Cascade phase change energy storage system combined with thermal power generating unit

Abstract

The cascade phase change energy storage system combined with the thermal power generating unit comprises a power generator system and an energy storage system, the power generator system comprises a boiler, a steam turbine, a cooling tower and a heat regenerator system, and water circulation of the power generator system flows in the direction of the boiler, the steam turbine, the cooling tower, the heat regenerator system and the boiler; the energy storage system comprises a cascade heat storage tank and an air heat exchange system, the temperature of the cascade heat storage tank is gradually reduced from bottom to top, the air heat exchange system comprises a heat storage side and a heat release side, the heat storage side uses renewable green electricity to drive an electric heater to serve as a heat source, and the heat release side uses compressed and heated air to drive a gas turbine. The high-temperature waste heat assists a heat regeneration system of the generator system to heat feed water; under the condition that the boiler is abandoned, the high-temperature waste heat replaces evaporation and overheating of the boiler, steam supply of the steam turbine is guaranteed, the steam turbine operates normally, and then normal power generation of a generator system is guaranteed.

Description

Technical Field

[0001] The embodiments of the present disclosure belong to the field of energy storage technology, and specifically relate to a cascade phase change energy storage system for a combined thermal power unit. Background Art

[0002] With the growth of energy demand and the improvement of environmental protection standards, existing energy utilization methods are facing two major challenges: efficiency and environment. As one of the main ways to produce electricity, thermal power generation usually requires boilers to provide steam. However, as the service life of the boiler gradually decreases, the boiler is difficult to maintain the steam demand of the turbine. Therefore, there is an urgent need for a system that can solve the steam demand of thermal power generation. Summary of the invention

[0003] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a cascade phase change energy storage system for a combined thermal power unit.

[0004] An embodiment of the present disclosure provides a cascade phase change energy storage system for a combined thermal power plant, the cascade phase change energy storage system for a combined thermal power plant comprising:

[0005] A generator system, the generator system comprising: a boiler, a steam turbine, a cooling tower and a regenerator system, wherein the water circulation of the power generation system flows along the direction of the boiler, the steam turbine, the cooling tower, the regenerator system and the boiler;

[0006] An energy storage system, the energy storage system comprising a cascade heat storage tank and an air heat exchange system, the hot end outlet of the cascade heat storage tank is connected to the hot end inlet of the air heat exchange system, and the air heat exchange system is configured to vaporize water output from the regenerator system and transport it to the inlet of the steam turbine; and / or to vaporize water output from the cooling tower and transport it to the inlet of the steam turbine.

[0007] In some embodiments of the present disclosure, the air heat exchange system comprises:

[0008] A high-temperature heat exchanger, wherein the hot end outlet of the stepped heat storage tank is used to connect to the hot end inlet of the high-temperature heat exchanger, the cold end inlet of the high-temperature heat exchanger is connected to the outlet of the cooling tower, and the cold end outlet of the high-temperature heat exchanger is connected to the inlet of the steam turbine.

[0009] In some embodiments of the present disclosure, the air heat exchange system comprises:

[0010] A high-temperature heat exchanger, wherein the hot end outlet of the stepped heat storage tank is used to connect to the hot end inlet of the high-temperature heat exchanger, the cold end inlet of the high-temperature heat exchanger is connected to the outlet of the regenerator system, and the cold end outlet of the high-temperature heat exchanger is connected to the inlet of the steam turbine.

[0011] In some embodiments of the present disclosure, the air heat exchange system comprises:

[0012] A low-temperature heat exchanger, wherein the cold end outlet of the high-temperature heat exchanger is connected to the hot end inlet of the low-temperature heat exchanger, the cold end outlet of the low-temperature heat exchanger is connected to the atmosphere, the cold end inlet of the low-temperature heat exchanger is connected to the outlet of the cooling tower, and the hot end outlet of the low-temperature heat exchanger is connected to the inlet of the boiler.

[0013] In some embodiments of the present disclosure, the power generation system further includes a gas turbine, the hot end outlet of the stepped heat storage tank is connected to the inlet of the gas turbine, and the outlet of the gas turbine is connected to the hot end inlet of the high-temperature heat exchanger.

[0014] In some embodiments of the present disclosure, the power generation system further includes a generator, wherein the generator is connected to the gas turbine, and the generator is connected to the steam turbine.

