Water working medium cascade energy storage system for wide peak regulation of thermoelectric unit

Abstract

A water working medium cascade energy storage system for wide peak regulation of a thermoelectric unit comprises a thermoelectric main machine system, a machine-furnace decoupling system and a water working medium heat storage system. The thermoelectric main engine system comprises a main steam pipeline, a steam turbine high-pressure cylinder, a steam turbine intermediate-pressure cylinder and a boiler reheater. A high-pressure bypass is connected into the main steam pipeline, and part of high-temperature and high-pressure main steam of the main steam pipeline passes through the high-pressure bypass and then is connected into the water working medium heat storage system; a medium-pressure bypass is connected to a steam inlet pipeline of the medium-pressure cylinder, and part of hot resteam passes through the medium-pressure bypass and then is connected into the water working medium heat storage system; the turbine-boiler decoupling system comprises a steam ejector and an electric steam boiler and has the function of providing high-capacity heat supply / steam supply while deeply adjusting a unit, and a high-pressure bypass and a medium-pressure bypass which are generated by decoupling can be connected with a high-capacity energy storage system, so that a low-investment, high-efficiency and high-capacity two-way peak regulation means is provided for a thermal power plant; and the coordination requirement between new energy development and power grid stability faced by the power grid is better met.

Description

Technical Field

[0001] The present invention belongs to the field of flexible peak regulation of thermal power plants, and is particularly suitable for thermal power plants with large heating scales. It meets the needs of large-scale and long-term up and down peak regulation of the power grid. The system can smoothly achieve ultra-large capacity heat storage scale, and uses water as the energy storage working fluid, with simple operation and maintenance, high cost performance and wide adaptability. It meets the urgent needs of power carbon reduction, thermal power transformation, and new energy expansion under the dual carbon strategy. The present invention relates to the field of peak regulation and energy storage technology of thermal power units, and specifically relates to a multi-redundant, wide-range, bidirectional, and smoothly adjustable large-capacity energy storage system, which aims to enhance the bidirectional peak regulation capability of thermal power units and meet the coordination needs of power grid stability and new energy development. Background Art

[0002] Traditional thermal power generating units (especially combined heat and power units) have a significant thermal-electric coupling phenomenon. With the rapid development of renewable energy (wind power, photovoltaic power) and the continuous expansion of combined heat and power, the flexibility 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, they are restricted in deep regulation, resulting in huge "coal / electricity inverted losses"; restrictions during peak hours reduce potential profits; during the deep regulation period during the non-heating season, they must also passively generate electricity according to the boiler's minimum stable combustion load, and also suffer considerable "coal-electricity inverted losses."

[0004] For new energy, the inherent thermal-electric coupling and minimum stable combustion load of thermal power units, as well as the huge startup capacity and power generation base, have all become "meaningless invalid electricity" during the peak period of new energy, and have generated huge amounts of invalid carbon emissions.

[0005] Thermal power plants are the cornerstone of grid security, but they also come at a significant cost. This reduction in flexibility, especially during the heating season, makes grid dispatching extremely difficult, forcing a significant reduction in green power generation. This severely hinders the development of the new energy industry, hinders progress in carbon reduction in the electricity sector, and even threatens the safe operation of the grid.

[0006] In order to solve the problem of thermal power flexibility, the existing mainstream technical routes include electrochemical energy storage, electrically heated molten salt energy storage, high bypass steam molten salt energy storage, or high bypass steam superimposed on electrically heated molten salt energy storage, but all have the following limitations.

[0007] When using electrochemical energy storage, the base power consumption is too high when coupled with heat and electricity. Deep regulation based solely on "storage" would require significant investment. For example, a two-300MW cogeneration unit, operating at rated steam extraction during severe cold weather, would still generate more than 60% of power during deep regulation. Based on a six-hour operation of two units, this would result in 2,160MWh of ineffective power. Therefore, thermal power plants must first decouple heat and electricity to reduce power generation and storage requirements.

[0008] The disadvantages of electrically heated molten salt energy storage include: the complex molten salt module system, high cold-end losses during the off-season and / or heating season when the heating system is not switched off, resulting in low energy storage efficiency and a poor investment value. Molten salt modules are suitable for frequency regulation but not for large-scale peak load regulation. Molten salt modules also present challenges such as the corrosive nature of the molten salt, difficulty in draining the salt in the event of an accident, and a high maintenance workload.

[0009] Using high-bypass steam molten salt energy storage, the energy storage efficiency is higher than electric heating under non-cylinder cutting conditions, but the molten salt module also has the previous shortcomings. At the same time, due to the greater thermal power of steam energy storage and the greater amount of molten salt used, 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 in operation and maintenance. The thermal power industry is still looking for a cost-effective energy storage system that is simple to operate and maintain, can perform wide-range bidirectional peak regulation, and operates smoothly. Summary of the Invention

[0011] In response to the problems existing in the above-mentioned system, the present invention proposes a new decoupling and energy storage solution. First, an electric steam boiler is introduced as one of the main means of decoupling, which can reset the invalid online power to zero instead of starting the boiler, and the cold section steam flow regulation is smoother; at the same time, water is used as the energy storage medium, the working fluid is single, the operation and maintenance are more convenient, and the 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 regulation of thermal power units, comprising a thermal power main unit system, a turbine-boiler decoupling system, and a water-based heat storage system; and characterized by: The main thermal power system includes the main steam pipeline, steam turbine high-pressure cylinder, steam turbine intermediate-pressure cylinder, and boiler reheater; A high-pressure bypass is connected to the main steam pipeline, and part of the high-temperature and high-pressure main steam in the main steam pipeline is connected to the water working fluid 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 hot resteam is connected to the water working fluid heat storage system after passing through the medium-pressure bypass; The turbine-boiler decoupling system includes a steam ejector. Part of the high-temperature and high-pressure main steam is drawn out from the main steam pipeline through a branch and connected to the high-pressure inlet of the steam ejector. Part of the hot resteam is drawn out from the medium-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.

