Resonance elimination method and system based on PT primary side neutral point connected with zinc oxide nonlinear resistor

Abstract

The invention discloses a resonance elimination method and system based on a PT primary side neutral point connected with a zinc oxide nonlinear resistor, and belongs to the technical field of ferromagnetic resonance suppression in an electric power system. The method comprises the following steps: collecting a real-time zero-sequence voltage amplitude and a real-time zero-sequence current amplitude; obtaining the maximum real-time signal frequency; judging the relationship between the maximum real-time signal frequency and a signal frequency threshold value so as to identify the type of ferromagnetic resonance; and according to the type of the ferromagnetic resonance, selecting and controlling the disconnection or connection of the zinc oxide nonlinear resistor so as to suppress the ferromagnetic resonance. Two zinc oxide non-linear resistance valve plates with different volt-ampere characteristics are connected to the neutral point of the primary side of the PT, the zero-sequence voltage and the zero-sequence current are combined to comprehensively judge and control the power electronic switch to input one resistor, and the purpose of effective resonance elimination is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of ferromagnetic resonance suppression in power systems, and in particular to a detuning method and system based on connecting a zinc oxide nonlinear resistor to a neutral point on a primary side of a PT. Background Art

[0002] In a 10kV neutral point ungrounded distribution system, electromagnetic voltage transformers (PTs) are prone to ferromagnetic resonance, such as frequency division ferromagnetic resonance, fundamental frequency ferromagnetic resonance, and high frequency ferromagnetic resonance, which can cause system overvoltage and affect the safe and stable operation of the power system.

[0003] The existing detuning methods mainly include: connecting a damping resistor to the neutral point of the primary side of the PT, connecting a damping resistor or a microcomputer detuning device to the PT open delta, grounding the neutral point of the system through an arc suppression coil, increasing the inflection point voltage of the PT excitation characteristics, increasing the system capacitance to ground, short-circuiting the 4PT method, and opening the 4PT method. However, the above detuning methods have certain limitations in suppressing ferromagnetic resonances of different frequencies, especially for 25Hz frequency division, 50Hz base frequency and 240Hz high frequency ferromagnetic resonances. Specifically: When suppressing 25Hz frequency division ferromagnetic resonance and 50Hz fundamental frequency ferromagnetic resonance, the three methods of increasing the inflection point voltage of PT excitation characteristics, grounding the system neutral point through an arc suppression coil, and grounding the system neutral point through a small resistor will fail to suppress the ferromagnetic resonance. When increasing the system capacitance to ground and the 4PT method are used to suppress the 240Hz high-frequency ferromagnetic resonance, the suppression fails. When the PT open delta-connected damping resistor suppresses the 50Hz fundamental frequency ferromagnetic resonance, the suppression fails. Although the damping resistor connected to the neutral point of the primary side of the PT has a good suppression effect on the three types of ferromagnetic resonance, there are still problems such as the required linear resistance is too large and the manufacturing process is difficult.

[0004] At present, although there is a technology to suppress ferromagnetic resonance by grounding the neutral point of the distribution network through a zinc oxide nonlinear resistor, it is mainly based on the principle of power frequency ferromagnetic resonance and has poor suppression effect on frequency division and high frequency ferromagnetic resonance. For example, Chinese invention patent CN106443145A (named as a method for suppressing ferromagnetic resonance by grounding the neutral point of a distribution network through a ZnO nonlinear resistor) obtains the voltage value of the distribution network neutral point ungrounded system. When the voltage value of the distribution network neutral point ungrounded system is greater than or equal to the preset voltage value, the magnetic flux and current value of the electromagnetic voltage transformer in the distribution network neutral point ungrounded system are calculated to obtain the inductance value of the electromagnetic voltage transformer in the neutral point ungrounded system. Then, according to the inductance value of the electromagnetic voltage transformer in the neutral point ungrounded system, the volt-ampere characteristic curve of the connected ZnO nonlinear resistor is obtained by using the power frequency ferromagnetic resonance principle, thereby preparing the ZnO nonlinear resistor to be connected, and then the neutral point of the distribution network neutral point ungrounded system is led out through a grounding transformer, and then the ZnO nonlinear resistor to be connected is connected to the grounding transformer, thereby eliminating the ferromagnetic resonance overvoltage in the distribution network neutral point ungrounded system. Since the volt-ampere characteristic curve of the connected ZnO nonlinear resistor is obtained by the power frequency ferromagnetic resonance principle, the suppression effect on frequency division and high frequency ferromagnetic resonance is poor. Summary of the invention

[0005] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description and other drawings of the description.

