A method, medium, device and system for detecting high-frequency fault current of an inverter

Abstract

The application discloses an inverter high-frequency fault current detection method, medium, equipment and system. The method comprises the following steps: a first current directly output by an inverter passes through a magnetic core window of a current sensor in a first direction; a second current formed after the first current is low-pass filtered by a filter circuit passes through the magnetic core window of the same current sensor in a second direction opposite to the first direction; a high-frequency detection signal output by the current sensor is processed and compared with a set dynamic threshold value; if the high-frequency detection signal exceeds the dynamic threshold value and the duration exceeds a set value, it is determined that the inverter has a fault. The system, the equipment and the medium are used to implement the above method. The application has the beneficial effects that: since the current sensor actually only detects high-frequency ripple current, the sensor magnetic core and the coil can be made smaller, so that the sensor volume and cost are reduced; since no additional signal processing is required to separate the power frequency and high-frequency current, the detection difficulty is reduced.

Description

Technical Field

[0001] This application relates to the field of new energy power generation technology, and in particular to a method, medium, equipment and system for detecting high-frequency fault current in inverters. Background Technology

[0002] In power electronic devices such as photovoltaic inverters and energy storage converters, accurate detection of AC-side fault current is crucial for the safe operation of the system. Traditional fault current detection methods typically involve installing a current sensor on the AC side to directly measure the total current, which includes both power frequency and high-frequency ripple components. The total current is then analyzed to determine whether a fault has occurred or if potential faults exist in the system. However, in practical applications, traditional fault current detection methods have the following drawbacks:

[0003] (1) Detecting high-frequency components requires a wideband sensor, which is usually large and expensive.

[0004] (2) The amplitude of the power frequency current is much greater than that of the high frequency ripple, which leads to high requirements for the dynamic range of the sensor.

[0005] (3) Extracting weak high-frequency signals under strong power frequency background is difficult and the signal-to-noise ratio is low. For example, in the traditional scheme, a standard voltage output current transformer is used for current detection, and its primary and secondary sides follow a fixed turns ratio relationship. When a large power frequency current passes through the primary side, the secondary side current is designed to be very small in order to obtain a standard voltage signal on the secondary side, resulting in significant signal attenuation. If the primary side current also contains a small high-frequency ripple component, the high-frequency component will also be attenuated by the same proportion and become extremely weak on the secondary side. Therefore, the high-frequency signal is masked by the power frequency signal, and the signal-to-noise ratio is extremely low. It is necessary to rely on complex subsequent signal processing circuits to extract it, which significantly increases the system complexity and detection difficulty.

[0006] Therefore, traditional fault current detection methods generally judge the safety and quality of energy transmission based on the amplitude, frequency and waveform distortion rate of the power frequency current. They cannot accurately identify resonant current caused by circuit distributed parameters and partial discharge caused by equipment insulation aging, because the characteristics of high-frequency harmonic components are usually more obvious. Summary of the Invention

[0007] One objective of this application is to provide a method for detecting high-frequency fault current in inverters that can solve at least one of the defects in the aforementioned background art.

[0008] Another objective of this application is to provide a system capable of implementing a method for detecting high-frequency fault current in inverters that addresses at least one of the deficiencies in the aforementioned background art.

[0009] Another object of this application is to provide a computer-readable storage medium capable of implementing a method for detecting high-frequency fault current in an inverter that addresses at least one of the deficiencies in the aforementioned background art.

[0010] Another object of this application is to provide an electronic device capable of implementing a method for detecting high-frequency fault current in an inverter that addresses at least one of the deficiencies in the aforementioned background technology.

