Wind power frequency regulation droop coefficient correction method and system considering time delay characteristics

Abstract

The application provides a wind power frequency modulation droop coefficient correction method and system considering the influence of delay characteristics, establishes a system frequency response model considering wind power frequency modulation delay characteristics and speed recovery control, obtains a system transfer function through the system frequency response model, and obtains system frequency key indexes through analytical solution; analyzes the influence mechanism of the delay characteristics on the power grid frequency dynamics, determines the relationship between each key index and the delay; on the basis of the relationship result, the droop control coefficient is corrected, so that the system frequency minimum point meets the preset requirement. The application can effectively improve the system frequency minimum point, so that the system frequency minimum point is consistent with that when the delay characteristics are not considered.

Description

Technical Field

[0001] This invention belongs to the field of wind power frequency regulation control technology, and relates to a method and system for correcting the droop coefficient of wind power frequency regulation considering the influence of delay characteristics. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] To address the global climate change and environmental pollution crisis, clean energy sources such as wind and solar power have received increasing attention. However, because renewable energy generation is connected to the grid through power electronic devices, its rotor speed is decoupled from the grid frequency. As the penetration rate of renewable energy increases, the frequency security of the grid will inevitably weaken. Therefore, renewable energy participation in the primary frequency regulation of the grid has become an inevitable choice. Currently, fruitful research has been conducted both domestically and internationally on wind turbine participation in grid frequency control, mainly using two methods: utilizing rotor kinetic energy and power reserve. Among these, wind turbines utilizing rotor kinetic energy operate in Maximum Power Point Tracking (MPPT) mode, offering better economic efficiency. Meanwhile, current research on wind turbine participation in grid frequency regulation largely focuses on simulating synchronous machines, primarily including virtual inertia control and droop control. Virtual inertia control aims to simulate the inertial response of a synchronous machine, using the rate of frequency change as the input signal; droop control aims to simulate the primary frequency regulation of a synchronous machine, using the frequency deviation as the input signal. The combination of these two methods is known as integrated inertial control.

[0004] However, the use of integrated inertial control in wind turbines for grid frequency regulation is essentially a rapid power response, which differs from the instantaneous inertial response of synchronous machines. It requires frequency measurement, communication, and response stages, resulting in a certain delay. Currently, there is limited research on the power response delay characteristics of wind turbines, and the mechanism by which these delay characteristics affect grid frequency dynamics remains unclear. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a method and system for correcting the droop coefficient of wind power frequency regulation that considers the influence of delay characteristics. This invention can effectively improve the minimum system frequency, making the minimum system frequency consistent with that when delay characteristics are not considered.

[0006] According to some embodiments, the present invention adopts the following technical solution:

[0007] A method for correcting the droop coefficient of wind power frequency regulation considering the influence of time delay characteristics includes the following steps:

[0008] A system frequency response model considering the frequency regulation delay characteristics of wind power and speed recovery control is established. The system transfer function is calculated through the system frequency response model, and the key system frequency indicators are obtained by analytical solution.

[0009] Analyze the impact mechanism of delay characteristics on power grid frequency dynamics, and determine the relationship between key indicators and delay.

[0010] Based on the determined relationship, the droop control coefficient is adjusted so that the minimum system frequency reaches the preset requirement.

[0011] As an alternative implementation method, the specific process of establishing a system frequency response model that considers the frequency regulation delay characteristics of wind power and speed recovery control includes constructing a comprehensive inertial control structure for wind turbine units, approximating the delay of wind power frequency regulation power response as a first-order inertial element, and representing the active response of the wind turbine.

[0012] The system parameters are converted and the active power control link of the wind turbine is added to the classic system frequency response model. The wind turbine adopts comprehensive inertial control during frequency regulation. The wind power penetration rate and the delay of wind power frequency regulation are considered to obtain the final system frequency response model.

