Multi-stage frequency support method, system, device and medium for wind storage combined field group

Abstract

This invention provides a multi-stage frequency support method, system, equipment, and medium for wind and energy storage combined power plants, belonging to the field of new energy power generation grid connection technology. The method includes: dividing wind turbines and energy storage units into multiple power plants; when the grid bus frequency deviates from a first safety range, triggering each wind turbine in the power plant to enter frequency support stage 1; when the grid bus frequency deviates from a second safety range, triggering each energy storage unit to enter the frequency support stage; when the torque of any wind turbine exceeds a preset torque threshold, switching the wind turbine to frequency support stage 2, and the energy storage unit entering the frequency support stage; after the grid frequency reaches its lowest point, respectively initiating progressive speed recovery control of the wind turbines and grouped ramp power recovery control of the energy storage system. This invention achieves dynamic complementarity and synergistic optimization of wind and energy storage resources in multi-stage frequency support, effectively improving grid frequency stability and the lowest point while avoiding wind turbine overload.

Description

Technical Field

[0001] This invention relates to the field of new energy power generation grid connection technology, and in particular to a multi-stage frequency support method, system, equipment and medium for wind-storage combined power plants. Background Technology

[0002] In recent years, wind power, as an important component of renewable energy, has seen continuous growth in installed capacity. To improve grid frequency stability, grid connection guidelines in various countries require wind turbines to have frequency support capabilities. Currently, grid-connected doubly-fed induction generator (DFIG) wind turbines typically participate in grid frequency regulation by adjusting rotor speed through droop control or virtual inertia control to release or absorb kinetic energy.

[0003] However, this technical solution has significant limitations. First, due to differences in geographical location, wind speed, and wake effect, the operating status and frequency regulation capabilities of individual wind turbines within a wind farm vary considerably. If a unified frequency regulation strategy is adopted, weaker wind turbines are prone to premature shutdown due to over-output, affecting the duration of frequency regulation across the entire farm and potentially causing safety issues such as excessive wind turbine speed and torque. Second, with the increasing penetration of new energy sources and the weakening of the power grid, the operational stability of purely grid-connected wind farms under weak grid conditions faces challenges.

[0004] To compensate for the insufficient frequency regulation capability of wind turbines, energy storage systems are often introduced to assist in frequency regulation. However, if energy storage is configured independently or simply operated in parallel with wind power without coordinated optimization, the dynamic characteristics of wind-storage complementarity cannot be fully utilized, resulting in poor frequency regulation economy and suboptimal overall performance. Therefore, how to design a coordinated multi-stage frequency support strategy in wind-storage integrated power grids, based on the real-time frequency regulation capability of wind turbines and the state of charge of energy storage, has become a key technical issue for improving grid frequency stability and operational economy. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-stage frequency support method, system, equipment, and medium for wind-storage integrated power farms. When wind turbines play a primary role in frequency support, energy storage units supplementarily output droop control additional power according to the energy release state of the wind farm group, coordinating frequency support with the wind farm group. When wind turbines enter torque-limited control and the frequency support effect weakens, energy storage is used to compensate for the power deficit caused by the control mode switch. A state variable that can reflect the frequency regulation capability of energy storage is designed, denoted as the energy storage balance factor. Each energy storage unit exchanges its balance factor with two adjacent energy storage units in sequence. Each energy storage unit generates energy storage state power by exchanging its own balance factor with the balance factors of the two adjacent energy storage units through a PI circuit. This ensures that the states of each energy storage unit in the wind-storage integrated power farm are similar during the frequency support process. Combined with the droop control additional power, the energy storage output is adjusted. This avoids excessive output and excessive torque of wind turbines while raising the minimum grid frequency, thereby solving the technical problem of poor overall frequency regulation capability of existing wind farms and the frequent occurrence of excessive wind turbine output.

