A rapid ice melting method for catenary based on resonant impedance

Abstract

The present invention provides a method for quickly deicing an overhead catenary based on resonant impedance. The method includes: obtaining the resonant frequency of a target line on the overhead catenary to be deiced, and finding a measuring point with a relatively large impedance amplitude based on the resonant frequency with the line position as a variable; installing a deicing device at the position of the measuring point, the deicing device injecting a harmonic current of the resonant frequency into the target line, and generating Joule heat by using the resistance value at the position of the measuring point to melt and shed the ice covering the target line. The present invention utilizes the characteristics that the impedance takes a maximum value and is purely resistive at the inherent resonant point of the overhead catenary, reduces the requirement for short-circuit current, alleviates the design difficulty of the deicing device, and at the same time does not need to consider the reactive power flow of the line, reducing communication interference, line insulation and aging risks.

Description

Technical Field

[0001] The invention relates to the technical field of thermal ice melting, and in particular to a method for rapidly melting ice of a contact network based on resonant impedance. Background Art

[0002] my country has a vast territory, and railways are distributed in many climate zones and geological conditions. There are freezing conditions in both the north and the south. In addition, trains are intermittent loads. When the train density is low and the load is intermittent, the contact network is very prone to ice. Line icing will seriously affect the normal operation of high-speed rail lines and interfere with people's normal production and life. Therefore, it has gradually attracted the attention of the transportation industry and the electrical industry. Contact network icing is not only easy to cause line break problems, but also very easy to cause flashover accidents, resulting in frequent line tripping, and even carbonization damage of insulators, destroying line insulation; contact line icing will also cause ice to appear between the contact line and the pantograph slide, which will then affect the current collection of the pantograph network, and even arc burns the pantograph slide and contact line. Therefore, the study of contact network ice melting is of great significance to ensure the smooth operation of railways.

[0003] Thermal de-icing is the most widely used and effective method for de-icing overhead contact networks. The thermal de-icing method short-circuits the overhead contact network to form a short-circuit loop, and uses the Joule heating effect of the short-circuit current to increase the temperature of the ice-covered conductors to melt and fall off the ice. However, with the development of railways, the power demand for de-icing current continues to expand. Due to the limitations of line quotas and system safety, it is difficult to achieve a very high de-icing current. In addition, large-scale de-icing tasks have high requirements for the adjustment capabilities and technical design of de-icing technology and related equipment, which are difficult to meet with current technology and equipment.

[0004] The main function of the contact network is to provide electric energy for train traction. However, due to the influence of low temperature, wet snow and other climatic conditions, once ice appears on the surface of the contact network, it will seriously affect the normal current collection of the pantograph, and the reliability of the train power supply cannot be guaranteed. In severe cases, major accidents such as line breakage and tripping will occur, and driving safety will be greatly threatened. Therefore, continuous and in-depth research on high-quality and efficient ice melting technology has great guiding significance for improving the reliability of the power transmission system.

[0005] At present, the de-icing technology in the existing technology mostly adopts thermal de-icing method. Thermal de-icing has a short de-icing time and simple operation, so it is widely used in engineering. Thermal de-icing is an de-icing technology that converts electrical energy into thermal energy. Based on the principle of Joule heat, traditional technology usually increases the AC and DC currents in the conductors to make the conductors heat up and generate enough heat to achieve the purpose of de-icing the contact network. Thermal de-icing methods mainly include AC de-icing method, DC de-icing method and high-frequency excitation de-icing method. Among them, AC and DC short-circuit de-icing methods have been widely used in engineering practice and are also the main de-icing technologies currently used.

[0006] The de-icing power supply of the AC de-icing technology generally uses the transformer of the traction substation. Considering that it is necessary to make the short-circuit connection of the line as convenient as possible and to restore it quickly after de-icing, the short-circuit point is generally selected at the section post. The catenary on the upper line of the railway is connected to the feeder of the traction substation, and the catenary on the lower line is connected to the ground wire of the substation to form a de-icing loop. The de-icing current should be large enough to achieve de-icing (from several hundred to thousands of amperes). At the same time, the line parameters should also be adjusted to restrict the de-icing current to avoid damage to the line and equipment due to excessive current. AC short-circuit de-icing is suitable for lines with weak anti-icing ability and difficult technical upgrading, especially for lines with slow icing speed. However, it also has deficiencies - the power consumption is very large. In addition, AC de-icing also needs to consider the reactive power flow of the line, requires a relatively large capacity to be provided, and has low de-icing efficiency.

