Power distribution network ice melting circuit and device without power interruption

Abstract

The application discloses a power distribution network non-power-off ice melting circuit and equipment, and relates to the technical field of circuits.The circuit comprises a static var generator, a first switch and an interface device.The static var generator is connected with a power supply area on an alternating current side and connected with the first end of the first switch on a direct current side;the interface device is connected with the second end of the first switch and the first end of an icing line respectively, and the second end of the icing line is used for grounding.When ice melting, the first switch is closed and the second end of the icing line is grounded.When the icing line contains multiple-phase sub-lines, only the target sub-line is grounded, each phase sub-line has a corresponding grounding switch, and the icing line can be upstream or downstream of the power supply area.The interface device contains the first and second switch elements in parallel, when controlling the ice melting current, one switch element is chopped and the other switch element is disconnected, or the two elements are alternately turned on at a first frequency;when injecting a direct current, a single switch element is turned on and the other is disconnected.The circuit can melt ice without power-off of the power distribution network.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit, and particularly relates to an ice melting circuit and equipment for power distribution network without power outage. BACKGROUND

[0002] In the power system, the power distribution network as a link connecting the power transmission network and the user terminal, the safe and stable operation is related to the power quality of social production and residents' life. In many regions, the climate is cold in winter, and the humidity in the air is relatively large. The power distribution network line is prone to icing in low temperature environment. Icing not only increases the weight of the line, causes the tower to tilt, breaks the line, and even causes the tower to collapse, but also may cause problems such as insulator flashover and line short circuit, which seriously threatens the safe and reliable operation of the power distribution network. Therefore, timely and effective ice melting measures are crucial to ensure the normal operation of the power distribution network.

[0003] For the icing problem of the power distribution network, the traditional ice melting scheme mainly relies on the additional construction of a dedicated ice melting circuit. Specifically, during the planning or reconstruction of the power distribution network, a set of ice melting circuit system independent of the normal power transmission line is designed and constructed in advance. When the icing of the line reaches a certain degree, the power distribution network in the relevant area needs to be powered off first, and the line is switched from the normal operation state to the ice melting mode. By starting the dedicated ice melting power supply (such as a direct current power supply or a specific alternating current power supply device), a large current is delivered to the ice melting circuit, and the ice layer on the line is melted by the Joule heat generated by the current. The premise of this scheme is that the line must be powered off first. Only in the state of power failure, the ice melting process can be started to avoid damage to normal electrical equipment caused by large current during ice melting.

[0004] However, the power outage operation will directly cause the interruption of user power supply, causing inconvenience to residents' daily life, especially in cold winter, the power outage may affect the basic life needs such as heating and lighting; for industrial users, power outage will cause production equipment to stop, disrupt production plans, and cause economic losses. The power outage range of the power distribution network is often difficult to accurately control, and may involve a large area, affecting many users, and in severe cases, it may even cause energy supply crisis in local areas. In addition, frequent power outage and power supply operations will also cause certain wear and tear to the power equipment itself, affecting the service life and reliability of the equipment. At the same time, since the traditional scheme needs to be started after power failure, there is a certain time interval from the discovery of icing to the implementation of ice melting, which may cause the ice layer to thicken further, increasing the difficulty and time cost of ice melting. Moreover, during the ice melting process, since the line is in a power failure state, the running state of the power distribution network and the ice melting effect cannot be monitored in real time, and it is difficult to adjust the ice melting strategy in a timely manner according to the actual situation, affecting the ice melting efficiency and safety.

[0005] It can be seen that the main disadvantage of the traditional ice melting scheme for the power distribution network is that the power outage has a greater negative impact. SUMMARY

[0006] The application provides an ice melting circuit and equipment for power distribution network without power interruption, which can melt ice without power interruption of the power distribution network.

[0007] To achieve the above object, the application adopts the following technical scheme:

[0008] In the first aspect, the application provides an ice melting circuit for power distribution network without power interruption, which comprises a static var generator, a first switch and an interface device.

[0009] The AC side of the static var generator is used to be connected with a power supply area, and the DC side of the static var generator is used to be connected with the first end of the first switch.

[0010] The first end of the interface device is used to be connected with the second end of the first switch, and the second end of the interface device is used to be connected with the first end of an icing line.

[0011] The second end of the icing line is used to be grounded.

[0012] The interface device comprises a first switch element and a second switch element, and the first switch element and the second switch element are connected in parallel, and the two ends of the first switch element and the second switch element are respectively connected with the first end and the second end of the interface device.

[0013] Optionally, when the icing line needs to be melted, the first switch is closed, and the second end of the icing line is grounded.

[0014] Optionally, the icing line comprises a plurality of phase sub-lines.

[0015] When a target sub-line in the plurality of phase sub-lines needs to be melted, the first switch is closed, the target sub-line is grounded, and the sub-lines other than the target sub-line in the plurality of phase sub-lines are not grounded.

[0016] Optionally, the icing line is downstream of a power supply area; or,

[0017] The icing line is upstream of a power supply area.

[0018] Optionally, when the ice melting current flowing through the icing line needs to be controlled:

[0019] The first switch element is controlled to be in a chopping mode, and the second switch element is controlled to be in an open state; or,

[0020] The second switch element is controlled to be in a chopping mode, and the first switch element is controlled to be in an open state.

[0021] Optionally, when it is required to control the ice-melting current flowing through the icing line:

[0022] The first switch element and the second switch element are controlled to be in an alternating conduction mode at a first frequency.

[0023] Optionally, when it is required to inject a direct current into the icing line:

[0024] The first switch element is controlled to be on, and the second switch element is controlled to be off; or,

[0025] The first switch element is controlled to be off, and the second switch element is controlled to be on.

[0026] Optionally, each phase sub-line in the multi-phase sub-line is grounded through a corresponding grounding switch.

[0027] In a second aspect, the application provides a power distribution network non-stop ice-melting device, which comprises the power distribution network non-stop ice-melting circuit described above.

[0028] From the above technical solution, the application has at least the following beneficial effects:

[0029] Firstly, compared with the traditional scheme which needs to be powered off to start ice-melting, causing inconvenience to residents and economic loss to industrial users, the scheme forms a loop through the static var generator direct current side, the interface device and the icing line grounding, which can realize ice-melting without interrupting the normal power supply of the power distribution network, fundamentally avoiding the influence on people's livelihood and economic loss caused by power failure, and reducing the wear and tear of power equipment caused by frequent power failure, prolonging the service life of the equipment.

[0030] Secondly, the traditional scheme relies on special ice-melting power supply main equipment and is passive, while the present scheme directly uses the existing static var generator in the transformer area for upgrading and modification, without the need to add a large number of special equipment, reducing the cost investment, and the ice-melting power can be flexibly expanded by increasing the number of static var generators participating in the transformer area, solving the problems of transportation difficulty and insufficient ice-melting power of traditional ice-melting equipment.

