A water working medium cascade energy storage system for wide-range peak regulation of a thermoelectric unit

Abstract

A kind of water working medium cascade energy storage system of thermal power unit wide width peak regulation, comprising, thermal power main engine system, machine furnace decoupling system, water working medium heat storage system;Thermal power main engine system includes main steam pipeline, steam turbine high pressure cylinder, steam turbine middle pressure cylinder, boiler reheater;High pressure bypass is connected in main steam pipeline, and part of high temperature and high pressure main steam of main steam pipeline is connected into water working medium heat storage system after high pressure bypass;Middle pressure cylinder admission pipe is connected with middle pressure bypass, and part of heat re-vapor is connected into water working medium heat storage system after middle pressure bypass;Machine furnace decoupling system includes steam ejector, electric steam boiler, with the function of providing large-capacity heating / steam supply while deep regulating unit, the high pressure bypass and middle pressure bypass generated by decoupling can also be connected with large-capacity energy storage system, to provide low investment, high efficiency, large-capacity two-way peak regulation means for thermal power plant, better meet the coordination demand between new energy development and power grid stability faced by power grid.

Description

Technical Field

[0001] This invention belongs to the field of flexible peak shaving in thermal power plants, and is particularly suitable for large-scale thermal power plants. It meets the grid's demand for large-scale, long-term peak shaving. The system can smoothly achieve ultra-large capacity thermal storage, uses water as the energy storage medium, is simple to operate and maintain, cost-effective, and widely adaptable. It aligns with the urgent needs of power generation carbon reduction, thermal power transformation, and new energy expansion. This invention relates to the field of peak shaving and energy storage technology for thermal power units, specifically to a multi-redundant, wide-range, bidirectional, and smoothly adjustable large-capacity energy storage system, aiming to improve the bidirectional peak shaving capability of thermal power units and meet the coordinated needs of grid stability and new energy development. Background Technology

[0002] Traditional thermal power generating units (especially combined heat and power units) exhibit significant thermoelectric coupling. With the rapid development of renewable energy (wind power, photovoltaic) and the continuous expansion of combined heat and power scale, the flexibility issue of heating units has become a major pain point in the industry.

[0003] For thermal power plants, in order to ensure heating supply during the heating season, the restrictions during deep regulation lead to huge "coal / electricity inversion losses"; the restrictions during peak hours reduce potential revenue; during the non-heating season, they must also passively generate electricity according to the minimum stable combustion load of the boiler during deep regulation periods, and also suffer considerable "coal / electricity inversion losses".

[0004] For new energy sources, the inherent thermoelectric coupling and minimum stable combustion load of thermal power units, as well as the huge number of units in operation and the large base of power generation, generate massive emissions during the peak period of new energy generation.

[0005] For the power grid, thermal power plants are the ballast stone for grid security, but the accompanying costs are too high. In particular, the significant reduction in flexibility during the heating season makes grid dispatching extremely difficult, forcing a substantial reduction in the scale of green electricity fed into the grid, seriously hindering the development of the new energy industry, affecting the process of reducing carbon emissions in the power sector, and even threatening the safe operation of the power grid.

[0006] To address the flexibility issue of thermal power, existing mainstream technologies include electrochemical energy storage, electrically heated molten salt energy storage, high-voltage steam molten salt energy storage, or high-voltage steam combined with electrically heated molten salt energy storage, but all of them have the following limitations.

[0007] Using electrochemical energy storage results in a very large base energy quantity when thermoelectrically coupled. Purely relying on the "storage" approach for deep regulation leads to excessively large investments. For example, with a 2*300MW cogeneration unit operating at its rated extraction steam volume during severe cold weather, deep regulation still results in over 60% power generation. Assuming a 6-hour duration for both units, this translates to a waste energy quantity of up to 2160 MWh. Therefore, cogeneration plants must first "decouple thermoelectricity" to reduce power generation and thus decrease the scale of energy storage.

[0008] The disadvantages of using electrically heated molten salt energy storage are: the molten salt module system is complex; the electric heating method results in significant cold-end losses during the off-season and / or during the heating season when the cylinder is not shut down, leading to low energy storage efficiency and reduced cost-effectiveness. It is suitable as a frequency regulation method, but not as a large-capacity peak-shaving method. Molten salt modules also face challenges such as molten salt corrosion, difficulty in salt removal during accidents, and a large workload for operation and maintenance.

[0009] Using high-pressure steam molten salt energy storage, the energy storage efficiency is higher than that of electric heating under non-cylinder-cutting conditions. However, the molten salt module also has the same shortcomings in the preceding process. At the same time, because steam energy storage has a larger thermal power, more molten salt is used, and the investment is higher than that of electric heating molten salt.

[0010] In summary, the advantage of molten salt modules lies in their low high-temperature saturation pressure, but their system complexity leads to a large workload for operation and maintenance. The thermal power industry is still looking for an energy storage system that is cost-effective, easy to operate and maintain, capable of wide-range bidirectional peak shaving, and has smooth operation. Summary of the Invention

[0011] To address the problems existing in the above-mentioned system, this invention proposes a new decoupling and energy storage solution. First, an electric steam boiler is introduced as one of the main decoupling methods, which can eliminate invalid grid-connected electricity and replace boiler startup, and the cold section steam flow regulation is smoother. At the same time, water is used as the energy storage medium, which is a single working medium, making operation and maintenance more convenient. In addition, high-pressure saturated water has a large heat storage capacity, low technical risk, good scalability of the heat storage module, and high cost performance.

[0012] A water-based cascade energy storage system for wide-range peak-shaving of thermal power units, comprising a thermal power unit system, a boiler-turbine decoupling system, and a water-based thermal storage system; characterized in that:

[0013] The main thermal power system includes the main steam pipeline, the high-pressure cylinder of the steam turbine, the intermediate-pressure cylinder of the steam turbine, and the boiler reheater;

[0014] A high-pressure bypass is connected to the main steam pipeline, and part of the high-temperature and high-pressure main steam from the main steam pipeline is connected to the water-based heat storage system after passing through the high-pressure bypass.

[0015] A medium-pressure bypass is connected to the steam inlet pipe of the medium-pressure cylinder, and part of the reheat steam is connected to the water-based thermal storage system after passing through the medium-pressure bypass.

[0016] The boiler-turbine decoupling system includes a steam ejector. A portion of high-temperature, high-pressure main steam is drawn from the main steam pipeline via a branch and connected to the high-pressure inlet of the steam ejector. A portion of hot reheat steam is drawn from the intermediate-pressure bypass via a branch and enters the low-pressure inlet of the steam ejector. The exhaust outlet of the steam ejector is connected to the cold section inlet of the reheater.

