Steam temperature control method for tower type solar photo-thermal power station

Abstract

The invention discloses a steam temperature control method for a tower type solar photo-thermal power station, which fuses the control of a hot molten salt delivery pump and the control of inlet hot molten salt regulating valves of a superheater and a reheater according to the control characteristics of a regulating loop so as to effectively relieve the influence of temperature lag. Compared with the prior art, the method provided by the invention is based on an independent and decoupled operation mode of a superheated steam and reheated steam temperature adjusting loop so as to efficiently respond to the requirement of power change of the steam turbine generator unit. Meanwhile, the operation state and the change trend of the superheated steam temperature adjusting loop and the reheated steam temperature adjusting loop can adjust the operation of the hot salt pump flow adjusting loop. In order to organically coordinate the mutual relation, a control method based on the valve position of a regulating valve and the deviation characteristic of a control loop is set, and the valve position relation characteristic of the regulating valve in the superheated steam and reheated steam temperature regulating loop and the deviation state and trend information of the regulating loop are introduced into a combined valve position integrator and a combined monitor; operation of the hot salt pump flow adjusting loop is adjusted in real time through monitoring and judgment of the two.

Description

Technical Field

[0001] The present invention relates to a molten salt transportation system, and particularly to a method for controlling the steam temperature of a molten salt transportation system for a tower-type solar thermal power station. Background Art

[0002] The utilization of solar energy resources is an effective way to achieve the goal of energy conservation and emission reduction. A tower-type solar thermal power station equipped with a sufficient-capacity energy storage device decouples the steam generation system and its power generation unit from the solar energy collection system, and the system has relatively high reliability. In addition, as a heating medium for water and steam, molten salt has stable properties and convenient transmission control, which improves the control performance of the power generation island of the solar thermal power station.

[0003] In the traditional molten salt transportation and distribution system, since the molten salt main pipe branches to supply the superheater and the reheater, in existing engineering practices, either the superheat and reheater steam temperatures are not controlled or a time-sharing control method is adopted, that is, only one temperature adjustment loop operates at the same time, and the other temperature adjustment loop needs to wait until the valve position of the regulating valve in the operating adjustment loop reaches the maximum or the time accumulation reaches the set value before taking action. This control method is obviously a rough adjustment means, which will cause large deviations in the parameter adjustment in a large time period in the corresponding control loop, and the deviation control is not timely.

[0004] At present, the control scheme of the molten salt transportation and distribution system usually uses a hot salt pump to control the pressure of the molten salt main pipe and sets a flow regulating valve on the molten salt main pipe to adjust the flow of the molten salt flow main pipe. There are basically two configuration methods for the molten salt branch pipes leading to the superheater and the reheater: 1. Set a regulating valve at the inlet branch pipes of the superheater and the reheater; 2. Set a regulating valve at the outlet branch pipes of the superheater and the reheater. The control scheme adopted by the branch molten salt regulating valve either does not control the superheat and reheater steam temperatures or adopts a time-sharing control method, and it has the following disadvantages: 1. Setting a flow regulating valve on the molten salt main pipe causes a large throttling loss in the molten salt transportation pipeline system, resulting in waste of resources. 2. The molten salt medium has a high temperature and strong corrosion, which causes great wear on the valves, and it is difficult to guarantee the regulating performance of the valves on the molten salt main pipe. 3. The superheat steam and reheater steam temperature adjustment loops adopt time-sharing control, and it cannot ensure that the steam generation system generates steam that meets the power regulation requirements of the steam turbine generator set in real time. 4. The steam regulation and the molten salt flow regulation are isolated from each other, and it is difficult to respond in a timely manner to the change in the molten salt flow regulation brought about by the steam flow regulation, so that the hysteresis problem of the two sides of the loop stubbornly exists, which is not conducive to the realization of the rapid response function of the system. Summary of the Invention

[0005] The purpose of the present application is to provide a method for controlling the steam temperature of a tower-type solar thermal power station, so that it can respond quickly and alleviate the influence of temperature hysteresis.

