A molten salt heat storage participates in thermal power unit operation optimization method

Abstract

The application discloses a molten salt heat storage participating in operation optimization method of a thermal power generating unit, and relates to the technical field of molten salt heat storage coupling a thermal power generating unit. The method comprises the following steps: a unit variable condition model of the molten salt participating in operation of the thermal power generating unit is established; a unit technical parameter model of a heat storage stage and a heat release stage is established based on the unit variable condition model; a whole-process heat efficiency calculation model and a net profit calculation model are determined according to the unit technical parameter model; a target function containing the whole-process heat efficiency calculation model and the net profit calculation model is constructed according to the Pareto optimal thought; based on the target function, the molten salt parameters are taken as optimization variables, the beluga whale optimization algorithm is adopted to make the whole-process heat efficiency and the net profit simultaneously reach the Pareto optimal condition, and the optimal molten salt parameters are determined; and the optimal unit technical parameters of the heat storage stage and the heat release stage are obtained by using the unit technical parameter model according to the optimal molten salt parameters. The application can realize the optimal operation of the molten salt heat storage coupling the thermal power generating unit in the whole process of heat storage and heat release.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coupling molten salt heat storage technology of thermal power generating units, in particular to a molten salt heat storage participating in operation optimization method of thermal power generating units. BACKGROUND

[0002] The installed capacity of new energy power generation such as wind power and solar power is increasing day by day, but new energy power generation is affected by geographical environment, weather and other factors, and has the characteristics of volatility, intermittency and unpredictability. Large-scale grid connection will have adverse effects on the safe and stable operation of the power grid. Therefore, in order to cooperate with the output of new energy power generation, thermal power generating units have become the main power source for deep peak shaving due to their large installed capacity and strong controllability, which puts forward higher requirements for the flexibility of thermal power generating units, that is, they need to have the ability of fast response, precise regulation and long-term stable operation to adapt to the volatility and uncertainty brought by new energy grid connection and ensure the safe and stable and economic operation of the power system.

[0003] In recent years, the development of energy storage technology has gradually made great progress. The use of energy storage technology to participate in the peak shaving of thermal power generating units can be carried out without modifying the boiler and the turbine body, and by adding external equipment directly connected to the thermal system, it is a very potential unit flexibility modification method. Among many heat storage media, molten salt has the advantages of high safety, environmental friendliness, large specific heat capacity and cheapness, and is one of the important directions of research in the field of energy storage. At present, molten salt heat storage technology has been applied in the field of photothermal, and has laid the foundation for supporting the large-scale development of photothermal power generation. In summary, coupling molten salt heat storage technology is an important technology to promote the flexibility modification of thermal power, and has great development potential.

[0004] However, existing related researches mainly focus on the optimization of a single operation process or only consider the benefits of the coupling system, and few of them involve the research of the whole process of heat storage and heat release and the comprehensive research of various indicators. There are also few researches on the use of steam extraction to heat molten salt. Existing researches mostly use electric heating to heat molten salt. In addition, existing researches are mostly scheme design and index analysis comparison, and do not optimize the parameters of the designed scheme, resulting in that the designed scheme cannot achieve the best operating conditions. SUMMARY

[0005] The purpose of the present application is to provide a molten salt heat storage participating in operation optimization method of thermal power generating units, which can realize the best operation of molten salt heat storage coupled with thermal power generating units in the whole process of heat storage and heat release.

[0006] To achieve the above-mentioned purpose, the present application provides the following scheme:

[0007] The application provides a molten salt heat storage participating in operation optimization method of a thermal power generating unit, comprising the following steps: establishing a unit variable condition model of the molten salt participating in operation of the thermal power generating unit; the unit variable condition model comprises molten salt parameters; based on the unit variable condition model, a unit technical parameter model of a heat storage stage and a heat release stage is established; according to the unit technical parameter model, a whole-process heat efficiency calculation model and a net profit calculation model comprising the heat storage stage and the heat release stage are determined; according to the Pareto optimal thought, a target function comprising the whole-process heat efficiency calculation model and the net profit calculation model is constructed; based on the target function, the molten salt parameters are taken as optimization variables, the whole-process heat efficiency and the net profit are simultaneously made to reach the Pareto optimal condition by using the beluga whale optimization algorithm, and the optimal molten salt parameters are determined; and according to the optimal molten salt parameters, the optimal unit technical parameters of the heat storage stage and the heat release stage are obtained by using the unit technical parameter model.

[0008] According to the specific embodiments provided in the application, the following technical effects are achieved.

