Wind-solar integrated power generation system and method coupled with biomass heat storage

Abstract

The invention provides a wind-solar integrated power generation system and method coupled with biomass heat storage. The wind-solar integrated power generation system comprises a wind-solar power supply, electrochemical energy storage equipment, an electric heater, a low-temperature molten salt tank, a high-temperature molten salt tank, a biomass boiler, a steam generator, a turboset and a condenser. A set of fused salt heat storage system is additionally arranged for the biomass boiler and the wind-solar power supply, on one hand, the biomass boiler is combined with the wind-solar power supply, so that the utilization hours of the biomass boiler can be remarkably reduced, the consumption of biomass fuel is reduced, the power generation economy is improved, and the scale of a biomass power generation monomer project is favorably improved; and on the other hand, the fused salt heat storage system can amplify the output level of the biomass boiler, and deep peak regulation service can be provided for the wind-solar power supply through long-time heat storage. In general, the wind-solar integrated power generation system coupled with biomass heat storage can stably output power, has excellent load following performance, maintains lower power generation cost, and realizes green, efficient and low-cost power generation.

Description

Technical Field

[0001] The present invention belongs to the technical field of renewable energy power generation, and specifically relates to a wind-solar integrated power generation system and method coupled with biomass heat storage. Background Art

[0002] With the rapid growth of wind power and photovoltaic power generation, the volatility and randomness of wind and solar power output have brought great challenges to the stable operation of the power grid. How to improve the output stability of wind and solar power generation systems by coupling with other energy categories or energy storage systems is an important issue in the current energy transformation and development. Biomass resources are abundant, widely available and easy to store. Biomass power generation can be used as one of the supporting power sources for wind and solar power, which helps reduce dependence on traditional fossil energy and promote the transformation of energy structure towards low-carbon, clean and renewable.

[0003] However, due to factors such as the high cost of collecting biomass fuel and the difficulty in supplying biomass fuel, the scale of biomass power station projects is relatively small. Limited by the small installed capacity, using biomass power stations as supporting power sources alone has little effect on suppressing the fluctuations in wind power and photovoltaic output in the power system.

[0004] In addition, due to the limitations of biomass boiler combustion technology, the energy conversion efficiency of biomass combustion power generation is not high. The energy conversion efficiency is even lower when the load output is variable and participating in peak load regulation, which further reduces the economic efficiency of biomass power generation and limits the application of biomass power stations in participating in power system peak regulation.

[0005] Therefore, there is currently no power generation system and method that can effectively combine wind and solar power generation with biomass power generation. Summary of the invention

[0006] In view of the defects of the prior art, the present invention provides a wind-solar integrated power generation system and method coupled with biomass heat storage, which can effectively solve the above problems.

[0007] The technical solution adopted by the present invention is as follows:

[0008] The present invention provides a wind-solar integrated power generation system coupled with biomass heat storage, comprising: a wind-solar power source, an electrochemical energy storage device, an electric heater, a low-temperature molten salt tank, a high-temperature molten salt tank, a biomass boiler, a steam generator, a steam turbine unit and a condenser;

[0009] The first power generation end of the wind and solar power source is connected to the power grid;

[0010] The charging end of the electrochemical energy storage device is connected to the second power generation end of the wind and solar power source, and the power generation end of the electrochemical energy storage device is connected to the power grid;

[0011] The molten salt outlet of the low-temperature molten salt tank is directly connected to the molten salt inlet of the heat exchange coil in the furnace of the biomass boiler through a pipeline; the molten salt outlet of the low-temperature molten salt tank is connected to the molten salt inlet of the electric heater, and the molten salt outlet of the electric heater is connected to the molten salt inlet of the heat exchange coil in the furnace of the biomass boiler; and the power supply end of the electric heater is connected to the third power generation end of the wind and solar power source;

[0012] The biomass boiler uses biomass fuel combustion in the furnace to heat the molten salt in the heat exchange coil in the furnace; the molten salt outlet of the heat exchange coil in the furnace of the biomass boiler is connected to the molten salt inlet of the high-temperature molten salt tank through a pipeline;

[0013] The molten salt outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the steam generator, and after the high-temperature molten salt is released by the steam generator, the molten salt outlet of the steam generator is connected to the molten salt inlet of the low-temperature molten salt tank; thereby forming a molten salt circulation loop;

[0014] The high-temperature and high-pressure steam outlet of the steam generator is connected to the steam turbine of the steam turbine unit through a pipeline, driving the steam turbine to work, thereby generating electricity to the power grid through the generator of the steam turbine unit; the steam outlet of the steam turbine is connected to the steam inlet of the condenser, where it is cooled and condensed into liquid water, and then connected to the water working medium inlet of the steam generator, forming a water circuit circulation.

[0015] Preferably, a molten salt pump for controlling the circulation flow rate of the molten salt working medium is installed on the pipeline from the high-temperature molten salt tank to the steam generator; and a water pump is installed on the pipeline from the condenser to the steam generator.

