Integrated high-temperature energy storage and high-temperature energy storage and high-temperature energy storage and high-temperature energy storage and high-temperature energy storage and high-temperature energy storage and high-temperature energy storage

Abstract

The application provides a coupling system and a control method for integrating high-medium temperature energy storage to improve the flexibility of a coal-fired unit, wherein the coupling system comprises a coal-fired unit and a high-medium temperature energy storage system; the high-medium temperature energy storage system comprises a cold-hot energy storage medium tank, a cold-hot energy storage medium tank outlet regulating valve, a cold-hot energy storage medium pump, a high-medium temperature heat exchanger and other devices; in the energy storage process, the medium at the inlet of the medium-pressure cylinder is taken out and sent to the high-medium temperature energy storage system, the medium after heat release is sent to the outlet of the deaerator, and the condensate water is corrected at the same time, so as to reduce the minimum load of the coal-fired unit; in the energy release process, a load distribution module is designed, the work amount of the coal-fired unit boiler coordination system is reset, part of the medium at the inlet of the deaerator is taken out and sent to the high-medium temperature energy storage system to generate steam, then the steam enters the high-pressure cylinder exhaust or the low-pressure cylinder inlet to work and improve the load change amount of the whole unit, and the variable load rate of the coal-fired unit is accelerated. The application reduces the minimum load of the coal-fired unit and improves the variable load rate of the coal-fired unit, and the flexibility of the coal-fired unit is obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of coal-fired power unit configuration optimization and flexibility enhancement technology, specifically involving a coupling system and control method for integrating high- and medium-temperature energy storage to enhance the flexibility of coal-fired power units. Background Technology

[0002] my country is accelerating the construction of a new power system, with new energy sources such as wind and solar power becoming the mainstay of energy supply. However, the large-scale grid connection of intermittent energy sources like wind and solar power has significantly impacted the safe and stable operation of the power system. To build a power system with a high proportion of new energy generation, coal-fired power generation will serve as an important peak-shaving resource due to my country's energy endowment of being rich in coal, poor in oil, and lacking in gas. However, coal-fired units are limited by the boiler-turbine energy flow coupling, resulting in insufficient flexibility and restricting the proportion of renewable energy connected to the grid. Therefore, flexibility retrofitting is an inevitable choice to improve the flexibility of coal-fired units. Summary of the Invention

[0003] This invention addresses the inherent inflexibility of coal-fired power units by focusing on energy transfer and seeking methods to improve their flexibility. The objective is to provide a coupled system and control method integrating high- and medium-temperature energy storage to enhance the flexibility of coal-fired power units. This system enables multi-condition and multi-process energy transfer within the unit, reducing minimum load and increasing load change rate, thereby significantly improving the unit's inherent flexibility.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] A coupling system integrating high- and medium-temperature energy storage to enhance the flexibility of coal-fired power units is proposed. The coupling system comprises the coal-fired power unit and the high- and medium-temperature energy storage system. In the coal-fired power unit, the superheated steam outlet of boiler 1 is connected to the steam inlet of ultra-high-pressure cylinder 2 via a pipeline; the exhaust outlet of ultra-high-pressure cylinder 2 is connected to the primary cold / reheat steam inlet of boiler 1 via a pipeline; the primary hot / reheat steam outlet of boiler 1 is connected to the steam inlet of high-pressure cylinder 3 via a pipeline; the exhaust outlet of high-pressure cylinder 3 is connected to the secondary cold / reheat steam inlet of boiler 1 via a pipeline; and the secondary hot / reheat steam outlet of boiler 1 is connected to the high-temperature energy storage system. The steam inlet of the intermediate-pressure cylinder 4 is connected to the steam inlet of the low-pressure cylinder 5 via a pipeline. The steam outlet of the low-pressure cylinder 5 is connected to the steam inlet of the condenser 6 via a pipeline. The condensate outlet of the condenser 6 is connected to the condensate inlet of the low-pressure regenerative heater 8 via a pipeline through the condensate pump 7. The condensate outlet of the low-pressure regenerative heater 8 is connected to the condensate inlet of the deaerator 9 via a pipeline. The feedwater outlet of the deaerator 9 is connected to the feedwater inlet of the high-pressure regenerative heater 11 via the feedwater pump 10 via a pipeline. The feedwater outlet of the heat heater 11 is connected to the feedwater inlet of the boiler 1 via a pipeline. The steam extraction port of the ultra-high pressure cylinder 2 is connected to the steam extraction inlet of the high-pressure regenerative heater 11 via a pipeline. The steam extraction port of the high-pressure cylinder 3 is connected to the steam extraction inlet of the high-pressure regenerative heater 11 via a pipeline. The first-stage steam extraction port of the intermediate-pressure cylinder 4 is connected to the steam extraction inlet of the high-pressure regenerative heater 11 via a pipeline. The second-stage steam extraction port of the intermediate-pressure cylinder 4 is connected to the steam extraction inlet of the deaerator 9 via a pipeline. The remaining stages of the intermediate-pressure cylinder 4 are connected to the steam extraction inlet of the low-pressure regenerative heater 8 via pipelines. The extraction port of the low-pressure cylinder 5 is connected to the extraction inlet of the low-pressure regenerative heater 8 via a pipeline; the high-temperature and medium-temperature energy storage system consists of extraction valve 12, high-temperature heat exchanger 13, phase change energy storage tank 14, medium-temperature heat exchanger 15, cold energy storage medium tank 16, hot energy storage medium tank 17, cold energy storage medium tank outlet regulating valve 18, cold energy storage medium pump 19, feedwater regulating valve 20, hot energy storage medium tank outlet regulating valve 21, hot energy storage medium pump 22, and booster pump 23; the coupling method between the high-temperature and medium-temperature energy storage system and the coal-fired unit is different in the energy storage process and the energy release process;

