Inverter residual leakage current abrupt change protection method and device

Abstract

The invention provides an inverter residual leakage current abrupt change protection method and device, and the method comprises the steps: carrying out the sampling of a residual leakage current signal in an inverter, and obtaining a sampling signal; determining a current reference value of the residual leakage current signal based on the sampling signal; determining a benchmark reference value of the residual leakage current signal based on the sampling signal; the current reference value is input into a first-order low-pass digital filter, level filtering values corresponding to a plurality of reference current levels are obtained, the first-order low-pass digital filter has smoothing coefficients corresponding to the plurality of reference current levels, and the smoothing coefficients are the maximum smoothing coefficients meeting the requirement delay corresponding to the reference current levels; and performing a protection action on the inverter based on comparison between the level filtering values corresponding to the plurality of reference current levels and the standard reference value. And through a multi-channel parallel filtering strategy, the filtering process is synchronous with the delay requirement, and the interference immunity of the system is ensured while quick response is realized.

Description

Technical Field

[0001] This application relates to the field of photovoltaic inverter technology, and more specifically, to a method and device for protecting inverter residual leakage current from sudden changes. Background Technology

[0002] In related technologies, the residual leakage current protection of photovoltaic inverters adopts a scheme that compares a fixed delay with a threshold. This means that the filtering and noise suppression function and the protection delay required by the standard are treated as two independent and contradictory aspects. If the interference is suppressed by enhancing the filtering, the signal establishment time will be much longer than the protection time specified by the standard, resulting in a delay in protection action. Conversely, if the filtering is weakened in order to meet the requirements of fast response, high-frequency interference cannot be effectively filtered out, resulting in insufficient system immunity. Summary of the Invention

[0003] This application aims to solve the technical problems of poor filtering and delay adaptability and low protection accuracy in existing or related technologies.

[0004] Therefore, the first aspect of this application proposes a method for protecting against sudden changes in residual leakage current in inverters.

[0005] The second aspect of this application proposes a device for protecting against sudden changes in residual leakage current in an inverter.

[0006] The third aspect of this application proposes a device for protecting against sudden changes in residual leakage current in inverters.

[0007] In view of this, according to the first aspect of this application, a method for protecting inverter residual leakage current from sudden changes is proposed, comprising: sampling the residual leakage current signal in the inverter to obtain a sampled signal; determining a current reference value of the residual leakage current signal based on the sampled signal; determining a reference value of the residual leakage current signal based on the sampled signal; inputting the current reference value into a first-order low-pass digital filter to obtain level filter values ​​corresponding to multiple reference current levels, wherein the first-order low-pass digital filter has smoothing coefficients corresponding to multiple reference current levels, and the smoothing coefficients are the maximum smoothing coefficients that meet the required delay corresponding to the reference current levels; and performing protection actions on the inverter based on the comparison between the level filter values ​​corresponding to the multiple reference current levels and the reference reference value.

[0008] The inverter residual leakage current mutation protection method provided in this application includes the following steps: First, the residual leakage current signal in the inverter is sampled to obtain a sampling signal. The residual leakage current signal refers to the vector sum of all unexpected currents flowing between the normally energized parts of the system and the ground, collected by the monitoring circuit, and is a key indicator for measuring the insulation status and operational safety of the equipment.

[0009] Then, the current reference value of the residual leakage current signal is determined based on the sampled signal. The current reference value refers to the signal obtained by preliminary processing of the residual leakage current signal in the inverter, i.e., the original sampled signal, which reflects the recent leakage current level.

[0010] The reference value of the residual leakage current signal is determined based on the sampled signal. The reference value is a stable benchmark that can reflect the inherent leakage level of the system in which the inverter is located, obtained through long-time window statistical processing.

[0011] The current reference value is input into a first-order low-pass digital filter, resulting in level-based filter values ​​for multiple reference current levels. Each first-order low-pass digital filter has a smoothing coefficient corresponding to a specific reference current level; this smoothing coefficient is the maximum smoothing coefficient that satisfies the required delay for each reference current level. Specifically, the level-based filter value obtained in this process refers to the output signal that combines anti-interference characteristics and a defined delay after processing by a first-order low-pass digital filter with a specific smoothing coefficient. Furthermore, the smoothing coefficient is a parameter controlling the filter's inertia and response speed in the first-order low-pass digital filter. The selection principle for the smoothing coefficient is to ensure that the filter's inherent delay precisely meets the standard protection time requirement for the corresponding level. By inputting the current reference value into the first-order low-pass digital filter, "signal filtering" and "protection delay" can be implemented in parallel; specifically, the first-order low-pass digital filter achieves a coordinated design of filtering and delay.

[0012] Since the time constant τ, smoothing coefficient α, and sampling period T_avg of a first-order low-pass digital filter have a definite mathematical relationship τ=-T_avg / lnα, this relationship can be used to calculate the smoothing coefficient corresponding to each level by using the protection delay requirements for different reference current levels (30mA, 60mA, 150mA) in the NB / T32004-2018 standard as constraints. The maximum smoothing coefficient that meets the required delay is selected, that is, maximizing the filter's inertia effect while ensuring the response speed meets the standard, thereby achieving optimal anti-interference performance under the constraint of fixed system resources.

[0013] In other words, the recursive calculation process of the filter can directly generate a relatively accurate inherent delay, avoiding the randomness of delay affected by task scheduling, controlling the delay error within a reasonable range, and ensuring the compliance and consistency of protection.

[0014] Specifically, the protection process involves preprocessing to initially suppress high-frequency interference above 10kHz, and then establishing a stable reference value to eliminate the effects of slow fluctuations. Next, the maximum permissible smoothing coefficient corresponding to each reference current level is calculated based on the standard protection time requirement, ensuring that the output time of the signal after processing by a specific filter meets the regulatory delay conditions. Finally, by comparing the level filter values ​​corresponding to each of the multiple reference current levels with the reference reference value, protection actions are executed on the inverter, accurately extracting pure abrupt changes and triggering corresponding protection actions.