[0011] To achieve at least one of the above objectives, one aspect of this application provides a method for detecting high-frequency fault current in an inverter, comprising the following steps: passing a first current directly output by the inverter through the core window of a current sensor along a first direction; passing a second current formed by low-pass filtering the first current through a filter circuit through the core window of the same current sensor along a second direction opposite to the first direction; processing the high-frequency detection signal output by the current sensor and comparing it with a set dynamic threshold; if the high-frequency detection signal exceeds the dynamic threshold and the duration exceeds a set value, determining that the inverter has a fault; the dynamic threshold I at the current time t. th The expression for calculating (t) is:

[0012] ;

[0013] ;

[0014] In the formula, P out (t) represents the instantaneous output active power of the inverter at time t, α represents the power-threshold proportional coefficient, and I th (0) represents the base threshold; P rated I represents the rated output power of the inverter. ripplemax (f) represents the maximum permissible value of the absolute value of the high-frequency ripple current in a specific frequency band f as a function of frequency, and β represents the safety margin coefficient; where the specific frequency band f is a resonant frequency band predetermined based on the distributed parameters of the AC side circuit of the inverter, or a partial discharge characteristic frequency band predetermined based on the aging characteristics of the equipment.

[0015] Preferably, the instantaneous output active power of the inverter is subjected to a first-order low-pass filter that attenuates the high-frequency signal components, and then substituted into the expression for the dynamic threshold for calculation.

[0016] Preferably, when the high-frequency detection signal output by the current sensor exceeds the dynamic threshold and lasts for more than 5 switching cycles, the inverter is determined to be faulty.

[0017] Another aspect of this application provides a high-frequency fault current detection system for an inverter, used to implement the aforementioned high-frequency fault current detection method for an inverter; it includes an inverter, a current sensor, and a signal processing module; the AC side of the inverter is connected to the power grid through a filter circuit; the current sensor is disposed on the AC side of the inverter such that both the input AC bus and the output AC bus of the filter circuit pass through the magnetic core window of the current sensor, and the current directions of the two AC buses within the magnetic core window are opposite; the signal processing module is signal-connected to the current sensor, used to perform absolute value processing on the high-frequency detection signal output by the current sensor and compare it with a built-in dynamic threshold; when the high-frequency detection signal exceeds the dynamic threshold and the duration exceeds a set value, the signal processing module outputs an inverter fault signal.

[0018] Preferably, when the inverter is a three-phase inverter, three current sensors are provided, and each current sensor is correspondingly provided on each phase of the AC side of the inverter, so that the current of each phase of the inverter is detected at high frequency through the corresponding current sensor.

[0019] Another aspect of this application provides a computer-readable storage medium storing a computer program; when the computer program is executed by a processor, it implements the above-described inverter high-frequency fault current detection method.

[0020] Another aspect of this application provides an electronic device including a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program to implement the above-described inverter high-frequency fault current detection method.

[0021] Compared with the prior art, the beneficial effects of this application are as follows:

[0022] Since the current sensor in this application actually only detects high-frequency ripple current, rather than the sum of the huge power frequency current and high-frequency ripple current, the sensor core and coil can be made smaller, greatly reducing the sensor size and cost. At the same time, since no additional signal processing is required to separate the power frequency and high-frequency current, the detection difficulty is reduced; and the power frequency signal can be suppressed, while the high-frequency fault component is amplified, making the fault characteristics more obvious and improving the detection sensitivity and accuracy. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the working steps of the inverter high-frequency fault current detection method in this application.

[0024] Figure 2 This is a schematic diagram showing the first and second currents passing through the magnetic core window of the current sensor in this application.

[0025] Figure 3 This is a schematic diagram of the architecture of the inverter high-frequency fault current detection system in this application.

[0026] Figure 4 This is a schematic diagram of the filter circuit in this application, which passes through the current sensor via the input and output side buses.

[0027] Figure 5 This is a schematic diagram of the working process of the inverter high-frequency fault current detection system in this application.

[0028] In the diagram: Inverter 100, Current sensor 200, Signal processing module 300, Filter circuit 400. Detailed Implementation

[0029] The present application will now be further described in conjunction with specific embodiments. It should be noted that, in the description of this specification, the use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0030] In the description of this application, it should be noted that the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., which indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of this application.