[0013] Furthermore, the water working fluid heat 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 feed water heat exchanger, a condensate water heat exchanger, and a heat network water heat exchanger; they respectively constitute a heat absorption module, a heat storage module and a heat release module. The water working fluid 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.

[0014] Furthermore, the turbine-boiler decoupling system also includes an electric steam boiler, which is connected to the plant electrical system and uses electricity to produce steam during the off-peak period. The steam is input into the cold section of the unit boiler through a pipeline.

[0015] Furthermore, the turbine-boiler decoupling system also has a one-to-one decoupling module, and a decoupling communication pipe is set between the units to drag the adjacent units to decouple synchronously. It is connected between the medium-pressure bypass of the active unit and the boiler cold section inlet of the passive unit.

[0016] Furthermore, the heat absorption module is configured with two medium paths. One path is to draw out working medium water from the non-pressure water tank and connect it to the energy storage low-pressure heater and energy storage high-pressure heater in sequence, and enter the high-pressure water storage tank after being heated; the other path is to draw out part of the high-temperature feed water from the main water supply pipeline and connect it to the energy storage high-pressure heater, and enter the high-pressure water storage tank after being heated; the steam side of the energy storage high-pressure heater is connected to the high-pressure bypass of the host system, and the steam side of the energy storage low-pressure heater is connected to the medium-pressure bypass of the host system.

[0017] Furthermore, the heat 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 and the main feed water after being heated by the energy storage high-pressure heater; the low-pressure water storage tank is connected to the energy storage working fluid water and the condensate from the deaerator after being heated by the energy storage low-pressure heater.

[0018] Furthermore, the heat release module includes a feed water heat exchanger and a condensate heat exchanger; the feed water heat exchanger and the condensate heat exchanger are sequentially connected between the high-pressure water storage tank and the pressureless water tank; a low-pressure water storage tank is connected in series on the pipeline between the feed water heat exchanger and the condensate heat exchanger.

[0019] Furthermore, the heat release module further includes a heat network water heat exchanger; the high-pressure water storage tank and the low-pressure water storage tank are connected to the heat release side water inlet of the heat network water heat exchanger through pipelines; the heat release side water outlet of the heat network water heat exchanger is connected to the energy storage low-pressure heater, the pressureless water tank and the condensate pipeline.

[0020] Furthermore, the high-temperature feed water after being heated by the energy storage high-pressure heater can be directly introduced into the main feed water pipe of the boiler. When the steam turbine is in low-load condition, the feed water temperature is increased and the flue gas temperature at the tail of the boiler is increased.

[0021] Furthermore, the high-pressure water storage tank is connected to the adjacent high-pressure heater through a high-pressure steam side connecting pipe; the low-pressure water storage tank is connected to the adjacent low-pressure heater through a low-pressure steam side connecting pipe; the steam in the connecting pipe is designed for bidirectional flow, and the steam in the tank is discharged to a suitable low-pressure point through the connecting pipe during the heat storage stage, ensuring that there is no overpressure in the tank; in the heat release stage, the high-pressure heater steam side and the low-pressure heater steam side charge steam into the storage tank through the connecting pipe, driving the working medium water in the tank body to flow.

[0022] Furthermore, the condensate is drawn out from the outlet of the condensate pump and enters the pipe side of the condensate heat exchanger, and flows back to the main pipe after being heated; the cold source water is drawn out from the outlet of the feed water pump and enters the pipe side of the feed water heat exchanger, and returns to the main pipe after being heated. There are two access points back 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.

[0023] Furthermore, the design pressure of the high-pressure water storage tank is selected in the range of 3~10MPa.

[0024] Furthermore, a minimum flow valve is provided in parallel with the shut-off valve on the high-pressure bypass. During the exit of the steam ejector of the decoupled turbine and boiler, the minimum flow valve allows flow to maintain the high-pressure bypass in a hot state.

[0025] Furthermore, the drain of the energy storage high-pressure heater is connected to the drain side of the #1 high-pressure heater, and the drain of the energy storage low-pressure heater is connected to the deaerator.

[0026] Furthermore, the high-pressure bypass can provide high-pressure steam to the outside; the medium-pressure bypass can provide medium-pressure steam to the outside or connect to the first station of the heating network.

[0027] Furthermore, the steam production of the electric steam boiler can be flexibly adjusted, and it can independently bear the decoupling of the machine and boiler when the ejector is not in operation. The steam volume 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 energy storage low-pressure heater or various levels of high-pressure heaters.

[0028] The beneficial effects of the present invention are: The purpose of the present invention is to provide a large-capacity energy storage system with multiple redundancies, wide-range, bidirectional and smooth adjustment. Through decoupling of the turbine and boiler and storage of working fluid water, it can achieve wide-range peak regulation of thermal power units, improve the flexibility and economy of unit operation, and meet the power grid's needs for new energy consumption and stability.

[0029] Integrating the electric boiler into the machine-boiler decoupling module can achieve zero grid power consumption and make the primary frequency regulation function more prominent; it makes up for the shortcomings of simple ejector decoupling and simple electric boiler decoupling. The introduction of electric boilers allows this unit and its neighboring units to achieve zero grid connection. The retained ejector reduces the amount of steam entering the intermediate pressure cylinder under pure condensing conditions, minimizing cold end losses during deep regulation. Using water energy storage instead of molten salt can achieve a larger capacity of heat storage. At the same cost, the heat storage capacity of water working fluid is more than twice that of molten salt, and the investment cost-effectiveness is better than molten salt. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a system connection diagram.