[0017] Furthermore, the water-based thermal energy storage system includes a high-pressure energy storage heater, a low-pressure energy storage heater, a high-pressure water storage tank, a low-pressure water storage tank, a pressureless water tank, a feedwater heat exchanger, a condensate heat exchanger, and a heating network water heat exchanger; these respectively constitute a heat absorption module, a heat storage module, and a heat release module. The water-based thermal energy storage system operates in two processes: heat storage and heat release. The heat storage process is implemented by the heat absorption module and the heat storage module, and the heat release process is implemented by the heat storage module and the heat release module.

[0018] Furthermore, the decoupling system also includes an electric steam boiler, which is connected to the plant's electrical system and uses electricity to produce steam during off-peak periods. The steam is then piped into the cold section of the unit's boiler.

[0019] Furthermore, the boiler-turbine decoupling system also has a one-to-one decoupling module, which sets up a decoupling connection pipe between the units to drive the synchronous decoupling of adjacent units. It is connected between the medium-pressure bypass of the active unit and the boiler cold section inlet of the passive unit.

[0020] Furthermore, the heat absorption module is configured with two media paths. One path involves drawing working fluid water from the unpressurized water tank and sequentially connecting it to the low-pressure and high-pressure energy storage heaters. After being heated, the water enters the high-pressure water storage tank. The other path involves drawing a portion of high-temperature feedwater from the main feedwater pipeline and connecting it to the high-pressure energy storage heater. After being heated, the water enters the high-pressure water storage tank. The steam side of the high-pressure energy storage heater is connected to the high-pressure bypass of the main unit system, and the steam side of the low-pressure energy storage heater is connected to the medium-pressure bypass of the main unit system.

[0021] Furthermore, the thermal storage module includes a high-pressure water storage tank and a low-pressure water storage tank; the high-pressure water storage tank is connected to the energy storage working fluid water heated by the energy storage high-pressure heater and the main feed water; the low-pressure water storage tank is connected to the energy storage working fluid water heated by the energy storage low-pressure heater and the condensate from the deaerator.

[0022] Furthermore, the heat release module includes a feedwater heat exchanger and a condensate heat exchanger; the feedwater heat exchanger and the condensate heat exchanger are sequentially connected between a high-pressure water storage tank and a non-pressurized water tank; a low-pressure water storage tank is connected in series on the pipeline between the feedwater heat exchanger and the condensate heat exchanger.

[0023] Furthermore, the heat release module further includes a heat network water heat exchanger; a high-pressure water storage tank and a low-pressure water storage tank are connected to the heat release side inlet of the heat network water heat exchanger through pipelines; the heat release side outlet of the heat network water heat exchanger is connected to the energy storage low-pressure heater, the unpressurized water tank and the condensate pipeline.

[0024] Furthermore, after being heated by the energy storage high-temperature heater, the high-temperature feedwater can be directly fed into the main feedwater pipeline of the boiler, increasing the feedwater temperature and raising the flue gas temperature at the tail end of the boiler when the turbine is under low load.

[0025] Furthermore, the high-pressure water storage tank is connected to the adjacent high-pressure heater via a high-pressure steam-side connecting pipe; the low-pressure water storage tank is connected to the adjacent low-pressure heater via a low-pressure steam-side connecting pipe; the steam in the connecting pipe is designed for bidirectional flow. During the heat storage stage, the steam in the tank is discharged to a suitable low-pressure point through the connecting pipe, ensuring that the tank does not exceed the pressure limit; during the heat release stage, the high-pressure heater steam side and the low-pressure heater steam side charge the storage tank through the connecting pipe, driving the working fluid water in the tank to flow.

[0026] Furthermore, condensate is drawn from the outlet of the condensate pump into the tube side of the condensate heat exchanger, heated, and then flows back to the main pipe; cold source water is drawn from the outlet of the feed water pump into the tube side of the feed water heat exchanger, heated, and then flows back to the main pipe. There are two connection points for returning to the main pipe. If the temperature is high enough, it enters the #1 high-pressure heater outlet; otherwise, it enters the #2 high-pressure heater outlet.

[0027] Furthermore, the design pressure of the high-pressure water storage tank is selected in the range of 3~10MPa.

[0028] Furthermore, a minimum flow valve is installed in parallel with the shut-off valve on the high-pressure bypass. During the period when the steam ejector of the decoupled boiler and turbine is shut off, the minimum flow valve keeps the high-pressure bypass in a hot state.

[0029] Furthermore, the condensate drain of the high-pressure heater is connected to the condensate drain side of the #1 high-pressure heater, and the condensate drain of the low-pressure heater is connected to the deaerator.

[0030] Furthermore, the high-pressure bypass can provide high-pressure steam to external users; the medium-pressure bypass can provide medium-pressure steam to external users or connect to the first station of the heating network.

[0031] Furthermore, the steam production of the electric steam boiler can be flexibly adjusted. When the ejector is not running, it can independently undertake the decoupling of the boiler and turbine. The steam is distributed and transported to the cold section of the reheater of multiple adjacent boilers, or it can be directly sent to the first station of the heating network, the low-pressure heater of the energy storage, or the high-pressure heaters at all levels.

[0032] The beneficial effects of this invention are:

[0033] The purpose of this invention is to provide a large-capacity energy storage system with multiple redundancies, wide-range, bidirectional, and smooth adjustment. By decoupling the boiler and turbine and storing energy in working fluid water, it can achieve wide-range peak shaving of thermal power units, improve the operational flexibility and economy of the units, and meet the grid's requirements for the absorption and stability of new energy sources.

[0034] By integrating the electric boiler into the boiler-machine decoupling module, the grid-connected power consumption can be reduced to zero, and the primary frequency regulation function is more prominent; this overcomes the shortcomings of simple injector decoupling and simple electric boiler decoupling.

[0035] The introduction of the electric boiler allows this unit to achieve zero-grid connection with adjacent units. Because the ejector is retained, the steam intake to the intermediate-pressure cylinder can be reduced under pure condensing conditions, thus minimizing cold-end losses during deep-heating periods.

[0036] Using water for energy storage instead of molten salt can achieve a larger capacity of thermal storage. At the same cost, the thermal storage capacity of water is more than twice that of molten salt, making it more cost-effective than molten salt. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the system connections.

