Steam temperature control method for solar power tower plant

Abstract

Disclosed in the present invention is a steam temperature control method for a solar power tower plant. The method integrates the control of a hot molten salt transfer pump with the control of inlet hot molten salt regulating valves of a superheater and a reheater on the basis of regulating loop control characteristics, so as to effectively mitigate the effect of temperature lag. Compared with the prior art, the method provided by the present application is based on an independent decoupled operating mode for superheated steam and reheated steam temperature regulating loops, so as to effectively meet the power change requirements of turbo-generator units. In addition, the operation of a hot salt pump flow regulating loop is adjusted on the basis of the operating states and variation trends of the superheated steam and reheated steam temperature regulating loops. To organically coordinate the interrelation, a control method based on a regulating valve position and control loop deviation characteristics is provided. The characteristics of a regulating valve position relationship within the superheated steam and reheated steam temperature regulating loops, along with the deviation states and trend information of the regulating loops, are introduced into a unified valve position integrator and a unified monitor, and by means of the unified valve position integrator and the unified monitor, monitoring and determination are performed, so as to adjust the operation of the hot salt pump flow regulating loop in real time.

Description

Steam temperature control method for tower type solar thermal power station TECHNICAL FIELD

[0001] The present application relates to a hot molten salt conveying system, in particular to a steam temperature control method for a hot molten salt conveying system of a tower type solar thermal power station. BACKGROUND

[0002] The utilization of solar energy is an effective way to achieve the goal of energy saving and emission reduction. The tower type solar thermal power station with sufficient capacity energy storage device makes the steam generation system and its power generation unit decoupled from the solar energy collection system, and the system has high reliability. In addition, hot molten salt as a heating medium for water and steam has stable state and convenient transmission control, so that the control performance of the power generation island of the solar thermal power station is improved.

[0003] However, the conventional hot molten salt conveying and distribution system has the following problems. The hot molten salt mother pipe is branched to supply the superheater and the reheater. In existing engineering practices, the superheated steam temperature and the reheated steam temperature are not controlled, or a staggered control method is adopted, that is, only one temperature regulation loop operates at the same time, and the other temperature regulation loop needs to wait until the valve position of the regulation valve in the operating regulation loop reaches the maximum or the time accumulation reaches the set value before acting. This control method is obviously a rough regulation method, which may cause a large deviation of the parameter regulation in the corresponding control loop in a large time section, and the control is not timely.

[0004] At present, the control scheme of the hot molten salt conveying and distribution system usually adopts a hot salt pump to control the pressure of the hot molten salt mother pipe, and a flow regulating valve is arranged on the hot molten salt mother pipe to regulate the flow of the hot molten salt. The hot molten salt branch pipes to the superheater and the reheater have two basic configuration modes: 1. regulating valves are arranged on the inlet branch pipes of the superheater and the reheater; and 2. regulating valves are arranged on the outlet branch pipes of the superheater and the reheater. The control scheme of the branch pipe molten salt regulating valve has the following disadvantages: 1. the flow regulating valve arranged on the hot molten salt mother pipe causes a large throttling loss in the hot molten salt conveying pipe system, resulting in waste of resources; 2. the hot molten salt medium has high temperature and large corrosion, which causes large wear of the valve, and the regulating performance of the valve in the hot molten salt mother pipe is difficult to guarantee; 3. the superheated steam and the reheated steam temperature regulation loop adopts staggered control, which cannot guarantee that the steam generation system can generate steam meeting the power regulation demand of the steam turbine generator unit in real time; and 4. the steam regulation and the hot molten salt flow regulation are isolated from each other, which makes it difficult to respond to the change of the hot molten salt flow regulation caused by the steam flow regulation in a timely manner, and the hysteresis problem of the two sides is stubborn, which is not conducive to the realization of the fast response function of the system. SUMMARY

[0005] The application aims to provide a tower type solar thermal power station steam temperature control method which can quickly respond and relieve the influence of temperature hysteresis.

