Alternating current and direct current dual-purpose ice melting device

Abstract

The embodiment of the invention provides an alternating-current and direct-current dual-purpose ice melting device. The device comprises an ice-melting circuit breaker, the input end of the ice-melting circuit breaker is used for being connected with an ice-melting power supply, and the output end of the ice-melting circuit breaker is electrically connected with the primary side of an ice-melting transformer; a secondary side of the ice-melting transformer has a voltage regulation function, and the secondary side is electrically connected with the alternating-current mode isolation switch and the direct-current mode isolation switch respectively; the alternating-current mode isolating switch is connected between the secondary side and the alternating-current output port; the direct current mode isolation switch is connected between the secondary side and the input end of the rectification module, and an interlocking structure is arranged between the alternating current mode isolation switch and the direct current mode isolation switch; the direct current output end of the rectification module is electrically connected with the input ends of the multiple groups of output disconnecting links; the output ends of the multiple groups of output disconnecting links are used for being connected with a direct-current ice melting loop; and the protection module is in signal connection with the ice-melting circuit breaker, the ice-melting transformer and the rectification module and is used for monitoring and controlling the operation of the device.

Description

Technical Field

[0001] This application relates to the field of electrical engineering technology, specifically to an AC / DC dual-use ice-melting device. Background Technology

[0002] Ice storms are one of the most common natural disasters in power systems. At best, they can cause line tripping and outages due to ice flashovers; at worst, they can cause tower (pole) collapses, line breaks, or even paralyze the power grid, seriously threatening the safe and stable operation of the power grid.

[0003] AC de-icing can directly utilize existing AC power sources in the power grid (such as substation transformers), making it suitable for short-distance lines or emergency scenarios. Currently, it is mainly used in 10kV distribution networks. However, if AC de-icing is used for main grid de-icing, the required equipment capacity is enormous. 110kV and above voltage level transmission lines mainly use DC de-icing, which has an energy conversion efficiency of over 90% (far higher than the 60%-70% of AC de-icing), making it particularly suitable for rapid de-icing of long-distance, large-section conductors. If DC de-icing is used for distribution network de-icing, it requires manually disconnecting the high-voltage side of all distribution transformers, circuit breakers, and the coil windings of metering instruments such as PTs and voltage regulators along the de-icing circuit, making the operation complex and time-consuming. If both the main and distribution networks require de-icing, both AC and DC de-icing devices must be configured simultaneously, resulting in high equipment costs.

[0004] Therefore, there is an urgent need for an ice-melting device that can operate on both AC and DC power. Summary of the Invention

[0005] The purpose of this application is to provide an AC / DC dual-use ice-melting device.

[0006] To achieve the above objectives, the first aspect of this application provides an AC / DC dual-purpose ice-melting device, comprising: The input terminal of the de-icing circuit breaker is used to connect to the de-icing power supply, and the output terminal of the de-icing circuit breaker is connected to the primary side of the de-icing transformer. The de-icing transformer has a voltage regulation function on its secondary side, and the secondary side is electrically connected to both the AC mode disconnect switch and the DC mode disconnect switch. An AC mode isolating switch is connected between the secondary side and the AC output port; A DC-mode isolating switch is connected between the secondary side and the input terminal of the rectifier module, and an interlocking structure is provided between the AC-mode isolating switch and the DC-mode isolating switch. The rectifier module has its DC output terminal electrically connected to the input terminals of multiple output switches. Multiple sets of output switches, the output terminals of which are used to connect to the DC de-icing circuit; The protection module is connected to the de-icing circuit breaker, de-icing transformer, and rectifier module for signal monitoring and control of the device's operation.

[0007] In this embodiment, the voltage regulation function of the ice-melting transformer is achieved through multiple taps on the secondary winding to achieve multi-level voltage regulation.

[0008] In this embodiment, when the AC mode isolating switch is closed and the DC mode isolating switch is open, the device is in AC de-icing mode; when the DC mode isolating switch is closed and the AC mode isolating switch is open, the device is in DC de-icing mode.

[0009] In this embodiment of the application, the rectifier module is a three-phase bridge rectifier circuit.

[0010] In this embodiment, the rectifier module is specifically a six-pulse rectifier valve, which includes six commutation valves made of power semiconductor devices.

[0011] In this embodiment, the six-pulse rectifier valve is equipped with a forced air cooling device.