[0009] The application provides a molten salt heat storage participating in operation optimization method of a thermal power generating unit, which comprehensively considers the whole-process operation of a molten salt heat storage thermal power generating unit in the heat storage and heat release stages, and according to the Pareto optimal thought, a target function comprising the whole-process heat efficiency and the net profit is constructed, the whole-process heat efficiency and the net profit in the whole process are balanced, the optimal unit technical parameters of the heat storage stage and the heat release stage are obtained, and then the optimal operation of the thermal power generating unit coupled with the molten salt heat storage in the whole process of the heat storage and heat release stages is realized based on the optimal unit technical parameters. BRIEF DESCRIPTION OF DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the application or the related art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described in the following are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0011] Figure 1 A flowchart of a molten salt heat storage participating in operation optimization method provided by an embodiment of the application. DETAILED DESCRIPTION

[0012] The technical solutions in the embodiments of the application will be described clearly and completely in the following with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0013] The above objects, features and advantages of the present application will become more apparent from the following detailed description of the application, when taken in conjunction with the accompanying drawings and specific embodiments.

[0014] The molten salt participates in the operation of the unit in two stages: heat storage stage and heat release stage. In the heat storage stage, the molten salt stores the heat of the steam, and the output power of the unit decreases due to the decrease of the work steam; in the heat release stage, the molten salt releases the stored heat, and the output power of the unit is improved. The participation of the molten salt improves the peak shaving capacity of the unit, and also changes the operation mode of the unit, and various indexes of the coupling system will also change, and the influence of the molten salt needs to be considered when calculating the energy utilization efficiency and the benefit of the unit. In addition to changing the output power, the participation of the molten salt in the peak shaving of the unit will also change the coal consumption. In addition, the addition of the molten salt will bring a series of equipment and operation and maintenance costs. Considering the whole process of heat storage and heat release, the energy utilization efficiency and the benefit will change due to the changes of the output power and the coal consumption, and the degree of change of the indexes will be different due to the different flow and temperature of the molten salt in the operation process, and the trends of some technical indexes and other indexes with the change of the molten salt parameters also exist differences. Therefore, to find the appropriate molten salt parameters participating in the operation of the unit, the whole process of heat storage and heat release of the unit needs to be considered, and the differences of the technical indexes and other indexes with the change of the molten salt parameters also need to be considered, so as to find the optimal molten salt parameters.

[0015] Reasonably balancing the technical indexes and other indexes in the whole process of heat storage and heat release of the unit is helpful to realize the maximization of the benefit of the unit while meeting the basic requirements of the peak shaving of the unit, and promotes the optimal configuration.

[0016] In view of the above, in an exemplary embodiment, as shown in Figure 1 The present application provides a molten salt heat storage participating in the operation optimization method of a thermal power unit, which comprises the following steps 101 to 106. Wherein:

[0017] Step 101: establishing a unit variable condition model of the molten salt participating in the operation of the thermal power unit; the unit variable condition model comprises molten salt parameters.

[0018] Step 102: based on the unit variable condition model, establishing a unit technical parameter model of the heat storage stage and the heat release stage.

[0019] Step 103: according to the unit technical parameter model, determining a whole process heat efficiency calculation model and a net profit calculation model comprising the heat storage stage and the heat release stage.

[0020] Step 104: constructing a target function comprising the whole process heat efficiency calculation model and the net profit calculation model.

[0021] Step 105: based on the objective function, taking the molten salt parameters as optimization variables, using the white whale optimization algorithm to make the whole process thermal efficiency and net profit reach the Pareto optimal condition, and determining the optimal molten salt parameters.

[0022] Step 106: according to the optimal molten salt parameters, using the unit technical parameter model to obtain the optimal unit technical parameters in the heat storage stage and the heat release stage.

[0023] The above steps 101 to 106 are implemented, the whole process operation of the coupled molten salt heat storage thermal power unit is comprehensively considered, the objective function containing the whole process thermal efficiency and the net profit is constructed according to the Pareto optimal idea, the whole process thermal efficiency and the net profit are balanced, the optimal unit technical parameters in the heat storage stage and the heat release stage are obtained, and then the optimal operation of the coupled molten salt heat storage thermal power unit in the whole process of heat storage and heat release is realized based on the optimal unit technical parameters.