[0007] The DC de-icing technology requires additional rectification on the basis of AC de-icing. The traction transformer of the traction substation is used to provide de-icing power, and the matching rectification device is used to connect the railway catenary and the de-icing line. The rectification device can be configured based on devices such as insulated gate bipolar transistors. Under the same icing conditions of the line, the DC short-circuit de-icing requires much less capacity than the AC short-circuit de-icing, only about 1 / 6 of that of AC de-icing, and does not need to consider the reactive power flow of the line. However, the deficiency of the DC short-circuit de-icing method is that it requires an external de-icing power supply and a rectification device, and the cost is expensive.

[0008] The above two de-icing technologies are both based on a short-circuit closed loop. According to the Joule heat principle, they generate high enough heat to melt the ice on the wire surface. However, at the same time, they have high requirements for the current value, consume more energy, and have high technical requirements for the device. Even the improved methods such as adding de-icing devices and based on static var generators also face problems such as complex system structure, high investment cost, and great difficulty in long-term popularization and application. The high-frequency high-voltage excitation de-icing is a de-icing method based on the skin effect of the line and the dielectric loss theory. Under high-frequency excitation, a high-frequency current is generated. The resistance inside the wire increases significantly. For the same current, the skin effect on the wire surface is more obvious, and the Joule heat generated inside the wire increases. The ice layer is repeatedly polarized in the high-frequency alternating electric field, and the ice layer, as a dielectric, generates dielectric loss heat. Under the combined action of the Joule heat and the dielectric loss heat, the temperature of the wire and the ice layer rises, so as to achieve the purpose of de-icing. However, there is no unified theoretical calculation method for the optimal de-icing voltage and frequency, and its de-icing model is too simple to be applied to actual engineering.

[0009] Although the AC de-icing technology can achieve a good de-icing effect and reduce the accident rate, its disadvantages are also quite obvious:

[0010] 1) The short-circuit current is large. The AC impedance of a 20-km railway catenary is about 6 - 10 Ω, and a relatively large short-circuit current (the short-circuit current value usually reaches several hundred to thousands of amperes) is required to complete de-icing.

[0011] 2) The device has a large capacity but a relatively low de-icing efficiency. The resistance component of the line's AC impedance accounts for about 1 / 5 to 1 / 3. When generating the same de-icing current, the de-icing power supply voltage used in AC de-icing technology is higher, and a large amount of reactive power needs to be provided. Therefore, the capacity of its AC de-icing power supply is very large, and since reactive power does not generate heat, its de-icing efficiency is relatively low.

[0012] 3) The cost is relatively high. The inductance component in the line's AC impedance accounts for a larger proportion, and reactive power is the main part. The reactive power flow of the line needs to be considered, and the capacity of the AC de-icing power supply is usually very large, resulting in a relatively high equipment cost.

[0013] The traditional DC de-icing method is based on the short-circuit principle. Taking the traction substation as the center, it forms a closed circulation path for the de-icing current in the up and down supply arms of the substation. Depending on a high-power DC de-icing power supply, a DC current is injected into the loop to achieve the DC de-icing effect. The defects of the traditional DC de-icing method are as follows:

[0014] 1) The short-circuit current is large. DC de-icing utilizes the DC resistance of the line, and its resistance value is small. A large current needs to be injected to complete the de-icing task. For example, the minimum de-icing current required for 4*LGJ-500 type conductors is approximately as high as 3894.4 A; the actual line test results show that for a 20-km railway line with a resistance of about 2 Ω, a current of up to several thousand amperes is required to complete the de-icing task.

[0015] 2) An additional rectification device is required, and the cost is high. The DC short-circuit de-icing method needs to provide a high-power DC de-icing power supply, but its DC de-icing power supply is expensive and the cost is too high. Moreover, the development technology requirements for high-power power supplies are high, and the design difficulty is large.

