Dual-extraction heating unit deep peak regulation system and deep peak regulation method

Abstract

The present application relates to power generation control technical field, specifically relates to a kind of double-extraction heating unit depth peak regulation system and depth peak regulation method, peak regulation system includes steam source extraction pipe network, variable cross-section ejection device, hot flow stabilizing buffer device and control system;Peak regulation method includes obtaining operation data, calculating target cross-section, dynamic cross-section adjustment and hot flow collaborative stabilizing;The present application realizes the physical peak shaving and valley filling to high-frequency transient pressure disturbance by stabilizing buffer device;By collecting the feedforward prediction signal of power grid and heat network and combining current thermal state, target flow area is outputted in advance, realizes valve front drive, eliminates the phase lag and system oscillation caused by traditional fixed pressure difference control.

Description

Technical Field

[0001] This invention relates to the field of power generation control technology, specifically to a deep peak shaving system and method for a dual-extraction heating unit. Background Technology

[0002] For dual-extraction heating units, when the power grid is in a low-load phase, the unit needs to reduce its power generation output. However, at the same time, the heating demand on the heating network side often remains at a high level or is in a rigid demand state. As a result, the unit generally faces the bottleneck of limited steam extraction capacity for heating under medium and low load conditions, which restricts the lower limit of deep peak-shaving load for cogeneration units.

[0003] To overcome the limitations of thermoelectric coupling, the current common technical approach in the industry is to introduce regulating valves (commonly known as intermediate regulating valves) in the low-pressure connecting pipes of the steam turbine to participate in heating regulation. The basic operating logic is as follows: when the unit is operating at low load, the opening of the intermediate regulating valve is reduced to physically throttle the steam entering the low-pressure cylinder, thereby forcing more steam to flow into the heating extraction network to meet heating demand.

[0004] First, inefficient regulation of the intermediate control valve can lead to insufficient adjustment precision, affecting heating stability. Second, it increases energy loss and reduces the unit's economic efficiency. Intermediate control valve regulation essentially adjusts the steam supply through throttling, which results in significant throttling losses and a decrease in the unit's thermal efficiency. Finally, it exacerbates wear and tear on the intermediate control valve and related equipment, affecting the unit's service life.

[0005] During the heating process, the intermediate control valve needs to frequently adjust its opening according to the load and heating demand. The wear and erosion between the valve core and valve seat will be significantly aggravated. The actuator of the intermediate control valve will also have an increased probability of failure due to frequent operation, such as overheating of the servo motor and jamming of the actuator, which increases the risk of unplanned shutdown of the unit. Summary of the Invention

[0006] In order to solve the above-mentioned technical problems, the present invention provides a deep peak shaving system and method for a dual-extraction heating unit, which breaks the rigid constraint of thermoelectric coupling on the unit and solves the problems of pressure fluctuations and component wear in the heating network caused by load changes.

[0007] This invention is achieved through the following technical solution:

[0008] A deep peak-shaving system for a dual-extraction heating unit includes:

[0009] The steam source extraction pipeline network is connected to the extraction or exhaust ports of each stage of the steam turbine unit to obtain the driving steam source and the ejected steam source.

[0010] The variable cross-section ejector device has a high-pressure steam inlet connected to the driving steam source, a low-pressure steam inlet connected to the ejected steam source, and an exhaust end connected to the heating network; the variable cross-section ejector device is equipped with a cross-section adjustment mechanism inside, which is used to dynamically change the flow cross-sectional area of ​​the working nozzle.

[0011] A heat flow stabilizing buffer device is installed on the connecting pipeline between the ejected steam source and the low-pressure steam inlet end of the variable cross-section ejector device, and is used to absorb or release steam flow during unit operating conditions to smooth out pressure fluctuations on the steam inlet side.

[0012] The control system is communicatively connected to the cross-section adjustment mechanism of the variable cross-section ejector and the unit's operating parameter acquisition terminal, respectively, and is used to send dynamic adjustment commands to the cross-section adjustment mechanism based on the unit's real-time operating parameters and peak-shaving commands.

[0013] Optionally, the variable cross-section ejector device includes a first variable cross-section ejector and a second variable cross-section ejector;

[0014] The high-pressure steam inlet of the first variable cross-section ejector is connected to the hot reheat steam pipeline of the unit, its low-pressure steam inlet is connected to the medium-pressure cylinder exhaust pipeline, and its exhaust end is connected to the medium-pressure steam supply manifold.

[0015] The high-pressure steam inlet of the second variable cross section ejector is connected to the exhaust pipe of the first variable cross section ejector or the exhaust pipe of the intermediate pressure cylinder, its low-pressure steam inlet is connected to the low-pressure cylinder steam inlet or the low-pressure steam supply manifold, and its exhaust is connected to the low-pressure steam supply manifold.

[0016] Optionally, the cross-section adjustment mechanism includes: a servo drive actuator, a transmission link, and a needle-type throttle valve; the servo drive actuator is disposed outside the variable cross-section ejector and is communicatively connected to the control system; one end of the transmission link is connected to the power output end of the servo drive actuator; the other end of the transmission link is dynamically sealed and inserted into the interior of the variable cross-section ejector; the needle-type throttle valve is installed at the end of the transmission link and is coaxially and concentrically arranged with the working nozzle of the variable cross-section ejector.

[0017] The servo drive actuator drives the needle valve to reciprocate axially to continuously change the effective flow cross-sectional area of ​​the throat of the working nozzle;

[0018] The heat flow stabilizing buffer device is a phase change steam heat storage buffer tank; the phase change steam heat storage buffer tank is equipped with a gas-liquid separation component and a phase change heat storage medium.

[0019] When the actual pressure at the low-pressure steam inlet is higher than the set buffer pressure, the buffer tank absorbs and condenses part of the steam to store thermal energy; when the actual pressure is lower than the set buffer pressure, the phase change heat storage medium releases heat to cause the internal condensate to flash into steam for replenishment.

[0020] Optionally, the steam source extraction pipeline network further includes multiple regulating valves, specifically including:

[0021] The ejector inlet valve assembly includes a high-pressure side high-pressure inlet valve and a high-pressure side low-pressure inlet valve respectively disposed at the high-pressure and low-pressure inlet ends of the first variable cross-section ejector, and a low-pressure side high-pressure inlet valve and a low-pressure side low-pressure inlet valve respectively disposed at the high-pressure and low-pressure inlet ends of the second variable cross-section ejector.

[0022] The bypass direct-connect valve assembly includes an intermediate-pressure cylinder exhaust steam to low-pressure steam supply header inlet valve installed on the direct-connection pipeline from the intermediate-pressure cylinder exhaust steam pipeline to the low-pressure steam supply header, and a hot reheat steam to intermediate-pressure steam supply header inlet valve installed on the direct-connection pipeline from the hot reheat steam pipeline to the intermediate-pressure steam supply header.

[0023] The medium- and low-pressure connecting pipe valve is installed on the connecting pipe from the medium-pressure cylinder exhaust to the low-pressure cylinder inlet;

[0024] The control system is electrically connected to each regulating valve to coordinate the start, stop and opening degree of each valve, and switches to the deep adjustment load mode of direct connection of bypass valve when the system exceeds the adjustment range of the variable cross section ejector device.

