Control method and device for reducing harms of higher harmonics

Abstract

The invention provides a control method and device for reducing harms of higher harmonics, and is applied to the technical field of automatic control. The method comprises the following steps: when the whole locomotive is switched on and switched off and enters an uncontrolled rectification mode, acquiring the running speed and the network side voltage of the locomotive; if the locomotive running speed is smaller than or equal to a first threshold value and the network side voltage is larger than a second threshold value, all pulse width modulation (PWM) switches are turned off, and the uncontrolled rectification mode is maintained; otherwise, switching from the uncontrolled rectification mode to a four-quadrant working mode, and executing a dynamic adjustment mechanism; wherein the dynamic adjustment mechanism comprises the following steps: dynamically adjusting the switching frequency according to a network side harmonic analysis result; and / or controlling the multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference.

Description

Technical Field

[0001] The present invention relates to the field of automatic control technology, and in particular to a control method and device for reducing the hazards of high-order harmonics. Background Art

[0002] The stable operation of locomotives is crucial in railway transportation systems. However, the high-order harmonics generated by locomotives during operation have become a key threat to the safe and stable operation of the railway system. These high-frequency harmonics not only cause grid voltage distortion and equipment overheating and damage, but can also trigger resonance in the traction power supply system, seriously affecting the safety and reliability of railway transportation.

[0003] In existing technology, passive filters are typically installed on the grid side of the converter to suppress harmonics. While this traditional LC filtering solution can mitigate harmonics to a certain extent, it suffers from numerous issues, including bulky hardware, limited suppression of a fixed frequency band, and potential failure if the system's resonance point shifts. Summary of the Invention

[0004] The present invention provides a control method and device for reducing the hazards of high-order harmonics, which are used to reduce the hazards caused by high-order harmonics on the locomotive network side and ensure the safe and stable operation of the railway transportation system.

[0005] The present invention provides a control method for reducing the hazards of high-order harmonics, comprising: when a locomotive closes the main circuit breaker and enters an uncontrolled rectification mode, obtaining the locomotive operating speed and the grid-side voltage; if the locomotive operating speed is less than or equal to a first threshold and the grid-side voltage is greater than a second threshold, turning off all pulse width modulation (PWM) switches to maintain the uncontrolled rectification mode; otherwise, switching from the uncontrolled rectification mode to a four-quadrant operating mode and executing a dynamic adjustment mechanism; wherein the dynamic adjustment mechanism comprises: dynamically adjusting the switching frequency according to the results of a grid-side harmonic analysis; and / or controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference.

[0006] According to a control method for reducing the hazards of high-order harmonics provided by the present invention, the dynamic adjustment mechanism includes dynamically adjusting the switching frequency according to the grid-side harmonic analysis results; the execution of the dynamic adjustment mechanism includes: performing real-time spectrum analysis on the grid-side voltage harmonics; when it is detected that the harmonic amplitude within the first preset frequency band exceeds the safety threshold, updating the switching frequency of the four-quadrant circuit from the first basic frequency to the second high-frequency operating frequency; wherein, the second high-frequency operating frequency is higher than the first basic frequency, and the first preset frequency band covers the inherent resonance risk frequency band of the locomotive traction network.

[0007] According to a control method for reducing the hazards of high-order harmonics provided by the present invention, before performing real-time spectrum analysis on the grid-side voltage harmonics, the method further includes: measuring the leakage current of the lightning arrester at different voltage levels and frequencies, and establishing an equivalent circuit transfer function of the lightning arrester in the high-frequency region based on the test data, and determining the equivalent impedance at each harmonic frequency based on the equivalent circuit transfer function; performing real-time spectrum analysis on the grid-side voltage harmonics to obtain harmonic voltage components, calculating the power loss of each harmonic based on the equivalent impedance and the harmonic voltage components, and obtaining the comprehensive heat loss of the lightning arrester under actual working conditions; calculating the safe operation time of the lightning arrester based on the comprehensive heat loss, the heat capacity parameters of the lightning arrester material, and the temperature rise limit, and determining the safety threshold based on the safe operation time.

[0008] According to a control method for reducing the hazards of high-order harmonics provided by the present invention, the IGBT module in the four-quadrant circuit of the locomotive is a hybrid SiC module, and the hybrid SiC module includes a silicon-based IGBT and an anti-parallel silicon carbide diode.

[0009] According to a control method for reducing the hazards of high-order harmonics provided by the present invention, the dynamic adjustment mechanism includes controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference; the execution of the dynamic adjustment mechanism includes: controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference, so that the characteristic harmonic components generated by each four-quadrant module cancel each other out; wherein the preset phase difference is determined based on the total number of four-quadrant modules, and the characteristic harmonic component refers to the main harmonic component generated by PWM modulation.

