A wind-solar-thermal storage system and a regulating method thereof

Abstract

The application belongs to the technical field of molten salt heat storage system, and proposes a wind-solar-heat storage system and a regulating method suitable for seasonal climate change. The molten salt heat storage unit comprises a low-temperature molten salt electric heating unit and a high-temperature molten salt electric heating unit. The high-temperature molten salt electric heating unit adopts high-temperature molten salt, a part of which is used for heating main steam feed water, and another part of which is used for heating reheat steam, and then the two parts of molten salt are mixed. The low-temperature molten salt electric heating unit is connected in parallel to the high-pressure heater unit loop in the Rankine cycle power generation unit, and a part of the feed water is branched and heated to a preheating temperature matched with the output of the high-pressure heater unit, and then mixed with the feed water heated by the high-pressure heater unit, realizing differentiated operation, dynamic power distribution and seasonal working condition optimization of the electric heater, being capable of dividing the operation cycle according to four seasons, supporting independent control of each electric heater, and realizing flexible adjustment of the total power of the system.

Description

Technical Field

[0001] This invention belongs to the technical field of molten salt thermal storage systems, and particularly relates to a wind-solar thermal storage system adapted to seasonal climate changes and its control method. Background Technology

[0002] Wind and solar power generation is significantly affected by fluctuations in natural resources, exhibiting randomness, intermittency, and uncertainty in its output, making it difficult to achieve stable load following capability. This characteristic not only poses a challenge to grid dispatch but also exacerbates the spatiotemporal mismatch between power system supply and demand, leading to "wind and solar curtailment." To improve the system's capacity to accommodate new energy sources and ensure the safe and stable operation of the power system, it is necessary to simultaneously construct energy storage facilities with rapid response and energy regulation capabilities. Among various energy storage technologies, electrochemical energy storage offers fast response speeds, but it faces bottlenecks in terms of capacity scalability, system security, and total lifespan cost. Thermal energy storage technology using molten salt as a medium, with its advantages of high energy density, low cost, long lifespan, and good security, has become the mainstream technology choice for current high-temperature energy storage systems, especially suitable for large-scale, long-term energy storage and release. By using electric heaters to directly convert surplus electricity from wind and solar power into heat energy and storing it in molten salt with high specific heat capacity and high stability, the utilization rate of new energy power generation can be significantly improved, alleviating system peak-shaving pressure and reducing curtailment rates.

[0003] In existing technologies, such as Chinese patent CN114216108B, a hybrid heating molten salt thermal storage peak-shaving system is disclosed. This system stores excess heat and electricity from power plants during load reduction and peak shaving, as well as excess electricity from wind and solar power generation, in high-temperature molten salt. This solution can store excess heat and electricity from thermal power plants during peak shaving, as well as excess electricity from wind and solar power, in high-temperature molten salt, and release it to assist power generation when the unit increases its load, thus possessing a certain degree of regulation capability. However, this solution does not disclose the specific operation and control method of the electric heater, lacking a refined control strategy for wind and solar power curtailment at different power levels, making it difficult to achieve dynamic response and flexible adjustment.

[0004] Currently, most molten salt electric heating systems used in practical engineering applications adopt fixed capacity configurations and a single control strategy. This means that the electric heaters operate at a uniform power level within the system, and the start-stop logic is typically based on threshold judgments or time-based schedules. This static configuration approach struggles to achieve flexible response and efficient matching when facing significant seasonal fluctuations in wind and solar power resources and dynamic changes in electricity load, leading to system operation problems: Firstly, the electric heaters exhibit lag in response, failing to quickly adjust power output according to real-time changes in renewable energy output, resulting in some surplus electricity not being converted into heat energy and being wasted. Secondly, the coarse control of the thermal storage process causes uneven temperature distribution within the molten salt tank and low thermal storage efficiency, affecting the stability and economy of the heating system. Furthermore, due to the lack of refined scheduling strategies, some heater equipment operates at low loads or in idle standby states for extended periods, making it difficult to guarantee equipment utilization and return on investment, and even shortening equipment lifespan. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a wind-solar thermal storage system and its control method that adapts to seasonal climate changes. This system enables differentiated operation of electric heaters, dynamic power distribution, and seasonal operating condition optimization. It can divide the operating cycle into four seasons and supports independent control and parallel operation of each electric heater, thereby achieving flexible adjustment of the total system power.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a wind-solar-thermal-storage system adapted to seasonal climate changes, employing the following technical solution:

[0007] A wind-solar-thermal-storage system adapted to seasonal climate change includes interconnected molten salt thermal storage units and Rankine cycle power generation units.

[0008] The molten salt thermal storage unit includes a low-temperature molten salt electric heating unit and a high-temperature molten salt electric heating unit; each of the low-temperature molten salt electric heating unit and the high-temperature molten salt electric heating unit includes at least one electric heater, as well as a high-temperature molten salt tank and a low-temperature molten salt tank connected to the electric heater;

[0009] The high-temperature molten salt electric heating unit uses high-temperature molten salt, part of which is used to heat the main steam feedwater and the other part is used to heat the reheat steam. The low-temperature molten salt electric heating unit is connected in parallel to the high-pressure heater unit circuit in the Rankine cycle power generation unit. It diverts a portion of the feedwater and heats it to a preheating temperature that matches the output of the high-pressure heater unit. Then it mixes with the feedwater heated by the high-pressure heater unit to achieve differentiated operation, dynamic power distribution and seasonal operating condition optimization of the electric heater.

