Method for optimizing operation of thermal power generating unit through participation of fused salt heat storage

Abstract

The invention discloses an optimization method for fused salt heat storage participating in thermal power generating unit operation, and relates to the technical field of thermal power generating unit coupling fused salt heat storage. The method comprises the steps of establishing a unit variable working condition model in which fused salt participates in thermal power unit operation; establishing unit technical parameter models of a heat storage stage and a heat release stage based on the unit variable working condition model; determining a whole-course thermal efficiency calculation model and a net profit calculation model according to the unit technical parameter model; according to the Pareto optimal idea, constructing an objective function comprising a whole-course thermal efficiency calculation model and a net profit calculation model; on the basis of the objective function, taking the fused salt parameters as optimization variables, adopting a whale optimization algorithm to enable the thermal efficiency and the net profit in the whole process to reach Pareto optimal conditions at the same time, and determining the optimal fused salt parameters; and according to the optimal fused salt parameters, the optimal unit technical parameters of the heat storage stage and the heat release stage are obtained through the unit technical parameter model. The optimal operation of thermal power generating unit coupling fused salt heat storage in the whole heat storage and heat release process can be achieved.

Description

Technical Field

[0001] The present application relates to the technical field of thermal power unit coupled with molten salt heat storage, and in particular to a method for optimizing the operation of a thermal power unit with the participation of molten salt heat storage. Background Art

[0002] The proportion of 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 factors such as geographical environment and weather, and has the characteristics of volatility, intermittency, and unpredictability. Large-scale grid connection will have an adverse impact 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 units have become the main power source for deep peak regulation with their advantages of large installed capacity and strong controllability, which puts forward higher requirements for the flexibility of thermal power units, that is, they need to have the ability to respond quickly, accurately adjust and operate stably for a long time, so as to adapt to the volatility and uncertainty brought by the grid connection of new energy, and ensure the safe, 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 load regulation of thermal power units can be carried out without modifying the boiler and turbine body. Adding external equipment directly connected to the thermal system is a very promising method for unit flexibility transformation. Among the many heat storage media, molten salt has the advantages of high safety, environmental friendliness, large specific heat capacity, low cost and easy availability. It is one of the important directions of scientific research in the field of energy storage. At present, molten salt heat storage technology has been applied in the field of solar thermal power generation and has the foundation to support the large-scale development of solar thermal power generation. In summary, coupled molten salt heat storage technology is an important technology to promote the flexibility transformation of thermal power generation and has great development potential.

[0004] However, existing related research mostly focuses on the technical optimization of a single operating process or only considers the benefits of the coupled system. It rarely involves the study of the entire process of heat storage and release and the comprehensive study of various indicators. There is also little research on the use of extraction steam to heat molten salt. Most existing studies use electric heating to heat molten salt. In addition, most existing studies are scheme design and indicator analysis and comparison, but no parameter optimization is performed on the designed scheme, resulting in the designed scheme failing to achieve optimal operating conditions. Summary of the invention

[0005] The purpose of this application is to provide a method for optimizing the operation of a thermal power unit using molten salt heat storage, which can achieve optimal operation of the thermal power unit coupled with molten salt heat storage in the entire process of heat storage and heat release.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] The present application provides a method for optimizing the operation of a thermal power unit in which molten salt heat storage participates, comprising: establishing a unit variable operating condition model in which molten salt participates in the operation of a thermal power unit; the unit variable operating condition model includes molten salt parameters; based on the unit variable operating condition model, establishing a unit technical parameter model for a heat storage stage and a heat release stage; according to the unit technical parameter model, determining a full-process thermal efficiency calculation model including a heat storage stage and a heat release stage and a net profit calculation model; according to the Pareto optimality concept, constructing an objective function including a full-process thermal efficiency calculation model and a net profit calculation model; based on the objective function, taking molten salt parameters as optimization variables, adopting the Beluga optimization algorithm to make the full-process thermal efficiency and net profit simultaneously reach the Pareto optimal conditions, and determining the optimal molten salt parameters; according to the optimal molten salt parameters, using the unit technical parameter model, obtaining the optimal unit technical parameters for the heat storage stage and the heat release stage.