[0010] According to a control method for reducing the hazards of high-order harmonics provided by the present invention, the switching from the uncontrolled rectification mode to the four-quadrant operating mode includes: if the grid-side voltage is less than a third threshold, or the locomotive operating speed is greater than a fourth threshold, switching from the uncontrolled rectification mode to the four-quadrant operating mode; wherein the third threshold is less than the second threshold, and the fourth threshold is greater than or equal to the first threshold.

[0011] The present invention also provides a control device for reducing the hazards of high-order harmonics, comprising the following modules: an acquisition module and a processing module; the acquisition module is used to obtain the locomotive operating speed and grid-side voltage after the locomotive closes the main circuit breaker and enters the uncontrolled rectification mode; the processing module is used to turn off all pulse width modulation (PWM) switches to maintain the uncontrolled rectification mode if the locomotive operating speed is less than or equal to a first threshold and the grid-side voltage is greater than a second threshold; otherwise, switch from the uncontrolled rectification mode to the four-quadrant operating mode and execute a dynamic adjustment mechanism; wherein the dynamic adjustment mechanism includes: dynamically adjusting the switching frequency according to the grid-side harmonic analysis results; and / or controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference.

[0012] According to a control device for reducing the hazards of high-order harmonics provided by the present invention, the dynamic adjustment mechanism includes dynamically adjusting the switching frequency according to the results of the grid-side harmonic analysis; the processing module is used to perform real-time spectrum analysis on the grid-side voltage harmonics; when it is detected that the harmonic amplitude within the first preset frequency band exceeds the safety threshold, the switching frequency of the four-quadrant circuit is updated from the first basic frequency to the second high-frequency operating frequency; wherein, the second high-frequency operating frequency is higher than the first basic frequency, and the first preset frequency band covers the inherent resonance risk frequency band of the locomotive traction network.

[0013] According to a control device for reducing the hazards of high-order harmonics provided by the present invention, before performing real-time spectrum analysis on the grid-side voltage harmonics, the processing module is used to measure the leakage current of the lightning arrester at different voltage levels and frequencies, and establish an equivalent circuit transfer function of the lightning arrester in the high-frequency region based on the test data, and determine the equivalent impedance at each harmonic frequency based on the equivalent circuit transfer function; perform real-time spectrum analysis on the grid-side voltage harmonics to obtain harmonic voltage components, calculate the power loss of each harmonic based on the equivalent impedance and the harmonic voltage components, and obtain the comprehensive heat loss of the lightning arrester under actual working conditions; calculate the safe operation time of the lightning arrester based on the comprehensive heat loss, the heat capacity parameters of the lightning arrester material, and the temperature rise limit, and determine the safety threshold based on the safe operation time.

[0014] According to a control device for reducing the hazards of high-order harmonics provided by the present invention, the IGBT module in the four-quadrant circuit of the locomotive is a hybrid SiC module, and the hybrid SiC module includes a silicon-based IGBT and an anti-parallel silicon carbide diode.

[0015] According to a control device for reducing the hazards of high-order harmonics provided by the present invention, the dynamic adjustment mechanism includes controlling multiple groups of four-quadrant PWM carriers to perform phase-shift control according to a preset phase difference; the processing module is used to control the multiple groups of four-quadrant PWM carriers to perform phase-shift control according to a preset phase difference, so that the characteristic harmonic components generated by each four-quadrant module cancel each other out; wherein the preset phase difference is determined based on the total number of four-quadrant modules, and the characteristic harmonic component refers to the main harmonic component generated by PWM modulation.

[0016] According to a control device for reducing the hazards of high-order harmonics provided by the present invention, the processing module is used to switch from the uncontrolled rectification mode to the four-quadrant operating mode if the grid-side voltage is less than a third threshold, or the locomotive operating speed is greater than a fourth threshold; wherein the third threshold is less than the second threshold, and the fourth threshold is greater than or equal to the first threshold.

[0017] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the control method for reducing the hazards of high-order harmonics as described above is implemented.

[0018] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the control method for reducing the hazards of high-order harmonics as described above is implemented.

[0019] The present invention also provides a computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the computer program implements any of the above-mentioned control methods for reducing the hazards of high-order harmonics.