[0038] In the diagram: Steam ejector (1), electric steam boiler (2), high-pressure heater (3), low-pressure heater (4), high-pressure water tank (5), feedwater heat exchanger (6), low-pressure water tank (7), condensate heat exchanger (8), unpressurized water tank (9), heating network water heat exchanger (10), booster pump (11), turbine high-pressure cylinder (HD), turbine intermediate-pressure cylinder (MD), high-pressure heater (#1GJ, #2GJ, #3GJ), low-pressure heater (#5DJ, #6DJ, #7DJ), deaerator (CY), valves (V0-V14, S0, S1, H1, H2, M1, M2). Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] The technical solution of the present invention is not limited by the capacity of power plant units.

[0041] The technical solution of the present invention is not limited to whether the power plant unit is newly built or already in operation.

[0042] The technical solution of the present invention is not limited by the number of power plant units participating in deep thermoelectric decoupling and the number of heating units, nor by the destination of steam at each level after decoupling, and can be flexibly adjusted.

[0043] The technical solution of the present invention is not limited by the steam parameters of power plant units.

[0044] The technical solution of the present invention is not limited by the combined heat and power or pure condensing operation of power plant units.

[0045] The technical solution of this invention is not limited by the energy storage medium (water or heat transfer oil), energy storage heater, water storage tank, or other heat exchanger types, locations, or ejector equipment (or steam compressors, electric steam boilers, or other equipment with equivalent functions). At the same time, the de-cooling and de-pressure device can also be other equipment, such as a small steam turbine for generating electricity with residual pressure (which can operate according to different working conditions, such as reducing plant power consumption or achieving peak power), or it can be an additional thermal energy storage device.

[0046] like Figure 1 As shown, no modifications are required to the boiler body and turbine body, all boiler auxiliary equipment does not need modification, and the tail flue does not require low-load modification. No modifications are needed to any rotating machinery on the turbine side. The regenerative system requires appropriate modifications to accommodate changes in feedwater volume. The turbine load rate can be set according to grid dispatch, and the boiler load can be determined based on the sum of electrical and thermal loads. During this process, the unit can smoothly transition from conventional extraction / condensing or heating mode to a completely decoupled boiler-turbine state.

[0047] Host system composition, such as Figure 1 As shown, the host system can be composed of multiple standalone systems.

[0048] Taking Unit #1 as an example, the single-unit system includes the main steam pipeline, the high-pressure cylinder (HD) of the turbine, and the boiler; the boiler contains a superheater and a reheater. The main steam pipeline of the power plant is connected to the high-pressure cylinder of the turbine. High-temperature and high-pressure main steam from the main steam pipeline enters the high-pressure cylinder of the turbine. The exhaust steam from the high-pressure cylinder enters the cold section inlet of the boiler reheater; the system also includes the intermediate-pressure cylinder (MD) of the turbine, the intermediate-pressure cylinder inlet steam pipeline, and hot reheat steam introduced through the intermediate-pressure cylinder inlet steam pipeline. The hot section outlet of the boiler reheater is connected to the intermediate-pressure cylinder inlet steam pipeline. The hot reheat steam from the hot section outlet enters the intermediate-pressure cylinder of the turbine to perform work.

[0049] A high-pressure bypass is connected to the main steam pipeline. Valves and desuperheating and pressure reducing devices are installed on the high-pressure bypass. Part of the high-temperature and high-pressure main steam from the main steam pipeline is connected to the high-pressure heater (3) in the energy storage system after passing through the high-pressure bypass. It can also provide high-pressure steam to the outside. The high-pressure bypass is further connected to the cold section inlet pipeline of the boiler reheater through a branch. Steam enters the cold section inlet of the boiler reheater after passing through valve V14 and desuperheating and pressure reducing devices. A medium-pressure bypass is connected to the steam inlet pipeline of the medium-pressure cylinder. Valves and desuperheating and pressure reducing devices are installed on the medium-pressure bypass. Part of the hot reheat steam is connected to the low-pressure heater (4) in the energy storage system after passing through the medium-pressure bypass. It can also provide medium-pressure steam to the outside or connect to the first station of the heating network.

[0050] like Figure 1 As shown, the same system configuration can be used for other single-unit systems, namely, setting up high-pressure bypass and medium-pressure bypass for connecting to the energy storage system or for external steam supply. The high-pressure bypass and medium-pressure bypass of each single-unit system can be uniformly connected to the main pipeline system for unified output, or they can be output separately using independent pipelines.

[0051] Furthermore, by setting up a boiler-turbine decoupling system in the unit, peak shaving of the thermal power unit was achieved.

[0052] The boiler-machine decoupling system is built based on a steam ejector (1) as the core equipment. The ejector is connected to three steam lines: power steam, ejector steam, and exhaust steam. The power steam is the main steam generated by the boiler superheater. Part of it enters the high-pressure cylinder, and the other branch of the main steam serves as the power steam for the ejector. The ejector steam is the hot reheat steam generated by the boiler reheater. Part of the hot reheat steam enters the medium-pressure cylinder, and the split part of the hot reheat steam enters the ejector through hot reheat recirculation and is pressurized. After being pressurized by the ejector, the steam is discharged to the cold section of the boiler reheater and merges with the exhaust steam from the original high-pressure cylinder into the boiler. Each pipeline can be equipped with a matching de-heating and de-pressure device according to actual needs.

[0053] Taking Unit #1 as an example, a steam ejector (1) is added to Unit #1. A steam ejector (1) is connected between the cold section inlet and the hot section outlet of the boiler reheater. The steam ejector has a power steam inlet, an ejector steam inlet, and an exhaust outlet. A portion of high-temperature and high-pressure main steam is drawn from the main steam pipeline through a branch and connected to the power steam inlet of the steam ejector. A portion of reheat steam is drawn from the medium-pressure bypass through a branch and, after being desuperheated and depressurized, enters the ejector steam inlet of the steam ejector. The exhaust outlet of the steam ejector is connected to the cold section inlet of the reheater. A portion of the main steam, after being desuperheated and depressurized, enters the steam ejector as power steam, which is used to draw in a portion of the reheat steam introduced by the ejector inlet of the steam ejector. After the power steam and the portion of reheat steam are mixed, they re-enter the cold section inlet of the reheater.

[0054] The steam ejector system can use a single or multiple steam ejectors. Multiple steam ejectors can be combined in series, parallel or series-parallel to form a steam ejector group, so as to adjust and optimize parameters such as the injection ratio and complete the variable operating conditions. The nozzles of the steam ejectors can be fixed nozzles or adjustable nozzles.