[0006] The application discloses a tower type solar thermal power station steam temperature control method, characterized in that the control method comprises a hot molten salt system, a superheated steam temperature regulation loop, a reheated steam regulation loop, a hot molten salt pump regulation loop, a joint valve position integration module and a joint monitor, wherein:

[0007] The superheated steam temperature regulation loop is composed of a cascade PID control loop, an outer loop is configured with a superheated steam temperature PID controller, and an inner loop is configured with a superheated molten salt flow PID controller, a superheater hot molten salt flow regulation valve, a difference calculator and a superheater molten salt flow detection device;

[0008] The reheated steam temperature regulation loop is composed of a cascade PID control loop, an outer loop is configured with a reheated steam temperature PID controller, and an inner loop is configured with a reheated molten salt flow PID controller, a reheater hot molten salt flow regulation valve, a difference calculator and a reheater molten salt flow detection device;

[0009] The hot molten salt pump regulation loop comprises a hot molten salt flow regulation PID control loop and a hot molten salt main pipe minimum set pressure regulation PID control loop, and the PID output of the above quantity regulation loop is connected to the hot molten salt pump through a high selection module;

[0010] The joint valve position integration module is arranged between the steam temperature regulation loop and the hot molten salt flow regulation PID control loop, the input end of the joint valve position integration module receives signals including a difference value between a set value and an actual detection value of the superheated steam temperature in the superheated steam temperature regulation loop calculated by the difference calculator, a difference value between a set value and an actual detection value of the reheated steam temperature in the reheated steam temperature regulation loop calculated by the difference calculator, a valve position of the reheater hot molten salt flow regulation valve and a valve position of the superheater hot molten salt flow regulation valve, and the joint valve position integration module is configured to perform the following steps according to the signals of the input end:

[0011] 1) detecting whether the difference value is greater than a set threshold value, if yes, step 2) is performed, and if no, step 3) is performed;

[0012] 2) starting a timer and repeatedly performing step 1;

[0013] 3) closing the timer and obtaining an accumulated time, the accumulated time being a time elapsed from starting the timer to closing the timer;

[0014] 4) reading the valve position of the regulation valve corresponding to the steam temperature regulation loop and bringing the valve position into a corresponding valve position value function respectively;

[0015] 5) input the output of the valve position function into a joint valve position integration function to obtain the output of the joint valve position integration and input the output into a multiplier;

[0016] The input of the multiplier is also connected to the output of the PID controller of the hot molten salt pump flow regulation loop and superimposed with the output of the PID controller of the hot molten salt pump regulation loop via a conditional module as the final output of the hot molten salt pump regulation loop and the output of the hot molten salt main pipe minimum set pressure regulation PID control loop are input into a high selection module, finally obtaining the final instruction input into the hot molten salt pump;

[0017] The conditional module is connected to the joint monitor and is configured to determine whether to introduce the output of the joint valve position integration module to the hot molten salt pump regulation loop according to the output of the joint monitor, thereby determining whether to enable the on or off instruction;

[0018] The joint monitor is configured to monitor the state and trend of the independently running superheated steam regulation control loop and the reheat steam regulation loop in real time, and output according to the state and trend.

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

[0020] Wherein x is the detection value of the valve position transmitter of the regulating valve; the values of A1 and A2 are determined according to the type and performance index of the regulating valve configured by the system, so as to meet the interval [A1, A2] in the optimal regulation characteristic interval of the valve.

[0021] In a preferred example, the input of the joint valve position integration function includes the superheater steam temperature regulating valve position and the reheat steam temperature regulating valve position, the values of the superheater steam temperature regulating valve position and the reheat steam temperature regulating valve position are taken from the group: Z1, Z2, Z3, null and *; the two regulating valve positions are combined to obtain the output of the joint valve position integration function;

[0022] The output of the joint valve position integration function is divided into the following four categories:

[0023] Wherein K is the adjustment center value determined by debugging, 0.1-0.3; a is the section adjustment value, 0-13; τ is the delay coefficient determined by debugging, which is configured to determine specific output b1, b2 or b3 according to the input values of the superheater and the reheater; wherein the joint valve position integration module is configured to output b1 when combined as Z1, Z2; Z1, Z2 and Z2, Z1; output b2 when combined as Z3, Z3; output b3 when combined as 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 superheater steam temperature regulating valve position, and the second number is the value of the reheater steam temperature regulating valve position.

