Grid-connected inverter network side capacitor overcurrent detection method, device, equipment and medium

Abstract

The invention discloses a grid-connected inverter grid-side capacitor overcurrent detection method, device and equipment and a medium, and relates to the technical field of new energy power generation, and the method comprises the steps: collecting a grid-connected current signal and a power grid voltage signal of a grid-connected inverter; performing coordinate transformation on the signal to obtain a component under a two-phase rotating coordinate system, and performing high-pass filtering processing to retain a high-frequency component; calculating a discrete degree value of the high-frequency component as a characteristic signal; and comparing the discrete degree value with a preset threshold value, updating the first counter and the second counter based on a comparison result, and judging whether the grid-side capacitive current is over-current or not according to the values of the counters. According to the over-current detection circuit, the existing sampling signal of the inverter is directly utilized, over-current detection is realized through a software algorithm, a hardware current sampling circuit does not need to be additionally arranged, and the cost and complexity are reduced. Meanwhile, according to the method, a detection function is conveniently given to stock equipment through software upgrading, and applicability and economical efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of new energy power generation technology, and in particular to a method, device, equipment and medium for detecting overcurrent of grid-side capacitors in grid-connected inverters. Background Technology

[0002] With the rapid development of new energy power generation technologies, the penetration rate and single-unit capacity of distributed power sources such as photovoltaics and wind power are constantly increasing. The connection of numerous power electronic devices to the grid alters the network impedance characteristics at the point of common coupling, easily leading to high-frequency resonance problems in the system. High-frequency resonance causes high-frequency currents far exceeding the rated values ​​to flow through the grid-side filter capacitors of the grid-connected inverter, resulting in capacitor overheating or even permanent damage. Capacitor failure further deteriorates the output power quality of the inverter, increasing the harmonic content of the grid-connected current. This not only affects the reliable operation of the inverter itself but also poses a potential threat to the safety and stability of the power grid and the electrical equipment of other users at the same connection point. Therefore, real-time monitoring of the operating status of the grid-side capacitors of the grid-connected inverter and timely detection of overcurrent faults are of great significance for ensuring the safety of new energy power generation systems and the power quality of the power grid.

[0003] In existing technical solutions, traditional grid-connected inverters typically do not have dedicated overcurrent detection functionality for grid-side capacitors. If overcurrent protection for such AC capacitors is indeed required in specific application scenarios, the conventional approach is to directly add corresponding capacitor current sampling circuits to the hardware. For example, for a three-phase grid-connected inverter, three independent current sampling channels need to be configured to directly measure the current flowing through the capacitors and make a judgment. While this method is direct and effective, it inevitably increases the number of sensors, the corresponding signal conditioning circuits, and the sampling interface requirements of the controller, directly leading to increased hardware costs and system complexity. Summary of the Invention

[0004] This invention provides a method, apparatus, device, and medium for detecting overcurrent of grid-side capacitor in a grid-connected inverter. The technical problem it aims to solve is: how to provide an accurate and reliable method for detecting overcurrent of grid-side capacitor in a grid-connected inverter that does not require the addition of a dedicated hardware sampling circuit, can utilize the existing signals of the inverter through software processing, and is accurate and reliable.

[0005] In a first aspect, embodiments of the present invention provide a method for detecting overcurrent of the grid-side capacitor of a grid-connected inverter, comprising: Collect the grid-connected current signal and grid voltage signal from the grid-connected inverter; Extract feature signals reflecting the current state of the grid-side capacitors from the grid-connected current signal and the grid voltage signal; Based on the characteristic signal, it is determined whether the current of the grid-side capacitor is overcurrent.

[0006] Optionally, extracting the feature signal reflecting the current state of the grid-side capacitor from the grid-connected current signal and the grid voltage signal includes: The grid-connected current signal and the grid voltage signal are subjected to coordinate transformation to obtain the current component and voltage component in a two-phase rotating coordinate system. The current and voltage components are filtered to remove the fundamental frequency and low-frequency harmonics, while retaining the high-frequency components, to obtain the filtered current signal and the filtered voltage signal. The characteristic signal is calculated based on the filtered current signal and the filtered voltage signal.

[0007] Optionally, the filtering process is a high-pass filtering process, including: The current and voltage components are passed through a high-pass filter to remove the fundamental frequency and low-frequency harmonics, resulting in filtered current and voltage signals that contain only high-order harmonic components.

[0008] Optionally, the step of calculating the characteristic signal based on the filtered current signal and the filtered voltage signal includes: The dispersion values ​​of the filtered current signal and the filtered voltage signal are calculated respectively, and the dispersion values ​​are used as the feature signals.

[0009] Optionally, the method for calculating the dispersion value includes: For each of the filtered current signal and filtered voltage signal, a signal sequence of a preset data length is obtained, and the standard deviation of the signal sequence is calculated. The standard deviation is used as the dispersion value of the corresponding signal.