[0031] In the figure: steam ejector (1), electric steam boiler (2), energy storage high pressure heater (3), energy storage low pressure heater (4), high pressure water storage tank (5), feed water heat exchanger (6), low pressure water storage tank (7), condensate heat exchanger (8), non-pressure water tank (9), hot network water heat exchanger (10), booster pump (11), turbine high pressure cylinder (HD), turbine medium 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 DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] The technical solution of the present invention is not limited by the capacity of the power plant units.

[0034] The technical solution of the present invention is not restricted by whether the power plant units are newly built or already in operation.

[0035] The technical solution of the present invention is not limited by the deep thermal-electric decoupling and the number of heating units in the power plant, and is not limited by the destination of steam at each level after decoupling, and can be flexibly adjusted.

[0036] The technical solution of the present invention is not limited by the steam parameters of the power plant units.

[0037] The technical solution of the present invention is not limited by the cogeneration or pure condensing operating conditions of the power plant units.

[0038] The technical solution of the present invention is not limited by the energy storage medium (water or thermal oil), energy storage heater, water storage tank and other heat exchanger types, locations, and ejector equipment (it can also be steam compressors, electric steam boilers and other equipment with equivalent functions). At the same time, the temperature and pressure reduction device can also be other equipment, such as a small steam turbine for power generation (which can be operated according to different working conditions, such as reducing plant electricity consumption or achieving peak power consumption), or additional heat and energy storage equipment.

[0039] like Figure 1 As shown, the boiler and turbine bodies remain unchanged, as do all auxiliary equipment and the tail flue. Low-load modifications are not required for all rotating machinery on the turbine side. The heat recovery system requires appropriate modifications to accommodate changes in feedwater flow. The turbine load factor can be set based on 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 condensing or heating mode to a fully decoupled boiler and turbine state.

[0040] Host system composition, such as Figure 1 As shown, the host system can be composed of multiple stand-alone systems.

[0041] Taking Unit 1 as an example, the single-unit system includes its main steam piping, the turbine's high-pressure cylinder (HD), and the boiler, which is equipped with a superheater and reheater. The power plant's main steam piping connects to the turbine's HP cylinder. High-temperature, high-pressure main steam from the main steam piping enters the turbine's HP cylinder. HP cylinder exhaust steam enters the cold-end inlet of the boiler's reheater. The system also includes the turbine's intermediate-pressure cylinder (MD) and the MD steam inlet piping, which carries hot reheat steam. The hot-end outlet of the boiler's reheater is connected to the MD steam inlet piping. Hot reheat steam at the hot-end outlet enters the turbine's MD to perform work.

[0042] A high-pressure bypass is connected to the main steam pipeline. A valve and a temperature-reducing and pressure-reducing device are installed on the high-pressure bypass. Part of the high-temperature and high-pressure main steam in the main steam pipeline is connected to the energy storage 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 boiler reheater cold section inlet pipeline through a branch line. The steam passes through valve V14 and the temperature-reducing and pressure-reducing device and enters the boiler reheater cold section inlet. A medium-pressure bypass is connected to the medium-pressure cylinder steam inlet pipeline. A valve and a temperature-reducing and pressure-reducing device are installed on the medium-pressure bypass. Part of the hot reheat steam is connected to the energy storage 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 heat network.

[0043] like Figure 1 As shown, the same system configuration can be used for other stand-alone systems, namely, high-pressure and medium-pressure bypasses for connecting to the energy storage system or supplying steam to external sources. The high-pressure and medium-pressure bypasses of each stand-alone system can be connected to the main pipe system for unified output, or they can be output separately using independent pipelines.

[0044] Furthermore, by setting up a turbine-boiler decoupling system in the unit, the peak reduction of the thermal power unit was achieved.

[0045] The turbine-boiler decoupling system is constructed based on the steam ejector (1) as the core equipment. The ejector is connected to three steam lines, namely, power steam, induced steam and exhaust steam. The power steam is the main steam generated by the boiler superheater, a part of which enters the high-pressure cylinder, and the other branched part of the main steam is used as the power steam of the ejector. The induced steam is the hot reheat steam generated by the boiler reheater, a part of which enters the medium-pressure cylinder, and the diverted part of the hot reheat steam enters the ejector through the hot recirculation and is pressurized. After being pressurized by the ejector, the steam is exhausted to the cold section of the boiler reheater and merged with the original high-pressure cylinder exhaust steam to enter the boiler. Each pipeline can be equipped with a matching temperature reduction and pressure reduction device according to actual needs.

[0046] Taking the #1 unit as an example, a steam ejector (1) is added to the #1 unit. A steam ejector (1) is connected between the cold section inlet and the hot end outlet of the boiler reheater. The steam ejector has a motive steam inlet, an ejector steam inlet, and an exhaust outlet. Part of the high-temperature and high-pressure main steam is drawn out from the main steam pipeline through a branch and connected to the motive steam inlet of the steam ejector. Part of the reheated steam is drawn out from the medium-pressure bypass through a branch and enters the ejector steam inlet of the steam ejector after being cooled and reduced in pressure. The exhaust outlet of the steam ejector is connected to the cold section inlet of the reheater. Part of the main steam enters the steam ejector as motive steam after being cooled and reduced in pressure, and is used to extract part of the reheated steam connected to the ejector inlet of the steam ejector. After the motive steam and part of the reheated steam are mixed, they enter the cold section inlet of the reheater again.

[0047] The steam ejector system can adopt single or multiple steam ejectors. Multiple steam ejectors are connected in series, in parallel or in series-parallel to form a steam ejector group, so as to realize the adjustment and optimization of parameters such as injection ratio and complete variable working conditions. The nozzle of the steam ejector can adopt fixed nozzle or adjustable nozzle.

[0048] Since the boiler-turbine decoupling system ensures safe flow of the boiler reheater, a large amount of main steam and hot resteam can be extracted. In this system, the main steam goes to the energy storage high-pressure heater through the high-pressure bypass, and the hot resteam goes to the energy storage low-pressure heater after the medium-pressure bypass or to the heating network heater after desuperheating and pressure reduction. The steam branched on the high-pressure bypass can also enter the cold section of the boiler reheater through valve V14, the desuperheating and pressure reduction device and the pipeline where it is located.

