A control system and method for improving flexibility of a combined heat and power unit by heat storage

Abstract

The application discloses a control system and method for improving flexibility of a combined heat and power unit through heat storage, and belongs to the field of combined heat and power units. When the unit is in the process of load increase, an LQR controller increases the opening degree of a steam turbine regulating valve, so that part of steam originally serving as a heat source is actively responded to and controlled to enter a medium-pressure cylinder of the steam turbine to continue to work in the early stage of load change, the heat supply extraction steam flow generated by a machine-boiler-heat system is reduced, and a heat storage control device increases the opening degree of a heat release regulating valve according to the reduced heat supply extraction steam flow, so that the heat storage system supplements the heat supply extraction steam to heat users, to meet the heat supply demand of the heat users. Through the introduction of the heat storage system and the heat storage control device, the application makes up the gap of the reduced heat supply in the early stage of load change, improves the load response rate of the unit, and meanwhile, the heat supply quality is ensured.

Description

Technical Field

[0001] This invention relates to the field of combined heat and power (CHP) units, and in particular to a control system and method for improving the flexibility of CHP units through thermal energy storage. Background Technology

[0002] In recent years, the large-scale grid connection of new energy sources has presented new challenges to coal-fired power units. In the future, combined heat and power (CHP) units may need to simultaneously face severe peak shaving, frequency regulation, and heating tasks during the heating season, requiring the units to have a rapid load response rate. However, due to the thermoelectric coupling effect, the current flexible supply capacity provided by CHP units cannot meet the growing flexibility demands of the power grid.

[0003] Chinese patent CN110716425A, entitled "A Method for Coordinated Electricity and Heat Control of Cogeneration Units," only considers utilizing the heat storage of the heating network to support load response, without addressing how to handle the resulting fluctuations in the steam extraction flow rate for heating. With the increasing demand for frequency regulation and peak shaving in current cogeneration units, frequent adjustments to the steam extraction flow rate for heating will inevitably affect the quality of heating. Summary of the Invention

[0004] The purpose of this invention is to provide a control system and method for improving the flexibility of cogeneration units through thermal storage, which can improve the load response rate of the unit without affecting the heating quality.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A control system for improving the flexibility of a combined heat and power unit through thermal storage includes: an LQR controller, a thermal storage system, and a thermal storage control device;

[0007] The first input terminal of the LQR controller is connected to the first output terminal of the machine-furnace-heat system; the second input terminal of the LQR controller is connected to the second output terminal of the machine-furnace-heat system; the third input terminal of the LQR controller is connected to the third output terminal of the machine-furnace-heat system; and the output terminal of the LQR controller is connected to the input terminal of the machine-furnace-heat system.

[0008] The LQR controller is used to track and control the turbine inlet pressure, heating extraction steam pressure, and unit load of the turbine-boiler-heater system, generating fuel quantity, turbine regulating valve opening, and heating butterfly valve opening. When the unit load increases, it increases the turbine regulating valve opening, so that some of the steam originally used as a heat source enters the turbine intermediate pressure cylinder to continue doing work in the early stage of load change through active response control of the heat source. The turbine-boiler-heater system operates according to the fuel quantity, turbine regulating valve opening, and heating butterfly valve opening generated by the LQR controller, and generates turbine inlet pressure, heating extraction steam pressure, unit load, and heating extraction steam flow rate.

[0009] The first input terminal of the thermal storage control device is connected to the fourth output terminal of the machine-furnace-heat system, the second input terminal of the thermal storage control device is connected to the first output terminal of the thermal storage system, and the output terminal of the thermal storage control device is connected to the control terminal of the thermal storage system.

[0010] The thermal storage control device is used to control the opening of the thermal storage regulating valve and the heat release regulating valve of the thermal storage tank according to the steam extraction flow rate of the boiler-heater system and the water level in the thermal storage tank of the thermal storage system. When the unit increases the load, the opening of the heat release regulating valve is increased so that the thermal storage system can supplement the heat extraction steam to the heat users and generate the water level in the thermal storage tank at the same time.

