Integrated medium-temperature energy storage for improving variable load rate of double-reheat unit and control method

Abstract

The application provides a coupling system and a control method for improving the variable load rate of a secondary reheat unit integrated with a medium-temperature energy storage, wherein the medium-temperature energy storage system is connected with the high-pressure cylinder outlet through a high-pressure cylinder outlet steam extraction valve during the energy storage process, is connected with the deaerator outlet through a pressure relief valve, is connected with the feed water pump outlet through a deaerator outlet regulating valve during the energy release process, and is connected with the boiler feed water inlet through a pipeline, so as to form a secondary reheat unit integrated with the medium-temperature energy storage; and a load splitting method is provided, which splits the whole unit load instruction into a medium-temperature energy storage system load instruction and a secondary reheat unit boiler coordination system load instruction, and the medium-temperature energy storage system load instruction is realized through high-pressure cylinder exhaust valve opening degree control and deaerator outlet regulating valve opening degree control in the load decreasing and increasing processes; through the coupling system and the load splitting method, the time-space transfer of the unit energy in the variable load process is realized, the variable load rate of the secondary reheat unit is improved, and the flexibility of the unit is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of energy storage system and secondary reheat unit integration method and thermal control technology, specifically involving a coupling system and control method for integrating medium-temperature energy storage to improve the load change rate of secondary reheat units. Background Technology

[0002] Under the dual carbon targets, coal-fired power units are transitioning from a basic energy source to a regulatory and supporting energy source, and rapid load changes have become the norm, including for double reheat units. However, the difference in response speed between the heat transfer and power generation processes in double reheat units creates a significant inertial difference, seriously threatening operational safety and thus limiting the unit's load change rate, hindering rapid load changes in double reheat units. Summary of the Invention

[0003] This invention addresses the problem of limited load change rate in reheat units by providing a coupled system and control method that integrates medium-temperature energy storage to enhance the load change rate of reheat units from the perspective of spatiotemporal complementary matching of energy in multiple transient processes. This enables spatiotemporal transfer of energy during load increases and decreases, thereby improving the load change rate of reheat units and enhancing their flexibility.

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

[0005] A coupling system integrating medium-temperature energy storage to enhance the load change rate of a secondary reheat unit is proposed. The coupling system includes a medium-temperature energy storage system and a secondary reheat unit. In the secondary reheat 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; and the exhaust outlet of high-pressure cylinder 3 is connected to the secondary cold reheat steam inlet of boiler 1 via a pipeline. The outlet of the steam turbine is connected to the steam inlet of the 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 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 a feedwater pump 10. The feedwater outlet of the high-pressure regenerative heater 11... The water outlet is connected to the feedwater inlet of boiler 1 via a pipeline; the steam extraction port of ultra-high pressure cylinder 2 is connected to the steam extraction inlet of high-pressure regenerative heater 11 via a pipeline; the steam extraction port of high-pressure cylinder 3 is connected to the steam extraction inlet of high-pressure regenerative heater 11 via a pipeline; the first-stage steam extraction port of intermediate pressure cylinder 4 is connected to the steam extraction inlet of high-pressure regenerative heater 11 via a pipeline; the second-stage steam extraction port of intermediate pressure cylinder 4 is connected to the steam extraction inlet of deaerator 9 via a pipeline; the remaining stages of steam extraction ports of intermediate pressure cylinder 4 are connected to the steam extraction inlet of low-pressure regenerative heater 8 via pipelines; and the steam extraction port of low-pressure cylinder 5 is connected to the low-pressure regenerative heater 8 via a pipeline. The extraction steam inlet of the pressure return heater 8 is connected via a pipeline; the medium-temperature energy storage system consists of the high-pressure cylinder outlet extraction steam valve 16, the energy storage tank 12, the pressure relief valve 17, and the deaerator outlet regulating valve 18; during the energy storage process, the exhaust steam outlet of the high-pressure cylinder 3 is connected to the energy storage tank 12 via the high-pressure cylinder outlet extraction steam valve 16, and the energy storage tank 12 is connected to the outlet of the deaerator 9 via the pressure relief valve 17; during the energy release process, the feedwater outlet of the feedwater pump 10 is connected to the energy storage tank 12 via the deaerator outlet regulating valve 18, and the outlet of the energy storage tank 12 is connected to the feedwater inlet of the boiler 1 via a pipeline.

[0006] The energy storage tank 12 is composed of multi-stage phase change materials. The method for selecting phase change materials is to match the melting temperature of the phase change materials with the exhaust temperature of the high-pressure cylinder.