[0012] In this embodiment of the application, the DC output combined switch includes a set of positive switches and a set of negative switches; the positive switches are connected between the DC output positive terminal of the rectifier module and the DC de-icing circuit; The negative switch is connected between the negative DC output of the rectifier module and the DC de-icing circuit, and an interlocking circuit is provided between the positive and negative switches corresponding to the same phase line in the DC de-icing circuit.

[0013] In the embodiments of this application, the combined closed state of the positive and negative disconnect switches is configured to form one of the following DC de-icing topologies: a single-loop topology with two-phase conductors connected in series; or a composite loop topology with a single-phase conductor and two-phase parallel conductors connected in series.

[0014] In this embodiment, the protection and control module includes a status monitoring unit and a circuit breaker control unit; The status monitoring unit is used to collect the output voltage and current of the de-icing transformer and / or the output voltage and current of the rectifier module in real time; the circuit breaker control unit is used to automatically control the de-icing circuit breaker to trip when the status monitoring unit detects that the electrical quantity exceeds the preset threshold.

[0015] In the embodiments of this application, the device is a fixed installation structure or a movable structure mounted on a mobile platform.

[0016] This solution allows for flexible switching between AC and DC de-icing modes, making it adaptable to power transmission and distribution lines of different voltage levels. This avoids the limitations of traditional de-icing devices in application at different voltage levels and reduces equipment configuration costs.

[0017] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. In the drawings: Figure 1 A schematic diagram of an AC / DC dual-use ice-melting device according to an embodiment of this application is shown. Figure 2 This diagram schematically illustrates the operating status of each switch (knife switch) unit in the AC output mode of the AC-DC dual-purpose ice-melting device according to an embodiment of this application. Figure 3 This schematically illustrates the operating status diagram of each switch (knife switch) unit in the DC output mode of the AC-DC dual-purpose ice-melting device according to an embodiment of this application (taking phases A and B connected to the positive pole and phase C connected to the negative pole as an example). Figure 4 This illustration shows a schematic diagram of a "one-way" wiring method according to an embodiment of this application; Figure 5 A schematic diagram of a "one-way, two-way" wiring method according to an embodiment of this application is shown. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for illustration and explanation of the embodiments of this application and are not intended to limit the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0020] In one embodiment, a dual-purpose AC / DC de-icing device is provided, the device comprising: The input terminal of the de-icing circuit breaker is used to connect to the de-icing power supply, and the output terminal of the de-icing circuit breaker is connected to the primary side of the de-icing transformer. The de-icing transformer has a voltage regulation function on its secondary side, and the secondary side is electrically connected to both the AC mode disconnect switch and the DC mode disconnect switch. An AC mode isolating switch is connected between the secondary side and the AC output port; A DC-mode isolating switch is connected between the secondary side and the input terminal of the rectifier module, and an interlocking structure is provided between the AC-mode isolating switch and the DC-mode isolating switch. The rectifier module has its DC output terminal electrically connected to the input terminals of multiple output switches. Multiple sets of output switches, the output terminals of which are used to connect to the DC de-icing circuit; The protection module is connected to the de-icing circuit breaker, de-icing transformer, and rectifier module for signal monitoring and control of the device's operation.