[0006] To achieve the above objectives, this invention provides a multi-stage frequency support method for wind-storage integrated power plants, wherein the wind-storage integrated power plant includes grid-connected doubly-fed wind turbines and lithium-ion battery energy storage, comprising the following steps: Step S1: Divide the wind turbines and energy storage units in the wind-storage integrated cluster into multiple sites based on their geographical location, wind speed and direction, and the state of charge of the energy storage units. Step S2: Based on the divided site structure, the frequency of the grid-connected bus is detected in real time; when the frequency of the grid-connected bus deviates from the first safe range defined by the first frequency threshold and the second frequency threshold, each wind turbine in the site is triggered to enter the frequency support stage 1. Step S3: When the frequency of the grid-connected bus deviates further from the second safe range defined by the third and fourth frequency thresholds, each energy storage unit is triggered to enter the frequency support phase. ; Step S4: During the execution of steps S2 and S3, the torque of each wind turbine is monitored in real time; when the torque of any wind turbine exceeds a preset torque threshold, the wind turbine is switched to frequency support stage 2, and the energy storage unit enters the frequency support stage. ; Step S5: After the grid frequency reaches its lowest point, start the progressive speed recovery control of the wind turbine and the grouped ramp power recovery control of the energy storage system respectively.

[0007] Preferably, step S2 specifically includes: Step S21: When the grid-connected bus frequency is greater than the first frequency threshold, calculate the balance factor for each wind turbine unit used for downward frequency regulation. : ; Step S22: When the grid-connected bus frequency is less than the second frequency threshold, calculate the balance factor for each wind turbine unit used for upward frequency regulation. : ; in, This indicates that each wind turbine in the wind farm has entered the frequency support phase at time 1. The initial kinetic energy of the rotor, This indicates the wind turbine units during the frequency support phase 1 period. Real-time rotor kinetic energy, Indicates the upper limit of rotor kinetic energy. Indicates the lower limit of rotor kinetic energy; Step S23: Each wind turbine determines the additional power reference value and the state power reference value for frequency support stage 1 based on the real-time frequency deviation and its own calculated balance factor.

[0008] Preferably, step S3 specifically includes: Step S31: Based on the site structure divided in step S1, calculate the energy release factor of each wind turbine in each site, and then calculate the energy release factor of each site and the average energy release factor of the entire wind farm group. ; ; ; in, This represents the energy release factor for each wind turbine. This represents the energy release factor of each station. This represents the average energy release factor of the entire wind farm complex. Indicates the wind farm number. This indicates the total number of wind turbine units within the site. Indicates the total number of wind farms; Step S32: Calculate the energy storage frequency regulation parameters using the Logistic function based on the real-time state of charge of each energy storage unit. ; ; Step S33: Use the average energy release factor of the wind farm cluster as the input to the energy storage system, and obtain the energy storage participation factor: ; in, Indicates the maximum operating limit of energy storage. Indicates the upper limit of normal operation of energy storage. This indicates the minimum operating limit for energy storage. This indicates the lower limit of normal operation for energy storage. Indicates the state of charge of the energy storage. This represents the maximum value of the droop coefficient. Indicates the calculated coefficient. This indicates the value of the initial point of the curve. The base of the natural logarithm; Then, the energy storage frequency support stage The power reference value is : ; in, This indicates the frequency deviation between the grid-connected bus frequency and the reference frequency of 50Hz.

[0009] Preferably, step S4 specifically includes: Step S41: Calculate the energy storage balance factor of each energy storage unit based on its output power, rated capacity, and state of charge. : ; ; in, Indicates number The output power of the energy storage unit, Indicates its rated capacity, Indicates number The state of charge of the energy storage unit, Indicates about The function, and These represent the upper and lower bounds of the state of charge of the energy storage unit, respectively; Step S42: Each energy storage unit in the site exchanges energy storage balance factors with adjacent units, and generates a first-state power reference value through a proportional-integral control loop. : ; in, This represents the proportional gain of the PI controller. This represents the integral coefficient of the PI controller. , These respectively represent the same station number. , The balance factor for energy exchange between energy storage units; Step S43: Select a dominant energy storage unit from each power station, exchange energy storage balance factors among the dominant energy storage units and perform coordinated control to generate a second-state power reference value. : ; in, Indicates the proportional coefficient of the PI controller, This represents the integral coefficient of the PI controller. , These respectively represent the fields within the group numbered as , The balance factor for the exchange between dominant energy storage units; Step S44: For the dominant energy storage unit within the cluster, frequency support stage The power reference value is: ; in, Indicates the number is The power reference value of the dominant energy storage unit; For non-dominant energy storage units within a cluster, frequency support phase The power reference value is: .

