Method for Monitoring, Warning and Forecasting Return Current Harmonics of Rail Transit Vehicles

Abstract

The present invention discloses a method for monitoring and warning of return current harmonics in rail transit vehicles. During the operation of rail transit vehicles, the present invention continuously monitors multiple aspects related to the formation of harmonics by using online dynamic monitoring to measure the current value of traction return current on the rail, and by real-time monitoring of the traction voltage and current during the operation of rail transit vehicles and the unbalanced traction current on the two rails, so as to improve the comprehensiveness of harmonic monitoring. The threshold value set by converting harmonics into a mathematical model is lower than the value that meets the track circuit compatibility standard, which is used as a primary warning during subsequent operation. And the value after harmonic analysis is used as a secondary warning with the value that meets the track circuit compatibility standard, playing a role of multi-level warning, so as to facilitate timely responses to various harmonics. Through its design, it can timely detect the harmonics that are likely to have an impact during the operation of rail transit vehicles, providing good guarantee for the stable operation of rail transit vehicles.

Description

Technical Field

[0001] The present invention belongs to the technical field of rail transit monitoring, and particularly relates to a method for monitoring and warning the harmonic current of the return current of rail transit vehicles. Background Art

[0002] Rail transit refers to a type of transportation means or transportation system in which the operating vehicles need to run on specific tracks. The most typical rail transit is the railway system composed of traditional trains and standard railways. With the diversified development of train and railway technologies, rail transit presents more and more types, which are not only spread over long-distance land transportation, but also widely used in medium and short-distance urban public transportation.

[0003] With the continuous development of science and technology, the use of various non-linear electrical devices in the power system is very common, which causes certain harmonic pollution to the power system, reduces the quality of power supply, and disrupts the sustainable development of the power system. The content of power harmonics will affect the quality of the waveform, and at the same time pose a great threat to the power system, resulting in overheating of power equipment, reduction of service life, current resonance or voltage resonance, etc., which will have an adverse impact on the orderly operation of the overall power system. Therefore, it is necessary to analyze the causes of the power harmonic distribution and formulate feasible countermeasures. Therefore, it is of great practical significance to study the impact of power harmonics on power equipment and its countermeasures.

[0004] In the actual operation of existing urban rail transit vehicles, the harmonics formed in the power system are likely to affect the rail transit vehicles. When the existing urban rail transit vehicles monitor and deal with harmonics, their monitoring performance is usually not comprehensive enough, resulting in certain deficiencies in dealing with the impact of harmonics and being prone to excessive influence on the rail transit vehicles. For this reason, we propose a method for monitoring and warning the harmonic current of the return current of rail transit vehicles to solve the above problems. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a method for monitoring and warning the harmonic current of the return current of rail transit vehicles, avoiding the problems that when the existing urban rail transit vehicles monitor and deal with harmonics, their monitoring performance is usually not comprehensive enough, resulting in certain deficiencies in dealing with the impact of harmonics and being prone to excessive influence on the rail transit vehicles.

[0006] To solve the above technical problems, the present invention provides the following technical solution: A method for monitoring and warning the harmonic current of the return current of rail transit vehicles, including the following steps:

[0007] S1. First, measure the real-time value of the current of the traction return current of the rail transit vehicle on the rail. Before the measurement, the monitoring system uses the harmonic current limit standard of the rail transit vehicle adopted according to the type of the track circuit on which the rail transit vehicle travels as a reference benchmark.

[0008] S2. When the current value of the traction return current on the rail is measured in real time, a notch filter is used to attenuate the 50 Hz fundamental wave signal to improve the measurement accuracy of the harmonic signal. At the same time, an anti-aliasing filter is also used to filter out signals outside the measurement frequency band to prevent frequency aliasing when performing FFT analysis on the sampled digital signal. And the measurement frequency is determined according to the specific track circuit type, so that the measurement frequency meets the detection requirements of the rail transit vehicle.