[0031] It should be noted that the terms "first," "second," etc., in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0032] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0034] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0035] One aspect of this application provides a method for detecting high-frequency fault current in an inverter, such as... Figures 1 to 3 As shown, one preferred embodiment includes the following steps: passing a first current directly output by the inverter 100 through the core window of the current sensor 200 along a first direction; passing a second current formed by low-pass filtering of the first current through the filter circuit 400 along a second direction opposite to the first direction through the core window of the same current sensor 200; processing the high-frequency detection signal output by the current sensor 200 and comparing it with a set dynamic threshold; if the high-frequency detection signal exceeds the dynamic threshold and the duration exceeds the set value, it is determined that the inverter 100 has a fault.

[0036] Understandably, the core of the technical solution in this application is to allow the currents on the input and output sides of the filter circuit 400 on the AC side of the inverter 100 to pass through the same current sensor 200 in opposite directions, thereby canceling the power frequency signals of the currents on the input and output sides of the filter circuit 400 and obtaining a high-frequency current component. By analyzing this high-frequency current component and a preset threshold, the AC side fault current of the inverter 100 can be detected.

[0037] Specifically, such as Figure 2 and Figure 3 As shown, the first current directly output from the AC side of the inverter 100, i.e., the current at the input side of the filter circuit 400, can be denoted as i1, which includes the power frequency component and the high-frequency ripple component. After the first current i1 is low-pass filtered by the filter circuit 400 (mainly including the power frequency component), the output second current is denoted as i2. The first current i1 and the second current i2 are passed through the magnetic core window of the same current sensor 200 in opposite directions.

[0038] At this moment, the total magnetic flux generated by the first current i1 on the sensor is Φ1=Φ Hf +Φ Lf1 ; where Φ Hf Φ represents the high-frequency magnetic flux, which is generated by the high-frequency component of the first current i1; Lf1 The first low-frequency magnetic flux is generated by the power frequency component of the first current i1. The total magnetic flux generated by the second current i2 on this sensor is Φ2 = Φ Lf2 ; where Φ Lf2 The second low-frequency magnetic flux is generated by the power frequency component of the second current i2. Since the filter circuit 400 only filters high-frequency ripple, the currents on the input and output sides of the filter circuit 400 correspond to the same power frequency component. Therefore, the second low-frequency magnetic flux Φ is given. Lf2 Equal to the first low-frequency magnetic flux Φ Lf1 .

[0039] Since the first current i1 and the second current i2 pass through the magnetic core window in opposite directions, the magnetic flux they establish also has opposite directions. Therefore, the net magnetic flux in the sensor core is the difference between Φ1 and Φ2, i.e., Φ1 - Φ2 = Φ Hf Since at this time only high-frequency magnetic flux Φ exists in the magnetic core. Hf Therefore, the signal detected by the current sensor 200 is the high-frequency ripple current i in the first current i1. ripple .

[0040] Since the current sensor 200 in this application only detects the high-frequency ripple current i rippleInstead of the sum of a huge power frequency current and a high-frequency ripple current, the sensor core and coil can be made smaller, significantly reducing the sensor's size and cost. At the same time, since no additional signal processing is needed to separate the power frequency and high-frequency currents, the detection difficulty is reduced; and the power frequency signal can be suppressed, while high-frequency fault components (such as specific harmonics or abrupt changes) can be amplified specifically, making the fault characteristics more obvious and improving detection sensitivity and accuracy.

[0041] In this embodiment, taking a photovoltaic system as an example, during the actual operation of inverter 100, the output power of inverter 100 will change with conditions such as sunlight and load. When the output power increases, the amplitude of the normal high-frequency ripple current will also increase accordingly (because the amplitude of the switching current increases with the output power). Therefore, comparing the high-frequency detection signal output by current sensor 200 with a fixed threshold may result in the following: if the threshold is set too low, normal ripple will frequently trigger false faults under high-power conditions; if the threshold is set too high, real minor fault signals will be missed under low-power conditions. Therefore, in this embodiment, the threshold used to determine the fault condition of inverter 100 is a dynamic threshold, calculated using the instantaneous output active power of inverter 100 at the current moment.