[0011] A control method for improving the flexibility of a combined heat and power (CHP) unit through thermal energy storage, wherein the control method is applied to the aforementioned control system for improving the flexibility of a CHP unit through thermal energy storage, and the control method includes:

[0012] In power supply priority mode, when the unit is increasing the load, the opening of the turbine regulating valve in the turbine-boiler-heat system is increased, so that some of the steam that was originally used as a heat source enters the intermediate pressure cylinder of the turbine through the heat source active response control in the early stage of load change and continues to do work.

[0013] Obtain the steam extraction flow rate for heating in the turbine-furnace-heat system;

[0014] Based on the steam extraction flow rate of the boiler-heater system, increase the opening of the heat storage tank's heat release regulating valve so that the heat storage system can supplement the heat extraction steam to the heat users.

[0015] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0016] This invention discloses a control system and method for improving the flexibility of a combined heat and power (CHP) unit through thermal energy storage. When the unit increases load, the LQR controller increases the opening of the turbine regulating valve, allowing some of the steam originally intended as a heat source to enter the turbine's intermediate-pressure cylinder during the initial load change phase through active heat source response control. This reduces the flow rate of the extraction steam from the turbine-boiler-heater system. The thermal energy storage control device then increases the opening of the heat release regulating valve based on this reduced extraction steam flow, enabling the thermal energy storage system to supplement the extraction steam supply to heat users, thus meeting their heating needs. This invention, by introducing a thermal energy storage system and control device, compensates for the reduced heating capacity during the initial load change phase, improves the unit's load response rate, and simultaneously ensures heating quality. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart of the operation of a thermal storage system provided in an embodiment of the present invention;

[0019] Figure 2 A structural diagram of the thermal storage control device provided in an embodiment of the present invention;

[0020] Figure 3 A structural diagram of a control system for improving the flexibility of a combined heat and power unit through thermal storage, provided in an embodiment of the present invention;

[0021] Figure 4 This is a schematic diagram illustrating the equivalent steam extraction flow rate trend of the thermal storage system before and after participating in coordinated control, as provided in an embodiment of the present invention.

[0022] Figure 5 This is a schematic diagram of the equivalent heating steam extraction flow rate trend of the thermal storage system provided in an embodiment of the present invention;

[0023] Figure 6 This is a schematic diagram of the water level trend inside the heat storage tank provided in an embodiment of the present invention;

[0024] Figure 7 This is a schematic diagram of the thermocline trend after the thermal storage system participates in coordinated control, as provided in an embodiment of the present invention.

[0025] Figure 8 A flowchart of a control method for improving the flexibility of a combined heat and power unit through thermal storage, provided as an embodiment of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] This invention provides a control system for improving the flexibility of cogeneration units through thermal storage, including: an LQR controller, a thermal storage system, and a thermal storage control device.

[0029] The first input terminal of the LQR controller is connected to the first output terminal of the turbine-boiler-heat system, the second input terminal of the LQR controller is connected to the second output terminal of the turbine-boiler-heat system, and the third input terminal of the LQR controller is connected to the third output terminal of the turbine-boiler-heat system; the output terminal of the LQR controller is connected to the input terminal of the turbine-boiler-heat system. The LQR controller is used to track and control the turbine inlet pressure, heating extraction steam pressure, and unit load of the turbine-boiler-heat system, generating fuel quantity, turbine regulating valve opening, and heating butterfly valve opening. When the unit load increases, it increases the turbine regulating valve opening, allowing some of the steam originally intended as a heat source to enter the turbine intermediate-pressure cylinder through active heat source response control during the early stages of load change to continue performing work. The turbine-boiler-heat system operates according to the fuel quantity, turbine regulating valve opening, and heating butterfly valve opening generated by the LQR controller, and generates turbine inlet pressure, heating extraction steam pressure, unit load, and heating extraction steam flow rate.

[0030] The first input terminal of the thermal storage control device is connected to the fourth output terminal of the turbine-boiler-heat system, and the second input terminal of the thermal storage control device is connected to the first output terminal of the thermal storage system; the output terminal of the thermal storage control device is connected to the control terminal of the thermal storage system. The thermal storage control device is used to control the opening degree of the thermal storage regulating valve and the heat release regulating valve of the thermal storage tank according to the steam extraction flow rate of the turbine-boiler-heat system and the water level in the thermal storage tank. When the unit increases its load, the opening degree of the heat release regulating valve is increased, allowing the thermal storage system to supplement the heat extraction steam to the heat users, while simultaneously increasing the water level in the thermal storage tank.