[0049] A minimum flow valve (V0) is installed in parallel with the shutoff valve on the high-pressure bypass. During the decoupling of the steam ejectors from the turbine and boiler, flow through this valve maintains the high-pressure bypass in a hot state. The extracted main steam and hot resteam can also be used for external steam supply, heat supply, or other forms of heat storage during peak load reduction.

[0050] In order to facilitate the decoupling of multiple units, the decoupling auxiliary module is also set up. Figure 1As shown, the decoupling auxiliary module is used to synchronously decouple adjacent units (i.e., a one-to-one decoupling module). It includes a decoupling liaison pipe connected between the medium-pressure bypass of Unit 1 (the active unit) and the cold-end inlet of the boiler of Unit 2 (the passive unit). After decoupling the boiler and turbine of Unit 1, a large amount of hot resteam can be extracted and sent to the cold-end of the boiler of Unit 2 via the pipeline (decoupling liaison pipe) where valve V1 is located. The hot resteam transported by the decoupling liaison pipe also ensures safe flow in the reheater of Unit 2's boiler, enabling simultaneous decoupling and peak load reduction. Unit 2 can also extract large amounts of main steam and hot resteam for the energy storage high-pressure and low-pressure heaters or the heat network heaters.

[0051] Furthermore, the decoupling auxiliary module can also be realized by setting up an electric steam boiler (2), which is connected to the plant electrical system, and consumes the generated electric energy during the off-peak period, and uses the electric energy to produce suitable steam, which can be input into the cold section of the unit boiler through the pipeline.

[0052] like Figure 1 As shown, the electric steam boiler (2) is connected to the cold section of the boiler of unit #1 and unit #2 through a pipeline. It can go to the cold section of the boiler of unit #1 through the pipeline where valve V2 is located, and go to the cold section of the boiler of unit #2 through the pipeline where valve V3 is located. The purpose of ensuring the safe flow of the reheater of each unit can also be achieved by supplementing steam from the electric steam boiler. The steam production of the electric steam boiler can be flexibly adjusted and operated. It can completely or partially replace the turbine-boiler decoupling system. When the ejector is not running, it can independently bear the turbine-boiler decoupling. The distribution of steam to a single unit or two units can also be flexibly adjusted according to demand. The steam volume is distributed and transported to the cold section of the reheater of multiple adjacent boilers, or directly to the first station of the heat network, the energy storage low-pressure heater, or various high-pressure heaters.

[0053] Steam ejectors and electric steam boilers jointly feed steam to the cold section of the reheater, displacing the high bypass and achieving decoupling between the turbine and boiler. To decouple multiple units throughout the plant, a decoupling communication pipe is configured, with Unit 1 serving as the active unit. After desuperheating, steam from its hot section enters the cold section of the adjacent unit, achieving decoupling. This one-to-one decoupling of adjacent units can be repeated and extended to subsequent units. For example, steam from the hot section of Unit 2 can be fed to the cold section of the reheater of Unit 3.

[0054] The water-based heat storage system achieves decoupled heat storage and release. It is built on the boiler feedwater system. The boiler feedwater system includes the condenser, condensate pump, various low-pressure heaters, deaerator, feedwater pump, and various high-pressure heaters. Condensate from the condenser flows through the condensate pump, low-pressure heater, deaerator, feedwater pump, and high-pressure heater before being connected to the boiler's main feedwater pipeline.

[0055] The water working medium heat storage system includes a high-pressure energy storage heater (3), a low-pressure energy storage heater (4), a high-pressure water storage tank (5), a feed water heat exchanger (6), a low-pressure water storage tank (7), a condensate water heat exchanger (8), a pressureless water tank (9), and a heat network water heat exchanger (10). They respectively constitute a heat absorption module, a heat storage module, and a heat release module. The water working medium energy storage system can be divided into 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.

[0056] The heat absorption module includes a high-pressure energy storage heater (3) and a low-pressure energy storage heater (4). Pipes are drawn out from the non-pressure water tank and sequentially connected to the water sides of the low-pressure energy storage heater and the high-pressure energy storage heater, and then enter the high-pressure water storage tank after passing through the working medium water energy storage valve H1.

[0057] The steam side of the energy storage high-pressure heater is connected to the high-pressure bypass of the main engine system, while the steam side of the energy storage low-pressure heater is connected to the medium-pressure bypass of the main engine system. The working water in the non-pressure water tank passes through the energy storage low-pressure heater and energy storage high-pressure heater, where it undergoes heat exchange with the hot resteam from the medium-pressure bypass and the main steam from the high-pressure bypass in the energy storage low-pressure heater and energy storage high-pressure heater. After absorbing heat and heating, the working water flows into the high-pressure water storage tank for storage.

[0058] In addition, when a low-pressure water storage tank is configured, a branch line can be connected to the low-pressure water storage tank on the downstream side of the energy storage low-pressure heater (4), and part of the working fluid water enters the low-pressure water storage tank (7) through the energy storage valve M1, the pressure reducing valve and the pipeline for storage.

[0059] The water side of the energy storage high-pressure heater (3) can also be connected to the main feed water. A branch is drawn from the main feed water pipeline to connect some high-temperature feed water to the energy storage high-pressure heater (3). After being heated, it flows through the feed water storage valve H2 and enters the high-pressure water storage tank (5) for storage. After being heated, the high-temperature feed water can also be directly connected to the main feed water pipeline of the boiler. When the steam turbine is in low load condition, the feed water temperature can be increased, thereby increasing the flue gas temperature at the tail of the boiler.

