Thermal power generating unit combined frequency modulation and peak regulation system and operation method thereof

Abstract

The invention provides a thermal power generating unit combined frequency modulation and peak regulation system and an operation method thereof.The thermal power generating unit combined frequency modulation and peak regulation system comprises a thermal power generating unit, a frequency modulation electric heater, a frequency modulation fused salt storage tank, a peak regulation electric heater, a cold salt tank, a hot salt tank and a fused salt heat exchanger; when a lower discharge port of the frequency-modulated fused salt storage tank is communicated with a feed port of the frequency-modulated electric heater, fused salt is extracted from the lower part in the frequency-modulated fused salt storage tank to the frequency-modulated electric heater to be heated, and the fused salt absorbs heat from the frequency-modulated electric heater to be heated and then is discharged into the upper part in the frequency-modulated fused salt storage tank; and when the lower discharge port of the frequency-modulated fused salt storage tank is communicated with the feed port of the hot salt tank, high-temperature fused salt in the frequency-modulated fused salt storage tank flows into the hot salt tank through the lower discharge port of the frequency-modulated fused salt storage tank, and cold salt is extracted from the cold salt tank to the frequency-modulated electric heater to absorb heat and increase the temperature and then is discharged into the upper part in the frequency-modulated fused salt storage tank. The system has the advantages of being high in frequency modulation and peak regulation performance and simple.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal power generation and molten salt energy storage, and in particular to a combined frequency and peak regulation system for thermal power units and an operating method thereof. Background Art

[0002] Coal-fired power is a major component of my country's power system, and coal-fired units are excellent peak-shaving units. With the increasing proportion of renewable energy installed capacity and the lack of frequency and peak-shaving technologies in the power system, the demand for high-performance frequency regulation and deep peak-shaving upgrades for thermal power units is increasing. Frequency regulation and peak-shaving for thermal power units differ significantly in their operating timescales. Frequency regulation primarily stabilizes the power system's frequency and maintains power balance on a minute-by-minute basis. Peak-shaving, on the other hand, primarily balances power within the power system and operates on an hourly scale. In actual operation, frequency regulation systems require continuous 24-hour operation and respond to grid regulation commands within minutes, but their regulation capacity is relatively small. Peak-shaving systems, on the other hand, only operate when the units are deeply load-shedding, with a daily operating time ranging from 0 to 8 hours, but they offer a large regulation capacity. Currently, existing technologies use lithium batteries for frequency and peak-shaving, but this approach often increases system operation and maintenance complexity and costs. The existing technology also uses molten salt electric heaters, but since frequency modulation requires the molten salt electric heater to quickly increase or decrease the load within minutes, the frequency modulation molten salt pump adjustment rate cannot meet the rate requirements, resulting in the problem of molten salt easily overheating. Summary of the Invention

[0003] In view of the deficiencies in the prior art, the present invention provides a combined frequency and peak regulation system for thermal power units and an operating method thereof, which has the advantages of strong frequency regulation performance, deep peak regulation depth, fast regulation speed, simple system and low cost.

[0004] The above technical objectives of the present invention are achieved through the following technical solutions:

