Charging pile state evaluation method

Abstract

The invention relates to the technical field of charging pile state evaluation, in particular to a charging pile state evaluation method, which adopts a signal conditioning function, enhances signal strength, removes noise and interference, can comprehensively obtain weak signals of an output interface of a charging pile, and uses a time domain and frequency domain analysis algorithm to evaluate the state of the charging pile. Discrete sampling and fast Fourier transform are accurately carried out, so that a voltage effective value and a current effective value are accurately calculated, a signal spectrogram is accurately obtained, harmonic related indexes are accurately calculated, a charging pile electrical performance evaluation system is established, the influence of multiple factors on the electrical performance of a charging pile output interface is comprehensively considered, and the evaluation accuracy is improved. The state of the charging pile is effectively evaluated, the state of the charging pile is accurately obtained, potential problems can be found in time by accurately evaluating the state of the charging pile, powerful support is provided for maintenance and management of the charging pile, the maintenance efficiency of the charging pile is improved, and manpower and time cost is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of charging pile status assessment, and in particular to a method for assessing the status of a charging pile. Background Art

[0002] Charging pile status assessment is an important technology. With the rapid development of electric vehicles, charging piles, as important supporting facilities for electric vehicles, have been greatly improved in quantity and quality. However, during the long-term operation of charging piles at charging stations, the charging pile output interface is often maliciously or improperly plugged in and out by charging personnel, resulting in certain wear and tear on the charging pile output interface, thereby affecting the electrical performance of the charging pile output interface. The decline in the electrical performance of the charging pile output interface will lead to a decrease in the charging efficiency of the charging pile and an increase in the frequency of failures.

[0003] The traditional charging pile status evaluation method lacks effective signal conditioning function, resulting in insufficient signal strength, making the signal easily lost in subsequent processing, and there are various electromagnetic interference sources in the environment where the charging pile is located, so that the acquired signal contains noise and interference, resulting in the signal being not pure enough, making it difficult to fully obtain the weak signal of the charging pile output interface. Due to the loss and impurity of the signal, and the traditional charging pile status evaluation method uses a relatively simple analysis algorithm, it is impossible to accurately perform discrete sampling and fast Fourier transform, resulting in inaccurate calculation of the voltage effective value and current effective value, and the inability to accurately obtain the signal spectrum diagram, so it is difficult to calculate harmonic-related indicators. In addition, the traditional charging pile evaluation method has a relatively simple evaluation and judgment on the electrical performance of the charging pile. It collects the electrical performance prediction values ​​of the output interface of the same batch and the same model of charging piles, and establishes a comparison database, so that the above factors are not comprehensively considered. The influence on the electrical performance of the output interface of the charging pile is not comprehensive enough, so that the electrical performance analysis of the output interface of the charging pile is not comprehensive enough, so that the status of the charging pile cannot be effectively evaluated, and the status of the charging pile cannot be accurately obtained. In order to solve this technical problem, we provide a charging pile status evaluation method. Summary of the invention

[0004] The purpose of the present invention is to provide a method for evaluating the status of a charging pile to solve the problems raised in the above background technology.

[0005] To achieve the above object, one of the objects of the present invention is to provide a method for evaluating the status of a charging pile, comprising the following steps:

[0006] S1. Install a sensor between the charging pile output interface and the electric vehicle connection point, collect the current signal and voltage signal of the charging pile output interface in the constant current charging state and the constant voltage charging state in real time, perform digital preprocessing on the current signal and voltage signal, obtain the current signal and voltage signal between the charging pile output interface and the electric vehicle connection point, and store them in the central processing unit;

[0007] S2. Extract the collected current signal and voltage signal from the central processing unit, and perform time domain and frequency domain analysis on the collected current signal and voltage signal, calculate the voltage effective value, current effective value, voltage fluctuation coefficient and current fluctuation coefficient, and then analyze the charging power and power factor of the charging pile output interface to obtain the energy utilization efficiency of the charging pile;