[0025] A deep peak-shaving method for a dual-extraction heating unit, applied to the deep peak-shaving system of the dual-extraction heating unit as described above, the method comprising the following steps:

[0026] Acquire operational data: Obtain real-time thermal operating parameters and variable load peak-shaving commands from the unit;

[0027] Calculate the target cross-section: Based on the acquired thermodynamic operating parameters and the variable load peak shaving command, determine the target flow cross-sectional area required by the variable cross-section ejector device during the variable operating condition process;

[0028] Dynamic cross-section adjustment: The control system sends a dynamic adjustment command to the cross-section adjustment mechanism to change the flow cross-sectional area of ​​the working nozzle to the target flow cross-sectional area, dynamically matching the parameter changes of the ejector steam source and the driving steam source;

[0029] Heat flow synergistic pressure stabilization: During peak shaving and variable operating conditions of the unit, the heat flow pressure stabilization buffer device is used to spontaneously absorb or supplement steam flow to smooth out pressure fluctuations on the steam inlet side of the variable cross-section ejector device.

[0030] Optionally, the thermal operating parameters include the load change rate signal of the grid automatic generation control command and the heating demand prediction signal on the heating network side;

[0031] The specific steps for calculating the target cross section include:

[0032] Construct a feedforward prediction optimization model and, in conjunction with the current unit thermodynamic operating parameters, predict the optimal ejector coefficient of the unit under the target operating conditions.

[0033] Based on the optimal ejection coefficient, the effective flow cross-sectional area of ​​the working nozzle target throat required to maintain this state is calculated. ;

[0034] Specifically, before the actual exhaust steam pressure difference of the unit changes to a preset passive trigger threshold, the control system determines the effective flow cross-sectional area of ​​the target throat of the working nozzle. An adjustment command is sent to the cross-section adjustment mechanism in advance.

[0035] Optionally, the steps for solving the effective flow cross-sectional area after constructing the feedforward prediction optimization model specifically include:

[0036] Step S11: Based on the current unit thermal operating parameters, the load change rate signal, and the heating demand prediction signal, a state-space sliding window prediction model is used to predict the thermodynamic boundary conditions of the unit under future target operating conditions.

[0037] The thermodynamic boundary conditions include: the absolute temperature of the driving steam under predicted operating conditions. With absolute pressure Predicting the absolute pressure on the inlet side of the ejected steam under operating conditions. The target mixed steam mass flow rate required for the heating network ;

[0038] Step S12: Based on one-dimensional gas dynamics and non-equilibrium thermodynamics theory, establish the optimal entrainment coefficient solution equation and calculate the optimal entrainment coefficient under this target operating condition. The solution equation is: ,in: For dynamic operating conditions, adaptive compensation coefficients are used. , , These are the velocity coefficients of the working nozzle, receiving chamber, mixing chamber, and diffuser in the variable cross-section ejector device, respectively. To predict the enthalpy drop of isentropic expansion of driving steam within the working nozzle under operating conditions; To predict the isentropic expansion enthalpy drop of the ejected steam in the receiving chamber under operating conditions; To predict the isentropic compression enthalpy rise of the mixed steam in the diffuser under operating conditions;

[0039] Step S13: Based on the critical flow characteristics of gas, and incorporating the transient buffering effect of the heat flow stabilizing buffer device as a feedforward compensation term for mass flow rate, establish the cross-sectional area solution equation and solve for the effective flow cross-sectional area of ​​the target throat of the working nozzle. The equation for calculating the cross-sectional area is: ,in: This represents the required mass flow rate of the driving steam base under steady-state conditions. To predict the compressibility factor of the driving steam under operating conditions; is the universal gas constant for steam; The flow rate discharge coefficient of the working nozzle; The isentropic exponent for driving steam; This represents the absolute pressure of the injected steam on the inlet side at the current moment. This is the transient mass flow coupling coefficient of the voltage stabilizing buffer device.

[0040] Optionally, the method further includes a cooperative control step based on maximizing the exergy efficiency of the entire system:

[0041] Establish a real-time pyroefficiency model for the system and obtain the real-time main steam pressure, intermediate pressure cylinder exhaust temperature and low pressure cylinder inlet pressure as model input parameters.

[0042] Based on the real-time exergy efficiency model of the system, and under the constraint of satisfying the minimum allowable steam inlet pressure limit of the low-pressure cylinder, the optimal opening change rate of the regulating valve in the medium and low-pressure connecting pipe is solved. ;

[0043] With the optimal rate of change of opening The system drives the regulating valve of the medium and low pressure connecting pipe to operate, and coordinates the opening and closing of the bypass direct-connection valve in the system to minimize the overall thermodynamic work capacity loss of the system under deep peak shaving and variable operating conditions.

[0044] Optionally, the steps of establishing a real-time pyroefficiency model for the system and controlling the valves specifically include:

[0045] Step S21: Obtain the real-time ambient reference temperature. Compared with environmental benchmark pressure ;

[0046] Based on the real-time collected main steam pressure, intermediate pressure cylinder exhaust temperature, and low pressure cylinder inlet pressure, the real-time specific refractory force of each key node in the system is calculated. : ;

[0047] And establish a transient total firepower loss rate model for the entire system: ;

[0048] in, For the first Real-time fire comparison of each node; and These are the real-time specific enthalpy and specific entropy of the steam at this node, respectively; and These are the fundamental specific enthalpy and specific entropy of water under environmental baseline conditions, respectively. The total transient fire loss rate of the entire system; and The system number Mass flow rate and specific fire rate at each input boundary; and The system number Mass flow rate and specific firepower at each output boundary; This represents the current real-time power output of the steam turbine unit.

[0049] Step S22, set the minimum allowable steam inlet pressure limit for the low-pressure cylinder. As a hard constraint, the transient total firepower loss rate of the entire system is used as the basis. Minimize the objective function, and find the optimal rate of change of opening that results in the fastest gradient descent of the objective function. : , ;in, This refers to the real-time steam inlet pressure of the low-pressure cylinder. To predict the control time step;

[0050] Step S23: Calculate in real time the marginal emissivity of steam passing through the variable cross-section ejector device under the current variable operating conditions, and the expected marginal emissivity of steam directly throttling and depressurizing through the bypass direct-connect valve.

[0051] When the unit's deep peak shaving demand exceeds the economic ejection range of the variable cross section ejector device, resulting in the marginal fire loss rate of the ejection process being greater than the expected marginal fire loss rate, the control system issues a coordinated switching command.

[0052] Using the optimal opening change rate Continue to adjust the regulating valve of the medium and low pressure connecting pipe, and at the same time open the intake valve of the medium pressure cylinder exhaust steam to the low pressure steam supply manifold or the hot reheat steam to the medium pressure steam supply manifold, so as to reduce the overload fire loss of the variable cross section ejector device by bypass diversion.