[0024] In a preferred example, a cascade control method is adopted between the superheated steam temperature regulating loop and the reheated steam temperature regulating loop and they are decoupled from each other.

[0025] In a preferred example, the joint monitor realizes the monitoring of the control state and trend of the superheated steam regulating control loop and the reheated steam regulating control loop by the following steps:

[0026] 1) reading the error values of the superheated steam regulating loop and the reheated steam regulating loop

[0027] 2) and inputting them into two control loop state monitors respectively, and performing corresponding operations;

[0028] 3) performing AND logic calculation on the outputs of the calculation of the two control loop state monitors, and outputting a conclusion according to the input-output logic table, which is used to evaluate the state and trend of the superheated steam regulating control loop and the reheated regulating control loop; wherein the control loop state monitor is configured to perform the following actions: obtaining the control loop control deviation e s , and calculating the control loop control deviation change rate de s / dt, when e s and de s / dt are of the same sign, the output is 0; when e s and de s / dt are of different signs, the output is 1.

[0029] The advantages of the present application mainly include:

[0030] 1) The present application sets independent regulating valves in the superheater and the reheater hot molten salt inlet branch. The superheated steam and the reheated steam temperature are independently regulated by the superheater and the reheater hot molten salt regulating valves, so that they are decoupled and the temperature regulating loop adopts a cascade control method composed of an inner loop flow controller and an outer loop temperature controller, so that the reaction is more rapid.

[0031] 2) The application does not set up a mother pipe flow regulating valve to reduce throttling loss and increase system economy in molten salt conveying. The hot salt pump adopts 2-3 frequency conversion pumps, and the hot molten salt pump regulating loop adopts a parallel mode of set flow regulating PID control loop and hot molten salt mother pipe minimum set pressure regulating PID control loop, so that the conveying capacity of the hot molten salt pump meets the basic demand in any operating condition of the system, avoiding waste of conveying capacity or insufficient conveying capacity, and affecting the steam quality of the steam generating system.

[0032] 3) The application sets up a joint valve position integration function and a joint monitor function between the steam temperature regulating loop and the hot molten salt flow regulating loop, so as to adjust the steam temperature in real time to reduce the influence of temperature control hysteresis characteristics.

[0033] A large number of technical features are described in the specification of the application, which are distributed in various technical solutions. If all possible combinations of technical features (i.e. technical solutions) of the application are listed, the specification will be too long. In order to avoid this problem, each technical feature disclosed in the above invention content, each technical feature disclosed in the following embodiments and examples, and each technical feature disclosed in the drawings can be freely combined to form various new technical solutions (these technical solutions are considered to have been described in the specification), unless such combination of technical features is technically infeasible. For example, features A+B+C are disclosed in one example, features A+B+D+E are disclosed in another example, features C and D are equivalent technical means that play the same role, and can only be used at the same time, and feature E can be combined with feature C technically. Therefore, the scheme of A+B+C+D should not be considered to have been described because it is technically infeasible, and the scheme of A+B+C+E should be considered to have been described. BRIEF DESCRIPTION OF DRAWINGS

[0034] Fig. 1 is a schematic system diagram of hot molten salt conveying and distribution of a tower type solar thermal power station according to the application;

[0035] Fig. 2 is a schematic diagram of a combined regulating and control scheme of hot molten salt flow and superheated and reheated steam temperature according to an embodiment of the application;

[0036] Fig. 3 is a schematic diagram of a control strategy of a joint valve position integration function module according to an embodiment of the application;

[0037] Fig. 4 is a functional flowchart of a joint monitor according to an embodiment of the application.

[0038] Explanation of reference signs: HSP-hot salt pump; first temperature detection element-T A61 ; first flow detection element-F A61; first flow regulating valve-CV H6S ; second flow detecting element-F A62 ; second temperature detecting element-T A62 ; first pressure detecting element-P S1 ; third flow detecting element-F S1 ; third temperature detecting element-T S1 ; first motorized isolation valve-MV SHS ; second motorized isolation valve-MV HSR ; second flow regulating valve-CV HSR ; fourth flow detecting element-F A64 ; fourth temperature detecting element-T A64 ; second pressure detecting element-P R1 ; fifth flow detecting element-F R1 ; fifth temperature detecting element-T R1 ; third motorized isolation valve-MV RHS .

