A steam-electric coupled molten salt heat storage peak-shaving system for a thermal power unit and its working method

Abstract

The present invention discloses a steam-electric coupled molten salt heat storage and peak-shaving system for a thermal power unit and its operating method. The system includes a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a condenser, a condensing pump, a low-pressure heating unit, a feedwater pump, a high-pressure heating unit, a generator, a molten salt cold tank, a low-temperature molten salt pump, a steam cooler, a bypass regulating valve, a molten salt electric heater, a molten salt hot tank, a high-temperature molten salt pump, and a feedwater heater. The present invention reduces the amount of electricity consumed by the unit through steam extraction and electricity consumption. It can store heat in large capacity, for a long time, and at low cost, achieving deep peak-shaving of the unit. At the same time, the stored heat energy heats the boiler feedwater, reducing high-pressure steam extraction and reducing the unit's heat consumption, thus achieving good economic benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage, and in particular relates to a steam-electric coupled molten salt heat storage peak-shaving system for a thermal power unit and a working method thereof. Background Art

[0002] To conserve energy and reduce emissions, higher requirements are being placed on the flexibility of coal-fired power units. To further enhance flexibility and regulation capabilities and promote the clean, low-carbon transformation of the power industry, coal-fired power units need to be retrofitted and upgraded. When retrofitting and upgrading coal-fired power units, all new units must be designed with flexibility, and existing units should be retrofitted with flexibility as much as possible. When retrofitting and upgrading coal-fired power units, the general requirement for peak-shaving capacity under pure condensing conditions is a minimum power output of 35% of rated load. During the heating season, heating-use thermal power units should strive to achieve a minimum power output of 40% of rated load for a single six-hour day through thermoelectric decoupling. Other types of units should take measures to minimize their minimum power output.

[0003] Coal-fired power units, due to their large base capacity, require large and high-quality energy storage for deep peak shaving. Existing electrochemical energy storage and hot water tank energy storage cannot meet these requirements. However, molten salt thermal storage, due to its large capacity and high thermal energy quality, is suitable for deep peak shaving of coal-fired power units. Molten salt thermal storage is a sensible heat storage method using molten inorganic salts, which uses changes in the molten salt temperature to store heat. It typically uses a dual-tank molten salt thermal storage system. Molten salt thermal storage is primarily used in solar thermal power plants, but is rarely used in large-scale coal-fired power units for peak shaving.

[0004] Coal-fired power units generally operate in sliding pressure mode. Under low-load conditions, the main steam (hot resteam) pressure is low, and the steam condensation temperature is low. For example, under THA conditions, the main steam pressure of a certain ultra-supercritical unit is 25.2 MPa and the hot resteam pressure is 5.4 MPa. However, under 40% THA conditions, the main steam pressure drops to 10 MPa and the hot resteam pressure drops to 2.2 MPa, with corresponding steam condensation temperatures of 311°C and 217°C, respectively. Under THA conditions, the main steam pressure of a certain subcritical unit is 16.7 MPa and the hot resteam pressure is 3.3 MPa. However, under 40% THA conditions, the main steam pressure drops to 8.6 MPa and the hot resteam pressure drops to 1.3 MPa, with corresponding steam condensation temperatures of 300°C and 192°C, respectively. Of the heat contained in steam, sensible heat accounts for approximately 30%, and latent heat accounts for 70%. To store latent heat of steam, the outlet temperature of the hot molten salt from the steam condenser must be below the condensation temperature corresponding to the steam pressure. At the same time, the inlet temperature of the cold molten salt from the steam condenser must be above the condensation point of the molten salt plus a safety margin of approximately 40°C. Therefore, when storing latent heat of steam, the temperature rise of the molten salt in a molten salt thermal storage system is generally between 180°C and 300°C. This large latent heat volume results in a large hourly flow rate of molten salt. This, combined with the long-term peak-shaving operation of coal-fired power plants, results in a large total amount of molten salt, high project investment, and low feasibility. Molten salt thermal storage in coal-fired power plants can only store sensible heat of steam, resulting in a low heat storage ratio and limited peak-shaving capability. Furthermore, under low-load conditions, the superheater and reheater tube walls of coal-fired power plants face the risk of overheating, severely limiting the amount of main steam extraction. Extracting too much hot reheat steam can also cause changes in the axial thrust of the turbine, similarly limiting the amount of hot reheat steam that can be extracted. In the process of steam-electric coupling heating of molten salt, the final temperature of the hot molten salt is affected by steam heating and electric heating at the same time, causing the final temperature of the hot molten salt to be unstable, thereby causing the temperature of the hot molten salt storage tank to fluctuate, which is detrimental to its safety.