[0005] A thermal power unit combined frequency modulation and peak regulation system, comprising a thermal power unit and a molten salt electric heating energy storage unit, wherein the molten salt electric heating energy storage unit comprises a frequency modulation electric heater, a frequency modulation molten salt storage tank with a feed port located at the top and a discharge port located at the bottom, a peak regulation electric heater, a cold salt tank, a hot salt tank and a molten salt heat exchanger, wherein the thermal power unit supplies power to the frequency modulation electric heater and the peak regulation electric heater; the discharge port of the frequency modulation electric heater is connected to the upper feed port of the frequency modulation molten salt storage tank, and the frequency modulation electric heater is connected to the upper feed port of the frequency modulation molten salt storage tank. The flow direction of the molten salt in the frequency modulation molten salt storage tank is from top to bottom, and the lower discharge port of the frequency modulation molten salt storage tank is connected to the feed port of the frequency modulation electric heater or the feed port of the hot salt tank; when the molten salt in the frequency modulation molten salt storage tank (3) is passed from the lower part of the frequency modulation molten salt storage tank (3) to the feed port of the frequency modulation electric heater (1), the system performs a heating cycle of the frequency modulation molten salt, extracts the molten salt from the lower part of the frequency modulation molten salt storage tank to the frequency modulation electric heater for heating, and the molten salt is heated from the lower part of the frequency modulation molten salt storage tank to the frequency modulation electric heater. The frequency modulation electric heater absorbs heat and heats up before discharging into the upper part of the frequency modulation molten salt storage tank; when the lower discharge port of the frequency modulation molten salt storage tank is connected to the feed port of the hot salt tank, the discharge port of the cold salt tank is connected to the feed port of the frequency modulation electric heater. At this time, the system discharges hot salt and replenishes cold salt from the frequency modulation molten salt storage tank. The high-temperature molten salt in the frequency modulation molten salt storage tank flows into the hot salt tank through the lower discharge port of the frequency modulation molten salt storage tank, and the cold salt is drawn from the cold salt tank to the frequency modulation electric heater to absorb heat and heat up before discharging into The upper part of the frequency-modulated molten salt storage tank; the discharge port of the cold salt tank is also connected to the feed port of the peak-shaving electric heater, and the discharge port of the peak-shaving electric heater is connected to the feed port of the hot salt tank. The molten salt flowing out of the cold salt tank flows through the low-temperature side of the peak-shaving electric heater to absorb heat and then flows into the hot salt tank; a molten salt heat exchanger is also connected between the cold salt tank and the hot salt tank, and the molten salt flowing out of the hot salt tank flows through the high-temperature side of the molten salt heat exchanger to release heat and then flows into the cold salt tank.

[0006] Furthermore, a salt inlet sparger is provided at the upper part of the frequency-modulation molten salt storage tank, and the salt inlet sparger is located below the upper inlet of the frequency-modulation molten salt storage tank; a salt outlet sparger is provided at the lower part of the frequency-modulation molten salt storage tank, and the salt outlet sparger is located above the lower outlet of the frequency-modulation molten salt storage tank; the molten salt flows into the frequency-modulation molten salt storage tank through the salt inlet sparger, and the molten salt flows out of the frequency-modulation molten salt storage tank through the salt outlet sparger.

[0007] Furthermore, a first thermocouple is provided at the upper portion of the frequency-modulated molten salt storage tank, and a second thermocouple is provided at the lower portion of the frequency-modulated molten salt storage tank.

[0008] Furthermore, when the second thermocouple detects that the molten salt temperature reaches the upper limit of the operating temperature, the system discharges hot salt and replenishes cold salt from the frequency-modulated molten salt storage tank. Otherwise, the system performs a heating cycle of the frequency-modulated molten salt.

[0009] Furthermore, a frequency-modulation molten salt pump and a first molten salt valve are provided on the passage between the lower feed port of the frequency-modulation molten salt storage tank and the feed port of the frequency-modulation electric heater, a second molten salt valve is provided on the passage between the lower feed port of the frequency-modulation molten salt storage tank and the feed port of the hot salt tank, a cold salt pump is provided on the passage from the discharge port of the cold salt tank to the frequency-modulation electric heater and the peak-shaving electric heater, a third molten salt valve is provided on the passage between the discharge port of the cold salt tank and the feed port of the frequency-modulation electric heater, a fourth molten salt valve is provided on the passage between the discharge port of the cold salt tank and the feed port of the peak-shaving electric heater, and a hot salt pump is provided on the passage between the discharge port of the hot salt tank and the feed port of the molten salt heat exchanger.

[0010] Furthermore, when the system performs a frequency-modulated molten salt heating cycle, the molten salt flow rate of the frequency-modulated molten salt pump is maintained constant, and the temperature rise rate of the molten salt in a single heating is controlled not to exceed 30°C / min.

[0011] Furthermore, binary salt is used as an energy storage medium for frequency and peak modulation.