[0015] By employing a multi-stage parallel filtering architecture and precisely designed smoothing coefficients, a balance can be achieved between anti-interference and response speed. This ensures that different levels meet different standard delays while reducing the risk of false protection. Simultaneously, the combination of a long-window reference and smoothed filter output improves the stability of abrupt change detection. Finally, through a software algorithm-based filtering-delay mechanism, precise delay control can be achieved without additional hardware circuitry, improving protection performance while reducing the cost of residual leakage current protection.

[0016] In some technical solutions, optionally, determining the current reference value of the residual leakage current signal based on the sampled signal includes: every first cycle duration, obtaining sampled values ​​of multiple sampling periods within the first cycle duration from the sampled signal; averaging the obtained sampled values ​​of multiple sampling periods to obtain the average sampled value of the first cycle duration; and determining the average sampled value of the first cycle duration at which the current time is located as the current reference value.

[0017] In this technical solution, determining the current reference value of the residual leakage current signal based on the sampled signal includes: acquiring sampled values ​​from the sampled signal for multiple sampling periods within the first cycle duration every first cycle duration; averaging the acquired sampled values ​​for multiple sampling periods to obtain the average sampled value for the first cycle duration; and determining the average sampled value of the first cycle duration at which the current time is located as the current reference value. By performing an arithmetic average operation on the continuous sampled values ​​within a fixed time window, signal components above their cutoff frequency are significantly attenuated, effectively suppressing switching noise above a certain range.

[0018] In some technical solutions, the first loop duration is optionally 20ms.

[0019] In this technical solution, the first cycle duration is 20ms, that is, the time window is set to 20ms, thereby suppressing high-frequency interference. At the same time, since the duration of 20ms is much less than the minimum delay required by each level of protection, the delay introduced in the preprocessing stage will not affect the standard protection time requirements of the entire system.

[0020] In some technical solutions, optionally, determining the reference value of the residual leakage current signal based on the sampled signal includes: obtaining the second cycle duration before the current time, the second cycle duration including multiple first cycle durations; averaging the average sampled values ​​of the multiple first cycle durations in the second cycle duration to obtain the reference value.

[0021] In this technical solution, the second cycle duration refers to a long window, such as 10 seconds, used to calculate the baseline reference value. By setting an observation window much longer than the system disturbance period, i.e., the second cycle duration, the statistical properties of the arithmetic mean are used to filter out all short-term fluctuations and disturbances. Since the second cycle duration includes multiple first cycle durations, any short-term disturbances can be sufficiently diluted during the averaging process. Simultaneously, a "first-in, first-out" sliding window update mechanism is adopted, ensuring that the baseline value reflects the latest long-term operating state of the system while avoiding the step jumps of traditional fixed-window updates. This allows the baseline reference value to accurately track the slowly changing inherent leakage level of the system, while completely suppressing the effects of transient disturbances and short-term fluctuations.

[0022] In some technical solutions, the second cycle may optionally last for 10 seconds.

[0023] In this technical solution, the second cycle duration is 10 seconds. The second cycle duration includes multiple first cycle durations. For example, if the first cycle duration is 20 ms, then the second cycle duration contains 500 consecutive average sampled values. This reduces the impact of short-term disturbances, dilutes abnormal interference, and establishes a stable reference value, which facilitates the judgment of subsequent protection actions.

[0024] In some technical solutions, optionally, the smoothing coefficients corresponding to multiple reference current levels are preset in the following way: obtaining the required delays corresponding to multiple reference current levels; establishing a filter delay function based on the first cycle duration and the smoothing coefficients; for each reference current level, solving for the maximum smoothing coefficient when the filter delay function is not greater than the required delay corresponding to the reference current level, and using it as the smoothing coefficient corresponding to the reference current level.

[0025] In this technical solution, the reference current level refers to the different fault severity levels classified according to safety standards, such as the three protection levels of 30mA, 60mA, and 150mA.

[0026] The required delay refers to the standard protection time corresponding to each reference current level. For example, the 30mA level requires less than or equal to 0.3s, the 60mA level requires less than or equal to 0.15s, and the 150mA level requires less than or equal to 0.04s.

[0027] The filter delay function is a mathematical model that describes the relationship between the inherent delay of a filter and its parameters. Specifically, the filter delay T_delay≈3τ and τ=-T_avg / lnα, where T_avg is 20ms.

[0028] The maximum smoothness coefficient is the α value that provides the strongest anti-interference capability while meeting the delay requirements. For example, for the 30mA level, the maximum α obtained by solving under the condition that T_delay≤0.3s is 0.8, which means that the optimal anti-interference parameter is selected within the compliance range.

[0029] This application transforms performance requirements into design constraints by establishing an accurate mathematical model. First, based on the step response characteristics of a first-order linear system, a functional relationship is established between the filtering delay T_delay and the smoothing coefficient α: T_delay=f(α, T_avg). Then, the standard-specified protection time is used as a constraint. Since the system's anti-interference performance increases with the increase of α, under the premise of satisfying the delay constraint, choosing the largest α value naturally corresponds to the optimal anti-interference capability.

[0030] In some technical solutions, optionally, the transfer function of the first-order low-pass digital filter at each reference current level is preset in the following way: a first transfer term is set based on the smoothing coefficient corresponding to the reference current level and the current reference value; a second transfer term is set based on the smoothing coefficient corresponding to the reference current level and the transfer function of the previous sampling period of the current sampling period; and the transfer function of the current sampling period is set based on the first transfer term and the second transfer term.

[0031] In this technical solution, the transfer function is a mathematical expression describing the relationship between the filter's input and output, specifically H(z) = (1-α) × I_20ms_avg(n) + α × H(z-1). Here, H(z) is the current output or filtered value, H(z-1) is the output at the previous time step, I_20ms_avg(n) is the current input or observed value, and α is the smoothing factor or smoothing coefficient.

[0032] The first transitive term is (1-α)×I_20ms_avg(n) in the above formula, which is the immediate contribution of the new input data, while the second transitive term corresponds to α×H(z-1) in the formula, which represents the inertial preservation of the historical output data.