[0031] The thermal storage system used in this invention is implemented by a single thermal storage tank using water as the working fluid, and its operation process is as follows: Figure 1 As shown in the diagram, the thermal storage system comprises two systems: a thermal storage cycle and a thermal release cycle. When the combined heat and power (CHP) unit's heat supply exceeds the demand of heat users, the thermal storage cycle is activated. After heat exchange between the CHP heater and the extracted steam, part of the circulating water in the heating network enters the heating network to supply heat to users, while the other part passes through the hot water inlet regulating valve 1 (…). Figure 1 Valve 1) enters the upper layer of the heat storage tank. Simultaneously, cold water from the lower part of the tank enters through outlet regulating valve 4. Figure 1 Valve 4) enters the heating network heater to ensure mass balance. When the heat load demand is high, the heat release circulation loop is started. At this time, a portion of the heating network circulating water returns through the cold water inlet regulating valve 3 ( Figure 1 Valve 3) enters the lower layer of the heat storage tank, and the hot water in the upper layer of the heat storage tank enters through the outlet regulating valve 2. Figure 1 Valve 2) in the middle enters the heating network for heating. The heat storage tank has three layers: hot water layer, inclined temperature layer and cold water layer.

[0032] Before designing a thermal energy storage control system, a mathematical model needs to be established. During system operation, the change in internal water level is related to the fluid flow rate at the tank inlet and outlet.

[0033]

[0034] Among them, C TES Indicates the heat storage / release coefficient of the heat storage tank; l TES The value indicates the water level inside the thermal storage tank; ρ and m represent the density and mass flow rate of the fluid interacting between the tank and the outside environment; the subscript i is the serial number of the regulating valve.

[0035] Considering the dynamic response process of the valve, the flow rates of hot water at the inlet and cold water at the outlet of the thermal storage tank can be expressed as:

[0036]

[0037] Where, μ i T represents the opening degree of the i-th regulating valve; v and K v These are the dynamic parameters of the control valve.

[0038] Formulas (1) and (2) constitute the water level change model inside the thermal storage tank.

[0039] According to energy balance, the heat power H of the heat storage / release process can be expressed as:

[0040]

[0041] Where c represents the isobaric specific heat capacity of hot water; t i This represents the water temperature after passing through the i-th regulating valve. It can be seen that when H is greater than zero, the system is in a heat-releasing state. When H is less than zero, the system is in a heat-storing state.

[0042] Formula (3) constitutes the thermal power model.

[0043] Assuming the heat storage tank can only be in one state of heat storage / release at any given time, i.e., there is no scenario where heat is stored and released simultaneously, then the opening of either the inlet or outlet regulating valve for hot or cold water must be zero, i.e.:

[0044] μ1μ4=μ2μ3=0 (4)

[0045] Wherein, μ1 represents the opening degree of the first regulating valve, which is located at the hot water inlet of the heat storage tank; μ2 represents the opening degree of the second regulating valve, which is located at the hot water outlet of the heat storage tank; μ3 represents the opening degree of the third regulating valve, which is located at the cold water inlet of the heat storage tank; and μ4 represents the opening degree of the fourth regulating valve, which is located at the cold water outlet of the heat storage tank.

[0046] Formula (4) constitutes the control valve opening relationship model.

[0047] To more accurately represent the improvement in unit operational flexibility provided by the thermal storage system, we convert the heat power supplied by the thermal storage system into the heat extraction steam flow rate. According to energy balance, the heat released by the thermal storage tank should equal the heat released by the converted heat extraction steam flow rate in the heating network heater, that is:

[0048]

[0049] in, This indicates the steam extraction flow rate corresponding to the output thermal power of the thermal storage tank, with the same sign as the output thermal power of the thermal storage tank; h H Indicates the enthalpy of steam extracted for heating; h HS This indicates the enthalpy of the saturated steam at the outlet after the extracted steam has exchanged heat with the heater in the heating network.