[0007] The control method for the coupled system of integrated medium-temperature energy storage to enhance the load rate of the secondary reheat unit proposes a load splitting method, which splits the overall unit load command into the load command of the medium-temperature energy storage system and the load command of the secondary reheat unit boiler-generator coordination system. The splitting method of the overall unit load command is different during the load increase and decrease process.

[0008] The method for decomposing the load command of the whole unit during the load reduction process is to design the steam extraction amount of the high-pressure cylinder to obtain the load command of the thermal energy storage system during the load reduction process, and at the same time correct the condensate flow rate during the load reduction process. Then, the load command of the secondary reheat unit boiler-generator coordination system during the load reduction process is obtained by using the steam extraction amount of the high-pressure cylinder, the original load change rate, the target load of the secondary reheat unit and the initial load.

[0009] The method for decomposing the overall load command during the load increase process is to calculate the energy storage capacity of the intermediate temperature energy storage system, obtain the load command of the intermediate temperature energy storage system during the load increase process, and then obtain the load command of the secondary reheat unit boiler-generator coordination system during the load increase process through the load command of the intermediate temperature energy storage system during the load increase process, the original planned load change rate, the target load of the secondary reheat unit and the initial load.

[0010] The calculation method for the load command of the thermal energy storage system during the load reduction process is as follows:

[0011] ① Calculate the steam extraction rate G of the high-pressure cylinder exhaust. h

[0012] G h =G h,s ·Ra

[0013] In the formula: G h,s The setpoint for high-pressure cylinder exhaust is kg / s; Ra is the extraction ratio of high-pressure cylinder exhaust.

[0014] ② Calculate the load command fh of the thermal energy storage system during the load reduction process. m,d

[0015]

[0016] In the formula: Pe h Pe represents the work done by high-pressure cylinder exhaust per unit mass flow rate, expressed in kW / (kg / s). c Pe represents the change in work done by the secondary reheat unit when the unit mass flow rate of condensate changes, in kW / (kg / s); Pe is the rated load of the secondary reheat unit, in kW.

[0017] During the load reduction process, the load command for the thermal energy storage system is implemented by controlling the opening degree of the high-pressure cylinder outlet extraction valve 16, as follows:

[0018]

[0019] K h,16,rt =K h,16 +f PID (fh 0,d ,fh rt ,fh m,d )

[0020] Where: K h,16 The design value for the high-pressure cylinder outlet extraction valve opening of 16 degrees; k v,16 The resistance coefficient s is the pipe connecting the high-pressure cylinder exhaust outlet to the medium-temperature energy storage system. 2 ·MPa / (kg·m 3 );ρ h The exhaust gas density of the high-pressure cylinder is kg / m³. 3 ;Δp 16 The pressure difference between the exhaust outlet of high-pressure cylinder 3 and energy storage tank 12 is expressed in MPa and K. h,16,rt f is the real-time value of the opening degree of the high-pressure cylinder outlet extraction valve 16; PID To correct the opening value of the high-pressure cylinder outlet extraction valve 16 obtained through PID control using real-time load deviation, the real-time load deviation is calculated as follows: real-time load of the secondary reheat unit minus the load command of the secondary reheat unit boiler-generator coordination system during the load reduction process minus the load command of the intermediate temperature energy storage system; fh 0,d For load reduction processes, load commands are issued to the boiler-generator coordination system of the secondary reheat unit; fh rt This represents the real-time load of the secondary reheat unit.

[0021] The calculation method for correcting the condensate flow rate during the load reduction process is as follows:

[0022] G cond,rt =G cond,s -G h

[0023] In the formula: G cond,rt This is a correction value for condensate volume, in kg / s; G cond,s The setpoint for condensate flow rate is kg / s.

[0024] The calculation method for the load command of the secondary reheat unit boiler-generator coordination system during the load reduction process is as follows:

[0025] Pe 1,n =Pe1-G h ·(Pe h -Pe c )

[0026] t s0 =(Pe2-Pe1) / rate0·60

[0027]

[0028] t s0,1 =(Pe2-Pe1) / rate 0,1 ·60

[0029]

[0030] In the formula: Pe1,n The initial load of the secondary reheat unit integrating medium-temperature energy storage is the new initial load of the secondary reheat unit, kW; Pe1 is the original initial load of the secondary reheat unit, kW; Pe2 is the target load of the secondary reheat unit, kW; t s0 The time (in seconds) for the load command to reach the target load under the original variable load rate; rate0 is the original variable load rate (kW / min); rate 0,1 The load change rate of the secondary reheat unit boiler-generator coordination system after load splitting, in kW / min; t s0,1 The time, s, for the load command from the secondary reheat unit's boiler-generator coordination system to reach the target load after load splitting; fh 0,d Load commands for the boiler-generator coordination system of the secondary reheat unit during the load reduction process.