[0016] 3) The system compatibility is poor. The DC de-icing technology has poor compatibility with the existing AC catenary system and AC equipment. DC de-icing is likely to cause communication interference, line insulation, and aging problems. 4) The line applicability is poor. The DC de-icing power supply is applicable to double-track traction networks. Due to the complex characteristics of the earth impedance, it cannot be applied to single-track traction networks where the contact wire and the earth form a short-circuit loop.

[0017] High-frequency high-voltage excitation de-icing is a de-icing method based on the skin effect and dielectric loss theory of the line. A high-frequency current is applied to the line, and the heat generation is relatively uniform. The higher the frequency, the more significant the skin effect and the better the de-icing effect. And high-frequency high-voltage excitation de-icing well improves the requirement of a large short-circuit current, but the defects are also very obvious:

[0018] 1) There is no unified theoretical calculation method for the optimal de-icing voltage and frequency, and its calculation model cannot adapt to different voltage levels, different ice-covering types, and different types of conductors;

[0019] 2) Newly structured conductors are required, and the economy is too poor;

[0020] 3) The existing ice melting models are too simple to be applied to practical engineering. Summary of the Invention

[0021] An embodiment of the present invention provides a rapid ice melting method for catenary based on resonance impedance to effectively perform ice melting treatment on the catenary.

[0022] To achieve the above object, the present invention adopts the following technical solutions.

[0023] A rapid ice melting method for catenary based on resonance impedance includes:

[0024] Measuring the resonance frequency of the target line on the catenary to be ice melted, and finding the measuring point with a larger impedance amplitude based on the resonance frequency with the line position as a variable;

[0025] Installing an ice melting device at the position of the measuring point, injecting current from the ice melting device into the target line, and using the resistance value at the position of the measuring point to generate Joule heat to melt and shed the ice on the target line.

[0026] Preferably, the step of measuring the resonance frequency of the target line on the catenary to be ice melted and finding the measuring point with a larger impedance amplitude based on the resonance frequency with the line position as a variable includes:

[0027] The traction power supply system consists of a traction substation and a traction network line. The traction network consists of a feeder, a catenary, and a return line. The traction network delivers the electric energy of the traction substation to the locomotives running along the line. Let the common connection point PCC represent the train position. The impedance of the external power supply and the traction substation is equivalent to a lumped parameter Zus. The transmission line is equivalent using a π-type distributed parameter equivalent circuit. z is the series impedance per unit length of the equivalent single-phase line, c is the shunt capacitance per unit length of the equivalent single-phase line, the distance between the train and the traction substation is x, and the total length of the traction network is D;

[0028] The equivalent impedance between the PCC and the traction substation is:

[0029]

[0030] Where and are the characteristic impedance and propagation constant of the equivalent single-phase circuit respectively;

[0031] The equivalent impedance between the PCC and the section post is:

[0032]

[0033] The frequency-domain impedance at the PCC is:

[0034]

[0035] When Z S When the modulus value is the largest, resonance occurs in the traction power supply system. At the resonance frequency of the resonance point of the traction power supply system, there is an extreme point at the end of the line on the amplitude-position curve, and the resistance characteristic is presented at this extreme point, and the impedance amplitude is the largest.

[0036] Preferably, installing the ice melting device at the measuring point position includes:

[0037] At the resonance frequency of the traction power supply system, taking the line position as a variable, testing at different positions of the target line to obtain the impedance frequency characteristic curves at different positions, finding the position with the largest resonance impedance amplitude, and determining this position as the installation position of the ice melting device.

[0038] Preferably, installing the ice melting device at the measuring point position includes:

[0039] When the target line on the catenary adopts the direct supply mode of single wire with return line or the single wire autotransformer AT power supply mode, the access mode of the ice melting device includes: the contact wire in the target line is connected to the substation ground wire, and the ice melting device is connected to the section post to form a short-circuit closed loop of contact wire - ground;

[0040] When the target line on the catenary adopts the direct supply mode of double line with return line or the double line AT, the access mode of the ice melting device includes: the up and down line contact wires at the substation are short-circuited, and the ice melting device is connected to the section post to form a short-circuit closed loop of contact wire T1 - contact wire T2.

