Coupled systems and control methods for improving the variable load performance of coal-fired power units using medium-temperature energy storage

Abstract

This invention proposes a coupled system and control method for improving the load-changing performance of coal-fired power units using intermediate-temperature energy storage: During load reduction, a portion of the exhaust steam from the intermediate-pressure cylinder is sent to the intermediate-temperature energy storage system, and the working fluid, after heat release, returns to the deaerator, completing the energy storage process; during load increase, a portion of the deaerator outlet feedwater is sent to the intermediate-temperature energy storage system, and the working fluid, after heat absorption, returns to the feedwater inlet, completing the energy release process; simultaneously, the work done per unit flow rate of deaerator outlet feedwater / intermediate-pressure cylinder exhaust steam is calculated to obtain the load setpoint of the intermediate-temperature energy storage system; the load setpoint of the coal-fired power unit boiler-turbine coordination system is obtained through parameters such as the original load change rate, the target load, and the load setpoint of the intermediate-temperature energy storage system; furthermore, during load reduction, to ensure that the deaerator water level remains within a safe range, the condensate flow rate needs to be corrected by adjusting the steam extraction rate from the intermediate-pressure cylinder exhaust steam. Through the above methods, the pressure of rapid load change in the boiler-turbine coordination system is alleviated, and the unit parameter control effect is improved.

Description

Technical Field

[0001] This invention belongs to the field of thermal control technology for thermal power plants, specifically relating to a coupled system and control method for improving the variable load performance of coal-fired units by utilizing medium-temperature energy storage. Background Technology

[0002] my country is accelerating the construction of a "clean, low-carbon, safe, and efficient" modern energy system, with coal-fired power units gradually transitioning from a primary energy source to a regulating energy source. Coal-fired power units involve diverse equipment and various thermodynamic processes, including flow, combustion, heat transfer, and work. Different thermodynamic processes have varying response time scales, making it difficult for existing coal-fired power unit thermal system structures to maintain parameter stability during rapid load changes over extended periods. Reconstructing the thermal system structure of coal-fired power units by coupling energy storage systems is a crucial means of addressing these response time differences. This paper also proposes a reconstructed control method for coal-fired power units, where the overall unit commands are shared by the boiler-turbine coordination system and external energy storage devices. This mitigates significant parameter fluctuations during rapid load changes and improves the safety of thermal power plants during such processes. Summary of the Invention

[0003] This invention addresses the problem of significant parameter fluctuations during rapid load changes in coal-fired power units. It proposes a coupling system and control method between a medium-temperature energy storage system and the coal-fired power unit, focusing on the assistance provided by a medium-temperature energy storage system during load changes. The purpose of this invention is to provide a coupling system and control method that improves the load change performance of coal-fired power units by utilizing medium-temperature energy storage. Through temperature matching, the medium-temperature energy storage system is coupled to the coal-fired power unit. Based on the concept of shared load, a control method is proposed for the coal-fired power unit during load changes with coupled medium-temperature energy storage. This alleviates the pressure on the boiler-turbine coordination system to bear the load change rate, improves the parameter control effect during load changes, and enhances the safety of unit operation.

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

[0005] A coupled system for improving the variable load performance of a coal-fired power unit using intermediate-temperature energy storage is disclosed. The coupled system includes a coal-fired power unit and an intermediate-temperature energy storage system. In the coal-fired power unit, the superheated steam outlet of boiler 1 is connected to the steam inlet of high-pressure cylinder 2 via a pipeline; the exhaust outlet of high-pressure cylinder 2 is connected to the cold reheat steam inlet of boiler 1 via a pipeline; the hot reheat steam outlet of boiler 1 is connected to the steam inlet of intermediate-pressure cylinder 3 via a pipeline; the exhaust outlet of intermediate-pressure cylinder 3 is connected to the steam inlet of low-pressure cylinder 4 via a pipeline; the exhaust outlet of low-pressure cylinder 4 is connected to the exhaust inlet of condenser 5 via a pipeline; the condensate outlet of condenser 5 is connected to the condensate inlet of low-pressure regenerative heater 7 via a condensate pump 6 via a pipeline; the condensate outlet of low-pressure regenerative heater 7 is connected to the condensate inlet of deaerator 8 via a pipeline; the feedwater outlet of deaerator 8 is connected to the feedwater inlet of high-pressure regenerative heater 10 via a feedwater pump 9; and the high-pressure regenerative heater 10... The feedwater outlet of the high-pressure cylinder 2 is connected to the feedwater inlet of the high-pressure regenerative heater 10 via a pipeline. The steam extraction port of the intermediate-pressure cylinder 3 (excluding the final stage) is connected to the steam extraction inlet of the high-pressure regenerative heater 10 via a pipeline. The final stage steam extraction port of the intermediate-pressure cylinder 3 is connected to the steam extraction inlet of the deaerator 8 via a pipeline. The steam extraction port of the low-pressure cylinder 4 is connected to the steam extraction inlet of the low-pressure regenerative heater 7 via a pipeline. The intermediate-temperature energy storage system consists of an intermediate-pressure cylinder exhaust steam extraction valve 11, an energy storage tank 12, and a deaerator outlet water extraction valve 16. During energy storage, the exhaust outlet of the intermediate-pressure cylinder 3 is connected to the inlet of the energy storage tank 12 via the intermediate-pressure cylinder exhaust steam extraction valve 11, and the outlet of the energy storage tank 12 is connected to the feedwater outlet of the deaerator 8. During energy release, the feedwater outlet of the feedwater pump 9 is connected to the inlet of the energy storage tank 12 via the deaerator outlet water extraction valve 16, and the outlet of the energy storage tank 12 is connected to the feedwater inlet of the boiler 1.

