Switching frequency control method and control system of four-quadrant rectifier

Abstract

The invention discloses a switching frequency control method and a switching frequency control system for a four-quadrant rectifier. The control method comprises the following steps: acquiring an operation condition and a contact network voltage of an electric locomotive; decomposing the overhead line system voltage according to the frequency to obtain a harmonic parameter of the overhead line system voltage; determining the harmonic state of the contact network according to the harmonic parameter of the voltage of the contact network; and adjusting the switching frequency of the four-quadrant rectifier to a target frequency according to the operation condition of the electric locomotive, or adjusting the switching frequency of the four-quadrant rectifier to the target frequency according to the operation condition of the electric locomotive and the harmonic state of the contact network. The switching frequency control method of the four-quadrant rectifier provided by the invention can adapt to the operation condition of a motor locomotive and the dynamic change of the harmonic state of a contact network, and is relatively high in adaptability.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply for electric locomotives, and particularly to a switching frequency control method and control system for a four-quadrant rectifier. Background Art

[0002] An electric locomotive vehicle obtains electric energy from an overhead contact line through a pantograph. The four-quadrant rectifier in the electric locomotive traction system is responsible for converting alternating current into direct current, while achieving power factor correction and bidirectional power flow. However, the high-frequency operation of the rectifier switch will inject a large amount of harmonics into the overhead contact line, especially when the locomotive is operating at light load and multiple locomotives are operating.

[0003] Currently, traditional electric locomotives use a four-quadrant rectifier with a fixed switching frequency, and a harmonic filter is added between the traction system and the overhead contact line to weaken harmonic current. Or a four-quadrant rectifier frequency doubling switching adaptive control method is used to solve the harmonic suppression problem of the rectifier under different loads. However, the switching frequency of the above methods is fixed or the frequency adjustment is not flexible enough, lacking real-time monitoring of the overhead contact line voltage and the operating conditions of the electric locomotive, and the dynamic adjustment ability and self-adaptability are poor. Summary of the Invention

[0004] The present invention provides a switching frequency control method and control system for a four-quadrant rectifier to solve the problem of poor dynamic adjustment ability and self-adaptability in the switching frequency control of the four-quadrant rectifier in the prior art.

[0005] According to one aspect of the present invention, a switching frequency control method for a four-quadrant rectifier is provided, including:

[0006] Obtaining the operating conditions of the electric locomotive and the overhead contact line voltage;

[0007] Decomposing the overhead contact line voltage according to frequency to obtain harmonic parameters of the overhead contact line voltage;

[0008] Determining the harmonic state of the overhead contact line according to the harmonic parameters of the overhead contact line voltage;

[0009] Adjusting the switching frequency of the four-quadrant rectifier to a target frequency according to the operating conditions of the electric locomotive, or adjusting the switching frequency of the four-quadrant rectifier to a target frequency according to the operating conditions of the electric locomotive and the harmonic state of the overhead contact line.

[0010] Optionally, the decomposing the overhead contact line voltage according to frequency to obtain harmonic parameters of the overhead contact line voltage includes: based on the wavelet packet decomposition algorithm, decomposing the overhead contact line voltage according to frequency according to a preset decomposition layer number to obtain the odd harmonic amplitudes after decomposition; the harmonic parameters include the odd harmonic amplitudes after decomposition.

[0011] Optionally, before determining the harmonic state of the catenary according to the harmonic parameters of the catenary voltage, it includes: determining the fundamental wave amplitude of the catenary voltage.

[0012] Optionally, the determining the harmonic state of the catenary according to the harmonic parameters of the catenary voltage includes: determining the total harmonic distortion rate of the catenary voltage according to the decomposed odd harmonic amplitude and the fundamental wave amplitude; determining the harmonic state of the catenary according to the difference between the peak value of the catenary voltage and the preset voltage threshold, the difference between the odd harmonic amplitude and the preset amplitude threshold, or the difference between the total harmonic distortion rate of the catenary voltage and the preset harmonic distortion rate threshold.

[0013] Optionally, the determining the harmonic state of the catenary according to the difference between the peak value of the catenary voltage and the preset voltage threshold, the difference between the odd harmonic amplitude and the preset amplitude threshold, or the difference between the total harmonic distortion rate of the catenary voltage and the preset harmonic distortion rate threshold includes: when the peak value of the catenary voltage is greater than the preset voltage threshold, the odd harmonic amplitude is greater than the preset amplitude threshold, or the total harmonic distortion rate of the catenary voltage is greater than the preset harmonic distortion rate threshold, determining that the harmonic state of the catenary is an abnormal state; when the peak value of the catenary voltage is less than or equal to the preset voltage threshold, the odd harmonic amplitude is less than or equal to the preset amplitude threshold, and the total harmonic distortion rate of the catenary voltage is less than or equal to the preset harmonic distortion rate threshold, determining that the harmonic state of the catenary is a normal state.