[0041] Preferably, the ice melting device injects current into the target line, and uses the resistance value at the measuring point position to generate Joule heat to melt and shed the ice on the target line, including:

[0042] The ice melting device is composed of a cascaded H-bridge harmonic generator, including: a step-down transformer TP, a cascaded converter HG, and a converter reactor L c , the primary side winding of the step-down transformer TP is connected in series with the traction network, and the main secondary side winding of the step-down transformer TP passes through the converter reactor L c to connect the cascaded converter HG and provide the power supply voltage for the cascaded converter HG;

[0043] The rated voltage of the primary side winding of the step-down transformer TP is taken as the rated voltage of the traction network. The secondary side winding of the step-down transformer TP is connected to the harmonic source, and the rated voltage value of the secondary side winding is matched with the harmonic source. The step-down transformer TP reduces the 27.5 kV high voltage on the primary side to the rated voltage value range of the secondary side winding of the step-down transformer TP. The harmonic source consists of a single-phase H-bridge converter and a converter reactor Lc is constituted and implemented by a power electronic converter; the converter reactor L c is used for filtering and current control;

[0044] The ice melting device injects a current with controllable frequency and amplitude into the target line, and uses the resonant impedance of the catenary to generate Joule heat for catenary ice melting.

[0045] Preferably, the method further includes: the ice melting device injects a single-frequency harmonic current into the traction network within the range of 100 - 5000 Hz, detects the voltage and current waveforms on the target line on the traction network side, performs Fourier analysis to calculate the voltage and current at the test frequency, and uses the interharmonic interpolation and frequency scanning algorithm to obtain the impedance-frequency characteristic information within the entire set test frequency range.

[0046] It can be seen from the technical solutions provided by the embodiments of the present invention that the present invention utilizes the characteristics that the impedance at the inherent resonance point of the catenary takes the maximum value and is purely resistive, reduces the requirement for short-circuit current, reduces the design difficulty of the ice melting device, and at the same time does not need to consider the reactive power flow of the line, reducing communication interference, line insulation and aging risks.

[0047] Additional aspects and advantages of the present invention will be given in part in the following description, and these will become obvious from the following description, or can be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0049] Figure 1 is a schematic diagram of a traction power supply system proposed by an embodiment of the present invention;

[0050] Figure 2 is a simplified circuit diagram of a single-line direct supply traction network proposed by an embodiment of the present invention;

[0051] Figure 3 is a schematic diagram of the impedance-position-frequency characteristic modeling result provided by an embodiment of the present invention;

[0052] Figure 4 is a schematic diagram of the measuring point layout for traction power supply system impedance testing provided by an embodiment of the present invention;

[0053] Figure 5A graph showing the actual test results of the impedance-position-frequency characteristics provided by the embodiments of the present invention. (a) The impedance magnitude-frequency curves of two tests, (b) The R+jX curves of two tests;

[0054] Figure 6 A schematic diagram showing the method for connecting a de-icing device under different line conditions provided by the embodiments of the present invention;

[0055] Figure 7 A schematic structural diagram of a catenary rapid de-icing device based on resonant impedance provided by the embodiments of the present invention. Detailed implementation manners

[0056] The following details the implementation manners of the present invention. The examples of the implementation manners are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The implementation manners described below by referring to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be construed as a limitation of the present invention.

[0057] Those skilled in the art of the present technology can understand that, unless specifically stated otherwise, the singular forms "a", "an", "the" and "said" used herein may also include the plural forms. It should be further understood that the term "including" used in the specification of the present invention means the presence of the described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. It should be understood that when we say an element is "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, or there may also be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or coupling. The phrase "and / or" used herein includes any unit and all combinations of one or more related listed items.

[0058] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the field to which the present invention belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined as here.

[0059] For the convenience of understanding the embodiments of the present invention, the following will further explain with several specific embodiments as examples in conjunction with the accompanying drawings, and each embodiment does not constitute a limitation to the embodiments of the present invention.