[0021] An ice-melting circuit breaker is a switching device capable of carrying, connecting, and disconnecting current under normal circuit conditions, and capable of carrying, connecting, and disconnecting current under abnormal circuit conditions (such as short circuits) within a specified time. In this scheme, the ice-melting circuit breaker is the main switch and safety gate of the entire ice-melting device. It is responsible for safely introducing external ice-melting power into the device, and can be manually closed when the device starts up. In case of a fault or when it needs to be stopped, it can quickly disconnect the circuit to protect downstream equipment. An ice-melting transformer is an electrical device that uses the principle of electromagnetic induction to change AC voltage and current. It usually has a primary side (input side, also known as the high-voltage side) and a secondary side (output side, also known as the low-voltage side). In this scheme, the ice-melting transformer is mainly used for voltage transformation and voltage regulation. Voltage transformation refers to reducing the input high voltage (such as 10kV) to a low voltage suitable for ice-melting operation (such as 3.6kV and below). Voltage regulation refers to the ability to flexibly output the most suitable voltage based on the adjustable secondary voltage, according to the resistance and length (ice-melting distance) requirements of different lines, thereby controlling the magnitude of the ice-melting current. AC-mode and DC-mode disconnect switches are switching devices used to isolate power supplies. When in the open position, they have a specified insulation distance between contacts and a clear disconnection mark. They typically do not have the ability to interrupt load current or short-circuit current; operation must be performed after the circuit breaker has opened. For AC-mode disconnect switches, when closed, the low-voltage AC power from the de-icing transformer can be directly led to the AC output port, establishing an AC de-icing path. For DC-mode disconnect switches, when closed, the low-voltage AC power from the de-icing transformer can be led to the subsequent rectifier module, establishing a DC de-icing path. Furthermore, a mechanical or electrical interlock is installed between the AC-mode and DC-mode disconnect switches, a critical safety design that ensures the two switches will not close simultaneously, preventing AC power from accidentally entering the DC path or causing a short circuit, forcing operators to select only one operating mode. A rectifier module is a power electronic device that converts AC power to DC power. Specifically, it can be a six-pulse rectifier valve, a mature rectifier circuit topology composed of multiple thyristors or diodes and other power devices. In this scheme, when the device switches to DC mode, the rectifier module can rectify the AC power from the transformer into smooth DC power, providing energy for DC de-icing. The energy efficiency of DC de-icing (>90%) is much higher than that of AC de-icing (60-70%), making it particularly suitable for long-distance, large-section conductors. Multi-output disconnectors are simple in structure and intuitive in operation, commonly used in power distribution lines as isolation and clear disconnection points. In this scheme, in DC de-icing mode, the multi-output disconnectors are divided into two groups: one group connects to the positive terminal of the rectifier module output; the other group connects to the negative terminal. By selectively closing specific disconnector combinations, the positive and negative terminals of the DC power can be flexibly distributed to different phase conductors of the line to be de-iced, thus forming different DC circuit connection methods (such as "one-way" or "one-way") to adapt to different line conditions and de-icing requirements.The protection module is an automated unit integrating measurement, monitoring, logic judgment, and control output. It can collect electrical parameters such as voltage and current at key points like transformers and rectifier modules in real time, and perform remote or automatic opening and closing operations on circuit breakers. When abnormal conditions such as overcurrent or overvoltage are detected, it quickly issues commands to trip the de-icing circuit breaker, cutting off the power supply and protecting the device and the power grid. The AC / DC output port is the external electrical interface of the de-icing device. In this solution, the AC / DC output port is used to connect to the transmission or distribution lines requiring de-icing via cables, delivering the electrical energy needed for de-icing to the lines.

[0022] Specifically, during the de-icing operation, the external de-icing power supply is first connected to the de-icing circuit breaker. This circuit breaker controls the connection and disconnection of the power supply. After passing through the circuit breaker, the current enters the primary side of the de-icing transformer. The transformer reduces the voltage to a safe and suitable level for de-icing. The operator can set the optimal secondary output voltage by adjusting the transformer's tap position according to the line length and conductor type required for this de-icing task. This is the first key to achieving "widely adaptable" to different lines. When rapid or emergency de-icing is required for short-distance lines (such as distribution network lines), the operator disconnects the DC mode disconnect switch (QS2) and closes the AC mode disconnect switch (QS1). At this time, the low-voltage AC power output from the transformer is directly sent to the AC output port through QS1 and then connected to the line. This mode utilizes the line's own impedance to generate heat, is simple to operate, and is suitable for distribution network scenarios. When efficient de-icing is required for long-distance, large-section transmission lines, the operator disconnects the AC mode disconnect switch (QS1) and closes the DC mode disconnect switch (QS2). At this point, low-voltage AC power enters the rectifier module through QS2. An interlocking structure ensures the safety of this switching process, preventing path conflicts. In DC mode, the rectifier module converts AC to DC. The DC power is led out from its positive and negative output terminals and connected to multiple sets of output switches. Operators can manually operate these switches (e.g., closing K1 and K5) according to the line conditions (e.g., the phase requiring de-icing) to connect the positive DC terminal to the A-phase conductor and the negative terminal to the B-phase conductor, forming an "A-phase → B-phase" DC loop. This is the second key to achieving "flexible application." Different switch combinations allow for easy changes to the DC de-icing wiring without altering the internal wiring. Furthermore, the protection module operates continuously throughout the de-icing process. It monitors the output status of the transformer and rectifier module. Upon detecting abnormal current increases (e.g., short circuits) or abnormal voltage, it immediately issues an automatic command to trip the de-icing circuit breaker instantly, cutting off the power supply to the entire device and protecting both the device itself and the power grid equipment from damage.

[0023] This solution allows for flexible switching between AC and DC de-icing modes, making it adaptable to power transmission and distribution lines of different voltage levels. This avoids the limitations of traditional de-icing devices in application at different voltage levels and reduces equipment configuration costs.

