Mobile ice-melting filter system and control method thereof

Abstract

The application provides a mobile ice-melting filter system and a control method thereof, and relates to the technical field of power transmission and distribution. The mobile ice-melting filter system comprises: an ice-melting power switch cabinet for connecting a three-phase ice-melting power source of a power grid; an ice-melting valve group device for converting alternating current into direct current and delivering ice-melting direct current to an ice-covered power transmission line; an ice-melting filter device for absorbing 6n±1 characteristic harmonics generated by the operation of the ice-melting valve group device and preventing the harmonics from flowing back to the three-phase ice-melting power source of the power grid; an ice-melting valve group vehicle and an ice-melting filter vehicle for carrying the power switch cabinet, the ice-melting valve group device and the ice-melting filter device. The application adopts a double-vehicle split arrangement structure, the ice-melting valve group device and the ice-melting filter device are loaded in separate vehicles, the single-vehicle space and load constraints are broken, the ice-melting power and the filter capacity can be individually selected and configured as needed, and the problem of insufficient filter capacity and excessive harmonics of the same-vehicle integrated filter is solved from the hardware level.

Description

Technical Field

[0001] This application relates to the field of power transmission and distribution technology, and more specifically, to a mobile de-icing filter system and its control method. Background Technology

[0002] Ice accumulation on power transmission lines during winter can easily lead to power accidents such as line breaks and tower collapses. DC de-icing, with its advantages of high output power and suitability for long-distance transmission lines, has become the mainstream emergency de-icing method. Most existing DC de-icing equipment uses a thyristor phase-controlled rectifier architecture, which generates 6n±1 characteristic harmonics during rectification. These harmonics entering the power grid can easily cause numerous power quality problems, including bus voltage distortion, equipment insulation aging, system resonance, and relay protection malfunctions.

[0003] Existing harmonic mitigation solutions mainly fall into two categories: The first involves centrally deploying filter equipment on the substation busbar. However, the filter devices are far from the de-icing rectifier equipment, resulting in long connecting cables, high harmonic circuit impedance, poor harmonic filtering effect, and easy parallel resonance with the grid impedance during load fluctuations. The second approach integrates the rectifier equipment and filter equipment on the same vehicle chassis. However, due to vehicle load and size regulations, the installation space per vehicle is limited, the number of filter branches is insufficient, and the harmonic mitigation effect does not meet national standards, thus failing to meet the harmonic control requirements under high-power de-icing conditions.

[0004] Therefore, there is an urgent need for a mobile de-icing filter solution that can bypass vehicle space limitations and efficiently filter out harmonics nearby. Summary of the Invention

[0005] The purpose of this application is to overcome the shortcomings of existing vehicle-mounted de-icing equipment, such as limited single-vehicle layout, long filtering distance, and poor harmonic suppression effect. It provides a mobile de-icing filter system and its control method, which achieves decoupling of the rectifier unit and filter unit by separating the two vehicles, shortening the harmonic flow path. With the help of a hierarchical switching control strategy, it can efficiently filter out the characteristic harmonics generated by rectification while meeting road traffic regulations, and ensure that the power quality of the power grid meets national standards.

[0006] According to a first aspect of this application, at least one embodiment of this application provides a mobile de-icing filtering system, comprising: a de-icing power switch cabinet for connecting to a three-phase de-icing power supply in the power grid and branching out at least two independent power supply circuits; a de-icing valve group device, the AC side of which is connected to the output terminal of one of the power supply circuits, for rectifying and converting AC power into DC power to supply de-icing DC power to the transmission line to be covered with ice; a de-icing filter device, the AC side of which is connected in phase sequence with the AC side of the de-icing valve group device and connected to the output terminal of the other power supply circuit, for absorbing the 6n±1th characteristic harmonic generated by the operation of the de-icing valve group device and preventing harmonic backflow to the three-phase de-icing power supply in the power grid, wherein n is an integer greater than or equal to 1; a de-icing valve group vehicle for carrying the de-icing power switch cabinet and the de-icing valve group device; and a de-icing filter vehicle for carrying the de-icing filter device, wherein the de-icing filter vehicle and the de-icing valve group vehicle are arranged in a rear-facing configuration to shorten the wiring length between the de-icing valve group device and the de-icing filter device.

[0007] For example, in some embodiments of this application, the de-icing power switch cabinet includes a circuit breaker, and the three-phase de-icing power supply of the power grid is connected to the circuit breaker and divided into at least two independent power supply circuits.

[0008] For example, in some embodiments of this application, the ice-melting valve assembly adopts a three-phase fully controlled bridge six-pulse rectifier topology, and the firing angle adjustment range of the thyristors in the three-phase fully controlled bridge six-pulse rectifier topology is 5°~150°.

[0009] For example, in some embodiments of this application, the de-icing valve assembly includes: an anode reactor connected to the AC side of the de-icing valve assembly; a DC surge arrester, a digital voltage divider, a Hall current sensor, and a single-phase electric disconnect switch connected to the DC side of the de-icing valve assembly.

[0010] For example, in some embodiments of this application, the ice-melting filter device includes a single-tuned filter branch, which is used to adapt to the frequency of the 6n+1th or 6n-1st characteristic harmonic.

[0011] For example, in some embodiments of this application, the quality factor of the single-tuned filter branch is 20 to 40.

[0012] For example, in some embodiments of this application, the ice-melting filter device includes four single-tuned filter branches, wherein the four single-tuned filter branches are respectively: a 5th harmonic tuning branch, a 7th harmonic tuning branch, an 11th harmonic tuning branch, and a 13th harmonic tuning branch.

[0013] For example, in some embodiments of this application, each of the single-tuned filter branches includes: a current transformer, a filter capacitor, and a filter reactor connected in series to form a series branch; a discharge coil connected in parallel with the filter capacitor for power-off discharge of residual voltage; and a surge arrester connected in parallel with the series branch.

[0014] According to a second aspect of this application, at least one embodiment of this application provides a mobile de-icing filter control method, which is executed by a mobile de-icing filter system as described in any one of the first aspects. The mobile de-icing filter control method includes: adjusting the firing angle of the thyristor of the de-icing valve group device according to a preset current increase rate to increase the de-icing DC current; acquiring the value of the de-icing DC current in real time, and combining it with the harmonic spectrum characteristics corresponding to the firing angle of the thyristor, and engaging a single-tuned filter branch of the de-icing filter device with a matching frequency; maintaining the de-icing DC current within a set target de-icing DC current range, and controlling the de-icing filter device to continuously absorb the characteristic harmonics generated by the de-icing valve group device in real time; when the de-icing operation is completed, adjusting the firing angle of the thyristor according to a preset current decrease rate to disconnect the engaged single-tuned filter branch; and locking the de-icing valve group device when the de-icing DC current drops to zero.