[0053] Furthermore, the control system incorporates dual-mode switching logic; when the system operation encounters preset boundary conditions or the algorithm optimization fails, the control system automatically switches to a degraded deep-load adjustment mode; the deep-load adjustment mode includes a first deep-load adjustment unit and a second deep-load adjustment unit, and the specific control method is as follows:

[0054] Control method of the first deep adjustment unit during load reduction: If the difference between the reheat pressure and the target steam supply pressure of the intermediate pressure steam supply header is... When the first preset pressure difference value is reached, open the high-pressure steam inlet valve and the low-pressure steam inlet valve of the high-pressure side variable cross section ejector device, and close the steam inlet valve of the heat reheat to medium-pressure steam supply manifold.

[0055] Control method of the second deep adjustment unit during load reduction: If the difference between the intermediate pressure cylinder exhaust pressure and the target steam supply pressure of the low pressure steam supply header is... When the second preset pressure difference value is reached, open the high-pressure steam inlet valve and the low-pressure steam inlet valve of the variable cross section ejector device on the low-pressure side, and close the steam inlet valve of the intermediate pressure cylinder exhaust to the low-pressure steam supply manifold.

[0056] Control method of the second deep adjustment unit during load increase: If the difference between the intermediate pressure cylinder exhaust pressure and the target steam supply pressure of the low pressure steam supply header is... When the third preset pressure difference value is reached, open the air inlet valve of the medium-pressure cylinder exhaust steam to the low-pressure steam supply manifold, and close the high-pressure steam inlet valve and the low-pressure steam inlet valve of the low-pressure side variable cross section ejector device.

[0057] Control method of the first deep adjustment unit during load increase: If the difference between the reheat pressure and the target steam supply pressure of the intermediate pressure steam supply header is... When the fourth preset pressure difference value is reached, open the inlet valve of the hot reheat to medium pressure steam supply manifold and close the high pressure steam inlet valve and low pressure steam inlet valve of the high pressure side variable cross section ejector device.

[0058] The downgrade support mode also includes a control method for the medium and low pressure connecting pipe valves: when the difference between the medium pressure cylinder exhaust pressure and the target steam supply pressure of the low pressure steam supply manifold... When the fifth preset differential pressure value is reached, the medium and low pressure connecting pipe valve will gradually close at the first preset closing rate; if the opening degree of the medium and low pressure connecting pipe valve is... Minimum allowable opening value, or low-pressure cylinder inlet pressure Minimum allowable inlet steam pressure, or the difference between the intermediate pressure cylinder exhaust pressure and the target steam supply pressure of the low-pressure steam supply header. When the fifth preset differential pressure value is reached, the medium and low pressure connecting pipe valve stops closing and maintains its current opening.

[0059] Compared with the prior art, the present invention has the following features and beneficial effects:

[0060] This invention connects a variable cross-section ejector device in series between the steam source extraction network and the heating network, and arranges a heat flow stabilizing buffer device. Then, the effective flow cross-sectional area of ​​the variable cross-section ejector device is calculated through a predictive model and servo drive is implemented in advance. At the same time, an exergy efficiency model is established to solve the optimal opening change rate of the regulating valve in the medium and low pressure connecting pipe.

[0061] This invention achieves physical peak shaving and valley filling for high-frequency transient pressure disturbances through a pressure stabilizing buffer device; by collecting feedforward prediction signals from the power grid and heating network and combining them with the current thermal state to output the target flow cross-sectional area in advance, it realizes valve pre-drive, eliminating the phase hysteresis and system oscillation caused by traditional fixed differential pressure control; by solving for the optimal action rate of the connecting pipe valves, it realizes the identification of the actual work capacity loss under different steam distribution paths, and optimizes the overall energy efficiency of the unit in the ultra-low load range. Attached Figure Description

[0062] The accompanying drawings illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, but do not constitute a limitation on the embodiments of the present invention.

[0063] Figure 1 This is a schematic diagram of the topology of a deep peak-shaving system for a dual-extraction heating unit according to the present invention.

[0064] Figure 2 This is a schematic diagram of a deep peak shaving process for a dual-extraction heating unit according to the present invention. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0066] It should also be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0067] Where there is no conflict, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0068] Dual-extraction heating unit: refers to a steam turbine generator unit with two main steam extraction ports, used to provide heat energy at different pressure levels to the outside world.

[0069] Deep peak shaving: refers to the operating condition in which a generator set reduces its own power output to an extremely low level when responding to a low load on the power grid.

[0070] Driving steam source and ejected steam source: The driving steam source usually has high pressure and internal kinetic energy, which is used to form a high-speed jet inside the ejector device, thereby drawing in the lower-pressure "ejected steam source" and mixing them to do work.

[0071] Example 1

[0072] This embodiment provides a deep peak-shaving system for a dual-extraction heating unit. It extracts steam with different parameters from the turbine unit through a pipeline network, uses a core ejector device to mix and pressurize the steam, and installs a buffer device in the low-pressure steam supply path to smooth out instantaneous pressure fluctuations in the system. The system mainly includes the following mutually cooperating equipment modules:

[0073] The steam source extraction pipeline network is connected to the extraction or exhaust ports of the steam turbine unit at each stage to obtain the driving steam source and the ejected steam source. As the fluid transport foundation of the system, the steam source extraction pipeline network is physically connected to the extraction or exhaust ports of the steam turbine unit at each stage to obtain high-pressure steam inside the unit as the driving steam source and to intercept low-pressure steam as the ejected steam source.

[0074] The variable cross-section ejector device has a high-pressure steam inlet end connected to the driving steam source and a low-pressure steam inlet end connected to the ejected steam source. The mixed and pressurized steam is finally connected to the heating network through the exhaust end. The variable cross-section ejector device is equipped with a cross-section adjustment mechanism to dynamically change the flow cross-sectional area of ​​the working nozzle.

[0075] A heat flow stabilizing buffer device is installed on the connecting pipeline between the ejected steam source and the low-pressure steam inlet end of the variable cross-section ejector device. It is used to absorb or release steam flow during unit operating conditions to smooth out pressure fluctuations on the steam inlet side. The buffer device acts as a thermodynamic "reservoir" that can absorb part of the steam flow when the steam inlet side pressure is too high and release the steam flow when the pressure is too low.

[0076] The control system is communicatively connected to the cross-section adjustment mechanism of the variable cross-section ejector and the unit's operating parameter acquisition terminal, respectively, and is used to send dynamic adjustment commands to the cross-section adjustment mechanism based on the unit's real-time operating parameters and peak-shaving commands.

[0077] Example 2

[0078] This embodiment provides a detailed description of some of the structures based on Embodiment 1.

[0079] The variable cross-section ejector device includes a first variable cross-section ejector and a second variable cross-section ejector;

[0080] The high-pressure steam inlet of the first variable cross-section ejector is connected to the unit's hot reheat steam pipeline, its low-pressure steam inlet is connected to the intermediate-pressure cylinder exhaust pipeline, and its exhaust end is connected to the intermediate-pressure steam supply header. The first variable cross-section ejector is mainly responsible for the cascade utilization of high-grade thermal energy. Its high-pressure steam inlet extracts high-grade hot reheat steam from the unit as the driving steam source, and its low-pressure steam inlet extracts the intermediate-pressure cylinder exhaust steam as the ejected steam source. The two are mixed to do work and then delivered to the intermediate-pressure steam supply header.

