-end interface of the cold-end optimization system, and record the cold-end operating mode update time T. update Given the current time, the specified parameter fluctuation thresholds in this case are (Q) C -4MW, Q C +4MW), (t0-1℃, t0+1℃). In the first calculation, all parameter fluctuations were 0, so the optimization results were output directly.

[0086] Step 7: As long as the current time is within the cold end operation mode update time T update If the difference exceeds 20-30 minutes, the optimal result will be forcibly updated to the front-end interface.

[0087] Step 8: If the calculated optimal cold-end operation mode differs significantly from the actual cold-end operation mode of the current unit, then select the suboptimal cold-end operation mode that is closer to the actual cold-end operation mode of the current unit, and gradually recommend the optimal cold-end optimization mode. The optimization result calculated in this case differs from the current operation mode by only one fan, so there is no need to reselect the optimal operating condition. Therefore, cold-end operation mode G5 and optimal back pressure of 5.07 kPa are the final cold-end optimization results.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for optimizing the cold end of a combined cycle power unit considering deviations in unit operating conditions, characterized in that, Includes the following steps: Obtain the combined cycle unit operating parameters and all possible cold-end operating modes at a preset time, calculate the theoretical back pressure value and the increase in net power of the unit under each cold-end operating mode, and obtain the calculation results; among them, the operating condition with the largest increase in net power of the unit is the optimal cold-end operating mode; Based on the calculation results, the theoretical back pressure value under the actual cold-end operation mode at the preset time is selected and denoted as P. cur_cal The actual back pressure value of the combined cycle unit at the preset time is collected and recorded as P. cur_act According to the calculation expression ΔP=P cur_cal -P cur_act The system correction value ΔP for the theoretical back pressure value is calculated. Based on the system correction value ΔP, according to the calculation expression P i_cor =P i +ΔP is used to systematically correct the theoretical back pressure value under each cold-end operation mode, resulting in the corrected theoretical back pressure value P for each cold-end operation mode. i_cor Among them, P i This represents the actual back pressure value under the i-th cold-end operation mode; Based on the corrected theoretical back pressure value P for each cold-end operation mode i_cor The corrected theoretical optimal back pressure and the corresponding optimal cold end operation mode are obtained and used as the initial optimization result. The rationality of the initial optimization result is verified based on the actual back pressure value, ambient temperature, and condenser inlet circulating water temperature of the combined cycle unit at the preset time. The final optimization result is determined based on the verification result.

2. The combined cycle unit cold end optimization method considering unit operating state deviations according to claim 1, characterized in that, In the step of obtaining the combined cycle unit operating parameters and all possible cold-end operating modes at a preset time, calculating the theoretical back pressure value and the net power increase of the unit under each cold-end operating mode, and obtaining the calculation results... The calculation expressions for the theoretical back pressure value and the net power increase of the unit are as follows: ΔW i =ΔW Ti -ΔW Ci ,ΔW Ti =C0(P i -P cur_cal )W T ; In the formula, ΔW represents the net increase in unit power; ΔW T For a slight increase in output of the steam turbine; ΔW C C0 is the change in power consumption of the cold-end system equipment; C0 is the incremental output coefficient determined by the condenser heat load; P cur_cal This is the theoretical back pressure value under actual cold-end operation; W T is the steam turbine shaft power; P is the actual back pressure value under actual cold-end operation mode; The subscript i is the number of each cold end operation mode, and the value of i ranges from 1 to n, where n is the total number of all possible cold end operation modes.

3. The combined cycle unit cold end optimization method considering unit operating state deviations according to claim 1, characterized in that, The step of verifying the rationality of the initial optimization result based on the actual back pressure value, ambient temperature, and condenser inlet circulating water temperature of the combined cycle unit at the preset time, and determining the final optimization result based on the verification result, includes: If the actual back pressure value is greater than the maximum allowable back pressure, then the combination method that reduces the cold end operating power in the calculation results is eliminated; in the remaining operating conditions, ΔW i The cold-end operation mode under the maximum operating condition is taken as the optimal cold-end operation mode, corresponding to P. i_cor The theoretically optimal back pressure is obtained through optimization.

4. The combined cycle unit cold end optimization method considering unit operating state deviations according to claim 1, characterized in that, The step of verifying the rationality of the initial optimization result based on the actual back pressure value, ambient temperature, and condenser inlet circulating water temperature of the combined cycle unit at the preset time, and determining the final optimization result based on the verification result, includes: If the actual back pressure is less than the blocking back pressure, then the combination that reduces the cold-end operating power in the calculation results is eliminated; in the remaining operating conditions, ΔW i The cold-end operation mode under the maximum operating condition is taken as the optimal cold-end operation mode, corresponding to P. i_cor The theoretically optimal back pressure is obtained through optimization.

5. The combined cycle unit cold end optimization method considering unit operating state deviations according to claim 1, characterized in that, The step of verifying the rationality of the initial optimization result based on the actual back pressure value, ambient temperature, and condenser inlet circulating water temperature of the combined cycle unit at the preset time, and determining the final optimization result based on the verification result, includes: If the condenser inlet circulating water temperature is lower than the ambient temperature, then the operating condition of increasing the number of operating fans under the same pump is excluded; in the remaining operating conditions, ΔW i The cold-end operation mode under the maximum operating condition is taken as the optimal cold-end operation mode, corresponding to P. i_cor The theoretically optimal back pressure is obtained through optimization.

6. The combined cycle unit cold-end optimization method considering unit operating state deviations according to claim 1, characterized in that, After determining the final optimization result based on the verification result, the process also includes: When the condenser heat load and ambient temperature change are less than the preset threshold, the optimized cold end operation mode maintains the optimization result of the previous moment. When the condenser heat load and ambient temperature change are greater than or equal to the preset threshold, the optimal cold end operation mode and theoretical optimal back pressure are updated.

7. The combined cycle unit cold end optimization method considering unit operating state deviations according to claim 1, characterized in that, After determining the final optimization result based on the verification result, the process also includes: A gradual, incremental approach is adopted to recommend the optimal cold-end optimization method.

8. A combined cycle unit cold-end optimization method considering unit operating state deviations according to any one of claims 1 to 7, characterized in that, The cold end system of the combined cycle unit includes a circulating water pump and a mechanically driven cooling tower fan.

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