[0015] For example, in some embodiments of this application, the ice-melting filter device includes a single-tuned filter branch adapted to low-frequency dominant characteristic harmonics, a single-tuned filter branch adapted to mid-frequency dominant characteristic harmonics, and / or a single-tuned filter branch adapted to high-frequency dominant characteristic harmonics. The step of real-time acquisition of the ice-melting DC current value, combined with the harmonic spectrum characteristics corresponding to the thyristor's firing angle, and engaging the single-tuned filter branch of the ice-melting filter device with a matching frequency includes: when the ice-melting DC current reaches a first engagement threshold within the set target ice-melting DC current range. When the value is reached, the single-tuned filter branch adapted to the low-frequency dominant characteristic harmonic is activated; when the ice-melting DC current reaches the second activation threshold of the set target ice-melting DC current range, the single-tuned filter branch adapted to the mid-frequency dominant characteristic harmonic is activated; when the ice-melting DC current reaches the third activation threshold of the set target ice-melting DC current range, the single-tuned filter branch adapted to the high-frequency dominant characteristic harmonic is activated, wherein the first activation threshold, the second activation threshold, and the third activation threshold increase progressively.

[0016] For example, in some embodiments of this application, the step of real-time acquisition of the value of the de-icing DC current range and, in combination with the harmonic spectrum characteristics corresponding to the firing angle of the thyristor, gradually activating the single-tuned filter branch of the de-icing filter device with matching frequency includes: when activating the single-tuned filter branch, selecting the power frequency cycle with the smallest potential difference between the two ends of the single-tuned filter branch to perform closing, so as to achieve zero-voltage switching and suppress the generation of closing inrush current.

[0017] For example, in some embodiments of this application, the step of adjusting the firing angle of the thyristor according to a preset current reduction rate and cutting off the engaged single-tuned filter branch after the ice-melting operation is completed includes: cutting off the single-tuned filter branch adapted to the high-frequency dominant characteristic harmonic when the ice-melting DC current drops to a first cut-off threshold of the set target ice-melting DC current range; cutting off the single-tuned filter branch adapted to the mid-frequency dominant characteristic harmonic when the ice-melting DC current drops to a second cut-off threshold of the set target ice-melting DC current range; and cutting off the single-tuned filter branch adapted to the low-frequency dominant characteristic harmonic when the ice-melting DC current drops to a third cut-off threshold of the set target ice-melting DC current range, wherein the values ​​of the first cut-off threshold, the second cut-off threshold, and the third cut-off threshold decrease progressively.

[0018] Through the above embodiments, the mobile ice-melting filter system and its control method provided in this application have at least one of the following beneficial effects: The system adopts a dual-vehicle split layout structure, with the ice-melting valve assembly and the ice-melting filter assembly installed separately in different vehicles. This breaks the constraints of single-vehicle space and load capacity, and the ice-melting power and filter capacity can be selected and configured separately as needed. This solves the problems of insufficient integrated filter capacity and excessive harmonics in the same vehicle from a hardware perspective.

[0019] The filter and rectifier are connected in parallel on the AC side, and the flexible connection line is shortened by the rear-end alignment. The harmonic flow loop impedance is small, characteristic harmonics are absorbed nearby, the harmonic suppression efficiency is high, and the harmonic distortion rate of the bus is effectively controlled.

[0020] The filter branch is switched on and off in stages according to the de-icing DC current. The current is increased and the current is decreased in stages, avoiding the drawbacks of no reactive power compensation under light load and insufficient filter capacity under heavy load. It prevents system resonance and is suitable for the working conditions of large-range fluctuation of de-icing DC current.

[0021] The filter branch adopts zero-differential periodic closing and switching to eliminate inrush current when capacitors are connected and improve the stability of equipment operation; the single-tuned branch parameter limits the Q value to 20~40, taking into account both the filtering accuracy and the detuning problem caused by outdoor temperature and component deviation.

[0022] The vehicle can be transported by road and only requires connection to flexible cables on site for deployment, making it highly efficient for emergency de-icing.

[0023] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0024] The above and other objects, features, and advantages of this application will become more apparent from the detailed description of exemplary embodiments with reference to the accompanying drawings. The drawings described below are merely some embodiments of this application and are not intended to limit the scope of this application.

[0025] Figure 1 This is a schematic diagram of the overall layout structure of the mobile ice-melting filter system according to an embodiment of this application; Figure 2 This is a schematic diagram of the electrical topology of the mobile ice-melting filter system according to an embodiment of this application; Figure 3 This is a schematic diagram of the structure of the de-icing power switch cabinet according to an embodiment of this application; Figure 4 This is a schematic diagram of the structure of the ice-melting valve assembly device according to an embodiment of this application; Figure 5 This is a schematic diagram of the rectifier unit structure according to an embodiment of this application; Figure 6 This is a schematic diagram of the ice-melting filter device according to an embodiment of this application; Figure 7 This is a schematic diagram of a single-tuned filter branch structure according to an embodiment of this application; Figure 8 This is a schematic flowchart of the mobile ice-melting filtering control method according to an embodiment of this application. Detailed Implementation

[0026] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0027] The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of these specific details, or other methods, components, materials, devices, etc. In these cases, well-known structures, methods, devices, implementations, materials, or operations will not be shown or described in detail.

[0028] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily need to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0029] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0030] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily essential for implementing this application, and therefore cannot be used to limit the scope of protection of this application.

[0031] Figure 1 This is a schematic diagram of the overall layout structure of the mobile ice-melting filter system according to an embodiment of this application.

[0032] like Figure 1 As shown, the mobile de-icing and filtering system includes: a de-icing power switch cabinet 1, a de-icing valve assembly 2, a de-icing filter 3, a de-icing valve assembly vehicle 4, and a de-icing filter vehicle 5.

[0033] Among them, the ice-melting power switch cabinet 1 is used to connect to the three-phase ice-melting power supply of the power grid and to branch out at least two independent power supply circuits to provide working power to the downstream ice-melting valve group device 2 and the ice-melting filter device 3 respectively.

[0034] The AC side of the de-icing valve assembly 2 is connected to the output terminal of one of the power supply circuits of the de-icing power switch cabinet 1. It is used to rectify and convert the incoming AC power into DC power, and continuously supply de-icing DC power to the transmission line to be covered with ice on site. The line ice is melted by relying on DC heating.

[0035] The AC side of the de-icing filter device 3 is connected to the AC side of the de-icing valve assembly device 2 via a flexible conductor in phase sequence. It is also connected to the output terminal of another power supply circuit in the de-icing power switch cabinet 1. This is used to absorb the 6n±1th characteristic harmonic generated by the operation of the de-icing valve assembly device 2 nearby, preventing the harmonics from flowing back to the three-phase de-icing power supply of the grid. Here, n is an integer greater than or equal to 1.

[0036] The ice-melting valve assembly vehicle 4 is used to carry the ice-melting power switch cabinet 1 and the ice-melting valve assembly device 2, realizing the vehicle-mounted integrated fixed arrangement of the entire rectifier power supply unit and meeting the requirements for road transportation.

[0037] The ice-melting filter cart 5 is used to carry the ice-melting filter device. The ice-melting filter cart 5 and the ice-melting valve assembly cart 4 are arranged in a rear-facing configuration to shorten the wiring length of the flexible conductor between the ice-melting valve assembly device 2 and the ice-melting filter device 3, reduce the harmonic circuit impedance, and improve the harmonic absorption efficiency.

[0038] According to some embodiments, the flexible conductors of the two vehicles are made of ERF flexible cables that are heat-resistant and bend-resistant, suitable for temporary field installation conditions.