[0006] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a method and system for detuning based on connecting zinc oxide nonlinear resistors to the neutral point of the primary side of the PT. The present invention connects two zinc oxide nonlinear resistor valve plates with different volt-ampere characteristics to the neutral point of the primary side of the PT, and comprehensively judges and controls the power electronic switch to switch on one of the resistors in combination with the zero-sequence voltage and zero-sequence current, thereby achieving the purpose of effective detuning.

[0007] To achieve the above object, the technical solution of the present invention is: a detuning method based on connecting a zinc oxide nonlinear resistor to the neutral point of the primary side of a PT, the method comprising the following steps: Collect real-time zero-sequence voltage amplitude and real-time zero-sequence current amplitude; Get the maximum real-time signal frequency; Determine the relationship between the maximum real-time signal frequency and the signal frequency threshold to identify the type of ferromagnetic resonance; According to the type of ferromagnetic resonance, the disconnection or connection of the zinc oxide nonlinear resistor is selected and controlled to suppress the ferromagnetic resonance.

[0008] In some implementations, the real-time zero-sequence voltage amplitude and the real-time zero-sequence current amplitude are collected, specifically: the real-time zero-sequence voltage amplitude and the real-time zero-sequence current amplitude are collected using a zero-sequence voltage detector and a zero-sequence current detector, respectively.

[0009] In some embodiments, the zero-sequence voltage detector is located at the opening of the secondary side of the PT, and the zero-sequence current detector is located at the neutral point of the primary side of the PT.

[0010] In some implementations, the maximum real-time signal frequency is obtained by analyzing the collected real-time zero-sequence voltage amplitude and real-time zero-sequence current amplitude using a fast Fourier transform, and filtering the signal frequencies of the two spectrum graphs to obtain the maximum real-time signal frequency.

[0011] In some embodiments, the signal frequency threshold includes a first signal frequency threshold and a second signal frequency threshold, and the first signal frequency threshold is smaller than the second signal frequency threshold.

[0012] In some implementations, the relationship between the maximum real-time signal frequency and the signal frequency threshold is determined to identify the type of ferromagnetic resonance, specifically: If the maximum real-time signal frequency is less than the first signal frequency threshold, the ferromagnetic resonance is a frequency-divided ferromagnetic resonance; If the maximum real-time signal frequency is between the first signal frequency threshold and the second signal frequency threshold, the ferromagnetic resonance is the fundamental frequency ferromagnetic resonance; If the maximum real-time signal frequency is greater than the second signal frequency threshold, the ferromagnetic resonance is a high-frequency ferromagnetic resonance.

[0013] In some embodiments, the zinc oxide nonlinear resistor includes a first zinc oxide nonlinear resistor and a second oxidative nonlinear resistor, and the volt-ampere characteristic of the first zinc oxide nonlinear resistor is inconsistent with the volt-ampere characteristic of the second oxidative nonlinear resistor.

[0014] In some implementations, the disconnection or connection of the zinc oxide nonlinear resistor is selected and controlled according to the type of ferromagnetic resonance to suppress ferromagnetic resonance, specifically: If the ferromagnetic resonance is the fundamental frequency ferromagnetic resonance, the zinc oxide nonlinear resistor 1 is controlled to be turned on and the zinc oxide nonlinear resistor 2 is controlled to be turned off to suppress the ferromagnetic resonance; If the ferromagnetic resonance is frequency division or high frequency ferromagnetic resonance, the zinc oxide nonlinear resistor 1 is controlled to be disconnected and the zinc oxide nonlinear resistor 2 is controlled to be connected to suppress the ferromagnetic resonance.

