Wind power short-time frequency support method comprehensively applying independent and schedulable resources

Abstract

The invention discloses a wind power short-time frequency support method comprehensively using independent and schedulable resources. Limited by wide-area distribution of a power grid and cost and reliability of real-time communication, a current wind power short-time frequency support method is difficult to realize by acquiring rotating speed information of all fans through a central controller and performing centralized scheduling. Therefore, a wind power short-time frequency support unified control form based on a frequency-active power transfer function is deduced by constructing a power grid frequency boundary time domain track and fitting the power grid frequency boundary time domain track into a unit step response of a first-order system; on the basis of the form, independent wind turbine generator spontaneous short-time frequency support control is designed, and control parameters are set according to the magnitude of kinetic energy of a rotor of the independent wind turbine generator; short-time frequency support control for coordinating an independent wind turbine generator with a dispatchable wind turbine generator is designed, and unit control parameters are optimized in a centralized mode. Short-time frequency support is provided for the power grid by comprehensively applying independent and dispatchable wind turbine generators, and finally the frequency effect of the power grid is improved as much as possible under the constraint that wide-area real-time communication is difficult to realize through engineering.

Description

Technical Field

[0001] This invention belongs to the field of primary frequency regulation control technology for grid-connected wind turbines, and in particular, it is a method for short-time frequency support of wind power that comprehensively utilizes independent and dispatchable resources. Background Technology

[0002] With the high proportion of renewable energy generation integrated into the grid, grid frequency regulation and stability face severe challenges, urgently requiring wind turbines with active power regulation capabilities to actively participate in primary frequency regulation. Generally, wind turbines can reserve capacity by reducing load and increase output power during frequency events; alternatively, they can normally use Maximum Power Point Tracking (MPPT), and when a power deficit in the grid causes a frequency drop, they can participate in primary frequency regulation by releasing the kinetic energy stored in their large-inertia rotors to maintain the grid's active power balance. Considering the unpredictable nature of frequency events, the latter approach is more conducive to balancing the power generation efficiency of frequency-regulated wind turbines.

[0003] In existing wind turbine primary frequency regulation control technologies based on wind turbine kinetic energy release, how to release limited wind turbine kinetic energy to raise the minimum grid frequency—a key time-domain indicator—is currently a hot topic of discussion. Considering the flexible power adjustment characteristics of wind power brought about by the converter, some scholars have recognized that wind power primary frequency regulation control does not necessarily need to be confined to the mindset of analog synchronous turbines. Therefore, from the perspective of suppressing grid power deviation after frequency events, current research proposes two types of short-time frequency support methods for wind turbines: one utilizing the time-active power function based on the flexible active power adjustment characteristics, and the other based on the frequency-active power function based on the unified frequency characteristics.

[0004] However, the aforementioned technical research requires a central controller to uniformly optimize the time-active power and frequency-active power functions of all frequency-regulated wind turbines based on their rotor speeds at the time of the frequency event. Since frequency events occur randomly, these two methods essentially require the central controller to acquire the rotational speed information of the frequency-regulated wind turbines in real time and centrally schedule them. Limited by the wide distribution of the power grid and the cost and reliability of real-time communication, making all wind turbines eligible for scheduling as frequency-regulated wind turbines is currently difficult to achieve in engineering. Summary of the Invention

[0005] The purpose of this invention is to address the difficulty in engineering implementation of existing wind power short-time frequency support methods that rely on a central controller to obtain wind turbine speed information and perform centralized scheduling. This invention provides a wind power short-time frequency support method that comprehensively utilizes both independent and dispatchable resources. First, by constructing the time-domain trajectory of the grid frequency boundary and fitting it as the unit step response of a first-order system, a unified control form for wind power short-time frequency support based on the frequency-active power transfer function is derived. Based on this form, a spontaneous short-time frequency support control for independent wind turbines is designed, with control parameters set according to their own rotor kinetic energy. A short-time frequency support control for dispatchable wind turbines coordinating with independent wind turbines is also designed, with centralized optimization of turbine control parameters. By comprehensively utilizing both independent and dispatchable wind turbines to provide short-time frequency support to the grid, the grid frequency performance is improved as much as possible under the constraint of the difficulty in engineering implementation of wide-area real-time communication.