[0006] The coupling method between the high-temperature and medium-temperature energy storage system and the coal-fired unit in the energy storage process is as follows: the steam at the inlet of the medium-pressure cylinder 4 flows into the high-temperature and medium-temperature energy storage system through the extraction valve 12, and flows sequentially through the high-temperature heat exchanger 13, the phase change energy storage tank 14, and the medium-temperature heat exchanger 15, and then is sent to the feedwater outlet of the deaerator 9; the cold molten salt flows out from the cold energy storage medium tank 16 and flows sequentially through the cold energy storage medium tank outlet regulating valve 18, the cold energy storage medium pump 19, the medium-temperature heat exchanger 15, and the high-temperature heat exchanger 13, and is heated to become hot molten salt and sent to the hot energy storage medium tank 17;

[0007] The coupling method between the high-temperature and medium-temperature energy storage system and the coal-fired unit in the energy release process is as follows: the working fluid at the inlet of the deaerator 9 is connected to the high-temperature and medium-temperature energy storage system through the feedwater regulating valve 20, and flows sequentially through the medium-temperature heat exchanger 15, the phase change energy storage tank 14, and the high-temperature heat exchanger 13. Then, the working fluid is sent to the inlet of the low-pressure cylinder 5 or the outlet of the high-pressure cylinder 3 through the inlet point judgment method. The hot molten salt flows out of the hot energy storage medium tank 17 and flows sequentially through the hot energy storage medium tank outlet regulating valve 21, the hot energy storage medium pump 22, the high-temperature heat exchanger 13, and the medium-temperature heat exchanger 15 before becoming cold molten salt and being sent to the cold energy storage medium tank 16.

[0008] The method for determining the inlet point is as follows: if the required load rate is too high, the working fluid is sent to the outlet of the high-pressure cylinder 3 via the booster pump 23; otherwise, the working fluid is sent to the inlet of the low-pressure cylinder 5; when the working fluid is sent to the outlet of the high-pressure cylinder 3, the reheat steam temperature regulation method needs to be corrected.

[0009] BA xz =BA·f(G r2 )

[0010] In the formula: BA xz The corrected reheat steam temperature regulation method; BA represents the original reheat steam temperature regulation method; f(G) r2 The working fluid flow rate G entering the high-temperature energy storage system during the energy release process is... r2 Relevant correction factors;

[0011] The energy storage process reduces the minimum load of the coal-fired unit, while the energy release process increases the load change rate of the coal-fired unit, thus achieving a comprehensive improvement in the flexibility of the coal-fired unit.

[0012] The control method for the integrated high-temperature and medium-temperature energy storage system that enhances the flexibility of coal-fired power units is as follows: During the energy storage process, the control method for the high-temperature and medium-temperature energy storage system coupled with the coal-fired power unit is as follows: The steam extraction flow rate at the inlet of the intermediate-pressure cylinder 4 is controlled by the extraction valve 12. The required molten salt flow rate is calculated based on the steam extraction flow rate at the inlet of the intermediate-pressure cylinder 4, and the opening degree of the outlet regulating valve 18 of the cold energy storage medium tank is obtained. The released working fluid is sent to the deaerator feedwater outlet, and the condensate flow rate is corrected based on the safety considerations of the deaerator water level. During the energy release process, the control method for the high-temperature and medium-temperature energy storage system coupled with the coal-fired power unit is as follows: A load distribution module is designed to calculate the feedwater flow rate entering the high-temperature and medium-temperature energy storage system, obtain the opening degree of the feedwater regulating valve 20, calculate the steam work done by the high-temperature and medium-temperature energy storage system, and reset the work setpoint of the coal-fired power unit boiler-machine coordination system.

[0013] The specific calculation steps in the control method of the high-temperature energy storage coupled with the coal-fired power unit in the energy storage process are as follows:

[0014] ① Calculate the opening degree K of the extraction steam valve 12. 12

[0015]

[0016] In the formula: G r1 The steam extraction rate at the inlet of the intermediate-pressure cylinder, obtained by operators based on the minimum flow rate of the low-pressure cylinder, is expressed in kg / s; k. v,12 The resistance coefficient s is the connecting pipe between the inlet of the intermediate-pressure cylinder 4 and the high-temperature heat exchanger 13. 2 ·MPa / (kg·m 3 );ρ 12 The density of the working fluid at the inlet of the intermediate-pressure cylinder is kg / m³. 3 ;Δp 12 The pressure difference between the inlet of the intermediate-pressure cylinder 4 and the high-temperature heat exchanger 13 is expressed in MPa.