[0010] To achieve the above objectives, in a second aspect, the present invention also provides a method for regulating a wind-solar-thermal-storage system that adapts to seasonal climate changes, employing the following technical solution:

[0011] A method for regulating a wind-solar-thermal-storage system adapted to seasonal climate change, using the wind-solar-thermal-storage system adapted to seasonal climate change as described in any one of claims 1-4, includes: the high-temperature molten salt electric heating unit uses high-temperature molten salt, part of which is used to heat the main steam feedwater and the other part is used to heat the reheat steam; the low-temperature molten salt electric heating unit is connected in parallel to the high-pressure heater unit circuit in the Rankine cycle power generation unit, diverts a portion of the feedwater and heats it to a preheating temperature matching the output of the high-pressure heater unit, and then mixes it with the feedwater heated by the high-pressure heater unit, thereby realizing differentiated operation, dynamic power distribution and seasonal operating condition optimization of the electric heater.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] 1. In this invention, the molten salt thermal storage unit includes a low-temperature molten salt electric heating unit and a high-temperature molten salt electric heating unit. The high-temperature molten salt electric heating unit uses high-temperature molten salt, part of which is used to heat the main steam feedwater and the other part is used to heat the reheat steam. The low-temperature molten salt electric heating unit is connected in parallel to the high-pressure heater unit circuit in the Rankine cycle power generation unit. It diverts a portion of the feedwater and heats it to a preheating temperature that matches the output of the high-pressure heater unit. Then, it mixes with the feedwater heated by the high-pressure heater unit. This realizes differentiated operation, dynamic power distribution, and seasonal operating condition optimization of the electric heaters. It can divide the operating cycle into four seasons and supports independent control and parallel operation of each electric heater, thereby realizing flexible adjustment of the total power of the system.

[0014] 2. This invention achieves multi-energy complementarity and efficient coordinated operation: wind power generation, photovoltaic power generation and solar thermal power generation are deeply coupled into the electric heater molten salt thermal storage system. Through mechanisms such as dual-path photovoltaic output structure, direct solar thermal heat exchange and wind power priority drive, an electric-thermal-storage coordinated linkage system is formed, which significantly improves the comprehensive utilization efficiency of new energy.

[0015] 3. This invention improves system flexibility and control precision: The electric heater is divided into two groups, which are used for main steam reheating and high-pressure cylinder feedwater heating respectively. Combined with the output characteristics of wind power and photovoltaic power, independent power regulation is carried out, which significantly improves the system's adaptability to load changes and energy input fluctuations.

[0016] 4. This invention enhances seasonal adaptability and operational stability: It can design different operating cycle strategies to address the differences in operating characteristics across spring, summer, autumn, and winter, and implement dynamic power adjustments based on the molten salt tank capacity status, effectively ensuring the stability of main steam temperature and feedwater heating requirements. In summer, when surplus wind and solar power is less, the system and control strategies proposed in this invention can significantly increase power generation to cope with peak grid demand. Simultaneously, through an electric heat tracing system and low-power protection strategies, it prevents molten salt from solidifying in low-temperature seasons, improving the system's annual availability and enabling real-time absorption of surplus wind and solar power (e.g., activating more heaters for heat storage during power surpluses). This effectively solves the problem of wind and solar curtailment caused by supply-demand mismatch in existing technologies. Traditional curtailment rates often reach 15%-22%, while through tiered power allocation and predictive optimization, the curtailment rate can be controlled to ≤8%.

[0017] 5. This invention achieves intelligent prediction and dynamic control scheduling. By integrating the ARIMA model and multi-source meteorological information, it establishes a high-temporal-resolution (less than 15 minutes) wind and solar power output prediction mechanism, driving the dynamic power adjustment strategy of the electric heater. This enables the linkage control of new energy power output prediction and molten salt thermal state, effectively improving the system's intelligence and autonomous adjustment capabilities. It features precise temperature gradient control and utilization of the sensible heat range of the molten salt working fluid, reducing heat loss and increasing thermal storage efficiency to ≥90% (7%-9% higher than traditional uniform distribution schemes). Simultaneously, the PID algorithm dynamically adjusts power and molten salt temperature constraints (e.g., automatic power reduction or disconnection from the grid when the temperature exceeds the limit), ensuring the system operates efficiently within a safe range.

[0018] 6. This invention employs inter-group rotation operation and redundant configuration (2 main and 2 standby parallel architecture), which ensures balanced operating time for each heater group, avoids premature aging caused by continuous high-load operation of a single device, and extends system life. For example, when the temperature of the main unit drops suddenly or fails, the standby unit can take over the load within 2 seconds, reducing equipment wear. Traditional equipment has a lifespan of only about 5 years due to continuous full-load operation; this invention can extend it to ≥8 years through a load distribution strategy.

[0019] 7. This invention employs a rotating start-stop control strategy among heater groups, combined with peak-valley electricity price characteristics and thermal storage status adjustment strategies, to achieve load transfer for electric heating and peak shaving and valley filling. It integrates dynamic strategies considering seasonal electricity prices, curtailment losses, and energy storage efficiency, reducing grid purchase costs during peak periods (e.g., driving thermal storage with off-peak electricity) and lowering equipment maintenance frequency (extending lifespan by 60%). Predictive models (ARIMA + real-time weather fusion) improve control accuracy, preventing thermal storage overflow or insufficiency, and reducing the total lifecycle cost by 15%-25% compared to traditional solutions, thus improving overall economic efficiency.

[0020] 8. This invention possesses fault adaptation and safety assurance capabilities. The system design supports maintaining the minimum operating power mode under grid fault conditions, ensuring that critical pipelines do not condense salt and the main steam system does not become unstable, thus improving the system's safety and robustness. Through power-level control (e.g., activating one group when excess power is ≤5MW, and triggering an early warning when it exceeds 20MW), the impact on grid fluctuations is reduced, meeting relevant standards. Redundancy design and a fast switching mechanism (fault response ≤2 seconds) ensure high system availability, avoiding molten salt solidification or energy storage interruptions due to equipment failure.

[0021] 9. This invention supports thermal management optimization for multi-salt systems. The system is compatible with the combined use of binary and ternary molten salts. Through temperature division and heat source allocation, the thermal storage system has a wider operating temperature range and higher thermal management flexibility, adapting to different cycle conditions and power generation requirements. Attached Figure Description

[0022] The accompanying drawings, which form part of this embodiment, are used to provide a further understanding of this embodiment. The illustrative embodiments and their descriptions are used to explain this embodiment and do not constitute an improper limitation of this embodiment.