[0014] Optionally, adjusting the switching frequency of the four-quadrant rectifier to the target frequency according to the operating condition of the electric locomotive and the harmonic state of the catenary includes: when the operating condition of the electric locomotive is the first target condition, configuring the switching frequency of the four-quadrant rectifier to the first target frequency according to the harmonic state of the catenary; the first target condition includes the normal operating condition of the electric locomotive and / or the electric locomotive axles cut-off operation;

[0015] Adjusting the switching frequency of the four-quadrant rectifier to the target frequency according to the operating condition of the electric locomotive includes: when the operating condition of the electric locomotive is the second target condition, configuring the switching frequency of the four-quadrant rectifier to the second target frequency; the second target condition includes the operating condition where only the auxiliary system of the electric locomotive is running and / or the electric locomotive is in an extreme condition; the second target frequency is greater than the first target frequency.

[0016] Optionally, when the operating condition of the electric locomotive is the first target condition, configuring the switching frequency of the four-quadrant rectifier to the first target frequency includes: when the electric locomotive is operating normally and there is no harmonic abnormality in the catenary, adjusting the switching frequency of the four-quadrant rectifier to the first frequency; when the electric locomotive is in axle-cut operation and there is no harmonic abnormality, adjusting the switching frequency of the four-quadrant rectifier to the second frequency; the first target frequency includes the first frequency and the second frequency; the first frequency is less than the second frequency.

[0017] Optionally, when the operating condition of the electric locomotive is the second target condition, configuring the switching frequency of the four-quadrant rectifier to the second target frequency includes: when only the auxiliary system of the electric locomotive is operating, adjusting the switching frequency of the four-quadrant rectifier to the third frequency; when the electric locomotive is in an extreme condition and / or in the harmonic abnormal state, adjusting the switching frequency of the four-quadrant rectifier to the fourth frequency; the second target frequency includes the third frequency and the fourth frequency; the third frequency is greater than the fourth frequency.

[0018] Optionally, after decomposing the catenary voltage according to the frequency to obtain the harmonic parameters of the catenary voltage, it further includes: normalizing the operating condition of the electric locomotive, the harmonic parameters, and the catenary voltage within a preset historical time period; determining the correlation between the operating condition of the electric locomotive, the harmonic parameters, and the catenary voltage; constructing a prediction model according to the correlation, the prediction model being an autoregressive moving average model; predicting the operating condition of the electric locomotive, the harmonic parameters, and the catenary voltage at a future moment according to the prediction model; judging whether the catenary is in a harmonic abnormal state or a normal state according to the difference between the predicted harmonic parameters and a preset amplitude threshold, combined with the operating condition of the electric locomotive and the catenary voltage at the same moment; obtaining the harmonic states at multiple moments and determining the harmonic abnormal probability of the catenary voltage.

[0019] According to another aspect of the present invention, a control system is provided, which includes a voltage sensing module, a signal processing module, and a main control module; the voltage sensing module is connected to the catenary, and the voltage sensing module is used to detect the voltage signal of the catenary; the signal processing module is connected to the voltage sensing module, and the signal processing module is used to perform voltage stabilization processing on the voltage signal output by the voltage sensing module; the main control module is connected to the signal processing module, and the main control module is used to obtain the voltage signal of the catenary and the operating condition of the electric locomotive; the main control module is further used to decompose the catenary voltage according to the frequency to obtain the harmonic parameters of the catenary voltage, determine the harmonic state of the catenary according to the harmonic parameters of the catenary voltage; and adjust the switching frequency of the four-quadrant rectifier to the target frequency according to the operating condition of the electric locomotive, or adjust the switching frequency of the four-quadrant rectifier to the target frequency according to the operating condition of the electric locomotive and the harmonic state of the catenary.

[0020] The technical solution of the embodiment of the present invention, the switching frequency control method of the four-quadrant rectifier includes: obtaining the operating condition of the electric locomotive and the catenary voltage; decomposing the catenary voltage according to the frequency to obtain the harmonic parameters of the catenary voltage; determining the harmonic state of the catenary according to the harmonic parameters of the catenary voltage; adjusting the switching frequency of the four-quadrant rectifier to the target frequency according to the operating condition of the electric locomotive, or adjusting the switching frequency of the four-quadrant rectifier to the target frequency according to the operating condition of the electric locomotive and the harmonic state of the catenary. The switching frequency control method of the four-quadrant rectifier provided in this embodiment, since it takes into account both the operating condition of the electric locomotive and the harmonic state of the catenary, can adapt to the dynamic changes of the operating condition of the electric locomotive and the harmonic state of the catenary. By obtaining the operating condition of the electric locomotive and the harmonic state of the catenary in real time, the switching frequency of the four-quadrant rectifier is dynamically adjusted, improving the dynamic adjustment ability and self-adaptability. It solves the problem of poor dynamic adjustment ability and self-adaptability in the switching frequency control of the four-quadrant rectifier in the prior art.

