Combined frequency modulation method and apparatus for main steam valve and heat supply

Abstract

The present invention provides a combined frequency modulation method and apparatus for a main steam valve and heat supply. Combined frequency modulation aims to further exert the advantage of relatively high thermoelectric power after flexibility improvement, on the basis of an original main steam valve regulation strategy, and to provide a primary frequency modulation capability for a power grid, by using unit thermal energy storage provided by steam extraction heat supply. Under the strategy of combining main steam valve and heat supply frequency regulation, when a frequency difference of the power grid exceeds a dead zone, a speed regulator system of a power plant obtains, through calculation, a power increment instruction, then parses the power increment instruction into valve opening degree and heat supply butterfly valve opening degree regulation amounts, and sends the instruction to the main steam valve and heat supply butterfly valve by means of an electro-hydraulic servo mechanism. The present invention further provides a dynamic simulation method for the combined frequency modulation strategy, which mainly comprises the impact of boiler dynamic heat exchange on a power increment after a main steam regulating valve is changed, the impact of a change in the opening degree of the butterfly valve on an output of a steam turbine, and simplification of a total power increase as a superposition of the two strategies. The dynamic simulation method can be used to quantitatively evaluate the primary frequency modulation capability of the combined frequency modulation strategy, to provide reference for quantitative improvement of frequency modulation optimization of a power plant and frequency safety analysis of a power grid.

Description

Main steam valve and heating combined frequency modulation method and device TECHNICAL FIELD

[0001] The present application relates to the technical field of power systems, and in particular to a main steam valve and heating combined frequency modulation method and device. BACKGROUND

[0002] Under the double-carbon development goal, with the increasing proportion of renewable energy, the frequency stability of the power system is under great pressure and challenge. Frequency is a key indicator of power grid operation. In an alternating current power system, frequency is a reflection of system active power balance. On the one hand, new energy with power electronic interface does not have the rotational inertia and primary frequency modulation capability of traditional synchronous machines, and large-scale access leads to a decrease in system synchronous rotational inertia and primary frequency modulation capability, and a decrease in system power disturbance resistance. On the other hand, the random volatility of renewable energy output is large, and the amplitude and frequency of power disturbance in system operation increase, resulting in an increase in the requirement for system frequency modulation capability.

[0003] Especially in relatively independent power grids, the disturbance to the power grid caused by the great uncertainty of wind and light is increasing. The flexibility resources of relatively independent power grids are relatively limited, and the demand and challenge for frequency modulation are great. China's energy endowment is "rich in coal, poor in oil and gas", which determines that coal-fired power will still be the adjustment resource in China for a very long period of time. The role of thermal power units in the power system will gradually change from providing long-term power supply as base load power supply to providing short-term power supply as adjustment power supply. In a double-high power system, thermal power units will bear the main frequency modulation task, and providing primary frequency modulation capability will become one of the most important tasks of future thermal power plants.

[0004] Currently, there are two problems in the primary frequency modulation of the power grid. First, the frequency modulation capability is not fully tapped, and the overall capability is relatively insufficient compared to the increasing amount of wind and light power connected to the grid, and it is urgent to quantitatively improve the frequency modulation capability of thermal power units. Second, the power grid does not grasp the real capability of existing units, resulting in a lack of appropriate power distribution method even if the capability is sufficient.

[0005] In terms of frequency modulation capability evaluation, the power grid does not fully grasp the primary frequency modulation capability of the thermal power unit. At present, the power grid mainly uses the recording wave data after disturbance to perform offline calculation, evaluates the frequency modulation performance of the unit according to the integral electric quantity, or identifies key parameters such as the modulation difference coefficient, can only perform post evaluation on the frequency modulation performance of the unit, and cannot accurately grasp the real primary frequency modulation capability of the unit in time. In addition, it has been proved that the actual frequency curve cannot be simulated by using experience parameters and models, and the power grid estimates the frequency stability of the system too optimistically. The post analysis points out that the influence of the boiler main steam pressure model on the frequency response of the system is rarely considered in the previous frequency simulation analysis, and it is suggested that attention should be paid to it in the subsequent frequency simulation analysis. This shows that the state of the thermal system has a great influence on the primary frequency modulation capability of the unit, and the coupling relationship between the thermal system of the thermal power unit and the power system needs to be analyzed, so as to establish an accurate primary frequency modulation simulation model of the thermal power unit.

[0006] In terms of frequency modulation capability improvement, the traditional strategy of thermal power frequency modulation is the main steam valve regulation strategy, but the supercritical unit adopts the direct current boiler valve which is usually opened to the maximum, and the valve margin is limited in the sliding pressure mode; it is necessary to find a new frequency modulation energy source.

[0007] Some researches dig out the capability other than the boiler heat storage capability as the frequency modulation energy source on the basis of the main steam valve regulation strategy, such as the capability of the steam turbine regenerative system and the heating system. However, due to the fact that the low-pressure cylinder is cut off and there is no extraction regenerative system between the low-pressure heater, the condensate throttling strategy cannot be applied. In winter, most of the heating units are started, and for the primary frequency modulation task issued by the power grid, especially when facing unit large disturbance, the primary frequency modulation capability provided by the main steam valve of the thermal power unit is limited. The low-pressure cylinder cut-off peak shaving flexibility modified thermal power unit is the main unit for heating, power supply and peak shaving in the cold winter area, but due to the fact that the low-pressure cylinder is cut off and the condensate throttling frequency modulation modification cannot be performed, the peak shaving capability and the frequency modulation capability are restricted to a certain extent, so there is still a difference between the unmodified thermal power and the modified thermal power in frequency modulation optimization, and therefore it is necessary to propose an adaptive frequency modulation method for the modified thermal power.

[0008] SUMMARY

[0009] The present application provides a main steam valve and heating combined frequency modulation method and device to solve the defect of limited frequency modulation capability in the prior art, and realize the frequency modulation of the thermal power unit with better performance after modification.

[0010] The present application provides a main steam valve and heating combined frequency modulation method applied to a low-pressure cylinder cut-off type thermal power unit, comprising:

[0011] In response to the fact that the frequency difference of the power grid exceeds the dead zone, the power expected increment instruction of the thermal power unit is obtained;

[0012] According to the pre-calculated first influence factor and second influence factor, the power expected increment instruction of the thermal power unit is distributed to the main steam valve and the heating butterfly valve according to a pre-set priority order, so as to obtain a main steam valve opening degree adjustment amount and a heating butterfly valve opening degree adjustment amount; wherein the first influence factor is the influence of the opening degree of the main steam valve on the power increment, and the second influence factor is the influence of the opening degree of the heating butterfly valve on the power increment;

[0013] According to the main steam valve opening degree adjustment amount and the heating butterfly valve opening degree adjustment amount, the main steam valve and the heating butterfly valve are adjusted, so as to obtain a frequency modulation result.

[0014] According to the method, the first influence factor is calculated based on the boiler dynamic heat exchange model of the low-pressure cylinder cut-off type thermal power unit, the second influence factor is calculated based on the steam turbine volume effect model of the low-pressure cylinder cut-off type thermal power unit, and the priority order is the main steam valve first and the heating butterfly valve second.

[0015] According to the method, the boiler dynamic heat exchange model comprises the following steps:

[0016] The boiler of the low-pressure cylinder cut-off type thermal power unit is evenly divided into multiple heat exchange units along the flow direction of the working medium, for each heat exchange unit, a steam-water working medium heat balance equation and a pipe wall metal heat balance equation are obtained according to energy conservation;

[0017] A temperature expression of the working medium at the outlet of the heat exchange unit is obtained according to the steam-water working medium heat balance equation, and then an average temperature expression of the working medium along the length of the heat exchange unit is obtained; a metal wall temperature expression is obtained according to the pipe wall metal heat balance equation and the average temperature expression;

[0018] A heat exchange unit dynamic heat exchange model of each heat exchange unit is obtained according to the metal wall temperature expression and the average temperature expression;

[0019] A working medium flow process equation is obtained according to mass conservation and momentum conservation equations;

[0020] The heat exchange unit dynamic heat exchange model is connected in series according to the delay effect caused by the heat capacity of the fluid and the working medium flow process equation, so as to obtain a boiler dynamic heat exchange model.