[0042] It's important to understand that by employing a dynamic threshold based on instantaneous output active power, the fault detection threshold automatically adapts to changes in the inverter 100's operating state. When the inverter 100's output power increases and normal ripple increases, the threshold automatically rises; when the output power decreases, the threshold automatically falls. This avoids false triggering under high-power conditions while ensuring the detection capability for minor faults under low-power conditions, achieving adaptive and reliable detection across the entire power range.

[0043] Specifically, the dynamic threshold I used at time t for comparison with the high-frequency detection signal output by the current sensor 200. th The expression for calculating (t) is:

[0044] .

[0045] In the formula, P out (t) represents the instantaneous output active power of inverter 100 at time t; α represents the power-threshold proportional coefficient, which determines the slope of the threshold change with power; I th (0) represents the base threshold, which represents the allowable ripple current amplitude under no-load or very light-load conditions, used to suppress noise and minor disturbances.

[0046] To make it easier to understand, a specific example will be used to illustrate this in detail below.

[0047] Assuming a certain model of 5kW photovoltaic inverter, the measured normal high-frequency ripple amplitude under no-load conditions is 0.05A, therefore, a basic threshold I is set. th (0) = 0.05A; the power-threshold proportionality coefficient α = 0.00012A / W was obtained through calibration. When the photovoltaic inverter outputs 3kW power, the dynamic threshold I... th (t) = 0.00012 × 3000 + 0.05 = 0.36 + 0.05 = 0.41A. If the absolute value of the high-frequency detection signal detected by the sensor exceeds 0.41A, a timing judgment is triggered. If the duration exceeds the set value, the photovoltaic inverter is determined to be faulty.

[0048] Understandably, since the power-threshold ratio coefficient α directly determines the sensitivity of the dynamic threshold to power changes, if the power-threshold ratio coefficient α is too large, the dynamic threshold will be too high, which may cause the inverter 100 to be missed in fault detection; if the power-threshold ratio coefficient α is too small, the dynamic threshold will be too small, and when the inverter 100 outputs high power, it is easy to trigger the fault alarm falsely.

[0049] Meanwhile, high-frequency faults in inverter 100 during actual operation exhibit significant frequency band characteristics. Specifically, the output side of inverter 100 contains filter inductors, capacitors, and distributed line inductors and capacitors. When system parameters are not properly matched, resonance may occur near a certain characteristic frequency (e.g., several kHz to tens of kHz). During resonance, the ripple current amplitude in that frequency band will amplify sharply, while the ripple current in other frequency bands may remain normal. If only the total high-frequency ripple amplitude is detected without distinguishing frequency bands, the resonance characteristics may be masked by the high ripple background in normal frequency bands, or conversely, normal broadband ripple may be misjudged as resonance. Furthermore, partial discharge may occur in AC cables, insulation materials, or filter capacitors as the equipment ages. Partial discharge generates steep current pulses within a very short time (nanoseconds to microseconds), with a spectrum distributed over a wide frequency range, but the energy is mainly concentrated in a certain characteristic frequency band (e.g., 1MHz to 10MHz).

[0050] Therefore, setting the power-threshold scaling factor α to a globally fixed value using traditional methods may not simultaneously meet the detection requirements of all frequency bands. If the power-threshold scaling factor α is set too small to meet the sensitivity detection requirements of the resonant frequency band, frequent false triggering may occur in the main frequency band of the switching ripple due to an excessively low threshold. Conversely, if the power-threshold scaling factor α is set too large to avoid false triggering, resonance or partial discharge faults may be missed. Therefore, in this embodiment, a frequency-related threshold function needs to be established for calculating the power-threshold scaling factor α to ensure that the power-threshold scaling factor α can achieve frequency band-based adaptive adjustment. For ease of understanding, the specific calculation process of the frequency band-based adaptive power-threshold scaling factor α will be described in detail below.

[0051] Specifically, the specific calculation expression for the power-threshold proportional coefficient α based on frequency band adaptive adjustment is as follows:

[0052] .

