Co2 heat pump-carnot cell coupling system and control method for power plant peak shaving

Abstract

The present application belongs to the technical field of heat pump energy storage and thermal power generation, and discloses a CO2 heat pump-Carnot cell coupling system and control method for power plant peak shaving, to solve the technical problems of high energy consumption caused by the dependence of existing molten salt heat storage on electric heating, low coupling degree of heat pump and steam cycle, difficulty in collaborative utilization of exhaust steam waste heat and extraction steam heat, and lack of electricity price response control means. The system comprises a power cycle loop, a heat storage loop, a heat pump loop, a heat release loop, a heat pump low-temperature heat source loop and an extraction steam branch. The heat storage medium flows from the low-temperature tank to the high-temperature tank through the first heat exchanger and the second heat exchanger in sequence, the heat pump releases heat to the heat storage medium through the first heat exchanger and absorbs exhaust steam waste heat through the fourth heat exchanger, and the extraction steam branch draws steam from the boiler outlet and heats the heat storage medium through the second heat exchanger. The technical solution disclosed by the present application can improve the economic efficiency and energy utilization efficiency of thermal power unit peak shaving.

Description

Technical Field

[0001] This invention belongs to the field of heat pump energy storage and thermal power generation technology, and specifically relates to a CO2 heat pump-Carnot battery coupling system and control method for power plant peak shaving. Background Technology

[0002] Due to the limited absorption capacity of the power grid, the electricity market experiences temporary supply-demand imbalances, potentially leading to low or even zero electricity prices. For traditional thermal power units, continuing to operate during periods of low or zero electricity prices can easily result in decreased operational economics. Thermal energy storage technology, as an effective means of energy time-shifting, can efficiently store surplus electricity during periods of low electricity prices and release it for utilization during periods of high electricity prices, becoming a key technology for improving the flexible peak-shaving capacity and operational economics of thermal power units.

[0003] Molten salt thermal energy storage is one of the most common thermal energy storage methods for thermal power units. It has the advantages of simple system structure, convenient control and high thermal energy storage efficiency. This method heats the thermal energy storage system by electric heating combined with high-temperature steam extracted from the steam power circulation loop. However, the power consumption required to drive the thermal energy storage is large, making it difficult to fully utilize the energy storage value of surplus electricity during periods of low electricity prices.

[0004] Heat pump technology is a highly efficient energy conversion technology that uses a small amount of electricity to drive a compressor, upgrading low-grade heat energy into high-grade heat energy. It is an effective way to improve the heat source supply of thermal storage systems. Applying heat pump technology to thermal storage systems of thermal power units to replace traditional electric heating methods, and combining it with existing steam extraction heating methods to supply heat to the thermal storage system, can significantly reduce system energy consumption, thereby further improving thermal storage efficiency and system energy utilization. However, in existing solutions, heat pump thermal storage systems mostly operate independently, with a low degree of coupling with the steam power cycle of the thermal power unit, resulting in the failure to achieve synergistic utilization of steam extraction heat energy and waste heat resources. Therefore, new technical solutions are urgently needed to deeply couple the steam power cycle, heat pump system, and thermal storage system, improving the flexible peak-shaving capability, operational economy, and comprehensive energy utilization efficiency of thermal power units. Summary of the Invention

[0005] The purpose of this invention is to provide a CO2 heat pump-Carnot battery coupling system and control method for power plant peak shaving, addressing the technical problems of high energy consumption from electric heating and low coupling between the heat pump and steam cycle in existing thermal storage technologies, which makes it difficult to coordinate the utilization of waste heat and extracted steam heat. The technical solution disclosed in this invention replaces electric heating with a CO2 heat pump, coupling exhaust waste heat recovery and extracted steam heating, thereby improving the peak shaving economy and energy utilization efficiency of thermal power units. Furthermore, addressing the lack of electricity price response control mechanisms in existing technologies, this invention also discloses a control method based on a comprehensive risk potential function, using real-time electricity price criteria to achieve adaptive switching between power generation and thermal storage modes, and dynamically optimizing operating parameters to ensure efficient and stable operation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, this invention provides a CO2 heat pump-Carnot battery coupling system for power plant peak shaving, comprising: a power circulation loop, a heat storage loop, a heat pump loop, a heat release loop, a low-temperature heat source loop for the heat pump, and an extraction steam branch; wherein, The power circulation loop includes: a boiler, a high-pressure cylinder of a steam turbine, an intermediate-pressure cylinder of a steam turbine, a low-pressure cylinder of a steam turbine, a condenser, a low-pressure feedwater heater, a deaerator, and a high-pressure feedwater heater; wherein, the steam outlet of the boiler is connected in sequence to the high-pressure cylinder of the steam turbine, the reheater of the boiler, the intermediate-pressure cylinder of the steam turbine, the low-pressure cylinder of the steam turbine, and the steam inlet of the condenser via a first solenoid valve, and the condensate outlet of the condenser is connected to the high-pressure feedwater heater via the low-pressure feedwater heater and the deaerator via a second solenoid valve and then returns to the feedwater inlet of the boiler; The thermal storage circuit includes: a low-temperature thermal storage medium tank, a first heat exchanger, a second heat exchanger, a high-temperature thermal storage medium tank, and a third heat exchanger; wherein, the thermal storage medium outlet of the low-temperature thermal storage medium tank is connected to the thermal storage medium inlet of the high-temperature thermal storage medium tank in sequence through the thermal storage medium channel of the first heat exchanger and the thermal storage medium channel of the second heat exchanger; the thermal storage medium outlet of the high-temperature thermal storage medium tank is connected to the thermal storage medium inlet of the low-temperature thermal storage medium tank through a third solenoid valve and the thermal storage medium channel of the third heat exchanger. The heat pump circuit includes: a compressor, an expander, a first heat exchanger, and a fourth heat exchanger; wherein, the heat pump working fluid outlet of the compressor is connected to the heat pump working fluid inlet of the compressor in sequence through the heat pump working fluid channel of the first heat exchanger, the expander, and the heat pump working fluid channel of the fourth heat exchanger. The heat release circuit is led out from the pipeline between the deaerator's feedwater outlet and the second solenoid valve, passes through the fourth solenoid valve and the feedwater channel of the third heat exchanger, and then returns to the pipeline between the second solenoid valve and the feedwater inlet of the high-pressure feedwater heater. The low-temperature heat source circuit of the heat pump is led out from the pipeline between the steam outlet of the low-pressure cylinder of the steam turbine and the steam inlet of the condenser, and returns to the pipeline between the steam inlet of the condenser and the feed water inlet of the low-pressure feed water heater after passing through the low-temperature heat source channel of the fifth solenoid valve and the fourth heat exchanger. The extraction steam branch is led out from the pipeline between the steam outlet of the boiler and the steam inlet of the high-pressure cylinder of the steam turbine, and then connected to the outlet of the extraction steam branch after passing through the steam passage of the sixth solenoid valve and the second heat exchanger.

[0007] A further improvement to the technical solution of the present invention lies in that, The extraction steam outlet of the high-pressure cylinder of the steam turbine is connected to the heating steam inlet of the high-pressure feedwater heater; The extraction steam outlet of the intermediate pressure cylinder of the steam turbine is connected to the heating steam inlet of the low-pressure feedwater heater, the heating steam inlet of the deaerator, and the heating steam inlet of the high-pressure feedwater heater, respectively. The extraction steam outlet of the low-pressure cylinder of the steam turbine is connected to the heating steam inlet of the low-pressure feedwater heater.

