Method for identifying excitation inrush of large-scale wind farm sending transformer based on high-frequency component and application thereof
By performing Parker transformation on the transient current of the output transformer of a large-scale wind farm, the maximum value of the high-frequency component is identified, which solves the accuracy problem of identifying inrush current and internal faults in traditional methods, realizes fast and reliable fault identification, and improves the operational reliability of the power system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- KUNMING UNIV OF SCI & TECH
- Filing Date
- 2026-04-19
- Publication Date
- 2026-07-24
AI Technical Summary
In large-scale wind farm systems, traditional second harmonic braking elements cannot accurately identify internal faults and inrush currents in the output transformer, leading to malfunctions in protection systems and affecting the reliability of the power system.
The Parker transform method based on high-frequency components is adopted. By performing Parker transform on the transient currents on both sides of the output transformer, the d-axis and q-axis components are obtained. The maximum value of the high-frequency components is determined to be zero, so as to determine whether inrush current or internal fault has occurred.
It improves the accuracy and sensitivity of identifying faults and inrush currents in large-scale wind farm transmission transformers, reduces protection malfunctions, and enhances the reliability of the power system.
Smart Images
Figure CN122051867B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of relay protection technology, and in particular to a method for identifying inrush current in large-scale wind farm transmission transformers based on high-frequency components and its application. Background Technology
[0002] If an internal fault occurs in the power transmission transformer of a large-scale wind farm, the internal fault and inrush current can be identified quickly and accurately, which can prevent protection malfunctions caused by inrush current and thus improve the reliability of power system operation.
[0003] In traditional transformer protection, second harmonic suppression elements primarily rely on detecting the content of the second harmonic. When the second harmonic content exceeds a threshold, it is identified as an inrush current. However, in large-scale wind farm systems, the second harmonic content is significantly higher than in traditional power grids. Furthermore, in the event of a fault, the short-circuit current in the doubly-fed induction generator (DFIG) cannot be accurately identified by traditional second harmonic suppression elements for both internal transformer faults and inrush currents.
[0004] In view of this, this application proposes a new method for identifying inrush current of the sending transformer in a large-scale wind farm, aiming to achieve reliable identification of transformer inrush current. Summary of the Invention
[0005] The main objective of this application is to provide a method for identifying inrush current in large-scale wind farm transmission transformers based on high-frequency components, aiming to solve the problem of how to identify inrush current phenomena in large-scale wind farm transmission transformers.
[0006] To achieve the above objectives, this application provides a method for identifying inrush current in large-scale wind farm transmission transformers based on high-frequency components. The method includes:
[0007] S10, when a differential current amplitude greater than a preset threshold is detected, Parker transformation is performed on the transient current collected on both sides of the output transformer to obtain the d-axis component and the q-axis component.
[0008] S20, determine the high-frequency component based on the d-axis component and the q-axis component, and determine whether the maximum value of the high-frequency component is zero;
[0009] If S30 is true, then it is determined that an inrush current has occurred.
[0010] Optionally, the step of determining the high-frequency component based on the d-axis component and the q-axis component includes:
[0011] Squaring the d-axis and q-axis components and then summing them, we get ;
[0012] right The high-frequency components are obtained by performing wavelet transform.
[0013] Optionally, the expression for the high-frequency component is:
[0014]
[0015] In the formula, h[np] is the shift coefficient of the wavelet high-pass filter, p is the p-th sampling point, and N is the number of sampling points within the time window.
[0016] Optionally, the transformation matrix of the Park transform is:
[0017]
[0018] In the formula, a, b, c represent the stationary coordinate system of phases a, b, and c; d, q represent the rotating coordinate system. Indicates the rotation angle.
[0019] Optionally, after S30, it also includes:
[0020] If not, then it is determined that the sending transformer has an internal fault.
[0021] In addition, to achieve the above objectives, this application also provides an application of the above-described method for identifying inrush current in large-scale wind farm power transmission transformers based on high-frequency components in the identification of inrush current.
[0022] In addition, to achieve the above objectives, this application also provides a power transmission transformer, which includes: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the steps of the above-described method for identifying inrush current of a power transmission transformer for large-scale wind farms based on high-frequency components.
[0023] In addition, to achieve the above objectives, this application also provides a computer system, the computer system comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, it implements the steps of the method for identifying inrush current of large-scale wind farm output transformers based on high-frequency components as described in any of the preceding claims.
[0024] In addition, to achieve the above objectives, this application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the method for identifying inrush current of a large-scale wind farm output transformer based on high-frequency components as described in any of the preceding claims.
