Multifunctional hybrid emergency supporting device for online ice melting and electric energy management

Abstract

The invention provides a multifunctional hybrid emergency supporting device for online ice melting and electric energy management, which comprises a multifunctional active device connected to the head end of a line and a grounding transformer connected to the tail end of the line, the multifunctional active device comprises a first cascade H-bridge module K1, a first midpoint clamping module D1, a second cascade H-bridge module K2, a second midpoint clamping module D2, a third cascade H-bridge module K3, a third midpoint clamping module D3, a fourth cascade H-bridge module K4, a fourth midpoint clamping module D4, a first direct current split capacitor C1, a second direct current split capacitor C2, a first filter inductor L1 and a second filter inductor L2. The device is matched with the grounding transformer through the multifunctional active device to form a zero-sequence ice melting loop, and has the advantages of no influence on normal power utilization of a user, high equipment utilization rate and low cost.

Description

Technical Field

[0001] The present application relates to the field of online ice melting in distribution networks, and specifically to a multifunctional hybrid emergency support device for online ice melting and power management and a line current determination method. Background Art

[0002] As global climate change intensifies, power systems are increasingly vulnerable to extreme disasters. Snowstorms, in particular, can trigger a series of serious problems, including tower collapse, insulator flashover due to ice buildup, and conductor breakage. These can lead to tripping and widespread power outages, reducing the reliability of distribution networks. However, current de-icing methods for distribution networks still rely primarily on manual de-icing, which suffers from low efficiency and difficulty ensuring personal safety. By proactively intervening in conductor icing, ice-melting technology can significantly improve power supply reliability during extreme climate events and effectively prevent regional power outages caused by snowstorms. It is a key measure for ensuring the safe and stable operation of modern power grids.

[0003] De-icing solutions can be categorized as online or offline, depending on whether users can access electricity normally during the de-icing period. AC offline de-icing, a widely used de-icing technology, short-circuits the line ends to ground, utilizing the thermal effect of the short-circuit current in the overhead line to melt the ice. However, this solution's significant reactance leads to a sharp increase in reactive power demand during the de-icing period. To address this issue, DC offline de-icing technology, leveraging the direct current (DC) conduction and alternating current (AC) resistance characteristics of inductors, has been widely adopted in high-voltage, high-reactance scenarios. However, the ice-covered period is limited throughout the year, leaving de-icing equipment idle for extended periods. The flexible control potential of power electronics equipment is not fully utilized, and existing offline de-icing solutions cannot guarantee normal power supply to loads connected to the de-icing lines.

[0004] Online ice-melting technology, with its unique advantages of simultaneously de-icing lines and providing grid power, has garnered widespread attention from scholars both domestically and internationally. Taking into account the zero-sequence isolation provided by the distribution transformers at both ends of the distribution network, online ice-melting of distribution lines can be achieved without disrupting grid power supply by flexibly regulating the zero-sequence current in the distribution network. Existing online ice-melting solutions only operate during periods of grid icing, resulting in low equipment utilization. Therefore, breakthroughs in online ice-melting technology that balances equipment cost and utilization efficiency are urgently needed. Summary of the Invention

[0005] In order to overcome the above technical defects, the present application provides a multifunctional hybrid emergency support device for online ice melting and power management.

[0006] To achieve the above objectives, this application is implemented according to the following technical solutions: In the first aspect, the present application provides a multifunctional hybrid emergency support device for online ice melting and power management, including: The device consists of a multifunctional active device connected to the head end of the line and a grounding transformer connected to the end of the line; The multifunctional active device includes a first cascaded H-bridge module K 1. First midpoint clamp module D 1. Second cascade H-bridge module K 2. Second midpoint clamp module D 2. The third cascade H-bridge module K 3. Third midpoint clamp module D 3. The fourth cascade H-bridge module K 4. Fourth midpoint clamp module D 4. First DC split capacitor C 1. Second DC splitting capacitor C 2. First filter inductor L 1. Second filter inductor L 2.

[0007] Optionally, the first cascade H-bridge module K 1. The second cascade H-bridge module K 2. The third cascade H-bridge module K 3 and the fourth cascaded H-bridge module K 4 each includes a plurality of submodules connected in series.

[0008] Optionally, the first midpoint clamping module D 1. The second midpoint clamp module D 2. The third midpoint clamping module D 3. The fourth midpoint clamping module D The DC bus positive terminals of 4 are connected to the first DC splitting capacitor C 1's positive terminal.