[0020] The control method and device for reducing the hazards of high-order harmonics provided by the present invention can realize mode switching between uncontrolled rectification mode and dynamic adjustment mechanism through dual threshold judgment of speed and voltage. Since all pulse width modulation (PWM) switches can be turned off and switched to uncontrolled rectification mode, the high-order harmonics generated by the switching action can be completely eliminated, and zero harmonic output can be achieved when the locomotive is stationary or at low speed; since the switching frequency can be dynamically adjusted according to the results of the grid-side harmonic analysis, the harmonic energy in the dangerous frequency band can be migrated to a higher frequency band, effectively avoiding the inherent resonant frequency band of the traction network; since multiple groups of four-quadrant PWM carriers can be controlled to perform phase shift control according to a preset phase difference, the amplitude of specific harmonics can be significantly reduced through the principle of harmonic phase cancellation. In this way, high-order harmonics can be synergistically reduced from three aspects: harmonic elimination, harmonic migration, and harmonic cancellation, thereby achieving full-band suppression of high-order characteristic harmonics, reducing the grid-side voltage harmonic distortion rate, while avoiding the risk of resonant overvoltage, and significantly improving the safety and reliability of the railway traction power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is one of the flow charts of the control method for reducing the hazards of high-order harmonics provided by the present invention; Figure 2 This is a circuit diagram of the locomotive converter cabinet provided by the present invention; Figure 3 This is the second flow chart of the control method for reducing the hazards of high-order harmonics provided by the present invention; Figure 4This is a schematic diagram of the structure of a control device for reducing the hazards of high-order harmonics provided by the present invention; Figure 5 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0024] It should be noted that in the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be interpreted as being more preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0025] It should be noted that, in this article, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. In addition, it should be noted that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the opposite order according to the functions involved. For example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0026] In order to facilitate a clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, words such as "first" and "second" are used to distinguish between identical or similar items with basically the same functions and effects. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order.

[0027] The embodiments of the present application describe some exemplary embodiments for the purpose of explanation. It should be understood that the present application can be implemented in other ways that are not specifically shown in the drawings.

[0028] In a locomotive's power conversion system, four-quadrant converters typically utilize single-phase or three-level pulse width modulation (PWM) rectifiers, which play a crucial role in the power conversion process. Furthermore, the traction converter's power transistors typically utilize insulated gate bipolar transistors (IGBTs) or intelligent power modules (IPMs), which control current and voltage to ensure proper operation of the locomotive's power system. However, in actual operation, the switching frequency of the four-quadrant converters is typically in the hundreds of hertz range, and the locomotive is equipped with multiple four-quadrant rectifier circuits. These factors combine to result in high-order characteristic harmonics primarily concentrating below the 50th order.

[0029] When high-frequency harmonic currents propagate through the traction network, if the harmonic frequency coincides with the network's inherent resonant frequency, a severe harmonic amplification effect can be triggered. Resonant high-order harmonics can cause distortion in the traction network's voltage waveform. This distortion, in turn, increases the harmonic currents in the EMUs or electric locomotives, creating a mutually excitation mechanism similar to positive feedback, ultimately leading to resonant overvoltages in the traction network. Resonant overvoltages are extremely harmful. They can not only expose lightning arresters in the traction network to the risk of burning or rupturing, but can also significantly shorten the service life of high-voltage electrical equipment in electric locomotives, posing a significant safety hazard to the stable operation of this vital railway artery. Given these circumstances, there is an urgent need to develop an effective control method to mitigate the hazards posed by high-order harmonics on the locomotive network side and ensure the safe and stable operation of the railway transportation system.

[0030] like Figure 1 As shown, the embodiment of the present application provides a control method for reducing the harm of high-order harmonics, and the control method for reducing the harm of high-order harmonics can be applied to a control device for reducing the harm of high-order harmonics. The control method for reducing the harm of high-order harmonics may include S101-S102: S101. After the locomotive closes the main circuit breaker and enters the uncontrolled rectification mode, the control device for reducing the hazards of high-order harmonics obtains the locomotive running speed and the grid-side voltage.

[0031] like Figure 2The figure below shows the circuit schematic of the locomotive converter cabinet. The converter cabinet utilizes a dual-circuit independent design with symmetrical upper and lower sections. Each section contains a four-quadrant circuit 201, a DC intermediate circuit 202, a three-phase inverter module 203, and an auxiliary power supply module. The four-quadrant circuit 201 utilizes IGBT modules to form a four-quadrant converter for AC-to-DC conversion. The DC intermediate circuit 202 connects to a capacitor bank to stabilize the DC bus voltage and reduce ripple interference. The three-phase inverter module 203 converts DC power into variable-frequency and variable-voltage three-phase AC power to drive the traction motor (M). The three-phase inverter module 203 utilizes PWM modulation technology to control the output voltage and frequency to match the motor's requirements. The auxiliary power supply module, which includes a three-phase inverter, a step-down transformer, and filter capacitors, supplies power to the locomotive's non-traction equipment.

[0032] like Figure 3 As shown in the figure, when the locomotive is switched on and off, all four-quadrant circuits on the locomotive are switched to the four-quadrant working mode by default. At this time, the switching frequency of the four-quadrant circuit is less than 550Hz, which can ensure that there are no harmonics below 50. After a running delay of 5s, the four-quadrant circuit automatically switches to the uncontrolled rectification mode. After that, the control device for reducing the hazards of high-order harmonics can obtain the locomotive running speed and grid-side voltage, and use this as a basis to determine whether to switch the working mode.

