A feedwater heat storage peak shaving system for AGC load fast response of a coal-fired unit

Abstract

The application discloses a feedwater heat storage peak shaving system for AGC load rapid response of a coal-fired unit, which comprises low-pressure heater groups, a deaerator, a feedwater pump, high-pressure heater groups and a boiler which are sequentially connected; the high-temperature hot water tank is provided with a fluid inlet and a fluid outlet, the fluid inlet is connected with an outlet main pipe of the high-pressure heater groups, the fluid outlet is connected with a boiler feedwater main pipe, the boiler feedwater main pipe is located between a fluid outlet of the feedwater pump and a fluid inlet of the boiler, and an isolation assembly and an adjusting assembly are serially installed on a high-temperature heat storage inlet bypass and a high-temperature energy release outlet bypass; the low-temperature cold water tank is provided with a fluid inlet and a fluid outlet, the fluid inlet is connected with a condensate water main pipe, and the fluid outlet is connected with an outlet main pipe of the deaerator; an isolation assembly and an adjusting assembly are serially installed on a low-temperature cold storage inlet bypass and a low-temperature energy release outlet bypass. The system is deeply coupled with the original thermal system of the coal-fired unit, and can realize bidirectional dead-zone-free rapid regulation of ascending and descending loads.

Description

Technical Field

[0001] This invention belongs to the field of thermal power generation and relates to a feedwater thermal storage peak-shaving system for rapid load response of coal-fired power units using AGC (Automatic Generation Control) technology. Background Technology

[0002] With the continuous advancement of the construction of new power systems, renewable energy sources such as wind power and photovoltaics have achieved a high proportion of large-scale grid connection. The output of these power sources has significant intermittent, fluctuating and random characteristics, which leads to a continuous increase in the pressure of active power balance regulation of the power grid. This places higher demands on the response speed, regulation accuracy, bidirectional regulation frequency and continuous regulation capability of the power grid frequency regulation resources.

[0003] As the main power source in my country's power system, coal-fired power generating units are gradually transforming from a traditional main source of electricity supply to a power source that emphasizes both basic security and system regulation. They are currently the core supplier of AGC (Automatic Generation Control) frequency regulation services for the power grid. The AGC frequency regulation performance of coal-fired units is directly related to the safe and stable control of the power grid frequency and also directly affects the absorption capacity of high-proportion renewable energy.

[0004] Traditional coal-fired power units primarily achieve AGC (Automatic Generation Control) frequency regulation through a coordinated control system (CCS). The core regulation method involves synchronously adjusting boiler fuel quantity, feedwater flow, air distribution, and turbine regulating valve opening to alter the unit's output power. However, due to the inherent large inertia and lag characteristics of boiler combustion heat transfer and steam-water circulation thermodynamic processes, conventional regulation methods typically experience response delays of tens of seconds to AGC commands, limiting load regulation rates and making it difficult to adapt to the high-frequency, rapid-amplitude bidirectional regulation demands of the power grid. Furthermore, frequent adjustments to core operating parameters such as fuel and feedwater in response to AGC commands can easily lead to fluctuations in boiler combustion conditions and deviations in main and reheat steam parameters from rated values. This not only increases coal consumption during unit operation but also exacerbates fatigue wear on boiler heating surfaces, turbines, and auxiliary equipment, impacting the long-term safety and economic efficiency of the unit.

[0005] Feedwater thermal storage technology based on unit regenerative systems has become a research hotspot in the field of unit flexibility retrofitting due to its high coupling with the original thermal process of the unit, the absence of additional heat sources, and controllable retrofit costs. Existing feedwater thermal storage solutions are mostly based on single-phase high-temperature feedwater thermal storage, which can effectively shorten the response delay of the unit during load increase and adapt to the grid peak shaving and unidirectional load increase regulation requirements. However, in the core application scenario of AGC frequency regulation, the grid commands have the characteristics of frequent bidirectional load increase and decrease switching. Such single-phase thermal storage solutions can only achieve rapid adjustment in the direction of load increase and cannot simultaneously solve the thermal lag problem in the load decrease process. This results in a limitation of mismatch in bidirectional regulation capabilities and makes it difficult to fully cover the regulation requirements of AGC frequency regulation under all operating conditions.

[0006] In addition, technologies such as condensate throttling, turbine regulating valve pre-throttling, and boiler low-load stable combustion retrofitting can also improve the unit's regulation performance to some extent. However, condensate throttling technology has limited regulation capacity and a short sustainable regulation time, failing to meet the long-cycle AGC frequency regulation requirements. Turbine regulating valve pre-throttling technology generates continuous throttling losses, reducing the unit's operating economy. Low-load stable combustion retrofitting is mainly used to expand the unit's peak-shaving depth, with limited improvement on AGC frequency regulation response speed and bidirectional regulation capability. All of these technologies have corresponding applicability boundaries and cannot fully meet the comprehensive regulation requirements of coal-fired units for AGC frequency regulation under the new power system, demanding high performance and high economy across all operating conditions. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a feedwater thermal storage peak-shaving system for rapid load response of coal-fired power units with AGC (Automatic Guided Vehicle) system. This system is deeply coupled with the original thermal system of the coal-fired power unit and can achieve bidirectional, dead-zone-free, rapid adjustment of load.

[0008] To achieve the above objectives, the present invention employs the following technical solution: A feedwater thermal storage peak-shaving system for rapid load response of AGC in coal-fired power units includes a low-pressure heater group, a high-temperature hot water tank and a low-temperature cold water tank; The fluid outlet of the low-pressure heater group is connected to the fluid inlet of the deaerator through the condensate header. The fluid outlet of the deaerator is connected to the fluid inlet of the feedwater pump through the deaerator outlet header. The fluid outlet of the feedwater pump is connected to the fluid inlet of the high-pressure heater group through the feedwater pump outlet header. The fluid outlet of the high-pressure heater group is connected to the fluid inlet of the boiler through the high-pressure heater group outlet header. The high-temperature hot water tank shell is equipped with a fluid inlet and a fluid outlet. The fluid inlet on the high-temperature hot water tank shell is connected to a high-temperature heat storage inlet bypass, which is connected to the outlet header of the high-pressure heater group. The fluid outlet on the high-temperature hot water tank shell is connected to a high-temperature energy release outlet bypass, which is connected to the boiler feedwater header. The boiler feedwater header is located between the feedwater pump fluid outlet and the boiler fluid inlet. Isolation components and regulating components are installed in series on both the high-temperature heat storage inlet bypass and the high-temperature energy release outlet bypass. The low-temperature cold water tank shell is equipped with a fluid inlet and a fluid outlet. The fluid inlet on the low-temperature cold water tank shell is connected to a low-temperature cold storage inlet bypass, which is connected to the condensate header. The fluid outlet on the low-temperature cold water tank shell is connected to a low-temperature energy release outlet bypass, which is connected to the deaerator outlet header. Isolation components and regulating components are installed in series on both the low-temperature cold storage inlet bypass and the low-temperature energy release outlet bypass.