[0060] In view of the ice melting requirements of the railway catenary, an embodiment of the present invention proposes a rapid ice melting method for the catenary based on resonance impedance. According to the principle that the resistance is extremely large at the natural resonance point of the catenary, harmonic current is injected to generate heat when flowing through the transmission wire, so as to achieve the purpose of melting and shedding the ice on the wire.

[0061] A circuit schematic diagram of a traction power supply system proposed in an embodiment of the present invention is as Figure 1 shown. The traction power supply system consists of a traction substation and a traction network line. The main equipment of the traction substation is a traction transformer, which converts the external power supply, that is, the three-phase alternating current of the power system, into the single-phase alternating current of the railway system (rated voltage is 27.5 kV or 2×27.5 kV). The traction network mainly consists of a feeder, a catenary, a return line, etc. The traction network transmits the electric energy of the traction substation to the locomotives running along the line.

[0062] An embodiment of the present invention simplifies the circuit diagram of the direct supply traction power supply system of a single line by using distributed parameters. Figure 2 This is a simplified circuit diagram of a single-line direct supply traction power supply system proposed in an embodiment of the present invention. Among them, the left side is the traction substation, the right side is the section post, and the PCC (Point of Common Coupling) point represents the train position. The impedance of the external power supply and the traction substation is equivalent to the lumped parameter Zus, and the transmission line is equivalent by using the π-type distributed parameter equivalent circuit. Among them, z is the series impedance per unit length of the equivalent single-phase line, and c is the shunt capacitance per unit length of the equivalent single-phase line. The distance between the train and the traction substation is x, and the total length of the traction network is D. The system impedance is the impedance of the railway power supply side seen from the PCC point, and the uniform transmission line theory is used for analysis.

[0063] The equivalent impedance between the PCC and the traction substation is:

[0064]

[0065] Among them and are the characteristic impedance and propagation constant of the equivalent single-phase circuit respectively;

[0066] The equivalent impedance between the PCC and the section post is:

[0067]

[0068] The frequency-domain impedance at the PCC is:

[0069]

[0070] When Z SWhen the modulus value is the largest, resonance occurs in the traction power supply system. At the resonance frequency of the resonance point in the traction power supply system, there is an extreme point at the end of the line on the amplitude-position curve, where a resistance characteristic is presented and the impedance amplitude is the largest.

[0071] The fact that the modulus value of Zs obtains the maximum value indicates that resonance occurs, as Figure 3 shown; this point is the resonance point (referring to frequency), and the corresponding frequency is the resonance frequency. The resonance frequency of the same line does not change with the test point, but the impedance amplitude of the resonance point will change with the test point, as Figure 3 shown; the resonance impedance amplitude of the extreme point at the end of the line is the largest. Using this characteristic, the ice melting device is installed at the end of the line and an alternating current with the resonance frequency is sent out to achieve ice melting.

[0072] The present invention explores the characteristics of the inherent resonance phenomenon of the traction power supply system through the method of modeling calculation. Figure 3 FIG. is a schematic diagram of the modeling result of the impedance-position-frequency characteristic provided by an embodiment of the present invention. From Figure 3 the modeling calculation results, it can be seen that at a certain fixed position of the traction network, there is an extreme point (also called the resonance point) on the amplitude-frequency curve in the middle frequency band. The impedance at this extreme point is called the resonance impedance. When the position of the traction network changes, the impedance modulus value also changes, but the frequency of the extreme point remains unchanged, and the closer the position of the traction network is to the end of the line, the larger the impedance modulus value. At the impedance extreme point, the phase changes from π / 2 to -π / 2. Therefore, the impedance characteristics presented by the traction power supply system at different frequencies are different. It presents an inductive characteristic below the extreme point frequency, a capacitive characteristic above the extreme point frequency, and a resistance characteristic at the extreme point, and the resistance value is as high as several thousand ohms. Therefore, at the resonance point of the traction network, there is an extreme point at the end of the line on the amplitude-position curve, where the impedance amplitude is the largest. Using the impedance amplitude here to carry out ice melting work will obtain a better ice melting effect.