[0025] This application has at least the following beneficial effects:
[0026] 1. Compared with the traditional second harmonic braking method, the wind farm power transmission transformer excitation inrush current identification method using high-frequency transient quantities has higher accuracy and sensitivity;
[0027] 2. This application has a short time window, which can quickly identify internal faults and inrush currents in transformers, thus improving the reliability of protection for power transmission transformers in large-scale wind farms. Attached Figure Description
[0028] Figure 1 This is a flowchart illustrating the inrush current identification method for large-scale wind farm output transformers based on high-frequency components, as described in an embodiment of this application.
[0029] Figure 2 This is a schematic diagram of a simulation model of a wind farm grid-connected system involved in an embodiment of this application;
[0030] Figure 3 This is a graph showing the high-frequency component variation of the sending transformer under inrush current in an embodiment of this application.
[0031] Figure 4 This is a graph showing the high-frequency component variation under a phase-A ground fault on the high-voltage side of the transmitting transformer, as described in the embodiments of this application.
[0032] Figure 5 This is a graph showing the high-frequency component variation under a two-phase (BC) short-circuit fault on the high-voltage side of the transformer involved in this application embodiment.
[0033] Figure 6 This is a high-frequency component variation curve of a fault with a transition resistance of 200Ω occurring on the high-voltage side of the transmitting transformer in the embodiments of this application when a two-phase short circuit of phases B and C occurs on the high-voltage side.
[0034] Figure 7 This is a schematic diagram of the hardware operating environment of the computer system involved in the embodiments of this application.
[0035] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0036] To better understand the above technical solutions, exemplary embodiments of this disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.
[0037] First Embodiment
[0038] Reference Figure 1This embodiment provides a method for identifying inrush current in large-scale wind farm transmission transformers based on high-frequency components. The method includes the following steps:
[0039] S10, when a differential current amplitude greater than a preset threshold is detected, Parker transformation is performed on the transient current collected on both sides of the output transformer to obtain the d-axis component and the q-axis component.
[0040] In this embodiment, firstly, transient currents on both sides of the output transformer are collected, differential current is calculated, and then it is determined whether the amplitude of differential current exceeds the limit. If so, the criterion for inrush current identification is activated, that is, Park transformation is performed on the transient currents collected on both sides of the output transformer to obtain the d-axis component and q-axis component.
[0041] In some optional implementations, it is determined whether the differential current is greater than a threshold. If it is greater than the threshold, the criterion is activated; otherwise, the criterion is not activated. The criterion is:
[0042]
[0043] In the formula, For differential current, The threshold value is used.
[0044] Alternatively, the transformation matrix of the Park transform is:
[0045]
[0046] In the formula, a, b, c represent the stationary coordinate system of phases a, b, and c; d, q represent the rotating coordinate system. Indicates the rotation angle.
[0047] It should be noted that the transient current is converted into d-axis and q-axis components through the Parker transformation matrix, and its form is as follows:
[0048]
[0049] In the formula, i d i q i and i0 represent the d-axis component, q-axis component, and zero-sequence component after transformation by the Parker transformation matrix, respectively; i a i b i c These represent phases A, B, and C of the transient current, respectively.
[0050] S20, determine the high-frequency component based on the d-axis component and the q-axis component, and determine whether the maximum value of the high-frequency component is zero;
[0051] In this embodiment, the high-frequency component is calculated based on the obtained d-axis and q-axis components, and the high-frequency component is used as a criterion for inrush current identification.
[0052] It should be noted that the principle behind this distinction is as follows: When an internal fault occurs in a transformer, the differential current waveform contains high-frequency transients generated by the fault. Under inrush current conditions, the transformer differential current mainly contains second and third harmonics, but does not contain high-frequency transients. However, by using the Parker transform to transform the three-phase circuit into a rotating coordinate system, the power frequency component of the pre-fault steady-state waveform is filtered out after the Parker transform, making the transients more apparent.
[0053] Based on this principle, after an internal fault occurs in a transformer, the value of the high-frequency component generated by the fault in the differential current waveform should be significantly greater than 0. When an inrush current occurs, the differential current waveform only contains harmonics generated by the inrush current, and the high-frequency component generated by the fault tends to be 0. Therefore, the transformer fault and the inrush current can be distinguished based on the magnitude of the maximum value of the high-frequency component.
[0054] Optionally, d-axis components are set. q-axis components The high-frequency components are The steps for determining high-frequency components include:
[0055] S21, squaring the d-axis and q-axis components and then summing them, yields... ;
[0056] Specifically, .