[0006] The present application discloses a method for controlling the steam temperature of a tower-type solar thermal power generation station, characterized in that the control method includes: a molten salt system, a superheated steam temperature regulation loop, a reheated steam regulation loop, a molten salt pump regulation loop, a combined valve position integration module, and a combined monitor, wherein:

[0007] The superheated steam temperature regulation loop consists of a cascade PID control loop. The outer loop is equipped with a superheated steam temperature PID controller, and the inner loop is equipped with a superheated molten salt flow PID controller, a superheater molten salt flow regulating valve, a differentiator, and a superheater molten salt flow detection device;

[0008] The reheated steam temperature regulation loop consists of a cascade PID control loop. The outer loop is equipped with a reheated steam temperature PID controller, and the inner loop is equipped with a reheated molten salt flow PID controller, a reheater molten salt flow regulating valve, a differentiator, and a reheater molten salt flow detection device;

[0009] The molten salt pump regulation loop includes a molten salt flow regulation PID control loop and a molten salt main pipe minimum set pressure regulation PID control loop. The PID outputs of the above two regulation loops are connected to the molten salt pump through a high selector module;

[0010] The combined valve position integration module is arranged between the steam temperature regulation loop and the molten salt flow regulation PID control loop. The signals received at the input end of the combined valve position integration module include: the difference between the set value and the actual detected value of the superheated steam temperature in the superheated steam temperature regulation loop calculated by the differentiator, the difference between the set value and the actual detected value of the reheated steam temperature in the reheated steam temperature regulation loop calculated by the differentiator, the valve position of the reheater molten salt flow regulating valve, and the valve position of the superheater molten salt flow regulating valve. The combined valve position integration module is configured to perform the following steps according to the signals at the input end:

[0011] 1) Detect whether the difference is greater than a set threshold. If it is greater, go to step 2); if it is less, execute step 3);

[0012] 2) Start a timer and repeat step 1;

[0013] 3) Stop the timer and obtain the cumulative time, which is the time elapsed from starting the timer to stopping the timer;

[0014] 4) Read the valve position of the regulating valve corresponding to the steam temperature regulation loop and substitute it into the corresponding valve position value-taking function respectively;

[0015] 5) Input the output of the valve position value-taking function into the combined valve position integration function to obtain the output of the combined valve position integration and input the output into a multiplier;

[0016] The input end of the multiplier is also connected to the output of the PID controller of the molten salt pump flow regulation loop and is superimposed with the output of the PID controller of the molten salt pump regulation loop via a condition module as the final output of the molten salt pump regulation loop, and is input into the high selector module together with the output of the minimum set pressure regulation PID control loop of the molten salt main pipe, and finally the final command input to the molten salt pump is obtained;

[0017] The condition module is connected to the combined monitor and is configured to determine whether to enable the on command or the off command according to the output of the combined monitor, so as to determine whether to introduce the output of the combined valve position integration module into the molten salt pump regulation loop;

[0018] The combined monitor is configured to monitor in real time the control states and trends of the superheated steam regulation control loop and the reheated steam regulation loop operating independently, and output according to the states and trends.

[0019] In a preferred example, the valve position value function is set as follows:

[0020]

[0021] Wherein, x is the detection value of the regulating valve position transmitter; the values of A1 and A2 are comprehensively determined according to the type and performance indexes of the regulating valves configured in the system, so as to satisfy that the interval [A1, A2] is within the optimal regulation characteristic interval of the valve.

[0022] In a preferred example, the inputs of the combined valve position integration function include the valve position of the superheater steam temperature regulating valve and the valve position of the reheater steam temperature regulating valve, and the values of the valve position of the superheater steam temperature regulating valve and the valve position of the reheater steam temperature regulating valve are taken from the following group: Z1, Z2, Z3, null value, and *; the valve positions of the two regulating valves are combined to obtain the output of the combined valve position integration function;

[0023] The output of the combined valve position integration function is divided into the following four categories:

[0024]

[0025] Where K is the adjusted center value determined through debugging, which is 0.1 - 0.3; α is the section adjustment value, which is 0 - 13; τ is the delay coefficient determined through debugging, and it is configured to determine the specific output b1, b2, or b3 according to the input values of the superheater and the reheater. Among them, the combined valve position integration module is configured to output b1 when the combination is Z1, Z2; Z1, Z2, and Z2, Z1; output b2 when the combination is Z3, Z3; output b3 when the combination is Z1, Z3 and Z3, Z1, and output 0 for the rest of the combinations. The first number of the combination is the value of the valve position of the superheater steam temperature regulating valve, and the second number is the value of the valve position of the reheater steam temperature regulating valve.