[0031] The calculation methods for the load commands of the secondary reheat unit and the boiler-generator coordination system during the load increase process are as follows:

[0032] ① Calculate the energy storage capacity of the medium-temperature energy storage system

[0033]

[0034] In the formula: E m The energy storage capacity of the medium-temperature energy storage system is used to heat the deaerator outlet water, in kJ / C. p denoted as , where is the specific heat capacity of the phase change material in the medium-temperature energy storage system (kJ / kg / ℃); is the mass of the phase change material in the medium-temperature energy storage system (kg); is the hot-end temperature of the phase change material in the medium-temperature energy storage system (℃); is the melting temperature of the phase change material in the medium-temperature energy storage system (℃); is the cold-end temperature of the phase change material in the medium-temperature energy storage system (℃); is the latent heat of the phase change material in the medium-temperature energy storage system (kJ); and is the number of phase change materials in the medium-temperature energy storage system.

[0035] ② Calculate the maximum duration of heat release during the intermediate-temperature energy storage system.

[0036]

[0037] In the formula: t m Pe1 represents the maximum duration of heat release during the medium-temperature energy storage system, in seconds; Pe2 represents the target load of the secondary reheat unit, in kW; Pe1 represents the original initial load of the secondary reheat unit, in kW.

[0038] ③ Calculate the load command fh of the secondary reheat unit boiler-generator coordination system during the load increase process. 0,u

[0039] t s0 =(Pe2-Pe1) / rate0·60

[0040] ts1 =t s0 -t m

[0041] rate1=(Pe2-Pe1) / t s1 ·60

[0042]

[0043] In the formula: t s0 The time it takes for the load command to reach the target load at the original variable load rate, in seconds; rate0 is the original variable load rate, in kW / min; t s1 The time (s) for the load command of the secondary reheat unit boiler-generator coordination system after coupling the medium-temperature energy storage system to reach the target load; rate1 is the new load change rate of the secondary reheat unit boiler-generator coordination system after integrating the medium-temperature energy storage system, kW / min; t is the real-time recording time (s).

[0044] ④ Calculate the load command fh of the thermal energy storage system during the load increase process. m,u

[0045]

[0046] fh m,u =fh old -fh 0,u

[0047] In the formula: fh old This is the load command for the entire machine under the original variable load rate.

[0048] During the load increase process, the load command for the thermal energy storage system is achieved by adjusting the opening degree of the deaerator outlet regulating valve 18. The calculation method for the opening degree of the deaerator outlet regulating valve 18 is as follows:

[0049]

[0050] Where: K m,18 The opening degree of the deaerator outlet regulating valve 18; Pe fw k represents the increase in power of the secondary reheat unit when the feedwater flow rate at the deaerator outlet changes, expressed in kW / (kg / s). v,18 s is the resistance coefficient of the pipeline connecting the water pump outlet and the medium-temperature energy storage system. 2 ·MPa / (kg·m 3 );ρ m,18 For water supply density, kg / m³ 3 ;Δp m,18 The pressure difference between the outlet of the feedwater pump and the outlet of the high-pressure regenerator 11 is expressed in MPa.

[0051] During the load reduction and load increase processes, the load commands from the secondary reheat unit's boiler-turbine coordination system are sent to the boiler-turbine coordination control system to obtain boiler commands and turbine commands.

[0052] Energy storage systems can realize the spatial and temporal transfer of energy, reduce the load changes borne by the secondary reheat unit, and alleviate the large parameter changes caused by the difference in response speed. When coupled with the secondary reheat unit, it can significantly improve the load change rate of the secondary reheat unit while realizing energy transfer, and give full play to the rapid load change potential of the secondary reheat unit.

[0053] Compared with the prior art, the advantages of the present invention are as follows:

[0054] (1) Based on the concept of temperature matching, this invention proposes a coupling system between a secondary reheat unit and a medium-temperature energy storage system, which realizes the spatiotemporal transfer of energy in multiple transient processes and provides the possibility for rapid load change of the unit.

[0055] (2) The load splitting method proposed in this invention reduces the load commands borne by the boiler-generator coordination system of the secondary reheat unit and improves the load change rate of the secondary reheat unit.