[0053] In the formula, P rated I represents the rated output power of inverter 100. ripplemax (f) represents the maximum permissible absolute value of high-frequency ripple current in a specific frequency band f as a function of frequency; β represents the safety margin coefficient, typically taken as 1.2 to 1.5. This value is introduced to provide a certain buffer zone for normal ripple and prevent false triggering due to slight disturbances. The specific frequency band f is either a resonant frequency band predetermined based on the distributed parameters of the inverter's AC side circuit, or a partial discharge characteristic frequency band predetermined based on the aging characteristics of the equipment.

[0054] It's important to understand that if a specific frequency band f is a resonant frequency band predetermined based on the distributed parameters of the inverter's AC side circuit, its acquisition process involves: calculating or measuring the resonant frequency of the resonant network composed of the filter circuit 400, distributed line inductance, and capacitance through impedance analysis of the AC side of the inverter 100; considering that the actual system also has bus capacitance and inductance, the resonant frequency will deviate. The actual resonant frequency point and the frequency band within a set range before and after it can be obtained as a characteristic frequency band through frequency sweep testing or modeling simulation. If a specific frequency band f is a partial discharge characteristic frequency band predetermined based on equipment aging characteristics, its acquisition process involves: directly determining the partial discharge characteristic frequency band of a specific type of equipment (such as photovoltaic cables and filter capacitors) through experimental or literature data. Within this frequency band, there is almost no switching ripple during normal operation (because it has been attenuated by filtering); once a significant high-frequency current is detected in this frequency band, it can be determined as a partial discharge fault.

[0055] It is also necessary to know that function I ripplemax(f) can be a piecewise constant function, a linear interpolation function, or an analytical expression, which can be pre-calibrated through simulation or experimental statistics. For ease of understanding, the piecewise constant function will be used as an example below to illustrate the function I through a specific example. ripplemax (f) describes the specific construction process.

[0056] In a specific example, assuming a 5kW photovoltaic inverter has a switching frequency of 10kHz and a filter circuit 400 has a cutoff frequency of 1kHz, the following frequency band characteristics can be obtained through simulation or actual measurement: In the 0~5kHz frequency band, the main components are switching ripple and its harmonics, with amplitude increasing with power. The maximum allowable absolute value of the high-frequency ripple current is 0.5A, corresponding to normal operation of the inverter 100. In the 5kHz~15kHz frequency band, resonance may occur, with the maximum allowable absolute value of the high-frequency ripple current being 0.1A, corresponding to a resonance fault. In the 15kHz~100kHz frequency band, the ripple attenuates normally with a very small amplitude, with the maximum allowable absolute value of the high-frequency ripple current being 0.05A, corresponding to general high-frequency interference. In the 1MHz~10MHz frequency band, the ripple is almost zero during normal operation, with the maximum allowable absolute value of the high-frequency ripple current being 0.01A (close to 0), corresponding to a partial discharge fault.

[0057] In this embodiment, during the actual operation of the inverter 100, due to factors such as harmonics in the grid voltage, sudden changes in the load, and sampling noise in the power calculation itself, the instantaneous output active power P of the inverter 100 varies. out (t) often contains high-frequency fluctuations. If the original power value is used directly to calculate the dynamic threshold, it will cause severe fluctuations in the dynamic threshold, leading to frequent jumps in the comparison result between the high-frequency detection signal and the dynamic threshold, decreasing system stability, and potentially causing false triggering due to a sudden drop in the dynamic threshold. Therefore, in this embodiment, it is necessary to measure the instantaneous output active power P of the inverter 100. out (t) is smoothed. Specifically, the instantaneous output active power P of inverter 100 can be smoothed. out (t) Perform a first-order low-pass filter to attenuate rapidly changing high-frequency signal components, allowing only slowly changing low-frequency signal components to pass. Then, the instantaneous output active power P after the first-order low-pass filter is calculated. out (t) is substituted into the calculation expression for the dynamic threshold for calculation.

[0058] Specifically, the instantaneous output active power after first-order low-pass filtering The expression is as follows:

[0059] .