[0024] In one embodiment, the voltage regulation function of the ice-melting transformer is achieved through multiple taps on the secondary winding to realize multi-level voltage regulation.

[0025] The secondary winding refers to the coil winding in a transformer connected to the output terminal (load side). When alternating current is applied to the primary winding, an induced electromotive force is generated in the secondary winding through electromagnetic induction. The number of turns in the secondary winding directly determines the output voltage. The secondary winding is the direct source of electrical energy ultimately used for ice melting. Its electrical parameters (voltage, current) are key to determining the ice melting effect (distance, speed). Taps are electrical connection points led out from specific turns positions in the transformer winding (specifically the secondary winding). By changing the effective number of turns connected to the circuit (i.e., selecting different taps), the transformer's turns ratio can be finely adjusted, thereby changing its output voltage while keeping the input voltage constant. Transformers have multiple (usually three or more) discrete, preset voltage output values ​​(taps), which can be switched between via an operating mechanism. Specifically, when it is necessary to change the ice melting conditions, the operator switches the circuit connection to another tap on the secondary winding by operating the tap switch (usually linked to a knife switch or knob). This switching alters the effective number of turns in the secondary winding connected to the circuit. Understandably, with the primary voltage and number of turns remaining constant, reducing the effective number of turns on the secondary side will decrease the output voltage; conversely, increasing it will increase it. Ultimately, the de-icing voltage and current transmitted to the line change accordingly. Therefore, voltage regulation is essentially the core means of precisely controlling the de-icing power and current.

[0026] In practical applications, the de-icing requirements of the main grid (high voltage) and distribution grid (low voltage) lines differ, and traditional solutions require different equipment. This device can output different voltages from hundreds to thousands of volts by adjusting the tap of a single transformer, thus meeting both the lower voltage / current requirements of the distribution grid lines and the high current required for de-icing of the main grid lines through a higher tap.

[0027] In one embodiment, when the AC mode disconnect switch is closed and the DC mode disconnect switch is open, the device is in AC de-icing mode; when the DC mode disconnect switch is closed and the AC mode disconnect switch is open, the device is in DC de-icing mode.

[0028] AC de-icing mode refers to the configuration and operation of the device's energy transmission path, internal component operating status, and external wiring method all based on the principle of de-icing using the thermal effect of AC electricity (mainly Joule heating and part of the skin effect). DC de-icing mode refers to the configuration and operation of the device's energy transmission path, internal component operating status, and external wiring method all based on the principle of efficient de-icing using the pure resistive heating effect (Joule heating) of DC electricity. The two modes are not merely a difference between AC and DC output; they signify a switch in the entire operating system of the device, including its internal components (whether the rectifier module is engaged), protection logic (monitoring AC / DC quantities), and even external line operations (such as considering transformer isolation along the line in DC mode).

[0029] Specifically, the interlocking structure mechanically or electrically ensures that the AC-mode disconnect switch QS1 and the DC-mode disconnect switch QS2 cannot be simultaneously closed. This eliminates the most dangerous possibility of misoperation—a short circuit caused by simultaneous conduction of AC and DC paths. Under the physical constraint of the interlock, the two switches can only present two valid combination states: 1. Combination A (QS1=Closed, QS2=Open): The AC path is unobstructed, and the DC path is physically isolated. At this time, the current output from the transformer secondary can only flow to the AC output port. The rectifier module is completely disconnected from the circuit and does not operate. The device is forcibly and explicitly defined to operate in AC de-icing mode.

[0030] 2. Combination B (QS1=Open, QS2=Closed): The AC path is physically isolated, while the DC path remains open. In this configuration, the current output from the transformer secondary can only flow to the rectifier module. The rectifier module then operates, converting the AC to DC before outputting it. The device is explicitly and forcibly defined to operate in DC de-icing mode.

[0031] This solution allows for a risk-free switching between AC dedicated machine and DC dedicated machine identities through a simple switching operation.

[0032] In one embodiment, the rectifier module is a three-phase bridge rectifier circuit.

