A charging pile overload protection method and system for ensuring charging efficiency

Abstract

The application relates to the technical field of charging pile overload protection, in particular to a charging pile overload protection method and system for guaranteeing charging efficiency, which comprises the following steps: collecting three-phase current data of each charging pile position under charging pile networking. A first interference index is determined according to the current amplitude variation degree and the phase shift variation degree in the three-phase current data. A second interference index is determined according to the consistency variation value of the three-phase current data between each charging pile position under charging pile networking. An overload interference index is determined according to the first interference index and the second interference index. The overload protection current threshold is adjusted according to the overload interference index, and an overload protection action is performed on the corresponding charging pile position according to the adjusted overload protection current threshold. The application provides a method for avoiding unnecessary interruption of the charging process caused by the protection misoperation triggered by instantaneous current fluctuation, and guaranteeing the charging efficiency.

Description

Technical Field

[0001] This application relates to the field of charging pile overload protection technology, specifically to a charging pile overload protection method and system that ensures charging efficiency. Background Technology

[0002] With the rapid development of the electric vehicle industry, charging piles have been widely used as a key supporting facility, and their operational safety and stability are receiving increasing attention. When charging piles are connected to the power grid, they need to continuously bear high current and high power loads. Especially during peak hours when multiple vehicles are charging simultaneously, they are prone to overload faults due to excessive load, which may lead to equipment damage or even fire accidents in severe cases. Therefore, timely and reliable overload protection for charging piles is of great practical significance.

[0003] Existing overload protection methods for charging piles typically rely on preset fixed current thresholds. When the real-time monitored operating current exceeds the set threshold, it is determined to be an overload, and the power supply is immediately cut off to implement protection. However, charging piles are directly connected to the power grid, and the actual operating conditions are quite complex. There are various complex disturbances in the power supply network, which may cause non-fault-related abnormal fluctuations in the charging current. Such current fluctuations can seriously interfere with the fixed threshold-based overload protection mechanism, making it difficult to accurately implement overload protection, easily causing protection malfunctions, resulting in unnecessary interruptions to the charging process, and significantly reducing charging efficiency. Summary of the Invention

[0004] To address the technical problem of low charging efficiency caused by unnecessary interruptions in the current charging process, this application aims to provide a charging pile overload protection method and system that ensures charging efficiency. The specific technical solution adopted is as follows: Firstly, a method for overload protection of charging piles to ensure charging efficiency is provided. This method includes: collecting three-phase current data from each charging pile location within a charging pile network; determining a first interference index based on the degree of change in current amplitude and phase shift in the three-phase current data; determining a second interference index based on the consistency of the three-phase current data among the charging pile locations within the charging pile network; determining an overload interference index based on the first and second interference indices; adjusting the overload protection current threshold based on the overload interference index; and performing overload protection actions on the corresponding charging pile location based on the adjusted overload protection current threshold.

[0005] One possible implementation involves determining a first interference index based on the degree of variation in current amplitude and phase shift in the three-phase current data. This includes: determining the peak sequence of the three-phase current based on the three-phase current data; determining the degree of variation in current amplitude based on the first-order forward difference value in the peak sequence; determining the instantaneous phase sequence based on the three-phase current data; determining the degree of phase shift based on the phase difference variation information between each phase in the instantaneous phase sequence; and determining the first interference index based on the degree of variation in current amplitude and phase shift.

[0006] One possible implementation involves determining the degree of current amplitude variation based on the first-order forward difference value in the three-phase current peak sequence. This includes: calculating the first-order forward difference value of the current peak value of each phase in the three-phase current peak sequence; determining the net current change of each phase based on the first-order forward difference value of the current peak value of each phase; normalizing the net current change of each phase based on the maximum absolute value of the net current change of each phase; and determining the mean of the normalized net current change of each phase as the degree of current amplitude variation.

[0007] One possible implementation involves determining the degree of phase shift change based on the phase difference change information between each phase in the instantaneous phase sequence. This includes: calculating the original phase difference sequence between each phase in the instantaneous phase sequence, and determining the phase difference deviation sequence between each phase based on the standard three-phase rated phase difference; identifying the sampling point in the phase difference deviation sequence where the mean of the phase difference deviation value between each phase at the same sampling point first exceeds a preset phase threshold as the phase abrupt change point; determining the mean of the phase difference deviation between each phase based on the phase difference deviation sequence after the phase abrupt change point; normalizing the mean of the phase difference deviation between each phase based on a preset maximum phase deviation threshold; and determining the average value of the normalized mean of the phase difference deviation between each phase as the degree of phase shift change.

[0008] One possible implementation involves determining a second interference index based on the consistency variation value of the three-phase current data among different charging pile locations within a charging pile network. This includes: normalizing the three-phase current data at each charging pile location to obtain normalized current data for each location; determining the local peak sequence for each charging pile location based on the normalized current data; determining the consistency variation value based on the correlation index between the local peak sequences of each location; and performing a pre-defined mapping process on the consistency variation value to obtain the second interference index.