[0017] ② Selection of phase change materials in phase change energy storage tank 14

[0018] The melting temperature of the phase change material in the phase change energy storage tank 14 should be lower than the saturation temperature corresponding to the inlet steam pressure of the intermediate pressure cylinder;

[0019] ③ Calculate the opening degree K of the outlet regulating valve of the cold energy storage medium tank. 18

[0020]

[0021]

[0022] Where: h l The enthalpy of saturated water is given by the steam pressure at the inlet of the intermediate-pressure cylinder, in kJ / kg; h. d,out The enthalpy of the working fluid at the deaerator outlet is expressed in kJ / kg; h. c The enthalpy of cold-melted salt is expressed in kJ / kg; h h1 The enthalpy of molten salt at the outlet of the medium-temperature heat exchanger 15 is given in kJ / kg; G c,18 The flow rate of molten salt is kg / s; k v,18 The resistance coefficient of the pipe connecting the cold energy storage medium tank 16 and the cold energy storage medium pump 19 is s. 2 ·MPa / (kg·m 3 );ρ 18 Density of cold molten salt, kg / m³ 3 ;Δp 18 The pressure difference between the cold energy storage medium tank 16 and the cold energy storage medium pump 19 is in MPa.

[0023] ④ Calculate the correction value G for condensate volume. cond,xz

[0024] G cond,xz =G cond -G r1

[0025] In the formula: Gcond This is the original value for condensate volume, kg / s.

[0026] The specific calculation steps in the control method of the high-temperature energy storage and coal-fired power unit coupling system during the energy release process are as follows:

[0027] ① Calculate the design opening K of the water supply regulating valve 20 20

[0028]

[0029]

[0030]

[0031] In the formula: G r2 The feedwater flow rate into the high-temperature energy storage system is the pumping rate at the deaerator inlet, expressed in kg / s and h. m The enthalpy of the steam at the inlet of the intermediate-pressure cylinder under energy storage conditions is expressed in kJ / kg; h. d,in The enthalpy of the working fluid at the deaerator inlet is expressed in kJ / kg; h. i The enthalpy of the working fluid at the inlet is kJ / kg; Ra is the extraction ratio of the working fluid at the deaerator inlet; k v,20 The resistance coefficient, s, is the resistance coefficient of the pipe connecting the inlet of deaerator 9 and the medium-temperature heat exchanger 15. 2 ·MPa / (kg·m 3 );ρ 20 The density of the working fluid at the deaerator inlet is kg / m³. 3 ;Δp 20 The pressure difference between the inlet of deaerator 9 and medium-temperature heat exchanger 15, in MPa;

[0032] ② Calculate the work done by the steam generated by the high-temperature energy storage system, Pe. es

[0033]

[0034] In the formula: The work done by a high-temperature energy storage system per unit mass flow rate to generate steam, expressed in kW / (kg / s). The reduction in unit work done when the condensate volume per unit mass flow rate increases, expressed in kW / (kg / s).

[0035] ③ Calculate the real-time opening value K of the water supply regulating valve 20. 20,rt

[0036] K 20,rt =K 20 +f PID (Pe es Pe w Peb )

[0037] In the formula: Pe w The real-time output power of the coal-fired unit is expressed in kW; Pe b The reset work done by the boiler-generator coordination system of a coal-fired unit, in kW; f PID The correction factor is related to the real-time power deviation, where the real-time power deviation is calculated as the real-time output power of the coal-fired unit minus the reset work value of the coal-fired unit boiler-machine coordination system minus the steam work generated by the high-temperature and medium-temperature energy storage system.

[0038] ④ Calculate the reset work value Pe of the coal-fired power unit's boiler-generator coordination system. b

[0039] Pe 1,n =Pe1+Pe es

[0040]

[0041]

[0042]

[0043]

[0044] Where: Pe1 is the initial load of the coal-fired unit, kW; Pe 1,n Pe2 represents the initial load of the coal-fired unit after coupling with the high-temperature and medium-temperature energy storage system, in kW; Pe2 represents the target load of the coal-fired unit, in kW; rate0 represents the original load change rate of the coal-fired unit, in kW / s; t s0 The time for the coal-fired unit to reach the target load is 1, in seconds; rate1 is the load change rate of the coal-fired unit's boiler-generator coordination system after coupling with the high-temperature and medium-temperature energy storage system, in kW / s; t s1 The time, in seconds, for the coordinated system of the coal-fired unit and boiler to reach the target load after coupling the high-temperature and high-temperature energy storage system;

[0045] ⑤ Input the reset work value of the coal-fired unit boiler-turbine coordination system into the coal-fired unit boiler-turbine coordination control system to obtain boiler commands and turbine commands.

[0046] Coupling external energy storage devices is an effective means of enhancing the flexibility of coal-fired power units. It not only effectively reduces the minimum stable combustion load but also improves the unit's load change rate by resetting the work output, achieving energy matching across all operating conditions and time periods of the thermal system, thus significantly improving the flexibility of the coal-fired power unit. Compared with existing technologies, the advantages of this invention are as follows:

[0047] (1) The integrated high-temperature and medium-temperature energy storage coupling system proposed in this invention reduces the minimum load of the coal-fired unit during the energy storage process and increases the load change rate of the coal-fired unit during the energy release process, thus realizing a comprehensive improvement in the flexibility of the coal-fired unit.

[0048] (2) The control method of the integrated high-temperature and medium-temperature energy storage to enhance the flexible coupling system of coal-fired power units proposed in this invention takes into account different load rate requirements and different entry points during the energy release process, which can realize multiple increases in load rate and adapt to various needs during the operation of coal-fired power units.