[0024] In another exemplary embodiment of the application, the unit variable condition model in step 101 includes a steam turbine model, a regenerative system model and a molten salt heat exchanger model. The steam turbine model includes a steam turbine intermediate stage model and a steam turbine final stage model. The steam turbine intermediate stage model is obtained according to the Frigal formula to obtain the steam pressure before each stage (steam extraction pressure), and the steam turbine intermediate stage model is:

[0025]

[0026] In the formula, D g,i represents the steam flow rate through the i th stage of the steam turbine under the variable condition g, kg / s; D g0,i represents the steam flow rate through the i th stage of the steam turbine under the design condition, kg / s; p g,i represents the steam pressure before the i th stage of the steam turbine under the variable condition g, MPa; p g0,i represents the steam pressure before the i th stage of the steam turbine under the design condition, MPa.

[0027] The change of the steam turbine final stage condition can be calculated according to the thermal change of the previous stage, and the steam turbine final stage model is:

[0028]

[0029] h c = h7- η7(h7- h' c ) (3)

[0030] In the formula, η6, η7 respectively represent the relative internal efficiency of the 6 th stage and the 7 th stage of the steam turbine, %; h6, h7 respectively represent the enthalpy value of the 6 th stage extraction steam and the enthalpy value of the 7 th stage extraction steam, kJ / kg; h ch7 represents the ideal enthalpy value of the 7th stage extraction steam of the steam turbine, kJ / kg; h represents the ideal enthalpy value of the last stage exhaust steam of the steam turbine, kJ / kg. c h7 represents the ideal enthalpy value of the 7th stage extraction steam of the steam turbine, kJ / kg; h represents the ideal enthalpy value of the last stage exhaust steam of the steam turbine, kJ / kg.

[0031] The heat balance equation of the regenerator is:

[0032] The heat balance equation of the regenerator is:

[0033] α H,j τ j = α j q j + β j γ j (4)

[0034] In the formula, α H,j , α j , β j respectively represent the water supply share, extraction steam share and drainage share of the jth regenerator, %; τ j , q j , γ j respectively represent the water supply enthalpy rise, extraction steam enthalpy drop and drainage enthalpy drop, kJ / kg; j = 1, 2, …, 7.

[0035] The steam balance equation of the thermal power unit is:

[0036]

[0037] In the formula, D i represents the i th stage extraction steam flow of the steam turbine, kg / s; i = 1, 2, …, 7; D fw represents the high-pressure heater water supply flow, kg / s; D wc represents the condensate flow, kg / s.

[0038] The molten salt heat exchanger model describes the heat exchange process between the molten salt and the main steam or the condensate water, and calculates the enthalpy value of the main steam or the condensate water after heat exchange according to the change of the molten salt temperature. The molten salt heat exchanger model is:

[0039] c ms D ms (T ms,h -T ms,l ) = D w (h w,h -h w,l ) (6)

[0040] In the formula, c msrepresents the specific heat capacity of molten salt at constant pressure, kJ / (kg·K); D ms represents the mass flow of molten salt, kg / s; T ms,h represents the high-temperature temperature of molten salt before heat exchange, ℃; T ms,l represents the low-temperature temperature of molten salt after heat exchange, ℃; D w represents the mass flow of water or steam for heat exchange with molten salt, kg / s; h w,h , h w,l respectively represent the enthalpy values before and after water or steam heat exchange, kJ / kg.

[0041] In another exemplary embodiment of the present application, the molten salt parameters are the mass flow of molten salt D ms and the high-temperature temperature of molten salt before heat exchange T ms,h . According to the above unit variable condition model and molten salt parameters, the technical parameters under variable conditions are calculated, including the unit peak shaving capacity and coal consumption in the heat storage stage and the heat release stage. Then, the unit technical parameter model in the above step 102 is:

[0042] ΔP c = P0- P c (7)

[0043] ΔP s = P s - P e (8)

[0044]

[0045] In the formula, ΔP c , ΔP s respectively represent the peak shaving capacity in the heat storage stage and the heat release stage, MW; P c , P s respectively represent the actual output power of the thermal power unit in the heat storage stage and the heat release stage, MW; P0, P e respectively represent the rated output power under 50% THA condition and 100% THA condition of the original thermal power unit, MW; m coal represents the coal consumption in the heat storage stage or the heat release stage, kg / s; D st represents the main steam flow, kg / s; h st , h fw respectively represent the main steam enthalpy and the feedwater enthalpy, kJ / kg; D1, D2 respectively represent the first-stage extraction steam flow and the second-stage extraction steam flow, and σ represents the unit reheat steam heat absorption, kJ / kg; LHV represents the low calorific value of coal, kJ / kg; η b , η gd respectively represent the boiler efficiency and the pipeline efficiency, %.