[0009] S3. Then, a Rogowski coil is used to measure the current value. During the process of measuring the current value, an integrator is added and an amplifier circuit is added behind it for amplification to increase the restored signal, and the presence of a capacitor is used to filter out unnecessary interference.

[0010] S4. After the return current value of the rail transit vehicle is measured in real time, a transient recorder is used to record its data value in real time.

[0011] S5. While the above process is being implemented, the traction currents of the tracks on both sides of the rail transit vehicle are monitored in real time to monitor whether the traction currents on both sides of the tracks are balanced, and their detection data are transmitted and recorded. Secondly, an online dynamic monitoring system is used to monitor the traction voltage and current during the operation of the rail transit vehicle in real time.

[0012] S6. After the data values in the above steps are recorded, the FFT algorithm is immediately used to perform harmonic analysis on the track return current in the time domain in the frequency domain.

[0013] S7. After the harmonic analysis of the data values detected each time, the analysis results are stored. At the same time, they are immediately compared with the values that meet the track circuit compatibility standard, and they are converted into a mathematical model, and a threshold is set in the system of the rail transit vehicle according to the mathematical model for real-time warning.

[0014] As a preferred technical solution of the present invention, in step S3, using a Rogowski coil to measure the current value is based on the electromagnetic induction law and Ampere's circuital law as the theoretical basis.

[0015] As a preferred technical solution of the present invention, in steps S1 and S2, the number of input frequency points during detection should be selected according to the frequency response characteristics of the notch filter, and multiple representative frequency points are selected, and linear interpolation is performed for other frequency points.

[0016] As a preferred technical solution of the present invention, in step S5, during the monitoring of the traction voltage and current, the traction voltage and current that change according to the running state of the rail transit vehicle need to be converted into a mathematical model to pay attention to the harmonic energy caused by them, and the data is fed back to the rail transit vehicle monitoring system.

[0017] As a preferred technical solution of the present invention, in step S5, the formula used is:

[0018]

[0019] In the formula: K is the traction current unbalance coefficient, L S1 is the traction return current in the first rail, L S2 is the traction return current in the second rail.

[0020] As a preferred technical solution of the present invention, in step S6, the FFT algorithm design adopts the time extraction method to perform time-frequency transformation on the track return current.

[0021] As a preferred technical solution of the present invention, in step S7, the disturbing harmonic locations encountered by the rail transit vehicle are recorded and marked for subsequent processing.

[0022] As a preferred technical solution of the present invention, in step S7, after monitoring and warning the harmonics that are likely to affect the rail transit vehicle when exceeding the threshold, secondly, the data is synchronously transmitted to the monitoring system to control the operation of the filter, and the filter adopts one or both of the active filter and the passive filter.

[0023] As a preferred technical solution of the present invention, in step S7, the value after harmonic analysis that meets the track circuit compatibility standard is the secondary warning, while the threshold set by converting multiple harmonics into a mathematical model is lower than the value that meets the track circuit compatibility standard, which is the primary warning.

[0024] As a preferred technical solution of the present invention, in step S4, the transient recorder is set at a frequency of 200 kHz.

[0025] Compared with the prior art, the beneficial effects that the present invention can achieve are:

[0026] 1. During the operation of a rail transit vehicle, the present invention continuously monitors multiple aspects related to harmonic formation by using online dynamic monitoring to measure the current value of traction return on the rail, and by real-time monitoring of the traction voltage and current during the operation of the rail transit vehicle and the unbalanced traction current on the two rails, so as to improve the comprehensiveness of harmonic monitoring. During this process, a notch filter is used to attenuate the 50Hz fundamental wave signal in cooperation with an anti-aliasing filter to improve the measurement accuracy of harmonic signals and filter out unnecessary interference during monitoring, thereby improving the accuracy during monitoring. Through its design, it can timely detect the harmonics that are likely to have an impact during the operation of the rail transit vehicle, providing good guarantee for the stable operation of the rail transit vehicle.