[0005] In summary, the peak-shaving capacity of the molten salt heat storage technology of coal-fired power units is limited by the steam temperature, molten salt temperature and steam extraction volume. The peak-shaving capacity is limited and deep peak-shaving cannot be achieved. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a steam-electric coupled molten salt heat storage peak-shaving system for a thermal power unit and its working method. The system can store heat in a large capacity, for a long time and at a low cost to achieve deep peak-shaving of the unit. At the same time, the stored heat energy heats the boiler feed water, reduces high-pressure steam extraction, reduces the heat consumption of the unit, and has good economic benefits.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A steam-electric coupled molten salt heat storage peak-shaving system for a thermal power unit, comprising a thermal power unit, a molten salt heat storage and release system, a steam condenser, and a heat network water heater;

[0009] The molten salt heat storage and heat release system includes a molten salt cold tank, a steam cooler, a molten salt hot tank and a feed water heater. The outlet of the molten salt cold tank is provided with a low-temperature molten salt pump, the outlet of the low-temperature molten salt pump is connected to the cold inlet of the steam cooler, the cold outlet of the steam cooler is connected to the inlet of the molten salt hot tank, the outlet of the molten salt hot tank is provided with a high-temperature molten salt pump, the outlet of the high-temperature molten salt pump is connected to the hot inlet of the feed water heater, and the hot outlet of the feed water heater is connected to the inlet of the molten salt cold tank; a molten salt electric heater is provided on the pipeline connecting the cold outlet of the steam cooler and the inlet of the molten salt hot tank, a bypass molten salt pipe is connected between the cold inlet and the cold outlet of the steam cooler, and a bypass regulating valve is provided on the bypass molten salt pipe; the hot inlet of the steam cooler is connected to the steam outlet in the thermal power unit; the cold inlet and the cold outlet of the feed water heater are respectively connected to the inlet and outlet of the high-pressure heating unit of the thermal power unit; the power input end of the molten salt electric heater is connected to the generator of the thermal power unit;

[0010] The cold inlet and cold outlet of the steam condenser are respectively connected to the inlet and outlet of the low-pressure heating unit of the thermal power unit. The hot outlet of the steam cooler is divided into two routes, one of which is connected to the hot inlet of the hot network water heater, and the other is connected to the hot inlet of the steam condenser. The hot outlet of the steam condenser and the hot outlet of the hot network water heater are both connected to the pipelines of condensate and / or hot network water of the thermal power unit.

[0011] Preferably, the cold outlet of the steam cooler is provided with a first temperature measuring device, the first temperature measuring device is connected to the No. 1 controller, and the No. 1 controller is connected to the low-temperature molten salt pump.

[0012] Preferably, a second temperature measuring device is provided on the pipeline connecting the cold outlet of the steam cooler and the inlet of the molten salt hot tank downstream of the molten salt electric heater. The second temperature measuring device is connected to the No. 2 controller, and the No. 2 controller is connected to the molten salt electric heater.

[0013] Preferably, the second controller adopts a power regulating device, and the second controller is arranged on the line connecting the power input end of the molten salt electric heater and the generator.

[0014] Preferably, the hot inlet of the steam cooler is connected to the steam outlet of the boiler and / or the hot re-steam outlet of the boiler.

[0015] Preferably, the low-pressure heating unit of the thermal power unit is composed of one or more stages of low-pressure heaters connected in series, the pipeline connection point between the low-pressure heating unit and the steam condenser is located at the inlet or outlet of any low-pressure heater, water is taken at a single point or multiple points, and a regulating valve is provided on the water intake pipeline; the high-pressure heating unit is composed of one or more stages of high-pressure heaters connected in series, the pipeline connection point between the high-pressure heating unit and the feed water heater is located at the inlet or outlet of any high-pressure heater, water is taken at a single point or multiple points, and a regulating valve is provided on the water intake pipeline.

[0016] Preferably, the hot outlet of the steam condenser and the hot outlet of the hot network water heater are connected to the condenser, deaerator, interstage drain pipe of the high-pressure heating unit or the interstage drain pipe of the low-pressure heating unit of the thermal power unit.