[0081] The high-pressure steam inlet of the second variable cross-section ejector is connected to the exhaust pipe of the first variable cross-section ejector or the exhaust pipe of the intermediate-pressure cylinder. Its low-pressure steam inlet is connected to the low-pressure cylinder inlet pipe or the low-pressure steam supply header, and its exhaust is connected to the low-pressure steam supply header. The second variable cross-section ejector is mainly responsible for the recovery and utilization of low-grade thermal energy. Its high-pressure steam inlet flexibly connects to the exhaust of the first ejector or the exhaust of the intermediate-pressure cylinder, while its low-pressure steam inlet draws low-pressure steam from the low-pressure cylinder inlet or the low-pressure steam supply header, mixes and pressurizes it, and then sends it to the low-pressure steam supply header.

[0082] In this embodiment, the steam source extraction pipeline network is a collection of pipelines that are jointly modified from the existing hot reheat steam pipeline, intermediate pressure cylinder exhaust pipeline, and low pressure cylinder inlet pipeline of the unit.

[0083] For the first variable cross section ejector, the required driving steam source is high-temperature and high-pressure steam from the hot reheat steam pipeline; the required ejected steam source is low-pressure steam from the intermediate-pressure cylinder exhaust pipeline.

[0084] For the second variable cross section ejector, the required driving steam source is medium-pressure steam from the medium-pressure cylinder exhaust pipe; the required ejected steam source is low-pressure steam from the low-pressure cylinder inlet pipe.

[0085] This embodiment provides a specific cross-section adjustment mechanism, including: a servo drive actuator, a transmission link, and a needle-type throttle valve; the servo drive actuator is disposed outside the variable cross-section ejector and is communicatively connected to the control system; one end of the transmission link is connected to the power output end of the servo drive actuator, and the other end of the transmission link is dynamically sealed and inserted into the interior of the variable cross-section ejector; the needle-type throttle valve is installed at the end of the transmission link and is coaxially and concentrically arranged with the working nozzle of the variable cross-section ejector; the servo drive actuator drives the needle-type throttle valve to reciprocate axially to continuously change the effective flow cross-sectional area of ​​the throat of the working nozzle.

[0086] While allowing mechanical movement of the connecting rod, it effectively prevents the leakage of high and low pressure steam from inside the device. A needle-type throttle valve is mounted at the end of the transmission connecting rod, arranged coaxially and concentrically with the working nozzle inside the ejector. During operation, the servo actuator drives the connecting rod to cause the needle valve to reciprocate axially. Due to the specific geometric cross-section of the needle valve, its forward and backward movement within the nozzle can continuously and smoothly change the effective flow area of ​​steam as it passes through the throat of the working nozzle.

[0087] The heat flow stabilizing buffer device is a phase change steam heat storage buffer tank; the phase change steam heat storage buffer tank is equipped with a gas-liquid separation component and a phase change heat storage medium, preferably demineralized water in a two-phase saturated state of gas and liquid; phase change heat storage refers to the storage and release of energy by utilizing the physical property of a substance to absorb or release a large amount of latent heat when it transforms between the gaseous and liquid states.

[0088] When the actual pressure at the low-pressure steam inlet is higher than the set buffer pressure, the buffer tank absorbs and condenses part of the steam to store thermal energy; when the actual pressure is lower than the set buffer pressure, the phase change heat storage medium releases heat to cause the internal condensate to flash into steam for replenishment.

[0089] In actual operation, when the pipeline pressure at the low-pressure steam inlet rises sharply due to changing operating conditions and exceeds the set buffer pressure, excess steam rushes into the buffer tank. The heat storage medium absorbs the latent heat of vaporization of the steam, causing it to condense into liquid water, thus converting excess pressure potential energy into stored heat energy. Conversely, when the actual pipeline pressure drops sharply and falls below the set buffer pressure, the heat storage medium rapidly releases the stored heat, causing the saturated condensate in the tank to undergo "flash evaporation." Flash evaporation is the thermodynamic process by which high-temperature liquid water instantly boils and vaporizes when it encounters a sudden drop in ambient pressure. The large amount of secondary steam generated is rapidly returned to the low-pressure steam inlet, effectively filling the pressure trough in the pipeline.

[0090] Example 3

[0091] The steam source extraction pipeline network also includes multiple regulating valves, specifically:

[0092] The ejector inlet valve assembly includes a high-pressure side high-pressure inlet valve and a high-pressure side low-pressure inlet valve respectively disposed at the high-pressure and low-pressure inlet ends of the first variable cross-section ejector, and a low-pressure side high-pressure inlet valve and a low-pressure side low-pressure inlet valve respectively disposed at the high-pressure and low-pressure inlet ends of the second variable cross-section ejector.

[0093] The bypass direct-connect valve assembly includes an intermediate-pressure cylinder exhaust steam to low-pressure steam supply header inlet valve installed on the direct-connection pipeline from the intermediate-pressure cylinder exhaust steam pipeline to the low-pressure steam supply header, and a hot reheat steam to intermediate-pressure steam supply header inlet valve installed on the direct-connection pipeline from the hot reheat steam pipeline to the intermediate-pressure steam supply header.

[0094] The medium- and low-pressure connecting pipe valve is installed on the connecting pipe from the medium-pressure cylinder exhaust to the low-pressure cylinder inlet;

[0095] The control system is electrically connected to each regulating valve to coordinate the start, stop and opening degree of each valve, and switches to the deep adjustment load mode of direct connection of bypass valve when the system exceeds the adjustment range of the variable cross section ejector device.

[0096] like Figure 1 As shown, this embodiment provides a specific example of a connection structure.

[0097] For the first variable cross section ejector 5 (medium-pressure heating circuit): a high-pressure side high-pressure steam inlet valve 7 is set at its high-pressure steam inlet end, which directly controls the high-pressure driving steam from boiler 1 (hot reheat steam flow direction); a high-pressure side low-pressure steam inlet valve 8 is set at its low-pressure steam inlet end, which receives the low-pressure ejected steam after passing through the phase change steam heat storage buffer tank.

[0098] For the second variable cross section ejector 6 (low-pressure heating circuit): a low-pressure side high-pressure steam inlet valve 9 is provided at its high-pressure steam inlet end, which is connected to the exhaust end of the intermediate-pressure cylinder 3; a low-pressure side low-pressure steam inlet valve 10 is provided at its low-pressure steam inlet end, which is led from the intermediate-low pressure connecting pipe valve 13 and passes through the pipeline of the phase change steam heat storage buffer tank.

[0099] When the system is within the normal depth peak shaving range, these steam inlet valve groups are in the open state, and the steam from each path smoothly flows into the first variable cross section ejector 5 and the second variable cross section ejector 6 for mixing and pressurization.

[0100] A reheat steam inlet valve to the medium-pressure steam supply header is installed on the direct bypass pipeline from the reheat steam from boiler 1 to the medium-pressure steam supply header.

[0101] An intake valve for the intermediate pressure cylinder exhaust to the low-pressure steam supply header is installed on the direct bypass pipeline from the exhaust of intermediate pressure cylinder 3 to the low-pressure steam supply header.