[0006] The energy storage material in the energy storage tank 12 is a phase change energy storage material, which is composed of one or more stages of phase change energy storage material, and needs to be determined according to the exhaust temperature of the intermediate pressure cylinder 3.

[0007] The aforementioned control method for improving the load-changing performance coupling system of a coal-fired power unit using intermediate-temperature energy storage involves the intermediate-temperature energy storage system in a storage phase during load reduction. The heat release medium is the extracted steam from the intermediate-pressure cylinder exhaust. The flow rate of the heat release medium entering the intermediate-temperature energy storage system is regulated by the intermediate-pressure cylinder exhaust extraction valve 11. The heat-released medium is then sent to the deaerator outlet. To ensure the deaerator water level remains within a safe range during load reduction, the real-time condensate flow rate is corrected. Subsequently, the load setting of the intermediate-temperature energy storage system and the coal-fired power unit boiler-generator coordination system is obtained using the original load change rate of the coal-fired power unit, the target load of the coal-fired power unit, the initial load of the coal-fired power unit, and the extraction ratio of the intermediate-pressure cylinder exhaust. The set value is used to obtain the real-time opening degree of the intermediate pressure cylinder exhaust steam extraction valve 11, boiler command, and turbine command. During the load increase process, the intermediate temperature energy storage system is in the energy release process. The heat absorption medium is the water pumped out of the feed water pump 9. The flow rate of the heat absorption medium entering the intermediate temperature energy storage system is regulated by the deaerator outlet water extraction valve 16. The heat-absorbing medium is sent to the boiler feed water inlet. Then, the load set value of the intermediate temperature energy storage system and the coal-fired unit boiler-machine coordination system is calculated by the energy storage capacity of the intermediate temperature energy storage system, the original load change rate of the coal-fired unit, the target load of the coal-fired unit, and the initial load of the coal-fired unit. Thus, the opening degree of the deaerator outlet water extraction valve 16, boiler command, and turbine command are obtained.

[0008] The method for correcting the real-time value of condensate volume during the load reduction process is as follows:

[0009] ① Calculate the steam extraction rate G of the intermediate pressure cylinder exhaust. m

[0010] G m =G s ·Ra

[0011] In the formula: G s The setpoint for the intermediate pressure cylinder exhaust is kg / s; Ra is the extraction ratio of the intermediate pressure cylinder exhaust.

[0012] ② Calculate the corrected real-time value of condensate flow rate G cond,rt =G cond,s -G m

[0013] In the formula: G cond,rt The corrected real-time value for condensate flow rate is kg / s; G cond,s The setpoint for condensate flow rate, in kg / s, is related to the current load of the coal-fired unit.

[0014] The calculation process for the load setpoint of the medium-temperature energy storage system during the load reduction process is as follows:

[0015]

[0016] In the formula: fh m,dPe represents the load setpoint of the medium-temperature energy storage system during load reduction; Pe is the rated load of the coal-fired unit, in kW. m Pe represents the work done by the exhaust steam from the intermediate pressure cylinder per unit mass flow rate, expressed in kW / (kg / s). c The work done by condensate per unit mass flow rate is expressed in kW / (kg / s).

[0017] The calculation process for the load setpoint of the coal-fired unit boiler-generator coordination system during the load reduction process is as follows:

[0018] Pe 1,n =Pe1-G m ·(Pe m -Pe c )

[0019] t s0 =(Pe2-Pe1) / rate0·60

[0020]

[0021] t s0,1 =(Pe2-Pe1) / rate 0,1 ·60

[0022]

[0023] In the formula: Pe 1,n Pe1 represents the initial load of the coal-fired power unit after adopting the coupled system control method, i.e., the new initial load of the coal-fired power unit, in kW; Pe2 represents the original initial load of the coal-fired power unit, in kW; t represents the target load of the coal-fired power unit. s0 The time (in seconds) for the unit load command to reach the target load under the original variable load rate; rate0 is the original variable load rate of the coal-fired unit, in kW / min; rate 0,1 The variable load rate (kW / min) of the boiler-generator coordination system of a coal-fired power unit after adopting the coupled system control method; t s0,1 The time, s, for the load command to reach the target load in the boiler-generator coordination system of a coal-fired power unit after adopting the coupled system control method; fh 0,d The load setting value for the boiler-generator coordination system of a coal-fired unit.