[0006] The technical solution to achieve the purpose of this invention is: a method for short-time frequency support of wind power that comprehensively utilizes independent and dispatchable resources, the method comprising the following steps:

[0007] Step 1, Construct the time-domain trajectory of the power grid frequency boundary: at the initial stage of a frequency event, along the lower limit of the power grid frequency change rate. Descending, at time Lowest value at a certain frequency of trailing edge Remain unchanged;

[0008] Step 2: Fit the time-domain trajectory of the power grid frequency boundary in Step 1 to the unit step response of a first-order system;

[0009] Step 3: Combining the unit step response from Step 2 with the actual power grid frequency response model, construct a unified control form for wind power short-time frequency support based on the frequency-active power transfer function.

[0010] Step 4: Based on the unified control form of wind power short-time frequency support in Step 3, design an independent wind turbine spontaneous short-time frequency support control based on the frequency-active power transfer function.

[0011] Step 5: Set the control parameters in Step 4 based on the kinetic energy that the independent wind turbine can release.

[0012] Step 6: Combining Step 3 and Step 4, design a short-time frequency support control for dispatchable wind turbine units based on the frequency-active power transfer function.

[0013] Step 7, with The highest target is to construct a parameter optimization model, and to focus on optimizing the control parameters of each schedulable unit in step 6.

[0014] Step 8: Determine the operational status recovery mechanism for the end of frequency support for each wind turbine, and realize the short-term frequency support for wind power by comprehensively utilizing independent and dispatchable resources.

[0015] Furthermore, the time-domain trajectory of the power grid frequency boundary in step 1 Represented as:

[0016]

[0017] In the formula, .

[0018] Furthermore, in step 2, the time-domain trajectory of the power grid frequency boundary from step 1 is fitted to the unit step response of a first-order system, with the time-domain and frequency-domain expressions being respectively... , :

[0019] ;

[0020] In the formula, , , .

[0021] Furthermore, in step 3, combining the unit step response from step 2 and the actual power grid frequency response model, a unified control form for short-time frequency support of wind power based on the frequency-active power transfer function is constructed. The specific process includes:

[0022] Power Deficit Due to Grid Disturbance The time-domain and frequency-domain expressions are as follows:

[0023] ;

[0024] In the formula, , They are respectively The time domain and frequency domain, For frequency domain variables;

[0025] Define the system transfer function as follows, and make the frequency response of the power grid achieve a unit step response:

[0026] ;

[0027] According to the actual power grid frequency response model, its system transfer function is:

[0028] ;

[0029] In the formula, It is the equivalent inertial time constant of the power grid. It is the equivalent damping coefficient of the power grid. It is the transfer function for the frequency regulation control of the synchronous generator unit. Let be the frequency regulation control transfer function of the wind turbine j-type generator, where m and n represent the number of synchronous generators and wind turbines in the power grid, respectively. By making the formulas for the transfer functions of the two systems equal, we obtain the unified control form for short-time frequency support of wind power based on the frequency-active power transfer function:

[0030] .

[0031] Furthermore, the frequency-active power transfer function of the independent wind turbine's spontaneous short-time frequency support control in step 4 is: :

[0032] ;

[0033] In the formula, the subscript k represents the k-th independent wind turbine unit. o represents the total number of independent wind turbine units; This is the lowest set frequency value for all independent wind turbine units. It is the support coefficient of wind turbine k and These are all parameters that need to be set for independent wind turbine units.

[0034] Furthermore, in step 5, the control parameters from step 4 are set based on the kinetic energy that the independent wind turbine itself can release, specifically including:

[0035] The limits for power grid frequency deviation are set in accordance with national standards.

[0036] Based on the releaseable kinetic energy of the independent wind turbine itself;

[0037] The time-domain curve of the change in output power of the independent wind turbine k is obtained by combining the unit step response from step 2. :

[0038] ;

[0039] In the formula, Indicates the inverse Laplace transform;

[0040] Combining the rotor motion equations and the kinetic energy that the wind turbine itself can release, the following solution is obtained regarding... The nonlinear equation system:

[0041] ;

[0042] In the formula, This is the lower limit of the k-speed for independent wind turbine units. This refers to the moment when the speed k of an independent wind turbine reaches its lower limit. It is the change in aerodynamic power of the independent wind turbine unit k. , These represent the changes in aerodynamic power and electromagnetic power when the wind turbine's speed k reaches its lower limit, respectively. Calculated directly based on the lower limit of the rotational speed;

[0043] when When, wind turbine k does not participate in frequency regulation and there is no rotor kinetic energy release; when At that time, wind turbine k is solely responsible for short-term frequency support. However, in the actual scenario of large-scale wind power grid connection, wind turbine k will obviously become unstable and shut down due to excessive kinetic energy release; therefore, there is always a possibility... The above nonlinear equations can be solved using the bisection method.