[0009] Optionally, it also includes a condenser and a condensate pump; the bottom volume space of the condenser is connected to the fluid inlet of the condensate pump through a pipe, and the fluid outlet of the condensate pump is connected to the low-pressure heater group through the main condensate pipeline.

[0010] Optionally, it also includes a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder on the same axis. The high-pressure cylinder, intermediate-pressure cylinder, and low-pressure cylinder are connected to form a turbine shaft system, and the generator is mechanically connected to the turbine shaft system. The boiler superheater outlet is connected to the high-pressure cylinder inlet via the main steam pipeline. The high-pressure cylinder exhaust port is connected to the reheater inlet inside the boiler via a pipeline. The boiler reheater outlet is connected to the intermediate-pressure cylinder inlet via a reheat steam pipeline. The intermediate-pressure cylinder exhaust port is connected to the low-pressure cylinder inlet. The low-pressure cylinder exhaust port is connected to the condenser interior.

[0011] Optionally, the high-pressure cylinder housing is provided with a steam extraction port, which is connected to the shell side of the high-pressure heater group through a steam extraction pipe; the intermediate-pressure cylinder housing is provided with a steam extraction port, which is connected to the deaerator through a steam extraction pipe; and the low-pressure cylinder housing is provided with a steam extraction port, which is connected to the shell side of the low-pressure heater group through a steam extraction pipe.

[0012] Optionally, it also includes a small steam turbine and a heating network heater; the small steam turbine is coaxially connected to the feedwater pump, the steam inlet of the small steam turbine receives working steam through a pipeline, and the extraction steam pipeline of the intermediate pressure cylinder or low pressure cylinder branches into the interior of the heating network heater.

[0013] A method for feedwater thermal storage peak shaving for rapid load response in coal-fired power units using AGC (Automatic Generation Control) includes the following operating conditions: Standby energy storage pre-control mode: When the isolation component on the high temperature heat storage inlet bypass is turned on, the feedwater in the outlet header of the high pressure heater group flows into the high temperature heat storage inlet bypass, and the feedwater flows into the high temperature hot water tank for storage through the regulating component on the high temperature heat storage inlet bypass; when the isolation component on the low temperature cold storage inlet bypass is turned on, the condensate in the condensate header flows into the low temperature cold storage inlet bypass, and the condensate flows into the low temperature cold water tank for storage. Load increase frequency regulation control mode: Open the isolation component on the high temperature energy release outlet bypass, the liquid water inside the high temperature hot water tank flows out and mixes with the feed water in the boiler feed water header, and the feed water flows to the boiler after mixing; open the isolation component on the low temperature cold storage inlet bypass, the condensate in the condensate header is drawn into the low temperature cold storage inlet bypass and flows into the low temperature cold water tank for storage. Load reduction frequency regulation control mode: Open the isolation component on the low temperature energy release outlet bypass, the condensate inside the low temperature cold water tank flows out and mixes with the feed water in the deaerator outlet header, and the mixed fluid enters the feed water pump; open the isolation component on the high temperature heat storage inlet bypass, the feed water in the high pressure heater group outlet header is drawn into the high temperature heat storage inlet bypass and flows into the high temperature hot water tank for storage.

[0014] Optional, in standby energy storage pre-control mode: The feedwater entering the high-temperature thermal storage inlet bypass is throttled by the regulating component on the high-temperature thermal storage inlet bypass, the feedwater pressure decreases and flows into the internal volume of the high-temperature hot water tank, and the liquid level inside the high-temperature hot water tank rises. Condensate entering the low-temperature cold storage inlet bypass flows into the internal volume of the low-temperature cold water tank, causing the liquid level inside the low-temperature cold water tank to rise.

[0015] Optionally, in the load increase frequency regulation control condition: The water flowing out of the high-temperature hot water tank is injected into the boiler feed water header at the node between the fluid outlet of the feed water pump and the fluid inlet of the boiler economizer. The temperature and specific enthalpy of the water flowing out of the high-temperature hot water tank are higher than those of the water flowing out of the feed water pump, resulting in a jump in the overall enthalpy of the feed water after mixing. The mass flow rate of condensate extracted into the low-temperature cold storage inlet bypass is matched with the mass flow rate of liquid water discharged from the high-temperature hot water tank into the boiler feedwater header.

[0016] Optionally, the load increase frequency regulation control mode also includes: after the feedwater enters the boiler and mixes, it absorbs heat and is converted into steam and discharged, and the steam flow rate inside the main steam pipeline increases.

[0017] Optionally, in the load reduction frequency regulation control condition: The water flowing out of the low-temperature cold water tank is injected into the deaerator outlet header at the node between the deaerator fluid outlet and the feed water pump fluid inlet. The temperature of the water flowing out of the low-temperature cold water tank is lower than the temperature of the feed water at the deaerator outlet when it is in a saturated state, and the overall temperature and specific enthalpy of the mixed fluid entering the feed water pump decrease. The mass flow rate of feedwater entering the high-temperature thermal storage inlet bypass is matched with the mass flow rate of condensate discharged from the low-temperature cold water tank into the deaerator outlet header. The feedwater pump pressurizes and delivers the mixed fluid to the high-pressure heater group. The feedwater flows through the high-pressure heater group and reaches the inlet of the boiler economizer, where the overall enthalpy value decreases.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention directly utilizes the unit's existing feedwater and condensate as the primary working fluid. Without altering the main steam flow of the boiler and turbine, it establishes buffer pools for high-grade thermal energy and low-grade cold energy through bypass connections in both high-pressure and low-pressure sections. The advantage of this architecture is that it bypasses the inherent large inertia and lag limitations of traditional regulation methods in boiler combustion heat transfer and steam-water circulation, providing a dedicated structural foundation for the unit to achieve rapid, bidirectional, dead-zone-free, and minimally disruptive AGC load frequency regulation.

[0019] Furthermore, the source of low-grade cold energy and the initial power transmission link were clarified, and the lowest temperature benchmark of the thermodynamic cycle and the starting point of fluid mass compensation were established. This ensures that the system can obtain a continuous, stable and clearly defined low-temperature liquid water supply when performing load reduction frequency regulation or cold energy storage, thereby ensuring the reliability of the mass flow rate and energy conversion of the entire thermal storage peak shaving system on the low-pressure side.