[0024] The calculation process for the real-time opening degree of the intermediate pressure cylinder exhaust steam extraction valve 11 during the load reduction process is as follows:

[0025]

[0026] K m,11,rt =K m,11 +f PID (fh 0,d ,fh rt ,fhm,d )

[0027] In the formula: K m,11 The design opening degree of the intermediate pressure cylinder exhaust and extraction valve 11; k v,11 The resistance coefficient s is the connecting pipe between the intermediate-pressure cylinder exhaust outlet and the intermediate-temperature energy storage system. 2 ·MPa / (kg·m 3 );ρ m The exhaust gas density of the intermediate-pressure cylinder is kg / m³. 3 ;Δp 11 The pressure difference between the exhaust outlet of intermediate pressure cylinder 3 and energy storage tank 12 is expressed in MPa and K. m,11,rt The real-time opening degree of the intermediate pressure cylinder exhaust and extraction valve 11; f PID To utilize the real-time load deviation obtained through PID control to correct the opening degree of the intermediate-pressure cylinder exhaust steam extraction valve 11, the specific real-time load deviation calculation method is fh. rt Subtract fh 0,d Subtract fh m,d ;fh rt This represents the real-time load of the coal-fired power unit.

[0028] The calculation process for the load setpoint of the coal-fired unit boiler-generator coordination system during the load increase process is as follows:

[0029] ① Calculate the energy storage capacity of the medium-temperature energy storage system

[0030]

[0031] In the formula: E m The energy storage capacity of the medium-temperature energy storage system is used to heat the deaerator outlet feedwater, in kJ / C. p denoted as , where is the specific heat capacity of the phase change energy storage material (kJ / kg / ℃); is the mass of the phase change energy storage material (kg); is the hot-end temperature of the phase change energy storage material (℃); is the melting temperature of the phase change energy storage material (℃); is the cold-end temperature of the phase change energy storage material (℃); is the latent heat of the phase change energy storage material (kJ); and is the number of phase change energy storage materials in the medium-temperature energy storage system.

[0032] ② Calculate the maximum duration of energy release during the intermediate-temperature energy storage system.

[0033]

[0034] In the formula: t m Pe1 represents the maximum duration of energy release during the medium-temperature energy storage system, in seconds; Pe2 represents the target load of the coal-fired unit, in kW; Pe1 represents the original initial load of the coal-fired unit, in kW.

[0035] ③ Calculate the load setpoint fh of the coal-fired unit's boiler-generator coordination system. 0,u

[0036] t s0 =(Pe2-Pe1) / rate0·60

[0037] t s1 =t s0 -t m

[0038] rate1=(Pe2-Pe1) / t s1 ·60

[0039]

[0040] In the formula: t s0 The time (in seconds) for the unit load setpoint to reach the target load under the original variable load rate; rate0 is the original variable load rate of the coal-fired unit (kW / min); t s1 The setpoint of the coal-fired power unit's boiler-unit coordination system after coupling the medium-temperature energy storage system reaches the target load in seconds; rate1 is the new load change rate of the coal-fired power unit's boiler-unit coordination system after coupling the medium-temperature energy storage system in kW / min; t is the real-time recorded time in seconds.

[0041] During the load increase process, the calculation process for the opening degree of the deaerator outlet pumping valve 16 and the load setpoint of the medium-temperature energy storage system is as follows:

[0042] ① Calculate the load setpoint fh of the medium-temperature energy storage system m,u

[0043]

[0044] fh m,u =fh old -fh 0,u

[0045] In the formula: fh old This is the setpoint for the overall load of the coal-fired unit under the original variable load rate.

[0046] ② Calculate the opening degree K of the deaerator outlet pumping valve 16. m,16

[0047]

[0048] In the formula: Pe fw The change in power output of a coal-fired unit when the feedwater flow rate at the deaerator outlet changes, expressed in kW / (kg / s); k v,16 The resistance coefficient s is the pipe connecting the outlet of water pump 9 to the medium-temperature energy storage system. 2 ·MPa / (kg·m 3 );ρ m,16 For water supply density, kg / m³ 3;Δp m,16 The pressure difference between the water supply at the outlet of the water pump and the energy storage tank 12 is expressed in MPa.

[0049] The load setpoint of the coal-fired unit's boiler-machine coordination system is sent to the boiler-machine coordination control system of the coal-fired unit to obtain boiler commands and turbine commands.