[0033] S102. If the locomotive operating speed is less than a first threshold and the grid-side voltage is greater than a second threshold, the control device for reducing the hazards of high-order harmonics turns off all pulse width modulation (PWM) switches and maintains an uncontrolled rectification mode; otherwise, the uncontrolled rectification mode is exited and a dynamic adjustment mechanism is executed.

[0034] The dynamic adjustment mechanism includes: dynamically adjusting the switching frequency according to the grid-side harmonic analysis result; and / or controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference.

[0035] Optionally, if the locomotive operating speed is less than a first threshold and the grid-side voltage is greater than a second threshold, the control device for reducing the hazards of high-order harmonics turns off all pulse width modulation (PWM) switches to maintain an uncontrolled rectification mode; if the grid-side voltage is less than a third threshold, or the locomotive operating speed is greater than a fourth threshold, it switches from the uncontrolled rectification mode to the four-quadrant operating mode; wherein the third threshold is less than the second threshold, and the fourth threshold is greater than or equal to the first threshold.

[0036] Specifically, if Figure 3As shown, after the four-quadrant circuit enters the uncontrolled rectification mode, if there is a handle position and the locomotive running speed is less than or equal to the first threshold, it means that it is currently in a stationary or low-speed working condition, and all pulse width modulation PWM switches can be turned off to maintain the uncontrolled rectification mode; if there is a handle position and the locomotive running speed is greater than the fourth threshold, it switches from the uncontrolled rectification mode to the four-quadrant working mode. At this time, the switching frequency of the four-quadrant circuit is generally less than 550Hz; and when the four-quadrant circuit works in the uncontrolled rectification mode, it is also necessary to make a judgment based on the grid side voltage. In order to ensure the normal operation of the auxiliary power supply module, the grid side voltage must be greater than the second threshold. Therefore, when the grid side voltage is greater than the second threshold, all pulse width modulation PWM switches are turned off to maintain the uncontrolled rectification mode; when the grid side voltage is less than the third threshold, it switches from the uncontrolled rectification mode to the four-quadrant working mode.

[0037] For example, the first threshold and the fourth threshold may be 3 km / h, the second threshold may be 24.5 kv, and the third threshold may be 23.5 kv.

[0038] Optionally, the dynamic adjustment mechanism includes controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference; the control device for reducing the hazards of high-order harmonics executes the dynamic adjustment mechanism, including: controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference, so that the characteristic harmonic components generated by each four-quadrant module cancel each other out; wherein, the preset phase difference is determined based on the total number of four-quadrant modules, and the characteristic harmonic component refers to the main harmonic component generated by PWM modulation.

[0039] Specifically, when in high-speed operation, in order to eliminate the harmonics of the converter to the grid side, the triangular carriers of the converter units in the four-quadrant module can be staggered by a certain phase angle in sequence. , and then compare them with their respective modulation waves to control the on and off of the power switch tubes of each converter unit. For a four-quadrant converter using unipolar double-frequency PWM modulation, the phase angle of the phase shift between each triangular carrier in the phase shift control is The formula is: ; Wherein, M is the total number of four-quadrant modules.

[0040] For example, if the locomotive includes 8 four-quadrant modules, then .

[0041] It should be noted that the application of PWM control technology for four-quadrant control of traction converters causes a certain amount of harmonics in the current of the secondary winding of the traction transformer. If no measures are taken, the harmonic currents in multiple sets of traction windings will be superimposed together, resulting in a large amount of harmonics in the primary winding, causing great harmonic pollution to the power grid. Since the traction control unit has four sets of traction windings, the multiple control technology can effectively reduce the harmonic content of the primary current of the transformer. The carrier phases of the four sets of PWM pulses of the four-quadrant converter are staggered by an angle. , the harmonic currents on the secondary winding can offset each other, so as to achieve the purpose of eliminating the harmonic current of the primary winding.

[0042] Optionally, the IGBT module in the locomotive's four-quadrant circuit is a hybrid silicon carbide (SiC) module, comprising a silicon-based IGBT and an anti-parallel silicon carbide diode. The dynamic adjustment mechanism includes dynamically adjusting the switching frequency based on the results of a grid-side harmonic analysis. The control device for reducing the hazards of high-order harmonics executes the dynamic adjustment mechanism, including: performing real-time spectrum analysis of grid-side voltage harmonics; and updating the switching frequency of the four-quadrant circuit from a first base frequency to a second high-frequency operating frequency when it is detected that the harmonic amplitude within a first preset frequency band exceeds a safety threshold. The second high-frequency operating frequency is higher than the first base frequency, and the first preset frequency band covers the inherent resonance risk frequency band of the locomotive traction network.