[0009] One possible implementation involves determining the consistency change value based on the correlation index between the local peak sequences of each charging pile location. This includes: calculating the correlation index between the local peak sequences of the phase current data at the current charging pile location and the corresponding phase current sequences at other charging pile locations in the charging pile network, based on the correspondence between in-phase current data. Then, based on the correlation index between the local peak sequences of the phase current data at the current charging pile location and other charging pile locations, determining the average correlation index between the current charging pile location and other charging pile locations. Finally, determining the average correlation index as the consistency change value.

[0010] One possible implementation involves adjusting the overload protection current threshold based on the overload interference index, and then performing overload protection actions on the corresponding charging station based on the adjusted overload protection current threshold. This includes: adjusting a preset initial value of the overload protection current threshold based on the overload interference index to determine an adaptive overload protection current threshold. When the current in any one phase of the three-phase current data of the charging station exceeds the adaptive overload protection current threshold, an overload fault is determined to exist at the charging station. Overload protection actions are then performed on the charging station determined to have an overload fault.

[0011] One possible implementation involves collecting three-phase current data from each charging station within the charging pile network. This includes: real-time acquisition of three-phase current waveform signals at each charging station using current transformers built into the charging piles within the network; digitizing the acquired three-phase current waveform signals according to a preset sampling frequency to obtain a sequence of instantaneous three-phase current values ​​at each sampling point; segmenting the digitized three-phase current data according to the duration of an overload fault detection window to obtain three-phase current waveform segments within each overload fault detection window; and using these three-phase current waveform segments as the three-phase current data to be analyzed.

[0012] Secondly, an overload protection system for charging piles that ensures charging efficiency is provided, comprising: a data acquisition unit for acquiring three-phase current data of each charging pile location within a charging pile network; a first index determination unit for determining a first interference index based on the degree of change in current amplitude and phase shift in the three-phase current data; a second index determination unit for determining a second interference index based on the consistency change value of the three-phase current data among the charging pile locations within the charging pile network; an interference index fusion unit for determining an overload interference index based on the first and second interference indices; and an overload protection unit for adjusting the overload protection current threshold based on the overload interference index and performing overload protection actions on the corresponding charging pile location based on the adjusted overload protection current threshold.

[0013] As one possible implementation, the first index determination unit includes: a peak detection module for determining the three-phase current peak sequence based on three-phase current data; an amplitude determination module for determining the degree of current amplitude change based on the first-order forward difference value in the three-phase current peak sequence; a phase transformation module for determining the instantaneous phase sequence based on the three-phase current data; a phase offset determination module for determining the degree of phase offset change based on the phase difference change information between each phase in the instantaneous phase sequence; and an index calculation module for determining a first interference index based on the degree of current amplitude change and the degree of phase offset change.

[0014] This application offers the following advantages: By collecting three-phase current data from each charging pile location within a charging pile network, a first interference index is determined based on the degree of change in current amplitude and phase shift, quantifying the impact of grid surges on the three-phase current from the perspective of a single charging pile location. Simultaneously, a second interference index is determined based on the consistency change value of the three-phase current data among the charging pile locations within the network, quantifying the interference of grid surges on overload fault detection from a network perspective. The first and second interference indices are then fused to obtain an overload interference index. The overload protection current threshold is dynamically adjusted based on the overload interference index, and overload protection actions are executed according to the adjusted threshold. This effectively distinguishes between real, continuous overload faults and instantaneous grid surge interference. When grid surge disturbances occur, the protection threshold is automatically increased, preventing unnecessary interruptions in the charging process due to false protection actions triggered by instantaneous current fluctuations, thus ensuring charging efficiency. Furthermore, it ensures timely execution of protection actions even in the event of a real overload fault, thus prioritizing charging safety. Attached Figure Description

[0015] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic flowchart of one embodiment of a charging pile overload protection method to ensure charging efficiency provided in this application; Figure 2 This is a second schematic flowchart illustrating a charging pile overload protection method to ensure charging efficiency, provided as an embodiment of this application. Detailed Implementation

[0017] To further illustrate the technical means and effects adopted by this application to achieve the intended purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a charging pile overload protection method for ensuring charging efficiency proposed in this application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0019] The following description, in conjunction with the accompanying drawings, details a specific scheme for an overload protection method for charging piles that ensures charging efficiency, provided in this application.

[0020] Please see Figure 1 It shows a flowchart of a charging pile overload protection method to ensure charging efficiency according to an embodiment of this application, such as... Figure 1 As shown, the method includes the following steps: S101-S105.

[0021] In S101, the three-phase current data of each charging pile location under the charging pile network are collected.

[0022] In this embodiment, a charging pile network can refer to a collection of multiple charging pile locations connected to the same power grid. Each charging pile location is independently controlled for charging, but they are all affected by disturbances on the power grid side. For the charging pile network, each charging pile location has a built-in current transformer for collecting current data. The obtained data for each charging pile location in the charging pile network... B Three-phase current data can be expressed as follows: , , ,in , This indicates the number of charging stations in a charging station network within an independent grid connection. For example, the data sampling frequency can be set to 2kHz to ensure sufficient sampling points are included within one power frequency cycle to capture the instantaneous changes in current.