[0021] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1Flow chart of a switching frequency control method for a four - quadrant rectifier provided by an embodiment of the present invention;

[0024] Figure 2 Structural schematic diagram of a control system provided by an embodiment of the present invention. Detailed implementation manners

[0025] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above - mentioned drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non - exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0027] Figure 1 Flow chart of a switching frequency control method for a four - quadrant rectifier provided by an embodiment of the present invention. This embodiment is applicable to the switching frequency situation of the four - quadrant rectifier in the traction system of an electric locomotive. This method can be executed by a control device, which can be implemented in the form of hardware and / or software, and the control device can be configured in an electric locomotive. As Figure 1 shown, the method includes:

[0028] S110. Obtain the operating condition of the electric locomotive and the catenary voltage.

[0029] In the embodiment of the present invention, the operating condition of the electric locomotive refers to different working states and corresponding operating modes of the electric locomotive during operation, which can reflect the working characteristics of the electric locomotive at different stages, the coordinated operation of electrical equipment, etc. The catenary voltage refers to the voltage supplied to the electric locomotive through the catenary in the electrified railway power supply system. Among them, the catenary is a special power supply network erected along the railway line. The catenary slides in contact with the pantograph on the top of the electric locomotive to transmit electric energy to the electric locomotive to drive the train to run.

[0030] Exemplarily, when the electric locomotive is operating under light load or multiple locomotives are operating, the high-frequency operation of the rectifier switch will inject a large amount of harmonics into the catenary. Among them, light-load operation includes axle-cut operation or only starting the auxiliary system, and multiple-locomotive operation includes multiple locomotives parked in the neutral section and only operating the auxiliary system. By simultaneously obtaining the operating conditions of the electric locomotive and the catenary voltage, subsequent adjustment of the switching frequency of the four-quadrant rectifier can be made more in line with the actual situation.

[0031] S120. Decompose the catenary voltage according to the frequency to obtain the harmonic parameters of the catenary voltage.

[0032] In the embodiment of the present invention, during the actual power supply process and the operation process of the electric locomotive, the catenary voltage contains complex signals with various frequency components. Decomposing the catenary voltage according to the frequency includes splitting and analyzing the catenary voltage signal that changes with time according to different frequency components by using a specific mathematical transformation method, so as to obtain the frequency structure inside the catenary voltage signal and the relevant characteristics of each frequency component.

[0033] After decomposing the catenary voltage, the complex catenary voltage signal is disassembled into multiple components with different frequencies. Furthermore, the amplitude, phase, energy and other characteristics of each frequency component can be detected separately, as well as the influence of the above characteristics on the entire catenary voltage signal and the operation of the electric locomotive. Among them, the harmonic parameters can be the amplitude, phase, energy, etc. of each frequency component.

[0034] S130. Determine the harmonic state of the catenary according to the harmonic parameters of the catenary voltage.

[0035] In the embodiment of the present invention, the harmonic state of the catenary includes a normal harmonic state and an abnormal harmonic state. Among them, the normal harmonic state means that the harmonics in the catenary voltage are within an acceptable range and will not cause adverse effects on the normal operation of the system and each electrical equipment. The abnormal harmonic state means that the harmonics in the catenary voltage exceed the reasonable range and have a negative impact on the system itself, electrical equipment or power quality. According to the harmonic parameters of the catenary voltage, that is, by detecting whether the amplitude, phase or energy and other characteristics of each frequency component after decomposition are within the acceptable range, the harmonic state of the catenary is determined as the normal harmonic state or the abnormal harmonic state.

[0036] S140. Adjust the switching frequency of the four-quadrant rectifier to the target frequency according to the operating conditions of the electric locomotive, or adjust the switching frequency of the four-quadrant rectifier to the target frequency according to the operating conditions of the electric locomotive and the harmonic state of the catenary.

[0037] In the embodiments of the present invention, under different operating conditions of the electric locomotive, there are differences in aspects such as power demand, energy conversion efficiency, and harmonic impact. When the four-quadrant rectifier switch operates under high-frequency conditions for a long time, the heating intensifies, which may pose a safety hazard and affect the service life and reliability. Therefore, under different operating conditions of the electric locomotive, by reasonably adjusting the switching frequency to the target frequency according to factors such as the actual power demand and power quality requirements, the performance of the device can be fully utilized, and device damage caused by overuse can be avoided, ensuring the long-term stable operation of the rectifier and even the entire locomotive electrical system.

[0038] For the technical solution of this embodiment, the method for controlling the switching frequency of the four-quadrant rectifier includes: obtaining the operating condition of the electric locomotive and the catenary voltage; decomposing the catenary voltage according to the frequency to obtain the harmonic parameters of the catenary voltage; determining the harmonic state of the catenary according to the harmonic parameters of the catenary voltage; adjusting the switching frequency of the four-quadrant rectifier to the target frequency according to the operating condition of the electric locomotive, or adjusting the switching frequency of the four-quadrant rectifier to the target frequency according to the operating condition of the electric locomotive and the harmonic state of the catenary. The method for controlling the switching frequency of the four-quadrant rectifier provided in this embodiment, by considering both the operating condition of the electric locomotive and the harmonic state of the catenary, can adapt to the dynamic changes of the operating condition of the electric locomotive and the harmonic state of the catenary. By obtaining the operating condition of the electric locomotive and the harmonic state of the catenary in real time and dynamically adjusting the switching frequency of the four-quadrant rectifier, the dynamic adjustment ability and self-adaptability are improved. It solves the problem of poor dynamic adjustment ability and self-adaptability in the prior art when controlling the switching frequency of the four-quadrant rectifier.