[0033] The transfer function H(z) for the current sampling period is the sum of the first two sub-terms, resulting in the current output value. For example, for a 30mA level (α=0.8), when the new I_20ms_avg(n)=35mA and the previous period's H(z-1)=15mA, the first transfer sub-term is (1-0.8)×35=7mA, the second transfer sub-term is 0.8×15=12mA, and the current output H(z)=7+12=19mA.

[0034] The transfer function of the first-order low-pass digital filter at each reference current level is preset in the following way: a first transfer term is set based on the smoothing coefficient corresponding to the reference current level and the current reference value; a second transfer term is set based on the smoothing coefficient corresponding to the reference current level and the transfer function of the previous sampling period of the current sampling period; and the transfer function of the current sampling period is set based on the first and second transfer terms. That is, the design of the system inertia is controlled by adjusting the weights of the two transfer terms, so that different reference current levels can obtain the anti-interference characteristics most suitable for their protection requirements.

[0035] In some technical solutions, optionally, protection actions are performed on the inverter based on a comparison between the level filter value corresponding to each of the multiple reference current levels and the reference reference value, including: calculating the difference between the level filter value corresponding to each of the multiple reference current levels and the reference reference value; obtaining the difference threshold corresponding to each of the multiple reference current levels; and performing protection actions on the inverter if the difference corresponding to at least one reference current level is greater than the difference threshold corresponding to the reference current level.

[0036] In this technical solution, the level filter value refers to the output signal after being processed by a first-order low-pass digital filter with different smoothing coefficients. For example, the level filter values ​​correspond to the filtering results of three reference current levels: 30mA, 60mA, and 150mA.

[0037] The benchmark reference value refers to the long-term stable benchmark calculated using a 10-second sliding window.

[0038] The difference is the magnitude of the sudden change obtained by subtracting the level filter value from the reference value and taking the absolute value. The difference threshold is the protection trigger threshold preset for each reference current level, such as 28mA, 58mA, and 145mA, which are all slightly lower than the standard value to reserve a safety margin.

[0039] For example, when the filter value I_f1, which is at the 30mA level, rises to 33mA due to a fault, while the reference I_10s_avg remains at 5mA, the difference ΔI is calculated to be 28mA. When the 28mA threshold is reached, the system immediately executes the corresponding protection action.

[0040] By calculating the absolute difference between the "current filter value" and the "long-term benchmark", the influence of the system's inherent static operating point is eliminated, allowing the protection decision to focus only on the dynamically changing part, which greatly improves the detection sensitivity.

[0041] Furthermore, each reference current level has its own dedicated filter signal channel and matched threshold, forming a parallel processing link that ensures that faults of varying severity can be detected by the most suitable channel. Since the level filter values ​​have undergone filtering with a standard required delay, the difference calculation result indicates that both the sudden change amplitude and the protection delay are met the instant the limit is exceeded, thus supporting immediate protection action.

[0042] According to a second aspect of this application, an inverter residual leakage current sudden change protection device is proposed, comprising: a first sampling module, a first determining module, a second determining module, a third determining module, and a first execution module; the first sampling module is used to sample the residual leakage current signal in the inverter to obtain a sampled signal; the first determining module is used to determine the current reference value of the residual leakage current signal based on the sampled signal; the second determining module is used to determine the reference value of the residual leakage current signal based on the sampled signal; the third determining module is used to input the current reference value into a first-order low-pass digital filter to obtain level filter values ​​corresponding to multiple reference current levels, wherein the first-order low-pass digital filter has smoothing coefficients corresponding to multiple reference current levels, and the smoothing coefficients are the maximum smoothing coefficients that meet the required delay corresponding to the reference current levels; the first execution module is used to perform protection actions on the inverter based on the comparison between the level filter values ​​corresponding to the multiple reference current levels and the reference reference value.

[0043] The inverter residual leakage current sudden change protection device provided in this application includes: a first sampling module, a first determining module, a second determining module, a third determining module, and a first execution module; the first sampling module is used to sample the residual leakage current signal in the inverter to obtain a sampled signal; the first determining module is used to determine the current reference value of the residual leakage current signal based on the sampled signal; the second determining module is used to determine the reference value of the residual leakage current signal based on the sampled signal; the third determining module is used to input the current reference value into a first-order low-pass digital filter to obtain the level filter value corresponding to each of the multiple reference current levels, wherein the first-order low-pass digital filter has smoothing coefficients corresponding to the multiple reference current levels respectively, and the smoothing coefficients are the maximum smoothing coefficients that meet the required delay corresponding to the reference current levels; the first execution module is used to perform protection actions on the inverter based on the comparison between the level filter values ​​corresponding to the multiple reference current levels and the reference reference value. The multi-stage first-order low-pass digital filter in the third determination module is configured with a maximum smoothing coefficient to meet the delay requirements of each reference current level. This ensures that the inherent delay of the filtering process precisely matches the standard protection time (e.g., 30mA / 0.3s, 60mA / 0.15s, 150mA / 0.04s). While maintaining millisecond-level delay accuracy, it achieves "filtering as delay," allowing the first execution module to act immediately after judgment without additional delay. By combining the real-time preprocessing of the first determination module (e.g., 20ms averaging) with the long-term benchmark establishment of the second determination module (e.g., 10s sliding window), high-frequency interference above 10kHz is effectively suppressed, and benchmark fluctuations are controlled within ±0.5mA. This ensures that the level filter value output by the third determination module is pure and stable, eliminating false protection at the source and preventing missed judgments in critical scenarios. The device employs a multi-channel parallel processing architecture, providing independent optimized channels for different fault levels. While ensuring extremely rapid response to 150mA-level emergency faults (α=0.2), it also provides strong anti-interference capability for 30mA-level minor faults (α=0.8), achieving optimal protection performance. The entire device achieves full-function protection solely through modular algorithms, eliminating the need for external hardware circuitry and significantly reducing system cost and complexity.