[0039] . DETAILED DESCRIPTION

[0040] The inventor has developed a steam temperature control method for a tower type solar thermal power station through in-depth research and a large number of screening. The method fuses the hot molten salt delivery pump and the inlet hot molten salt regulating valve of the superheater and the reheater according to the regulating loop control characteristics, so as to effectively alleviate the influence of temperature hysteresis. Compared with the prior art, the method proposed in the application is based on the independent and decoupled operation mode of the superheated steam and reheated steam temperature regulating loop, so as to efficiently respond to the demand for power change of the steam turbine generator set. At the same time, the operation state and change trend of the superheated steam and reheated steam temperature regulating loop will affect the operation of the hot salt pump flow regulating loop. In order to organically coordinate the mutual relationship, a control method based on the regulating valve position and the control loop deviation characteristics is set, the regulating valve position relationship characteristics and the regulating loop deviation state and trend information in the superheated steam and reheated steam temperature regulating loop are introduced into the joint valve position integrator and the joint monitor, and the operation of the hot salt pump flow regulating loop is adjusted in real time through monitoring and judgment of the two.

[0041] TERMS

[0042] Hot molten salt system

[0043] The hot molten salt system described in the application is a hot molten salt system suitable for a tower type solar thermal power station. Taking FIG. 1 as an example, it comprises 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 salt tank is delivered to the hot molten salt main pipe by the hot salt pump HSP, and the hot molten salt is input to the superheater, the reheater and back to the hot salt tank in three ways. The hot molten salt main pipe is provided with first temperature and first flow monitoring elements TA61 and F A61 . The first flow regulating valve CV HSS , the second flow detecting element F A62 and the second temperature detecting element T A62 . The first pressure detecting element P S1 , the third flow detecting element F S1 and the third temperature detecting element T S1 are arranged in the superheater outlet superheated steam pipeline respectively, and the first electric isolation valve MV SHS is arranged simultaneously. The second electric isolation valve MV HSR and the second flow regulating valve CV HSR are arranged in the reheater hot molten salt pipeline, and the fourth flow detecting element F A64 and the fourth temperature detecting element T A64 are arranged. The second pressure detecting element P R1 , the fifth flow detecting element F R1 and the fifth temperature detecting element T R1 are arranged in the reheater outlet reheated steam pipeline respectively, and the third electric isolation valve MV RHS is arranged simultaneously. It should be noted that the above system only shows the principle system diagram, and the specific number is not emphasized. The number of device configuration can be configured according to the system demand. For example, the hot salt pump can be arranged 2-3 according to the system conveying demand and the reliability demand. The detecting element is designed with redundancy according to the reliability of the device, such as three redundancies of superheated steam temperature and reheated steam temperature. Similar settings will increase the stability and reliability of the system, which is not the focus of this article.

[0044] Steam temperature control method

[0045] The steam temperature control method of the present application aims to solve the characteristics of large delay and strong temperature induction lag when molten salt exchanges heat with steam. The superheated steam temperature regulation loop and the reheated steam temperature regulation loop both adopt a reliable performance cascade control method. The outer ring is a steam temperature control loop, which adopts a PID control method. The PID output of the temperature control loop is converted into the set value of the inner loop flow control loop, and the real-time difference between the real-time detected fast reaction parameter, i.e. the real-time molten salt flow, is used as the input of the molten salt flow PID controller. 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 demand.

[0046] The hot melt salt pump adopts frequency regulation to adjust the pump according to the system conveying demand, so as to reduce the waste of electric energy. The hot melt salt pump adjustment loop adopts a parallel mode of a set flow adjustment PID control loop and a hot melt salt main pipe minimum set pressure adjustment PID control loop, and two-way output is sent into a high selection module, so that the conveying capacity of the hot melt salt pump meets the basic demand in any operating condition of the system, and waste or insufficient conveying capacity is avoided, and the steam quality of the steam generation system is affected. The set flow adjustment PID control loop set value is based on the hot melt salt flow demand value calculated by taking the steam turbine generator set power value as the independent variable, and the hot melt salt main pipe minimum set pressure adjustment PID control loop set value is the minimum pressure set for the safety of the system operation.