[0023] Figure 1 This is a schematic diagram of the thermal storage system structure according to Embodiment 1 of the present invention;

[0024] Figure 2 This is a schematic diagram of the operating structure of the dual-group electric heater in Embodiment 1 of the present invention;

[0025] Figure 3 This is a detailed diagram of the electric heater heating molten salt according to Embodiment 1 of the present invention;

[0026] The components include: 1. Electric heater; 2. High-temperature molten salt tank; 3. Low-temperature molten salt tank; 4. Low-temperature molten salt pump; 5. High-temperature molten salt pump; 6. Reheater; 7. Low-temperature molten salt-water heat exchanger; 8. Molten salt thermal storage unit; 9. Low-temperature molten salt electric heating unit; 10. High-temperature molten salt electric heating unit; 11. Rankine cycle power generation unit; 12. High-pressure heater unit; and 13. Low-pressure heater unit. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0029] Renewable energy technologies such as wind power and photovoltaic power have developed rapidly, with installed capacity continuously expanding, becoming the main source of new power generation capacity. However, wind and solar power are significantly affected by fluctuations in natural resources, exhibiting randomness, intermittency, and uncertainty in their output, making it difficult to achieve stable load following capability. This characteristic not only poses a challenge to grid dispatch but also exacerbates the spatiotemporal mismatch between power system supply and demand, leading to "wind and solar curtailment." The effective absorption and efficient utilization of new energy sources urgently need to be addressed. To improve the system's capacity to accept new energy sources and ensure the safe and stable operation of the power system, energy storage facilities with rapid response and energy regulation capabilities need to be constructed simultaneously. Among various energy storage technologies, electrochemical energy storage has a fast response speed, but it faces bottlenecks in terms of capacity scalability, system security, and total life cycle cost. Thermal energy storage technology using molten salt as a medium, with its advantages of high energy density, low cost, long lifespan, and good security, has become the mainstream technology choice for current high-temperature energy storage systems, especially suitable for large-scale, long-term energy storage and release.

[0030] In terms of thermal storage system configuration, traditional molten salt thermal storage systems have been widely validated for their good performance in terms of economy and thermal stability. To further improve response speed and system regulation capabilities, some studies have introduced electric heater configurations. By converting electrical energy into heat energy and storing it in molten salt, an "electricity-heat-electricity" path is formed, enabling cross-time-period energy transfer and multi-source complementary optimized operation. In particular, by using electric heaters to directly convert surplus electricity from wind power, photovoltaic power, etc., into heat energy and storing it in molten salt with high specific heat capacity and high stability, the utilization rate of new energy power generation can be significantly improved, alleviating system peak-shaving pressure and reducing curtailment rate. During peak load periods, the release of heat energy to drive steam turbines or heating systems can improve system operational flexibility and expand the boundaries of renewable energy utilization. Due to its wide regulation time scale and strong heat output stability, electrically heated molten salt thermal storage systems are becoming an important technical support for promoting the coordinated operation of "source-grid-load-storage". Furthermore, traditional centralized thermal energy storage systems struggle to adapt flexibly to dynamic load demands in the face of seasonal fluctuations and intraday peak-valley differences in wind and solar power output. Therefore, constructing an electrically heated molten salt thermal energy storage system with multi-mode operation capabilities, supporting group control and multi-level energy utilization, has become a crucial direction for improving system operating efficiency and addressing diverse scenario demands. By rationally configuring the number and power levels of electric heater groups and optimizing heating strategies and thermal energy storage control schemes, a deep response to fluctuations in renewable energy output and time-of-use utilization can be achieved, improving the continuity and stability of the system's external energy supply.

[0031] Therefore, conducting research on the operation mechanism and control strategy of electric heating molten salt thermal energy storage system for wind-solar coupling can effectively improve the renewable energy absorption capacity and provide support for building a modern integrated energy system that is multi-energy complementary and highly efficient.

[0032] Existing technology discloses a hybrid heating molten salt thermal storage peak-shaving system, including but not limited to a superheater, reheater, main steam control valve, high-pressure cylinder, reheat steam control valve, intermediate-pressure cylinder, low-pressure steam control valve, low-pressure cylinder, generator, electrical switch, regenerative heater, deaerator, feedwater pump, condenser, condensate pump, steam-pressure water heat exchanger, pressure water pump, atmospheric pressure water tank, pressure water tank, high-temperature molten salt pump, steam-molten salt heat exchanger, electric heater, low-temperature molten salt pump, low-temperature molten salt storage tank, high-temperature molten salt storage tank, molten salt-pressure water heat exchanger, wind turbine generator set, and valves. This scheme stores excess heat and electricity from unit load reduction and peak shaving, as well as excess electricity from wind and solar power generation, in high-temperature molten salt. During unit load increase, the high-temperature molten salt heats the pressure water to generate high-temperature pressure water or high-temperature high-pressure steam, which enters the original unit's thermal system to increase power generation, achieving flexible peak shaving for thermal power plants. This scheme can store surplus thermal power and surplus electricity from wind and solar power during peak shaving in high-temperature molten salt, and release it to assist power generation when the unit load increases, thus possessing a certain degree of regulation capability. However, the scheme does not disclose the specific operation and control methods of the electric heater, and lacks refined control strategies for wind and solar power curtailment at different power levels, making it difficult to achieve dynamic response and flexible adjustment.

[0033] As described in the background section, most molten salt electric heating systems currently used in practical engineering applications employ fixed capacity configurations and a single control strategy. This means that the electric heaters operate at a uniform power level within the system, and the start-stop logic is typically based on threshold judgments or time-based schedules. This static configuration approach struggles to achieve flexible response and efficient matching when facing significant seasonal fluctuations in wind and solar power resources and dynamic changes in electricity load, leading to system operational problems: Firstly, the electric heaters exhibit lag in response, failing to quickly adjust power output according to real-time changes in renewable energy output, resulting in some surplus electricity being wasted as it cannot be converted into heat energy in a timely manner. Secondly, the coarse control of the thermal storage process causes uneven temperature distribution within the molten salt tank and low thermal storage efficiency, affecting the stability and economy of the heating system. Furthermore, due to the lack of refined scheduling strategies, some heater equipment operates at low loads or in idle standby states for extended periods, making it difficult to guarantee equipment utilization and return on investment, and even shortening equipment lifespan.