[0044] According to a third aspect of this application, an inverter residual leakage current sudden change protection device is proposed, comprising a processor and a memory. The memory stores a program or instructions, and when the processor executes the program or instructions in the memory, it implements the steps of the inverter residual leakage current sudden change protection method as described in any of the above-described technical solutions. Therefore, the inverter residual leakage current sudden change protection device possesses all the beneficial effects of the inverter residual leakage current sudden change protection method as described in any of the above-described technical solutions.

[0045] Additional aspects and advantages of this application will become apparent in the following description or may be learned by practice of this application. Attached Figure Description

[0046] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0047] Figure 1 A flowchart of a method for protecting inverter residual leakage current from sudden changes, provided in some embodiments of this application, is shown.

[0048] Figure 2 The following is a schematic diagram of leakage current protection based on a 30mA transient threshold provided in some embodiments of this application;

[0049] Figure 3 The following is a schematic diagram of leakage current protection based on a 60mA transient threshold provided in some embodiments of this application;

[0050] Figure 4 The following is a schematic diagram of leakage current protection based on a 150mA transient threshold provided in some embodiments of this application;

[0051] Figure 5 This application provides a structural block diagram of one of the embodiments of an inverter residual leakage current sudden change protection device.

[0052] Figure 6 The second block diagram of a residual leakage current surge protection device for an inverter is shown in some embodiments of this application. Detailed Implementation

[0053] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, these embodiments and the features described herein can be combined with each other.

[0054] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0055] The following reference Figures 1 to 6 This application describes a method, apparatus, and readable storage medium for protecting inverter residual leakage current from sudden changes according to some embodiments.

[0056] According to one embodiment of this application, such as Figure 1 As shown, a method for protecting inverter residual leakage current from sudden changes is provided, the steps of which include:

[0057] Step 102: Sample the residual leakage current signal in the inverter to obtain the sampled signal;

[0058] Step 104: Determine the current reference value of the residual leakage current signal based on the sampled signal;

[0059] Step 106: Determine the reference value of the residual leakage current signal based on the sampled signal;

[0060] Step 108: Input the current reference value into a first-order low-pass digital filter to obtain the level filter values ​​corresponding to each of the multiple reference current levels. The first-order low-pass digital filter has smoothing coefficients corresponding to the multiple reference current levels. The smoothing coefficient is the maximum smoothing coefficient that satisfies the required delay corresponding to the reference current level.

[0061] Step 110: Based on the comparison between the level filter value corresponding to each of the multiple reference current levels and the reference reference value, perform protection actions on the inverter.

[0062] The inverter residual leakage current mutation protection method provided in this application includes the following steps: First, the residual leakage current signal in the inverter is sampled to obtain a sampling signal. The residual leakage current signal refers to the vector sum of all unexpected currents flowing between the normally energized parts of the system and the ground, collected by the monitoring circuit, and is a key indicator for measuring the insulation status and operational safety of the equipment.

[0063] Then, the current reference value of the residual leakage current signal is determined based on the sampled signal. The current reference value refers to the signal obtained by preliminary processing of the residual leakage current signal in the inverter, i.e., the original sampled signal, which reflects the recent leakage current level.

[0064] The reference value of the residual leakage current signal is determined based on the sampled signal. The reference value is a stable benchmark that can reflect the inherent leakage level of the system in which the inverter is located, obtained through long-time window statistical processing.

[0065] The current reference value is input into a first-order low-pass digital filter, resulting in level-based filter values ​​for multiple reference current levels. Each first-order low-pass digital filter has a smoothing coefficient corresponding to a specific reference current level; this smoothing coefficient is the maximum smoothing coefficient that satisfies the required delay for each reference current level. Specifically, the level-based filter value obtained in this process refers to the output signal that combines anti-interference characteristics and a defined delay after processing by a first-order low-pass digital filter with a specific smoothing coefficient. Furthermore, the smoothing coefficient is a parameter controlling the filter's inertia and response speed in the first-order low-pass digital filter. The selection principle for the smoothing coefficient is to ensure that the filter's inherent delay precisely meets the standard protection time requirement for the corresponding level. By inputting the current reference value into the first-order low-pass digital filter, "signal filtering" and "protection delay" can be implemented in parallel; specifically, the first-order low-pass digital filter achieves a coordinated design of filtering and delay.

[0066] Since the time constant, smoothing coefficient, and sampling period of a first-order low-pass filter have a definite mathematical relationship, a first-order low-pass digital filter can be used to calculate the smoothing coefficient corresponding to each level by using the protection delay requirements for different reference current levels in relevant standards as constraints. The maximum smoothing coefficient that meets the required delay is selected, that is, maximizing the filter's inertia effect while ensuring the response speed meets the standard, thereby achieving optimal anti-interference performance under the constraint of fixed system resources.

[0067] In other words, the recursive calculation process of the filter can directly generate a relatively accurate inherent delay, avoiding the randomness of delay affected by task scheduling, controlling the delay error within a reasonable range, and ensuring the compliance and consistency of protection.

[0068] Specifically, the protection process involves preprocessing to initially suppress high-frequency interference above 10kHz, and then establishing a stable reference value to eliminate the effects of slow fluctuations. Next, the maximum permissible smoothing coefficient corresponding to each reference current level is calculated based on the standard protection time requirement, ensuring that the output time of the signal after processing by a specific filter meets the regulatory delay conditions. Finally, by comparing the level filter values ​​corresponding to each of the multiple reference current levels with the reference reference value, protection actions are executed on the inverter, accurately extracting pure abrupt changes and triggering corresponding protection actions.

[0069] By employing a multi-stage parallel filtering architecture and precisely designed smoothing coefficients, a balance can be achieved between anti-interference and response speed. This ensures that different levels meet different standard delays while reducing the risk of false protection. Simultaneously, the combination of a long-window reference and smoothed filter output improves the stability of abrupt change detection. Finally, through a software algorithm-based filtering-delay mechanism, precise delay control can be achieved without additional hardware circuitry, improving protection performance while reducing the cost of residual leakage current protection.