[0023] As one possible implementation, S101 may include S1011 to S1013.

[0024] S1011. The three-phase current waveform signal at each charging pile location is collected in real time through the current transformer built into each charging pile location in the charging pile network.

[0025] In this embodiment, each charging station has an integrated three-phase current transformer (e.g., a Hall effect current sensor) installed on the input side (grid connection end) of the charging station to detect A, B, ... The instantaneous current of the three phases. The range of the current transformer is selected according to the rated current of the charging pile. For example, for a charging pile with a rated current of 32A, the transformer range can be selected from 0 to 100A. The acquisition method can be continuous real-time acquisition, that is, the charging pile control system periodically reads the output signal of the current transformer in an interrupt manner. The sampling interval is controlled by the system clock to ensure that the current waveform is captured without omission.

[0026] S1012. The collected three-phase current waveform signals are digitized according to the preset sampling frequency to obtain the instantaneous value sequence of the three-phase current at each sampling point.

[0027] In this embodiment, the preset sampling frequency can be set to 2kHz. Specifically, the analog-to-digital converter in the charging pile control system samples the analog voltage signal output by the current transformer at a rate of 2kHz, with each sampling point corresponding to the instantaneous current value of the three phases. The selection of the sampling frequency must satisfy the Nyquist sampling theorem. Since the power grid frequency is 50Hz, its 20th harmonic frequency is 1kHz, and a sampling frequency of 2kHz can effectively capture the waveform characteristics of the main harmonic components and transient impact current. If the harmonic components in the implementation scenario are more complex (such as in situations where there is high-frequency interference from rail transit), the sampling frequency can be appropriately increased to 4kHz or higher, but the system's computational load must be comprehensively considered. The digitized data is stored in floating-point form in amperes (A) and timestamped for subsequent segmented processing.

[0028] S1013. The digitized three-phase current data is segmented according to the duration of the overload fault detection window to obtain the three-phase current waveform segments under each overload fault detection window. The three-phase current waveform segments are used as the three-phase current data to be analyzed.

[0029] It should be noted that the overload fault detection window is used to define the time range for subsequent overload fault detection and analysis. The size of the overload fault detection window can be set by the operation and maintenance personnel according to the implementation scenario. Setting the overload fault detection window too large may lead to protection response delays, while setting it too small will result in insufficient analysis data, affecting the accuracy of the judgment.

[0030] For example, the duration of the overload fault detection window is... Second, For example, The size can be set to 1 second. For a given detection window, the first... The three-phase current data at each charging station can be expressed as follows: , , ,in This indicates the most recent overload fault detection window.

[0031] S102. Determine the first interference index based on the degree of change in current amplitude and the degree of change in phase offset in the three-phase current data.

[0032] Overload faults in charging piles are usually caused by excessive current load during peak hours or by internal circuit faults leading to a continuous increase in load and causing the current to exceed the safety threshold. Similarly, inrush currents caused by harmonic interference and lightning strikes from the power grid can also significantly increase the current data detected in the charging pile, even exceeding preset thresholds, leading to malfunctions of overload protection. From the perspective of their impact on current and phase, both overload faults and power grid interference will cause abnormal current increases and larger phase differences. However, overload faults are a continuous change in current and phase caused by the load side; the cause is that the current load continuously exceeds the charging pile's safety limit, causing overheating and damage to the equipment. In contrast, power grid interference is essentially due to the nonlinear effects of the power grid altering the current waveform, resulting in transient differences and shifts in both amplitude and phase of the three-phase current. Based on these differences, this application's embodiments analyze the net change characteristics of current amplitude and the continuous shift characteristics of phase from two dimensions to construct a first interference index.

[0033] As one possible implementation, S102 may include S1021 to S1025.

[0034] S1021. Determine the peak sequence of the three-phase current based on the three-phase current data.

[0035] For example, for the first The three-phase current data of each charging station under the most recent overload fault detection window. , , A preset peak detection algorithm is used to extract the peak values ​​of the current data for each phase, obtaining the peak value of the current in each phase in each cycle, thus forming a three-phase current peak sequence. , , The preset peak detection algorithm can be the Automatic Multi-scale Peak Detection (AMPD) algorithm or other algorithms capable of automatically detecting local peaks; this application does not impose specific limitations on this. For example, the AMPD peak detection algorithm is used as an example: the current sequence is processed using a multi-scale sliding window, where the window length for the k-th scale is... , , For the largest scale; for each scale A sliding window is applied to the current sequence, and the center point of the window is compared with all points within the window. If the center point is the maximum value within the window, it is marked as a candidate peak. Statistics are then compiled at each scale. The number of candidate peaks is used to form a peak number sequence; the minimum value in the peak number sequence is found, and its corresponding scale is taken as the optimal scale; the candidate peaks extracted at the optimal scale are taken as the final peak sequence.