[0039] According to some embodiments, the vehicle-mounted ice-melting equipment of this application has the advantage of vehicle-machine integration. Both the ice-melting filter vehicle and the ice-melting valve assembly meet the requirements of the national vehicle transportation announcement and can be registered as a whole. After the equipment is integrated and fixed, it does not need to be disassembled during the annual vehicle inspection. The whole vehicle has a high degree of integration, convenient transportation, and simple operation and maintenance.

[0040] According to some embodiments, this application adopts a detachable tractor head and body separation structure design, which greatly improves the adaptability of on-board equipment and the integration capability of large-capacity equipment. Specifically, the ice-melting filter vehicle includes a tractor head, a tractor platform, and an ice-melting filter device, wherein the tractor head and the tractor platform are detachably rigidly connected by a traction pin; the ice-melting valve assembly vehicle includes a tractor head, a tractor platform, an ice-melting valve assembly device, and an ice-melting power switch cabinet, which also adopts a detachable tractor head and body structure. This detachable architecture breaks through the limitations of cabinet size, load capacity, and installation space of traditional integrated van vehicles. It is not subject to the constraints of standard van volume and can directly carry large-size, large-capacity power cabinet equipment, which can meet the integrated installation requirements of multi-branch filter devices, high-power rectifier valve groups, and supporting switch cabinets, effectively solving the drawbacks of traditional integrated ice-melting vehicles such as small capacity, compact equipment layout, and difficulty in expansion. At the same time, the detachable design of the tractor head and platform facilitates the individual transportation, inspection, and maintenance of equipment, and provides greater flexibility in mobile deployment, further adapting to complex ice-melting operation scenarios in the field.

[0041] Figure 2 This is a schematic diagram of the electrical topology of a mobile ice-melting filter system according to an embodiment of this application.

[0042] like Figure 2 As shown, the electrical topology of the mobile de-icing and filtering system of this application includes: a three-phase de-icing power supply from the power grid, a de-icing power supply switch cabinet 1, a de-icing valve group device 2, a de-icing and filtering device 3, and a transmission line to be de-iced.

[0043] The three-phase de-icing power supply from the power grid serves as the system's main input power supply and is connected to the incoming terminal of the de-icing power supply switch cabinet 1. The de-icing power supply switch cabinet 1 internally utilizes SF6 circuit breakers to achieve power convergence and branching, distributing the single incoming power supply into at least two independent and non-interfering power supply circuits. These circuits independently power the downstream de-icing valve assembly 2 and the de-icing filter device 3, achieving a topology where the rectifier unit and filter unit have separate power supplies.

[0044] The first output of the power supply circuit of the de-icing power switch cabinet 1 is electrically connected to the AC side of the de-icing valve assembly 2, providing operating power to the de-icing rectifier unit. The de-icing valve assembly 2 rectifies the industrial frequency AC power into controllable DC power through an internal three-phase fully controlled bridge six-pulse rectifier topology. The DC output is directly connected to the transmission line to be de-iced. The DC side of the de-icing valve assembly 2 is connected to the transmission line to be de-iced through a single-phase electric disconnect switch. The opposite ends of the line are shorted using special shorting fittings to form a complete and reliable DC de-icing circuit, realizing the de-icing of the transmission line. The second output of the power supply circuit of the de-icing power switch cabinet 1 is electrically connected to the AC side of the de-icing filter device 3, providing independent operating power to the filter unit. At the same time, the AC side of the de-icing filter device 3 is connected to the AC side node of the de-icing valve assembly 2 in the same phase sequence through flexible conductors, forming a parallel topology on the AC side.

[0045] Based on this electrical topology, the 6n±1th characteristic harmonic generated during the rectification operation of the de-icing valve group 2 can be directly absorbed and filtered out by the de-icing filter device 3 on the AC side, significantly shortening the harmonic flow path, reducing the loop impedance, suppressing harmonic diffusion from the source, effectively preventing harmonic backflow into the three-phase de-icing power supply of the front-end grid, and ensuring the power quality on the grid side. Here, n is an integer greater than or equal to 1.

[0046] This topology adopts a "dual-circuit independent power supply + AC side parallel filtering" architecture, which is different from the traditional remote centralized filtering topology. It can effectively avoid the problems of insufficient harmonic attenuation, large circuit impedance and poor filtering effect of long lines. At the same time, with the dual-vehicle rear-facing arrangement structure, the flexible conductor wiring distance between the two vehicles is minimized, further optimizing the system electrical topology parameters and improving the overall de-icing efficiency and harmonic control accuracy.

[0047] In the aforementioned system design, by separating the ice-melting rectification and harmonic filtering onto two independent vehicles that can be registered as a single unit, the limitations of single-vehicle space and axle load are overcome. The number and parameters of the filtering branches can be flexibly configured according to actual needs, without being constrained by the size of the rectifier. More importantly, the ice-melting filter is connected in parallel with the ice-melting valve assembly on the AC side, limiting the flow path of harmonic current to the short connection line between the two vehicles. The circuit impedance is extremely low, and harmonic voltage distortion is effectively suppressed at the filter connection point, thus ensuring the power quality of the bus voltage. This dual-vehicle decoupling and AC-side local filtering architecture overcomes the fundamental contradictions of existing technologies, such as "poor centralized filtering effect and limited integrated capacity within the same vehicle."

[0048] Figure 3 This is a schematic diagram of the de-icing power switch cabinet according to an embodiment of this application.

[0049] like Figure 3 As shown, the de-icing power switch cabinet 1 is equipped with a circuit breaker 11. After the three-phase de-icing power from the grid passes through the circuit breaker 11, it is divided into two independent power supply circuits. The two outgoing lines are respectively connected to the AC input terminals of the de-icing valve group device 2 and the de-icing filter device 3.

[0050] Among them, the circuit breaker 11 realizes the disconnection, short circuit and overload protection of the incoming power supply, and quickly cuts off the input power supply in the event of equipment failure, so as to ensure the safe operation of the vehicle electrical equipment.

[0051] According to some embodiments, circuit breaker 11 includes: SF6 circuit breaker and other circuit breakers.

[0052] According to some embodiments, the de-icing power switch cabinet 1 further includes: an incoming voltage transformer 12, a fuse 13, a harmonic suppression resistor 14, a live indicator 15, a surge arrester 16, a main incoming current transformer 17, a branch current transformer 18, and an outdoor cabinet 19.

[0053] The 35kV incoming line, after passing through circuit breaker 11 and main incoming current transformer 17, splits into two independent branch power supply circuits: one connected to the AC side of the de-icing valve assembly 2 via circuit breaker 11, and the other connected to the AC side of the de-icing filter device 3 via circuit breaker 11. Both branch circuits are equipped with branch current transformers 18, enabling independent power metering and relay protection functions for each circuit. A harmonic suppression resistor 14 is connected in parallel to the secondary side of the incoming voltage transformer 12, effectively suppressing system ferroresonance, preventing overvoltage faults caused by ferroresonance, and ensuring stable operation of the electrical equipment inside the switchgear.

[0054] Figure 4 This is a schematic diagram of the structure of the ice-melting valve assembly device according to an embodiment of this application.