[0027] 2. After detecting the harmonics, the present invention converts them into a mathematical model and sets a threshold value in the system of the rail transit vehicle according to the mathematical model, so that the threshold value set by converting the harmonics into a mathematical model is lower than the value that meets the rail circuit compatibility standard, serving as a primary warning for subsequent operation. And the value after harmonic analysis uses the value that meets the rail circuit compatibility standard as a secondary warning, playing a role of multi-level early warning, so as to facilitate timely response to various harmonics. Through its design, it can improve the warning effect when monitoring the operation of the rail transit vehicle encountering harmonics with excessive influence. Specific embodiments

[0028] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the following specific embodiments are used to further elaborate the present invention. However, the following embodiments are only the preferred embodiments of the present invention, not all of them. Based on the embodiments in the implementation mode, other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present invention. The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0029] Embodiment

[0030] A method for monitoring and warning of traction return harmonics of rail transit vehicles includes the following steps:

[0031] S1. First, the current value of traction return on the rail of the rail transit vehicle is measured in real time. Before the measurement, the monitoring system uses the harmonic current limit standard of the rail transit vehicle adopted according to the type of rail circuit on which the rail transit vehicle travels as a reference benchmark.

[0032] S2. When the current value of the traction return current on the rail is measured in real time, a notch filter is used to attenuate the 50 Hz fundamental wave signal to improve the measurement accuracy of the harmonic signal. At the same time, an anti-aliasing filter is also used to filter out signals outside the measurement frequency band to prevent frequency aliasing when performing FFT analysis on the sampled digital signal. And the measurement frequency is determined according to the specific track circuit type, so that the measurement frequency meets the detection requirements of measuring the rail transit vehicle.

[0033] S3. Then, a Rogowski coil is used to measure the current value. During the process of measuring the current value, an integrator is added and an amplifier circuit is added behind it for amplification to increase the restored signal, and the presence of a capacitor is used to filter out unnecessary interference.

[0034] S4. After the return current value of the rail transit vehicle is measured in real time, a transient recorder is used to record its data value in real time.

[0035] S5. While the above process is being implemented, the traction currents on both sides of the rail of the rail transit vehicle are monitored in real time to monitor whether the traction currents on both sides of the rail are balanced, and their detection data is transmitted and recorded. Secondly, an online dynamic monitoring system is used to monitor the traction voltage and current during the operation of the rail transit vehicle in real time.

[0036] S6. After the data values in the above steps are recorded, the FFT algorithm is immediately used to perform harmonic analysis on the rail return current in the time domain in the frequency domain.

[0037] S7. After the harmonic analysis of the data values detected each time, the analysis results are stored. At the same time, they are immediately compared with the values that meet the rail circuit compatibility standard, and then they are converted into a mathematical model. A threshold is set in the system of the rail transit vehicle according to the mathematical model for real-time warning.

[0038] Embodiment 1

[0039] A method for monitoring and warning of the return current harmonics of a rail transit vehicle includes the following steps:

[0040] S1. First, the current value of the traction return current on the rail of the rail transit vehicle is measured in real time. Before the measurement, the monitoring system uses the rail transit vehicle harmonic current limit standard adopted according to the track circuit type on which the rail transit vehicle travels as a reference benchmark.

[0041] S2. When measuring the current value of the traction return current on the rail in real time, a notch filter is used to attenuate the 50 Hz fundamental wave signal to improve the measurement accuracy of the harmonic signal. At the same time, an anti-aliasing filter is also used to filter out signals outside the measurement frequency band to prevent frequency aliasing when performing FFT analysis on the sampled digital signal. And the measurement frequency is determined according to the specific track circuit type, so that the measured frequency meets the detection requirements for measuring this rail transit vehicle.

[0042] S3. Then, a Rogowski coil is used to measure the current value. During the process of measuring the current value, an integrator is added and an amplifier circuit is added behind it for amplification to increase the restored signal. And the existence of a capacitor is used to filter out unnecessary interference.

[0043] S4. After measuring the return current value of the rail transit vehicle in real time, a transient recorder is used to record its data value in real time.