[0049] (3) The control method of the integrated high-temperature and medium-temperature energy storage to enhance the flexible coupling system of coal-fired power units proposed in this invention resets the power setting value of the boiler-machine coordination system, which greatly improves the load change rate of coal-fired power units. Attached Figure Description

[0050] Figure 1 A schematic diagram of a coupling system for integrating high- and medium-temperature energy storage to enhance the flexibility of coal-fired power units.

[0051] Figure 2 A schematic diagram of the control method for a coupled system of a coal-fired power unit integrating high-temperature and medium-temperature energy storage.

[0052] Figure 3 This is a comparison chart of the minimum load of the unit before and after integrating high- and medium-temperature energy storage during the energy storage process.

[0053] Figure 4 This diagram illustrates the increase in the unit's load change rate before and after integrating high- and medium-temperature energy storage during the energy release process (taking the inlet of the low-pressure cylinder as an example). Detailed Implementation

[0054] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0055] This invention integrates a high- and medium-temperature energy storage system and control method to enhance the flexibility of coal-fired power units. A 660MW double reheat unit is selected as a case study. The specific implementation method is as follows:

[0056] 1. Case study: Integrated high- and medium-temperature energy storage coupling system, such as... Figure 1As shown: The coupling system includes a coal-fired power unit and a high- and medium-temperature energy storage system; in the coal-fired power unit, the superheated steam outlet of boiler 1 is connected to the steam inlet of ultra-high pressure cylinder 2 via a pipeline; the exhaust outlet of ultra-high pressure cylinder 2 is connected to the primary cold reheat steam inlet of boiler 1 via a pipeline; the primary hot reheat steam outlet of boiler 1 is connected to the steam inlet of high-pressure cylinder 3 via a pipeline; the exhaust outlet of high-pressure cylinder 3 is connected to the secondary cold reheat steam inlet of boiler 1 via a pipeline; and the secondary hot reheat steam outlet of boiler 1 is connected to the steam inlet of intermediate-pressure cylinder 4 via a pipeline. The exhaust outlet of the intermediate-pressure cylinder 4 is connected to the steam inlet of the low-pressure cylinder 5 via a pipeline. The exhaust outlet of the low-pressure cylinder 5 is connected to the exhaust inlet of the condenser 6 via a pipeline. The condensate outlet of the condenser 6 is connected to the condensate inlet of the low-pressure regenerative heater 8 via a pipeline through the condensate pump 7. The condensate outlet of the low-pressure regenerative heater 8 is connected to the condensate inlet of the deaerator 9 via a pipeline. The feedwater outlet of the deaerator 9 is connected to the feedwater inlet of the high-pressure regenerative heater 11 via the feedwater pump 10 via a pipeline. The feedwater outlet of the high-pressure regenerative heater 11... The steam extraction port of the ultra-high pressure cylinder 2 is connected to the steam extraction inlet of the high-pressure regenerative heater 11 via a pipeline; the steam extraction port of the high-pressure cylinder 3 is connected to the steam extraction inlet of the high-pressure regenerative heater 11 via a pipeline; the first-stage steam extraction port of the intermediate-pressure cylinder 4 is connected to the steam extraction inlet of the high-pressure regenerative heater 11 via a pipeline; the second-stage steam extraction port of the intermediate-pressure cylinder 4 is connected to the steam extraction inlet of the deaerator 9 via a pipeline; the remaining stages of the intermediate-pressure cylinder 4 are connected to the steam extraction inlet of the low-pressure regenerative heater 8 via pipelines; and the low-pressure cylinder 5... The extraction port is connected to the extraction inlet of the low-pressure regenerative heater 8 via a pipeline; the high-temperature and medium-temperature energy storage system consists of extraction valve 12, high-temperature heat exchanger 13, phase change material 14, medium-temperature heat exchanger 15, cold energy storage medium tank 16, hot energy storage medium tank 17, cold energy storage medium tank outlet regulating valve 18, cold energy storage medium pump 19, feedwater regulating valve 20, hot energy storage medium tank outlet regulating valve 21, hot energy storage medium pump 22, and booster pump 23; the coupling method and control method between the high-temperature and medium-temperature energy storage system and the coal-fired unit are different in the energy storage process and energy release process.

[0057] 2. For example Figure 1 As shown, the coupling method between the energy storage process of the case unit and the high-temperature and medium-temperature energy storage system is as follows: the steam at the inlet of the intermediate-pressure cylinder 4 flows into the high-temperature and medium-temperature energy storage system through the extraction valve 12, and flows sequentially through the high-temperature heat exchanger 13, the phase change material 14, and the intermediate-temperature heat exchanger 15, and then is sent to the feedwater outlet of the deaerator 9 to mix with the remaining working fluid; the cold molten salt flows out from the cold energy storage medium tank 16 and flows sequentially through the cold energy storage medium tank outlet regulating valve 18, the cold energy storage medium pump 19, the intermediate-temperature heat exchanger 15, and the high-temperature heat exchanger 13, and is heated to become hot molten salt and sent to the hot energy storage medium tank 17.

[0058] 3. For example Figure 1As shown, the coupling method between the energy release process of the case unit and the high-temperature and medium-temperature energy storage system is as follows: the working fluid at the deaerator inlet is connected to the high-temperature and medium-temperature energy storage system through the feedwater regulating valve 20, and flows sequentially through the medium-temperature heat exchanger 15, the phase change material 14, and the high-temperature heat exchanger 13. Then, the working fluid is sent to the inlet of the low-pressure cylinder 5 or the outlet of the high-pressure cylinder 3 through the inlet point judgment method. The hot molten salt flows out from the hot energy storage medium tank 17 and flows sequentially through the hot energy storage medium tank outlet regulating valve 21, the hot energy storage medium pump 22, the high-temperature heat exchanger 13, and the medium-temperature heat exchanger 15 before becoming cold molten salt and being sent to the cold energy storage medium tank 16.