[0009] Optionally, the first midpoint clamping module D 1. The second midpoint clamp module D 2. The third midpoint clamping module D 3. The fourth midpoint clamping module D The negative terminals of the DC busbars 4 are connected to the second DC splitting capacitors C 2, the negative terminal of the first DC splitting capacitor C 1 is connected to the negative terminal of the second DC splitting capacitor C 2's positive terminal.

[0010] Optionally, the first midpoint clamping module D 1. The second midpoint clamp module D 2. The third midpoint clamping module D 3. The fourth midpoint clamping moduleD The clamp midpoints of 4 are connected to the first DC splitting capacitor C 1 and the second DC splitting capacitor C At the midpoint of 2.

[0011] Optionally, the first midpoint clamping module D 1. The second midpoint clamp module D 2. The third midpoint clamping module D The output ports of 3 are respectively connected to the first cascade H-bridge module K 1. The second cascade H-bridge module K 2. The third cascade H-bridge module K 3.

[0012] Optionally, the fourth midpoint clamping module D The output port of 4 is connected to the first filter inductor L 1, the fourth cascaded H-bridge module K One end of 4 is connected to the first filter inductor L 1, the other end of the fourth cascaded H-bridge module K The other end of 4 is connected to the second filter inductor L 2, the second filter inductor L The other end of 2 is connected to the ground.

[0013] This application has the following beneficial effects: The device proposed in this application forms a zero-sequence ice-melting circuit through the cooperation of MAID and grounding transformer, which has the advantages of not affecting the normal electricity consumption of users, high equipment utilization rate and low cost.

[0014] In addition to the above-described purposes, features and advantages, the present application has other purposes, features and advantages. The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings: Figure 1 This is a schematic diagram of the topological structure of a multifunctional hybrid emergency support device for online ice melting and power management provided in an embodiment of the present application; Figure 2 Schematic diagram of reactive compensation principle of the multifunctional hybrid emergency support device provided in an embodiment of the present application in reactive compensation mode; Figure 3This is a schematic diagram of the online ice melting principle of the multifunctional hybrid emergency support device provided by an embodiment of the present application in the online ice melting mode; Figure 4 Schematic diagram of an equivalent circuit of the multifunctional hybrid emergency support device provided in an embodiment of the present application in an online ice melting mode. DETAILED DESCRIPTION

[0016] The embodiments of the present application are described in detail below with reference to the accompanying drawings, but the present application can be implemented in many different ways as defined and covered by the claims.

[0017] It should be noted that the terms "first", "second", "third", etc. in the claims, description and drawings of the present application are used to distinguish similar objects and are not used to describe a specific order or sequence. The data used in this way are interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including", "having" and their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or modules is not necessarily limited to those steps or modules clearly listed, but may include other steps or modules that are not clearly listed or inherent to these processes, methods, products or devices.

[0018] In order to provide a more vivid explanation of the issues raised in the background technology, Figure 1 As shown, this application proposes a multifunctional hybrid emergency support device for online ice melting and power management, including: The device consists of a multi-functional active ice-melting device (MAID) connected to the line headend and a grounding transformer (GT) connected to the line end. The multifunctional active device includes a first cascaded H-bridge module K 1 (cascaded H-bridge, CHB), first midpoint clamp module D 1 (neutral point clamped, NPC), second cascade H-bridge module K 2. Second midpoint clamp module D 2. The third cascade H-bridge module K 3. Third midpoint clamp module D 3. The fourth cascade H-bridge module K 4. Fourth midpoint clamp module D 4. First DC split capacitor C 1. Second DC splitting capacitorC 2. First filter inductor L 1. Second filter inductor L 2; First cascade H-bridge module K 1. Second cascade H-bridge module K 2. The third cascade H-bridge module K 3 and 4 cascaded H-bridge modules K 4 each includes a plurality of submodules connected in series; First midpoint clamp module D 1. Second midpoint clamp module D 2. Third midpoint clamp module D 3. Fourth midpoint clamp module D The positive terminals of the DC busbars 4 are connected to the first DC splitting capacitor C 1's positive terminal; First midpoint clamp module D 1. Second midpoint clamp module D 2. Third midpoint clamp module D 3. Fourth midpoint clamp module D The negative terminals of the DC busbars 4 are connected to the second DC splitting capacitor C 2, the negative terminal of the first DC split capacitor is connected to the negative terminal of the second DC split capacitor C 2's positive end; First midpoint clamp module D 1. Second midpoint clamp module D 2. Third midpoint clamp module D 3. Fourth midpoint clamp module D The clamping midpoints of 4 are connected to the first DC splitting capacitor C 1 and 2nd DC splitting capacitors C The midpoint of 2; First midpoint clamp module D 1. Second midpoint clamp module D 2. Third midpoint clamp module D The output ports of 3 are connected to the first cascade H-bridge module K 1. Second cascade H-bridge module K 2. The third cascade H-bridge module K 3; Fourth midpoint clamp module D The output port of 4 is connected to the first filter inductor L One end of 1, the fourth cascade H-bridge module K One end of 4 is connected to the first filter inductor L The other end of 1, the fourth cascade H-bridge module K The other end of 4 is connected to the second filter inductor L2, one end of the second filter inductor L The other end of 2 is connected to the ground.