[0013] As a further clarification, the specific process of constructing the integrated inertial control structure of a wind turbine includes: a droop control loop, a virtual inertia control loop, and a speed recovery control loop, wherein:

[0014] The output power of the virtual inertia control loop is proportional to the system frequency change rate to simulate the inertia response of the synchronous machine; the output power of the droop control loop is proportional to the system frequency deviation to simulate the primary frequency regulation of the synchronous machine.

[0015] When the wind turbine is operating normally in maximum power point tracking mode, it uses integrated inertial control to participate in grid frequency regulation when power disturbance occurs. The response power is proportional to the system frequency change rate and the system frequency deviation. During frequency regulation, the speed controller is locked. When the wind turbine exits frequency regulation, the rotor speed is restored to the rated value under the action of the speed controller, and the wind turbine returns to maximum power point tracking operation mode.

[0016] As an alternative implementation, in the process of calculating the system transfer function through the system frequency response model, the power mutation is assumed to be a step disturbance to express the system frequency response.

[0017] As an alternative implementation, the key system frequency indicators include the lowest system frequency, the maximum rate of change of system frequency, and the steady-state frequency deviation of the system.

[0018] As a further step, the maximum rate of change of the system frequency is calculated using the initial value theorem of the Laplace transform;

[0019] The steady-state frequency deviation of the system is calculated using the final value theorem of the Laplace transform.

[0020] The system frequency response model is reduced in order, and the reduced model is solved analytically to re-express the frequency response. Then, an inverse Laplace transform is performed to obtain the time-domain solution of the system frequency response expression. The system frequency derivative is set to zero, and the time to reach the minimum frequency and the minimum frequency point of the system are obtained.

[0021] As an alternative implementation method, the results of determining the relationship between each key indicator and the delay include that the maximum rate of change of the system frequency is independent of the delay magnitude;

[0022] The steady-state frequency deviation of the system is independent of the delay.

[0023] The lowest point of the system frequency will decrease as the delay increases.

[0024] As an alternative implementation method, the specific process of correcting the droop control coefficient includes calculating the lowest point of the system frequency without considering the delay characteristics, calculating the lowest point of the system frequency without considering the delay characteristics of wind power frequency regulation, setting the two to be equal, and then obtaining the corrected droop coefficient that is equal to the lowest point of the system frequency without considering the delay characteristics.

[0025] Frequency modulation is achieved by correcting the droop control coefficient based on the corrected droop coefficient.

[0026] A wind power frequency regulation droop coefficient correction system considering the influence of delay characteristics includes:

[0027] The system frequency key index calculation module is configured to establish a system frequency response model that considers the frequency regulation delay characteristics of wind power and speed recovery control. The system transfer function is calculated through the system frequency response model, and the system frequency key index is obtained by analytical solution.

[0028] The impact analysis module is configured to analyze the impact mechanism of delay characteristics on power grid frequency dynamics and determine the relationship between key indicators and delay.

[0029] The correction control module is configured to adjust the droop control coefficient based on the determined relationship results, so that the minimum system frequency reaches the preset requirement.

[0030] A control device includes a processor and a computer-readable storage medium, the processor being configured to implement instructions; the computer-readable storage medium being configured to store a plurality of instructions adapted to be loaded by the processor and executed in accordance with the steps of the method.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The droop control coefficient correction method of this invention first determines the key indicators of system frequency by considering the system frequency response model of wind power frequency regulation delay characteristics. Then, it analyzes the influence mechanism of delay characteristics on grid frequency dynamics, determines the influence of delay on each indicator, and concludes that the maximum frequency change rate and steady-state frequency deviation of the system are independent of the delay magnitude, while the minimum system frequency decreases as the delay increases. Based on this conclusion, correcting the droop control coefficient can effectively improve the minimum system frequency, making the minimum system frequency consistent with other values ​​when delay characteristics are not considered. Attached Figure Description

[0033] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0034] Figure 1 This is the integrated inertial control structure for the wind turbine in this embodiment;

[0035] Figure 2 This is a schematic diagram of the active power response principle of the wind turbine frequency regulation in this embodiment;

[0036] Figure 3 This is the extended SFR model for wind turbine participation in grid frequency regulation in this embodiment;

[0037] Figure 4 This embodiment illustrates the impact of the wind turbine delay characteristics on the system frequency dynamics.