[0044] Furthermore, the frequency-active power transfer function for the short-time frequency support control of the schedulable wind turbine in step 6 is:

[0045] ;

[0046] In the formula, the subscript l represents the l-th dispatched wind turbine unit. , It is the overall short-time frequency support transfer function of the dispatched wind turbine units, where p is the total number of dispatched wind turbine units; It is the minimum frequency setting value for scheduling wind turbine units. It is the support coefficient of the wind turbine unit l and These are all parameters that need to be optimized for scheduling wind turbine units; It is the sum of the support coefficients of independent wind turbine units, that is .

[0047] Furthermore, step 7 involves constructing a parameter optimization model, specifically including:

[0048] Based on the frequency-active power transfer function in step 6, the frequency support of dispatched wind turbines is complementary to that of independent wind turbines, ensuring that the grid frequency trajectory remains a unit step response of a first-order system. At this point, the time-domain curve of the output power of dispatched wind turbine l is... :

[0049] ;

[0050] By superimposing the frequency-active power transfer function from step 4 and the frequency-active power transfer function from step 6, a unified control method for wind power short-time frequency support is achieved, resulting in wind power frequency support. ;

[0051] Build with The parameter optimization model with the objective function as the highest priority and the wind turbine speed stability as the constraint condition is:

[0052] ;

[0053] In the formula, This is the lower limit of the wind turbine's rotational speed, determined by the operating range of the wind turbine's generator speed. It is the change in aerodynamic power of the wind turbine unit l. It is the change in electromagnetic power of the wind turbine unit l; It is the moment of inertia of the wind turbine unit l. It is the rotor speed of wind turbine unit l. It is the rotational speed acceleration of the wind turbine unit l.

[0054] Furthermore, in the parameter optimization model Can be replaced with ,in This is the lowest speed point of wind turbine unit l, i.e. .

[0055] Furthermore, the operational status recovery mechanism for each wind turbine unit after the frequency support ends in step 8 is as follows:

[0056] ;

[0057] In the formula, The actual output electromagnetic power of the wind turbine j The power command for the maximum power point tracking control of the wind turbine; This serves as the power judgment threshold; specifically, as the frequency regulation power of synchronous turbines gradually increases, they gradually assume the task of balancing active power in the power grid, while the output electromagnetic power of each wind turbine gradually decreases; when a wind turbine satisfies the above formula, that wind turbine switches to... Power command, wind turbine speed returns to initial state, grid frequency gradually rises and returns to steady state frequency value.

[0058] Compared with the prior art, the significant advantages of this invention are:

[0059] (1) Construct the grid frequency boundary trajectory to derive the unified control form of wind power short-time frequency support based on the frequency-active power transfer function. By complementing the frequency regulation characteristics of wind turbine units and synchronous units, the key indicators of grid frequency can be improved efficiently.

[0060] (2) By comprehensively utilizing independent and dispatchable wind power frequency regulation resources to provide frequency support for the power grid, the wind turbine speed information is obtained through the central controller and centralized scheduling is avoided. Under the constraint that wide-area real-time communication is difficult to implement in engineering, the frequency effect of the power grid is improved as much as possible.

[0061] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0062] Figure 1 This is a flowchart of a wind power short-time frequency support method that integrates independent and schedulable resources in one embodiment.

[0063] Figure 2 The diagram shows the power grid frequency boundary trajectory and fitted frequency trajectory designed in one embodiment.

[0064] Figure 3 This is a block diagram illustrating the implementation of a wind power short-time frequency support method designed in one embodiment.

[0065] Figure 4 This is a topology diagram of an IEEE 39-node system containing 5 equivalent wind farms in one embodiment.

[0066] Figure 5 This is a graph comparing the grid frequency under adaptive droop control in one embodiment and the method proposed in this invention.