[0026] In a preferred example, a cascade control method is adopted between the superheated steam temperature regulation loop and the reheater steam temperature regulation loop and they are decoupled from each other.

[0027] In a preferred example, the combined monitor monitors the control states and trends of the superheated steam regulation control loop and the reheater steam regulation loop through the following steps:

[0028] 1) Read the error values of the superheated steam regulation loop and the reheater steam regulation loop

[0029] 2) And input them into two control loop state monitors respectively to perform corresponding operations;

[0030] 3) Perform an AND logic calculation on the outputs calculated by the two control loop state monitors and output a conclusion according to the input-output logic table. The conclusion is used to evaluate the states and trends of the superheated steam regulation control loop and the reheater steam regulation control loop. Among them, the control loop state monitor is configured to perform the following actions: obtain the control loop control deviation e s , and calculate the control loop control deviation change rate de s / dt. When the signs of e s and de s / dt are the same, the output is 0; when the signs of e s and de s / dt are different, the output is 1.

[0031] The advantages of the present invention include;

[0032] 1) In the present invention, independent regulating valves are provided in the molten salt inlet branches of both the superheater and the reheater. The superheated steam and reheater steam temperatures are independently regulated by the molten salt regulating valves of the superheater and the reheater respectively, so that they are decoupled from each other and the temperature regulation loop adopts a cascade control method composed of an inner-loop flow controller and an outer-loop temperature controller, thus making the reaction faster.

[0033] 2) The present invention does not provide a master pipe flow regulating valve in molten salt transportation to reduce throttling losses and increase system economy. The hot salt pump consists of 2 - 3 variable frequency pumps. The regulating loop of the hot molten salt pump adopts a parallel mode of a set flow regulating PID control loop and a minimum set pressure regulating PID control loop for the hot molten salt main pipe, so that in any operating condition of the system, the conveying capacity of the hot molten salt pump can meet the basic requirements, avoiding waste or insufficiency of the conveying capacity, which may affect the steam quality of the steam generation system.

[0034] 3) The present application sets a combined valve position integration function and a combined monitor function between the steam temperature regulating loop and the molten salt flow regulating loop, so as to adjust the steam temperature in real time and reduce the influence of the temperature control lag characteristic.

[0035] A large number of technical features are recorded in the description of the present application, distributed in various technical solutions. If all possible combinations of technical features (i.e., technical solutions) of the present application are to be listed, the description will be too long. To avoid this problem, each technical feature disclosed in the above - mentioned invention content of the present application, each technical feature disclosed in the following embodiments and examples, and each technical feature disclosed in the drawings can be freely combined with each other to form various new technical solutions (these technical solutions should all be regarded as having been recorded in this specification), unless the combination of such technical features is technically infeasible. For example, in one example, features A + B + C are disclosed, and in another example, features A + B + D + E are disclosed, and features C and D are equivalent technical means with the same function, and only one of them can be used technically and it is impossible to use both at the same time. Feature E can be combined with feature C technically. Then, the solution of A + B + C + D should not be regarded as having been recorded due to technical infeasibility, while the solution of A + B + C + E should be regarded as having been recorded. Description of the Drawings

[0036] Figure 1 It is a schematic diagram of the principle system for molten salt transportation and distribution of the tower - type solar thermal power generation station according to the present invention;

[0037] Figure 2 It is a schematic diagram of the combined regulation and control scheme for molten salt flow and superheated and reheated steam temperature according to an embodiment of the present invention;

[0038] Figure 3 It is a schematic diagram of the control strategy of the combined valve position integration function module according to an embodiment of the present invention;

[0039] Figure 4 It is a functional flowchart of the combined monitor according to an embodiment of the present invention.