[0038] Figure 5 This is the virtual inertia power response in this embodiment;

[0039] Figure 6 This is the active power response of the wind turbine during frequency regulation in this embodiment;

[0040] Figure 7 This is the droop control coefficient correction strategy in this embodiment;

[0041] Figure 8 This is the system frequency dynamics under different delay values ​​in this embodiment;

[0042] Figure 9 This is the system frequency derivative when the delay values ​​are different in this embodiment;

[0043] Figure 10 This describes the dynamic system frequency under different conditions in this embodiment;

[0044] Figure 11 These are the synchronous machine response powers under different conditions in this embodiment;

[0045] Figure 12 This refers to the wind turbine response power under different conditions in this embodiment;

[0046] Figure 13 This is a schematic diagram of the method for implementing the corrected droop control coefficient in this embodiment. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0048] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0049] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0050] Example 1

[0051] This embodiment provides a method for correcting the droop coefficient of wind power frequency regulation considering the influence of delay characteristics. First, a system frequency response (SFR) model considering the delay characteristics of wind power frequency regulation is established. Then, the system transfer function is obtained through the SFR model, and the key system frequency indicators are obtained by analytically solving it. Furthermore, the influence mechanism of delay characteristics on grid frequency dynamics is analyzed through expressions, and it is concluded that the maximum rate of change of system frequency and steady-state frequency deviation are independent of the delay magnitude, while the minimum system frequency decreases as the delay increases. Based on this, the droop control coefficient is corrected using the minimum system frequency as an indicator so that the minimum system frequency achieves the expected effect.

[0052] The following is a detailed introduction:

[0053] The first step is to analyze and model the frequency regulation delay characteristics of wind power.

[0054] (1) Modeling and analysis of wind power frequency regulation delay characteristics

[0055] Currently, research on wind turbine participation in grid frequency control mainly focuses on simulating synchronous machines, primarily including virtual inertia control and droop control. Integrated inertia control is a combination of the two, as shown in equation (1), and the control structure block diagram is as follows. Figure 1As shown in the figure. Among them, the output power of the virtual inertia control is proportional to the system frequency change rate, aiming to simulate the inertia response of the synchronous machine; the output power of the droop control is proportional to the system frequency deviation, aiming to simulate the primary frequency regulation of the synchronous machine.

[0056]

[0057] In the formula, ΔP f k is the response power of the wind turbine during frequency regulation. d k is the virtual inertia control coefficient. p This is the droop control coefficient.

[0058] The wind turbine operates normally in MPPT mode. When power disturbances occur, integrated inertial control is used to participate in grid frequency regulation. The response power is proportional to the system frequency change rate and the system frequency deviation. During frequency regulation, the speed controller is locked. When the wind turbine exits frequency regulation, the rotor speed is restored to the rated value under the action of the speed controller, and the wind turbine returns to MPPT operation mode.

[0059] In the diagram, P wind ΔP1 is the output power of the wind turbine; ΔP2 is the droop control response power; ΔP is the virtual inertia control response power; ΔP... f It is the response power of the wind turbine during frequency regulation, ΔP f =ΔP1 + ΔP2; P MPPT ω represents the output power of the wind turbine when it is operating normally in MPPT mode. r ΔP is the rotor speed; ω k is the response power of the speed controller. ωp k is the proportional coefficient of the speed controller. ωi f0 is the integral coefficient of the speed controller; T1 and T2 are the time constants of the high-pass filter and low-pass filter, respectively.