[0010] Preferably, step S5 specifically includes: Step S51: After the wind turbine reaches its maximum output power, it enters the speed recovery phase. The output power during the recovery period is as follows: : ; in, This represents any moment during the rotor speed recovery phase of the wind turbine. Indicates MPPT power. Indicates the time when the rotational speed begins to recover. Indicates the preset recovery time. This represents the additional output power at the moment of speed recovery control, and can be set to an appropriate value according to the actual system conditions; Step S52: After the energy storage unit reaches its maximum output power, it maintains this position for a preset time, and then performs ramp power recovery in groups. The recovery slope of each group is proportional to its average state of charge. The output power during the recovery phase is... : ; in, This represents any moment during the energy storage power recovery phase. This indicates the moment when the energy storage capacity begins to recover. Indicates the time when the energy storage power recovery ends. Indicates a fixed slope. Indicates a variable slope. and Proportional This represents the field group communication factor, if the unit is a field group control object. Select 1 if the value is 1, otherwise select 0.

[0011] Preferably, the first frequency threshold is set to 1.001 pu, the second frequency threshold is set to 0.999 pu, the third frequency threshold is set to 1.004 pu, and the fourth frequency threshold is set to 0.996 pu.

[0012] Preferably, the torque threshold is 1.15 pu, when the wind turbine torque... When the torque exceeds the threshold, the wind turbine switches to frequency support stage 2, i.e., torque-limited control, with the output power reference value being [value missing]. ,in, This indicates the rotational speed of the wind turbine.

[0013] This invention also provides a multi-stage frequency support system for wind-storage integrated wind farm clusters, comprising: The site division module is used to divide the wind turbines and energy storage units in the wind-storage integrated cluster into multiple sites based on their geographical location, wind speed and direction, and the state of charge of the energy storage units. The frequency detection and wind turbine control module is used to detect the grid-connected bus frequency in real time based on the station structure output by the station division module; when the grid-connected bus frequency deviates from the first safety range defined by the first frequency threshold and the second frequency threshold, it triggers each wind turbine in the station to enter the frequency support stage 1. The energy storage control module is used to trigger each energy storage unit to enter the frequency support phase when the grid-connected bus frequency deviates further from the second safety range defined by the third and fourth frequency thresholds. ; The torque monitoring and switching module is used to monitor the torque of each wind turbine in real time during the execution of the frequency detection, wind turbine control module, and energy storage control module. When the torque of any wind turbine exceeds a preset torque threshold, the wind turbine is switched to frequency support stage 2, and the energy storage unit enters the frequency support stage. ; The recovery control module is used to initiate the gradual speed recovery control of the wind turbine and the grouped ramp power recovery control of the energy storage system respectively after the grid frequency reaches its lowest point. The balance factor calculation unit is used to calculate the balance factor of each wind turbine when it is up-regulating and down-regulating frequency, the energy storage balance factor of each energy storage unit, the energy release factor of each station, and the average energy release factor of the entire wind farm group. The power reference value generation unit is used to generate additional power reference values ​​and state power reference values ​​for wind turbines and energy storage units at each frequency support stage based on various balance factors, energy storage state of charge and frequency deviation output by the balance factor calculation unit.

[0014] The present invention also provides a computer device, including: a memory and a processor; the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described multi-stage frequency support method for wind-storage combined field clusters.

[0015] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the above-described multi-stage frequency support method for wind-storage combined field clusters.

[0016] Therefore, the present invention employs the above-mentioned multi-stage frequency support method, system, equipment, and medium for wind-storage integrated wind farm clusters, and the beneficial technical effects are as follows: (1) By dividing the frequency support process of wind turbines and energy storage into two stages, the frequency regulation potential of wind power and energy storage is fully utilized. Wind turbines and energy storage systems undertake the main frequency support tasks in different stages, which improves the timing coordination of the overall frequency regulation capability and the reliability of the system.

[0017] (2) Introduce a state variable that reflects the real-time frequency regulation capability of wind turbines and energy storage—the balance factor—and exchange balance factor information among the dominant and non-dominant units through a collaborative mechanism within and between the wind farms. Each unit generates a state power reference value based on its own and its neighboring units' balance factors through a PI control loop, and then dynamically adjusts the frequency regulation output to ensure that the state of each unit in the wind-storage joint farm group tends to be consistent during the frequency support process, thereby improving the overall coordination and stability.

[0018] (3) In order to promote the complementary advantages of wind and energy storage in multi-stage frequency support, the energy storage participation factor is calculated based on the average energy release factor of the wind farm group, and the reference value of the droop control additional power of energy storage is generated accordingly, so as to realize the reasonable matching and coordinated response of wind and energy storage output.