[0021] According to the method, the first influence factor is calculated based on the boiler dynamic heat exchange model of the low-pressure cylinder cut-off type thermal power unit, and the calculation specifically comprises the following steps:

[0022] S401: acquire predetermined model parameters and state quantity initial values; wherein the state quantity initial values include temperature, pressure, density and metal wall temperature of working medium in each section heat exchange unit;

[0023] S402: acquire the opening of the main steam valve at the current time, in the case that the current time is less than the preset simulation time length, jump to step S403, in the case that the current time is equal to the preset simulation time length, jump to step S407;

[0024] S403: input the model parameters and the state quantity initial values into the boiler dynamic heat exchange model, and calculate the density of working medium in each section heat exchange unit in the next step length by using the mass conservation of the boiler dynamic heat exchange model;

[0025] S404: set the qualitative temperature of working medium in each section heat exchange unit as the temperature of inlet working medium, and calculate the property parameters of working medium in each section heat exchange unit by using a pre-selected property database; calculate the temperature, pressure and flow of working medium in each section heat exchange unit in the next step length by using the boiler dynamic heat exchange model according to the property parameters, and obtain state parameters;

[0026] S405: calculate the average temperature of working medium of each section heat exchange unit according to the state parameters, in the case that the difference between the average temperature of working medium and the qualitative temperature is greater than the allowable error, update the qualitative temperature, repeat steps S404-S405 until the difference between the average temperature of working medium and the qualitative temperature is not greater than the allowable error;

[0027] S406: add the current time by the current step length, update the state quantity initial values according to the state parameters, and jump to step S402;

[0028] S407: obtain the first influence factor according to the state parameters and the opening of the main steam valve at each time in the preset simulation time length.

[0029] According to the main steam valve and heat supply combined frequency modulation method provided by the application, the second influence factor is calculated based on the steam turbine volume effect model of the low-pressure cylinder cut-off type thermal power unit, and specifically includes:

[0030] Acquire the linear relationship between the opening of the heat supply butterfly valve and the steam extraction flow;

[0031] Input the linear relationship into the pre-constructed steam turbine volume effect model to obtain the second influence factor.

[0032] According to the main steam valve and heat supply combined frequency modulation method provided by the application, the model parameters include heat transfer rate and working medium flow resistance coefficient;

[0033] Correspondingly, the acquisition of the predetermined model parameters and the state quantity initial values specifically includes:

[0034] S601: obtaining a boiler steady-state model according to the boiler dynamic heat exchange model, obtaining boiler structure parameters, measured data and the number of heat exchange units;

[0035] S602: setting initial values of the heat transfer rate and the working fluid flow resistance coefficient, and setting i=1;

[0036] S603: obtaining the working fluid inlet temperature of the i-th heat exchange unit according to the measured data, and setting the qualitative temperature of the i-th heat exchange unit as the working fluid inlet temperature;

[0037] S604: calculating the density and specific heat capacity of the working fluid by using a pre-selected property database, and calculating the state parameters of the working fluid of the i+1-th heat exchange unit according to the boiler steady-state model;

[0038] S605: calculating the average temperature of the working fluid of the i-th heat exchange unit according to the state parameters of the working fluid of the i+1-th heat exchange unit, updating the qualitative temperature when the difference between the average temperature and the qualitative temperature is greater than the allowable error, and repeating step S604 until the difference is less than the allowable error;

[0039] S606: setting i=i+1; if i is less than the number of heat exchange units, jumping to step S603; if i is not less than the number of heat exchange units, jumping to step S607;

[0040] S607: calculating a first difference between the temperature of the working fluid of the current heat exchange unit and the main steam temperature in the measured data, and calculating a second difference between the pressure of the working fluid of the current heat exchange unit and the pressure in the measured data; if the first difference and / or the second difference is greater than the allowable error, setting i=1 and repeating steps S603-S607 until the first difference and the second difference are less than the allowable error;

[0041] S608: outputting the heat transfer rate and the working fluid flow resistance coefficient as model parameters, and outputting the state parameters of each heat exchange unit as initial values of state quantities.

[0042] The application also provides a main steam valve and heat supply combined frequency modulation device, which is applied to a low-pressure cylinder cut-off type thermal power unit and comprises:

[0043] The instruction unit is configured to obtain a thermal power unit power expected increment instruction in response to a power grid frequency difference exceeding a dead zone.

[0044] The opening degree unit is configured to distribute the power expected increment instruction of the thermal power unit to the main steam valve and the heating butterfly valve according to a preset priority order based on the first influence factor and the second influence factor, so as to obtain a main steam valve opening degree adjustment amount and a heating butterfly valve opening degree adjustment amount, wherein the first influence factor is the influence of the opening degree of the main steam valve on the power increment, and the second influence factor is the influence of the opening degree of the heating butterfly valve on the power increment.

[0045] The control unit is configured to adjust the main steam valve and the heating butterfly valve based on the main steam valve opening degree adjustment amount and the heating butterfly valve opening degree adjustment amount, so as to obtain a frequency modulation result.

[0046] The application further provides an electronic device, which comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the method for combined frequency modulation of the main steam valve and heating when executing the program.

[0047] The application further provides a non-transitory computer readable storage medium, which stores a computer program, and the computer program implements the method for combined frequency modulation of the main steam valve and heating when executed by a processor.

[0048] The application further provides a computer program product, which comprises a computer program, and the computer program implements the method for combined frequency modulation of the main steam valve and heating when executed by a processor.

[0049] The application provides a method and device for combined frequency modulation of a main steam valve and heating, which are applied to a low-pressure cylinder cut-off type thermal power unit. The method obtains a power expected increment instruction of the thermal power unit in response to a grid frequency difference exceeding a dead zone. The power expected increment instruction of the thermal power unit is distributed to the main steam valve and the heating butterfly valve according to a preset priority order based on a first influence factor and a second influence factor, so as to obtain a main steam valve opening degree adjustment amount and a heating butterfly valve opening degree adjustment amount. The first influence factor is the influence of the opening degree of the main steam valve on the power increment, and the second influence factor is the influence of the opening degree of the heating butterfly valve on the power increment. The main steam valve and the heating butterfly valve are adjusted based on the main steam valve opening degree adjustment amount and the heating butterfly valve opening degree adjustment amount, so as to obtain a frequency modulation result. The application utilizes the heating butterfly valve to enable the thermal energy storage of a heating system connected to the extraction heating to participate in frequency modulation. The opening degree control strategy is formulated according to the influence of the opening degree of the main steam valve on the power increment and the influence of the opening degree of the heating butterfly valve on the power increment. The combined frequency modulation of the main steam valve and heating is realized, the frequency modulation capability of the thermal power unit is improved, and the frequency modulation of the thermal power unit with better performance after modification is realized. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to make the technical solutions in the present application or prior art clearer, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings described below are some embodiments of the present application, and all other embodiments obtained by those skilled in the art without creative effort based on these drawings also belong to the protection scope of the present application.