[0033] A three-phase bridge rectifier circuit is a classic circuit topology that uses at least six power semiconductor devices (such as diodes or thyristors) to convert three-phase alternating current (AC) to direct current (DC). At any given time, the circuit automatically selects the phase with the highest instantaneous voltage to flow to the positive terminal through the common cathode group, and simultaneously selects the phase with the lowest instantaneous voltage to flow back to the negative terminal through the common anode group. This mechanism allows the three-phase power supply to be used alternately and continuously, resulting in a DC voltage with low ripple and a high average value on the DC side. The secondary output of the de-icing transformer in this device is precisely three-phase AC. The inherent input requirement of a three-phase bridge rectifier circuit is three-phase AC, which allows for direct and efficient connection between the two without any additional phase conversion or complex matching.

[0034] In one embodiment, the rectifier module is specifically a six-pulse rectifier valve, which includes six commutation valves made of power semiconductor devices.

[0035] A six-pulse rectifier valve specifically refers to a complete functional module or device in industrial power applications, integrating multiple power semiconductor devices, voltage equalizing elements, triggering units, heat sinks, and mechanical structures to achieve three-phase bridge rectification. Six pulses refer to the six pulsating wavefronts appearing on the DC side voltage within one power frequency cycle (50Hz). This is an inherent characteristic of a three-phase bridge rectifier circuit; therefore, a six-pulse rectifier valve is essentially a specific implementation of a three-phase bridge rectifier circuit. A commutation single valve constitutes the basic unit of the six-pulse rectifier valve. In this embodiment, a commutation single valve typically refers to an integrated unit of a power semiconductor device capable of withstanding high voltage and conducting large current, along with its necessary auxiliary and protection circuits. It is the smallest controllable switching unit. The six commutation single valves correspond to the six arms (three common cathode arms and three common anode arms) in the three-phase bridge rectifier circuit. Specifically, the power semiconductor device can be a thyristor.

[0036] In one embodiment, the six-pulse rectifier valve is equipped with a forced air cooling device.

[0037] Forced air cooling systems utilize an electric fan to generate forced airflow, directly blowing onto or flowing over heat-generating components (such as heat sinks), rapidly removing heat through convection. A forced air cooling system can consist of a fan, air ducts, and a heat sink (such as a finned metal substrate). Power semiconductor devices (thyristors) in a six-pulse rectifier valve experience significant conduction losses when conducting large currents, and also incur switching losses during switching. Semiconductor devices have strict upper limits for junction temperature. If heat cannot be dissipated in time, the device temperature will continue to rise, leading to operational abnormalities. In actual operation, the rated power of rectifier modules can reach up to 13.75MW (DC 6250V, 2200A). At this power level, heat dissipation can reach tens to hundreds of kilowatts, making natural cooling insufficient and necessitating active cooling. Forced air cooling achieves the optimal balance between reliability, cost, complexity, and maintainability.

[0038] In one embodiment, the DC output combination switch includes a set of positive switches and a set of negative switches; the positive switches are connected between the positive DC output of the rectifier module and the DC de-icing circuit; the negative switches are connected between the negative DC output of the rectifier module and the DC de-icing circuit, and an interlocking circuit is provided between the positive switches and the negative switches corresponding to the same phase line in the DC de-icing circuit.

[0039] Positive and negative disconnect switches are classifications of DC output switch groups based on electrical polarity. A positive disconnect switch refers to any disconnect switch with one end connected to the positive busbar of the rectifier module's DC output. A negative disconnect switch refers to any disconnect switch with one end connected to the negative busbar of the rectifier module's DC output. Positive and negative disconnect switches are branch switches that lead the positive and negative terminals of the DC power supply to different phase conductors of the external line. An interlock circuit refers to a specially designed electrical or mechanical interlock device between positive and negative disconnect switches corresponding to the same phase conductor. Its purpose is to prevent operators from accidentally connecting the same phase conductor to both the positive and negative terminals of the DC power supply simultaneously, thus preventing a direct short circuit on the DC busbar through that phase conductor.

[0040] This solution standardizes the potentially chaotic multi-output circuits into two polarity groups: positive and negative. This structure mirrors the basic characteristics of a DC power supply, making the wiring logic clear: to establish a DC circuit, at least one switch must be closed from both the positive and negative groups. Furthermore, this positive-negative pairing selection structure allows for diverse wiring methods through simple switch operations.

[0041] In one embodiment, the combined closed state of the positive and negative disconnect switches is configured to form one of the following DC de-icing topologies: a single-loop topology with two-phase conductors connected in series; or a composite loop topology with a single-phase conductor and two-phase parallel conductors connected in series.

