A control strategy for a CSP plant adapted to multiple operating scenarios

Abstract

The present invention discloses a control strategy for a CSP plant that adapts to multiple operating modes. The strategy firstly considers weather factors to achieve system energy optimization, determining whether the CSP plant's heat absorber absorbs sufficient heat to heat the molten salt entering the heat tank, and the CSP plant's heat storage and power generation status. Secondly, the strategy analyzes the CSP plant's heat storage capacity and operating constraints, including the energy constraints of the heat storage system, heat loss and heat storage / release power during the storage / release process, and the operating constraints of the CSP plant when generating electricity through a steam turbine generator set. Thirdly, the CSP plant's operating mode is determined, dividing the system's operation into different modes based on the direct energy source for generating the superheated steam entering the steam turbine. Fourthly, the strategy for controlling the CSP plant is determined. This invention can adapt to different operating modes of CSP plants and plays a key role in achieving safe and friendly grid connection for large-scale CSP plants, reducing renewable energy curtailment, and promoting the safe and economical operation and absorption of various types of renewable energy generation.

Description

Technical Field

[0001] The present invention relates to the field of renewable energy power generation technology, and in particular to a control strategy for a solar thermal power station that is adaptable to multiple operating scenarios. Background Art

[0002] Concentrated solar power generation (CSP) is a renewable energy generation method with inherent energy storage, which can mitigate the impact of random solar fluctuations on power generation. Furthermore, CSP, connected to the grid through steam turbine generators, shares some of the responsiveness and regulatory characteristics of conventional units, making it a dispatchable and controllable renewable energy generation method. With the completion and commissioning of my country's first batch of CSP demonstration projects, several tower and trough CSP plants of 50 MW and above have been or will soon be connected to the grid, making CSP's participation in grid dispatch and control imperative. The mainstream forms of large-scale CSP are tower, trough, and Fresnel CSP, which can be configured with various sizes of mirror fields and thermal storage systems. The regulatory characteristics and actual response of CSP plants of various types and configurations to support grid demand, as well as their ability to replace conventional units in terms of power balance and stable support, are key issues requiring attention in CSP's participation in grid dispatch and control, and are crucial to the safe and friendly integration of large-scale CSP plants. In addition, in a high-proportion new energy sending-end system, solar thermal power generation coordinates and optimizes scheduling operations with mature new energy power generation forms such as wind power and photovoltaic power generation, which is conducive to reducing the new energy power abandonment rate and promoting the safe and economic operation and absorption of various types of new energy power generation. It is of great significance to the construction of a comprehensive energy and power system at the sending end based on renewable energy.

[0003] In recent years, several CSP demonstration power stations have been built and put into operation both domestically and internationally, with power plant sizes ranging from tens of megawatts to tens of megawatts. Researchers have also conducted extensive research on the mechanisms of key CSP equipment and the operational characteristics of CSP power stations. There is still limited research on the regulatory characteristics and control technologies of CSP in response to grid demand. The differences in scheduling and operation between CSP and conventional thermal power units, as well as CSP's ability to replace conventional thermal power, lack theoretical support and practical evidence. Due to the current small scale of CSP, there is still a lack of in-depth research on CSP's participation in grid scheduling and its coordinated control of promoting wind and photovoltaic power generation. To this end, we have designed a CSP control strategy that adapts to multiple operating scenarios to fill the above technical gaps. Summary of the Invention

[0004] This paper proposes a control strategy for CSP plants that adapts to multiple operating scenarios. This strategy addresses the varying degrees of safety and stability issues associated with large-scale photovoltaic grid access under different operating modes. Considering the multiple operating scenarios of CSP plants that meet the requirements of power balance for external power transmission, the paper proposes a CSP plant operation mode and control strategy that comprehensively meets both power balance and stable support requirements. This strategy plays a key role in enabling safe and friendly grid connection for large-scale CSP plants, reducing renewable energy curtailment, and promoting the safe and economical operation and absorption of diverse renewable energy generation types.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A control strategy for a CSP plant adapted to multiple operating modes includes the following steps:

[0007] Step 1: Consider weather factors to optimize system energy. Based on the DNI value, determine whether the CSP plant's receiver absorbs enough heat to heat the molten salt into the heat tank, as well as the CSP plant's heat storage and power generation status.

[0008] Step 2: Analyze the thermal storage capacity and operating constraints of the CSP plant, including the energy constraints of the thermal storage system, the heat loss and thermal power during the storage and release process, and the operating constraints of the CSP plant when generating electricity through the steam turbine generator set.