[0051] Fig. 1 is a flowchart of the method for combined frequency regulation of main steam valve and heat supply provided by the present application;

[0052] Fig. 2 is a flowchart of the method for combined frequency regulation of main steam valve and heat supply provided by the present application;

[0053] Fig. 3 is a flowchart of the method for combined frequency regulation of main steam valve and heat supply provided by the present application;

[0054] Fig. 4 is a heat exchange schematic diagram of a single heat exchange unit of the method for combined frequency regulation of main steam valve and heat supply provided by the present application;

[0055] Fig. 5 is a schematic diagram of series connection structure of heat exchange unit of the method for combined frequency regulation of main steam valve and heat supply provided by the present application;

[0056] Fig. 6 is a flowchart of the method for combined frequency regulation of main steam valve and heat supply provided by the present application;

[0057] Fig. 7 is a flowchart of the method for combined frequency regulation of main steam valve and heat supply provided by the present application;

[0058] Fig. 8 is a structural schematic diagram of the device for combined frequency regulation of main steam valve and heat supply provided by the present application;

[0059] Fig. 9 is a structural schematic diagram of the electronic device provided by the present application. DETAILED DESCRIPTION

[0060] In order to make the technical solutions in the present application or prior art clearer, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings described below are some embodiments of the present application, and all other embodiments obtained by those skilled in the art without creative effort based on these drawings also belong to the protection scope of the present application.

[0061] The method for combined frequency regulation of main steam valve and heat supply provided by the present application will be described below in combination with Figs. 1-7. As shown in Fig. 1, the method comprises:

[0062] Step 110: obtaining power expected increment instruction of thermal power generating unit in response to grid frequency difference exceeding dead zone;

[0063] It needs to be explained that the present application is aimed at the thermal power generating unit after low-pressure cylinder cut-off peak-shaving flexibility modification in winter. It can be understood that the thermal power generating unit after low-pressure cylinder cut-off modification has high heat-electricity ratio, has the characteristics of large heat supply, large mass flow and large heat supply transmission delay. The main steam valve and heat supply combined frequency modulation method provided by the present application aims to play the advantages of low-pressure cylinder cut-off type thermal power generating unit based on the original main steam valve adjustment strategy, and uses the heat storage energy of steam extraction heat supply to provide primary frequency modulation capacity for the power grid.

[0064] However, frequent operation of the heat supply butterfly valve may cause jamming, causing risks such as unstable operation of the unit, but the sufficient heat storage capacity of the large heat supply system is a good source of primary frequency modulation energy. In order to reduce the cost of primary frequency modulation and not affect the safe performance of the unit, the main steam valve adjustment is used as the main strategy, and the heat supply butterfly valve frequency modulation is used as the supplementary frequency modulation strategy, as shown in FIG. 2.

[0065] In actual operation, under the strategy of combination of the main steam valve and heat supply frequency modulation, when the grid frequency difference exceeds the dead zone, the power plant governor system can calculate the expected power increment instruction of the thermal power generating unit according to the grid frequency difference. It needs to be explained that the grid frequency difference exceeding the dead zone means that the frequency of the power grid deviates from the normal operating range and exceeds the action interval set by the protection device. In the power system, the frequency dead zone refers to the sensitivity limit of the protection device to frequency change.

[0066] Further, the power plant governor system calculates the expected power increment instruction of the thermal power generating unit according to the grid frequency difference, which specifically includes: the power plant governor system calculates the frequency difference according to the detected grid frequency and the set threshold, and calculates the power difference value according to the frequency difference value, and then generates the corresponding expected power increment instruction of the thermal power generating unit according to the calculated power difference value.

[0067] Step 120: According to the first influence factor and the second influence factor calculated in advance, the expected power increment instruction of the thermal power generating unit is distributed to the main steam valve and the heat supply butterfly valve according to the priority order set in advance, to obtain the opening adjustment amount of the main steam valve and the opening adjustment amount of the heat supply butterfly valve; wherein the first influence factor is the influence of the opening of the main steam valve on the power increment, and the second influence factor is the influence of the opening of the heat supply butterfly valve on the power increment;

[0068] After obtaining the expected power increment instruction of the thermal power generating unit, it is distributed to the main steam valve and the heat supply butterfly valve. As shown in FIG. 2, the grid frequency difference drives the power plant governor system to issue frequency modulation instructions, and the power plant governor system (DEH, digital electro-hydraulic control system) and the coordinated control system (CCS, Continuious Control System) simultaneously issue instructions to the main steam regulating valve and the heat supply butterfly valve.

[0069] Before the specific instruction is issued, the power expected increment instruction of the thermal power unit needs to be decomposed into the main steam valve opening degree adjustment amount and the heating butterfly valve opening degree adjustment amount. Specifically, the power distribution adopts a sequential manner, and is distributed according to a pre-set priority order, that is, the main steam valve first and the heating butterfly valve second. That is, the opening degrees of the main steam high-pressure regulating valve and the heating butterfly valve are sequentially increased, the heating butterfly valve is opened after the opening degree of the main steam valve reaches the limit, the control priority is the main steam regulating valve first and the heating butterfly valve second, and the clogging failure caused by the frequent starting of the heating butterfly valve is minimized on the premise of ensuring the load response.

[0070] Further, the specific calculation manner of the main steam valve opening degree adjustment amount and the heating butterfly valve opening degree adjustment amount is related to the influence of the boiler dynamic heat exchange after the main steam valve is changed on the power increment (a first influence factor) and the influence of the butterfly valve opening degree change on the power increment (a second influence factor).

[0071] In some embodiments, the first influence factor is calculated based on a boiler dynamic heat exchange model of the low-pressure cylinder cut-off type thermal power unit, and the second influence factor is calculated based on a steam turbine volume effect model of the low-pressure cylinder cut-off type thermal power unit.

[0072] The calculation manner of the first influence factor and the second influence factor proposed by the present application can also be understood as a simulation method, which can be used to provide a reference for the quantitative improvement of power plant frequency modulation optimization, and at the same time, it can also be used to quantitatively evaluate the primary frequency modulation capability of the joint frequency modulation strategy and the power grid frequency safety analysis. That is, the simulation method includes analyzing the influence of the boiler dynamic heat exchange after the main steam regulating valve opening degree is changed on the main steam pressure, the main steam flow and the steam turbine work by using a boiler dynamic heat exchange model, and analyzing the relationship among the butterfly valve opening degree, the steam heating flow and the steam turbine work by using a steam turbine volume effect model.

[0073] In some embodiments, the construction steps of the boiler dynamic heat exchange model include:

[0074] The boiler of the low-pressure cylinder cut-off type thermal power unit is evenly divided into multiple heat exchange units along the flow direction of the working medium, and for each heat exchange unit, the steam-water working medium heat balance equation and the pipe wall metal heat balance equation are obtained according to the energy conservation;

[0075] The temperature expression of the working medium at the outlet of the heat exchange unit is obtained according to the steam-water working medium heat balance equation, and then the average temperature expression of the working medium over the length of the heat exchange unit is obtained; the metal wall temperature expression is obtained according to the pipe wall metal heat balance equation and the average temperature expression;

[0076] According to the metal wall temperature expression and the average temperature expression, a heat exchange unit dynamic heat exchange model of each heat exchange unit is obtained;

[0077] According to mass conservation and momentum conservation equations, a working medium flow process equation is obtained;

[0078] According to a delay effect caused by fluid heat capacity and the working medium flow process equation, the heat exchange unit dynamic heat exchange model is connected in series to obtain a boiler dynamic heat exchange model.

[0079] Specifically, in order to facilitate calculation, the following simplifications and assumptions are set in the construction process of the boiler dynamic heat exchange model in the embodiment:

[0080] 1) The boiler heating pipeline is simplified as a regular geometric heat exchanger with a certain length and thickness, and all parallel pipes are equivalent to a heating pipe with the same cross-sectional area.

[0081] 2) The heat transfer amount of flue gas to the pipe wall is constant in the primary frequency modulation time scale.