[0073] The present invention has mastered the characteristics of the inherent resonance phenomenon of the traction power supply system through the method of on-site testing. An on-site test was carried out on the Beijing-Harbin High-Speed Railway (350 km / h) line in Liaoning Province, China, based on the frequency scanning method. The layout of the power supply measurement points is as Figure 4 shown. Figure 4Only the traction substation and section post are marked. The test section is the power supply section between two traction substations. There is a section post between two traction substations, which divides the traction network into different power supply sections. The main circuit inlet of the test system is connected to the catenary, and the loop is formed through the rail. Measuring point 1 is located at substation 1. The inlet of the test system is connected to the inner side of the isolating switch at the outlet of the catenary feeder of the traction network, and the return cable is connected to the neutral busbar of the traction transformer in the substation. Measuring point 2 is located at section post 1. The test inlet is connected to the inner side of the isolating switch at the outlet of the catenary feeder of the traction network, and the return cable is connected to the neutral busbar of the autotransformer in the substation.

[0074] What is obtained at measuring point 1 is the impedance of the traction power supply system at the beginning of the traction network (corresponding to Figure 5 the dotted line in Figure 5 ), and what is obtained at measuring point 2 is the impedance of the traction power supply system at the end of the traction network (corresponding to Figure 5 the solid line in Figure 5 ). Figure 5 Figure (a) is a graph of the actual test results of the impedance-position-frequency characteristics provided by an embodiment of the present invention. Among them, (a) is the impedance amplitude-frequency curve of two tests, and (b) is the R + jX curve of two tests. It can be seen from

[0075] The present invention is applicable to power supply methods such as direct power supply and AT (Auto-Transformer) power supply. For single-track and double-track traction network structures, Figure 6 Figure (a) is a schematic diagram of the access method of the ice melting device under different line conditions provided by an embodiment of the present invention. Figure 6 (a) is the direct power supply method with a return line for a single track, Figure 6 (b) is the AT power supply method for a single track. The access method of the ice melting device is similar: the catenary is connected to the ground wire of the substation, and the ice melting device is connected to the section post to form a short-circuit closed loop of catenary-ground. Figure 6 (c) is the direct power supply method with a return line for a double track, Figure 6(d) is the double-track AT power supply mode, and the access mode of the de-icing device is similar: the overhead contact lines of the up and down lines are short-circuited at the substation, and the de-icing device is connected to the section post to form a short-circuit closed loop of overhead contact line T1 - overhead contact line T2.

[0076] The structure of a catenary fast de-icing device based on resonance impedance provided by an embodiment of the present invention is as Figure 7 shown. As Figure 7 shown, the main body of the de-icing device is composed of a cascaded H-bridge harmonic generator, including: a step-down transformer TP, a cascaded converter HG, and a converter reactor L c . The primary side winding of the step-down transformer TP is connected in series with the traction network, and the main secondary side winding of the step-down transformer TP is connected to the cascaded converter HG through the converter reactor L c to provide the power supply voltage for the cascaded converter HG.

[0077] The rated voltage of the primary side winding of the step-down transformer TP is taken according to the rated voltage of the traction network; the secondary side winding of the step-down transformer TP is connected to the harmonic source, and the rated voltage value of the secondary side winding is matched with the harmonic source, about 200V - 2000V; the function of the step-down transformer is to step down the 27.5kV high voltage on the primary side to the rated voltage value range of the secondary side winding of the step-down transformer TP, which can reduce the number of cascaded converter units and reduce the complexity of the control system. The harmonic source is composed of a single-phase H-bridge converter and a converter reactor L c and is realized by a power electronic converter; the main function of the converter reactor L c is filtering and current control.

[0078] The de-icing device proposed by the present invention is applicable to various railway de-icing scenarios. The de-icing device injects medium and high frequency currents with controllable frequency and amplitude, and uses the resonance impedance of the catenary to generate Joule heat, thereby generating enough heat to achieve the purpose of catenary de-icing. Usually, a line position (the end of the line) with a larger resonance impedance amplitude is selected to inject current at the resonance point frequency to improve the de-icing efficiency. The device can inject pure and single-frequency harmonic currents into the traction network in the range of 100 - 5000Hz, detect the voltage and current waveforms on the traction network side, perform Fourier analysis to calculate the voltage and current at this test frequency, and use the inter-harmonic interpolation and frequency scanning algorithms to obtain the impedance-frequency characteristic information within the entire set test frequency range.