[0015] In some embodiments, the volt-ampere characteristic parameters of the zinc oxide nonlinear resistor 1 are I / A = [0.001, 671.34, 1217.35, 5000, 10000], U / V = [200, 2773.5, 3086.75, 3400, 4150]; the volt-ampere characteristic parameters of the oxidative nonlinear resistor 2 are I / A = [0.001, 671.34, 1217.35, 5000, 10000], U / V = [2400, 4903.5, 5286.75, 5600, 6350].

[0016] The present invention also provides a detuning system based on connecting a zinc oxide nonlinear resistor to the neutral point of a PT primary side, comprising: An acquisition module, which is used to acquire real-time zero-sequence voltage amplitude and real-time zero-sequence current amplitude; An acquisition module, which is used to acquire the maximum real-time signal frequency; An identification module, which is used to determine the relationship between the maximum real-time signal frequency and the signal frequency threshold to identify the type of ferromagnetic resonance; The control module is used for selecting and controlling the disconnection or connection of the zinc oxide nonlinear resistor according to the type of ferromagnetic resonance to suppress the ferromagnetic resonance.

[0017] In some embodiments, the acquisition module includes a zero-sequence voltage detector located at the opening of the secondary side of the PT and a zero-sequence current detector located at the neutral point of the primary side of the PT.

[0018] In some embodiments, the zinc oxide nonlinear resistor includes a first zinc oxide nonlinear resistor and a second oxidative nonlinear resistor, and the volt-ampere characteristic of the first zinc oxide nonlinear resistor is inconsistent with the volt-ampere characteristic of the second oxidative nonlinear resistor.

[0019] In some embodiments, the control module includes an insulated gate bipolar transistor, which is used to control the disconnection or connection of the zinc oxide nonlinear resistor.

[0020] In summary, the beneficial effects of the present invention are as follows: by arranging a triangle detector at the opening of the PT secondary side and a current detector at the neutral point of the PT primary side, the present invention can collect zero-sequence voltage and zero-sequence current in real time, and control the insulated gate bipolar transistor through a control loop according to the judgment result of the collected data, thereby putting zinc oxide nonlinear resistor valve plates with different volt-ampere characteristics into use, realizing alternating disconnection or conduction of two zinc oxide nonlinear resistor valve plates connected in series, and achieving the purpose of effectively suppressing three types of ferromagnetic resonance overvoltages.

[0021] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure.

[0022] Undoubtedly, these and other objects of the present invention will become more apparent after the following detailed description of the preferred embodiment described with reference to various figures and drawings.

[0023] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, one or several preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation of the present invention.

[0025] In the drawings, the same reference numerals are used for the same components and the drawings are schematic and not necessarily drawn to scale.

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only one or several embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on such drawings without paying creative work.

[0027] Figure 1 is a flow chart of the harmonic elimination method of the present invention; Figure 2 It is a control flow chart of the harmonic elimination method of the present invention; Figure 3 This is a three-phase voltage waveform diagram of the primary side of the PT for suppressing 25Hz frequency division resonance in the present invention; Figure 4 This is a three-phase current waveform diagram of the primary side of the PT for suppressing 25Hz frequency division resonance in the present invention; Figure 5 This is a three-phase voltage waveform diagram of the primary side of the PT for suppressing 240Hz high-frequency resonance in the present invention; Figure 6 This is a three-phase current waveform diagram of the primary side of the PT for suppressing 240Hz high-frequency resonance in the present invention; Figure 7 This is a three-phase voltage waveform diagram of the primary side of the PT for suppressing the 50Hz fundamental frequency resonance of the present invention; Figure 8 This is a three-phase current waveform diagram of the primary side of the PT for suppressing the 50Hz fundamental frequency resonance of the present invention; Fig. 9 It is the principle diagram of the harmonic elimination system of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but are not used to limit the present invention.

