Thermal system and method for improving variable load capacity of supercritical thermal power unit

Abstract

The present application belongs to the field of power generation, and particularly relates to a thermal system and method for improving variable load capacity of a supercritical thermal power unit, comprising a boiler, a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder and a feed water pump; new steam generated by a boiler superheater is connected to the high-pressure cylinder through a pipeline, exhaust steam of the high-pressure cylinder is connected to a boiler reheater through a pipeline, and exhaust steam of the medium-pressure cylinder is connected to the low-pressure cylinder through a pipeline; the new steam generated by the boiler superheater is connected to an accumulator through a pipeline, cold section reheated steam of the boiler reheater is connected to the accumulator through a pipeline, feed water of the feed water pump is connected to the accumulator through a pipeline, an outlet of the accumulator is connected to the cold section reheated steam of the boiler reheater through a pipeline, and the outlet of the accumulator is connected to an inlet of the low-pressure cylinder through a pipeline. The present application can effectively improve the variable load capacity of the supercritical thermal power unit under deep peak regulation, and solve the problem of decreased operation flexibility of the unit while providing a large peak regulation margin.

Description

Technical Field

[0001] This invention belongs to the field of power generation technology, and in particular relates to a thermal system and method for improving the load-changing capacity of supercritical thermal power units. Background Technology

[0002] With the rapid increase in the proportion of renewable energy in the power system, thermal power units are required to provide more and more flexible supply. To address the issue of wind and solar curtailment, deep peak shaving has become the norm for coal-fired power plants. However, the load-changing capacity of coal-fired power plants is weakened under deep peak shaving, making it impossible to simultaneously achieve high peak-shaving margin and high load-changing capacity. Therefore, new methods are needed to address the problem of insufficient rapid load-changing capability of coal-fired power plants under low-load operation.

[0003] Based on the above analysis, the problems and shortcomings of the existing technology are as follows:

[0004] (1) Reduced unit efficiency: When operating at low load, the fuel utilization efficiency of coal-fired power plants decreases, resulting in increased fuel consumption per unit of electricity and reduced economic efficiency of the power plant.

[0005] (2) Shortened equipment life: During the variable load process under deep peak shaving, the unit needs to frequently adjust the combustion, which will lead to frequent changes in equipment stress and shorten the service life of the equipment.

[0006] (3) System stability risk: Insufficient speed of load change under low load operation may cause coal-fired power plants to lag in responding to grid load fluctuations, affecting the stability of the power system. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a thermal system and method for improving the variable load capacity of supercritical thermal power units.

[0008] The present invention is implemented as follows: a thermal system for improving the load-changing capacity of supercritical thermal power units, the thermal system for improving the load-changing capacity of supercritical thermal power units includes a boiler, a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder, and a feedwater pump;

[0009] The new steam generated by the boiler superheater is connected to the high-pressure cylinder through a pipeline. The exhaust steam from the high-pressure cylinder is connected to the boiler reheater through a pipeline. The exhaust steam from the intermediate-pressure cylinder is connected to the low-pressure cylinder through a pipeline.

[0010] The new steam generated by the boiler superheater is connected to the accumulator through pipelines. The cold section reheat steam of the boiler reheater is connected to the accumulator through pipelines. The feed water from the feedwater pump is connected to the accumulator through pipelines. The outlet of the accumulator is connected to the cold section reheat steam of the boiler reheater through pipelines. The outlet of the accumulator is connected to the inlet of the low-pressure cylinder through pipelines.

[0011] Furthermore, a first regulating valve is installed on the connecting pipeline between the new steam of the boiler superheater and the accumulator, and a fifth regulating valve is installed on the connecting pipeline between the cold section reheater of the boiler reheater and the accumulator.

[0012] Furthermore, a fourth regulating valve is installed on the pipe leading from the accumulator to the cold section reheater of the boiler reheater, and a second regulating valve is installed on the pipe leading from the accumulator to the inlet of the low-pressure cylinder.