[0055] Because the boiler-machine decoupling system ensures a safe flow rate for the boiler reheater, it can extract a large amount of main steam and hot reheat steam. In this system, the main steam goes to the high-pressure storage heater via a high-pressure bypass, and the hot reheat steam goes to the low-pressure storage heater via a medium-pressure bypass or to the heating network heater after desuperheating and pressure reduction. The steam branching off the high-pressure bypass can also enter the cold section of the boiler reheater via valve V14, the desuperheating and pressure reduction device and the pipeline.

[0056] The shut-off valves on the high-pressure bypass are equipped with a minimum flow valve V0 in parallel. During the decoupling of the steam ejector from the boiler and turbine, the flow through the minimum flow valve V0 maintains the high-pressure bypass in a hot state. The extracted main steam and reheat steam can also be used for external steam supply, heating, or other forms of thermal storage during the off-peak season.

[0057] To facilitate coordination among multiple units, a decoupling auxiliary module is also included in the boiler-turbine decoupling system. For example... Figure 1As shown, the decoupling auxiliary module is used to drive the synchronous decoupling of adjacent units (i.e., a one-to-one decoupling module). It includes a decoupling connecting pipe, which connects the medium-pressure bypass of Unit #1 (the active unit) and the boiler cold section inlet of the adjacent Unit #2 (the passive unit). After Unit #1 sets up a boiler-machine decoupling system to achieve boiler-machine decoupling, it can extract a large amount of hot resteam, which can be sent to the boiler cold section of Unit #2 through the pipeline where valve V1 is located (the decoupling connecting pipe). The safe flow rate of the boiler reheater of Unit #2 can also be guaranteed by using the hot resteam transported by the decoupling connecting pipe, and peak shaving can be achieved synchronously through decoupling. In addition, Unit #2 can also extract a large amount of main steam and hot resteam to the high-pressure and low-pressure heaters of the energy storage unit or the heaters of the heating network.

[0058] Furthermore, the decoupling auxiliary module can also be achieved by setting up an electric steam boiler (2). The electric steam boiler is connected to the plant electrical system and consumes the generated electrical energy during the off-peak period. The electrical energy is used to produce suitable steam, which can be input into the cold section of the unit boiler through pipelines.

[0059] like Figure 1 As shown, the electric steam boiler (2) is connected to the cold sections of the boilers of Unit #1 and Unit #2 through pipelines. It can go to the cold section of the boiler of Unit #1 through the pipeline where valve V2 is located, and to the cold section of the boiler of Unit #2 through the pipeline where valve V3 is located. The supplementary steam from the electric steam boiler can also achieve the purpose of ensuring the safe flow of the reheaters of each unit. The steam production of the electric steam boiler can be flexibly adjusted and can completely or partially replace the boiler-machine decoupling system. When the ejector is not running, it can independently undertake the boiler-machine decoupling. The steam distribution to a single unit or two units can also be flexibly adjusted according to the needs. The steam is distributed and transported to the cold sections of the reheaters of multiple adjacent boilers, or directly to the first station of the heating network, the low-level heating of the energy storage, or the high-level heating of each level.

[0060] Both the steam ejector and the electric steam boiler jointly input steam into the cold section of the reheater, displacing the high-pressure bypass and achieving decoupling of the boiler and turbine. Simultaneously, to achieve decoupling of multiple units throughout the plant, a decoupling interconnection pipe is configured, designating Unit #1 as the active unit. Its hot section steam, after being de-cooled, enters the cold section of the adjacent unit, achieving decoupling of the adjacent unit. This one-to-one decoupling method can be repeatedly extended to subsequent units; for example, the hot section steam of Unit #2 can continue to be supplied to the cold section of the reheater of Unit #3.

[0061] The water-based thermal energy storage system achieves decoupled heat storage and release. It is built upon the boiler feedwater system, which includes a condenser, condensate pump, low-pressure heaters at various stages, a deaerator, feedwater pumps, and high-pressure heaters at various stages. Condensate from the condenser flows through the condensate pump, low-pressure heater, deaerator, feedwater pump, and high-pressure heater before entering the main boiler feedwater pipeline.

[0062] The water-based heat storage system includes a high-pressure heat exchanger (3), a low-pressure heat exchanger (4), a high-pressure water tank (5), a feedwater heat exchanger (6), a low-pressure water tank (7), a condensate heat exchanger (8), an unpressurized water tank (9), and a heating network water heat exchanger (10). These components respectively constitute heat absorption modules, heat storage modules, and heat release modules. The water-based heat storage system operates in two processes: heat storage and heat release. The heat storage process is implemented by the heat absorption module and the heat storage module, while the heat release process is implemented by the heat storage module and the heat release module.

[0063] The heat absorption module includes a high-energy storage heater (3) and a low-energy storage heater (4). Pipelines are drawn from the unpressurized water tank and sequentially connected to the water side of the low-energy storage heater and the high-energy storage heater. After passing through the working fluid energy storage valve H1, the water enters the high-pressure water storage tank.

[0064] The steam side of the high-pressure energy storage heater is connected to the high-pressure bypass of the main unit system, and the steam side of the low-pressure energy storage heater is connected to the medium-pressure bypass of the main unit system. The working fluid water in the unpressurized water tank passes through the low-pressure energy storage heater and the high-pressure energy storage heater, and exchanges heat with the reheat steam of the medium-pressure bypass and the main steam of the high-pressure bypass in the low-pressure energy storage heater and the high-pressure energy storage heater. The working fluid water that has absorbed heat and increased in temperature flows into the high-pressure water storage tank for storage.

[0065] In addition, when a low-pressure water storage tank is selected, a branch can be connected to the low-pressure water storage tank on the downstream side of the energy storage low-pressure heater (4), and a portion of the working fluid water can be stored in the low-pressure water storage tank (7) through the energy storage valve M1, the pressure reducing valve and the pipeline.

[0066] The high-temperature feedwater in the energy storage heater (3) can also be connected to the main feedwater. A branch is drawn from the main feedwater pipeline to connect some high-temperature feedwater to the energy storage heater (3). After being heated, it flows through the feedwater storage valve H2 into the high-pressure water storage tank (5) for storage. After being heated, the high-temperature feedwater can also be directly fed into the boiler main feedwater pipeline. When the turbine is under low load, the feedwater temperature can be increased, thereby increasing the flue gas temperature at the tail of the boiler.