[0031] Thirdly, the present method supports sequential phase-by-phase ice-melting of multi-phase sub-lines, which is controlled through independent grounding switches of each phase, and can accurately control the size and type (direct current or high-frequency alternating current) of ice-melting current by means of the chopping mode and alternating conduction mode of the switch elements in the interface device, avoiding damage to the equipment by large current, and improving the ice-melting efficiency by using the skin effect of high-frequency current, and at the same time, the real-time monitoring of the operation state of the power distribution network and the ice-melting effect can be realized without power failure, which facilitates timely adjustment of strategies and solves the problems of long time interval and difficult control of effect in traditional ice-melting.

[0032] In addition, the scheme compatible icing line is suitable for different scenes of upstream and downstream of power supply stations, has wide application range, and further guarantees the safe and stable operation of the distribution network in the ice and snow weather, and provides effective technical support for constructing a strong and resilient distribution network.

[0033] It should be understood that the description of technical features, technical solutions, beneficial effects or similar language in the present application does not imply that all features and advantages can be achieved in any single embodiment. On the contrary, it can be understood that the description of a feature or a beneficial effect means that the specific technical feature, technical solution or beneficial effect is included in at least one embodiment. Therefore, the description of technical features, technical solutions or beneficial effects in the specification does not necessarily refer to the same embodiment. Further, the technical features, technical solutions and beneficial effects described in the embodiments can be combined in any appropriate manner. Those skilled in the art will understand that the embodiments can be implemented without one or more specific technical features, technical solutions or beneficial effects of a specific embodiment. In other embodiments, additional technical features and beneficial effects can be identified in specific embodiments that do not embody all embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A schematic diagram of an ice melting circuit of a distribution network without power interruption is provided for embodiments of the present application;

[0035] Figure 2 A current flow schematic diagram of an ice melting circuit of a distribution network without power interruption is provided for embodiments of the present application;

[0036] Figure 3 A current flow schematic diagram of another ice melting circuit of a distribution network without power interruption is provided for embodiments of the present application;

[0037] Figure 4 An icing line containing a multi-phase sub-line is provided for embodiments of the present application;

[0038] Figure 5 A schematic diagram of an icing line upstream and downstream of a power supply station is provided for embodiments of the present application;

[0039] Figure 6 A schematic diagram of a multi-power supply station is provided for embodiments of the present application. DETAILED DESCRIPTION

[0040] The terms "first", "second" and "third" and the like in the specification and drawings of the present application are used to distinguish different objects, and are not used to limit a specific order.

[0041] In the embodiments of the present application, the words such as "exemplary" or "for example" are used to mean serving as an example, instance, or illustration, in no way implying any preference or relation by equivalency. In fact, the use of such words is intended to present concepts in a concrete manner.

[0042] For the sake of clear and concise description of the following embodiments, first give a brief introduction of the related art:

[0043] As a key link connecting the power transmission network and user terminals in the power system, the main function of the distribution network is to convert the high-voltage power transmitted by the power transmission network into medium and low-voltage power that meets the needs of residents' life and industrial production through transformer step-down and other ways, and distribute it to each power consumption node, which is directly related to the power quality and stability of social production and residents' life.

[0044] Iced line refers to the line on which ice layer is condensed on the surface of the line under the climate conditions of cold and high humidity. The ice layer will increase the weight of the line, which may cause mechanical failures such as tower tilting, wire breaking, and tower collapse, and also damage the insulation performance of the line, leading to electrical failures such as insulator flashover and line short circuit, which seriously threatens the safe operation of the distribution network.

[0045] Static var generator (SVG) is a kind of reactive power compensation device based on power electronic technology, which can quickly and continuously adjust the reactive power in the distribution network, improve the power factor of the power grid, and stabilize the voltage of the power grid. Its structure includes an AC side and a DC side. The AC side can be directly connected with the power supply area and connected to the main loop of the distribution network. The DC side can be used as an energy output end to supply power to specific loads or functional modules.

[0046] The interface device is used in the present application to connect the DC side of the static var generator and the key components of the iced line, which is composed of a first switching element S1 and a second switching element S2 in parallel. By controlling the on-off state or working mode of the two switching elements, the working mode is chopping mode and alternate conduction mode, the type, size and frequency of the ice-melting current can be accurately controlled, which is a control unit to ensure the safety and efficiency of the ice-melting process.

[0047] The power supply area is the basic power supply facility in the distribution network, which is mainly responsible for stepping down the power transmitted by the upper power grid to the voltage level suitable for the users in the area, and is an important hub between the distribution network and the user terminals. The upstream and downstream lines of the power supply area may have icing problems due to climate factors.

[0048] In the ice control scene of the power distribution network, the traditional ice melting scheme needs to rely on power failure to start, which leads to user power interruption and obvious economic loss. Moreover, the ice melting efficiency is low and the flexibility is poor, which cannot meet the dual needs of safe and stable operation of the power distribution network and uninterrupted power supply. This is the main problem to be solved in the current ice control field of the power distribution network.

[0049] The traditional ice melting scheme needs to build a special ice melting circuit independent of the main loop of the power distribution network. When ice melting, the icing line needs to be disconnected from the main loop of the power distribution network and then connected to the special ice melting power source, such as a direct current power source or a specific alternating current power source. Because the ice melting current intensity output by the special ice melting power source is much larger than the normal power supply current, if power is not cut off, the large current will flow into the main loop of the power distribution network, damaging normal power equipment such as household appliances and industrial production equipment. Therefore, power failure is a necessary prerequisite for the traditional scheme to start ice melting, which directly leads to user power interruption.

[0050] From the actual application, power failure will not only affect the basic living needs of residents such as heating and lighting, but also cause industrial users' production equipment to shut down, disrupt production plans, and cause direct economic losses. At the same time, the power failure range of the power distribution network is difficult to accurately control and is easy to involve a large area, which may cause local energy supply crisis. In addition, frequent power failure and power transmission operations will impact power supply areas, line switches and other power equipment, accelerate equipment wear and tear, and shorten the service life.

[0051] The traditional scheme has a long time interval from discovering ice to completing power failure switching and then starting ice melting. During this period, the ice layer may further thicken, increasing the difficulty and time cost of ice melting. Moreover, the line is in a power failure state during ice melting, which cannot monitor the operating parameters of the power distribution network in real time, such as line current, voltage, and ice thickness. It is difficult to dynamically adjust the ice melting strategy according to the ice melting effect, such as current size and ice melting duration. The problems of incomplete ice melting or excessive energy consumption may occur, and the efficiency and safety of ice melting cannot be guaranteed.

[0052] The traditional special ice melting circuit needs to be pre-constructed during the planning or reconstruction stage of the power distribution network. Not only is the initial investment cost high, but it can only cover the pre-set icing line. For icing lines at different positions such as upstream and downstream of the power supply area, different ice melting circuits need to be designed accordingly, which has poor scene adaptability. At the same time, the special ice melting power source is mostly a large device, which is difficult to transport and install. It cannot flexibly expand the ice melting power according to the icing range, further limiting its application scenarios.

[0053] In view of the problems of the traditional ice melting scheme, such as the need for power failure, low efficiency, and poor adaptability, the inventive concept of the present application focuses on activating existing equipment resources and realizing accurate ice melting without power failure. The specific scheme is as follows.