[0019] (4) When the torque of the wind turbine exceeds the limit, its control mode is automatically switched to torque limiting control, and the resulting power deficit is compensated in a timely manner through the energy storage system. This mechanism not only prevents the wind turbine from shutting down due to excessive output, but also effectively raises the minimum point of the grid frequency and enhances the system's ability to recover from frequency disturbances.

[0020] (5) The designed energy storage balance factor takes into account the energy storage output power, rated capacity and state of charge, and can accurately reflect the dynamic changes in its frequency regulation capability. The increase of the balance factor indicates the decrease of the remaining frequency regulation capability of the energy storage, thus providing a quantitative basis for power allocation and supporting more refined coordinated control. Attached Figure Description

[0021] Figure 1 This is a flowchart of the multi-stage frequency support method for wind-storage combined wind farm clusters of the present invention; Figure 2This is a multi-stage frequency support control framework diagram for a wind-storage integrated wind farm cluster, in which... Figure 2 (a) in the diagram represents the control framework of the wind turbine unit. Figure 2 (b) in the diagram represents the energy storage control framework; Figure 3 The results are simulations of the synchronous power grid frequency in Embodiment 1 of the present invention. Figure 4 The above are the simulation results of the energy storage balance factor in Embodiment 1 of the present invention, wherein, Figure 4 (a) in the text indicates that there is a balance factor controlling the process. Figure 4 (b) in the diagram represents control without an equilibrium factor; Figure 5 The above are the simulation results of the active power output of energy storage in Embodiment 1 of the present invention, wherein, Figure 5 (a) in the text indicates that there is a balance factor controlling the process. Figure 5 (b) in the figure represents control without balance factor. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0024] Example 1 like Figures 1-2 A multi-stage frequency support method for wind and energy storage combined wind farm clusters (including grid-connected doubly-fed wind turbines and lithium-ion battery energy storage) includes the following steps: Step S1: Divide the wind turbines and energy storage units within the wind-storage integrated cluster into multiple sites based on their geographical location, wind speed and direction, and the state of charge of the energy storage units.

[0025] Step S11: Construct a single-unit model of a grid-connected doubly-fed wind turbine and lithium-ion battery energy storage. Aggregate wind turbine single-unit models with short geographical intervals and similar wind speeds, and energy storage single-unit models with short geographical intervals and similar states of charge, into a wind-storage joint power station. Aggregate wind-storage joint power stations with different geographical locations, wind speeds, and states of charge into a wind-storage joint power cluster.

[0026] Step S12: Select any wind turbine unit and number it 1. Test the communication time between wind turbine unit 1 and the other wind turbine units. The wind turbine unit with the shortest communication time is numbered 2.

[0027] Step S13: Test the communication time between wind turbine No. 2 and the other unnumbered wind turbines. The wind turbine with the shortest communication time is numbered as wind turbine No. 3, and so on, to complete the numbering of all wind turbines and energy storage in the wind-storage integrated farm group.

[0028] Step S2: Based on the divided wind farm structure, the grid-connected bus frequency is detected in real time; when the grid-connected bus frequency deviates from the first safety range defined by the first frequency threshold and the second frequency threshold, each wind turbine in the wind farm is triggered to enter the frequency support stage 1. In this embodiment, the first frequency threshold is set to 1.001 pu, and the second frequency threshold is set to 0.999 pu.

[0029] Step S21: When the grid-connected bus frequency is greater than the first frequency threshold, calculate the balance factor for each wind turbine unit used for downward frequency regulation. : .

[0030] Step S22: When the grid-connected bus frequency is less than the second frequency threshold, calculate the balance factor for each wind turbine unit used for upward frequency regulation. : ; in, This indicates that each wind turbine in the wind farm has entered the frequency support phase at time 1. The initial kinetic energy of the rotor, This indicates the wind turbine units during the frequency support phase 1 period. Real-time rotor kinetic energy, Indicates the upper limit of rotor kinetic energy. This indicates the lower limit of rotor kinetic energy.

[0031] Step S23, Wind turbine unit using formula Generate additional power Adaptive droop and inertia control are implemented, among which Indicates wind turbine The droop coefficient, Indicates wind turbine The coefficient of inertia, Indicates the frequency of the grid-connected bus. This represents any moment in the frequency support phase 1 of the wind turbine.