[0039] Optionally, decomposing the catenary voltage according to the frequency to obtain the harmonic parameters of the catenary voltage includes: based on the wavelet packet decomposition algorithm, decomposing the catenary voltage according to the frequency according to the preset decomposition level to obtain the odd harmonic amplitudes after decomposition; the harmonic parameters include the odd harmonic amplitudes after decomposition.

[0040] In the embodiments of the present invention, the wavelet packet decomposition algorithm is a signal analysis method based on wavelet transform. The wavelet packet decomposition algorithm is based on a wavelet function. By decomposing a signal in a multi-scale and multi-level manner, the original signal is decomposed into sub-signals in different frequency bands, realizing a more refined frequency analysis of the signal. Odd harmonics refer to harmonic components with frequencies that are odd multiples of the fundamental frequency. Exemplarily, the catenary voltage is decomposed into four layers using the wavelet packet decomposition algorithm. The decomposed frequency bands include the 3rd harmonic (150 Hz), 5th harmonic (250 Hz) of the high-precision catenary voltage with an error less than 5%, and odd harmonics from the 15th to 75th (750 Hz - 3750 Hz). The harmonic parameters include the harmonic amplitudes corresponding to the 3rd (150 Hz), 5th (250 Hz), and 15th to 75th (750 Hz - 3750 Hz) frequency bands of the catenary voltage. By performing wavelet packet decomposition on the catenary voltage, it is possible to accurately locate when these non-steady-state harmonics appear and the corresponding frequency changes of the non-steady-state harmonics. It can improve the capture ability of non-steady-state harmonics. At the same time, it can accurately avoid the inherent frequency of the power grid, resulting in unstable harmonic suppression effects.

[0041] After performing wavelet packet decomposition on the catenary voltage, it also includes band-pass filtering and low-pass filtering processes. For example, the center frequency of the 3rd harmonic is set to 150 Hz, and the cut-off frequencies are ±5 Hz. The center frequency of the 5th harmonic is set to 250 Hz, and the cut-off frequencies are ±5 Hz. The center frequency of the odd harmonics from the 15th to 75th is set to 1650 Hz, and the bandwidth is 750 Hz - 3750 Hz. The cut-off frequency of the low-pass filter is 10 Hz. By performing band-pass filtering and low-pass filtering on the harmonic amplitudes of each order, the signal quality can be improved.

[0042] Based on the above embodiments, before determining the harmonic state of the catenary according to the harmonic parameters of the catenary voltage, it includes: determining the fundamental amplitude of the catenary voltage.

[0043] In the embodiments of the present invention, the fundamental wave is a wave band with a frequency the same as the originally set fundamental frequency. For example, in the environment of an industrial-frequency AC power grid, the industrial frequency is 50 Hz. Then, in the voltage signal of the power grid, the component with a frequency of 50 Hz is the fundamental wave. The fundamental wave is the core of the catenary voltage and the key to driving various electrical equipment to operate normally. The fundamental amplitude refers to the amplitude of the fundamental component in the catenary voltage. By determining the fundamental amplitude of the catenary, a basis is provided for the subsequent determination of the harmonic state.

[0044] Optionally, determine the harmonic state of the catenary according to the harmonic parameters of the catenary voltage, including: determine the total harmonic distortion rate of the catenary voltage according to the decomposed odd harmonic amplitude and fundamental wave amplitude. Determine the harmonic state of the catenary according to the difference between the peak value of the catenary voltage and the preset voltage threshold, the difference between the odd harmonic amplitude and the preset amplitude threshold, or the difference between the total harmonic distortion rate of the catenary voltage and the preset harmonic distortion rate threshold.

[0045] In the embodiments of the present invention, the total harmonic distortion rate is an important indicator for measuring the harmonic content in the catenary voltage. The calculation process of the total harmonic distortion rate includes taking the square root of the sum of the squares of the effective values of all harmonic amplitudes included in the catenary voltage, dividing by the fundamental wave amplitude, and then multiplying by 100%. Numerically, the total harmonic distortion rate intuitively reflects the proportion of the harmonic component relative to the fundamental wave component in the electrical signal. The peak value of the catenary voltage refers to the maximum value of the voltage amplitude that appears during the change of the catenary voltage over time, and the peak value of the catenary voltage is affected by harmonics. The harmonic amplitude is the amplitude of each harmonic component, and the harmonic amplitude can intuitively reflect the intensity of the corresponding harmonic in the catenary voltage. The peak value of the catenary voltage, the odd harmonic amplitude, and the total harmonic distortion rate, as key indicators for evaluating the power quality, are compared with the corresponding preset thresholds to determine whether the electric energy meets the corresponding quality standards, and to timely detect the deterioration of the power quality and take measures to improve it.