[0060] Two medium paths are configured in the heat absorption module: one is a dedicated path for energy storage, which flows from the non-pressure water tank (9) through the booster pump (11) into the energy storage low-pressure heater (4) and the energy storage high-pressure heater (3), flows through the working medium water energy storage valve H1 and enters the high-pressure water storage tank (5). The other path draws high-temperature feed water from the main water supply pipeline, flows through the energy storage high-pressure heater (3), the feed water energy storage valve H2 and enters the high-pressure water storage tank (5).

[0061] The pipework of the energy storage high-pressure heater (3) is equipped with two independent water-side channels, one for the energy storage working medium water and the other for the main feed water. The energy storage high-pressure heater can also be configured as two dedicated heaters in a split manner, namely, a dedicated energy storage high-pressure heater and a feed water heating high-pressure heater, both of which are connected to the energy storage working medium water and the main feed water respectively. The drain of the energy storage high-pressure heater (3) is connected to the drain side of the #1 high-pressure heater, and the drain of the energy storage low-pressure heater (4) is connected to the deaerator (CY).

[0062] The heat 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 medium water and the main feed water after being heated by the energy storage high-pressure heater (3). The high-pressure water storage tank is connected to the energy storage high-pressure heater (3) and the #1 high-pressure heater through a high-pressure steam side connecting pipe. The low-pressure water storage tank (7) is connected to the energy storage working medium water and the condensate from the deaerator after being heated by the energy storage low-pressure heater (4). The low-pressure water storage tank is connected to the #5 low-pressure heater and the #6 low-pressure heater through a low-pressure steam side connecting pipe.

[0063] The heat storage process operates during peak load regulation or low spot electricity price periods when the turbine and boiler are decoupled. The two high-quality steam streams generated after the decoupling of the turbine and boiler in Unit 1, the main steam from the high-pressure bypass and the hot resteam from the medium-pressure bypass, are respectively fed into the energy storage high-pressure heater (3) and energy storage low-pressure heater (4) to heat the working water.

[0064] The working medium water first enters the energy storage low-pressure heater (4) and is heated by the hot re-steam. After being heated, part of the working medium water enters the low-pressure water storage tank (7) for storage through the energy storage valve M1, the pressure reducing valve and the pipeline. At this time, the condensate from the deaerator can also be stored according to the working conditions (that is, through the pipeline where the condensate storage valve M2 is located). The hot re-steam is heated in the energy storage low-pressure heater and then becomes drain water and returns to the deaerator. In addition, part of the working water heated by the energy storage low-pressure heater (4) continues to enter the energy storage high-pressure heater (3) to continue to be heated. The heating steam of the energy storage high-pressure heater is steam from the high-pressure bypass. After being heated, this part of the working water enters the high-pressure water storage tank (5) through the pipeline where the energy storage valve H1 is located. The high-pressure water storage tank can also receive the feed water heated by the energy storage high-pressure heater (this part of the feed water is the part of the feed water diverted after the #1 high-pressure heater, and enters the high-pressure water storage tank through the pipeline where the feed water storage valve H2 is located. This part of the feed water can also be diverted according to the working conditions and directly collected into the main feed water of the boiler). The high-pressure bypass steam that has completed heating in the energy storage high-pressure heater becomes the drain and returns to the drain side of the #1 high-pressure heater.

[0065] When the heated working water enters the high-pressure water storage tank and the low-pressure water storage tank, the remaining steam in the high-pressure water storage tank and the low-pressure water storage tank needs to enter the nearest high-pressure steam side, low-pressure steam side or deaerator through the steam side connecting pipe.

[0066] The high-pressure water storage tank is connected to the energy storage high-pressure heater (3) and the #1 high-pressure heater through a high-pressure steam side connecting pipe. The low-pressure water storage tank is connected to the #5 low-pressure heater and the #6 low-pressure heater through a low-pressure steam side connecting pipe. The steam in the connecting pipe is designed to flow in both directions. During the heat storage stage, as the high-temperature saturated water enters the tank body, the steam in the tank is discharged to a suitable low-pressure point, such as the high-pressure steam side and the low-pressure steam side, through the connecting pipe, ensuring that the tank is not over-pressurized. During the heat release stage, pressurized steam is introduced into the storage tank from the high-pressure steam side and the low-pressure steam side through the connecting pipe to drive the working medium water in the tank body to flow and discharge (the pressurized water storage tank is not equipped with a water pump). A pressure regulating valve is set on the connecting pipe to adapt the pressure of the tank body and each steam extraction side to each other. The required working medium water for heat storage can be injected into the non-pressure water tank (9) or the low-pressure water storage tank (7) in advance.

[0067] There are two paths for working fluid water energy storage: Heat storage path 1: The two steam paths generated after the decoupling of the turbine and boiler can be used in the heat storage link. The high-pressure bypass steam enters the energy storage high-pressure heater (3), and the hot section steam enters the energy storage low-pressure heater (4), to heat the working water. The working water comes from the non-pressure water tank, or from the part of the system condensate diverted (the working water bypass through valve V8), passes through the booster pump (11) and valve V9 to enter the energy storage low-pressure heater (4). After passing through the energy storage low-pressure heater, it can be branched into two paths. One path enters the low-pressure water storage tank (7) through valve M1, and the other path is heated by the energy storage high-pressure heater (3) and then flows through valve H1 to enter the high-pressure water storage tank (5). The drain water heated by the two steam paths enters the drain side of the high-pressure heater of unit #1 and the deaerator respectively.

[0068] Heat storage path 2: High-temperature water comes from the heat recovery system. When the boiler is at a medium or low load rate, the water supply is controlled to increase. The excess water is heated by the energy storage high-pressure heater (3) and then flows through valve H2 to the high-pressure water storage tank (5). The saturated water in the deaerator is input into the low-pressure water storage tank (7) through valve M2.