[0020] Furthermore, the work path of converting thermal energy into mechanical energy and then into electrical energy is clearly defined, and the drastic change in the enthalpy of the feedwater at the front end is directly linked to the electrical power output at the back end. This ensures that after the feedwater state entering the boiler is intervened through the energy storage system, the resulting changes in steam flow and work capacity can be smoothly and unimpededly transmitted along the turbine shaft system, ultimately achieving a second-level rapid response in generator output power.

[0021] Furthermore, by connecting the extraction steam at each stage of the steam turbine to the regenerative heating system, the dynamic distribution of the extraction steam volume is used to influence the amount of steam that performs work inside the steam turbine. When the bypass system extracts or injects fluid, causing a change in the flow rate in the main pipeline, it will disrupt the original thermal balance of the heater, prompting the steam extraction steam volume of the steam turbine to undergo a passive adaptive change. This mechanism allows more (or less) steam to remain inside the steam turbine to continue expanding and performing work, further amplifying and accelerating the response amplitude of the unit's output from within the thermodynamic cycle.

[0022] Furthermore, the small steam turbine and the heating network heater ensure the system's driving force for high-pressure fluid transportation and the tiered utilization of overall thermal energy. On the one hand, it ensures that even when the main feedwater system experiences transient disturbances in flow and pressure, the feedwater pump can still obtain stable mechanical driving force to maintain boiler feedwater safety. On the other hand, it ensures that the peak-shaving retrofit scheme is compatible with the unit's existing heating function, improving AGC response capability without compromising the unit's overall economic efficiency and safety.

[0023] Furthermore, a global operation method covering three operating conditions—standby, load increase, and load decrease—is proposed. By controlling the opening and closing of various bypass isolation components, the directional transfer of the medium between the main circulation system and the energy storage tank is realized, endowing the unit with complete bidirectional collaborative control logic. This enables the unit to accumulate energy without interfering with the operation of the main system under normal circumstances, and to release or absorb energy instantly when needed, based on real-time instructions from the power grid. This perfectly meets the stringent requirements of the new power system for high-frequency, fast-amplitude bidirectional regulation of coal-fired power units.

[0024] Furthermore, by throttling and depressurizing, the high-pressure, high-temperature feedwater and low-temperature condensate from the main system are slowly and continuously introduced into the two tanks for accumulation. Utilizing the gaps during the unit's stable operation, sufficient heat and cold margins are pre-stored at the thermodynamic boundary. This storage of media is equivalent to pre-setting a huge potential energy for subsequent rapid load increases and decreases. Moreover, because the extraction process is slow, the unit's original control system can automatically compensate, achieving zero disturbance in the energy storage process.

[0025] Furthermore, by directly injecting high-temperature water, the overall enthalpy of the boiler feedwater jumps, while simultaneously extracting an equal amount of condensate. The high-enthalpy feedwater directly reduces the sensible heat required for the boiler to heat the water to saturation, allowing heat to be instantly concentrated in the vaporization process, increasing steam production by seconds without increasing fuel. Meanwhile, the simultaneous extraction of an equal amount perfectly offsets the increase in mass flow rate caused by the injection action, maintaining the dynamic balance between the deaerator level and the feedwater pump back pressure, achieving a rapid load increase without disturbance.

[0026] Furthermore, by directly injecting low-temperature water to lower the overall temperature and specific enthalpy of the feedwater pump inlet fluid, and simultaneously extracting high-pressure feedwater, the low-enthalpy water forces the boiler to consume more of its existing heat to make up for the sensible heat deficit, thereby instantly cutting off the vaporization process and achieving a precipitous drop in steam production without waiting for the furnace to cool down. At the same time, the equal extraction from the high-pressure side avoids excess mass from flooding into the boiler and disrupting the water balance, ensuring equipment safety and accumulating high-grade thermal energy for the next load increase.

[0027] Furthermore, by utilizing the limited heat exchange capacity of the high-pressure heater unit under transient conditions, when the cooled mixed feedwater flows through the high-pressure heater, due to the limitations of the heat exchange area and steam extraction rate, the feedwater cannot be fully heated to the original temperature, resulting in a substantial reduction in the enthalpy of the feedwater reaching the inlet of the boiler economizer. This thermodynamic cold wave transmission greatly amplifies the depth and speed of load reduction regulation, ensuring the precise and efficient execution of commands. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the feedwater thermal storage peak-shaving system for rapid load response of coal-fired power units according to the present invention.

[0029] Wherein: 1-High temperature hot water tank; 2-Low temperature cold water tank; 3-Boiler; 4-High pressure heater group; 5-Low pressure heater group; 6-Deaerator; 7-Feed water pump; 8-High pressure cylinder; 9-Medium pressure cylinder; 10-Low pressure cylinder; 11-Generator; 12-Small steam turbine; 13-Heating network heater; 14-Condenser; 15-Condensate pump. Detailed Implementation

[0030] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terms “installation,” “connection,” and “linkage” should be interpreted broadly, for example, as a fixed connection, a detachable connection, or an integral connection; a mechanical connection, an electrical connection, or a connection that allows communication; a direct connection or an indirect connection via an intermediate medium; or a connection within two elements or an interaction between two elements. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art will understand the specific meaning of the above terms in this invention according to the specific circumstances. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0032] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0033] The feedwater thermal storage peak-shaving system for rapid load response of coal-fired power units described in this invention stores high-grade thermal energy and low-grade cold energy in the regenerative system through high- and low-temperature dual tanks, using the unit's own feedwater / condensate as the energy storage medium. Through bypass-type non-intrusive access, it realizes bidirectional rapid adjustment of the unit load, perfectly matching the frequency regulation requirements of the power grid's AGC.

[0034] like Figure 1 As shown, the feedwater thermal storage peak-shaving system used for AGC load rapid response of coal-fired units does not change the original main thermal process of the unit and achieves uninterrupted access only through bypass pipelines.

[0035] High-temperature thermal storage unit: A high-temperature hot water tank 1 is installed, the inlet of which is connected to the outlet header of the high-pressure heater group through a bypass pipe, and the outlet is connected to the boiler feed water header (between the feed water pump outlet and the economizer inlet) through a bypass pipe. Isolation and regulation components are installed for each bypass pipe.

[0036] Low-temperature cold storage unit: A low-temperature cold water tank 2 is installed. Its inlet is connected to the condensate header of the deaerator 6 inlet of the unit through a bypass pipe, and its outlet is connected to the outlet header of the deaerator 6 (before the inlet of the feed water pump 7) through a bypass pipe. Each bypass pipe is equipped with isolation and regulation components.