[0029] In addition, in the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0030] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral body; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. However, if it is indicated as a direct connection, it means that the two connected bodies are not connected through a transition structure, but are connected to form a whole through a connecting structure. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0031] In the present invention, unless otherwise clearly specified and limited, the first feature "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments or examples.

[0032] In the 10kV neutral point ungrounded distribution system, the electromagnetic voltage transformer (PT) is prone to ferromagnetic resonance, resulting in system overvoltage and affecting the safe and stable operation of the power system. The existing detuning methods mainly include connecting the neutral point of the PT primary side to a damping resistor, connecting the PT open delta to a damping resistor or a microcomputer detuning device, grounding the neutral point of the system through an arc suppression coil, increasing the inflection point voltage of the PT excitation characteristics, increasing the system capacitance to ground, 4PT method short circuit, 4PT method open circuit, etc. However, the above methods have certain limitations in suppressing ferromagnetic resonance of different frequencies, especially for 25Hz frequency division, 50Hz base frequency and 240Hz high frequency ferromagnetic resonance.

[0033] Chinese invention patent CN106443145A (named as a method for suppressing ferromagnetic resonance by grounding the neutral point of a distribution network via a ZnO nonlinear resistor) proposes a method for suppressing ferromagnetic resonance by grounding the neutral point of a distribution network via a ZnO nonlinear resistor. However, it is mainly based on the principle of power frequency ferromagnetic resonance, and has poor suppression effect on frequency division and high frequency ferromagnetic resonance. Therefore, an improved solution that can effectively suppress ferromagnetic resonance of multiple frequencies is urgently needed.

[0034] In view of the above technical problems, the basic concept of the present invention is to provide a detuning method based on connecting a zinc oxide nonlinear resistor to the neutral point of the primary side of a PT, by connecting two zinc oxide nonlinear resistor valve plates in series to the neutral point of the primary side of the PT, namely zinc oxide nonlinear resistor one and zinc oxide nonlinear resistor two, wherein the zinc oxide nonlinear resistor one is used to suppress fundamental frequency ferromagnetic resonance, and the zinc oxide nonlinear resistor two is used to suppress frequency division and high-frequency ferromagnetic resonance; at the same time, a triangle detector is set at the opening of the secondary side of the PT and a current detector is set at the neutral point of the primary side of the PT to collect zero-sequence voltage and zero-sequence current in real time, and the insulated gate bipolar transistor (IGBT) is controlled through a control loop according to the judgment result of the collected data, so that the zinc oxide nonlinear resistor one or the zinc oxide nonlinear resistor two is put into operation, thereby effectively suppressing the occurrence of frequency division, fundamental frequency and high-frequency ferromagnetic resonance.

[0035] Reference Figure 1-Figure 2 The present invention provides a detuning method based on connecting a zinc oxide nonlinear resistor to the neutral point of the primary side of a PT. The detuning method comprises the following steps: Collect real-time zero-sequence voltage amplitude 3 U 0 and real-time zero-sequence current amplitude I 0; Get the maximum real-time signal frequency f 3U0 , f I0 ; Determine the maximum real-time signal frequency f 3U0 , fI0 Relationship with signal frequency threshold to identify the type of ferromagnetic resonance; According to the type of ferromagnetic resonance, the disconnection or connection of the zinc oxide nonlinear resistor is selected and controlled to suppress the ferromagnetic resonance.

[0036] According to some embodiments of the present invention, optionally, the real-time zero-sequence voltage amplitude 3 is collected. U 0 and real-time zero-sequence current amplitude I 0, specifically: using a zero-sequence voltage detector and a zero-sequence current detector to collect real-time zero-sequence voltage amplitude 3 U 0 and real-time zero-sequence current amplitude I 0.

[0037] According to some embodiments of the present invention, optionally, the zero-sequence voltage detector is located at the opening of the secondary side of the PT, and the zero-sequence current detector is located at the neutral point of the primary side of the PT.