[0008] A further improvement to the technical solution of the present invention is that it further includes: The first circulation pump is used to connect the condensate outlet of the condenser and the feed water inlet of the low-pressure feed water heater. The second circulation pump is used to connect the water supply outlet of the deaerator and the water supply inlet of the high-pressure water heater. The third circulation pump is used to connect the heat storage medium outlet of the low-temperature heat storage medium tank and the heat storage medium inlet of the first heat exchanger. The fourth circulating pump is used to connect the third solenoid valve and the heat storage medium inlet of the third heat exchanger in the pipeline. The fifth circulation pump is used to connect the fifth solenoid valve and the low-temperature heat source inlet of the fourth heat exchanger in the pipeline. The sixth circulation pump is used in the connecting pipeline between the sixth solenoid valve and the steam inlet of the second heat exchanger.

[0009] A further improvement of the technical solution of the present invention is that the heat storage medium used is molten salt.

[0010] A second aspect of the present invention provides a control method for a CO2 heat pump-Carnot battery coupling system for power plant peak shaving, applied to the CO2 heat pump-Carnot battery coupling system for power plant peak shaving as described in any one of the first aspects of the present invention, comprising: Obtain the real-time electricity price of the power grid and with the preset high electricity price threshold P H and low electricity price threshold P L For comparison, if real-time electricity price Above the high electricity price threshold P H The system then enters power generation mode, if the real-time electricity price... Below the low electricity price threshold P L The system then enters heat storage mode; In the power generation mode, the extraction steam branch and heat pump circuit are closed, and the heat release circuit is opened. The heat storage medium releases heat through the third heat exchanger to heat the unit feedwater. In the heat storage mode, the extraction steam branch and heat pump circuit are opened, and the heat release circuit is closed. High-temperature steam is drawn from the boiler steam outlet and heats the heat storage medium through the second heat exchanger. The exhaust heat of the turbine low-pressure cylinder is absorbed by the heat pump working fluid through the fourth heat exchanger and then heated by the heat pump working fluid through the first heat exchanger to heat the heat storage medium.

[0011] A further improvement of the technical solution of this invention lies in that, during system operation, a state variable matrix is ​​constructed using the temperature of the high-temperature thermal storage medium, the output power of the steam turbine, the boiler inlet feedwater temperature, and the compressor power; a control variable matrix is ​​constructed using the extraction steam flow rate, the compressor power, the thermal storage medium circulation flow rate, and the boiler input power; a comprehensive risk potential function is then constructed; the optimal control variable is obtained by solving a dynamic optimization model that minimizes the comprehensive risk potential function; the optimal control variable is then distributed as a setpoint to each actuator to coordinate the control of the extraction steam flow rate, the compressor power, the thermal storage medium circulation flow rate, and the boiler input power, so that each state variable of the system approaches its respective target value; and the deviation of the state variable is fed back to the dynamic optimization model to participate in the iterative calculation of the next control cycle. The dynamic optimization model is expressed as follows: ; ; In the formula, The optimal control variable matrix; This is the comprehensive risk potential function; The state variable matrix; For the control variable matrix; Let be the state variable matrix of the system at the next time step t+1. Let be the state variable matrix of the system at time t. Let be the control variable matrix at time t; This is the system state transition function; , These are the lower and upper bound constraint matrices for the state variables, respectively; , These are the lower and upper bound constraint matrices for the control variables, respectively. ; In the formula, This is the risk weight matrix for the state variables; This is the state deviation penalty matrix; This is the normalized deviation matrix.

[0012] A further improvement to the technical solution of the present invention lies in that, ; In the formula, It is the inverse of the diagonal scaling matrix D, used to normalize the dimensions of the deviations of each state variable to the dimensionless range. The state variable target reference value matrix; These represent the upper and lower limits (in K) of the permissible operating temperature for high-temperature thermal storage media. Rated output power of the steam turbine (kW); Rated temperature of boiler inlet feedwater (K); The compressor's rated power is in kW. Real-time temperature of the high-temperature thermal storage medium in K; Target temperature of the high-temperature thermal storage medium (K); The real-time output power of the steam turbine is expressed in kW. The target output power of the steam turbine is given in kW. Real-time feedwater temperature at boiler inlet (K); Target feedwater temperature at boiler inlet / K; The compressor's real-time output power is given in kW. Target output power of the compressor (kW); ; In the formula, , , , The risk weight coefficients are, in order: high-temperature heat storage medium temperature deviation, turbine output power deviation, boiler inlet feedwater temperature deviation, and compressor power deviation. ; In the formula, , , , The penalty coefficients are, in order: the penalty coefficient for the temperature deviation of the high-temperature heat storage medium, the penalty coefficient for the deviation of the steam turbine output power, the penalty coefficient for the deviation of the boiler inlet feedwater temperature, and the penalty coefficient for the deviation of the compressor power.

[0013] A further improvement to the technical solution of this invention lies in that, in the power generation mode, the difference between the optimal power generation obtained by comprehensive risk potential function optimization and the real-time output power of the unit is used as an error signal, and a PID controller is employed to adjust the boiler input power. The control equation is: ; In the formula, The boiler input power for the current cycle is in kW. The boiler input power (kW) for the previous cycle; This is the proportional gain coefficient. The first-order difference between the power deviation of the current control cycle and the previous control cycle; This is the integral gain coefficient. This is the power deviation signal for the current control cycle; The differential gain coefficient, The second-order difference of the power deviation in the current control cycle; k is the number of calculations; The difference between the optimized feedwater temperature and the actual feedwater temperature is used as the error signal. A PID controller is used to adjust the opening of the third solenoid valve to regulate the flow rate of the high-temperature heat storage medium. The control equation is as follows: ; In the formula, This represents the opening degree of the third solenoid valve in the current control cycle. This refers to the opening degree of the third solenoid valve in the previous control cycle; This is the proportional gain coefficient. This is the first-order difference of the feedwater temperature deviation in the current control cycle; This is the integral gain coefficient. This is the feedwater temperature deviation signal for the current control cycle; The differential gain coefficient, This is the second-order difference of the feedwater temperature deviation in the current control cycle.

[0014] A further improvement to the technical solution of this invention lies in that, in the thermal storage mode, the difference between the optimal power generation obtained by comprehensive risk potential function optimization and the real-time output power of the unit is used as an error signal. A PID controller is employed to adjust the opening of the sixth solenoid valve to regulate the extraction steam flow. The control equation is: (10) In the formula, This refers to the opening degree of the sixth solenoid valve in the current control cycle. This refers to the opening degree of the sixth solenoid valve in the previous control cycle; This is the proportional gain coefficient. This is the first-order difference of the extraction deviation signal for the current control cycle; This is the integral gain coefficient. This is the extraction deviation signal for the current control cycle; The differential gain coefficient, The second-order difference of the extraction deviation signal for the current control cycle; k is the number of calculations; Using the difference between the optimized high-temperature heat storage medium temperature and the real-time temperature as the error signal, a PID controller is used to adjust the compressor speed. The control equation is: ; In the formula, The compressor speed in the current control cycle is expressed in r·min.- ¹, used to control the temperature of the heat storage medium; The compressor speed in the previous control cycle (r·min) - ¹; This is the proportional gain coefficient. This is the first-order difference of the thermal storage medium temperature deviation signal during the current control cycle; This is the integral gain coefficient. This is the temperature deviation signal of the thermal storage medium in the current control cycle; The differential gain coefficient, The second-order difference of the thermal storage medium temperature deviation signal in the current control cycle; k is the number of calculations; Using the difference between the optimized compressor power and the real-time power as the error signal, a PID controller is used to adjust the compressor speed. The control equation is: ; In the formula, The compressor speed in the current control cycle is expressed in r·min. - ¹, used to control compressor power; The compressor speed in the previous control cycle (r·min) - ¹; This is the proportional gain coefficient. This is the first-order difference of the compressor power deviation signal in the current control cycle; This is the integral gain coefficient. This is the compressor power deviation signal for the current control cycle; The differential gain coefficient, The second-order difference of the compressor power deviation signal in the current control cycle; Among them, the final operating speed of the compressor is Based on, when When the corresponding compressor power deviates from the optimal value calculated by the risk potential function, it is based on Correct the rotational speed.