[0067] Figure 6 This is a comparison curve of wind power output and rotor speed under adaptive droop control and the method proposed in this invention in one embodiment, wherein... Figure 6 In the figure, (a) shows the output power curves of each wind farm under adaptive droop control. Figure 6 (b) shows the rotor speed curves for each wind farm under adaptive droop control. Figure 6 (c) in the figure represents the output power curves of various wind farms under the method proposed in this invention. Figure 6 In the figure, (d) represents the wind turbine rotation speed curves of various wind farms under the method proposed in this invention. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0069] It should be noted that if the embodiments of the present invention involve descriptions such as "first" and "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0070] In one embodiment, combined Figure 1 This paper provides a method for short-time frequency support of wind power that comprehensively utilizes independent and schedulable resources, including the following steps:

[0071] Step 1, Construct the time-domain trajectory of the power grid frequency boundary: at the initial stage of a frequency event, along the lower limit of the power grid frequency change rate. Descending, at time Lowest value at a certain frequency of trailing edge Remain unchanged (e.g.) Figure 2 (as shown)

[0072] Step 2: Fit the time-domain trajectory of the power grid frequency boundary in Step 1 to the unit step response of a first-order system;

[0073] Step 3: Combining the unit step response from Step 2 with the actual power grid frequency response model, construct a unified control form for wind power short-time frequency support based on the frequency-active power transfer function.

[0074] Step 4: Based on the unified control form of wind power short-time frequency support in Step 3, design an independent wind turbine spontaneous short-time frequency support control based on the frequency-active power transfer function.

[0075] Step 5: Set the control parameters in Step 4 based on the kinetic energy that the independent wind turbine can release.

[0076] Step 6: Combining Step 3 and Step 4, design a short-time frequency support control for dispatchable wind turbine units based on the frequency-active power transfer function.

[0077] Step 7, with The highest target is to construct a parameter optimization model, and to focus on optimizing the control parameters of each schedulable unit in step 6.

[0078] Step 8: Determine the operational status recovery mechanism for the end of frequency support for each wind turbine, and realize the short-term frequency support for wind power by comprehensively utilizing independent and dispatchable resources.

[0079] Furthermore, in one embodiment, the time-domain trajectory of the power grid frequency boundary in step 1 Represented as:

[0080]

[0081] In the formula, .

[0082] Furthermore, in one embodiment, in step 2, the time-domain trajectory of the power grid frequency boundary in step 1 is fitted to the unit step response of a first-order system, with the time-domain and frequency-domain expressions being respectively... , :

[0083] ;

[0084] In the formula, , , .

[0085] Furthermore, in one embodiment, step 3 combines the unit step response from step 2 with the actual grid frequency response model to construct a unified control form for wind power short-time frequency support based on the frequency-active power transfer function. The specific process includes:

[0086] Power Deficit Due to Grid Disturbance The time-domain and frequency-domain expressions are as follows:

[0087] ;

[0088] In the formula, , They are respectively The time domain and frequency domain, For frequency domain variables;

[0089] Define the system transfer function as follows, so that the power grid achieves the frequency response of the unit step response formula:

[0090] ;

[0091] According to the actual power grid frequency response model, its system transfer function is:

[0092] ;

[0093] In the formula, It is the equivalent inertial time constant of the power grid. It is the equivalent damping coefficient of the power grid. It is the transfer function for the frequency regulation control of the synchronous generator unit. Let be the frequency regulation control transfer function of the wind turbine j-type generator, where m and n represent the number of synchronous generators and wind turbines in the power grid, respectively. By making the formulas for the transfer functions of the two systems equal, we obtain the unified control form for short-time frequency support of wind power based on the frequency-active power transfer function:

[0094] .

[0095] Furthermore, in one embodiment, the frequency-active power transfer function of the independent wind turbine's spontaneous short-time frequency support control in step 4 is: :

[0096] ;

[0097] In the formula, the subscript k represents the k-th independent wind turbine unit. o represents the total number of independent wind turbine units; This is the lowest set frequency value for all independent wind turbine units. It is the support coefficient of wind turbine k and These are all parameters that need to be set for independent wind turbine units.

[0098] Furthermore, in one embodiment, step 5 sets the control parameters from step 4 based on the releaseable kinetic energy of the independent wind turbine itself, specifically including:

[0099] Independent wind turbines are designed to ensure the safe and stable operation of the power grid frequency. The limits for power grid frequency deviation are set in accordance with national standards. Based on the releaseable kinetic energy of the independent wind turbine itself;

[0100] The time-domain curve of the change in output power of the independent wind turbine k is obtained by combining the unit step response from step 2. :

[0101] ;

[0102] In the formula, Indicates the inverse Laplace transform;

[0103] Combining the rotor motion equations and the kinetic energy that the wind turbine itself can release, the following solution is obtained regarding... The nonlinear equation system:

[0104] ;

[0105] In the formula, This is the lower limit of the k-speed for independent wind turbine units. This refers to the moment when the speed k of an independent wind turbine reaches its lower limit. It is the change in aerodynamic power of the independent wind turbine unit k. , These represent the changes in aerodynamic power and electromagnetic power when the wind turbine's speed k reaches its lower limit, respectively. Calculated directly based on the lower limit of the rotational speed;

[0106] when When, wind turbine k does not participate in frequency regulation and there is no rotor kinetic energy release; when At that time, wind turbine k is solely responsible for short-term frequency support. However, in the actual scenario of large-scale wind power grid connection, wind turbine k will obviously become unstable and shut down due to excessive kinetic energy release; therefore, there is always a possibility... The above nonlinear equations can be solved using the bisection method.