[0008] According to the specific embodiments provided in this application, this application has the following technical effects:

[0009] The present application provides a method for optimizing the operation of a thermal power unit involving molten salt heat storage, which comprehensively considers the operation of the entire process of heat storage and heat release of the coupled molten salt heat storage thermal power unit, and constructs an objective function including the entire thermal efficiency and net profit according to the Pareto optimality idea, balances the entire thermal efficiency and net profit of the entire process, and obtains the optimal unit technical parameters in the heat storage stage and the heat release stage, and then based on the optimal unit technical parameters, realizes the optimal operation of the thermal power unit coupled with molten salt heat storage in the entire process of heat storage and heat release. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 A schematic flow chart of a method for optimizing the operation of a thermal power unit using molten salt heat storage provided in one embodiment of the present application. DETAILED DESCRIPTION

[0012] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0013] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0014] The operation of the unit with molten salt is divided into two stages: heat storage stage and heat release stage. In the heat storage stage, molten salt stores the heat of steam, and the output power of the unit decreases due to the reduction of working steam; in the heat release stage, molten salt releases the stored heat, and the output power of the unit is improved. The participation of molten salt improves the peak-shaving capacity of the unit, and also changes the operation mode of the unit. Various indicators of the coupling system will also change. The impact of molten salt needs to be considered when calculating the energy utilization efficiency and benefits of the unit. In addition to changing the output power, the participation of molten salt in the peak-shaving of the unit will also change the coal consumption. In addition, the addition of molten salt will bring a series of equipment and operation and maintenance costs. Taking into account the whole process of heat storage and heat release, the energy utilization efficiency and benefits will change with the changes in the output power and coal consumption of the unit, and the degree of change of the indicators will vary with the flow rate and temperature of the molten salt during operation. There are also differences in the changing trends of some technical indicators and other indicators with the molten salt parameters. Therefore, to find suitable molten salt parameters for unit operation, it is necessary to comprehensively consider the whole process of heat storage and release of the unit, as well as the differences in the technical indicators of the whole process and other indicators as the molten salt parameters change, in order to find the optimal molten salt parameters.

[0015] Reasonable balance of the technical indicators of the entire process of heat storage and release of the unit and other indicators can help to maximize the unit's benefits and promote optimal configuration while meeting the basic requirements of the unit's peak load regulation.

[0016] In view of the above, in an exemplary embodiment, Figure 1 As shown, the present application provides a method for optimizing the operation of a thermal power unit by using molten salt heat storage, comprising the following steps 101 to 106. Among them:

[0017] Step 101: Establish a variable operating condition model of a thermal power unit in which molten salt participates in operation; the variable operating condition model of the unit includes molten salt parameters.

[0018] Step 102: Based on the variable operating condition model of the unit, a technical parameter model of the unit in the heat storage stage and the heat release stage is established.

[0019] Step 103: According to the unit technical parameter model, a full-process thermal efficiency calculation model including a heat storage stage and a heat release stage and a net profit calculation model are determined.

[0020] Step 104: Construct an objective function including a full-process thermal efficiency calculation model and a net profit calculation model.

[0021] Step 105: Based on the objective function, taking the molten salt parameters as optimization variables, the White Whale optimization algorithm is used to make the overall thermal efficiency and net profit reach the Pareto optimal conditions at the same time, and the optimal molten salt parameters are determined.

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

[0023] By implementing the above steps 101 to 106, the operation of the entire process of heat storage and heat release of the coupled molten salt heat storage thermal power unit is comprehensively considered, and according to the Pareto optimal idea, an objective function including the overall thermal efficiency and net profit is constructed, the overall thermal efficiency and net profit of the entire process are balanced, and the optimal unit technical parameters in the heat storage stage and the heat release stage are obtained. Then, based on the optimal unit technical parameters, the optimal operation of the thermal power unit coupled with molten salt heat storage in the entire process of heat storage and heat release is achieved.

[0024] In another exemplary embodiment of the present application, the variable operating condition model of the unit in the above step 101 includes: a steam turbine model, a heat recovery 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 Flugel formula to obtain the steam pressure before each stage (the steam extraction pressure at each stage). The steam turbine intermediate stage model is:

[0025]

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

[0027] The change of the last stage operating condition of the steam turbine can be calculated based on the thermal change of the previous stage. The last stage model of the steam turbine is:

[0028]

[0029] h c =h7-η7(h7-h' c ) (3)

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

[0031] The heat recovery system model is derived based on the relationship between the extraction steam, drain water and feed water share of each regenerator, and the steam-water balance equation of the unit is used to calculate the extraction steam flow rate at each level. The heat recovery system model includes the heat balance equation of the regenerator and the steam-water balance equation of the thermal power unit.