[0015] A further improvement to the technical solution of the present invention is that, if P L < < P H The system will then maintain its current operating state.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The CO2 heat pump-Carnot battery coupling system disclosed in this invention for power plant peak shaving connects the boiler's steam outlet via a first solenoid valve to the turbine's high-pressure cylinder, the boiler's reheater, the turbine's intermediate-pressure cylinder, the turbine's low-pressure cylinder, and the condenser's steam inlet, forming the main steam power circulation path. The condensate outlet of the condenser, after passing through the low-pressure feedwater heater and deaerator, is connected to the high-pressure feedwater heater via a second solenoid valve and returns to the boiler's feedwater inlet, forming a complete feedwater regenerative cycle. In the heat storage loop, the heat storage medium outlet of the low-temperature heat storage medium tank is connected sequentially via the heat storage medium channels of the first and second heat exchangers to the heat storage medium inlet of the high-temperature heat storage medium tank. The heat storage medium outlet of the high-temperature heat storage medium tank is connected via a third solenoid valve and the heat storage medium channel of the third heat exchanger to the heat storage medium inlet of the low-temperature heat storage medium tank, realizing the circulation of the heat storage medium between the low-temperature and high-temperature tanks. In the heat pump circuit, the heat pump working fluid outlet of the compressor is sequentially connected to the heat pump working fluid inlet of the compressor via the heat pump working fluid channel of the first heat exchanger, the expander, and the heat pump working fluid channel of the fourth heat exchanger. This allows the heat pump working fluid to release heat to the heat storage medium in the first heat exchanger and absorb heat from the low-temperature heat source in the fourth heat exchanger. The low-temperature heat source circuit of the heat pump is led out from between the steam outlet of the turbine's low-pressure cylinder and the steam inlet of the condenser. After passing through the low-temperature heat source channel of the fourth heat exchanger, it returns to the space between the steam inlet of the condenser and the feedwater inlet of the low-pressure feedwater heater, making the waste heat from the turbine exhaust steam the low-temperature heat source of the heat pump circuit. The extraction steam branch is led out from between the steam outlet of the boiler and the steam inlet of the turbine's high-pressure cylinder. After passing through the sixth solenoid valve and the steam channel of the second heat exchanger, it connects to the outlet of the extraction steam branch, allowing the high-temperature steam from the boiler outlet to partially bypass to the second heat exchanger before entering the turbine to heat the heat storage medium. In addition, the first solenoid valve is installed in the pipeline between the boiler steam outlet and the turbine high-pressure cylinder steam inlet, controlling whether steam enters the turbine to perform work by opening and closing; the third solenoid valve is installed at the outlet of the high-temperature heat storage medium tank, controlling the flow rate of the high-temperature heat storage medium in the heat release circuit by adjusting the opening degree; the fourth solenoid valve is installed in the heat release circuit, controlling the on / off state of the heat release circuit; the fifth solenoid valve is installed in the heat pump low-temperature heat source circuit, controlling the on / off state of exhaust waste heat recovery; the sixth solenoid valve is installed in the extraction steam branch, controlling the extraction steam flow rate by adjusting the opening degree, thereby regulating the amount of steam entering the turbine; the configuration of the above solenoid valves provides executable operation nodes for the system to switch between power generation mode and heat storage mode and to adjust the flow of each circuit, providing a hardware foundation for the implementation of the control method. Compared to traditional electrically heated molten salt thermal storage solutions, the coupling system of this invention replaces the power consumption of electric heating with the power consumption of a heat pump, uses the waste heat from the exhaust steam of the steam turbine as a low-temperature heat source for the heat pump, and uses extracted steam as an auxiliary heat source. The three heat source forms work together to heat the thermal storage medium, reducing the direct consumption of high-grade electrical energy in the thermal storage process and improving the energy storage economy of thermal power units during periods of low electricity prices.

[0017] This invention further specifies that the extraction steam outlet of the high-pressure cylinder of the steam turbine is connected to the heating steam inlet of the high-pressure feedwater heater; the extraction steam outlet of the intermediate-pressure cylinder of the steam turbine is connected to the heating steam inlet of the low-pressure feedwater heater, the heating steam inlet of the deaerator, and the heating steam inlet of the high-pressure feedwater heater, respectively; and the extraction steam outlet of the low-pressure cylinder of the steam turbine is connected to the heating steam inlet of the low-pressure feedwater heater. These connections ensure that the extraction steam from each pressure level of the steam turbine is delivered to the corresponding pressure level feedwater heater, achieving staged heating of condensate and feedwater. The feedwater temperature is matched and increased according to the pressure level between each level of heater, ensuring that the boiler inlet feedwater temperature remains relatively stable during the commissioning and shutdown of the thermal storage system, avoiding deterioration of boiler combustion conditions due to large fluctuations in feedwater temperature.

[0018] This invention further specifies that: a first circulating pump is installed in the connecting pipeline between the condensate outlet of the condenser and the feedwater inlet of the low-pressure feedwater heater, driving condensate to flow from the condenser to the low-pressure feedwater heater; a second circulating pump is installed in the connecting pipeline between the feedwater outlet of the deaerator and the feedwater inlet of the high-pressure feedwater heater, driving feedwater to flow from the deaerator to the high-pressure feedwater heater; a third circulating pump is installed in the connecting pipeline between the heat storage medium outlet of the low-temperature heat storage medium tank and the heat storage medium inlet of the first heat exchanger, driving the heat storage medium to flow from the low-temperature tank to the first heat exchanger; a fourth circulating pump is installed in the connecting pipeline between the third solenoid valve and the heat storage medium inlet of the third heat exchanger, driving the high-temperature heat storage medium to flow from the high-temperature tank to the third heat exchanger; a fifth circulating pump is installed in the connecting pipeline between the fifth solenoid valve and the low-temperature heat source inlet of the fourth heat exchanger, driving the low-temperature heat source medium to flow from the turbine exhaust pipeline to the fourth heat exchanger; and a sixth circulating pump is installed in the connecting pipeline between the sixth solenoid valve and the steam inlet of the second heat exchanger, driving extracted steam to flow from the boiler outlet pipeline to the second heat exchanger. The configuration of the above-mentioned circulating pumps enables the power circulation loop, heat storage loop, heat pump low-temperature heat source loop and extraction steam branch to each have independent fluid drive capabilities, and the flow rate of the medium in each loop can be actively adjusted by the speed of the corresponding circulating pump.