[0050] Compared with the prior art, the advantages of the present invention are as follows:

[0051] (1) This invention couples an external energy storage device into a coal-fired unit through temperature matching. By having the external energy storage device and the boiler-machine coordination system share the load of the whole unit, the pressure of rapid load change of the boiler-machine coordination system is alleviated, the parameter control effect of the coal-fired unit is improved, and the safety of the coal-fired unit during operation is enhanced.

[0052] (2) This invention proposes a control method for external energy storage equipment to assist coal-fired power units in changing load. By adding and modifying some control logic in the DCS control system of an actual power plant, the external energy storage equipment can assist coal-fired power units in changing load, which is a simple method. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the coupling system between medium-temperature energy storage and the case unit.

[0054] Figure 2 This study presents a control method for rapid load changes in auxiliary units of medium-temperature energy storage systems.

[0055] Figure 3 This is a comparison chart of parameter fluctuation ranges during the load reduction process of the case unit.

[0056] Figure 4 This is a comparison chart of parameter fluctuation ranges during the load increase process of the case unit. Detailed Implementation

[0057] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0058] This invention relates to a coupled system and control method for improving the variable load performance of coal-fired power units using medium-temperature energy storage. A 660MW coal-fired power unit is selected as a case study. The specific implementation method is as follows:

[0059] 1. A coupling system for improving the variable load performance of coal-fired power units using medium-temperature energy storage.

[0060] like Figure 1As shown, the coupling system includes a coal-fired power unit and a 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 high-pressure cylinder 2 via a pipeline; the exhaust outlet of high-pressure cylinder 2 is connected to the cold reheat steam inlet of boiler 1 via a pipeline; the hot reheat steam outlet of boiler 1 is connected to the steam inlet of intermediate-pressure cylinder 3 via a pipeline; the exhaust outlet of intermediate-pressure cylinder 3 is connected to the steam inlet of low-pressure cylinder 4 via a pipeline; the exhaust outlet of low-pressure cylinder 4 is connected to the exhaust inlet of condenser 5 via a pipeline; the condensate outlet of condenser 5 is connected to the condensate inlet of low-pressure regenerative heater 7 via condensate pump 6 via a pipeline; the condensate outlet of low-pressure regenerative heater 7 is connected to the condensate inlet of deaerator 8 via a pipeline; the feedwater outlet of deaerator 8 is connected to the feedwater inlet of high-pressure regenerative heater 10 via feedwater pump 9 via a pipeline; and the feedwater outlet of high-pressure regenerative heater 10 is connected to boiler 1... The feedwater inlet of the boiler 1 is connected by a pipeline. The steam extraction port of the high-pressure cylinder 2 is connected by a pipeline to the steam extraction inlet of the high-pressure regenerative heater 10. The steam extraction ports of the intermediate-pressure cylinder 3 (excluding the last stage) are connected by a pipeline to the steam extraction inlet of the high-pressure regenerative heater 10. The steam extraction port of the last stage of the intermediate-pressure cylinder 3 is connected by a pipeline to the steam extraction inlet of the deaerator 8. The steam extraction port of the low-pressure cylinder 4 is connected by a pipeline to the steam extraction inlet of the low-pressure regenerative heater 7. The intermediate-temperature energy storage system consists of an intermediate-pressure cylinder exhaust steam extraction valve 11, an energy storage tank 12, and a deaerator outlet water extraction valve 16. During energy storage, the exhaust outlet of the intermediate-pressure cylinder 3 is connected to the inlet of the energy storage tank 12 through the intermediate-pressure cylinder exhaust steam extraction valve 11, and the outlet of the energy storage tank 12 is connected to the feedwater outlet of the deaerator 8. During energy release, the feedwater outlet of the feedwater pump 9 is connected to the inlet of the energy storage tank 12 through the deaerator outlet water extraction valve 16, and the outlet of the energy storage tank 12 is connected to the feedwater inlet of the boiler 1.

[0061] 2. Material selection for energy storage tank 12

[0062] The exhaust temperature of the intermediate pressure cylinder of the case unit is between 359 and 369°C. The energy storage tank 12 is composed of one layer of phase change energy storage material 13, which is LiCl(37)-63LiOH with a melting temperature of 262°C.

[0063] 3. For example Figure 2 As shown, the implementation steps of the coupled system control method for improving the variable load performance of coal-fired power units by utilizing medium-temperature energy storage during load reduction are as follows:

[0064] ① The operator sets the extraction ratio Ra of the intermediate pressure cylinder exhaust based on the original load change rate and the minimum flow of the low pressure cylinder. The intermediate pressure cylinder exhaust setting value under different unit loads is obtained through the heat balance diagram of the case unit, and the extraction amount of the intermediate pressure cylinder exhaust is calculated.

[0065] G m =G s ·Ra

[0066] In the formula: Gm G represents the steam extraction rate of the intermediate-pressure cylinder, in kg / s. s The intermediate-pressure cylinder exhaust setpoint, kg / s, is related to the current coal-fired unit load.

[0067] ② Calculate the corrected real-time value of condensate volume.