[0008] S3. Analyze and calculate the harmonic data to obtain the total harmonic distortion rate of the charging pile output interface, establish a historical database of the electrical performance of the charging pile, and comprehensively process the voltage effective value, current effective value, voltage fluctuation coefficient, current fluctuation coefficient, energy utilization efficiency and total harmonic distortion rate to obtain the electrical performance value of the charging pile output interface. By comparing the change trend of the electrical performance value with the historical electrical performance value, the predicted value of the electrical performance of the charging pile output interface is obtained;

[0009] S4. Collect the electrical performance prediction values ​​of multiple charging piles from the same batch, establish a comparison database, calculate the mean of the electrical performance prediction values ​​of the charging piles from the same batch, compare the electrical performance prediction value of the charging pile to be evaluated with the mean of similar charging piles, and judge the status of the charging pile based on the comparison results.

[0010] As a further improvement of the technical solution, the method of digitally processing the current signal and the voltage signal in S1 specifically includes:

[0011] The digital processing includes signal conditioning and analog-to-digital conversion. The signal conditioning includes amplification and filtering. The amplification is used to enhance the strength of the current signal and the voltage signal. The filtering is used to filter the current signal and the voltage signal. The current signal and the voltage signal after signal conditioning are sampled and quantized to obtain the current signal and the voltage signal between the charging pile output interface and the electric vehicle connection point, and are stored in the central processing unit.

[0012] As a further improvement of the technical solution, the method of performing time domain and frequency domain analysis on the collected current signal and voltage signal in S2, and calculating the voltage effective value, current effective value, voltage fluctuation coefficient, and current fluctuation coefficient, specifically comprises the following steps:

[0013] S2.1. In the time domain, the voltage signal within one cycle is discretely sampled to obtain n voltage values ​​u(n). Substitute u(n) into the formula to calculate the voltage effective value U yx , The one cycle is a standard cycle of the AC signal;

[0014] S2.2, repeat the steps of S2.1 to obtain n current values ​​i(n), substitute i(n) into the formula to calculate the effective value of the current I yx ,

[0015] S2.3. Sort the n voltage values ​​u(n) obtained in S2.1 in descending order to obtain the maximum voltage U max , minimum voltage U min And the average voltage but Where K u Expressed as voltage fluctuation coefficient, repeat the above steps to obtain the current fluctuation coefficient K i ,

[0016] As a further improvement of the technical solution, the charging power and power factor of the charging pile output interface are analyzed in S2 to obtain the energy utilization efficiency of the charging pile, which specifically includes:

[0017] The voltage and current signals are collected in real time by using the voltage sensor and current sensor installed at the output interface of the charging pile. The voltage and current signals are analyzed in time domain and frequency domain to obtain the instantaneous voltage U(t) and instantaneous current I(t). The instantaneous voltage U(t) and instantaneous current I(t) are substituted into the formula to calculate the instantaneous power P(t) of the output interface of the charging pile, that is, P(t) = U(t) × I(t). Then the average charging power of the output interface of the charging pile is:

[0018]

[0019] Among them, P out is the average charging power of the charging pile output interface. In actual use, the charging pile has energy loss. Let the loss power of the charging pile be P loss , substitute the average charging power, power loss, voltage RMS and current RMS of the charging pile output interface into the formula to calculate the power factor cosφ of the charging pile output interface. The specific calculation formula is:

[0020]

[0021] The energy efficiency of the charging pile is:

[0022]

[0023] As a further improvement of the technical solution, the harmonic data is analyzed and calculated in S3 to obtain the total harmonic distortion rate of the charging pile output interface, and the method of evaluating the harmonic pollution degree of the charging pile to the power grid according to the total harmonic distortion rate of the charging pile output interface specifically includes:

[0024] The current signal between the charging pile output interface and the electric vehicle connection point is extracted from the central processing unit, and the current signal is subjected to fast Fourier transform to obtain the spectrum of the current signal. According to the spectrum of the current signal, the fundamental current frequency f1 and the fundamental current amplitude I1 are obtained. The fundamental current frequency is the grid current frequency, and the harmonic current frequency f h =hf1, then the harmonic current amplitude is I h , then the total harmonic distortion is:

[0025]

[0026] Wherein, h = (2, 3, ..., r), r is the highest harmonic order considered, and the value range of α is set to [0, 0.5]. If the value of the total harmonic distortion rate α is smaller, it means that the harmonic pollution degree of the charging pile to the power grid is lower.