[0036] S1022. Determine the degree of change in current amplitude based on the first-order forward difference value in the three-phase current peak sequence.

[0037] The first-order forward difference of the current peak represents the net trend of current change within an overload fault detection window. When the load current continuously increases within this window, the peak current increases cycle by cycle, and all first-order forward differences are positive with a relatively large mean. Conversely, when grid interference causes an abnormal increase in the charging pile's current amplitude, it manifests as a short-term random surge. The current amplitude randomly increases within a certain cycle and then quickly decays back to normal. The first-order forward differences cancel each other out, and the mean approaches zero. Even if an abnormal increase occurs in the final cycle of the overload fault detection window, the increase in current amplitude in the final cycle will be mitigated under the mean calculation, resulting in a smaller change in the final current amplitude.

[0038] As one possible implementation, such as Figure 2 As shown, S1022 may include S201 to S204.

[0039] S201. Calculate the first-order forward difference of the peak current of each phase in the three-phase current peak sequence.

[0040] The first-order forward difference value refers to the difference between the peak value of the next period and the peak value of the previous period in a peak sequence of the same phase current. Calculate separately. B Peak sequence of three-phase current , , The first-order forward difference of adjacent peaks in the data.

[0041] S202. Determine the net change in current for each phase based on the first-order forward difference of the peak current for each phase.

[0042] Specifically, for For each phase, the net change in phase A current is obtained by summing all the calculated first-order forward difference values. .Right now: The above formula is mathematically equivalent to the difference between the final peak value and the initial peak value, reflecting the overall trend of current peak value change within the detection window. When the current rises overall within the window, this value is positive and relatively large; when it falls overall, it is negative; when there is only a momentary impact and the initial and final values ​​are close, this value approaches zero.

[0043] in, for The first phase peak sequence First-order forward difference value for The total number of peaks in the phase peak sequence. When the current continues to rise, the first-order forward difference values ​​are mostly positive, and the cumulative sum is positive and relatively large; when the current fluctuates due to impacts, the positive and negative differences cancel each other out, and the cumulative sum approaches zero. Accordingly, we obtain... Mutually, Net change in phase current , .

[0044] S203. Normalize the net change in current of each phase based on the maximum absolute value of the net change in current of each phase.

[0045] Specifically, take the maximum absolute value of the net change in three-phase current, for example, And superimpose a very small positive number. This serves as a normalized denominator to avoid a denominator of zero. Among these, ,For example, A value of 0.01 can be used. Divide the net change in current of each phase by this normalized denominator to complete the normalization process.

[0046] S204. The mean value of the net change in current of each phase after normalization is determined as the degree of change in current amplitude.

[0047] For example, taking the degree of change in current amplitude as... The normalized net change in three-phase current is respectively... , , ,but: Current amplitude variation The larger the value, the more significant the overall continuous upward trend of the three-phase current within the overload fault detection window, and the higher the probability of an overload fault. The smaller the value, the closer the net change in three-phase current is to zero, and the current fluctuations are more likely to be caused by instantaneous impacts on the power grid.

[0048] S1023. Determine the instantaneous phase sequence based on the three-phase current data.

[0049] For example, for the first The three-phase current data of each charging station under the most recent overload fault detection window. , , The analytic signals of each phase current are obtained using the Hilbert transform. Then, the arctangent of the ratio of the imaginary part to the real part of the analytic signal is taken to obtain the instantaneous phase sequence of each phase current. , , .

[0050] S1024. Determine the degree of phase shift change based on the phase difference change information between each phase in the instantaneous phase sequence.

[0051] When an overload fault causes abnormal changes in the phase of the three-phase current, the phase fluctuations often begin to drift as the three-phase current increases, until the overload fault disappears. Throughout the entire phase sequence after the phase abrupt change point, all three phases drift, resulting in a larger average phase difference between the three phases calculated after the abrupt change point. Conversely, grid disturbances such as lightning strikes are transient disturbances. The phase deviation calculated after the phase abrupt change point only exists at local sampling points. As the grid disturbance disappears, this phase imbalance also disappears, resulting in a smaller average phase difference across all sampling points after the phase abrupt change point.

[0052] As one possible implementation, S1024 may include S205 to S209.

[0053] S205. Calculate the original phase difference sequence between each phase in the instantaneous phase sequence, and determine the phase difference deviation sequence between each phase based on the standard three-phase rated phase difference.

[0054] For example, calculate the instantaneous phase sequence of the three-phase current separately. , , The absolute value of the phase difference between each pair of pairs yields the original phase difference sequence. , , .in, , as well as They represent Mutually, Mutually, The original phase difference sequence of the phases. Due to the standard three-phase electricity Mutually, The rated phase difference is 120°. With a phase of 240°, the phase difference deviation sequence can be: in, , as well as They represent Mutually, Mutually, The phase difference of the phase deviates from the sequence.

[0055] S206. The sampling point where the average value of the phase difference deviation between each phase exceeds the preset phase threshold for the first time at the same sampling point in the phase difference deviation sequence is taken as the phase change point.