[0102] like Figure 1 As shown, the medium-low pressure connecting pipe valve 13 is connected in series on the main connecting pipe between the exhaust end of the medium-pressure cylinder 3 and the inlet end of the low-pressure cylinder 4. This valve directly controls the amount of steam in the main flow channel for the turbine unit to perform work. The size of its opening directly affects the back pressure level of the front exhaust pipe (i.e., the low-pressure / high-pressure steam source side of the ejector).

[0103] In actual operation, when the unit is in the economically adjustable range of the ejector device, the control system coordinates the opening of the low-pressure connecting pipe valve 13 and instructs each ejector inlet valve group to work; once the unit faces the extreme peak shaving command, the control system will quickly execute the mode switch - immediately instruct the corresponding ejector inlet valve to close and simultaneously open the corresponding bypass direct connection valve group.

[0104] Example 4

[0105] like Figure 2 As shown, a deep peak-shaving method for a dual-extraction heating unit is applied to the deep peak-shaving system of the dual-extraction heating unit described above. The method includes the following steps:

[0106] Acquire operational data: acquire the unit's thermal operating parameters and variable load peak shaving commands in real time; the thermal operating parameters include the load change rate signal of the grid automatic generation control command and the heating demand prediction signal on the heating network side.

[0107] Calculate the target cross-section: Based on the acquired thermodynamic operating parameters and the variable load peak shaving command, determine the target flow cross-sectional area required by the variable cross-section ejector device during the variable operating condition process.

[0108] Dynamic cross-section adjustment: The control system sends a dynamic adjustment command to the cross-section adjustment mechanism to change the flow cross-sectional area of ​​the working nozzle to the target flow cross-sectional area, dynamically matching the parameter changes of the ejector steam source and the driving steam source.

[0109] Heat-flow coordinated pressure stabilization: During peak-shaving and variable operating conditions of the unit, the heat-flow pressure stabilization buffer device spontaneously absorbs or replenishes steam flow to smooth pressure fluctuations on the steam inlet side of the variable cross-section ejector device. During periods of deep peak-shaving and large fluctuations in pipeline parameters, the heat-flow pressure stabilization buffer device pre-installed in the pipeline will spontaneously operate according to the actual pressure difference within the pipeline. When the pressure on the steam inlet side pipeline surges instantaneously, it will spontaneously absorb excess steam flow; when the pressure drops suddenly, it will quickly release previously stored steam flow for replenishment.

[0110] Peak shaving and condensation heat storage process: When the unit's peak shaving and operating conditions change, the actual pressure on the side of the injected steam source rises rapidly, and the real-time pressure is higher than the set upper limit threshold of the phase change buffer pressure. The excess steam in the steam inlet pipeline spontaneously enters the heat flow stabilizing buffer device under the action of pressure difference. The phase change heat storage medium absorbs the latent heat of vaporization of the excess steam and condenses it into liquid, thereby reducing the pressure peak on the steam inlet side.

[0111] Valley-filling flash evaporation energy release process: When the unit's peak-shaving operation causes the actual pressure on the injected steam source side to drop rapidly, and the real-time pressure is lower than the set lower limit threshold of the phase change buffer pressure, an instantaneous pressure drop is generated inside the heat flow stabilizing buffer device. The phase change heat storage medium releases the heat energy stored in the early stage, causing the liquid water in the saturated state inside to undergo pressure reduction flash evaporation. The generated flash steam spontaneously flows back to replenish the steam inlet side pipeline, thereby filling the pressure valley value on the steam inlet side.

[0112] By alternating spontaneous operation of the peak-shaving condensation and heat storage process and the valley-filling flash evaporation and energy release process, the pressure fluctuation amplitude on the low-pressure steam inlet side of the variable cross-section ejector device is limited within a preset smooth dead zone, providing stable ejected steam source boundary conditions for the dynamic cross-section adjustment.

[0113] Example 5

[0114] This embodiment provides a detailed explanation of the steps for calculating the target cross section, including the following core steps:

[0115] Construct a feedforward prediction optimization model and, in conjunction with the current unit thermodynamic operating parameters, predict the optimal ejector coefficient of the unit under the target operating conditions.

[0116] Based on the optimal ejection coefficient, the effective flow cross-sectional area of ​​the working nozzle target throat required to maintain this state is calculated. ;

[0117] Specifically, before the actual exhaust steam pressure difference of the unit changes to a preset passive trigger threshold, the control system determines the effective flow cross-sectional area of ​​the target throat of the working nozzle. An adjustment command is sent to the cross-section adjustment mechanism in advance.

[0118] The specific steps for solving the effective flow cross-sectional area after constructing the feedforward prediction optimization model include:

[0119] Step S11: Based on the current unit thermal operating parameters, the load change rate signal, and the heating demand prediction signal, a state-space sliding window prediction model is used to predict the thermodynamic boundary conditions of the unit under future target operating conditions.

[0120] The thermodynamic boundary conditions include: the absolute temperature of the driving steam under predicted operating conditions. With absolute pressure Predicting the absolute pressure on the inlet side of the ejected steam under operating conditions. The target mixed steam mass flow rate required for the heating network .

[0121] Step S12: Based on one-dimensional gas dynamics and non-equilibrium thermodynamics theory, establish the optimal entrainment coefficient solution equation and calculate the optimal entrainment coefficient under this target operating condition. The solution equation is: ,in: For dynamic operating conditions, adaptive compensation coefficients are used. , , These are the velocity coefficients of the working nozzle, receiving chamber, mixing chamber, and diffuser in the variable cross-section ejector device, respectively, and represent the velocity loss coefficients of different flow channel sections. To predict the enthalpy drop of isentropic expansion of driving steam within the working nozzle under operating conditions; To predict the isentropic expansion enthalpy drop of the ejected steam in the receiving chamber under operating conditions; To predict the isentropic compression enthalpy rise of the mixed steam in the diffuser under operating conditions.

[0122] Step S13: Based on the critical flow characteristics of gas, and incorporating the transient buffering effect of the heat flow stabilizing buffer device as a feedforward compensation term for mass flow rate, establish the cross-sectional area solution equation and solve for the effective flow cross-sectional area of ​​the target throat of the working nozzle. The equation for calculating the cross-sectional area is: ,in: This represents the required mass flow rate of the driving steam base under steady-state conditions. To predict the compressibility factor of the driving steam under operating conditions; is the universal gas constant for steam; The flow rate discharge coefficient of the working nozzle; The isentropic exponent for driving steam; This represents the absolute pressure of the injected steam on the inlet side at the current moment. This represents the transient mass flow coupling coefficient of the pressure stabilizing buffer device. The numerator on the right side of the equation represents the total driving steam mass flow rate required by the system, while the denominator utilizes the compressibility factor, universal constant, emission coefficient, absolute pressure, and isentropic exponent of the steam to accurately convert the required mass flow rate into the physical geometric area of ​​the fluid channel.

[0123] Example 6

[0124] This embodiment provides a collaborative control step based on maximizing the exergy efficiency of the entire system. By evaluating the actual work capacity loss of steam in the complex pipeline network, the optimal operating rate of the core valve is solved.

[0125] The maximum useful work that a system or fluid can perform when it reaches thermodynamic equilibrium with the environment under given environmental conditions, and the coordinated control steps specifically include the following steps:

[0126] Establish a real-time pyroefficiency model for the system and obtain the real-time main steam pressure, intermediate pressure cylinder exhaust temperature and low pressure cylinder inlet pressure as model input parameters.