[0056] (3) The coupling system and control method proposed in this invention take into account the safety of the unit during operation. For example, during energy storage, the pressure relief valve alleviates the parameter fluctuations in the deaerator, and the condensate volume is adjusted to avoid fluctuations in the deaerator water level. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of a secondary reheat unit coupling system that integrates medium-temperature energy storage.

[0058] Figure 2 A control method for a coupled system of a secondary reheat unit with integrated medium-temperature energy storage.

[0059] Figure 3 This is a schematic diagram of the unit's load instructions before and after load splitting during the load reduction process of the case unit.

[0060] Figure 4 This is a schematic diagram of the unit load instructions before and after load splitting during the load increase process of the case unit. Detailed Implementation

[0061] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0062] This invention integrates a coupled system and control method for improving the load change rate of a double reheat unit using medium-temperature energy storage. A 660MW double reheat unit is selected as a case study. The specific implementation method is as follows:

[0063] 1. A schematic diagram of the case unit after integrating a medium-temperature energy storage system is shown below. Figure 1As shown: In the double reheat 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; the secondary hot reheat steam outlet of boiler 1 is connected to the steam inlet of intermediate pressure cylinder 4 via a pipeline; and the exhaust outlet of intermediate pressure cylinder 4 is connected to the low pressure cylinder 5. The steam inlet of the boiler is connected 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 is connected to the feedwater inlet of the boiler 1 via a pipeline. The extraction ports of the ultra-high pressure cylinder 2 and the high-pressure regenerative heater 11 are connected via pipelines. Similarly, the extraction port of the high-pressure cylinder 3 is connected to the extraction inlet of the high-pressure regenerative heater 11 via a pipeline. The first-stage extraction port of the intermediate-pressure cylinder 4 is connected to the extraction inlet of the high-pressure regenerative heater 11 via a pipeline. The second-stage extraction port of the intermediate-pressure cylinder 4 is connected to the extraction inlet of the deaerator 9 via a pipeline. The remaining extraction ports of the intermediate-pressure cylinder 4 are connected to the extraction inlet of the low-pressure regenerative heater 8 via pipelines. The extraction port of the low-pressure cylinder 5 is connected to the low-pressure regenerative heater... The extraction steam inlet of 8 is connected via a pipeline; the medium-temperature energy storage system consists of the high-pressure cylinder outlet extraction steam valve 16, the energy storage tank 12, the pressure relief valve 17, and the deaerator outlet regulating valve 18; during the energy storage process, the exhaust steam outlet of the high-pressure cylinder 3 is connected to the energy storage tank 12 via the high-pressure cylinder outlet extraction steam valve 16, and the energy storage tank 12 is connected to the deaerator inlet via the pressure relief valve 17; during the energy release process, the feedwater outlet of the deaerator 9 is connected to the energy storage tank 12 via the deaerator outlet regulating valve 18, and the outlet of the energy storage tank 12 is connected to the feedwater inlet of the boiler 1 via a pipeline.

[0064] 2. Material selection for energy storage tank 12

[0065] The high-pressure cylinder exhaust temperature of the case unit is between 446 and 455°C. The energy storage tank 12 is composed of two layers of phase change material. The first layer of phase change material 13 is KNO3 with a melting temperature of 330°C, and the second layer of phase change material 14 is LiCl(37)-63LiOH with a melting temperature of 262°C.

[0066] 3. Load splitting methods during load reduction

[0067] ① The operator sets the extraction ratio Ra of the high-pressure cylinder exhaust based on the original variable load rate and the minimum flow rate of the low-pressure cylinder, and then calculates the extraction amount of the high-pressure cylinder exhaust.

[0068] G h =G h,s ·Ra

[0069] In the formula: G h,s The high-pressure cylinder exhaust setting value is obtained from the case unit design document, in kg / s; Ra is the extraction ratio of the high-pressure cylinder exhaust.

[0070] ② Calculate the load command fh of the thermal energy storage system during the load reduction process. m,d

[0071]

[0072] In the formula: Pe h Pe represents the work done per unit mass flow rate of high-pressure cylinder exhaust, and the work done in relation to the overall machine load after fitting the high-pressure cylinder exhaust disturbance, expressed in kW / (kg / s). c Pe represents the change in work done by the secondary reheat unit when the unit mass flow rate of condensate changes, in kW / (kg / s); Pe is the rated load of the unit in the case study, 660000kW.

[0073] ③ Calculate the opening degree of the high-pressure cylinder outlet extraction valve 16.