[0017] Preferably, the thermal power unit includes a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a condenser, a condensate pump, a low-pressure heating unit, a deaerator, a feed water pump, a high-pressure heating unit and a generator; the steam outlet of the boiler is connected to the high-pressure cylinder inlet through a pipeline, the high-pressure cylinder outlet is connected to the boiler reheat steam inlet through a pipeline, the boiler reheat steam outlet is connected to the intermediate-pressure cylinder inlet through a pipeline, the intermediate-pressure cylinder, the low-pressure cylinder and the condenser are connected in sequence through pipelines, the condenser outlet, the condensate pump, the low-pressure heating unit, the deaerator, the feed water pump and the high-pressure heating unit are connected in sequence through pipelines, and the high-pressure heating unit outlet is connected to the boiler feed water inlet through a pipeline; the main shafts of the high-pressure cylinder, the intermediate-pressure cylinder and the low-pressure cylinder are connected to the generator.

[0018] The working method of the steam-electric coupled molten salt heat storage peak-shaving system of the thermal power unit of the present invention includes the following steps:

[0019] During peak load regulation, the thermal power unit provides steam to the steam cooler, and water to the steam condenser. The low-temperature molten salt pump and the molten salt electric heater are turned on. The cold molten salt drawn from the molten salt cold tank by the low-temperature molten salt pump is heated by the steam cooler and the molten salt electric heater. After absorbing heat, the cold molten salt becomes hot molten salt and is stored in the molten salt hot tank. The bypass regulating valve controls the bypass molten salt flow of the steam cooler to control the peak load depth.

[0020] When the unit is not in peak load regulation, the high-temperature molten salt pump is turned on to transport the hot molten salt in the molten salt hot tank to the feedwater heater for heat exchange. A portion of the water at the inlet of the high-pressure heating unit is heated by the feedwater heater and then flows to the outlet of the high-pressure heating unit. The molten salt after heat exchange in the feedwater heater flows back to the molten salt cold tank.

[0021] Other operating conditions: The molten salt heat storage and release system and the heat network water heater are isolated from the thermal power unit, and the thermal power unit operates normally.

[0022] Preferably, the heating temperature of the molten salt by the molten salt electric heater is not higher than the maximum operating temperature of the molten salt; by controlling the speed of the low-temperature molten salt pump, the set value of the outlet steam temperature of the steam cooler is not lower than the saturation temperature at the set value corresponding to the pressure plus a margin of more than 5°C.

[0023] The present invention has the following beneficial effects:

[0024] The steam-electric coupled molten salt heat storage and peak-shaving system of the thermal power unit of the present invention utilizes molten salt to simultaneously store steam thermal energy and electric energy, thereby realizing deep peak-shaving of the thermal power unit and improving the flexibility of the thermal power unit. The sensible heat of steam is stored in molten salt through a steam cooler, and the latent heat of steam is used to heat condensate or hot network water through a steam condenser or a hot network water heater, thereby greatly reducing the amount of molten salt in the heat storage process. The molten salt is heated by the self-generated electricity of the unit through the molten salt electric heater, thereby reducing the online power consumption of the unit and improving the peak-shaving capability of the system. A part of the water at the inlet of the high-pressure heating unit is heated by the feed water heater and then flows to the outlet of the high-pressure heating unit. In this way, the heat stored in the molten salt can be used to heat the boiler feed water of the thermal power unit through the feed water heater, reducing the steam extraction of the high-pressure heater and reducing the heat consumption of the thermal power unit. The power consumption of the molten salt electric heater is controlled by the hot molten salt temperature measuring point, and the steam outlet temperature is controlled by the cold molten salt pump, thereby achieving temperature stability of the hot molten salt tank and ensuring its safety. In summary, the present invention extracts the main steam or hot resteam from the unit, stores the sensible heat of the steam in molten salt, and uses the latent heat of the steam to heat condensate or hot network water, reducing the amount of steam used for power generation and the power generation of the unit. On this basis, the system uses the molten salt electric heating system to utilize the self-generated electricity of the unit to heat the molten salt, reducing the amount of electricity connected to the grid and improving the peak-shaving capacity of the system. The system is capable of large-capacity, high-quality heat storage, achieving deep peak-shaving of the unit. The system's molten salt flow rate is in the hundreds of tons, significantly reducing project investment and making it feasible. At the same time, the stored heat energy heats the boiler feed water, reducing high-pressure steam extraction and reducing the heat consumption of the unit, thus achieving good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a structural diagram of the steam-electric coupled molten salt heat storage peak-shaving system for a thermal power unit of the present invention.