[0127] Based on the real-time exergy efficiency model of the system, and under the constraint of satisfying the minimum allowable steam inlet pressure limit of the low-pressure cylinder, the optimal opening change rate of the regulating valve in the medium and low-pressure connecting pipe is solved. ;

[0128] With the optimal rate of change of opening The system drives the regulating valve of the medium and low pressure connecting pipe to operate, and coordinates the opening and closing of the bypass direct-connection valve in the system to minimize the overall thermodynamic work capacity loss of the system under deep peak shaving and variable operating conditions.

[0129] In the specific operational process, the execution of this collaborative control step is strictly divided into three core stages:

[0130] Step S21: Obtain the real-time ambient reference temperature. Compared with environmental benchmark pressure ;

[0131] Based on the real-time collected main steam pressure, intermediate pressure cylinder exhaust temperature, and low pressure cylinder inlet pressure, the real-time specific refractory force of each key node in the system is calculated. : ;

[0132] And establish a transient total firepower loss rate model for the entire system: The total power consumption at all input boundaries of the system is subtracted from the total power consumption at all output boundaries, and then the current real-time power output of the turbine unit is deducted, thereby calculating the overall power loss rate of the entire system caused by irreversible processes at the current moment with extremely high accuracy.

[0133] in, For the first Real-time fire comparison of each node; and These are the real-time specific enthalpy and specific entropy of the steam at this node, respectively; and These are the fundamental specific enthalpy and specific entropy of water under environmental baseline conditions, respectively. The total transient fire loss rate of the entire system; and The system number Mass flow rate and specific fire rate at each input boundary; and The system number Mass flow rate and specific firepower at each output boundary; This represents the current real-time power output of the steam turbine unit.

[0134] Step S22: After obtaining the total fire loss model of the system, the control system uses it as the objective function for optimization.

[0135] Minimum allowable inlet pressure limit for low-pressure cylinder As a hard constraint, the transient total firepower loss rate of the entire system is used as the basis. Minimize the objective function, and find the optimal rate of change of opening that results in the fastest gradient descent of the objective function. : , ;in, This refers to the real-time steam inlet pressure of the low-pressure cylinder. To predict the control time step, the valve action rate that causes the gradient of the objective function to decrease most rapidly is found by dynamically integrating the fire loss within the predicted control time step.

[0136] Step S23: Calculate in real time the marginal emissivity of steam passing through the variable cross-section ejector device under the current variable operating conditions, and the expected marginal emissivity of steam directly throttling and depressurizing through the bypass direct-connect valve.

[0137] When the unit's deep peak shaving demand exceeds the economic ejection range of the variable cross section ejector device, resulting in the marginal fire loss rate of the ejection process being greater than the expected marginal fire loss rate, the control system issues a coordinated switching command.

[0138] Using the optimal opening change rate Continue to adjust the regulating valve of the medium and low pressure connecting pipe, and at the same time open the intake valve of the medium pressure cylinder exhaust steam to the low pressure steam supply manifold or the hot reheat steam to the medium pressure steam supply manifold, so as to reduce the overload fire loss of the variable cross section ejector device by bypass diversion.

[0139] Example 7

[0140] In actual power plant operation, feedforward prediction or exergy optimization algorithms may fail for various reasons. In order to avoid peak shaving failure, this embodiment also provides a method and steps for instantly switching from dynamic "optimization mode" to "degradation support mode" based on hard physical pressure difference threshold.

[0141] That is, the control system has a built-in dual-mode switching logic; when the system operation encounters preset boundary conditions or the algorithm optimization fails, the control system automatically switches to a degraded deep-load adjustment mode; the deep-load adjustment mode includes a first deep-load adjustment unit and a second deep-load adjustment unit, and the specific control method is as follows:

[0142] When the unit load continues to decrease, causing the difference between the reheat pressure and the target steam supply pressure of the intermediate pressure steam supply header to be less than the seventh preset pressure difference value (preferably 0.5MPa), the system determines that the current operating condition has reached the boundary of normal regulation, and formally triggers and enters the deep adjustment load mode.

[0143] Control method of the first deep adjustment unit during load reduction: If the difference between the reheat pressure and the target steam supply pressure of the intermediate pressure steam supply header is... When the first preset pressure difference value is reached, open the high-pressure steam inlet valve and the low-pressure steam inlet valve of the high-pressure side variable cross section ejector device, and close the steam inlet valve of the hot reheat to medium-pressure steam supply manifold; the first preset pressure difference value can be 0.2MPa.

[0144] Control method of the second deep adjustment unit during load reduction: If the difference between the intermediate pressure cylinder exhaust pressure and the target steam supply pressure of the low pressure steam supply header is... When the second preset pressure difference value is reached, the high-pressure steam inlet valve and the low-pressure steam inlet valve of the variable cross section ejector device on the low-pressure side are opened, and the steam exhaust valve from the intermediate-pressure cylinder to the low-pressure steam supply manifold is closed; the second preset pressure difference value can be 0.2MPa.

[0145] When the grid load recovers and the generating units gradually move away from the deep peak-shaving zone, the system adopts a "low voltage first, then high voltage" deregulation strategy that is completely opposite to the load reduction.

[0146] Control method of the second deep adjustment unit during load increase: If the difference between the intermediate pressure cylinder exhaust pressure and the target steam supply pressure of the low pressure steam supply header is... When the third preset pressure difference value is reached, the intake valve of the intermediate pressure cylinder exhaust steam to the low pressure steam supply manifold is opened, and the high pressure steam inlet valve and the low pressure steam inlet valve of the low pressure side variable cross section ejector are closed; the third preset pressure difference value can be 0.5MPa.

[0147] Control method of the first deep adjustment unit during load increase: If the difference between the reheat pressure and the target steam supply pressure of the intermediate pressure steam supply header is... When the fourth preset differential pressure value is reached, open the intake valve of the hot reheat to medium-pressure steam supply manifold, and close the high-pressure steam inlet valve and low-pressure steam inlet valve of the high-pressure side variable cross-section ejector device; the fourth preset differential pressure value can be 0.5MPa.

[0148] The control of the medium and low pressure connecting pipe valves has independent limit constraint logic in the bottoming-out mode. The control method of the medium and low pressure connecting pipe valves is as follows: when the difference between the medium pressure cylinder exhaust pressure and the target steam supply pressure of the low pressure steam supply header is... When the fifth preset differential pressure value is reached, the medium and low pressure connecting pipe valve will gradually close at the first preset closing rate;

[0149] To prevent overheating and damage to the turbine blades due to steam interruption in the low-pressure cylinder, the opening degree of the intermediate and low-pressure connecting pipe valve should be adjusted accordingly. Minimum allowable opening value, or low-pressure cylinder inlet pressure Minimum allowable inlet steam pressure, or the difference between the intermediate pressure cylinder exhaust pressure and the target steam supply pressure of the low-pressure steam supply header. At the fifth preset differential pressure value, the medium and low pressure connecting pipe valve stops closing and maintains its current opening. The fifth preset differential pressure value can be 0.3 MPa; the minimum allowable opening value of the medium and low pressure connecting pipe valve can be 20%; the minimum allowable inlet steam pressure value of the low-pressure cylinder can be 0.1 MPa.