[0027] As a further improvement of the technical solution, the method of obtaining the predicted value of the electrical performance of the output interface of the charging pile by comparing the change trend of the electrical performance value with the historical electrical performance value in S3 specifically includes:

[0028] The historical voltage effective value, current effective value, voltage fluctuation coefficient, current fluctuation coefficient, energy utilization efficiency and total harmonic distortion rate of the charging pile output interface are collected and a charging pile electrical performance history database is established. By analyzing the charging pile electrical performance history database, the influence weights of the voltage effective value, current effective value, voltage fluctuation coefficient, current fluctuation coefficient, energy utilization efficiency and total harmonic distortion rate of the charging pile output interface on the electrical performance are obtained, and the electrical performance value of the charging pile output interface is obtained through comprehensive processing:

[0029] Q=ω1U yx +ω2I yx +ω3K u +ω4K i +ω5η-ω6α

[0030] The electrical performance of the charging pile output interface is calculated at one-hour intervals and stored in the charging pile electrical performance history database to form a historical data sequence {Q1, Q2, ..., Q s}, smooth the historical data series, and perform trend analysis on the historical data series after smoothing. The specific trend analysis is as follows:

[0031] Assume that the electrical performance value of the charging pile output interface at the current moment is Q t , the current moment predicted by the previous moment is The smoothing coefficient is σ, (0<σ<1), which is obtained from historical experience and is used to give a weight to the electrical performance prediction value at the next moment. The electrical performance prediction value at the next moment is:

[0032]

[0033] As a further improvement of the technical solution, the method of establishing a comparison database in S4 and calculating the average of the predicted values ​​of the electrical performance of the same batch of charging piles respectively includes:

[0034] According to the method steps S1-S3, the electrical performance prediction values ​​of the output interfaces of the same batch and model of charging piles are collected, and a comparison database is established. Suppose a total of j charging piles are collected, and the jth charging pile has a total of m w The electrical performance prediction value is ψ, and the average electrical performance prediction value is:

[0035]

[0036] The mean of the predicted electrical performance values As the normal range boundary, the predicted value of the electrical performance of the charging pile to be evaluated The average of the electrical performance predictions For comparison, if the predicted value of the charging pile electrical performance is Beyond This indicates that the status of the charging pile is abnormal.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] In the evaluation method of the charging pile status, effective signal conditioning functions are adopted, including amplification and filtering, which enhances the signal strength and reduces the signal loss in subsequent processing. At the same time, noise and interference are removed to make the signal purer, and the weak signal of the charging pile output interface can be fully acquired. The time domain and frequency domain analysis algorithms can be used to accurately perform discrete sampling and fast Fourier transform, so as to accurately calculate the effective value of voltage and current, and accurately obtain the spectrum diagram of the signal, and then accurately calculate the harmonic related indicators, and establish a complete charging pile electrical performance evaluation system, which comprehensively considers the influence of multiple factors on the electrical performance of the charging pile output interface, and makes the electrical performance analysis of the charging pile output interface more comprehensive, which can effectively evaluate the status of the charging pile and accurately acquire the status of the charging pile. By accurately evaluating the status of the charging pile, potential problems can be discovered in time, which provides strong support for the maintenance and management of the charging pile, improves the maintenance efficiency of the charging pile, and saves manpower and time costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is the overall workflow diagram of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Example 1

[0042] See also Figure 1 As shown, this embodiment provides a method for evaluating the status of a charging pile, comprising the following steps:

[0043] S1. Install a sensor between the charging pile output interface and the electric vehicle connection point, collect the current signal and voltage signal of the charging pile output interface in the constant current charging state and the constant voltage charging state in real time, perform digital preprocessing on the current signal and voltage signal, obtain the current signal and voltage signal between the charging pile output interface and the electric vehicle connection point, and store them in the central processing unit;

[0044] The current and voltage signals at the output interface of the charging pile are usually weak and may be affected by noise and interference. In order to accurately acquire and process these signals, digital processing is required.