[0079] The operation steps of the above-mentioned catenary fast de-icing device based on resonance impedance include:

[0080] ① According to the line conditions, short-circuit the catenary line to form a short-circuit closed loop;

[0081] ② At a certain fixed line position, measure the line impedance-frequency characteristic curve by the frequency scanning method to find the resonance frequency point of the target line;

[0082] ③ At this resonant frequency, taking the line position as a variable, tests are carried out at different positions of the target line to obtain the impedance-frequency characteristic curves at different positions, as Figure 5 shown in (a). Find the position where the amplitude of the resonant impedance is the largest, and determine this position as the installation position of the de-icing device. Usually, when the de-icing device is connected to the sectional substation, the system can obtain a very large resistance value, inject harmonic current at the resonant frequency, and continuously generate more Joule heat with a smaller current at the very large resistance value to complete efficient de-icing.

[0083] To sum up, the present invention uses medium-high frequency AC input. According to the characteristics that the impedance at the line resonance point takes the maximum value and is purely resistive, the medium-high frequency AC current generated at low voltage flows through the transmission line to generate heat, so that the ice covering on the wire melts and falls off. This can still ensure a good de-icing effect on the basis of low design difficulty and low current input, and has the advantages of simple operation and low cost.

[0084] Traditional AC de-icing technology has a large demand for short-circuit current, a large device capacity, and a large reactive power component. The reactive power flow of the line needs to be considered, and the de-icing efficiency is relatively low. Traditional DC de-icing technology has a high cost, a low device utilization rate, poor economy, and uses DC resistance with a relatively small resistance value, so a large current needs to be injected. Therefore, DC de-icing devices usually have design requirements of low voltage and large current, high technical requirements, and great design difficulty. DC de-icing technology has weak compatibility with the existing AC catenary, and is prone to communication interference, line insulation, and aging problems.

[0085] However, the present invention utilizes the characteristics that the impedance at the inherent resonance point of the catenary takes the maximum value and is purely resistive, reduces the demand for short-circuit current, and can achieve the goal of de-icing with a small current, thus reducing the design cost of the de-icing device; since the resonant impedance presents a resistance characteristic, the reactive power flow of the line does not need to be considered, reducing the device capacity and power consumption; the AC injection method is adopted to avoid the communication interference, line insulation, and aging risks caused by DC injection; according to the analysis results, the device is installed at a specified position (such as the end of the catenary) for de-icing, and the amplitude of the resonant impedance is larger, and the de-icing effect is better; it has a wide range of applications and can be applied to scenarios of single-track railways (contact wire and ground) and double-track railways (contact wires form a loop), and the de-icing speed is relatively fast.

[0086] To visually compare the differences among the three schemes, the three schemes are compared with short-circuit current, capacity, economy, compatibility, applicability, and de-icing speed as performance indicators. Among them, in terms of capacity, taking the index value of the resonant impedance as unit 1, quantitative analysis is carried out, and qualitative analysis is carried out on economy, compatibility, applicability, etc.

[0087] Table 1 Comparison of performance indicators of three de-icing schemes

[0088]

[0089] Those of ordinary skill in the art can understand that the accompanying drawings are only schematic diagrams of an embodiment, and the modules or processes in the accompanying drawings are not necessarily essential for implementing the present invention.

[0090] From the description of the above embodiments, it can be clearly understood by those skilled in the art that the present invention can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present invention, in essence or the part 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 storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of the present invention.

[0091] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiments, since they are basically similar to the method embodiments, the description is relatively simple. For the relevant parts, reference can be made to the partial description of the method embodiments. The device and system embodiments described above are only illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative work.