[0019] This invention also discloses a control method. This method acquires the real-time electricity price from the power grid and compares it with preset high and low electricity price thresholds. If the real-time electricity price is higher than the high electricity price threshold, the system enters power generation mode; if the real-time electricity price is lower than the low electricity price threshold, the system enters thermal storage mode. In power generation mode, the extraction steam branch and heat pump circuit are closed, and the heat release circuit is opened. The thermal storage medium releases heat through a third heat exchanger to heat the unit feedwater. Closing the extraction steam branch allows all steam from the boiler steam outlet to enter the high-pressure cylinder of the turbine through a first solenoid valve, increasing the steam flow through the turbine and improving power generation output. Opening the heat release circuit allows the high-temperature thermal storage medium in the high-temperature thermal storage tank to release heat to the feedwater system through the third heat exchanger, increasing the boiler inlet feedwater temperature and reducing boiler fuel consumption. In the thermal storage mode, the extraction steam branch and heat pump circuit are opened, while the heat release circuit is closed. High-temperature steam is drawn from the boiler steam outlet and used to heat the thermal storage medium via the second heat exchanger. Meanwhile, the waste heat from the turbine low-pressure cylinder exhaust is absorbed by the heat pump working fluid via the fourth heat exchanger, and then used by the heat pump working fluid to heat the thermal storage medium via the first heat exchanger. The opening of the extraction steam branch allows some high-temperature steam to be bypassed to the second heat exchanger, and the opening of the heat pump circuit allows the waste heat from the exhaust to be boosted and used to heat the thermal storage medium via the first heat exchanger. The two heat sources heat the thermal storage medium sequentially as it flows through the first and second heat exchangers. The closure of the heat release circuit ensures that all the heat in the thermal storage circuit is used to raise the temperature of the thermal storage medium, rather than being released to the feedwater system. This invention's control method directly uses the electricity price signal as the criterion for mode switching, prioritizing power generation when the electricity price is high and prioritizing thermal storage when the electricity price is low. It automatically adjusts the unit's operating mode according to electricity price fluctuations, improving the thermal power unit's responsiveness to electricity market price signals.

[0020] This invention further defines a state variable matrix composed of four physical quantities: high-temperature thermal storage medium temperature, turbine output power, boiler inlet feedwater temperature, and compressor power; and a control variable matrix composed of four physical quantities: extraction steam flow rate, compressor power, thermal storage medium circulation flow rate, and boiler input power. The state variable matrix describes the system's operating state at time t, while the control variable matrix describes the control variables that the controller can actively adjust. The dynamic optimization model aims to minimize the comprehensive risk potential function, using the system state transition equation, state variable safety constraints, and control variable physical constraints as constraints to obtain the optimal control variables. The optimal control variables are then distributed as setpoints to each actuator to coordinate the control of extraction steam flow rate, compressor power, thermal storage medium circulation flow rate, and boiler input power, causing each state variable to approach its target value. Simultaneously, the state variable deviations are fed back to the dynamic optimization model to participate in the next control cycle iteration calculation, forming a closed-loop control. This invention's optimized control framework incorporates the deviations of the four controlled variables—thermal storage temperature, power generation, feedwater temperature, and compressor power—into a risk function, obtaining the optimal control variables while satisfying safety constraints, thus solving the problem of difficult parameter tuning for each PID loop in a multivariable coupled system. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a CO2 heat pump-Carnot battery coupling system for power plant peak shaving in an embodiment of the present invention. Figure 2 This is a flowchart illustrating a control method for a CO2 heat pump-Carnot battery coupling system for power plant peak shaving, as described in an embodiment of the present invention. The explanations of the reference numerals in the figure are as follows: 1. Boiler; 2. High-pressure cylinder of steam turbine; 3. Intermediate-pressure cylinder of steam turbine; 4. Low-pressure cylinder of steam turbine; 5. Condenser; 6. Low-pressure feedwater heater; 7. Deaerator; 8. High-pressure feedwater heater; 9. Extraction steam branch outlet; 10. Low-temperature thermal storage medium tank; 11. First heat exchanger; 12. Second heat exchanger; 13. High-temperature thermal storage medium tank; 14. Third heat exchanger; 15. Compressor; 16. Expander; 17. Fourth heat exchanger; 201. First circulating pump; 202. Second circulating pump; 203. Third circulating pump; 204. Fourth circulating pump; 205. Fifth circulating pump; 206. Sixth circulating pump; 101. First solenoid valve; 102. Second solenoid valve; 103. Third solenoid valve; 104. Fourth solenoid valve; 105. Fifth solenoid valve; 106. Sixth solenoid valve. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of protection of the present invention, but rather to illustrate specific selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0024] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other.

[0025] Existing traditional thermal power units often face the dilemma of declining economic efficiency during periods of low electricity prices and insufficient regulation capacity during periods of high electricity prices. Furthermore, the heat source supply of existing molten salt thermal storage systems relies on electric heating, resulting in high power consumption. Although heat pump systems can replace electric heating to supply heat to the thermal storage system and reduce additional power consumption, existing heat pump systems mostly operate independently of thermal power units, making it difficult to fully utilize low-grade waste heat resources, resulting in low overall energy utilization efficiency.

[0026] In view of the above problems, this invention specifically discloses a CO2 heat pump-Carnot battery coupling system for power plant peak shaving. It uses a CO2 heat pump to replace traditional electric heating as the core heat source of the thermal storage system, and recovers waste heat from turbine exhaust as a low-temperature heat source for the heat pump. Simultaneously, it couples the extraction steam branch to collaboratively supply heat to the thermal storage system. Through this system architecture improvement, power consumption in the thermal storage process can be effectively reduced, and the utilization rate of low-grade waste heat can be improved, thereby enhancing the peak shaving economy and overall energy utilization efficiency of thermal power units. Furthermore, addressing the problem that existing systems lack electricity price response control measures and are difficult to adapt to the decline in operational economy caused by electricity price fluctuations, this invention also discloses a coordinated control method based on a comprehensive risk potential function. This method uses real-time electricity price as the operating mode criterion, and dynamically optimizes the extraction steam flow, compressor power, and thermal storage medium flow by constructing a comprehensive risk potential function. This allows the system to switch to power generation mode when electricity prices are high and to thermal storage mode when electricity prices are low, and to respond quickly to parameter changes during system operation. The control method provided by this invention can ensure efficient and stable operation of the coupling system under different electricity price levels.

[0027] In summary, the technical solution disclosed in this invention couples a steam power cycle, a thermal storage system, and a heat pump system. It replaces traditional electric heating with a heat pump, working in conjunction with existing high-temperature steam extraction to heat the thermal storage system. This allows for automatic adjustment of the system's operating mode based on real-time electricity price changes. During periods of high electricity prices, the amount of steam extracted during the thermal storage process is reduced, allowing boiler-generated steam to preferentially enter the turbine for power generation, thus improving the unit's power generation capacity and economic benefits. During periods of low electricity prices, the heat pump system utilizes the turbine's exhaust heat as a low-temperature heat source to heat the thermal storage system. Combined with existing steam extraction from the turbine, this converts low-cost electrical energy into high-grade thermal energy stored in the thermal storage medium, improving the power plant's ability to absorb off-peak electricity and reducing economic losses caused by power curtailment and low-price operation.

[0028] Please see Figure 1The present invention provides a CO2 heat pump-Carnot battery coupling system for power plant peak shaving, comprising: a power circulation loop, a heat storage loop, a heat pump loop, a heat release loop, a heat pump low-temperature heat source loop, and a steam extraction branch.

[0029] The power circulation loop constitutes the main body of the power plant's steam power circulation. The outlet of boiler 1 is connected to the inlet of the high-pressure cylinder 2 of the turbine via a corresponding first solenoid valve 101. Steam enters the high-pressure cylinder 2, performs work, and then returns to the reheater of boiler 1 for reheating. The reheated steam enters the intermediate-pressure cylinder 3 of the turbine to continue expanding and performing work. The outlet of the intermediate-pressure cylinder 3 is connected to the inlet of the low-pressure cylinder 4 of the turbine, and the outlet of the low-pressure cylinder 4 is connected to the inlet of the condenser 5. After condensation in the condenser 5, the steam is sequentially pumped by the first circulation pump 201 into the low-pressure feedwater heater 6, the deaerator 7, the second circulation pump 202, and the second solenoid valve 102, and then transported to the high-pressure feedwater heater 8, finally returning to boiler 1 to complete the main circulation. Furthermore, the high-pressure cylinder 2 of the turbine is connected to the high-pressure feedwater heater 8, the intermediate-pressure cylinder 3 is connected to the low-pressure feedwater heater 6, the deaerator 7, and the high-pressure feedwater heater 8 respectively, and the low-pressure cylinder 4 is connected to the low-pressure feedwater heater 6 to complete the regenerative heating process at each stage.