[0040] Description of the Reference Numerals:

[0041] HSP - Heat salt pump; First temperature detection element - T A61 ; First flow monitoring element - F A61 ; First flow regulating valve - CV HSS ; Second flow detection element - F A62 ; Second temperature detection element - T A62 ; First pressure detection element - P S1 ; Third flow monitoring element - F S1 ; Third temperature detection element - T S1 ; First electric isolation valve - MV SHS ; Second electric isolation valve - MV HSR ; Second flow regulating valve - CV HSR ; Fourth flow detection element - F A64 ; Fourth temperature detection element - T A64 ; Second pressure detection element - P R1 ; Fifth flow detection element - F R1 ; Fifth temperature detection element - T R1 ; Third electric isolation valve - MV RHS 。 Detailed implementation manner

[0042] Through in - depth research and extensive screening, the inventor has developed a method for controlling the steam temperature of a tower - type solar thermal power generation station. This method integrates the molten salt transfer pump with the inlet molten salt regulating valves of the superheater and reheater according to the control characteristics of the regulating loop to effectively alleviate the influence of temperature lag. Compared with the prior art, the method proposed in this application is based on the independent and decoupled operation mode of the superheated steam and reheated steam temperature regulating loops to efficiently respond to the power change requirements of the steam turbine - generator set. At the same time, the operating state and change trend of the superheated steam and reheated steam temperature regulating loops will affect the operation of the heat salt pump flow regulating loop. In order to organically coordinate their mutual relationships, a control method based on the valve position of the regulating valve and the deviation characteristics of the control loop is set. The valve position relationship characteristics and the deviation state and trend information of the regulating loop in the superheated steam and reheated steam temperature regulating loops are introduced into the joint valve position integrator and the joint monitor, and through the two for monitoring and judgment, the operation of the heat salt pump flow regulating loop is adjusted in real - time.

[0043] Term

[0044] Molten salt system

[0045] The molten salt system described in the present invention is a molten salt system applicable to a tower - type solar thermal power station, in order to Figure 1For example, it includes a hot salt tank, a hot salt pump, a superheater, a reheater, a steam drum, an evaporator, and a steam turbine generator set. The hot molten salt in the hot molten salt tank is transported by the hot salt pump HSP to the hot molten salt main pipe, and the hot molten salt is divided into three paths and respectively input into the superheater, the reheater, and returned to the hot salt tank. The hot molten salt main pipe is provided with a first temperature and a first flow rate monitoring element T A61 and F A61 . A first flow regulating valve CV HSS , a second flow detection element F A62 , and a second temperature detection element T A62 are provided in the hot molten salt pipeline leading to the superheater. The superheated steam pipeline at the outlet of the superheater is respectively provided with a first pressure monitoring element P S1 , a third flow detection element F S1 , and a third temperature detection element T S1 , and a first electric isolation valve MV SHS is also provided. A second electric isolation valve MV HSR and a second flow regulating valve CV HSR , a fourth flow detection element F A61 , and a fourth temperature detection element T A64 are provided in the hot molten salt pipeline leading to the reheater. The reheated steam pipeline at the outlet of the reheater is respectively provided with a second pressure detection element P R1 , a fifth flow detection element F R1 , and a fifth temperature detection element T R1 , and a third electric isolation valve MV RHS is also provided. It should be noted that the above system only shows the schematic system diagram, without emphasizing the specific quantity. The quantity of its equipment configuration can be configured according to the system requirements. For example, 2 to 3 hot salt pumps can be set according to the system transportation requirements and reliability requirements; the detection elements are designed with redundancy according to the equipment reliability, such as triple redundancy for the superheated and reheated steam temperatures. Similar settings will increase the stability and reliability of the system, which are not the focus of this article.