[0074]

[0075] K h,16,rt =K h,16 +f PID (fh 0,d ,fh rt ,fh m,d )

[0076] Where: K h,16 The design value for the high-pressure cylinder outlet extraction valve opening of 16 degrees; k v,16 The resistance coefficient s is the pipe connecting the high-pressure cylinder exhaust outlet to the medium-temperature energy storage system. 2 ·MPa / (kg·m 3 );ρ h The exhaust gas density of the high-pressure cylinder is kg / m³. 3 ;Δp 16 The pressure difference between the exhaust outlet of high-pressure cylinder 3 and energy storage tank 12 is expressed in MPa and K. h,16,rt f is the real-time value of the opening degree of the high-pressure cylinder outlet extraction valve 16; PID To correct the opening value of the high-pressure cylinder outlet extraction valve 16 obtained through PID control using real-time load deviation, the real-time load deviation is calculated as follows: real-time load of the secondary reheat unit minus the load command of the secondary reheat unit boiler-generator coordination system during the load reduction process minus the load command of the intermediate temperature energy storage system; fh 0,d For load reduction processes, load commands are issued to the boiler-generator coordination system of the secondary reheat unit; fh rtThis represents the real-time load of the secondary reheat unit.

[0077] ④ Calculate the correction value G for condensate flow rate cond,rt

[0078] G cond,rt =G cond,s -G h

[0079] In the formula: G cond,rt This is a correction value for condensate volume, in kg / s; G cond,s The condensate flow setpoint, in kg / s, is related to the current load of the case unit.

[0080] ⑤ The calculation method for the load command of the secondary reheat unit boiler-generator coordination system during the load reduction process is as follows:

[0081] Pe 1,n =Pe1-G h ·(Pe h -Pe c )

[0082] t s0 =(Pe2-Pe1) / rate0·60

[0083]

[0084] t s0,1 =(Pe2-Pe1) / rate 0,1 ·60

[0085]

[0086] In the formula: Pe 1,n The initial load of the secondary reheat unit integrating medium-temperature energy storage is the new initial load of the secondary reheat unit, kW; Pe1 is the original initial load of the secondary reheat unit, kW; Pe2 is the target load of the secondary reheat unit, kW; t s0 The time (in seconds) for the load command to reach the target load under the original variable load rate; rate0 is the original variable load rate (kW / min); rate 0,1 The load change rate of the secondary reheat unit boiler-generator coordination system after load splitting, in kW / min; t s0,1 The time, s, for the load command from the secondary reheat unit's boiler-generator coordination system to reach the target load after load splitting; fh 0,d Load commands for the boiler-generator coordination system of the secondary reheat unit during the load reduction process.

[0087] ⑥ The load command fh of the secondary reheat unit boiler coordination system during the load reduction process 0,d The commands are sent to the boiler-turbine coordination control system of the secondary reheat unit to obtain boiler commands and turbine commands.

[0088] 4. Load splitting methods during load increase process

[0089] ① Based on the phase change material selected in step 2 of the implementation method, obtain the specific heat capacity and latent heat of the phase change material, obtain the cold end temperature and hot end temperature of the phase change material based on the temperature measuring point, and calculate the energy storage capacity of the medium temperature energy storage system.

[0090]

[0091] In the formula: E m The energy storage capacity of the medium-temperature energy storage system is used to heat the deaerator outlet water, in kJ / C. p denoted as , where is the specific heat capacity of the phase change material in the medium-temperature energy storage system (kJ / kg / ℃); is the mass of the phase change material in the medium-temperature energy storage system (kg); is the hot-end temperature of the phase change material in the medium-temperature energy storage system (℃); is the melting temperature of the phase change material in the medium-temperature energy storage system (℃); is the cold-end temperature of the phase change material in the medium-temperature energy storage system (℃); is the latent heat of the phase change material in the medium-temperature energy storage system (kJ); and is the number of phase change materials in the medium-temperature energy storage system (j = 2 in the case unit).

[0092] ② Calculate the maximum duration of heat release during the intermediate-temperature energy storage system.

[0093]

[0094] In the formula: t m Pe1 represents the maximum duration of heat release during the medium-temperature energy storage system, in seconds; Pe2 represents the target load of the secondary reheat unit, in kW; and Pe1 represents the original initial load of the secondary reheat unit, in kW.