[0009] Step 3: Determine the operation mode of the CSP plant and divide the system operation into different modes according to the direct energy source for generating the superheated steam entering the steam turbine;

[0010] Step 4: Divide the system into different modes according to operation and determine the control strategy of the CSP plant.

[0011] Further preferably, in step 1, the DNI value is used to determine whether the CSP absorber absorbs enough heat to heat the molten salt into the heat tank, and the heat storage and power generation process of the CSP is as follows:

[0012] (1) When DNI < 650W / ㎡, the solar thermal power station absorber is not enough to absorb enough heat to heat the molten salt into the hot tank. At this time, if the heat storage system has no heat storage, then P CSP =0, that is, the CSP station is not connected to the grid for power generation; if the thermal storage system has heat storage, then P CSP ∈[0,σ1P CSP_r ], the CSP station does not connect to the grid for power generation, but relies on the heat storage system for power generation; CSP Indicates the reliable output of the CSP station, P CSP_r represents the rated power of the CSP station, and σ1 represents the output correction coefficient of the CSP station under low irradiance;

[0013] (2) When 650W / ㎡≤DNI<800W / ㎡, the heat absorbed by the CSP station absorber can heat the molten salt to the set temperature and enter the hot tank. At this time, the molten salt entering the hot tank can be directly used for power generation or storage. If the heat storage system has no heat storage, then P CSP ∈[0,σ2P CSP_r ], that is, the CSP station can only store heat, or rely on newly heated molten salt to generate electricity; if the heat storage system has heat storage, then P CSP ∈[P CSPmin , P CSP_r ], that is, the CSP station relies on the heat storage system to ensure operation at rated power, where P CSPmin is the minimum technical output of the CSP plant, σ2 represents the output correction coefficient of the CSP plant under medium irradiance;

[0014] (3) When DNI ≥ 800W / ㎡, the irradiance can ensure that the CSP station can store heat and generate electricity at the same time. Therefore, the CSP station can reliably output power to meet P CSP ∈[P CSPmin , P CSP_r ]

[0015] Further preferably, in the step 2, assuming that at time t, the total energy stored in the heat storage system is W t TS , the energy constraint of the heat storage system is:

[0016]

[0017] Where, Represents the minimum heat storage capacity of the heat storage system, h FLH Indicates the maximum capacity of the thermal storage system described in FLH, Indicates the maximum generating power of the steam turbine generator set.

[0018] Further preferably, in step 2, the heat loss during the heat storage and release process of the heat storage system is expressed by heat storage and release efficiency:

[0019] P t TS-c =η c P t HTF-TS (2)

[0020] P t TS-d =P t TS-HTF / η d (3)

[0021] Where, P t TS-c represents the heat storage power of the heat storage system at time t, P t TS-dP represents the heat release power of the heat storage system at time t, t HTF-TS P represents the thermal power transferred from the heat transfer medium to the heat storage system at time t. t TS-HTF It represents the heat power transferred by the heat storage system to the heat transfer medium at time t, η c represents the heat storage efficiency, η d Indicates heat release efficiency;

[0022] During the heat storage and release process, the heat storage and release power can be continuously adjusted within the limit range, that is:

[0023]

[0024]

[0025] Where, represents the maximum heat storage power of the heat storage system, Indicates the maximum heat release power of the heat storage system;

[0026] At the same time, the operating constraints of the CSP plant when generating electricity through the turbine generator set are:

[0027]

[0028]

[0029]

[0030] In the above formula, P t e and They represent the active power output of the CSP station at time t and time t-1, respectively. t RsvUp , P t RsvDown Respectively represent the upper and lower backup of the solar thermal power station, and They represent the maximum and minimum output of the steam turbine generator set in the CSP station, R U and R U Respectively represent the maximum up and down climbing capabilities of the unit.

[0031] Further preferably, in step 3, the system operation is divided into different modes according to the direct energy source for generating the superheated steam entering the steam turbine, including the following six modes:

[0032] M1 mode, direct power generation; M2 mode, heat storage process; M3 mode, power generation by heat storage system; M4 mode, power generation while storing heat; M5 mode, power generation assisted by heat storage system; M6 mode, power generation supplemented by complementary fuel;

[0033] To determine the operation mode of the solar thermal power station, first determine the startup conditions based on the irradiance. If they are met, enter M2 mode; determine whether the heat storage system is preheated or fully stored. If so, enter M1 mode, otherwise maintain M2 mode; determine whether the power of the solar collection system is greater than the load. If so, enter M4 mode; otherwise, determine whether the power of the solar collection system is less than the load. If so, enter M5 mode; otherwise, determine whether the heat storage system is faulty. If faulty, enter M6 mode, otherwise enter M3 mode.