[0047] In order to improve the control quality, further reduce the temperature control hysteresis characteristic, make the hot melt salt flow respond to the steam control loop control characteristic early, reduce the steam control deviation caused by the heat source medium, i.e. the hot melt salt supply conveying and heat exchange process, and finally quickly respond to the fast response of the steam turbine generator set to the demand of the power grid end load, so that the performance of the solar thermal power station in the aspect of fast response to power demand is further improved, the application proposes a control method based on the adjustment valve position and the control loop deviation characteristic. A joint valve position integration function and a joint monitor are arranged between the steam temperature adjustment loop and the hot melt salt flow adjustment loop.

[0048] Reheating hot melt salt flow set value

[0049] The reheating hot melt salt flow set value is calculated according to the reheating steam temperature set value, the reheating steam temperature detection value, the reheating steam flow and the reheating hot melt salt temperature according to the heat transfer conservation relationship.

[0050] Superheated hot melt salt flow set value

[0051] The superheated hot melt salt flow set value is calculated according to the superheated steam temperature set value, the superheated steam temperature detection value, the superheated steam flow and the superheated hot melt salt temperature according to the heat transfer conservation relationship.

[0052] In order to make the purpose, technical scheme and advantages of the application more clear, the embodiments of the application will be further described in detail below with reference to the drawings.

[0053] Embodiment

[0054] An embodiment of the application is shown in FIGS. 1-4, which discloses a tower type solar thermal power station steam temperature control method, characterized in that the control method comprises a hot melt salt system, a superheated steam temperature adjustment loop, a reheating steam adjustment loop, a hot melt salt pump adjustment loop, a joint valve position integration module and a joint monitor, wherein:

[0055] The superheated steam temperature regulating loop is composed of a cascade PID control loop, an outer loop is configured with a superheated steam temperature PID controller, and an inner loop is configured with a superheated molten salt flow PID controller, a superheater hot molten salt flow regulating valve, a difference calculator and a superheater molten salt flow detection device;

[0056] The reheated steam temperature regulating loop is composed of a cascade PID control loop, an outer loop is configured with a reheated steam temperature PID controller, and an inner loop is configured with a reheated molten salt flow PID controller, a reheater hot molten salt flow regulating valve, a difference calculator and a reheater molten salt flow detection device;

[0057] The hot molten salt pump regulating loop includes a hot molten salt flow regulating PID control loop and a hot molten salt main pipe minimum set pressure regulating PID control loop, and the PID output of the above quantity regulating loop is connected to the hot molten salt pump through a high selection module;

[0058] The joint valve position integration module is configured between the steam temperature regulating loop and the hot molten salt flow regulating PID control loop, and the signals accepted by the input end of the joint valve position integration module include: the difference between the set value and the actual detection value of the superheated steam temperature in the superheated steam temperature regulating loop calculated by the difference calculator, the difference between the set value and the actual detection value of the reheated steam temperature in the reheated steam temperature regulating loop calculated by the difference calculator, the valve position of the reheater hot molten salt flow regulating valve and the valve position of the superheater hot molten salt flow regulating valve, and the joint valve position integration module is configured to execute the steps shown in FIG. 3 according to the signals of the input end, specifically as follows:

[0059] 1) Detecting whether the difference is greater than a set threshold, if yes, step 2) is performed, if no, step 3) is executed;

[0060] 2) Starting a timer and repeatedly executing step 1;

[0061] 3) Closing the timer and obtaining the cumulative time, which is the time elapsed from starting the timer to closing the timer;

[0062] 4) Reading the regulating valve valve position corresponding to the steam temperature regulating loop and bringing it into the corresponding valve position value function respectively;

[0063] 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;

[0064] The input of the multiplier is also connected to the PID controller output of the hot molten salt pump flow regulation loop and superimposed with the PID controller output of the hot molten salt pump regulation loop via a conditional module as the final output of the hot molten salt pump regulation loop and the output of the hot molten salt main pipe minimum set pressure regulation PID control loop are input into a high selection module, finally obtaining the final instruction input into the hot molten salt pump;

[0065] The conditional module is connected to the joint monitor and configured to determine whether to enable the on instruction or the off instruction according to the output of the joint monitor, so as to determine whether to introduce the output of the joint valve position integration module to the hot molten salt pump regulation loop;

[0066] The joint monitor is configured to monitor the control state and trend of the independently running superheated steam regulation control loop and the reheated steam regulation loop in real time, and output according to the state and trend.