[0045] The method of digitally processing the current signal and the voltage signal in S1 specifically includes:

[0046] Digital processing includes signal conditioning and analog-to-digital conversion. Signal conditioning includes amplification and filtering. Amplification is used to enhance the strength of current signals and voltage signals, making them more obvious and stable in subsequent processing, reducing the possibility of signal loss or distortion, and being able to more accurately obtain the current signal and voltage signal between the output interface of the charging pile and the connection point of the electric vehicle, providing a reliable data basis for subsequent electrical performance analysis. Filtering is used to filter the current signal and voltage signal. Filtering can effectively remove noise and interference in the signal, making the signal purer, thereby improving the accuracy of subsequent analysis and processing. The current signal and voltage signal after signal conditioning are sampled and quantized to obtain the current signal and voltage signal between the output interface of the charging pile and the connection point of the electric vehicle. Through signal conditioning and digital processing, the reliability and stability of the entire charging pile status assessment system can be improved, the occurrence of misjudgment and failure can be reduced, and the signals can be stored in the central processing unit.

[0047] The current and voltage signals of the charging pile change with time. Time domain and frequency domain analysis can provide a more comprehensive understanding of the characteristics of the signal. Calculating parameters such as voltage RMS, current RMS, voltage fluctuation coefficient, and current fluctuation coefficient can quantitatively evaluate the electrical performance of the charging pile. These parameters are crucial for judging the stability and reliability of the charging pile.

[0048] S2. Extract the collected current signal and voltage signal from the central processing unit, and perform time domain and frequency domain analysis on the collected current signal and voltage signal, calculate the voltage effective value, current effective value, voltage fluctuation coefficient and current fluctuation coefficient, and then analyze the charging power and power factor of the charging pile output interface to obtain the energy utilization efficiency of the charging pile;

[0049] In S2, the collected current signal and voltage signal are analyzed in the time domain and frequency domain, and the voltage effective value, current effective value, voltage fluctuation coefficient, and current fluctuation coefficient are calculated. The specific steps are as follows:

[0050] S2.1. In the time domain, the voltage signal within one cycle is discretely sampled to obtain n voltage values ​​u(n). Substitute u(n) into the formula to calculate the voltage effective value U yx , One cycle is the standard cycle of AC signal;

[0051] S2.2, repeat the steps of S2.1 to obtain n current values ​​i(n), substitute i(n) into the formula to calculate the effective value of the current I yx ,

[0052] S2.3. Sort the n voltage values ​​u(n) obtained in S2.1 in descending order to obtain the maximum voltage Umax , minimum voltage U min And the average voltage but Where K u Expressed as voltage fluctuation coefficient, repeat the above steps to obtain the current fluctuation coefficient K i , The calculation of the voltage fluctuation coefficient and the current fluctuation coefficient can help discover potential problems that may exist in the charging pile, such as excessive voltage or current fluctuations, so that maintenance and adjustments can be carried out in a timely manner.

[0053] The charging power and power factor of a charging pile are important indicators for measuring its energy efficiency. By performing time domain and frequency domain analysis on the voltage and current signals to obtain the instantaneous voltage and instantaneous current, the instantaneous power can be calculated more accurately, and then the average charging power can be obtained. At the same time, considering the energy loss of the charging pile, the power factor needs to be calculated through relevant formulas to comprehensively evaluate the energy utilization of the charging pile.