[0055] like Figure 4As shown, the de-icing valve assembly 2 includes: an anode reactor 21, a de-icing valve assembly 22, a DC surge arrester 23, a digital voltage divider 24, a Hall current sensor 25, a single-phase electric disconnect switch 26, a load-bearing housing 27, a cooling assembly 28, and a control assembly 29.

[0056] Among them, the anode reactor 21 is connected in series on the AC side of the ice-melting valve group device 2 to limit the current rise rate di / dt during thyristor commutation, providing reliable protection for the thyristor, and effectively suppressing the propagation of commutation gap harmonics to the grid side, thereby reducing grid harmonic pollution.

[0057] The ice-melting valve assembly 22 includes multi-stage rectifier units 20 connected in series.

[0058] Figure 5 This is a schematic diagram of the rectifier unit structure according to an embodiment of this application.

[0059] like Figure 5 As shown, each rectifier unit 20 includes: a thyristor 201, a heat sink 202, a control unit 203, a voltage equalizing capacitor 204, and a voltage equalizing resistor 205.

[0060] The control unit 203 can autonomously draw power from the voltage divider circuit of the equalizing resistor 205, receive the trigger pulse sent by the control component 29 through the optical fiber, and then precisely control the on / off state of the thyristor 201 through the built-in gate drive circuit to ensure the stable operation of the rectifier unit 20.

[0061] In this embodiment, the de-icing valve assembly 22 adopts a three-phase fully controlled bridge six-pulse rectifier topology, with a rated DC output voltage of ±6.25kV and a rated DC current of 1000A. The thyristor firing angle corresponding to the control unit 203 can be continuously adjusted within the range of 5° to 150°, enabling smooth stepless adjustment of the DC output voltage from near the rated value to zero, adapting to the de-icing DC current requirements of different operating conditions. Simultaneously, the trigger pulse adopts a wide pulse output mode with a pulse width ≥ 60° electrical angle, effectively ensuring the reliability and stability of the commutation operation of the thyristor 201.

[0062] The DC side of the ice-melting valve assembly 2 is equipped with a DC surge arrester 23, a digital voltage divider 24, a Hall current sensor 25, and a single-phase electric disconnect switch 26. These components work together to achieve DC side safety protection and parameter acquisition.

[0063] Specifically, the DC surge arrester 23 is connected in parallel to the DC output terminal of the de-icing valve assembly 2, effectively suppressing induced lightning overvoltages and operational overvoltages generated during line operation, protecting downstream electrical equipment, and preventing overvoltage damage. The digital voltage divider 24 has an accuracy class of 0.5, and the Hall current sensor 25 has an accuracy class of 0.2, enabling high-precision real-time acquisition of output DC voltage and current, providing accurate sampling data for the system's closed-loop feedback control. The single-phase electric disconnect switch 26 is used to achieve electrical isolation between the DC side and the line to be de-iced, ensuring equipment maintenance and operational safety.

[0064] Figure 6 This is a schematic diagram of the ice-melting filter device according to an embodiment of this application.

[0065] like Figure 6 As shown, the ice-melting filter device 3 includes: a single-tuned filter branch 31, a forced air cooling assembly 32, and a support housing 33. The single-tuned filter branch 31 is used to adapt to the frequencies of the 6n+1th or 6n-1st characteristic harmonics.

[0066] According to some embodiments, the de-icing filter device 3 of this application is preferably configured with four single-tuned filter branches 31. The four single-tuned filter branches 31 are: a branch for tuning the 5th harmonic, a branch for tuning the 7th harmonic, a branch for tuning the 11th harmonic, and a branch for tuning the 13th harmonic, respectively, corresponding to the tuning of the 5th, 7th, 11th, and 13th characteristic harmonics of the power grid, with corresponding harmonic frequencies of 250Hz, 350Hz, 550Hz, and 650Hz. By using four-level branches to cover the four most important characteristic harmonics of the thyristor rectifier, the total harmonic distortion rate of the bus voltage can be controlled below 4% under rated de-icing conditions.

[0067] The ice-melting valve assembly 2 adopts a three-phase fully controlled bridge six-pulse rectifier topology, which mainly generates 6n±1 harmonics during operation. Among them, the 5th and 7th harmonics have the largest current amplitudes, followed by the 11th and 13th harmonics, which are the main sources of harmonic interference in the system. By configuring four single-tuned filter branches 31 corresponding to the frequencies, the main harmonic components under rectification conditions can be fully covered, and the system harmonic distortion rate can be controlled within the national standard allowable range. For the 17th and higher harmonics, since their current amplitudes are extremely small, there is no need to configure separate filter branches. The low impedance characteristics of the 5th single-tuned filter branch can be used to achieve auxiliary attenuation, which simplifies the equipment structure, controls the size and weight of the equipment, and meets the requirements of harmonic control for the entire network.

[0068] Figure 7 This is a schematic diagram of a single-tuned filter branch structure according to an embodiment of this application.

[0069] like Figure 7As shown, a single-tuned filter branch 31 includes: a current transformer 311, a surge arrester 312, a filter capacitor 313, a discharge coil 314, a filter reactor 315, and a support frame 316.

[0070] The current transformer 311, filter capacitor 313, and filter reactor 315 are connected in series to form the main series structure of the branch. The surge arrester 312 is connected in parallel across the entire single-tuned filter branch 31 and reliably grounded. It is used to absorb and suppress lightning overvoltages and switching overvoltages during line operation, achieving overvoltage protection for the branch equipment. The discharge coil 314 is connected in parallel across the filter capacitor 313, which can quickly release the residual voltage inside the filter capacitor 313 after power failure, completely eliminating the risk of residual voltage and ensuring the safety of equipment maintenance operations.

[0071] The quality factor Q of each single-tuned filter branch 31 in this application is controlled in the range of 20 to 40, with Q=30 being preferred.

[0072] The following section uses the 5th harmonic branch as an example to explain in detail the specific design parameters, tuning performance, and Q-value selection logic of the filter branch in this application.

[0073] The specific design parameters of the 5th harmonic branch are as follows: the filter capacitor 313 has a rated voltage of 11kV, a rated capacity of 7.8Mvar, and an equivalent capacitance of approximately 68.4μF in a three-phase star connection; the filter reactor 315 has an inductance of approximately 6.05mH, a rated current of 238.2A, and a quality factor Q=30 under 250Hz operating conditions.

[0074] To ensure the branch accurately aligns with the target harmonic frequency, the fifth filter branch was tuned and verified. The formula for calculating the resonant frequency is as follows: Substituting the parameters, we can calculate: With a frequency tuning deviation of ≤0.1%, it has high tuning accuracy and can stably align with the 5th 250Hz characteristic harmonic.

[0075] Simultaneously based on the quality factor formula The equivalent series resistance R of the filter reactor 315 can be calculated to be approximately 3.16Ω, which meets the requirements of low-loss and high-selectivity filtering design.

[0076] The quality factor Q characterizes the frequency selectivity of the single-tuned filter branch. In this application, Q=30 is preferred, at which point the half-power bandwidth of the branch is Δf=f / Q≈8.3Hz, allowing the branch to primarily absorb harmonic currents within the range of 250Hz±4Hz. This bandwidth can completely cover the target harmonic frequency band under the normal ±0.5Hz frequency fluctuation of the power grid, ensuring the filtering effectiveness under harsh power grid conditions. At the same time, the bandwidth is moderate, preventing the shunting of adjacent harmonic frequencies due to excessive bandwidth, effectively maintaining the decoupling between filter branches and avoiding mutual coupling interference of harmonic currents between branches.