[0037] Condenser 14 is located at the exhaust end of the steam turbine system. Low-pressure cylinder 10 has an exhaust port. The exhaust port of low-pressure cylinder 10 is connected to the interior of condenser 14. A heat exchange tube bundle structure exists inside condenser 14. Low-pressure exhaust steam from low-pressure cylinder 10 enters condenser 14 after performing work. The exhaust steam exchanges heat with the cooling medium inside condenser 14. The exhaust steam releases its latent heat of vaporization. The phase of the exhaust steam changes from gaseous to liquid. This liquid water is called condensate. Condensate accumulates by gravity in the volumetric space at the bottom of condenser 14. Condensate pump 15 is located downstream of condenser 14. The fluid inlet of condensate pump 15 is connected to the bottom volumetric space of condenser 14 via a pipe. The fluid outlet of condensate pump 15 is connected to the unit's main condensate pipeline. The operation of condensate pump 15 provides kinetic energy to the condensate. Condensate pump 15 increases the fluid pressure of the condensate. The pressurized condensate flows forward in the main pipeline.

[0038] The low-pressure heater group 5 is located downstream of the condensate pump 15. The low-pressure heater group 5 consists of multiple surface heat exchangers connected in series. The main condensate pipe is connected to the tube side inside the low-pressure heater group 5. The shell of the low-pressure cylinder 10 has multiple extraction steam ports of different pressure levels. The extraction steam ports of the low-pressure cylinder 10 are connected to the shell side inside the low-pressure heater group 5 via extraction steam pipes. Condensate flows inside the tube side of the low-pressure heater group 5. The extraction steam from the low-pressure cylinder 10 flows inside the shell side of the low-pressure heater group 5. The extraction steam transfers heat to the condensate in the tube side. The condensate absorbs heat, and its temperature rises. The heated condensate flows out of the low-pressure heater group 5. The deaerator 6 is located downstream of the low-pressure heater group 5. The outlet pipe of the low-pressure heater group 5 is connected to the inlet condensate header of the deaerator 6. The deaerator 6 is a mixing heat exchange component. The shell of the intermediate-pressure cylinder 9 has an extraction steam port. The extraction steam interface of intermediate-pressure cylinder 9 is connected to deaerator 6 via an extraction steam pipe. Condensate and the extracted steam from intermediate-pressure cylinder 9 are in direct contact inside deaerator 6. The condensate absorbs heat from the extracted steam and reaches saturation temperature. Dissolved oxygen and other non-condensable gases in the condensate precipitate out. The deaerated water is called unit feedwater. Feedwater is stored in a feedwater tank at the bottom of deaerator 6.

[0039] Feedwater pump 7 is located downstream of deaerator 6. The fluid inlet of feedwater pump 7 is connected to the outlet of the feedwater tank at the bottom of deaerator 6 via a pipeline. Feedwater pump 7 is the core rotating fluid machinery for increasing feedwater pressure. The mechanical driving force of feedwater pump 7 comes from small steam turbine 12. The steam inlet of small steam turbine 12 receives working steam extracted from the turbine system via a pipeline. The steam expands and does work inside small steam turbine 12. Small steam turbine 12 rotates. Small steam turbine 12 is coaxially connected to feedwater pump 7. Small steam turbine 12 drives feedwater pump 7. Feedwater pump 7 performs work on the feedwater. The fluid pressure of the feedwater is significantly increased and reaches the operating pressure required by boiler 3. High-pressure feedwater flows out from the fluid outlet of feedwater pump 7 and enters the feedwater pump outlet header. High-pressure heater group 4 is located downstream of feedwater pump 7. High-pressure heater group 4 consists of multiple high-pressure surface heat exchangers connected in series. The feedwater pump outlet header is connected to the tube side inside high-pressure heater group 4. A steam extraction port is provided on the shell of high-pressure cylinder 8. The extraction steam interface of high-pressure cylinder 8 is connected to the shell side of high-pressure heater group 4 via an extraction steam pipe. High-pressure feedwater flows inside the tube side of high-pressure heater group 4. The extraction steam from high-pressure cylinder 8 flows inside the shell side of high-pressure heater group 4. The extraction steam releases heat. The high-pressure feedwater absorbs heat. The temperature of the high-pressure feedwater continues to rise. High-pressure, high-temperature feedwater flows out of high-pressure heater group 4. The outlet pipes of high-pressure heater group 4 converge to form the outlet header of high-pressure heater group.

[0040] Boiler 3 is located downstream of the high-pressure heater group 4. The outlet header of the high-pressure heater group extends and connects to the inlet header of boiler 3. The inlet header specifically connects to the economizer inlet inside boiler 3. Boiler 3 includes heat-receiving surface components such as economizer, water-cooled walls, superheater, and reheater. High-pressure, high-temperature feedwater enters the economizer of boiler 3. Inside the economizer, the feedwater absorbs the sensible heat of the flue gas at the tail end of boiler 3. The feedwater flows into the water-cooled walls. Inside the water-cooled walls, the feedwater absorbs the radiant heat released by the combustion of fuel in the furnace. The feedwater undergoes a vaporization phase change, transforming into saturated steam. The saturated steam enters the superheater. Inside the superheater, the saturated steam continues to absorb heat, transforming into main steam that meets the rated parameters of the unit. The main steam flows out of boiler 3. The steam inlet of high-pressure cylinder 8 is connected to the superheater outlet of boiler 3 through the main steam pipe. The main steam flows into high-pressure cylinder 8, where it expands and performs work. The exhaust port of high-pressure cylinder 8 is connected to the reheater inlet inside boiler 3 via a pipe. The steam, after performing work, flows back to boiler 3 for reheating. The steam absorbs heat inside the reheater. The reheated steam flows out of boiler 3. The steam inlet of intermediate-pressure cylinder 9 is connected to the reheater outlet of boiler 3 via a reheat steam pipe. The reheated steam flows into intermediate-pressure cylinder 9. The reheated steam expands and performs work inside intermediate-pressure cylinder 9. The exhaust port of intermediate-pressure cylinder 9 is connected to the steam inlet of low-pressure cylinder 10. Steam flows into low-pressure cylinder 10 and continues to expand and perform work inside.

[0041] High-pressure cylinder 8, intermediate-pressure cylinder 9, and low-pressure cylinder 10 are located on the same axis. The cylinders are rigidly connected via couplings to form the turbine shaft system. Generator 11 is mechanically connected to the turbine shaft system. The turbine converts the internal energy of steam into mechanical energy. The turbine drives generator 11 to rotate. Generator 11 converts mechanical energy into electrical energy for output. A heat exchanger 13 is installed on the unit's extraction steam circuit. A branch of the extraction steam pipe from intermediate-pressure cylinder 9 or low-pressure cylinder 10 is connected to the heat exchanger 13. Steam releases heat inside the heat exchanger 13 to heat the external pipeline medium. The unit achieves continuous energy conversion through the aforementioned basic thermal system.