[0015] In some embodiments of the present disclosure, the steam extraction outlet of the steam turbine is connected to the hot end inlet of the regenerator system, and the cold end outlet of the regenerator system is connected to the inlet of the boiler.

[0016] In some embodiments of the present disclosure, the energy storage system also includes a heat storage system, which includes: a heat storage blower, an ultra-high temperature electric heater and a renewable energy device, the air outlet of the heat storage blower is connected to the inlet of the ultra-high temperature electric heater, the outlet of the ultra-high temperature electric heater is connected to the hot end inlet of the stepped heat storage tank, and the renewable energy device is connected to the ultra-high temperature electric heater.

[0017] In some embodiments of the present disclosure, the heat storage system further includes a heat storage heat exchanger, and a hot end inlet of the heat storage heat exchanger is connected to a cold end outlet of the stepped heat storage tank.

[0018] In some embodiments of the present disclosure, the air heat exchange system also includes a heat release blower and an air compressor, the inlet of the heat release blower is connected to the air, the outlet of the heat release blower is connected to the inlet of the air compressor, and the outlet of the air compressor is connected to the cold end inlet of the stepped heat storage tank.

[0019] The cascade phase change energy storage system of the combined thermal power unit of the embodiment of the present disclosure can transfer the heat energy of the cascade heat storage tank to the water circulation of the generator system through the air heat exchange system of the energy storage system, so as to provide another branch for supplying steam to the generator system. When the boiler of the generator system cannot normally provide steam for the steam turbine, the water output by the cooling tower or / and the water output by the regenerator system can be vaporized through the energy storage system, and the vaporized steam is then transported to the inlet of the steam turbine, thereby ensuring the steam supply of the steam turbine, enabling the normal operation of the steam turbine, and further providing a guarantee for the normal power generation of the generator system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the cascade phase change energy storage system of the combined thermal power unit of the embodiment of the present disclosure (the boiler is working normally);

[0021] Figure 2 for Figure 1 The structural schematic diagram of the cascade phase change energy storage system of the combined thermal power unit shown (the boiler cannot work).

[0022] The reference numerals in the accompanying drawings represent the following:

[0023] 100. Cascade phase change energy storage system for combined thermal power units;

[0024] 10. Generator system; 11. Boiler; 12. Steam turbine; 13. Cooling tower; 14. Regenerator system; 15. Generator; 16. Gas turbine;

[0025] 20. Energy storage system; 21. Stepped energy storage tank; 22. Air heat exchange system; 221. High temperature heat exchanger; 222. Low temperature heat exchanger; 223. Heat release blower; 224. Air compressor; 23. Heat storage system; 231. Heat storage blower; 232. Ultra-high temperature electric heater; 233. Renewable energy equipment; 234. Heat storage heat exchanger;

[0026] L1, first low-temperature branch; L2, second low-temperature branch; H1, first high-temperature branch; H2, second high-temperature branch. DETAILED DESCRIPTION

[0027] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0028] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0029] Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

[0030] For ease of description, spatial relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figure, such as "inside", "outside", "inner side", "outer side", "below", "below", "above", "above", etc. Such spatial relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figure. For example, if the device in the figure is turned over, then the elements described as "below other elements or features" or "below other elements or features" will subsequently be oriented as "above other elements or features" or "above other elements or features". Therefore, the example term "below..." can include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or in other directions) and the spatial relative descriptors used in the text are interpreted accordingly.

[0031] like Figure 1As shown, an embodiment of the present disclosure provides a cascade phase change energy storage system 100 of a combined thermal power unit, the cascade phase change energy storage system 100 of the combined thermal power unit comprising: a generator system 10 and an energy storage system 20, specifically, the generator system 10 comprises: a boiler 11, a steam turbine 12, a cooling tower 13 and a regenerator system 14, the water circulation of the power generation system flows along the direction of the boiler 11, the steam turbine 12, the cooling tower 13, the regenerator system 14 and the boiler 11, the energy storage system 20 comprises a cascade heat storage tank and an air heat exchange system 22, the hot end outlet of the cascade heat storage tank is connected to the hot end inlet of the air heat exchange system 22, the air heat exchange system 22 is configured to vaporize the water output from the regenerator system 14 and transport it to the inlet of the steam turbine 12; and / or to vaporize the water output from the cooling tower 13 and transport it to the inlet of the steam turbine 12.