[0010] Optionally, determining whether the current of the grid-side capacitor is overcurrent based on the characteristic signal includes: Each of the discreteness values ​​is compared with its corresponding preset threshold; The first and second counters are updated based on the comparison results; wherein, when any discrete value is greater than the corresponding preset threshold, the value of the first counter increases and the value of the second counter increases; when all discrete values ​​are less than their corresponding preset thresholds, the value of the first counter decreases until it reaches zero. The value of the second counter is reset to zero every preset time period; Determine whether the value of the first counter reaches or exceeds a first preset threshold, or determine whether the value of the second counter reaches or exceeds a second preset threshold; If the value of the first counter reaches or exceeds the first set threshold, or the value of the second counter reaches or exceeds the second set threshold, then it is determined that the current of the grid-side capacitor is overcurrent.

[0011] Optionally, the grid-connected current signal is the instantaneous value of the three-phase grid-connected current, and the grid voltage signal is the instantaneous value of the three-phase grid line voltage.

[0012] Secondly, embodiments of the present invention also provide a grid-side capacitor overcurrent detection device for a grid-connected inverter, which includes a unit for performing the above-described method.

[0013] Thirdly, embodiments of the present invention also provide a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the above-described method.

[0014] Fourthly, embodiments of the present invention also provide a computer-readable storage medium storing a computer program that, when executed by a processor, can implement the above-described method.

[0015] This invention provides a method, apparatus, device, and medium for detecting overcurrent in the grid-side capacitor of a grid-connected inverter. The method includes: acquiring the grid-connected current signal and grid voltage signal of the grid-connected inverter; extracting a feature signal reflecting the current state of the grid-side capacitor from the grid-connected current signal and the grid voltage signal; and determining whether the current of the grid-side capacitor is overcurrent based on the feature signal. This invention utilizes the existing grid-connected current and grid voltage sampling signals of the grid-connected inverter and extracts the feature signal through a software algorithm to achieve overcurrent judgment, eliminating the need for additional dedicated capacitor current sampling hardware circuitry. This technical feature directly eliminates the cost of additional sensors, signal conditioning circuits, and related interfaces, reducing system complexity and hardware bill of materials costs. Furthermore, since the entire detection function is implemented based on a software algorithm, it possesses good configurability and upgradeability. For existing inverter equipment already deployed in the field but without hardware detection capabilities, grid-side capacitor overcurrent detection capability can be added through remote or local firmware upgrades, thereby extending the effective lifespan of the equipment, improving the flexibility and economy of system maintenance, and providing a basis for resolving the cost and flexibility contradiction caused by relying solely on hardware solutions. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating a grid-side capacitor overcurrent detection method for a grid-connected inverter provided in an embodiment of the present invention. Figure 2 This is a schematic block diagram of a computer device provided in an embodiment of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0020] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0021] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0022] As used in this specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [described condition or event] is detected," or "in response to detection of [described condition or event]."

[0023] Please see Figure 1 This invention provides a method for detecting overcurrent of the grid-side capacitor in a grid-connected inverter, the method comprising the following steps: S1 collects the grid-connected current signal and grid voltage signal of the grid-connected inverter.

[0024] In practice, the instantaneous values ​​of the grid-connected current signal and the grid voltage signal are synchronously acquired through pre-installed current and voltage sensors in the inverter. These sensors are typically standard hardware configurations in the inverter control system for grid-connected control and protection functions, such as a voltage sampling circuit consisting of a Hall current sensor, a resistor divider network, and an isolated operational amplifier. The acquired raw signals are then converted from analog to digital to become a discrete sequence that can be processed by a digital processor.

[0025] In this embodiment of the invention, the grid-connected current and grid voltage signals inherent in the grid-connected inverter control system are collected. These signals are necessary for the inverter to realize grid-connected control and protection functions. Therefore, existing hardware resources are directly utilized, avoiding the increase in hardware costs and system complexity caused by adding additional sensors, conditioning circuits and interfaces to detect capacitor current.

[0026] In some preferred embodiments, the grid-connected current signal is the instantaneous value of the three-phase grid-connected current, and the grid voltage signal is the instantaneous value of the three-phase grid line voltage.

[0027] In practice, three current sensors collect the instantaneous values ​​of the three-phase grid-connected current, denoted as Ia, Ib, and Ic. Simultaneously, a voltage sampling circuit collects the instantaneous values ​​of the three-phase grid line voltages, denoted as Uab, Ubc, and Uca, or the phase voltages are collected and the line voltages are calculated. These instantaneous signals are synchronously sampled at a fixed high sampling rate and converted into digital quantities. Using the three-phase instantaneous values ​​as input preserves complete three-phase system information, providing the necessary data foundation for subsequent coordinate transformations. For example, in subsequent steps, these three-phase instantaneous values ​​are converted into components in a two-phase stationary coordinate system using the Clarke transform, and then into direct-axis and quadrature-axis components in a two-phase rotating coordinate system using the Park transform. Real-time processing using instantaneous values ​​ensures the detection system's rapid response capability to dynamic processes.