[0046] On the basis of the above embodiments, determine the harmonic state of the catenary according to the difference between the peak value of the catenary voltage and the preset voltage threshold, the difference between the odd harmonic amplitude and the preset amplitude threshold, or the difference between the total harmonic distortion rate of the catenary voltage and the preset harmonic distortion rate threshold, including: when the peak value of the catenary voltage is greater than the preset voltage threshold, the odd harmonic amplitude is greater than the preset amplitude threshold, or the total harmonic distortion rate of the catenary voltage is greater than the preset harmonic distortion rate threshold, determine that the harmonic state of the catenary is an abnormal state; when the peak value of the catenary voltage is less than or equal to the preset voltage threshold, the odd harmonic amplitude is less than or equal to the preset amplitude threshold, and the total harmonic distortion rate of the catenary voltage is less than or equal to the preset harmonic distortion rate threshold, determine that the harmonic state of the catenary is a normal state.

[0047] In an embodiment of the present invention, when any one of the following conditions is met: the peak value of the catenary voltage is greater than a preset voltage threshold, the odd - harmonic amplitude is greater than a preset amplitude threshold, or the total harmonic distortion rate of the catenary voltage is greater than a preset harmonic distortion rate threshold, it can be determined that the harmonic state of the catenary is an abnormal state. When the peak value of the catenary voltage is less than or equal to the preset voltage threshold, the odd - harmonic amplitude is less than or equal to the preset amplitude threshold, and the total harmonic distortion rate of the catenary voltage is less than or equal to the preset harmonic distortion rate threshold, and all these conditions are met simultaneously, it can be determined that the harmonic state of the catenary is a normal state. Among them, the preset amplitude threshold for the 3 - rd harmonic amplitude is 5A - 10A, the preset amplitude threshold for the 5 - th harmonic amplitude is 8A - 12A, and the preset amplitude threshold for the odd - harmonic amplitudes from the 15 - th to the 75 - th is 2A - 5A. The preset voltage threshold is 50kV. The preset harmonic distortion rate threshold is 10%.

[0048] Specifically, according to the operating conditions of the electric locomotive and the harmonic state of the catenary, adjusting the switching frequency of the four - quadrant rectifier to the target frequency includes: when the operating condition of the electric locomotive is the first target operating condition, configuring the switching frequency of the four - quadrant rectifier to the first target frequency according to the harmonic state of the catenary; the first target operating condition includes the normal operating condition of the electric locomotive and / or the axle - cut operation of the electric locomotive; according to the operating conditions of the electric locomotive, adjusting the switching frequency of the four - quadrant rectifier to the target frequency includes: when the operating condition of the electric locomotive is the second target operating condition, configuring the switching frequency of the four - quadrant rectifier to the second target frequency; the second target operating condition includes the operating condition where only the auxiliary system of the electric locomotive is running and / or the electric locomotive is in an extreme condition; the second target frequency is greater than the first target frequency.

[0049] In an embodiment of the present invention, the normal operating condition of the electric locomotive means that all axles of the electric locomotive are working properly. Each axle of the electric locomotive is equipped with a traction motor, and these traction motors work together to provide traction or braking force for the train, ensuring the smooth and efficient operation of the train. The axle - cut operation of the electric locomotive means that during the operation of the electric locomotive, one or some axles malfunction, for example, the axle breaks, the bearing is damaged, etc., resulting in the inability of this axle to work properly, and the locomotive continues to run relying on the remaining normal axles. When the operating condition of the electric locomotive is the first target operating condition, the switching frequency of the four - quadrant rectifier is configured to the first target frequency according to the harmonic state of the catenary. Among them, the harmonic state of the catenary includes the harmonic normal state and the harmonic abnormal state, and the first target frequency includes the target frequency corresponding to the harmonic normal state and the target frequency corresponding to the harmonic abnormal state. Dynamically adjusting the switching frequency of the four - quadrant rectifier according to different locomotive operating conditions and the harmonic state of the catenary improves the self - adaptability of the switching frequency adjustment, and at the same time can improve the electric energy conversion efficiency and improve the power quality.

[0050] The operating condition where only the auxiliary system of an electric locomotive is running refers to a running state in specific situations such as when the locomotive is parked and waiting to move. In this state, the main traction, braking and other functions of the electric locomotive are suspended or not enabled, and only the auxiliary system is working to provide necessary support for the locomotive itself and related equipment inside the locomotive. The extreme operating condition of an electric locomotive refers to a working state that is very special, severe and beyond the normal operating conditions during the running process of the locomotive. These operating conditions pose great challenges to the performance, reliability and safety of the locomotive. For example, heavy-load overspeed operating conditions, sudden failure operating conditions, multi-locomotive operation, etc., result in a ±5% voltage fluctuation of the power grid. When the operating condition of the electric locomotive is the second target operating condition, the switching frequency of the four-quadrant rectifier is configured as the second target frequency. According to different locomotive operating conditions, the switching frequency of the four-quadrant rectifier is dynamically adjusted, which improves the self-adaptability of the switching frequency adjustment, and at the same time can improve the electric energy conversion efficiency and improve the power quality.