[0034] Further preferably, in step 4, determining the control strategy of the CSP plant according to different modes includes:

[0035] In M1 mode, the concentrated solar heat collection system of the CSP station heats the heat transfer medium to the operating temperature, then enters the steam generation system to heat the feed water, and the generated superheated steam is transported to the steam turbine generator set to generate electricity. The current active power of the CSP station is P1. e , the heat storage system has not yet stored heat;

[0036] When the active power of the CSP station adopts maximum power tracking control, the CSP station does not have the power increase capability, and the power decrease capacity P1 Down for:

[0037]

[0038] Where P1 Down The capacity of the active power of the CSP station under M1 mode is reduced. is the maximum power of the steam turbine generator set;

[0039] When the active power of the CSP station is not controlled by maximum power tracking and is in a reduced output state, the active power of the CSP station has the ability to adjust up and down. The active power adjustment capacity of the CSP station is P1. Up for:

[0040] Where P1 Up Indicates the active power increase capacity of the CSP station under M1 mode. Indicates the active power of the maximum power tracking of the CSP station under the current irradiance condition;

[0041] In M2 mode, the concentrated solar collector system of the CSP power station heats the heat transfer medium to the operating temperature, and then enters the heat storage system, which is completely used to store heat in the energy storage system. In M2 mode, the output of the CSP power station is 0, and it has not yet been connected to the grid for power generation. It does not have the ability to adjust the active power downward. To increase the active power, it is necessary to release heat energy through the heat storage system to generate electricity. The power adjustment capacity of the CSP power station is:

[0042] Where, P2 UpIndicates the active power increase capacity of the CSP station in M2 mode;

[0043] If it is M3 mode, the high-temperature heat storage medium released by the heat storage system enters the steam generation system to heat the feed water, and the generated superheated steam is transported to the steam turbine generator set for power generation. At this time, the CSP station is in the grid-connected power generation state, and the output of the CSP station is P3. e , power generation has been completed for t3 hours, and the heat storage system has a heat storage capacity of The peak regulation capacity of active power of CSP station is:

[0044]

[0045] The peak-shaving capacity of the active power of the CSP station is:

[0046]

[0047] Where P3 Up Indicates the peak capacity of the active power of the CSP station in M3 mode, P3 Down Indicates the peak-down regulation capacity of the active power of the CSP station in M3 mode;

[0048] If it is M4 mode, the CSP station can generate electricity at full load, and the heat storage system has reached its maximum storage capacity. If the CSP station is used as a peak-shaving power source, some of the concentrators in the CSP station's mirror field will be in a defocused state, reducing the absorption of solar energy, thus making the CSP station in a reduced output state. The output of the CSP station is P4. e At this time, the solar thermal power station has the ability to adjust the power up and down.

[0049] The peak regulation capacity of active power of CSP station is:

[0050]

[0051] The peak-shaving capacity of the active power of the CSP station is:

[0052]

[0053] In the above formula, P4 Up When the thermal power station does not adopt the maximum power tracking control in the M4 mode, the active power of the photothermal power station adjusts the peak capacity upwards. Down When the CSP station does not use the maximum power point tracking control in M4 mode, the active power of the CSP station adjusts the peak capacity downward;

[0054] If the M5 mode is used, the current operation status of the CSP station is determined. The current CSP output is P5. e , the heat storage system is in the heat release process, and the heat release power is P5 TS-d , after releasing heat for t5 hours, calculate the active power peak capacity of the CSP station according to the following formula:

[0055]

[0056] The peak-shaving capacity of the active power of a CSP station is calculated as follows:

[0057]

[0058] In the above formula, P5 Up Indicates the peak capacity of the active power of the CSP station in M5 mode, P5 Down Indicates the peak-down regulation capacity of the active power of the CSP station in M5 mode.