[0013] Furthermore, the new steam generated by the boiler superheater is connected to the high-pressure cylinder through a pipeline. The exhaust steam from the high-pressure cylinder is connected to the boiler reheater through a pipeline. The boiler reheater is connected to the intermediate-pressure cylinder through a pipeline. The exhaust steam from the intermediate-pressure cylinder is connected to the low-pressure cylinder through a pipeline. The exhaust steam from the low-pressure cylinder is connected to the condenser through a pipeline. The condensate water from the condenser is connected to the condensate pump through a pipeline. The condensate pump is connected to the water-side inlet of the low-pressure heater group through a pipeline. The water-side outlet of the low-pressure heater group is connected to the water-side inlet of the deaerator. The outlet of the deaerator is connected to the feedwater pump. The feedwater from the feedwater pump outlet is connected to the water-side inlet of the high-pressure heater group and the accumulator through pipelines respectively. A third regulating valve is installed on the pipeline between the feedwater pump and the accumulator. The water-side outlet of the high-pressure heater group is connected to the main feedwater inlet of the boiler through a pipeline.

[0014] The extraction steam and part of the exhaust steam from the high-pressure cylinder are connected to the high-pressure heater group through pipelines. Part of the extraction steam from the intermediate-pressure cylinder is connected to the high-pressure heater group through pipelines. Part of the extraction steam from the intermediate-pressure cylinder is connected to the turbines of the deaerator and the feedwater pump through pipelines. Part of the extraction steam from the intermediate-pressure cylinder is connected to the low-pressure heater group through pipelines. The extraction steam from the low-pressure cylinder is connected to the low-pressure heater group through pipelines. The overall condensate of the high-pressure heater group is connected to the deaerator through pipelines. The overall condensate of the low-pressure heater group is connected to the condenser through pipelines.

[0015] The high-pressure cylinder is connected to the medium-pressure cylinder, low-pressure cylinder, and generator via a coupling.

[0016] Furthermore, under low unit load, the accumulator's sliding pressure operating range is 2.4–8 MPa;

[0017] Furthermore, under high load conditions in the unit, the accumulator sliding pressure operating range is 0.2–4.5 MPa.

[0018] Furthermore, when the unit needs to rapidly reduce load, the main steam pressure setpoint after speed limiting is used as the setpoint for the PID controller, and the 3S value of the steam pressure before the high-pressure main steam valve is used as the tracking value for the PID controller. The control signal is generated after passing through the PID controller and manual / automatic operation. The difference between the accumulator pressure and the accumulator full-load pressure signal is used to measure the degree of accumulator fullness. This difference is used to generate a fullness signal via a function generator, which is multiplied by the PID control signal to obtain the accumulator flow command. This accumulator flow command is then output as the speed-limited accumulator flow command after passing through the speed limiter. Under low load, this command is used to control the opening of the first regulating valve, and under medium-to-high load, it is used to control the opening of the fifth regulating valve.

[0019] Furthermore, when the unit needs to rapidly increase load or frequently adjust load in small increments, the unit load command value is subtracted from a specified constant and used as the setpoint for the low-value limiter. The unit load value is used as the tracking value for the low-value limiter. When the unit load value is lower than the low-value limiter setting, the low-value limiter sends a tracking command to the venting PID controller. At this time, the venting PID controller is activated, using the unit load value as the tracking value and the unit load command as the setpoint. Its output value is processed manually / automatically to generate a venting command. The unit load value is processed by a function to generate the main reheat steam temperature difference limit. The main steam temperature is subtracted from the reheat steam temperature and the main reheat temperature difference limit, and then processed by a function to generate a temperature difference correction coefficient. The temperature difference correction coefficient is multiplied by the venting command, and after speed limiting, a speed-limited accumulator flow command is generated. This command is used to control the opening of the fourth regulating valve under low load and to control the opening of the second regulating valve under medium and high load.

[0020] Furthermore, the unit load command value is added to a specified constant and used as the setpoint for the high-value limiter. The unit load value is used as the tracking value for the high-value limiter. When the unit load value is higher than the high-value limiter setpoint, the high-value limiter sends a tracking command to the charging PID controller. At this time, the charging PID controller is activated, using the unit load value as the tracking value and the unit load command as the setpoint. Its output value is processed manually / automatically to generate a charging command. The difference between the accumulator pressure and the accumulator full-fill pressure signal is used to measure the degree of accumulator filling. This difference is used to generate a fullness signal via a function generator, which is multiplied by the charging PID control signal. After speed limiting, a speed-limited accumulator charging flow command is generated. This command is used to control the opening of the first regulating valve under low load and to control the opening of the fifth regulating valve under medium to high load.