[0050] Formula (5) constitutes an equivalent model of the steam extraction flow rate for heating.

[0051] During the heat storage / release process, the dynamic change in the position of the thermocline effectively reflects the state of heat storage or release. Ignoring the change in the thickness of the thermocline during heat exchange, the height of the thermocline can be expressed as:

[0052]

[0053] Among them, l TC ρ3 represents the height of the inclined temperature layer inside the thermal storage tank, ρ4 represents the density of the fluid interacting with the outside world through the third regulating valve, m3 represents the mass flow rate of the fluid interacting with the outside world through the third regulating valve, and m4 represents the mass flow rate of the fluid interacting with the outside world through the fourth regulating valve.

[0054] Formula (6) constitutes the thermocline height model.

[0055] Based on the above analysis, the thermal storage tank system is a four-input, four-output system. The input parameters are the opening degrees of the four valves at the inlet and outlet of the thermal storage tank, and the output parameters are the water level in the thermal storage tank, the heat release power, the equivalent steam flow rate for heating from the thermal storage tank, and the height of the thermocline.

[0056] The structure of the thermal storage control system is as follows Figure 2 As shown in the figure. H d and l TES,dThese represent the setpoints for thermal power and water level, respectively. As shown in the diagram, the system comprises two control loops: power control and water level control. The power controller manages the supply and demand balance of thermal power by adjusting the hot water inlet and outlet valves. Correspondingly, the water level stability in the storage tank is controlled by the water level controller by adjusting the cold water inlet and outlet valves. The outputs of each controller enter the thermal storage system through their respective valve settings. The allocation follows two principles: First, the system's state is considered—whether it's storing or releasing heat. If it's storing heat, the controller's valve commands are executed by the opening degrees μ1 of the hot water inlet regulating valve and μ4 of the cold water outlet regulating valve; otherwise, they are executed by the opening degrees μ2 of the hot water outlet regulating valve and μ3 of the cold water inlet regulating valve. Second, the real-time height of the thermocline is monitored. If the thermocline height exceeds the safety limit, heat storage or release must be stopped immediately.

[0057] Depend on Figure 2 As can be seen, the thermal storage control device includes a power controller and a water level controller. The input terminal of the power controller is connected to the second output terminal of the thermal storage system, and the output terminals of the power controller are respectively connected to the control terminals of the hot water inlet regulating valve and the hot water outlet regulating valve of the thermal storage tank. The power controller is used to control the opening degree of the hot water inlet regulating valve and the hot water outlet regulating valve according to the set value of thermal power and the thermal power output from the second output terminal of the thermal storage system, so as to achieve a balance between thermal power supply and demand. The input terminal of the water level controller is connected to the first output terminal of the thermal storage system, and the output terminals of the water level controller are respectively connected to the control terminals of the cold water inlet regulating valve and the cold water outlet regulating valve of the thermal storage tank. The water level controller is used to control the opening degree of the cold water inlet regulating valve and the cold water outlet regulating valve according to the set value of the water level and the water level in the thermal storage tank output from the first output terminal of the thermal storage system, so as to ensure the stability of the water level in the thermal storage tank.

[0058] The third output of the thermal storage system is used to generate the equivalent steam flow rate for heat extraction from the thermal storage tank. The fourth output of the thermal storage system is used to generate the height of the inclined temperature layer inside the thermal storage tank; when the height of the inclined temperature layer inside the thermal storage tank exceeds the height safety threshold, the thermal storage or heat release of the thermal storage tank is stopped.