[0059] Compared with the existing technology, the beneficial effects of the present invention are: the present invention proposes a solar thermal power station operation mode and control strategy that comprehensively meets the needs of power balance and stable support, can adapt to different operation modes of solar thermal power stations, and play a key role in achieving safe and friendly grid connection of large-scale solar thermal power stations, reducing the renewable energy power abandonment rate, and promoting the safe and economic operation and absorption of various types of renewable energy power generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a logic flow chart of operation mode determination and switching in this embodiment;

[0061] Figure 2 This is a control flow chart of a CSP plant in the M1 mode in the embodiment;

[0062] Figure 3 This is a control flow chart of a CSP plant in M2 mode in an embodiment;

[0063] Figure 4 This is a control flow chart of a CSP plant in M3 mode in an embodiment;

[0064] Figure 5 This is a control flow chart of a CSP plant in M4 mode in an embodiment;

[0065] Figure 6 This is a control flow chart of a CSP plant in the M5 mode in the embodiment. DETAILED DESCRIPTION

[0066] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0067] Example:

[0068] This embodiment proposes a control strategy for a CSP plant that is adaptable to multiple operating modes. The control strategy can be summarized into the following process: 1) taking weather factors into account to achieve system energy optimization; 2) analyzing the heat storage capacity and operating limitations of the CSP plant; 3) determining the operating mode of the CSP plant; and 4) determining the control strategy of the CSP plant.

[0069] The specific control strategy includes the following steps:

[0070] Step 1: Consider weather factors to optimize system energy. Based on the DNI value (Direct Normal Irradiance, which refers to the direct radiation energy received per unit time and per unit area on a plane perpendicular to the sun's rays, expressed in watts per square meter), we determine whether the CSP station's receiver absorbs enough heat to heat the molten salt and feed it into the heat tank, as well as the CSP station's heat storage and power generation. The specific process is as follows:

[0071] (1) When DNI < 650W / ㎡, the solar thermal power station absorber is not enough to absorb enough heat to heat the molten salt into the hot tank. At this time,

[0072] 1) If the heat storage system has no heat storage, then P CSP =0, that is, the CSP station is not connected to the grid for power generation;

[0073] 2) If the heat storage system has heat storage, then P CSP ∈[0,σ1P CSP_r ], that is, a solar thermal power station can generate electricity without being connected to the grid, or it can rely on a heat storage system to generate electricity, but in order to ensure continuous operation under low irradiance, it is generally not operated at full power.

[0074] Where, P CSP Indicates the reliable output of the CSP station; P CSP_r represents the rated power of the CSP plant; σ1 represents the output correction coefficient of the CSP plant under low irradiance.

[0075] (2) When 650W / ㎡≤DNI<800W / ㎡, the solar thermal power station absorber absorbs heat to heat the molten salt to the set temperature and enters the hot tank. At this time, the molten salt entering the hot tank can directly generate electricity or be stored.

[0076] 1) If the heat storage system has no heat storage, then P CSP ∈[0,σ2P CSP_r ], that is, a CSP plant can either store heat only or generate electricity from the newly heated molten salt.

[0077] 2) If the heat storage system has heat storage, then P CSP ∈[P CSPmin , P CSP_r], that is, the CSP station relies on the heat storage system and can guarantee the maximum operation at rated power, where P CSPmin is the minimum technical output of the CSP station, and σ2 represents the output correction coefficient of the CSP station under medium irradiance (650W / ㎡≤DNI<800W / ㎡).

[0078] (3) When DNI ≥ 800W / ㎡, the solar irradiance value can ensure that the CSP station can store heat and generate electricity at the same time. Therefore, the CSP station can reliably output power to meet P CSP ∈[P CSPmin , P CSP_r ].

[0079] Step 2: Analyze the thermal storage capacity and operating limitations of the CSP plant. The specific process is as follows:

[0080] Assume that at time t, the total energy stored in the heat storage system is W t TS , then the energy constraint of the heat storage system is:

[0081]

[0082] Where, Indicates the minimum heat storage capacity of the heat storage system; h FLH Indicates the maximum capacity of the thermal storage system described in FLH; Indicates the maximum generating power of the steam turbine generator set.

[0083] During the heat storage and release process of the heat storage system, there will be some heat loss, which is expressed by the heat storage and release efficiency:

[0084] P t TS-c =η c P t HTF-TS (2)

[0085] P t TS-d =P t TS-HTF / η d (3)

[0086] Where, P t TS-c represents the heat storage power of the heat storage system at time t; P t TS-d P represents the heat release power of the heat storage system at time t; t HTF-TS P represents the thermal power transferred from the heat transfer medium to the heat storage system at time t; t TS-HTF represents the heat power transferred from the heat storage system to the heat transfer medium at time t; η c represents the heat storage efficiency; ηd Indicates heat release efficiency.

[0087] During the heat storage and release process, the heat storage and release power must also be continuously adjustable within a limited range, that is:

[0088]

[0089]

[0090] Where, represents the maximum heat storage power of the heat storage system, Indicates the maximum heat release power of the heat storage system.