[0046] In another exemplary embodiment of the present application, P cP in formula (8) s The specific form is:

[0047]

[0048] In the formula, P represents the actual output power of the thermal power generating unit in the heat storage stage or the heat release stage, MW; η represents the energy conversion efficiency of the steam turbine, h r2 represents the enthalpy of the reheated steam, kJ / kg; h2 represents the enthalpy of the second-stage steam extraction, kJ / kg; D i represents the steam extraction flow rate of the i-th stage of the steam turbine, kg / s; h i represents the enthalpy of the i-th stage of the steam turbine, kJ / kg; D0 represents the exhaust steam flow rate of the steam turbine, kg / s; h0 represents the enthalpy of the exhaust steam of the steam turbine, kJ / kg.

[0049] In another exemplary embodiment of the present application, the overall thermal efficiency is calculated according to the output power and the coal consumption in the heat storage and heat release processes of the unit. Then, the variation law of the index with the molten salt is analyzed by changing the molten salt parameters, so as to facilitate the selection of a suitable target to construct an optimization problem. The overall thermal efficiency calculation model in the above step 103 is:

[0050]

[0051] In the formula, η Th,q represents the overall thermal efficiency, %; P c and P s respectively represent the actual output power of the thermal power generating unit in the heat storage stage and the heat release stage, m coal,c and m coal,s respectively represent the coal consumption in the heat storage stage and the heat release stage, kg / s; and LHV represents the low calorific value of coal.

[0052] In another exemplary embodiment of the present application, the net profit brought by the molten salt is calculated according to the peak regulation capacity, the coal consumption and the molten salt heat storage cost. The net profit calculation model in the above step 103 is:

[0053] L r =(365(S c +S s )-C om )·n-(C dc +C ic +C coc ) (12)

[0054] In the formula, L r represents the net profit, $; S c and S s respectively represent the total income in the heat storage stage and the heat release stage of the molten salt, $; C om , C dc , and C icC coc These represent annual operation and maintenance costs, direct costs, indirect costs, accident costs, and owner fees, respectively, where $ represents the annual operating cost, direct costs, indirect costs, accident costs, and owner fees; n represents the unit's operating years, in years. Where:

[0055] S c =t c (1000ξΔP c -1000S e ΔP c +3600S coal Δm coal,c (13)

[0056] ξ represents the peak load subsidy, $ / (kW·h); ΔP c S represents the peak-shaving capacity during the thermal storage phase. e Electricity price, expressed as $ / (kW·h); S coal The price of coal is expressed in $ / kg; Δm coal,c This indicates the change in unit coal consumption during the thermal storage phase relative to the original load condition, expressed in kg / s and t. c Indicates the duration of heat storage.

[0057] S s =t s (1000S e ΔP s -3600S coal Δm coal,s (14)

[0058] ΔP s Δm represents the peak-shaving capacity during the heat release phase. coal,s This indicates the change in unit coal consumption during the heat release phase relative to the original load condition, expressed in kg / s or t. s Indicates the duration of heat release.

[0059] C dc =C tank +C msp +C ex +0.9×43200D ms +0.25C eq +0.08C eq +0.1C eq +0.1C eq +0.04C eq (15)

[0060] C tank C represents the cost of the molten salt tank equipment. msp C represents the cost of molten salt pump equipment. ex D represents the cost of molten salt heat exchanger equipment. ms C represents the molten salt mass flow rate. eq This represents the total equipment cost.

[0061] C ic = 0.14C eq (16)

[0062] C coc = 0.15(C dc +C ic ) (17)

[0063] C om = 0.01(C dc +C ic +C coc )+0.008(C dc +C ic +C coc )+0.02(C dc +C ic +C coc )+0.01(C dc +C ic

[0064] +C coc )+0.02(C dc +C ic +C coc ) (18)

[0065] C om ,C dc ,C ic ,C coc The cost is shown in Table 1.

[0066] Table 1 Cost

[0067]

[0068]

[0069] In another exemplary embodiment of the present application, the various costs caused by the molten salt are calculated according to the molten salt parameters, including the molten salt cost, equipment cost, installation cost, operation and maintenance cost, etc. Then the calculation formulas of the above-mentioned C tank ,C msp ,C ex and C eq are as follows:

[0070] C tank = 9295.8V 0.513 (19)

[0071]

[0072] C eq = C tank +Cmsp +C ex (22)

[0073] wherein V represents the volume of the molten salt tank, m 3 ; D V represents the volumetric flow rate, m 3 / kg; H represents the pump head height, A represents the heat exchange area, m 2 ; F L , F M , F P respectively represent the pipe length correction factor, the material correction factor, and the pressure correction factor.

[0074]

[0075] p ms = 2317.5 - 0.7878 (T ms + 273.15) (24)

[0076] wherein p ms represents the molten salt density, kg / m 3 ; T ms represents the molten salt temperature, °C.