[0016] The present invention also provides a method for a wind-solar integrated power generation system coupled with biomass heat storage, comprising the following steps:

[0017] Step S1, obtaining the current power demand w of the power grid and the wind and solar power output power p of the wind and solar power source;

[0018] Step S2, obtaining the electrochemical energy storage capacity d of the electrochemical energy storage device at the current moment y And the existing heat of molten salt heat storage r y ;

[0019] Step S3, judging whether the relationship pw>0 holds; if so, it indicates that the wind and solar power output of the wind and solar power source at the current moment exceeds the grid demand, and executing step S4; if not, it indicates that the wind and solar power output of the wind and solar power source at the current moment is less than or equal to the grid demand, and executing step S5;

[0020] Step S4, the wind and solar power supplies power to the grid through the booster station. At the same time, the excess power of the wind and solar power is preferentially fed into the electrochemical energy storage device for storage. After the storage is full, if there is still surplus, the surplus power is converted into heat energy through the electric heater and stored in the molten salt, and the existing power of the electrochemical energy storage is updated. y And the existing heat of molten salt heat storage r y , return to step S1;

[0021] Step S5, the wind and solar power sources directly supply power to the grid through the booster station; at the same time, the electrochemical energy storage device is discharged to the grid to release the electric energy in the electrochemical energy storage device; if there is no system power gap after the electrochemical energy storage device is discharged, there is no need to start the molten salt exothermic power generation; if there is still a system power gap after the electrochemical energy storage device is discharged, the molten salt exothermic power generation is started; the existing amount of electrochemical energy storage d is updated y And the existing heat of molten salt heat storage r y , return to step S1.

[0022] Preferably, the calculation method of wind-solar output power p is: wind-solar output power p = wind power installed capacity*wind power output coefficient+photovoltaic installed capacity*photovoltaic output coefficient.

[0023] Preferably, step S4 is specifically:

[0024] Step S4.1: The excess power of the wind and solar power sources is fed into the electrochemical energy storage device for storage. The electrochemical energy storage charging power d is determined by formula (1). c ; By formula (2), determine the amount of electrochemical energy storage when the electrochemical energy storage is fully charged: y2 :

[0025] d c =min(pw, d, d z -d y ) (1)

[0026] d y2 =d y +d c *η c (2)

[0027] Where: d is the electrochemical energy storage output power; d z is the total electrochemical storage capacity; η c Charging efficiency for electrochemical energy storage;

[0028] Step S4.2: When the electrochemical energy storage device is fully charged, the wind and solar surplus power p is determined using formula (3). y :

[0029] p y = pwd c(3)

[0030] Step S4.3, determine the relationship p y > 0 is true;

[0031] If it is not true, it means that after being stored in the electrochemical energy storage device, there is no more excess wind and solar power. Therefore, the molten salt is no longer heated by wind and solar power, and the molten salt heat storage does not change. Therefore, the heat of the molten salt after the end of this cycle, that is, the heat stored in the molten salt at the next moment, is r y2 =r y ; Then let r y =r y2 , d y =d y2 , enter the next moment and return to step S1;

[0032] If so, execute step S4.4;

[0033] Step S4.4, judging whether the wind and solar surplus electricity stored in the electrochemical energy storage device can meet the molten salt heat storage demand, that is, judging whether formula (4) is established; if formula (4) is established, executing step S4.5; if not, executing step S4.6;

[0034] p y *η j >r z / η d -r y (4)

[0035] Where: η j The efficiency of heating molten salt for wind and photovoltaic power generation; z is the total amount of electricity that can be stored in molten salt heat storage; η d The efficiency of thermal power generation by molten salt;

[0036] Step S4.5, molten salt is heated and stored only by wind and solar power:

[0037] Specifically, using formula (5), the molten salt heat absorption r is obtained x , then execute step S4.7;

[0038] r x = r z / η d -r y (5)

[0039] Step S4.6, molten salt is heated by wind and solar power and biomass boilers to store heat:

[0040] Specifically, using formula (6), the molten salt heat absorption r is obtained x , then execute step S4.7;

[0041] rx =min(s*η s / η d +p y *η j , r z / η d -r y ) (6)

[0042] Where: s is the installed power of biomass power generation; η s for biomass power generation efficiency;

[0043] Step S4.7, using formula (7), obtain the heat of the molten salt after the current cycle ends, that is, the heat r stored in the molten salt at the next moment y2 :

[0044] r y2 =r y +r x (7)

[0045] This step is finished.

[0046] Preferably, the electrochemical energy storage output power d = the total electrochemical storage capacity d z / Electrochemical energy storage output hours.