[0059] Based on the control system of the aforementioned thermal storage tank, a control system structure is designed to improve the flexibility of the cogeneration unit through thermal storage, such as... Figure 3 As shown, Figure 3 The subscript "d" in each parameter indicates the set value of the corresponding parameter. Figure 3 It can be seen that the electrothermal coordinated control system is divided into two parts: the machine-furnace-heat system and the thermal storage system. The machine-furnace-heat system is a system based on fuel quantity (μg / μm). B ), turbine regulating valve opening (μ) T Heating butterfly valve opening degree (μ) H ) as input, with unit load (P) and inlet pressure (p) as input. T), heating extraction steam pressure (p) H ), heating steam extraction flow rate (m³) H This invention relates to a three-input, four-output system. The research object includes boilers, steam turbines, and heating systems, and the control effects of each component on power generation and heating power can be adjusted by an LQR controller. Compared to PID control, LQR can more easily achieve different power supply and heating priority control requirements by adjusting the weights of various state and input variables. In power supply priority mode, a portion of the steam originally intended as a heat source enters the intermediate-pressure cylinder to continue doing work during the early stages of load variation through active heat source response control, in response to AGC load commands. In addition, the LQR controller can also achieve energy balance through tracking control of the system output. This process is LQR control based on active heat source response. Figure 3 The LQR control based on active heat source response is implemented by the LQR controller, while the heating system recovery control is implemented by the thermal storage control device.

[0060] The three outputs P, p of the unit coordination system T m H Under the action of the LQR control system based on active heat source response, the output parameter tracks the setpoint by adjusting three input parameters. During the adjustment process, the steam extraction flow rate for heating is tracked to the setpoint through the heating recovery control loop.

[0061] The thermal storage system controls the flow rate of extracted steam for heating, playing a role in restoring and supporting heating supply. In power priority mode, a portion of the extracted steam, acting as a heat source, enters the low-pressure cylinder of the turbine to perform work, causing a decrease in the extracted steam flow rate. Even with the heat source restoration control loop, the heating capacity recovers to its initial value, but the initial shortfall is difficult to compensate for. The control method proposed in this invention, by introducing a thermal storage system, effectively solves this problem. When the unit increases load, a portion of the extracted steam, acting as a heat source, is used to respond to AGC load commands, while the thermal storage system supplements the extracted steam to meet the heating needs of users.

[0062] This invention improves the load response rate of the unit without significantly affecting the heating quality.

[0063] This invention also provides a control method for improving the flexibility of cogeneration units through thermal energy storage. This control method is applied to the aforementioned control system for improving the flexibility of cogeneration units through thermal energy storage, such as... Figure 8 As shown, the control method includes:

[0064] Step 1: In power supply priority mode, when the unit is increasing the load, the opening of the turbine regulating valve in the turbine-boiler-heat system is increased, so that part of the steam that was originally used as a heat source enters the intermediate pressure cylinder of the turbine through the heat source active response control in the early stage of load change to continue to do work.

[0065] Step 2: Obtain the steam flow rate for heating extraction in the turbine-furnace-heat system.

[0066] Step 3: Based on the steam extraction flow rate of the boiler-heater system, increase the opening of the heat storage tank's heat release regulating valve so that the heat storage system can supplement the heat extraction steam to the heat users.

[0067] This invention provides a control method for applying a thermal storage system in a combined heat and power (CHP) unit, which improves the load response rate of the unit and further promotes the consumption of new energy sources.

[0068] The control system and control method of this invention are applied to a 300MW combined heat and power (CHP) unit. The CHP unit has a capacity of 300MW. The LQR controller parameters in the turbine-boiler-heater system are as follows:

[0069] Q = diag(1, 10) 5 ,1,10 5 10 5 ,6050,10 5 ),R=diag(1,1,1) (7)

[0070] In the thermal storage control system, the equivalent heating steam flow rate supplied to the heating network is controlled by the hot water outlet regulating valve. The flow controller (power controller) adopts a PI controller with parameters P = 1 and I = 0.01. The water level in the thermal storage tank is controlled by the cold water inlet regulating valve, and the water level controller also adopts a PI controller with parameters P = 100 and I = 0.6. The unit is in a stable state for the first 100 seconds. At the 100th second, the unit load command increases from 235MW to 245MW at a rate of 12MW / min. The trend of the equivalent heating steam flow rate supplied to the heating network is as follows. Figure 4 As shown in the figure, without the use of a thermal storage tank, when the turbine-boiler-heater system is under the original coordinated control strategy, the heating extraction steam flow rate reaches its minimum value of 322.7 t / h at the 51st second of the adjustment process. After 188 seconds of adjustment, the heating extraction steam flow rate returns to the set value. In contrast, after using a thermal storage tank to support heating, the equivalent heating extraction steam flow rate supplied to the heating network almost coincides with the set value, with a maximum deviation of only about 1.1 t / h, proving the effectiveness of the strategy.