[0054] In S2, the charging power and power factor of the charging pile output interface are analyzed to obtain the energy utilization efficiency of the charging pile, including:

[0055] The voltage and current signals are collected in real time by using the voltage sensor and current sensor installed at the output interface of the charging pile. The voltage and current signals are analyzed in time domain and frequency domain to obtain the instantaneous voltage U(t) and instantaneous current I(t). The instantaneous voltage U(t) and instantaneous current I(t) are substituted into the formula to calculate the instantaneous power P(t) of the output interface of the charging pile, that is, P(t) = U(t) × I(t). Then the average charging power of the output interface of the charging pile is:

[0056]

[0057] Among them, P out is the average charging power of the charging pile output interface. In actual use, the charging pile has energy loss. Let the loss power of the charging pile be P loss , substitute the average charging power, power loss, voltage RMS and current RMS of the charging pile output interface into the formula to calculate the power factor cosφ of the charging pile output interface. The specific calculation formula is:

[0058]

[0059] By introducing the power loss to calculate the power factor, it is more in line with the actual situation and makes the evaluation of energy efficiency more accurate. The energy efficiency of the charging pile is:

[0060]

[0061] Taking multiple factors into consideration can scientifically evaluate the energy efficiency of charging piles, provide a basis for optimizing the performance of charging piles, and help discover the shortcomings of charging piles in energy utilization, so as to take corresponding measures to optimize and improve energy efficiency.

[0062] S3. Analyze and calculate the harmonic data to obtain the total harmonic distortion rate of the charging pile output interface, establish a historical database of the electrical performance of the charging pile, and comprehensively process the voltage effective value, current effective value, voltage fluctuation coefficient, current fluctuation coefficient, energy utilization efficiency and total harmonic distortion rate to obtain the electrical performance value of the charging pile output interface. By comparing the change trend of the electrical performance value with the historical electrical performance value, the predicted value of the electrical performance of the charging pile output interface is obtained;

[0063] Charging piles may generate harmonics when working, which will pollute the power grid and affect the power quality of the grid. Therefore, it is necessary to analyze and calculate the harmonic data to obtain the total harmonic distortion rate in order to evaluate the degree of harmonic pollution of charging piles to the power grid.

[0064] In S3, the harmonic data is analyzed and calculated to obtain the total harmonic distortion rate of the charging pile output interface, and the method of evaluating the harmonic pollution degree of the charging pile to the power grid is based on the total harmonic distortion rate of the charging pile output interface, which specifically includes:

[0065] The current signal between the charging pile output interface and the electric vehicle connection point is extracted from the central processing unit, and the current signal is subjected to fast Fourier transform to obtain the spectrum of the current signal. The fundamental current frequency, fundamental current amplitude, and harmonic current frequency and amplitude can be accurately obtained, so as to accurately calculate the total harmonic distortion rate. The fundamental current frequency f1 and fundamental current amplitude I1 are obtained according to the spectrum of the current signal. The fundamental current frequency is the grid current frequency, and the harmonic current frequency f h =hf1, then the harmonic current amplitude is I h , then the total harmonic distortion is:

[0066]

[0067] Wherein, h = (2, 3, ..., r), r is the highest harmonic order considered, and the value range of α is [0, 0.5]. It can clearly evaluate the harmonic pollution degree of the charging pile to the power grid. If the value of the total harmonic distortion rate α is smaller, it means that the harmonic pollution degree of the charging pile to the power grid is lower. By evaluating the harmonic pollution degree of the charging pile to the power grid, corresponding measures can be taken to reduce harmonic pollution, protect the power quality of the power grid, and ensure the stable operation of the power grid.

[0068] The electrical performance of charging piles will change over time. By comparing the changing trends of historical electrical performance values, future electrical performance can be better predicted. By establishing and analyzing a historical database of charging pile electrical performance, we can gain an in-depth understanding of the weight of each parameter on electrical performance, thereby more accurately evaluating the status of the charging pile.