[0067] The heat absorption module is configured with two media paths: one is a dedicated energy storage path, which flows from the unpressurized water tank (9) through the booster pump (11) into the low-pressure energy storage heater (4) and the high-pressure energy storage heater (3), and then through the working fluid energy storage valve H1 into the high-pressure water storage tank (5). The other path draws high-temperature feedwater from the main water supply pipeline, which flows through the high-pressure energy storage heater (3) and the feedwater energy storage valve H2 into the high-pressure water storage tank (5).

[0068] The high-pressure heater (3) for energy storage has two independent water-side channels, one for the energy storage working fluid and the other for the main feedwater. The high-pressure heater for energy storage can also be set up as two separate heaters, namely, a high-pressure heater for energy storage and a high-pressure heater for feedwater heating, which are connected to the energy storage working fluid and the main feedwater respectively. The drain of the high-pressure heater (3) for energy storage is connected to the drain side of the #1 high-pressure heater, and the drain of the low-pressure heater (4) for energy storage is connected to the deaerator (CY).

[0069] The thermal energy storage module includes a high-pressure water storage tank (5) and a low-pressure water storage tank (7). As described above, the high-pressure water storage tank (5) is connected to the energy storage working fluid water heated by the energy storage high-pressure heater (3) and the main feedwater. The high-pressure water storage tank is connected to the energy storage high-pressure heater (3) and the #1 high-pressure heater via a high-pressure steam-side connecting pipe. The low-pressure water storage tank (7) is connected to the energy storage working fluid water heated by the energy storage low-pressure heater (4) and the condensate from the deaerator. The low-pressure water storage tank is connected to the #5 low-pressure heater and the #6 low-pressure heater via a low-pressure steam-side connecting pipe.

[0070] The thermal storage process operates during peak shaving under decoupling of the boiler and turbine or during periods of low spot electricity prices. The two high-quality steam generated after the decoupling of the boiler and turbine of Unit #1, the main steam of the high-pressure bypass and the hot reheat steam of the medium-pressure bypass, enter the set high-pressure heater (3) and low-pressure heater (4) of the energy storage system respectively to heat the working fluid water.

[0071] The working fluid water first enters the energy storage low heater (4) and is heated by the reheat steam. After being heated, part of the working fluid water enters the low pressure water tank (7) through the energy storage valve M1, the pressure reducing valve and the pipeline. At this time, condensate from the deaerator (i.e., through the pipeline where the condensate energy storage valve M2 is located) can also be stored according to the working conditions. After the reheat steam is heated in the energy storage low heater, it becomes condensate and returns to the deaerator.

[0072] In addition, some of the working water heated by the low-pressure heater (4) continues to enter the high-pressure heater (3) for further heating. The heating steam of the high-pressure heater is steam from the high-pressure bypass. After being heated, this part of the working water enters the high-pressure water tank (5) through the pipeline where the energy storage valve H1 is located. The high-pressure water tank can also accept feedwater heated by the high-pressure heater (this part of the feedwater is the feedwater diverted after the #1 high-pressure heater, which enters the high-pressure water tank through the pipeline where the feedwater energy storage valve H2 is located. This part of the feedwater can also be diverted and directly fed to the boiler main feedwater according to the working conditions). The high-pressure bypass steam that has been heated in the high-pressure heater becomes the condensate return to the condensate side of the #1 high-pressure heater.

[0073] When the heated working fluid water enters the high-pressure water tank and the low-pressure water tank, the remaining steam in the high-pressure water tank and the low-pressure water tank needs to enter the nearest high-pressure steam side, low-pressure steam side or deaerator through the steam side connecting pipe.

[0074] The high-pressure water storage tank is connected to the high-pressure heater (3) and the #1 high-pressure heater via a high-pressure steam-side connecting pipe. The low-pressure water storage tank is connected to the #5 and #6 low-pressure heaters via a low-pressure steam-side connecting pipe. The steam in the connecting pipe is designed for bidirectional flow. During the heat storage stage, as high-temperature saturated water enters the tank, the steam in the tank is discharged to a suitable low-pressure point, such as the high-pressure heater steam side or the low-pressure heater steam side, through the connecting pipe, ensuring that the tank does not exceed the pressure limit. During the heat release stage, pressurized steam is introduced into the storage tank from the high-pressure heater steam side and the low-pressure heater steam side through the connecting pipe, driving the working fluid water in the tank to flow out (the pressurized water storage tank is not equipped with a water pump). A pressure regulating valve is installed on the connecting pipe to make the pressure of the tank and each extraction steam side compatible. The heat storage working fluid water can be injected in advance into the unpressurized water tank (9) or the low-pressure water storage tank (7).

[0075] There are two pathways in the working fluid water energy storage process:

[0076] Thermal storage path one: The two steam streams generated after decoupling the boiler and turbine can be used in the thermal storage process. The high-pressure bypass steam enters the high-pressure heater (3) and the hot section steam enters the low-pressure heater (4) to heat the working fluid water. The working fluid water comes from the unpressurized water tank or from the part of the system condensate flow (the working fluid bypass via valve V8), and enters the low-pressure heater (4) via the booster pump (11) and valve V9. After passing through the low-pressure heater, it can be divided into two streams. One stream enters the low-pressure water tank (7) via valve M1, and the other stream flows through the high-pressure heater (3) and then through valve H1 into the high-pressure water tank (5). The condensate from the two streams of steam enters the condensate side of the #1 high-pressure heater and the deaerator, respectively.

[0077] Heat storage path 2: High-temperature water comes from the regeneration system. When the boiler is at a medium or low load rate, the feedwater is increased and the excess feedwater is heated by the energy storage high heater (3) and then flows through valve H2 into the high-pressure water storage tank (5); the saturated water in the deaerator is fed into the low-pressure water storage tank (7) through valve M2.

[0078] The heat release module includes a feedwater heat exchanger (6) and a condensate heat exchanger (8), both of which are water-to-water heat exchangers. The shell side is the heat release side, and the tube side is the heat absorption side. The feedwater heat exchanger (6) and the condensate heat exchanger (8) are connected sequentially between the high-pressure water storage tank and the unpressurized water tank.

[0079] On the heat release side, the high-pressure water storage tank is connected to the heat release side inlet of the feedwater heat exchanger through the branch pipe where valve V11 is located; the heat release side outlet of the feedwater heat exchanger is connected to the heat release side inlet of the condensate heat exchanger through the branch pipe where valve V13 is located; and the heat release side outlet of the condensate heat exchanger is connected to the unpressurized water tank through a branch pipe.