[0077] If the Q value is selected too low (less than 20), the branch bandwidth will be too wide, which can easily cause the working ranges of adjacent 5th and 7th order filter branches to overlap, leading to harmonic interference and significantly reducing the filtering accuracy. If the Q value is selected too high (greater than 40), the branch frequency selection characteristics will be too sharp, making it extremely sensitive to temperature changes and reactor parameter drift caused by device aging in outdoor vehicle environments. This can easily lead to detuning problems and reduce the long-term operational reliability of the equipment.

[0078] Therefore, this application limits the quality factor of the single-tuned filter branch to the range of 20 to 40, which can simultaneously take into account the filter selectivity, power grid condition adaptability and vehicle-mounted outdoor operation stability.

[0079] The 7th, 11th, and 13th single-tuned filter branches 31 all adopt the same tuning design logic as the 5th branch. They are precisely tuned by matching the corresponding capacitor and inductor parameters according to their respective target harmonic frequencies. The specific parameter iterative calculation process is the same, so it will not be repeated here.

[0080] All four single-tuned filter branches 31 are connected in parallel to the same AC bus of the system. Each branch is installed based on the support frame 316, and the spacing between the branches is not less than 300mm. The reasonable structural spacing design effectively reduces the electromagnetic coupling interference between the branches, and further improves the operational stability and filtering accuracy of the entire ice melting filter device.

[0081] This application also provides a mobile de-icing filter control method, which is executed by the mobile de-icing filter system described above.

[0082] Figure 8 This is a schematic flowchart of the mobile ice-melting filtering control method according to an embodiment of this application.

[0083] like Figure 8 As shown, the mobile ice-melting filter control method of this application includes steps S801 to S805.

[0084] Before operation, complete the overall vehicle setup and safety grounding. Park the ice-melting filter truck and ice-melting valve assembly truck tail-to-tail on the hardened, level ground around the power transmission line to be melted, strictly controlling the relative distance between the two vehicles to 2m-3m. This distance meets the operational requirements for convenient splicing of flexible cables on site, while avoiding excessively long wiring and increased loop impedance due to excessive spacing, ensuring the effectiveness of subsequent harmonic mitigation. After the vehicles are parked and braked, grounding operations are performed on both on-board devices. Both vehicles use dedicated yellow-green bicolor grounding wires with a cross-sectional area of ​​not less than 50mm² to reliably connect to the on-site grounding grid. After the operation, the measured grounding resistance of the entire vehicle is ≤1Ω, meeting the safety operation specifications for high-voltage electrical equipment, effectively avoiding safety risks caused by equipment leakage, static electricity accumulation, and induced overvoltage, and providing a safe foundation for subsequent electrical wiring and live-line work.

[0085] After completing the site layout and grounding work, standardized electrical wiring work was carried out. The 10kV three-phase de-icing power supply was reliably connected to the incoming terminal of the de-icing power supply switchgear via a dedicated outdoor cable terminal, ensuring a stable power supply from the grid. The de-icing power supply switchgear is equipped with dual independent outgoing circuits. The two outgoing lines use ERF flexible cables that are resistant to bending and outdoor environments, connecting to the AC input side of the de-icing valve assembly and the input terminal of the de-icing filter device, respectively, achieving an electrical architecture where the rectifier and filter units have independent power supply. Simultaneously, the DC output side of the de-icing valve assembly is reliably connected to the de-icing transmission line. At the substation at the far end of the line, all phases are reliably shorted using dedicated three-phase shorting fittings, forming a complete and closed DC de-icing working circuit. This ensures that the subsequent DC de-icing current can stably flow through the iced line, meeting the requirements of the de-icing operation.

[0086] After all wiring work was completed and verified to be correct, the DC220V station secondary power supply was switched on, and a comprehensive power-on self-test and status verification of the entire system was performed. Each item was checked and confirmed: the equipment control and protection devices had no abnormal fault alarms during the overall self-test; the fiber optic communication and CAN bus communication links were unobstructed; the equipment data interaction and remote control functions were normal; the cooling component fans started normally, and the start-stop control logic was reliable; all disconnectors and circuit breakers in the system were in the initial open standby position, with no incorrect closing or jamming issues; the protection settings of the entire equipment were strictly set and solidified according to the on-site de-icing operation plan, and the protection parameters matched the on-site operating conditions. After completing the static inspection, a no-load voltage boost performance test was performed to verify the equipment control logic and operational stability: the incoming circuit breaker was closed, and the control component gradually and smoothly reduced the thyristor trigger angle from 150° to 100°, observing the DC output voltage change in real time to confirm that the DC voltage changed continuously and stably, without sudden changes or fluctuations; the equipment control logic responded accurately; and the entire unit had no abnormal discharge sounds, vibrations, or localized overheating. After all no-load commissioning tests are completed, the control component resets the thyristor trigger angle to 150°, the system DC output returns to zero, and the equipment enters the de-icing standby ready state, preparing for subsequent current boost de-icing and filter branch switching operations.

[0087] Step S801: Adjust the firing angle of the thyristor of the ice-melting valve assembly according to the preset current-increasing rate to increase the ice-melting DC current.

[0088] During the formal current ramp-up phase, the control component gradually reduces the thyristor firing angle according to the preset current ramp-up rate (preferably 200A / min), so that the rectified output DC voltage gradually increases, driving the ice-melting DC current to rise steadily from zero.

[0089] In step S802, the value of the DC current for ice melting is collected in real time, and combined with the harmonic spectrum characteristics corresponding to the firing angle of the thyristor, the single-tuned filter branch of the ice melting filter device with matching frequency is put into operation.

[0090] The thyristor firing angle is a core parameter determining harmonic characteristics. Under the same DC current, the proportion and amplitude of each harmonic differ depending on the firing angle. Relying solely on the current threshold cannot accurately match filtering requirements. Therefore, this application uses both the firing angle harmonic spectrum and DC current as dual parameters for branch switching determination, ensuring that the filtering branch is compatible with the characteristics of the real-time harmonic source. During the current ramp-up process, the value of the de-icing DC current is collected in real time and combined with the harmonic spectrum corresponding to the current thyristor firing angle to provide a basis for the filtering branch to be put into operation. Furthermore, the branch closing is selected to complete zero-voltage or zero-current switching during the power frequency cycle with the smallest potential difference across the switch, suppressing inrush current.

[0091] According to the example embodiment, when multiple filter branches are included, this application adopts a hierarchical progressive branch input strategy. According to the order of harmonic amplitude from large to small and harmonic contribution ratio from high to low, three levels of incremental input thresholds are set. Different current thresholds are matched with the input of single-tuned filter branches of corresponding frequencies. The ice melting filter device is configured with single-tuned filter branches, including single-tuned filter branches adapted to low-frequency dominant characteristic harmonics, single-tuned filter branches adapted to mid-frequency dominant characteristic harmonics, and / or single-tuned filter branches adapted to high-frequency dominant characteristic harmonics.