[0067] In this embodiment, the valve position value function is set as follows:

[0068] Wherein, x is the detection value of the regulation valve valve position transmitter; the values of A1 and A2 are determined according to the type and performance index of the regulation valve configured by the system, so as to meet the interval [A1, A2] in the optimal regulation characteristic interval of the valve.

[0069] In a preferred example, the input of the joint valve position integration function includes the superheater steam temperature regulation valve position and the reheater steam temperature regulation valve position, the values of the superheater steam temperature regulation valve position and the reheater steam temperature regulation valve position are taken from the group: Z1, Z2, Z3, null and *; the two regulation valve positions are combined to obtain the output of the joint valve position integration function;

[0070] The output of the joint valve position integration function is divided into the following four categories:

[0071] Wherein, K is the adjustment center value determined by debugging, 0.1-0.3; a 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 the reheater; wherein, 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 rest of the combinations; the first number of the combination is the value of the superheater steam temperature regulation valve position, and the second number is the value of the reheater steam temperature regulation valve position, and the specific setting is shown in Table 1.

[0072] Optionally, in an 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.

[0073] Table 1

[0074] Optionally, in an embodiment, the joint monitor realizes the monitoring of the control states and trends of the superheated steam regulation control loop and the reheated steam regulation control loop through the steps shown in Fig. 4, specifically as follows:

[0075] 1) Read the superheated steam regulation loop error value and the reheated steam regulation loop error value

[0076] 2) and input them into two control loop state monitors respectively, and perform corresponding calculations;

[0077] 3) Perform AND logic calculation on the outputs of the calculations of the two control loop state monitors, and output a conclusion according to the input-output logic table, which is used to evaluate the states and trends of the superheated steam regulation control loop and the reheated regulation control loop; wherein 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 e s and de s / dt are of the same sign, the output is 0; when e s and de s / dt are of different signs, the output is 1.

[0078] The above-mentioned embodiments introduce the joint valve position integration function and the joint monitor function, which organically link the two independently running steam regulation loops and the molten salt pump regulation loop together, i.e. the following functions are realized: the independently running superheated steam and reheated steam regulation loop execution elements, i.e. the branch regulation valves, are operated in the respective optimal performance intervals to realize the control performance and avoid excessive throttling, which causes waste of the heat salt pump conveying capacity. The independently running superheated steam and reheated steam regulation loop states and their change performances are introduced and fed forward to the molten salt pump flow regulation loop to respond to the demand of the steam temperature regulation loop changed due to the change of the steam turbine generator unit power in advance, and reduce the corresponding interference.

[0079] It should be noted that in this patent application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this patent application, if it refers to performing an action according to an element, it means performing the action at least according to that element, including two cases: performing the action only according to that element, and performing the action according to that element and other elements. Expressions such as "multiple," "repeatedly," and "various" include two, two times, two kinds, and more than two, more than two times, and more than two kinds.

[0080] This specification includes combinations of various embodiments described herein. Individual references to “one embodiment” or a particular embodiment, etc., do not necessarily refer to the same embodiment; however, these embodiments are not mutually exclusive unless indicated to be mutually exclusive or are readily apparent to those skilled in the art. It should be noted that the word “or” is used in a non-exclusive sense throughout this specification unless the context explicitly indicates or requires it.