[0026] In the figure, 1 is a boiler, 2 is a high-pressure cylinder, 3 is a medium-pressure cylinder, 4 is a low-pressure cylinder, 5 is a condenser, 6 is a condensate pump, 7 is a low-pressure heating unit, 8 is a deaerator, 9 is a feed water pump, 10 is a high-pressure heating unit, 11 is a generator, 12 is a molten salt cold tank, 13 is a low-temperature molten salt pump, 14 is a steam condensing device, 15 is a bypass regulating valve, 16 is a molten salt electric heater, 17 is a molten salt hot tank, 18 is a high-temperature molten salt pump, 19 is a feed water heater, 20 is a steam condenser, 21 is a heat network water heater, 22 is a No. 1 controller, 23 is a No. 2 controller, and 24 is a power regulation device. DETAILED DESCRIPTION

[0027] The present invention is described in further detail below with reference to the accompanying drawings:

[0028] like Figure 1As shown, the steam-electric coupled molten salt heat storage and peak-shaving system of a thermal power unit of the present invention includes a boiler 1, a high-pressure cylinder 2, a medium-pressure cylinder 3, a low-pressure cylinder 4, a condenser 5, a condensate pump 6, a low-pressure heating unit 7, a deaerator 8, a feedwater pump 9, a high-pressure heating unit 10, and a generator 11; it also includes a molten salt cold tank 12, a low-temperature molten salt pump 13, a steam cooler 14, a bypass regulating valve 15, a molten salt electric heater 16, a molten salt hot tank 17, a high-temperature molten salt pump 18, a feedwater heater 19, a steam condenser 20, and a heat network water heater 21; it also includes a No. 1 controller 22, a No. 2 controller 23 and a power regulation device 24.

[0029] The steam outlet of boiler 1 is connected to the inlet of high-pressure cylinder 2 through a pipeline, the outlet of high-pressure cylinder 2 is connected to the reheat steam inlet of boiler 1 through a pipeline, the reheat steam outlet of boiler 1 is connected to the inlet of medium-pressure cylinder 3 through a pipeline, the medium-pressure cylinder 3, the low-pressure cylinder 4 and the condenser 5 are connected in sequence through pipelines, the outlet of condenser 5, condensate pump 6, low-pressure heating unit 7, deaerator 8, feed water pump 9 and high-pressure heating unit 10 are connected in sequence through pipelines, and the outlet of high-pressure heating unit 10 is connected to the feed water inlet of boiler 1 through a pipeline; the high-pressure cylinder 2, the medium-pressure cylinder 3 and the low-pressure cylinder 4 are connected in sequence through pipelines. The main shaft is connected to the generator 11; the low-pressure heating unit 7 is composed of one or more low-pressure heaters connected in series, and the pipe connection point between it and the steam condenser 20 is located at the inlet or outlet of any low-pressure heater, and water can be taken at a single point or multiple points. A regulating valve is provided on the water intake pipeline, and the water intake temperature and flow rate are adjustable; the high-pressure heating unit 10 is composed of one or more high-pressure heaters connected in series, and the pipe connection point between it and the feed water heater 19 is located at the inlet or outlet of any high-pressure heater, and water can be taken at a single point or multiple points. A regulating valve is provided on the water intake pipeline, and the water intake temperature and flow rate are adjustable.

[0030] The molten salt cold tank 12, the low-temperature molten salt pump 13, the steam cooler 14, the molten salt electric heater 16, the molten salt hot tank 17, the high-temperature molten salt pump 18 and the molten salt side of the feedwater heater 19 are connected in sequence through a molten salt pipeline to form a closed loop, wherein a bypass is provided between the inlet and outlet of the molten salt side (heat absorption side) of the steam cooler 14, and a bypass regulating valve 15 is provided on the bypass; a temperature measuring device is provided on the molten salt pipeline at the outlet of the molten salt electric heater 16;