[0042] A single-loop topology with two-phase conductors in series refers to a single closed loop through which direct current flows, consisting of two conductors of different phases connected end-to-end. The current flows out from the positive terminal of the rectifier, enters the first conductor (e.g., phase A), flows to the end of the line, enters the second conductor connected in series with it (e.g., phase B), and finally flows back to the negative terminal of the rectifier from the second conductor. In this topology, the total resistance of the de-icing circuit is the sum of the resistances of the two phase conductors. According to Ohm's law, under a given DC voltage, the de-icing current generated by this topology is relatively moderate. A composite loop topology with a single-phase conductor and two parallel conductors in series refers to a composite closed loop through which direct current flows, consisting of one conductor connected in series with two other parallel conductors. The current flows out from the positive terminal of the rectifier, enters the single conductor (e.g., phase A), flows to the end of the line, splits into the two parallel conductors (e.g., phases B and C), and finally converges back to the negative terminal of the rectifier. In this topology, the total resistance of the de-icing circuit is the sum of the resistance of the single conductor and the resistance of the two parallel conductors. Because parallel connection reduces the loop resistance, this topology can generate a larger de-icing current than the first topology under the same DC voltage.

[0043] As can be seen, Topology 1 (two phases in series) is suitable for scenarios where the conductor resistance is relatively small, the required de-icing current is moderate, or where both phases need to be de-iced simultaneously. Its current is uniform and control is simple. Topology 2 (one phase going to two phases) is suitable for scenarios where the line resistance is large and a larger current is needed to generate sufficient heat (especially for large cross-section conductors or severely iced conductors). By reducing the total circuit resistance through parallel connection, a larger current can be output within the equipment's voltage capability range.

[0044] In one embodiment, the protection and control module includes a status monitoring unit and a circuit breaker control unit; the status monitoring unit is used to collect the output voltage and current of the de-icing transformer and / or the output voltage and current of the rectifier module in real time; the circuit breaker control unit is used to automatically control the de-icing circuit breaker to trip when the status monitoring unit detects that the electrical quantity exceeds a preset threshold.

[0045] The status monitoring unit (SMU) is the hardware and software combination within the protection and control module responsible for sensing and collecting key operating parameters of the protected equipment. It typically includes voltage transformers, current transformers, signal conditioning circuits, analog-to-digital converters, and corresponding data acquisition programs. The SMU's monitoring objects are explicitly defined as the output electrical quantities of the de-icing transformer and rectifier module. Specifically, this includes the transformer's output voltage and current, and / or the rectifier module's output voltage and current. The transformer's output voltage and current directly reflect the output power status in AC de-icing mode and the rectifier module's input energy status in DC de-icing mode. The rectifier module's output voltage and current directly determine the output power and line heating effect in DC de-icing mode. The circuit breaker control unit is the core of the protection and control module responsible for logical judgment and executing protection actions. The circuit breaker control unit continuously receives data from the SMU, runs protection algorithms, and issues a tripping command when a fault is detected. When any electrical quantity (voltage or current) collected by the SMU exceeds a preset threshold, the circuit breaker control unit automatically sends a control signal to drive the de-icing circuit breaker to trip. Preset thresholds are a set of safety limits that are pre-set and stored in the protection control unit. These limits are scientifically set based on the rated parameters, insulation level, thermal stability, and line withstand capacity of the protected equipment (transformer, rectifier module). For example, the overvoltage threshold may be set to 1.2 times the rated voltage, the overcurrent threshold to 1.3 times the rated current, or based on the inverse time curve of thermal accumulation.

[0046] In one embodiment, the device is a fixed installation structure or a movable structure mounted on a mobile platform.

[0047] A fixed-installation structure refers to the permanent or semi-permanent installation of all or core components of the AC / DC dual-purpose de-icing device of this application in a fixed location or foundation. This structure is typically closely integrated with specific power facilities (such as substations or switchyards). If the AC / DC dual-purpose de-icing device is integrated into a dedicated area or building within a substation, its input power is directly drawn from the substation busbar, and its output port is connected to the substation outgoing line via a fixed cable trench or overhead line. A mobile structure mounted on a mobile platform refers to the integrated installation of all core components of the AC / DC dual-purpose de-icing device of this application on a carrier with autonomous or traction mobility. For example, a vehicle-mounted type integrates the AC / DC dual-purpose de-icing device into the cargo compartment of a large truck or trailer. Alternatively, a containerized / modular type installs the AC / DC dual-purpose de-icing device of this application within a standard container or customized modular container, which can be transported by truck, trailer, or rail. Upon arrival at the site, external wiring is required for operation. As can be seen, the AC / DC dual-use ice-melting device of this application, as a complete functional unit, can be easily transferred and deployed between different locations.

