Multi-functional fast emergency management and control device for active distribution network ice disaster scenario

Abstract

The application provides a multifunctional rapid emergency management and control device for an active power distribution network ice disaster scene, comprising: the multifunctional rapid emergency management and control device is jointly constituted by a back-to-back modular multilevel converter arranged at a line head, a grounding transformer module at a line tail, and a power distribution network module connected between the back-to-back modular multilevel converter. The multifunctional rapid emergency management and control device provided by the application realizes online ice melting by the coordinated operation of the back-to-back modular multilevel converter and the grounding transformer, and by the use of zero sequence ice melting current and power flow control current, not only reduces the capacity and cost of the multifunctional rapid emergency management and control device, but also realizes the time-sharing multiplexing of the emergency management and control device, effectively improves the equipment utilization efficiency, and realizes the time-sharing multiplexing of the power electronic device.

Description

Technical Field

[0001] This application relates to the field of online ice melting in distribution networks, specifically to a multi-functional rapid emergency control device for ice disaster scenarios in active distribution networks. Background Technology

[0002] Snow and ice disasters can trigger a series of serious problems, such as tower collapse, insulator flashover due to ice accumulation, and conductor galloping and breakage, leading to power outages and widespread blackouts, thus reducing the reliability of power distribution networks. Emergency control devices have gained widespread attention due to their multi-functional integration of line de-icing and grid power supply. Considering the zero-sequence isolation function of the distribution transformers at both ends of the distribution network, emergency control devices can achieve online de-icing of distribution lines without affecting grid power supply by regulating the zero-sequence current. However, existing emergency control devices only operate during periods of distribution network icing, resulting in low equipment utilization. Furthermore, the high cost of equipment is a bottleneck restricting the application of emergency control devices. Therefore, further development and breakthroughs are needed to develop emergency control devices that balance low cost and high equipment utilization.

[0003] With the large-scale integration of renewable energy sources such as photovoltaics and wind power, as well as distributed power sources such as electric vehicle charging facilities, the operation and dispatch of traditional AC distribution networks face increasingly severe challenges. The inherent randomness and intermittency of these distributed power sources bring multiple negative impacts to the distribution network, including higher peak power demand, greater voltage fluctuations, and more unbalanced feeder power. These problems make it difficult for AC distribution networks to maintain a safe and efficient operating state, and may even lead to serious issues such as localized congestion, reverse power flow, voltage exceeding limits, and protection system malfunctions. Summary of the Invention

[0004] To overcome the aforementioned technical deficiencies, this application provides a multi-functional rapid emergency control device for ice disaster scenarios in active power distribution networks.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] This application provides a multi-functional rapid emergency control device for active power distribution networks in ice storm scenarios, including:

[0007] The multi-functional rapid emergency control device consists of a back-to-back modular multilevel converter configured at the beginning of the line, a grounding transformer module at the end of the line, and a distribution network module connected to both ends of the back-to-back modular multilevel converter.

[0008] Optionally, the back-to-back modular multilevel converter includes two identical first three-phase circuit topologies and second three-phase circuit topologies, as well as a DC split capacitor module, wherein the first three-phase circuit topologies and the second three-phase circuit topologies are connected to the two ends of the DC split capacitor module.

[0009] Optionally, the distribution network module includes a first distribution network side and a second distribution network side with the same structure. The first distribution network side includes a first three-phase line topology, and the second distribution network side includes a second three-phase line topology. The first three-phase line topology corresponds to the first three-phase circuit topology, and the second three-phase line topology corresponds to the second three-phase circuit topology.

[0010] Optionally, the DC split capacitor module includes a first DC split capacitor and a second DC split capacitor, with the negative terminal of the first DC split capacitor and the positive terminal of the second DC split capacitor connected to a ground terminal.

[0011] Optionally, the first three-phase circuit topology and the second three-phase circuit topology include three identical single-phase circuit topologies. The single-phase circuit topology includes an upper bridge arm module, an upper bridge arm inductor, a lower bridge arm module, and a lower bridge arm inductor. One end of the upper bridge arm module is connected to the positive terminal of the first DC split capacitor, and one end of the lower bridge arm module is connected to the negative terminal of the second DC split capacitor.

[0012] Optionally, the first three-phase line topology and the second three-phase line topology include three identical single-phase line topologies. The single-phase line topology includes line resistance and line inductance. The other end of the upper bridge arm module is connected to one end of the upper bridge arm inductor, and the other end of the lower bridge arm module is connected to one end of the lower bridge arm inductor. The other ends of the upper bridge arm inductor and the other ends of the lower bridge arm inductor are both connected to one end of the line resistance.

