CN-121976866-A - Auxiliary frequency modulation method and device for fused salt heat storage system and thermal power unit

CN121976866ACN 121976866 ACN121976866 ACN 121976866ACN-121976866-A

Abstract

The application discloses an auxiliary frequency modulation method and device for a molten salt heat storage system and a thermal power generating unit. The method comprises the steps of dividing steam extraction and heat storage working conditions based on a matching relation between real-time steam flow of each steam extraction pipeline and a steam flow judgment threshold value, adjusting opening degrees of electric adjusting valves on the main steam superheating steam extraction pipeline, the hot superheating steam extraction pipeline and the four steam extraction pipelines according to target load variation in a frequency modulation instruction issued by a power grid, real-time output of a thermal power unit, main steam pressure of a boiler, hot re-steam pressure of the boiler, steam discharge pressure of a pressure cylinder in a steam turbine, molten salt temperature in a low-temperature molten salt tank and the steam extraction and heat storage working conditions, adjusting operation parameters of a molten salt conveying power device according to steam flow and heat exchange requirements of each pipeline, driving molten salt in the low-temperature molten salt tank to flow into each heat exchanger respectively, and conveying high-temperature molten salt after heat exchange in each heat exchanger to the high-temperature molten salt tank for storage according to a load adjustment direction in the frequency modulation instruction.

Inventors

YOU MO
GAO AIGUO
LIU LEI
KANG JINGQIU
SHANG YONG
YANG ZHENYONG
HU SONG
XIANG JUN
SU SHENG
ZHANG JINZHE
LI ZHAN
XU KAI
MA NING
XING ZHIWEI
LI CHENGLONG
LIU TAO

Assignees

华北电力科学研究院有限责任公司
国家电网有限公司
华中科技大学

Dates

Publication Date: 20260505
Application Date: 20251229

Claims (10)