[0077]

[0078] wherein c ms represents the specific heat capacity of the molten salt at constant pressure, T ms,h represents the high temperature before heat exchange of the molten salt, T ms,l represents the low temperature after heat exchange of the molten salt, k represents the heat transfer coefficient, kW / (m 2 · °C); At m represents the average heat exchange temperature difference, °C; T w,h represents the high temperature before heat exchange of the steam or water, °C; T w,l represents the low temperature after heat exchange of the steam or water, °C.

[0079]

[0080] wherein P s ' represents the shell side pressure, MPa.

[0081] In another example embodiment of the present application, according to the above formula, the overall thermal efficiency decreases with the increase of the molten salt parameters, and the net profit increases with the increase of the molten salt parameters. According to this rule, the maximum overall thermal efficiency and the maximum net profit are obtained, and then the objective function is designed according to the Pareto optimal idea, and the point at which the overall thermal efficiency and the net profit are maximized at the same time is regarded as the ideal point, and the point closest to the ideal point is the optimal point. Therefore, the overall thermal efficiency and the net profit are selected as the optimization objectives, the molten salt mass flow and the high temperature are selected as the parameters to be optimized, and the objective function is designed according to the Pareto optimal idea:

[0082] y = [(L r -L r,b ) 2 +(η Th,q -η Th,q,b ) 2 ] 0.5 (30)

[0083] In the formula, y represents the target value, L r represents the net profit, L r,b represents the optimal value of the net profit, $; η Th,q represents the overall thermal efficiency, and η Th,q,b represents the optimal value of the overall thermal efficiency, %.

[0084] In another example embodiment of the present application, the above step 105 is used to determine the optimal molten salt parameters by using the white whale optimization algorithm, and after updating the molten salt parameters each time, the operating conditions of the new working condition are determined, which specifically includes the following steps 201 to 204:

[0085] Step 201: According to the updated molten salt parameters, the water or steam mass flow exchanged with the molten salt is obtained by using the molten salt heat exchanger model; the molten salt parameters include the molten salt mass flow and the high temperature of the molten salt; the water mass flow exchanged with the molten salt is the condensate extraction amount when releasing heat, and the steam mass flow exchanged with the molten salt is the main steam extraction flow when storing heat.

[0086] Step 202: According to the water or steam mass flow exchanged with the molten salt, the steam pressure before each stage of the steam turbine is obtained by using the intermediate stage model of the steam turbine.

[0087] Step 203: According to the steam pressure before each stage of the steam turbine, the enthalpy value of each stage of the steam turbine is obtained by using the IAPWS_IF97 model and the last stage model of the steam turbine.

[0088] Step 204: Based on the enthalpy value of each stage of the steam turbine, the extraction flow of each stage of the steam turbine is obtained by using the regenerative system model, as the operating conditions of the new working condition.

[0089] The target point is found by using the Beluga whale optimization (BWO) algorithm, and the process is as follows:

[0090] 1) Fix the temperature of the low-temperature molten salt, set the optimization parameters, i.e., the range of the mass flow rate of the molten salt and the high-temperature temperature of the molten salt, set the population size and the maximum number of iterations, and initialize the population;

[0091] 2) According to the parameters of the molten salt, the steam extraction amount of the main steam during heat storage and the extraction amount of the condensate water during heat release are calculated by using the molten salt heat exchanger model in step 1, and the steam extraction amount of the turbine is calculated by using the steam turbine model and the regenerative system model in step 1: Due to the change of the main steam or condensate water flow rate, the extraction flow rate of each stage will change, the extraction pressure and enthalpy of each stage are calculated according to the steam turbine model, and the extraction flow rate of the turbine is obtained according to the share relationship and enthalpy between the feedwater, drain and extraction steam according to the regenerative system model, the operating conditions of the new working condition are determined, so as to obtain the target value of each individual, and the target value is compared, and the best parameters at this time are determined among these individuals.

[0092] 3) The balance factor B is calculated according to the BWO algorithm rule f and the whale falling probability W f , the update mode of the individual is determined according to the size of B f , if B f is greater than 0, the exploration stage formula is updated, if B f is less than 0, the development stage formula is updated. The calculation formula of the balance factor B f and the whale falling probability W f is:

[0093]

[0094] In the formula, B0 represents a random value in the range of 0-1; t represents the current iteration number; T represents the maximum iteration number.

[0095] 4) Determine the size of B f and W f , if B f is greater than W f , the whale falling stage formula is used to update the population, otherwise the population is not updated, then the target value of each individual is recalculated and the best parameters are determined;

[0096] 5) Repeat the above steps until the maximum iteration number is reached, output the best molten salt parameters and the optimal fitness, and end the algorithm.