[0028] This embodiment limits the use of instantaneous values ​​of three-phase grid-connected current and three-phase grid line voltage as the input signal source for the detection method. This ensures that the detection algorithm can perform calculations based on the most complete and original electrical information. Using three-phase instantaneous values, rather than effective values ​​or single-phase signals, can fully reflect the imbalance state of the three-phase system and the high-frequency dynamic characteristics of each phase. This is crucial for accurate coordinate transformation, as the correctness of the coordinate transformation algorithm depends on the simultaneous three-phase data. Complete instantaneous information allows the extracted feature signals to more comprehensively capture resonances or asymmetric disturbances that may exist in the three-phase system related to capacitor overcurrent. Furthermore, by utilizing the three-phase instantaneous values ​​that the inverter control system itself must sample for closed-loop control, the need for additional signal acquisition channels is completely avoided. This maximizes the implementation of the design intention of achieving advanced detection functions based on existing hardware, ensuring comprehensive detection results while maintaining the cost and compatibility advantages of the solution.

[0029] S2, extract the feature signal reflecting the current state of the grid-side capacitor from the grid-connected current signal and the grid voltage signal.

[0030] In practice, feature signals that indirectly and effectively reflect the operating status of the grid-side capacitor current are extracted from the collected grid-connected current signal and grid voltage signal. This extraction process is completed in a digital processor by executing a specific algorithm. Its core lies in performing mathematical transformation and feature mining on the original signal to highlight the modal information associated with capacitor overcurrent, rather than directly measuring the capacitor current itself.

[0031] In some preferred embodiments, extracting the feature signal reflecting the current state of the grid-side capacitor from the grid-connected current signal and the grid voltage signal includes: performing coordinate transformation on the grid-connected current signal and the grid voltage signal to obtain current components and voltage components in a two-phase rotating coordinate system; filtering the current components and voltage components to remove the fundamental wave and low-frequency harmonics, and retaining high-frequency components to obtain filtered current signals and filtered voltage signals; and calculating the feature signal based on the filtered current signals and the filtered voltage signals.

[0032] In practice, the first step is to perform coordinate transformation on the acquired instantaneous values ​​of the three-phase grid current and the three-phase grid voltage. Specifically, a combination of Clarke and Parker transforms is used to convert the three-phase AC quantities in the time domain to a two-phase rotating coordinate system, obtaining the direct-axis current component, quadrature-axis current component, direct-axis voltage component, and quadrature-axis voltage component. This transformation converts the time-varying AC signal into a relatively stable DC component, facilitating subsequent processing.

[0033] Next, the current and voltage components obtained after coordinate transformation are filtered. The purpose of this filtering is to remove the fundamental component and lower-order characteristic harmonic components from the signal. These components mainly reflect the steady-state power transmission of the system and have low correlation with high-frequency overcurrent of the capacitor. By filtering out these low-frequency components, high-frequency components that may be caused by resonance or other reasons can be effectively highlighted.

[0034] Then, based on the high-frequency current signal and high-frequency voltage signal obtained after filtering, a characteristic signal for characterizing the capacitor current state is calculated. This calculation process aims to quantify certain statistical characteristics or mathematical features of the high-frequency signal, such as calculating its fluctuation intensity, energy, or amplitude of a specific frequency band. This invention is not specifically limited, thereby condensing the time-domain waveform information into one or more feature values ​​that can be used for threshold comparison.

[0035] This embodiment constructs an effective processing path from the original sampled signal to a signal characterizing high-frequency state features by introducing coordinate transformation and targeted filtering. Coordinate transformation decouples the three-phase AC signal into a DC component that is easier to analyze, laying the foundation for independent filtering and feature extraction of specific current and voltage components directly in a rotating coordinate system. Filtering, especially the removal of the fundamental frequency and low-frequency harmonics, effectively suppresses interference from the dominant signal components under normal operating conditions, thereby enhancing the ability to extract weak signal components implicit in the high-frequency band that characterize potential resonance or abnormal overcurrent. This series of processing steps makes it possible to indirectly and accurately capture electrical features strongly correlated with grid-side capacitor overcurrent from conventional sampled signals, improving the inherent sensitivity and reliability of the detection method.

[0036] In some preferred embodiments, the filtering process is a high-pass filtering process, which includes passing the current component and voltage component through a high-pass filter to filter out the fundamental frequency and low-frequency harmonics, and obtaining a filtered current signal and a filtered voltage signal containing only high-order harmonic components.

[0037] In practice, a digital high-pass filter is designed and applied in the digital signal processor to filter the direct-axis current component, quadrature-axis current component, and direct-axis voltage component, as well as the quadrature-axis voltage component. The cutoff frequency of this high-pass filter needs to be appropriately set to ensure effective filtering of the power frequency fundamental wave and its main low-order harmonics, while retaining high-order harmonic components that may be caused by system resonance or switching frequency ripple. For example, the cutoff frequency can be set to a specific value several times higher than the power grid fundamental frequency. After processing by this high-pass filter, the DC and low-frequency AC components in the original signal are significantly attenuated, and the output signal mainly consists of filtered current and voltage signals containing high-order harmonic components. These high-frequency components are key information carriers for analyzing abnormal grid-side capacitor currents.