[0150] Meanwhile, once the temperature of the middle drain exceeds 350°C or the pressure of the middle drain exceeds 1.3MPa, the connecting pipe valve will open urgently at the second preset rate to release pressure; if the pressure difference increases sharply beyond the sixth preset value (0.4MPa), it will open at the third preset rate, thereby completely eliminating the safety hazard at the physical level.

[0151] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0152] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0153] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above invention, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A deep peak-shaving system for a dual-extraction heating unit, characterized in that, include: The steam source extraction pipeline network is connected to the extraction or exhaust ports of each stage of the steam turbine unit to obtain the driving steam source and the ejected steam source. The variable cross-section ejector device has a high-pressure steam inlet connected to the driving steam source, a low-pressure steam inlet connected to the ejected steam source, and an exhaust end connected to the heating network; the variable cross-section ejector device is equipped with a cross-section adjustment mechanism inside, which is used to dynamically change the flow cross-sectional area of ​​the working nozzle. A heat flow stabilizing buffer device is installed on the connecting pipeline between the ejected steam source and the low-pressure steam inlet end of the variable cross-section ejector device, and is used to absorb or release steam flow during unit operating conditions to smooth out pressure fluctuations on the steam inlet side. The control system is communicatively connected to the cross-section adjustment mechanism of the variable cross-section ejector and the unit's operating parameter acquisition terminal, respectively, and is used to send dynamic adjustment commands to the cross-section adjustment mechanism based on the unit's real-time operating parameters and peak-shaving commands.

2. The deep peak-shaving system for a dual-extraction heating unit according to claim 1, characterized in that, The variable cross-section ejector device includes a first variable cross-section ejector and a second variable cross-section ejector; The high-pressure steam inlet of the first variable cross-section ejector is connected to the hot reheat steam pipeline of the unit, its low-pressure steam inlet is connected to the medium-pressure cylinder exhaust pipeline, and its exhaust end is connected to the medium-pressure steam supply manifold. The high-pressure steam inlet of the second variable cross section ejector is connected to the exhaust pipe of the first variable cross section ejector or the exhaust pipe of the intermediate pressure cylinder, its low-pressure steam inlet is connected to the low-pressure cylinder steam inlet or the low-pressure steam supply manifold, and its exhaust is connected to the low-pressure steam supply manifold.

3. The deep peak-shaving system for a dual-extraction heating unit according to claim 1, characterized in that, The cross-section adjustment mechanism includes: a servo drive actuator, a transmission link, and a needle-type throttle valve; the servo drive actuator is disposed outside the variable cross-section ejector and is communicatively connected to the control system; one end of the transmission link is connected to the power output end of the servo drive actuator, and the other end of the transmission link is dynamically sealed and inserted into the interior of the variable cross-section ejector; the needle-type throttle valve is installed at the end of the transmission link and is coaxially and concentrically arranged with the working nozzle of the variable cross-section ejector. The servo drive actuator drives the needle valve to reciprocate axially to continuously change the effective flow cross-sectional area of ​​the throat of the working nozzle; The heat flow stabilizing buffer device is a phase change steam heat storage buffer tank; the phase change steam heat storage buffer tank is equipped with a gas-liquid separation component and a phase change heat storage medium. When the actual pressure at the low-pressure steam inlet is higher than the set buffer pressure, the buffer tank absorbs and condenses part of the steam to store thermal energy; when the actual pressure is lower than the set buffer pressure, the phase change heat storage medium releases heat to cause the internal condensate to flash into steam for replenishment.

4. A deep peak-shaving system for a dual-extraction heating unit according to claim 2, characterized in that, The steam source extraction pipeline network also includes multiple regulating valves, specifically: The ejector inlet valve assembly includes a high-pressure side high-pressure inlet valve and a high-pressure side low-pressure inlet valve respectively disposed at the high-pressure and low-pressure inlet ends of the first variable cross-section ejector, and a low-pressure side high-pressure inlet valve and a low-pressure side low-pressure inlet valve respectively disposed at the high-pressure and low-pressure inlet ends of the second variable cross-section ejector. The bypass direct-connect valve assembly includes an intermediate-pressure cylinder exhaust steam to low-pressure steam supply header inlet valve installed on the direct-connection pipeline from the intermediate-pressure cylinder exhaust steam pipeline to the low-pressure steam supply header, and a hot reheat steam to intermediate-pressure steam supply header inlet valve installed on the direct-connection pipeline from the hot reheat steam pipeline to the intermediate-pressure steam supply header. The medium- and low-pressure connecting pipe valve is installed on the connecting pipe from the medium-pressure cylinder exhaust to the low-pressure cylinder inlet; The control system is electrically connected to each regulating valve to coordinate the start, stop and opening degree of each valve, and switches to the deep adjustment load mode of direct connection of bypass valve when the system exceeds the adjustment range of the variable cross section ejector device.

5. A deep peak-shaving method for a dual-extraction heating unit, characterized in that, The method, applied to the deep peak-shaving system of a dual-extraction heating unit as described in any one of claims 1 to 4, comprises the following steps: Acquire operational data: Obtain real-time thermal operating parameters and variable load peak-shaving commands from the unit; Calculate the target cross-section: Based on the acquired thermodynamic operating parameters and the variable load peak shaving command, determine the target flow cross-sectional area required by the variable cross-section ejector device during the variable operating condition process; Dynamic cross-section adjustment: The control system sends a dynamic adjustment command to the cross-section adjustment mechanism to change the flow cross-sectional area of ​​the working nozzle to the target flow cross-sectional area, dynamically matching the parameter changes of the ejector steam source and the driving steam source; Heat flow synergistic pressure stabilization: During peak shaving and variable operating conditions of the unit, the heat flow pressure stabilization buffer device is used to spontaneously absorb or supplement steam flow to smooth out pressure fluctuations on the steam inlet side of the variable cross-section ejector device.

6. The deep peak-shaving method for a dual-extraction heating unit according to claim 5, characterized in that, The thermal operating parameters include the load change rate signal of the grid automatic generation control command and the heating demand prediction signal on the heating network side. The specific steps for calculating the target cross section include: Construct a feedforward prediction optimization model and, in conjunction with the current unit thermodynamic operating parameters, predict the optimal ejector coefficient of the unit under the target operating conditions. Based on the optimal ejection coefficient, the effective flow cross-sectional area of ​​the working nozzle target throat required to maintain this state is calculated. ; Specifically, before the actual exhaust steam pressure difference of the unit changes to a preset passive trigger threshold, the control system determines the effective flow cross-sectional area of ​​the target throat of the working nozzle. An adjustment command is sent to the cross-section adjustment mechanism in advance.