[0060] In the formula, τ represents the time constant, which needs to be much larger than the power frequency period in order to effectively filter out the secondary power ripple caused by power frequency voltage and current fluctuations. However, it needs to be smaller than the set value of the duration required for fault judgment to avoid missing faults due to slow threshold updates. s represents the Laplace operator, which is a complex frequency domain variable. Its specific value is well known to those skilled in the art and will not be elaborated here.

[0061] In this embodiment, when determining a fault in inverter 100, both amplitude and duration exceeding the limit must be met simultaneously. The duration exceeding the limit is set to prevent false triggering due to non-faulty transient events such as brief electromagnetic interference or switching transient spikes. If the duration exceeding the limit is too short, the anti-interference capability is poor; if it is too long, the protection action is too slow after a fault occurs, potentially causing equipment damage. Therefore, a reasonable value needs to be selected that effectively filters transient disturbances while ensuring rapid protection. One preferred example is a duration exceeding the limit set to 5 switching cycles. That is, when the high-frequency detection signal output by current sensor 200 exceeds the dynamic threshold and the duration exceeds 5 switching cycles, a fault in inverter 100 can be determined.

[0062] It should be noted that the switching frequency range of a typical inverter 100 is 2kHz to 20kHz, corresponding to a switching period of 0.5ms to 0.05ms. Taking a switching frequency of 10kHz as an example, the switching period is 0.1ms; the set value for the duration exceeding the limit can be 10 switching cycles, or 1ms. Therefore, an inverter 100 fault is only determined when the high-frequency detection signal output by the current sensor 200 exceeds the dynamic threshold and lasts for more than 1ms. Generally, the duration of common electromagnetic interference spikes is several microseconds, far less than 1ms, and therefore will not trigger false alarms.

[0063] Another aspect of this application provides an inverter high-frequency fault current detection system for implementing the above-described inverter high-frequency fault current detection method; such as Figures 3 to 5As shown, one preferred embodiment includes an inverter 100, a current sensor 200, and a signal processing module 300. The AC side of the inverter 100 is connected to the power grid via a filter circuit 400. The current sensor 200 is disposed on the AC side of the inverter 100, such that both the input and output AC buses of the filter circuit 400 pass through the core window of the current sensor 200, and the current directions of the two AC buses within the core window are opposite. The signal processing module 300 is signal-connected to the current sensor 200 and performs absolute value processing on the high-frequency detection signal output by the current sensor 200, comparing it with a built-in dynamic threshold. When the high-frequency detection signal exceeds the dynamic threshold and the duration exceeds a set value, the signal processing module 300 outputs a fault signal for the inverter 100.

[0064] Specifically, taking a photovoltaic inverter as an example, the inverter 100 includes a DC / DC circuit (not shown) and a DC / AC circuit connected in series. The input side of the DC / DC circuit is connected to the output terminal of the photovoltaic module to boost the DC power output by the photovoltaic module. The input side of the DC / AC circuit is connected to the output side of the DC / DC circuit, and the DC / AC circuit is used to convert the DC power output by the DC / DC circuit into AC power for output, i.e., the first current i1. The output terminal of the DC / AC circuit is connected to the power grid through a filter circuit 400. After being filtered by the filter circuit 400, the first current i1 output by the DC / AC circuit can be converted into a second current i2 and sent to the power grid.

[0065] The current sensor 200 can be positioned on one side of the filter circuit 400, allowing the AC bus on the input side of the filter circuit 400 to pass through the current sensor 200 from left to right, while simultaneously allowing the AC bus on the output side of the filter circuit 400 to pass through the same current sensor 200 from right to left, thus reversing the first current i1 and the second current i2 corresponding to the two AC buses. At this time, the current signal detected by the current sensor 200 is a high-frequency ripple current signal.

[0066] The current sensor 200 transmits the detected high-frequency ripple current signal to the signal processing module 300. The module then performs absolute value processing on the conditioned high-frequency ripple current signal and compares it with a dynamic threshold. If the absolute value of the high-frequency ripple current signal exceeds the dynamic threshold, a timer is started to record the duration of the over-limit. When the over-limit time exceeds the set value, a fault is determined to exist.