[0030] The heat storage and release processes of the coupled system are completed by two loops. In the heat storage loop, the heat storage medium in the low-temperature heat storage medium tank 10 flows through the first heat exchanger 11 and the second heat exchanger 12 sequentially via the third circulation pump 203 to absorb heat and increase its temperature, and then enters the high-temperature heat storage medium tank 13 to complete the heat storage process. When heat needs to be released, the high-temperature heat storage medium in the high-temperature heat storage medium tank 13 enters the third heat exchanger 14 via the corresponding third solenoid valve 103 and the fourth circulation pump 204 to exchange heat with the medium in the heat release loop. The heat storage medium after releasing heat returns to the low-temperature heat storage medium tank 10. In the heat release loop, the heat release medium is led out from the pipeline between the outlet of the deaerator 7 and the inlet of the high-pressure feedwater heater 8, enters the third heat exchanger 14 via the corresponding fourth solenoid valve 104, exchanges heat with the high-temperature heat storage medium, and then returns to the original pipeline, releasing the stored heat energy back to the unit's feedwater system.

[0031] The heating process of the heat storage medium is achieved through a heat pump loop, a heat pump low-temperature heat source loop, and an extraction steam branch. In the heat pump loop, the heat pump working fluid is compressed and heated by the compressor 15 before entering the first heat exchanger 11 to heat the heat storage medium. After being cooled and depressurized by the expander 16, it enters the fourth heat exchanger 17 to absorb heat from the low-temperature heat source. The heat pump low-temperature heat source loop utilizes the waste heat from the turbine exhaust as the heat source on the evaporator side of the heat pump. The low-temperature heat source medium is led out from the pipeline between the outlet of the turbine low-pressure cylinder 4 and the inlet of the condenser 5, and enters the fourth heat exchanger 17 through the corresponding fifth solenoid valve 105 and the fifth circulating pump 205 to exchange heat with the heat pump working fluid. After the heat exchange is completed, it returns to the pipeline between the condenser 5 and the low-pressure feedwater heater 6, realizing the recovery and utilization of low-grade waste heat. The extraction steam branch draws high-temperature steam from the main pipeline between the boiler 1 and the inlet of the high-pressure cylinder 2 of the steam turbine, and directly releases heat to the heat storage circuit through the second heat exchanger 12. The high-temperature steam enters the second heat exchanger 12 through the corresponding sixth solenoid valve 106 and the sixth circulating pump 206, exchanges heat with the heat storage medium, and is discharged through the extraction steam branch outlet 9, thus realizing the heat input of high-temperature steam to the heat storage circuit.

[0032] Please see Figure 2 In this embodiment of the invention, a control method for the CO2 heat pump-Carnot battery coupling system for flexible peak shaving in power plants is further provided. This control method uses real-time electricity price as the criterion for system operation mode, and comprehensively considers the temperature of the heat storage medium, the unit load demand, and the operating status of the heat pump. It coordinates and adjusts the extraction steam flow rate, heat pump compressor power, heat storage medium flow rate, and operating parameters of each circulating pump to realize dynamic switching between unit power generation and heat storage, thereby improving system economy and energy utilization efficiency.

[0033] Specifically, the implementation process is as follows: The controller initializes each detection element and collects real-time electricity prices from the power grid. .

[0034] When the controller detects the real-time electricity price Exceeding the set high electricity price threshold P H At this time, the system enters power generation mode. Based on optimization results, the controller closes the fifth and sixth solenoid valves and the compressor, allowing the high-temperature, high-pressure steam generated by the boiler to preferentially enter the high-pressure, intermediate-pressure, and low-pressure cylinders of the turbine for expansion and work, thus increasing the turbine's output power. Simultaneously, the thermal storage system enters heat release mode. The controller opens the high-temperature thermal storage medium outlet solenoid valve and the heat release circuit solenoid valve, allowing the high-temperature thermal storage medium to be transported via the fourth circulation pump to the third heat exchanger and heat release circuit for heat exchange, increasing the boiler inlet feedwater temperature and reducing boiler fuel consumption.

[0035] When the controller detects the real-time electricity price Below the set low electricity price threshold PL When the system enters the heat storage mode, the controller opens the fifth and sixth solenoid valves, closes the third and fourth solenoid valves, and simultaneously starts the compressor in the heat pump circuit. By adjusting the compressor frequency converter, the power is changed so that the low-grade heat energy in the low-temperature heat source is absorbed and raised to a high-temperature state, and then the heat is released to the heat storage medium through the first heat exchanger.

[0036] when P L < < P H At this time, the system maintains its current operating state and makes minor optimizations and adjustments based on the thermal storage status to avoid frequent switching of operating modes. Furthermore, during system operation, the controller dynamically corrects the operating status of each device based on the optimal values ​​of each parameter calculated using the comprehensive risk potential function. In power generation mode, when the turbine output power deviates from the optimal value, it is corrected by adjusting the boiler fuel input; when the boiler inlet feedwater temperature deviates from the optimal value, it is corrected by adjusting the opening of the third solenoid valve. In thermal storage mode, when the turbine output power deviates from the optimal value, it is corrected by adjusting the opening of the sixth solenoid valve; when the thermal storage medium temperature deviates from the optimal value, it is corrected by adjusting the compressor speed; when the heat pump compressor power deviates from the optimal value, it is corrected by adjusting the compressor speed. These control quantities, after optimization calculation, are input to the underlying PID controller, which enables rapid tracking of the target parameters by the actual operating parameters.

[0037] Through the aforementioned control method, the coupled system can automatically adjust its operating mode according to real-time electricity price changes. During periods of high electricity prices, it fully utilizes the steam power cycle for power generation, improving the unit's economic benefits. During periods of low electricity prices, it uses low-cost electricity to drive the heat pump and combines it with steam extraction from the turbine for heat storage, improving the power conversion efficiency. Simultaneously, by comprehensively constraining the heat storage temperature, equipment load, and energy balance state through a risk potential function, the boiler, turbine, heat storage system, and heat pump system are always operating in a safe and stable range, achieving intelligent coordinated control of the power plant's steam power cycle and heat storage system.

[0038] In this embodiment of the invention, to ensure the safe, stable, and efficient operation of the power plant's steam power cycle, thermal storage system, and heat pump system under different electricity prices, loads, and thermal storage conditions, a matrix-based dynamic optimization control model based on a comprehensive risk potential function is specifically disclosed. First, the system operating state parameters are constructed into a state variable matrix. A normalized deviation matrix is ​​established based on the allowable operating range of each parameter. The matrix can be represented as: (1) In the formula, This is the normalized deviation matrix; It is the inverse of the diagonal scaling matrix D, used to normalize the dimensions of the deviations of each state variable to the dimensionless range. The state variable matrix; The state variable target reference value matrix; These represent the upper and lower limits (in K) of the permissible operating temperature for high-temperature thermal storage media. Rated output power of the steam turbine (kW); Rated temperature of boiler inlet feedwater (K); The compressor's rated power is in kW. Real-time temperature of the high-temperature thermal storage medium in K; Target temperature of the high-temperature thermal storage medium (K); The real-time output power of the steam turbine is expressed in kW. The target output power of the steam turbine is given in kW. Real-time feedwater temperature at boiler inlet (K); Target feedwater temperature at boiler inlet / K; The compressor's real-time output power is given in kW. The target output power of the compressor is given in kW.