[0032] Step S24: The wind turbine generates its own balance factor and the balance factors of the two adjacent wind turbines through a PI circuit to generate state power. : ; in, Indicates number Proportional coefficient of PI controller for wind turbine unit Indicates number Integral coefficient of wind turbine PI controller , Representing the number respectively , Balance factor exchanged between wind turbine units.

[0033] Step S25: The total power reference value of the wind turbine is the sum of the additional power reference value and the state power reference value. : .

[0034] Step S3: When the frequency of the grid-connected bus deviates further from the second safe range defined by the third and fourth frequency thresholds, each energy storage unit is triggered to enter the frequency support phase. In this embodiment, the third frequency threshold is set to 1.004 pu, and the fourth frequency threshold is set to 0.996 pu.

[0035] Step S31: Based on the site structure divided in step S1, calculate the energy release factor of each wind turbine in each site, and then calculate the energy release factor of each site and the average energy release factor of the entire wind farm group. ; ; ; in, This represents the energy release factor for each wind turbine. This represents the energy release factor of each station. This represents the average energy release factor of the entire wind farm complex. Indicates the wind farm number. This indicates the total number of wind turbine units within the site. This indicates the total number of wind farms.

[0036] Step S32: Calculate the energy storage frequency regulation parameters using the logistic function based on the real-time state of charge of each energy storage unit. ; .

[0037] Step S33: Use the average energy release factor of the wind farm cluster as the input to the energy storage system, and obtain the energy storage participation factor: ; in, Indicates the maximum operating limit of energy storage. Indicates the upper limit of normal operation of energy storage. This indicates the minimum operating limit for energy storage. This indicates the lower limit of normal operation for energy storage. Indicates the state of charge of the energy storage. This represents the maximum value of the droop coefficient. Indicates the calculated coefficient. This indicates the value of the initial point of the curve. The base of the natural logarithm; and The value of affects the shape of the curve. Affecting the rate of change of the curve The size of the interval that affects the growth process of the curve.

[0038] Then, the energy storage frequency support stage The power reference value is : ; in, This indicates the frequency deviation between the grid-connected bus frequency and the reference frequency of 50Hz.

[0039] Step S4: During the execution of steps S2 and S3, the torque of each wind turbine is monitored in real time; when the torque of any wind turbine exceeds a preset torque threshold, the wind turbine is switched to frequency support stage 2, and the energy storage unit enters the frequency support stage. .

[0040] The torque threshold is 1.15 pu. When the wind turbine torque exceeds the torque threshold, the wind turbine switches to frequency support stage 2, i.e., torque-limited control, with the output power reference value being [value missing]. ,in This indicates the rotational speed of the wind turbine.

[0041] Step S41: Calculate the energy storage balance factor of each energy storage unit based on its output power, rated capacity, and state of charge. : ; ; in, Indicates number The output power of the energy storage unit, Indicates its rated capacity, Indicates number The state of charge of the energy storage unit, Indicates about The function, and These represent the upper and lower bounds of the state of charge of the energy storage unit, respectively, and are set to 0.9 and 0.1.

[0042] Step S42: Each energy storage unit in the site exchanges energy storage balance factors with adjacent units, and generates a first-state power reference value through a proportional-integral control loop. : ; in, This represents the proportional gain of the PI controller. This represents the integral coefficient of the PI controller. , These respectively represent the same station number. , The balance factor for the exchange between energy storage units.

[0043] Step S43: Select a dominant energy storage unit from each power station, exchange energy storage balance factors among the dominant energy storage units and perform coordinated control to generate a second-state power reference value. : ; in, Indicates the proportional coefficient of the PI controller, This represents the integral coefficient of the PI controller. , These respectively represent the fields within the group numbered as , The dominant balance factor for energy storage unit exchange.

[0044] Step S44: For the dominant energy storage unit within the cluster, frequency support stage The power reference value is: ; in, Indicates the number is The power reference value of the dominant energy storage unit; For non-dominant energy storage units within a cluster, frequency support phase The power reference value is: .

[0045] Step S5: After the grid frequency reaches its lowest point, start the progressive speed recovery control of the wind turbine and the grouped ramp power recovery control of the energy storage system respectively.