[0097] In another example embodiment of the present application, the step 106 is performed by obtaining the optimal molten salt parameters, calculating the peak shaving capacity of the heat storage stage and the heat release stage and the technical index of the whole process according to the unit technical parameter model, and obtaining the final optimization result. After the step 106, the method can further include: obtaining the net profit according to the optimal unit technical parameters by using a net profit calculation model.

[0098] In another example embodiment of the present application, the method of the present application is applied to a 660 MW supercritical thermal power unit, which uses main steam as a heat source, extracts main steam to exchange heat with molten salt in the heat storage stage, and extracts condensate to exchange heat with molten salt in the heat release stage. The method of the present application helps to find the most ideal operating conditions for the coupled molten salt heat storage thermal power unit.

[0099] The advantages of the present application over the prior art are as follows:

[0100] 1. The whole process of the coupled molten salt heat storage thermal power unit is considered to improve the overall performance of the coupled system. Compared with only considering the heat storage process or the heat release process, the whole process of the molten salt participating in the peak shaving of the unit is included, the overall operation process is considered more fully and comprehensively, which helps to improve the performance of the unit in the whole process of heat storage and heat release, realizes the harmonious cooperation of the unit in the heat storage and heat release stages, and avoids the situation that the efficiency of a single operation process is too low.

[0101] 2. Balance the technical index and economic index of the whole process to ensure that the values of various indexes are balanced and the values of the indexes are not too low. During the change of the molten salt parameters, the change trends of the technical index and the economic index are not the same. Only considering the technical or economic index, the optimization result is too one-sided, other factors of the coupled system are ignored, and the performance of the coupled system in many aspects is insufficient. By balancing the technical and economic indexes of the whole process, the energy utilization efficiency and the peak shaving capacity of the unit can be optimized, and the revenue of the unit can be ensured, so that the optimal molten salt parameter configuration is realized.

[0102] 3. Selecting the Pareto optimality as the construction method of the objective function to ensure that the optimization result meets the expected requirements. The Pareto optimality finds the point closest to the ideal point as the optimization result in the operation optimization of the coupled molten salt heat storage thermal power unit, and each optimization index is considered. The final optimization result shows that the Pareto optimality focuses on the peak shaving capacity of the unit, and compared with other methods, it has greater advantages in the peak shaving capacity, cycle efficiency and net profit of the unit in the heat storage and heat release stages. Especially in the peak shaving capacity, the optimization result is more in line with the requirements and expectations of the thermal power unit, and it has obvious advantages in improving the flexibility of the thermal power unit.

[0103] Any technical features in the above embodiments can be combined, and for the sake of brevity, not all possible combinations are described above, however, it should be understood that the application encompasses all possible combinations of the technical features described above.

[0104] The principles and implementation manners of the present application are described herein by using specific examples, and the above embodiments are only used to help understand the method of the present application and its core idea; meanwhile, according to the idea of the present application, the specific implementation manners and application scopes will be changed by those skilled in the art. In conclusion, the content of the present specification should not be understood as a limitation of the present application.

Claims

1. A molten salt heat storage participates in the operation optimization method of thermal power generating unit, characterized in that, The application relates to a molten salt heat storage participating in operation optimization of a thermal power generating unit. A unit variable condition model is established by participating in operation of the molten salt; The unit variable condition model contains molten salt parameters; The unit variable condition model comprises a steam turbine model, a regenerative system model and a molten salt heat exchanger model; Based on the unit variable condition model, a unit technical parameter model of a heat storage stage and a heat release stage is established; According to the unit technical parameter model, a whole-process heat efficiency calculation model and a net profit calculation model containing the heat storage stage and the heat release stage are determined; According to the Pareto optimal thought, a target function containing the whole-process heat efficiency calculation model and the net profit calculation model is constructed; Based on the target function, the molten salt parameters are taken as optimization variables, and the white whale optimization algorithm is adopted to make the whole-process heat efficiency and the net profit reach the Pareto optimal condition at the same time, so that the optimal molten salt parameters are determined; According to the optimal molten salt parameters, the optimal unit technical parameters of the heat storage stage and the heat release stage are obtained by using the unit technical parameter model.