[0039] The comprehensive risk potential function uses a weight matrix and a risk penalty matrix to describe the degree of impact of different operating parameters deviating from the target state on system safety, and solves for the control variable matrix. The optimal solution minimizes the system's overall risk potential function. The system's overall risk potential function can be expressed as: (2) In the formula, The comprehensive risk potential function is used to quantify the comprehensive risk level caused by the deviation of the system's operating state from the target state. The smaller the value of this function, the closer the system is to the optimal state of safety and efficiency. This is the risk weight matrix for the state variables; This is the state deviation penalty matrix.

[0040] The risk weight matrix of state variables is represented as follows: (3) In the formula, , , , The risk weight coefficients are, in order: the risk weight coefficient for temperature deviation of high-temperature heat storage medium, the risk weight coefficient for output power deviation of steam turbine, the risk weight coefficient for temperature deviation of boiler inlet feedwater, and the risk weight coefficient for power deviation of compressor.

[0041] The state deviation penalty matrix is ​​represented as follows: (4) In the formula, , , , These are the penalty coefficients for temperature deviation of the high-temperature heat storage medium, the penalty coefficient for turbine output power deviation, the penalty coefficient for boiler inlet feedwater temperature deviation, and the penalty coefficient for compressor power deviation, respectively.

[0042] The controller adjusts the steam extraction valve opening, circulating pump speed, compressor frequency, and boiler load in real time based on the optimization results, ensuring that the system state variables remain within the allowable operating range. This achieves dynamic coordinated control, prioritizing power generation under high electricity prices and prioritizing thermal energy storage under low electricity prices. The system control variables can be expressed as: (5) In the formula, For the control variable matrix; Extraction steam flow rate / kg·s -1 ; The power of the heat pump compressor is expressed in kW. The circulation flow rate of the heat storage medium is expressed as kg·s. -1 ; The boiler input power is expressed in kW.

[0043] The controller obtains the optimal control variables by solving the following dynamic optimization model: (6) In the formula, The optimal control variable matrix is ​​the set of control variable values ​​that minimize the comprehensive risk potential function, obtained through optimization. (7) In the formula, Let be the state variable matrix of the system at the next time step (t+1); This is the system state transition function; , These are the lower and upper bound constraint matrices for the state variables, respectively; , These are the lower and upper bound constraint matrices for the control variables, respectively.

[0044] When the system enters power generation mode, the controller closes the extraction branch solenoid valve, reduces the flow rate of the sixth circulation pump, and ensures that all the steam generated by the boiler enters the high-pressure, intermediate-pressure, and low-pressure cylinders of the turbine to complete expansion and work. Simultaneously, the heat release circuit is opened, and the solenoid valve at the outlet of the high-temperature heat storage medium tank is opened, allowing the high-temperature heat storage medium to enter the third heat exchanger, transferring the stored heat to the feedwater system, increasing the boiler inlet feedwater temperature, and thus reducing boiler fuel consumption. To ensure stable turbine output power, the difference between the optimal power generation obtained from the comprehensive risk potential function optimization and the real-time output power of the unit is used as an error signal. A PID controller is employed to adjust the boiler input power, and its control equation is: (8) In the formula, The boiler input power for the current cycle is in kW. The boiler input power (kW) for the previous cycle; This is the proportional gain coefficient. The first-order difference between the power deviation of the current control cycle and the previous control cycle; This is the integral gain coefficient. This is the power deviation signal for the current control cycle; The differential gain coefficient, This is the second-order difference of the power deviation in the current control cycle; where K P1 K I1 K D1 To achieve the best control effect, adjustments are made based on the calculation results of the comprehensive risk potential function, where k represents the number of calculations.

[0045] While continuously adjusting the boiler input power, it is also necessary to stabilize the boiler inlet feedwater temperature by regulating the flow rate of the high-temperature heat storage medium. The difference between the optimal feedwater temperature obtained by optimization using the comprehensive risk potential function and the actual feedwater temperature is used as an error signal. This error signal is input to the PID control unit to control the opening of solenoid valve 103 to regulate the flow rate of the high-temperature heat storage medium. The control equation is as follows: (9) In the formula, For the current control cycle (the 1st cycle) The opening degree of the third solenoid valve (calculated in the next step); For the previous control cycle (the first) The opening degree of the third solenoid valve (calculated in the next step); This is the proportional gain coefficient. This is the first-order difference of the feedwater temperature deviation in the current control cycle; This is the integral gain coefficient. This is the feedwater temperature deviation signal for the current control cycle; The differential gain coefficient, K is the second-order difference of the feedwater temperature deviation in the current control cycle. P2 K I2 K D2 Adjustments are made based on the calculation results of the comprehensive risk potential function to obtain the best control effect, where k is the number of calculations.

[0046] When the real-time electricity price drops to the low-price range, the system enters the thermal storage mode. The controller activates the corresponding solenoid valves and circulating pumps on the extraction steam branch, allowing the high-temperature steam from the boiler outlet to enter the second heat exchanger, providing a high-temperature heat source for the thermal storage medium. Simultaneously, the heat pump system starts, utilizing the waste heat from the turbine exhaust as a low-temperature heat source. After absorbing heat in the fourth heat exchanger, the steam enters the compressor for heating and then releases heat to the thermal storage medium in the first heat exchanger. To ensure that the turbine output power is optimal, the difference between the optimal power generation obtained by optimization using the comprehensive risk potential function and the real-time output power of the unit is used as an error signal. A PID controller is used to adjust the extraction steam flow to regulate the steam flow entering the turbine. The control equation is as follows: (10) In the formula, For the current control cycle (the 1st cycle) The opening degree of the sixth solenoid valve (calculated in the next step); For the previous control cycle (the first) The opening degree of the sixth solenoid valve (calculated in the next step); This is the proportional gain coefficient. This is the first-order difference of the extraction deviation signal for the current control cycle; This is the integral gain coefficient. This is the extraction deviation signal for the current control cycle; The differential gain coefficient, K is the second-order difference of the extraction deviation signal for the current control cycle; P3 K I3 K D3 Adjustments are made based on the calculation results of the comprehensive risk potential function to obtain the best control effect, where k is the number of calculations.

[0047] To ensure the optimal temperature of the heat storage medium for the best heat storage effect, the compressor in the heat pump circuit is equipped with a frequency converter to regulate its speed, thereby adjusting the heat pump power. The difference between the optimal high-temperature heat storage medium temperature obtained by optimization using the comprehensive risk potential function and the real-time temperature of the high-temperature heat storage medium is used as an error signal and input to the PID control unit for adjustment via the frequency converter. The control equation is as follows: (11) In the formula, For the current control cycle (the 1st cycle) (Calculation) Compressor speed / r·min -¹, This rotational speed is used to control the temperature of the heat storage medium; For the previous control cycle (the first) (Calculation) Compressor speed / r·min - ¹; This is the proportional gain coefficient. This is the first-order difference of the thermal storage medium temperature deviation signal during the current control cycle; This is the integral gain coefficient. This is the temperature deviation signal of the thermal storage medium in the current control cycle; The differential gain coefficient, K is the second-order difference of the thermal storage medium temperature deviation signal during the current control cycle; P4 K I4 K D4 Adjustments are made based on the calculation results of the comprehensive risk potential function to obtain the best control effect, where k is the number of calculations.