[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 feed water share, extraction steam share, and drainage share of the j-th stage regenerator, %; τ j ,q j , γ j They represent feed water enthalpy rise, extraction steam enthalpy drop, and drain enthalpy drop, respectively, in kJ / kg; j=1,2,…,7.

[0035] The steam-water balance equation of a thermal power unit is:

[0036]

[0037] Where D i Indicates the steam extraction flow rate of the i-th stage of the steam turbine, kg / s; i = 1, 2, ..., 7; D fw Indicates the feed water flow rate of the high-pressure heater, kg / s; D wc Indicates the condensate flow rate, kg / s.

[0038] The molten salt heat exchanger model describes the process of heat exchange between molten salt and main steam or condensate. The enthalpy value of the main steam or condensate after heat exchange is calculated according to the change of 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 constant pressure specific heat capacity of molten salt, kJ / (kg·K); D ms Indicates the mass flow rate of molten salt, kg / s; T ms,h Indicates the high temperature before molten salt heat exchange, °C; T ms,l Indicates the low temperature after molten salt heat exchange, °C; D w Indicates the mass flow rate of water or steam exchanging heat with molten salt, kg / s; h w,h 、h w,l Respectively represent the enthalpy value of water or steam before and after heat exchange, kJ / kg.

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

[0042] ΔP c =P0-P c (7)

[0043] ΔP s =P s -P e (8)

[0044]

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

[0046] In another exemplary embodiment of the present application, P in formula (7) cand P in formula (8) s The specific form is:

[0047]

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

[0049] In another exemplary embodiment of the present application, the overall thermal efficiency is calculated based on the output power and coal consumption of the unit's heat storage and heat release process. Then, the molten salt parameters are changed, and the change law of the indicators with the molten salt is analyzed, so as to facilitate the selection of appropriate targets to construct optimization problems. The overall thermal efficiency calculation model in the above step 103 is:

[0050]

[0051] Where η Th,q Indicates the overall thermal efficiency, %; P c , P s Respectively represent the actual output power of thermal power units in the heat storage stage and heat release stage, m coal,c 、m coal,s They represent the coal consumption in the heat storage stage and the heat release stage, kg / s respectively; 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 based on the peak load capacity, coal consumption and molten salt heat storage cost. Then 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] Where, L r represents net profit, $; S c , S s Respectively represent the total benefits of molten salt heat storage stage and heat release stage, $; C om , C dc , C ic, C coc Respectively represent annual operation and maintenance costs, direct costs, indirect costs, accidents and owner expenses, $; n represents the operating years of the unit, years. Among them:

[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 represents the peak load capacity in the heat storage stage, S e Indicates the electricity price, $ / (kW·h); S coal Indicates coal price, $ / kg; Δm coal,c Indicates the change of unit coal consumption during the heat storage stage relative to the original load conditions, kg / s; t c Indicates the heat storage time.

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

[0058] ΔP s Indicates the peak load capacity during the heat release phase, Δm coal,s Indicates the change of unit coal consumption during the heat release stage relative to the original load conditions, kg / s; t s Indicates heat release time.

[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 represents the equipment cost of the molten salt tank, C msp represents the cost of molten salt pump equipment, C ex represents the equipment cost of molten salt heat exchanger, D ms represents the mass flow rate of molten salt, C eq 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 costs are shown in Table 1.

[0066] Table 1 Cost

[0067]

[0068]

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

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

[0071]

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

[0073] Where V represents the volume of the molten salt tank, m 3 ;D V Indicates volume 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 They represent pipeline length correction factor, material correction factor, and pressure correction factor respectively.

[0074]

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

[0076] Among them, ρ ms Indicates the density of molten salt, kg / m 3 ; T ms Indicates the molten salt temperature, ℃.

[0077]

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

[0079]

[0080] Among them, P s ′ represents the shell side pressure, MPa.

[0081] In another exemplary 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 value of the overall thermal efficiency and the maximum value of the net profit are obtained, and then the objective function is designed according to the Pareto optimal idea, and the point where the overall thermal efficiency and the net profit reach the maximum value at the same time is set as the ideal point, and the point closest to the ideal point is the optimal point. Then this application selects the overall thermal efficiency and net profit as the optimization targets, the molten salt mass flow rate and the high temperature temperature as the parameters to be optimized, and the objective function designed using the Pareto optimal idea is:

[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 net profit, L r,b represents the optimal value of net profit, $; η Th,q Represents the overall thermal efficiency, η Th,q,b Indicates the optimal value of the overall thermal efficiency, %.