[0071] During the regulation process of the thermal storage tank, the dynamic changes in the equivalent steam flow rate and water level of the thermal storage tank are as follows: Figure 5 and Figure 6 As shown. Comparison Figure 4 and Figure 5 It can be seen that, under the control of the hot water outlet flow rate, the adjustment process of the heat storage tank can effectively compensate for the reduction in the amount of steam extracted for heating in a short period of time. From Figure 6It can be seen that, under the control of the cold water inlet flow rate, the water level in the heat storage tank gradually recovers to the set value after a brief drop. Figure 7 The change process of the inclined temperature layer height inside the thermal storage tank is presented. It can be seen that the inclined temperature layer height gradually increases as the heat release process proceeds. Moreover, as the heat release power decreases, the rate of increase in the inclined temperature layer height also gradually slows down, eventually stabilizing at 15.022m. During this process, since we only conducted one load increase experiment, and the heat release power eventually returned to zero, the change in the inclined temperature layer height was not significant. When the load is frequently adjusted, the height of the inclined temperature layer needs to be constantly monitored.

[0072] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The methods disclosed in the embodiments are described simply because they correspond to the systems disclosed in the embodiments; relevant details can be found in the method section.

[0073] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A control system for improving the flexibility of a combined heat and power (CHP) unit through thermal energy storage, characterized in that, include: LQR controller, thermal storage system and thermal storage control device; The first input terminal of the LQR controller is connected to the first output terminal of the machine-furnace-heat system; the second input terminal of the LQR controller is connected to the second output terminal of the machine-furnace-heat system; the third input terminal of the LQR controller is connected to the third output terminal of the machine-furnace-heat system; and the output terminal of the LQR controller is connected to the input terminal of the machine-furnace-heat system. The LQR controller is used to track and control the turbine inlet pressure, heating extraction steam pressure, and unit load of the turbine-boiler-heater system, generating fuel quantity, turbine regulating valve opening, and heating butterfly valve opening. When the unit load increases, it increases the turbine regulating valve opening, so that some of the steam originally used as a heat source enters the turbine intermediate pressure cylinder to continue doing work in the early stage of load change through active response control of the heat source. The turbine-boiler-heater system operates according to the fuel quantity, turbine regulating valve opening, and heating butterfly valve opening generated by the LQR controller, and generates turbine inlet pressure, heating extraction steam pressure, unit load, and heating extraction steam flow rate. The first input terminal of the thermal storage control device is connected to the fourth output terminal of the machine-furnace-heat system, the second input terminal of the thermal storage control device is connected to the first output terminal of the thermal storage system, and the output terminal of the thermal storage control device is connected to the control terminal of the thermal storage system. The thermal storage control device is used to control the opening of the thermal storage regulating valve and the heat release regulating valve of the thermal storage tank according to the steam extraction flow rate of the boiler-heater system and the water level in the thermal storage tank of the thermal storage system. When the unit increases the load, the opening of the heat release regulating valve is increased so that the thermal storage system can supplement the heat extraction steam to the heat users and generate the water level in the thermal storage tank at the same time.

2. The control system for improving the flexibility of a combined heat and power unit through thermal storage according to claim 1, characterized in that, The thermal storage control device includes: a power controller and a water level controller; The input terminal of the power controller is connected to the second output terminal of the thermal storage system, and the output terminal of the power controller is connected to the control terminal of the hot water inlet regulating valve and the control terminal of the hot water outlet regulating valve of the thermal storage tank, respectively. The power controller is used to control the opening of the hot water inlet regulating valve and the hot water outlet regulating valve according to the set value of the heat power and the heat power output from the second output terminal of the heat storage system, so as to achieve a balance between the supply and demand of heat power. The input terminal of the water level controller is connected to the first output terminal of the thermal storage system, and the output terminal of the water level controller is connected to the control terminal of the cold water inlet regulating valve and the control terminal of the cold water outlet regulating valve of the thermal storage tank, respectively. The water level controller is used to control the opening of the cold water inlet regulating valve and the cold water outlet regulating valve according to the water level set value and the water level in the heat storage tank output by the first output terminal of the heat storage system, so as to ensure the stability of the water level in the heat storage tank.