2. The molten salt heat storage participates in the operation optimization method of the thermal power unit according to claim 1, characterized in that, The steam turbine model comprises a steam turbine intermediate stage model and a steam turbine final stage model; The intermediate stage model of the steam turbine is: In the formula, D g,i represents the steam flow rate through the i-th stage of the steam turbine under the variable working condition g, D g0,i represents the steam flow rate through the i-th stage of the steam turbine under the design working condition, p g,i represents the steam pressure before the i-th stage of the steam turbine under the variable working condition g, p g0,i represents the steam pressure before the i-th stage of the steam turbine under the design working condition; The turbine's final stage model is as follows: and h c =h7-η7(h7-h') c In the formula, η6 and η7 represent the relative internal efficiencies of the 6th and 7th stages of the steam turbine, respectively, and h6 and h7 represent the extraction enthalpy values ​​of the 6th and 7th stages of the steam turbine, respectively. c h'7 represents the enthalpy of the exhaust steam from the last stage of the steam turbine, and h'7 represents the ideal enthalpy of the extraction steam pressure from the 7th stage of the steam turbine. c 'Indicates the ideal enthalpy of the exhaust steam from the last stage of the steam turbine; The regenerative system model comprises a heat balance equation of a regenerator and a steam balance equation of the thermal power generating unit; The heat balance equation of the regenerator is: α H,j τ j = α j q j + β j γ j ; in the formula, α H,j , α j , β j respectively represent the feed water share, the extraction steam share, the drain share of the jth regenerator, τ j , q j , γ j respectively represent the feed water enthalpy rise, the extraction steam enthalpy drop, the drain enthalpy drop, j=1, 2, …, 7; The steam balance equation of the thermal power unit is: In the formula, D i represents the steam extraction flow rate of the i-th stage of the steam turbine, i = 1, 2, …, 7; D fw represents the feed water flow rate of the high-pressure heater, D wc represents the condensate flow rate; The molten salt heat exchanger model is: c ms D ms (T ms,h -T ms,l ) = D w (h w,h -h w,l In the formula, c ms D represents the isobaric specific heat capacity of molten salt. ms T represents the molten salt mass flow rate. ms,h T represents the high temperature before molten salt heat exchange. ms,l D represents the low-temperature temperature after molten salt heat exchange. w The mass flow rate of water or steam exchanged with molten salt, h w,h h w,l These represent the enthalpy values ​​before and after heat exchange with water or steam, respectively.

3. The molten salt heat storage participates in the operation optimization method of the thermal power unit according to claim 1, characterized in that, The unit technical parameter model is: ΔP c = P0- P c ; ΔP s = P s - P e ; In the formula, ΔP c , ΔP s respectively represent the peak shaving capacity in the heat storage stage and the heat release stage, P c , P s respectively represent the actual output power of the thermal power unit in the heat storage stage and the heat release stage, P0, P e respectively represent the rated output power under 50% THA and 100% THA conditions of the original thermal power unit, m coal represents the coal consumption in the heat storage stage or the heat release stage, D st represents the main steam flow, h st , h fw respectively represent the main steam enthalpy and the feedwater enthalpy, D1, D2 respectively represent the first-stage extraction steam flow and the second-stage extraction steam flow, σ represents the unit reheat steam heat absorption, LHV represents the low calorific value of coal, η b , η gd respectively represent the boiler efficiency and the pipeline efficiency.

4. The molten salt heat storage participates in the operation optimization method of the thermal power unit according to claim 3, characterized in that, The specific form of the actual output power of the thermal power generating unit in the heat storage stage or the heat release stage is: In the formula, P represents the actual output power of the thermal power unit in the heat storage or heat release stage, η represents the energy conversion efficiency of the steam turbine, h r2 represents the enthalpy value of the reheated steam, h2 represents the enthalpy value of the second-stage steam extraction, D i represents the steam extraction flow rate of the i-th stage of the steam turbine, h i represents the enthalpy value of the i-th stage of the steam extraction of the steam turbine, D0 represents the exhaust steam flow rate of the steam turbine, and h0 represents the enthalpy value of the exhaust steam of the steam turbine.

5. The molten salt heat storage participates in the operation optimization method of the thermal power unit according to claim 1, characterized in that, The whole-process heat efficiency calculation model is: In the formula, η Th,q represents the overall thermal efficiency, P c , P s respectively represent the actual output power of the thermal power generating unit in the heat storage stage and the heat release stage, m coal,c , m coal,s respectively represent the coal consumption in the heat storage stage and the heat release stage, and LHV represents the low calorific value of coal.