[0032] The cascade phase change energy storage system 100 of the combined thermal power unit of the embodiment of the present disclosure includes a generator system 10 and an energy storage system 20, wherein the generator system 10 includes a boiler 11, a steam turbine 12, a cooling tower 13 and a regenerator system 14, and the water cycle of the generator system 10 flows along the direction of the boiler 11, the steam turbine 12, the cooling tower 13 and the regenerator system 14, and the form of the water changes from gas to liquid, and finally returns to the boiler 11, and the form of the water changes from liquid to gas, thereby forming a water cycle; the energy storage system 20 0 comprises: a cascade heat storage tank and an air heat exchange system 22, the hot end outlet of the cascade heat storage tank is connected to the hot end inlet of the air heat exchange system 22, the air heat exchange system 22 can vaporize the water output by the regenerator system 14, and transport the vaporized water vapor to the inlet of the steam turbine 12, so as to provide energy for the steam turbine 12 to do work, or / and the air heat exchange system 22 can vaporize the water output by the cooling tower 13, and transport the vaporized water vapor to the inlet of the steam turbine 12, so as to provide energy for the steam turbine 12 to do work. The cascade phase change energy storage system 100 of the combined thermal power unit of this embodiment can transfer the heat energy of the cascade heat storage tank to the water cycle of the generator system 10 through the air heat exchange system 22 of the energy storage system 20, so as to provide another branch for supplying steam to the generator system 10. When the boiler 11 of the generator system 10 cannot normally provide steam for the steam turbine 12, the water output from the cooling tower 13 or / and the water output from the heat regenerator system 14 can be vaporized through the energy storage system 20, and the vaporized steam is then transported to the inlet of the steam turbine 12, thereby ensuring the steam supply of the steam turbine 12, allowing the steam turbine 12 to operate normally, and further providing a guarantee for the normal power generation of the generator system 10.

[0033] In some embodiments of the present disclosure, Figure 1As shown, the air heat exchange system 22 includes: a high-temperature heat exchanger 221, the hot end outlet of the cascade heat storage tank is used to connect to the hot end inlet of the high-temperature heat exchanger 221, the cold end inlet of the high-temperature heat exchanger 221 is connected to the outlet of the regenerator system 14, and the cold end outlet of the high-temperature heat exchanger 221 is connected to the inlet of the steam turbine 12. Specifically, the hot air of the cascade heat storage tank can be transported to the hot end inlet of the high-temperature heat exchanger 221 through the hot end outlet of the cascade heat storage tank, and the hot air transfers part of the heat to the water cycle of the generator system 10 through the high-temperature heat exchanger 221, and the hot air after heat dissipation is discharged through the cold end outlet of the high-temperature heat exchanger 221. At the same time, the water output from the outlet of the regenerator system 14 of the generator system 10 is transported to the high-temperature heat exchanger 221 through the first high-temperature branch H1, the water absorbs the heat of the hot air output from the stepped heat storage tank, the condensed water is vaporized to form steam, and then output through the hot end outlet of the high-temperature heat exchanger 221, and finally transported to the inlet of the turbine 12 through the second high-temperature branch H2 to provide steam for the turbine 12.

[0034] In some embodiments of the present disclosure, the air heat exchange system 22 includes: a high-temperature heat exchanger 221, the hot end outlet of the cascade heat storage tank is used to connect to the hot end inlet of the high-temperature heat exchanger 221, the cold end inlet of the high-temperature heat exchanger 221 is connected to the outlet of the cooling tower 13 (not shown in the figure), and the cold end outlet of the high-temperature heat exchanger 221 is connected to the inlet of the steam turbine 12. Specifically, the hot air of the cascade heat storage tank can be transported to the hot end inlet of the high-temperature heat exchanger 221 through the hot end outlet of the cascade heat storage tank, and the hot air transfers part of the heat to the water cycle of the generator system 10 through the high-temperature heat exchanger 221, and the hot air after heat dissipation is discharged through the cold end outlet of the high-temperature heat exchanger 221. At the same time, the condensed water output from the outlet of the cooling tower 13 of the generator system 10 is transported to the high-temperature heat exchanger 221, and the condensed water absorbs the heat of the hot air output from the cascade heat storage tank, and the condensed water is vaporized to form steam, and then output through the hot end outlet of the high-temperature heat exchanger 221, and finally enters the inlet of the steam turbine 12 to provide steam for the steam turbine 12.