[0031] The steam side (exothermic side) inlet of the steam cooler 14 is connected to the steam outlet of the boiler 1 through a pipeline. The steam extraction point of the steam cooler 14 is located at the steam outlet of the boiler 1 or the hot re-steam outlet of the boiler 1. The steam side (exothermic side) outlet is divided into two routes, namely, they are connected to the steam inlet of the steam condenser 20 and the steam inlet of the hot network water heater 21 through pipelines respectively. A temperature measuring device is provided on the outlet main pipe on the steam side of the steam cooler 14; the condensate outlet of the steam condenser 20 and the condensate outlet of the hot network water heater 21 are combined through a pipeline and connected to the interstage drain pipe of the condenser 5 or the deaerator 8 or the high-pressure heating unit 10 or the interstage drain pipe of the low-pressure heating unit 7; the hot network water inlet and outlet of the hot network water heater 21 are provided with a hot network inlet and return pipe; the condensate inlet of the steam condenser 20 is connected to the inlet of the low-pressure heating unit 7 through a pipeline, and the condensate outlet of the steam condenser 20 is connected to the outlet of the low-pressure heating unit 7 through a pipeline. The water side (heat absorption side) inlet of the feedwater heater 19 is connected to the inlet of the high-pressure heating unit 10 through a pipeline, and the water side outlet of the feedwater heater 19 is connected to the outlet of the high-pressure heating unit 10 through a pipeline.

[0032] The terminals of the molten salt electric heater 16, the power regulator 24, and the generator 11 are connected by cables. The molten salt electric heater 16 uses self-generated energy from the thermal power unit, which is then regulated by a transformer to heat the molten salt. The outlet temperature of the molten salt electric heater 16 is controlled by a second controller 23. The setpoint value of the outlet temperature of the molten salt electric heater 16 is not higher than the maximum operating temperature of the molten salt.

[0033] In the steam-electricity-coupled molten salt thermal storage and peak-shaving system for thermal power units of the present invention, the sensible heat of steam is stored in the molten salt via the steam cooler 14, while the latent heat of steam is stored in condensate via the steam condenser 20 or heated via the hot water network heater 21. The speed of the low-temperature molten salt pump 13 is linked to the outlet steam temperature of the steam cooler 14 via a first controller 22. The outlet steam temperature of the steam cooler 14 is set to a value not lower than the saturation temperature at the corresponding pressure plus a margin of 5°C.

[0034] In the above solution, the boiler 1 is a device for generating steam, such as a coal-fired boiler, a gas-fired boiler, an oil-fired boiler, a biomass boiler, a waste heat boiler or an electrode boiler.

[0035] like Figure 1 As shown, the working method of the steam-electric coupled molten salt heat storage peak-shaving system of a thermal power unit of the present invention includes the following process:

[0036] When the unit is peak-shaving, the inlet and outlet steam pipes of the steam cooler 14 are opened, the inlet and outlet water pipes of the steam condenser 20 and the hot network water heater 21, and the condensate collecting pipe of the steam condenser 20 and the hot network water heater 21 are opened, and the low-temperature molten salt pump 13 and the molten salt electric heater 16 are turned on. The sensible heat energy and electrical energy of the steam are converted into molten salt thermal energy, and the latent heat energy of the steam is converted into sensible heat of condensate or sensible heat of hot network water. The amount of steam used for power generation by the unit is reduced, and the power generation power is reduced. At the same time, the electricity produced by the unit is heated by the molten salt electric heater 16 to further reduce the unit's online power consumption and achieve deep peak-shaving of the unit. The power consumption of the molten salt electric heater 16 is controlled by the No. 2 controller 23, and the set value is not higher than the maximum operating temperature of the molten salt. The speed of the low-temperature molten salt pump 13 and the outlet steam temperature of the steam cooler 14 are controlled by the No. 1 controller 22, and the set value is not lower than the saturation temperature at the corresponding pressure plus a margin of more than 5°C. The bypass regulating valve 15 controls the bypass molten salt flow of the steam cooler 14 to achieve control of the overall peak regulation depth of the system.

[0037] When the unit is not peak-shaving, the high-temperature molten salt pump 18 is turned on, and the molten salt flows from the molten salt hot tank 17 to the molten salt cold tank 12 through the feed water heater 19, and the inlet and outlet feed water pipes of the feed water heater 19 are opened; the sensible heat of the molten salt is converted into the sensible heat of the feed water. Under the condition that the evaporation amount of the boiler remains unchanged, the steam extraction amount of the high-pressure heating unit 10 is reduced, the power generation steam amount is increased, and the heat consumption of the unit is reduced.