[0091] At the same time, the CSP power station generates electricity through steam turbine generator sets and must also have similar operating constraints as conventional steam turbine sets:

[0092]

[0093]

[0094]

[0095] Where, P t e and They represent the active power output of the CSP station at time t and time t-1 respectively; P t RsvUp and P t RsvDown They are the upper and lower backup of the CSP station respectively; and are the maximum and minimum outputs of the steam turbine generator set in the CSP station; R U and R D They are the maximum up and down climbing capabilities of the unit respectively.

[0096] Step 3: Determine the operation mode of the CSP plant. The specific process is as follows:

[0097] According to the different direct energy sources for generating the superheated steam entering the steam turbine, the system operation mode can be divided into the following six modes: (1) M1 mode, indicating direct power generation; (2) M2 mode, indicating heat storage process; (3) M3 mode, indicating power generation by the heat storage system; (4) M4 mode, indicating power generation while storing heat; (5) M5 mode, indicating auxiliary power generation by the heat storage system; (6) M6 mode, indicating power generation supplemented by complementary fuel.

[0098] like Figure 1 As shown, first determine the power-on condition based on the irradiance, calculate the available optical power based on the irradiance, and determine whether the device status meets the power-on condition. If the irradiance meets the power-on condition, enter M2 mode.

[0099] Then determine whether the heat storage system is preheated or full. If the heat storage system is full, enter M1 mode, otherwise maintain M2 mode;

[0100] Then determine whether the power of the solar thermal power station's solar collection system is greater than the load. If the power of the solar collection system is greater than the load, enter M4 mode. Otherwise, determine whether the power of the solar collection system is less than the load. If the power of the solar collection system is less than the load, enter M5 mode. Otherwise, determine whether the thermal storage system has a fault. If the thermal storage system has a fault, enter M6 mode. If the thermal storage system has not a fault, it is determined to be cloud cover, collector failure, sliding pressure shutdown, or night operation, and enter M3 mode.

[0101] Step 4: Determine the control strategy of the CSP plant based on different modes. The specific process is as follows:

[0102] like Figure 2 As shown, if it is M1 mode, the concentrated solar heat collection system of the CSP station heats the heat transfer medium to the operating temperature, then enters the steam generation system to heat the feed water, and the generated superheated steam is transported to the steam turbine generator set to generate electricity. The current active power of the CSP station is P1 e , the heat storage system has not yet stored heat.

[0103] When the active power of the CSP station adopts maximum power tracking control, the CSP station does not have the power upward adjustment capability, and the downward adjustment peak capacity P1 of the CSP station Down for:

[0104]

[0105] Where P1 Down The capacity of the CSP station is reduced for active power under M1 mode; is the maximum power of the steam turbine generator set;

[0106] When the active power of the CSP station is not controlled by maximum power tracking and is in a reduced output state, the active power of the station has the ability to adjust up and down. The above formula (9) is used to calculate the peak-down capacity of the CSP station. The peak-up capacity of the active power of the CSP station is P1 Up for:

[0107]

[0108] Where P1 Up Increase the capacity of the active power of the CSP station under M1 mode; It is the active power of the maximum power tracking of the CSP station under the current irradiance condition.

[0109] And the above P1 Up and Report to the dispatching agency, the dispatching agency issues the peak-shaving operation curve, the active power of the CSP station tracks the peak-shaving operation curve, increases the flow of heat transfer medium, and increases the power output. The power increase change ∈ [0, P1 Up ], reduce the heat transfer medium flow rate, lower the power output, the power reduction change ∈ [0, P1 Down ], track and complete the scheduling and peak-shaving operation instructions.

[0110] like Figure 3 As shown, in M2 mode, the concentrated solar thermal system of the CSP power station heats the heat transfer medium to the operating temperature, and then enters the heat storage system, which is completely used to store heat in the energy storage system. In this mode, the output of the CSP power station is 0, that is, the current active power of the CSP power station is 0, and it has not yet been connected to the grid for power generation, and it does not have the ability to adjust the active power downward. In order to increase the active power, it is necessary to release heat energy through the heat storage system to generate electricity. The power adjustment capacity of the CSP power station is:

[0111] Where, P2 Up To increase the active power capacity of the CSP station in M2 mode;

[0112] Determine the peak load demand. If there is no demand, continue the heat storage process until it ends. If there is a peak load demand, stop the heat storage process. Heat has been stored for t2 hours and the heat storage power is P2 TS-c ,

[0113] At this time, electricity is generated by the heat storage system, and the real-time heat storage of the heat storage system is W2 TS =P2 TS-c t2, calculate the continuous power generation time of the thermal storage system to maintain the rated power of the CSP station. Report H2 to the dispatching agency, which issues the peak-shaving operation curve. The active power of the CSP station tracks the peak-shaving operation curve, increases the flow of heat transfer medium, and adjusts the power output. The power increase change Track and complete the scheduling and peak-shaving operation instructions.