[0034] To address at least one of the aforementioned problems, this application provides a wind-solar thermal energy storage system and method adapted to seasonal climate changes. It enables adaptive regulation under complex and variable renewable energy output environments, supports independent control of multiple heaters, and has the capability for individual heater start-up and shutdown and time-of-day power allocation. It can adjust the operating status of each device based on real-time power supply and demand, and achieve multi-objective optimized operation based on seasonal resource allocation, thermal storage tank temperature field distribution, and grid dispatch signals. By introducing a dynamic power allocation mechanism, the system can efficiently absorb fluctuating power sources while ensuring stable thermal storage, improving the overall system's flexible peak-shaving capability. Furthermore, the hierarchical control strategy allows different heaters to be configured at different thermal nodes such as main steam heating, reheat steam boosting, or feedwater preheating, achieving cascaded utilization of molten salt energy and multi-energy synergy, thus expanding the system's operating scenarios and overall benefits.

[0035] The wind-solar-thermal-storage (wind power-photovoltaic-solar thermal power plant coupled with electric heater and molten salt thermal storage) system, adapted to seasonal climate changes, includes a wind power generation unit, a photovoltaic power generation unit, a solar thermal power generation unit, an electric heating unit, and a molten salt thermal storage unit. When the wind power and photovoltaic power generation devices in the wind power generation unit and the photovoltaic power generation unit cannot be fully absorbed by the grid, the surplus electrical energy is transmitted to the electric heating unit via a DC transmission and transformation device. The electric heating device then heats the molten salt and stores it in the molten salt thermal storage unit.

[0036] like Figure 1 As shown, one type of wind-solar-thermal-storage system includes an interconnected molten salt thermal storage unit 8 and a Rankine cycle power generation unit 11. The molten salt thermal storage unit 8 includes an electric heater 1, and a high-temperature molten salt tank 2 and a low-temperature molten salt tank 3 connected to the electric heater 1. The Rankine cycle power generation unit 11 includes a steam generator, a high-pressure cylinder, and a generator connected in sequence, and also includes a condenser, a deaerator, a high-pressure heater unit 10, and a low-pressure heater unit 13.

[0037] exist Figure 1 Based on the medium-wind solar thermal energy storage system, such as Figure 2 As shown, this invention proposes a "dual-component independent heating operation mode" system. Optionally, the molten salt thermal storage unit 8 is divided into a low-temperature molten salt electric heating unit 9 and a high-temperature molten salt electric heating unit 10; both the low-temperature molten salt electric heating unit 9 and the high-temperature molten salt electric heating unit 10 include at least one electric heater 1, and a high-temperature molten salt tank 2 and a low-temperature molten salt tank 3 connected to the electric heater 1.

[0038] The high-temperature molten salt tank 2 in the low-temperature molten salt electric heating unit 9 is connected to a low-temperature molten salt-water heat exchanger 7 via a pipe and a high-temperature molten salt pump 5. The low-temperature molten salt-water heat exchanger 7 is connected to the low-temperature molten salt tank 3 in the low-temperature molten salt electric heating unit 9 via a pipe and a low-temperature molten salt pump 4. The low-temperature molten salt-water heat exchanger 7 is also connected to the deaerator in the Rankine cycle power generation unit 11, and is connected in parallel with the high-pressure heater unit 12 to the steam generator via a pipe.

[0039] The high-temperature molten salt tank 2 in the high-temperature molten salt electric heating unit 10 is connected to the steam generator via a pipe and a high-temperature molten salt pump 5. The steam generator is connected to the low-temperature molten salt tank 3 in the high-temperature molten salt electric heating unit 10 via a pipe and a low-temperature molten salt pump 4. The steam generator is connected to the high-pressure cylinder, which is connected to a reheater 6. The reheater 6 is also connected to the output pipe of the high-temperature molten salt tank 2 in the high-temperature molten salt electric heating unit 10 and the input pipe of the low-temperature molten salt tank 3.

[0040] Specifically, the electric heaters are divided into two groups. The first group of electric heaters in the high-temperature molten salt electric heating unit 10 uses high-temperature molten salt, part of which is used to heat the main steam feedwater, and the other part is used to heat the reheat steam. The two portions of molten salt are then mixed. The second group of electric heaters in the low-temperature molten salt electric heating unit 9 is connected in parallel to the high-pressure heater unit 12 circuit. It diverts a portion of the feedwater and heats it to a preheating temperature matching the output of the high-pressure heater unit 12, before mixing it with the feedwater heated by the high-pressure heater unit 12. This scheme achieves differentiated operation, dynamic power allocation, and seasonal operating condition optimization for the electric heater 1. The system operates according to four seasons: spring, summer, autumn, and winter. Combined with seasonal fluctuations in wind and solar resources and load changes, two groups of molten salt electric heating units are set up, supporting independent control and parallel operation of each electric heater, thereby achieving flexible adjustment of the total system power. When there is excess power, more heaters can be activated to increase heat storage; when there is insufficient power, the number of operating heaters is reduced, achieving a dynamically optimized power allocation strategy. This invention can effectively improve the renewable energy absorption rate and the utilization rate of photovoltaic curtailment, extend the service life of equipment, and improve the overall thermal storage efficiency.

[0041] The wind-solar-thermal-storage system also includes a wind power generation unit, a photovoltaic power generation unit, a solar thermal power generation unit; it also includes a solar thermal power plant, a concentrating solar collector and heat exchange system, an electric heating unit, a molten salt thermal storage unit, a grid interaction unit, etc.