[0038] This embodiment explicitly defines the filtering process as high-pass filtering, providing a concrete and efficient technical means for signal preprocessing before feature extraction. A high-pass filter can systematically remove low-frequency components from the signal that are irrelevant to capacitor overcurrent detection or cause significant interference, including the fundamental component used for energy transfer. This allows subsequent processing stages to focus on the high-frequency band of the signal, where signal variations are often directly related to the resonance phenomenon, switching behavior, and abnormal current stress of the capacitor in power electronic systems. High-pass filtering effectively improves the signal-to-noise ratio, making the high-frequency characteristics representing the capacitor overcurrent state stand out from the strong background signal. This lays a clear signal foundation for accurate calculation of feature signals and enhances the targeting and extraction efficiency of the detection method for high-frequency fault features.

[0039] In some preferred embodiments, the step of calculating the feature signal based on the filtered current signal and the filtered voltage signal includes: calculating the dispersion value of the filtered current signal and the filtered voltage signal respectively, and using the dispersion value as the feature signal.

[0040] In practice, the dispersion of the high-frequency signals obtained after high-pass filtering—namely, the direct-axis current high-frequency signal, the quadrature-axis current high-frequency signal, the direct-axis voltage high-frequency signal, and the quadrature-axis voltage high-frequency signal—is calculated. The dispersion value is a statistic used to quantify the volatility or dispersion of a data sequence. During calculation, each filtered high-frequency signal is treated as a data sequence, and a value representing the range of fluctuation of that sequence around its mean is obtained through specific statistical operations. A larger dispersion value indicates more drastic fluctuations in the corresponding high-frequency signal; conversely, a smaller value indicates greater stability. Finally, the four calculated dispersion values ​​are combined to form a set of characteristic signals reflecting the state of the grid-side capacitor current.

[0041] This embodiment uses the dispersion value as a feature signal, providing a stable and sensitive quantitative indicator for judging the overcurrent state of the capacitor. When the grid-side capacitor experiences overcurrent due to resonance or other reasons, the high-frequency current flowing through the capacitor increases sharply. This change couples to the high-frequency components of the grid voltage and grid-connected current, leading to a significant increase in their volatility. The dispersion value, such as variance or standard deviation, can accurately capture this change in volatility. Compared with directly using the instantaneous amplitude or the amplitude of a certain harmonic, the dispersion value summarizes the overall fluctuation pattern of the signal, has the ability to respond to both periodic and non-periodic high-frequency disturbances, and is less affected by a single abnormal sampling point, thus being more robust. This technical feature enables the detection method to transform complex time-domain waveform information into a concise and effective feature scalar, facilitating stable comparison with a threshold.

[0042] In some preferred embodiments, the method for calculating the degree of dispersion includes: for each of the filtered current signal and the filtered voltage signal, obtaining a signal sequence of a preset data length, calculating the standard deviation of the signal sequence, and using the standard deviation as the degree of dispersion value of the corresponding signal.

[0043] In practice, the method for calculating the dispersion value is specifically implemented as calculating the standard deviation of the signal sequence. Specifically, for each filtered high-frequency signal to be calculated, such as a direct-axis current high-frequency signal, a first-in-first-out (FIFO) data buffer of length N is maintained in the digital processor. Each time a new sampling point arrives, the buffer is updated, and the standard deviation of the sequence is calculated in real time based on the N data points in the current buffer. The standard deviation is calculated as the square root of the average of the squares of the differences between each data point in the sequence and the sequence mean. This calculation process is repeated cyclically, continuously outputting the latest dispersion value for each high-frequency signal. The selection of the preset data length N requires a trade-off between response speed and statistical stability; for example, a number of sampling points corresponding to several fundamental cycles or a specific time window can be selected. By calculating the standard deviation, the fluctuation amplitude of the high-frequency signal around its average level can be objectively and quantitatively measured, and this can be output as the dispersion value.

[0044] Specifically, let x(i) represent the value of the i-th sampling point in the signal sequence (any one of the direct-axis current high-frequency signal, quadrature-axis current high-frequency signal, direct-axis voltage high-frequency signal, and quadrature-axis voltage high-frequency signal), where i ranges from 1 to N, and N is a positive integer. Calculate the algebraic sum of all sampled values ​​in the signal sequence, denoted as Sum_x, i.e., Sum_x = x(1) + x(2) + ... + x(N).

[0045] Simultaneously, the algebraic sum of the squares of all sampled values ​​in the sequence is calculated and denoted as Sum_x2.

[0046] Sum_x2=[x(1)]^2+[x(2)]^2+...+[x(N)]^2.

[0047] Subsequently, the standard deviation σ of the signal sequence is calculated based on the above two sums, and the formula is as follows: σ=sqrt((Sum_x2 / N)-(Sum_x / N)^2) In this formula, Sum_x² / N represents the arithmetic mean of the squares of the signal sequence, and Sum_x / N represents the arithmetic mean of the signal sequence itself. The difference between the two terms, (Sum_x² / N) - (Sum_x / N)², is the variance of the signal sequence. Taking the square root of the variance yields the standard deviation σ.