[0044] S5. While the above process is being implemented, the traction currents on both sides of the rail of the rail transit vehicle are monitored in real time to monitor whether the traction currents on both sides of the rail are balanced, and their detection data are transmitted and recorded. Secondly, an on-line dynamic monitoring system is used to monitor the traction voltage and current during the operation of the rail transit vehicle in real time.

[0045] S6. After recording the data values in the above steps, the FFT algorithm is immediately used to perform harmonic analysis on the rail return in the time domain by converting it to the frequency domain.

[0046] S7. After performing harmonic analysis on the data values detected each time, the analysis results are stored. At the same time, they are immediately compared with the values that meet the rail circuit compatibility standard, and then they are converted into a mathematical model. A threshold is set in the system of the rail transit vehicle according to the mathematical model for real-time warning.

[0047] In step S6, the FFT algorithm design adopts the time extraction method to perform time-frequency transformation on the rail return.

[0048] The FFT algorithm is used to perform harmonic analysis on the rail return in the time domain by converting it to the frequency domain. The formula used is:

[0049]

[0050] Where:

[0051]

[0052]

[0053]

[0054] Let \(N\) be the number of sampling points, \(S\) be the time-domain signal sequence, \(G(k)\) be the even-point sequence of the original signal sequence, and \(H(k)\) be the base-point sequence. When calculating, the input signal sequence is divided into continuously smaller subsequences according to the time decimation algorithm for discrete Fourier transform calculation.

[0055] Embodiment 2

[0056] A method for monitoring and warning of return current harmonics in rail transit vehicles includes the following steps:

[0057] S1. First, the current value of the traction return current of the rail transit vehicle on the rail is measured in real time. Before measurement, the monitoring system uses the rail transit vehicle harmonic current limit standard adopted according to the type of track circuit where the rail transit vehicle travels as a reference benchmark.

[0058] S2. When measuring the current value of the traction return current on the rail in real time, a notch filter is used to attenuate the 50Hz fundamental wave signal to improve the measurement accuracy of the harmonic signal. At the same time, an anti-aliasing filter is also used to filter out signals outside the measurement frequency band to prevent frequency aliasing when performing FFT analysis on the sampled digital signal. And the measurement frequency is determined according to the specific type of track circuit, so that the measurement frequency meets the detection requirements of the rail transit vehicle.

[0059] S3. Then, a Rogowski coil is used to measure the current value. During the process of measuring the current value, an integrator is added and an amplifier circuit is added behind it for amplification to increase the restored signal, and the presence of a capacitor is used to filter out unnecessary interference.

[0060] S4. After measuring the return current value of the rail transit vehicle in real time, a transient recorder is used to record its data value in real time.

[0061] S5. While the above process is being implemented, the traction currents on both sides of the rail transit vehicle are monitored in real time to monitor whether the traction currents on both sides of the track are balanced, and their detection data are transmitted and recorded. Secondly, an online dynamic monitoring system is used to monitor the traction voltage and current of the rail transit vehicle in real time during operation.

[0062] S6. After recording the data values in the above steps, the FFT algorithm is immediately used to perform harmonic analysis on the track return current in the time domain in the frequency domain.

[0063] S7. After performing harmonic analysis on the data values of each detection, the analysis results are stored. At the same time, they are immediately compared with the values that meet the track circuit compatibility standard, and then converted into a mathematical model. A threshold is set in the system of the rail transit vehicle according to the mathematical model for real-time warning.

[0064] In step S7, after monitoring and warning about the harmonics that are likely to affect the rail transit vehicle when exceeding the threshold, secondly, the data is synchronously transmitted to the monitoring system to control the operation of the filter, and the filter uses one or both of an active filter and a passive filter.

[0065] The active power filter, abbreviated as (APF), is a new type of power electronic device used for dynamic harmonic suppression and reactive power compensation. It can compensate for any change in harmonics. By using an active power filter, the stability of the communication system and the power distribution system can be improved, the service life of communication equipment can be extended, and the power distribution system can better meet the design specifications of the harmonic environment. Due to the continuous improvement of the precision of mechanical and electrical components, the active power filter has become the primary choice for treating harmonics in the power system and the biggest nemesis of harmonics.