[0042] The high-temperature hot water tank 1 has an internal cavity for storing liquid water. A fluid inlet is located on the shell of the high-temperature hot water tank 1. This fluid inlet is connected to a high-temperature heat storage inlet bypass. The starting end of the high-temperature heat storage inlet bypass is connected to the outlet header of the high-pressure heater group 4 of the unit via a tee fitting. This connection point is located downstream of the fluid outlet of the high-pressure heater group 4. An isolation component and a regulating component are installed in series on this high-temperature heat storage inlet bypass pipe. The isolation component is used to block or open the fluid path inside the pipe. The regulating component is used to change the area of ​​the flow interface in the pipe to control the fluid mass flow rate. The shell of the high-temperature hot water tank 1 also has a fluid outlet. This fluid outlet is connected to a high-temperature energy release outlet bypass. The end of the high-temperature energy release outlet bypass is connected to the feedwater header of the boiler 3 via a tee fitting or other connection methods. The specific spatial location of this connection point is downstream of the fluid outlet of the feedwater pump 7 and upstream of the economizer fluid inlet of the boiler 3. Matching isolation components and regulating components are also installed in series on the high-temperature energy release outlet bypass pipe. The high-temperature hot water tank 1 exchanges mass independently with the unit's high-pressure section water supply system through these two bypass pipes.

[0043] A fluid inlet is provided on the shell of the cryogenic chilled water tank 2. This fluid inlet connects to the cryogenic storage inlet bypass. The starting end of the cryogenic storage inlet bypass connects to the inlet condensate header of the deaerator 6. This connection point is located downstream of the fluid outlet of the low-pressure heater group 5 and upstream of the fluid inlet of the deaerator 6. Isolation and regulating components are installed in series on the cryogenic storage inlet bypass pipe. A fluid outlet is also provided on the shell of the cryogenic chilled water tank 2. This fluid outlet connects to the cryogenic energy release outlet bypass. The end of the cryogenic energy release outlet bypass connects to the outlet header of the deaerator 6. This connection point is located downstream of the fluid outlet of the deaerator 6 and upstream of the fluid inlet of the feedwater pump 7. Matching isolation and regulating components are also installed in series on the cryogenic energy release outlet bypass pipe. The system directly uses the feedwater and condensate circulating inside the unit as the energy storage medium. The system does not introduce external heat exchange media or intermediate heat exchange equipment.

[0044] The above-mentioned system's feedwater thermal storage peak-shaving method for rapid load response in coal-fired power units' AGC includes three operating conditions. The first condition is standby energy storage pre-control. The unit is operating during a period when the grid's automatic generation control commands maintain stability. The unit has not received any external commands that significantly change its output power. The current energy storage status is assessed. The control system initiates the standby energy storage pre-control program. The system sends electrical signals to synchronously execute the thermal storage operation of high-temperature hot water tank 1 and the cold water storage operation of low-temperature cold water tank 2. The purpose of this process is to maintain the energy storage margin inside both high-temperature hot water tank 1 and low-temperature cold water tank 2.

[0045] The control system issues commands to the high-temperature thermal storage unit. The control system sends a signal to open the isolation component on the inlet bypass pipe of high-temperature hot water tank 1. The inlet of high-temperature hot water tank 1 is connected to the outlet main pipe of the high-pressure heater group. The control system controls the opening area of ​​the regulating component. The high-pressure, high-temperature feedwater heated by the high-pressure heater group 4 flows through the main pipe and is diverted. A portion of the high-pressure, high-temperature feedwater deviates from the main pipe and enters the high-temperature thermal storage inlet bypass. This portion of feedwater undergoes throttling by the regulating component. The feedwater pressure decreases to match the design pressure range of high-temperature hot water tank 1. The depressurized high-temperature feedwater flows into the internal volume of high-temperature hot water tank 1. The high-temperature liquid level inside high-temperature hot water tank 1 gradually rises. The system completes the collection and storage of high-grade thermal energy. Since this portion of water has already absorbed the heat provided by the high-pressure heater group 4 and is at a high temperature, storing it in high-temperature hot water tank 1 is equivalent to pre-storing redundant thermal energy and evaporation reserves required for the vaporization of boiler 3 for the unit.

[0046] While performing high-temperature thermal storage, the control system sends synchronization commands to the low-temperature cold storage unit. The control system signals to open the isolation component on the inlet bypass pipe of low-temperature cold water tank 2. The inlet of low-temperature cold water tank 2 is connected to the condensate header of the deaerator inlet. The control system controls the opening area of ​​the regulating component. The condensate flowing out of the low-pressure heater group 5 in the main header is diverted. A portion of the relatively lower-temperature condensate deviates from the main pipe and enters the low-temperature cold storage inlet bypass. This portion of low-temperature condensate flows into the internal volume of low-temperature cold water tank 2. The low-temperature liquid level inside low-temperature cold water tank 2 gradually rises. The system completes the collection and storage of low-grade cold energy. This portion of the low-temperature fluid stored in low-temperature cold water tank 2 has the ability to reduce the thermodynamic state of the main system in subsequent processes, which is equivalent to pre-storing the thermodynamic boundary potential for load reduction for the unit. In the standby energy storage pre-control step, the fluid extraction process maintains a relatively slow rate. The unit's original automatic control loop for feedwater and condensate compensates for this slow flow change by adjusting the output of feedwater pump 7 and condensate pump 15, thus maintaining the liquid level balance of boiler 3 and deaerator 6.

[0047] The second operating condition is automatic power generation control for load increase and frequency regulation. The power grid sends a command to the coal-fired unit to increase the output power of generator 11. The control system receives the command and initiates the load increase procedure. The system sends control signals to simultaneously execute the energy release operation of the high-temperature hot water tank 1 and the energy replenishment operation of the low-temperature cold water tank 2. These two operations highly overlap in time, forming the basis for the bidirectional, non-disruptive, and coordinated operation of the system.