[0046] Step S51: After the wind turbine reaches its maximum output power, it enters the speed recovery phase. The output power during the recovery period is as follows: : ; in, This represents any moment during the rotor speed recovery phase of the wind turbine. Indicates MPPT power. Indicates the time when the rotational speed begins to recover. Indicates the preset recovery time. This represents the additional output power at the moment of speed recovery control, and can be set to an appropriate value according to the actual system conditions.

[0047] Step S52: After the energy storage unit reaches its maximum output power, it maintains this position for a preset time, and then performs ramp power recovery in groups. The recovery slope of each group is proportional to its average state of charge. The output power during the recovery phase is... : ; in, This represents any moment during the energy storage power recovery phase. This indicates the moment when the energy storage capacity begins to recover. Indicates the time when the energy storage power recovery ends. Indicates a fixed slope. Indicates a variable slope. and Proportional This represents the field group communication factor, if the unit is a field group control object. Select 1 if the value is 1, otherwise select 0.

[0048] The invention will be further illustrated below with specific examples.

[0049] To verify the effectiveness of the method provided by this invention, a wind-storage combined power station consisting of 12 grid-connected wind turbines and 6 energy storage units with different states of charge was built on the Matlab / Simulink platform. The initial speeds of wind turbines 1 to 12 were 1.1175 pu, 1.1175 pu, 0.9120 pu, 0.9120 pu, 0.8772 pu, 0.8772 pu, 0.8631 pu, 0.8631 pu, 0.8561 pu, 0.8561 pu, 0.85 pu, and 0.85 pu, respectively. Each wind turbine has a rated output power of 100 MW and a load of 550 MW. At 5 seconds, the load suddenly increases by 200 MW. The grid frequency is as follows: Figure 3 As shown. TLDC+TLC, MSSC, and WECC represent multi-stage frequency support control for wind turbines without ESS, multi-stage frequency support control for wind-storage integrated farms without considering state power, and multi-stage frequency support control for wind-storage integrated farms, respectively. Comparing the three control modes TLDC+TLC, MSSC, and WECC, it can be seen that after adopting the multi-stage frequency support method for wind-storage integrated farms, the minimum grid frequency increases, such as... Figure 3 As shown; Figure 4 As shown, under MSCC control, the balance factors of the six energy storage units are dispersed, and the energy storage output power is not concentrated enough. Figure 5 As shown, under WECC control, the balance factors of the six energy storage units coincide, and the energy storage output power is concentrated.

[0050] Example 2 The multi-stage frequency support system for the wind-storage integrated wind farm cluster includes: The site division module is used to divide the wind turbines and energy storage units in the wind-storage integrated cluster into multiple sites based on their geographical location, wind speed and direction, and the state of charge of the energy storage units. The frequency detection and wind turbine control module is used to detect the grid-connected bus frequency in real time based on the station structure output by the station division module; when the grid-connected bus frequency deviates from the first safety range defined by the first frequency threshold and the second frequency threshold, it triggers each wind turbine in the station to enter the frequency support stage 1. The energy storage control module is used to trigger each energy storage unit to enter the frequency support phase when the grid-connected bus frequency deviates further from the second safety range defined by the third and fourth frequency thresholds. ; The torque monitoring and switching module is used to monitor the torque of each wind turbine in real time during the execution of the frequency detection, wind turbine control module, and energy storage control module. When the torque of any wind turbine exceeds a preset torque threshold, the wind turbine is switched to frequency support stage 2, and the energy storage unit enters the frequency support stage. ; The recovery control module is used to initiate the gradual speed recovery control of the wind turbine and the grouped ramp power recovery control of the energy storage system respectively after the grid frequency reaches its lowest point. The balance factor calculation unit is used to calculate the balance factor of each wind turbine when it is up-regulating and down-regulating frequency, the energy storage balance factor of each energy storage unit, the energy release factor of each station, and the average energy release factor of the entire wind farm group. The power reference value generation unit is used to generate additional power reference values ​​and state power reference values ​​for wind turbines and energy storage units at each frequency support stage based on various balance factors, energy storage state of charge and frequency deviation output by the balance factor calculation unit.

[0051] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0052] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-including system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0053] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0054] It is worth noting that all contents not described in detail in this invention are existing technologies and are well known to those skilled in the art.