[0021] Another objective of this invention is to provide a thermal system control method for enhancing the load-changing capacity of supercritical thermal power units, comprising the following steps:

[0022] Step 1: A portion of the feedwater is diverted into the accumulator to absorb superheated steam;

[0023] Step 2: When the unit is operating at low load and changing load, part of the main steam is diverted into the accumulator for storage, thereby accelerating the unit's load reduction rate. The accumulator supplies steam to the reheater, thereby accelerating the unit's load increase rate.

[0024] Step 3: When the unit changes load under medium or high load, part of the reheater inlet steam is diverted into the accumulator for storage, thereby accelerating the unit's load reduction rate. The accumulator supplies steam to the low-pressure cylinder, thereby accelerating the unit's load increase rate.

[0025] Another object of the present invention is to provide a computer device, the computer device including a memory and a processor, the memory storing a computer program, and when the computer program is executed by the processor, causing the processor to perform the steps of the thermal system control method for improving the variable load capacity of supercritical thermal power units.

[0026] Another object of the present invention is to provide a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the thermal system control method for improving the variable load capacity of supercritical thermal power units.

[0027] Another objective of this invention is to provide an information data processing terminal for implementing the aforementioned thermal system that enhances the variable load capacity of supercritical thermal power units.

[0028] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0029] First, during load reduction, this invention extracts main steam and stores it in an accumulator, reducing the turbine working fluid flow rate and thus accelerating unit load adjustment. During load increase, the accumulator exhaust steam is mixed with cold reheat steam or low-pressure cylinder inlet steam, significantly increasing the turbine working fluid flow rate and further accelerating unit load adjustment. Compared to existing methods that use accumulator steam to replace heater extraction, this invention, because the accumulator steam supply is limited by the turbine inlet steam temperature rather than the heater's heat exchange self-balancing capability, can guarantee a higher steam supply rate under low unit load, thus providing superior load increase performance. Simultaneously, the preferred accumulator pressure matches the main steam pressure under low unit load conditions, resulting in higher round-trip efficiency and expanding the unit's peak-shaving margin.

[0030] Secondly, this invention can effectively improve the variable load capacity of supercritical thermal power units under deep peak shaving, and solve the problem of reduced operational flexibility of the units while providing a large peak shaving margin.

[0031] This invention can be used to expand the peak-shaving margin of supercritical thermal power units, while having good energy storage efficiency, which can help power plants better reduce peak loads and fill valleys.

[0032] Third, this invention can improve the regulation performance of supercritical thermal power units across the entire load range, especially by providing a large amount of additional steam during low-load operation, thus accelerating the adjustment of the unit load. Simultaneously, this invention possesses energy storage capabilities, which can assist in boiler-turbine decoupling and expand the peak-shaving margin of supercritical thermal power units.

[0033] Fourth, supercritical thermal power units suffer from unstable combustion, low heat storage, and weakened regulation capabilities of the pulverized combustion system under low loads, resulting in reduced load-shifting capacity. In recent years, power system demands have required supercritical thermal power units to possess deep peak-shaving capabilities, maintain long-term low-load operation, and provide stronger load-shifting capacity to cope with frequently changing grid demands. This invention can effectively improve the load-shifting capacity of supercritical thermal power units under deep peak-shaving, solving the problem of reduced operational flexibility while providing a large peak-shaving margin.

[0034] The additional variable load capacity provided by traditional operating methods such as steam extraction and throttling is weakened as the unit load decreases, and is insufficient to meet demand under deep peak shaving.

[0035] Other existing technical solutions, such as CN202210588006.X "A Flexible Control System and Working Method for Thermal Power Units with Integrated Steam Accumulators," use steam heat storage and steam release to replace heater extraction, which can provide additional load reduction capacity. However, the accumulator used in these solutions is limited by the heater's self-balancing during energy release, and the principle of providing load increase capacity is similar to traditional extraction and throttling methods. Therefore, its assistance in increasing the unit's load is also limited under deep peak shaving. Another example is CN202120847796.X "Rapid Load Adjustment System for Thermal Power Units Coupled with Steam Energy Storage," which uses steam heat storage and steam release to directly supply power to the turbine. However, the dry steam storage tank used in this solution is fundamentally different from the steam accumulator used in this invention. The steam accumulator used in this invention has a much higher energy storage density than the dry steam storage tank, and can provide steam supply for a longer period. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the thermal system structure for improving the variable load capacity of supercritical thermal power units provided in an embodiment of the present invention;

[0038] Figure 2 This is a control logic diagram for a rapid load reduction scenario provided in an embodiment of the present invention;

[0039] Figure 3 This is a control logic diagram for scenarios involving rapid load increases or frequent small-scale load changes, provided in an embodiment of the present invention.