[0047] Preferably, step S5 is specifically:

[0048] Step S5.1, discharge the electrochemical energy storage device to the grid, and use formula (8) to determine the electrochemical energy storage discharge power d f ; By formula (9), the amount of electrochemical energy storage capacity d when the electrochemical energy storage is discharged is determined y2 :

[0049] d f =min(wp, d y *η f ) (8)

[0050] d y2 =d y -d f *η f (9)

[0051] Where: η f is the discharge efficiency of electrochemical energy storage;

[0052] Step S5.2, when the electrochemical energy storage device completes discharge, the system power demand power gap q is determined using formula (10):

[0053] q=wpd f (10)

[0054] Step S5.3, judging whether the relation q≥0 holds;

[0055] If it is not true, it means that after the electrochemical energy storage device discharges, there is no longer a power gap in the system power demand. Therefore, the molten salt no longer needs to participate in the heat release and power generation process, and the molten salt heat storage does not change. Therefore, the heat of the molten salt after the end of this cycle, that is, the heat stored in the molten salt at the next moment, is r y2 =r y ; Then let r y =r y2 , d y =d y2 , enter the next moment and return to step S1;

[0056] If so, execute step S5.4;

[0057] Step S5.4: Molten salt participates in the heat release power generation process. Formula (11) is used to determine the heat release r of the molten salt. f :

[0058] r f =min(q / η d ,r / η d , r y +r x ) (11)

[0059] Where: η d is the thermal power generation efficiency of molten salt; r x is the heat absorbed by the molten salt; r is the molten salt heat storage output power;

[0060] Step S5.5, using formula (12), obtain the heat of the molten salt after the current cycle ends, that is, the heat r stored in the molten salt at the next moment y2 :

[0061] r y2 =r y -r f (12)

[0062] This step is finished.

[0063] Preferably, the calculation method of the molten salt heat storage output power r is: molten salt heat storage output power r = molten salt heat storage total storage capacity r z / Hours of thermal storage power generation.

[0064] The wind-solar integrated power generation system and method coupled with biomass heat storage provided by the present invention have the following advantages:

[0065] The present invention aims to propose a wind-solar integrated power generation system and method coupled with biomass heat storage, and decouples the heat production of the biomass boiler, the heat production of the wind-solar power source, and the power generation process of the steam turbine by adding a molten salt heat storage system to the biomass boiler and the wind-solar power source. On the one hand, the combination of the biomass boiler and the wind-solar power source can significantly reduce the utilization hours of the biomass boiler, reduce the consumption of biomass fuel, improve the economic efficiency of power generation, and help to increase the scale of biomass power generation single project; on the other hand, the molten salt heat storage system can amplify the output level of the biomass boiler, and can provide deep peak-shaving services for the wind-solar power source through long-term heat storage. In general, the present invention can make the wind-solar integrated power generation system coupled with biomass heat storage have a stable output like a traditional thermal power system, have excellent load following performance, and maintain a low power generation cost, so as to achieve green, efficient, and low-cost power generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 A structural diagram of a wind-solar integrated power generation system coupled with biomass heat storage provided by the present invention;

[0067] Figure 2 A flow chart of a wind-solar integrated power generation method coupled with biomass heat storage provided by the present invention.

[0068] in:

[0069] 1- wind and solar power source; 2- electrochemical energy storage equipment; 3- electric heater; 4- low-temperature molten salt tank; 5- high-temperature molten salt tank; 6- biomass boiler; 7- steam generator; 8- steam turbine; 9- generator; 10- condenser; 11- molten salt pump; 12- water pump; 13- booster station; 14- power grid. DETAILED DESCRIPTION

[0070] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0071] The present invention aims to propose a wind-solar integrated power generation system and method coupled with biomass heat storage, and decouples the heat production of the biomass boiler, the heat production of the wind-solar power source, and the power generation process of the steam turbine by adding a molten salt heat storage system to the biomass boiler and the wind-solar power source. On the one hand, the combination of the biomass boiler and the wind-solar power source can significantly reduce the utilization hours of the biomass boiler, reduce the consumption of biomass fuel, improve the economic efficiency of power generation, and help to increase the scale of biomass power generation single project; on the other hand, the molten salt heat storage system can amplify the output level of the biomass boiler, and can provide deep peak-shaving services for the wind-solar power source through long-term heat storage. In general, the present invention can make the wind-solar integrated power generation system coupled with biomass heat storage have a stable output like a traditional thermal power system, have excellent load following performance, and maintain a low power generation cost, so as to achieve green, efficient, and low-cost power generation.

[0072] See also Figure 1 , the present invention provides a wind-solar integrated power generation system coupled with biomass heat storage, including: a wind-solar power source, an electrochemical energy storage device, an electric heater, a low-temperature molten salt tank, a high-temperature molten salt tank, a biomass boiler, a steam generator, a steam turbine unit and a condenser;

[0073] The first power generation end of the wind and solar power source is connected to the power grid;

[0074] The charging end of the electrochemical energy storage device is connected to the second power generation end of the wind and solar power source, and the power generation end of the electrochemical energy storage device is connected to the power grid;