[0082] 3) The boiler heat absorption amount is proportional to the boiler volume, and the boiler volume is equal to the length of the geometric heat exchanger.

[0083] 4) The flow is one-dimensional, and the flow velocity and thermal properties of the steam-water working medium are the same in the direction perpendicular to the flow direction, and the heat exchange is only performed in the radial direction.

[0084] 5) During the primary frequency modulation, the temperature and pressure of the feed water entering the boiler remain unchanged.

[0085] It should be noted that the above simplifications and assumptions are for the convenience of calculation and for the purpose of explaining the embodiment on the basis of calculation, and do not represent a limitation on the present application.

[0086] On this basis, the boiler is evenly divided into n heat exchange units along the working medium flow direction. The working medium qualitative temperature of each heat exchange unit is the arithmetic mean of the inlet and outlet working medium port temperatures, and the working medium property parameters such as density and constant-pressure specific heat capacity can be determined by the qualitative temperature and pressure of the working medium in this section.

[0087] In the specific implementation process, first, each heat exchange unit is analyzed and modeled. Considering a heat exchanger with a length of L i as shown in FIG. 4, the inlet steam-water working medium temperature is T c,in , and the heat transfer rate of flue gas to the pipe wall is q h .

[0088] Further, the heat exchange process is described by energy conservation, and the heat storage of steam-water working medium and pipe wall metal is considered. The steam-water working medium heat balance equation and the pipe wall metal heat balance equation are written respectively:

[0089] where, and T w,i are the temperatures of the steam-water mixture and the tube wall metal, respectively. C c,i and C w are the heat capacities of the steam-water mixture and the tube wall metal, respectively. Ae is the heat transfer area, is the heat transfer coefficient between the steam-water mixture and the tube wall. q h represents the heat transfer rate from the flue gas to the boiler tube wall. G c,i is the heat capacity flow rate of the steam-water mixture, which is equal to the mass flow rate and the constant-pressure specific heat c c,p,i . λ is the tube wall metal diffusion coefficient. t and x represent time and space, respectively.

[0090] On the basis of the above, the effect of the unsteady term in equation (1) is ignored, and it is assumed that the metal wall temperature does not vary with position in the heat transfer unit, to obtain the following equation:

[0091] Integrating the above equation from the fluid inlet to a position x gives:

[0092] where T c,in,i represents the steam-water mixture inlet temperature. Taking x = L i , the temperature of the steam-water mixture at the outlet of the i-th heat transfer unit, i.e., the temperature of the steam-water mixture at the inlet of the i+1-th heat transfer unit, is given by:

[0093] where T c,out,i is the temperature of the steam-water mixture at the outlet of the i-th heat transfer unit, i.e., the temperature of the steam-water mixture at the inlet of the i+1-th heat transfer unit.

[0094] Integrating equation (4) from 0 to L i and dividing by L i gives the average temperature of the steam-water mixture over the length L i of the heat transfer unit:

[0095] In the case of the piecewise modeling, it is assumed that the temperature of the tube wall is uniformly distributed in each heat transfer unit, and the diffusion term of the metal wall temperature in equation (2) is ignored, to obtain the following equation:

[0096] Integrating the above equation from the fluid inlet to the outlet and dividing by L i gives:

[0097] Substituting equation (6) into equation (8) gives:

[0098] Integrating equation (9) from 0 to t gives the metal wall temperature expression:

[0099] where T w,i,0 is the initial temperature of the tube wall metal. t0 is the heat transfer time constant, which is related to the heat capacity of the tube wall metal, the performance of the heat exchanger, and the heat capacity flow rate of the fluid.

[0100] As shown in Figure 5, the heat exchanger units are connected in series to form a boiler heat exchanger model. Assuming that the pressure and density in each heat exchanger unit are uniform, the flow resistance of the working fluid is concentrated at the inlet and outlet, and an equation is added to describe the flow process of the working fluid.

[0101] Specifically, p c,i and p c,i are the density and pressure of the i-th stage of steam-water working fluid, is the mass flow rate of the i-th stage of steam-water working fluid at the inlet. The qualitative temperature of the i-th stage of fluid should be determined according to the arithmetic mean of the inlet and outlet temperatures. The pressure p c,i and the constant-pressure specific heat capacity c c,p,i are obtained from the qualitative temperature and density using a pre-selected property database:

[0102] In one specific embodiment, the property database is selected as coolprop.

[0103] Considering the compressibility of the fluid and ignoring the acceleration pressure difference caused by the change of the flow velocity of the fluid along the position and time, the flow process of the steam-water working fluid is described by the mass conservation and momentum conservation equations:

[0104] where A c is the cross-sectional area of the pipe. f is the resistance coefficient, which is related to the pipe wall friction coefficient and the cross-sectional area of the pipe.

[0105] Since the influence of the heat capacity of the working fluid is ignored in the process of establishing the heat exchanger model, when the heat exchanger units are connected in series to form the overall boiler, the delay effect caused by the heat capacity of the fluid should be further considered, and the relationship between the inlet and outlet temperatures of adjacent heat exchanger units should satisfy the following equation:

[0106] The delay time At c,i is determined by the length L i of the i-th stage and the flow velocity u c,i of the steam-water working fluid:

[0107] The working fluid with an inlet temperature of T c,i at the i-th stage of heat exchanger unit at time t passes through Atc,i flow to the i-th heat exchange unit outlet, the temperature changes to T c,i+1 . Therefore, at the time (t+Δt c,i ), the temperature of the i+1-th heat exchange unit inlet becomes T c,i+1 .

[0108] Further, when the thermal power unit reaches a steady state, the mass flow of the working medium at each location is the same, the metal wall temperature and the working medium temperature at each location do not change with time, the enthalpy of the intermediate point steam is equal to the set value, and the feedwater flow is the feedwater flow reference value. The steady-state form of the boiler model is as follows:

[0109] On this basis, in some embodiments, the first influence factor is calculated based on the boiler dynamic heat exchange model of the low-pressure cylinder cut-off type thermal power unit, specifically comprising:

[0110] S401: acquiring pre-determined model parameters and state quantity initial values; wherein the state quantity initial values include the temperature, pressure, density and metal wall temperature of the working medium in each heat exchange unit;

[0111] S402: acquiring the opening of the main steam valve at the current time, in the case that the current time is less than the preset simulation time length, jumping to step S403, in the case that the current time is equal to the preset simulation time length, jumping to step S407;

[0112] S403: inputting the model parameters and the state quantity initial values into the boiler dynamic heat exchange model, and calculating the density of the working medium in each heat exchange unit at the next step length by using the mass conservation calculation of the boiler dynamic heat exchange model;

[0113] S404: setting the qualitative temperature of the working medium in each heat exchange unit as the temperature of the inlet working medium, and calculating the property parameters of the working medium in each heat exchange unit by using a pre-selected property database; calculating the temperature, pressure and flow of the working medium in each heat exchange unit at the next step length by using the boiler dynamic heat exchange model according to the property parameters, to obtain state parameters;

[0114] S405: calculating the average temperature of the working medium of each heat exchange unit according to the state parameters, in the case that the difference between the average temperature of the working medium and the qualitative temperature is greater than the allowable error, updating the qualitative temperature, repeating steps S404-S405, until the difference between the average temperature of the working medium and the qualitative temperature is not greater than the allowable error;

[0115] S406: adding the current time by the current step length, updating the state quantity initial values according to the state parameters, and jumping to step S402;

[0116] S407: Obtain a first influence factor according to the state parameters at each time in the preset simulation time length and the opening degree of the main steam valve.

[0117] Specifically, the solving step is shown in FIG. 6, and the specific steps are as follows:

[0118] In step S401, the predetermined model parameters, the temperature, pressure, density and metal wall temperature of each section of working medium and other state quantity initial values need to be input.