[0035] In some embodiments of the present disclosure, the air heat exchange system 22 includes: a low-temperature heat exchanger 222, the cold end outlet of the high-temperature heat exchanger 221 is connected to the hot end inlet of the low-temperature heat exchanger 222, the cold end outlet of the low-temperature heat exchanger 222 is connected to the atmosphere, the cold end inlet of the low-temperature heat exchanger 222 is connected to the outlet of the cooling tower 13 through the first low-temperature branch L1, and the hot end outlet of the low-temperature heat exchanger 222 is connected to the hot end outlet of the regenerator system 14 through the second low-temperature branch L2, that is, the hot end outlet of the low-temperature heat exchanger 222 is connected to the inlet of the boiler 11 through the second low-temperature branch L2.

[0036] When the boiler 11 is operating normally, the air with a certain amount of heat discharged from the cold end outlet of the high-temperature heat exchanger 221 enters the low-temperature heat exchanger 222 through the hot end inlet of the low-temperature heat exchanger 222. The air passes through the low-temperature heat exchanger 222 to transfer heat to the water cycle of the generator system 10. After the air dissipates heat, it is discharged into the atmosphere through the cold end outlet of the low-temperature heat exchanger 222. At the same time, the condensed water at the outlet of the cooling tower 13 reaches the cold end inlet of the low-temperature heat exchanger 222 through the first low-temperature branch L1, and then enters the low-temperature heat exchanger 222 through the cold end inlet of the low-temperature heat exchanger 222. After the condensed water absorbs the heat of the air in the low-temperature heat exchanger 222, the temperature of the condensed water rises. The heated water is discharged into the second low-temperature branch L2 through the hot end outlet of the low-temperature heat exchanger 222, and enters the inlet of the boiler 11 through the second low-temperature branch L2.

[0037] When the boiler 11 is not operating normally (such as Figure 2 As shown), the condensed water at the outlet of the cooling tower 13 reaches the cold end inlet of the low-temperature heat exchanger 222 through the first low-temperature branch L1, and then enters the low-temperature heat exchanger 222 through the cold end inlet of the low-temperature heat exchanger 222. After the condensed water absorbs the heat of the air in the low-temperature heat exchanger 222, the temperature of the condensed water increases. The heated water is discharged into the second low-temperature branch L2 through the hot end outlet of the low-temperature heat exchanger 222, and enters the first high-temperature branch H1 connected thereto through the second low-temperature branch L2. The heated water enters the high-temperature heat exchanger 221 through the first high-temperature branch H1 and is heated, and then is discharged to the inlet of the steam turbine 12 through the second high-temperature branch H2.

[0038] In some embodiments of the present disclosure, the power generation system further includes a gas turbine 16, the hot end outlet of the cascade heat storage tank is connected to the inlet of the gas turbine 16, and the outlet of the gas turbine 16 is connected to the hot end inlet of the high-temperature heat exchanger 221. Specifically, the hot air of the cascade energy storage tank 21 reaches the inlet of the gas turbine 16 through its hot end outlet, enters the gas turbine 16 through the inlet of the gas turbine 16, and provides a gas medium for the gas turbine 16. After the hot air does work in the gas turbine 16, it is discharged to the hot end inlet of the high-temperature heat exchanger 221 through the outlet of the gas turbine 16, so as to use the residual heat of the hot air to vaporize part of the water in the water cycle of the generator system 10, thereby improving the utilization rate of the hot air.

[0039] In some embodiments of the present disclosure, the power generation system also includes a generator 15, and the generator 15 is connected to the gas turbine 16, and the generator 15 is connected to the steam turbine 12, that is, the gas turbine 16 and the steam turbine 12 jointly provide mechanical energy for the generator 15. When the mechanical energy provided by the steam turbine 12 to the generator 15 is less, the gas turbine 16 can also provide a certain amount of mechanical energy to the generator 15 to provide sufficient mechanical energy guarantee for the generator 15 to generate electricity.