[0075] The molten salt outlet of the low-temperature molten salt tank is directly connected to the molten salt inlet of the heat exchange coil in the furnace of the biomass boiler through a pipeline; the molten salt outlet of the low-temperature molten salt tank is connected to the molten salt inlet of the electric heater, and the molten salt outlet of the electric heater is connected to the molten salt inlet of the heat exchange coil in the furnace of the biomass boiler; and the power supply end of the electric heater is connected to the third power generation end of the wind and solar power source;

[0076] The biomass boiler uses biomass fuel combustion in the furnace to heat the molten salt in the heat exchange coil in the furnace; the molten salt outlet of the heat exchange coil in the furnace of the biomass boiler is connected to the molten salt inlet of the high-temperature molten salt tank through a pipeline;

[0077] The molten salt outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the steam generator, and after the high-temperature molten salt is released by the steam generator, the molten salt outlet of the steam generator is connected to the molten salt inlet of the low-temperature molten salt tank; thereby forming a molten salt circulation loop;

[0078] The high-temperature and high-pressure steam outlet of the steam generator is connected to the steam turbine of the steam turbine unit through a pipeline, driving the steam turbine to work, thereby generating electricity to the power grid through the generator of the steam turbine unit; the steam outlet of the steam turbine is connected to the steam inlet of the condenser, where it is cooled and condensed into liquid water, and then connected to the water working medium inlet of the steam generator, forming a water circuit circulation.

[0079] In practical applications, a molten salt pump for controlling the circulation flow rate of the molten salt working medium is installed on the pipeline from the high-temperature molten salt tank to the steam generator; and a water pump is installed on the pipeline from the condenser to the steam generator.

[0080] Combine the following Figure 1 , the principles of each device are introduced in detail:

[0081] exist Figure 1 In: 1- wind and solar power source; 2- electrochemical energy storage device; 3- electric heater; 4- low-temperature molten salt tank; 5- high-temperature molten salt tank; 6- biomass boiler; 7- steam generator; 8- steam turbine; 9- generator; 10- condenser; 11- molten salt pump; 12- water pump; 13- booster station; 14- power grid.

[0082] according to Figure 1 , from left to right:

[0083] (1) Biomass boiler: The modified biomass boiler can directly heat the molten salt sent from the low-temperature molten salt tank through the heat exchanger inside the biomass boiler;

[0084] (2) Electric heater: Relying on the electricity provided by wind and solar power sources, the molten salt sent out from the low-temperature molten salt tank can be directly heated;

[0085] (3) High-temperature molten salt tank: It stores high-temperature molten salt heated by a biomass boiler or an electric heater. The molten salt is usually binary molten salt. The temperature in the high-temperature molten salt tank is generally around 560°C.

[0086] (4) Low-temperature molten salt tank: stores low-temperature molten salt after heat release in the steam generator. The temperature of the molten salt in the low-temperature molten salt tank is generally around 290°C;

[0087] (5) Wind and solar power: It consists of a certain amount of wind power and photovoltaic power. On the one hand, it transmits the generated electricity to the system booster station, and on the other hand, it uses the electricity to heat the molten salt in the electric heater;

[0088] (6) Electrochemical energy storage equipment: small-scale electrochemical energy storage equipment is used to absorb the excess wind and solar power output when the wind and solar power output is greater than the power load of the grid, and release the power in the electrochemical energy storage equipment to the grid when the power load demand is peak, thereby reducing the overall wind and solar power abandonment rate of the system;

[0089] (7) Molten salt pump: used to control the circulation speed of the molten salt working medium;

[0090] (8) Steam generator: used to transfer the heat in the high-temperature molten salt in the high-temperature molten salt tank to the liquid water at room temperature to generate high-temperature and high-pressure steam, which is used to drive the steam turbine to do work;

[0091] (9) Steam turbine: uses high-temperature and high-pressure steam from the steam generator to do work, and the generator connected to the steam turbine converts mechanical energy into electrical energy to complete the power generation process;

[0092] (10) Condenser: The steam discharged from the steam turbine is cooled and condensed into liquid water by exchanging heat with air or other low-temperature media. On the one hand, an internal vacuum is formed to reduce the exhaust pressure of the steam turbine; on the other hand, the water working medium is recovered and sent to the coal-fired boiler and steam generator through two water pumps to absorb heat again;

[0093] (11) Booster station: receives electricity from steam turbine generators and wind and solar power sources, and transmits electricity to the grid with stable output;

[0094] The arrow lines in the figure are all connected by pipes, except for the wire connections between the generator and the substation, the wind and solar power source and the substation, and the wind and solar power source and the electric heater.