[0119] In step S402, the opening degree of the main steam valve at the current time is read according to the governor output, it is judged whether the current time is less than the simulation time length, and the temperature, pressure, density and metal wall temperature of each section of working medium and other state quantities are output when t is not less than the simulation time length.

[0120] When t is less than the simulation time length, the density of each section of working medium at the next step is calculated according to the mass conservation. At the same time, the qualitative temperature initial value of each section of working medium is set as the temperature of the inlet working medium, and the property database selected in advance is used to calculate the property parameters such as working medium pressure and specific heat capacity. The temperature, pressure and flow of each section of working medium at the next step are calculated according to the boiler dynamic heat exchange model, and the metal wall temperature can also be included, that is, the state parameters are obtained.

[0121] In step S405, the average value of the inlet and outlet temperatures of each section of heat exchange unit working medium is calculated to obtain the average temperature of the working medium, and the average temperature is compared with the qualitative temperature (the qualitative temperature is the average value of the current node temperature and the next node temperature at the current time step), when it is greater than the allowable error, the qualitative temperature is updated, and steps S404-S405 are repeated, when it is less than the error, the next step is performed.

[0122] In step S406, t=t+delta_t (delta_t is the step length), the initial value of the state quantity is updated, the state variable at the current time is updated to the initial value calculated at the next time, and step S402 is jumped.

[0123] In step S407, a first influence factor is obtained according to the state parameters at each time in the preset simulation time length and the opening degree of the main steam valve.

[0124] It can be understood that steps S401-S406 can be used as a simulation method for quantitative evaluation of the primary frequency modulation capability of the combined frequency modulation strategy and power grid frequency safety analysis. It can be understood that in the prior art, the power grid does not have a sufficient understanding of the primary frequency modulation capability of the thermal power unit. At present, off-line calculation is mainly used after disturbance occurs, and then the integral electric quantity is used to evaluate the frequency modulation performance of the unit or identify key parameters such as the modulation difference coefficient. This is only suitable for post-evaluation of the frequency modulation performance of the unit and cannot accurately grasp the real primary frequency modulation capability of the unit in time. The simulation method provided by the present application can analyze the coupling relationship between the thermal system of the thermal power unit and the power system, perform effective online calculation, and thus accurately perform dynamic simulation and accurately grasp the real primary frequency modulation capability of the unit in time.

[0125] Further, in the specific implementation process, taking a once-through supercritical thermal power unit as an example, considering the pre-sequence dynamic process and the current working condition frequency modulation dynamics of the unit, it is considered that the superposition of the regulation capability caused by the pre-sequence dynamic and the current working condition is the actual regulation capability. First, a method of superimposing the primary frequency modulation effect on the historical trend reaching power is used, a historical 5-minute power characteristic curve is input, and an interpolation method is used to obtain the power reaching value of the next minute; second, a boiler dynamic heat exchange model of the once-through boiler is established, only the superheating section is considered, and the steady-state working condition at the disturbance occurrence time is taken as the initial value. Taking a frequency difference step or a single-machine power grid power disturbance as an example, the primary frequency modulation dynamic characteristics of the unit under the main steam valve regulation strategy are calculated, and the valve opening degree is obtained by superimposing the valve opening degree command signal of the speed regulator system and the valve opening degree command signal of the boiler coordination control at this time. It can be understood that the primary frequency modulation acceptance guideline is a set of specifications for testing and evaluating the frequency modulation capability of power plants in the power system.

[0126] Based on the above embodiments, the determination of the model parameters and the initial values of the state quantities is further described. In some embodiments, the model parameters include a heat transfer rate and a working medium flow resistance coefficient;

[0127] Correspondingly, the obtaining of the predetermined model parameters and the initial values of the state quantities specifically includes:

[0128] S601: obtaining a boiler steady-state model according to the boiler dynamic heat exchange model, and obtaining boiler structure parameters, measured data, and the number of heat exchange units;

[0129] S602: setting initial values of the heat transfer rate and the working medium flow resistance coefficient, and setting i = 1;

[0130] S603: obtaining a working medium inlet temperature of an i-th heat exchange unit according to the measured data, and setting a qualitative temperature of the i-th heat exchange unit as the working medium inlet temperature;

[0131] S604: Calculate the density and specific heat capacity of the working medium by using the pre-selected property database, and calculate the state parameters of the working medium of the i+1th heat exchange unit according to the boiler steady-state model;

[0132] S605: Calculate the average temperature of the working medium of the i th heat exchange unit according to the state parameters of the working medium of the i+1th heat exchange unit, and update the qualitative temperature if the difference between the average temperature and the qualitative temperature is greater than the allowable error, and repeat step S604 until the difference is less than the allowable error;

[0133] S606: i=i+1; if i is less than the number of heat exchange units, jump to step S603; if i is not less than the number of heat exchange units, jump to step S607;

[0134] S607: Calculate the first difference between the temperature of the working medium of the current heat exchange unit and the main steam temperature in the measured data, and calculate the second difference between the pressure of the working medium of the current heat exchange unit and the pressure in the measured data; if the first difference and / or the second difference is greater than the allowable error, set i=1, and repeat steps S603-S607 until the first difference and the second difference is less than the allowable error;

[0135] S608: Output the heat transfer rate and the working medium flow resistance coefficient as model parameters, and output the state parameters of each heat exchange unit as initial values of state quantities.

[0136] Specifically, it needs to be noted that the execution of this step is based on the boiler steady-state model. Specifically, the working medium temperature and pressure at the outlet of the economizer in the measured data are taken as the thermal state parameters of the working medium of the first segment of the boiler model, the main steam temperature and main steam pressure are taken as the thermal state parameters of the working medium of the nth segment of the boiler model, and the main steam flow is taken as the flow of each segment of working medium. In the steady-state form of the boiler model, the state parameters of the working medium of each heat exchange unit can be obtained from the state parameters of the working medium of the previous heat exchange unit. Therefore, when the temperature, pressure and flow of the boiler inlet working medium are known, the model parameters are determined, and the temperature, pressure of the boiler outlet working medium can be obtained by recursive calculation. Subtract the calculated value from the measured temperature and pressure of the boiler outlet working medium, and iterate to obtain the model parameters qh and f.

[0137] In one specific embodiment, the measured data is obtained from a DCS (Distributed Control System).

[0138] In the specific solving process, the solving steps are divided into two layers, the inner layer is the iterative calculation of the thermal state parameters of each segment of working medium, and the outer layer is the iterative calculation of the heat transfer rate and resistance coefficient. As shown in FIG. 7, the main steps are:

[0139] In step S601, the boiler steady-state model is obtained according to the boiler dynamic heat exchange model, and the operating conditions are input according to the boiler structure parameters and the measured data, and the number of heat exchange units is set to n, that is, the number of heat exchange units is n.

[0140] In step S602, the initial value of the heat transfer rate q h And the initial value of the working fluid flow resistance coefficient f, let i = 1.

[0141] In step S603, starting from the ith segment, the initial value of the working fluid temperature is set to the inlet temperature of the working fluid of the ith segment according to the measured data (for i = 1, the outlet temperature of the economizer is set to the initial value of the working fluid temperature).

[0142] In step S604, the density and specific heat capacity of the working fluid are calculated using a pre-selected property database, and the inlet temperature, pressure and other state parameters of the working fluid of the i+1th segment are calculated according to the boiler steady-state model. The state parameters can also include the metal wall temperature.

[0143] In step S605, the average temperature of the working fluid of the ith segment is calculated, and compared with the qualitative temperature. When the difference between the average temperature and the qualitative temperature is greater than the allowable error, the qualitative temperature is updated (the qualitative temperature is the average value of the current node temperature and the next node temperature at this time step), and step S604 is repeated; when it is less than the allowable error, the next step is performed.