[0048] Please see Figure 1 , Figure 1 This is a schematic diagram of a preferred embodiment of an AC-DC dual-purpose ice-melting device provided by the present invention. This embodiment provides an AC-DC dual-purpose ice-melting device, including an ice-melting circuit breaker QF, an ice-melting transformer T, two sets of ice-melting disconnect switches QS1 and QS2, a rectifier module Z, DC output combination disconnect switches K1-K6, and a protection and control module S. The ice-melting circuit breaker QF is connected in series between the ice-melting power supply and the ice-melting transformer, used to control the on / off state of the ice-melting device and the ice-melting power supply. The ice-melting transformer T is connected in series between the ice-melting circuit breaker QF and the disconnect switches QS1 and QS2, and the output voltage and current can be controlled by controlling the position of the adjustment switch, realizing flexible adjustment of the ice-melting current and ice-melting distance. The disconnect switch QS1 is connected in series between the secondary side of the ice-melting transformer T and the AC output port. When QS1 is closed, the device operates in AC ice-melting mode, and can simultaneously melt ice on all three phases. The operating states of switches QS1, QS2, and K1-K6 (disconnect switches) at this time are as follows: Figure 2 As shown.

[0049] The input terminal of rectifier module Z is electrically connected to disconnector switch QS2 to rectify AC power into DC power. Its positive output terminal is connected to DC output combination switches K1-K3, and its negative output terminal is connected to DC output combination switches K4-K6. Specifically, rectifier module Z uses a six-pulse rectifier valve, comprising six single-valve converters. Every two single-valve converters are connected in series to form a converter branch, and every two converter branches are connected in parallel. A cooling fan is used for heat dissipation. Interlocking circuits are installed between DC output combination switches K1-K6, K1 and K4, K2 and K5, and K3 and K6, preventing simultaneous closure. These switches are electrically connected to the three phases A, B, and C of the AC output port, respectively. When K1 is closed, phase A output is positive; when K4 is closed, phase A output is negative. When K2 is closed, phase B output is positive; when K5 is closed, phase B output is negative. When K3 is closed, phase C output is positive; when K6 is closed, phase C output is negative. When two phases are connected in series for de-icing, de-icing can be performed on both phase conductors at a time (this is called a "one-way" connection method, see...). Figure 4 When two phases are connected in parallel and a third phase is connected in series for de-icing, de-icing can be performed on one phase conductor at a time. After switching phases, de-icing can be performed on the other phases (this is called the "one-out-two-back" wiring method, see...). Figure 5 ).

[0050] Disconnector QS2 is connected in series between the secondary side of the de-icing transformer T and the rectifier module Z. When QS2 is closed, the device operates in AC de-icing mode. Taking phases A and B connected to the positive terminal and phase C connected to the negative terminal as an example, the operating states of switches QS1, QS2, and K1-K6 (disconnectors) are as follows: Figure 3 As shown; The ice-melting device is equipped with a protection and control module S, including a circuit breaker QF control unit, an ice-melting transformer T, and a status monitoring unit for the rectifier module Z. The ice-melting circuit breaker QF control unit can manually or automatically open and close the ice-melting circuit. When ice melting begins, the circuit breaker can be manually closed; in case of an emergency, the circuit breaker can be manually opened. During ice melting, the status monitoring unit monitors the output voltage and current of the ice-melting transformer T and the rectifier module Z. When an abnormal electrical quantity is detected, the protection and control module S outputs a trip protection signal to the ice-melting circuit breaker QF. The circuit breaker QF automatically trips after responding to the trip protection signal.

[0051] To facilitate understanding, this project uses a real-world case to demonstrate the practicality of the device. The main component parameters of the device are as follows: (1) De-icing transformer: rated capacity 17MVA, rated voltage 10kV / 3.6kV, rated current 982A / 1370A, voltage range adjustable from 3600V to 500V; (2) Rectifier module: rated power 13.75MW, rated output DC voltage 6250V, rated output DC current 2200A.

[0052] The ice melting distance for AC and DC ice melting modes can be calculated using equations (1) and (2) respectively: (1) (2) Where U is the secondary output voltage of the de-icing transformer; This represents the selected ice-melting current. Wherein, To communicate the ice-melting distance under the ice-melting mode; This refers to the ice-melting distance in DC ice-melting mode. , These represent the resistance and reactance values ​​per unit length of the conductor, respectively; m is related to the connection method of the de-icing circuit during DC de-icing, with a value of 2 when using a "one-to-one-back" connection method and a value of 1.5 when using a "one-to-two-back" connection method.