[0060] However, the use of integrated inertial control for wind turbines in grid frequency regulation inherently involves a power response with a certain time delay. Considering the virtual inertia delay characteristics, the active power response diagram of the wind turbine during frequency regulation is as follows: Figure 2 As shown. Compared to system power surplus, power deficit is more dangerous; therefore, this embodiment only discusses the situation where the system experiences power deficit, leading to a frequency drop. Assume the initial output of the wind turbine is P0, the rotational speed is ω0, and it participates in grid frequency regulation using integrated inertial control, with an active power response delay time of T. d Assume the system experiences a disturbance at time A, and after a delay T... d Upon reaching point B, the wind turbine begins to respond to the system frequency change. At this point, the rotor speed ω(t) decreases, releasing rotor kinetic energy and outputting power P to the grid. WAs (t) increases, and at the same time, due to the decrease in rotational speed, the wind turbine deviates from the optimal rotational speed, resulting in a decrease in the wind energy utilization coefficient and mechanical power P. m (t) decreases. During frequency regulation, the wind turbine outputs power P to the grid. W (t) is represented by the solid line ABCDEF, and the mechanical power P of the wind turbine itself is shown as t. m The change of (t) is shown by the dashed line ABEF, and the change of the wind turbine's own speed is shown by the dotted line GHIJ.

[0061] To simplify the analysis, this embodiment approximates the delay of the wind power frequency regulation power response as a first-order inertial element. The active power response expression of the wind turbine is then:

[0062]

[0063] In the formula, ΔP f ΔP represents the actual frequency-modulated power output of the wind turbine. f0 T represents the theoretical frequency-modulated power output of the wind turbine. d It is the equivalent time constant for the delay of the active power control link of the wind turbine.

[0064] (2) SFR model considering wind power frequency regulation delay characteristics

[0065] Because the rotor speed of wind turbines is decoupled from the grid frequency, they lack the inertial response capability of traditional synchronous turbines during grid-connected operation. As wind turbine penetration increases, the grid inertia level will inevitably decrease. Therefore, it is necessary to recalculate the parameters of the original system. The wind power penetration level α is defined as the percentage of actual wind turbine output relative to the total grid capacity, expressed as:

[0066]

[0067] In the formula, α is the wind power penetration rate, and S wind This is the actual generating capacity of the wind turbine, S sync This refers to the power generation capacity of the system's conventional generating units.

[0068] When wind turbines participate in grid frequency regulation using integrated inertial control, they can be considered as controlled power sources, providing additional power control to the grid during frequency regulation. Therefore, this embodiment adopts... Figure 3 The simplified system shown is analyzed by adding the active power control link of the wind turbine to the classic SFR model.

[0069] Based on the extended SFR model, the system transfer function is:

[0070]

[0071] This embodiment assumes a power mutation ΔP LSince the disturbance is a step disturbance, the system frequency response expression is:

[0072]

[0073] This section establishes the SFR model for wind turbine units participating in grid frequency regulation and derives the system frequency response expression based on it. The next section will analyze the system frequency response index based on the system frequency response expression.

[0074] (3) Analytical solution of system frequency response index

[0075] Currently, the main indicators for evaluating system frequency dynamics include: the system frequency minimum point Δf. max Maximum rate of change of system frequency (df / dt) max and the steady-state frequency deviation Δf of the system set This section will analyze and solve the frequency response indices of the three systems, laying the foundation for subsequent analysis of the impact of delay on the dynamics of the power grid frequency.

[0076] First, since the maximum rate of change of the system frequency usually occurs at the initial moment of the disturbance, we can use the Laplace transform initial value theorem to obtain:

[0077]

[0078] Then, the steady-state frequency deviation of the system can be obtained using the final value theorem of the Laplace transform, as follows:

[0079]

[0080] Finally, to find the lowest frequency point of the system, the original transfer function G(s) is first approximated as B(s) using the Routh reduction method.