[0040] Figure 4This is a schematic diagram of a 660MW supercritical coal-fired power unit provided in an embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram of the Ebsilon model provided in an embodiment of the present invention;

[0042] Figure 6 This is a schematic diagram of the process of the unit responding to the 40% THA-30% THA load reduction command provided in the embodiment of the present invention;

[0043] Figure 7 This is a schematic diagram of the unit responding to the 40% THA-30% THA load reduction command at -33MW / min after adopting a steam accumulator, provided by an embodiment of the present invention.

[0044] Figure 8 This is a diagram of the load reduction process of the units before and after the addition of the accumulator, with a response speed of -33MW / min to 40% THA-30% THA, provided in an embodiment of the present invention.

[0045] Figure 9 This is a diagram illustrating the load increase process of the units before and after the accumulator under 40% THA-50% THA conditions, provided in an embodiment of the present invention.

[0046] Figure 10 This invention provides an embodiment of the accumulated load deviation during the load increase process under 40% THA-50% THA conditions, where the units before and after the accumulator respond at different rates.

[0047] Figure 11 This is the maximum overshoot provided in the embodiment of the present invention, which uses the accumulator and the generator units before and after the accumulator to respond at different rates during the load increase process under the 40% THA-50% THA condition.

[0048] In the diagram: 1. Boiler; 2. High-pressure cylinder; 3. Medium-pressure cylinder; 4. Low-pressure cylinder; 5. Generator; 6. Condenser; 7. Condensate pump; 8. Low-pressure heater group; 9. Deaerator; 10. Feedwater pump; 11. High-pressure heater group; 12. Accumulator; 101. Superheater; 102. Reheater; 1201. First regulating valve; 1202. Second regulating valve; 1203. Third regulating valve; 1204. Fourth regulating valve; 1205. Fifth regulating valve. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0050] like Figure 1As shown, the thermal system for improving the variable load capacity of supercritical thermal power units provided in this embodiment of the invention includes a boiler 1, a high-pressure cylinder 2, a medium-pressure cylinder 3, a low-pressure cylinder 4, and a feedwater pump 10.

[0051] The new steam generated by the boiler superheater 101 is connected to the high-pressure cylinder 2 through a pipeline. The exhaust steam of the high-pressure cylinder 2 is connected to the boiler reheater 102 through a pipeline. The exhaust steam of the intermediate-pressure cylinder 3 is connected to the low-pressure cylinder 4 through a pipeline.

[0052] The new steam generated by the boiler superheater 101 is connected to the accumulator 12 through a pipeline. The cold section reheat steam of the boiler reheater 2 is connected to the accumulator 12 through a pipeline. The feed water from the feed pump 10 is connected to the accumulator 12 through a pipeline. The outlet of the accumulator 12 is connected to the cold section reheat steam of the boiler reheater 102 through a pipeline. The outlet of the accumulator 12 is connected to the inlet of the low-pressure cylinder 4 through a pipeline.

[0053] A first regulating valve 1201 is provided on the connecting pipe between the new steam of the boiler superheater 101 and the accumulator 12, and a fifth regulating valve 1205 is provided on the connecting pipe between the cold section reheater of the boiler reheater 102 and the accumulator 12.

[0054] A fourth regulating valve 1204 is provided on the pipe leading from the accumulator 12 to the cold section reheater of the boiler reheater 102, and a second regulating valve 1202 is provided on the pipe leading from the accumulator 12 to the inlet of the low-pressure cylinder 4.