[0051] Exemplarily, when the operating condition of the electric locomotive is the first target operating condition, according to the harmonic state of the catenary, the switching frequency of the four-quadrant rectifier is configured as the first target frequency, including: when the electric locomotive is running normally and there is no harmonic abnormality in the catenary, adjusting the switching frequency of the four-quadrant rectifier to the first frequency; when the electric locomotive is in axle-cut operation and there is no harmonic abnormality, adjusting the switching frequency of the four-quadrant rectifier to the second frequency; the first target frequency includes the first frequency and the second frequency; the first frequency is less than the second frequency.

[0052] Table 1 is a corresponding relationship table of an electric locomotive operating condition, harmonic state and the switching frequency of the four-quadrant rectifier. As shown in Table 1, when the electric locomotive is running normally and there is no harmonic abnormality in the catenary, the switching frequency of the four-quadrant rectifier is adjusted to the first frequency, where the first frequency is 450 Hz, to meet the power demand under the condition that the electric locomotive is running normally and there is no harmonic abnormality in the catenary. When the electric locomotive is in axle-cut operation and there is no harmonic abnormality, the switching frequency of the four-quadrant rectifier is adjusted to the second frequency, where the second frequency is 550 Hz, which can meet the power demand when the electric locomotive is in axle-cut operation and there is no harmonic abnormality, ensuring the basic quality of the electric energy and enabling the locomotive to operate stably and reliably.

[0053] When the operating condition of the electric locomotive is the second target operating condition, the switching frequency of the four-quadrant rectifier is configured as the second target frequency, including: when only the auxiliary system of the electric locomotive is running, adjusting the switching frequency of the four-quadrant rectifier to the third frequency; when the electric locomotive is in an extreme operating condition and / or in a harmonic abnormal state, adjusting the switching frequency of the four-quadrant rectifier to the fourth frequency; the second target frequency includes the third frequency and the fourth frequency; the third frequency is greater than the fourth frequency.

[0054] Continuing to refer to Table 1, when only the auxiliary system of the electric locomotive is operating, the switching frequency of the four-quadrant rectifier is adjusted to the third frequency, where the third frequency is 1100 Hz, meeting the power demand when only the auxiliary system of the electric locomotive is operating. When the electric locomotive is in an extreme working condition, the switching frequency of the four-quadrant rectifier is adjusted to the fourth frequency, where the fourth frequency is 750 Hz, which can meet the power demand of the electric locomotive under extreme working conditions. On the basis of the above embodiments, when the electric locomotive is operating normally or in the axle-cutting operation condition, when harmonic anomalies are detected, after a delay of 0.5 s, the switching frequency of the four-quadrant rectifier is adjusted to the fourth frequency. Based on the grid dynamic response time of 100 ms - 200 ms and the controller processing cycle of 50 ms, instantaneous interference can be filtered through delayed switching. When the harmonic state returns to normal, after a delay of 10 s, the switching frequency of the four-quadrant rectifier is adjusted to the first frequency. Since the grid harmonic stabilization time is 5 s - 8 s, through delayed recovery, frequent switching can be avoided, which is beneficial to the stable operation of the grid.

[0055] Table 1 Corresponding relationship table of operating conditions, harmonic states and switching frequencies of four-quadrant rectifiers of an electric locomotive

[0056]

[0057] On the basis of the above embodiments, after decomposing the catenary voltage according to the frequency to obtain the harmonic parameters of the catenary voltage, it further includes: normalizing the operating conditions, harmonic parameters, and catenary voltage of the electric locomotive within a preset historical time period; determining the correlation between the operating conditions, the harmonic parameters, and the catenary voltage of the electric locomotive; constructing a prediction model according to the correlation, and the prediction model is an autoregressive moving average model; predicting the operating conditions, harmonic parameters, and catenary voltage of the electric locomotive at a future moment according to the prediction model; judging whether the catenary is in a harmonic abnormal state or a normal state according to the difference between the predicted harmonic parameters and the preset amplitude threshold, combined with the operating conditions of the electric locomotive and the catenary voltage at the same moment; obtaining the harmonic states at multiple moments and determining the harmonic abnormal probability of the catenary voltage.

[0058] In the embodiment of the present invention, the storage period of historical data is 7 days, the sampling frequency is 10 kHz, and the memory is about 1 GB. The autoregressive moving average model is used to predict the harmonic resonance risk, and the prediction period is 1 second. Based on the verification results of 500 simulations, the accuracy rate reaches 85%, significantly improving the adaptability to dynamic working conditions. The preset historical time period is 24 hours. The operating conditions, harmonic parameters, and catenary voltage of the electric locomotive in the past 24 hours are input into the autoregressive moving average module, and the harmonic anomaly probability within the next 1 minute can be predicted. If the predicted risk is high, for example, the harmonic anomaly probability exceeds 80%, the switching frequency of the four-quadrant rectifier can be adjusted in advance to 750 Hz or 1100 Hz. By predicting the harmonic anomaly probability, the adaptability to dynamic working conditions can be improved.