[0046] Steam Temperature Control Method

[0047] The steam temperature control method of this application aims to solve the characteristics of large heat exchange time delay between molten salt and steam and strong temperature induction hysteresis. Both the superheated steam temperature regulation loop and the reheated steam temperature regulation loop adopt a reliable cascade control method. Among them, the outer loop is the steam temperature control loop, adopting the PID control method. The output of the temperature control loop PID is converted into the set value of the inner loop flow control loop, and the real-time difference between the real-time detected fast response parameter, that is, the branch molten salt flow rate, is used as the input of the molten salt flow rate PID controller. Among them, the superheated steam temperature regulation loop and the reheated steam temperature regulation loop are completely decoupled, and each loop only needs to respond to the steam temperature control requirements.

[0048] The molten salt pump adopts a variable-frequency regulated pump to adjust the rotational speed of the molten salt pump according to the system's transportation requirements, reducing power waste. The adjustment loop of the molten salt pump adopts a method of parallel connection of a set flow rate adjustment PID control loop and a minimum set pressure adjustment PID control loop for the molten salt main pipe. The outputs of the two paths are sent to a high-selection module, enabling the transportation capacity of the molten salt pump to meet the basic requirements under any operating conditions of the system, avoiding waste of transportation capacity or insufficient transportation capacity, which may affect the steam quality of the steam generation system. Among them, the set value of the set flow rate adjustment PID control loop is based on the molten salt flow rate demand value calculated with the power value of the steam turbine generator set as the independent variable, and the set value of the minimum set pressure adjustment PID control loop for the molten salt main pipe is the minimum pressure set considering the safe operation of the system.

[0049] In order to improve the control quality, further reduce the temperature control lag characteristic, enable the molten salt flow rate to respond earlier to the control characteristic of the steam control loop, reduce the heat source medium, that is, the steam control deviation caused by the supply, transportation, and heat exchange process of the molten salt, so as to finally quickly respond to the demand of the steam turbine generator set to quickly respond to the grid-end load, and further improve the performance of the solar thermal power station in quickly responding to power demand, the present invention proposes a control method based on the valve position of the regulating valve and the deviation characteristic of the control loop. A combined valve position integration function and a combined monitor are set between the steam temperature adjustment loop and the molten salt flow rate adjustment loop.

[0050] The set value of the reheat molten salt flow rate

[0051] The set value of the reheat molten salt flow rate is calculated based on the reheat steam temperature set value, the reheat steam temperature detection value, the reheat steam flow rate, and the reheat molten salt temperature according to the heat transfer conservation relationship.

[0052] The set value of the superheated molten salt flow rate

[0053] The set value of the reheat molten salt flow rate is calculated based on the reheat steam temperature set value, the reheat steam temperature detection value, the reheat steam flow rate, and the reheat molten salt temperature according to the heat transfer conservation relationship.

[0054] To make the objectives, technical solutions, and advantages of this application clearer, the following will further describe the embodiments of this application in detail with reference to the accompanying drawings.

[0055] Embodiment

[0056] One embodiment of this application is as Figures 1 - 4 shown, which discloses a method for controlling the steam temperature of a tower-type solar thermal power generation station. The control method is characterized in that the control method includes: a molten salt system, a superheated steam temperature adjustment loop, a reheat steam adjustment loop, a molten salt pump adjustment loop, a combined valve position integration module, and a combined monitor, where:

[0057] The superheated steam temperature regulation loop consists of a cascade PID control loop. The outer loop is equipped with a superheated steam temperature PID controller, and the inner loop is equipped with a superheated molten salt flow PID controller, a superheater molten salt flow regulating valve, a differentiator, and a superheater molten salt flow detection device;

[0058] The reheated steam temperature regulation loop consists of a cascade PID control loop. The outer loop is equipped with a reheated steam temperature PID controller, and the inner loop is equipped with a reheated molten salt flow PID controller, a reheater molten salt flow regulating valve, a differentiator, and a reheater molten salt flow detection device;

[0059] The molten salt pump regulation loop includes a molten salt flow regulation PID control loop and a molten salt main pipe minimum set pressure regulation PID control loop. The PID outputs of the above two regulation loops are connected to the molten salt pump through a high selector module;