[0038] Under other operating conditions, shut down the pipelines and equipment of the heat storage peak-shaving system, keep the heating system on, isolate the heat storage peak-shaving system from the thermal power units, and allow the thermal power units to operate normally.

[0039] From the above, it can be seen that the present invention extracts the main steam or hot re-steam of the unit, and the sensible heat of the steam is stored in the molten salt, while the latent heat of the steam heats the condensate or hot network water, reducing the amount of steam used for power generation and the power generation of the unit. On this basis, the system uses the molten salt electric heating system to utilize the self-generated electricity of the unit to heat the molten salt, further increasing the temperature of the hot molten salt, reducing the amount of molten salt used, greatly reducing the amount of electricity connected to the grid of the unit, and improving the peak-shaving capacity of the system. The power consumption of the molten salt electric heater is controlled by the hot molten salt temperature measuring point, and the steam outlet temperature is controlled by the cold molten salt pump to achieve the temperature stability of the hot molten salt tank and ensure its safety. The system can store heat in large capacity, for a long time and at low cost, realize deep peak regulation of the unit, and the molten salt flow rate of the system is hundreds of tons, which greatly reduces the project investment and is feasible. At the same time, the stored heat energy heats the boiler feed water, reduces the high-pressure steam extraction, reduces the heat consumption of the unit, and has good economic benefits.

Claims

1. A steam-electric coupled molten salt heat storage peak-shaving system for a thermal power unit, characterized in that: It includes a thermal power unit, a molten salt heat storage and heat release system, a steam condenser (20) and a heat network water heater (21); The molten salt heat storage and heat release system includes a molten salt cold tank (12), a steam cooler (14), a molten salt hot tank (17) and a feed water heater (19). The outlet of the molten salt cold tank (12) is provided with a low-temperature molten salt pump (13). The outlet of the low-temperature molten salt pump (13) is connected to the cold inlet of the steam cooler (14). The cold outlet of the steam cooler (14) is connected to the inlet of the molten salt hot tank (17). The outlet of the molten salt hot tank (17) is provided with a high-temperature molten salt pump (18). The outlet of the high-temperature molten salt pump (18) is connected to the hot inlet of the feed water heater (19). The hot outlet of the feed water heater (19) is connected to the molten salt cold tank (12). ); a molten salt electric heater (16) is provided on a pipeline connecting the cold outlet of the steam cooler (14) and the inlet of the molten salt hot tank (17); a bypass molten salt pipe is connected between the cold inlet and the cold outlet of the steam cooler (14); a bypass molten salt pipe is provided on the bypass molten salt pipe; the hot inlet of the steam cooler (14) is connected to the steam outlet of the thermal power unit; the cold inlet and the cold outlet of the feedwater heater (19) are respectively connected to the inlet and outlet of the high-pressure heating unit (10) of the thermal power unit; the power input end of the molten salt electric heater (16) is connected to the generator (11) of the thermal power unit; The cold inlet and cold outlet of the steam condenser (20) are respectively connected to the inlet and outlet of the low-pressure heating unit (7) of the thermal power unit. The hot outlet of the steam cooler (14) is divided into two paths, one of which is connected to the hot inlet of the hot network water heater (21), and the other is connected to the hot inlet of the steam condenser (20). The hot outlet of the steam condenser (20) and the hot outlet of the hot network water heater (21) are both connected to the pipeline of condensate water and / or hot network water of the thermal power unit. A first temperature measuring device is provided at the cold outlet of the steam cooler (14), the first temperature measuring device is connected to a No. 1 controller (22), and the No. 1 controller (22) is connected to a low-temperature molten salt pump (13); A second temperature measuring device is provided on a pipeline connecting the cold outlet of the steam cooler (14) and the inlet of the molten salt hot tank (17) downstream of the molten salt electric heater (16). The second temperature measuring device is connected to a second controller (23), and the second controller (23) is connected to the molten salt electric heater (16).

2. A steam-electric coupled molten salt heat storage peak-shaving system for a thermal power unit according to claim 1, characterized in that: The second controller (23) uses a power regulating device (24), and the second controller (23) is set on the line connecting the power input end of the molten salt electric heater (16) and the generator (11).

3. The steam-electric coupled molten salt heat storage peak-shaving system for thermal power generation units according to claim 1, characterized in that: The hot inlet of the steam cooler (14) is connected to the steam outlet of the boiler (1) and / or the hot resteam outlet of the boiler (1).