[0059] 4. The method for selecting the inlet point during the energy release process of the case unit is as follows: If the required load change rate is too large, the working fluid is sent to the outlet of the high-pressure cylinder 3 through the booster pump 23; otherwise, the working fluid is sent to the inlet of the low-pressure cylinder 5; when the working fluid is sent to the outlet of the high-pressure cylinder 3, the reheat steam temperature regulation method needs to be modified:

[0060] BA xz =BA·f(G r2 )

[0061] In the formula: BA xz The corrected reheat steam temperature regulation method; BA represents the original reheat steam temperature regulation method; f(G) r2 The working fluid flow rate G entering the high-temperature energy storage system during the energy release process is... r2 The relevant correction factor.

[0062] 5. For example Figure 2 As shown, the control method for the energy storage process of the case unit is as follows:

[0063] The steam extraction flow rate at the inlet of the intermediate pressure cylinder is controlled by the steam extraction valve 12. The required molten salt flow rate is calculated based on the steam extraction flow rate at the inlet of the intermediate pressure cylinder, and the opening degree of the outlet regulating valve 18 of the cold energy storage medium tank is obtained. The working medium after heat release is sent to the deaerator feedwater outlet. At the same time, the condensate flow rate is corrected based on the safety consideration of the deaerator water level.

[0064] ① Based on the operating conditions of the case unit during the energy storage process, the density and pressure of the working medium at the inlet of the intermediate-pressure cylinder are obtained. The resistance coefficient is obtained through the resistance characteristic curve of the valve. After calculation, the opening degree K of the extraction steam valve 12 is obtained. 12

[0065]

[0066] In the formula: G r1 The steam flow rate at the inlet of the intermediate-pressure cylinder, obtained by operators based on the minimum flow rate of the low-pressure cylinder, is expressed in kg / s; k v,12 S is the drag coefficient. 2 ·MPa / (kg·m 3 );ρ 12The density of the working fluid at the inlet of the intermediate-pressure cylinder is kg / m³. 3 ;Δp 12 The pressure difference between the inlet of the intermediate-pressure cylinder and the high-temperature heat exchanger 13 is expressed in MPa.

[0067] ② Selection of phase change materials in phase change energy storage tank 14

[0068] The steam pressure at the inlet of the intermediate pressure cylinder in the case unit is 0.955 MPa, and the corresponding saturation temperature is 177℃. Therefore, the phase change material selected for the phase change energy storage tank 14 has a melting temperature of 160℃: LiNO3(55.4)-4.5NaNO3-40.1KCl.

[0069] ③ Based on the operating conditions of the case unit during energy storage, the temperature and pressure of the working fluid at the deaerator outlet are obtained. After consulting the steam property table, the enthalpy of the working fluid is obtained. After calculation with parameters such as the enthalpy of the molten salt, the opening degree K of the regulating valve 18 at the outlet of the cold energy storage medium tank is obtained. 18

[0070]

[0071]

[0072] Where: h l The enthalpy of saturated water is given by the steam pressure at the inlet of the intermediate-pressure cylinder, in kJ / kg; h. d,out The enthalpy of the working fluid at the deaerator outlet is expressed in kJ / kg; h. c The enthalpy of cold-melted salt is expressed in kJ / kg; h h1 The enthalpy of molten salt at the outlet of the medium-temperature heat exchanger 15 is given in kJ / kg; G c,18 The flow rate of molten salt is kg / s; k v,18 The resistance coefficient of the pipe connecting the cold energy storage medium tank 16 and the cold energy storage medium pump 19 is s. 2 ·MPa / (kg·m 3 );ρ 18 Density of cold molten salt, kg / m³ 3 ;Δp 18 The pressure difference between the cold energy storage medium tank 16 and the cold energy storage medium pump 19 is expressed in MPa.

[0073] ④ Based on the original value of condensate flow obtained from the operating conditions of the unit during the energy release process, the corrected value G of condensate flow is obtained by calculating the pumping rate during the energy release process and the original value of condensate flow. cond,xz .

[0074] G cond,xz =G cond -G r1

[0075] In the formula: G cond This is the original value for condensate volume, kg / s.

[0076] 6. For example Figure 2 As shown, the control method of the system after the energy release process of the case unit is coupled with the high-temperature and medium-temperature energy storage is as follows: design a load distribution module, calculate the feedwater flow rate entering the high-temperature and medium-temperature energy storage system, obtain the opening degree of the feedwater regulating valve 20, calculate the steam work generated by the high-temperature and medium-temperature energy storage system, reset the work set value of the boiler-turbine coordination system, and input it into the boiler-turbine coordination control system.