[0012] The present application also provides an operation method of a combined frequency and peak regulation system for thermal power generation units, comprising the following stages:

[0013] FM stage:

[0014] The thermal power unit supplies power to the frequency-modulated electric heater, closes the third molten salt valve, the second molten salt valve and the cold salt pump, opens the first molten salt valve and the frequency-modulated molten salt pump, and the system performs a frequency-modulated molten salt heating cycle. When the grid frequency is stable, the operating load of the frequency-modulated electric heater remains stable, and molten salt is drawn from the lower part of the frequency-modulated molten salt storage tank to the frequency-modulated electric heater. The molten salt absorbs heat from the frequency-modulated electric heater and is discharged into the upper part of the frequency-modulated molten salt storage tank. When the grid frequency increases, the operating load of the frequency-modulated electric heater is increased. The molten salt flow rate of the frequency-modulated molten salt pump remains unchanged, and the frequency-modulated electric heater continuously circulates and heats the molten salt. The temperature of the molten salt in the frequency-modulated molten salt storage tank continues to rise. At this time, the output of the thermal power unit decreases and the grid frequency decreases. When the grid frequency decreases, the operating load of the frequency-modulated electric heater is reduced. Since the molten salt flow rate of the frequency-modulated molten salt pump remains unchanged, the outlet molten salt temperature of the frequency-modulated electric heater is lower than before and mixes with the higher temperature molten salt generated when the grid frequency increases. At this time, the output of the thermal power unit increases and the grid frequency increases.

[0015] After repeated frequency modulation operation, the molten salt in the frequency modulation molten salt storage tank will be continuously heated and the temperature will gradually increase. The temperature is measured at the lower part of the frequency modulation molten salt storage tank. When the second thermocouple detects that the molten salt temperature reaches the upper limit of the use temperature, the system discharges hot salt and replenishes cold salt in the frequency modulation molten salt storage tank. At this time, the third molten salt valve, the cold salt pump and the second molten salt valve are opened, and the first molten salt valve and the frequency modulation molten salt pump are closed to discharge the hot salt in the frequency modulation molten salt storage tank to the hot salt tank. At the same time, the cold salt in the cold salt tank is discharged to the frequency modulation electric heater through the cold salt pump for heating and then introduced into the frequency modulation molten salt storage tank; until the second thermocouple detects that the temperature of the molten salt in the lower part of the frequency modulation molten salt storage tank is close to the lower limit of the use temperature, the second molten salt valve, the third molten salt valve and the cold salt pump are closed, and the first molten salt valve and the frequency modulation molten salt pump are opened to restart the heating cycle of the frequency modulation molten salt;

[0016] Peak shaving stage: The thermal power unit supplies power to the peak-shaving electric heater, and the thermal power unit is reduced to the lowest economic load state to maintain stable combustion operation. The molten salt heat exchanger does not participate in the operation; the cold salt pump and the fourth molten salt valve are opened to maintain the molten salt outlet temperature of the peak-shaving electric heater at the upper limit of the use temperature, and the molten salt is pumped from the cold salt tank to the low-temperature side of the peak-shaving electric heater for heat absorption and temperature increase, and then sent to the hot salt tank, thereby converting the peak-shaving electrical energy into the thermal energy of the molten salt for storage;

[0017] Peak stage: The thermal power unit gradually increases the load, the frequency modulation electric heater and the peak-shaving electric heater stop running, and the thermal power unit gradually increases the steam volume of the main steam and the hot reheat steam to generate power. At the same time, the molten salt flowing out of the hot salt tank flows through the high-temperature side of the molten salt heat exchanger to release heat and then flows into the cold salt tank. The feed water flows through the low-temperature side of the molten salt heat exchanger to absorb heat and generate reflux steam for further flowing into the thermal power unit to generate power.

[0018] The present invention has the following beneficial effects:

[0019] 1. The system of the present invention adopts a molten salt electric heating energy storage unit, namely, a frequency modulation electric heater and a peak modulation electric heater, to realize the joint frequency modulation and peak modulation of the thermal power unit, and has the advantages of strong frequency modulation performance, deep peak modulation depth, and fast regulation speed.

[0020] 2. After repeated frequency modulation and heating by the frequency modulation electric heater, the molten salt can be raised to the upper limit of the operating temperature, avoiding the phenomenon of molten salt overheating or low temperature during continuous and rapid load adjustment operation, and ensuring the parameter quality of steam.

[0021] 3. The integration of peak and frequency regulation greatly reduces the complexity of system operation and maintenance, and is lower in cost compared with traditional lithium battery frequency and peak regulation technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1Schematic diagram of the connection structure of an embodiment of the present invention.