1. The method is characterized by being applied to a thermal power unit, the thermal power unit at least comprises a boiler, a steam turbine and a molten salt heat storage system, the molten salt heat storage system comprises a main steam superheating heat exchanger, a hot re-superheating heat exchanger, a four-extraction superheating heat exchanger, a low-temperature molten salt tank and a high-temperature molten salt tank, and electric regulating valves are arranged on a main steam superheating steam extraction pipeline, a hot re-superheating steam extraction pipeline and the four-extraction steam extraction pipeline, and the method comprises the following steps: Dividing steam extraction heat storage working conditions based on the matching relation between the real-time steam flow of each steam extraction pipeline and the steam flow judgment threshold value; According to target load variable quantity in a frequency modulation instruction issued by an electric network, real-time output of the thermal power generating unit, main steam pressure of the boiler, hot re-steam pressure of the boiler, steam exhaust pressure of a middle pressure cylinder of a steam turbine, molten salt temperature in the low-temperature molten salt tank and steam extraction heat storage working conditions, opening degrees of electric regulating valves on the main steam overheated steam extraction pipeline, the hot re-overheated steam extraction pipeline and the four steam extraction pipelines are regulated so as to control steam flow of each pipeline into a corresponding heat exchanger; According to the steam flow and heat exchange requirements of each pipeline fed into the corresponding heat exchanger, the operation parameters of a molten salt conveying power device are regulated, molten salt in a low-temperature molten salt tank is driven to flow into the main steam superheating heat exchanger, the hot re-superheating heat exchanger and the four-extraction superheating heat exchanger respectively, so that the molten salt exchanges heat with steam fed into the corresponding pipeline in each heat exchanger respectively; And conveying the high-temperature molten salt subjected to heat exchange in each heat exchanger to the high-temperature molten salt tank for storage according to the load adjusting direction in the frequency modulation instruction, so as to realize quick response to the power grid frequency modulation instruction.
2. The method of claim 1, wherein dividing the extraction and heat storage conditions based on a matching relationship of real-time steam flow of each extraction line to a steam flow decision threshold comprises: when the real-time steam flow of the four steam extraction pipelines is in a first preset flow interval and the real-time steam flow of the hot re-overheated steam extraction pipeline and the real-time steam flow of the main steam overheated steam extraction pipeline are in a no-flow state, judging that the four steam extraction pipelines are independent; When the real-time steam flow of the hot re-superheating steam extraction pipeline is in a second preset flow interval and the real-time steam flow of the four steam extraction pipelines and the real-time steam flow of the main steam superheating steam extraction pipeline are in a no-flow state, judging that the hot re-extraction pipeline is in a single hot re-extraction working condition; When the real-time steam flow of the four-extraction steam extraction pipeline reaches a first steam flow judgment threshold value, the real-time steam flow of the hot re-superheating steam extraction pipeline reaches a second steam flow judgment threshold value, and the real-time steam flow of the main steam superheating steam extraction pipeline is in a no-flow state, judging that the four-extraction and hot re-extraction working conditions are combined; When the real-time steam flow of the hot re-superheating steam extraction pipeline reaches a second steam flow judging threshold value, the real-time steam flow of the main steam superheating steam extraction pipeline is in a third preset flow interval, and the real-time steam flow of the four steam extraction pipelines is in a no-flow state, judging a working condition that the hot re-steam and the main steam are extracted together; when the real-time steam flow of the four-extraction steam extraction pipeline reaches a first steam flow judgment threshold, the real-time steam flow of the hot re-superheating steam extraction pipeline reaches a second steam flow judgment threshold, and the real-time steam flow of the main steam superheating steam extraction pipeline reaches a third steam flow judgment threshold, judging that the working conditions of four-extraction and heat re-extraction and main steam are adopted together.
3. The method of claim 2, wherein adjusting the opening of the main steam superheating extraction pipeline, the thermal re-superheating extraction pipeline and the electric adjustment valve on the four extraction pipelines according to a target load variation in a frequency modulation command issued by an electric network, real-time output of the thermal power generating unit, main steam pressure of the boiler, thermal re-steam pressure of the boiler, steam discharge pressure of a medium-pressure cylinder of the steam turbine, molten salt temperature in the low-temperature molten salt tank and a steam extraction heat storage condition comprises: Determining a load adjustment quantity to be supplemented by steam extraction adjustment according to the target load change quantity and the real-time output of the thermal power generating unit; judging the steam availability of each steam extraction pipeline based on the main steam pressure of the boiler, the hot re-steam pressure of the boiler and the steam discharge pressure of the medium-pressure cylinder of the steam turbine; Determining the fused salt heat absorption capacity of each heat exchanger according to the fused salt temperature in the low-temperature fused salt tank, the rated heat exchange power of each heat exchanger and the fused salt outlet temperature limit value of each heat exchanger; And respectively determining the opening of an electric regulating valve on each steam extraction pipeline according to the load regulating quantity, the steam availability, the fused salt heat absorption capacity and the current steam extraction heat storage working condition.