[0069] The heat release module includes a feed water heat exchanger (6) and a condensate water heat exchanger (8), both of which are water-to-water heat exchangers, with their shell side serving as the heat release side and their tube side serving as the heat absorption side. The feed water heat exchanger (6) and the condensate water heat exchanger (8) are sequentially connected between the high-pressure water storage tank and the non-pressure water tank.

[0070] On the heat release side, the high-pressure water storage tank is connected to the heat release side water inlet of the feed water heat exchanger through the branch pipe where the valve V11 is located; the heat release side water outlet of the feed water heat exchanger is connected to the heat release side water inlet of the condensate heat exchanger through the branch pipe where the valve V13 is located; the heat release side water outlet of the condensate heat exchanger is connected to the pressureless water tank through the branch pipe.

[0071] When a low-pressure water storage tank is installed, it is connected in series to the heat-dissipating piping between the feedwater heat exchanger and the condensate heat exchanger. Water flowing out of the feedwater heat exchanger enters the low-pressure water storage tank before flowing into the condensate heat exchanger for a second heat exchange. This reduces the shell-side pressure of the condensate heat exchanger downstream of the low-pressure water storage tank, thereby reducing both the cost and the shell-side operating pressure of the condensate heat exchanger.

[0072] On the heat absorption side, the outlet branch of the condensate pump is connected to the heat absorption side inlet of the condensate heat exchanger through the branch where valve V7 is located, and the heat absorption side outlet of the condensate heat exchanger is connected to the deaerator through the branch where valve V6 is located; the outlet branch of the feed water pump is connected to the heat absorption side inlet of the feed water heat exchanger through the branch where valve V5 is located, and the heat absorption side outlet of the feed water heat exchanger is connected to the main feed water pipe of the boiler through a pipeline; there are two access points for the main feed water pipe back to the boiler. If the temperature is high enough, it enters the outlet of #1 high-pressure heater through valve V4. On the contrary, when the temperature is undertemperature, it enters the outlet of #2 high-pressure heater through valve V4'.

[0073] 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 a heat release side and its tube side serving as a heat absorption side.

[0074] On the heat release side, the high-pressure water storage tank is connected to the heat release side water inlet of the heat network water heat exchanger through the branch pipe where the 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 water inlet of the heat network water heat exchanger through the branch pipe where the valve V12 is located.

[0075] The heat-dissipating outlet of the heat exchanger in the heat network is connected to the energy storage low-pressure heater, the pressureless water tank, and the condensate pipeline via a branch pipe. The cooled working water can then flow into the energy storage low-pressure heater for the next heat storage cycle. Alternatively, it can flow to the pressureless water tank or enter the condensate pipeline via the working water bypass (valve V8), depending on operating conditions.

[0076] On the heat absorption side, the water from the heating network is connected to the heat absorption side, and the heat absorption and temperature increase are returned to the heating network as heat supply water.

[0077] The heat release process is run during peak load or high spot electricity price periods. The steam-side connecting pipe connected to the low-pressure water storage tank (7) is opened, and the low-pressure steam side is charged into the low-pressure water storage tank (7) through the connecting pipe, so that the working medium water in the low-pressure water storage tank is driven to the heat network water heat exchanger (10) through valve V12 and the pipeline to heat the heat network water. The cooled working medium water can enter the next heat storage cycle stage (de-energy storage low-pressure heating), or it can go to the non-pressure water tank or enter the condensate pipeline through the working medium water bypass according to the working condition requirements; The heat-storage working medium water in the low-pressure water storage tank (7) can also enter the condensate heat exchanger (8) through valve V13 and the pipeline to heat the condensate. The condensate comes from the condensate diversion part of the main system. It enters the condensate heat exchanger through valve V7 before the #7 low-pressure injection inlet and is heated. It then merges to the #5 low-pressure injection outlet through valve V6. The working medium water in the condensate heat exchanger enters the non-pressure water tank after passing through the pressure reducing valve. The steam-side connecting pipe connected to the high-pressure water storage tank is opened. The high-pressure steam side of the high-pressure water storage tank (5) is charged with steam through the connecting pipe, which drives the working medium water in the high-pressure water storage tank to flow through valve V11 and the pipeline to the feedwater heater (6) to heat the feedwater. The feedwater diverted from the feedwater pump outlet enters the feedwater heat exchanger through valve V5, where it is heated and then flows through valve V4 to the main feedwater pipeline #1 high-pressure water outlet. The working medium water flowing out of the feedwater heat exchanger then flows through valve V13, is decompressed, enters the condensate heat exchanger (8), and finally returns to the pressureless water tank (9). When releasing heat, it can also enter the hot water network water heat exchanger (10) downstream of the feedwater heat exchanger (6) through valve V12.

[0078] The design pressure of a high-pressure water storage tank can be selected between 3 and 10 MPa. To reduce the cost of the pressure vessel, a lower pressure can be selected, but this will also reduce energy storage efficiency. To improve energy storage efficiency, the high-pressure water storage tank should be selected at a higher pressure. 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, if it is designed to 4.5 MPa, the feed water heat exchanger will not heat the feed water to a sufficient temperature. The heated feed water will then flow through valve V4' and return to the main feed water pipeline after the #2 high-pressure heater.

[0079] The working medium water in the high-pressure water storage tank can also enter the hot network water heat exchanger (10) through the valve V10, the pressure reducing valve and the high-pressure working medium water bypass, and enter the non-pressure water tank (9) after cooling and pressure reduction.

[0080] During heat release, condensate, feed water, and grid water are heated by the energy storage working fluid, reducing the corresponding steam extraction volume and increasing the generating capacity of the units. These two factors work together to restore the system to full power generation. Furthermore, the generating capacity of the unit and adjacent units in the host system (multiple units) can also be increased, restoring full power generation.