[0107] Furthermore, in one embodiment, the frequency-active power transfer function of the schedulable wind turbine short-time frequency support control in step 6 is:

[0108] ;

[0109] In the formula, the subscript l represents the l-th dispatched wind turbine unit. , It is the overall short-time frequency support transfer function of the dispatched wind turbine units, where p is the total number of dispatched wind turbine units; It is the minimum frequency setting value for scheduling wind turbine units. It is the support coefficient of the wind turbine unit l and These are all parameters that need to be optimized for scheduling wind turbine units; It is the sum of the support coefficients of independent wind turbine units, that is .

[0110] Furthermore, in one embodiment, step 7, constructing the parameter optimization model, specifically includes:

[0111] Based on the frequency-active power transfer function in step 6, the frequency support of dispatched wind turbines is complementary to that of independent wind turbines, ensuring that the grid frequency trajectory remains a unit step response of a first-order system. At this point, the time-domain curve of the output power of dispatched wind turbine l is... :

[0112] ;

[0113] By superimposing the frequency-active power transfer function from step 4 and the frequency-active power transfer function from step 6, a unified control method for wind power short-time frequency support is achieved, resulting in wind power frequency support. ;

[0114] Build with The parameter optimization model with the objective function as the highest priority and the wind turbine speed stability as the constraint condition is:

[0115] ;

[0116] In the formula, This is the lower limit of the wind turbine's rotational speed, determined by the operating range of the wind turbine's generator speed. It is the change in aerodynamic power of the wind turbine unit l. It is the change in electromagnetic power of the wind turbine unit l; It is the moment of inertia of the wind turbine unit l. It is the rotor speed of wind turbine unit l. It is the rotor speed acceleration of wind turbine unit l. This optimization model can be solved using optimization algorithms such as gradient descent.

[0117] Preferably, in the parameter optimization model Can be replaced with ,in This is the lowest speed point of wind turbine unit l, i.e. .

[0118] Furthermore, in one embodiment, the operational status recovery mechanism for each wind turbine unit after the frequency support ends in step 8 is specifically as follows:

[0119] ;

[0120] In the formula, The actual output electromagnetic power of the wind turbine j The power command for the maximum power point tracking control of the wind turbine; This serves as the power judgment threshold; specifically, as the frequency regulation power of synchronous turbines gradually increases, they gradually assume the task of balancing active power in the power grid, while the output electromagnetic power of each wind turbine gradually decreases; when a wind turbine satisfies the above formula, that wind turbine switches to... Power command, wind turbine speed returns to initial state, grid frequency gradually rises and returns to steady state frequency value.

[0121] Ultimately, by comprehensively utilizing independent and dispatchable wind turbines, short-term frequency support can be provided to the power grid (such as...). Figure 3 As shown in the figure, efforts are being made to improve the power grid frequency performance as much as possible under the constraint that wide-area real-time communication is difficult to implement in engineering.

[0122] In one embodiment, a wind power short-time frequency support system that integrates independent and dispatchable resources is provided, the system comprising:

[0123] The first module is used to construct the time-domain trajectory of the power grid frequency boundary: along the lower limit of the power grid frequency change rate at the initial stage of a frequency event. Descending, at time Lowest value at a certain frequency of trailing edge Remain unchanged;

[0124] The second module is used to fit the time-domain trajectory of the power grid frequency boundary in step 1 into the unit step response of a first-order system.

[0125] The third module is used to combine the unit step response of the second module and the actual power grid frequency response model to construct a unified control form for wind power short-time frequency support based on the frequency-active power transfer function.

[0126] The fourth module is used to design a spontaneous short-time frequency support control for independent wind turbine units based on the frequency-active power transfer function, using the unified control form for wind power short-time frequency support based on the third module.