[0081]

[0082] In the formula:

[0083]

[0084]

[0085] The frequency response expression of a reduced-order system is:

[0086]

[0087] Therefore, the time-domain solution of the frequency response expression of the reduced-order system can be obtained as follows:

[0088]

[0089] In the formula:

[0090]

[0091] By setting the system frequency derivative to zero, the time t to reach the lowest frequency can be calculated. m , will t m Substituting into the system frequency response expression shown in equation (10), we can obtain the lowest point of the system frequency:

[0092]

[0093] This section uses the Laplace transform theorem and the model reduction method to analytically solve for the expression of the system frequency response index. The next section will analyze the influence mechanism of wind power frequency regulation delay characteristics on the dynamic frequency of the power grid based on the expression.

[0094] The following section introduces the impact of wind power frequency regulation delay characteristics on frequency dynamics and the coefficient correction method.

[0095] The first is the mechanism by which the frequency regulation delay characteristics of wind power affect the dynamic frequency of the system.

[0096] The influence of wind power frequency regulation delay characteristics on the maximum rate of change of system frequency and the steady-state frequency deviation of system can be obtained by analyzing equation (6). Equation (6) shows that the maximum rate of change of system frequency is related to the magnitude of the disturbance, system inertia, and wind power penetration level, but not to the magnitude of the delay. Similarly, the steady-state frequency deviation of system is independent of the magnitude of the delay. Therefore, both the maximum rate of change of system frequency and the steady-state frequency deviation of system are independent of the wind power frequency regulation delay characteristics.

[0097] The influence of wind power frequency regulation delay characteristics on the maximum frequency drop of the system can be obtained by analyzing equation (11). First, the irrelevant variables in the expression are assigned typical values, as shown in Table 1. Based on this, it is found that the minimum frequency of the system decreases as the delay increases, such as... Figure 4 As shown.

[0098] Table 1 Parameter Settings

[0099]

[0100] An analysis was conducted on the impact of the delay characteristics of wind turbine units on the output power of the wind turbines.

[0101] First, solve for the frequency response expression of the system without considering the delay characteristic, and let T d =0, at this time the system model is second order, so it can be solved directly. By referring to equation (8) and substituting the coefficients of each term in the transfer function, the system frequency response expression without considering the delay characteristics can be obtained as follows:

[0102]

[0103] In the formula, the subscript "1" indicates that the system variables are not considered when the delay characteristics are not taken into account, and the variables are the same as those in formula (8).

[0104] First, without considering the frequency regulation delay characteristics of wind power, the active power response of the wind turbine during frequency regulation using integrated inertial control is as follows:

[0105] ΔP(s)=(αk p +αk d s)Δf(s) (13)

[0106] Transformed into time-domain form by inverse Laplace transform:

[0107]

[0108] In the formula, This refers to the output power of the wind turbine during frequency regulation to control droop. The output power is controlled by the droop control.

[0109] Considering the frequency regulation delay characteristics of wind power, the active power response of the wind turbine during frequency regulation using integrated inertial control is as follows:

[0110]

[0111] Since equation (14) is in the form of a product of two complex functions, the time-domain solution needs to be convolved with it, as follows:

[0112]

[0113] In the formula, This refers to the active power response of the wind turbine droop control during frequency regulation. This is for droop control of active response.

[0114] The time-domain form obtained after Laplace transform is:

[0115]

[0116] In the formula, This refers to the output power of the wind turbine during frequency regulation to control droop. Let the output power be the droop control output power. By calculating the virtual inertia and the active response of the droop control respectively, we can obtain:

[0117]

[0118]

[0119] Assign typical values ​​to the irrelevant variables in equations (18) and (19), and assume that the frequency regulation parameter of the wind turbine is k. d =10,k p=20, and the active power response of the wind turbine during frequency regulation can be obtained when the delay size is different, as follows: Figure 5 and Figure 6 As shown, where Figure 5 It is the virtual inertia power response. Figure 6 It is a droop control power response.