[0092] When the de-icing DC current reaches the first threshold within the set target de-icing DC current range, a single-tuned filter branch adapted to low-frequency dominant characteristic harmonics is activated. When the de-icing DC current reaches the second threshold within the set target de-icing DC current range, a single-tuned filter branch adapted to mid-frequency dominant characteristic harmonics is activated. When the de-icing DC current reaches the third threshold within the set target de-icing DC current range, a single-tuned filter branch adapted to high-frequency dominant characteristic harmonics is activated, achieving dynamic matching between harmonic mitigation capacity and real-time harmonic content. The first, second, and third thresholds increase progressively.

[0093] During the closing and commissioning process of any filter branch, the controller monitors the instantaneous voltage status at both ends of the branch circuit breaker in real time, selects the power frequency cycle with the smallest potential difference at both ends to perform the closing operation, and greatly suppresses the inrush current through zero voltage or zero current switching mode to avoid damage to power devices by the impact current.

[0094] Correspondingly, the four single-tuned filter branches of this application can be divided into the above three types of harmonic branches. Among them, the low-frequency dominant characteristic harmonic branch corresponds to the 5th harmonic branch, the mid-frequency dominant characteristic harmonic branch corresponds to the 7th harmonic branch, and the high-frequency dominant characteristic harmonic branch corresponds to the 11th and 13th harmonic branches.

[0095] According to some embodiments, this application uses a rated target de-icing DC current range of 1000A as an example to perform refined threshold configuration, with a preset current ramp rate preferably of 200A / min. The target de-icing DC current is set as a continuously adjustable range, and this application uses a rated DC current of 1000A as a typical example for explanation. Specifically, the first input threshold is set to 25% of the target de-icing DC current range, corresponding to a current value of 250A, used to input the single-tuned filter branch corresponding to the low-frequency dominant characteristic harmonic, specifically tuning the 5th harmonic branch. At this point, the 5th harmonic current begins to increase significantly and needs to be addressed. The second input threshold is set to 50% of the target de-icing DC current range, corresponding to a current value of 500A, used to input the single-tuned filter branch corresponding to the secondary dominant characteristic harmonic, specifically tuning the 7th harmonic branch. The third input threshold is set to 75% of the target de-icing DC current range, corresponding to a current value of 750A, used to simultaneously input two single-tuned filter branches corresponding to the high-frequency secondary characteristic harmonic, specifically tuning the 11th harmonic branch and the 13th harmonic branch. This hierarchical matching logic ensures that when harmonic content increases during the ice-melting current rise process, the corresponding filter branch is activated in a timely manner, accurately matching the real-time harmonic operating conditions. Simultaneously, each branch employs zero-voltage switching control logic, which can stably control the inrush current to within 1.5 times the branch's rated current, effectively protecting the filter capacitors, reactors, and switching equipment.

[0096] Step S803: Maintain the de-icing DC current within the set target de-icing DC current range, and control the de-icing filter device to continuously absorb the characteristic harmonics generated by the de-icing valve group device in real time.

[0097] Once the de-icing DC current has steadily risen to the set target de-icing DC current range and stabilized, all the 5th, 7th, 11th, and 13th single-tuned filter branches that have been put into operation will continue to run synchronously. They will absorb the 6n±1th characteristic harmonics generated during the rectification process of the de-icing valve group device, suppress the propagation of harmonics from the source, effectively prevent harmonics from flowing back to the three-phase de-icing power supply of the grid, and ensure the stability of the power quality of the grid.

[0098] In step S804, after the ice-melting operation is completed, the firing angle of the thyristor is adjusted according to the preset current reduction rate, and the single-tuned filter branch is disconnected.

[0099] Once the de-icing time reaches the preset value or the line temperature rises to the required level, the control component gradually increases the thyristor firing angle at a set rate, causing the DC current to smoothly decrease from the set target de-icing DC current range to zero, thus initiating the whole machine current reduction shutdown process.

[0100] During the current reduction process, the DC current value of ice melting is collected in real time. Combined with the harmonic attenuation characteristics under the current rectification operation conditions, the basis for the filter branch to be removed is provided, and the filter branch is cut off.

[0101] As the thyristor firing angle increases, the rectified output power decreases, and the characteristic harmonic currents of each order continue to decay. Based on the harmonic decay law brought about by the change in firing angle, the system reversely cuts off the filter branch in conjunction with the DC current threshold to avoid the filter branch being idle under light load conditions, which would lead to excessive reactive power.

[0102] According to the example embodiment, when multiple filter branches are included, each single-tuned filter branch is exited step by step according to the multi-level cut-off threshold, and the capacitor residual voltage discharge logic is quickly executed after the branch is cut off to ensure the safety of the equipment when it is powered off.

[0103] This application adopts a reverse step-by-step branch cutoff strategy, setting three decreasing cutoff thresholds according to the order of harmonic contribution from small to large and the order of activation followed by deactivation. Different current thresholds are matched to cutoff single-tuned filter branches of corresponding frequencies. The ice-melting filter device is equipped with three types of single-tuned filter branches, namely single-tuned filter branches adapted to low-frequency dominant characteristic harmonics, mid-frequency dominant characteristic harmonics, and high-frequency dominant characteristic harmonics.

[0104] When the de-icing DC current drops to a first cutoff threshold within the set target de-icing DC current range, the single-tuned filter branch adapted to the high-frequency dominant characteristic harmonics is cut off. When the de-icing DC current drops to a second cutoff threshold within the set target de-icing DC current range, the single-tuned filter branch adapted to the mid-frequency dominant characteristic harmonics is cut off. When the de-icing DC current drops to a third cutoff threshold within the set target de-icing DC current range, the single-tuned filter branch adapted to the low-frequency dominant characteristic harmonics is cut off. This achieves dynamic matching between harmonic mitigation capacity and real-time harmonic content during the de-icing current reduction process, avoiding reactive power excess and system resonance problems under light load conditions. The first, second, and third cutoff thresholds decrease progressively.

[0105] After any filter branch is disconnected, the corresponding circuit breaker is locked, and the discharge coil of the branch is automatically put into operation to quickly discharge the residual voltage inside the filter capacitor. In a short time, the residual voltage is reduced to a safe voltage range, completely eliminating the risk of residual voltage in the equipment and ensuring the safety of equipment operation and maintenance.

[0106] Correspondingly, the four single-tuned filter branches of this application can be divided into the above three types of harmonic branches. Among them, the low-frequency dominant characteristic harmonic branch corresponds to the 5th harmonic branch, the mid-frequency dominant characteristic harmonic branch corresponds to the 7th harmonic branch, and the high-frequency dominant characteristic harmonic branch corresponds to the 11th and 13th harmonic branches. The branch cut-off order is completely opposite to the branch input order.