[0092] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A rapid ice melting method for catenary based on resonant impedance, characterized in that, Including: Measuring the resonance frequency of the target line on the catenary to be de-iced, and finding the measuring point with a larger impedance amplitude based on the resonance frequency with the line position as a variable; Installing the de-icing device at the position of the measuring point, injecting current into the target line by the de-icing device, generating Joule heat by using the resistance value at the position of the measuring point, and melting and shedding the ice on the target line; The measuring the resonance frequency of the target line on the catenary to be de-iced, and finding the measuring point with a larger impedance amplitude based on the resonance frequency with the line position as a variable includes: The traction power supply system consists of a traction substation and traction network lines. The traction network consists of feeder lines, catenaries, and return lines. The traction network delivers the electrical energy of the traction substation to the locomotives running along the line. Let the common connection point PCC represent the train position. The impedance of the external power supply and the traction substation is equivalent to a lumped parameter Zus. The transmission line is equivalent by using a π-type distributed parameter equivalent circuit. z is the series impedance per unit length of the equivalent single-phase line, c is the shunt capacitance per unit length of the equivalent single-phase line, the distance between the train and the traction substation is x, and the total length of the traction network is D; The equivalent impedance between the PCC and the traction substation is: wherein and are the characteristic impedance and propagation constant of the equivalent single-phase circuit, respectively; The equivalent impedance between the PCC and the section post is: The frequency-domain impedance at the PCC is: When Z S When the modulus value is the largest, resonance occurs in the traction power supply system. At the resonance frequency of the resonance point of the traction power supply system, there is an extreme point at the end of the line on the amplitude-position curve, presenting a resistance characteristic at this extreme point and the impedance amplitude is the largest; The installing the de-icing device at the position of the measuring point includes: At the resonance frequency of the traction power supply system, with the line position as a variable, testing at different positions of the target line to obtain the impedance-frequency characteristic curves at different positions, finding the position with the largest resonance impedance amplitude, and determining this position as the installation position of the de-icing device; The de-icing device injecting current into the target line, generating Joule heat by using the resistance value at the position of the measuring point, and melting and shedding the ice on the target line includes: The ice melting device is composed of a cascaded H-bridge harmonic generator, including: a step-down transformer TP, a cascaded converter HG, and a converter reactor L c , the primary side winding of the step-down transformer TP is connected in series with the traction network, and the secondary side main winding of the step-down transformer TP passes through the converter reactor L c to connect the cascaded converter HG and provide the power supply voltage for the cascaded converter HG; The rated voltage of the primary side winding of the step-down transformer TP is taken according to the rated voltage of the traction network. The secondary side winding of the step-down transformer TP is connected to the harmonic source, and the rated voltage value of the secondary side winding is matched with the harmonic source. The step-down transformer TP steps down the 27.5 kV high voltage on the primary side to the rated voltage value range of the secondary side winding of the step-down transformer TP. The harmonic source consists of a single-phase H-bridge converter and a converter reactor L c and is realized by a power electronic converter; the converter reactor L c is used for filtering and current control; The de-icing device injects current with controllable frequency and amplitude into the target line, generates Joule heat by using the resonance impedance of the catenary, and conducts catenary de-icing.

2. The method according to claim 1, characterized in that, The installing the de-icing device at the position of the measuring point includes: When the target line on the catenary adopts the direct supply mode of a single line with a return line or the single-line auto-transformer AT power supply mode, the access mode of the de-icing device includes: the contact wire in the target line is connected to the substation ground wire, and the de-icing device is connected to the section post to form a short-circuit closed loop of contact wire - ground; When the target line on the catenary adopts the direct supply mode of a double line with a return line or the double-line AT, the access mode of the de-icing device includes: the up and down contact wires at the substation are short-circuited, and the de-icing device is connected to the section post to form a short-circuit closed loop of contact wire T1 - contact wire T2.

3. The method according to claim 1, characterized in that The method further includes: the de-icing device injects a single-frequency harmonic current into the traction network in the range of 100 - 5000 Hz, detects the voltage and current waveforms on the target line on the traction network side, conducts Fourier analysis to calculate the voltage and current at the test frequency, and uses the inter-harmonic interpolation and frequency scanning algorithm to obtain the impedance-frequency characteristic information within the entire set test frequency range.

Images