[0048] The standard deviation σ is a statistic used to quantify the dispersion or fluctuation range of a digital signal sequence around its mean. The input signal x(i) is a component reflecting the high-frequency state (e.g., high-frequency signals of direct-axis current, quadrature-axis current, direct-axis voltage, or quadrature-axis voltage) obtained after coordinate transformation and high-pass filtering. When the grid-side capacitor current is normal, the relevant high-frequency components fluctuate smoothly, and the calculated standard deviation σ remains at a low baseline level. When the grid-side capacitor experiences overcurrent due to system resonance or other reasons, the oscillation of the relevant high-frequency components intensifies, leading to increased dispersion of the signal sequence and a significant increase in the calculated standard deviation σ. Therefore, this standard deviation σ is extracted as a key characteristic signal characterizing the grid-side capacitor current state; its numerical change directly indicates the overcurrent risk, providing a core basis for subsequent software logic judgments.

[0049] This embodiment explicitly uses standard deviation as the specific calculation method for the degree of dispersion, providing a feature extraction method that is easy to implement in engineering and has a rigorous mathematical definition. Standard deviation is a classic indicator in probability theory and statistics for measuring the degree of data dispersion. Its calculation process is standardized and can be efficiently implemented in digital signal processors through iterative algorithms, meeting real-time requirements. By calculating the standard deviation of the signal within a continuous sampling window, instantaneous noise interference can be effectively smoothed, reflecting the average intensity of signal fluctuations within that time period. When the capacitor current is normal, the high-frequency component fluctuations are gentle, and the standard deviation remains at a low level; when overcurrent occurs, high-frequency oscillations intensify, and the standard deviation value increases significantly. This clear correspondence makes standard deviation a very direct and reliable feature quantity, used to transform the time-domain energy intensity information of high-frequency signals into a stable scalar value, creating conditions for subsequently setting a unified threshold for judgment.

[0050] S3, determine whether the current of the grid-side capacitor is overcurrent based on the characteristic signal.

[0051] In practice, the current of the grid-side capacitor is judged to be in an overcurrent state based on the extracted characteristic signals. This judgment process compares and decides based on preset logic rules and thresholds. When the judgment logic determines that the characteristic signal indicates an overcurrent risk, it outputs an overcurrent fault flag, and the inverter control system can then execute corresponding protection actions, such as derating operation or shutdown alarm.

[0052] This invention utilizes the existing grid-connected current and grid voltage sampling signals of the grid-connected inverter and extracts characteristic signals through software algorithms to achieve overcurrent detection, eliminating the need for additional dedicated capacitor current sampling hardware circuitry. This technical feature directly eliminates the cost of additional sensors, signal conditioning circuits, and related interfaces, reducing system complexity and hardware bill of materials costs. Furthermore, since the entire detection function is implemented based on software algorithms, it possesses excellent configurability and upgradeability. For existing inverter equipment already deployed in the field but without hardware detection capabilities, grid-side capacitor overcurrent detection capabilities can be added through remote or local firmware upgrades, thereby extending the effective lifespan of the equipment, improving the flexibility and economy of system maintenance, and providing a foundation for resolving the cost and flexibility contradiction caused by relying solely on hardware solutions.

[0053] In some preferred embodiments, determining whether the current of the grid-side capacitor is overcurrent based on the feature signal includes: comparing each discrete value with its corresponding preset threshold; updating a first counter and a second counter according to the comparison result; wherein, when any discrete value is greater than the corresponding preset threshold, the value of the first counter increases, and the value of the second counter increases; when all discrete values ​​are less than their corresponding preset thresholds, the value of the first counter decreases until it reaches zero; resetting the value of the second counter to zero every preset time period; determining whether the value of the first counter reaches or exceeds a first preset threshold, or determining whether the value of the second counter reaches or exceeds a second preset threshold; if the value of the first counter reaches or exceeds the first preset threshold, or the value of the second counter reaches or exceeds the second preset threshold, then it is determined that the current of the grid-side capacitor is overcurrent.

[0054] In practice, each calculated dispersion value is first compared with a pre-set corresponding threshold. These pre-set thresholds are determined based on the statistical characteristics or experimental data of the dispersion of high-frequency signals under normal operating conditions, and are not specifically limited in this invention.

[0055] Based on the comparison results, two independent counters are updated in parallel: the first counter and the second counter. The update rules are as follows: Within each judgment period, if any of the four discrete values ​​is greater than its corresponding preset threshold, the current count value of the first counter is increased by one step, and the current count value of the second counter is also increased by one step; if all discrete values ​​are less than their corresponding preset thresholds, the current count value of the first counter is decreased by one step, but its value is guaranteed not to be lower than zero. The second counter is managed according to an independent time rule: every fixed preset time period, the value of the second counter is reset to zero, regardless of its current value.

[0056] Finally, the judgment logic is executed: after each counter update, it is determined whether the value of the first counter reaches or exceeds the first set threshold, and simultaneously, it is determined whether the value of the second counter reaches or exceeds the second set threshold. If either of these two conditions is met, i.e., the first counter exceeds the limit or the second counter exceeds the limit, it is immediately determined that the grid-side capacitor current has exceeded the limit, triggering a fault signal.