[0095] ③ Calculate the load command fh of the secondary reheat unit boiler-generator coordination system during the load increase process. 0,u

[0096] t s0 =(Pe2-Pe1) / rate0·60

[0097] t s1 =t s0 -t m

[0098] rate1=(Pe2-Pe1) / t s1 ·60

[0099]

[0100] In the formula: t s0 The time it takes for the load command to reach the target load at the original variable load rate, in seconds; rate0 is the original variable load rate, in kW / min; t s1The time (s) for the load command of the secondary reheat unit boiler-generator coordination system to reach the target load after coupling the medium-temperature energy storage system; rate1 is the new variable load rate (kW / min) of the secondary reheat unit boiler-generator coordination system with integrated medium-temperature energy storage; t is the real-time recorded time (s).

[0101] ④ Calculate the load command fh of the thermal energy storage system during the load increase process. m,u

[0102]

[0103] fh m,u =fh old -fh 0,u

[0104] In the formula: fh old This is the load command for the entire machine under the original variable load rate.

[0105] ⑤ Calculate the opening degree K of the deaerator outlet regulating valve 18. m,18

[0106]

[0107] Where: K m,18 The opening degree of the deaerator outlet regulating valve 18; Pe fw k represents the increase in power of the secondary reheat unit when the feedwater flow rate at the deaerator outlet changes, expressed in kW / (kg / s). v,18 s is the resistance coefficient of the pipeline connecting the water pump outlet and the medium-temperature energy storage system. 2 ·MPa / (kg·m 3 );ρ m,18 For water supply density, kg / m³ 3 ;Δp m,18 The pressure difference between the outlet of the feedwater pump and the outlet of the high-pressure regenerator 11 is expressed in MPa.

[0108] ⑥ The load command fh of the secondary reheat unit boiler coordination system during the load increase process 0,u The commands are sent to the boiler-turbine coordination control system of the secondary reheat unit to obtain boiler commands and turbine commands.

[0109] 5. Optimization effect of the case unit

[0110] Figure 3 The diagram shows the load commands of the unit before and after load splitting during the load reduction process of the case unit. It can be seen that during the load reduction process, the original load change rate was 39.6 MW / min, and after load splitting, the unit's load change rate was 26.4 MW / min. The load change pressure borne by the boiler-turbine coordination system was significantly reduced, and the overall unit load change rate was significantly improved under the same parameter fluctuation range.

[0111] Figure 4 The diagram shows the load commands of the unit before and after load splitting during the load increase process of the case unit. It can be seen that during the load increase process, the original load change rate was 26.4 MW / min. After load splitting, the unit's load change rate was 20.0 MW / min. The load change pressure borne by the boiler-turbine coordination system was significantly reduced, and the overall unit load change rate was significantly improved under the same parameter fluctuation range.

[0112] In summary, the integrated medium-temperature energy storage coupled system and control method for improving the load change rate of a secondary reheat unit, as proposed in this invention, increases the overall load change rate by reducing the load variation of the boiler-generator coordination system of the secondary reheat unit, thereby enhancing the unit's flexibility.