[0023] In the above drawings: 1. Frequency-modulated electric heater; 2. Peak-shaving electric heater; 3. Frequency-modulated molten salt storage tank; 4. Cold salt tank; 5. Hot salt tank; 6. Frequency-modulated molten salt pump; 7. Cold salt pump; 8. Hot salt pump; 9. Molten salt heat exchanger; 10. Fourth molten salt valve; 11. Third molten salt valve; 12. First molten salt valve; 13. Second molten salt valve; 15. Thermal power unit; 301. Salt inlet sparger; 302. Salt outlet sparger; 303. First thermocouple; 304. Second thermocouple. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0025] A combined frequency modulation and peak shaving system for a thermal power unit 15 includes the thermal power unit 15 and a molten salt electric heating energy storage unit. The molten salt electric heating energy storage unit comprises a frequency modulation electric heater 1, a frequency modulation molten salt storage tank 3 with an upper feed port and a lower discharge port, a peak shaving electric heater 2, a cold salt tank 4, a hot salt tank 5, and a molten salt heat exchanger 9. In this embodiment, binary salt is used as the energy storage medium for frequency modulation and peak shaving, with an operating temperature range of 290-565°C. The full load power of the frequency modulation electric heater 1 is 20MW, and the full load power of the peak shaving electric heater 2 is 100MW.

[0026] A frequency-modulation molten salt pump 6 and a first molten salt valve 12 are provided on the passage between the lower feed port of the frequency-modulation molten salt storage tank 3 and the feed port of the frequency-modulation electric heater 1, a second molten salt valve 13 is provided on the passage between the lower feed port of the frequency-modulation molten salt storage tank 3 and the feed port of the hot salt tank 5, a cold salt pump 7 is provided on the passage from the discharge port of the cold salt tank 4 to the frequency-modulation electric heater 1 and the peak-shaving electric heater 2, a third molten salt valve 11 is provided on the passage between the discharge port of the cold salt tank 4 and the feed port of the frequency-modulation electric heater 1, a fourth molten salt valve 10 is provided on the passage between the discharge port of the cold salt tank 4 and the feed port of the peak-shaving electric heater 2, and a hot salt pump 8 is provided on the passage between the discharge port of the hot salt tank 5 and the feed port of the molten salt heat exchanger 9.

[0027] The thermal power generation unit 15 supplies power to the frequency-modulated electric heater 1 and the peak-shaving electric heater 2. The discharge port of the frequency-modulated electric heater 1 is connected to the upper feed port of the frequency-modulated molten salt storage tank 3. The flow direction of the molten salt in the frequency-modulated molten salt storage tank 3 is from top to bottom. The molten salt in the frequency-modulated molten salt storage tank 3 is introduced from the lower part of the frequency-modulated molten salt storage tank 3 into the feed port of the frequency-modulated electric heater 1 or the feed port of the hot salt tank 5. A salt feed sparger 301 is provided at the upper portion of the storage tank 3, and is located below the upper feed port of the frequency-modulated molten salt storage tank 3. A salt discharge sparger 302 is provided at the lower portion of the frequency-modulated molten salt storage tank 3, and is located above the lower discharge port of the frequency-modulated molten salt storage tank 3. Molten salt flows into the frequency-modulated molten salt storage tank 3 through the salt feed sparger 301, and flows out of the frequency-modulated molten salt storage tank 3 through the salt discharge sparger 302. Both the salt feed sparger 301 and the salt discharge sparger 302 are conventional existing technologies. A first thermocouple 303 is provided at the upper portion of the frequency-modulated molten salt storage tank 3, and a second thermocouple 304 is provided at the lower portion of the frequency-modulated molten salt storage tank 3.

[0028] When the molten salt in the frequency modulation molten salt storage tank 3 is passed from the lower part of the frequency modulation molten salt storage tank 3 to the feed port of the frequency modulation electric heater 1, the system now performs a heating cycle of the frequency modulation molten salt, extracts molten salt from the lower part of the frequency modulation molten salt storage tank 3 to the frequency modulation electric heater 1 for heating, and the molten salt absorbs heat and heats up from the frequency modulation electric heater 1 and is discharged into the upper part of the frequency modulation molten salt storage tank 3; when the lower discharge port of the frequency modulation molten salt storage tank 3 is connected to the feed port of the hot salt tank 5, the discharge port of the cold salt tank 4 is connected to the feed port of the frequency modulation electric heater 1, and the system now discharges hot salt and replenishes cold salt from the frequency modulation molten salt storage tank 3, and the high-temperature molten salt in the frequency modulation molten salt storage tank 3 flows into the hot salt tank 5 through the lower discharge port of the frequency modulation molten salt storage tank 3, and draws cold salt from the cold salt tank 4 to the frequency modulation electric heater 1 and absorbs heat and heats up and is discharged into the upper part of the frequency modulation molten salt storage tank 3;