[0084] In another exemplary embodiment of the present application, in the process of determining the optimal molten salt parameters using the White Whale optimization algorithm, the above step 105 determines the operating conditions of the new operating condition each time the molten salt parameters are updated, specifically including the following steps 201 to 204:

[0085] Step 201: According to the updated molten salt parameters, using the molten salt heat exchanger model, the mass flow rate of water or steam for heat exchange with the molten salt is obtained; the molten salt parameters include the molten salt mass flow rate and the molten salt high temperature; the water mass flow rate for heat exchange with the molten salt is the condensate water extraction amount during heat release, and the steam mass flow rate for heat exchange with the molten salt is the main steam extraction flow rate during heat storage.

[0086] Step 202: According to the mass flow of water or steam for heat exchange 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 values ​​of each stage of the steam turbine, the steam extraction flow rate of each stage of the steam turbine is obtained by using the heat recovery system model as the operating condition of the new operating condition.

[0089] The Belugawhale optimization (BWO) algorithm is used to find the target point. The process is as follows:

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

[0091] 2) According to the molten salt parameters, the main steam extraction amount of the computer group during heat storage and the condensate extraction amount during heat release are calculated using the molten salt heat exchanger model in step one, and the turbine extraction amount is calculated using the turbine model and the heat recovery system model in step one: due to the change in the main steam or condensate flow rate, the extraction flow rate of each stage will change. The extraction pressure and enthalpy value of each stage are calculated according to the turbine model, and then the turbine extraction flow rate is obtained according to the share relationship and enthalpy value between the feed water, drain and extraction in the heat recovery system model, and the operating conditions of the new operating condition are determined, thereby obtaining the target value of each individual, and comparing the target values ​​to determine the optimal parameters at this time among these individuals.

[0092] 3) Calculate the balance factor B according to the BWO algorithm rules f and whale fall probability W f , according to B f The size of determines the way individuals update. f If B is greater than 0, the exploration phase formula is used for update. f If it is less than 0, the development phase formula is used to update. Balance factor B f and whale fall probability W f The calculation formula is:

[0093]

[0094] Where: B0 represents a random value in the range of 0 to 1; t represents the current number of iterations; T represents the maximum number of iterations.

[0095] 4) Judge B f and W f The size of B f Greater than W f , the whale fall stage formula is used to update the population, otherwise the population is not updated, and then each target value is recalculated and the optimal parameters are determined;

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

[0097] In another exemplary embodiment of the present application, the above step 106 calculates the peak load capacity of the heat storage stage and the heat release stage and the technical indicators of the whole process according to the obtained optimal molten salt parameters according to the unit technical parameter model to obtain the final optimization result. After the above step 106, the method may also include: according to the optimal unit technical parameters, using the net profit calculation model to obtain the net profit.

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

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

[0100] 1. Comprehensively consider the operation of the whole process of heat storage and heat release of the coupled molten salt thermal power unit, and improve the overall performance of the whole process of the coupled system. Compared with only considering the heat storage process or the heat release process, the whole process of molten salt participating in the peak load regulation of the unit is included, and the overall operation process is considered more fully and comprehensively, which is helpful to improve the performance of the unit in the whole process of heat storage and heat release, realize the harmonious cooperation of the unit in the two stages of heat storage and heat release, and avoid the situation where the efficiency of a single operation process is too low.

[0101] 2. Balance the technical and economic indicators of the whole process, ensure the balance of the values ​​of various indicators, and avoid too low values. In the process of molten salt parameter changes, the trend of technical indicators and economic indicators is not the same. Considering only technical or economic indicators, the optimization result is too one-sided, ignoring other factors of the coupling system, resulting in insufficient performance of the coupling system in many aspects. Weighing the technical and economic indicators of the whole process can optimize the energy utilization efficiency and peak load capacity of the unit, ensure the benefits of the unit, and achieve the optimal molten salt parameter configuration.

[0102] 3. Select Pareto optimality as the construction method of the objective function to ensure that the optimization results meet the expected requirements. In the operation optimization of coupled molten salt heat storage thermal power units, the Pareto optimal idea finds the point closest to the ideal point as the optimization result, and every optimization indicator is taken into account. The final optimization results show that Pareto optimality focuses on the peak-shaving capacity of the unit. Compared with other methods, it has greater advantages in terms of unit heat storage, heat release peak-shaving capacity, cycle efficiency, and net profit. Especially in terms of peak-shaving capacity, its optimization results are more in line with the requirements and expectations for thermal power units, and it has obvious advantages in optimizing the flexibility of thermal power units.