[0068] G cond,rt =G cond,s -G m

[0069] In the formula: G cond,rt The corrected real-time value for condensate flow rate is kg / s; G cond,s The setpoint for condensate flow rate, in kg / s, is related to the current load of the coal-fired unit.

[0070] ③ Calculate the load setpoint fh of the medium-temperature energy storage system. m,d

[0071]

[0072] In the formula: fh m,d Pe represents the load setpoint of the medium-temperature energy storage system during load reduction; Pe is the rated load of the coal-fired unit, in kW, 660,000 kW; Pe m Pe represents the work done by the exhaust steam from the intermediate pressure cylinder per unit mass flow rate, expressed in kW / (kg / s). c The work done by condensate per unit mass flow rate is expressed in kW / (kg / s).

[0073] ④ Calculate the load setpoint fh of the boiler-turbine coordination system during the load reduction process. 0,d

[0074] Pe 1,n =Pe1-G m ·(Pe m -Pe c )

[0075] t s0 =(Pe2-Pe1) / rate0·60

[0076]

[0077] t s0,1 =(Pe2-Pe1) / rate 0,1 ·60

[0078]

[0079] In the formula: Pe 1,nPe1 represents the initial load of the coal-fired power unit after adopting the coupled system control method, i.e., the new initial load of the coal-fired power unit, in kW; Pe2 represents the original initial load of the coal-fired power unit, in kW; t represents the target load of the coal-fired power unit. s0 The time (in seconds) for the unit load command to reach the target load under the original variable load rate; rate0 is the original variable load rate of the coal-fired unit, in kW / min; rate 0,1 The variable load rate (kW / min) of the boiler-generator coordination system of a coal-fired power unit after adopting the coupled system control method; t s0,1 The time, s, for the load command to reach the target load in the boiler-generator coordination system of a coal-fired power unit after adopting the coupled system control method; fh 0,d The load setting value for the boiler-generator coordination system of a coal-fired unit.

[0080] ⑤ Calculate the opening degree of the intermediate pressure cylinder exhaust and extraction valve 11.

[0081]

[0082] K m,11,rt =K m,11 +f PID (fh 0,d ,fh rt ,fh m,d )

[0083] In the formula: K m,11 The design opening degree of the intermediate pressure cylinder exhaust and extraction valve 11; k v,11 The resistance coefficient s is the connecting pipe between the intermediate-pressure cylinder exhaust outlet and the intermediate-temperature energy storage system. 2 ·MPa / (kg·m 3 );ρ m The exhaust gas density of the intermediate-pressure cylinder is kg / m³. 3 ;Δp 11 The pressure difference between the exhaust outlet of intermediate pressure cylinder 3 and energy storage tank 12 is expressed in MPa and K. m,11,rt The real-time opening degree of the intermediate pressure cylinder exhaust and extraction valve 11; f PID To utilize the real-time load deviation obtained through PID control to correct the opening degree of the intermediate-pressure cylinder exhaust steam extraction valve 11, the specific real-time load deviation calculation method is fh. rt Subtract fh 0,d Subtract fh m,d ;fh rt This represents the real-time load of the coal-fired power unit.

[0084] ⑥ Set the load setpoint fh of the boiler-turbine coordination system of the case unit. 0,d The commands are sent to the boiler-turbine coordination control system of the case unit to obtain boiler commands and turbine commands.

[0085] 4. For example Figure 2As shown, the implementation steps of the coupled system control method for improving the variable load performance of coal-fired power units by utilizing medium-temperature energy storage during load increase are as follows:

[0086] ① Based on the phase change energy storage material 13 selected in step 2, obtain the specific heat capacity and melting temperature of the phase change energy storage material. Obtain the cold end temperature and hot end temperature of the energy storage phase change material through temperature measuring points, and calculate the energy storage capacity of the medium-temperature energy storage system.

[0087]

[0088] In the formula: E m The energy storage capacity of the medium-temperature energy storage system is used to heat the deaerator outlet feedwater, in kJ / C. p denoted as , where is the specific heat capacity of the phase change energy storage material (kJ / kg / ℃); is the mass of the phase change energy storage material (kg); is the hot-end temperature of the phase change energy storage material (℃); is the melting temperature of the phase change energy storage material (℃); is the cold-end temperature of the phase change energy storage material (℃); is the latent heat of the phase change energy storage material (kJ); and is the number of phase change energy storage materials in the medium-temperature energy storage system (j = 1 in the case unit).

[0089] ②Based on the initial load and target load of the case unit and the original variable load rate, calculate the maximum duration of the energy release process of the medium-temperature energy storage system.

[0090]

[0091] In the formula: t m Pe2 represents the maximum duration of energy release during the medium-temperature energy storage system, in seconds; Pe1 represents the target load of the case unit, in kW; and Pe2 represents the original initial load of the case unit, in kW.