[0055] The new steam generated by the boiler superheater 101 is connected to the high-pressure cylinder 2 through a pipeline. The exhaust steam of the high-pressure cylinder 2 is connected to the boiler reheater 102 through a pipeline. The boiler reheater 102 is connected to the intermediate-pressure cylinder 3 through a pipeline. The exhaust steam of the intermediate-pressure cylinder 3 is connected to the low-pressure cylinder 4 through a pipeline. The exhaust steam of the low-pressure cylinder 4 is connected to the condenser 6 through a pipeline. The condensate water of the condenser 6 is connected to the condensate pump 7 through a pipeline. The condensate pump 7 is connected to the water-side inlet of the low-pressure heater group 8 through a pipeline. The water-side outlet of the low-pressure heater group 8 is connected to the water-side inlet of the deaerator 9. The outlet of the deaerator 9 is connected to the feed water pump 10. The feed water from the outlet of the feed water pump 10 is connected to the water-side inlet of the high-pressure heater group 11 and the accumulator 12 through pipelines. A third regulating valve 1203 is installed on the pipeline between the feed water pump 10 and the accumulator 12. The water-side outlet of the high-pressure heater group 11 is connected to the main feed water inlet of the boiler 1 through a pipeline.

[0056] The extraction steam and part of the exhaust steam from high pressure cylinder 2 are connected to high pressure heater group 11 through pipelines. Part of the extraction steam from intermediate pressure cylinder 3 is connected to high pressure heater group 11 through pipelines. Part of the extraction steam from intermediate pressure cylinder 3 is connected to the turbine of deaerator 9 and feedwater pump 10 through pipelines respectively. Part of the extraction steam from intermediate pressure cylinder is connected to low pressure heater group 8 through pipelines. The extraction steam from low pressure cylinder 4 is connected to low pressure heater group 8 through pipelines. The overall condensate drain of high pressure heater group 11 is connected to deaerator 9 through pipelines. The overall condensate drain of low pressure heater group 8 is connected to condenser 6 through pipelines.

[0057] High-pressure cylinder 2 is connected to medium-pressure cylinder 3, low-pressure cylinder 4, and generator 5 via couplings.

[0058] A power plant thermal system that uses a steam accumulator to enhance the load-changing capacity of a supercritical thermal power unit under deep peak shaving includes the following steps:

[0059] The first regulating valve 1201, the second regulating valve 1202, the fourth regulating valve 1204, and the fifth regulating valve 1205 are closed. The third regulating valve 1203 is adjusted to allow part of the feedwater to flow into the accumulator 12 for absorbing superheated steam.

[0060] When the unit is operating at low load and reducing load, by closing the second regulating valve 1202, the third regulating valve 1203, the fourth regulating valve 1204, and the fifth regulating valve 1205, some of the main steam is diverted into the accumulator 12 for storage, thereby accelerating the unit's load reduction rate.

[0061] When the unit is operating at low load and increasing load, the first regulating valve 1201, the second regulating valve 1202, the third regulating valve 1203, and the fifth regulating valve 1205 are closed, and the fourth regulating valve 1204 is adjusted to allow the accumulator to supply steam to the reheater 102, thereby accelerating the unit's load increase rate.

[0062] When the unit is reducing load under medium or high load, the first regulating valve 1201, the second regulating valve 1202, the third regulating valve 1203, and the fourth regulating valve 1204 are closed. The fifth regulating valve 1205 is adjusted to allow part of the cold reheat steam to be diverted into the accumulator for storage, thereby accelerating the unit's load reduction rate.

[0063] When the unit increases its load under medium or high load conditions, the first regulating valve 1201, the second regulating valve 1202, the third regulating valve 1203, and the fifth regulating valve 1205 are closed. Steam is supplied to the low-pressure cylinder 4 by regulating the fourth regulating valve 1204 accumulator, thereby accelerating the unit's load increase rate.

[0064] Under low load conditions, the sliding pressure operating range of accumulator 12 is 8MPa to 2.4MPa.

[0065] Under high load conditions in the unit, the sliding pressure operating range of accumulator 12 is 4.5–0.2 MPa.

[0066] When the unit needs to rapidly reduce load, the following methods are used: Figure 2The control logic shown uses the main steam pressure setpoint after speed limiting as the setpoint for the PID controller, and the 3S value of the steam pressure before the high-pressure main steam valve as the tracking value for the PID controller. The control signal is generated after passing through the PID controller and manual / automatic operation. The difference between the accumulator pressure and the accumulator full-fill pressure signal is used to measure the degree of accumulator fullness. This difference is used to generate a fullness signal via a function generator, which is multiplied by the PID control signal to obtain the accumulator flow command. The accumulator flow command is then output as the speed-limited accumulator flow command after passing through the speed limiter. Under low load, this command is used to control the opening of the first regulating valve 1201; under medium-high load, it is used to control the opening of the fifth regulating valve 1205.