[0042] Optionally, in this embodiment, a synergistic system of electricity, heat, and energy storage is formed through mechanisms such as a dual-path photovoltaic output structure, direct solar thermal heat exchange, and wind power priority drive, significantly improving the comprehensive utilization efficiency of new energy sources. The dual-path photovoltaic output structure refers to the DC output of the photovoltaic array being split into two output paths. One path connects to the grid via an inverter to supply power to the grid, meeting grid-connected power generation requirements; the other path transmits the remaining power to the electric heating unit via a DC transmission and transformation device, converting the photovoltaic power into heat energy and storing it in the molten salt thermal storage unit. The two paths can be dynamically allocated according to the real-time photovoltaic output, thermal storage status, and grid dispatch requirements, achieving flexible switching and optimal allocation of photovoltaic power between grid-connected power generation and thermal storage, improving photovoltaic utilization and reducing curtailment. Direct solar thermal heat exchange refers to the direct heat exchange between the high-temperature heat-conducting medium output from the collector in the solar thermal power generation system and the working fluid of the Rankine cycle power generation unit, without the need for intermediate heat exchange loops or additional heat transfer media. Specifically, high-temperature molten salt can directly heat the main steam feedwater or reheat steam through a high-temperature molten salt electric heating unit, realizing the direct transfer of heat from the solar thermal system to the steam cycle. Wind power priority drive refers to the practice in multi-energy complementary systems where, when there is surplus wind power output and it meets grid connection requirements, the surplus wind power is preferentially allocated to a second set of electric heaters (high-pressure feedwater heating group) with rapid response capabilities to heat the feedwater. This achieves efficient utilization and dynamic regulation of surplus wind power, improves wind power utilization, and ensures the stability of system operation.

[0043] like Figure 1 and Figure 2 In this system, the electric heater 1 is used to convert wind or solar power waste into heat energy to heat molten salt; the high-temperature molten salt tank 2 is used to store the heated high-temperature molten salt; the low-temperature molten salt tank 3 is used to store the molten salt after its temperature has decreased, enabling recycling; the low-temperature molten salt pump 4 is used to transport the low-temperature molten salt to the heat exchange unit; the high-temperature molten salt pump 5 is used to transport the high-temperature molten salt to the heat exchange unit; the reheater 6 is used to reheat the steam extracted from the steam turbine; the low-temperature molten salt-water heat exchanger 7 is used to transfer the heat from the low-temperature molten salt to the water for preheating; and the molten salt heat storage unit... Unit 8 is used to store heat from the solar collector of the solar thermal system and heat converted from wind power-photovoltaic surplus electricity by an electric heater; the low-temperature molten salt electric heating unit 9 uses the low-temperature molten salt heat for feedwater preheating; the high-temperature molten salt electric heating unit 10 heats the feedwater to the main steam temperature and heats the cold reheat steam; the Rankine cycle power generation unit 11 is used to drive the steam turbine to generate electricity using high-temperature steam; the high-pressure heater unit 12 is used to preheat the high-pressure feedwater in stages; and the low-pressure heater unit 13 is used to preheat the low-pressure feedwater in stages.

[0044] Optionally, the photovoltaic power generation unit includes a photovoltaic array, an inverter, and a grid-connected controller, etc., and the output is divided into two paths: the first path is directly connected to the grid for power supply, and the second path is connected to the molten salt electric heating system.

[0045] The heat exchange system of the solar thermal power generation unit is directly connected to the high-temperature molten salt tank 2 of the molten salt thermal storage unit 8. The thermal coupling of solar thermal energy and electric heating energy is achieved through sensible heat storage of molten salt. The excess heat energy of the solar thermal power plant is preferentially used for heating the main steam feedwater.

[0046] The electric heating unit includes two sets of electric heater units: in the first set of heater units (main steam heating set), part of the high-temperature molten salt is used to heat the main steam feedwater, and part of it is used to heat the cold reheat steam and then mixed with the molten salt used to heat the feedwater; the second set of heater units (high pressure heater feedwater heating set) is connected in parallel with the high pressure heater unit 12, and a portion of the water entering the high pressure heater unit 12 is diverted to heat it to the preheater feedwater temperature in the steam generator and then mixed with the feedwater heated by the high pressure heater unit 12; each set of heaters includes N 5MW molten salt electric heaters, which are connected to the molten salt circulation system through a parallel circuit.

[0047] Each electric heating unit includes molten salt electric heating, an electric heat tracing system, and an intelligent coordination controller. The electric heater 1 is installed on the molten salt pipeline from the outlet of the low-temperature molten salt tank 3 to the inlet of the high-temperature molten salt tank 2. It is connected to the second path of the photovoltaic power generation system through a power regulation module to convert surplus wind and solar power into molten salt heat energy. The electric heat tracing tape is wrapped around the outer wall of the molten salt pipeline. The heat tracing power is dynamically adjusted through a temperature control module to prevent the molten salt from solidifying. The intelligent coordination controller controls the power distribution of the electric heater 1 and the start and stop of the electric heat tracing tape in real time based on wind power and photovoltaic output forecasts, grid load demand, and molten salt heat storage status.

[0048] The electric heater 1 of the electric heating unit is connected to the molten salt circulation system through a parallel circuit, forming a parallel topology of electrical and thermal power. The input of each heater 1 is connected to the power grid / central controller, and the output is connected in parallel to the circulation loop of the molten salt storage tank. During the operation of the molten salt energy storage system, the sensible heat range of the molten salt working medium is used to drive the molten salt electric heater 1 to heat the low-temperature molten salt during off-peak hours, so that it is heated to the design temperature and then stored in the molten salt storage tank. During peak power periods, the molten salt heat exchange system is used to transfer heat from the high-temperature molten salt in the molten salt tank to replace part of the heat during peak periods and reduce peak energy consumption.

[0049] The molten salt thermal storage unit 8 runs parallel to the electric heating unit. The molten salt used for heating the main steam feedwater and cold reheat steam is a binary salt, while the thermal storage unit connected in parallel with the high-pressure heater uses a ternary salt.

[0050] One control method for the wind-solar-thermal-storage system of the present invention includes the following steps:

[0051] S1. Real-time monitoring:

[0052] Optionally, real-time collected parameters include the total output power of the wind power generation unit, photovoltaic power generation unit and solar thermal power generation unit, grid load demand, temperature, liquid level and thermal storage capacity of the high temperature molten salt tank 2 and low temperature molten salt tank 3 of the molten salt thermal storage unit, and the operating status and power output of the two sets of electric heater units (main steam heating group and high pressure water supply group).

[0053] S2. Dynamic power allocation and regulation: Based on wind and solar power output prediction data, the power of electric heater 1 is allocated according to the following rules:

[0054] When there is sufficient surplus power: Excess power from wind and solar power is allocated to two sets of electric heater units according to a preset ratio. Specifically, excess power from wind power is preferentially allocated to the second set of electric heaters (high-pressure feedwater heating group); excess power from solar power is preferentially allocated to the first set of electric heaters (main steam heating group); if the surplus power exceeds the total capacity of the two sets, the off-grid standby mode is activated or an energy storage overflow warning is triggered.