[0144] In step S606, let i = i + 1, when i >= n, jump to step S607; when i < n, jump to step S603;

[0145] In step S607, the temperature and pressure of the working fluid of the nth segment are compared with the difference between the main steam temperature and pressure of the measured data, and the first difference and the second difference are obtained, respectively. When the difference is greater than the allowable error, let i = 1, and repeat steps S603-S607. When the difference is less than the allowable error, the iteration is stopped, and the heat transfer rate and the resistance coefficient are output as the model parameters, and the temperature, pressure, density and metal wall temperature of each segment of the working fluid are output as the initial value of the state quantity.

[0146] Further, the second influence factor is calculated based on the steam turbine volume effect model of the low-pressure cylinder cut-off type thermal power generating unit, and specifically includes:

[0147] Obtaining a linear relationship between the opening of the heating butterfly valve and the extraction flow rate;

[0148] Inputting the linear relationship into a pre-constructed steam turbine volume effect model to obtain a second influence factor.

[0149] Specifically, the linear relationship between the heating butterfly valve opening and the extraction flow is measured by an empirical formula, and the change in the extraction flow caused by the change in the butterfly valve opening is superimposed on the change in the main steam flow at the main steam valve. In addition, for the heating frequency modulation strategy, the linear relationship between the butterfly valve opening and the extraction flow is used to calculate the change in the extraction flow caused by the change in the butterfly valve opening, without considering the extraction point pressure and temperature changes caused by the change in the butterfly valve opening. The flow change is input into the steam turbine volume effect model to obtain the relationship between the butterfly valve opening, the extraction flow and the steam turbine work, i.e. the second influence factor.

[0150] Step 130: adjusting the main steam valve and the heating butterfly valve according to the main steam valve opening adjustment amount and the heating butterfly valve opening adjustment amount to obtain the frequency modulation result.

[0151] As shown in FIG. 3, in actual operation, the instructions for distribution are issued to the main steam valve and the heating butterfly valve through an electro-hydraulic servo mechanism, the total power increase is simplified as the superposition of the two strategies, and finally the power control result under the combined frequency modulation of the main steam valve and the heating is obtained.

[0152] Further, the power control result is compared with the thermal power generating unit power expected increment included in the thermal power generating unit power expected increment instruction, and if the thermal power generating unit power expected increment condition is met, the frequency modulation is completed.

[0153] The main steam valve and heating combined frequency modulation method provided by the application is applied to a low-pressure cylinder cut-off type thermal power generating unit. The method obtains a thermal power generating unit power expected increment instruction in response to a grid frequency difference exceeding a dead zone. According to a first influence factor and a second influence factor calculated in advance, the thermal power generating unit power expected increment instruction is distributed to a main steam valve and a heating butterfly valve according to a pre-set priority order to obtain a main steam valve opening adjustment amount and a heating butterfly valve opening adjustment amount. The first influence factor is the influence of the opening of the main steam valve on the power increment, and the second influence factor is the influence of the opening of the heating butterfly valve on the power increment. The main steam valve and the heating butterfly valve are adjusted according to the main steam valve opening adjustment amount and the heating butterfly valve opening adjustment amount to obtain a frequency modulation result. The application utilizes the heating butterfly valve to make the heat storage of the heating system connected subsequently participate in frequency modulation, formulates a specific opening control strategy according to the influence of the opening of the main steam valve on the power increment and the influence of the opening of the heating butterfly valve on the power increment, realizes the combined frequency modulation of the main steam valve and the heating, improves the frequency modulation capability of the thermal power generating unit, and realizes the performance better thermal power generating unit frequency modulation after the modification of the thermal power.

[0154] The main steam valve and heating combined frequency modulation device provided by the application is described below, and the main steam valve and heating combined frequency modulation device described below can be correspondingly referred to the main steam valve and heating combined frequency modulation method described above. As shown in FIG. 8, the device comprises:

[0155] The instruction unit 810 is configured to acquire a power expected increment instruction of the thermal power unit in response to the grid frequency difference exceeding the dead zone;

[0156] The opening unit 820 is configured to distribute the power expected increment instruction of the thermal power unit to the main steam valve and the heating butterfly valve according to a pre-calculated first influence factor and a second influence factor and a pre-set priority order to obtain a main steam valve opening adjustment amount and a heating butterfly valve opening adjustment amount, wherein the first influence factor is an influence of the opening of the main steam valve on the power increment, and the second influence factor is an influence of the opening of the heating butterfly valve on the power increment.

[0157] The control unit 830 is configured to adjust the main steam valve and the heating butterfly valve according to the main steam valve opening adjustment amount and the heating butterfly valve opening adjustment amount to obtain a frequency modulation result.

[0158] According to the device for combined frequency modulation of the main steam valve and the heating provided by the application, the first influence factor is calculated based on a boiler dynamic heat exchange model of the low-pressure cylinder cut-off type thermal power unit, and the second influence factor is calculated based on a steam turbine volume effect model of the low-pressure cylinder cut-off type thermal power unit; and the priority order is the main steam valve first and the heating butterfly valve second.

[0159] According to the device for combined frequency modulation of the main steam valve and the heating provided by the application, the construction steps of the boiler dynamic heat exchange model include:

[0160] The boiler of the low-pressure cylinder cut-off type thermal power unit is evenly divided into multiple heat exchange units along the flow direction of the working medium, and for each heat exchange unit, a steam-water working medium heat balance equation and a tube wall metal heat balance equation are obtained according to the law of conservation of energy;

[0161] A temperature expression of the working medium at the outlet of the heat exchange unit is obtained according to the steam-water working medium heat balance equation, and then an average temperature expression of the working medium along the length of the heat exchange unit is obtained; and a metal wall temperature expression is obtained according to the tube wall metal heat balance equation and the average temperature expression;

[0162] A heat exchange unit dynamic heat exchange model of each heat exchange unit is obtained according to the metal wall temperature expression and the average temperature expression;

[0163] A working medium flow process equation is obtained according to the law of conservation of mass and the law of conservation of momentum;

[0164] The heat exchange unit dynamic heat exchange model is connected in series according to the delay effect caused by the heat capacity of the fluid and the working medium flow process equation to obtain a boiler dynamic heat exchange model.

[0165] According to the application, a main steam valve and heat supply combined frequency modulation device is provided, and the first influence factor is calculated based on a boiler dynamic heat exchange model of the low-pressure cylinder cut-off type thermal power unit, and specifically includes the following steps:

[0166] S401: acquiring predetermined model parameters and state quantity initial values; wherein the state quantity initial values include temperatures, pressures, densities and metal wall temperatures of working medium in each heat exchange unit;

[0167] S402: acquiring an opening of the main steam valve at a current time; if the current time is less than a preset simulation time length, jumping to step S403; if the current time is equal to the preset simulation time length, jumping to step S407;

[0168] S403: inputting the model parameters and the state quantity initial values into the boiler dynamic heat exchange model, and calculating the density of working medium in each heat exchange unit at a next step length by using mass conservation of the boiler dynamic heat exchange model;

[0169] S404: setting a qualitative temperature of working medium in each heat exchange unit as a temperature of inlet working medium, and calculating property parameters of working medium in each heat exchange unit by using a preselected property database; and calculating the temperature, pressure and flow of working medium in each heat exchange unit at the next step length by using the boiler dynamic heat exchange model according to the property parameters, to obtain state parameters;

[0170] S405: calculating an average temperature of working medium in each heat exchange unit according to the state parameters; if a difference between the average temperature of working medium and the qualitative temperature is greater than an allowable error, updating the qualitative temperature, and repeating steps S404-S405 until the difference between the average temperature of working medium and the qualitative temperature is not greater than the allowable error;

[0171] S406: adding a current step length to the current time, updating the state quantity initial values according to the state parameters, and jumping to step S402;

[0172] S407: obtaining a first influence factor according to the state parameters and the opening of the main steam valve at each time in the preset simulation time length.