[0040] In some embodiments of the present disclosure, the extraction steam outlet of the steam turbine 12 is connected to the hot end inlet of the regenerator system 14, and the cold end outlet of the regenerator system 14 is connected to the inlet of the boiler 11. The extraction steam of the steam turbine 12 is used to heat the condensed water flowing through the regenerator system 14 to increase the temperature of the condensed water. Specifically, the extraction steam of the steam turbine 12 reaches the hot end inlet of the regenerator system 14 through the extraction steam outlet of the steam turbine 12, enters the regenerator system 14 through the hot end inlet of the regenerator system 14, and transfers heat to the condensed water. Part of the heat of the extraction steam is absorbed and then discharged to the inlet of the boiler 11 through the cold end outlet of the regenerator system 14. When the boiler 11 is in an abnormal working state (such as Figure 2 As shown), water at the cold end outlet of the regenerator system 14 enters the cold end inlet of the high-temperature regenerator system 14 through the first high-temperature branch H1.

[0041] In some embodiments of the present disclosure, the energy storage system 20 further includes a heat storage system 23, which includes: a heat storage and heat supply fan 231, an ultra-high temperature electric heater 232, and a regenerative energy device 233. The inlet of the heat storage and heat supply fan 231 is connected to the atmosphere, the air outlet of the heat storage and heat supply fan 231 is connected to the inlet of the ultra-high temperature electric heater 232, the outlet of the ultra-high temperature electric heater 232 is connected to the hot end inlet of the cascade heat storage tank, and the regenerative energy device 233 is connected to the ultra-high temperature electric heater 232. Specifically, the heat storage and heat supply fan 231 transports air to the ultra-high temperature electric heater 232, the ultra-high temperature electric heater 232 heats the air, and the heated air enters the hot end inlet of the cascade energy storage tank 21 through the outlet of the ultra-high temperature electric heater 232, so as to enter the cascade energy storage tank 21, and then stores the heat in the cascade-distributed heat storage material. The ultra-high temperature air enters the step energy storage tank 21 from the bottom of the step energy storage tank 21, flows from the bottom to the top, and is discharged through the cold end outlet at the top of the step energy storage tank 21. Specifically, the renewable energy device 233 can be a renewable natural energy such as solar energy and wind energy to improve the utilization rate of renewable energy. It should be noted that the heating temperature range of the ultra-high temperature electric heater 232 in this embodiment is 1200°C to 1500°C.

[0042] From the bottom to the top, the phase change temperature of the heat storage material in the stepped energy storage tank 21 gradually decreases. For example, the stepped energy storage tank 21 contains three layers of heat storage materials, the phase change temperature of the heat storage material at the bottom is 1500°C, the phase change temperature of the heat storage material in the middle is 1200°C, and the phase change temperature of the heat storage material at the top is 1000°C. In the process of hot air flowing from the bottom to the top, the ultra-high temperature hot air first contacts the heat storage material at the bottom, the heat storage material at the bottom undergoes a phase change at 1500°C, and stores a large amount of heat energy in the heat storage material at the bottom. As the hot air that has lost part of its heat continues to flow to the heat storage material in the middle, the heat storage material in the middle undergoes a phase change at 1200°C, and stores a large amount of heat energy in the heat storage material in the middle. The hot air that has lost a large amount of heat continues to flow to the heat storage material at the top, the heat storage material at the top undergoes a phase change at 1000°C, and stores a large amount of heat energy in the heat storage material at the top. After the hot air stores most of the heat in the stepped heat storage material, some heat still remains. The hot air with the remaining heat is discharged through the cold end outlet of the stepped energy storage tank 21.

[0043] In some embodiments of the present disclosure, the heat storage system 23 also includes a heat storage heat exchanger 234, the hot end inlet of the heat storage heat exchanger 234 is connected to the cold end outlet of the stepped heat storage tank, the hot air flows through the stepped energy storage tank 21 and stores most of the heat in the stepped material, and the hot air with the remaining heat is discharged to the hot end inlet of the heat storage heat exchanger 234 through the cold end outlet of the stepped energy storage tank 21, and the heat is transferred to other fluids through the heat storage heat exchanger 234 to improve the utilization rate of thermal energy. After the heat of the hot air is absorbed, it is discharged into the atmosphere through the cold end outlet of the heat storage heat exchanger 234.

[0044] In some embodiments of the present disclosure, the air heat exchange system 22 also includes a heat release blower 223 and an air compressor 224. The inlet of the heat release blower 223 is connected to the air, and the outlet of the heat release blower 223 is connected to the inlet of the air compressor 224. The outlet of the air compressor 224 is connected to the cold end inlet of the stepped heat storage tank. Specifically, the heat release blower 223 delivers air to the air compressor 224, and the air compressor 224 compresses the air and delivers it to the cold end inlet of the stepped energy storage tank 21. The compressed air flows from the top to the bottom of the stepped energy storage tank 21, absorbs the heat of each level of energy storage material during the flow of the compressed air, and finally discharges the high-heat air through the hot end outlet at the bottom of the stepped energy storage tank 21.