7. The deep peak-shaving method for a dual-extraction heating unit according to claim 6, characterized in that, The specific steps for solving the effective flow cross-sectional area after constructing the feedforward prediction optimization model include: Step S11: Based on the current unit thermal operating parameters, the load change rate signal, and the heating demand prediction signal, a state-space sliding window prediction model is used to predict the thermodynamic boundary conditions of the unit under future target operating conditions. The thermodynamic boundary conditions include: the absolute temperature of the driving steam under predicted operating conditions. With absolute pressure Predicting the absolute pressure on the inlet side of the ejected steam under operating conditions. The target mixed steam mass flow rate required for the heating network ; Step S12: Based on one-dimensional gas dynamics and non-equilibrium thermodynamics theory, establish the optimal entrainment coefficient solution equation and calculate the optimal entrainment coefficient under this target operating condition. The solution equation is: ,in: For dynamic operating conditions, adaptive compensation coefficients are used. , , These are the velocity coefficients of the working nozzle, receiving chamber, mixing chamber, and diffuser in the variable cross-section ejector device, respectively. To predict the enthalpy drop of isentropic expansion of driving steam within the working nozzle under operating conditions; To predict the isentropic expansion enthalpy drop of the ejected steam in the receiving chamber under operating conditions; To predict the isentropic compression enthalpy rise of the mixed steam in the diffuser under operating conditions; Step S13: Based on the critical flow characteristics of gas, and incorporating the transient buffering effect of the heat flow stabilizing buffer device as a feedforward compensation term for mass flow rate, establish the cross-sectional area solution equation and solve for the effective flow cross-sectional area of ​​the target throat of the working nozzle. The equation for calculating the cross-sectional area is: ,in: This represents the required mass flow rate of the driving steam base under steady-state conditions. To predict the compressibility factor of the driving steam under operating conditions; is the universal gas constant for steam; The flow rate discharge coefficient of the working nozzle; The isentropic exponent for driving steam; This represents the absolute pressure of the injected steam on the inlet side at the current moment. This is the transient mass flow coupling coefficient of the voltage stabilizing buffer device.

8. A deep peak-shaving method for a dual-extraction heating unit according to claim 5, characterized in that, The method also includes a collaborative control step based on maximizing the exergy efficiency of the entire system: Establish a real-time pyroefficiency model for the system and obtain the real-time main steam pressure, intermediate pressure cylinder exhaust temperature and low pressure cylinder inlet pressure as model input parameters. Based on the real-time exergy efficiency model of the system, and under the constraint of satisfying the minimum allowable steam inlet pressure limit of the low-pressure cylinder, the optimal opening change rate of the regulating valve in the medium and low-pressure connecting pipe is solved. ; With the optimal rate of change of opening The system drives the regulating valve of the medium and low pressure connecting pipe to operate, and coordinates the opening and closing of the bypass direct-connection valve in the system to minimize the overall thermodynamic work capacity loss of the system under deep peak shaving and variable operating conditions.

9. A deep peak-shaving method for a dual-extraction heating unit according to claim 8, characterized in that, The specific steps for establishing a real-time pyroefficiency model for the system and controlling the valves include: Step S21: Obtain the real-time ambient reference temperature. Compared with environmental benchmark pressure ; Based on the real-time collected main steam pressure, intermediate pressure cylinder exhaust temperature, and low pressure cylinder inlet pressure, the real-time specific refractory force of each key node in the system is calculated. : ; And establish a transient total firepower loss rate model for the entire system: ; in, For the first Real-time fire comparison of each node; and These are the real-time specific enthalpy and specific entropy of the steam at this node, respectively; and These are the fundamental specific enthalpy and specific entropy of water under environmental baseline conditions, respectively. The total transient fire loss rate of the entire system; and The system number Mass flow rate and specific fire rate at each input boundary; and The system number Mass flow rate and specific firepower at each output boundary; This represents the current real-time power output of the steam turbine unit. Step S22, set the minimum allowable steam inlet pressure limit for the low-pressure cylinder. As a hard constraint, the transient total firepower loss rate of the entire system is used as the basis. Minimize the objective function, and find the optimal rate of change of opening that results in the fastest gradient descent of the objective function. : , ;in, This refers to the real-time steam inlet pressure of the low-pressure cylinder. To predict the control time step; Step S23: Calculate in real time the marginal emissivity of steam passing through the variable cross-section ejector device under the current variable operating conditions, and the expected marginal emissivity of steam directly throttling and depressurizing through the bypass direct-connect valve. When the marginal fire loss rate is greater than the expected marginal fire loss rate, a coordinated switching command is issued; Using the optimal opening change rate Continue to adjust the regulating valve of the medium and low pressure connecting pipe, and at the same time open the intake valve of the medium pressure cylinder exhaust steam to the low pressure steam supply manifold or the hot reheat steam to the medium pressure steam supply manifold, so as to reduce the overload fire loss of the variable cross section ejector device by bypass diversion.

10. A deep peak-shaving method for a dual-extraction heating unit according to claim 5, characterized in that, The control system has a built-in dual-mode switching logic; when the system operation encounters preset boundary conditions or the algorithm optimization fails, the control system automatically switches to a degraded deep load adjustment mode; the deep load adjustment mode includes a first deep adjustment unit and a second deep adjustment unit, and the specific control method is as follows: Control method of the first deep adjustment unit during load reduction: If the difference between the reheat pressure and the target steam supply pressure of the intermediate pressure steam supply header is... When the first preset pressure difference value is reached, open the high-pressure steam inlet valve and the low-pressure steam inlet valve of the high-pressure side variable cross section ejector device, and close the steam inlet valve of the heat reheat to medium-pressure steam supply manifold. Control method of the second deep adjustment unit during load reduction: If the difference between the intermediate pressure cylinder exhaust pressure and the target steam supply pressure of the low pressure steam supply header is... When the second preset pressure difference value is reached, open the high-pressure steam inlet valve and the low-pressure steam inlet valve of the variable cross section ejector device on the low-pressure side, and close the steam inlet valve of the intermediate pressure cylinder exhaust to the low-pressure steam supply manifold. Control method of the second deep adjustment unit during load increase: If the difference between the intermediate pressure cylinder exhaust pressure and the target steam supply pressure of the low pressure steam supply header is... When the third preset pressure difference value is reached, open the air inlet valve of the medium-pressure cylinder exhaust steam to the low-pressure steam supply manifold, and close the high-pressure steam inlet valve and the low-pressure steam inlet valve of the low-pressure side variable cross section ejector device. Control method of the first deep adjustment unit during load increase: If the difference between the reheat pressure and the target steam supply pressure of the intermediate pressure steam supply header is... When the fourth preset pressure difference value is reached, open the inlet valve of the hot reheat to medium pressure steam supply manifold and close the high pressure steam inlet valve and low pressure steam inlet valve of the high pressure side variable cross section ejector device. The degradation mode also includes the control method for the medium and low pressure connecting pipe valves: when the difference between the medium pressure cylinder exhaust pressure and the target steam supply pressure of the low pressure steam supply header is... When the fifth preset differential pressure value is reached, the medium and low pressure connecting pipe valve will gradually close at the first preset closing rate; If the opening degree of the medium and low pressure connecting pipe valve is Minimum allowable opening value, or low-pressure cylinder inlet pressure Minimum allowable inlet steam pressure, or the difference between the intermediate pressure cylinder exhaust pressure and the target steam supply pressure of the low-pressure steam supply header. When the fifth preset differential pressure value is reached, the medium and low pressure connecting pipe valve stops closing and maintains its current opening.

Images