[0055] When residual power is insufficient: ensure that the power of the first group of electric heaters (main steam heating group) is not lower than the preset minimum threshold (e.g., P). min =50% of the rated power), prioritize the heating needs of the steam generator feedwater; the remaining power is allocated proportionally to the second group of electric heaters, or the operation of the second group of electric heaters is suspended.

[0056] S3. Operation mode switching: Based on the operating conditions of the molten salt thermal storage unit 8 and the grid load demand, perform the following operations:

[0057] When the grid load is less than the total output of wind, solar and solar thermal power, the electric heater 1 is started to store heat: the excess heat energy of the solar thermal power plant is directly stored in the high-temperature molten salt tank 2 through the molten salt working medium; the excess power of wind power and photovoltaic power drives two sets of electric heater units to heat the molten salt respectively; priority is given to storing solar thermal energy: when the temperature of the molten salt tank has not reached the upper limit, the heat energy of the solar thermal power plant is given priority to heating the main steam feedwater.

[0058] When the grid load is greater than the total output of wind, solar and thermal power, molten salt thermal energy is released first for power generation: the thermal energy of high-temperature molten salt tank 2 is used first for main steam heating and power generation; if the molten salt thermal storage is insufficient, the number of operating groups of the second electric heater (high-temperature feedwater group) is reduced, and the first electric heater is retained to maintain the basic power.

[0059] S4. Inter-group rotation and equalization control: The heater runtime equalization is achieved through the following strategies:

[0060] Rotate the main / standby units according to time; dynamically adjust the start-up priority based on the cumulative operating time of each group; increase the rotation frequency of the second group of electric heaters during seasonal operating cycles (such as summer) to cope with high load demand.

[0061] S5. Threshold Response and Safety Control: Temperature Triggering Conditions for High-Temperature Molten Salt Tanks

[0062] Low temperature threshold (temperature of high temperature molten salt tank is less than or equal to the preset low temperature threshold): immediately start all four groups of electric heaters to rated power, and prioritize the power of the first group of electric heaters; High temperature threshold (temperature of high temperature molten salt tank is greater than or equal to the preset high temperature threshold): gradually reduce the number of electric heater groups in operation until only the first group of electric heaters is kept at the minimum power (to prevent molten salt from solidifying), or switch to off-grid standby mode.

[0063] Molten salt thermal storage capacity constraint: When the thermal storage capacity is ≥90% (first preset percentage), the electric heater thermal storage is suspended; when the thermal storage capacity is ≤10% (second preset percentage), all heaters are forcibly started and solar thermal energy is used to supplement electric heating.

[0064] Understandably, when surplus power is abundant, wind power exhibits significant intermittency and volatility, with output power greatly affected by climate and wind speed, resulting in frequent fluctuations and high response requirements. The second group of electric heaters (high-pressure feedwater heating group) heats feedwater at low temperatures and possesses strong rapid adjustment capabilities, making it suitable for absorbing and regulating surplus wind power. Therefore, surplus wind power is preferentially allocated to the second group. Photovoltaic power generation output is relatively stable and concentrated during the day, matching the timing of the main steam heating load of the solar thermal power plant. The first group of electric heaters (main steam heating group) is preferentially allocated surplus photovoltaic power to improve the stability of steam parameters and the efficiency of main steam heating. When surplus power is insufficient, to ensure the safe and stable operation of the unit, priority is given to ensuring that the power of the first group of electric heaters (main steam heating group) is not lower than the preset minimum threshold (e.g., 50% of rated power) to meet the feedwater heating requirements of the steam generator and avoid unit instability caused by steam parameter fluctuations. The second group of electric heaters (high-pressure feedwater heating group) dynamically adjusts its power based on the remaining power or suspends operation when power is insufficient, flexibly adapting to power supply fluctuations and avoiding equipment overload and ineffective energy consumption.

[0065] Optional, such as Figure 3 As shown, the second group of electric heaters includes four units operating in parallel (1). These four electric heaters are configured in dynamic power regulation mode: each electric heater independently adjusts its power. - ), total power ; Fluctuations in wind and solar power It exhibits negative feedback and is automatically adjusted through a PID algorithm; the control is constrained by the molten salt temperature and the heat storage capacity (≥20%).

[0066] Optionally, the wind and solar power output forecast data is generated using the following methods: historical data is modeled using the ARIMA(2,1,2) model; real-time meteorological data (wind speed, irradiance, temperature, humidity, cloud cover) is integrated with the ARIMA forecast results, and a weighted formula is used. Where the weight α∈[0.6, 0.8] represents the degree of confidence in the prediction results of the ARIMA model; The predicted wind and solar power output at time t; The predicted output at time t is obtained based on the ARIMA(2,1,2) model; It provides the predicted output for time t calculated based on real-time meteorological data (wind speed, irradiance, temperature, humidity, cloud cover, etc.); the prediction time resolution is ≤15 minutes, covering the current time to the next 3 hours.

[0067] Optionally, in step S5, the off-grid standby mode is as follows: when a grid failure occurs, the connection between the electric heater and the grid is cut off, and the system switches to the self-powered mode of the molten salt thermal storage system to maintain the electric heater at the lowest power to prevent the molten salt from solidifying.

[0068] The electric heaters are configured with redundancy: two main and two standby units operate in parallel. The main steam heating group (binary salt circuit) includes one main unit and one standby unit; the high-pressure feedwater group (ternary salt circuit) includes one main unit and one standby unit. The temperature difference between the standby unit inlet temperature and the main unit temperature is ≤5°C. When a sudden drop in temperature of ≥3°C / min in the main unit is detected for 10 seconds or a hardware failure, the standby unit will take over the load within 2 seconds. The power ramp-up rate is limited as follows: main steam heating group: ≤5% rated power / second; high-pressure feedwater group: ≤3% rated power / second (because the ternary salt high-temperature circuit requires more stable power regulation).