[0127] The fifth module is used to set the control parameters in the fourth module based on the releaseable kinetic energy of the independent wind turbine itself;

[0128] The sixth module is used to combine the third and fourth modules to design short-time frequency support control for dispatchable wind turbines based on the frequency-active power transfer function.

[0129] Module 7, used for The highest target is to construct a parameter optimization model, and to focus on optimizing the control parameters of each schedulable unit in the sixth module;

[0130] The eighth module is used to determine the operation status recovery mechanism when the frequency support of each wind turbine unit ends, so as to realize the short-term frequency support of wind power by comprehensively utilizing independent and dispatchable resources.

[0131] Specific limitations regarding the wind power short-time frequency support system that integrates independent and dispatchable resources can be found in the limitations of the wind power short-time frequency support method mentioned above, and will not be repeated here. Each module in the aforementioned wind power short-time frequency support system that integrates independent and dispatchable resources can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the corresponding operations of each module.

[0132] In one embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the wind power short-time frequency support method that integrates independent and schedulable resources.

[0133] For specific limitations on each step, please refer to the limitations on the wind power short-time frequency support method that comprehensively utilizes independent and dispatchable resources mentioned above, which will not be repeated here.

[0134] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the wind power short-time frequency support method that integrates independent and schedulable resources.

[0135] For specific limitations on each step, please refer to the limitations on the wind power short-time frequency support method that comprehensively utilizes independent and dispatchable resources mentioned above, which will not be repeated here.

[0136] As a specific example, the invention will be further verified and illustrated in one embodiment.

[0137] This embodiment verifies the effectiveness of the proposed method using an IEEE 39-bus system comprising five aggregated wind farms. The topology of the IEEE 39-bus system is as follows: Figure 4 As shown, the total active power output of the power source is 4910.81MW. G1 represents the connected external power grid, which is an infinite power source without a governor-prime motor system; G2~G10 are steam turbine synchronous units equipped with governor-prime motor systems. Three aggregated wind farms with a rated capacity of 300MW are connected to nodes 5, 9, 16, 23, and 28 of the IEEE 39 system, respectively, denoted as WF1, WF2, WF3, WF5. Each wind farm consists of 60 5MW wind turbine units, all of which are NREL 5MW standard models, and their parameters are shown in Table 1. Furthermore, the following settings are provided... Set up independent STFS wind turbine units .

[0138] Table 1 Parameters of NREL 5MW Wind Turbine Unit

[0139] name value Rated power 5 MW Maximum wind energy utilization coefficient 0.4865 Optimal tip speed ratio 7.6 Cut-in, rated, and cut-out wind speeds 3 m / s, 11.4 m / s, 25 m / s Cut-in, rated speed 6.9 rpm (0.72rad / s), 12.1 rpm (1.27rad / s) Gearbox speed ratio 97 wind turbine radius 63 m Wind turbine rotational inertia <![CDATA[35444067 kgm 2 ]]> Generator moment of inertia <![CDATA[534.116 kgm 2 ]]>

[0140] Taking the frequency drop event caused by a sudden increase of 400MW of active power at system node 4 at 10s as an example, wind farms WF1, WF2, WF3, WF4, and WF5 face harsh scenarios with low constant wind speeds of 7, 7.5, 8, 8.5, and 9 m / s, respectively. The wind farms participate in the primary frequency regulation of the power grid through adaptive droop control and the method proposed in this invention, respectively. The lower limit of the frequency change rate under the method proposed in this invention is... The frequency is set to -0.08 Hz / s. In this embodiment, wind power does not provide frequency support (i.e., it always operates at MPPT), and the grid frequency is adaptively drooping under the method proposed in this invention. Wind power output Wind turbine speed The comparison curves are as follows: Figure 5 and Figure 6 As shown.

[0141] Depend on Figure 5 It is evident that adaptive droop control and the method proposed in this invention can improve the frequency minimum point to varying degrees. Among them, the adaptive droop control method shows the best improvement effect on the frequency change rate in the initial stage of a frequency event, but its effect on improving the frequency minimum point is poor. The reason for this is that the practice of each wind farm independently participating in frequency regulation makes it difficult to achieve coordinated frequency regulation between wind power and synchronous turbines, and also makes it difficult to achieve coordinated scheduling between wind farms. In contrast, the method proposed in this invention reasonably considers the characteristics of independent resources and scheduling resources in designing a short-term frequency support method for wind power. It not only improves the frequency change rate in the initial stage of a frequency event according to grid requirements, but also improves the grid frequency minimum point as much as possible under the constraint that wide-area real-time communication is difficult to implement in engineering.