[0057] This embodiment significantly improves the accuracy and adaptability of overcurrent detection by designing a dual-counter decision mechanism with different response characteristics. The increment and decrement rules of the first counter give it the characteristics of integral accumulation and release, enabling it to identify persistent minor overcurrent signs. An alarm is only triggered when overcurrent characteristics occur frequently over a prolonged period and the accumulated value exceeds a first set threshold. This effectively filters out occasional transient interference, prevents false alarms, and enhances the reliability of detecting chronic, progressive overcurrent risks. The second counter, combined with a periodic zeroing mechanism, forms a short-term observation window. It is specifically designed to capture sudden, severe overcurrent events. Even if the event is short-lived, the count value may rapidly climb and exceed the second set threshold within a zeroing cycle, thus quickly triggering protection. This dual-path parallel decision logic combines the advantages of long-term accumulation criteria and short-term rapid criteria, enabling the detection system to robustly handle continuous anomalies while responding sensitively to sudden faults, comprehensively covering overcurrent risks at different time scales and greatly improving the overall performance of the protection system.

[0058] Corresponding to the above-described method for detecting overcurrent in the grid-side capacitor of a grid-connected inverter, the present invention also provides a device for detecting overcurrent in the grid-side capacitor of a grid-connected inverter. This device includes a unit for executing the above-described method for detecting overcurrent in the grid-side capacitor of a grid-connected inverter, and can be configured in a terminal or server. Specifically, the device includes: The acquisition unit is used to acquire the grid-connected current signal and grid voltage signal of the grid-connected inverter; The extraction unit is used to extract feature signals reflecting the current state of the grid-side capacitor from the grid-connected current signal and the grid voltage signal; The judgment unit is used to determine whether the current of the grid-side capacitor is overcurrent based on the characteristic signal.

[0059] In some preferred embodiments, extracting the feature signal reflecting the current state of the grid-side capacitor from the grid-connected current signal and the grid voltage signal includes: The grid-connected current signal and the grid voltage signal are subjected to coordinate transformation to obtain the current component and voltage component in a two-phase rotating coordinate system. The current and voltage components are filtered to remove the fundamental frequency and low-frequency harmonics, while retaining the high-frequency components, to obtain the filtered current signal and the filtered voltage signal. The characteristic signal is calculated based on the filtered current signal and the filtered voltage signal.

[0060] In some preferred embodiments, the filtering process is a high-pass filtering process, including: The current and voltage components are passed through a high-pass filter to remove the fundamental frequency and low-frequency harmonics, resulting in filtered current and voltage signals that contain only high-order harmonic components.

[0061] In some preferred embodiments, calculating the characteristic signal based on the filtered current signal and the filtered voltage signal includes: The dispersion values ​​of the filtered current signal and the filtered voltage signal are calculated respectively, and the dispersion values ​​are used as the feature signals.

[0062] In some preferred embodiments, the method for calculating the degree of dispersion includes: For each of the filtered current signal and filtered voltage signal, a signal sequence of a preset data length is obtained, and the standard deviation of the signal sequence is calculated. The standard deviation is used as the dispersion value of the corresponding signal.

[0063] In some preferred embodiments, determining whether the current of the grid-side capacitor is overcurrent based on the characteristic signal includes: Each of the discreteness values ​​is compared with its corresponding preset threshold; The first and second counters are updated based on the comparison results; wherein, when any discrete value is greater than the corresponding preset threshold, the value of the first counter increases and the value of the second counter increases; when all discrete values ​​are less than their corresponding preset thresholds, the value of the first counter decreases until it reaches zero. The value of the second counter is reset to zero every preset time period; Determine whether the value of the first counter reaches or exceeds a first preset threshold, or determine whether the value of the second counter reaches or exceeds a second preset threshold; If the value of the first counter reaches or exceeds the first set threshold, or the value of the second counter reaches or exceeds the second set threshold, then it is determined that the current of the grid-side capacitor is overcurrent.

[0064] In some preferred embodiments, the grid-connected current signal is the instantaneous value of the three-phase grid-connected current, and the grid voltage signal is the instantaneous value of the three-phase grid line voltage.

[0065] It should be noted that those skilled in the art can clearly understand that the specific implementation process of the above-mentioned grid-connected inverter grid-side capacitor overcurrent detection device and each unit can be referred to the corresponding description in the foregoing method embodiments. For the sake of convenience and brevity, it will not be repeated here.

[0066] The aforementioned grid-side capacitor overcurrent detection device for grid-connected inverters can be implemented as a computer program, which can, for example... Figure 2 It runs on the computer device shown.

[0067] Please see Figure 2 , Figure 2 This is a schematic block diagram of a computer device provided in an embodiment of this application. The computer device 500 can be a terminal or a server, wherein the server can be a standalone server or a server cluster composed of multiple servers.

[0068] The computer device 500 includes a processor 502, a memory, and a network interface 505 connected via a system bus 501. The memory may include a non-volatile storage medium 503 and internal memory 504.

[0069] The non-volatile storage medium 503 can store an operating system 5031 and a computer program 5032. When the computer program 5032 is executed, it causes the processor 502 to execute a method for detecting overcurrent of the grid-side capacitor of a grid-connected inverter.

[0070] The processor 502 provides computing and control capabilities to support the operation of the entire computer device 500.

[0071] The internal memory 504 provides an environment for the operation of the computer program 5032 in the non-volatile storage medium 503. When the computer program 5032 is executed by the processor 502, the processor 502 can execute a grid-connected inverter grid-side capacitor overcurrent detection method.