[0067] When the unit needs to rapidly increase load or frequently adjust load with small fluctuations, the following methods can be used: Figure 3 The control logic shown subtracts the unit load command value from a specified constant and uses this as the setpoint for the low-value limiter. The unit load value is used as the tracking value for the low-value limiter. When the unit load value is lower than the low-value limiter setting, the low-value limiter sends a tracking command to the steam release PID controller. At this time, the steam release PID controller is activated, using the unit load value as the tracking value and the unit load command as the setpoint. Its output value is processed manually / automatically to generate a steam release command. The unit load value is processed by a function to generate the main reheat steam temperature difference limit. The main steam temperature is subtracted from the reheat steam temperature and the main reheat temperature difference limit, and then processed by a function to generate a temperature difference correction coefficient. The temperature difference correction coefficient is multiplied by the steam release command, and after speed limiting, a speed-limited accumulator flow command is generated. This command is used to control the opening of the fourth regulating valve 1204 under low load and to control the opening of the second regulating valve 1202 under medium and high load.

[0068] The unit load command value is added to a specified constant and used as the setpoint for the high-value limiter. The unit load value is used as the tracking value for the high-value limiter. When the unit load value is higher than the high-value limiter setpoint, the high-value limiter sends a tracking command to the charging PID controller. At this time, the charging PID controller is activated, using the unit load value as the tracking value and the unit load command as the setpoint. Its output value is processed manually / automatically to generate the charging command. The difference between the accumulator pressure and the accumulator full-fill pressure signal is used to measure the degree of accumulator filling. This difference is used to generate a fullness signal via a function generator, which is multiplied by the charging PID control signal. After speed limiting, a speed-limited accumulator charging flow command is generated. Under low load, this command is used to control the opening of the first regulating valve 1201, and under medium-high load, it is used to control the opening of the fifth regulating valve 1205.

[0069] The thermal system control method for improving the load-changing capacity of supercritical thermal power units provided in this embodiment of the invention includes the following steps:

[0070] Step 1: A portion of the feedwater is diverted into the accumulator to absorb superheated steam;

[0071] Step 2: When the unit is operating at low load and changing load, part of the main steam is diverted into the accumulator for storage, thereby accelerating the unit's load reduction rate. The accumulator supplies steam to the reheater, thereby accelerating the unit's load increase rate.

[0072] Step 3: When the unit changes load under medium or high load, part of the reheater inlet steam is diverted into the accumulator for storage, thereby accelerating the unit's load reduction rate. The accumulator supplies steam to the low-pressure cylinder, thereby accelerating the unit's load increase rate.

[0073] Example 1: Applying the present invention to, for example Figure 4 The 660MW supercritical coal-fired unit shown has maximum pressure ratings of 8MPa and 4.5MPa, and a volume of 300m³. 3 450m 3 The accumulator can stably charge or release steam when the unit itself is operating stably at 40% THA.

[0074] Example 2: Applying the present invention to, for example Figure 4 The 660MW supercritical coal-fired unit shown has a maximum pressure of 8MPa and a volume of 300m³. 3 The accumulator is charged or discharged during the unit's load reduction process (40%-30% THA) or load increase process (40%-50% THA). Only the method of extracting main steam and supplying it to the intermediate pressure cylinder is considered.

[0075] 1. Establish as described in Example 1 Figure 5 The Ebsilon model shown is used to calculate the performance parameters of a 660MW supercritical unit during a complete charge-discharge process of the accumulator under steady-state conditions at 40% THA. Calculations show that this invention can provide an average additional flexibility of over 2% Pe during energy release, which is a significant improvement compared to the 0.6% Pe of condensate throttling and the 1.4% Pe of high-pressure heater throttling under the same conditions. Furthermore, it can be used in conjunction with condensate throttling and high-pressure heater throttling methods to maximize unit load in the shortest possible time. Specific data are shown in Table 1.

[0076] Table 1

[0077]

[0078] 2. A SimStore dynamic simulation model was established for Example 2, and the accumulator was put into automatic operation, performing load reduction operations of 40% THA-30% THA and load increase operations of 40% THA-50% THA under CCS coordinated control. For example... Figure 6 The diagram shows the process of a unit responding to a 40% THA-30% THA load reduction command before using an accumulator. For example... Figure 7The diagram shows the unit responding to the 40% THA-30% THA load reduction command at -33 MW / min after adopting the accumulator.