[0048] To ensure the compressor power remains within a safe range, the difference between the optimal compressor power obtained from the comprehensive risk potential function optimization and the real-time compressor power is used as an error signal. This error signal is input to the PID control unit for adjustment via the frequency converter. The control equation is as follows: (12) In the formula, For the current control cycle (the 1st cycle) (Calculation) Compressor speed / r·min - ¹, This rotational speed is used to control the compressor power; For the previous control cycle (the first) (Calculation) Compressor speed / r·min - ¹; This is the proportional gain coefficient. This is the first-order difference of the compressor power deviation signal in the current control cycle; This is the integral gain coefficient. This is the compressor power deviation signal for the current control cycle; The differential gain coefficient, K is the second-order difference of the compressor power deviation signal in the current control cycle; P5 K I5 K D5 Adjustments are made based on the calculation results of the comprehensive risk potential function to obtain the best control effect, where k is the number of calculations.

[0049] Throughout the operation, the system controller collects parameters from various measuring points in real time, dynamically coordinating the operating states of the boiler, turbine, extraction steam branch, thermal storage system, and heat pump system. This enables intelligent coordinated control, prioritizing power generation during high electricity prices and thermal storage during low electricity prices. This control method features continuous control, fast response, high adjustment accuracy, and good operational stability, making it suitable for the automatic control of thermal power units coupled with molten salt thermal storage and heat pump systems.

[0050] In summary, this invention discloses a CO2 heat pump energy storage-Carnot battery system and its control method for flexible peak shaving in power plants, including a power cycle loop, a thermal storage loop, a heat pump loop, a heat release loop, a low-temperature heat source loop of the heat pump, and an extraction steam branch. This invention uses real-time electricity prices as the primary control basis for system operation. When electricity prices are high, the system switches to power generation mode and releases the heat energy stored in the thermal storage loop to improve the unit's power generation capacity. When electricity prices are low, the system switches to thermal storage mode, using a heat pump to replace the electric heating components in the traditional molten salt thermal storage loop, and utilizing the waste heat from the turbine exhaust as the heat source on the evaporator side of the heat pump. This is combined with existing extraction steam heating technology to heat the thermal storage medium, achieving efficient heat energy storage. This invention effectively addresses the problem of decreased economic efficiency of thermal power units due to electricity price fluctuations, improves the overall energy utilization rate of the system, and enhances the flexible peak shaving capability and adaptability of thermal power units to the electricity market.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A CO2 heat pump-Carnot battery coupling system for peak shaving in power plants, characterized in that, include: The circuit includes a power cycle loop, a heat storage loop, a heat pump loop, a heat release loop, a low-temperature heat source loop for the heat pump, and an extraction steam branch; among which, The power circulation loop includes: boiler (1), high-pressure cylinder of steam turbine (2), intermediate-pressure cylinder of steam turbine (3), low-pressure cylinder of steam turbine (4), condenser (5), low-pressure feedwater heater (6), deaerator (7) and high-pressure feedwater heater (8); wherein, the steam outlet of boiler (1) is connected in sequence to the high-pressure cylinder of steam turbine (2), reheater of boiler (1), intermediate-pressure cylinder of steam turbine (3), low-pressure cylinder of steam turbine (4) and steam inlet of condenser (5) via the first solenoid valve (101), and the condensate outlet of condenser (5) is connected to the high-pressure feedwater heater (8) via the second solenoid valve (102) after passing through the low-pressure feedwater heater (6) and deaerator (7) and then returns to the feedwater inlet of boiler (1); The heat storage circuit includes: a low-temperature heat storage medium tank (10), a first heat exchanger (11), a second heat exchanger (12), a high-temperature heat storage medium tank (13), and a third heat exchanger (14); wherein, the heat storage medium outlet of the low-temperature heat storage medium tank (10) is connected to the heat storage medium inlet of the high-temperature heat storage medium tank (13) in sequence through the heat storage medium channel of the first heat exchanger (11) and the heat storage medium channel of the second heat exchanger (12), and the heat storage medium outlet of the high-temperature heat storage medium tank (13) is connected to the heat storage medium inlet of the low-temperature heat storage medium tank (10) through the third solenoid valve (103) and the heat storage medium channel of the third heat exchanger (14); The heat pump circuit includes: a compressor (15), an expander (16), a first heat exchanger (11), and a fourth heat exchanger (17); wherein, the heat pump working fluid outlet of the compressor (15) is connected to the heat pump working fluid inlet of the compressor (15) in sequence through the heat pump working fluid channel of the first heat exchanger (11), the expander (16), and the heat pump working fluid channel of the fourth heat exchanger (17); The heat release circuit is led out from the pipeline between the water outlet of the deaerator (7) and the second solenoid valve (102), and returns to the pipeline between the second solenoid valve (102) and the water inlet of the high-pressure water heater (8) after passing through the water supply channels of the fourth solenoid valve (104) and the third heat exchanger (14). The low-temperature heat source circuit of the heat pump is led out from the pipeline between the steam outlet of the low-pressure cylinder (4) of the steam turbine and the steam inlet of the condenser (5), and returns to the pipeline between the steam inlet of the condenser (5) and the feed water inlet of the low-pressure feed water heater (6) after passing through the low-temperature heat source channel of the fifth solenoid valve (105) and the fourth heat exchanger (17). The extraction steam branch is led out from the pipeline between the steam outlet of the boiler (1) and the steam inlet of the high-pressure cylinder (2) of the steam turbine, and then connected to the extraction steam branch outlet (9) after passing through the sixth solenoid valve (106) and the steam passage of the second heat exchanger (12).

2. The CO2 heat pump-Carnot battery coupling system for power plant peak shaving according to claim 1, characterized in that, The extraction steam outlet of the high-pressure cylinder (2) of the steam turbine is connected to the heating steam inlet of the high-pressure feedwater heater (8); The extraction steam outlet of the intermediate pressure cylinder (3) of the steam turbine is connected to the heating steam inlet of the low pressure feedwater heater (6), the heating steam inlet of the deaerator (7) and the heating steam inlet of the high pressure feedwater heater (8), respectively. The extraction steam outlet of the low-pressure cylinder (4) of the steam turbine is connected to the heating steam inlet of the low-pressure feedwater heater (6).

3. The CO2 heat pump-Carnot battery coupling system for power plant peak shaving according to claim 1, characterized in that, Also includes: The first circulation pump (201) is used to connect the condensate outlet of the condenser (5) and the feed water inlet of the low-pressure feed water heater (6). The second circulation pump (202) is used to connect the water supply outlet of the deaerator (7) and the water supply inlet of the high-pressure water heater (8); The third circulation pump (203) is used to connect the heat storage medium outlet of the low temperature heat storage medium tank (10) and the heat storage medium inlet of the first heat exchanger (11) in the pipeline. The fourth circulating pump (204) is used to connect the heat storage medium inlet between the third solenoid valve (103) and the third heat exchanger (14); The fifth circulating pump (205) is used to connect the fifth solenoid valve (105) and the low-temperature heat source inlet of the fourth heat exchanger (17) in the pipeline; The sixth circulation pump (206) is used for the connecting pipeline between the sixth solenoid valve (106) and the steam inlet of the second heat exchanger (12).

4. The CO2 heat pump-Carnot battery coupling system for power plant peak shaving according to claim 1, characterized in that, The heat storage medium used is molten salt.