[0103] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0104] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for optimizing the operation of a thermal power unit using molten salt heat storage, characterized in that: include: Establishing a unit variable operating condition model in which molten salt participates in the operation of a thermal power unit; the unit variable operating condition model includes molten salt parameters; Based on the variable operating condition model of the unit, a technical parameter model of the unit in the heat storage stage and the heat release stage is established; According to the technical parameter model of the unit, a full-process thermal efficiency calculation model including a heat storage stage and a heat release stage and a net profit calculation model are determined; According to the Pareto optimality concept, an objective function including the whole-process thermal efficiency calculation model and the net profit calculation model is constructed; Based on the objective function, the molten salt parameters are used as optimization variables, and the White Whale optimization algorithm is used to make the overall thermal efficiency and net profit reach the Pareto optimal conditions at the same time, and determine the optimal molten salt parameters; According to the optimal molten salt parameters, the optimal unit technical parameters in the heat storage stage and the heat release stage are obtained using the unit technical parameter model.

2. The method for optimizing the operation of a thermal power unit using molten salt heat storage according to claim 1 is characterized in that: The variable operating condition model of the unit includes: a steam turbine model, a heat recovery 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: Where D g,i represents the steam flow rate through the i-th stage of the turbine under variable operating condition g, D g0,i represents the steam flow rate through the i-th stage of the turbine under design conditions, p g,i represents the steam pressure before the i-th stage of the steam turbine under variable operating condition g, p g0,i It represents the steam pressure before the i-th stage of the steam turbine under the design condition; The final stage model of the steam turbine is: and h c =h7-η7(h7-h' c );where η6 and η7 represent the relative internal efficiency of the 6th and 7th stage of the steam turbine, respectively; h6 and h7 represent the extraction enthalpy of the 6th and 7th stage of the steam turbine, respectively; h c represents the exhaust enthalpy of the last stage of the steam turbine, h'7 represents the ideal enthalpy of the seventh stage extraction pressure of the steam turbine, h c ' represents the ideal enthalpy of the last stage exhaust steam of the steam turbine; The regenerative system model includes the heat balance equation of the regenerator and the steam-water balance equation of the thermal power unit; The heat balance equation of the regenerator is: H,j τ j =α j q j +β j γ j ; In the formula, α H,j , α j , β j denote the feed water share, extraction steam share, and drainage share of the j-th stage regenerator, τ j ,q j , γ j They represent feedwater enthalpy rise, extraction steam enthalpy drop, and drainage enthalpy drop, respectively, j = 1, 2, ..., 7; The steam-water balance equation of the thermal power unit is: Where D i represents the steam extraction flow rate of the i-th stage of the steam turbine, i=1,2,…,7; D fw Indicates the feed water flow rate of the high-pressure heater, D wc Indicates condensate flow rate; The molten salt heat exchanger model is: ms D ms (T ms,h -T ms,l )=D w (h w,h -h w,l );where c ms represents the constant pressure specific heat capacity of molten salt, D ms represents the mass flow rate of molten salt, T ms,h Indicates the high temperature before molten salt heat exchange, T ms,l Indicates the low temperature after molten salt heat exchange, D w represents the mass flow rate of water or steam exchanging heat with molten salt, h w,h 、h w,l They represent the enthalpy values ​​of water or steam before and after heat exchange respectively.

3. The method for optimizing the operation of a thermal power unit using molten salt heat storage according to claim 1 is characterized in that: The technical parameter model of the unit is: ΔP c =P0-P c ; ΔP s =P s -P e ; Where ΔP c , ΔP s Respectively represent the peak load capacity of the heat storage stage and the heat release stage, P c , P s Respectively represent the actual output power of thermal power units in the heat storage stage and heat release stage, P0, P e Respectively represent the rated output power of the original thermal power unit under 50% THA condition and 100% THA condition, m coal Indicates the coal consumption in the heat storage stage or heat release stage, D st Indicates the main steam flow rate, h st 、h fw They represent the main steam enthalpy and feed water enthalpy respectively, D1 and D2 represent the first stage extraction flow rate and the second stage extraction flow rate respectively, σ represents the unit reheat steam absorption heat, LHV represents the low calorific value of coal, η b , η gd They represent boiler efficiency and pipeline efficiency respectively.