[0080] When a low-pressure water storage tank is selected, it is connected in series on the heat dissipation side pipeline between the feedwater heat exchanger and the condensate heat exchanger. After flowing out of the feedwater heat exchanger, the water first enters the low-pressure water storage tank and then flows out to the condensate heat exchanger for a second heat exchange. The shell-side pressure of the condensate heat exchanger downstream of the low-pressure water storage tank is reduced, which can lower the cost of the condensate heat exchanger and the shell-side operating pressure.

[0081] On the heat absorption side, the outlet branch of the condensate pump is connected to the heat absorption inlet of the condensate heat exchanger via the branch containing valve V7, and the heat absorption outlet of the condensate heat exchanger is connected to the deaerator via the branch containing valve V6; the outlet branch of the feedwater pump is connected to the heat absorption inlet of the feedwater heat exchanger via the branch containing valve V5, and the heat absorption outlet of the feedwater heat exchanger is connected to the boiler main feedwater pipeline via a pipeline; there are two connection points to the boiler main feedwater pipeline. If the temperature is high enough, it enters the outlet of the #1 high-pressure heater via valve V4; otherwise, if the temperature is low, it enters the outlet of the #2 high-pressure heater via valve V4'.

[0082] The heat release module may further include a heat network water heat exchanger (10), which is a water-to-water heat exchanger, with its shell side serving as the heat release side and its tube side serving as the heat absorption side.

[0083] On the heat release side, the high-pressure water storage tank is connected to the heat release side inlet of the heating network water heat exchanger through the branch pipe where valve V10 is located; when a low-pressure water storage tank is selected, the low-pressure water storage tank is also connected to the heat release side inlet of the heating network water heat exchanger through the branch pipe where valve V12 is located.

[0084] The heat release side outlet of the heat exchanger is connected to the energy storage low-pressure heater, the unpressurized water tank, and the condensate pipeline via a branch pipe. The cooled working water can enter the energy storage low-pressure heater for the next heat storage cycle stage, or it can go to the unpressurized water tank or enter the condensate pipeline via the working water bypass (valve V8) according to the operating conditions.

[0085] On the heat absorption side, the water from the heating network enters the heat absorption side, absorbs heat to increase its temperature, and is then returned to the heating network as water for supply.

[0086] The heat release process operates during peak shaving or periods of high spot electricity prices. Open the steam-side connecting pipe connected to the low-pressure water tank (7), and the low-pressure heater steam side charges the low-pressure water tank (7) with steam through the connecting pipe, so that it drives the working water in the low-pressure water tank, and goes to the heat network water heat exchanger (10) through valve V12 and the pipeline thereon to heat the heat network water. The cooled working water can enter the next heat storage cycle stage (to the energy storage low heater), or it can go to the unpressurized water tank or enter the condensate pipeline through the working water bypass according to the operating conditions.

[0087] The heat storage working fluid in the low-pressure water storage tank (7) can also enter the condensate heat exchanger (8) through valve V13 and the pipeline thereon to heat the condensate. The condensate comes from the condensate diversion of the main system. It enters the condensate heat exchanger through valve V7 before the #7 low inlet and is heated. Then it is merged into the #5 low outlet through valve V6. The working fluid in the condensate heat exchanger enters the pressureless water tank after passing through the pressure reducing valve.

[0088] Open the steam-side connecting pipe connected to the high-pressure water tank. Steam is charged into the high-pressure water tank (5) through the connecting pipe, which drives the working water in the high-pressure water tank. The working water is then sent to the feedwater heater (6) through valve V11 and the corresponding pipeline to heat the feedwater. The feedwater diverted from the feedwater pump outlet enters the feedwater heat exchanger through valve V5 and is heated. After being heated, it flows into the main feedwater pipeline #1 high-pressure heater outlet through valve V4. The working water flowing out of the feedwater heat exchanger then flows through valve V13, and is then depressurized to enter the condensate heat exchanger (8). Finally, it returns to the unpressurized water tank (9). When releasing heat, the water can also enter the heating network water heat exchanger (10) downstream of the feedwater heat exchanger (6) through valve V12.

[0089] The design pressure of the high-pressure water storage tank can be selected in the range of 3~10MPa. To reduce the cost of the pressure vessel, a lower pressure can be selected, but the energy storage efficiency will also decrease accordingly. If the energy storage efficiency is to be improved, the high-pressure water storage tank should be selected according to the higher pressure value. In order to reduce the cost of the high-pressure water storage tank, the operating pressure of the high-pressure water storage tank can be set according to different needs. For example, when designed at 4.5MPa, the heating temperature of the feedwater heat exchanger will be insufficient, and the heated feedwater will return to the main feedwater pipeline through valve V4' and after the #2 high-pressure heater.

[0090] The working fluid water in the high-pressure water storage tank can also enter the heat network water heat exchanger (10) through valve V10, pressure reducing valve and the high-pressure working fluid water bypass, and after cooling, the pressure is reduced and it enters the unpressurized water tank (9).

[0091] During energy storage and heat release, the condensate, feedwater, and heating network water can be heated by the energy storage medium, thus reducing the corresponding steam extraction and increasing the unit's power generation capacity. Together, these factors allow the system to return to full power generation. Furthermore, the power generation capacity of the main unit (multiple units) and adjacent units in the main system can also be increased, restoring full power generation.

[0092] There are three pathways for the heat release of the working fluid, water:

[0093] Instead of the regenerative system, the first heat release path is as follows: the steam-side connecting pipe connected to the high-pressure water storage tank is opened, and the saturated water in the high-pressure water storage tank is driven by high-pressure steam to the feedwater heater (6). After the feedwater is heated, it is connected to the feedwater header at a suitable location. The working fluid is depressurized and enters the low-pressure water storage tank (7), and then enters the condensate heat exchanger (8) to heat the condensate, and finally returns to the unpressurized water tank. It can also release heat to the heating network. The second heat release path is that the high-pressure water heats the heating network water, which can enter the heating network water heat exchanger (10) through valve V10, and after cooling, it is depressurized and enters the unpressurized water tank (9). The third path is that the low-pressure water storage tank (7) enters the heating network water heat exchanger (10) through valve V12 to heat the heating network water. When the system is releasing heat, the above three paths can operate simultaneously. The energy storage working fluid releases heat to the feedwater and heating network water at maximum power, reducing the amount of regenerative steam extraction and heating steam extraction, so that the entire plant unit can obtain the maximum peak capacity.

[0094] The typical working process of the system is illustrated by an example of a 300MW unit.

[0095] In winter operation mode,

[0096] Heating season: Select the corresponding operating conditions according to the three levels of electricity price: high, medium, and low.