[0029] The discharge port of the cold salt tank 4 is also connected to the feed port of the peak-shaving electric heater 2, and the discharge port of the peak-shaving electric heater 2 is connected to the feed port of the hot salt tank 5. The molten salt flowing out of the cold salt tank 4 flows through the low-temperature side of the peak-shaving electric heater 2 to absorb heat and then flows into the hot salt tank 5;

[0030] A molten salt heat exchanger 9 is further connected between the cold salt tank 4 and the hot salt tank 5 . The molten salt flowing out of the hot salt tank 5 flows through the high temperature side of the molten salt heat exchanger 9 to release heat before flowing into the cold salt tank 4 .

[0031] The operation method of the combined frequency regulation and peak regulation system of the thermal power generation units 15 in this application includes the following stages:

[0032] FM stage:

[0033] The thermal power unit 15 supplies power to the frequency-modulated electric heater 1, closes the third molten salt valve 11, the second molten salt valve 13 and the cold salt pump 7, opens the first molten salt valve 12 and the frequency-modulated molten salt pump 6, and the system performs a heating cycle of the frequency-modulated molten salt. When the grid frequency is stable, the frequency-modulated electric heater 1 is set to operate at 50% load for 24 hours, that is, the operating power of the frequency-modulated electric heater 1 is 10MW, and the operating load of the frequency-modulated electric heater 1 remains stable. The salt temperature of the frequency-modulated molten salt storage tank 3 is 290°C, and the outlet salt temperature of the frequency-modulated electric heater 1 is 320°C. At this time, molten salt is extracted from the lower part of the frequency-modulated molten salt storage tank 3 to the frequency-modulated electric heater 1. The molten salt absorbs heat from the frequency-modulated electric heater 1 and is discharged into the upper part of the frequency-modulated molten salt storage tank 3;

[0034] When the grid frequency increases, the grid requires thermal power unit 15 to reduce its power by 10MW within 1 minute. This means that frequency-modulated electric heater 1 needs to increase its power by 10MW to a full load of 20MW. At this time, the operating power of frequency-modulated electric heater 1 is increased to 20MW within 1 minute. The frequency-modulated electric heater 1 continuously circulates and heats the molten salt, and the temperature of the molten salt in the frequency-modulated molten salt storage tank 3 continues to rise. At this time, the output of thermal power unit 15 decreases, and the grid frequency drops. Furthermore, due to the large flow rate of frequency-modulated molten salt pump 6, which remains unchanged, the outlet molten salt temperature of frequency-modulated electric heater 1 increases from 320°C to 350°C, which does not exceed the temperature rise limit of 30°C / min, effectively avoiding thermal fatigue of the equipment caused by the excessively fast heating rate of frequency-modulated electric heater 1.

[0035] When the grid frequency decreases, the grid requires the thermal power unit 15 to increase its power by 10MW within 1 minute, which means that the frequency-modulated electric heater 1 needs to reduce its power by 10MW to 0MW. At this time, the operating power of the frequency-modulated electric heater 1 is reduced to 0MW within 1 minute, and the outlet molten salt temperature of the frequency-modulated electric heater 1 is reduced from 320°C to 290°C, which does not exceed the temperature rise limit of 30°C / min. It is mixed with the higher temperature molten salt generated when the grid frequency increases. At this time, the output of the thermal power unit 15 increases and the grid frequency rises. Since the molten salt flow rate of the frequency-modulated molten salt pump 6 remains unchanged, the outlet molten salt temperature of the frequency-modulated electric heater 1 is lower than before, effectively avoiding thermal fatigue of the equipment caused by the excessively fast cooling rate of the frequency-modulated electric heater 1.