Claims

1. A control method for a coupling system integrating medium-temperature energy storage to enhance the load change rate of a secondary reheat unit, wherein the coupling system includes a medium-temperature energy storage system and a secondary reheat unit; in the secondary reheat unit, the superheated steam outlet of the boiler (1) is connected to the steam inlet of the ultra-high pressure cylinder (2) via a pipeline, the exhaust outlet of the ultra-high pressure cylinder (2) is connected to the primary cold reheat steam inlet of the boiler (1) via a pipeline, the primary hot reheat steam outlet of the boiler (1) is connected to the steam inlet of the high pressure cylinder (3) via a pipeline, the exhaust outlet of the high pressure cylinder (3) is connected to the secondary cold reheat steam inlet of the boiler (1) via a pipeline, and the secondary hot reheat steam outlet of the boiler (1) is connected to the secondary cold reheat steam inlet of the boiler (1) via a pipeline. 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 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 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 a feedwater pump (10). The feedwater outlet of the high-pressure regenerative heater (11) is connected to the feedwater inlet of the high-pressure regenerative heater (11). The outlet is connected to the feedwater inlet of the boiler (1) via a pipe; the extraction port of the ultra-high pressure cylinder (2) is connected to the extraction port of the high-pressure regenerative heater (11) via a pipe; the extraction port of the high pressure cylinder (3) is connected to the extraction port of the high-pressure regenerative heater (11) via a pipe; the first stage extraction port of the intermediate pressure cylinder (4) is connected to the extraction port of the high-pressure regenerative heater (11) via a pipe; the second stage extraction port of the intermediate pressure cylinder (4) is connected to the extraction port of the deaerator (9) via a pipe; the remaining stages of the intermediate pressure cylinder (4) are connected to the extraction port of the low-pressure regenerative heater (8) via a pipe; and the extraction port of the low-pressure cylinder (5) is connected to the low-pressure regenerative heater... The steam extraction inlet of the heater (8) is connected by a pipeline; the medium-temperature energy storage system consists of a high-pressure cylinder outlet steam extraction valve (16), an energy storage tank (12), a pressure relief valve (17), and a deaerator outlet regulating valve (18); during the energy storage process, the exhaust outlet of the high-pressure cylinder (3) is connected to the energy storage tank (12) through the high-pressure cylinder outlet steam extraction valve (16), and the energy storage tank (12) is connected to the outlet of the deaerator (9) through the pressure relief valve (17); during the energy release process, the feedwater outlet of the feedwater pump (10) is connected to the energy storage tank (12) through the deaerator outlet regulating valve (18), and the outlet of the energy storage tank (12) is connected to the feedwater inlet of the boiler (1) through a pipeline; Its features are: The control method proposes a load splitting method, which splits the overall load command into the load command of the medium-temperature energy storage system and the load command of the secondary reheat unit boiler coordination system. The splitting method of the overall load command during the load increase process is different from the splitting method of the overall load command during the load decrease process. The method for decomposing the load command of the whole unit during the load reduction process is to design the steam extraction amount of the high-pressure cylinder to obtain the load command of the thermal energy storage system during the load reduction process, and at the same time correct the condensate flow rate during the load reduction process. Then, the load command of the secondary reheat unit boiler-generator coordination system during the load reduction process is obtained by using the steam extraction amount of the high-pressure cylinder, the original load change rate, the target load of the secondary reheat unit and the initial load. The method for decomposing the overall load command during the load increase process is to calculate the energy storage capacity of the intermediate temperature energy storage system, obtain the load command of the intermediate temperature energy storage system during the load increase process, and then obtain the load command of the secondary reheat unit boiler-generator coordination system during the load increase process through the load command of the intermediate temperature energy storage system during the load increase process, the original planned load change rate, the target load of the secondary reheat unit and the initial load.

2. The control method for the coupled system of integrated medium-temperature energy storage to enhance the load rate of a secondary reheat unit according to claim 1, characterized in that: The energy storage tank (12) is composed of multi-stage phase change materials. The method for selecting phase change materials is to match the melting temperature of the phase change materials with the exhaust temperature of the high-pressure cylinder.

3. The control method for the coupled system for enhancing the load rate of a secondary reheat unit by integrating medium-temperature energy storage according to claim 1, characterized in that: The calculation method for the load command of the thermal energy storage system during the load reduction process is as follows: ① Calculate the steam extraction volume of the high-pressure cylinder exhaust. G h In the formula: G h,s The setpoint for high-pressure cylinder exhaust, kg / s; Ra The extraction ratio for exhaust steam from the high-pressure cylinder; ② Calculate the load command of the thermal energy storage system during the load reduction process fh m,d In the formula: Pe h The power output per unit mass flow rate of high-pressure cylinder exhaust steam, expressed in kW / (kg / s); Pe c The change in work done by the secondary reheat unit when the unit mass flow rate of condensate changes, in kW / (kg / s); Pe The rated load of the secondary reheat unit is kW.

4. The control method for the coupled system for enhancing the load rate of a secondary reheat unit by integrating medium-temperature energy storage according to claim 1, characterized in that: The load command for the thermal energy storage system during the load reduction process is achieved by controlling the opening of the high-pressure cylinder outlet extraction valve (16), as follows: In the formula: K h,16 The design value for the opening of the high-pressure cylinder outlet extraction valve (16); k v,16 The resistance coefficient s is the pipe connecting the high-pressure cylinder exhaust outlet to the medium-temperature energy storage system. 2 ·MPa / (kg·m 3 ); The exhaust gas density of the high-pressure cylinder is kg / m³. 3 ; The pressure difference between the exhaust outlet of the high-pressure cylinder (3) and the energy storage tank (12) is MPa; K h,16,rt The real-time value of the opening degree of the high-pressure cylinder outlet extraction valve (16); f PID To use the real-time load deviation to obtain the correction value of the opening of the high-pressure cylinder outlet extraction valve (16) through PID, the real-time load deviation is calculated as the real-time load of the secondary reheat unit minus the load command of the secondary reheat unit boiler-generator coordination system during the load reduction process minus the load command of the intermediate temperature energy storage system. fh 0,d Load commands for the boiler-generator coordination system of the secondary reheat unit during load reduction process; fh rt This represents the real-time load of the secondary reheat unit.