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

5. The method for optimizing the operation of a thermal power unit using molten salt heat storage according to claim 1, characterized in that: The overall thermal efficiency calculation model is: Where η Th,q Represents the overall thermal efficiency, P c , P s Respectively represent the actual output power of thermal power units in the heat storage stage and heat release stage, m coal,c 、m coal,s They represent the coal consumption in the heat storage stage and the heat release stage respectively, and LHV represents the low calorific value of coal.

6. The method for optimizing the operation of a thermal power unit using molten salt heat storage 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 ); Where, L r represents net profit, S c , S s They represent the total benefits of the molten salt heat storage stage and the heat release stage, respectively, and C om , C dc , C ic , C coc They represent annual operation and maintenance costs, direct costs, indirect costs, accidents and owner expenses respectively, and n represents the operating years of the unit; Among them, S c =t c (1000ξΔP c -1000S e ΔP c +3600S coal Δm coal,c );ξ represents the peak load subsidy, ΔP c represents the peak load capacity in the heat storage stage, S e represents the electricity price, S coal represents the coal price, Δm coal,c represents the change of unit coal consumption during the heat storage phase relative to the original load condition, t c Indicates the heat storage time; S s =t s (1000S e ΔP s -3600S coal Δm coal,s );ΔP s Indicates the peak load capacity during the heat release phase, Δm coal,s It represents the change of coal consumption of the unit under the heat release stage relative to the original load condition, t s Indicates the heat release time; 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 ; C tank represents the equipment cost of the molten salt tank, C msp represents the cost of molten salt pump equipment, C ex represents the equipment cost of molten salt heat exchanger, D ms represents the mass flow rate of molten salt, C eq represents the 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 method for optimizing the operation of a thermal power unit using molten salt heat storage according to claim 6, characterized in that: C tank =9295.8V 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 volume flow rate, H represents pump head height, A represents heat exchange area, F represents L 、F M 、F P They represent the pipe length correction factor, material correction factor, and pressure correction factor respectively; and ρ ms =2317.5-0.7878(T ms +273.15); Among them, ρ ms represents the density of molten salt, T ms Indicates the molten salt temperature; and Among them, c ms represents the constant pressure specific heat capacity of molten salt, T ms,h Indicates the high temperature before molten salt heat exchange, T ms,l represents the low temperature after molten salt heat exchange, k represents the heat transfer coefficient, Δt m represents the average heat transfer temperature difference, T w,h Indicates the high temperature of steam or water before heat exchange, T w,l Indicates the low temperature after steam or water heat exchange; Among them, P s ' indicates the shell side pressure.

8. The method for optimizing the operation of a thermal power unit using molten salt heat storage according to claim 1, characterized in that: The objective function is: y=[(L r -L r,b ) 2 +(the Th,q -or Th,q,b ) 2 ] 0.5 ; In the formula, y represents the target value, L r represents net profit, L r,b represents the optimal value of net profit, η Th,q Represents the overall thermal efficiency, η Th,q,b It indicates the optimal value of the overall thermal efficiency.

9. The method for optimizing the operation of a thermal power unit using molten salt heat storage according to claim 2, characterized in that: In the process of determining the optimal molten salt parameters using the White Whale optimization algorithm, each time the molten salt parameters are updated, the operating conditions of the new working condition are determined, including: According to the updated molten salt parameters, the mass flow rate of water or steam for heat exchange with the molten salt is obtained by using the molten salt heat exchanger model; the molten salt parameters include the molten salt mass flow rate and the molten salt high temperature; the water mass flow rate for heat exchange with the molten salt is the condensate water extraction amount during heat release, and the steam mass flow rate for heat exchange with the molten salt is the main steam extraction flow rate during heat storage; According to the mass flow of water or steam exchanging heat with the molten salt, using the turbine intermediate stage model, the steam pressure before each stage of the turbine is obtained; According to the steam pressure before each stage of the steam turbine, the enthalpy values ​​of each stage of the steam turbine are obtained by using the IAPWS_IF97 model and the last stage model of the steam turbine; Based on the enthalpy values ​​of each stage of the steam turbine and using the heat recovery system model, the steam extraction flow rate of each stage of the steam turbine is obtained as the operating condition of the new operating condition.

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

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