[0060] The combined valve position integration module is configured between the steam temperature regulation loop and the molten salt flow regulation PID control loop. The signals received by the input end of the combined valve position integration module include: the difference between the set value and the actual detected value of the superheated steam temperature in the superheated steam temperature regulation loop calculated by the differentiator, the difference between the set value and the actual detected value of the reheated steam temperature in the reheated steam temperature regulation loop calculated by the differentiator, the valve position of the reheater molten salt flow regulating valve, and the valve position of the superheater molten salt flow regulating valve. The combined valve position integration module is configured to execute the steps as Figure 3 shown below:

[0061] 1) Detect whether the difference is greater than the set threshold. If it is greater, go to step 2); if it is less, execute step 3);

[0062] 2) Start the timer and repeat step 1;

[0063] 3) Stop the timer and obtain the accumulated time, which is the time elapsed from starting the timer to stopping the timer;

[0064] 4) Read the valve position of the regulating valve corresponding to the steam temperature regulation loop and substitute it into the corresponding valve position value-taking function respectively;

[0065] 5) Input the output of the valve position value-taking function into the combined valve position integration function to obtain the output of the combined valve position integration and input the output into a multiplier;

[0066] The input end of the multiplier is also connected to the output of the PID controller of the molten salt pump flow regulation loop and is superimposed with the output of the PID controller of the molten salt pump regulation loop via a condition module as the final output of the molten salt pump regulation loop, and is input into the high-select module together with the output of the minimum set pressure regulation PID control loop of the molten salt main pipe, and finally the final instruction input to the molten salt pump is obtained;

[0067] The condition module is connected to the combined monitor and is configured to determine whether to enable the on instruction or the off instruction according to the output of the combined monitor, so as to determine whether to introduce the output of the combined valve position integration module into the molten salt pump regulation loop;

[0068] The combined monitor is configured to monitor in real time the control states and trends of the superheated steam regulation control loop and the reheated steam regulation loop operating independently, and output according to the states and trends.

[0069] In this embodiment, the valve position value function is set as follows:

[0070]

[0071] Wherein, x is the detection value of the valve position transmitter of the regulating valve; the values of A1 and A2 are determined comprehensively according to the type and performance indexes of the regulating valve configured by the system, so as to satisfy that the interval [A1, A2] is in the optimal regulation characteristic interval of the valve.

[0072] In a preferred example, the inputs of the combined valve position integration function include the valve positions of the superheater steam temperature regulating valve and the reheater steam temperature regulating valve, and the valve positions of the superheater steam temperature regulating valve and the reheater steam temperature regulating valve are taken from the following group: Z1, Z2, Z3, null value, and *; the valve positions of the two regulating valves are combined to obtain the output of the combined valve position integration function;

[0073] The output of the combined valve position integration function is divided into the following four categories:

[0074]

[0075] Where K is the adjusted center value determined through debugging, which is 0.1 - 0.3; α is the section adjustment value, which is 0 - 13; τ is the delay coefficient determined through debugging, and it is configured to determine the specific output b1, b2, or b3 according to the input values of the superheater and reheater; among them, the combined valve position integration module is configured to output b1 when the combination is Z1, Z2; Z1, Z2, and Z2, Z1; output b2 when the combination is Z3, Z3; output b3 when the combination is Z1, Z3 and Z3, Z1, and output 0 for the rest of the combinations; the first number of the combination is the value of the valve position of the superheater steam temperature regulating valve, and the second number is the value of the valve position of the reheater steam temperature regulating valve, and the specific settings are shown in Table 1.

[0076]

[0077] Table 1

[0078] Optionally, in one embodiment, a cascade control method is adopted between the superheated steam temperature regulation loop and the reheated steam temperature regulation loop and they are decoupled from each other.