[0048] The control system issues an energy release command to the high-temperature thermal storage unit. The control system signals the activation of the isolation component on the bypass pipe at the outlet of high-temperature hot water tank 1. The control system calculates the opening degree of the adjustment component based on the increase in power demand and executes the activation operation. The high-temperature, high-pressure liquid water stored inside high-temperature hot water tank 1 flows out rapidly through the bypass pipe. The high-temperature, high-pressure water is injected into the main feedwater header at the pipe node between the outlet of feedwater pump 7 and the economizer inlet. The temperature and specific enthalpy of the water released from high-temperature hot water tank 1 are much higher than the temperature and specific enthalpy of the feedwater from feedwater pump 7 in the header. The two fluids mix in the pipe. The mixed feedwater flows to the economizer. The overall enthalpy of the feedwater entering the economizer of boiler 3 increases dramatically. The fuel combustion rate inside boiler 3 remains unchanged or only slightly increases. The total radiant and convective heat generated by combustion remains essentially constant. Because the initial state of the feedwater is closer to the saturation vaporization point, the sensible heat required to heat the water to saturation within the water-cooled walls and other heating surfaces of boiler 3 is significantly reduced. This allows more heat to be directly used in the water vaporization process. The steam generation rate inside the heating surface of boiler 3 immediately increases. The effective steam output rises rapidly in a very short time. The steam flow rate inside the main steam pipe increases. The high-pressure cylinder 8 receives more superheated steam. The output mechanical torque increases. The output power of generator 11 rises rapidly accordingly. By relying on the direct intervention of the feedwater enthalpy value, the system avoids the large inertia and long lag problems that inevitably come with increasing boiler fuel, and shortens the unit's output response time.

[0049] While the high-temperature hot water tank 1 injects additional mass flow into the main feedwater system, the control system issues a synchronous energy replenishment command to the low-temperature cold storage unit. The control system signals to open the isolation component on the inlet bypass pipe of the low-temperature cold water tank 2. The regulating component matches the opening degree according to the energy release flow data of the high-temperature hot water tank 1. The system rapidly extracts a portion of condensate from the condensate header upstream of the deaerator 6 inlet. This portion of condensate flows into the low-temperature cold water tank 2 for storage. In terms of fluid dynamics balance, the injection of high-temperature water downstream will cause an incremental disturbance in the total mass flow of the feedwater system. If left uncontrolled, this disturbance will negatively affect the operating back pressure of the feedwater pump 7. By simultaneously extracting an equal amount of condensate from the upstream deaerator inlet condensate side, the system artificially creates a flow reduction. The fluid mass changes caused by these two actions cancel each other out within the macroscopic closed-loop boundary of the system. The total amount of fluid entering the deaerator 6 and the total amount of fluid flowing out of the deaerator 6 maintain a dynamic balance. The operating water level inside the deaerator 6 remains stable. The pressure parameters of the unit's main feedwater system do not fluctuate significantly. Simultaneously, this extraction action allows more condensate to accumulate inside the cryogenic chilled water tank 2, replenishing its energy storage capacity. The system is prepared with a reserve of media to cope with potential future reverse load reduction commands from the power grid.

[0050] The third operating condition is automatic power generation control, load reduction, and frequency regulation control. The power grid sends a command to the coal-fired unit to reduce the output power of generator 11. The control system receives the command and initiates the load reduction procedure. The system sends control signals to simultaneously execute the energy release operation of the low-temperature cold water tank 2 and the energy replenishment operation of the high-temperature hot water tank 1.

[0051] The control system issues a release command to the cryogenic storage unit. The control system signals the activation of the isolation component on the bypass pipe at the outlet of cryogenic cold water tank 2. The control system adjusts the opening degree of the regulating component based on the decrease in power demand. The relatively low-temperature condensate stored inside cryogenic cold water tank 2 flows out rapidly through the bypass pipe. The cryogenic condensate is injected into the main feedwater header at the pipe node between the outlet of deaerator 6 and the inlet of feedwater pump 7. The temperature of the water released from cryogenic cold water tank 2 is much lower than the saturated feedwater temperature at the outlet of deaerator 6. The cryogenic condensate mixes with the high-temperature saturated feedwater inside the pipe. The mixed fluid enters feedwater pump 7. The overall temperature and specific enthalpy of the fluid at the inlet of feedwater pump 7 drop instantaneously. Feedwater pump 7 pressurizes the cooled fluid and delivers it to the downstream high-pressure heater group 4. The high-pressure heater group 4 has an upper limit to the heat exchanged within a certain time range. After the feedwater flows through the high-pressure heater group 4, its overall enthalpy value at the economizer inlet is significantly reduced. The mixed fluid enters boiler 3. The fuel combustion rate inside boiler 3 remains unchanged or undergoes only a slight reduction. The total heat released by the fuel remains essentially constant. Because the initial state of the feedwater is further from the saturation vaporization point, more heat must be used to heat the feedwater to compensate for the enthalpy drop. This drastically reduces the share of heat available for water vaporization. The steam generation rate inside the water-cooled walls of boiler 3 is suppressed. Effective steam production drops rapidly within a very short time. Steam flow rate inside the main steam pipe decreases. The steam received by high-pressure cylinder 8 performs less work. The output mechanical torque decreases. The output power of generator 11 subsequently drops rapidly. The system avoids the lag effect of waiting for furnace cooling after fuel reduction by directly intervening with the feedwater temperature, thus shortening the response time to unit load reduction.

[0052] While the low-temperature cold water tank 2 injects additional mass flow into the main feedwater system, the control system issues a synchronous energy replenishment command to the high-temperature thermal storage unit. The control system signals to activate the isolation component on the inlet bypass pipe of the high-temperature hot water tank 1. The regulating component precisely matches the energy release flow data of the low-temperature cold water tank 2. The system rapidly draws a portion of high-temperature, high-pressure feedwater from the main header at the outlet of the high-pressure heater group 4. This portion of high-pressure fluid flows into the high-temperature hot water tank 1 for storage after throttling and depressurization. In terms of fluid dynamics balance, the injection of low-temperature water upstream of the feedwater pump 7 leads to an increase in the total mass of the fluid flowing through the feedwater pump 7. If left uncontrolled, the boiler 3 will receive excessive feedwater, thus disrupting its internal mass balance. By synchronously drawing an equal amount of high-temperature feedwater at the outlet of the high-pressure heater group downstream of the feedwater pump 7, the system artificially transfers the excess mass flow. The drawn flow rate is numerically consistent with the injected flow rate. The total amount of fluid flowing into the boiler 3 remains within the stable target range. This adaptive flow matching mechanism offsets the impact of the bypass action on the pressure and flow of the unit's main feedwater system. The safe operation of the unit's original thermal equipment is ensured. Simultaneously, this extraction action allows high-grade, high-temperature water to be replenished inside the high-temperature hot water tank 1. The thermal energy margin of the high-temperature hot water tank 1 is thus replenished. The system regains sufficient regulatory capacity to cope with potential subsequent reverse load increases from the power grid.

[0053] This invention combines high-temperature thermal storage with low-temperature cold storage, which can rapidly increase and decrease the unit's output respectively. The response speed is significantly faster than conventional methods that adjust fuel and feedwater, which helps improve the unit's ability to track AGC commands.

[0054] 1. Minimal modifications to the original unit system, making engineering implementation simple.