[0097] Operating Condition 1, Winter Peak: High Electricity Price / Peak Operating Condition: During this period, the high-pressure water storage tank releases heat to the feedwater, replacing 70% of the regenerative steam extraction, thus increasing the unit's power generation capacity. Simultaneously, the low-pressure water tank releases heat to the heating network at a power output of 225MW, reducing the unit's steam extraction. Together, these two processes enable the 2*300MW units to provide 15 million cubic meters of heating during severe cold periods. 2 At that time, the system resumes full-power power generation. The system only releases heat.

[0098] Operating Condition 2, Winter Off-Peak: Electricity price near the break-even point / efficient heating or energy storage, extended dual-unit shut-off time. In this condition, efficient heating can reduce power generation costs, specifically by maintaining dual-unit shut-off, thus lowering power generation costs and improving grid competitiveness. However, during the early to late cold season, when heating supply is low, dual-unit shut-off is not possible. This system can increase the feedwater volume to extend the "dual-unit shut-off" operating condition. Excess feedwater has two destinations: direct external heating (i.e., immediate storage and release), in which case the boiler load rate can be reduced; or storage in a high-pressure tank, achieving efficient thermal storage; the system can both store and release feedwater.

[0099] Operating Condition 3A, Deep Winter Adjustment: Low or zero electricity price / boiler decoupling, high-voltage bypass heating + electric steam boiler heating, high-capacity energy storage. In this condition, the boiler and turbine are decoupled and put into operation. The decoupled steam is split in two: most of it is extracted from the hot section via the high-voltage bypass for heating; a small portion is stored in the energy storage system at a high / low price. Simultaneously, to reduce losses from the "coal-electricity price inversion," the electric steam boiler operates at maximum power. The system only stores energy.

[0100] Operating Condition 3B, Winter Deep Adjustment: When the decoupling limit is reached in Operating Condition 3A, the energy storage system releases heat to the heating network. Since there is no external reheater, there is an upper limit to the decoupling range (high-speed bypass flow Mby / boiler main steam flow Gb). When this limit is reached, the high-speed bypass flow Mby must be reduced or the boiler main steam flow Gb must be increased. However, reducing the high-speed bypass flow will lead to a decrease in heating capacity, while increasing Gb while keeping the high-speed bypass flow unchanged will lead to an increase in turbine power generation. In this case, the energy storage module can release heat to the heating network to share 225MW of heating capacity. The system only releases heat.

[0101] During summer operation mode,

[0102] There is no peak issue in summer. This system mainly operates in two modes: deep regulation and heat storage, and heat release during other periods.

[0103] Operating Condition 5, Summer Peak Condition: In summer, the unit operates under pure condensing conditions, eliminating peak capacity issues. However, some power plants use poor-quality coal, resulting in insufficient peak capacity. In this case, the high-pressure storage tank can release heat to the feedwater, eliminating the need for special modifications during peak periods (such as blending with high-quality coal). The system only releases heat.

[0104] Operating Condition 6, Summer Deep Adjustment Condition: The boiler operates at 30-35% of its minimum stable combustion load, assuming a load of 300 tons; the turbine operates at its minimum safe steam inlet (assuming 190 tons), with 110 tons bypassed (flow velocity exceeding limits is controllable). A small amount of feedwater is heated to 245-250℃; hot section extraction steam reaches approximately 105 tons; a single unit can heat 500 tons of working fluid water for energy storage; the system only stores heat; the high-pressure water tank is 6000 m³. 3 The setting allows for the storage of deep-water volume for 6 hours between two units.

[0105] Operating Condition 7, Heat Release During Off-Peak Summer Periods: When the boiler load rate is within the safe zone, the boiler load rate can be set slightly lower than the required turbine load rate. The difference is compensated by heat release from the energy storage system, and the energy storage tank should be emptied promptly. The system only releases heat.

[0106] In summary, the present invention has the following advantages:

[0107] Wide-range peak-shaving capability: Through water-based thermal storage, combined with the decoupling of the boiler and turbine modules and the coordinated operation of different operating modules, multiple units can flexibly shave peaks within a wide range, which can better adapt to changes in grid load and meet the grid stability requirements after the integration of new energy sources.

[0108] Two-way flexible operation: After the modules are stacked, they have the function of two-way flexible operation for peak shaving. When the grid load is high, the stored heat can be released to increase power generation; when the grid load is low, energy storage can be carried out to improve the flexibility and adaptability of the unit operation.

[0109] Improved economic efficiency: It combines the unique large-capacity heating / steam supply function of decoupling boiler and turbine, and makes full use of the unit's energy through different operating conditions during the heating season and non-heating season, so as to maximize the revenue of thermal power plants at both ends of the peak and valley, regulate peak and frequency, reduce the losses caused by low electricity prices due to coal-fired power inversion, increase capacity price subsidies, reduce operating costs, and improve the economic efficiency of thermal power plants.

[0110] Large-capacity energy storage: Transforms thermal power plants into low-investment, high-efficiency, and large-capacity rapid peak-shaving centers, effectively alleviating the contradiction between the development of new energy sources and grid stability, and promoting the consumption of new energy sources and the sustainable development of the grid.

[0111] The above demonstrates the system's advantages in terms of structure, function, and operation. The application of the above-mentioned case system in this application can be replicated in other thermal power plants, and its operation is flexible. For example, after deep coupling adjustment, the turbine steam inlet method can be flexibly adjusted, and the steam inlet volume can also be varied under different operating conditions to meet various grid dispatching needs.