[0081] There are three paths for the heat release of working fluid water: Instead of the heat recovery system, the heat release path 1 is to open the steam-side connecting pipe connected to the high-pressure water storage tank, and use high-pressure steam to drive the saturated water in the high-pressure water storage tank to the feed water heater (6). After the feed water is heated, it is merged into the feed water main pipe at a suitable position. The working medium water is decompressed 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 pressureless water tank. Heat can also be released to the heat network, where the heat release path 2 is high-pressure water heating the hot network water, which can enter the hot network water heat exchanger (10) from valve V10, and then decompress and enter the pressureless water tank (9) after cooling. Path 3 is the low-pressure water storage tank (7) through valve V12 into the hot network water heat exchanger (10) to heat the hot network water. When the system releases heat, the above three paths can operate simultaneously, and the energy storage working medium water releases heat to the feed water and hot network water at maximum power, reducing the heat recovery steam extraction volume and heating steam extraction volume, so that the entire plant unit can obtain the maximum peak capacity.

[0082] The 300MW unit is used as an example to illustrate the typical working process of the system.

[0083] In winter operation mode, Heating season: Select the following operating conditions according to the three electricity price levels of high, medium and low.

[0084] Operating Condition 1: Winter Peak: High electricity price / peak operating condition: At this time, the high-pressure water storage tank releases heat to the feed water, replacing 70% of the heat recovery steam extraction, thereby increasing the unit's power generation capacity; at the same time, the low-pressure water tank releases heat to the heating network at a power of 225MW, reducing the unit's steam extraction. The combined effect of these two can enable the 2*300MW units to heat 15 million cubic meters during the severe cold season. 2 When the power is restored to full power, the system only releases heat.

[0085] Operating Condition 2, Winter Off-Peak: Electricity prices near the break-even point / efficient heating or energy storage, and extended dual-engine shedding periods. Efficient heating can reduce power generation costs during this period. This is achieved by maintaining dual-engine shedding, reducing power generation costs and improving grid competitiveness. However, during the early and late cold seasons, when heat supply is low, dual-engine shedding is not possible. This system can increase the water flow to extend dual-engine shedding periods. Excess water can be used in two ways: directly for external heat supply (both storage and release), reducing boiler load; or stored in high-pressure water tanks, achieving efficient heat storage; the system can store and release heat simultaneously.

[0086] Operating Condition 3A, Winter Deep Adjustment: Low or zero electricity prices / decoupling of the turbine and boiler, high- and low-pressure bypass heating plus electric steam boiler heating, and high-power energy storage. During this period, the turbine and boiler are decoupled and operated. The decoupled steam is split into two parts: the majority is extracted from the hot section via the high- and low-pressure bypass for heating; a smaller portion is stored via energy storage at the high-pressure / low-pressure stage. Furthermore, to mitigate losses due to the "coal-to-electricity inversion," the electric steam boiler is operated at maximum capacity. The system only uses energy storage.

[0087] Condition 3B, Winter Deep Adjustment: When the decoupling limit is reached in Condition 3A, the energy storage system releases heat to the heating network. Because there is no external reheater, the decoupling amplitude (high bypass Mby / boiler main steam flow Gb) has an upper limit. When this limit is reached, the high bypass flow Mby must be reduced or the boiler main steam flow Gb must be increased. However, reducing the high bypass will reduce heating capacity, while maintaining the high bypass and increasing Gb will increase turbine power generation. At this point, the energy storage module can release heat to the heating network to share 225 MW of heating water. The system only releases heat.

[0088] In summer operation mode, There is no peak problem in summer. The system mainly works in two modes: deep adjustment and heat storage, and heat release in other periods.

[0089] Operating Condition 5: Summer Peak Condition: In summer, the unit operates in pure condensing conditions, so peak loads are not an issue. However, some power plants have poor coal quality, and the units may have insufficient peak capacity. In this case, the high-pressure storage tank can release heat to the feedwater, eliminating the need for special modifications (such as blending high-quality coal) during peak loads. The system only releases heat.

[0090] Working condition 6, summer deep adjustment working condition: at this time, the boiler is operated at the lowest stable combustion load of 30~35%, assuming it is 300t; the steam turbine is operated at the minimum safe steam inlet (assuming it is 190t), with a high bypass of 110t (the flow rate is controllable at this time), of which a small amount of heating feed water is raised to 245~250℃; the hot section extracts steam of ~105t, and a single unit can heat 500 tons of working fluid water for energy storage. The system only stores heat, and the high-pressure water tank is 6000m 3 Setting, can store the deep adjustment water volume of dual machines for 6 hours.

[0091] Condition 7: Heat release during off-peak periods in summer: When the boiler load rate is within the safe zone, the boiler load rate can be adjusted slightly lower than the turbine load rate. The difference between the two can be compensated by heat release from the energy storage system, allowing the energy storage tank to be emptied in a timely manner. The system only releases heat.

[0092] In summary, the present invention has the following advantages: Wide-range peak-shaving capability: Through water-based heat storage, combined with the collaborative work of the boiler-turbine decoupling module and different operating modules, multiple units can flexibly adjust their peaks within a wide range, better adapting to changes in grid load and meeting the needs of grid stability after the integration of new energy. Bidirectional flexible operation: After the modules are stacked, they have the bidirectional flexible operation function of up and down peak load regulation. When the grid load is peak, the stored heat can be released to increase power generation; when the grid load is low, energy can be stored to improve the flexibility and adaptability of the unit operation. Improved Economic Benefits: The system combines the large-capacity heating and steam supply capabilities unique to turbine-boiler decoupling. Through different operating conditions during the heating and off-seasons, it fully utilizes the unit's energy, maximizing the plant's revenue at both peak and valley levels. This system also enables peak and frequency regulation, reduces losses from coal-fired power generation caused by low electricity prices, increases capacity-based electricity price subsidies, reduces operating costs, and improves the plant's economic benefits. Large-capacity energy storage: Transforming thermal power plants into low-investment, high-efficiency, large-capacity rapid peak-shaving centers, effectively alleviating the contradiction between the development of renewable energy and grid stability faced by the power grid, and promoting the absorption of renewable energy and the sustainable development of the power grid. The above system advantages are demonstrated in terms of structure, function, and operation. The application of the above-mentioned system can be replicated in other thermal power plants, and the operation mode is flexible. For example, after deep decoupling, the steam inlet method of the steam turbine can be flexibly adjusted, and the steam inlet volume can also be changed to meet various dispatching requirements of the power grid.