[0072] The network interface 505 is used for network communication with other devices. Those skilled in the art will understand that the above structure is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device 500 to which the present application is applied. A specific computer device 500 may include more or fewer components than shown in the figures, or combine certain components, or have different component arrangements.

[0073] The processor 502 is used to run a computer program 5032 stored in the memory to perform the following steps: Collect the grid-connected current signal and grid voltage signal from the grid-connected inverter; Extract feature signals reflecting the current state of the grid-side capacitors from the grid-connected current signal and the grid voltage signal; Based on the characteristic signal, it is determined whether the current of the grid-side capacitor is overcurrent.

[0074] In some preferred embodiments, extracting the feature signal reflecting the current state of the grid-side capacitor from the grid-connected current signal and the grid voltage signal includes: The grid-connected current signal and the grid voltage signal are subjected to coordinate transformation to obtain the current component and voltage component in a two-phase rotating coordinate system. The current and voltage components are filtered to remove the fundamental frequency and low-frequency harmonics, while retaining the high-frequency components, to obtain the filtered current signal and the filtered voltage signal. The characteristic signal is calculated based on the filtered current signal and the filtered voltage signal.

[0075] In some preferred embodiments, the filtering process is a high-pass filtering process, including: The current and voltage components are passed through a high-pass filter to remove the fundamental frequency and low-frequency harmonics, resulting in filtered current and voltage signals that contain only high-order harmonic components.

[0076] In some preferred embodiments, calculating the characteristic signal based on the filtered current signal and the filtered voltage signal includes: The dispersion values ​​of the filtered current signal and the filtered voltage signal are calculated respectively, and the dispersion values ​​are used as the feature signals.

[0077] In some preferred embodiments, the method for calculating the degree of dispersion includes: For each of the filtered current signal and filtered voltage signal, a signal sequence of a preset data length is obtained, and the standard deviation of the signal sequence is calculated. The standard deviation is used as the dispersion value of the corresponding signal.

[0078] In some preferred embodiments, determining whether the current of the grid-side capacitor is overcurrent based on the characteristic signal includes: Each of the discreteness values ​​is compared with its corresponding preset threshold; The first and second counters are updated based on the comparison results; wherein, when any discrete value is greater than the corresponding preset threshold, the value of the first counter increases and the value of the second counter increases; when all discrete values ​​are less than their corresponding preset thresholds, the value of the first counter decreases until it reaches zero. The value of the second counter is reset to zero every preset time period; Determine whether the value of the first counter reaches or exceeds a first preset threshold, or determine whether the value of the second counter reaches or exceeds a second preset threshold; If the value of the first counter reaches or exceeds the first set threshold, or the value of the second counter reaches or exceeds the second set threshold, then it is determined that the current of the grid-side capacitor is overcurrent.

[0079] In some preferred embodiments, the grid-connected current signal is the instantaneous value of the three-phase grid-connected current, and the grid voltage signal is the instantaneous value of the three-phase grid line voltage.

[0080] It should be understood that in the embodiments of this application, the processor 502 may be a central processing unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0081] It will be understood by those skilled in the art 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 may be stored in a storage medium, which is a computer-readable storage medium. The computer program is executed by at least one processor in the computer system to implement the process steps of the embodiments of the above methods.

[0082] Therefore, the present invention also provides a storage medium. This storage medium can be a computer-readable storage medium. The storage medium stores a computer program. When executed by a processor, the computer program causes the processor to perform the following steps: Collect the grid-connected current signal and grid voltage signal from the grid-connected inverter; Extract feature signals reflecting the current state of the grid-side capacitors from the grid-connected current signal and the grid voltage signal; Based on the characteristic signal, it is determined whether the current of the grid-side capacitor is overcurrent.

[0083] In some preferred embodiments, extracting the feature signal reflecting the current state of the grid-side capacitor from the grid-connected current signal and the grid voltage signal includes: The grid-connected current signal and the grid voltage signal are subjected to coordinate transformation to obtain the current component and voltage component in a two-phase rotating coordinate system. The current and voltage components are filtered to remove the fundamental frequency and low-frequency harmonics, while retaining the high-frequency components, to obtain the filtered current signal and the filtered voltage signal. The characteristic signal is calculated based on the filtered current signal and the filtered voltage signal.

[0084] In some preferred embodiments, the filtering process is a high-pass filtering process, including: The current and voltage components are passed through a high-pass filter to remove the fundamental frequency and low-frequency harmonics, resulting in filtered current and voltage signals that contain only high-order harmonic components.

[0085] In some preferred embodiments, calculating the characteristic signal based on the filtered current signal and the filtered voltage signal includes: The dispersion values ​​of the filtered current signal and the filtered voltage signal are calculated respectively, and the dispersion values ​​are used as the feature signals.

[0086] In some preferred embodiments, the method for calculating the degree of dispersion includes: For each of the filtered current signal and filtered voltage signal, a signal sequence of a preset data length is obtained, and the standard deviation of the signal sequence is calculated. The standard deviation is used as the dispersion value of the corresponding signal.