[0055] Therefore, the present invention adopts the above-mentioned multi-stage frequency support method, system, equipment and medium for wind-storage combined systems, which can significantly improve the coordinated frequency support capability of wind-storage combined systems and effectively improve the dynamic characteristics of grid frequency while ensuring the safe operation of wind turbine units.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A multi-stage frequency support method for wind-storage integrated power plant clusters, wherein the wind-storage integrated power plant cluster includes grid-connected doubly-fed wind turbines and lithium-ion battery energy storage, characterized in that, Includes the following steps: Step S1: Divide the wind turbines and energy storage units in the wind-storage integrated cluster into multiple sites based on their geographical location, wind speed and direction, and the state of charge of the energy storage units. Step S2: Based on the divided site structure, the frequency of the grid-connected bus is detected in real time; when the frequency of the grid-connected bus deviates from the first safe range defined by the first frequency threshold and the second frequency threshold, each wind turbine in the site is triggered to enter the frequency support stage 1. Step S3: When the frequency of the grid-connected bus deviates further from the second safe range defined by the third and fourth frequency thresholds, each energy storage unit is triggered to enter the frequency support phase. ; Step S4: During the execution of steps S2 and S3, the torque of each wind turbine is monitored in real time; when the torque of any wind turbine exceeds a preset torque threshold, the wind turbine is switched to frequency support stage 2, and the energy storage unit enters the frequency support stage. ; Step S5: After the grid frequency reaches its lowest point, start the progressive speed recovery control of the wind turbine and the grouped ramp power recovery control of the energy storage system respectively.

2. The multi-stage frequency support method for wind-storage integrated wind farm clusters according to claim 1, characterized in that, Step S2 specifically includes: Step S21: When the grid-connected bus frequency is greater than the first frequency threshold, calculate the balance factor for each wind turbine unit used for downward frequency regulation. : ； Step S22: When the grid-connected bus frequency is less than the second frequency threshold, calculate the balance factor for each wind turbine unit used for upward frequency regulation. : ； in, This indicates that each wind turbine in the wind farm has entered the frequency support phase at time 1. The initial kinetic energy of the rotor, This indicates the wind turbine units during the frequency support phase 1 period. Real-time rotor kinetic energy, Indicates the upper limit of rotor kinetic energy. Indicates the lower limit of rotor kinetic energy; Step S23: Each wind turbine determines the additional power reference value and the state power reference value for frequency support stage 1 based on the real-time frequency deviation and its own calculated balance factor.

3. The multi-stage frequency support method for wind-storage integrated wind farm clusters according to claim 2, characterized in that, Step S3 specifically includes: Step S31: Based on the site structure divided in step S1, calculate the energy release factor of each wind turbine in each site, and then calculate the energy release factor of each site and the average energy release factor of the entire wind farm group. ； ； ； in, This represents the energy release factor for each wind turbine. This represents the energy release factor of each station. This represents the average energy release factor of the entire wind farm complex. Indicates the wind farm number. This indicates the total number of wind turbine units within the site. Indicates the total number of wind farms; Step S32: Calculate the energy storage frequency regulation parameters using the Logistic function based on the real-time state of charge of each energy storage unit. ; ； Step S33: Use the average energy release factor of the wind farm cluster as the input to the energy storage system, and obtain the energy storage participation factor: ； in, This indicates the maximum operating limit of energy storage. Indicates the upper limit of normal operation of energy storage. This indicates the minimum operating limit for energy storage. This indicates the lower limit of normal operation for energy storage. Indicates the state of charge of the energy storage. This represents the maximum value of the droop coefficient. Indicates the calculated coefficients. This indicates the value of the initial point of the curve. The base of the natural logarithm; Then, the energy storage frequency support stage The power reference value is : ； in, This indicates the frequency deviation between the grid-connected bus frequency and the reference frequency of 50Hz.