[0092] ③ Calculate the load setpoint fh of the boiler-turbine coordination system of the case unit. 0,u

[0093] t s0 =(Pe2-Pe1) / rate0*60

[0094] t s1 =t s0 -t m

[0095] rate1=(Pe2-Pe1) / t s1 ·60

[0096]

[0097] In the formula: t s0 The time (in seconds) for the unit load setpoint to reach the target load under the original variable load rate; rate0 is the original variable load rate of the case unit (kW / min); t s1The time (s) for the load setpoint of the boiler-generator coordination system of the case unit after coupling with the medium-temperature energy storage system to reach the target load; rate1 is the new load change rate of the boiler-generator coordination system of the case unit after coupling with the medium-temperature energy storage system, kW / min; t is the real-time recording time (s).

[0098] ④ Calculate the load setpoint fh of the medium-temperature energy storage system. m,u

[0099]

[0100] fh m,u =fh old -fh 0,u

[0101] In the formula: fh old This is the setpoint for the unit load of the case study under the original variable load rate.

[0102] ⑤ Calculate the opening degree K of the deaerator outlet pumping valve (16) m,16

[0103]

[0104] In the formula: Pe fw The change in unit power (kW / (kg / s)) when the feedwater flow rate at the deaerator outlet changes. v,16 The resistance coefficient s is the pipe connecting the outlet of water pump 9 to the medium-temperature energy storage system. 2 ·MPa / (kg·m 3 );ρ m,16 For water supply density, kg / m³ 3 ;Δp m,16 The pressure difference between the water supply at the outlet of the water pump 9 and the energy storage tank 12 is expressed in MPa.

[0105] ⑥ Set the load setpoint fh of the boiler-turbine coordination system of the case unit. 0,u The commands are sent to the boiler-turbine coordination control system of the case unit to obtain boiler commands and turbine commands.

[0106] 5. Optimization effect of the case unit

[0107] Figure 3 The graph shows a comparison of the fluctuation range of unit parameters before and after adopting the coupling system and control method of this invention during load reduction. It can be seen that the main steam pressure fluctuation range decreased by 0.4684 MPa, and the main steam temperature fluctuation range decreased by 7.7℃, indicating a significant improvement in parameter control performance.

[0108] Figure 4This is a comparison chart of the fluctuation range of unit parameters before and after adopting the coupling system and control method of this invention during load increase. It can be seen that the main steam pressure fluctuation range decreased by 0.0312 MPa, and the main steam temperature fluctuation range decreased by 1.0℃, indicating a significant improvement in parameter control performance.

[0109] In summary, the coupling system and control method of the present invention for improving the variable load performance of coal-fired power units by utilizing medium-temperature energy storage can significantly improve the parameter control effect, enhance the variable load performance of the unit, and improve the safety of the unit during operation.

Claims

1. A coupling system for improving the variable load performance of a coal-fired power unit using medium-temperature energy storage, characterized in that: The coupling system includes a coal-fired power unit and a medium-temperature energy storage system; in the coal-fired power unit, the superheated steam outlet of the boiler (1) is connected to the steam inlet of the high-pressure cylinder (2) through a pipeline, the exhaust outlet of the high-pressure cylinder (2) is connected to the cold reheat steam inlet of the boiler (1) through a pipeline, the hot reheat steam outlet of the boiler (1) is connected to the steam inlet of the intermediate-pressure cylinder (3) through a pipeline, the exhaust outlet of the intermediate-pressure cylinder (3) is connected to the steam inlet of the low-pressure cylinder (4) through a pipeline, and the exhaust outlet of the low-pressure cylinder (4) is connected to the condensate steam... The exhaust inlet of the condenser (5) is connected to the condensate outlet of the condenser (5) via a pipe. The condensate outlet of the condenser (5) is connected to the condensate inlet of the low-pressure regenerative heater (7) via a condensate pump (6). The condensate outlet of the low-pressure regenerative heater (7) is connected to the condensate inlet of the deaerator (8) via a pipe. The feedwater outlet of the deaerator (8) is connected to the feedwater inlet of the high-pressure regenerative heater (10) via a feedwater pump (9). The feedwater outlet of the high-pressure regenerative heater (10) is connected to the feedwater inlet of the boiler (1). The high-pressure cylinder (2) is connected to the high-pressure regenerative heater (10) via a pipeline. The intermediate-pressure cylinder (3), except for the final stage, is connected to the high-pressure regenerative heater (10) via a pipeline. The final stage extraction port of the intermediate-pressure cylinder (3) is connected to the deaerator (8) via a pipeline. The low-pressure cylinder (4) is connected to the low-pressure regenerative heater (7) via a pipeline. The intermediate-temperature energy storage system is connected by the intermediate-pressure cylinder exhaust and extraction valve (…). 11) The system consists of an energy storage tank (12) and a deaerator outlet water extraction valve (16). During the energy storage process, the exhaust outlet of the intermediate pressure cylinder (3) is connected to the inlet of the energy storage tank (12) through the intermediate pressure cylinder exhaust extraction valve (11), and the outlet of the energy storage tank (12) is connected to the feedwater outlet of the deaerator (8). During the energy release process, the feedwater outlet of the feedwater pump (9) is connected to the inlet of the energy storage tank (12) through the deaerator outlet water extraction valve (16), and the outlet of the energy storage tank (12) is connected to the feedwater inlet of the boiler (1).