[0019] In order to facilitate Figure 1 To understand it more vividly, Figure 1 To explain in more detail, MAID is composed of a neutral point clamped (NPC) unit and a cascaded H-bridge (CHB) unit in series. The NPC unit is a three-phase four-bridge structure, and each bridge arm consists of a CHB unit. N It is composed of H-bridge units. E x ( x = a, b, c) are the grid phase voltages, U 0 is the neutral point voltage; U x is the bus voltage, U npc is the output voltage of the NPC unit, U chb is the output voltage of the CHB unit, U c is the submodule capacitor voltage of the CHB unit, U dc is the DC side voltage of the NPC unit. I zx is the output current of the three-phase bridge arm of MAID, I z0 is the output current of the fourth bridge arm of MAID. I cx is the line-to-ground leakage current, I lx is the line current, I Lx is the load current, I t0 is the ice-melting current received by the transformer. C N is the NPC unit DC splitting capacitor, C h is the submodule capacitance of the CHB unit, L is the filter inductor, C 0x is the line-to-ground capacitance, r 0x is the line-to-ground resistance, Z x is the line impedance, Z x = R x + JX x ,inR x is the line resistance, X x is the line reactance.

[0020] When the power grid operates normally, MAID provides reactive power support for the grid; when the distribution lines are covered with ice, MAID and GT work together to achieve online ice melting using zero-sequence ice-melting current, effectively improving the equipment utilization rate and power supply reliability of the ice-melting device.

[0021] Existing de-icing solutions primarily rely on Joule's law to generate sufficient heat to melt ice from power lines. Related research indicates that the Joule's law de-icing process for power lines should comprehensively consider the influence of numerous factors, including temperature, wind speed, convection, and radiation heat transfer. Therefore, the Burgsdorff de-icing empirical model is generally used: (1) (2) (3) Where: is the critical ice melting current (A); is the ice melting time (h); is the thickness of the ice layer (cm); is the resistance per unit length of wire at 0°C ; is the difference between the conductor temperature and the outside air temperature (°C); is the equivalent ice layer conduction thermal resistance (℃·cm / W); is the equivalent thermal resistance of convection and radiation (℃·cm / W); is the ice density, generally taken as 0.9g / cm 3 ; is the outer diameter of the conductor after ice coating (cm); is the wire diameter (cm); is the wind speed (m / s); is the thermal conductivity (W / (℃·cm)), in the wet growth icing scenario, =2.27×10 -2 .

[0022] Combined with the above model, it can be seen that within the specified ice melting time When the effective value of the line current always remains at the critical ice melting current , the ice on the line can melt.

[0023] Based on the above ice melting principle and device, a method for determining line current in online ice melting mode can be simply proposed. According to the above device, it includes: Step S201: obtaining a zero-sequence equivalent circuit corresponding to the device in the online ice melting mode; First, when the device is in reactive power compensation mode, the three-phase bridge arm of MAID outputs reactive power, and the fourth bridge arm of MAID and GT are not put into operation. , the reactive power that needs to be compensated can be calculated The reactive power compensation principle is as follows. Figure 2 shown.

[0024] When the device is in online ice melting mode, the three-phase bridge arm of MAID provides energy support for the DC bus of NPC unit, and the fourth bridge arm and GT are put into operation. The principle of online ice melting of the device is as follows: Figure 3 As shown. Since distribution transformers are generally used The wiring method has no zero-sequence current flow path, so the load side line voltage remains symmetrical and does not affect the normal power consumption of the load. Since the current of the three-phase bridge arm and the fourth bridge arm can be controlled independently, the MAID can be equivalent to a controlled current source. At this time, the zero-sequence equivalent circuit formed by the MAID and GT in the device can be obtained, as shown in the figure below: Figure 4 The resistance of the distribution network to ground is , the capacitance to ground is .