[0069] In S3, by comparing the change trend of the electrical performance value with the historical electrical performance value, the method of obtaining the predicted value of the electrical performance of the charging pile output interface includes:

[0070] Collect the historical voltage effective value, historical current effective value, historical voltage fluctuation coefficient, historical current fluctuation coefficient, historical energy utilization efficiency and historical total harmonic distortion rate of the charging pile output interface and establish a historical database of charging pile electrical performance. Make full use of historical data to more comprehensively understand the performance changes of the charging pile and avoid the limitations of judging only based on current data. By analyzing the historical database of charging pile electrical performance, the influence weights of the voltage effective value, current effective value, voltage fluctuation coefficient, current fluctuation coefficient, energy utilization efficiency and total harmonic distortion rate of the charging pile output interface on the electrical performance are obtained, which can more accurately obtain the predicted value of the electrical performance of the charging pile output interface, provide an important basis for the maintenance and management of the charging pile, and carry out comprehensive processing to obtain the electrical performance value of the charging pile output interface:

[0071] Q=ω1U yx +ω2I yx +ω3K u +ω4K i +ω5η-ω6α

[0072] The electrical performance of the charging pile output interface is calculated at one-hour intervals and stored in the charging pile electrical performance history database to form a historical data sequence {Q1, Q2, ..., Q s}, calculate and store at one-hour intervals, can timely capture the changes in the electrical performance of the charging pile, predict the future electrical performance, so as to take corresponding measures for prevention and maintenance, avoid the occurrence of failures, smooth the historical data series, and perform trend analysis on the historical data series after smoothing, which can reduce the impact of data fluctuations and more accurately grasp the development trend of electrical performance. The specific trend analysis is as follows:

[0073] Assume that the electrical performance value of the charging pile output interface at the current moment is Q t , the current moment predicted by the previous moment is The smoothing coefficient is σ, (0<σ<1). The smoothing coefficient is obtained from historical experience and is used to give weight to the electrical performance prediction value at the next moment. The electrical performance prediction value at the next moment is:

[0074]

[0075] Based on the electrical performance prediction values ​​and trend analysis results, the maintenance strategy of the charging pile can be optimized, the maintenance efficiency can be improved, and the maintenance cost can be reduced.

[0076] S4. Collect the electrical performance prediction values ​​of multiple charging piles from the same batch, establish a comparison database, calculate the mean of the electrical performance prediction values ​​of the charging piles from the same batch, compare the electrical performance prediction value of the charging pile to be evaluated with the mean of similar charging piles, and judge the status of the charging pile based on the comparison results.

[0077] In order to more accurately assess the status of a charging pile, its electrical performance prediction needs to be compared with other charging piles in the same batch. By establishing a comparison database and calculating the mean, a relative standard can be determined to determine whether the performance of a single charging pile is abnormal.

[0078] In S4, a comparison database is established to calculate the average values ​​of the predicted electrical performance values ​​of the same batch of charging piles, including:

[0079] According to the method steps S1-S3, the electrical performance prediction values ​​of the output interfaces of the same batch and the same model of charging piles are collected. The electrical performance prediction values ​​of the same batch and the same model of charging piles are collected. The common characteristics and differences of the batch of charging piles can be taken into account to make the evaluation more targeted, and a comparison database is established. Suppose a total of j charging piles are collected, of which the jth charging pile has a total of m w The electrical performance prediction value is ψ, and the average electrical performance prediction value is:

[0080]

[0081] By calculating the mean value as the normal range boundary, a unified standard is provided for evaluating the status of charging piles, avoiding the uncertainty of subjective judgment, and taking the mean value of the electrical performance prediction value as the normal range boundary. As the normal range boundary, the predicted value of the electrical performance of the charging pile to be evaluated The average of the electrical performance predictions For comparison, if the predicted value of the charging pile electrical performance is Beyond This indicates that the status of the charging pile is abnormal. Based on the status assessment results of the charging pile, maintenance resources can be reasonably arranged to avoid waste and improve resource utilization efficiency.