[0095] The present invention provides a wind-solar integrated power generation method coupled with biomass heat storage, the principle of which is as follows:

[0096] (1) When the wind and solar power generation capacity is less than or equal to the grid demand, the wind and solar power will directly supply power to the grid through the booster station; when the wind and solar power generation capacity exceeds the grid demand, the excess power of the wind and solar power will be preferentially fed into the electrochemical energy storage device. After the storage is full, the remaining wind and solar power will be converted into heat energy through the electric heater and stored in the molten salt;

[0097] (2) Combined with the wind and solar weather forecast information, when the wind and solar resources are insufficient, the electric energy in the electrochemical energy storage device is first released, and then the biomass fuel is started to burn in the biomass boiler, and the heat is directly transferred to the low-temperature molten salt working fluid from the low-temperature molten salt tank through the heat exchange coil in the furnace;

[0098] (3) The molten salt working fluid can be heated by electric heaters or biomass boilers. The two methods can operate independently or simultaneously. The two methods share a set of molten salt pipelines and storage systems, which can reduce costs while ensuring that the molten salt working fluid can continue to obtain heat under extreme weather conditions.

[0099] (4) In combination with the wind and solar power output, the heat release power of the high-temperature molten salt working fluid in the steam generator is controlled by controlling the flow rate of the molten salt pump, thereby controlling the output of the steam turbine, so that the sum of the steam turbine power generation output and the wind and solar power output is at a stable level;

[0100] (5) The water medium absorbs the heat of the molten salt in the steam generator and becomes high-temperature and high-pressure steam. The high-temperature and high-pressure steam generates electricity in the steam turbine and then enters the condenser for condensation. The condensed water medium re-enters the steam generator to absorb heat under the action of the water pump.

[0101] (6) For the entire power generation system, when there are sufficient wind and solar resources, the wind and solar power sources not only supply power to the grid through the booster station, but also store the energy of the abandoned power during peak hours in the high-temperature molten salt tank through the electric heater. At this time, the biomass boiler is shut down, and the steam turbine is kept at a low load state or shut down;

[0102] (7) Through weather forecasts and early assessment, before the wind and solar resources are insufficient, the biomass boiler is started to heat the molten salt. When the wind and solar resources are insufficient, the wind and solar power sources stop working or maintain a relatively low output. The wind and solar power sources only supply power to the grid through the booster station. At this time, the steam turbine uses the heat of the high-temperature molten salt in the high-temperature molten salt tank to generate electricity at full capacity and supply it to the booster station, so that the power output of the booster station meets the load demand of the grid;

[0103] (8) In the different operation modes of this system, the biomass boiler is always in the most efficient power generation state or shutdown state, which can reduce the amount of biomass while using a larger biomass boiler unit and improve the biomass utilization efficiency.

[0104] (9) The system operation control system logic is as follows Figure 2 The physical symbols involved are shown in Table 1. Figure 2 In addition to the operating logic, to ensure safe operation, the operating strategy of this system must also follow the following operating principles based on the actual installed capacity of wind power, photovoltaics, molten salt, and biomass: the heat storage molten salt heat release power generation cannot consume all the heat in the power generation process again, and 10% to 20% must remain; when the biomass is started to heat the molten salt, it runs for about 4 to 6 hours each time; if extreme weather is known in advance through weather forecasts, the biomass boiler can be operated in advance to heat the molten salt.

[0105] The specific operation logic is:

[0106] A method for a wind-solar integrated power generation system coupled with biomass heat storage comprises the following steps:

[0107] Step S1, obtaining the current power demand w of the power grid and the wind and solar power output power p of the wind and solar power source;

[0108] Among them: the calculation method of wind and solar output power p is: wind and solar output power p = wind power installed capacity * wind power output coefficient + photovoltaic installed capacity * photovoltaic output coefficient.

[0109] Step S2, obtaining the electrochemical energy storage capacity d of the electrochemical energy storage device at the current moment y And the existing heat of molten salt heat storage r y ;

[0110] Step S3, judging whether the relationship pw>0 holds; if so, it indicates that the wind and solar power output of the wind and solar power source at the current moment exceeds the grid demand, and executing step S4; if not, it indicates that the wind and solar power output of the wind and solar power source at the current moment is less than or equal to the grid demand, and executing step S5;

[0111] Step S4, the wind and solar power supplies power to the grid through the booster station. At the same time, the excess power of the wind and solar power is preferentially fed into the electrochemical energy storage device for storage. After the storage is full, if there is still surplus, the surplus power is converted into heat energy through the electric heater and stored in the molten salt, and the existing power of the electrochemical energy storage is updated. y And the existing heat of molten salt heat storage r y , return to step S1;

[0112] Step S5, the wind and solar power sources directly supply power to the grid through the booster station; at the same time, the electrochemical energy storage device is discharged to the grid to release the electric energy in the electrochemical energy storage device; if there is no system power gap after the electrochemical energy storage device is discharged, there is no need to start the molten salt exothermic power generation; if there is still a system power gap after the electrochemical energy storage device is discharged, the molten salt exothermic power generation is started; the existing amount of electrochemical energy storage d is updated y And the existing heat of molten salt heat storage r y , return to step S1.

[0113] Step S4 and step S5 are the key points of the present invention, and the detailed steps are as follows:

[0114] Step S4 is specifically as follows:

[0115] Step S4.1: The excess power of the wind and solar power sources is fed into the electrochemical energy storage device for storage. The electrochemical energy storage charging power d is determined by formula (1). c ; By formula (2), determine the amount of electrochemical energy storage when the electrochemical energy storage is fully charged: y2 , and also the amount of electricity available for electrochemical energy storage at the next moment.