[0054] The existing device is multiplexed, special power supply investment is avoided, and the original function of the static var generator (SVG) which has been normalized in the power distribution network is used as the main source of ice melting energy. The original function of the static var generator (SVG) is to adjust the reactive power of the power grid and stabilize the voltage. The original function of the static var generator (SVG) is innovatively excavated to tap the output potential of the direct current side, so that the special ice melting power supply and the independent ice melting circuit do not need to be additionally built. Both the front-end equipment procurement and construction cost are reduced, and the problem of power grid equipment redundancy caused by special devices is avoided.

[0055] An independent ice melting circuit is constructed to ensure uninterrupted operation. By designing a closed loop circuit of a power supply area, an SVG, a switching element, an interface device, an iced line and a grounding end (the second end of the grounding end is connected with the iced line), the ice melting current is strictly limited in the independent circuit and is not connected with the main power supply circuit of the power distribution network. The interaction between the ice melting large current and the normal power equipment is isolated from the source, the impact and damage of the large current on household appliances and industrial equipment are completely avoided, and the goal of ice melting without power interruption is achieved.

[0056] Control and multi-scene adaptation. With the double switching element S1 and S2 structure of the interface device, the ice melting current type can be flexibly adjusted (direct current / high frequency alternating current), and the size can be controlled (chopper mode / alternate conduction mode). The optimal ice melting parameters can be dynamically matched according to the working conditions such as the thickness and material of the ice layer. At the same time, the independent grounding control logic is designed according to the differences of the iced line at the upstream and downstream of the transformer substation and the phase separation ice melting scene of the multi-phase sub-line, which greatly improves the scene coverage ability and operation flexibility of the ice melting scheme.

[0057] Real-time controllable regulation and improved ice melting efficiency. Due to the uninterrupted operation characteristics, the key parameters of the power distribution network can be monitored in real time during the ice melting process, such as line current, voltage, ice layer thickness, etc. Combined with the dynamic control function of the interface device, the ice melting strategy can be optimized in time according to the monitoring data, such as adjusting the current intensity and the ice melting time. The low efficiency problem of the ice layer not being melted through is avoided, and the waste of resources caused by excessive energy consumption is prevented. The ice melting efficiency and operation safety are double guaranteed.

[0058] In order to make the technical scheme of the present application clearer and easier to understand, the following will introduce a power distribution network uninterrupted ice melting circuit provided by the embodiment of the present application in combination with the drawings. As shown in Figure 1 The figure is a power distribution network uninterrupted ice melting circuit provided by the embodiment of the present application.

[0059] A power distribution network uninterrupted ice melting circuit comprises a static var generator, a first switch and an interface device. The alternating current side of the static var generator is used for connecting with a power supply area, and the direct current side of the static var generator is used for connecting with the first end of the first switch. The first end of the interface device is used for connecting with the second end of the first switch, and the second end of the interface device is used for connecting with the first end of an iced line. The second end of the iced line is used for grounding.

[0060] The static reactive generator is an SVG in Figure 1 The first switch includes two, respectively Figure 1 The S D1 and S D2 , S D1 represents the positive electrode, S D2 represents the negative electrode, and the interface device is Figure 1 The part surrounded by the red dashed line in GG S GG represents the grounding switch.

[0061] The SVG is a key device in the existing power distribution network, which not only retains the original grid regulation function, but also provides energy for ice melting.

[0062] From the perspective of connection, its AC side is directly connected to the power supply area, which has a dual role: on the one hand, through interaction with the main loop of the power distribution network, it continuously adjusts the reactive power in the power grid, stabilizes the user end voltage, and ensures the normal power use of residents and industrial production is not affected by ice melting operation, which is the basis of uninterrupted power supply;

[0063] On the other hand, after obtaining power from the power supply area, it is converted to DC power through internal power electronic modules and output through the DC side, becoming the source of energy needed for ice melting, without the need to build a dedicated ice melting power supply, greatly reducing the equipment investment cost.

[0064] Its DC side is specially connected to the first switch, which can strictly control the flow direction of ice melting energy and avoid energy from flowing into the main loop of the power distribution network, thereby isolating the damage of large ice melting current to normal power equipment from the source.

[0065] The first switch is a key component that determines the start and stop of the ice melting loop, and its function focuses on accurately controlling the loop on and off while ensuring the safety of the power grid in non-ice melting state.

[0066] In the non-ice melting phase, the first switch is in the open state, at which time the DC side of the static reactive generator is completely isolated from the subsequent interface device and ice-covered line, and the static reactive generator only focuses on grid reactive power regulation through the AC side, without any interference to the power supply of the main loop of the power distribution network, and the operation mode is completely consistent with the traditional power distribution network.

[0067] When it is monitored that the ice-covered line needs to be melted, the first switch is closed, immediately connecting the energy channel from the DC side of the static reactive generator to the interface device, allowing ice melting energy to be smoothly transmitted. Since the first switch only controls the ice melting exclusive loop and does not involve the switch operation of the main loop of the power distribution network, there is no need to power off the power distribution network, solving the problem of large power outage impact in traditional ice melting solutions.

[0068] The interface device is between the first switch and the icing line, and is a transition component connecting the two. Its functions mainly lie in current regulation and stable energy transmission.

[0069] From the perspective of physical connection, the first end of the interface device is closely connected with the second end of the first switch, and the second end of the interface device is directly connected with the first end of the icing line, forming an intermediate channel for energy transmission. The internal wires and insulation structure can withstand the large current during the ice melting process, prevent the line from overheating or insulation damage, and ensure the safety of energy transmission.

[0070] From the perspective of regulation capacity, the interface device can adjust the current characteristics according to the actual needs of the icing line: when it is necessary to inject direct current for ice melting, the on-off control of the internal switch element is used to output unidirectional direct current; when it is necessary to adjust the size of the ice melting current, the chopping mode or the alternate conduction mode can be switched to, and the current intensity can be accurately controlled by adjusting the conduction duty cycle, so as to adapt to the ice melting needs of different ice layer thicknesses and different material lines, and make the ice melting process more efficient and flexible.

[0071] The icing line is the direct object of the ice melting operation, and the connection design is to ensure that the current flows to generate heat and form a complete loop.

[0072] The first end of the icing line receives the ice melting current through the interface device. When the current flows through the wire, it will generate Joule heat due to the resistance of the wire itself, and the heat will directly act on the ice layer on the surface of the wire, causing the ice layer to gradually melt and achieve the ice melting goal.

[0073] The second end of the icing line is specially designed to be grounded, which is the key to forming a closed ice melting loop: the current output from the direct current side of the static var generator flows through the first switch, the interface device, and the icing line, and finally flows into the ground through the grounding end, and then flows back to the static var generator through the grounding system of the power supply area, forming a complete current loop. If the second end of the icing line is not grounded, the current cannot circulate, Joule heat cannot be generated, and the ice melting function will be completely disabled. At the same time, the grounding design can also stabilize the line potential and avoid the safety hazard of excessive voltage to ground during the ice melting process.