[0114] like Figure 4 As shown, if it is M3 mode, the high-temperature heat storage medium released by the heat storage system enters the steam generation system to heat the feed water, and the generated superheated steam is transported to the steam turbine generator set for power generation. At this time, the CSP station is in the grid-connected power generation state, and the output of the CSP station is P3 e , that is, the current active power of the CSP station is P3 e , power generation has been completed for t3 hours, and the heat storage capacity of the current heat storage system is calculated as Calculate the sustainable power generation time of the CSP station at rated power: The calculation of the peak regulation capacity of the active power of the CSP station is:

[0115]

[0116] The peak-shaving capacity of the active power of the CSP station is:

[0117]

[0118] Where P3 Up To increase the peak capacity of the active power of the CSP station under M3 mode; P3 Down To reduce the peak capacity of the active power of the CSP station under M3 mode.

[0119] H3, P3 Up and P3 Down Report to the dispatching agency, the dispatching agency issues the peak-shaving operation curve, the active power of the solar thermal power station tracks the peak-shaving operation curve, increases the flow rate of the heat transfer medium, and increases the power output. The power increase change ∈ [0, P3 Up ], reduce the heat transfer medium flow rate, lower the power output, the power reduction change ∈ [0, P3 Down ], track and complete the scheduling and peak-shaving operation instructions.

[0120] like Figure 5 As shown, if it is M4 mode, when the actual direct solar irradiance is greater than or equal to the preset irradiance of the CSP station, the concentrating heat collection system of the CSP station heats the heat transfer medium to the operating temperature and then enters the steam generation system to heat the feed water, and the generated superheated steam is transported to the steam turbine generator set, and the other part of the heat transfer medium enters the heat storage system for heat storage. In this mode, the CSP station can generate electricity at full load, and at the same time, the heat storage system has reached its maximum heat storage capacity. If the CSP station is used as a peak-shaving power source, part of the concentrators in the CSP station's mirror field will be in a defocused state, reducing the absorption of solar energy, thereby causing the CSP station to be in a reduced output operation state, and the output of the CSP station is P4. e , that is, the active power is P4 e , to determine whether the power is tracked to the maximum. If not, the CSP station has the ability to adjust power up and down. The peak capacity of the active power of the CSP station is:

[0121]

[0122] The peak-shaving capacity of the active power of the CSP station is:

[0123]

[0124] If so, calculate the down-regulated peak capacity according to the above formula (15);

[0125] Where, P4 Up When the CSP station is operating in M4 mode and the maximum power tracking control is not adopted, the active power of the CSP station is adjusted upward to the peak capacity; P4 DownWhen the CSP station is running in M4 mode and the maximum power tracking control is not adopted, the active power of the CSP station is adjusted downward to the peak capacity; Up and P4 Down Report to the dispatching agency, the dispatching agency issues the peak-shaving operation curve, the active power of the CSP station tracks the peak-shaving operation curve, the defocused concentrator is refocused, and the power output is increased. The power increase change ∈ [0, P4 Up ], run the concentrator and defocus again, adjust the power output downward, the power adjustment amount ∈ [0, P4 Down ], track and complete the scheduling and peak-shaving operation instructions.

[0126] like Figure 6 As shown, if it is M5 mode, the concentrating system of the CSP station is all in the state of focusing and absorbing solar radiation, and the peak load regulation is achieved by increasing the heat exchange of the heat storage system to increase the active output of the station. At night, the heat storage system is also used to maintain the power station connected to the grid, but the heat storage system is W5 TS Relatively small, the nighttime peak-shaving capacity will last for a short time.

[0127] Determine the current operating status of the CSP plant. The output of the CSP plant is P5. e , that is, the current active power of the CSP station is P5 e , the heat storage system is in the heat release process, and the heat release power is P5 TS-d , after releasing heat for t5 hours, calculate the active power peak capacity of the CSP station according to the following formula:

[0128]

[0129] The peak-shaving capacity of the active power of a CSP station is calculated as follows:

[0130]

[0131] Where, P5 Up To increase the peak capacity of the active power of the CSP station under M5 mode; P5 Down To reduce the peak capacity of the active power of the CSP station under M5 mode.