[0025] Step S202: determining the ice-melting current injected by the multifunctional active device based on the zero-sequence equivalent circuit; After determining the above zero-sequence equivalent circuit, ignoring the influence of the line on the ground branch, the KCL equation is written at the connection point to obtain: (4) Where, is the output current of the fourth bridge arm of MAID, Injects ice-melting current into multifunctional active devices.

[0026] At this time, the multifunctional active device can be further injected into the ice melting current Expressed as: (5) The entire line is three-phase symmetrical, which can be obtained from the superposition theorem; (6) Step S203: Obtain the load current of the distribution line; At this time, when melting ice, it is also necessary to obtain the load current of the distribution line .

[0027] Step S204: determining the line current based on one third of the injected ice-melting current and the load current.

[0028] Obtaining the load current of the MAID distribution line , the line current can be determined , which can be expressed as: (7) Assume that the total ice melting time is The critical ice melting current can be obtained from the Burgsdorff ice melting empirical model When the effective value of the line current reaches the critical ice melting current, within the specified time During the online ice melting mode, the ice melting current injected by the fourth bridge arm of the MAID is assumed to be expressed as: (8) Where, is the grid angular frequency.

[0029] Combining equations (7) and (8), the line current can be expressed as: (9) Where, is the effective value of the load current, is the effective value of the ice-melting current injected into each phase. is the load power factor, is the phase of the ice melting current.

[0030] Based on the above analysis, it can be seen that the device achieves the line de-icing effect by precisely controlling the output current of the fourth bridge arm so that the line current reaches the critical de-icing current.

[0031] In summary, the proposed device, which combines a MAID with a grounding transformer to form a zero-sequence ice-melting circuit, offers advantages such as no impact on normal user electricity consumption, high equipment utilization, and low cost. The proposed method, based on MAID, proposes a reactive power compensation mode and an online ice-melting mode. By calculating the ice-melting current, it effectively melts ice on distribution network lines.

[0032] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A multifunctional hybrid emergency support device for online ice melting and power management, characterized by: include: The device consists of a multifunctional active device connected to the head end of the line and a grounding transformer connected to the end of the line; The multifunctional active device includes a first cascaded H-bridge module K 1. First midpoint clamp module D 1. Second cascade H-bridge module K 2. Second midpoint clamp module D 2. The third cascade H-bridge module K 3. Third midpoint clamp module D 3. The fourth cascade H-bridge module K 4. Fourth midpoint clamp module D 4. First DC split capacitor C 1. Second DC splitting capacitor C 2. First filter inductor L 1. Second filter inductor L 2.

2. The device according to claim 1, characterized in that The first cascaded H-bridge module K 1. The second cascade H-bridge module K 2. The third cascade H-bridge module K 3 and the fourth cascaded H-bridge module K 4 each includes a plurality of submodules connected in series.

3. The device according to claim 1, characterized in that The first midpoint clamp module D 1. The second midpoint clamp module D 2. The third midpoint clamping module D 3. The fourth midpoint clamping module D The DC bus positive terminals of 4 are connected to the first DC splitting capacitor C 1's positive terminal.

4. The device according to claim 1, characterized in that The first midpoint clamp module D 1. The second midpoint clamp module D 2. The third midpoint clamping module D 3. The fourth midpoint clamping module D The negative terminals of the DC busbars 4 are connected to the second DC splitting capacitors C 2, the negative terminal of the first DC splitting capacitor C 1 is connected to the negative terminal of the second DC splitting capacitor C 2's positive terminal.

5. The device according to claim 1, characterized in that The first midpoint clamp module D 1. The second midpoint clamp module D 2. The third midpoint clamping module D 3. The fourth midpoint clamping module D The clamp midpoints of 4 are connected to the first DC splitting capacitor C 1 and the second DC splitting capacitor C At the midpoint of 2.

6. The device according to claim 1, characterized in that The first midpoint clamp module D 1. The second midpoint clamp module D 2. The third midpoint clamping module D The output ports of 3 are respectively connected to the first cascade H-bridge module K 1. The second cascade H-bridge module K 2. The third cascade H-bridge module K 3.

7. The device according to claim 1, characterized in that The fourth midpoint clamp module D The output port of 4 is connected to the first filter inductor L 1, the fourth cascaded H-bridge module K One end of 4 is connected to the first filter inductor L 1, the other end of the fourth cascaded H-bridge module K The other end of 4 is connected to the second filter inductor L 2, the second filter inductor L The other end of 2 is connected to the ground.

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