[0074] Combining the connection relationship of each component with its function, the running logic of the circuit can be clearly sorted out, and the advantage is that the ice melting loop and the main power supply loop are completely independent and do not interfere with each other.

[0075] From the perspective of energy acquisition and transmission path, the power of the power supply area is divided into two parts: one part is directly supplied to the main loop of the distribution network to ensure normal power consumption of users; the other part is input through the alternating current side of the static var generator, converted and output from the direct current side, and finally transmitted to the icing line through the closed first switch and the interface device.

[0076] From the perspective of loop closure, the grounding design at the second end of the icing line allows current to flow out of the icing line and return through the grounding end, forming a complete closed loop of static var generator, first switch, interface device, icing line, grounding end, and static var generator, ensuring that current continuously flows through the icing line to generate heat.

[0077] From the perspective of uninterrupted power supply mechanism, the AC side of the static var generator is always connected to the main loop of the distribution network, continuously performing the function of reactive power regulation; the ice-melting current only circulates in the independent ice-melting loop and does not flow into the main power supply loop, so there is no need to interrupt user power supply, perfectly achieving the goal of uninterrupted ice-melting.

[0078] The interface device includes a first switch element and a second switch element, and the first switch element and the second switch element are connected in parallel. The two ends of the first switch element and the second switch element are connected to the first end of the interface device and the second end of the interface device, respectively.

[0079] The first switch element is S1 in Figure 1 , and the second switch element is S2 in Figure 1 .

[0080] Parallel connection specifically means that one end of the two switch elements is commonly connected to form a common connection end, which is connected to the first end of the interface device; the other end of the two switch elements is also commonly connected to form a common connection end, which is connected to the second end of the interface device. In simple terms, after flowing into the first end of the interface device, the current will be divided into two independent paths, passing through the first switch element and the second switch element respectively, and then converging at the second end to flow out. This connection method allows the two switch elements to work independently and cooperatively, providing structural support for subsequent flexible control of ice-melting current.

[0081] It should be noted that the switch element here is not a simple switch that can only realize on / off in the traditional sense, but an element with power electronic control capability, such as IGBT, thyristor, etc. It can not only quickly switch between on and off states, but also accurately adjust the on time and frequency in a specific mode (such as chopper mode), which is the key prerequisite for the interface device to realize the regulation of current type and size.

[0082] Based on the parallel design of the two switch elements, the first end of the interface device and the second end of the interface device are clearly defined: among the common connection ends of the two switch elements, the end that receives external energy (energy from the current in the first switch) is the first end of the interface device; the end that transmits energy outward (energy flowing to the icing line) is the second end of the interface device.

[0083] When it is necessary to inject a direct current ice-melting current into the iced line, only one of the switch elements can be controlled to be conductive, at which time the current only passes through the single switch element to form a unidirectional path, and a stable direct current is output; if high-frequency alternating current needs to be injected subsequently, the two switch elements can be controlled to be conductively switched at a specific frequency to periodically change the direction of the output current, so that high-frequency alternating current output is realized, and no additional conversion module needs to be added, but only the conduction logic of the elements can switch the current type.

[0084] Two switch elements are connected in parallel to form a redundant backup: if one of the switch elements fails (such as being unable to conduct or being disconnected), the other switch element can be immediately switched to work alone to ensure that the ice-melting process is not interrupted. For example, the first switch element is originally used to control the chopper-regulated current, and if the first switch element fails, the first switch element can be disconnected, and the second switch element can be enabled to continue to operate in the chopper mode, so that the ice-melting process is not stalled due to the failure of a single element, and the overall reliability of the circuit is improved.

[0085] When the two switch elements are operated in cooperation, the current regulation range can be expanded and the accuracy can be improved. For example, when small current ice-melting is needed, a single switch element can be controlled to operate in a low-duty-cycle chopper mode; when large current ice-melting is needed, the two switch elements can be controlled to be conductive at the same time (or to be conductive alternately at a high duty cycle), so that the output intensity is improved by superimposing the currents; at the same time, by adjusting the alternating conduction frequency of the two elements, the impedance characteristics of different lines can be adapted, so that the ice-melting current is stable and meets the requirements, and the line is prevented from being damaged due to excessive current or from being incompletely melted due to insufficient current.

[0086] When ice-melting of the iced line is needed, the first switch is closed, and the second end of the iced line is grounded.

[0087] The closing of the first switch opens an energy output channel, so that ice-melting energy can be transmitted from the static var generator to the iced line; the grounding of the second end of the iced line builds an energy return channel, so that the current can circulate; only when the output channel and the return channel are opened at the same time, the ice-melting loop can be truly closed, the current can continuously flow through the iced line to generate heat, and the ice-melting can be started.

[0088] When it is necessary to control the ice-melting current flowing through the iced line: the first switch element is controlled to be in a chopper mode, and the second switch element is controlled to be in a disconnected state; or the second switch element is controlled to be in a chopper mode, and the first switch element is controlled to be in a disconnected state.

[0089] Chopper mode is a mode of operation in the field of power electronics that regulates electrical energy parameters (such as voltage and current) through high-frequency on-off switching elements. It uses the rapid switching of switching elements to cut continuous electrical energy into discrete pulses, which are then processed by subsequent circuits to obtain the required current or voltage output. Chopper mode is commonly used in scenarios that require accurate energy regulation, such as ice-melting current control.

[0090] From the working principle, the realization of chopper mode depends on switching elements with high-frequency on-off capability (such as IGBT). When the switching element is in chopper mode, it will switch on and off repeatedly at a very high frequency (usually up to tens of thousands of hertz) under the instruction of the control system. During the on period, electrical energy is transmitted to the load (in this case, the icing line) through the switching element; during the off period, the electrical energy transmission is temporarily interrupted. By adjusting the ratio of on time to on-off period, i.e., the duty cycle, the total amount of energy delivered to the load per unit time can be changed, thereby achieving accurate control of the output current size. The calculation expression of the duty cycle is:

[0091]

[0092] where, Duty cycle, value range: 0 ≤ D ≤ 1, can also be converted to percentage form, i.e., 0% ≤ D ≤ 100%; On time of switching element in one on-off period.

[0093] Total on-off period of switching element, i.e., on time and off time, units consistent with T, and period T is inversely proportional to switching on-off frequency f, expression:

[0094]

[0095] where, On-off frequency, unit: hertz (Hz).

[0096] For example: if the on-off period of the switching element is 100 microseconds, and the duty cycle is 50%, it means that the element is on for 50 microseconds and off for 50 microseconds in each period. The energy delivered per unit time is 50% of the full on state, and the output current is also 50% of the full on state. If the duty cycle is adjusted to 80%, the on time becomes 80 microseconds and the off time becomes 20 microseconds. The energy delivered per unit time and the output current are also increased to 80% of the full on state.

[0097] ​​​​​This way of regulating current by adjusting duty cycle is flexible and accurate, and can dynamically adjust the ice-melting current according to the actual needs of the iced line (such as ice thickness, wire material), avoiding damage to the line due to excessive current or incomplete ice melting due to insufficient current.