[0070] In some embodiments, optionally, determining the current reference value of the residual leakage current signal based on the sampled signal includes: acquiring sampled values ​​of multiple sampling periods within the first cycle duration from the sampled signal every first cycle duration; averaging the acquired sampled values ​​of the multiple sampling periods to obtain an average sampled value for the first cycle duration; and determining the average sampled value of the first cycle duration at which the current time is located as the current reference value.

[0071] In this embodiment, determining the current reference value of the residual leakage current signal based on the sampled signal includes: acquiring sampled values ​​from the sampled signal for multiple sampling periods within the first cycle duration every first cycle duration; averaging the acquired sampled values ​​for the multiple sampling periods to obtain the average sampled value for the first cycle duration; and determining the average sampled value of the first cycle duration at which the current time is located as the current reference value. By performing an arithmetic average operation on the continuous sampled values ​​within a fixed time window, signal components above their cutoff frequency are significantly attenuated, effectively suppressing switching noise above a certain range.

[0072] In some embodiments, the first loop duration is optionally 20ms.

[0073] In this embodiment, the first cycle duration is 20ms, that is, the time window is set to 20ms, thereby suppressing high-frequency interference. At the same time, since the duration of 20ms is much less than the minimum delay required by each level of protection, the delay introduced in the preprocessing stage will not affect the standard protection time requirements of the entire system.

[0074] In some embodiments, optionally, determining a reference value for the residual leakage current signal based on the sampled signal includes: obtaining a second cycle duration prior to the current time, the second cycle duration including a plurality of first cycle durations; averaging the average sampled values ​​of the plurality of first cycle durations in the second cycle duration to obtain the reference value.

[0075] In this embodiment, the second cycle duration refers to a long window, such as 10 seconds, used to calculate the baseline reference value. By setting an observation window much longer than the system disturbance period, i.e., the second cycle duration, the statistical properties of the arithmetic mean are used to filter out all short-term fluctuations and disturbances. Since the second cycle duration includes multiple first cycle durations, any short-term disturbances can be sufficiently diluted during the averaging process. Simultaneously, a "first-in, first-out" sliding window update mechanism is adopted, ensuring that the baseline value reflects the latest long-term operating state of the system while avoiding the step jumps of traditional fixed-window updates. This allows the baseline reference value to accurately track the slowly changing inherent leakage level of the system, while completely suppressing the effects of transient disturbances and short-term fluctuations.

[0076] In some embodiments, the second cycle may optionally last for 10 seconds.

[0077] In this embodiment, the second cycle duration is 10 seconds. The second cycle duration includes multiple first cycle durations. For example, if the first cycle duration is 20 ms, then the second cycle duration includes 500 consecutive average sampled values. This reduces the impact of short-term disturbances, dilutes abnormal interference, and establishes a stable reference value, which facilitates the judgment of subsequent protection actions.

[0078] In some embodiments, the smoothing coefficients corresponding to the multiple reference current levels can be preset in the following manner: obtaining the required delays corresponding to the multiple reference current levels; establishing a filter delay function based on the first cycle duration and the smoothing coefficients; and for each reference current level, solving for the maximum smoothing coefficient when the filter delay function is not greater than the required delay corresponding to the reference current level, and using it as the smoothing coefficient corresponding to the reference current level.

[0079] In this embodiment, the reference current level refers to the different fault severity levels classified according to safety standards, such as the three protection levels of 30mA, 60mA, and 150mA.

[0080] The required delay refers to the standard protection time corresponding to each reference current level. For example, the 30mA level requires less than or equal to 0.3s, the 60mA level requires less than or equal to 0.15s, and the 150mA level requires less than or equal to 0.04s.

[0081] The filter delay function is a mathematical model that describes the relationship between the inherent delay of a filter and its parameters. Specifically, it is T_delay≈3τ and τ=-T_avg / lnα, where T_avg is 20ms.

[0082] The maximum smoothness coefficient is the α value that provides the strongest anti-interference capability while meeting the delay requirements. For example, for the 30mA level, the maximum α obtained by solving under the condition that T_delay≤0.3s is 0.8, which means that the optimal anti-interference parameter is selected within the compliance range.

[0083] This application transforms performance requirements into design constraints by establishing an accurate mathematical model. First, based on the step response characteristics of a first-order linear system, a functional relationship between the filtering delay and the smoothing coefficient, T_delay=f(α, T_avg), is established. Then, the protection time specified by the standard is used as a constraint. Since the anti-interference performance of the system increases with the increase of α, under the premise of satisfying the delay constraint, choosing the largest value of α naturally corresponds to the optimal anti-interference capability.

[0084] In some embodiments, optionally, the transfer function of the first-order low-pass digital filter at each reference current level is preset in the following manner: a first transfer term is set based on the smoothing coefficient corresponding to the reference current level and the current reference value; a second transfer term is set based on the smoothing coefficient corresponding to the reference current level and the transfer function of the previous sampling period of the current sampling period; and the transfer function of the current sampling period is set based on the first transfer term and the second transfer term.

[0085] In this embodiment, the transfer function refers to the mathematical expression describing the relationship between the filter input and output, specifically H(z)=(1-α)×I_20ms_avg(n)+α×H(z-1).

[0086] The first transitive term is (1-α)×I_20ms_avg(n) in the above formula, which is the immediate contribution of the new input data, while the second transitive term corresponds to α×H(z-1) in the formula, which represents the inertial preservation of the historical output data.

[0087] The transfer function H(z) for the current sampling period is the sum of the first two sub-terms, resulting in the current output value. For example, for a 30mA level (α=0.8), when the new I_20ms_avg(n)=35mA and the previous period's H(z-1)=15mA, the first transfer sub-term is (1-0.8)×35=7mA, the second transfer sub-term is 0.8×15=12mA, and the current output H(z)=7+12=19mA.