4. The method of claim 3, wherein the steam turbine further comprises an adjustable rotating partition plate, and determining the opening of the electric regulating valve on each steam extraction pipeline according to the load regulating quantity, the steam availability, the fused salt heat absorption capacity and the current steam extraction heat storage working condition comprises the following steps: Under the independent four-extraction steam extraction working condition, only when the absolute value of the frequency deviation in the frequency modulation instruction reaches a preset deviation value and lasts for a preset duration, determining the opening of an electric four-extraction steam extraction regulating valve based on the load regulating quantity, the steam availability of a four-extraction steam extraction pipeline and the fused salt heat absorption capacity of a four-extraction heat exchanger, and regulating the opening of the adjustable rotary partition plate according to the real-time steam flow change of the four-extraction steam extraction pipeline and the real-time monitoring value of the four-extraction steam supply pressure of a small machine; Under the independent hot re-extraction working condition, determining the opening of an electric regulating valve for hot re-extraction according to a preset flow characteristic curve based on the load regulating quantity, the steam availability of a hot re-superheating extraction pipeline and the fused salt heat absorption capacity of the hot re-superheating heat exchanger; Under the working condition of four-extraction and hot re-extraction, respectively determining the opening of an electric regulating valve for four-extraction and hot re-extraction according to the steam availability of the four-extraction steam pipeline and the hot re-superheating steam extraction pipeline and the matching proportion of the fused salt heat absorption capacity of the corresponding heat exchanger based on the load regulating quantity; Under the working condition that the hot re-steam and the main steam are extracted together, based on the load adjustment quantity, steam flow is distributed according to the adaptation relation between the main steam pressure and the hot re-steam pressure of the boiler, and the opening of the electric adjustment valve of the hot re-steam extraction and the main steam extraction is respectively determined by combining the steam availability of the hot re-superheated steam extraction pipeline and the main steam superheated steam extraction pipeline and the fused salt heat absorption capacity of the corresponding heat exchanger; and under the working condition of four-extraction, heat re-extraction and main steam co-extraction, based on the load adjustment quantity, the steam availability of the four-extraction steam extraction pipeline, the heat re-superheating steam extraction pipeline and the main steam superheating steam extraction pipeline and the fused salt heat absorption capacity of the corresponding heat exchanger are combined, the steam flow duty ratio of the three-way steam extraction pipeline is dynamically distributed, and the opening degree of each electric adjustment valve is respectively determined.
5. The method of any one of claims 1-4, wherein adjusting the operating parameters of the molten salt delivery power device according to the steam flow and heat exchange requirements of each conduit to a corresponding heat exchanger comprises: collecting real-time steam flow of the main steam overheated steam extraction pipeline, the hot re-overheated steam extraction pipeline and the four steam extraction pipelines, which are led into corresponding heat exchangers, and respectively calculating heat to be absorbed by each heat exchanger by combining the heat exchange area, the steam specific heat capacity and the steam inlet and outlet temperature difference of each heat exchanger; Respectively calculating the required molten salt flow of each heat exchanger based on the heat required to be absorbed by each heat exchanger, the specific heat capacity of the molten salt, the temperature of the molten salt in the low-temperature molten salt tank and the target temperature difference of the molten salt in the high-temperature molten salt tank, and summing the required molten salt flow of each heat exchanger to obtain the total molten salt circulation flow; Correcting the molten salt flow required by each heat exchanger according to the total molten salt circulation flow and the heat exchange priority of each heat exchanger, so as to ensure that the molten salt flow required by the heat exchanger with high priority is preferentially met; And acquiring the real-time molten salt flow in the molten salt conveying main pipe, and if the real-time molten salt flow is not equal to the total molten salt circulating flow, adjusting the operation parameters of the molten salt conveying power device according to the deviation value of the real-time molten salt flow and the total molten salt circulating flow, the pipeline resistance characteristic of the molten salt conveying main pipe and the rated output range of the molten salt conveying power device.
6. The method of claim 5, wherein adjusting the operating parameters of the molten salt delivery power device based on the deviation of the real-time molten salt flow rate from the total molten salt circulation flow rate, the line resistance characteristics of the molten salt delivery manifold, and the rated output range of the molten salt delivery power device comprises: determining a pressure difference value to be changed in the molten salt conveying main pipe based on the inner diameter of a pipeline, the length of the pipeline, the roughness of the inner wall of the pipeline and the viscosity of the molten salt and combining the deviation value of the real-time molten salt flow and the total molten salt circulation flow; Determining the output power to be increased or the output power to be reduced of the molten salt conveying power device according to the corresponding relation between the output pressure of the molten salt conveying power device and the flow of the molten salt and the pressure difference value; If the calculated output power to be increased or the calculated output power to be reduced is in the rated output power range of the molten salt conveying power device, the output power of the molten salt conveying power device is adjusted according to the calculated output power to be increased or the calculated output power to be reduced, so that the real-time molten salt flow in the molten salt conveying main pipe approaches to the total molten salt circulating flow; And if the calculated output power to be increased or the calculated output power to be reduced exceeds the rated output power range of the molten salt conveying power device, adjusting the output power according to the rated output power upper limit or the rated output power lower limit of the molten salt conveying power device.