[0120] from Figure 5 As can be seen, when delay characteristics are not considered, virtual inertia control can share the disturbance power at the initial moment of the disturbance, causing a sudden change in output power and reducing the magnitude of the disturbance, thus playing the role of inertial response. However, when delay characteristics are considered, virtual inertia control cannot share the disturbance power to cause a sudden change in output power when a disturbance occurs, which is fundamentally different from the inertial response of a synchronous machine. It only plays the role of rapid power support. Meanwhile, from... Figure 6 It can be observed that, compared with virtual inertia, droop control is less affected by delay, and can provide strong support near the lowest frequency point regardless of whether delay characteristics are considered.

[0121] The third part is the coefficient correction method based on the lowest point of the system frequency.

[0122] As mentioned above, the minimum system frequency decreases as the delay of wind power frequency regulation increases. Considering that the maximum frequency drop is an important basis for evaluating the system frequency stability and is related to the action threshold of the protection device; at the same time, in practice, the droop control method is flexible and the measurement of the system frequency deviation signal has higher accuracy; based on this, this section proposes a droop control coefficient correction method to make the minimum system frequency when considering the delay characteristics of wind power frequency regulation equal to the minimum system frequency when not considering the delay characteristics.

[0123] From equation (11), we obtain the lowest system frequency without considering delay characteristics:

[0124]

[0125] The variables in the formula are consistent with those in formula (10).

[0126] The lowest system frequency, without considering the frequency regulation delay characteristics of wind power, is shown in equation (20). Therefore, let equation (11) equal equation (20), that is:

[0127] Δf max =Δf 1max (twenty one)

[0128] The corrected droop coefficient, which is equal to the lowest frequency point of the system when delay characteristics are not considered, can be obtained. That is:

[0129] k p2 =p(k d1 k p1 ) (twenty two)

[0130] In the formula, k p2 To account for delay characteristics, the corrected droop control coefficient, k d1 k p1 These are the frequency regulation control parameters for wind power without considering delay characteristics.

[0131] Since equation (20) contains a large number of trigonometric function terms and exponential terms, it is difficult to express k analytically. p2 With k d1 k p1 Therefore, this embodiment adopts a numerical solution method, assigning typical values ​​to variables in the formula that are unrelated to wind power frequency regulation parameters, as mentioned above, to obtain a corrected droop coefficient equal to the lowest point of the system frequency when delay characteristics are not considered. Figure 7 As shown. (Through) Figure 7 Therefore, by increasing a certain droop control coefficient, it is possible to achieve the same minimum system frequency as when delay characteristics are not considered.

[0132] The specific implementation method is as follows: Figure 13 As shown above, the lowest frequency points are analytically solved with and without considering the delay. Based on the lowest frequency points of the system, the corrected droop control coefficients corresponding to the case without considering the delay characteristics are obtained. The droop control coefficients are corrected in real time to achieve the expected frequency modulation effect.

[0133] Simulation verification:

[0134] To verify the correctness of the influence mechanism of wind power frequency regulation delay characteristics on system frequency dynamics and the droop coefficient correction method proposed in the paper, a system was built in MATLAB / Simulink. Figure 3 The simulation model is shown in Table 1, and the model parameters are shown in Table 1.

[0135] Finally, the impact of wind power frequency regulation delay on grid frequency dynamics was verified.

[0136] First, we verify the influence mechanism of wind power frequency regulation delay characteristics on system frequency dynamics, taking the wind turbine frequency regulation parameter as the virtual inertia control coefficient k. d =10, k p =25, simulation results are as follows Figure 8 and Figure 9 As shown.