[0082] The above-mentioned charging pile status evaluation method collects current and voltage signals in real time by installing sensors between the charging pile output interface and the electric vehicle connection point, and performs digital preprocessing and storage. Then, these signals are analyzed in time domain and frequency domain to calculate multiple electrical performance indicators, including voltage effective value, current effective value, voltage fluctuation coefficient, current fluctuation coefficient, energy utilization efficiency and total harmonic distortion rate, etc. Next, a charging pile electrical performance history database is established, these indicators are comprehensively processed to obtain electrical performance values, and electrical performance prediction values ​​are obtained by comparing historical data. Finally, the electrical performance prediction values ​​of multiple charging piles in the same batch are collected, a comparison database is established and the mean is calculated, and the electrical performance prediction value of the charging pile to be evaluated is compared with the mean, so as to judge the status of the charging pile. Compared with the prior art, the present invention has the advantages of comprehensive and real-time data collection, accurate and effective data analysis, perfect evaluation index system, strong fault prediction ability and high maintenance efficiency, and can evaluate the status of the charging pile more scientifically, accurately and in real time, providing strong support for the maintenance and management of the charging pile.

[0083] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for evaluating the status of a charging pile, characterized in that: The following steps are involved: S1. Install a sensor between the charging pile output interface and the electric vehicle connection point, collect the current signal and voltage signal of the charging pile output interface in the constant current charging state and the constant voltage charging state in real time, perform digital preprocessing on the current signal and voltage signal, obtain the current signal and voltage signal between the charging pile output interface and the electric vehicle connection point, and store them in the central processing unit; S2. Extract the collected current signal and voltage signal from the central processing unit, and perform time domain and frequency domain analysis on the collected current signal and voltage signal, calculate the voltage effective value, current effective value, voltage fluctuation coefficient and current fluctuation coefficient, and then analyze the charging power and power factor of the charging pile output interface to obtain the energy utilization efficiency of the charging pile; S3. Analyze and calculate the harmonic data to obtain the total harmonic distortion rate of the charging pile output interface, establish a historical database of the electrical performance of the charging pile, and comprehensively process the voltage effective value, current effective value, voltage fluctuation coefficient, current fluctuation coefficient, energy utilization efficiency and total harmonic distortion rate to obtain the electrical performance value of the charging pile output interface. By comparing the change trend of the electrical performance value with the historical electrical performance value, the predicted value of the electrical performance of the charging pile output interface is obtained; S4. Collect the electrical performance prediction values ​​of multiple charging piles from the same batch, establish a comparison database, calculate the mean of the electrical performance prediction values ​​of the charging piles from the same batch, compare the electrical performance prediction value of the charging pile to be evaluated with the mean of similar charging piles, and judge the status of the charging pile based on the comparison results.

2. The charging pile status evaluation method according to claim 1, characterized in that: The method of digitally processing the current signal and the voltage signal in S1 specifically includes: The digital processing includes signal conditioning and analog-to-digital conversion. The signal conditioning includes amplification and filtering. The amplification is used to enhance the strength of the current signal and the voltage signal. The filtering is used to filter the current signal and the voltage signal. The current signal and the voltage signal after signal conditioning are sampled and quantized to obtain the current signal and the voltage signal between the charging pile output interface and the electric vehicle connection point, and are stored in the central processing unit.

3. The method for evaluating the status of a charging pile according to claim 1, characterized in that: The method of performing time domain and frequency domain analysis on the collected current signal and voltage signal in S2, and calculating the voltage effective value, current effective value, voltage fluctuation coefficient, and current fluctuation coefficient, specifically comprises the following steps: S2.

1. In the time domain, the voltage signal within one cycle is discretely sampled to obtain n voltage values ​​u(n). Substitute u(n) into the formula to calculate the voltage effective value U yx , The one cycle is a standard cycle of the AC signal; S2.2, repeat the steps of S2.1 to obtain n current values ​​i(n), substitute i(n) into the formula to calculate the effective value of the current I yx , S2.