2. The coupling system for improving the variable load performance of a coal-fired unit using medium-temperature energy storage according to claim 1, characterized in that: The energy storage tank (12) is a phase change energy storage material, which is composed of one or more phase change energy storage materials. The energy storage material needs to be determined according to the exhaust temperature of the intermediate pressure cylinder (3).

3. The control method for a coupled system for improving the variable load performance of a coal-fired power unit using medium-temperature energy storage as described in claim 1 or 2, characterized in that: During the load reduction process, the intermediate temperature energy storage system is in the energy storage process. The heat release medium is the extraction steam from the intermediate pressure cylinder exhaust. The flow rate of the heat release medium entering the intermediate temperature energy storage system is regulated by the extraction steam valve (11) of the intermediate pressure cylinder exhaust. The heat-released medium is sent to the deaerator outlet. In order to ensure that the deaerator water level is within a safe range during the load reduction process, the real-time value of condensate volume is corrected. Subsequently, the load setting value of the intermediate temperature energy storage system and the coal-fired unit boiler-machine coordination system is obtained by using the original load change rate of the coal-fired unit, the target load of the coal-fired unit, the initial load of the coal-fired unit, and the extraction steam ratio of the intermediate pressure cylinder exhaust. Finally, the extraction steam valve (11) of the intermediate pressure cylinder exhaust is obtained. The real-time opening degree, boiler command and turbine command of the medium temperature energy storage system; during the load increase process, the medium temperature energy storage system is in the energy release process, and the heat absorption medium is the water pump (9) outlet pump water. The flow rate of the heat absorption medium entering the medium temperature energy storage system is adjusted by the deaerator outlet pump water valve (16). The heat-absorbing medium is sent to the boiler feed water inlet. Then, the load setting value of the medium temperature energy storage system and the coal-fired unit boiler-machine coordination system is calculated by the energy storage capacity of the medium temperature energy storage system, the original load change rate of the coal-fired unit, the target load of the coal-fired unit, and the initial load of the coal-fired unit, so as to obtain the opening degree of the deaerator outlet pump water valve (16), boiler command and turbine command.

4. The control method for improving the performance of a coal-fired power unit under variable load using medium-temperature energy storage as described in claim 3, characterized in that: The method for correcting the real-time value of condensate volume during the load reduction process is as follows: ① Calculate the steam extraction rate G of the intermediate pressure cylinder exhaust. m G m =G s ·Ra In the formula: G s The setpoint for the intermediate pressure cylinder exhaust is kg / s; Ra is the extraction ratio of the intermediate pressure cylinder exhaust. ② Calculate the corrected real-time value of condensate volume. G cond,rt =G cond,s -G m In the formula: G cond,rt The corrected real-time value for condensate flow rate is kg / s; G cond,s The setpoint for condensate flow rate, in kg / s, is related to the current load of the coal-fired unit.

5. The control method for improving the performance of a coal-fired power unit under variable load using medium-temperature energy storage as described in claim 3, characterized in that: The calculation process for the load setpoint of the medium-temperature energy storage system during the load reduction process is as follows: In the formula: fh m,d Pe represents the load setpoint of the medium-temperature energy storage system during load reduction; Pe is the rated load of the coal-fired unit, in kW. m Pe represents the work done by the exhaust steam from the intermediate pressure cylinder per unit mass flow rate, expressed in kW / (kg / s). c The work done by condensate per unit mass flow rate is expressed in kW / (kg / s).

6. The control method for improving the performance of a coal-fired power unit under variable load using a medium-temperature energy storage coupled system according to claim 3, characterized in that: The calculation process for the load setpoint of the coal-fired unit boiler-generator coordination system during the load reduction process is as follows: Instead 1,n =For1-G m ·(Instead m -Instead c ) t s0 =(Pe2-Pe1) / rate0·60 t s0,1 =(Pe2-Pe1) / rate 0,1 ·60 In the formula: Pe 1,n Pe1 represents the initial load of the coal-fired power unit after adopting the coupled system control method, i.e., the new initial load of the coal-fired power unit, in kW; Pe2 represents the original initial load of the coal-fired power unit, in kW; t represents the target load of the coal-fired power unit. s0 The time (in seconds) for the unit load command to reach the target load under the original variable load rate; rate0 is the original variable load rate of the coal-fired unit, in kW / min; rate 0,1 The variable load rate (kW / min) of the boiler-generator coordination system of a coal-fired power unit after adopting the coupled system control method; t s0,1 The time, in seconds, for the load command of the boiler-generator coordination system of a coal-fired power unit to reach the target load after adopting the coupled system control method; fh 0,d The load setting value for the boiler-generator coordination system of a coal-fired unit.