[0093] Finally, it should be noted that the foregoing description is merely an explanation of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail, those skilled in the art will be able to modify the aforementioned technical solutions or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A water-based cascade energy storage system for wide-range peak regulation of thermal power units, comprising a thermal power main unit system, a turbine-boiler decoupling system, and a water-based heat storage system; characterized in that: The main thermal power system includes the main steam pipeline, steam turbine high-pressure cylinder, steam turbine intermediate-pressure cylinder, and boiler reheater; A high-pressure bypass is connected to the main steam pipeline, and part of the high-temperature and high-pressure main steam in the main steam pipeline is connected to the water working fluid 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 hot resteam is connected to the water working fluid heat storage system after passing through the medium-pressure bypass; The turbine-boiler decoupling system includes a steam ejector. Part of the high-temperature and high-pressure main steam is drawn out from the main steam pipeline through a branch and connected to the high-pressure inlet of the steam ejector. Part of the hot resteam is drawn out from the medium-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.

2. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 1 is characterized in that: The water working fluid heat 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 feed water heat exchanger, a condensate water heat exchanger, and a heat network water heat exchanger; they respectively constitute a heat absorption module, a heat storage module, and a heat release module. The water working fluid 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.

3. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 1 is characterized in that: The turbine-boiler decoupling system also includes an electric steam boiler, which is connected to the plant electrical system and uses electricity to produce steam during the off-peak period. The steam is input into the cold section of the unit boiler through a pipeline.

4. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 1 is characterized in that: The turbine-boiler decoupling system also has a one-to-one decoupling module. A decoupling communication pipe is set between the units to drag the adjacent units to decouple synchronously. It is connected between the medium-pressure bypass of the active unit and the boiler cold section inlet of the passive unit.

5. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 2 is characterized in that: The heat absorption module is equipped with two medium paths. One path is to draw the working medium water from the non-pressure water tank and connect it to the energy storage low-pressure heater and energy storage high-pressure heater in sequence, and then enter the high-pressure water storage tank after being heated; the other path is to draw some high-temperature feed water from the main water supply pipeline and connect it to the energy storage high-pressure heater, and then enter the high-pressure water storage tank after being heated; the steam side of the energy storage high-pressure heater is connected to the high-pressure bypass of the host system, and the steam side of the energy storage low-pressure heater is connected to the medium-pressure bypass of the host system.

6. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 5 is characterized in that: The heat 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 and the main feed water after being heated by the energy storage high-pressure heater; the low-pressure water storage tank is connected to the energy storage working fluid water and the condensate from the deaerator after being heated by the energy storage low-pressure heater.

7. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 5, characterized in that: The heat release module includes a feed water heat exchanger and a condensate heat exchanger; the feed water heat exchanger and the condensate heat exchanger are sequentially connected between the high-pressure water storage tank and the pressureless water tank; a low-pressure water storage tank is connected in series on the pipeline between the feed water heat exchanger and the condensate heat exchanger.

8. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 7 is characterized in that: The heat release module further includes a heat network water heat exchanger; the high-pressure water storage tank and the low-pressure water storage tank are connected to the heat release side water inlet of the heat network water heat exchanger through pipelines; the heat release side water outlet of the heat network water heat exchanger is connected to the energy storage low-pressure heater, the pressureless water tank and the condensate pipeline.

9. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 5, characterized in that: After being heated by the energy storage high-pressure heater, the high-temperature feed water can be directly introduced into the main feed water pipe of the boiler. When the steam turbine is in low-load condition, the feed water temperature is increased and the flue gas temperature at the tail of the boiler is increased.

10. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 6, characterized in that: The high-pressure water storage tank is connected to the adjacent high-pressure heater through a high-pressure steam side connecting pipe; the low-pressure water storage tank is connected to the adjacent low-pressure heater through 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 the appropriate low-pressure point through the connecting pipe to ensure that there is no overpressure in the tank; in the heat release stage, the high-pressure heater steam side and the low-pressure heater steam side charge steam into the storage tank through the connecting pipe to drive the working medium water in the tank body to flow.

11. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 7, characterized in that: The condensate is drawn out from the condensate pump outlet and enters the pipe side of the condensate heat exchanger, and flows back to the main pipe after being heated; the cold source water is drawn out from the feed water pump outlet and enters the pipe side of the feed water heat exchanger, and flows back to the main pipe after being heated. There are two access points back 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.

12. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 6, characterized in that: The design pressure of the high-pressure water storage tank is selected in the range of 3~10MPa.

13. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 1, characterized in that: A minimum flow valve is set in parallel with the shut-off valve on the high-pressure bypass. During the exit of the steam ejector of the decoupled turbine and boiler, the minimum flow valve keeps the high-pressure bypass in a hot state.

14. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 5, characterized in that: The drain of the energy storage high-pressure heater is connected to the drain side of #1 high-pressure heater, and the drain of the energy storage low-pressure heater is connected to the deaerator.

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

16. The water-based cascade energy storage system for wide-range peak regulation of thermal power generation units according to claim 3, characterized in that: The steam production of the electric steam boiler can be flexibly adjusted. When the ejector is not in operation, it independently undertakes the decoupling of the machine and boiler. The steam volume is distributed and transported to the cold section of the reheater of multiple adjacent boilers. It can also be directly sent to the first station of the heating network, the energy storage low-pressure heating or various levels of high-pressure heating.

Images