[0088] The transfer function of the first-order low-pass digital filter at each reference current level is preset in the following way: a first transfer term is set based on the smoothing coefficient corresponding to the reference current level and the current reference value; a second transfer term is set based on the smoothing coefficient corresponding to the reference current level and the transfer function of the previous sampling period of the current sampling period; and the transfer function of the current sampling period is set based on the first and second transfer terms. That is, the design of the system inertia is controlled by adjusting the weights of the two transfer terms, so that different reference current levels can obtain the anti-interference characteristics most suitable for their protection requirements.

[0089] In some embodiments, optionally, protection actions are performed on the inverter based on a comparison between the level filter value corresponding to each of the multiple reference current levels and a reference reference value, including: calculating the difference between the level filter value corresponding to each of the multiple reference current levels and the reference reference value; obtaining the difference threshold corresponding to each of the multiple reference current levels; and performing protection actions on the inverter if the difference corresponding to at least one reference current level is greater than the difference threshold corresponding to the reference current level.

[0090] In this embodiment, the level filter value refers to the output signal after being processed by a first-order low-pass digital filter with different smoothing coefficients. For example, the level filter values ​​correspond to the filtering results of three reference current levels: 30mA, 60mA, and 150mA.

[0091] The benchmark reference value refers to the long-term stable benchmark calculated using a 10-second sliding window.

[0092] The difference is the magnitude of the sudden change obtained by subtracting the level filter value from the reference value and taking the absolute value. The difference threshold is the protection trigger threshold preset for each reference current level, such as 28mA, 58mA, and 145mA, which are all slightly lower than the standard value to reserve a safety margin.

[0093] For example, when the filter value I_f1, which is at the 30mA level, rises to 33mA due to a fault, while the reference I_10s_avg remains at 5mA, the difference ΔI is calculated to be 28mA. When the 28mA threshold is reached, the system immediately executes the corresponding protection action.

[0094] By calculating the absolute difference between the "current filter value" and the "long-term benchmark", the influence of the system's inherent static operating point is eliminated, allowing the protection decision to focus only on the dynamically changing part, which greatly improves the detection sensitivity.

[0095] Furthermore, each reference current level has its own dedicated filter signal channel and matched threshold, forming a parallel processing link that ensures that faults of varying severity can be detected by the most suitable channel. Since the level filter values ​​have undergone filtering with a standard required delay, the difference calculation result indicates that both the sudden change amplitude and the protection delay are met the instant the limit is exceeded, thus supporting immediate protection action.

[0096] Specifically, the low-pass digital filter is a first-order low-pass digital filter, and its transfer function is uniformly defined as: H(z)=(1-α)×I_20ms_avg(n)+α×H(z-1);

[0097] Where H(z) is the filter output value of the current cycle, H(z-1) is the filter value of the previous cycle, α is the smoothing coefficient, and I_20ms_avg(n) is the preprocessed signal updated every 20ms.

[0098] To achieve precise matching between the filtering delay and the standard protection time, three independent filters were configured for three different preset abrupt change threshold levels, corresponding to three standards: 30mA, 60mA, and 150mA. The smoothing coefficient α was then calculated based on the standard protection time requirements.

[0099] Specifically, for the 30mA level (standard protection time ≤ 0.3s), the smoothing coefficient α1 = 0.8 is configured. The corresponding inherent delay T_delay1 (≈3τ) = 3 × [-0.02s / ln(0.8)] ≈ 0.273s, which meets the ≤ 0.3s requirement.

[0100] Specifically, for the 60mA level (standard protection time ≤ 0.15s), the smoothing coefficient α2 = 0.6 is configured. The corresponding inherent delay T_delay2 (≈3τ) = 3 × [-0.02s / ln(0.6)] ≈ 0.114s, which meets the requirement of ≤ 0.15s.

[0101] Specifically, for the 150mA level (standard protection time ≤ 0.04s), the smoothing coefficient α3 = 0.2 is configured. The corresponding inherent delay T_delay3 (≈ 3τ) = 3 × [-0.02s / ln(0.2)] ≈ 0.0375s, which meets the requirement of ≤ 0.04s.

[0102] Where τ is the calculation time constant.

[0103] With the above configuration, the signal I_20ms_avg is processed by different filters to obtain filtered signals I_f1, I_f2, and I_f3 respectively. This not only enhances the anti-interference capability (for example, I_f1 attenuates interference above 1kHz by ≥95%), but also meets the standard protection delay requirements. This eliminates the need for a separate fixed delay module and resolves the contradiction between anti-interference and response speed.

[0104] Specifically, the absolute values ​​of the differences between the three filtered signals and the reference signal are calculated respectively, i.e.:

[0105] ΔI1=|I_f1-I_10s_avg|;

[0106] ΔI2=|I_f2-I_10s_avg|;

[0107] ΔI3=|I_f3-I_10s_avg|.

[0108] Since I_f1, I_f2, I_f3 and I_10s_avg involved in the calculation are smooth and stable, the calculation accuracy of ΔI is improved, specifically reaching ±1mA, which can accurately reflect the amplitude of pure mutation and avoid jitter and critical omissions near the threshold.

[0109] Specifically, the difference signals ΔI1, ΔI2, and ΔI3 are compared with preset mutation thresholds (such as 28mA, 58mA, and 145mA) that are slightly lower than the standard value, thus reserving a margin for interference. If the value of any difference signal exceeds its corresponding preset mutation threshold, the protection action corresponding to that threshold level is immediately executed, such as warning, power reduction, or shutdown.

[0110] Specifically, the standard corresponding to the preset mutation threshold can be preset according to the three protection delays required by the NB / T32004-2018 standard, and then three first-order filter values ​​are calculated for protection threshold judgment.