[0098] In addition, the high-frequency on-off characteristic of the chopping mode can also reduce current fluctuations, making the current output to the iced line more stable. Although the switching element switches at high frequency, the actual current received by the iced line will show a smooth average value because the on-off frequency is much higher than the response speed of the load, and there will be no obvious current impact due to the on-off of the switch, ensuring the safety and stability of the ice-melting process.

[0099] Next, the two cases are analyzed in turn:

[0100] The first case is that the first switching element S1 is in chopping mode, and the second switching element S2 is in an open state.

[0101] The second switching element S2 in the interface device remains completely disconnected and does not participate in any energy transmission, equivalent to being removed from the circuit, avoiding current shunting through the second switching element S2; at the same time, the first switching element S1 enters the chopping mode and works in a high-frequency on-off state.

[0102] Further, the circuit is configured with an overvoltage protector MOV in the interface device, effectively avoiding damage to the DC port and the low-voltage system caused by high-voltage system failure or overvoltage conditions; at the same time, the distribution network is always in a live operating state during the ice-melting process, and operation and maintenance personnel can monitor the power grid operating parameters and ice-melting effect in real time, facilitating timely adjustment of ice-melting strategies according to actual conditions, avoiding the problems of inability to monitor in real time and difficulty in controlling potential risks in traditional power-off ice-melting, and improving the safety and controllability of ice-melting operations.

[0103] Figure 2 A current flow direction diagram of the ice-melting circuit of the distribution network without power interruption provided by the embodiment of the present application, Figure 2 The green dashed line in the figure represents the current flow direction.

[0104] From the first switch S D1 The ice-melting energy (from the static reactive power generator) delivered to the interface device will all flow through the first switching element S1 in chopping mode. By adjusting the duty cycle of the first switching element S1, the energy delivered to the iced line per unit time can be controlled.

[0105] When the ice-melting current needs to be increased, the duty cycle is increased (the conduction time is increased), allowing more energy to flow into the iced line; when the ice-melting current needs to be reduced, the duty cycle is reduced (the conduction time is reduced), reducing energy delivery.

[0106] This way only relies on the first switch element for regulation, the control logic is simple, the response speed is fast, is suitable for the scene of uniform ice thickness, the current regulation precision requirement is medium; Meanwhile, the off state of the second switch element S2 can avoid the influence of fault (such as misdirecting on) on current regulation, and improve the safety of circuit operation.

[0107] The second case is that the second switch element S2 is controlled to be in the chopping mode, and the first switch element S1 is in the off state.

[0108] The control mode is consistent with the first case, only the main regulation unit is switched to the second switch element S2, and the first switch element S1 undertakes the isolation protection function, and the specific logic is as follows.

[0109] The first switch element S1 in the interface device remains completely off, cutting off the energy transmission of the path; the second switch element S2 enters the chopping mode and works in the high-frequency on-off state, becoming the only channel for ice melting energy transmission and regulation.

[0110] Figure 3 The current flow direction schematic diagram of another power distribution network uninterrupted ice melting circuit provided by the embodiment of the application, Figure 3 The blue dashed line in the figure indicates the current flow direction.

[0111] The ice melting energy from the first switch is all directed to the second switch element S2 in the chopping mode, and by adjusting the duty cycle of the second switch element S2, the size of the ice melting current is regulated, the higher the duty cycle, the more energy is transmitted to the iced line in unit time, and the larger the ice melting current; the lower the duty cycle, the smaller the energy and current, and the regulation principle is completely the same as the first case.

[0112] The advantage of this mode is redundancy backup and flexible switching: when the first switch element S1 cannot enter the chopping mode due to failure (such as damage, performance decline), it can be switched to the second switch element S2 for regulation to ensure that the ice melting process does not interrupt and improve the reliability of the circuit; at the same time, according to the performance difference (such as current carrying capacity, response speed) of the two switch elements, the element more suitable for the current ice melting demand can be selected for chopping control to further optimize the regulation effect, for example, for large current ice melting demand, the second switch element S2 with stronger current carrying capacity is selected.

[0113] No matter which control mode, the logic is single element dominant regulation and another element isolation: by avoiding the simultaneous work of the two switch elements, the current shunt is prevented to cause the regulation precision to decline, and by using the duty cycle regulation capacity of the chopping mode, the dynamic adaptation of the ice melting current is realized, so that the ice melting process can meet the ice layer melting demand and guarantee the line safety, and perfectly adapt to the ice melting current control demand in different working conditions.

[0114] The circuit also has an alternate conduction mode.

[0115] When it is necessary to control the ice-melting current flowing through the iced line: control the first switching element and the second switching element to be in the alternate conduction mode at the first frequency.

[0116] The first frequency refers to the frequency of the on-off cycle of the switching element set when controlling the first switching element S1 and the second switching element S2 to be in the alternate conduction mode, and the purpose is to define the speed of the alternate switching of the two switching elements.

[0117] For example, if the first frequency = 15 kHz, it means that the two switching elements will complete 15000 times of alternate conduction switching per second, that is, the time required for the first switching element S1 to complete one process of closing to opening while the second switching element S2 is opening to conducting is:

[0118]

[0119] wherein, represents the first frequency, represents the total cycle time of the first switching element S1 and the second switching element S2 to complete one alternate conduction.

[0120] The setting of the first frequency needs to be combined with the characteristics of the iced line (such as the conductor impedance and the ice thickness) and the performance of the switching element (such as the maximum on-off frequency): a too high frequency may cause an increase in switching element loss and serious heating; a too low frequency may cause a large fluctuation of the ice-melting current, affecting the stability of ice-melting, so the first frequency is a key parameter to ensure the efficient and safe operation of the alternate conduction mode.

[0121] The alternate conduction mode refers to the state that the first switching element S1 and the second switching element S2 are always in a complementary state of one closed and one open in the same cycle, that is, when the first switching element S1 is closed, the second switching element S2 must be open; when the first switching element S1 is open, the second switching element S2 is immediately conducting, and the two cannot be conducting at the same time or be open at the same time, and through this complementary switching, energy is continuously delivered to the iced line.

[0122] The difference between this mode and the single switching element chopper mode is that the single chopper mode only relies on the high-frequency on-off of one switching element to regulate the current, and the other element is always open; in the alternate conduction mode, both switching elements work together to complete energy transmission and current regulation through complementary switching, which is equivalent to converting the on-off of a single element into the alternate on-off of two elements, which can not only maintain the continuity of energy delivery, but also control the current size by adjusting the switching details (such as the conducting time ratio).

[0123] In the alternate conduction mode, the control system of the interface device sends complementary control signals to the first switch element S1 and the second switch element S2 according to the period set by the first frequency, and the specific process is as follows:

[0124] In one period , for example, the first stage is the first half of the period , and the first switch element S1 is closed for . The control system sends a signal to close the first switch element S1, and the second switch element S2 is opened. At this time, the ice-melting energy from the static reactive generator is transmitted to the iced line through the closed first switch element S1, and the current flows through the line to generate heat.