[0116] d c =min(pw, d, d z -d y ) (1)

[0117] d y2 =dy +d c *η c (2)

[0118] Where: d is the electrochemical energy storage output power; d z is the total electrochemical storage capacity; η c is the charging efficiency of electrochemical energy storage; where, electrochemical energy storage output power d = total electrochemical storage capacity d z / Electrochemical energy storage output hours;

[0119] Step S4.2: When the electrochemical energy storage device is fully charged, the wind and solar surplus power p is determined using formula (3). y :

[0120] p y = pwd c (3)

[0121] Step S4.3, determine the relationship p y > 0 is true;

[0122] If it is not true, it means that after being stored in the electrochemical energy storage device, there is no more excess wind and solar power. Therefore, the molten salt is no longer heated by wind and solar power, and the molten salt heat storage does not change. Therefore, the heat of the molten salt after the end of this cycle, that is, the heat stored in the molten salt at the next moment, is r y2 =r y ; Then let r y =r y2 , d y =d y2 , enter the next moment and return to step S1;

[0123] If so, execute step S4.4;

[0124] Step S4.4, judging whether the wind and solar surplus electricity stored in the electrochemical energy storage device can meet the molten salt heat storage demand, that is, judging whether formula (4) is established; if formula (4) is established, executing step S4.5; if not, executing step S4.6;

[0125] p y *η j >r z / η d -r y (4)

[0126] Where: η j The efficiency of heating molten salt for wind and photovoltaic power generation; z is the total amount of electricity that can be stored in molten salt heat storage; η d The efficiency of thermal power generation by molten salt;

[0127] Step S4.5, molten salt is heated and stored only by wind and solar power:

[0128] Specifically, using formula (5), the molten salt heat absorption r is obtained x , then execute step S4.7;

[0129] r x = r z / η d -r y (5)

[0130] Step S4.6, molten salt is heated by wind and solar power and biomass boilers to store heat:

[0131] Specifically, using formula (6), the molten salt heat absorption r is obtained x , then execute step S4.7;

[0132] r x =min(s*η s / η d +p y *η j , r z / η d -r y ) (6)

[0133] Where: s is the installed power of biomass power generation; η s for biomass power generation efficiency;

[0134] Step S4.7, using formula (7), obtain the heat of the molten salt after the current cycle ends, that is, the heat r stored in the molten salt at the next moment y2 :

[0135] r y2 =r y +r x (7)

[0136] This step is finished.

[0137] Step S5 is specifically as follows:

[0138] Step S5.1, discharge the electrochemical energy storage device to the grid, and use formula (8) to determine the electrochemical energy storage discharge power d f ; By formula (9), the amount of electrochemical energy storage capacity d when the electrochemical energy storage is discharged is determined y2 :

[0139] d f =min(wp, d y *η f ) (8)

[0140] d y2 =dy -d f *η f (9)

[0141] Where: η f is the discharge efficiency of electrochemical energy storage;

[0142] Step S5.2, when the electrochemical energy storage device completes discharge, the system power demand power gap q is determined using formula (10):

[0143] q=wpd f (10)

[0144] Step S5.3, judging whether the relation q≥0 holds;

[0145] If it is not true, it means that after the electrochemical energy storage device discharges, there is no longer a power gap in the system power demand. Therefore, the molten salt no longer needs to participate in the heat release and power generation process, and the molten salt heat storage does not change. Therefore, the heat of the molten salt after the end of this cycle, that is, the heat stored in the molten salt at the next moment, is r y2 =r y ; Then let r y =r y2 , d y =d y2 , enter the next moment and return to step S1;

[0146] If so, execute step S5.4;

[0147] Step S5.4: Molten salt participates in the heat release power generation process. Formula (11) is used to determine the heat release r of the molten salt. f :

[0148] r f =min(q / η d ,r / η d , r y +r x ) (11)

[0149] Where: η d is the thermal power generation efficiency of molten salt; r x is the amount of heat absorbed by the molten salt; r is the molten salt heat storage output power; the calculation method of the molten salt heat storage output power r is: molten salt heat storage output power r = molten salt heat storage total storage capacity r z / Hours of thermal storage power generation.

[0150] Step S5.5, using formula (12), obtain the heat of the molten salt after the current cycle ends, that is, the heat r stored in the molten salt at the next moment y2 :

[0151] r y2 =ry -r f (12)

[0152] This step is finished.

[0153] In summary, the wind-solar integrated power generation system and method coupled with biomass heat storage provided by the present invention can achieve the goals of low power generation cost, low biomass demand, low wind-solar power abandonment rate, and high grid power load following.