[0107] According to some embodiments, this application uses a rated target ice-melting DC current range of 1000A as an example to perform refined threshold configuration, with a preset current reduction rate preferably 200A / min, consistent with the current increase rate. Specifically, the first cutoff threshold is set to 60% of the target ice-melting DC current range, corresponding to a current value of 600A, used to cut off the two single-tuned filter branches corresponding to the high-frequency dominant characteristic harmonics, specifically tuning the 11th harmonic branch and the 13th harmonic branch; the second cutoff threshold is set to 35% of the target ice-melting DC current range, corresponding to a current value of 350A, used to cut off the single-tuned filter branch corresponding to the mid-frequency dominant characteristic harmonics, specifically tuning the 7th harmonic branch; and the third cutoff threshold is set to 15% of the target ice-melting DC current range, corresponding to a current value of 150A, used to cut off the single-tuned filter branch corresponding to the low-frequency dominant characteristic harmonics, specifically tuning the 5th harmonic branch. This reverse hierarchical cutoff logic ensures that as the harmonic content gradually decreases during the ice melting and flow reduction process, the corresponding filter branches exit in an orderly manner, always matching the real-time harmonic operating conditions and effectively improving the system's operational stability.

[0108] Step S805: When the DC current for ice melting drops to zero, the ice melting valve assembly is locked.

[0109] After the DC current for ice melting stabilizes and drops to zero in real time, the control component immediately issues a lockout command to lock the thyristor trigger circuit of the ice melting valve group device and terminate the rectification operation. Subsequently, the incoming SF6 circuit breaker and the two branch circuit breakers are disconnected in sequence, the on-site connection cables are removed step by step, the work site is cleaned up, and the equipment is removed. The entire ice melting and harmonic control operation process is completed in a closed loop.

[0110] According to some embodiments, the target current for de-icing, the current rise and fall rates, and the thresholds for each level of input and cut-off can all be flexibly matched and modified based on the parameters of the line to be de-iced, the ambient temperature, and the on-site power grid conditions, relying on the system's back-end monitoring terminal, to adapt to different on-site de-icing operation needs.

[0111] In the above-described method, the step-by-step switching of the filter branch and the coordinated operation of the rising and falling DC current during ice melting solve the problems that traditional fixed-supply filters may cause overcompensation of fundamental reactive power under light load and insufficient filter capacity under heavy load. By real-time detection of the ice melting DC current and prediction of the harmonic spectrum, the corresponding branch is only activated when the harmonic current of a certain frequency increases to the point where it needs to be addressed, thus balancing filter efficiency and system reactive power balance.

[0112] To verify the practical application effect of the dual-vehicle decoupling architecture and multi-stage step-by-step switching filtering technology of this invention, a field comparative test was conducted at a 110kV substation. Simulating real low-temperature icing and melting conditions, the power quality parameters on the grid side were tested and compared under different filtering activation modes to verify the harmonic mitigation performance and technical superiority of this solution. The unified test conditions for this field test were as follows: the length of the line to be melted was approximately 30km, the conductor type was LGJ-240 / 30, the ambient temperature was -5℃, and the system's rated target icing DC current range was set to 1000A, perfectly matching the aforementioned operating parameters.

[0113] To fully compare the performance differences between graded filtering, full-branch filtering, and no filtering, this test set up three operating modes to detect the total harmonic distortion rate and the content of each major characteristic harmonic of the 10kV bus voltage: Mode A: No filtering devices are put into operation, all single-tuned filter branches are completely disconnected, and only the ice-melting valve group is operated alone to test the grid harmonic level under pure rectification conditions. Mode B: Only the low-frequency and mid-frequency core filter branches are deployed, namely the 5th and 7th single-tuned filter branches, while the high-frequency 11th and 13th filter branches are deactivated to verify the treatment effect of the conventional low-frequency filter scheme. Mode C: The hierarchical switching control scheme of this invention is adopted, and all four single-tuned filter branches are activated step by step according to the DC current threshold of ice melting, which is the complete four-level filter activation condition.

[0114] Power quality data was collected synchronously for each mode and compared with the power quality limits required by the national standard GB / T 14549. The specific test data are shown in Table 1 below:

[0115] Table 1 Comparison of Power Quality Test Data under Different Operating Modes Field measurement data shows that under the rated 1000A ice-melting condition, the unfiltered pure rectification operation mode A causes severe exceedance of grid harmonics, with the total harmonic distortion rate of the bus voltage reaching as high as 8.7%, far exceeding the national standard limit of 5.0%. Among them, the fifth low-frequency dominant harmonic is the most severely exceeded, seriously affecting the power quality of the grid bus. Mode B, which only involves two low-frequency filter branches, can significantly reduce the content of low-frequency harmonics, but the total harmonic distortion rate of the voltage is still 5.6%, which still exceeds the national standard limit and cannot meet the grid-connected power quality requirements. This fully verifies that the traditional solution that relies solely on low-frequency filter branches and abandons high-frequency branches has the defects of insufficient filtering capacity and residual high-frequency harmonics.

[0116] By adopting Mode C of the step-by-step switching scheme for all branches in this application, the total harmonic distortion rate of the bus voltage can be effectively controlled at 4.0%, which is lower than the 5.0% limit specified in the national standard GB / T 14549. At the same time, the content of characteristic harmonic voltages of the 5th, 7th, 11th and 13th orders is significantly reduced and all are stably controlled within the national standard limit range, and the harmonic control effect fully meets the standard.

[0117] In summary, this field comparative test fully demonstrates that the dual-vehicle decoupled local filtering architecture adopted in this application, combined with the control strategy of four-level filtering branch hierarchical switching and dynamic matching of harmonic loads, can efficiently manage the 6n±1th characteristic harmonics generated by the rectifier device under the complex field conditions of vehicle-mounted mobile ice melting. It completely solves the problems of light load overcompensation, heavy load insufficient filtering, and incomplete harmonic management that exist in traditional fixed filtering and partial branch filtering schemes. It effectively ensures the power quality safety of the grid side during ice melting operations, and takes into account both the flexibility of mobile ice melting operations and the stability of grid operation.

[0118] Through the above-described examples, this application provides a mobile ice-melting filter system and its control method. This system employs a separate layout of the ice-melting valve assembly vehicle and the ice-melting filter vehicle, breaking the constraints of single-vehicle load and spatial dimensions. The ice-melting power and filtering capacity can be independently selected and arranged as needed, fundamentally solving the problems of insufficient filter branch configuration and excessive harmonics in integrated vehicle solutions. The opposing arrangement at the rear of the two vehicles shortens the length of the flexible connection cable, enabling the filter device to be connected in parallel on the AC side of the rectifier for filtering. This results in low impedance in the harmonic flow loop, efficiently absorbing the 6n±1st order characteristic harmonics, effectively preventing harmonic backflow and pollution of the power grid, and ensuring that the power quality of the power grid meets national standards. This application limits the quality factor of the filter branches to the range of 20-40, ensuring harmonic filtering accuracy while tolerating grid frequency fluctuations and component parameter deviations, thus preventing filter branch detuning and failure. Utilizing a tiered switching control strategy based on the de-icing DC current threshold, the filter branches are switched on sequentially with increasing current and switched off sequentially with decreasing current, avoiding issues of insufficient reactive power compensation under light loads and insufficient filter capacity under heavy loads, preventing grid resonance risks, and adapting to complex operating conditions with large fluctuations in de-icing DC current. Each filter branch selects zero-voltage switching with the minimum switch voltage difference at the power frequency cycle, significantly suppressing capacitor closing inrush current and improving the operational safety and service life of the vehicle-mounted equipment. The entire system can be transported on the road, requiring only flexible cable connection for rapid deployment on-site, resulting in high emergency deployment efficiency and facilitating rapid repair operations for grid icing disasters in winter. It demonstrates excellent engineering practicality and scalability.