[0173] According to the application, a main steam valve and heat supply combined frequency modulation device is provided, and the second influence factor is calculated based on a steam turbine volume effect model of the low-pressure cylinder cut-off type thermal power unit, and specifically includes the following steps:

[0174] Acquiring a linear relationship between the opening of the heat supply butterfly valve and the extraction flow;

[0175] Inputting the linear relationship into a preconstructed steam turbine volume effect model to obtain a second influence factor.

[0176] The application provides a main steam valve and heat supply combined frequency modulation device, wherein the model parameters include a heat transfer rate and a working medium flow resistance coefficient.

[0177] Correspondingly, the obtaining of the predetermined model parameters and state quantity initial values specifically comprises the following steps.

[0178] S601: obtaining a boiler steady-state model according to the boiler dynamic heat exchange model, and obtaining boiler structure parameters, measured data and a number of heat exchange units;

[0179] S602: setting initial values of the heat transfer rate and the working medium flow resistance coefficient, and setting i=1;

[0180] S603: obtaining a working medium inlet temperature of an i-th heat exchange unit according to the measured data, and setting a qualitative temperature of the i-th heat exchange unit as the working medium inlet temperature;

[0181] S604: calculating the density and specific heat capacity of the working medium by using a preselected property database, and calculating state parameters of working medium of an i+1-th heat exchange unit according to the boiler steady-state model;

[0182] S605: calculating an average temperature of working medium of the i-th heat exchange unit according to the state parameters of working medium of the i+1-th heat exchange unit, and updating the qualitative temperature and repeating step S604 until a difference between the average temperature and the qualitative temperature is less than an allowable error in the case that the difference is greater than the allowable error;

[0183] S606: setting i=i+1; jumping to step S603 in the case that i is less than the number of heat exchange units; and jumping to step S607 in the case that i is not less than the number of heat exchange units;

[0184] S607: calculating a first difference between a temperature of working medium of a current heat exchange unit and a main steam temperature in the measured data, and calculating a second difference between a pressure of working medium of the current heat exchange unit and a pressure in the measured data; setting i=1 and repeating steps S603-S607 until the first difference and the second difference are less than an allowable error in the case that the first difference and / or the second difference is greater than the allowable error;

[0185] S608: outputting the heat transfer rate and the working medium flow resistance coefficient as model parameters, and outputting the state parameters of the heat exchange units as state quantity initial values.

[0186] The main steam valve and heat supply combined frequency modulation device provided by the application is applied to a low-pressure cylinder cut-off type thermal power unit, and the method obtains a power expected increment instruction of the thermal power unit in response to a grid frequency difference exceeding a dead zone; according to a first influence factor and a second influence factor calculated in advance, the power expected increment instruction of the thermal power unit is distributed to a main steam valve and a heat supply butterfly valve according to a priority order set in advance, so as to obtain a main steam valve opening degree adjustment amount and a heat supply butterfly valve opening degree adjustment amount; the first influence factor is an influence of the opening degree of the main steam valve on the power increment, and the second influence factor is an influence of the opening degree of the heat supply butterfly valve on the power increment; the main steam valve and the heat supply butterfly valve are adjusted according to the main steam valve opening degree adjustment amount and the heat supply butterfly valve opening degree adjustment amount, so as to obtain a frequency modulation result. The application utilizes the heat supply butterfly valve to enable the heat storage of the heat supply system connected with steam extraction and heat supply to participate in frequency modulation, formulates a specific opening degree control strategy according to the influence of the opening degree of the main steam valve on the power increment and the influence of the opening degree of the heat supply butterfly valve on the power increment, realizes the combined frequency modulation of the main steam valve and the heat supply, improves the frequency modulation capability of the thermal power unit, and realizes the performance better thermal power unit frequency modulation of the reformed thermal power.

[0187] Fig. 9 shows an entity structure diagram of an electronic device, as shown in Fig. 9, the electronic device can include a processor 910, a communications interface 920, a memory 930 and a communications bus 940, wherein the processor 910, the communications interface 920, the memory 930 complete mutual communication through the communications bus 940. The processor 910 can call the logic instruction in the memory 930 to execute the main steam valve and heat supply combined frequency modulation method, the method includes: in response to a grid frequency difference exceeding a dead zone, obtaining a power expected increment instruction of a thermal power unit; according to a first influence factor and a second influence factor calculated in advance, the power expected increment instruction of the thermal power unit is distributed to a main steam valve and a heat supply butterfly valve according to a priority order set in advance, so as to obtain a main steam valve opening degree adjustment amount and a heat supply butterfly valve opening degree adjustment amount; the first influence factor is an influence of the opening degree of the main steam valve on the power increment, and the second influence factor is an influence of the opening degree of the heat supply butterfly valve on the power increment; the main steam valve and the heat supply butterfly valve are adjusted according to the main steam valve opening degree adjustment amount and the heat supply butterfly valve opening degree adjustment amount, so as to obtain a frequency modulation result.

[0188] Further, the logic instructions in the memory 930 described above can be implemented in the form of software functional units and sold or used as standalone products, which can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the parts that contribute to the prior art or the parts of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk, and various media that can store program codes.

[0189] In another aspect, the present application also provides a computer program product, which comprises a computer program, the computer program can be stored on a non-transitory computer readable storage medium, and the computer program can be executed by a processor to enable a computer to perform the main steam valve and heat supply combined frequency modulation method provided by the above-mentioned methods. The method comprises: in response to the power grid frequency difference exceeding a dead zone, obtaining a power expected increment instruction of a thermal power generating unit; according to a first influence factor and a second influence factor calculated in advance, the power expected increment instruction of the thermal power generating unit is distributed to a main steam valve and a heat supply butterfly valve according to a priority order set in advance, to obtain a main steam valve opening degree adjustment amount and a heat supply butterfly valve opening degree adjustment amount; wherein the first influence factor is the influence of the opening degree of the main steam valve on the power increment, and the second influence factor is the influence of the opening degree of the heat supply butterfly valve on the power increment; and the main steam valve and the heat supply butterfly valve are adjusted according to the main steam valve opening degree adjustment amount and the heat supply butterfly valve opening degree adjustment amount, to obtain a frequency modulation result.

[0190] In another aspect, the present application also provides a non-transitory computer readable storage medium, which stores a computer program. The computer program is executed by a processor to implement the main steam valve and heat supply combined frequency modulation method provided by the above-mentioned methods. The method comprises: in response to the power grid frequency difference exceeding a dead zone, obtaining a power expected increment instruction of a thermal power generating unit; according to a first influence factor and a second influence factor calculated in advance, the power expected increment instruction of the thermal power generating unit is distributed to a main steam valve and a heat supply butterfly valve according to a priority order set in advance, to obtain a main steam valve opening degree adjustment amount and a heat supply butterfly valve opening degree adjustment amount; wherein the first influence factor is the influence of the opening degree of the main steam valve on the power increment, and the second influence factor is the influence of the opening degree of the heat supply butterfly valve on the power increment; and the main steam valve and the heat supply butterfly valve are adjusted according to the main steam valve opening degree adjustment amount and the heat supply butterfly valve opening degree adjustment amount, to obtain a frequency modulation result.

[0191] The apparatus embodiments described above are merely illustrative, wherein the units described as separate components can or can not be physically separate, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed to multiple network units. Part or all of the modules can be selected to achieve the purposes of the embodiments according to actual needs. Those skilled in the art can understand and implement without creative labor.