[0055] This invention only adds a bypass and high and low temperature storage tanks to the unit's regenerative system, without changing the main steam and main feedwater flow, and without involving any changes to the boiler or turbine structure. The system structure is simple and easy to implement on existing units.

[0056] 2. The system uses the unit's own working fluid as the energy storage medium, making it simple and reliable.

[0057] Using the unit's feedwater and condensate as energy storage media, there is no need to add additional phase change materials, heat exchange working fluids, or complex heat exchange equipment. The system has a simple structure, high operational stability, and low maintenance workload.

[0058] 3. The adjustment process causes minimal disturbance to unit operation and ensures high safety.

[0059] The high and low temperature storage tank adopts a bypass connection method, and the energy release and energy storage processes can compensate each other for flow disturbances. It has little impact on the operation of equipment such as deaerator, high and low pressure heater group, and feed water pump, does not disrupt the original thermal system balance, and has a high safety margin.

[0060] 4. It is compatible with existing coordinated control systems.

[0061] This invention can work in conjunction with the existing CCS and AGC systems of the unit without requiring large-scale modifications to the original control architecture. It can be smoothly integrated into the unit's automatic control system and has strong applicability.

[0062] The present invention has the following advantages: Dedicated dual-tank dual-bypass access architecture: the inlet of the high-temperature hot water tank is connected to the outlet header of the high-pressure heater group, and the outlet is connected to the feed water header before the economizer; the inlet of the low-temperature cold water tank is connected to the inlet condensate header of the deaerator, and the outlet is connected to the feed water header before the feed water pump. The dual independent bypasses do not change the main steam-water process of the unit, providing a dedicated structural foundation for bidirectional frequency regulation.

[0063] Two-way collaborative AGC frequency regulation control method: For AGC load increase and decrease commands, a collaborative logic is adopted to release energy from the high-temperature tank and store energy synchronously in the low-temperature tank when the load increases, and to release energy from the low-temperature tank and store energy synchronously in the high-temperature tank when the load decreases, so as to realize the second-level two-way dead-zone-free adjustment of the unit load.

[0064] Minimalist energy storage design using native working fluid: The unit's own feedwater and condensate are used as energy storage media. No additional phase change materials, heat exchange working fluids and intermediate heat exchange equipment are required. The system structure is extremely simple, the modification cost is low, and the project is highly feasible.

[0065] Disturbance-free operation flow complementary control mechanism: During load adjustment, the flow injection on the energy release side and the flow extraction on the energy storage side are adaptively matched to offset the flow and pressure disturbances of the main feedwater system of the unit caused by the bypass action, and ensure the stable operation of the original thermal system of the unit.

[0066] This invention adopts a high- and low-pressure dual-stage precise direct control architecture, with both tanks directly connected to the core boiler feedwater system: the high-temperature tank is connected to the boiler main feedwater header from the outlet of the high-pressure heater group (high-pressure and high-temperature section) to the economizer, directly acting on the boiler inlet; the low-temperature tank is connected to the feedwater front section from the deaerator inlet to the feedwater pump inlet, which can directly change the enthalpy of the feedwater entering the boiler, which is completely different from the low-pressure side bypass architecture of the prior art.

[0067] The principle of this invention is direct control of the boiler feedwater enthalpy, which directly affects the core aspect of unit output: when the load increases, high-temperature and high-pressure feedwater is directly injected into the boiler inlet, which can significantly reduce the boiler's heat absorption demand and rapidly increase steam production without increasing fuel; when the load decreases, low-temperature water is directly mixed with the main feedwater, which can significantly increase the boiler's heat absorption demand and rapidly reduce steam production without reducing fuel. The response speed and adjustment range far exceed those of existing technical solutions.

[0068] This invention is a bidirectional collaborative and complementary control: when the load increases, the high-temperature tank releases energy and the low-temperature tank stores energy simultaneously; when the load decreases, the low-temperature tank releases energy and the high-temperature tank stores energy simultaneously. This not only achieves bidirectional, dead-zone-free regulation of the load increase and decrease, but also offsets the pressure and flow disturbances to the main system through the flow complementarity of the contraction and expansion actions, thus achieving disturbance-free operation.

[0069] The high-temperature tank of this invention stores high-pressure, high-temperature, and high-grade feedwater from the outlet of the high-pressure heater group. It has a large energy density and can directly enter the boiler after energy release, resulting in extremely high energy utilization. The low-temperature tank stores low-temperature condensate from the deaerator inlet, which can be directly mixed with the main feedwater to change the enthalpy of the boiler feedwater. Its cold energy utilization efficiency is far higher than that of existing technologies.

[0070] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0071] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0072] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0073] The units described as separate components may or may not be separate. Similarly, components shown as units may or may not be units; they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0074] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

[0075] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this patent should not be determined by reference to the above description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed inventive subject matter.

Claims

1. A feedwater thermal storage peak-shaving system for rapid load response in coal-fired power units using AGC (Automatic Guided Vehicle) technology, characterized in that, It includes a low-pressure heater assembly (5), a high-temperature hot water tank (1), and a low-temperature cold water tank (2). The fluid outlet of the low-pressure heater group (5) is connected to the fluid inlet of the deaerator (6) through the condensate header. The fluid outlet of the deaerator (6) is connected to the fluid inlet of the feed water pump (7) through the deaerator outlet header. The fluid outlet of the feed water pump (7) is connected to the fluid inlet of the high-pressure heater group (4) through the feed water pump outlet header. The fluid outlet of the high-pressure heater group (4) is connected to the fluid inlet of the boiler (3) through the high-pressure heater group outlet header. The shell of the high-temperature hot water tank (1) is provided with a fluid inlet and a fluid outlet. The fluid inlet of the high-temperature hot water tank (1) is connected to a high-temperature heat storage inlet bypass. The high-temperature heat storage inlet bypass is connected to the outlet header of the high-pressure heater group. The fluid outlet of the high-temperature hot water tank (1) is connected to a high-temperature energy release outlet bypass. The high-temperature energy release outlet bypass is connected to the boiler feed water header. The boiler feed water header is located between the fluid outlet of the feed water pump (7) and the fluid inlet of the boiler (3). Isolation components and regulating components are installed in series on both the high-temperature heat storage inlet bypass and the high-temperature energy release outlet bypass. The shell of the low-temperature cold water tank (2) is provided with a fluid inlet and a fluid outlet. The fluid inlet of the low-temperature cold water tank (2) is connected to a low-temperature cold storage inlet bypass, which is connected to the condensate header. The fluid outlet of the low-temperature cold water tank (2) is connected to a low-temperature energy release outlet bypass, which is connected to the deaerator outlet header. Isolation components and regulating components are installed in series on both the low-temperature cold storage inlet bypass and the low-temperature energy release outlet bypass.