[0043] Specifically, the present application replaces the IGBT module in the four-quadrant circuit with a hybrid SiC module. Since the hybrid SiC module has a lower thermal resistance, the switching frequency of the four-quadrant circuit can be appropriately increased for a short period of time. When in the four-quadrant operating mode, the grid-side voltage can be collected and the grid-side voltage harmonics can be analyzed in real time. When the amplitude of the higher-order harmonics exceeds the safety threshold, the switching frequency of the four-quadrant circuit can be increased from the first fundamental frequency to the second high-frequency operating frequency, thereby avoiding the impact of higher-order harmonics on high-voltage devices. For example, the switching frequency of the four-quadrant circuit can be increased from 550Hz to greater than 1000Hz.

[0044] Optionally, the spectrum analysis can be performed using a Fast Fourier Transform (FFT) analysis. To accurately represent each harmonic component during FFT analysis of grid-side voltage harmonics, the sampling time must be at least less than 100 μs to ensure accuracy. The FFT sampling and analysis process is as follows: The digital signal processor analyzes data from a 0.02-second period. The FFT algorithm primarily consists of three steps: calculation of rotation factors, calculation of butterfly factors, and a code inversion procedure. Harmonics below the 50th order are analyzed, primarily focusing on the voltage amplitudes of harmonics at the 49th, 47th, 45th, 43rd, 41st, and 39th orders, and comparing them with relevant safety thresholds.

[0045] Optionally, before performing real-time spectrum analysis on the grid-side voltage harmonics, the control device for reducing the hazards of high-order harmonics can measure the leakage current of the lightning arrester at different voltage levels and frequencies, and establish an equivalent circuit transfer function of the lightning arrester in the high-frequency region based on the test data, and determine the equivalent impedance at each harmonic frequency based on the equivalent circuit transfer function; perform real-time spectrum analysis on the grid-side voltage harmonics to obtain the harmonic voltage components, calculate the power loss of each harmonic based on the equivalent impedance and the harmonic voltage components, and obtain the comprehensive heat loss of the lightning arrester under actual working conditions; calculate the safe operation time of the lightning arrester based on the comprehensive heat loss, the heat capacity parameters of the lightning arrester material and the temperature rise limit, and determine the safety threshold based on the safe operation time.

[0046] Specifically, since the grid-side voltage harmonics are variable and may cause damage to high-voltage devices such as lightning arresters, the safety threshold can be determined starting from the lightning arrester.

[0047] Before performing real-time spectrum analysis on the grid-side voltage harmonics, a control device for reducing the hazards of higher harmonics can first apply voltages of different levels and frequencies to the arrester via a variable-frequency voltage-regulating power supply through a test transformer, and then detect the arrester's leakage current using a leakage current sensor. The arrester's equivalent circuit transfer function is then established based on the test data. This equivalent circuit transfer function can reflect the arrester's electrical characteristics. Based on this equivalent circuit transfer function, the equivalent impedance at each harmonic frequency can be determined: ; in, Indicates the equivalent reactance of the arrester, and represents the equivalent resistance of the arrester, and represents the equivalent capacitance of the arrester, Indicates harmonic frequencies.

[0048] Using the Cauerl type circuit to synthesize the equivalent circuit transfer function, we can get: in this equivalent circuit, changing The voltage and current phase of the arrester can be fine-tuned. The power loss of the equivalent arrester is mainly in On the production, It mainly adjusts the voltage and current phase of the equivalent circuit.

[0049] Thermal stability is a very important performance of the arrester, which directly determines the reliability and service life of the arrester. is the arrester limit temperature With stable operating temperature The difference depends on the maximum energy that the arrester is allowed to absorb during operation. : ; in, is the specific heat capacity of the arrester resistor, is the arrester resistor density.

[0050] After the electric locomotive arrester is manufactured, its heat dissipation performance is basically fixed. To simplify the calculation, it can be approximately considered that the heat dissipation of the arrester changes linearly. The heat dissipation of the arrester unit per minute is recorded as: ; in, is the volume unit of the arrester, is the initial temperature of the arrester, is the ambient temperature, is the heat dissipation time constant of the arrester.

[0051] Therefore, the energy absorbed by the electric locomotive arrester during operation is: ; Calculate the active power consumed by the arrester when operating under high-order harmonic voltage , needs to be calculated based on the measured results.

[0052] Fourier analysis of the grid voltage during resonance, collected during testing of electric locomotive harmonic characteristics, revealed that when traction network resonance occurs, the high-order harmonic voltages contained in the grid are often not of a single frequency. Therefore, when analyzing the impact of high-order harmonic voltages on electric locomotive lightning arresters, a composite frequency can be used to simulate the active power loss of the arrester. The active power loss at the composite frequency refers to the sum of the power at the 49th, 47th, 45th, 43rd, 41st, and 39th harmonics.