4. The steam-electric coupled molten salt heat storage peak-shaving system for thermal power generation units according to claim 1, characterized in that: The low-pressure heating unit (7) of the thermal power unit is composed of one or more low-pressure heaters connected in series. The pipe connection point between the low-pressure heating unit (7) and the steam condenser (20) is located at the inlet or outlet of any low-pressure heater. Water is taken at a single point or multiple points, and a regulating valve is provided on the water intake pipeline. The high-pressure heating unit (10) is composed of one or more high-pressure heaters connected in series. The pipe connection point between the high-pressure heating unit (10) and the feed water heater (19) is located at the inlet or outlet of any high-pressure heater. Water is taken at a single point or multiple points, and a regulating valve is provided on the water intake pipeline.

5. A steam-electric coupled molten salt heat storage peak-shaving system for thermal power generation units according to claim 4, characterized in that: The hot outlet of the steam condenser (20) and the hot outlet of the hot network water heater (21) are connected to the condenser (5), the deaerator (8), the interstage drain pipe of the high-pressure heating unit (10) or the interstage drain pipe of the low-pressure heating unit (7) of the thermal power unit.

6. A steam-electric coupled molten salt heat storage peak-shaving system for a thermal power unit according to any one of claims 1 to 5, characterized in that: The thermal power unit comprises a boiler (1), a high-pressure cylinder (2), an intermediate-pressure cylinder (3), a low-pressure cylinder (4), a condenser (5), a condensate pump (6), a low-pressure heating unit (7), a deaerator (8), a feed water pump (9), a high-pressure heating unit (10) and a generator (11); the steam outlet of the boiler (1) is connected to the inlet of the high-pressure cylinder (2) through a pipeline, the outlet of the high-pressure cylinder (2) is connected to the reheat steam inlet of the boiler (1) through a pipeline, the reheat steam outlet of the boiler (1) is connected to the inlet of the intermediate-pressure cylinder (3) through a pipeline, the intermediate-pressure cylinder (3), the low-pressure cylinder (4) and the condenser (5) are connected in sequence through pipelines, the outlet of the condenser (5), the condensate pump (6), the low-pressure heating unit (7), the deaerator (8), the feed water pump (9) and the high-pressure heating unit (10) are connected in sequence through pipelines, and the outlet of the high-pressure heating unit (10) is connected to the feed water inlet of the boiler (1) through a pipeline; the main shafts of the high-pressure cylinder (2), the intermediate-pressure cylinder (3) and the low-pressure cylinder (4) are connected to the generator (11).

7. The operating method of the steam-electric coupled molten salt heat storage peak-shaving system for a thermal power unit according to any one of claims 1 to 6, characterized in that: The process includes the following: When the unit is in peak load regulation, the thermal power unit provides steam to the steam cooler (14), and the thermal power unit supplies water to the steam condenser (20). The low-temperature molten salt pump (13) and the molten salt electric heater (16) are turned on. The cold molten salt drawn from the molten salt cold tank (12) by the low-temperature molten salt pump (13) is heated by the steam cooler (14) and the molten salt electric heater (16). The cold molten salt after absorbing heat is converted into hot molten salt and stored in the molten salt hot tank (17). The bypass molten salt flow of the steam cooler (14) is controlled by the bypass regulating valve (15) to control the peak load depth. When the unit is not in peak load regulation, the high-temperature molten salt pump (18) is turned on, and the high-temperature molten salt pump (18) transports the hot molten salt in the molten salt hot tank (17) to the feed water heater (19) for heat exchange. A portion of the water at the inlet of the high-pressure heating unit (10) is heated by the feed water heater (19) and then flows to the outlet of the high-pressure heating unit (10). The molten salt after heat exchange in the water heater (19) flows back to the molten salt cold tank (12); Other operating conditions: the molten salt heat storage and release system and the heat network water heater (21) are isolated from the thermal power unit, and the thermal power unit operates normally.

8. The operating method of the steam-electric coupled molten salt heat storage peak-shaving system for thermal power generation units according to claim 7, characterized in that: The heating temperature of the molten salt by the molten salt electric heater (16) is not higher than the maximum operating temperature of the molten salt; by controlling the rotation speed of the low-temperature molten salt pump (13), the set value of the outlet steam temperature of the steam cooler (14) is not lower than the saturation temperature at the set value corresponding to the pressure plus a margin of more than 5°C.

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