[0038] According to some embodiments of the present invention, optionally, the maximum real-time signal frequency is obtained f 3U0 , f I0 Specifically, the real-time zero-sequence voltage amplitude 3 is acquired by fast Fourier transform. U 0 and real-time zero-sequence current amplitude I 0 for analysis and filtering of the signal frequencies of the two spectrum graphs to obtain the maximum real-time signal frequency f 3U0 , f I0 .

[0039] According to some embodiments of the present invention, optionally, the signal frequency threshold includes a first signal frequency threshold and a second signal frequency threshold, and the first signal frequency threshold is smaller than the second signal frequency threshold.

[0040] According to some embodiments of the present invention, optionally, the maximum real-time signal frequency is determined f 3U0 , f I0 The relationship with the signal frequency threshold to identify the type of ferromagnetic resonance is: If the maximum real-time signal frequency f 3U0 = f I0 When it is less than the first signal frequency threshold, the ferromagnetic resonance is a frequency-divided ferromagnetic resonance; If the maximum real-time signal frequency f 3U0 = f I0When the frequency of the first signal is between the first signal frequency threshold and the second signal frequency threshold, the ferromagnetic resonance is the fundamental frequency ferromagnetic resonance; If the maximum real-time signal frequency f 3U0 = f I0 When it is greater than the second signal frequency threshold, the ferromagnetic resonance is a high-frequency ferromagnetic resonance.

[0041] According to some embodiments of the present invention, optionally, the first signal frequency threshold is 45 Hz, and the second signal frequency threshold is 70 Hz.

[0042] According to some embodiments of the present invention, optionally, the zinc oxide nonlinear resistor comprises a zinc oxide nonlinear resistor. R 1. Oxidative nonlinear resistor II R 2. Zinc oxide nonlinear resistor R 1. The volt-ampere characteristics of the oxidative nonlinear resistor II R 2's volt-ampere characteristics are inconsistent.

[0043] According to some embodiments of the present invention, optionally, the disconnection or connection of the zinc oxide nonlinear resistor is selected and controlled according to the type of ferromagnetic resonance to suppress ferromagnetic resonance, specifically: If the ferromagnetic resonance is the fundamental frequency ferromagnetic resonance, the zinc oxide nonlinear resistor is controlled. R 1 is turned on, zinc oxide nonlinear resistor 2 R 2 disconnect to suppress ferromagnetic resonance; If the ferromagnetic resonance is frequency division or high frequency ferromagnetic resonance, the zinc oxide nonlinear resistor is controlled. R 1 disconnect, zinc oxide nonlinear resistor 2 R 2 is turned on to suppress ferromagnetic resonance.

[0044] According to some embodiments of the present invention, optionally, the zinc oxide nonlinear resistor R The volt-ampere characteristic parameters of 1 are I / A = [0.001, 671.34, 1217.35, 5000, 10000], U / V = [200, 2773.5, 3086.75,3400, 4150]; the oxidized nonlinear resistor is R The volt-ampere characteristic parameters of 2 are I / A = [0.001, 671.34,1217.35, 5000, 10000], U / V = [2400, 4903.5, 5286.75, 5600, 6350].

[0045] Reference Fig. 9The present invention also provides a detuning system based on connecting a zinc oxide nonlinear resistor to the neutral point of the primary side of the PT. The detuning system includes an acquisition module, an acquisition module, an identification module and a control module. The acquisition module is used to collect the real-time zero-sequence voltage amplitude and the real-time zero-sequence current amplitude; the acquisition module is used to obtain the maximum real-time signal frequency; the identification module is used to determine the relationship between the maximum real-time signal frequency and the signal frequency threshold to identify the type of ferromagnetic resonance; the control module is used to select and control the disconnection or connection of the zinc oxide nonlinear resistor according to the type of ferromagnetic resonance to suppress ferromagnetic resonance.

[0046] According to some embodiments of the present invention, optionally, the acquisition module includes a zero-sequence voltage detector located at the opening of the secondary side of the PT and a zero-sequence current detector located at the neutral point of the primary side of the PT.