[0081] All documents mentioned in this application are considered to be incorporated in their entirety into the disclosure of this application so that they can serve as a basis for modifications if necessary. Furthermore, it should be understood that after reading the foregoing disclosure of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A method for controlling the steam temperature of a tower-type solar thermal power plant, 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: 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 regulation valve, a differential sensor, and a superheater molten salt flow detection device. The reheat steam temperature regulation loop consists 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 molten salt flow regulation valve, a differential meter, and a reheater molten salt flow detection device. The hot molten salt pump regulation circuit includes a hot molten salt flow regulation PID control circuit and a hot molten salt main pipe minimum set pressure regulation PID control circuit. The PID output of the above-mentioned flow regulation circuit is connected to the hot molten salt pump via a high-selection module. The combined valve position integration module is configured between the steam temperature regulation loop and the hot molten salt flow regulation PID control loop. The input signals received by the combined valve position integration module include: the difference between the superheated steam temperature setpoint and the actual detected value in the superheated steam temperature regulation loop calculated by the differential analyzer; the difference between the reheated steam temperature setpoint and the actual detected value in the reheated steam temperature regulation loop calculated by the differential analyzer; the valve position of the reheater hot molten salt flow regulation valve; and the valve position of the superheater hot molten salt flow regulation valve. The combined valve position integration module is configured to perform the following steps based on the input signals: 1) Detect whether the difference is greater than a set threshold. If it is greater, proceed to step 2); if it is less than, proceed to step 3. 2) Start the timer and repeat step 1; 3) Turn off the timer and obtain the cumulative time, which is the time elapsed from starting the timer to turning it off; 4) Read the valve position of the corresponding steam temperature regulation circuit and input them into the corresponding valve position value function; 5) Input the output of the valve position value function into the combined valve position integration function to obtain the combined valve position integration output, and input the output into the multiplier; The input of the multiplier is also connected to the output of the PID controller of the hot molten salt pump flow regulation loop. The output of the PID controller of the hot molten salt pump regulation loop is superimposed on the output of the PID controller of the hot molten salt pump regulation loop via a condition module as the final output of the hot molten salt pump regulation loop. Together with the output of the PID control loop for regulating the minimum set pressure of the hot molten salt main pipe, the output is input to the high selection module to finally obtain the final command input to the hot molten salt pump. The condition module is connected to the combined monitor and is configured to determine whether to enable or disable the command based on the output of the combined monitor, thereby determining whether to introduce the output of the combined valve position integration module to the hot molten salt pump regulation circuit. The joint monitor is configured to monitor the control status and trends of the independently operating superheated steam conditioning control loop and the reheated steam conditioning loop in real time, and to output based on the status and trends.

2. The steam temperature control method for a tower solar thermal power plant according to claim 1, characterized in that, The valve position value function is set as follows: Where x is the value detected by the valve position transmitter of the control valve; the values ​​of A1 and A2 are determined comprehensively based on the type and performance indicators of the control valve configured in the system, so as to satisfy the range [A1,A2] in the optimal control characteristic range of the valve.

3. The steam temperature control method for a tower solar thermal power plant according to claim 1, wherein the input of the combined 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 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 and *; the two regulating valve positions are combined to obtain the output of the combined valve position integration function; The output of the combined valve position integration function is divided into the following four categories: Where K is the adjustment center value determined by commissioning, ranging from 0.1 to 0.3; α is the section adjustment value, ranging from 0 to 13; τ is the delay coefficient determined by commissioning, which is configured to determine the specific output b1, b2, or b3 based on the input values ​​of the superheater and reheater; where, 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 other combinations; the first number of the combination is the value of the superheater steam temperature regulating valve position, and the second number is the value of the reheater steam temperature regulating valve position.

4. The steam temperature control method for 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 are controlled by a cascade control method and are decoupled from each other.

5. The steam temperature control method for a tower solar thermal power plant according to claim 1, characterized in that, The joint monitor monitors the control status and trends of the superheated steam conditioning control loop and the reheated steam conditioning loop through the following steps: 1) Read the error values ​​of the superheated steam regulating circuit and the reheated steam regulating circuit. 2) Input these values ​​into the status monitors of the two control loops respectively, and execute the corresponding calculations; 3) After performing an AND logic calculation on the outputs of the two control loop status monitors, a conclusion is output based on the input-output logic table. This conclusion is used to evaluate the status and trend of the superheated steam conditioning control loop and the reheat conditioning control loop. The control loop status monitors are configured to perform the following action: acquire the control loop control deviation e. s And calculate the rate of change of control deviation in the control loop. s / dt, when e s with de s When the / dt symbol is the same, the output is 0; when e s with de s When the symbols / dt are different, the output is 1.

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