[0079] like Figure 8 The diagram shows the process of the unit responding to a load reduction of 40% THA to 30% THA before and after the addition of the accumulator. Figure 8 In the middle, the accumulated deviation of the main steam pressure is: Ip=∫|p real -p set |dt;

[0080] Unit load accumulation deviation: Iw=∫|W real -W set |dt;p real W real The actual values ​​of the unit's main steam pressure and unit load; p set W set These are the set values ​​for the main steam pressure and unit load of the generator set.

[0081] like Figure 9 The diagram shows the load increase process of the units before and after using the accumulator, responding at 20MW / min to the 40% THA-50% THA conditions.

[0082] like Figure 10 The figure shows the accumulated load deviation of the units before and after the adoption of the accumulator during the load increase process under 40% THA-50% THA conditions at different rates. The accumulated load deviation of the units is: Iw=∫|W real -W set |dt;W real The actual values ​​of the unit's main steam pressure and unit load; W set These are the set values ​​for the main steam pressure and unit load of the generator set.

[0083] like Figure 11 The figure shows the maximum overshoot of the units before and after using the accumulator during the load increase process under 40% THA-50% THA conditions at different rates.

[0084] It should be noted that embodiments of the present invention can be implemented using hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by a suitable instruction execution system, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the above-described devices and methods can be implemented using computer-executable instructions and / or included in processor control code, for example, such code provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as read-only memory firmware, or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented using hardware circuitry such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field-programmable gate arrays, programmable logic devices, etc., or using software executed by various types of processors, or using a combination of the above-described hardware circuitry and software, such as firmware.

[0085] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A thermal system for enhancing the variable load capacity of supercritical thermal power units, characterized in that, This includes boilers, high-pressure cylinders, medium-pressure cylinders, low-pressure cylinders, and feedwater pumps; The new steam generated by the boiler superheater is connected to the high-pressure cylinder through a pipeline. The exhaust steam from the high-pressure cylinder is connected to the boiler reheater through a pipeline. The exhaust steam from the intermediate-pressure cylinder is connected to the low-pressure cylinder through a pipeline. The new steam generated by the boiler superheater is connected to the accumulator through pipelines. The cold section reheater of the boiler reheater is connected to the accumulator through pipelines. The feed water from the feed water pump is connected to the accumulator through pipelines. The outlet of the accumulator is connected to the cold section reheater of the boiler reheater through pipelines. The outlet of the accumulator is connected to the inlet of the low-pressure cylinder through pipelines. A first regulating valve is installed on the connecting pipe between the new steam of the boiler superheater and the accumulator, and a fifth regulating valve is installed on the connecting pipe between the cold section reheater of the boiler reheater and the accumulator. A fourth regulating valve is installed on the pipe leading from the accumulator to the cold section reheater of the boiler reheater, and a second regulating valve is installed on the pipe leading from the accumulator to the inlet of the low-pressure cylinder. The new steam generated by the boiler superheater is connected to the high-pressure cylinder through a pipeline. The exhaust steam from the high-pressure cylinder is connected to the boiler reheater through a pipeline. The boiler reheater is connected to the intermediate-pressure cylinder through a pipeline. The exhaust steam from the intermediate-pressure cylinder is connected to the low-pressure cylinder through a pipeline. The exhaust steam from the low-pressure cylinder is connected to the condenser through a pipeline. The condensate from the condenser is connected to the condensate pump through a pipeline. The condensate pump is connected to the water-side inlet of the low-pressure heater group through a pipeline. The water-side outlet of the low-pressure heater group is connected to the water-side inlet of the deaerator. The outlet of the deaerator is connected to the feedwater pump. The feedwater from the feedwater pump outlet is connected to the water-side inlet of the high-pressure heater group and the accumulator through pipelines. A third regulating valve is installed on the pipeline between the feedwater pump and the accumulator. The water-side outlet of the high-pressure heater group is connected to the main feedwater inlet of the boiler through a pipeline. When the unit needs to rapidly reduce load, the main steam pressure setpoint after speed limiting is used as the setpoint of the PID controller, and the 3S value of the steam pressure before the high-pressure main steam valve is used as the tracking value of the PID controller. After passing through the PID controller and manual / automatic operation, a control signal is generated. The difference between the accumulator pressure and the accumulator full-load pressure signal is used to measure the degree of accumulator fullness. The above difference is used to generate a fullness signal through a function generator, which is multiplied with the PID control signal to obtain the accumulator flow command. The accumulator flow command is output after speed limiting by the speed limiter as the accumulator flow command after speed limiting. Under low load, it is used to control the opening of the first regulating valve, and under medium and high load, it is used to control the opening of the fifth regulating valve.