[0079] Optionally, in one embodiment, the combined monitor monitors the control states and trends of the superheated steam regulation control loop and the reheated steam regulation loop through the steps as Figure 4 shown below:

[0080] 1) Read the error values of the superheated steam regulation loop and the reheated steam regulation loop

[0081] 2) And input them into two control loop state monitors respectively to perform corresponding operations;

[0082] 3) Perform an AND logic calculation on the outputs calculated by the two control loop state monitors and output a conclusion according to the input-output logic table, and the conclusion is used to evaluate the states and trends of the superheated steam regulation control loop and the reheated steam regulation control loop; among them, the control loop state monitor is configured to perform the following actions: obtain the control loop control deviation e s , and calculate the control loop control deviation change rate de s / dt. When the signs of e s and de s / dt are the same, output 0; when the signs of e s and de s / dt are different, output 1.

[0083] The above embodiments introduce the combined valve position integration function and the combined monitor function, which organically link two independently operating steam regulation circuits and the molten salt pump regulation circuit, that is, mainly to achieve the following functions: stimulate the actuators of the independently operating superheated steam and reheated steam regulation circuits, that is, the branch control valves operate in their respective optimal performance ranges, so as to achieve excellent control performance and avoid excessive throttling, resulting in waste of the conveying capacity of the hot salt pump. Introduce the states and their change performances of the independently operating superheated steam and reheated steam regulation circuits, and feed them forward to the molten salt pump flow regulation circuit to respond in advance to the demands of the steam temperature regulation circuit that changes due to the change in the power of the steam turbine generator set, and reduce the corresponding interference.

[0084] It should be noted that in the application documents of this patent, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one" does not exclude the existence of additional identical elements in the process, method, article or device comprising the element. In the application documents of this patent, if it is mentioned that an act is performed according to a certain element, it means at least performing the act according to the element, including two cases: performing the act only according to the element and performing the act according to the element and other elements. Expressions such as multiple, multiple times, multiple types, etc. include 2, 2 times, 2 types, and more than 2, more than 2 times, more than 2 types.

[0085] This specification includes combinations of various embodiments described herein. A separate reference to "an embodiment" or a specific embodiment, etc. does not necessarily refer to the same embodiment; however, unless indicated as mutually exclusive or clearly understood by those skilled in the art as mutually exclusive, these embodiments are not mutually exclusive. It should be noted that, unless the context clearly indicates or requires otherwise, the word "or" is used in a non-exclusive sense in this specification.

[0086] All documents mentioned in this application are considered to be integrally included in the disclosure of this application so that they can be used as a basis for modification if necessary. In addition, it should be understood that after reading the above disclosure of this application, those skilled in the art can make various changes or modifications to this application, and these equivalent forms also fall within the scope claimed by this application.

Claims

1. A method for controlling steam temperature in a tower solar thermal power station, characterized in that: The control method includes: a hot molten salt system, a superheated steam temperature regulating loop, a reheated steam regulating loop, a hot molten salt pump regulating loop, a joint valve position integration module and a joint monitor, wherein: The superheated steam temperature regulating loop is composed of a cascade PID control loop, the outer loop is equipped with a superheated steam temperature PID controller, the inner loop is equipped with a superheated molten salt flow PID controller, a superheater hot molten salt flow regulating valve, a differentiator and a superheater molten salt flow detection device; The reheat steam temperature regulating loop is composed of a cascade PID control loop, the outer loop is equipped with a reheat steam temperature PID controller, and the inner loop is equipped with a reheat molten salt flow PID controller, a reheater hot molten salt flow regulating valve, a differentiator and a reheater molten salt flow detection device; The hot molten salt pump regulating loop includes a hot molten salt flow regulating PID control loop and a hot molten salt mother pipe minimum set pressure regulating PID control loop, and the PID output of the above-mentioned flow regulating loop is connected to the hot molten salt pump through the high selection module; The joint valve position integration module is configured between the steam temperature control loop and the hot molten salt flow control PID control loop. The signal received by the input end of the joint valve position integration module includes: the difference between the superheated steam temperature setting value and the actual detection value in the superheated steam temperature control loop calculated by the differentiator, the difference between the reheated steam temperature setting value and the actual detection value in the reheated steam temperature control loop calculated by the differentiator, the valve position of the reheater hot molten salt flow control valve and the valve position of the superheater hot molten salt flow control valve. The joint valve position integration module is configured to perform the following steps according to the signal at the input end: 1) Detect whether the difference is greater than a set threshold, if so, proceed to step 2), if less than, proceed to step 3); 2) Start the timer and repeat step 1; 3) Turn off the timer and obtain the accumulated time, where the accumulated time is the time elapsed from starting the timer to turning off the timer; 4) Read the valve position of the control valve of the corresponding steam temperature control loop and bring it into the corresponding valve position value function respectively; 5) Inputting the output of the valve position value function into the joint valve position integration function to obtain the output of the joint valve position integration and inputting the output into a multiplier; The input end of the multiplier is also connected to the output of the PID controller of the hot molten salt pump flow control loop and is superimposed with the output of the PID controller of the hot molten salt pump control loop via a conditional module as the final output of the hot molten salt pump control loop and the output of the hot molten salt mother pipe minimum set pressure control PID control loop, and is input into the high selection module together, and finally the final instruction input to the hot molten salt pump is obtained; The condition module is connected to the joint monitor and is configured to determine whether to enable an on instruction or a off instruction according to an output of the joint monitor, thereby determining whether to introduce the output of the joint valve position integration module into the hot molten salt pump regulation loop; The joint monitor is configured to monitor in real time the control status and trend of the independently operated superheated steam regulation control loop and the reheated steam regulation control loop, and to output according to the status and trend.