[0036] After repeated frequency modulation operation, the molten salt in the frequency modulation molten salt storage tank 3 will be continuously heated and the temperature will gradually increase. The temperature is measured at the lower part of the frequency modulation molten salt storage tank 3. When the second thermocouple 304 detects that the molten salt temperature reaches the upper limit of the use temperature of 565°C, the system discharges hot salt and replenishes cold salt in the frequency modulation molten salt storage tank 3. At this time, the third molten salt valve 11, the cold salt pump 7 and the second molten salt valve 13 are opened, and the first molten salt valve 12 and the frequency modulation molten salt pump 6 are closed. 3 is discharged to the hot salt tank 5 at 565°C, and the cold salt at 290°C in the cold salt tank 4 is discharged to the frequency-modulated electric heater 1 through the cold salt pump 7 for heating and then introduced into the frequency-modulated molten salt storage tank 3; until the second thermocouple 304 detects that the temperature of the lower molten salt in the frequency-modulated molten salt storage tank 3 is lower than 320°C, the second molten salt valve 13, the third molten salt valve 11 and the cold salt pump 7 are closed, the first molten salt valve 12 and the frequency-modulated molten salt pump 6 are opened, and the heating cycle of the frequency-modulated molten salt is restarted;

[0037] Peak shaving stage: the thermal power unit 15 supplies power to the peak shaving electric heater 2, and the thermal power unit 15 is reduced to the minimum economic load state for maintaining stable combustion operation, and the molten salt heat exchanger 9 does not participate in the operation; when the thermal power unit 15 needs deep peak shaving, the duration and power of the peak shaving are determined by the day-ahead forecast, and when the peak shaving time arrives, the cold salt pump 7 and the fourth molten salt valve 10 are opened, the peak shaving electric heater 2 is started, and the molten salt outlet temperature of the peak shaving electric heater 2 is maintained at the upper limit use temperature, and molten salt is drawn from the cold salt tank 4 to the low temperature side of the peak shaving electric heater 2 for heat absorption and temperature rise, and the cold salt at 290°C in the cold salt tank 4 is directly heated to 565°C and sent to the hot salt tank 5, thereby converting the peak shaving electrical energy into the thermal energy of the molten salt for storage;

[0038] Peak phase: Thermal power unit 15 gradually increases its load, frequency-modulated electric heater 1 and peak-shaving electric heater 2 stop operating, and thermal power unit 15 gradually increases the amount of main steam and hot reheat steam to generate power. At the same time, the molten salt flowing out of the hot salt tank 5 flows through the high-temperature side of the molten salt heat exchanger 9 to release heat before flowing into the cold salt tank 4. Feedwater flows through the low-temperature side of the molten salt heat exchanger 9 to absorb heat and generate reflux steam, which is then further flowed into the thermal power unit 15 to generate power. Because the load increase rate of the molten salt heat exchanger 9 is much higher than that of a coal-fired boiler, the thermal power unit 15 has a faster load increase rate and can quickly reach full load and generate peak power.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A combined frequency and peak regulation system for thermal power generation units, comprising a thermal power generation unit (15), characterized in that: It also includes a molten salt electric heating energy storage unit, the molten salt electric heating energy storage unit includes a frequency modulation electric heater (1), a frequency modulation molten salt storage tank (3) with a feed port located at the top and a discharge port located at the bottom, a peak-shaving electric heater (2), a cold salt tank (4), a hot salt tank (5) and a molten salt heat exchanger (9), the thermal power generation unit (15) supplies power to the frequency modulation electric heater (1) and the peak-shaving electric heater (2); the discharge port of the frequency modulation electric heater (1) is connected to the upper feed port of the frequency modulation molten salt storage tank (3), the flow direction of the molten salt in the frequency modulation molten salt storage tank (3) is from top to bottom, and the molten salt in the frequency modulation molten salt storage tank (3) is passed from the bottom of the frequency modulation molten salt storage tank (3) to the feed port of the frequency modulation electric heater (1) or the feed port connected to the hot salt tank (5); When the molten salt in the frequency-modulated molten salt storage tank (3) is passed from the lower part of the frequency-modulated molten salt storage tank (3) to the feed port of the frequency-modulated electric heater (1), the system performs a heating cycle of the frequency-modulated molten salt, extracts the molten salt from the lower part of the frequency-modulated molten salt storage tank (3) and heats it at the frequency-modulated electric heater (1), and the molten salt absorbs heat and heats up at the frequency-modulated electric heater (1) and is then discharged into the upper part of the frequency-modulated molten salt storage tank (3); When the lower discharge port of the frequency-modulated molten salt storage tank (3) is connected to the feed port of the hot salt tank (5), the discharge port of the cold salt tank (4) is connected to the feed port of the frequency-modulated electric heater (1), and at this time, the system performs hot salt discharge and cold salt replenishment on the frequency-modulated molten salt storage tank (3), and the high-temperature molten salt in the frequency-modulated molten salt storage tank (3) flows into the hot salt tank (5) through the lower discharge port of the frequency-modulated molten salt storage tank (3), and the cold salt is extracted from the cold salt tank (4) and is heated at the frequency-modulated electric heater (1) to be discharged into the upper part of the frequency-modulated molten salt storage tank (3); The discharge port of the cold salt tank (4) is also connected to the feed port of the peak-shaving electric heater (2), and the discharge port of the peak-shaving electric heater (2) is connected to the feed port of the hot salt tank (5), and the molten salt flowing out of the cold salt tank (4) flows through the low-temperature side of the peak-shaving electric heater (2) to absorb heat and then flows into the hot salt tank (5); A molten salt heat exchanger (9) is also connected between the cold salt tank (4) and the hot salt tank (5), and the molten salt flowing out of the hot salt tank (5) flows through the high-temperature side of the molten salt heat exchanger (9) to release heat before flowing into the cold salt tank (4).