[0056] The preset phase threshold can be set by the implementer according to the operating error range of current and voltage phase angles for low-voltage power supply specified in the power industry. In this embodiment, the preset phase threshold... A value of 5° can be used. Within the overload fault detection window, starting from the initial moment, the average value of the three-phase phase difference deviation at each sampling point is calculated sequentially. When this average value first exceeds... When this occurs, the sampling point is recorded as a phase abrupt change point.

[0057] If, within the entire overload fault detection window, the average value of the three-phase phase difference deviation at all sampling points does not exceed the preset phase threshold... If no phase abrupt change point is found within the window, it is determined that there is no persistent phase shift anomaly. In this case, the phase shift change level is directly set. And skip the calculations in S207 to S209 below.

[0058] S207. Based on the phase difference deviation sequence after the phase abrupt change point, determine the mean phase difference deviation between each phase.

[0059] Specifically, from the point of phase change to the end of the overload fault detection window, the data within that time period is taken. Mutually, Mutually, For each phase difference deviation sequence, calculate the mean of the phase difference deviation values ​​of all sampling points in each phase difference deviation sequence to obtain... The mean of the phase difference deviation, The mean of the phase difference deviation, The mean of the phase difference deviation.

[0060] S208. Based on the preset maximum phase deviation threshold, normalize the phase difference deviation from the mean between each phase.

[0061] Preset maximum phase deviation threshold This can be set according to the allowable phase offset range of the charging pile equipment, for example, 30°. For example, for Let the phase difference deviation sequence after the phase abrupt change point be denoted as . Its length is The mean absolute value of the phase difference of this sequence is .but The normalized value can be: Among them, if the value If it is 0, then set it directly. It is 0.

[0062] Accordingly, process in the same way Harmony Phase, respectively obtained and .

[0063] S209. The average value of the phase difference between each phase after normalization is deviated from the mean value, and the phase shift change degree is determined.

[0064] For example, taking the degree of phase shift change as For example. It can be expressed as normalized Mutually, Mutually, The arithmetic mean of the absolute values ​​of the phase differences: Phase shift change degree The larger the value, the more likely the phase anomaly persists after the phase abrupt change point and the greater the magnitude, which is consistent with the phase drift characteristics of overload faults. The smaller the value, the more likely the phase anomaly exists only at local sampling points, which is more consistent with the transient characteristics of power grid impact interference.

[0065] S1025. Determine the first interference index based on the degree of change in current amplitude and the degree of change in phase offset.

[0066] First Interference Index This is used to quantify the impact of power grid shock interference on the overload fault detection of a single charging pile under the current detection window.

[0067] For example, the first interference index The calculation formula can be: in, For the natural constant An exponential function with base 0. The degree of change in current amplitude, This represents the degree of phase shift change.

[0068] The larger the value, the more significant the continuous change characteristics in both current amplitude and phase, and the more consistent with the characteristics of an overload fault. The smaller the value; The smaller the value, the more likely the current fluctuation is to be a transient change caused by grid impact. The larger the value, the better. Specifically: when... and When both are relatively large, Smaller values ​​correspond to a higher probability of overload failure; when... and When both are relatively small, Larger values ​​correspond to a higher probability of power grid impact interference; when and One hour The value is in the middle, reflecting the combined effect of the two.

[0069] It should be noted that S1021-S1022 and S1023-S1024 can be executed in parallel or sequentially, and this application does not limit this.

[0070] S103. Determine the second interference index based on the consistency change value of the three-phase current data between each charging pile location in the charging pile network.

[0071] In a charging pile network, each charging pile is controlled independently, and load changes at each charging pile location are reflected in the overall network. However, load changes between individual charging pile locations are relatively independent. For overload faults, the characteristic is that an overload occurs at a local charging pile location due to a continuous increase in load current. Only at that charging pile location does a slow, interpretable increase trend appear synchronously in the three-phase current, while the three-phase currents at other charging pile locations maintain their stable charging state. In other words, the changes in the three-phase current on the load side are not synchronous globally. Harmonics and lightning interference in the power grid inject inrush currents directly from the grid side to the load side, first disturbing the charging pile's connection to the grid, and then propagating through the distribution network to each charging pile location. This causes synchronous jumps in the global three-phase current. Although the amplitude of the inrush disturbance varies due to differences in line impedance at different charging pile locations, the overall change is synchronous. Thus, by calculating the consistency of the three-phase current changes at each charging pile location, a second interference index is determined.

[0072] As one possible implementation, S103 may include S1031 to S1034.

[0073] S1031. Normalize the three-phase current data at each charging pile location under the charging pile network to obtain the normalized current data for each charging pile location.

[0074] Specifically, the three-phase current data at each charging station location within the most recent overload fault detection window are normalized according to the maximum value of each phase current within that window. This is because grid impact interference affects the three-phase current at different locations with varying amplitudes. To analyze the coordinated changes at each charging station location, the current data needs to be normalized to quantify the relative changes of the three-phase current within an overload fault detection window, thus eliminating the interference of amplitude differences on synchronization analysis.