[0112] Finally, it should be noted that the above description is merely an explanation of the present invention and is not intended to limit the invention. Although the present invention has been described in detail, those skilled in the art can still modify the technical solutions described above or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A water-based cascade energy storage system for wide-range peak shaving of a thermal power unit, comprising a thermal power unit system, a boiler-turbine decoupling system, and a water-based thermal storage system; characterized in that: The main thermal power system includes the main steam pipeline, the high-pressure cylinder of the steam turbine, the intermediate-pressure cylinder of the steam turbine, and the boiler reheater; A high-pressure bypass is connected to the main steam pipeline, and part of the high-temperature and high-pressure main steam from the main steam pipeline is connected to the water-based heat storage system after passing through the high-pressure bypass. A medium-pressure bypass is connected to the steam inlet pipe of the medium-pressure cylinder, and part of the reheat steam is connected to the water-based thermal storage system after passing through the medium-pressure bypass. The boiler-turbine decoupling system includes a steam ejector. A portion of high-temperature and high-pressure main steam is drawn from the main steam pipeline through a branch and connected to the high-pressure inlet of the steam ejector. A portion of hot reheat steam is drawn from the intermediate-pressure bypass through a branch and enters the low-pressure inlet of the steam ejector. The exhaust outlet of the steam ejector is connected to the cold section inlet of the reheater. The water-based thermal energy storage system includes a high-pressure heat exchanger, a low-pressure heat exchanger, a high-pressure water tank, a low-pressure water tank, an unpressurized water tank, a feedwater heat exchanger, a condensate heat exchanger, and a heating network water heat exchanger; these respectively constitute heat absorption modules, heat storage modules, and heat release modules. The water-based thermal energy storage system operates in two processes: heat storage and heat release. The heat storage process is carried out by the heat absorption module and the heat storage module, and the heat release process is carried out by the heat storage module and the heat release module. The thermal energy storage module includes a high-pressure water storage tank and a low-pressure water storage tank. The high-pressure water storage tank is connected to the energy storage working fluid water that has been heated by the high-pressure energy storage heater and the main feed water. The low-pressure water storage tank is connected to the energy storage working fluid water that has been heated by the low-pressure energy storage heater and the condensate from the deaerator. The heat release module includes a feedwater heat exchanger and a condensate heat exchanger; the feedwater heat exchanger and the condensate heat exchanger are sequentially connected between a high-pressure water storage tank and a non-pressurized water tank; a low-pressure water storage tank is connected in series on the pipeline between the feedwater heat exchanger and the condensate heat exchanger; the heat absorption side of the condensate heat exchanger is connected to the parallel loop of the low-pressure heater in the boiler feedwater system, and the heat absorption side of the feedwater heat exchanger is connected to the parallel loop of the high-pressure heater in the boiler feedwater system.

2. The water-based cascade energy storage system for wide-range peak regulation of thermal power units according to claim 1, characterized in that, The decoupling system of the generator and boiler also includes an electric steam boiler, which is connected to the plant's electrical system. During the off-peak period, it uses electricity to produce steam, which is then fed into the cold section of the unit's boiler through pipelines.

3. The water-based cascade energy storage system for wide-range peak regulation of thermal power units according to claim 1, characterized in that, The boiler-turbine decoupling system also has a one-to-one decoupling module, which sets up a decoupling connection pipe between the units to drive the synchronous decoupling of adjacent units. It is connected between the medium-pressure bypass of the active unit and the boiler cold section inlet of the passive unit.

4. The water-based cascade energy storage system for wide-range peak regulation of thermal power units according to claim 1, characterized in that, The heat absorption module is configured with two media paths. One path draws working fluid water from the unpressurized water tank and sequentially connects it to the low-pressure and high-pressure energy storage heaters. After being heated, the water enters the high-pressure water storage tank. The other path draws a portion of high-temperature feedwater from the main feedwater pipeline and connects it to the high-pressure energy storage heater. After being heated, the water enters the high-pressure water storage tank. The steam side of the high-pressure energy storage heater is connected to the high-pressure bypass of the main unit system, and the steam side of the low-pressure energy storage heater is connected to the medium-pressure bypass of the main unit system.

5. The water-based cascade energy storage system for wide-range peak regulation of thermal power units according to claim 1, characterized in that, The heat release module further includes a heat exchanger for a heating network water; a high-pressure water storage tank and a low-pressure water storage tank are connected to the heat release side inlet of the heat exchanger for a heating network water through pipelines; and the heat release side outlet of the heat exchanger for a heating network water is connected to the energy storage low-pressure heater, the unpressurized water tank, and the condensate pipeline.

6. The water-based cascade energy storage system for wide-range peak regulation of thermal power units according to claim 4, characterized in that, After being heated by the energy storage high-temperature heater, the high-temperature feedwater can be directly fed into the main feedwater pipeline of the boiler, increasing the feedwater temperature and raising the flue gas temperature at the tail end of the boiler when the steam turbine is under low load.

7. The water-based cascade energy storage system for wide-range peak regulation of thermal power units according to claim 1, characterized in that, The high-pressure water storage tank is connected to the adjacent high-pressure heater via a high-pressure steam-side connecting pipe; the low-pressure water storage tank is connected to the adjacent low-pressure heater via a low-pressure steam-side connecting pipe; the steam in the connecting pipe is designed for bidirectional flow. During the heat storage stage, the steam in the tank is discharged to a suitable low-pressure point through the connecting pipe, ensuring that the tank does not exceed the pressure limit; during the heat release stage, the high-pressure heater steam side and the low-pressure heater steam side charge the storage tank through the connecting pipe, driving the working fluid water in the tank to flow.

8. The water-based cascade energy storage system for wide-range peak regulation of thermal power units according to claim 1, characterized in that, Condensate is drawn from the outlet of the condensate pump into the tube side of the condensate heat exchanger, and after being heated, it flows back to the main pipe. Cold source water is drawn from the outlet of the feed water pump into the tube side of the feed water heat exchanger, and after being heated, it returns to the main pipe. There are two connection points to the main pipe. If the temperature is high enough, it enters the #1 high-pressure heater outlet; otherwise, it enters the #2 high-pressure heater outlet.

9. The water-based cascade energy storage system for wide-range peak regulation of thermal power units according to claim 1, characterized in that, The design pressure of the high-pressure water storage tank is selected in the range of 3~10MPa.

10. The water-based cascade energy storage system for wide-range peak regulation of thermal power units according to claim 1, characterized in that, The shut-off valves on the high-pressure bypass are equipped with minimum flow valves in parallel. During the period when the steam ejector of the decoupled boiler and turbine is shut off, the minimum flow valves keep the high-pressure bypass in a hot state.

11. The water-based cascade energy storage system for wide-range peak regulation of thermal power units according to claim 4, characterized in that, The condensate drain of the high-pressure heater for energy storage is connected to the condensate drain side of the #1 high-pressure heater, and the condensate drain of the low-pressure heater for energy storage is connected to the deaerator.

12. The water-based cascade energy storage system for wide-range peak regulation of thermal power units according to claim 1, characterized in that, The high-pressure bypass can provide high-pressure steam to external users; the medium-pressure bypass can provide medium-pressure steam to external users or connect to the first station of the heating network.

13. The water-based cascade energy storage system for wide-range peak regulation of thermal power units according to claim 2, characterized in that, The steam production of the electric steam boiler can be flexibly adjusted. When the ejector is not running, it can independently undertake the decoupling of the boiler and turbine. The steam is distributed and delivered to the cold section of the reheater of multiple adjacent boilers.

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