[0137] Depend on Figure 8It can be seen that the system frequency minimum point is highest when the wind power frequency regulation delay characteristic is not considered, and decreases as the delay increases when the delay characteristic is considered. The steady-state frequency deviation of the system is independent of the delay magnitude; the steady-state frequency deviation of the system has no effect regardless of the presence or absence of a delay. The maximum rate of change of the system frequency occurs at the initial moment of the disturbance. When the wind power frequency regulation delay characteristic is not considered, the maximum rate of change of the system frequency is smaller than when the delay characteristic is considered. This is because the virtual inertia control shares the disturbance power at the initial moment of the disturbance, reducing the unbalanced power of the system and thus reducing the maximum rate of change of the system frequency. When the delay characteristic is considered, the virtual inertia control loses its instantaneous power support capability and cannot share the disturbance power at the initial moment of the disturbance. In this case, the maximum rate of change of the system frequency is larger than without delay. Furthermore, when the wind power frequency regulation delay characteristic is considered, the maximum rate of change of the system frequency is independent of the delay magnitude. Figure 9 As shown.

[0138] To verify the effectiveness of the droop control coefficient correction method proposed in this paper, this section compares and analyzes the system frequency dynamics and unit response power during frequency regulation under three scenarios. The simulation curves are shown in Table 2 and... Figures 10-12 As shown.

[0139] 1) The wind turbine adopts integrated inertial control, taking into account the frequency regulation delay characteristics of wind power.

[0140] 2) The wind turbine adopts integrated inertial control, without considering the frequency regulation delay characteristics of wind power.

[0141] 3) The wind turbine adopts integrated inertial control. Considering the frequency regulation delay characteristics of wind power, the droop control coefficient is corrected by the method mentioned in the article.

[0142] When a frequency disturbance event occurs, because the synchronous machine has a large primary frequency regulation time constant while the wind turbine has a small time constant, the wind turbine primarily provides power support in the initial stage of the disturbance. Figure 11 and Figure 12 As shown. Simultaneously by Figure 10 and Figure 12 It can be seen that in the initial stage of disturbance, the active power output of the wind turbine is smaller when considering the frequency regulation delay characteristics of wind power compared to when the delay characteristics are not considered. Simultaneously, the output power of the synchronous generator is relatively similar, thus the system's minimum frequency is lower at this time. However, after correcting the droop control coefficient using the method proposed in this paper, the frequency regulation power output of the wind turbine in the initial stage of disturbance can be increased. Therefore, it can effectively raise the system's minimum frequency, making it consistent with the minimum frequency when the delay characteristics are not considered, thus achieving the expected frequency regulation effect. Figure 10 As shown.

[0143] Table 2. Lowest system frequency under different scenarios

[0144]

[0145] Example 2

[0146] A wind power frequency regulation droop coefficient correction system considering the influence of delay characteristics includes:

[0147] The system frequency key index calculation module is configured to establish a system frequency response model that considers the frequency regulation delay characteristics of wind power and speed recovery control. The system transfer function is calculated through the system frequency response model, and the system frequency key index is obtained by analytical solution.

[0148] The impact analysis module is configured to analyze the impact mechanism of delay characteristics on power grid frequency dynamics and determine the relationship between key indicators and delay.

[0149] The correction control module is configured to adjust the droop control coefficient based on the determined relationship results, so that the minimum system frequency reaches the preset requirement.