3. The control system for improving the flexibility of a combined heat and power unit through thermal storage according to claim 1, characterized in that, The third output end of the thermal storage system is used to generate the equivalent heat extraction steam flow rate of the thermal storage tank. The fourth output terminal of the thermal storage system is used to generate the height of the inclined temperature layer inside the thermal storage tank; when the height of the inclined temperature layer inside the thermal storage tank is greater than the height safety threshold, the thermal storage or release of heat in the thermal storage tank is stopped.

4. The control system for improving the flexibility of a combined heat and power unit through thermal storage according to claim 1, characterized in that, The mathematical model of the thermal storage system includes: a water level change model in the thermal storage tank, a thermal power model, a regulating valve opening relationship model, an equivalent model of the steam extraction flow rate for heating, and a thermocline height model.

5. The control system for improving the flexibility of a combined heat and power unit through thermal storage according to claim 4, characterized in that, The water level change model inside the thermal storage tank is as follows: In the formula, C TES The heat storage / release coefficient of the heat storage tank, l TES Indicates the water level inside the thermal storage tank, ρ i This represents the density of the fluid interacting with the outside environment through the i-th regulating valve, m. i μ represents the mass flow rate of the fluid interacting with the outside environment through the i-th regulating valve; i T represents the opening degree of the i-th regulating valve. v and K v These represent the first dynamic parameter and the second dynamic parameter of the control valve, respectively.

6. The control system for improving the flexibility of a combined heat and power unit through thermal storage according to claim 5, characterized in that, The thermal power model is as follows: In the formula, H represents thermal power, c represents the isobaric specific heat capacity of hot water, and t i This represents the water temperature after passing through the i-th regulating valve.

7. The control system for improving the flexibility of a combined heat and power unit through thermal storage according to claim 6, characterized in that, The control valve opening relationship model is as follows: μ1μ4=μ2μ3=0; In the formula, μ1 represents the opening degree of the first regulating valve, which is located at the hot water inlet of the heat storage tank; μ2 represents the opening degree of the second regulating valve, which is located at the hot water outlet of the heat storage tank; μ3 represents the opening degree of the third regulating valve, which is located at the cold water inlet of the heat storage tank; and μ4 represents the opening degree of the fourth regulating valve, which is located at the cold water outlet of the heat storage tank.

8. The control system for improving the flexibility of a combined heat and power unit through thermal storage according to claim 7, characterized in that, The equivalent model for the steam extraction flow rate for heating is: In the formula, This represents the equivalent steam extraction flow rate for heat storage tank heat release, in h. H Indicates the enthalpy of steam extracted for heating, h HS This indicates the enthalpy of the saturated steam at the outlet after the extracted steam has exchanged heat with the heater in the heating network.

9. The control system for improving the flexibility of a combined heat and power unit through thermal storage according to claim 8, characterized in that, The thermocline height model is as follows: In the formula, l TC ρ3 represents the height of the inclined temperature layer inside the thermal storage tank, ρ4 represents the density of the fluid interacting with the outside world through the third regulating valve, m3 represents the mass flow rate of the fluid interacting with the outside world through the third regulating valve, and m4 represents the mass flow rate of the fluid interacting with the outside world through the fourth regulating valve.

10. A control method for improving the flexibility of a combined heat and power unit through thermal storage, characterized in that, The control method is applied to the control system for improving the flexibility of a cogeneration unit through thermal storage as described in any one of claims 1-9, and the control method includes: In power supply priority mode, when the unit is increasing the load, the opening of the turbine regulating valve in the turbine-boiler-heat system is increased, so that some of the steam that was originally used as a heat source enters the intermediate pressure cylinder of the turbine through the heat source active response control in the early stage of load change and continues to do work. Obtain the steam extraction flow rate for heating in the turbine-furnace-heat system; Based on the steam extraction flow rate of the boiler-heater system, increase the opening of the heat storage tank's heat release regulating valve so that the heat storage system can supplement the heat extraction steam to the heat users.

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