2. A thermal power unit combined frequency and peak regulation system according to claim 1, characterized in that: A salt inlet sparger (301) is provided at the upper portion of the frequency-modulated molten salt storage tank (3), and the salt inlet sparger (301) is located below the upper inlet of the frequency-modulated molten salt storage tank (3); a salt outlet sparger (302) is provided at the lower portion of the frequency-modulated molten salt storage tank (3), and the salt outlet sparger (302) is located above the lower outlet of the frequency-modulated molten salt storage tank (3); molten salt flows into the frequency-modulated molten salt storage tank (3) through the salt inlet sparger (301), and molten salt flows out of the frequency-modulated molten salt storage tank (3) through the salt outlet sparger (302).

3. The combined frequency and peak regulation system for thermal power generation units according to claim 1, characterized in that: A first thermocouple (303) is provided at the upper portion of the frequency-modulated molten salt storage tank (3), and a second thermocouple (304) is provided at the lower portion of the frequency-modulated molten salt storage tank (3).

4. A thermal power unit combined frequency and peak regulation system according to claim 3, characterized in that: When the second thermocouple (304) detects that the molten salt temperature reaches the upper limit of the operating temperature, the system discharges hot salt and replenishes cold salt from the frequency-modulated molten salt storage tank (3); otherwise, the system performs a heating cycle of the frequency-modulated molten salt.

5. The combined frequency and peak regulation system for thermal power generation units according to claim 1, characterized in that: A frequency-modulated molten salt pump (6) and a first molten salt valve (12) are provided on the passage between the lower feed port of the frequency-modulated molten salt storage tank (3) and the feed port of the frequency-modulated electric heater (1); a second molten salt valve (13) is provided on the passage between the lower feed port of the frequency-modulated molten salt storage tank (3) and the feed port of the hot salt tank (5); a cold salt pump (7) is provided on the passage from the discharge port of the cold salt tank (4) to the frequency-modulated electric heater (1) and the peak-shaving electric heater (2); a third molten salt valve (11) is provided on the passage between the discharge port of the cold salt tank (4) and the feed port of the frequency-modulated electric heater (1); a fourth molten salt valve (10) is provided on the passage between the discharge port of the cold salt tank (4) and the feed port of the peak-shaving electric heater (2); and a hot salt pump (8) is provided on the passage between the discharge port of the hot salt tank (5) and the feed port of the molten salt heat exchanger (9).

6. The combined frequency and peak regulation system for thermal power generation units according to claim 1, characterized in that: When the system performs a frequency-modulated molten salt heating cycle, the molten salt flow rate of the frequency-modulated molten salt pump (6) is maintained constant, and the temperature rise rate of the molten salt in a single heating is controlled not to exceed 30° C. / min.