[0125] The second stage is the second half of the period , and the second switch element S2 is closed for , and , the control system switches the signal synchronously: the first switch element S1 is opened, and the second switch element S2 is immediately closed. At this time, the ice-melting energy is continuously transmitted to the iced line through the closed second switch element S2, and the current continuously flows through the line without obvious interruption.

[0126] According to the rhythm of the first frequency, the two switch elements repeatedly switch between the first stage and the second stage, ensuring that in each period, one switch element is in the closed state, and the energy is continuously transmitted to the iced line, avoiding the interruption of energy transmission caused by the opening of a single element, and making the ice-melting current more stable.

[0127] Although the two switch elements are always alternately conducted, the conduction time of each element is not the same. By adjusting the ratio of the closing time of the first switch element S1 to the closing time of the second switch element S2 in the same period, the size of the ice-melting current can be controlled, and the specific logic is as follows:

[0128] The size of the ice-melting current depends on the total amount of energy transmitted to the iced line per unit time: the more energy, the greater the current; the less energy, the smaller the current. In the alternate conduction mode, the total amount of energy per unit time is determined by the total conduction time of the two switch elements, but by adjusting the ratio of and , the line impedance characteristics can be indirectly adapted, and the current stability can be optimized.

[0129] This control method is more suitable for the following scenarios compared to the single-element chopping mode, and has obvious advantages.

[0130] Two switching elements are alternately turned on to share the load of energy transmission. When a single element is used for chopping, all current needs to pass through the element. When the two elements are alternately turned on, the current can switch between the two elements, reducing the current-carrying pressure on a single element and avoiding damage to the element due to long-term bearing of large current and heating. Therefore, it is more suitable for the condition of thick ice layer and large current melting ice.

[0131] When a single element is used for chopping, there is no energy transmission during the off stage, and the current will be temporarily interrupted. Although it is not obvious at high frequency, there is still fluctuation. In the alternately turned-on mode, energy is continuously transmitted, and the current fluctuation is smaller, which can generate more uniform Joule heat and avoid uneven melting of ice layer due to current fluctuation, thereby improving the ice melting efficiency.

[0132] If one of the switching elements fails temporarily (such as conduction delay), the other element can be turned on in time within the switching period to avoid interruption of energy transmission and reduce the risk of ice melting stagnation caused by failure of a single element, thereby improving the operational reliability of the overall circuit.

[0133] When it is necessary to inject direct current into the iced line, the first switching element is turned on and the second switching element is turned off, or the first switching element is turned off and the second switching element is turned on.

[0134] The specific comparison of this control method with the above-mentioned single switching element chopping mode is shown in Table 1 below:

[0135] Table 1: Comparison of two control methods

[0136]

[0137] In simple terms, the chopping mode adjusts the current size through high-frequency on-off, and the output is pulse current. The injection of direct current is through fixed on-off state to output pure direct current, without the need to adjust the size, and only needs to ensure the stable flow of current in one direction.

[0138] When it is necessary to inject direct current into the iced line, the first switching element is turned on and the second switching element is turned off, or the first switching element is turned off and the second switching element is turned on.

[0139] The first switching element is turned on and the second switching element is turned off: at this time, the energy transmission path of the interface device is formed only through the first switching element S1: from the first switching S D1 The transmitted energy (from the static reactive generator direct current side) directly flows to the iced line through the continuously turned-on first switching element S1, and there is no other shunt path due to the continuous off of the second switching element S2. The current flows from the first end of the iced line and flows out from the second end of the iced line to the ground, the direction is fixed, and the current continuously flows without high-frequency on-off of the first switching element S1, finally forming pure direct current.

[0140] The first switching element is controlled to be off, and the second switching element is controlled to be on:

[0141] The above principle is completely consistent, only the energy transmission path is switched to the second switching element S2: the first switching element S1 is continuously off, cutting off the path; the second switching element S2 is continuously on, and the energy flows to the icing line through the second switching element. The current is also unidirectional and continuously flows, and the output is pure direct current. The only difference between the two control modes is to select which switching element as the direct current transmission channel, and the final effect is completely the same.

[0142] It should be noted that at this time the on of the switching element is continuous on, not periodic on in the chopping mode; off is continuous off, without any high-frequency switching, so the current does not appear pulse fluctuation, and always maintains a flat DC waveform, meeting the demand of stable current for DC deicing.

[0143] The pure direct current output by this control mode is more suitable for specific icing scenarios and has unique advantages.

[0144] For thick ice layers or high-impedance lines, the continuous heating characteristics of direct current can cause the icing line to continuously generate Joule heat, and the heat accumulates faster, which is more suitable for melting thick ice layers. At the same time, the direct current is not affected by the inductance and capacitance of the line (the alternating current will be lost due to impedance), and the energy loss is smaller when transmitted in a high-impedance line, and the deicing efficiency is higher.

[0145] Avoid the side effects of alternating current. If alternating current deicing is used, the periodic change of current direction may cause electromagnetic vibration of the line, affecting the stability of the tower; and the direct current has a fixed direction, without the risk of electromagnetic vibration, and is more suitable for power distribution network lines with high stability requirements.

[0146] The control logic is simple and the response speed is fast. There is no need to calculate the duty cycle and control high-frequency switching as in the chopping mode. Only the on-off state of the switching element needs to be switched, so that the DC deicing can be started quickly, which is suitable for scenes that require emergency deicing (such as when the ice layer thickens rapidly).

[0147] In summary, the control mode of injecting direct current is to achieve pure direct current output by continuously turning on a single switching element. The goal is to stabilize the current and continuously deice, which is completely different from the logic of regulating the current size in the chopping mode.

[0148] The circuit also includes deicing of a multi-phase sub-line, Figure 4 An icing line including a multi-phase sub-line is provided for the embodiments of the present application. Figure 4In the embodiment, the icing line includes a plurality of phase sub-lines; when ice melting is needed for a target sub-line in the plurality of phase sub-lines, the first switch is closed, the target sub-line is grounded, and the sub-lines other than the target sub-line in the plurality of phase sub-lines are not grounded. Each phase sub-line in the plurality of phase sub-lines is grounded through a corresponding grounding switch.

[0149] In the power distribution network, to meet the demand for high-power power transmission, the icing line is usually not a single conductor, but a multi-phase line composed of a plurality of independent conductors, and each independent conductor is a phase sub-line. A common multi-phase line is a three-phase line, which includes three sub-lines of A phase, B phase and C phase, and the three sub-lines are erected in parallel and jointly bear the task of power transmission. In the three-phase line, the three sub-lines are usually connected to a neutral line, and the neutral line is usually grounded. Figure 4 In the embodiment, the icing line includes an A-phase icing line, a B-phase icing line and a C-phase icing line.