[0154] The present invention provides a wind-solar integrated power generation system and method coupled with biomass heat storage, which has the following technical improvements:

[0155] (1) Technical improvement 1: A dual heating method is used to heat the molten salt directly using a biomass boiler and to heat the molten salt using wind and solar power sources, ensuring that the steam turbine can generate electricity stably with high-temperature molten salt under any wind and solar conditions;

[0156] (2) Technical improvement 2: In this system, by rationally configuring wind and solar power generation, biomass boiler generation, and molten salt storage tank capacity, the entire integrated power generation system can always maintain stable power output like traditional thermal power generation, with excellent load tracking capabilities, and meet the grid load demand with stable, green power;

[0157] (3) Technical improvement three: Traditional biomass boilers are small in size due to difficulties in collecting and supplying biomass, and are unable to exert their peak-shaving capacity in regulating power. The present invention couples biomass power generation with wind and solar power generation through a heat storage system, reduces the output hours of biomass boilers, reduces the demand for biomass fuel, and ensures a larger installed capacity. In addition, the cost of biomass power generation can be lowered with the help of low-cost wind and solar power generation, so as to better play the role of regulating power in biomass power station projects.

[0158] (4) Technical improvement 4: An operation control strategy for a wind-solar integrated power generation system with system-coupled biomass heat storage is proposed, which can enable the power generation system to have the advantages of low electricity cost, high load following capability and low wind-solar power abandonment rate.

[0159] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be considered as the scope of protection of the present invention.

Claims

1. A wind-solar integrated power generation system coupled with biomass heat storage, characterized in that: include: Wind and solar power sources, electrochemical energy storage equipment, electric heaters, low-temperature molten salt tanks, high-temperature molten salt tanks, biomass boilers, steam generators, steam turbine units and condensers; The first power generation end of the wind and solar power source is connected to the power grid; The charging end of the electrochemical energy storage device is connected to the second power generation end of the wind and solar power source, and the power generation end of the electrochemical energy storage device is connected to the power grid; The molten salt outlet of the low-temperature molten salt tank is directly connected to the molten salt inlet of the heat exchange coil in the furnace of the biomass boiler through a pipeline; the molten salt outlet of the low-temperature molten salt tank is connected to the molten salt inlet of the electric heater, and the molten salt outlet of the electric heater is connected to the molten salt inlet of the heat exchange coil in the furnace of the biomass boiler; and the power supply end of the electric heater is connected to the third power generation end of the wind and solar power source; The biomass boiler uses biomass fuel combustion in the furnace to heat the molten salt in the heat exchange coil in the furnace; the molten salt outlet of the heat exchange coil in the furnace of the biomass boiler is connected to the molten salt inlet of the high-temperature molten salt tank through a pipeline; The molten salt outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the steam generator, and after the high-temperature molten salt is released by the steam generator, the molten salt outlet of the steam generator is connected to the molten salt inlet of the low-temperature molten salt tank; thereby forming a molten salt circulation loop; The high-temperature and high-pressure steam outlet of the steam generator is connected to the steam turbine of the steam turbine unit through a pipeline, driving the steam turbine to work, thereby generating electricity to the power grid through the generator of the steam turbine unit; the steam outlet of the steam turbine is connected to the steam inlet of the condenser, where it is cooled and condensed into liquid water, and then connected to the water working medium inlet of the steam generator, forming a water circuit circulation.

2. The wind-solar integrated power generation system coupled with biomass thermal storage according to claim 1 is characterized in that: A molten salt pump for controlling the circulation flow rate of the molten salt working medium is installed on the pipeline from the high-temperature molten salt tank to the steam generator; and a water pump is installed on the pipeline from the condenser to the steam generator.

3. A method for a wind-solar integrated power generation system coupled with biomass thermal storage as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: Step S1, obtaining the current power demand w of the power grid and the wind and solar power output power p of the wind and solar power source; Step S2, obtaining the electrochemical energy storage capacity d of the electrochemical energy storage device at the current moment y And the existing heat of molten salt heat storage r y ; Step S3, judging whether the relationship pw>0 holds; if so, it indicates that the wind and solar power output of the wind and solar power source at the current moment exceeds the grid demand, and executing step S4; if not, it indicates that the wind and solar power output of the wind and solar power source at the current moment is less than or equal to the grid demand, and executing step S5; Step S4, the wind and solar power supplies power to the grid through the booster station. At the same time, the excess power of the wind and solar power is preferentially fed into the electrochemical energy storage device for storage. After the storage is full, if there is still surplus, the surplus power is converted into heat energy through the electric heater and stored in the molten salt, and the existing power of the electrochemical energy storage is updated. y And the existing heat of molten salt heat storage r y , return to step S1; Step S5, the wind and solar power sources directly supply power to the grid through the booster station; at the same time, the electrochemical energy storage device is discharged to the grid to release the electrical energy in the electrochemical energy storage device; If there is no system power gap after the electrochemical energy storage device is discharged, there is no need to start the molten salt heat release power generation; if there is still a system power gap after the electrochemical energy storage device is discharged, the molten salt heat release power generation is started; update the existing electrochemical energy storage power d y And the existing heat of molten salt heat storage r y , return to step S1.