[0047] According to some embodiments of the present invention, optionally, the zinc oxide nonlinear resistor comprises a zinc oxide nonlinear resistor. R 1. Oxidative nonlinear resistor II R 2. Zinc oxide nonlinear resistor R 1. The volt-ampere characteristics of the oxidative nonlinear resistor II R 2's volt-ampere characteristics are inconsistent.

[0048] According to some embodiments of the present invention, optionally, the control module includes an insulated gate bipolar transistor, which is used to control the disconnection or connection of the zinc oxide nonlinear resistor.

[0049] Example 1 Reference Figure 1-Figure 2 This embodiment provides a detuning method based on connecting a zinc oxide nonlinear resistor to the neutral point of the primary side of a PT. The detuning method includes the following steps: Step 1: Collect real-time zero-sequence voltage amplitude 3 U 0 and real-time zero-sequence current amplitude I 0.

[0050] Use the zero-sequence voltage detector located at the opening of the PT secondary side to collect the real-time zero-sequence voltage amplitude 3 U 0, use the zero-sequence current detector located at the neutral point of the primary side of the PT to collect the real-time zero-sequence current amplitude I 0.

[0051] Step 2: Get the maximum real-time signal frequency f 3U0 , f I0 .

[0052] The real-time zero-sequence voltage amplitude 3 is collected by fast Fourier transform. U 0 and real-time zero-sequence current amplitude I0 for analysis and filtering of the signal frequencies of the two spectrum graphs to obtain the maximum real-time signal frequency f 3U0 , f I0 .

[0053] Step 3: Determine the maximum real-time signal frequency f 3U0 , f I0 Relationship with signal frequency threshold to identify the type of ferromagnetic resonance.

[0054] If the maximum real-time signal frequency f 3U0 = f I0 When it is less than the first signal frequency threshold, the ferromagnetic resonance is a frequency-divided ferromagnetic resonance; If the maximum real-time signal frequency f 3U0 = f I0 When the frequency of the first signal is between the first signal frequency threshold and the second signal frequency threshold, the ferromagnetic resonance is the fundamental frequency ferromagnetic resonance; If the maximum real-time signal frequency f 3U0 = f I0 When it is greater than the second signal frequency threshold, the ferromagnetic resonance is a high-frequency ferromagnetic resonance.

[0055] Among them, the first signal frequency threshold is 45 Hz, and the second signal frequency threshold is 70 Hz.

[0056] Step 4: Select and control the disconnection or connection of the zinc oxide nonlinear resistor according to the type of ferromagnetic resonance to suppress the ferromagnetic resonance.

[0057] If the ferromagnetic resonance is the fundamental frequency ferromagnetic resonance, the zinc oxide nonlinear resistor is controlled. R 1 is turned on, zinc oxide nonlinear resistor 2 R 2 disconnect to suppress ferromagnetic resonance; If the ferromagnetic resonance is frequency division or high frequency ferromagnetic resonance, the zinc oxide nonlinear resistor is controlled. R 1 disconnect, zinc oxide nonlinear resistor 2 R 2 is turned on to suppress ferromagnetic resonance.

[0058] Among them, zinc oxide nonlinear resistor RThe volt-ampere characteristic parameters of 1 are I / A = [0.001, 671.34,1217.35, 5000, 10000], U / V = [200, 2773.5, 3086.75, 3400, 4150]; the oxidized nonlinear resistor is R The volt-ampere characteristic parameters of 2 are I / A = [0.001, 671.34, 1217.35, 5000, 10000], U / V = [2400, 4903.5, 5286.75, 5600, 6350].

[0059] The detuning method of this embodiment is used to suppress ferromagnetic resonance, and simulation analysis is performed. The simulation results are as follows: Figure 3-Figure 8 shown.