[0066] The passive filter, abbreviated as (LC), is passive in the power system. It mainly uses a combination of inductors, capacitors, and resistors to design a filter circuit that can filter out one or multiple harmonics. The simplest passive filter structure is to connect an inductor and a capacitor in series, which can form a low-impedance bypass for the main sub-harmonics (3, 5, 7). There are many types of passive filters, and monotonic filters, double-tuned filters, and high-pass filters all belong to it.

[0067] From the above comparison, it can be obtained that when dealing with various monitored harmonics, the active filter should be preferred.

[0068] Embodiment 3

[0069] A method for monitoring and warning of the return current harmonics of a rail transit vehicle includes the following steps:

[0070] S1. First, the current value of the traction return current of the rail transit vehicle on the rail is measured in real time. Before the measurement, the monitoring system uses the rail transit vehicle harmonic current limit standard adopted according to the type of the track circuit on which the rail transit vehicle travels as a reference benchmark.

[0071] S2. When measuring the current value of the traction return current on the rail in real time, a notch filter is used to attenuate the 50Hz fundamental wave signal to improve the measurement accuracy of the harmonic signal. At the same time, an anti-aliasing filter is also used to filter out signals outside the measurement frequency band to prevent frequency aliasing from occurring when performing FFT analysis on the sampled digital signal. And the measurement frequency is determined according to the specific type of the track circuit, so that the measurement frequency meets the detection requirements for measuring the rail transit vehicle.

[0072] S3. Then, a Rogowski coil is used to measure the current value. During the process of measuring the current value, an integrator is added and an amplifier circuit is added behind it for amplification to increase the restored signal, and the presence of a capacitor is used to filter out unnecessary interference.

[0073] After the return current value of the rail transit vehicle is measured in real time at S4, its data value is recorded in real time by using a transient recorder.

[0074] During the implementation of the above process, the traction currents of the tracks on both sides of the rail transit vehicle are monitored in real time to monitor whether the traction currents on both tracks are balanced, and their detection data are transmitted and recorded. Secondly, an on-line dynamic monitoring system is used to monitor the traction voltage and current during the operation of the rail transit vehicle in real time.

[0075] After the data values in the above steps are recorded, the FFT algorithm is immediately used to perform harmonic analysis on the track return current in the time domain in the frequency domain.

[0076] After the harmonic analysis of the data values detected each time, the analysis results are stored. At the same time, they are immediately compared with the values that meet the track circuit compatibility standard, and then converted into a mathematical model. A threshold is set in the system of the rail transit vehicle according to the mathematical model for real-time warning.

[0077] In step S5, the formula used is:

[0078]

[0079] In the formula: K is the traction current imbalance coefficient, L S1 is the traction return current in the first steel rail, L S2 is the traction return current in the second steel rail.

[0080] During the calculation, the imbalance of the impedances of the two steel rails will cause unequal current values to flow through the two rail strips of the traction current, thus forming an unbalanced voltage difference △V = Vleft rail - Vright rail between the rails. The harmonics formed by the superposition of this voltage difference and the track circuit signal, after the harmonics are detected, are converted into a mathematical model, and a threshold is set in the system of the rail transit vehicle according to the mathematical model, so that the threshold set by converting the harmonics into a mathematical model is lower than the value that meets the track circuit compatibility standard, as a primary warning during subsequent operation, and the values after the harmonic analysis are used as a secondary warning with the values that meet the track circuit compatibility standard, playing a multi-level early warning role to facilitate timely responses to various harmonics.