[0069] This invention validates a wind-solar-thermal-storage system and its regulation method adapted to seasonal climate change through four embodiments. The four embodiments select typical days (spring equinox, summer solstice, autumn equinox, and winter solstice) for each of the four seasons, and, combined with the seasonal wind and solar resource characteristics, climate conditions, and load demand characteristics of a specific location, systematically demonstrate the specific application and technical effects of the regulation strategy under different seasonal scenarios.

[0070] Example 1:

[0071] Spring Equinox Control Strategy: On the spring equinox, a dynamic balance between wind and solar power output needs to be achieved, coordinated with the molten salt thermal energy storage system. In terms of system configuration, the main steam unit uses a binary salt circuit, including two main and two backup 5MW electric heaters, while the EPDM unit uses a ternary salt circuit with the same number of electric heaters. The solar thermal power plant is directly coupled to the main steam circuit, with a maximum temperature limit of 320℃ for the high-temperature tank. During the solar-dominated period from 06:00 to 18:00, when solar power output exceeds 120MW and wind power exceeds 80MW, the main steam unit activates all four electric heaters (total power 20MW) to prioritize the absorption of solar power, keeping the molten salt outlet temperature below 300℃. The EPDM unit operates two main heaters at 50% power (total power 5MW) to primarily absorb surplus wind power, with the molten salt outlet temperature not exceeding 545℃. Excess heat from the solar thermal system is prioritized for heating the main steam feedwater, automatically switching to standby mode when the thermal energy storage capacity reaches 95%. During the wind-dominated period from 18:00 to 06:00, if the wind power output exceeds 150MW, the main steam turbine will operate two main units at 4MW power (total power 8MW), and the effluent heaters will activate all four electric heaters (total power 20MW) to primarily absorb excess wind power. The molten salt outlet temperature will not exceed 545℃. To improve system redundancy and reliability, if a main heater fails, the backup heater can seamlessly take over the load within 2 seconds. The power ramp-up rate of the main steam turbine will not exceed 5% / second, and that of the effluent heaters will not exceed 3% / second.

[0072] Example 2:

[0073] Summer Solstice Control Strategy: During the summer solstice, strong sunlight and high photovoltaic output necessitate optimizing photovoltaic absorption capacity and achieving coordinated operation of solar thermal and electric heating. The system's main steam units (binary salt) are configured with 3 primary units plus 1 backup electric heater (5MW each), while the blast furnace heater units (ternary salt) are configured with 4 primary units without backup, suitable for full operation when surplus power is available. Regarding the molten salt thermal storage unit, the main steam loop is equipped with a 500-ton binary salt tank, and the blast furnace heater loop is equipped with a 600-ton ternary salt tank. During peak photovoltaic (PV) hours (06:00-18:00), when PV output exceeds 150MW, the three heaters of the main steam unit operate at 70% power (total power 10.5MW), with the molten salt outlet temperature controlled below 300℃; the four heaters of the HPLC unit operate at full power (total power 20MW), fully absorbing surplus wind and PV power, with the molten salt outlet temperature not exceeding 545℃. During this phase, solar thermal resources are prioritized for heating the main steam unit. Once the thermal storage capacity reaches 90%, excess electricity is directly fed into the grid. During nighttime hours (18:00-06:00), if the electricity price is below 0.3 yuan / kWh, all four heaters of the HPLC unit (total power 20MW) are activated, prioritizing the use of surplus wind power to raise the ternary salt thermal storage temperature; one main steam unit remains operating at 2MW to maintain the molten salt temperature gradient and ensure the continuity of the thermal system.

[0074] Example 3:

[0075] Autumnal Equinox Control Strategy: Given the fluctuating wind and solar power outputs during the autumnal equinox, the system must possess rapid response capabilities and redundancy. The main steam generator uses a binary salt circuit, configured with 2 main and 2 standby heaters; the HPLC system (ternary salt) has 3 main and 1 standby heaters. Regarding the molten salt thermal storage temperature range, the main steam circuit is 280-300℃, and the HPLC circuit is 450-545℃. During the solar-dominated period from 08:00 to 16:00, when solar power output exceeds 110MW and wind power exceeds 60MW, the two heaters in the main steam generator operate at full load (total power 10MW), and the three main heaters in the HPLC system operate at 60% power (total power 9MW), with the molten salt outlet temperature controlled below 545℃. To ensure system stability, the main and standby units are rotated every 4 hours, maintaining the main steam generator inlet temperature difference within 5℃. During the period from 16:00 to 22:00 when wind power is rising, if the wind power output exceeds 140MW, all four heaters of the high-pressure heater group will be turned on (total power 20MW), and when the molten salt thermal storage capacity reaches 95%, the molten salt circulation rate will be increased by 15% to further enhance the thermal storage capacity.

[0076] Example 4:

[0077] Winter Solstice Control Strategy: During the winter solstice, temperatures are extremely low, and wind power penetration is high. The system must balance efficient operation with equipment reliability. Both the main steam unit (binary salt) and the blast furnace heater unit (ternary salt) are equipped with four main electric heaters, with no backup units, to achieve high-intensity operation. The lower limit of the temperature for the binary salt tank is 550℃, which is the forced heating trigger threshold; the upper limit of the temperature for the ternary salt tank is set at 565℃. During high wind speed periods at night (20:00-04:00), when wind power output exceeds 180MW, the four heaters of the main steam unit operate at full power (total power 20MW), with the molten salt outlet temperature not exceeding 300℃; the four heaters of the blast furnace heater unit operate at 4.5MW (total power 18MW), with the molten salt outlet temperature controlled below 545℃; the thermal energy from the solar thermal power plant is prioritized to supplement the main steam circuit demand. When the thermal storage capacity reaches 95%, the system will sell the excess electricity at the real-time electricity price (0.4 yuan / kWh). In extremely cold environments, if the ambient temperature is below -20°C, the system will activate all electric heating tapes, increasing the molten salt circulation rate by 30%; at the same time, the preheating channel of the redundant heaters will be activated to ensure that the temperature of the standby unit is maintained above 5°C, ensuring that it can quickly take over operation within 2 seconds.