[0111] In this embodiment, based on a 0.1ms sampling period and a 20ms arithmetic mean preprocessing combined with a 10s sliding window reference, smoothing coefficients of 0.8, 0.6, and 0.2 are configured for three parallel first-order low-pass digital filters, respectively. This ensures that the inherent delays of each filter (0.273s, 0.114s, and 0.0375s) precisely match the standard protection time requirements. Then, a stable difference signal is obtained by calculating the absolute value of the difference between the filtered signal and the reference signal. When the stable difference signal exceeds the thresholds corresponding to 28mA, 58mA, and 145mA, graded protection is immediately executed. Thus, the regulatory delay requirements are naturally met while the signal is being filtered, fundamentally solving the contradiction between anti-interference and fast response in traditional solutions, and achieving accurate and reliable protection against residual leakage current mutations.

[0112] like Figure 2 As shown, Figure 2 A leakage current protection scenario based on a 30mA transient threshold is shown. Figure 2 The curves clearly reveal the protection logic. Curve C (moving average) serves as a long-term stable reference (approximately 5mA), changing slowly after the 10.0s abrupt change indicated by curve D. Curve A (20ms periodic average) represents the original signal, experiencing a momentary jump. Curve B (filtered signal, α=0.8) tracks the abrupt change using a smoothing first-order low-pass filter; the difference between it and the reference is the basis for fault judgment. After the abrupt change, curve B rises steadily. When the difference between this value and curve C exceeds the 28.0mA threshold, the system triggers protection at 10.28s (as shown by curve E), resulting in a delay of approximately 0.28s. Region F indicates the state after protection triggering. The delay closely matches the theoretical value of 0.273s and meets the standard requirement (less than or equal to 0.3s), proving that this parameter configuration can reliably handle minor insulation damage while ensuring anti-interference capabilities.

[0113] like Figure 3 As shown, Figure 3 The protection scenario based on a 60mA sudden change threshold is shown, where the leakage current changes abruptly from 5.0mA to 65.0mA. To accelerate the response, the filter coefficient is adjusted to α=0.6. Figure 3 The rise rate of curve B (the filtered signal) is significantly faster. The smaller filter coefficient reduces smoothing inertia, making the filter response more agile, and the protection threshold is correspondingly set to 58.0 mA. After the abrupt change shown by curve D, curve B rapidly deviates from the reference curve C (the moving average), and the difference between the two quickly reaches the threshold, triggering protection at 10.14 s (time E on curve), with the delay shortened to approximately 0.14 s. Region F is the protection triggering area. This indicates that by optimizing the filter parameters, faster fault disconnection can be achieved, resulting in a better balance between safety and operational continuity.

[0114] like Figure 4 As shown, Figure 4 The protection scenario based on a 150mA sudden change threshold is illustrated, where the leakage current jumps abruptly from 5.0mA to 155.0mA. The system employs the fastest-responding filter coefficient α=0.2. Figure 4 The intermediate curve B (filtered signal) rises closely alongside curve A, which represents the original signal. With an extremely short filtering delay, the difference between curve B and the slowly changing curve C (moving average reference) rapidly exceeds the 145.0mA high threshold. The protection action is triggered at 10.04s (time E on curve), with a delay of only about 0.04s. Region F is the protection triggering area. This configuration, through a filtering channel with minimal inertia, achieves instantaneous system response, greatly ensuring equipment and personnel safety. Figure 4 The curve D in the middle indicates the moment when the mutation occurred.

[0115] According to one embodiment of this application, such as Figure 5 As shown, an inverter residual leakage current sudden change protection device 200 is provided, including: a first sampling module 202, a first determining module 204, a second determining module 206, a third determining module 208, and a first execution module 210; the first sampling module 202 is used to sample the residual leakage current signal in the inverter to obtain a sampled signal; the first determining module 204 is used to determine the current reference value of the residual leakage current signal based on the sampled signal; the second determining module 206 is used to determine the reference value of the residual leakage current signal based on the sampled signal; the third determining module 208 is used to input the current reference value into a first-order low-pass digital filter to obtain the level filter values ​​corresponding to multiple reference current levels, wherein the first-order low-pass digital filter has smoothing coefficients corresponding to multiple reference current levels, and the smoothing coefficients are the maximum smoothing coefficients that meet the required delay corresponding to the reference current levels; the first execution module 210 is used to perform protection actions on the inverter based on the comparison between the level filter values ​​corresponding to multiple reference current levels and the reference reference value.

[0116] The inverter residual leakage current mutation protection device 200 provided in this application includes: a first sampling module 202, a first determining module 204, a second determining module 206, a third determining module 208, and a first execution module 210; the first sampling module 202 is used to sample the residual leakage current signal in the inverter to obtain a sampled signal; the first determining module 204 is used to determine the current reference value of the residual leakage current signal based on the sampled signal; the second determining module 206 is used to determine the reference value of the residual leakage current signal based on the sampled signal; the third determining module 208 is used to input the current reference value into a first-order low-pass digital filter to obtain the level filter values ​​corresponding to multiple reference current levels, wherein the first-order low-pass digital filter has smoothing coefficients corresponding to multiple reference current levels, and the smoothing coefficients are the maximum smoothing coefficients that meet the required delay corresponding to the reference current levels; the first execution module 210 is used to perform protection actions on the inverter based on the comparison between the level filter values ​​corresponding to multiple reference current levels and the reference reference value. The multi-stage first-order low-pass digital filter in the third determination module 208 is configured with a maximum smoothing coefficient to meet the delay requirements of each reference current level. This ensures that the inherent delay of the filtering process precisely matches the standard protection time (e.g., 30mA / 0.3s, 60mA / 0.15s, 150mA / 0.04s). While maintaining millisecond-level delay accuracy, it achieves "filtering equals delay," allowing the first execution module 210 to act immediately after judgment without additional delay. By combining the real-time preprocessing of the first determination module 204 (e.g., 20ms averaging) with the long-term reference establishment of the second determination module 206 (e.g., 10s sliding window), high-frequency interference above 10kHz is effectively suppressed, and reference fluctuations are controlled within ±0.5mA. This ensures that the level filter value output by the third determination module 208 is pure and stable, eliminating false protection at the source and preventing missed judgments in critical scenarios. The device employs a multi-channel parallel processing architecture, providing independent optimized channels for different fault levels. While ensuring extremely rapid response to 150mA-level emergency faults (α=0.2), it also provides strong anti-interference capability for 30mA-level minor faults (α=0.8), achieving optimal protection performance. The entire device achieves full-function protection solely through modular algorithms, eliminating the need for external hardware circuitry and significantly reducing system cost and complexity.