[0053] In this way, the safe operation time of the arrester can be obtained as: The safety threshold can be further determined by testing the safe operating time of the lightning arrester to reach the theoretical limit temperature.

[0054] In the embodiment of the present application, the mode switching between the uncontrolled rectification mode and the dynamic adjustment mechanism can be achieved through the dual threshold judgment of speed and voltage. Since all pulse width modulation (PWM) switches can be turned off and switched to the uncontrolled rectification mode, the high-order harmonics generated by the switching action can be completely eliminated, and zero harmonic output can be achieved when the locomotive is stationary or at low speed. Since the switching frequency can be dynamically adjusted according to the grid-side harmonic analysis results, the harmonic energy in the dangerous frequency band can be migrated to a higher frequency band, effectively avoiding the inherent resonant frequency band of the traction network. Since multiple groups of four-quadrant PWM carriers can be controlled to perform phase shift control according to a preset phase difference, the amplitude of specific harmonics can be significantly reduced through the principle of harmonic phase cancellation. In this way, high-order harmonics can be synergistically reduced from three aspects: harmonic elimination, harmonic migration, and harmonic cancellation, thereby achieving full-band suppression of high-order characteristic harmonics, reducing the grid-side voltage harmonic distortion rate, and avoiding the risk of resonant overvoltage, significantly improving the safety and reliability of the railway traction power supply system.

[0055] The above mainly introduces the solution provided by the embodiment of the present application from the perspective of method. In order to realize the above functions, it includes hardware structures and / or software modules corresponding to the execution of each function. Those skilled in the art should easily appreciate that, in combination with the units and algorithm steps of each example described in the embodiments disclosed herein, the embodiments of the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in a hardware or computer software driven hardware manner depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0056] It should be noted that the device in the embodiment of the present application includes a virtual device and a physical device. The virtual device can be a control device for reducing the hazards of high-order harmonics, and the physical device can include an electronic device, a computer storage medium, and a computer program product.

[0057] The control method for reducing the harmonics provided in the embodiments of the present application can be executed by a control device for reducing the harmonics, or a control module within the control device for reducing the harmonics used to control the harmonics. In the embodiments of the present application, the control method for reducing the harmonics provided in the embodiments of the present application is described by taking the control device for reducing the harmonics as an example to illustrate the control device for reducing the harmonics.

[0058] It should be noted that, in the embodiment of the present application, the control device for reducing the hazards of high-order harmonics can be divided into functional modules according to the above-mentioned method example. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing module. The above-mentioned integrated module can be implemented in the form of hardware or in the form of software functional modules. Optionally, the division of modules in the embodiment of the present application is schematic and is only a logical functional division. In actual implementation, there may be other division methods.

[0059] like Figure 4 As shown, an embodiment of the present application provides a control device 400 for reducing the hazards of high-order harmonics. The control device 400 for reducing the hazards of high-order harmonics includes: an acquisition module 401 and a processing module 402. The acquisition module 401 is used to obtain the locomotive running speed and grid-side voltage after the locomotive closes the main circuit breaker and enters the uncontrolled rectification mode; the processing module 402 is used to turn off all pulse width modulation (PWM) switches and maintain the uncontrolled rectification mode if the locomotive running speed is less than or equal to a first threshold and the grid-side voltage is greater than a second threshold; otherwise, switch from the uncontrolled rectification mode to the four-quadrant working mode and execute a dynamic adjustment mechanism; wherein the dynamic adjustment mechanism includes: dynamically adjusting the switching frequency according to the grid-side harmonic analysis results; and / or controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference.

[0060] Optionally, the dynamic adjustment mechanism includes dynamically adjusting the switching frequency according to the grid-side harmonic analysis results; the processing module 402 is used to perform real-time spectrum analysis on the grid-side voltage harmonics; when it is detected that the harmonic amplitude within the first preset frequency band exceeds the safety threshold, the switching frequency of the four-quadrant circuit is updated from the first basic frequency to the second high-frequency operating frequency; wherein, the second high-frequency operating frequency is higher than the first basic frequency, and the first preset frequency band covers the inherent resonance risk frequency band of the locomotive traction network.

[0061] Optionally, before performing real-time spectrum analysis on the grid-side voltage harmonics, the processing module 402 is used to measure the leakage current of the lightning arrester at different voltage levels and frequencies, and establish an equivalent circuit transfer function of the lightning arrester in the high-frequency region based on the test data, and determine the equivalent impedance at each harmonic frequency based on the equivalent circuit transfer function; perform real-time spectrum analysis on the grid-side voltage harmonics to obtain the harmonic voltage components, calculate the power loss of each harmonic based on the equivalent impedance and the harmonic voltage components, and obtain the comprehensive heat loss of the lightning arrester under actual working conditions; calculate the safe operation time of the lightning arrester based on the comprehensive heat loss, the heat capacity parameters of the lightning arrester material and the temperature rise limit, and determine the safety threshold based on the safe operation time.