7. An auxiliary frequency modulation device for a molten salt heat storage system, which is characterized by comprising: The working condition judging module is used for dividing the working conditions of the steam extraction and heat storage based on the matching relation between the real-time steam flow of each steam extraction pipeline and the steam flow judging threshold value; The opening adjusting module is used for adjusting the opening of the main steam overheat steam extraction pipeline, the thermal reheat steam extraction pipeline and the electric adjusting valves on the four steam extraction pipelines according to the target load variable quantity in the frequency modulation instruction issued by the power grid, the real-time output of the thermal power generating unit, the main steam pressure of the boiler, the hot re-steam pressure of the boiler, the steam discharge pressure of the medium pressure cylinder of the steam turbine, the molten salt temperature in the low-temperature molten salt tank and the steam extraction and heat storage working condition so as to control the steam flow of each pipeline into the corresponding heat exchanger; The driving module is used for adjusting the operation parameters of the molten salt conveying power device according to the steam flow and heat exchange requirements of the corresponding heat exchangers fed into each pipeline, and driving molten salt in the low-temperature molten salt tank to flow into the main steam superheating heat exchanger, the hot re-superheating heat exchanger and the four-pump superheating heat exchanger respectively, so that the molten salt exchanges heat with the steam fed into the corresponding pipeline in each heat exchanger respectively; And the storage module is used for conveying the high-temperature molten salt subjected to heat exchange in each heat exchanger to the high-temperature molten salt tank for storage according to the load adjustment direction in the frequency modulation instruction, so that the quick response to the power grid frequency modulation instruction is realized.
8. The thermal power generating unit is characterized by comprising a molten salt heat storage system, a boiler, a steam turbine and an auxiliary steam header, wherein the molten salt heat storage system comprises a main steam superheating heat exchanger, a thermal re-superheating heat exchanger, a four-suction superheating heat exchanger, a low-temperature salt melting tank and a high-temperature salt melting tank, and the steam turbine comprises a medium-pressure cylinder and a high-pressure cylinder; The molten salt outlet of the low-temperature molten salt tank is divided into three parallel branches through a molten salt conveying main pipe, and the three branches are respectively communicated with the molten salt side inlet of the main steam superheating heat exchanger, the molten salt side inlet of the hot re-superheating heat exchanger and the molten salt side inlet of the four-pump superheating heat exchanger in a one-to-one correspondence manner; The molten salt side outlet of the main steam superheating heat exchanger, the molten salt side outlet of the heat re-superheating heat exchanger and the molten salt side outlet of the four-pump superheating heat exchanger are converged to a molten salt return main pipe through three molten salt branch pipes, and the molten salt return main pipe is communicated with a molten salt inlet of the high-temperature molten salt tank; The steam side inlet of the main steam superheating heat exchanger is communicated with the main steam outlet pipeline of the boiler through a main steam superheating steam extraction pipeline, the steam side inlet of the thermal superheating heat exchanger is communicated with the thermal re-steam outlet pipeline of the boiler through a thermal re-superheating steam extraction pipeline, and the steam side inlet of the four-extraction superheating heat exchanger is communicated with the steam exhaust pipeline of the medium-pressure cylinder through four-extraction steam extraction pipelines; The steam side outlet of the main steam superheating heat exchanger is divided into two paths, one path returns to the boiler low-temperature reheating pipeline through a pipeline, the other path is communicated with the steam inlet pipeline of the high-pressure cylinder through a pipeline, and the steam side outlet of the heat superheating heat exchanger and the steam side outlet of the four-extraction superheating heat exchanger are respectively communicated with the auxiliary steam header after being converged through independent pipelines.
9. The thermal power generating unit according to claim 8, wherein the main steam superheating steam extraction pipeline, the thermal superheating steam extraction pipeline and the four steam extraction pipelines are respectively provided with an electric regulating valve, and the electric regulating valves are used for regulating steam inflow of corresponding pipelines according to grid frequency modulation load requirements.
10. A thermal power plant according to claim 8 or 9, wherein the main steam superheating steam extraction pipeline and the thermal superheating steam extraction pipeline are provided with temperature and pressure reducing components, and the temperature and pressure reducing components are used for adjusting the temperature and pressure of steam fed into the corresponding heat exchanger, so as to avoid thermal fatigue of the corresponding heat exchanger caused by abrupt change of temperature or pressure.