6. The molten salt heat storage participates in the operation optimization method of the thermal power unit according to claim 1, characterized in that, The net profit calculation model is: L r = (365(S c + S s ) - C om ) · n - (C dc + C ic + C coc ); In the formula, L r represents net profit, S c , S s respectively represent total income of the molten salt heat storage stage and the heat release stage, C om , C dc , C ic , C coc respectively represent annual operation and maintenance cost, direct cost, indirect cost, unexpected accident and owner cost, and n represents the operation life of the unit; Wherein, S c = t c (1000ξΔP c -1000S e ΔP c +3600S coal Δm coal,c ); ξ represents peak load subsidy, ΔP c represents peak shaving capacity in the heat storage stage, S e represents electricity price, S coal represents coal price, Δm coal,c represents change of coal consumption of the unit under the condition of relative original load in the heat storage stage, t c represents heat storage duration; S s = t s (1000 e ΔP s -3600 coal Δm coal,s ); ΔP s represents the peak shaving capacity of the heat release stage, Δm coal,s represents the change of the coal consumption of the unit under the relative original load condition of the heat release stage, t s represents the heat release duration C dc = C tank + C msp + C ex + 0.9 x 43200 D ms + 0.25 C eq + 0.08 C eq + 0.1 C eq + 0.1 C eq + 0.04 C eq ; C tank represents molten salt tank equipment cost, C msp represents molten salt pump equipment cost, C ex represents molten salt heat exchanger equipment cost, D ms represents molten salt mass flow rate, C eq represents total equipment cost; C ic = 0.14C eq ; C coc = 0.15 (C dc + C ic ); C om = 0.01 (C dc + C ic + C coc ) + 0.008 (C dc + C ic + C coc ) + 0.02 (C dc + C ic + C coc ) + 0.01 (C dc + C ic + C coc ) + 0.02 (C dc + C ic + C coc ).

7. The molten salt heat storage participating in operation optimization method of the thermal power generating unit according to claim 6, characterized in that: C tank = 9295.8 V 0.513 ; C eq = C tank + C msp + C ex ; In the formula, V represents the volume of the molten salt tank, D V represents the volumetric flow rate, H represents the pump head height, A represents the heat exchange area, F L , F M , F P respectively represent the pipe length correction factor, the material correction factor, and the pressure correction factor. and p ms = 2317.5 - 0.7878(T ms + 273.15); where p ms represents the molten salt density, T ms represents the molten salt temperature; and wherein c ms represents the specific heat capacity at constant pressure of the molten salt, T ms,h represents the high temperature before heat exchange of the molten salt, T ms,l represents the low temperature after heat exchange of the molten salt, k represents the heat transfer coefficient, Δt m represents the average heat exchange temperature difference, T w,h represents the high temperature before heat exchange of the steam or water, T w,l represents the low temperature after heat exchange of the steam or water; where P s ' represents the shell side pressure.

8. The molten salt heat storage participates in the operation optimization method of the thermal power unit according to claim 1, characterized in that, The target function is: y = [(L r - L r,b ) 2 + (η Th,q - η Th,q,b ) 2 ] 0.5 ; where y represents a target value, L r represents net profit, L r,b represents a net profit optimum value, η Th,q represents overall thermal efficiency, η Th,q,b represents an overall thermal efficiency optimum value.

9. The molten salt heat storage participates in the operation optimization method of the thermal power unit according to claim 2, characterized in that, In the process of determining the optimal molten salt parameters by adopting the white whale optimization algorithm, the operation conditions of a new condition are determined after the molten salt parameters are updated each time, and the operation conditions of the new condition specifically comprise: According to the updated molten salt parameters, the water or steam mass flow rate exchanged with the molten salt is obtained by using the molten salt heat exchanger model; the molten salt parameters comprise a molten salt mass flow rate and a high-temperature temperature of the molten salt; the water mass flow rate exchanged with the molten salt is the condensate extraction amount in the heat release process, and the steam mass flow rate exchanged with the molten salt is the main steam extraction flow rate in the heat storage process; According to the water or steam mass flow rate exchanged with the molten salt, the steam turbine pre-stage steam pressure of each stage of the steam turbine is obtained by using the steam turbine intermediate stage model; According to the steam turbine pre-stage steam pressure of each stage of the steam turbine, the enthalpy value of each stage of the steam turbine is obtained by using the IAPWS_IF97 model and the steam turbine final stage model; Based on the enthalpy value of each stage of the steam turbine, the extraction flow rate of each stage of the steam turbine is obtained by using the regenerative system model, as the operation conditions of the new condition.

10. The molten salt heat storage participates in the operation optimization method of the thermal power unit according to claim 1, characterized in that, According to the optimal molten salt parameters, the optimal unit technical parameters of the heat storage stage and the heat release stage are obtained by using the unit technical parameter model, and the method further comprises the following steps: According to the optimal unit technical parameters, the net profit is obtained by using the net profit calculation model.

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