[0081] The foregoing has shown and described 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, and the above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for monitoring and warning the harmonic of the return current of a rail transit vehicle, characterized in that, It includes the following steps: S1. First, measure the real-time current value of the traction return of the rail transit vehicle on the rail. Before measurement, the monitoring system uses the harmonic current limit standard of the rail transit vehicle adopted according to the type of track circuit on which the rail transit vehicle travels as the reference benchmark; S2. When measuring the real-time current value of the traction return on the rail, use a notch filter to attenuate the 50Hz fundamental wave signal to improve the measurement accuracy of the harmonic signal. At the same time, use an anti-aliasing filter to filter out signals outside the measurement frequency band to prevent frequency aliasing when performing FFT analysis on the sampled digital signal. And the measurement frequency is determined according to the specific type of track circuit, so that the measurement frequency meets the detection requirements of measuring the rail transit vehicle; S3. Then, use a Rogowski coil to measure the current value. And during the process of measuring the current value, add an integrator and an amplifier circuit behind it to amplify and increase the restored signal. And use the existence of a capacitor to filter out unnecessary interference; S4. After measuring the real-time return current value of the rail transit vehicle, use a transient recorder to record its data value in real time; S5. While the above process is being implemented, monitor the traction current on both sides of the rail transit vehicle in real time to monitor whether the traction currents on both sides of the track are balanced, and transmit and record the detection data. Secondly, use an on-line dynamic monitoring system to monitor the traction voltage and current during the operation of the rail transit vehicle in real time; S6. After recording the data values in the above steps, immediately use the FFT algorithm to perform harmonic analysis on the track return in the time domain converted to the frequency domain; S7. After performing harmonic analysis on the data values of each detection, store the analysis results, and at the same time immediately compare them with the values that meet the track circuit compatibility standard, and convert them into a mathematical model. Set a threshold in the system of the rail transit vehicle according to the mathematical model for real-time warning.

2. The method for monitoring and warning of the return current harmonic of a rail transit vehicle according to claim 1, wherein: In step S3, using a Rogowski coil to measure the current value is based on the electromagnetic induction law and Ampere's circuital law as the theoretical basis.

3. The method for monitoring and warning of the return current harmonic of a rail transit vehicle according to claim 1, wherein: In steps S1 and S2, the number of input frequency points during detection should be selected according to the frequency response characteristics of the notch filter, select multiple representative frequency points, and perform linear interpolation for other frequency points.

4. The method for monitoring and warning of the return current harmonic of a rail transit vehicle according to claim 1, wherein: In step S5, during the monitoring of the traction voltage and current, it is necessary to convert the traction voltage and current that change according to the operating state of the rail transit vehicle into a mathematical model to pay attention to the harmonic energy caused by it, and feedback the data to the rail transit vehicle monitoring system.

5. The method for monitoring and warning of the return current harmonic of a rail transit vehicle according to claim 1, characterized in that: In step S5, the formula used is: Where: K is the traction current unbalance coefficient, and L S1 is the traction return current in the first rail, and L S2 is the traction return current in the second rail.

6. The method for monitoring and warning of the return current harmonic of a rail transit vehicle according to claim 1, wherein: In step S6, the FFT algorithm design adopts the time extraction method to perform time-frequency transformation on the track return.

7. The method for monitoring and warning of the return current harmonic of the rail transit vehicle according to claim 1, wherein: In step S7, record the disturbing harmonic locations encountered by the rail transit vehicle and mark them for subsequent processing.

8. The method for monitoring and warning the harmonic of the return current of a rail transit vehicle according to claim 1, characterized in that: In the step S7, after monitoring and warning the harmonics that are likely to affect the rail transit vehicle when exceeding the threshold, secondly, the data is synchronously transmitted to the monitoring system to control the operation of the filter, and the filter adopts one or both of an active filter and a passive filter.

9. The method for monitoring and warning of the return current harmonic of a rail transit vehicle according to claim 1, characterized in that: In the step S7, the value after harmonic analysis that meets the rail circuit compatibility standard is the secondary warning, while the threshold set by converting multiple harmonics into a mathematical model that is lower than the value that meets the rail circuit compatibility standard is the primary warning.

10. The method for monitoring and warning the harmonic of the return current of a rail transit vehicle according to claim 1, wherein: In the step S4, the transient recorder is set to a frequency of 200 kHz.

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