Description

Auxiliary frequency modulation method and device for fused salt heat storage system and thermal power unit Technical Field The application relates to the technical field of power grids, in particular to an auxiliary frequency modulation method and device for a fused salt heat storage system and a thermal power generating unit. Background In the running process of the power grid, the thermal power generating unit needs to adjust the generated output in real time according to the frequency change of the power grid so as to maintain the frequency stable, for example, the output needs to be quickly increased when the load of the power grid suddenly increases, and the output needs to be timely reduced when the load suddenly decreases. However, when the traditional thermal power generating unit participates in frequency modulation, the problem of insufficient synergy of energy regulation and storage is often faced, so that the response flexibility of the unit to frequency modulation instructions is limited, and the dynamic change of the load of the power distribution network is difficult to adapt quickly while the stable operation of the unit is guaranteed. For example, when the output is required to be quickly reduced, redundant steam energy of a unit cannot be effectively received and can only be wasted in a diffusing mode, so that energy loss is caused, stable operation of core equipment such as a boiler and a steam turbine is possibly influenced due to sudden change of steam parameters, when the output is required to be quickly lifted, a power notch cannot be quickly complemented due to lack of pre-stored energy support, response speed to a power grid frequency modulation instruction is delayed, and quick adaptation requirement of a power grid to load dynamic change is difficult to meet, so that stable control of the whole power grid frequency is influenced. Disclosure of Invention In view of the problems, the application provides an auxiliary frequency modulation method and device for a molten salt heat storage system and a thermal power generating unit. In order to solve the technical problems, the application provides the following scheme: The method comprises dividing the working conditions of the extraction heat storage according to the matching relation between the real-time steam flow of each extraction pipeline and the steam flow judgment threshold, adjusting the opening of the electric adjusting valve on each pipeline through the corresponding heat exchanger according to the steam flow of each pipeline, driving the steam flow to the corresponding heat exchanger according to the heat exchange parameters of the corresponding heat exchanger, driving the heat exchanger to the heat exchange device in the heat exchange device according to the heat exchange direction of each heat exchange device, and driving the heat exchange device to respectively respond to the heat exchange parameters of the heat exchange device in the heat exchange device according to the heat exchange direction of each heat exchange device in the heat exchange device after the heat exchange device is in the heat exchange direction of each heat exchange device. In a second aspect, the present application provides an auxiliary frequency modulation device for a molten salt heat storage system, the auxiliary frequency modulation device for the molten salt heat storage system comprising: The working condition judging module is used for dividing the working conditions of the steam extraction and heat storage based on the matching relation between the real-time steam flow of each steam extraction pipeline and the steam flow judging threshold value; The opening adjusting module is used for adjusting the opening of an electric adjusting valve on a main steam overheat steam extraction pipeline, a thermal reheat steam extraction pipeline and a four-steam extraction pipeline according to the target load variable quantity in a frequency modulation instruction issued by an electric network, the real-time output of a thermal power generating unit, the main steam pressure of a boiler, the thermal reheat steam pressure of the boiler, the steam discharge pressure of a middle pressure cylinder of a steam turbine, the fused salt temperature in a low-temperature molten salt tank and the steam extraction heat storage working condition so as to control the steam flow of each pipeline into a corresponding heat exchanger; The driving module is used for adjusting the operation parameters of the molten salt conveying power device according to the steam flow and heat exchange requirements of the corresponding heat exchangers of the pipelines, and driving molten salt in the low-temperature molten salt tank to flow into the main steam superheating heat exchanger, the hot re-superheating heat exchanger and the four-extraction superheating heat exchanger respectively, so that the molten salt exchanges heat with the steam of the corresponding pipeline in each heat exc