[0075] S1032. Based on the normalized current data, determine the local peak sequence of each charging station.

[0076] Specifically, for the normalized three-phase current data at each charging pile location, a preset peak detection algorithm is used to obtain the local peak sequence of each phase.

[0077] S1033. Determine the consistency change value based on the correlation index between the local peak sequences of each charging pile location.

[0078] The correlation index reflects the correlation changes among the local peak sequences of three-phase current at different charging pile locations. It is used to distinguish between overload faults and grid impact phenomena when the three-phase current rises. The larger the correlation index, the more synchronized the changes between the sequences, and the higher the probability of grid impact interference; the smaller the correlation index, the lower the synchronicity of the three-phase current changes at different charging pile locations, and the higher the probability of local overload faults.

[0079] It should be noted that when the charging piles are operating stably, without overload faults or grid impacts, each charging pile is in a normal charging state, and the calculated correlation index may be relatively large. However, the three-phase currents under normal operating conditions are all within the normal range.

[0080] As one possible implementation, S1033 may include S301 to S303.

[0081] S301. Based on the correspondence between the current data of the same phase, calculate the correlation index between the local peak sequence of the current data of each phase at the current charging pile location and the local peak sequence of the corresponding phase current data at other charging pile locations other than the current charging pile location under the charging pile network.

[0082] For example, with Let's take a phase as an example. Let the current charging station be the [number]th phase. The first charging station location, the other charging station location is the first one. One charging station ( ). Under the current overload fault detection window, the first Each charging station The phase local peak sequence is represented as , No. Each charging station The phase local peak sequence is represented as ,in This refers to the number of power frequency cycles contained within the overload fault detection window (i.e., the total number of local peak values; for example, when the overload fault detection window duration is 1 second and the power frequency is 50Hz). ).

[0083] Calculated using Pearson correlation coefficient and The correlation index between them is calculated using the following formula: in, , , respectively and The arithmetic mean. The range of values ​​is The closer the value is to 1, the stronger the positive correlation between the two sequences, that is, the more synchronous the current change trend.

[0084] It should be noted that when the denominator At this point, the Pearson correlation coefficient is undefined, indicating that at least one sequence is a constant sequence (typically occurring under normal operating conditions where the charging pile current is stable and without fluctuations). There is no meaningful synchronous change relationship between the two sequences; therefore, a correlation index is defined. This means that the two are considered uncorrelated. After this treatment, the second disturbance index in the steady state is... However, based on the starting current threshold judgment in S104 below, the current does not exceed the starting threshold in this state, so dynamic threshold adjustment will not be performed, and therefore it will not have a substantial impact on the overload protection threshold.

[0085] Similarly, the correlation indices for phases B and C are calculated using the same method and denoted as follows: and It should be noted that this embodiment uses the Pearson correlation coefficient as an example for illustration. This application does not limit the specific correlation algorithm used, and other algorithms that can measure the consistency of sequence changes (such as cosine similarity) are also applicable.

[0086] S302. Based on the correlation index of the local peak sequence of the current data of each phase between the current charging pile location and other charging pile locations, determine the average correlation index between the current charging pile location and other charging pile locations.

[0087] Specifically, for the first One charging station, and connect it with the rest Between each charging station Mutually, Mutually, The correlation indices of each component are aggregated, and the average of all correlation indices is calculated as the value of the first correlation index within the overload fault detection window. The mean correlation index between each charging station and other charging stations .

[0088] S303. The mean of the correlation index is determined as the consistency change value.

[0089] In some embodiments, the calculated mean correlation index is used. The value was determined to be a consistent change.

[0090] S1034. Perform a preset mapping process on the consistency change value to obtain the second interference index.

[0091] For example, taking the second interference index as The preset mapping process maps the value to the first disturbance index without changing the physical meaning represented by the magnitude of the consistency change value. The same value range is used to facilitate subsequent fusion calculations.

[0092] For example, the calculation formula for the preset mapping process can be: This fixes the value of the mapped second interference index within the range of [0,1].

[0093] S104. Determine the overload interference index based on the first interference index and the second interference index.

[0094] In this embodiment, the overload interference index is a fusion index that integrates the analysis results of a single charging pile location and the analysis results of the charging pile network. As one possible implementation, the first interference index can be... With the second interference index The overload disturbance index is obtained by performing a weighted average. .

[0095] For example, the arithmetic mean can be used for calculation, and the formula can be: The larger the overload interference index value, the higher the possibility that the three-phase current data at the current charging pile location is affected by grid inrush current interference; the smaller the overload interference index value, the more likely the three-phase current data at the current charging pile location is to reflect a true overload fault.

[0096] In some embodiments, the three-phase current at the current charging pile location is monitored in real time. If the instantaneous value of any phase current exceeds a preset starting current threshold... If the condition is met, dynamic threshold adjustment is required, and step S105 below is executed. Otherwise, dynamic adjustment is skipped, and the initial overload protection current threshold is used. As a protection criterion, the threshold should not be increased.