[0077] ① Based on the unit operating conditions during the energy storage process, obtain the enthalpy values ​​of the working fluid at the inlet of the intermediate-pressure cylinder and the enthalpy values ​​of the working fluid at the outlet of the deaerator. Based on the operating conditions of the coal-fired unit during the energy release process, obtain the working fluid temperature and pressure at the inlet of the coal-fired power plant and the working fluid temperature and pressure at the deaerator inlet. After consulting the steam property table, obtain the enthalpy values ​​of the working fluid at the inlet of the coal-fired power plant and the working fluid at the outlet of the deaerator. After calculating the above parameters, obtain the design opening degree K of the feedwater regulating valve 20. 20

[0078]

[0079]

[0080]

[0081] In the formula: G r2 The feedwater flow rate into the high-temperature energy storage system is the pumping rate at the deaerator inlet, expressed in kg / s and h. m The enthalpy of the steam at the inlet of the intermediate-pressure cylinder under energy storage conditions is expressed in kJ / kg; h. d,in The enthalpy of the working fluid at the deaerator inlet is expressed in kJ / kg; h. i The enthalpy of the working fluid at the inlet is kJ / kg; Ra is the extraction ratio of the working fluid at the deaerator inlet; k v,20 The resistance coefficient, s, is the resistance coefficient of the pipe connecting the inlet of deaerator 9 and the medium-temperature heat exchanger 15. 2 ·MPa / (kg·m 3 );ρ 20 The density of the working fluid at the deaerator inlet is kg / m³. 3 ;Δp 20 The pressure difference between the inlet of deaerator 9 and the medium-temperature heat exchanger 15 is expressed in MPa.

[0082] ② Calculate the work done by the steam generated by the high-temperature energy storage system, Pe. es

[0083]

[0084] In the formula: The work done by a unit of high-temperature energy storage system to generate steam is obtained through steam disturbance test, kW / (kg / s); The reduction in unit power output, measured in kW / (kg / s), is obtained through a condensate disturbance test when the condensate flow rate per unit mass increases.

[0085] ③Based on the real-time output power of the coal-fired unit obtained from the automatic power generation system of the coal-fired unit, calculate the real-time opening value K of the feedwater regulating valve (20). 20,rt

[0086] K 20,rt =K 20 +f PID (Pe es Pe w Pe b )

[0087] In the formula: Pe w The real-time output power of the coal-fired unit is expressed in kW; Pe b The reset work done by the boiler-generator coordination system of a coal-fired unit, in kW; f PID The correction factor is related to the real-time power deviation, which is calculated by subtracting the reset work value of the coal-fired unit's boiler-machine coordination system from the real-time output power of the coal-fired unit, and subtracting the steam work generated by the high-temperature and medium-temperature energy storage system.

[0088] ④ Calculate the reset work value Pe of the coal-fired power unit's boiler-generator coordination system. b

[0089] Pe 1,n =Pe1+Pe es

[0090]

[0091]

[0092]

[0093]

[0094] Where: Pe1 is the initial load of the coal-fired unit, kW; Pe 1,n Pe2 represents the initial load of the coal-fired unit after coupling with the high-temperature and medium-temperature energy storage system, in kW; Pe2 represents the target load of the coal-fired unit, in kW; rate0 represents the original unit load change rate, in kW / s; t s0 The time for the coal-fired unit to reach the target load is 1, in seconds; rate1 is the load change rate of the coal-fired unit's boiler-generator coordination system after coupling with the high-temperature and medium-temperature energy storage system, in kW / s; t s1 The time, in seconds, is the time required for the coal-fired unit's boiler-generator coordination system to reach the target load after coupling the high-temperature and medium-temperature energy storage system.

[0095] ⑤ Input the reset work value of the boiler-turbine coordination system of the coal-fired unit into the boiler-turbine coordination control system of the coal-fired unit to obtain boiler commands and turbine commands.

[0096] 7. Optimization effect of the case unit

[0097] Figure 3 A comparison chart of the minimum load of the case unit in the simulation system after coupling high-temperature and medium-temperature energy storage is given. It can be seen that after coupling the high-temperature and medium-temperature energy storage system, the minimum load of the case unit is reduced from 30.0% THA (THA represents rated operating conditions) to below 20.0% THA (19.4% THA) without changing the boiler load.

[0098] Figure 4 A comparison chart of unit control parameters during the energy release process of the case unit after coupling high-temperature and medium-temperature energy storage is presented. It can be seen that after coupling the high-temperature and medium-temperature energy storage system and distributing the load, the unit's load change rate increased from 15.97MW / min to 19.80MW / min, which is a significant improvement.

[0099] Therefore, the integrated high- and medium-temperature energy storage coupled system and control method for improving the flexibility of coal-fired power units proposed in this invention can improve the unit's load change rate while reducing the unit's minimum load, thus significantly improving the unit's flexibility.