5. The control method for the coupled system for enhancing the load rate of a secondary reheat unit by integrating medium-temperature energy storage according to claim 1, characterized in that: The calculation method for correcting the condensate flow rate during the load reduction process is as follows: In the formula: G cond,rt This is a correction value for condensate volume, in kg / s; G cond,s The setpoint for condensate flow rate is kg / s.

6. The control method for the coupled system for enhancing the load rate of a secondary reheat unit by integrating medium-temperature energy storage according to claim 1, characterized in that: The calculation method for the load command of the secondary reheat unit boiler-generator coordination system during the load reduction process is as follows: In the formula: Pe 1,n The initial load of the secondary reheat unit with integrated medium-temperature energy storage is the new initial load of the secondary reheat unit, in kW; Pe 1 represents the original initial load of the double reheat unit, in kW; Pe 2 represents the target load for the secondary reheat unit, in kW; t s0 The time, in seconds, for the load command to reach the target load under the original variable load rate. rate 0 represents the original variable load rate, in kW / min; rate 0,1 The load change rate of the boiler-generator coordination system of the secondary reheat unit after load splitting, in kW / min; t s0,1 The time, in seconds, for the load command from the secondary reheat unit's boiler-generator coordination system to reach the target load after load splitting; fh 0,d Load commands are issued to the boiler-generator coordination system of the secondary reheat unit during the load reduction process.

7. The control method for the coupled system for enhancing the load rate of a secondary reheat unit by integrating medium-temperature energy storage according to claim 1, characterized in that: The calculation methods for the load commands of the secondary reheat unit and the boiler-generator coordination system during the load increase process are 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 water, kJ; C p The specific heat capacity of the phase change material in a medium-temperature energy storage system is kJ / kg / °C. m The mass of the phase change material in the medium-temperature energy storage system is expressed in kg. T 2 represents the hot-end temperature of the phase change material in the medium-temperature energy storage system, in °C; T 0 represents the melting temperature of the phase change material in the medium-temperature energy storage system, in °C. T 1 represents the cold end temperature of the phase change material in the medium-temperature energy storage system, in °C; L The latent heat of phase change material in a medium-temperature energy storage system is kJ. j The number of phase change materials in the medium-temperature energy storage system; ② Calculate the maximum duration of heat release during the intermediate-temperature energy storage system. In the formula: t m The maximum duration, in seconds, is the heat release process of the medium-temperature energy storage system. Pe 2 represents the target load for the secondary reheat unit, in kW; Pe 1 represents the original initial load of the double reheat unit, in kW; ③ Calculate the load command of the secondary reheat unit's boiler-generator coordination system during the load increase process. fh 0,u In the formula: t s0 The time, in seconds, for the load command to reach the target load under the original variable load rate. rate 0 represents the original variable load rate, in kW / min; t s1 The time, in seconds, for the load command to reach the target load from the boiler-generator coordination system of the secondary reheat unit after coupling the medium-temperature energy storage system; rate 1 represents the new variable load rate (kW / min) of the boiler-generator coordination system for integrated medium-temperature energy storage and secondary reheat units. t The time s is the real-time recording time. ④ Calculate the load command of the thermal energy storage system during the load increase process fh m,u In the formula: fh old This is the load command for the entire machine under the original variable load rate.

8. The control method for the coupled system of integrated medium-temperature energy storage to enhance the load rate of a secondary reheat unit according to claim 1, characterized in that: During the load increase process, the load command of the thermal energy storage system is realized by adjusting the opening degree of the deaerator outlet regulating valve (18). The calculation method of the opening degree of the deaerator outlet regulating valve (18) is as follows: In the formula: K m,18 The opening degree of the deaerator outlet regulating valve (18); The change in power of the secondary reheat unit when the feedwater flow rate at the deaerator outlet changes, expressed in kW / (kg / s). k v,18 s is the resistance coefficient of the pipeline connecting the water pump outlet and the medium-temperature energy storage system. 2 ·MPa / (kg·m 3 ); For water supply density, kg / m³ 3 ; The pressure difference between the outlet of the water pump and the outlet of the high-pressure regenerator (11) is expressed in MPa.

9. The control method for the coupled system for enhancing the load rate of a secondary reheat unit by integrating medium-temperature energy storage according to claim 1, characterized in that: During the load reduction and load increase processes, the load commands from the secondary reheat unit boiler-generator coordination system are sent to the secondary reheat unit boiler-generator coordination control system to obtain boiler commands and turbine commands.

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