7. The control method for improving the performance of a coal-fired power unit under variable load using medium-temperature energy storage as described in claim 3, characterized in that: The calculation process for the real-time opening degree of the intermediate pressure cylinder exhaust steam extraction valve (11) during the load reduction process is as follows: K m,11,rt =K m,11 +f PID (fh 0,d ,fh rt ,fh m,d ) Where: K m,11 The design opening degree of the intermediate pressure cylinder exhaust and extraction valve (11); k v,11 The resistance coefficient s is the connecting pipe between the intermediate-pressure cylinder exhaust outlet and the intermediate-temperature energy storage system. 2 ·MPa / (kg·m 3 );ρ m The exhaust gas density of the intermediate-pressure cylinder is kg / m³. 3 ;Δp 11 The pressure difference between the exhaust outlet of the intermediate pressure cylinder (3) and the energy storage tank (12) is expressed in MPa and K. m,11,rt The real-time opening degree of the exhaust steam extraction valve (11) of the intermediate pressure cylinder; f PID To utilize the real-time load deviation obtained through PID control to correct the opening degree of the intermediate-pressure cylinder exhaust steam extraction valve (11), the specific real-time load deviation calculation method is as follows: fh rt Subtract fh 0,d Subtract fh m,d ;fh rt This represents the real-time load of the coal-fired power unit.

8. The control method for improving the performance of a coal-fired power unit under variable load using medium-temperature energy storage as described in claim 3, characterized in that: The calculation process for the load setpoint of the coal-fired unit boiler-generator coordination system during the load increase process is as follows: ① Calculate the energy storage capacity of the medium-temperature energy storage system In the formula: E m The energy storage capacity of the medium-temperature energy storage system is used to heat the deaerator outlet feedwater, in kJ / C. p denoted as , where is the specific heat capacity of the phase change energy storage material (kJ / kg / ℃); is the mass of the phase change energy storage material (kg); is the hot-end temperature of the phase change energy storage material (℃); is the melting temperature of the phase change energy storage material (℃); is the cold-end temperature of the phase change energy storage material (℃); is the latent heat of the phase change energy storage material (kJ); and is the number of phase change energy storage materials in the medium-temperature energy storage system. ② Calculate the maximum duration of energy release during the intermediate-temperature energy storage system. In the formula: t m Pe1 represents the maximum duration of energy release during the medium-temperature energy storage system, in seconds; Pe2 represents the target load of the coal-fired unit, in kW; Pe1 represents the original initial load of the coal-fired unit, in kW. ③ Calculate the load setpoint fh of the coal-fired unit's boiler-generator coordination system. 0,u t s0 =(Pe2-Pe1) / rate0·60 t s1 =t s0 -t m rate1=(Pe2-Pe1) / t s1 ·60 In the formula: t s0 The time (in seconds) for the unit load setpoint to reach the target load under the original variable load rate; rate0 is the original variable load rate of the coal-fired unit (kW / min); t s1 The setpoint of the coal-fired power unit's boiler-unit coordination system after coupling the medium-temperature energy storage system reaches the target load in seconds; rate1 is the new load change rate of the coal-fired power unit's boiler-unit coordination system after coupling the medium-temperature energy storage system in kW / min; t is the real-time recorded time in seconds.

9. The control method for improving the performance of a coal-fired power unit under variable load using a medium-temperature energy storage coupled system according to claim 3, characterized in that: During the load increase process, the calculation process for the load setpoint of the medium-temperature energy storage system and the opening degree of the deaerator outlet pumping valve (16) is as follows: ① Calculate the load setpoint fh of the medium-temperature energy storage system m,u fh m,u =fh old -fh 0,u In the formula: fh old This is the setpoint for the overall load of the coal-fired unit under the original variable load rate. ② Calculate the opening degree K of the deaerator outlet pumping valve (16). m,16 In the formula: Pe fw The change in power output of a coal-fired unit when the feedwater flow rate at the deaerator outlet changes, expressed in kW / (kg / s); k v,16 The resistance coefficient s is the pipe connecting the outlet of the water pump (9) to the medium-temperature energy storage system. 2 ·MPa / (kg·m 3 );ρ m,16 For water supply density, kg / m³ 3 ;Δp m,16 The pressure difference between the water supply at the outlet of the water pump and the energy storage tank (12) is expressed in MPa.

10. The control method for improving the performance of a coal-fired power unit under variable load using a medium-temperature energy storage system according to claim 3, characterized in that: The load setpoint of the coal-fired unit boiler-generator coordination system is sent to the coal-fired unit boiler-generator coordination control system to obtain boiler commands and turbine commands.

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