7. The combined frequency and peak regulation system for thermal power generation units according to claim 1, characterized in that: Binary salt is used as the energy storage medium for frequency and peak modulation.

8. An operating method of a combined frequency and peak regulation system for thermal power plants according to any one of claims 1 to 7, characterized in that: Frequency modulation stage: the thermal power generation unit (15) supplies power to the frequency modulation electric heater (1), closes the third molten salt valve (11), the second molten salt valve (13) and the cold salt pump (7), opens the first molten salt valve (12) and the frequency modulation molten salt pump (6), and the system performs a heating cycle of the frequency modulation molten salt. When the grid frequency is stable, the operating load of the frequency modulation electric heater (1) remains stable, and molten salt is extracted from the lower part of the frequency modulation molten salt storage tank (3) to the frequency modulation electric heater (1). The molten salt absorbs heat from the frequency modulation electric heater (1) and is discharged into the upper part of the frequency modulation molten salt storage tank (3); When the grid frequency increases, the operating load of the frequency-modulated electric heater (1) is increased. Since the molten salt flow rate of the frequency-modulated molten salt pump (6) remains unchanged, the frequency-modulated electric heater (1) continuously circulates and heats the molten salt, and the molten salt temperature in the frequency-modulated molten salt storage tank (3) continues to increase. At this time, the output of the thermal power unit (15) decreases and the grid frequency decreases. When the grid frequency decreases, the operating load of the frequency-modulated electric heater (1) is reduced. Since the molten salt flow rate of the frequency-modulated molten salt pump (6) remains unchanged, the outlet molten salt temperature of the frequency-modulated electric heater (1) is lower than before and is mixed with the higher temperature molten salt generated when the grid frequency increases. At this time, the output of the thermal power unit (15) increases and the grid frequency increases. After repeated frequency modulation operation, the molten salt in the frequency modulation molten salt storage tank (3) is continuously heated and the temperature gradually increases. The temperature is measured at the lower part of the frequency modulation molten salt storage tank (3). When the second thermocouple (304) detects that the molten salt temperature reaches the upper limit of the use temperature, the system discharges hot salt and replenishes cold salt in the frequency modulation molten salt storage tank (3). At this time, the third molten salt valve (11), the cold salt pump (7) and the second molten salt valve (13) are opened, and the first molten salt valve (12) and the frequency modulation molten salt pump (6) are closed. The frequency modulation molten salt storage tank (3) is filled with hot salt. ) is discharged to the hot salt tank (5), and at the same time, the cold salt in the cold salt tank (4) is discharged to the frequency-modulated electric heater (1) through the cold salt pump (7) for heating and then introduced into the frequency-modulated molten salt storage tank (3); until the second thermocouple (304) detects that the temperature of the lower molten salt in the frequency-modulated molten salt storage tank (3) is close to the lower limit of the operating temperature, the second molten salt valve (13), the third molten salt valve (11) and the cold salt pump (7) are closed, the first molten salt valve (12) and the frequency-modulated molten salt pump (6) are opened, and the heating cycle of the frequency-modulated molten salt is restarted; Peak shaving stage: the thermal power unit (15) supplies power to the peak shaving electric heater (2), the thermal power unit (15) is reduced to the lowest economic load state for maintaining stable combustion operation, and the molten salt heat exchanger (9) does not participate in the operation; the cold salt pump (7) and the fourth molten salt valve (10) are opened to maintain the molten salt outlet temperature of the peak shaving electric heater (2) at the upper limit use temperature, and the molten salt is extracted from the cold salt tank (4) to the low temperature side of the peak shaving electric heater (2) for heat absorption and temperature rise, and then sent to the hot salt tank (5), thereby converting the peak shaving electric energy into the thermal energy of the molten salt for storage; Peak stage: the thermal power generation unit (15) gradually increases the load, the frequency modulation electric heater (1) and the peak regulation electric heater (2) stop running, and the thermal power generation unit (15) gradually increases the steam volume of the main steam and the hot reheat steam to generate power. At the same time, the molten salt flowing out of the hot salt tank (5) flows through the high temperature side of the molten salt heat exchanger (9) to release heat and then flows into the cold salt tank (4). The feed water flows through the low temperature side of the molten salt heat exchanger (9) to absorb heat and generate reflux steam for further flowing into the thermal power generation unit (15) to generate power.

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