2. The method for controlling steam temperature of a tower solar thermal power plant according to claim 1, characterized in that: The valve position value function is set as follows: Among them, x is the detection value of the control valve position transmitter; the values ​​of A1 and A2 are determined comprehensively according to the type and performance indicators of the control valve configured in the system to meet the interval [A1, A2] in the optimal control characteristic interval of the valve.

3. According to the steam temperature control method of a tower solar thermal power plant in claim 1, the input of the joint valve position integration function includes the valve position of the superheater steam temperature regulating valve and the valve position of the reheater steam temperature regulating valve, and the values ​​of the valve position of the superheater steam temperature regulating valve and the valve position of the reheater steam temperature regulating valve are taken from the following group: Z1, Z2, Z3, null value and *; the valve positions of the two regulating valves are combined to obtain the output of the joint valve position integration function; The output of the joint valve position integration function is divided into the following four categories: Where K is the adjustment center value 0.1-0.3 determined by debugging; α is the section adjustment value 0-13; τ is the delay coefficient determined by debugging, which is configured to determine the specific output b1, b2 or b3 according to the input values ​​of the superheater and reheater; where, The joint valve position integration module is configured to output b1 when the combination is Z1, Z2; Z1, Z2 and Z2, Z1; output b2 when the combination is Z3, Z3; output b3 when the combination is Z1, Z3 and Z3, Z1, and output 0 for the other combinations; the first number of the combination is the value of the valve position of the superheater steam temperature control valve, and the second number is the value of the valve position of the reheater steam temperature control valve.

4. The method for controlling steam temperature of a tower solar thermal power plant according to claim 1, characterized in that: The superheated steam temperature regulating loop and the reheated steam temperature regulating loop adopt a cascade control method and are decoupled from each other.

5. The method for controlling steam temperature of a tower solar thermal power plant according to claim 1, characterized in that: The combined monitor monitors the control status and trend of the superheated steam regulation control loop and the reheated steam regulation control loop through the following steps: 1) Read the error values ​​of the superheated steam control loop and the reheated steam control loop 2) Input the data into two control loop status monitors respectively and perform corresponding operations; 3) Performing AND logic calculation on the calculated outputs of the two control loop state monitors and outputting a conclusion according to the input-output logic table, wherein the conclusion is used to evaluate the state and trend of the superheated steam regulation control loop and the reheat regulation control loop; wherein the control loop state monitor is configured to perform the following actions: obtaining the control loop control deviation e s , and calculate the control loop control deviation change rate de s / dt, when e s with de s When the signs of / dt are the same, the output is 0; when e s with de s When the signs of / dt are different, the output is 1.

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