4. The multi-stage frequency support method for wind-storage integrated wind farm clusters according to claim 3, characterized in that, Step S4 specifically includes: Step S41: Calculate the energy storage balance factor of each energy storage unit based on its output power, rated capacity, and state of charge. : ； ； in, Indicates number The output power of the energy storage unit, Indicates its rated capacity, Indicates number The state of charge of the energy storage unit, Indicates about The function, and These represent the upper and lower bounds of the state of charge of the energy storage unit, respectively; Step S42: Each energy storage unit in the site exchanges energy storage balance factors with adjacent units, and generates a first-state power reference value through a proportional-integral control loop. : ； in, This represents the proportional gain of the PI controller. This represents the integral coefficient of the PI controller. , These respectively represent the same station number. , The balance factor for energy exchange between energy storage units; Step S43: Select a dominant energy storage unit from each power station, exchange energy storage balance factors among the dominant energy storage units and perform coordinated control to generate a second-state power reference value. : ； in, Indicates the proportional coefficient of the PI controller, This represents the integral coefficient of the PI controller. , These respectively represent the fields within the group numbered as , The balance factor for the exchange between dominant energy storage units; Step S44: For the dominant energy storage unit within the cluster, frequency support stage The power reference value is: ； in, Indicates the number is The power reference value of the dominant energy storage unit; For non-dominant energy storage units within a cluster, frequency support phase The power reference value is: 。 5. The multi-stage frequency support method for wind-storage integrated wind farm clusters according to claim 4, characterized in that, Step S5 specifically includes: Step S51: After the wind turbine reaches its maximum output power, it enters the speed recovery phase. The output power during the recovery period is as follows: : ； in, This represents any moment during the rotor speed recovery phase of the wind turbine. Indicates MPPT power. Indicates the time when the rotational speed begins to recover. Indicates the preset recovery time. This indicates the additional output power at the moment of speed recovery control; Step S52: After the energy storage unit reaches its maximum output power, it maintains this position for a preset time, and then performs ramp power recovery in groups. The recovery slope of each group is proportional to its average state of charge. The output power during the recovery phase is... : ； in, This represents any moment during the energy storage power recovery phase. This indicates the moment when the energy storage capacity begins to recover. Indicates the time when the energy storage power recovery ends. Indicates a fixed slope. Indicates a variable slope. and Proportional This represents the field group communication factor, if the unit is a field group control object. Select 1 if the value is 1, otherwise select 0.

6. The multi-stage frequency support method for wind-storage integrated wind farm clusters according to claim 1, characterized in that, The first frequency threshold is set to 1.001 pu, the second frequency threshold is set to 0.999 pu, the third frequency threshold is set to 1.004 pu, and the fourth frequency threshold is set to 0.996 pu.

7. The multi-stage frequency support method for wind-storage integrated wind farm clusters according to claim 1, characterized in that, The torque threshold is 1.15 pu, when the wind turbine torque When the torque exceeds the threshold, the wind turbine switches to frequency support stage 2, i.e., torque-limited control, with the output power reference value being [value missing]. ,in, This indicates the rotational speed of the wind turbine.

8. A multi-stage frequency support system for a wind-storage integrated wind farm cluster, characterized in that, include: The site division module is used to divide the wind turbines and energy storage units in the wind-storage integrated cluster into multiple sites based on their geographical location, wind speed and direction, and the state of charge of the energy storage units. The frequency detection and wind turbine control module is used to detect the grid-connected bus frequency in real time based on the station structure output by the station division module; when the grid-connected bus frequency deviates from the first safety range defined by the first frequency threshold and the second frequency threshold, it triggers each wind turbine in the station to enter the frequency support stage 1. The energy storage control module is used to trigger each energy storage unit to enter the frequency support phase when the grid-connected bus frequency deviates further from the second safety range defined by the third and fourth frequency thresholds. ; The torque monitoring and switching module is used to monitor the torque of each wind turbine in real time during the execution of the frequency detection, wind turbine control module, and energy storage control module. When the torque of any wind turbine exceeds a preset torque threshold, the wind turbine is switched to frequency support stage 2, and the energy storage unit enters the frequency support stage. ; The recovery control module is used to initiate the gradual speed recovery control of the wind turbine and the grouped ramp power recovery control of the energy storage system respectively after the grid frequency reaches its lowest point. The balance factor calculation unit is used to calculate the balance factor of each wind turbine when it is up-regulating and down-regulating frequency, the energy storage balance factor of each energy storage unit, the energy release factor of each station, and the average energy release factor of the entire wind farm group. The power reference value generation unit is used to generate additional power reference values ​​and state power reference values ​​for wind turbines and energy storage units at each frequency support stage based on various balance factors, energy storage state of charge and frequency deviation output by the balance factor calculation unit.

9. A computer device, comprising: Memory and processor; The memory stores a computer program, characterized in that when the processor executes the computer program, it implements the steps of the multi-stage frequency support method for the wind-storage combined field group as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the multi-stage frequency support method for the wind-storage combined field group as described in any one of claims 1-7.

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