[0142] Depend on Figure 6 It is known that both adaptive droop control and the method proposed in this invention change the wind power output after a frequency event occurs, releasing the kinetic energy of the wind turbine rotor to provide short-term frequency support for the power grid. The method proposed in this invention designs short-term frequency support methods for independent resources and dispatched resources respectively. Independent wind farms WF2 and WF4 use a set grid frequency deviation limit as the support target to collect their own rotor kinetic energy and calculate control coefficients. Dispatch wind farms WF1, WF3, and WF5 use optimization algorithms to calculate the set minimum frequency value and control coefficients, fully utilizing the dispatched resource capabilities to further improve the grid frequency regulation effect. Simultaneously, the improved frequency effect reduces the output electromagnetic power and released kinetic energy of independent wind farms, thus contributing to the stable operation of independent resources. Therefore, Figure 6 The rotor kinetic energy of independent wind farms has not been fully released, while the rotor kinetic energy of dispatched wind farms has been basically fully released. Under the premise of stable operation, each frequency regulation resource can improve the grid frequency effect as much as possible.

[0143] In summary, addressing the challenge of implementing centralized scheduling of wind turbine rotational speed information via a central controller in traditional wind power short-time frequency support methods, this invention first constructs the time-domain trajectory of the grid frequency boundary and fits it as the unit step response of a first-order system, deriving a unified control form for wind power short-time frequency support based on the frequency-active power transfer function. Based on this form, a self-generated short-time frequency support control for independent wind turbines is designed, with control parameters set according to their own rotor kinetic energy. A short-time frequency support control for dispatchable wind turbines coordinating with independent wind turbines is also designed, with centralized optimization of turbine control parameters. By comprehensively utilizing independent and dispatchable wind turbines to provide short-time frequency support to the grid, the grid frequency performance is improved as much as possible under the constraint of the difficulty in implementing wide-area real-time communication.

[0144] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention without departing from its spirit and scope should be included within the protection scope of the present invention.

Claims

1. A wind power short-term frequency support method that comprehensively utilizes independent and dispatchable resources, characterized in that, The method comprises the following steps: Step 1, constructing grid frequency boundary time-domain trajectory: at the initial stage of the frequency event, along the lower limit of the grid frequency change rate down, at time trailing edge of a certain frequency minimum value remains unchanged; Step 2, fitting the grid frequency boundary time domain trajectory in step 1 into a unit step response of a first-order system; Step 3, combining the unit step response of step 2 and an actual grid frequency response model to construct a wind power short-time frequency support unified control form based on a frequency-active power transfer function; Step 4, designing an independent wind turbine self-generated short-time frequency support control based on the frequency-active power transfer function based on the wind power short-time frequency support unified control form of step 3; Step 5, setting the control parameters in step 4 according to the releasable kinetic energy of the independent wind turbine itself; Step 6, combining steps 3 and 4 to design a short-time frequency support control of a dispatchable wind turbine based on the frequency-active power transfer function; Step 7, to The highest target construction parameter optimization model is optimized, and the control parameters of each schedulable unit in step 6 are concentrated and optimized. Step 8, determining the operation state recovery mechanism of the end of the frequency support of each wind turbine to realize the comprehensive use of the wind power short-time frequency support of the independent and dispatchable resources.

2. The method of claim 1, wherein the method further comprises: The time domain trajectory at the grid frequency boundary in step 1 is represented as: ； In the formulae, .

3. The method of claim 2, wherein the method further comprises: The step 2 fits the grid frequency boundary time-domain trajectory in step 1 as a unit step response of a first-order system, with time-domain and frequency-domain expressions as , : ； In the formulae, , , .

4. The method of claim 3, wherein the wind power short-term frequency support method using integrated independent and dispatchable resources, characterized in that, In step 3, the wind power short-time frequency support unified control form based on the frequency-active power transfer function is constructed by combining the unit step response of step 2 and the actual grid frequency response model, and the specific process comprises: Grid disturbance input power deficit The time and frequency domain expressions are: ； wherein , are the time and frequency domains, respectively , is a frequency domain variable; The system transfer function is defined as follows to make the grid achieve the unit step response of the frequency response: ； According to the actual grid frequency response model, the system transfer function is: ； wherein is the equivalent inertia time constant of the power grid, is the equivalent damping coefficient of the power grid, is the frequency regulation control transfer function of the synchronous generator i, is the frequency regulation control transfer function of the wind turbine j, and m and n represent the number of synchronous generators and wind turbines in the power grid, respectively; by equating the above two system transfer functions, the unified control form of the short-time frequency support of wind power based on the frequency-active power transfer function is obtained: 。 5. The method of claim 4, wherein, The frequency-active power transfer function of the independent wind turbine generator self-generated short-time frequency support control in step 4 is : ； where subscript k represents the kth individual wind turbine, o is the total number of individual wind turbines; is the minimum set frequency of all individual wind turbines, is the support factor of wind turbine k and are parameters that need to be set for individual wind turbines.