3. Sort the n voltage values ​​u(n) obtained in S2.1 in descending order to obtain the maximum voltage U max , minimum voltage U min And the average voltage but Where K u Expressed as voltage fluctuation coefficient, repeat the above steps to obtain the current fluctuation coefficient K i , 4. The method for evaluating the status of a charging pile according to claim 1, characterized in that: In S2, the charging power and power factor of the charging pile output interface are analyzed to obtain the energy utilization efficiency of the charging pile, which specifically includes: The voltage and current signals are collected in real time by using the voltage sensor and current sensor installed at the output interface of the charging pile. The voltage and current signals are analyzed in time domain and frequency domain to obtain the instantaneous voltage U(t) and instantaneous current I(t). The instantaneous voltage U(t) and instantaneous current I(t) are substituted into the formula to calculate the instantaneous power P(t) of the output interface of the charging pile, that is, P(t) = U(t) × I(t). Then the average charging power of the output interface of the charging pile is: Among them, P out is the average charging power of the charging pile output interface. In actual use, the charging pile has energy loss. Let the loss power of the charging pile be P loss , substitute the average charging power, power loss, voltage RMS and current RMS of the charging pile output interface into the formula to calculate the power factor cosφ of the charging pile output interface. The specific calculation formula is: The energy efficiency of the charging pile is:

5. The charging pile status evaluation method according to claim 1, characterized in that: In S3, the harmonic data is analyzed and calculated to obtain the total harmonic distortion rate of the charging pile output interface, and the method of evaluating the harmonic pollution degree of the charging pile to the power grid according to the total harmonic distortion rate of the charging pile output interface specifically includes: The current signal between the charging pile output interface and the electric vehicle connection point is extracted from the central processing unit, and the current signal is subjected to fast Fourier transform to obtain the spectrum of the current signal. According to the spectrum of the current signal, the fundamental current frequency f1 and the fundamental current amplitude I1 are obtained. The fundamental current frequency is the grid current frequency, and the harmonic current frequency f h =hf1, then the harmonic current amplitude is I h , then the total harmonic distortion is: Wherein, h = (2, 3, ..., r), r is the highest harmonic order considered, and the value range of α is set to [0, 0.5]. If the value of the total harmonic distortion rate α is smaller, it means that the harmonic pollution degree of the charging pile to the power grid is lower.

6. The charging pile status evaluation method according to claim 1, characterized in that: The method of obtaining the predicted value of the electrical performance of the output interface of the charging pile by comparing the change trend of the electrical performance value with the historical electrical performance value in S3 specifically includes: The historical voltage effective value, current effective value, voltage fluctuation coefficient, current fluctuation coefficient, energy utilization efficiency and total harmonic distortion rate of the charging pile output interface are collected and a charging pile electrical performance history database is established. By analyzing the charging pile electrical performance history database, the influence weights of the voltage effective value, current effective value, voltage fluctuation coefficient, current fluctuation coefficient, energy utilization efficiency and total harmonic distortion rate of the charging pile output interface on the electrical performance are obtained, and the electrical performance value of the charging pile output interface is obtained through comprehensive processing: Q=ω1U yx +ω2I yx +ω3K u +ω4K i +ω5η-ω6α The electrical performance of the charging pile output interface is calculated at one-hour intervals and stored in the charging pile electrical performance history database to form a historical data sequence {Q1, Q2, ..., Q s }, smooth the historical data series, and perform trend analysis on the historical data series after smoothing. The specific trend analysis is as follows: Assume that the electrical performance value of the charging pile output interface at the current moment is Q t , the current moment predicted by the previous moment is The smoothing coefficient is σ, (0<σ<1), which is obtained from historical experience and is used to give a weight to the electrical performance prediction value at the next moment. The electrical performance prediction value at the next moment is:

7. The charging pile status evaluation method according to claim 1, characterized in that: The method of establishing a comparison database in S4 and calculating the average of the predicted values ​​of the electrical performance of the same batch of charging piles includes: According to the method steps S1-S3, the electrical performance prediction values ​​of the output interfaces of the same batch and model of charging piles are collected, and a comparison database is established. Suppose a total of j charging piles are collected, and the jth charging pile has a total of m w The electrical performance prediction value is ψ, and the average electrical performance prediction value is: The mean of the electrical performance prediction values As the normal range boundary, the predicted value of the electrical performance of the charging pile to be evaluated The average of the electrical performance predictions For comparison, if the predicted value of the charging pile electrical performance is Beyond This indicates that the status of the charging pile is abnormal.

Images