[0117] According to one embodiment of this application, such as Figure 6 As shown, an inverter residual leakage current sudden change protection device 300 is provided, including a processor 302 and a memory 304. The memory 304 stores programs or instructions. When the processor 302 executes the programs or instructions in the memory 304, it implements the steps of the inverter residual leakage current sudden change protection method as described in any of the above embodiments. Therefore, the inverter residual leakage current sudden change protection device 300 possesses all the beneficial effects of the inverter residual leakage current sudden change protection method as described in any of the above embodiments.

[0118] It should be clarified that in the claims, description, and accompanying drawings of this application, the term "multiple" refers to two or more objects. Unless otherwise explicitly defined, the terms "upper," "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description process, not to indicate or imply that the device or element referred to must have the described specific orientation, or be constructed and operated in a specific orientation. Therefore, these descriptions should not be construed as limitations on this application. The terms "connection," "installation," "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection between multiple objects, a detachable connection between multiple objects, or an integral connection; it can be a direct connection between multiple objects or an indirect connection between multiple objects through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in this application can be understood based on the specific circumstances of the above data.

[0119] In the claims, description, and accompanying drawings of this application, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In the claims, description, and accompanying drawings of this application, the illustrative expressions of the above terms do not necessarily refer 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.

[0120] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for protecting inverter residual leakage current from sudden changes, characterized in that, include: The residual leakage current signal in the inverter is sampled to obtain the sampled signal; The current reference value of the residual leakage current signal is determined based on the sampled signal; The reference value of the residual leakage current signal is determined based on the sampled signal; The current reference value is input into a first-order low-pass digital filter to obtain the level filter values ​​corresponding to each of the multiple reference current levels. The first-order low-pass digital filter has smoothing coefficients corresponding to the multiple reference current levels, and the smoothing coefficients are the maximum smoothing coefficients that meet the required delay corresponding to the reference current level. Based on the comparison between the level filter value corresponding to each of the multiple reference current levels and the reference reference value, the inverter performs protection actions.

2. The inverter residual leakage current sudden change protection method according to claim 1, characterized in that, Determining the current reference value of the residual leakage current signal based on the sampled signal includes: Every first cycle duration, sampled values ​​from multiple sampling periods within the first cycle duration are obtained from the sampled signal; The average of the sampled values ​​from the multiple sampling periods is calculated to obtain the average sampled value of the first cycle duration; The average sampled value at the current time being within the duration of the first cycle is determined as the current reference value.

3. The inverter residual leakage current sudden change protection method according to claim 2, characterized in that, The duration of the first loop is 20ms.

4. The inverter residual leakage current sudden change protection method according to claim 2, characterized in that, The step of determining the reference value of the residual leakage current signal based on the sampled signal includes: Get the duration of the second loop before the current time, where the second loop duration includes multiple durations of the first loop; The average of the average sampled values ​​of multiple first cycle durations within the second cycle duration is calculated to obtain the benchmark reference value.

5. The inverter residual leakage current sudden change protection method according to claim 4, characterized in that, The second cycle lasts for 10 seconds.

6. The inverter residual leakage current sudden change protection method according to claim 2, characterized in that, The smoothing coefficients corresponding to the multiple reference current levels are preset in the following manner: Obtain the required delay corresponding to each of the multiple reference current levels; Based on the first loop duration and the smoothing coefficient, a filtering delay function is established; For each reference current level, the maximum smoothing coefficient is calculated if the filter delay function is not greater than the required delay corresponding to the reference current level, and this coefficient is used as the smoothing coefficient corresponding to the reference current level.

7. The inverter residual leakage current sudden change protection method according to claim 1, characterized in that, The transfer function of the first-order low-pass digital filter at each reference current level is preset in the following manner: Based on the smoothing coefficient corresponding to the reference current level and the current reference value, a first transmission sub-item is set; Based on the smoothing coefficient corresponding to the reference current level and the transfer function of the previous sampling period of the current sampling period, a second transfer sub-item is set; Based on the first transfer sub-item and the second transfer sub-item, the transfer function of the current sampling period is set.

8. The inverter residual leakage current sudden change protection method according to claim 1, characterized in that, The step of performing protection actions on the inverter based on the comparison between the level filter values ​​corresponding to each of the plurality of reference current levels and the reference reference value includes: Calculate the difference between the level filter value corresponding to each of the multiple reference current levels and the reference reference value; Obtain the difference threshold corresponding to each of the multiple reference current levels; If the difference corresponding to at least one of the reference current levels is greater than the difference threshold corresponding to the reference current level, a protection action is performed on the inverter.

9. A device for protecting against sudden changes in residual leakage current in an inverter, characterized in that, include: The first sampling module is used to sample the residual leakage current signal in the inverter to obtain the sampled signal; The first determining module is used to determine the current reference value of the residual leakage current signal based on the sampled signal; The second determining module is used to determine a reference value for the residual leakage current signal based on the sampled signal; The third determining module is used to input the current reference value into a first-order low-pass digital filter to obtain the level filter value corresponding to each of the multiple reference current levels. The first-order low-pass digital filter has smoothing coefficients corresponding to the multiple reference current levels respectively. The smoothing coefficient is the maximum smoothing coefficient that satisfies the required delay corresponding to the reference current level. The first execution module is used to perform protection actions on the inverter based on the comparison between the level filter value corresponding to each of the plurality of reference current levels and the reference reference value.

10. A device for protecting against sudden changes in residual leakage current in an inverter, characterized in that, include: processor; A memory, wherein the memory stores programs or instructions, and the processor, when executing the programs or instructions in the memory, implements the steps of the inverter residual leakage current sudden change protection method as described in any one of claims 1 to 8.

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