[0059] Figure 2 It is a schematic structural diagram of a control system provided by an embodiment of the present invention. As Figure 2 shown, the control system includes: a voltage sensing module 210, a signal processing module 220, and a main control module 230; the voltage sensing module 210 is connected to the catenary, and the voltage sensing module 210 is used to detect the voltage signal of the catenary; the signal processing module 220 is connected to the voltage sensing module 210, and the signal processing module 220 is used to perform voltage stabilization processing on the voltage signal output by the voltage sensing module 210; the main control module 230 is connected to the signal processing module 220, and the main control module 230 is used to obtain the voltage signal of the catenary and the operating conditions of the electric locomotive; the main control module 230 is further used to decompose the catenary voltage according to the frequency to obtain the harmonic parameters of the catenary voltage, and determine the harmonic state of the catenary according to the harmonic parameters of the catenary voltage; and adjust the switching frequency of the four-quadrant rectifier to the target frequency according to the operating conditions of the electric locomotive, or adjust the switching frequency of the four-quadrant rectifier to the target frequency according to the operating conditions of the electric locomotive and the harmonic state of the catenary.

[0060] In an embodiment of the present invention, the sampling frequency of the voltage sensor 210 is 10 kHz, and the accuracy is ±0.5%. The signal processing module 220 is used to perform wavelet packet decomposition, band-pass and low-pass filtering, and supports redundant backup. The main control module 230 is a Traction Control Unit (TCU), which takes into account energy efficiency control and harmonic suppression, and can embed the maximum efficiency point tracking algorithm to optimize the system efficiency. The control system also includes a dual-channel Digital Signal Processor (DSP), which is used to run the harmonic detection algorithm. The harmonic decomposition time of each DPS is about 20 ms, meeting the real-time requirement. The digital signal processor is arranged inside the signal processing module, and the autoregressive moving average model is arranged inside the main control module. The control system also includes a human-machine interface. For example, the human-machine interface is a microcomputer display screen, which supports touch screen operation and can perform manual frequency locking and battery mode switching. The driver can lock the current frequency (such as 450 Hz) through the human-machine interface, pause the automatic switching logic until it is unlocked. In the parking state, the driver can switch to the battery power supply mode, turn off the four-quadrant rectifier, and eliminate harmonic injection. The application scenarios include the debugging stage, grid fault emergency operations, or specific operation requirements. In addition, the four-quadrant rectifier is a cascaded rectifier topology structure, including insulated gate bipolar transistors with a breakdown voltage of 3.3 kV, supporting stable switching between 450 Hz and 1100 Hz.

[0061] The control system provided by the embodiment of the present invention can execute the four-quadrant rectifier switching frequency control method provided by any of the above embodiments, and has the corresponding functional components and beneficial effects for executing the method.

[0062] It should be understood that various forms of the processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved, and no limitation is made herein.

[0063] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A switching frequency control method for a four - quadrant rectifier, characterized in that, Including: Obtaining the operating condition of the electric locomotive and the catenary voltage; Decomposing the catenary voltage according to frequency to obtain the harmonic parameters of the catenary voltage; Determining the harmonic state of the catenary according to the harmonic parameters of the catenary voltage; Adjusting the switching frequency of the four-quadrant rectifier to a target frequency according to the operating condition of the electric locomotive, or adjusting the switching frequency of the four-quadrant rectifier to the target frequency according to the operating condition of the electric locomotive and the harmonic state of the catenary.

2. The switching frequency control method of the four-quadrant rectifier according to claim 1, wherein The decomposing the catenary voltage according to frequency to obtain the harmonic parameters of the catenary voltage includes: Based on the wavelet packet decomposition algorithm, decomposing the catenary voltage according to frequency according to a preset decomposition level to obtain the odd harmonic amplitudes after decomposition; the harmonic parameters include the odd harmonic amplitudes after decomposition.

3. The switching frequency control method of the four-quadrant rectifier according to claim 2, wherein, Before determining the harmonic state of the catenary according to the harmonic parameters of the catenary voltage, it includes: Determining the fundamental wave amplitude of the catenary voltage.

4. The switching frequency control method of the four-quadrant rectifier according to claim 3, characterized in that, The determining the harmonic state of the catenary according to the harmonic parameters of the catenary voltage includes: Determining the total harmonic distortion rate of the catenary voltage according to the odd harmonic amplitudes after decomposition and the fundamental wave amplitude; Determining the harmonic state of the catenary according to the difference between the peak value of the catenary voltage and a preset voltage threshold, the difference between the odd harmonic amplitudes and a preset amplitude threshold, or the difference between the total harmonic distortion rate of the catenary voltage and a preset harmonic distortion rate threshold.