[0132] The sustainable power generation time of a CSP station at rated power is:

[0133]

[0134] H5, P5 Up and P5 Down Report to the dispatching agency, the dispatching agency issues the peak-shaving operation curve, the active power of the CSP station tracks the peak-shaving operation curve, increases the flow of heat transfer medium, and increases the power output. The power increase change ∈ [0, P5 Up], reduce the heat transfer medium flow rate, lower the power output, the power reduction change ∈ [0, P5 Down ], track and complete the scheduling and peak-shaving operation instructions.

[0135] This implementation proposes a control strategy for CSP plants that adapts to multiple operating scenarios, addressing the varying degrees of safety and stability issues associated with large-scale photovoltaic grid access under different operating modes. Considering the multiple operating scenarios of CSP plants that meet the needs of power transmission and electricity balance, this paper proposes a CSP plant operating model and control strategy that comprehensively meets both power balance and stable support requirements. This strategy plays a key role in enabling safe and friendly grid connection of large-scale CSP plants, reducing renewable energy curtailment, and promoting the safe and economical operation and absorption of various types of renewable energy generation.

[0136] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A control strategy for a CSP plant that adapts to multiple operating scenarios, characterized in that: The following steps are involved: Step 1: Consider weather factors to optimize system energy. Based on the DNI value, determine whether the CSP station's receiver absorbs enough heat to heat the molten salt into the heat tank, as well as the CSP station's heat storage and power generation status. The process is as follows: (1) When DNI < 650W / ㎡, the solar thermal power station absorber is not enough to absorb enough heat to heat the molten salt into the hot tank. At this time, if the heat storage system has no heat storage, then P CSP =0, that is, the CSP station is not connected to the grid for power generation; if the thermal storage system has heat storage, then P CSP ∈[0,σ1P CSP_r ], the CSP station does not generate electricity through the grid, but relies on the heat storage system to generate electricity; CSP Indicates the reliable output of the CSP station, P CSP_r represents the rated power of the CSP station, and σ1 represents the output correction coefficient of the CSP station under low irradiance; (2) When 650W / ㎡≤DNI<800W / ㎡, the heat absorbed by the CSP station absorber can heat the molten salt to the set temperature and enter the hot tank. At this time, the molten salt entering the hot tank can be directly used for power generation or storage. If the heat storage system has no heat storage, then P CSP ∈[0,σ2P CSP_r ], that is, the CSP station can only store heat, or rely on the newly heated molten salt to generate electricity; if the heat storage system has heat storage, then P CSP ∈[P CSPmin , P CSP_r ], that is, the CSP station relies on the heat storage system to ensure operation at rated power, where P CSPmin is the minimum technical output of the CSP plant, σ2 represents the output correction coefficient of the CSP plant under medium irradiance; (3) When DNI ≥ 800W / ㎡, the irradiance can ensure that the CSP station can store heat and generate electricity at the same time. Therefore, the CSP station can reliably output power to meet P CSP ∈[P CSPmin , P CSP_r ] Step 2: Analyze the thermal storage capacity and operating constraints of the CSP plant, including the energy constraints of the thermal storage system, the heat loss and thermal power during the storage and release process, and the operating constraints of the CSP plant when generating electricity through the steam turbine generator set. Step 3: Determine the operation mode of the CSP plant. Based on the direct energy source for generating the superheated steam that enters the steam turbine, the system operation is divided into different modes, including the following six modes: M1 mode, direct power generation; M2 mode, heat storage process; M3 mode, power generation by heat storage system; M4 mode, power generation while storing heat; M5 mode, power generation assisted by heat storage system; M6 mode, power generation supplemented by complementary fuel; Determine the operation mode of the solar thermal power station, judge the startup conditions based on the irradiance, and enter M2 mode if they are met; determine whether the heat storage system is preheated or fully stored, and if so, enter M1 mode, otherwise maintain M2 mode; determine whether the power of the heat collection system is greater than the load, and if so, enter M4 mode, otherwise determine whether the power of the heat collection system is less than the load, and if so, enter M5 mode, otherwise determine whether the heat storage system is faulty, and if so, enter M6 mode, otherwise enter M3 mode; Step 4: Divide the system into different modes according to operation and determine the control strategy of the CSP plant as follows: In M1 mode, the concentrated solar heat collection system of the CSP station heats the heat transfer medium to the operating temperature, then enters the steam generation system to heat the feed water, and the generated superheated steam is transported to the steam turbine generator set to generate electricity. The current active power of the CSP station is P1. e , the heat storage system has not yet stored heat; When the active power of the CSP station adopts maximum power tracking control, the CSP station does not have the power increase capability, and the power decrease capacity P1 Down for: Where P1 Down The capacity of the active power of the CSP station under M1 mode is reduced. is the maximum power of the steam turbine generator set; When the active power of the CSP station is not controlled by maximum power tracking and is in a reduced output state, the active power of the CSP station has the ability to adjust up and down. The active power adjustment capacity of the CSP station is P1. Up for: Where P1 Up Indicates the active power increase capacity of the CSP station under M1 mode. Indicates the active power of the maximum power tracking of the CSP station under the current irradiance condition; In M2 mode, the concentrated solar collector system of the CSP power station heats the heat transfer medium to the operating temperature, and then enters the heat storage system, which is completely used to store heat in the energy storage system. In M2 mode, the output of the CSP power station is 0, and it has not yet been connected to the grid for power generation. It does not have the ability to adjust the active power downward. To increase the active power, it is necessary to release heat energy through the heat storage system to generate electricity. The power adjustment capacity of the CSP power station is: Where, Indicates the active power increase capacity of the CSP station in M2 mode; If it is M3 mode, the high-temperature heat storage medium released by the heat storage system enters the steam generation system to heat the feed water, and the generated superheated steam is transported to the steam turbine generator set for power generation. At this time, the CSP station is in the grid-connected power generation state, and the output of the CSP station is After t3 hours of power generation, the heat storage system has a heat storage capacity of The peak regulation capacity of active power of CSP station is: The peak-shaving capacity of the active power of the CSP station is: Where, Indicates the peak capacity of the active power of the CSP station in M3 mode. Indicates the peak-shaving capacity of the active power of the CSP station under M3 mode, h FLH Indicates the maximum capacity of the thermal storage system described in FLH; If it is M4 mode, the CSP station can generate electricity at full load, and the heat storage system has reached its maximum heat storage capacity. If the CSP station is used as a peak-shaving power source, part of the concentrators in the CSP station's mirror field will be in a defocused state, reducing the absorption of solar energy, thus making the CSP station in a reduced output operation state. The output of the CSP station is At this time, the CSP station has the ability to adjust power up and down. The peak regulation capacity of active power of CSP station is: The peak-shaving capacity of the active power of the CSP station is: In the above formula, When the thermal power station does not adopt the maximum power tracking control in the M4 mode, the active power of the photothermal power station adjusts the peak capacity upward. When the CSP station does not use the maximum power point tracking control in M4 mode, the active power of the CSP station adjusts the peak capacity downward; If the M5 mode is used, the current operation status of the CSP station is determined. The current CSP output is The heat storage system is in the process of releasing heat, and the heat release power is After t5 hours of heat release, the active power peak capacity of the CSP station is calculated as follows: The peak-shaving capacity of the active power of a CSP station is calculated as follows: In the above formula, Indicates the peak capacity of the active power of the CSP station in M5 mode. Indicates the peak-down regulation capacity of the active power of the CSP station in M5 mode.