[0097] The above-mentioned starting current threshold It can be set to 0.8 times the rated operating current of the charging pile, or it can be set by the maintenance personnel according to the charging pile model, as long as it is ensured to be lower than the initial value of the overload protection current threshold. (For example, It can be 1.2 times the rated current.

[0098] S105. Adjust the overload protection current threshold according to the overload interference index, and perform overload protection action on the corresponding charging pile position according to the adjusted overload protection current threshold.

[0099] Based on the constructed overload interference index, an adaptive overload protection current threshold can be further constructed. When the overload interference index is large, it indicates that there may be strong grid inrush current interference in the three-phase current of the charging pile. In this case, the overload protection current threshold should be increased accordingly to provide a buffer margin for the inrush current, avoid the inrush current triggering false overload protection, and thus ensure the charging efficiency of the charging equipment. When the overload interference index is small, overload protection is executed according to a threshold close to the preset overload protection current to respond promptly to real overload faults.

[0100] As one possible implementation, S105 may include S1051 to S1052.

[0101] S1051. Adjust the initial value of the preset overload protection current threshold according to the overload interference index to determine the adaptive overload protection current threshold.

[0102] For example, using the interference index threshold For example, if the current overload interference index... If the threshold remains unchanged, then the original threshold is maintained. ;like The adaptive overload protection current threshold is calculated using the following formula: in, The initial value of the preset overload protection current threshold can be set to 1.2 times the rated operating current of the charging pile. This way, in the event of a real local overload (… The threshold remains unchanged when the disturbance is relatively small, ensuring timely protection action. Under power grid impact disturbances (… When the threshold is large, it should be appropriately increased to avoid false triggering.

[0103] S1052. When the current in any one of the three phases of the charging station exceeds the adaptive overload protection current threshold, an overload fault is determined to exist at the charging station. Overload protection action is executed for the charging station where an overload fault is determined to exist.

[0104] Specifically, the three-phase current of the charging station is monitored in real time. When the real-time value of any phase current exceeds the adaptive overload protection current threshold corresponding to the current overload fault detection window, it is determined that a real overload fault has occurred at that charging station, and the charging station control system executes overload protection actions. Overload protection actions include, but are not limited to, cutting off the power supply, reducing the charging power, or issuing an alarm signal.

[0105] In one design, an embodiment of this application provides a charging pile overload protection system to ensure charging efficiency, comprising: a data acquisition unit, a first index determination unit, a second index determination unit, an interference index fusion unit, and an overload protection unit. The units communicate bidirectionally via a communication link to ensure real-time interaction of collected data and analysis results. The communication link can employ wired or wireless transmission methods to meet communication requirements in different monitoring scenarios.

[0106] The data acquisition unit collects three-phase current data from each charging station within the charging pile network. The first index determination unit determines a first interference index based on the degree of change in current amplitude and phase shift in the three-phase current data. The second index determination unit determines a second interference index based on the consistency variation of the three-phase current data among the charging stations within the network. The interference index fusion unit determines an overload interference index based on the first and second interference indices. The overload protection unit adjusts the overload protection current threshold based on the overload interference index and performs overload protection actions on the corresponding charging station according to the adjusted overload protection current threshold.

[0107] As one possible implementation, the first index determination unit includes: a peak detection module for determining the three-phase current peak sequence based on three-phase current data; an amplitude determination module for determining the degree of current amplitude change based on the first-order forward difference value in the three-phase current peak sequence; a phase transformation module for determining the instantaneous phase sequence based on the three-phase current data; a phase offset determination module for determining the degree of phase offset change based on the phase difference change information between each phase in the instantaneous phase sequence; and an index calculation module for determining a first interference index based on the degree of current amplitude change and the degree of phase offset change.

[0108] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0109] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for overload protection of charging piles to ensure charging efficiency, characterized in that, The method includes: Collect three-phase current data for each charging pile location in the charging pile network; The first interference index is determined based on the degree of change in current amplitude and the degree of change in phase offset in the three-phase current data; The second interference index is determined based on the consistency change value of the three-phase current data among the charging piles in the charging pile network. The overload interference index is determined based on the first interference index and the second interference index; The overload protection current threshold is adjusted according to the overload interference index, and the overload protection action is performed on the corresponding charging pile position according to the adjusted overload protection current threshold.

2. The overload protection method for charging piles to ensure charging efficiency according to claim 1, characterized in that, The determination of the first interference index based on the degree of change in current amplitude and the degree of change in phase offset in the three-phase current data includes: Based on the three-phase current data, determine the three-phase current peak sequence; The degree of change in current amplitude is determined based on the first-order forward difference value in the three-phase current peak sequence; Based on the three-phase current data, determine the instantaneous phase sequence; The degree of phase shift change is determined based on the phase difference change information between each phase in the instantaneous phase sequence; The first interference index is determined based on the degree of change in current amplitude and the degree of change in phase offset.