[0060] from Figure 3-Figure 8 It can be seen that after the corresponding detuning resistor is input according to the ferromagnetic resonance of different frequencies, the three-phase voltage and three-phase current waveforms of the PT primary side are quickly restored to the normal voltage range. Specifically: For 25Hz crossover resonance, input R 2, the three-phase voltage on the primary side of the PT and the open triangle zero-sequence voltage were suppressed instantly, the power absorbed by the ZnO nonlinear resistor reached 1830.91W, and the heat generated reached 11.39J.

[0061] For 50Hz fundamental frequency resonance, input R 1, the three-phase voltage on the primary side of the PT experienced a process of voltage drop and voltage recovery to the normal voltage value. The power absorbed by the ZnO nonlinear resistor reached 41.42W and the heat generated reached 0.39J.

[0062] For 240Hz high frequency resonance, input R 2, the voltage waveform is suppressed in a short time, the power absorbed by the ZnO nonlinear resistor reaches 107.05W, and the heat generated reaches 0.19J.

[0063] Example 2 Reference Fig. 9 This embodiment provides a detuning system based on connecting a zinc oxide nonlinear resistor to the neutral point of the primary side of a PT. The detuning system includes an acquisition module, an acquisition module, an identification module, and a control module. The acquisition module is used to collect the real-time zero-sequence voltage amplitude and the real-time zero-sequence current amplitude; the acquisition module is used to obtain the maximum real-time signal frequency; the identification module is used to determine the relationship between the maximum real-time signal frequency and the signal frequency threshold to identify the type of ferromagnetic resonance; the control module is used to select and control the disconnection or connection of the zinc oxide nonlinear resistor according to the type of ferromagnetic resonance to suppress ferromagnetic resonance.

[0064] In this embodiment, the acquisition module includes a zero-sequence voltage detector located at the opening of the secondary side of the PT and a zero-sequence current detector located at the neutral point of the primary side of the PT.

[0065] In this embodiment, the zinc oxide nonlinear resistor includes a zinc oxide nonlinear resistor. R 1. Oxidative nonlinear resistor II R 2. Zinc oxide nonlinear resistor R 1. The volt-ampere characteristics of the oxidative nonlinear resistor II R 2's volt-ampere characteristics are inconsistent.

[0066] In this embodiment, the control module includes an insulated gate bipolar transistor, which is used to control the disconnection or connection of the zinc oxide nonlinear resistor.

[0067] It should be noted that many specific details are set forth in the above description to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

Claims

1. A detuning method based on connecting a zinc oxide nonlinear resistor to the neutral point of the primary side of a PT, characterized in that: The method comprises the following steps: Collect real-time zero-sequence voltage amplitude and real-time zero-sequence current amplitude; Get the maximum real-time signal frequency; Determine the relationship between the maximum real-time signal frequency and the signal frequency threshold to identify the type of ferromagnetic resonance; Select and control the disconnection or connection of the zinc oxide nonlinear resistor according to the type of ferromagnetic resonance to suppress ferromagnetic resonance; The maximum real-time signal frequency is obtained by: using fast Fourier transform to analyze the collected real-time zero-sequence voltage amplitude and real-time zero-sequence current amplitude, and screening the signal frequencies of the two spectrum graphs to obtain the maximum real-time signal frequency; The zinc oxide nonlinear resistor includes a zinc oxide nonlinear resistor 1 and an oxidative nonlinear resistor 2, and the volt-ampere characteristic of the zinc oxide nonlinear resistor 1 is inconsistent with the volt-ampere characteristic of the oxidative nonlinear resistor 2; According to the type of ferromagnetic resonance, the disconnection or connection of the zinc oxide nonlinear resistor is selected and controlled to suppress the ferromagnetic resonance, specifically: If the ferromagnetic resonance is the fundamental frequency ferromagnetic resonance, the zinc oxide nonlinear resistor 1 is controlled to be turned on and the zinc oxide nonlinear resistor 2 is controlled to be turned off to suppress the ferromagnetic resonance; If the ferromagnetic resonance is frequency division or high frequency ferromagnetic resonance, the zinc oxide nonlinear resistor 1 is controlled to be disconnected and the zinc oxide nonlinear resistor 2 is controlled to be connected to suppress the ferromagnetic resonance.