[0078] The above description is merely a preferred embodiment of this practice and is not intended to limit the scope of this practice. Various modifications and variations can be made to this practice by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this practice should be included within the protection scope of this practice.

Claims

1. A wind-solar-thermal storage system adapted to seasonal climate changes, characterized in that, This includes interconnected molten salt thermal storage units and Rankine cycle power generation units; The molten salt thermal storage unit includes a low-temperature molten salt electric heating unit and a high-temperature molten salt electric heating unit; each of the low-temperature molten salt electric heating unit and the high-temperature molten salt electric heating unit includes at least one electric heater, as well as a high-temperature molten salt tank and a low-temperature molten salt tank connected to the electric heater; The high-temperature molten salt electric heating unit uses high-temperature molten salt, part of which is used to heat the main steam feedwater and the other part is used to heat the reheat steam. The low-temperature molten salt electric heating unit is connected in parallel to the high-pressure heater unit circuit in the Rankine cycle power generation unit. It diverts a portion of the feedwater and heats it to a preheating temperature that matches the output of the high-pressure heater unit. Then it mixes with the feedwater heated by the high-pressure heater unit to achieve differentiated operation, dynamic power distribution and seasonal operating condition optimization of the electric heater.

2. A wind-solar-thermal storage system adapted to seasonal climate changes as described in claim 1, characterized in that, The high-temperature molten salt tank in the low-temperature molten salt electric heating unit is connected to the low-temperature molten salt-water heat exchanger via a pipeline and a high-temperature molten salt pump; the low-temperature molten salt-water heat exchanger is connected to the low-temperature molten salt tank in the low-temperature molten salt electric heating unit via a pipeline and a low-temperature molten salt pump; the low-temperature molten salt-water heat exchanger is also connected to the deaerator in the Rankine cycle power generation unit, and is connected in parallel with the high-pressure heater unit to the steam generator via a pipeline.

3. A wind-solar-thermal storage system adapted to seasonal climate changes as described in claim 1, characterized in that, The high-temperature molten salt tank in the high-temperature molten salt electric heating unit is connected to a steam generator via a pipe and a high-temperature molten salt pump; the steam generator is connected to the low-temperature molten salt tank in the high-temperature molten salt electric heating unit via a pipe and a low-temperature molten salt pump; the steam generator is connected to a high-pressure cylinder, the high-pressure cylinder is connected to a reheater, and the reheater is also connected to the output pipe of the high-temperature molten salt tank in the high-temperature molten salt electric heating unit and the input pipe of the low-temperature molten salt tank.

4. A wind-solar-thermal storage system adapted to seasonal climate changes as described in claim 1, characterized in that, The Rankine cycle power generation unit includes a steam generator, a high-pressure cylinder, and a generator connected in sequence; the Rankine cycle power generation unit also includes a condenser, a deaerator, a high-pressure heater unit, and a low-pressure heater unit.

5. A wind-solar-thermal storage system adapted to seasonal climate changes as described in claim 1, characterized in that, When there is a power surplus, the number of heaters in operation is increased to enhance heat storage; when there is a power shortage, the number of heaters in operation is reduced, thus achieving a dynamically optimized power allocation strategy.

6. A wind-solar-thermal storage system adapted to seasonal climate changes as described in claim 5, characterized in that, When there is sufficient surplus power, the excess power from wind power and photovoltaic power is allocated to the two sets of electric heater units according to a preset ratio. Among them, the excess power from wind power is preferentially allocated to the second set of electric heaters, and the excess power from photovoltaic power is preferentially allocated to the first set of electric heaters. If the surplus power exceeds the total capacity of the two sets of electric heater units, the off-grid standby mode is activated or the energy storage overflow warning is triggered. When there is insufficient surplus power, the power of the first set of electric heaters is ensured to be no less than the preset minimum threshold, and the heating needs of the steam generator feedwater are prioritized. The remaining power is allocated to the second set of electric heaters according to the ratio, or the operation of the second set of electric heaters is suspended.

7. A wind-solar-thermal storage system adapted to seasonal climate changes as described in claim 1, characterized in that, When the grid load is less than the total output of wind, solar, and solar thermal power, the excess heat energy of the solar thermal power plant is directly stored in a high-temperature molten salt tank through molten salt working fluid; the excess power from wind and solar power drives two sets of electric heater units to heat the molten salt; when the temperature of the molten salt tank has not reached the upper limit, the heat energy of the solar thermal power plant is preferentially used for heating the main steam feedwater; when the grid load is greater than the total output of wind, solar, and solar thermal power, the heat energy of the high-temperature molten salt tank is preferentially used for heating the main steam and generating electricity; if the molten salt heat storage is insufficient, the number of operating sets of the second set of electric heaters is reduced, and the first set of electric heaters is retained to maintain the base power.

8. A wind-solar-thermal storage system adapted to seasonal climate changes as described in claim 1, characterized in that, If the temperature of the high-temperature molten salt tank is less than or equal to the preset low-temperature threshold, all electric heaters will be started immediately at their rated power, with priority given to ensuring the power of the first group of electric heaters; if the temperature of the high-temperature molten salt tank is greater than or equal to the preset high-temperature threshold, the number of electric heaters in operation will be gradually reduced until only the first group of electric heaters is kept at its minimum power, or the system will be switched to off-grid standby mode; if the heat storage capacity is greater than or equal to the first preset percentage, the electric heaters will be suspended from storing heat; if the heat storage capacity is less than or equal to the second preset percentage, all heaters will be started and solar thermal energy will be used to supplement the electric heating.

9. A wind-solar-thermal storage system adapted to seasonal climate changes as described in claim 1, characterized in that, Historical data were modeled using the ARIMA model; real-time meteorological data and ARIMA forecast results were integrated. When a power grid failure occurs, the connection between the electric heater and the power grid is disconnected, and the system switches to the autonomous power supply mode of the molten salt thermal storage system to maintain the electric heater at the lowest power to prevent the molten salt from solidifying. The electric heater adopts a redundant configuration: two main units and two standby units operate in parallel; when the temperature drop rate of the main unit is detected to be greater than or equal to the preset rate and lasts for a preset time, the standby unit will take over the load within the preset time.

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