[0192] Through the description of the above embodiments, those skilled in the art can clearly understand that the embodiments can be realized by means of software plus necessary universal hardware platforms, and of course can also be realized by hardware. Based on such understanding, the above technical solutions can be embodied in the form of software products, and the computer software products can be stored in a computer readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and include a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the methods described in each embodiment or some parts of the embodiments.

[0193] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

A main steam valve and heat supply combined frequency modulation method is applied to a low-pressure cylinder cut-off type thermal power generating unit, characterized in that, The method comprises the steps of: in response to the power difference of the power grid exceeding a dead zone, obtaining a power expected increment instruction of a thermal power unit; according to a first influence factor and a second influence factor calculated in advance, distributing the power expected increment instruction to a main steam valve and a heating butterfly valve according to a preset priority order to obtain a main steam valve opening degree adjustment amount and a heating butterfly valve opening degree adjustment amount, wherein the first influence factor is an influence of the opening degree of the main steam valve on the power increment, and the second influence factor is an influence of the opening degree of the heating butterfly valve on the power increment; adjusting the main steam valve and the heating butterfly valve according to the main steam valve opening degree adjustment amount and the heating butterfly valve opening degree adjustment amount to obtain a frequency modulation result. The method according to claim 1, wherein The first influence factor is calculated based on a boiler dynamic heat exchange model of the low-pressure cylinder cut-off type thermal power unit, and the second influence factor is calculated based on a steam turbine volume effect model of the low-pressure cylinder cut-off type thermal power unit; and the priority order is the main steam valve first and the heating butterfly valve second. The method according to claim 2, wherein The boiler dynamic heat exchange model is constructed by the steps of: dividing the boiler of the low-pressure cylinder cut-off type thermal power unit into multiple heat exchange units along the flow direction of the working medium, and for each heat exchange unit, obtaining a steam-water working medium heat balance equation and a pipe wall metal heat balance equation according to the law of conservation of energy; obtaining a temperature expression of the working medium at the outlet of the heat exchange unit according to the steam-water working medium heat balance equation, and further obtaining an average temperature expression of the working medium along the length of the heat exchange unit; and obtaining a metal wall temperature expression according to the pipe wall metal heat balance equation and the average temperature expression; obtaining a heat exchange unit dynamic heat exchange model of each heat exchange unit according to the metal wall temperature expression and the average temperature expression; obtaining a working medium flow process equation according to the mass conservation and momentum conservation equations; obtaining the boiler dynamic heat exchange model by connecting the heat exchange unit dynamic heat exchange models in series according to the delay effect caused by the heat capacity of the fluid and the working medium flow process equation. The method according to claim 3, characterized in that, The first influence factor is calculated based on the boiler dynamic heat exchange model of the low-pressure cylinder cut-off type thermal power unit, and specifically includes the steps of: S401: obtaining predetermined model parameters and state quantity initial values; wherein the state quantity initial values include the temperature, pressure, density and metal wall temperature of the working medium in each heat exchange unit; S402: obtaining the opening degree of the main steam valve at the current time, and jumping to step S403 if the current time is less than a preset simulation time length, or jumping to step S407 if the current time is equal to the preset simulation time length; S403: inputting the model parameters and the state quantity initial values into the boiler dynamic heat exchange model, and calculating the density of the working medium in each heat exchange unit at the next step length by using the mass conservation calculation of the boiler dynamic heat exchange model; S404: setting the qualitative temperature of the working medium in each heat exchange unit as the temperature of the inlet working medium, and calculating the property parameters of the working medium in each heat exchange unit by using a pre-selected property database; and calculating the temperature, pressure and flow of the working medium in each heat exchange unit at the next step length by using the boiler dynamic heat exchange model according to the property parameters to obtain state parameters; S405: calculating the average temperature of the working medium of each section heat exchange unit according to the state parameters, updating the qualitative temperature in the case that the difference between the average temperature of the working medium and the qualitative temperature is greater than the allowable error, repeating steps S404-S405 until the difference between the average temperature of the working medium and the qualitative temperature is not greater than the allowable error; S406: adding the current time by the current step, updating the state quantity initial value according to the state parameters, and jumping to step S402; S407: obtaining a first influence factor according to the state parameters of each time in the preset simulation time length and the opening of the main steam valve. The method according to claim 2, wherein The second influence factor is calculated based on a steam turbine volume effect model of the low-pressure cylinder cut-off type thermal power generating unit, and specifically includes: obtaining a linear relationship between the opening of the heating butterfly valve and the steam extraction flow rate; inputting the linear relationship into a pre-constructed steam turbine volume effect model to obtain a second influence factor. The model parameters include a heat transfer rate and a working medium flow resistance coefficient; The method according to claim 4, wherein Correspondingly, the pre-determined model parameters and state quantity initial values are obtained, specifically including: S601: obtaining a boiler steady-state model according to the boiler dynamic heat exchange model, and obtaining boiler structure parameters, measured data and heat exchange unit numbers; S602: setting initial values of the heat transfer rate and the working medium flow resistance coefficient, and letting i = 1; S603: obtaining the working medium inlet temperature of the i-th section heat exchange unit according to the measured data, and setting the qualitative temperature of the i-th section heat exchange unit as the working medium inlet temperature; S604: calculating the density and specific heat capacity of the working medium by using a pre-selected property database, and calculating the state parameters of the working medium of the i+1-th section heat exchange unit according to the boiler steady-state model; S605: calculating the average temperature of the working medium of the i-th section heat exchange unit according to the state parameters of the working medium of the i+1-th section heat exchange unit, updating the qualitative temperature in the case that the difference between the average temperature and the qualitative temperature is greater than the allowable error, and repeating step S604 until the difference is less than the allowable error; S606: letting i = i+1; jumping to step S603 in the case that i is less than the heat exchange unit numbers; and jumping to step S607 in the case that i is not less than the heat exchange unit numbers; S607: calculating a first difference between the temperature of the working medium of the current section heat exchange unit and the main steam temperature in the measured data, and calculating a second difference between the pressure of the working medium of the current section heat exchange unit and the pressure in the measured data; letting i = 1 in the case that the first difference and / or the second difference is greater than the allowable error, and repeating steps S603-S607 until the first difference and the second difference is less than the allowable error; S608: outputting the heat transfer rate and the working medium flow resistance coefficient as model parameters, and outputting the state parameters of the heat exchange units as state quantity initial values. The instruction unit is configured to, in response to the grid frequency difference exceeding the dead zone, obtain a power expected increment instruction of the thermal power generating unit. A main steam valve and heat supply combined frequency modulation device is applied to a low-pressure cylinder cut-off type thermal power generating unit, and is characterized in that, ​ ​ The opening degree unit is configured to distribute the power expected increment instruction of the thermal power unit to the main steam valve and the heating butterfly valve according to a preset priority order according to the first influence factor and the second influence factor, so as to obtain a main steam valve opening degree adjustment amount and a heating butterfly valve opening degree adjustment amount; wherein the first influence factor is an influence of the opening degree of the main steam valve on the power increment, and the second influence factor is an influence of the opening degree of the heating butterfly valve on the power increment. The control unit is configured to adjust the main steam valve and the heating butterfly valve according to the main steam valve opening degree adjustment amount and the heating butterfly valve opening degree adjustment amount, so as to obtain a frequency modulation result. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the program to realize the method for jointly modulating the frequency of the main steam valve and the heating according to any one of claims 1 to 6. A non-transitory computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the method for jointly modulating the frequency of the main steam valve and the heating according to any one of claims 1 to 6. A computer program product comprising a computer program, characterized in that The computer program is executed by the processor to realize the method for jointly modulating the frequency of the main steam valve and the heating according to any one of claims 1 to 6.

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