6. The method of claim 5, wherein the wind power short-term frequency support method using integrated independent and dispatchable resources, further comprises: In step 5, the control parameters in step 4 are set according to the releasable kinetic energy of the independent wind turbine itself, and the specific process comprises: The grid frequency deviation limit value is set according to national standards; According to the independent wind turbine itself can be released kinetic energy set; The time-domain curve of the output power variation of the independent wind turbine k is obtained in combination with the unit step response of step 2 : ； wherein denotes the inverse Laplace transform; Combining the rotor motion equation and the wind turbine's own releasable kinetic energy, the following nonlinear equations are solved: ​ ； wherein is the lower limit value of the rotational speed of the individual wind turbine k, is the time at which the lower limit value of the rotational speed of the individual wind turbine k is reached, is the change in aerodynamic power of the individual wind turbine k, , denote the change in aerodynamic power and the change in electromagnetic power, respectively, at the time at which the lower limit value of the rotational speed of the wind turbine k is reached, is calculated directly from the lower limit value of the rotational speed. When , wind turbine k does not participate in frequency modulation and has no rotor kinetic energy release; when , wind turbine k fully undertakes the short-time frequency support task, and wind turbine k will obviously lose stability and exit operation due to excessive release of kinetic energy in the actual scenario of large-scale wind power grid connection; therefore, there is always to satisfy the above nonlinear equations, which can be solved by using the bisection method.

7. The method of claim 6, wherein the method further comprises: In step 6, the frequency-active power transfer function of the short-time frequency support control of the dispatchable wind turbine is: ； wherein subscript l represents the lth scheduled wind turbine, , is the overall short-term frequency support transfer function of the scheduled wind turbines, and p is the total number of scheduled wind turbines; is the minimum set frequency of the scheduled wind turbines, is the support coefficient of the lth scheduled wind turbine and , are the parameters to be optimized for the scheduled wind turbines; is the total sum of the individual wind turbine support coefficients, i.e. .

8. The method of claim 7, wherein, In step 7, the parameter optimization model is constructed, and the specific process comprises: According to the frequency-active power transfer function in step 6, the wind turbine frequency support is scheduled to complement the independent wind turbine frequency support, so that the power grid frequency trajectory is still the unit step response of a first-order system; at this time, the time-domain curve of the wind turbine l output power is : ； The frequency-active power transfer function of step 4 and the frequency-active power transfer function of step 6 are superimposed to realize the wind power frequency support effect in the form of unified control of wind power short-time frequency support, at this time ; Constructing the parameter optimization model with The parameter optimization model with the target function and the wind turbine speed stability as the constraint conditions ； In the formula, is the lower limit value of the rotational speed of the wind turbine l, which is determined by the generator rotational speed operating range of the wind turbine itself, is the aerodynamic power variation amount of the wind turbine l to be dispatched, is the electromagnetic power variation amount of the wind turbine l to be dispatched; is the rotational inertia of the wind turbine l, is the rotor rotational speed of the wind turbine l, is the rotor rotational speed acceleration of the wind turbine l.

9. The method of claim 8, wherein the wind power short-term frequency support method using integrated independent and dispatchable resources, characterized in that, in the parameter optimization model may be replaced by wherein is the lowest point of the rotational speed of the wind turbine l, i.e. .

10. The method of claim 9, wherein the method further comprises: In step 8, the operation state recovery mechanism of the end of the frequency support of each wind turbine is specific to: ； In the formula, is the actual output electromagnetic power of the wind turbine j, is the power instruction of the wind turbine maximum power point tracking control; is the power judgment threshold; specifically, as the frequency regulation power of the synchronous unit gradually increases, gradually undertakes the task of active power balance in the power grid, the output electromagnetic power of each wind turbine gradually decreases; when a certain wind turbine meets the above formula, the wind turbine switches to the power instruction, the rotor speed is restored to the initial state, the power grid frequency gradually rises and restores to the steady-state frequency value.

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