[0062] Optionally, the IGBT module in the four-quadrant circuit of the locomotive is a hybrid SiC module, which includes a silicon-based IGBT and an anti-parallel silicon carbide diode.

[0063] Optionally, the dynamic adjustment mechanism includes controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference; the processing module 402 is used to control multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference, so that the characteristic harmonic components generated by each four-quadrant module cancel each other out; wherein the preset phase difference is determined based on the total number of four-quadrant modules, and the characteristic harmonic component refers to the main harmonic component generated by PWM modulation.

[0064] Optionally, the processing module 402 is used to switch from the uncontrolled rectification mode to the four-quadrant operating mode if the grid-side voltage is less than a third threshold, or the locomotive operating speed is greater than a fourth threshold; wherein the third threshold is less than the second threshold, and the fourth threshold is greater than or equal to the first threshold.

[0065] In the embodiment of the present application, the mode switching between the uncontrolled rectification mode and the dynamic adjustment mechanism can be achieved through the dual threshold judgment of speed and voltage. Since all pulse width modulation (PWM) switches can be turned off and switched to the uncontrolled rectification mode, the high-order harmonics generated by the switching action can be completely eliminated, and zero harmonic output can be achieved when the locomotive is stationary or at low speed. Since the switching frequency can be dynamically adjusted according to the grid-side harmonic analysis results, the harmonic energy in the dangerous frequency band can be migrated to a higher frequency band, effectively avoiding the inherent resonant frequency band of the traction network. Since multiple groups of four-quadrant PWM carriers can be controlled to perform phase shift control according to a preset phase difference, the amplitude of specific harmonics can be significantly reduced through the principle of harmonic phase cancellation. In this way, high-order harmonics can be synergistically reduced from three aspects: harmonic elimination, harmonic migration, and harmonic cancellation, thereby achieving full-band suppression of high-order characteristic harmonics, reducing the grid-side voltage harmonic distortion rate, and avoiding the risk of resonant overvoltage, significantly improving the safety and reliability of the railway traction power supply system.

[0066] Figure 5 An example of a physical structure diagram of an electronic device is shown below. Figure 5As shown, the electronic device may include: a processor 510, a communications interface 520, a memory 530, and a communications bus 540, wherein the processor 510, the communications interface 520, and the memory 530 communicate with each other via the communications bus 540. The processor 510 may call logic instructions in the memory 530 to execute a control method for reducing the hazards of high-order harmonics. The method includes: when the locomotive closes the main circuit breaker and enters the uncontrolled rectification mode, obtaining the locomotive operating speed and the grid-side voltage; if the locomotive operating speed is less than or equal to a first threshold and the grid-side voltage is greater than a second threshold, turning off all pulse-width modulation (PWM) switches to maintain the uncontrolled rectification mode; otherwise, switching from the uncontrolled rectification mode to a four-quadrant operating mode and executing a dynamic adjustment mechanism; wherein the dynamic adjustment mechanism includes: dynamically adjusting the switching frequency according to the grid-side harmonic analysis results; and / or controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference.

[0067] Furthermore, the logic instructions in the aforementioned memory 530 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0068] On the other hand, the present invention also provides a computer program product, which includes a computer program, which can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the control method for reducing the hazards of high-order harmonics provided by the above methods. The method includes: when the locomotive closes the main circuit breaker and enters the uncontrolled rectification mode, obtaining the locomotive operating speed and grid-side voltage; if the locomotive operating speed is less than or equal to a first threshold and the grid-side voltage is greater than a second threshold, turning off all pulse width modulation (PWM) switches to maintain the uncontrolled rectification mode; otherwise, switching from the uncontrolled rectification mode to the four-quadrant operating mode, and executing a dynamic adjustment mechanism; wherein the dynamic adjustment mechanism includes: dynamically adjusting the switching frequency according to the grid-side harmonic analysis results; and / or controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference.

[0069] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to execute the control method for reducing the hazards of high-order harmonics provided by the above-mentioned methods, the method comprising: when the locomotive closes the main circuit breaker and enters the uncontrolled rectification mode, obtaining the locomotive operating speed and the grid-side voltage; if the locomotive operating speed is less than or equal to a first threshold, and the grid-side voltage is greater than a second threshold, turning off all pulse width modulation (PWM) switches to maintain the uncontrolled rectification mode; otherwise, switching from the uncontrolled rectification mode to the four-quadrant operating mode, and executing a dynamic adjustment mechanism; wherein the dynamic adjustment mechanism comprises: dynamically adjusting the switching frequency according to the grid-side harmonic analysis results; and / or controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference.