5. The switching frequency control method of the four-quadrant rectifier according to claim 4, characterized in that, The determining the harmonic state of the catenary according to the difference between the peak value of the catenary voltage and a preset voltage threshold, the difference between the odd harmonic amplitudes and a preset amplitude threshold, or the difference between the total harmonic distortion rate of the catenary voltage and a preset harmonic distortion rate threshold includes: When the peak value of the catenary voltage is greater than the preset voltage threshold, the odd harmonic amplitudes are greater than the preset amplitude threshold, or the total harmonic distortion rate of the catenary voltage is greater than the preset harmonic distortion rate threshold, determining that the harmonic state of the catenary is an abnormal state; When the peak value of the catenary voltage is less than or equal to the preset voltage threshold, the odd harmonic amplitudes are less than or equal to the preset amplitude threshold, and the total harmonic distortion rate of the catenary voltage is less than or equal to the preset harmonic distortion rate threshold, determining that the harmonic state of the catenary is a normal state.

6. The switching frequency control method of the four-quadrant rectifier according to claim 1, characterized in that Adjusting the switching frequency of the four-quadrant rectifier to a target frequency according to the operating condition of the electric locomotive and the harmonic state of the catenary includes: When the operating condition of the electric locomotive is the first target condition, configuring the switching frequency of the four-quadrant rectifier to the first target frequency according to the harmonic state of the catenary; the first target condition includes the normal operating condition of the electric locomotive and / or the axle-cut operation of the electric locomotive; Adjusting the switching frequency of the four-quadrant rectifier to a target frequency according to the operating condition of the electric locomotive includes: When the operating condition of the electric locomotive is the second target operating condition, configure the switching frequency of the four-quadrant rectifier to be the second target frequency; the second target operating condition includes the operating condition where only the auxiliary system of the electric locomotive is operating and / or the electric locomotive is in an extreme operating condition; the second target frequency is greater than the first target frequency.

7. The switching frequency control method of the four-quadrant rectifier according to claim 6, characterized in that, When the operating condition of the electric locomotive is the first target operating condition, configuring the switching frequency of the four-quadrant rectifier to be the first target frequency according to the harmonic state of the catenary includes: When the electric locomotive is operating normally and there is no harmonic anomaly in the catenary, adjust the switching frequency of the four-quadrant rectifier to the first frequency; When the electric locomotive is operating with an axle cut and there is no harmonic anomaly, adjust the switching frequency of the four-quadrant rectifier to the second frequency; the first target frequency includes the first frequency and the second frequency; the first frequency is less than the second frequency.

8. The switching frequency control method of the four-quadrant rectifier according to claim 5 or 6, characterized in that, When the operating condition of the electric locomotive is the second target operating condition, configuring the switching frequency of the four-quadrant rectifier to be the second target frequency includes: When only the auxiliary system of the electric locomotive is operating, adjust the switching frequency of the four-quadrant rectifier to the third frequency; When the electric locomotive is in an extreme operating condition and / or in the harmonic anomaly state, adjust the switching frequency of the four-quadrant rectifier to the fourth frequency; the second target frequency includes the third frequency and the fourth frequency; the third frequency is greater than the fourth frequency.

9. The method for controlling the switching frequency of the four-quadrant rectifier according to claim 1, wherein After decomposing the catenary voltage according to the frequency to obtain the harmonic parameters of the catenary voltage, it further includes: Normalize the operating condition of the electric locomotive, the harmonic parameters, and the catenary voltage within a preset historical time period; Determine the correlation between the operating condition of the electric locomotive, the harmonic parameters, and the catenary voltage; Construct a prediction model according to the correlation, and the prediction model is an autoregressive moving average model; According to the prediction model, predict the operating condition of the electric locomotive, the harmonic parameters, and the catenary voltage at a future moment; According to the difference between the predicted harmonic parameters and a preset amplitude threshold, combined with the operating condition of the electric locomotive and the catenary voltage at the same moment, judge whether the catenary is in a harmonic anomaly state or a normal state; Obtain the harmonic states at multiple moments and determine the harmonic anomaly probability of the catenary voltage.

10. A control system, characterized in that, It includes a voltage sensing module, a signal processing module, and a main control module; The voltage sensing module is connected to the catenary, and the voltage sensing module is used to detect the voltage signal of the catenary; The signal processing module is connected to the voltage sensing module, and the signal processing module is used to perform voltage stabilization processing on the voltage signal output by the voltage sensing module; The main control module is connected to the signal processing module, and the main control module is used to obtain the voltage signal of the catenary and the operating condition of the electric locomotive; The main control module is further used to decompose the catenary voltage according to the frequency to obtain the harmonic parameters of the catenary voltage, and determine the harmonic state of the catenary according to the harmonic parameters of the catenary voltage; And according to the operating conditions of the electric locomotive, adjust the switching frequency of the four-quadrant rectifier to the target frequency, or, according to the operating conditions of the electric locomotive and the harmonic state of the catenary, adjust the switching frequency of the four-quadrant rectifier to the target frequency.

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