4. The method of a wind-solar integrated power generation system coupled with biomass thermal storage according to claim 3, characterized in that: The calculation method of wind and solar power output p is: wind and solar power output p = wind power installed capacity * wind power output coefficient + photovoltaic installed capacity * photovoltaic output coefficient.

5. The method of a wind-solar integrated power generation system coupled with biomass thermal storage according to claim 3, characterized in that: Step S4 is specifically as follows: Step S4.1: The excess power of the wind and solar power sources is fed into the electrochemical energy storage device for storage. The electrochemical energy storage charging power d is determined by formula (1). c ; By formula (2), determine the amount of electrochemical energy storage when the electrochemical energy storage is fully charged: y2 : d c =min(p-w, d, d z -d y ) (1) d y2 =d y +d c *η c (2) Where: d is the electrochemical energy storage output power; d z is the total electrochemical storage capacity; η c Charging efficiency for electrochemical energy storage; Step S4.2: When the electrochemical energy storage device is fully charged, the wind and solar surplus power p is determined using formula (3). y : p y = p-w-d c (3) Step S4.3, determine the relationship p y > 0 is true; If it is not true, it means that after being stored in the electrochemical energy storage device, there is no more excess wind and solar power. Therefore, the molten salt is no longer heated by wind and solar power, and the molten salt heat storage does not change. Therefore, the heat of the molten salt after the end of this cycle, that is, the heat stored in the molten salt at the next moment, is r y2 =r y ; Then let r y =r y2 , d y =d y2 , enter the next moment and return to step S1; If so, execute step S4.4; Step S4.4, judging whether the wind and solar surplus electricity stored in the electrochemical energy storage device can meet the molten salt heat storage demand, that is, judging whether formula (4) is established; if formula (4) is established, executing step S4.5; if not, executing step S4.6; p y *or j >r z / or d -r y (4) Where: η j The efficiency of heating molten salt for wind and photovoltaic power generation; z is the total amount of electricity that can be stored in molten salt heat storage; η d The efficiency of molten salt in generating electricity through heat; Step S4.5, molten salt is heated and stored only by wind and solar power: Specifically, using formula (5), the molten salt heat absorption r is obtained x , then execute step S4.7; r x = r z / or d -r y (5) Step S4.6, molten salt is heated by wind and solar power and biomass boilers to store heat: Specifically, using formula (6), the molten salt heat absorption r is obtained x , then execute step S4.7; r x =min(s*η s / or d +p y *or j , r z / or d -r y ) (6) Where: s is the installed power of biomass power generation; η s for biomass power generation efficiency; Step S4.7, using formula (7), obtain the heat of the molten salt after the current cycle ends, that is, the heat r stored in the molten salt at the next moment y2 : r y2 ＝r y +r x (7) This step is finished.

6. The method of a wind-solar integrated power generation system coupled with biomass thermal storage according to claim 5, characterized in that: Electrochemical energy storage output power d = total electrochemical storage capacity d z / Electrochemical energy storage output hours.

7. The method of a wind-solar integrated power generation system coupled with biomass thermal storage according to claim 3, characterized in that: Step S5 is specifically as follows: Step S5.1, discharge the electrochemical energy storage device to the grid, and use formula (8) to determine the electrochemical energy storage discharge power d f ; By formula (9), the amount of electrochemical energy storage capacity d when the electrochemical energy storage completes discharge is determined y2 : d f =min(wp, d y *or f ) (8) d y2 =d y -d f *η f (9) Where: η f is the discharge efficiency of electrochemical energy storage; Step S5.2, when the electrochemical energy storage device completes discharge, the system power demand power gap q is determined using formula (10): q=w-p-d f (10) Step S5.3, judging whether the relation q≥0 holds; If it is not true, it means that after the electrochemical energy storage device discharges, there is no longer a power gap in the system power demand. Therefore, the molten salt no longer needs to participate in the heat release and power generation process, and the molten salt heat storage does not change. Therefore, the heat of the molten salt after the end of this cycle, that is, the heat stored in the molten salt at the next moment, is r y2 =r y ; Then let r y =r y2 , d y =d y2 , enter the next moment and return to step S1; If so, execute step S5.4; Step S5.4: Molten salt participates in the heat release power generation process. Formula (11) is used to determine the heat release r of the molten salt. f : r f =min(q / n) d ,r / n d , r y +r x ) (11) Where: η d is the thermal power generation efficiency of molten salt; r x is the heat absorbed by the molten salt; r is the molten salt heat storage output power; Step S5.5, using formula (12), obtain the heat of the molten salt after the current cycle ends, that is, the heat r stored in the molten salt at the next moment y2 : r y2 ＝r y -r f (12) This step is finished.

8. The method of the wind-solar integrated power generation system coupled with biomass thermal storage according to claim 7, characterized in that: The calculation method of molten salt heat storage output power r is: molten salt heat storage output power r = molten salt heat storage total storage capacity r z / Hours of thermal storage power generation.

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