[0067] It is understood that the specific structures and working principles of the current sensor 200, signal processing module 300, and filter circuit 400 are well known to those skilled in the art, and therefore will not be described in detail here. Commonly used current sensors 200 include current transformers, Hall effect sensors, etc.; the filter circuit 400 adopts an LC circuit; the signal processing module 300 includes amplifiers, filters, absolute value circuits, etc.

[0068] It should be noted that when the inverter 100 is a three-phase inverter, three current sensors 200 need to be set up, and each current sensor 200 is set up on each phase of the AC side of the inverter 100, so that the current of each phase of the inverter 100 is detected by the corresponding current sensor 200 at high frequency.

[0069] Another aspect of this application provides a computer-readable storage medium, in a preferred embodiment of which a computer program is stored on the storage medium; when the computer program is executed by a processor, the above-described inverter high-frequency fault current detection method is implemented.

[0070] Another aspect of this application provides an electronic device, in a preferred embodiment of which includes a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program to implement the above-described inverter high-frequency fault current detection method.

[0071] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A method for detecting high-frequency fault current in an inverter, characterized in that, Includes the following steps: The first current directly output by the inverter passes through the magnetic core window of the current sensor in the first direction; The second current, formed after the first current is low-pass filtered by the filter circuit, passes through the magnetic core window of the same current sensor in a second direction opposite to the first direction. The high-frequency detection signal output by the current sensor is processed and compared with the set dynamic threshold. If the high-frequency detection signal exceeds the dynamic threshold and the duration exceeds the set value, the inverter is determined to be faulty. The dynamic threshold I at time t th The expression for calculating (t) is: ； ； In the formula, P out (t) represents the instantaneous output active power of the inverter at time t, α represents the power-threshold proportional coefficient, and I th (0) represents the base threshold; P rated I represents the rated output power of the inverter. ripplemax (f) represents the maximum permissible value of the absolute value of the high-frequency ripple current in a specific frequency band f as a function of frequency, and β represents the safety margin coefficient; where the specific frequency band f is a resonant frequency band predetermined based on the distributed parameters of the AC side circuit of the inverter, or a partial discharge characteristic frequency band predetermined based on the aging characteristics of the equipment.

2. The inverter high-frequency fault current detection method as described in claim 1, characterized in that, The instantaneous output active power of the inverter is subjected to a first-order low-pass filter that attenuates the high-frequency signal components, and then substituted into the expression for the dynamic threshold for calculation.

3. The inverter high-frequency fault current detection method as described in claim 1, characterized in that, When the high-frequency detection signal output by the current sensor exceeds the dynamic threshold and lasts for more than 5 switching cycles, the inverter is determined to be faulty.

4. A high-frequency fault current detection system for an inverter, used to implement the high-frequency fault current detection method for an inverter as described in any one of claims 1-3, characterized in that, include: Inverter; The AC side of the inverter is connected to the power grid through a filter circuit; Current sensor; The current sensor is disposed on the AC side of the inverter, such that both the input AC bus and the output AC bus of the filter circuit pass through the magnetic core window of the current sensor, and the current directions of the two AC buses inside the magnetic core window are opposite. The signal processing module is connected to the current sensor and is used to process the absolute value of the high-frequency detection signal output by the current sensor and compare it with the built-in dynamic threshold. When the high-frequency detection signal exceeds the dynamic threshold and the duration exceeds a set value, the signal processing module outputs an inverter fault signal.

5. The inverter high-frequency fault current detection system as described in claim 4, characterized in that, When the inverter is a three-phase inverter, three current sensors are provided, and each current sensor is correspondingly provided on each phase of the AC side of the inverter, so that the current of each phase of the inverter is detected at high frequency through the corresponding current sensor.

6. An electronic device, characterized in that, It includes a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program to implement the inverter high-frequency fault current detection method as described in any one of claims 1-3.

7. A computer-readable storage medium, characterized in that, The storage medium stores a computer program; when the computer program is executed by a processor, it implements the inverter high-frequency fault current detection method as described in any one of claims 1-3.

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