Claims

1. A control method of a coupling system integrating a high-temperature energy storage and a high-temperature energy storage upgrading flexibility of a coal-fired unit, characterized in that: The coupling system comprises a coal-fired unit and a high-medium temperature energy storage system; a superheated steam outlet of a boiler (1) in the coal-fired unit is connected with a steam inlet of a super-high pressure cylinder (2) through a pipeline, an exhaust steam outlet of the super-high pressure cylinder (2) is connected with a primary cold-reheated steam inlet of the boiler (1) through a pipeline, a primary hot-reheated steam outlet of the boiler (1) is connected with a steam inlet of a high pressure cylinder (3) through a pipeline, an exhaust steam outlet of the high pressure cylinder (3) is connected with a secondary cold-reheated steam inlet of the boiler (1) through a pipeline, a secondary hot-reheated steam outlet of the boiler (1) is connected with a steam inlet of a medium pressure cylinder (4) through a pipeline, an exhaust steam outlet of the medium pressure cylinder (4) is connected with a steam inlet of a low pressure cylinder (5) through a pipeline, an exhaust steam outlet of the low pressure cylinder (5) is connected with an exhaust steam inlet of a condenser (6) through a pipeline, a condensate outlet of the condenser (6) is connected with a condensate inlet of a low pressure regenerative heater (8) through a pipeline by a condensate pump (7), a condensate outlet of the low pressure regenerative heater (8) is connected with a condensate inlet of a deaerator (9) through a pipeline, a feed water outlet of the deaerator (9) is connected with a feed water inlet of a high pressure regenerative heater (11) through a pipeline by a feed water pump (10), a feed water outlet of the high pressure regenerative heater (11) is connected with a feed water inlet of the boiler (1) through a pipeline, a steam extraction port of the super-high pressure cylinder (2) is connected with a steam extraction inlet of the high pressure regenerative heater (11) through a pipeline, a steam extraction port of the high pressure cylinder (3) is connected with the steam extraction inlet of the high pressure regenerative heater (11) through a pipeline, a first stage steam extraction port of the medium pressure cylinder (4) is connected with the steam extraction inlet of the high pressure regenerative heater (11) through a pipeline, a second stage steam extraction port of the medium pressure cylinder (4) is connected with a steam extraction inlet of the deaerator (9) through a pipeline, the rest stage steam extraction ports of the medium pressure cylinder (4) are connected with steam extraction inlets of the low pressure regenerative heater (8) through pipelines, and a steam extraction port of the low pressure cylinder (5) is connected with a steam extraction inlet of the low pressure regenerative heater (8) through a pipeline; the high-medium temperature energy storage system is composed of a steam extraction valve (12), a high temperature heat exchanger (13), a phase change energy storage tank (14), a medium temperature heat exchanger (15), a cold energy storage medium tank (16), a hot energy storage medium tank (17), a cold energy storage medium tank outlet adjusting valve (18), a cold energy storage medium pump (19), a feed water adjusting valve (20), a hot energy storage medium tank outlet adjusting valve (21), a hot energy storage medium pump (22) and a booster pump (23); the coupling modes of the energy storage process and the energy release process of the high-medium temperature energy storage system and the coal-fired unit are different; The coupling mode of the energy storage process of the high-medium temperature energy storage system and the coal-fired unit is that steam at the inlet of the medium pressure cylinder (4) flows into the high-medium temperature energy storage system through the steam extraction valve (12), sequentially flows through the high temperature heat exchanger (13), the phase change energy storage tank (14) and the medium temperature heat exchanger (15), and then is sent to the feed water outlet of the deaerator (9); cold molten salt flows out of the cold energy storage medium tank (16), sequentially flows through the cold energy storage medium tank outlet adjusting valve (18), the cold energy storage medium pump (19), the medium temperature heat exchanger (15) and the high temperature heat exchanger (13), is heated into hot molten salt and is sent into the hot energy storage medium tank (17); The coupling mode of the high-medium temperature energy storage system in the energy releasing process and the coal-fired unit is as follows: the working medium at the inlet of the deaerator (9) is connected with the high-medium temperature energy storage system through the feed water regulating valve (20), sequentially flows through the medium temperature heat exchanger (15), the phase change energy storage tank (14), and the high temperature heat exchanger (13), and then is sent to the inlet of the low pressure cylinder (5) or the outlet of the high pressure cylinder (3) by the merging point judgment method; the hot molten salt flows out of the hot energy storage medium tank (17), sequentially flows through the hot energy storage medium tank outlet regulating valve (21), the hot energy storage medium pump (22), the high temperature heat exchanger (13), and the medium temperature heat exchanger (15), and then becomes the cold molten salt and is sent to the cold energy storage medium tank (16); The merging point judgment method is as follows: if the required variable load rate is too large, the working medium is sent to the outlet of the high pressure cylinder (3) through the booster pump (23); otherwise, the working medium is sent to the inlet of the low pressure cylinder (5); when the working medium is sent to the outlet of the high pressure cylinder (3), the reheat steam temperature adjustment mode needs to be corrected: In the formula: BA xz is the modified post-reheat steam temperature control mode; BA is the modified pre-reheat steam temperature control mode; f G r2 is the modified coefficient related to the working fluid flow rate entering the high-temperature energy storage system during the energy release process G r2 is the modified coefficient related to the working fluid flow rate entering the high-temperature energy storage system during the energy release process​ The energy storage process reduces the minimum load of the coal-fired unit, the energy releasing process improves the variable load rate of the coal-fired unit, and the flexibility of the coal-fired unit is comprehensively improved; The control method is as follows: the control method of the high-medium temperature energy storage and the coal-fired unit coupling system in the energy storage process is as follows: the steam extraction flow rate of the medium pressure cylinder (4) inlet is controlled through the steam extraction valve (12), the required molten salt flow rate is calculated according to the steam extraction flow rate of the medium pressure cylinder (4) inlet, the opening degree of the cold energy storage medium tank outlet regulating valve (18) is obtained, the working medium after heat release is sent to the deaerator feed water outlet, and the condensate water amount is corrected based on the safety of the deaerator water level; the control method of the high-medium temperature energy storage and the coal-fired unit coupling system in the energy releasing process is as follows: a load distribution module is designed, the feed water flow rate entering the high-medium temperature energy storage system is calculated, the opening degree of the feed water regulating valve (20) is obtained, the steam work amount generated by the high-medium temperature energy storage system is calculated, and the work set value of the coal-fired unit boiler-turbine coordination system is reset; The specific calculation steps in the control method of the high-medium temperature energy storage and the coal-fired unit coupling system in the energy releasing process are as follows:

1. Calculate the design opening of the feedwater regulating valve (20) K 20 In the formula: G r1 is the steam extraction amount of the medium-pressure cylinder inlet steam obtained by the operating personnel according to the minimum flow of the low-pressure cylinder, kg / s; G r2 is the feed water flow entering the high-medium temperature energy storage system, i.e., the extraction amount at the inlet of the deaerator, kg / s; G cond is the original condensate amount, kg / s; h m is the enthalpy value of the medium-pressure cylinder inlet steam under the energy storage condition, kJ / kg; h d,out is the enthalpy value of the working medium at the outlet of the deaerator, kJ / kg; h d,in is the enthalpy value of the working medium at the inlet of the deaerator, kJ / kg; h i is the enthalpy value of the working medium at the confluence point, kJ / kg; Ra is the extraction ratio of the working medium at the inlet of the deaerator; k v,20 is the resistance coefficient of the connecting pipeline between the inlet of the deaerator (9) and the medium-temperature heat exchanger (15), s 2 ·MPa / (kg·m 3 ); is the density of the working medium at the inlet of the deaerator, kg / m 3 ; is the pressure difference between the inlet of the deaerator (9) and the medium-temperature heat exchanger (15), MPa; (ii) calculating the amount of work done by steam generated by the high-temperature energy storage system Pe es In the formula: is the work output of the steam generated by the high-temperature energy storage system per unit mass flow rate, kW / (kg / s); is the decrease in work output of the unit when the condensed water quantity increases per unit mass flow rate, kW / (kg / s); ③calculating the opening real-time value of the feedwater regulating valve (20) K 20,rt In the formula: Pe w is the real-time output power of the coal-fired unit, kW; Pe b is the reset work value of the coal-fired unit boiler coordination system, kW; f PID is a correction coefficient related to the real-time power deviation, wherein the calculation method of the real-time power deviation is the real-time output power of the coal-fired unit minus the reset work value of the coal-fired unit boiler coordination system minus the steam work amount generated by the high-medium temperature energy storage system; (iv) calculating a reset work value of a boiler-turbine coordination system of the coal-fired power unit Pe b In the formula: Pe 1 is the initial load of the coal-fired unit, kW; Pe 1,n is the initial load of the coal-fired unit after coupling with the medium-high temperature energy storage system, kW; Pe 2 is the target load of the coal-fired unit, kW; rate 0 is the variable load rate of the original coal-fired unit, kW / s; t s0 is the time for the coal-fired unit to reach the target load, s; rate 1 is the variable load rate of the boiler-turbine coordinated system of the coal-fired unit after coupling with the medium-high temperature energy storage system, kW / s; t s1 is the time for the boiler-turbine coordinated system of the coal-fired unit after coupling with the medium-high temperature energy storage system to reach the target load, s; ⑤The reset work value of the coal-fired unit boiler-turbine coordination system is input into the coal-fired unit boiler-turbine coordination control system, and the boiler command and the steam turbine command are obtained.

2. The control method of the integrated high-mid temperature energy storage and flexibility coupling system for coal-fired units of claim 1, characterized in that: The specific calculation steps in the control method of the high-medium temperature energy storage and the coal-fired unit coupling system in the energy storage process are as follows: calculating the opening of the extraction valve (12) K 12 In the formula: G r1 is the steam extraction amount of the medium-pressure cylinder inlet obtained by the operating personnel according to the minimum flow of the low-pressure cylinder, kg / s; k v,12 is the resistance coefficient of the connecting pipeline between the medium-pressure cylinder (4) inlet and the high-temperature heat exchanger (13), s 2 ·MPa / (kg·m 3 ); is the medium-pressure cylinder inlet working medium density, kg / m 3 ; is the pressure difference between the medium-pressure cylinder (4) inlet and the high-temperature heat exchanger (13), MPa; ②Selection of phase change material in the phase change energy storage tank (14) The melting temperature of the phase change material in the phase change energy storage tank (14) should be lower than the saturation temperature corresponding to the medium pressure cylinder inlet steam pressure; ③ Calculate the opening of the cold energy storage medium tank outlet regulating valve (18) K 18 In the formula: h l is the saturated water enthalpy value corresponding to the medium-pressure cylinder inlet steam pressure, kJ / kg; h d,out is the deaerator outlet working medium enthalpy value, kJ / kg; h c is the cold molten salt enthalpy value, kJ / kg; h h1 is the molten salt enthalpy value at the outlet of the medium-temperature heat exchanger (15), kJ / kg; G c,18 is the molten salt flow rate, kg / s; k v,18 is the resistance coefficient of the connecting pipeline between the cold energy storage medium tank (16) and the cold energy storage medium pump (19), s 2 ·MPa / (kg·m 3 ); is the cold molten salt density, kg / m 3 ; is the pressure difference between the cold energy storage medium tank (16) and the cold energy storage medium pump (19), MPa; (iv) calculating a condensate water amount correction value G cond,xz In the formula: G cond Qd is the original value of the condensate water, kg / s.

Images