[0053] In this specific example, when the secondary side of the de-icing transformer is selected at 3600V, the minimum de-icing current is used, and the DC de-icing mode is selected with a "one-way, two-way" connection, the maximum de-icing distance can be achieved in both AC and DC de-icing modes. The maximum de-icing distance for different conductor types applicable to this specific example is shown in Table 1 below. As can be seen from the table, this specific example can be used for transmission and distribution lines of different voltage levels from 10kV to 220kV, avoiding the limitations of traditional de-icing devices in application at different voltage levels and reducing equipment configuration costs. To meet the de-icing requirements of higher voltage levels and more conductor types, this can be achieved by optimizing the selection of components such as the de-icing transformer and rectifier module.

[0054] Table 1. Summary of Maximum Melting Distance for Specific Examples

[0055] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0056] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. An AC / DC dual-purpose ice-melting device, characterized by comprising: The device comprises: a de-icing circuit breaker, an input end of which is connected to a de-icing power supply, and an output end of which is electrically connected to a primary side of a de-icing transformer; the de-icing transformer, a secondary side of which has a voltage regulation function, and the secondary side is electrically connected to an AC mode disconnecting switch and a DC mode disconnecting switch respectively; the AC mode disconnecting switch is connected between the secondary side and an AC output port; the DC mode disconnecting switch is connected between the secondary side and an input end of a rectifier module, and an interlocking structure is arranged between the AC mode disconnecting switch and the DC mode disconnecting switch; the rectifier module, a DC output end of which is electrically connected to input ends of a plurality of output knife switches; the plurality of output knife switches, output ends of which are connected to a DC de-icing circuit; a protection module, which is signal-connected to the de-icing circuit breaker, the de-icing transformer and the rectifier module, and is used for monitoring and controlling the operation of the device.

2. The AC / DC dual-purpose ice melting device according to claim 1, characterized in that, The voltage regulation function of the de-icing transformer is realized by a plurality of tap-off taps of the secondary side winding to achieve multi-gear voltage regulation.

3. The AC / DC dual-purpose ice melting device according to claim 1, characterized in that, When the AC mode disconnecting switch is closed and the DC mode disconnecting switch is open, the device is in an AC de-icing mode. When the DC mode disconnecting switch is closed and the AC mode disconnecting switch is open, the device is in a DC de-icing mode.

4. The AC / DC dual-purpose ice melting device according to claim 1, characterized in that, The rectifier module is a three-phase bridge rectifier circuit.

5. The AC / DC dual-purpose ice melting device according to claim 4, characterized in that, The rectifier module is specifically a six-pulse rectifier valve, which comprises six commutation single valves composed of power semiconductor devices.

6. The AC / DC dual-purpose ice melting device according to claim 5, characterized in that, The six-pulse rectifier valve is equipped with a forced air cooling heat dissipation device.

7. The AC / DC dual-purpose ice melting device according to claim 1, characterized in that, The DC output combination knife switch comprises a positive electrode knife switch group and a negative electrode knife switch group. The positive electrode knife switch is connected between a DC output positive electrode of the rectifier module and the DC de-icing circuit. The negative electrode knife switch is connected between a DC output negative electrode of the rectifier module and the DC de-icing circuit, and an interlocking circuit is arranged between the positive electrode knife switch and the negative electrode knife switch corresponding to the same phase line in the DC de-icing circuit.

8. The AC / DC dual-purpose ice melting device according to claim 7, characterized in that, The combination closed state of the positive electrode knife switch and the negative electrode knife switch is configured to form one of the following DC de-icing topologies: a single-loop topology of two-phase conductors in series; or a composite loop topology of a single-phase conductor and two-phase parallel conductors in series.

9. The AC / DC dual-purpose ice melting device according to claim 1, characterized in that, The protection monitoring and control module comprises a state monitoring unit and a circuit breaker control unit. The state monitoring unit is used for real-time acquisition of output voltage and current of the de-icing transformer and / or output voltage and current of the rectifier module. The circuit breaker control unit is used for automatically controlling the de-icing circuit breaker to trip when the state monitoring unit detects that an electrical quantity exceeds a preset threshold.

10. The AC / DC dual-purpose ice melting device according to claim 1, characterized in that, The device is a fixed installation structure or a movable structure mounted on a mobile platform.

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