[0087] In some preferred embodiments, determining whether the current of the grid-side capacitor is overcurrent based on the characteristic signal includes: Each of the discreteness values ​​is compared with its corresponding preset threshold; The first and second counters are updated based on the comparison results; wherein, when any discrete value is greater than the corresponding preset threshold, the value of the first counter increases and the value of the second counter increases; when all discrete values ​​are less than their corresponding preset thresholds, the value of the first counter decreases until it reaches zero. The value of the second counter is reset to zero every preset time period; Determine whether the value of the first counter reaches or exceeds a first preset threshold, or determine whether the value of the second counter reaches or exceeds a second preset threshold; If the value of the first counter reaches or exceeds the first set threshold, or the value of the second counter reaches or exceeds the second set threshold, then it is determined that the current of the grid-side capacitor is overcurrent.

[0088] In some preferred embodiments, the grid-connected current signal is the instantaneous value of the three-phase grid-connected current, and the grid voltage signal is the instantaneous value of the three-phase grid line voltage.

[0089] The storage medium is a physical, non-transient storage medium, such as a USB flash drive, external hard drive, read-only memory (ROM), magnetic disk, or optical disk, or any other physical storage medium capable of storing program code. The computer-readable storage medium can be non-volatile or volatile.

[0090] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0091] In the several embodiments provided by this invention, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For example, the division of each unit is merely a logical functional division, and there may be other division methods in actual implementation. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0092] The steps in the method of this invention can be adjusted, merged, or reduced in order according to actual needs. The units in the device of this invention can be merged, divided, or reduced according to actual needs. Furthermore, the functional units in the various embodiments of this invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0093] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, a terminal, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention.

[0094] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0095] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Since these modifications and variations fall within the scope of the claims and their equivalents, this invention also intends to include these modifications and variations.

[0096] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for detecting overcurrent of the grid-side capacitor in a grid-connected inverter, characterized in that, include: Collect the grid-connected current signal and grid voltage signal from the grid-connected inverter; Extract feature signals reflecting the current state of the grid-side capacitors from the grid-connected current signal and the grid voltage signal; Based on the characteristic signal, it is determined whether the current of the grid-side capacitor is overcurrent.

2. The method for detecting overcurrent of the grid-side capacitor of a grid-connected inverter according to claim 1, characterized in that, The extraction of feature signals reflecting the current state of the grid-side capacitor from the grid-connected current signal and the grid voltage signal includes: The grid-connected current signal and the grid voltage signal are subjected to coordinate transformation to obtain the current component and voltage component in a two-phase rotating coordinate system. The current and voltage components are filtered to remove the fundamental frequency and low-frequency harmonics, while retaining the high-frequency components, to obtain the filtered current signal and the filtered voltage signal. The characteristic signal is calculated based on the filtered current signal and the filtered voltage signal.

3. The method for detecting overcurrent of the grid-side capacitor of a grid-connected inverter according to claim 2, characterized in that, The filtering process is a high-pass filtering process, including: The current and voltage components are passed through a high-pass filter to remove the fundamental frequency and low-frequency harmonics, resulting in filtered current and voltage signals that contain only high-order harmonic components.

4. The method for detecting overcurrent of the grid-side capacitor of a grid-connected inverter according to claim 3, characterized in that, The process of calculating the characteristic signal based on the filtered current signal and the filtered voltage signal includes: The dispersion values ​​of the filtered current signal and the filtered voltage signal are calculated respectively, and the dispersion values ​​are used as the feature signals.

5. The method for detecting overcurrent of the grid-side capacitor of a grid-connected inverter according to claim 4, characterized in that, The method for calculating the degree of dispersion includes: For each of the filtered current signal and filtered voltage signal, a signal sequence of a preset data length is obtained, and the standard deviation of the signal sequence is calculated. The standard deviation is used as the dispersion value of the corresponding signal.

6. The method for detecting overcurrent of the grid-side capacitor of a grid-connected inverter according to claim 5, characterized in that, The step of determining whether the current of the grid-side capacitor is overcurrent based on the characteristic signal includes: Each of the discreteness values ​​is compared with its corresponding preset threshold; The first and second counters are updated based on the comparison results; wherein, when any discrete value is greater than the corresponding preset threshold, the value of the first counter increases and the value of the second counter increases; when all discrete values ​​are less than their corresponding preset thresholds, the value of the first counter decreases until it reaches zero. The value of the second counter is reset to zero every preset time period; Determine whether the value of the first counter reaches or exceeds a first preset threshold, or determine whether the value of the second counter reaches or exceeds a second preset threshold; If the value of the first counter reaches or exceeds the first set threshold, or the value of the second counter reaches or exceeds the second set threshold, then it is determined that the current of the grid-side capacitor is overcurrent.

7. The method for detecting overcurrent of the grid-side capacitor of a grid-connected inverter according to any one of claims 1 to 6, characterized in that, The grid-connected current signal is the instantaneous value of the three-phase grid-connected current, and the grid voltage signal is the instantaneous value of the three-phase grid line voltage.

8. A grid-side capacitor overcurrent detection device for a grid-connected inverter, characterized in that, Includes a unit for performing the method as described in any one of claims 1-7.

9. A computer device, characterized in that, The computer device includes a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the method as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The storage medium stores a computer program that, when executed by a processor, can implement the method as described in any one of claims 1-7.

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