2. The thermal system for enhancing the variable load capacity of supercritical thermal power units as described in claim 1, characterized in that, The extraction steam and part of the exhaust steam from the high-pressure cylinder are connected to the high-pressure heater group through pipelines. Part of the extraction steam from the intermediate-pressure cylinder is connected to the high-pressure heater group through pipelines. Part of the extraction steam from the intermediate-pressure cylinder is connected to the turbines of the deaerator and the feedwater pump through pipelines. Part of the extraction steam from the intermediate-pressure cylinder is connected to the low-pressure heater group through pipelines. The extraction steam from the low-pressure cylinder is connected to the low-pressure heater group through pipelines. The overall condensate of the high-pressure heater group is connected to the deaerator through pipelines. The overall condensate of the low-pressure heater group is connected to the condenser through pipelines. The high-pressure cylinder is connected to the medium-pressure cylinder, low-pressure cylinder, and generator via a coupling. Under low load conditions, the accumulator's sliding pressure operating range is 8MPa~2.4MPa.

3. The thermal system for enhancing the variable load capacity of supercritical thermal power units as described in claim 1, characterized in that, Under high load conditions in the unit, the accumulator sliding pressure operating range is 4.5~0.2MPa.

4. The thermal system for enhancing the load-changing capacity of supercritical thermal power units as described in claim 1, characterized in that, When the unit needs to rapidly increase load or frequently adjust load in small increments, the unit load command value is subtracted from the specified constant and used as the set value of the low-value limiter. The unit load value is used as the tracking value of the low-value limiter. When the unit load value is lower than the low-value limiter setting, the low-value limiter sends a tracking command to the venting PID controller. At this time, the venting PID controller is activated, using the unit load value as the tracking value and the unit load command as the set value. Its output value is processed manually / automatically to generate the venting command. The unit load value is processed by the function unit to generate the main reheat steam temperature difference limit. The main steam temperature is subtracted from the reheat steam temperature and the main reheat temperature difference limit, and then processed by the function unit to generate the temperature difference correction coefficient. The temperature difference correction coefficient is multiplied by the venting command, and after speed limiting, the accumulator flow command is generated. Under low load, it is used to control the opening of the fourth regulating valve, and under medium and high load, it is used to control the opening of the second regulating valve.

5. The thermal system for enhancing the variable load capacity of supercritical thermal power units as described in claim 1, characterized in that, The unit load command value is added to a specified constant and used as the set value of the high-value limiter; the unit load value is used as the tracking value of the high-value limiter; when the unit load value is higher than the set value of the high-value limiter, the high-value limiter sends a tracking command to the charging PID controller; at this time, the charging PID controller is activated, using the unit load value as the tracking value and the unit load command as the set value, and its output value is processed manually / automatically to generate a charging command; the difference between the accumulator pressure and the accumulator full-fill pressure signal is used to measure the degree of accumulator filling, and the above difference is used to generate a fullness signal through a function, which is multiplied with the charging PID control signal, and after speed limiting, a speed-limited accumulator charging flow command is generated, which is used to control the opening of the first regulating valve under low load and to control the opening of the fifth regulating valve under medium and high load.

6. A control method for a thermal system for enhancing the variable load capacity of a supercritical thermal power unit as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: A portion of the feedwater is diverted into the accumulator to absorb superheated steam; Step 2: When the unit is operating at low load and changing load, part of the main steam is diverted into the accumulator for storage, thereby accelerating the unit's load reduction rate. The accumulator supplies steam to the reheater, thereby accelerating the unit's load increase rate. Step 3: When the unit changes load under medium or high load, part of the reheater inlet steam is diverted into the accumulator for storage, thereby accelerating the unit's load reduction rate. The accumulator supplies steam to the low-pressure cylinder, thereby accelerating the unit's load increase rate.

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