2. The feedwater thermal storage peak-shaving system for rapid load response in coal-fired power units according to claim 1, characterized in that, It also includes a condenser (14) and a condensate pump (15); the bottom volume space of the condenser (14) is connected to the fluid inlet of the condensate pump (15) through a pipe, and the fluid outlet of the condensate pump (15) is connected to the low-pressure heater group (5) through the main condensate pipe.

3. The feedwater thermal storage peak-shaving system for rapid load response in coal-fired power units according to claim 1, characterized in that, It also includes a high-pressure cylinder (8), a medium-pressure cylinder (9) and a low-pressure cylinder (10) on the same axis. The high-pressure cylinder (8), the medium-pressure cylinder (9) and the low-pressure cylinder (10) are connected to form a turbine shaft system. The generator (11) is mechanically connected to the turbine shaft system. The superheater outlet of boiler (3) is connected to the steam inlet of high-pressure cylinder (8) through the main steam pipeline. The exhaust port of high-pressure cylinder (8) is connected to the reheater inlet inside boiler (3) through the pipeline. The reheater outlet of boiler (3) is connected to the steam inlet of intermediate-pressure cylinder (9) through the reheat steam pipeline. The exhaust port of intermediate-pressure cylinder (9) is connected to the steam inlet of low-pressure cylinder (10). The exhaust port of low-pressure cylinder (10) is connected to the inside of condenser (14).

4. The feedwater thermal storage peak-shaving system for rapid load response of coal-fired power units according to claim 3, characterized in that, The high-pressure cylinder (8) has a steam extraction port on its shell, which is connected to the shell side of the high-pressure heater group (4) through a steam extraction pipe; the medium-pressure cylinder (9) has a steam extraction port on its shell, which is connected to the deaerator (6) through a steam extraction pipe; the low-pressure cylinder (10) has a steam extraction port on its shell, which is connected to the shell side of the low-pressure heater group (5) through a steam extraction pipe.

5. The feedwater thermal storage peak-shaving system for rapid load response in coal-fired power units according to claim 1, characterized in that, It also includes a small steam turbine (12) and a heat network heater (13); the small steam turbine (12) is coaxially connected to the feed water pump (7), the steam inlet of the small steam turbine (12) receives working steam through a pipeline, and the extraction steam pipeline of the medium-pressure cylinder (9) or the low-pressure cylinder (10) is branched into the heat network heater (13).

6. A method for feedwater thermal storage peak shaving for rapid load response in coal-fired power units using the system described in any one of claims 1-5, characterized in that, Including the following working conditions: Standby energy storage pre-control condition: When the isolation component on the high temperature heat storage inlet bypass is turned on, the feedwater in the outlet header of the high pressure heater group flows into the high temperature heat storage inlet bypass, and the feedwater flows into the high temperature hot water tank (1) for storage through the regulating component on the high temperature heat storage inlet bypass; when the isolation component on the low temperature cold storage inlet bypass is turned on, the condensate in the condensate header flows into the low temperature cold storage inlet bypass, and the condensate flows into the low temperature cold water tank (2) for storage. Load increase frequency regulation control condition: Open the isolation component on the high temperature energy release outlet bypass, the liquid water inside the high temperature hot water tank (1) flows out and mixes with the feed water in the boiler feed water header, and the feed water flows to the boiler (3) after mixing; Open the isolation component on the low temperature cold storage inlet bypass, the condensate in the condensate header is drawn into the low temperature cold storage inlet bypass and flows into the low temperature cold water tank (2) for storage; Load reduction frequency control mode: Open the isolation component on the low temperature energy release outlet bypass, the condensate inside the low temperature cold water tank (2) flows out and mixes with the feed water in the deaerator outlet header, and the mixed fluid enters the feed water pump (7); Open the isolation component on the high temperature heat storage inlet bypass, the feed water in the high pressure heater group outlet header is drawn into the high temperature heat storage inlet bypass and flows into the high temperature hot water tank (1) for storage.

7. The feedwater thermal storage peak-shaving method for rapid load response in coal-fired power units according to claim 6, characterized in that, In standby energy storage pre-control mode: The feedwater entering the high-temperature heat storage inlet bypass is throttled by the regulating component on the high-temperature heat storage inlet bypass, and the feedwater pressure drops and flows into the internal volume of the high-temperature hot water tank (1), and the liquid level inside the high-temperature hot water tank (1) rises. Condensate entering the low-temperature cold storage inlet bypass flows into the internal volume of the low-temperature cold water tank (2), and the liquid level inside the low-temperature cold water tank (2) rises.

8. The feedwater thermal storage peak-shaving method for rapid load response in coal-fired power units according to claim 6, characterized in that, During load increase frequency regulation control: The water flowing out of the high-temperature hot water tank (1) is injected into the boiler feed water header at the node between the fluid outlet of the feed water pump (7) and the fluid inlet of the economizer of the boiler (3); The temperature and specific enthalpy of the water flowing out of the high-temperature hot water tank (1) are higher than the temperature and specific enthalpy of the water flowing out of the water pump (7), and the overall enthalpy value of the water after mixing increases dramatically. The mass flow rate of condensate extracted into the low-temperature cold storage inlet bypass is matched with the mass flow rate of liquid water discharged from the high-temperature hot water tank (1) into the boiler feed water header.

9. The feedwater thermal storage peak-shaving method for rapid load response in coal-fired power units according to claim 8, characterized in that, The load increase frequency control operation also includes: after the feedwater enters the boiler (3) and mixes, it absorbs heat and is converted into steam and discharged, and the steam flow rate inside the main steam pipeline increases.

10. The feedwater thermal storage peak-shaving method for rapid load response in coal-fired power units according to claim 6, characterized in that, In the case of load reduction frequency regulation control: The water flowing out of the low-temperature cold water tank (2) is injected into the deaerator outlet header at the node between the fluid outlet of the deaerator (6) and the fluid inlet of the feed water pump (7); The temperature of the water flowing out of the low-temperature cold water tank (2) is lower than that of the deaerator (6) outlet, which is in a saturated state. The mixed fluid enters the feed water pump (7), and the overall temperature and specific enthalpy decrease. The mass flow rate of the feedwater entering the high-temperature thermal storage inlet bypass is matched with the mass flow rate of the condensate discharged from the low-temperature cold water tank (2) into the deaerator outlet header. The feedwater pump (7) pressurizes and delivers the mixed fluid to the high-pressure heater group (4). The feedwater flows through the high-pressure heater group (4) to reach the boiler (3), and the overall enthalpy value at the economizer inlet decreases.

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