5. A control method for a CO2 heat pump-Carnot battery coupled system for power plant peak shaving, characterized in that, The CO2 heat pump-Carnot battery coupling system for power plant peak shaving, as described in any one of claims 1 to 4, comprises: Obtain the real-time electricity price of the power grid and with the preset high electricity price threshold P H and low electricity price threshold P L For comparison, if real-time electricity price Above the high electricity price threshold P H The system then enters power generation mode, if the real-time electricity price... Below the low electricity price threshold P L The system then enters heat storage mode; In the power generation mode, the extraction steam branch and heat pump circuit are closed, and the heat release circuit is opened. The heat storage medium releases heat through the third heat exchanger to heat the unit feedwater. In the heat storage mode, the extraction steam branch and heat pump circuit are opened, and the heat release circuit is closed. High-temperature steam is drawn from the boiler steam outlet and heats the heat storage medium through the second heat exchanger. The exhaust heat of the turbine low-pressure cylinder is absorbed by the heat pump working fluid through the fourth heat exchanger and then heated by the heat pump working fluid through the first heat exchanger to heat the heat storage medium.

6. The control method for a CO2 heat pump-Carnot battery coupling system for power plant peak shaving according to claim 5, characterized in that, During system operation, the state variable matrix is ​​composed of the temperature of the high-temperature heat storage medium, the output power of the steam turbine, the inlet feedwater temperature of the boiler, and the power of the compressor, and the control variable matrix is ​​composed of the extraction steam flow rate, the compressor power, the circulation flow rate of the heat storage medium, and the input power of the boiler, thus constructing a comprehensive risk potential function. The optimal control variables are obtained by solving the dynamic optimization model that minimizes the comprehensive risk potential function. The optimal control variables are then sent to each actuator as setpoints to coordinate the control of steam extraction flow, compressor power, heat storage medium circulation flow and boiler input power, so that each state variable of the system approaches its target value. The deviation of the state variables is fed back to the dynamic optimization model to participate in the iterative calculation of the next control cycle. The dynamic optimization model is expressed as follows: ； ； In the formula, The optimal control variable matrix; This is the comprehensive risk potential function; The state variable matrix; For the control variable matrix; Let be the state variable matrix of the system at the next time step t+1. Let be the state variable matrix of the system at time t. Let be the control variable matrix at time t; This is the system state transition function; , These are the lower and upper bound constraint matrices for the state variables, respectively; , These are the lower and upper bound constraint matrices for the control variables, respectively. ； In the formula, This is the risk weight matrix for the state variables; This is the state deviation penalty matrix; This is the normalized deviation matrix.

7. The control method for a CO2 heat pump-Carnot battery coupling system for power plant peak shaving according to claim 6, characterized in that, ； In the formula, It is the inverse of the diagonal scaling matrix D, used to normalize the dimensions of the deviations of each state variable to the dimensionless range. The state variable target reference value matrix; These represent the upper and lower limits (in K) of the permissible operating temperature for high-temperature thermal storage media. Rated output power of the steam turbine (kW); Rated temperature of boiler inlet feedwater (K); The compressor's rated power is in kW. Real-time temperature of the high-temperature thermal storage medium in K; Target temperature of the high-temperature thermal storage medium (K); The real-time output power of the steam turbine is expressed in kW. The target output power of the steam turbine is given in kW. Real-time feedwater temperature at boiler inlet (K); Target feedwater temperature at boiler inlet / K; The compressor's real-time output power is given in kW. Target output power of the compressor (kW); ； In the formula, , , , The risk weight coefficients are, in order: high-temperature heat storage medium temperature deviation, turbine output power deviation, boiler inlet feedwater temperature deviation, and compressor power deviation. ； In the formula, , , , The penalty coefficients are, in order: the penalty coefficient for the temperature deviation of the high-temperature heat storage medium, the penalty coefficient for the deviation of the steam turbine output power, the penalty coefficient for the deviation of the boiler inlet feedwater temperature, and the penalty coefficient for the deviation of the compressor power.

8. The control method for a CO2 heat pump-Carnot battery coupling system for power plant peak shaving according to claim 6, characterized in that, In the power generation mode, the difference between the optimal power generation obtained by comprehensive risk potential function optimization and the real-time output power of the unit is used as the error signal. A PID controller is used to adjust the boiler input power, and the control equation is: ； In the formula, The boiler input power for the current cycle is in kW. The boiler input power (kW) for the previous cycle; This is the proportional gain coefficient. The first-order difference between the power deviation of the current control cycle and the previous control cycle; This is the integral gain coefficient. This is the power deviation signal for the current control cycle; The differential gain coefficient, The second-order difference of the power deviation in the current control cycle; k is the number of calculations; The difference between the optimized feedwater temperature and the actual feedwater temperature is used as the error signal. A PID controller is used to adjust the opening of the third solenoid valve to regulate the flow rate of the high-temperature heat storage medium. The control equation is as follows: ； In the formula, This represents the opening degree of the third solenoid valve in the current control cycle. This refers to the opening degree of the third solenoid valve in the previous control cycle; This is the proportional gain coefficient. This is the first-order difference of the feedwater temperature deviation in the current control cycle; This is the integral gain coefficient. This is the feedwater temperature deviation signal for the current control cycle; The differential gain coefficient, This is the second-order difference of the feedwater temperature deviation in the current control cycle.

9. The control method for a CO2 heat pump-Carnot battery coupling system for power plant peak shaving according to claim 6, characterized in that, In the aforementioned thermal storage mode, the difference between the optimal power generation obtained from the comprehensive risk potential function optimization and the real-time output power of the unit is used as the error signal. A PID controller is employed to adjust the opening of the sixth solenoid valve to regulate the extraction steam flow. The control equation is as follows: （10） In the formula, This refers to the opening degree of the sixth solenoid valve in the current control cycle. This refers to the opening degree of the sixth solenoid valve in the previous control cycle; This is the proportional gain coefficient. This is the first-order difference of the extraction deviation signal for the current control cycle; This is the integral gain coefficient. This is the extraction deviation signal for the current control cycle; The differential gain coefficient, The second-order difference of the extraction deviation signal for the current control cycle; k is the number of calculations; Using the difference between the optimized high-temperature heat storage medium temperature and the real-time temperature as the error signal, a PID controller is used to adjust the compressor speed. The control equation is: ； In the formula, The compressor speed in the current control cycle is expressed in r·min. - ¹, used to control the temperature of the heat storage medium; The compressor speed in the previous control cycle (r·min) - ¹; This is the proportional gain coefficient. This is the first-order difference of the thermal storage medium temperature deviation signal during the current control cycle; This is the integral gain coefficient. This is the temperature deviation signal of the thermal storage medium in the current control cycle; The differential gain coefficient, The second-order difference of the thermal storage medium temperature deviation signal in the current control cycle; k is the number of calculations; Using the difference between the optimized compressor power and the real-time power as the error signal, a PID controller is used to adjust the compressor speed. The control equation is: ； In the formula, The compressor speed in the current control cycle is expressed in r·min. - ¹, used to control compressor power; The compressor speed in the previous control cycle (r·min) - ¹; This is the proportional gain coefficient. This is the first-order difference of the compressor power deviation signal in the current control cycle; This is the integral gain coefficient. This is the compressor power deviation signal for the current control cycle; The differential gain coefficient, The second-order difference of the compressor power deviation signal in the current control cycle; Among them, the final operating speed of the compressor is Based on, when When the corresponding compressor power deviates from the optimal value calculated by the risk potential function, it is based on Correct the rotational speed.

10. The control method for a CO2 heat pump-Carnot battery coupling system for power plant peak shaving according to claim 5, characterized in that, like P L < < P H The system will then maintain its current operating state.

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