[0150] For example, in a low-voltage power distribution network (220V) for residential electricity, the three-phase sub-lines cooperate with the neutral line to provide 220V single-phase electricity or 380V three-phase electricity for different users; in a high-voltage power distribution network for industrial electricity, the three-phase sub-lines directly transmit high-voltage power. When the line is iced, some phase sub-lines may be iced, some may not be iced, or the thickness of ice on each phase sub-line may be different, so targeted ice melting is needed.

[0151] The target sub-line refers to a specific phase sub-line in the plurality of phase sub-lines that needs to be operated for ice melting. The basis for selecting the target sub-line is the line icing monitoring data: if it is monitored that the thickness of the A-phase icing line exceeds the safety threshold, while the B-phase icing line and the C-phase icing line are not iced, the A-phase icing line is the target sub-line; if the A-phase icing line and the B-phase icing line are iced, but the thickness of ice is different, the A-phase icing line with thicker ice can be taken as the target sub-line first, and after ice melting, the B-phase icing line can be taken as the target sub-line, so as to realize phase-by-phase ice melting.

[0152] The selection of the target sub-line is to accurately locate the icing line, avoid invalid ice melting of the uniced sub-line, and reduce energy waste.

[0153] To realize the separate control of the target sub-line, each phase sub-line in the plurality of phase sub-lines is equipped with an independent grounding switch, i.e., the A-phase icing line corresponds to an A-phase grounding switch S G , the B-phase icing line corresponds to a B-phase grounding switch S G1 , and the C-phase icing line corresponds to a C-phase grounding switch S G2 . Each grounding switch only controls the grounding state of the corresponding phase sub-line: closing a phase grounding switch can ground the phase sub-line; opening the phase sub-line, and the operation of each grounding switch does not affect each other, closing the A-phase grounding switch S G will not affect the grounding state of the B-phase and the C-phase.

[0154] This design is the key to phase ice melting. By independently controlling the grounding switches of each phase, the ice melting current can only flow through the target sub-line, without affecting other sub-lines.

[0155] The multi-phase sub-line ice melting is to build a dedicated ice melting circuit and isolate non-target sub-lines. The specific operation steps and current paths are as follows.

[0156] Step 1: Close the first switch to open the energy transmission channel.

[0157] Consistent with single-phase line ice melting, first close the first switch between the static var generator DC side and the interface device. At this time, the ice melting energy converted by the static var generator (DC power) is transmitted to the interface device through the first switch, preparing for ice melting.

[0158] Step 2: Close the grounding switch of the target sub-line to build a dedicated circuit.

[0159] Assuming the target sub-line is the A-phase icing line, only close the A-phase grounding switch S G , the second end of the A-phase icing line is grounded; at the same time, keep the B-phase grounding switch S G1 and the C-phase grounding switch S G2 open, the second ends of the B-phase icing line and the C-phase icing line are not grounded.

[0160] At this time, the path of the ice melting current is: static var generator DC side, first switch, interface device, A-phase icing line (from the first end of the icing line to the second end of the icing line), A-phase grounding switch, ground, power supply area grounding system, static var generator DC side, forming a complete closed loop. When the current flows through the A-phase icing line, the ice layer on the surface of the A-phase icing line is melted due to the Joule heat generated by the resistance.

[0161] Step 3: Open the grounding switch of the non-target sub-line to isolate the non-target line.

[0162] Keep the B-phase grounding switch S G1 and the C-phase grounding switch S G2 open, which means that the second ends of the B-phase icing line and the C-phase icing line are not grounded and cannot form a current loop. Even if the energy of the interface device can be transmitted to the first ends of the B-phase icing line and the C-phase icing line, the current cannot flow through the B-phase icing line and the C-phase icing line due to the lack of return path, so the B-phase icing line and the C-phase icing line will not have ice melting current passing through, but they can still normally transmit electric energy to supply power to users.

[0163] For example, if the B-phase icing line and the C-phase icing line are not iced and the grounding switches are open, their normal power supply function is not affected, and the power of residents or industrial users will not be interrupted, realizing the parallel of ice melting and power supply.

[0164] If only the A-phase icing line in the multi-phase sub-line is iced, but the A-phase, B-phase and C-phase are simultaneously de-iced, it will lead to invalid de-icing of the B-phase and C-phase, and waste a large amount of electric energy. The de-icing by phase only injects current to the target sub-line, and the energy is all used for melting the ice layer of the target line, so that the energy utilization rate is improved.

[0165] The non-target sub-line can still normally transmit electric energy because the grounding switch is disconnected and no de-icing current passes through, so that the overall de-icing does not cause all the multi-phase lines to be powered off. For example, if the three-phase motor of an industrial user only relies on the B-phase and C-phase for power supply, and the A-phase is de-iced, the B-phase and C-phase can still maintain the basic operation of the motor, so that the production loss is reduced.

[0166] If the icing thicknesses of the multi-phase sub-lines are different, for example, the A-phase icing line is iced by 5 mm and the B-phase icing line is iced by 2 mm, the A-phase icing line can be taken as the target sub-line first, and a larger de-icing current is output through the interface device; after the A-phase icing line is de-iced, the B-phase icing line is taken as the target sub-line, and a smaller de-icing current is output, so that the A-phase icing line is not de-iced incompletely or the B-phase icing line is overheated and damaged due to the unified current.

[0167] The circuit further includes de-icing of the icing lines at different positions:

[0168] Figure 5 A schematic diagram in which the icing lines are upstream and downstream of the power supply station area is provided for the embodiments of the present application. The icing lines are downstream of the power supply station area; or the icing lines are upstream of the power supply station area. Figure 5 In the embodiment, the A-phase icing line, the B-phase icing line and the C-phase icing line are downstream of the 1# power supply station area, and the A1-phase icing line, the B1-phase icing line and the C1-phase icing line are upstream of the 1# power supply station area.

[0169] The A-phase icing line, the B-phase icing line and the C-phase icing line are downstream of the 1# power supply station area, and these lines are connected to the output side of the 1# power supply station area: the electric energy flows from the 1# power supply station area, is processed by the SVG and other devices, or directly flows from the 400V bus to the A-phase icing line, the B-phase icing line and the C-phase icing line, and is further transmitted to the user side through the left switches S G , S G1 , S G2 Therefore, they belong to the line section that the output electric energy of the transformer substation flows through, that is, the downstream line.

[0170] The A1-phase icing line, the B1-phase icing line and the C1-phase icing line are upstream of the 1# power supply station area, and these lines are connected to the input side of the 1# power supply station area: the electric energy first flows from the right switches S Figure 5 , S G’ , S G1’ , S G2’The access part of the upper grid can be regarded as flowing to the A1-phase icing line, the B1-phase icing line, and the C1-phase icing line, and then entering the 1# power supply area for voltage reduction. Therefore, they belong to the line section through which the electric energy flows before entering the transformer substation, that is, the upstream line.

[0171] Briefly, the upstream is the line side of the electric energy entering the transformer substation, and the downstream is the line side of the electric energy output from the transformer substation. The connection relationship between the left and right lines and the 1# power supply area in the figure clearly reflects the difference between the upstream and the downstream.