2. A control strategy for a CSP plant adapted to multiple operating modes according to claim 1, characterized in that: In step 2, suppose at time t, the total energy stored in the heat storage system is W t TS , the energy constraint of the heat storage system is: Where, Represents the minimum heat storage capacity of the heat storage system, h FLH Indicates the maximum capacity of the thermal storage system described in FLH, Indicates the maximum generating power of the steam turbine generator set.

3. A control strategy for a CSP plant adapted to multiple operating modes according to claim 1, characterized in that: In step 2, the heat loss during the heat storage and release process of the heat storage system is expressed by the heat storage and release efficiency: Where, P t TS-c represents the heat storage power of the heat storage system at time t, P t TS-d P represents the heat release power of the heat storage system at time t, t HTF-TS P represents the thermal power transferred from the heat transfer medium to the heat storage system at time t. t TS-HTF It represents the heat power transferred by the heat storage system to the heat transfer medium at time t, η c represents the heat storage efficiency, η d Indicates heat release efficiency; During the heat storage and release process, the heat storage and release power can be continuously adjusted within the limit range, that is: Where, represents the maximum heat storage power of the heat storage system, Indicates the maximum heat release power of the heat storage system; At the same time, the operating constraints of the CSP plant when generating electricity through the turbine generator set are: In the above formula, P t e and They represent the active power output of the CSP station at time t and time t-1, respectively. t RsvUp , P t RsvDown Respectively represent the upper and lower backup of the solar thermal power station, and They represent the maximum and minimum output of the steam turbine generator set in the CSP station, R U and R D Respectively represent the maximum up and down climbing capabilities of the unit.

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