[0119] It should be clearly understood that this application describes how specific examples are formed and used, but this application is not limited to any details of these examples. Rather, based on the teachings of the disclosure of this application, these principles can be applied to many other embodiments.

[0120] Furthermore, it should be noted that the above figures are merely illustrative representations of the processes included in the method according to exemplary embodiments of this application, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0121] Exemplary embodiments of this application have been specifically shown and described above. It should be understood that this application is not limited to the detailed structures, arrangements, or implementation methods described herein; rather, this application is intended to cover various modifications and equivalent arrangements that fall within the objectives and scope of the appended claims.

Claims

1. A mobile ice-melting filter system, characterized in that, include: The de-icing power supply switch cabinet is used to connect to the three-phase de-icing power supply of the power grid and to branch out at least two independent power supply circuits. The ice-melting valve assembly has its AC side connected to the output terminal of one of the power supply circuits, which is used to rectify and convert AC power into DC power to deliver ice-melting DC power to the transmission line to be covered with ice. The ice-melting filter device has its AC side connected in phase sequence with the AC side of the ice-melting valve group device and connected to the output terminal of another path in the power supply circuit. It is used to absorb the 6n±1th characteristic harmonic generated by the operation of the ice-melting valve group device and prevent the harmonic from flowing back to the three-phase ice-melting power supply of the power grid, where n is an integer greater than or equal to 1. The ice-melting valve assembly vehicle is used to carry the ice-melting power switch cabinet and the ice-melting valve assembly device. The ice-melting filter vehicle is used to carry the ice-melting filter device. The ice-melting filter vehicle and the ice-melting valve assembly vehicle are arranged in a rear-facing configuration to shorten the wiring length between the ice-melting valve assembly device and the ice-melting filter device.

2. The mobile ice-melting filter system as described in claim 1, characterized in that, The ice-melting power switch cabinet includes: The circuit breaker, after the three-phase de-icing power supply of the power grid is connected to the circuit breaker, is divided into at least two independent power supply circuits.

3. The mobile ice-melting filter system as described in claim 1, characterized in that, The ice-melting valve assembly adopts a three-phase fully controlled bridge six-pulse rectifier topology, and the firing angle adjustment range of the thyristors in the three-phase fully controlled bridge six-pulse rectifier topology is 5°~150°.

4. The mobile ice-melting filter system as described in claim 1, characterized in that, The ice-melting valve assembly includes: An anode reactor is connected to the AC side of the ice-melting valve assembly. A DC surge arrester, a digital voltage divider, a Hall current sensor, and a single-phase electric disconnect switch are connected to the DC side of the ice-melting valve assembly.

5. The mobile ice-melting filter system as described in claim 1, characterized in that, The ice-melting filter device includes: A single-tuned filter branch is used to adapt to the frequency of the 6n+1th or 6n-1th characteristic harmonic.

6. The mobile ice-melting filter system as described in claim 5, characterized in that, The quality factor of the single-tuned filter branch is between 20 and 40.

7. The mobile ice-melting filter system as described in claim 1, characterized in that, The ice-melting filter device includes: The four single-tuned filter branches are: the 5th harmonic tuning branch, the 7th harmonic tuning branch, the 11th harmonic tuning branch, and the 13th harmonic tuning branch.

8. The mobile ice-melting filter system as described in any one of claims 5-7, characterized in that, Each of the aforementioned single-tuned filter branches includes: A current transformer, a filter capacitor, and a filter reactor connected in series form a series branch; A discharge coil is connected in parallel with the filter capacitor to discharge residual voltage when the power is off; The surge arrester is connected in parallel with the series branch.

9. A mobile ice-melting filter control method, characterized in that, The mobile ice-melting filter control method is executed by the mobile ice-melting filter system as described in any one of claims 1-8, and the mobile ice-melting filter control method includes: The firing angle of the thyristor in the ice-melting valve assembly is adjusted according to the preset current-increasing rate to increase the ice-melting DC current. The value of the de-icing DC current is collected in real time, and combined with the harmonic spectrum characteristics corresponding to the firing angle of the thyristor, the single-tuned filter branch of the de-icing filter device with matching frequency is put into operation. The de-icing DC current is maintained within the set target de-icing DC current range, and the de-icing filter device is controlled to continuously absorb the characteristic harmonics generated by the de-icing valve assembly device in real time. Once the ice-melting operation is completed, the firing angle of the thyristor is adjusted according to the preset current reduction rate to cut off the single-tuned filter branch that has been put into operation. When the de-icing DC current drops to zero, the de-icing valve assembly is locked.

10. The mobile ice-melting filtering control method as described in claim 9, characterized in that, The ice-melting filter device includes a single-tuned filter branch adapted to low-frequency dominant characteristic harmonics, a single-tuned filter branch adapted to mid-frequency dominant characteristic harmonics, and / or a single-tuned filter branch adapted to high-frequency dominant characteristic harmonics. The step of real-time acquisition of the de-icing DC current value, combined with the harmonic spectrum characteristics corresponding to the thyristor's firing angle, and inputting a single-tuned filter branch of the de-icing filter device with a matching frequency, includes: When the ice-melting DC current reaches the first input threshold of the set target ice-melting DC current range, the single-tuned filter branch adapted to the low-frequency dominant characteristic harmonic is put into operation. When the ice-melting DC current reaches the second input threshold of the set target ice-melting DC current range, the single-tuned filter branch that adapts to the dominant characteristic harmonic of the mid-frequency is put into operation. When the ice-melting DC current reaches the third input threshold of the set target ice-melting DC current range, the single-tuned filter branch adapted to the high-frequency dominant characteristic harmonic is put into operation, wherein the first input threshold, the second input threshold, and the third input threshold increase step by step.

11. The mobile ice-melting filtering control method as described in claim 9, characterized in that, The method of real-time acquisition of the DC current range for ice melting, combined with the harmonic spectrum characteristics corresponding to the firing angle of the thyristor, and step-by-step input of the single-tuned filter branch of the ice melting filter device with matching frequency, includes: When the single-tuned filter branch is activated, the power frequency cycle with the smallest potential difference between the two ends of the single-tuned filter branch is selected to perform the closing operation, so as to achieve zero-voltage switching and suppress the generation of inrush current during closing.

12. The mobile ice-melting filtering control method as described in claim 10, characterized in that, The step of adjusting the firing angle of the thyristor according to a preset current reduction rate and cutting off the engaged single-tuned filter branch after the ice-melting operation is completed includes: When the de-icing DC current drops to a first cut-off threshold within the set target de-icing DC current range, the single-tuned filter branch adapted to the high-frequency dominant characteristic harmonic is cut off. When the ice-melting DC current drops to the second cut-off threshold of the set target ice-melting DC current range, the single-tuned filter branch that adapts to the dominant characteristic harmonic of the mid-frequency is cut off. When the de-icing DC current drops to the third cut-off threshold within the set target de-icing DC current range, the single-tuned filter branch adapted to the low-frequency dominant characteristic harmonic is cut off, wherein the values ​​of the first cut-off threshold, the second cut-off threshold, and the third cut-off threshold decrease step by step.

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