[0070] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0071] Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented using software plus a necessary general-purpose hardware platform, or of course, hardware. Based on this understanding, the essence of the above technical solution, or the portion that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, or an optical disk, and includes a number of instructions for causing a computer device (such as a personal computer, server, or network device) to execute the methods described in each embodiment or certain portions of the embodiments.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A control method for reducing the hazards of high-order harmonics, characterized in that: include: When the locomotive closes the main circuit breaker and enters the uncontrolled rectification mode, the locomotive running speed and grid-side voltage are obtained; If the locomotive running speed is less than or equal to a first threshold and the grid-side voltage is greater than a second threshold, all pulse width modulation (PWM) switches are turned off to maintain the uncontrolled rectification mode; Otherwise, switching from the uncontrolled rectification mode to the four-quadrant operation mode and executing a dynamic adjustment mechanism; The dynamic adjustment mechanism includes: dynamically adjusting the switching frequency according to the grid-side harmonic analysis result; and / or controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference.

2. The control method for reducing the harm of high-order harmonics according to claim 1, characterized in that: The dynamic adjustment mechanism includes dynamically adjusting the switching frequency according to the grid-side harmonic analysis results; The execution dynamic adjustment mechanism includes: Perform real-time spectrum analysis on grid-side voltage harmonics; When it is detected that the harmonic amplitude within the first preset frequency band exceeds a safety threshold, the switching frequency of the four-quadrant circuit is updated from the first basic frequency to the second high-frequency operating frequency; The second high-frequency operating frequency is higher than the first basic frequency, and the first preset frequency band covers the inherent resonance risk frequency band of the locomotive traction network.

3. The control method for reducing the harm of high-order harmonics according to claim 2, characterized in that: Before performing real-time spectrum analysis on the grid-side voltage harmonics, the method further includes: Measuring the leakage current of the arrester at different voltage levels and frequencies, establishing an equivalent circuit transfer function of the arrester in the high-frequency region based on the test data, and determining the equivalent impedance at each harmonic frequency based on the equivalent circuit transfer function; Performing real-time spectrum analysis on the grid-side voltage harmonics to obtain harmonic voltage components, calculating the power loss of each harmonic based on the equivalent impedance and the harmonic voltage components, and obtaining the comprehensive heat loss of the arrester under actual working conditions; The safe operation time of the arrester is calculated according to the comprehensive heat loss, the heat capacity parameter of the arrester material and the temperature rise limit, and the safety threshold is determined based on the safe operation time.

4. The control method for reducing the harm of high-order harmonics according to claim 2, characterized in that: The IGBT module in the four-quadrant circuit of the locomotive is a hybrid SiC module, which includes a silicon-based IGBT and an anti-parallel silicon carbide diode.

5. The control method for reducing the harm of high-order harmonics according to claim 1, characterized in that: The dynamic adjustment mechanism includes controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference; the execution of the dynamic adjustment mechanism includes: Control multiple groups of four-quadrant PWM carriers to perform phase shift control according to the preset phase difference, so that the characteristic harmonic components generated by each four-quadrant module cancel each other out; The preset phase difference is determined based on the total number of four-quadrant modules, and the characteristic harmonic component refers to the main harmonic component generated by PWM modulation.

6. The control method for reducing the harm of high-order harmonics according to claim 1, characterized in that: The switching from the uncontrolled rectification mode to the four-quadrant operation mode includes: If the grid-side voltage is less than a third threshold, or the locomotive operating speed is greater than a fourth threshold, switching from the uncontrolled rectification mode to the four-quadrant operating mode; The third threshold is smaller than the second threshold, and the fourth threshold is greater than or equal to the first threshold.

7. A control device for reducing the hazards of high-order harmonics, characterized in that: include: Acquisition module and processing module; The acquisition module is used to obtain the locomotive running speed and grid-side voltage when the locomotive closes the main circuit breaker and enters the uncontrolled rectification mode; The processing module is configured to turn off all pulse width modulation (PWM) switches to maintain the uncontrolled rectification mode if the locomotive running speed is less than or equal to a first threshold and the grid-side voltage is greater than a second threshold; Otherwise, switching from the uncontrolled rectification mode to the four-quadrant operation mode and executing a dynamic adjustment mechanism; The dynamic adjustment mechanism includes: dynamically adjusting the switching frequency according to the grid-side harmonic analysis result; and / or controlling multiple groups of four-quadrant PWM carriers to perform phase shift control according to a preset phase difference.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the control method for reducing the hazards of high-order harmonics according to any one of claims 1 to 6 is implemented.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the control method for reducing the hazards of high-order harmonics as claimed in any one of claims 1 to 6 is implemented.

10. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the control method for reducing the hazards of high-order harmonics as claimed in any one of claims 1 to 6 is implemented.

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