[0045] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and substance of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A cascade phase change energy storage system for a combined thermal power unit, characterized in that: The cascade phase change energy storage system of the combined thermal power unit comprises: A generator system, the generator system comprising: a boiler, a steam turbine, a cooling tower and a regenerator system, wherein the water circulation of the power generation system flows along the direction of the boiler, the steam turbine, the cooling tower, the regenerator system and the boiler; An energy storage system, the energy storage system comprising a cascade heat storage tank and an air heat exchange system, the hot end outlet of the cascade heat storage tank is connected to the hot end inlet of the air heat exchange system, and the air heat exchange system is configured to vaporize water output from the regenerator system and transport it to the inlet of the steam turbine; and / or to vaporize water output from the cooling tower and transport it to the inlet of the steam turbine.

2. The cascade phase change energy storage system of the combined thermal power unit according to claim 1 is characterized in that: The air heat exchange system comprises: A high-temperature heat exchanger, wherein the hot end outlet of the stepped heat storage tank is used to connect to the hot end inlet of the high-temperature heat exchanger, the cold end inlet of the high-temperature heat exchanger is connected to the outlet of the cooling tower, and the cold end outlet of the high-temperature heat exchanger is connected to the inlet of the steam turbine.

3. The cascade phase change energy storage system of a combined thermal power unit according to claim 1, characterized in that: The air heat exchange system comprises: A high-temperature heat exchanger, wherein the hot end outlet of the stepped heat storage tank is used to connect to the hot end inlet of the high-temperature heat exchanger, the cold end inlet of the high-temperature heat exchanger is connected to the outlet of the regenerator system, and the cold end outlet of the high-temperature heat exchanger is connected to the inlet of the steam turbine.

4. The cascade phase change energy storage system of a combined thermal power unit according to claim 2 or 3, characterized in that: The air heat exchange system comprises: A low-temperature heat exchanger, wherein the cold end outlet of the high-temperature heat exchanger is connected to the hot end inlet of the low-temperature heat exchanger, the cold end outlet of the low-temperature heat exchanger is connected to the atmosphere, the cold end inlet of the low-temperature heat exchanger is connected to the outlet of the cooling tower, and the hot end outlet of the low-temperature heat exchanger is connected to the inlet of the boiler.

5. The cascade phase change energy storage system of a combined thermal power unit according to claim 2 or 3, characterized in that: The power generation system further comprises a gas turbine, the hot end outlet of the stepped heat storage tank is connected to the inlet of the gas turbine, and the outlet of the gas turbine is connected to the hot end inlet of the high temperature heat exchanger.

6. The cascade phase change energy storage system of the combined thermal power unit according to claim 5, characterized in that: The power generation system further includes a generator connected to the gas turbine, and the generator is connected to the steam turbine.

7. The cascade phase change energy storage system of a combined thermal power unit according to claim 1, characterized in that: The steam extraction outlet of the steam turbine is connected to the hot end inlet of the regenerator system, and the cold end outlet of the regenerator system is connected to the inlet of the boiler.

8. The cascade phase change energy storage system of a combined thermal power unit according to claim 1, characterized in that: The energy storage system also includes a heat storage system, which includes: a heat storage fan, an ultra-high temperature electric heater and a renewable energy device. The air outlet of the heat storage fan is connected to the inlet of the ultra-high temperature electric heater, the outlet of the ultra-high temperature electric heater is connected to the hot end inlet of the stepped heat storage tank, and the renewable energy device is connected to the ultra-high temperature electric heater.

9. The cascade phase change energy storage system of a combined thermal power unit according to claim 1, characterized in that: The heat storage system also includes a heat storage heat exchanger, and the hot end inlet of the heat storage heat exchanger is connected to the cold end outlet of the stepped heat storage tank.

10. The cascade phase change energy storage system of a combined thermal power unit according to claim 1, characterized in that: The air heat exchange system also includes a heat release blower and an air compressor, the inlet of the heat release blower is connected to the air, the outlet of the heat release blower is connected to the inlet of the air compressor, and the outlet of the air compressor is connected to the cold end inlet of the stepped heat storage tank.

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