3. The overload protection method for charging piles to ensure charging efficiency according to claim 2, characterized in that, The step of determining the degree of change in current amplitude based on the first-order forward difference value in the three-phase current peak sequence includes: Calculate the first-order forward difference of the peak current of each phase in the three-phase current peak sequence; Based on the first-order forward difference of the peak current of each phase, the net change in current of each phase is determined respectively; The net change in current of each phase is normalized based on the maximum absolute value of the net change in current of each phase. The mean value of the net change in current of each phase after normalization is determined as the degree of change in current amplitude.

4. The overload protection method for charging piles to ensure charging efficiency according to claim 2, characterized in that, The step of determining the degree of phase shift change based on the phase difference change information between each phase in the instantaneous phase sequence includes: Calculate the original phase difference sequence between each phase in the instantaneous phase sequence, and determine the phase difference deviation sequence between each phase based on the standard three-phase rated phase difference; The sampling point where the average value of the phase difference deviation between each phase exceeds a preset phase threshold for the first time at the same sampling point in the phase difference deviation sequence is taken as the phase abrupt change point. Based on the phase difference deviation sequence after the phase abrupt change point, the mean phase difference deviation between each phase is determined respectively; Based on the preset maximum phase deviation threshold, the phase difference deviation from the mean between each phase is normalized. The average value of the phase difference between each phase after normalization is taken as the degree of phase shift change.

5. The overload protection method for charging piles to ensure charging efficiency according to claim 1, characterized in that, The determination of the second interference index based on the consistency variation value of the three-phase current data among the charging pile locations in the charging pile network includes: The three-phase current data at each charging pile location in the charging pile network are normalized to obtain the normalized current data for each charging pile location. Based on the normalized current data, the local peak sequence of each charging station is determined; The consistency change value is determined based on the correlation index between the local peak sequences of each charging station. The consistency change value is subjected to a preset mapping process to obtain the second interference index.

6. The overload protection method for charging piles to ensure charging efficiency according to claim 5, characterized in that, The step of determining the consistency change value based on the correlation index between the local peak sequences of each charging pile location includes: Based on the correspondence between the current data of the same phase, calculate the correlation index between the local peak sequence of the current data of each phase at the current charging pile location and the local peak sequence of the corresponding current data of other charging pile locations under the charging pile network, excluding the current charging pile location. Based on the correlation index of the local peak sequence of the phase current data between the current charging pile location and the other charging pile locations, the mean value of the correlation index between the current charging pile location and the other charging pile locations is determined. The mean of the correlation index is determined as the consistency change value.

7. The overload protection method for charging piles to ensure charging efficiency according to claim 1, characterized in that, The step of adjusting the overload protection current threshold according to the overload interference index, and performing overload protection action on the corresponding charging pile position according to the adjusted overload protection current threshold, includes: The initial value of the preset overload protection current threshold is adjusted according to the overload interference index to determine the adaptive overload protection current threshold. When any one phase current in the three-phase current data of the charging pile exceeds the adaptive overload protection current threshold, it is determined that the charging pile has an overload fault. Overload protection actions are performed on charging stations that are determined to have overload faults.

8. The overload protection method for charging piles to ensure charging efficiency according to claim 1, characterized in that, The collection of three-phase current data for each charging pile location within the charging pile network includes: The three-phase current waveform signal at each charging pile location is collected in real time by the current transformer built into each charging pile location in the charging pile network. The collected three-phase current waveform signals are digitized according to a preset sampling frequency to obtain a sequence of instantaneous three-phase current values ​​at each sampling point. The digitized three-phase current data is segmented according to the duration of the overload fault detection window to obtain the three-phase current waveform segments under each overload fault detection window. The three-phase current waveform segment is used as the three-phase current data to be analyzed.

9. An overload protection system for charging piles to ensure charging efficiency, characterized in that, include: The data acquisition unit is used to collect the three-phase current data of each charging pile location in the charging pile network. The first index determination unit is used to determine the first interference index based on the degree of change in current amplitude and the degree of change in phase offset in the three-phase current data. The second index determination unit is used to determine the second interference index based on the consistency change value of the three-phase current data between each charging pile location in the charging pile network. An interference index fusion unit is used to determine an overload interference index based on the first interference index and the second interference index. The overload protection unit is used to adjust the overload protection current threshold according to the overload interference index, and to perform overload protection action on the corresponding charging pile position according to the adjusted overload protection current threshold.

10. The charging pile overload protection system for ensuring charging efficiency according to claim 9, characterized in that, The first index determining unit includes: The peak detection module is used to determine the three-phase current peak sequence based on the three-phase current data; The amplitude determination module is used to determine the degree of change in current amplitude based on the first-order forward difference value in the three-phase current peak sequence. The phase transformation module is used to determine the instantaneous phase sequence based on the three-phase current data; The phase offset degree determination module is used to determine the degree of phase offset change based on the phase difference change information between each phase in the instantaneous phase sequence; An index calculation module is used to determine the first interference index based on the degree of change in current amplitude and the degree of change in phase offset.

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