[0057] S22, for The high-frequency components are obtained by performing wavelet transform.
[0058] Specifically, the expression for the high-frequency components is:
[0059]
[0060] In the formula, h[np] is the shift coefficient of the wavelet high-pass filter, p is the p-th sampling point, and N is the number of sampling points within the time window.
[0061] If S30 is true, then it is determined that an inrush current has occurred.
[0062] In this embodiment, if the high-frequency component is determined... If the maximum value is 0, it is determined that an inrush current has occurred in the sending transformer.
[0063] Optionally, when an inrush current is detected, a blocking protection is implemented.
[0064] Furthermore, and optionally, if the maximum value of the high-frequency component is not zero, then it is determined that the transmitting transformer has an internal fault.
[0065] In the technical solution provided in this embodiment, when a differential current amplitude greater than a preset threshold is detected, the three-phase circuit is transformed to a rotating coordinate system using Parker transformation. This filters out the power frequency component in the steady-state waveform before the fault, ensuring that the differential current waveform only contains harmonics generated by inrush current. High-frequency components are used as the criterion; when the maximum value of the high-frequency component is zero, it is determined that an inrush current has occurred.
[0066] Furthermore, as an implementation scheme, this application also relates to an application of the above-described method for identifying inrush current in large-scale wind farm power transmission transformers based on high-frequency components in the identification of inrush current.
[0067] The following examples illustrate the application of the method involved in this embodiment in the identification of inrush current.
[0068] Example 1, see below Figure 2 The simulation model of the wind farm grid-connected system shown in this example has a total installed capacity of 200MW. The low voltage ride-through methods for the wind turbines are divided into two types: crowbar operation and continuous excitation by the frequency converter. The voltage level is 220kV. The simulation also includes scenarios of inrush current at the sending transformer and a phase-A ground fault on the high-voltage side of the transformer. The sampling rate is 10kHz.
[0069] Reference by Figure 3 and Figure 4 The graphs shown are the high-frequency component variation curves under inrush current and phase A ground fault on the high-voltage side of the transformer. It can be seen that the high-frequency component of the differential current is smaller under inrush current and larger under phase A ground fault, consistent with the principle described in this invention. Based on the calculated Dmax, it can be determined that Dmax equals 0.00007 under inrush current, approaching 0, with the integer part being 0, thus blocking protection. Under phase A ground fault, Dmax is 536, not equal to 0, thus triggering protection. Therefore, this method can accurately determine inrush current.
[0070] Example 2, also refer to... Figure 2 The simulation model of the wind farm grid-connected system shown in this example has a total installed capacity of 200MW. The low-voltage ride-through methods for the wind turbines are divided into two types: crowbar activation and continuous excitation by the frequency converter. The voltage level is 220kV. The fault is set to occur on the high-voltage side of the sending transformer, and the fault types are two-phase BC short-circuit fault and two-phase BC short-circuit fault with a transition resistance of 200Ω. The sampling rate is 10kHz.
[0071] Reference by Figure 5 The diagram shows the high-frequency component variation curves under a two-phase (BC) short-circuit fault on the high-voltage side of the transmitting transformer, and... Figure 6The diagram shows the high-frequency component variation curves under a two-phase (BC) short circuit fault with a transition resistance of 200Ω on the high-voltage side of the transmitting transformer. It can be seen that the high-frequency component of the differential current is larger under a two-phase (BC) short circuit fault, and also larger under a phase-A ground fault, which is consistent with the principle described in this invention. Based on the calculated Dmax, it can be determined that Dmax equals 4765 (not 0) under a two-phase (BC) short circuit fault, indicating protection activation; and Dmax equals 2126 (not 0) under a two-phase (BC) short circuit fault with a transition resistance of 200Ω, also indicating protection activation. Therefore, this method can accurately identify internal faults.
[0072] Furthermore, as an implementation scheme, the present application embodiment also relates to a power transmission transformer, the power transmission transformer including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, it implements the steps of the above-described method for identifying inrush current of a large-scale wind farm power transmission transformer based on high-frequency components.
[0073] Furthermore, as an implementation scheme, Figure 7 This is a schematic diagram of the hardware operating environment of the computer system involved in the embodiments of this application.
[0074] like Figure 7 As shown, the computer system may include: a processor 1001, such as a CPU; a memory 1005; a user interface 1003; a network interface 1004; and a communication bus 1002. The communication bus 1002 is used to enable communication between these components. The user interface 1003 may include a display screen or an input unit such as a keyboard; optionally, the user interface 1003 may also include a standard wired interface or a wireless interface. The network interface 1004 may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface). The memory 1005 may be high-speed RAM or non-volatile memory, such as a disk drive. Optionally, the memory 1005 may also be a storage device independent of the aforementioned processor 1001.