[0150] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0151] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0152] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0153] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0154] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0155] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for correcting the droop coefficient of wind power frequency regulation considering the influence of time delay characteristics, characterized in that, Includes the following steps: A system frequency response model considering the frequency regulation delay characteristics of wind power and speed recovery control is established. The system transfer function is calculated through the system frequency response model, and the key system frequency indicators are obtained by analytical solution. Analyze the impact mechanism of delay characteristics on power grid frequency dynamics, and determine the relationship between key indicators and delay. Based on the determined relationship results, the droop control coefficient is adjusted so that the minimum system frequency reaches the preset requirement; The specific process of establishing a system frequency response model that considers the frequency regulation delay characteristics of wind power and speed recovery control includes constructing a comprehensive inertial control structure for wind turbine units, approximating the delay of wind power frequency regulation power response as a first-order inertial element, and representing the active response of the wind turbine. The system parameters are converted, and the active power control link of the wind turbine is added to the classic system frequency response model. The wind turbine adopts comprehensive inertial control during frequency regulation. The wind power penetration rate and the delay of wind power frequency regulation are considered to obtain the final system frequency response model. The specific process of correcting the droop control coefficient includes calculating the lowest point of the system frequency without considering the delay characteristics, calculating the lowest point of the system frequency without considering the delay characteristics of wind power frequency regulation, setting the two to be equal, and then obtaining the corrected droop coefficient that is equal to the lowest point of the system frequency without considering the delay characteristics. The droop control coefficient is corrected based on the droop correction coefficient to achieve frequency modulation; The specific process of constructing a comprehensive inertial control structure for wind turbine generators includes: droop control, virtual inertia control, and speed recovery control, among which: The output power of the virtual inertia control loop is proportional to the system frequency change rate to simulate the inertia response of the synchronous machine; the output power of the droop control loop is proportional to the system frequency deviation to simulate the primary frequency regulation of the synchronous machine. When the wind turbine is operating normally in maximum power point tracking mode, it uses integrated inertial control to participate in grid frequency regulation when power disturbance occurs. The response power is proportional to the system frequency change rate and the system frequency deviation. During frequency regulation, the speed controller is locked. When the wind turbine exits frequency regulation, the rotor speed is restored to the rated value under the action of the speed controller, and the wind turbine returns to maximum power point tracking operation mode.

2. The wind power frequency regulation droop coefficient correction method considering the influence of delay characteristics as described in claim 1, characterized in that, In the process of calculating the system transfer function through the system frequency response model, the power mutation is a step disturbance that expresses the system frequency response.

3. The wind power frequency regulation droop coefficient correction method considering the influence of delay characteristics as described in claim 1, characterized in that, The key frequency indicators of the system include the lowest point of system frequency, the maximum rate of change of system frequency, and the steady-state frequency deviation of the system.

4. The wind power frequency regulation droop coefficient correction method considering the influence of delay characteristics as described in claim 1, characterized in that, Calculate the maximum rate of change of the system frequency using the Laplace transform initial value theorem; The steady-state frequency deviation of the system is calculated using the final value theorem of the Laplace transform. The system frequency response model is reduced in order, and the reduced model is solved analytically to re-express the frequency response. Then, an inverse Laplace transform is performed to obtain the time-domain solution of the system frequency response expression. The system frequency derivative is set to zero, and the time to reach the minimum frequency and the minimum frequency point of the system are obtained.

5. The wind power frequency regulation droop coefficient correction method considering the influence of delay characteristics as described in claim 1, characterized in that, The results of determining the relationship between key indicators and delay include that the system's maximum rate of frequency change is independent of the delay magnitude; The steady-state frequency deviation of the system is independent of the delay. The lowest point of the system frequency will decrease as the delay increases.

6. A wind power frequency regulation droop coefficient correction system considering the influence of delay characteristics, using the method described in claim 1, characterized in that, include: The system frequency key index calculation module is configured to establish a system frequency response model that considers the frequency regulation delay characteristics of wind power and speed recovery control. The system transfer function is calculated through the system frequency response model, and the system frequency key index is obtained by analytical solution. The impact analysis module is configured to analyze the impact mechanism of delay characteristics on power grid frequency dynamics and determine the relationship between key indicators and delay. The correction control module is configured to adjust the droop control coefficient based on the determined relationship results, so that the minimum system frequency reaches the preset requirement.

7. A control device, characterized in that, It includes a processor and a computer-readable storage medium, the processor being used to implement various instructions; the computer-readable storage medium being used to store a plurality of instructions adapted to be loaded by the processor and executed as steps in the method of any one of claims 1-5.

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