2. The detuning method based on connecting the primary neutral point of the PT to a zinc oxide nonlinear resistor according to claim 1, characterized in that: The real-time zero-sequence voltage amplitude and the real-time zero-sequence current amplitude are collected, specifically: the real-time zero-sequence voltage amplitude and the real-time zero-sequence current amplitude are collected respectively by using a zero-sequence voltage detector and a zero-sequence current detector.

3. The detuning method based on connecting the primary neutral point of the PT to a zinc oxide nonlinear resistor according to claim 2, characterized in that: The zero-sequence voltage detector is located at the opening of the secondary side of the PT, and the zero-sequence current detector is located at the neutral point of the primary side of the PT.

4. The detuning method based on connecting the primary neutral point of the PT to a zinc oxide nonlinear resistor according to claim 1, characterized in that: The signal frequency threshold includes a first signal frequency threshold and a second signal frequency threshold, and the first signal frequency threshold is smaller than the second signal frequency threshold.

5. The detuning method based on connecting the primary neutral point of the PT to a zinc oxide nonlinear resistor according to claim 4, characterized in that: Determine the relationship between the maximum real-time signal frequency and the signal frequency threshold to identify the type of ferromagnetic resonance, specifically: If the maximum real-time signal frequency is less than the first signal frequency threshold, the ferromagnetic resonance is a frequency-divided ferromagnetic resonance; If the maximum real-time signal frequency is between the first signal frequency threshold and the second signal frequency threshold, the ferromagnetic resonance is the fundamental frequency ferromagnetic resonance; If the maximum real-time signal frequency is greater than the second signal frequency threshold, the ferromagnetic resonance is a high-frequency ferromagnetic resonance.

6. The detuning method based on connecting the primary neutral point of the PT to a zinc oxide nonlinear resistor according to claim 1, characterized in that: The volt-ampere characteristic parameters of zinc oxide nonlinear resistor 1 are I / A = [0.001, 671.34, 1217.35, 5000, 10000], U / V = [200, 2773.5, 3086.75, 3400, 4150]; the volt-ampere characteristic parameters of oxide nonlinear resistor 2 are I / A = [0.001, 671.34, 1217.35, 5000, 10000], U / V = [2400, 4903.5, 5286.75, 5600, 6350].

7. A detuning system based on a PT primary neutral point connected to a zinc oxide nonlinear resistor, characterized in that: include: An acquisition module, which is used to acquire real-time zero-sequence voltage amplitude and real-time zero-sequence current amplitude; An acquisition module, which is used to acquire the maximum real-time signal frequency; An identification module, which is used to determine the relationship between the maximum real-time signal frequency and the signal frequency threshold to identify the type of ferromagnetic resonance; The control module is used to select and control the disconnection or connection of the zinc oxide nonlinear resistor according to the type of ferromagnetic resonance to suppress the ferromagnetic resonance.

8. The detuning system based on connecting the primary neutral point of the PT to a zinc oxide nonlinear resistor according to claim 7, characterized in that: The acquisition module includes a zero-sequence voltage detector located at the opening of the secondary side of the PT and a zero-sequence current detector located at the neutral point of the primary side of the PT.

9. The detuning system based on connecting the primary neutral point of the PT to a zinc oxide nonlinear resistor according to claim 7, characterized in that: The zinc oxide nonlinear resistor comprises a zinc oxide nonlinear resistor 1 and an oxidative nonlinear resistor 2. The volt-ampere characteristic of the zinc oxide nonlinear resistor 1 is inconsistent with the volt-ampere characteristic of the oxidative nonlinear resistor 2.

10. The detuning system based on connecting the primary neutral point of the PT to a zinc oxide nonlinear resistor according to claim 7, characterized in that: The control module comprises an insulated gate bipolar transistor, which is used for controlling the disconnection or connection of the zinc oxide nonlinear resistor.

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