[0075] Those skilled in the art will understand that Figure 7 The computer system architecture shown does not constitute a limitation on the computer system and may include more or fewer components than shown, or combine certain components, or have different component arrangements.
[0076] like Figure 7As shown, the memory 1005, as a storage medium, may include an operating system, a network communication module, a user interface module, and computer programs. The operating system is a program that manages and controls the hardware and software resources of the computer system, as well as the operation of the computer programs and other software or programs.
[0077] exist Figure 7 In the computer system shown, the user interface 1003 is mainly used to connect to the terminal and communicate with the terminal; the network interface 1004 is mainly used to communicate with the backend server; and the processor 1001 can be used to call the computer program stored in the memory 1005.
[0078] In this embodiment, the computer system includes: a memory 1005, a processor 1001, and a computer program stored in the memory and executable on the processor, wherein:
[0079] When processor 1001 calls a computer program stored in memory 1005, it performs the following operations:
[0080] S10, when a differential current amplitude greater than a preset threshold is detected, Parker transformation is performed on the transient current collected on both sides of the output transformer to obtain the d-axis component and the q-axis component.
[0081] S20, determine the high-frequency component based on the d-axis component and the q-axis component, and determine whether the maximum value of the high-frequency component is zero;
[0082] If S30 is true, then it is determined that an inrush current has occurred.
[0083] Furthermore, those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program includes program instructions and can be stored in a storage medium, which is a computer-readable storage medium. The program instructions are executed by at least one processor in a computer system to implement the process steps of the embodiments of the above methods.
[0084] Therefore, this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the various steps of the inrush current identification method for large-scale wind farm output transformers based on high-frequency components as described in the above embodiments.
[0085] The computer-readable storage medium can be any computer-readable storage medium capable of storing program code, such as a USB flash drive, portable hard drive, read-only memory (ROM), magnetic disk, or optical disk.
[0086] It should be noted that, since the storage medium provided in the embodiments of this application is the storage medium used to implement the methods of the embodiments of this application, those skilled in the art can understand the specific structure and variations of the storage medium based on the methods described in the embodiments of this application, and therefore will not be repeated here. All storage media used in the methods of the embodiments of this application fall within the scope of protection of this application.
[0087] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application 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.
[0088] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. 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... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.
[0089] 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.
[0090] 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.
[0091] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.
[0092] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.
Claims
1. A method for identifying inrush current in large-scale wind farm transmission transformers based on high-frequency components, characterized in that, The method includes the following steps: S10, when a differential current amplitude greater than a preset threshold is detected, Parker transformation is performed on the transient current collected on both sides of the output transformer to obtain the d-axis component and the q-axis component. S20, determine the high-frequency component based on the d-axis component and the q-axis component, and determine whether the maximum value of the high-frequency component is zero; S30, if yes, then it is determined that an inrush current has occurred; The steps for determining the high-frequency components based on the d-axis components and the q-axis components include: Squaring the d-axis and q-axis components and then summing them, we get ; right Perform wavelet transform to obtain the high-frequency components; The expression for the high-frequency component is: ； In the formula, h[np] is the shift coefficient of the wavelet high-pass filter, p is the p-th sampling point, and N is the number of sampling points within the time window.
2. The method for identifying inrush current of large-scale wind farm output transformers based on high-frequency components as described in claim 1, characterized in that, The transformation matrix of the Park transform is: ； In the formula, a, b, c represent the stationary coordinate system of phases a, b, and c; d, q represent the rotating coordinate system. Indicates the rotation angle.
3. The method for identifying inrush current in large-scale wind farm output transformers based on high-frequency components as described in claim 1, characterized in that, Following the S30, it also includes: If not, then it is determined that the sending transformer has an internal fault.
4. An application of the inrush current identification method for large-scale wind farm transmission transformers based on high-frequency components as described in any one of claims 1 to 3 in the identification of inrush current.
5. A transmitting transformer, characterized in that, The transmitting transformer includes: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the steps of the method for identifying inrush current of transmitting transformers in large-scale wind farms based on high-frequency components as described in any one of claims 1 to 3.
6. A computer system, characterized in that, The computer system includes: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the steps of the method for identifying inrush current of a large-scale wind farm output transformer based on high-frequency components as described in any one of claims 1 to 3.
7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the method for identifying inrush current of a large-scale wind farm output transformer based on high-frequency components as described in any one of claims 1 to 3.