[0172] The circuit further comprises a plurality of power supply areas:

[0173] Figure 6 A schematic diagram of the multiple power supply areas is provided for the embodiments of the present application. As shown in the figure, the power supply areas can be multiple, 1# power supply area, …, n# power supply area, n representing the number of power supply areas. Each power supply area is equipped with an independent static var generator SVG, an interface device, and a first switch. Figure 6 The AC side of each power supply area is connected with the medium voltage line in the distribution network, and the DC side is connected with the icing line in the jurisdiction area through the interface device and the switch of the power supply area. This multiple area configuration can realize collaborative ice melting of the icing line across the areas: when the long-distance line (spanning multiple area power supply ranges) is icing, the power supply areas along the line can simultaneously or in stages start the ice melting circuit to process the icing line in sections, avoiding the limitation of the ice melting capacity of a single area, and ensuring that the ice melting operations of each area are independent of each other, so that the ice melting of a certain area does not affect the normal power supply of other areas, greatly improving the coverage and flexibility of the distribution network ice melting without power cut in a large range.

[0174] 1# power supply area, 2# power supply area, …, n# power supply area correspond to different power supply regions of the distribution network, for example: 1# power supply area is responsible for the east city area, and 2# power supply area is responsible for the west city area, and the interface device of each power supply area is only connected with the icing line in the jurisdiction area.

[0175] For example, the interface device corresponding to the 1# power supply area is connected with the A-phase icing line, the B-phase icing line, and the C-phase icing line in the east city area, and the interface device corresponding to the 2# power supply area is connected with the A-phase icing line, the B-phase icing line, and the C-phase icing line in the west city area, avoiding repeated operation of the ice melting equipment of different areas on the same line and ensuring orderly management.

[0176] When a long-distance icing line across multiple areas appears in the distribution network, for example, a 10kV line extending from the 1# area in the east city area to the 2# area in the west city area,

[0177] the multiple power supply area configuration can realize collaborative ice melting. Figure 6

[0178] ​1# power supply area starts its own SVG, first switch and interface device, and melts ice on the icing line section in the jurisdiction; 2# power supply area synchronously starts its own device, and melts ice on the icing line section in the jurisdiction. The two interact through the current signal of the main line of the power distribution network, for example, share the icing thickness monitoring data, can realize synchronous starting and synchronous regulation of current, avoid incomplete melting of long lines due to limited melting range of a single area, and greatly improve the melting coverage capability.

[0179] If the melting equipment of a certain power supply area fails, for example, the SVG of 1# power supply area is damaged, only the melting operation in the jurisdiction of 1# area is affected, and the devices of 2# to n# power supply areas can still operate normally, continue to melt ice on the icing lines in their respective jurisdictions, avoid the paralysis of the entire power distribution network melting function due to the failure of a single area, and improve the overall reliability of the system.

[0180] Based on the above content description, the present application has the following beneficial effects:

[0181] Firstly, compared with the traditional scheme which needs to stop power supply to start melting ice, causing inconvenience to residents and economic loss to industrial users, the scheme realizes melting ice without interrupting normal power supply of the power distribution network through the loop composed of the direct current side of the static var generator, the interface device and the grounding of the icing line, fundamentally avoids the influence of power failure on people's livelihood and economic loss, and reduces the wear and tear of power equipment caused by frequent power failure, prolonging the service life of the equipment.

[0182] Secondly, the traditional scheme relies on special melting power supply main equipment and is passive, while the present scheme directly uses the existing static var generator in the area for upgrading and modification, without the need to add a large number of special equipment, reducing the cost investment, and the melting power can be flexibly expanded by increasing the number of static var generators participating in the area, solving the problems of transportation difficulty and insufficient melting power of traditional melting equipment.

[0183] Thirdly, the present method supports successive phase-by-phase melting of multi-phase sub-lines, controls through independent grounding switches of each phase, and can accurately control the size and type (direct current or high-frequency alternating current) of melting current through the chopping mode and alternate conduction mode of switch elements in the interface device, avoiding damage to equipment by large current, and improving melting efficiency by using the skin effect of high-frequency current, at the same time, the running state of the power distribution network and the melting effect can be monitored in real time without power failure, which is convenient for timely adjustment of strategies, solving the problems of long time interval and difficult control of effect in traditional melting.

[0184] In addition, the scheme is compatible with different scenes of icing lines on the upstream and downstream of the power supply area, has a wide range of applications, further ensures the safe and stable operation of the power distribution network in freezing, snowy and rainy weather, and provides effective technical support for building a strong and resilient power distribution network.

[0185] The embodiment of the present application also provides a power distribution network ice-melting device without power interruption, which comprises the ice-melting circuit in any one of the preceding embodiments, and the specific scheme is consistent with the above embodiments.

Claims

1. An ice-melting circuit that operates without power interruption in a power distribution network, characterized in that, The circuit includes: a static var generator, a first switch, and an interface device; The AC side of the static var generator is used to connect to the power supply area, and the DC side of the static var generator is used to connect to the first terminal of the first switch. The first end of the interface device is used to connect to the second end of the first switch, and the second end of the interface device is used to connect to the first end of the icing circuit. The second end of the icing line is used for grounding; The interface device includes a first switching element and a second switching element, which are connected in parallel. The two ends of the first switching element and the second switching element are respectively connected to the first end and the second end of the interface device. When it is necessary to melt the ice on the iced line, the first switch is closed and the second end of the iced line is grounded. When it is necessary to control the de-icing current flowing through the icing line: The first switching element is controlled to be in chopping mode, and the second switching element is in the off state; or, the second switching element is controlled to be in chopping mode, and the first switching element is in the off state. Alternatively, the first switching element and the second switching element can be controlled to be in an alternating conduction mode at a first frequency; When it is necessary to inject DC current into the icing line: The first switching element is turned on, and the second switching element is turned off; or... The first switching element is turned off, and the second switching element is turned on; The interface device adjusts the current characteristics according to the actual needs of the icing line: when a DC de-icing current needs to be injected, it outputs unidirectional DC through the on / off control of the internal switching element; when the de-icing current needs to be adjusted, it can switch to chopper mode or alternating conduction mode, and control the current intensity by adjusting the conduction duty cycle to adapt to the de-icing needs of lines with different ice thicknesses and materials.

2. The uninterrupted de-icing circuit for power distribution networks according to claim 1, characterized in that, The icing line includes multi-phase sub-lines; When it is necessary to melt ice on the target sub-line in the multi-phase sub-line, the first switch is closed, the target sub-line is grounded, and the sub-lines in the multi-phase sub-line other than the target sub-line are not grounded.

3. The uninterrupted de-icing circuit for power distribution networks according to claim 1, characterized in that, The icing line is downstream of the power supply area; or, the icing line is upstream of the power supply area.

4. The uninterrupted de-icing circuit for power distribution networks according to claim 2, characterized in that, Each phase sub-line in the multi-phase sub-line is grounded through its corresponding grounding switch.

5. An ice-melting device that operates without interrupting power supply to the power distribution network, characterized in that, Including the de-icing circuit for uninterrupted power supply to the power distribution network as described in any one of claims 1 to 4.

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