[0013] Optionally, the grounding transformer module includes two identical grounding transformers, one end of the line inductor is connected to the other end of the line resistor, and the other end of the line inductor is connected to the grounding transformer.

[0014] This application has the following beneficial effects:

[0015] The multi-functional rapid emergency control device proposed in this application achieves online de-icing by utilizing zero-sequence de-icing current and power flow control current through the coordinated operation of a back-to-back modular multilevel converter and a grounding transformer. This not only reduces the capacity and cost of the multi-functional rapid emergency control device, but also realizes the time-sharing reuse of the emergency control device, effectively improving equipment utilization efficiency and enabling the time-sharing reuse of power electronic devices.

[0016] In addition to the purposes, features, and advantages described above, this application has other purposes, features, and advantages. The application will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0018] Figure 1 This is a schematic diagram of the topology of a multi-functional rapid emergency control device for ice disaster scenarios in active power distribution networks, provided in an embodiment of this application.

[0019] Figure 2 This is a schematic diagram of the power flow regulation principle of the multifunctional rapid emergency control device provided in the embodiments of this application;

[0020] Figure 3 This is the zero-sequence equivalent diagram of the multifunctional rapid emergency control device solution provided in the embodiments of this application. Detailed Implementation

[0021] The embodiments of this application are described in detail below with reference to the accompanying drawings, but this application can be implemented in many different ways as defined and covered by the claims.

[0022] It should be noted that the terms "first," "second," "third," etc., in the claims, specification, and drawings of this application are used to distinguish similar objects and are not used to describe a specific order or sequence. Such data are interchangeable where appropriate so that the embodiments of this application described herein can be implemented in a sequence other than that shown or described herein. Furthermore, the terms "comprising," "having," and their variations are intended to cover non-exclusive inclusion; 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 explicitly listed, but may include other steps or modules not explicitly listed or inherent to these processes, methods, products, or devices.

[0023] To illustrate the problems raised in the background art more vividly, such as... Figure 1 As shown, the multi-functional rapid emergency control device for active distribution network ice storm scenarios proposed in this application includes:

[0024] The multifunctional rapid emergency control device consists of a back-to-back modular multilevel converter (BTB-MMC) at the beginning of the line, a grounding transformer (GT) at the end of the line, and a distribution network module connected to both ends of the BTB-MMC. The BTB-MMC includes two identical first three-phase circuit topologies and second three-phase circuit topologies, as well as a DC split capacitor module. The first and second three-phase circuit topologies are connected to both ends of the DC split capacitor module.

[0025] The distribution network module includes a first distribution network side with the same structure ( Figure 1 Left side) and second distribution network side ( Figure 1 (On the right side), the first distribution network side includes a first three-phase line topology, and the second distribution network side includes a second three-phase line topology. The first three-phase line topology corresponds to the first three-phase circuit topology, and the second three-phase line topology corresponds to the second three-phase circuit topology. The DC split capacitor module includes a first DC split capacitor. Second DC split capacitor First DC split capacitor The negative terminal and the second DC split capacitor The positive terminal is connected to the grounding terminal.

[0026] The first three-phase circuit topology and the second three-phase circuit topology both include three identical single-phase circuit topologies, and the single-phase circuit topology includes the upper bridge arm module. upper bridge arm inductor Lower bridge arm module Lower bridge arm inductor One end of the upper bridge arm module is connected to the first DC split capacitor. The positive terminal of the lower bridge arm module is connected to the second DC split capacitor. The negative terminal, the first three-phase line topology and the second three-phase line topology include three identical single-phase line topologies, the single-phase line topology includes line resistance and line inductance upper bridge arm module The other end is connected to the upper bridge arm inductor. One end, lower bridge arm module The other end is connected to the lower bridge arm inductor. One end, upper bridge arm inductor The other end, the lower bridge arm inductor The other end of each is connected to one end of the line resistor.

[0027] The grounding transformer module includes two identical grounding transformers GT, with one end of the line inductor connected to the other end of the line resistor, and the other end of the line inductor connected to the grounding transformer.

[0028] In addition, all the bridge arms in this application are made of It consists of a full bridge sub-module. This refers to the phase voltage of the power grid. This is the neutral point voltage; Bus voltage This refers to the capacitor voltage of the submodule. This refers to the output current at the grounding point of the DC-side split capacitor of the multi-functional rapid emergency control device. For load current, For line current, This refers to the de-icing current received by the grounding transformer. For line impedance, ,in It is the line resistance. It is the line reactance.

[0029] Based on the above device, the application principle of the above scheme is analyzed as follows:

[0030] Current de-icing methods primarily rely on Joule's law to generate sufficient heat to melt the ice on power lines. However, related research indicates that the Joule-based de-icing process for power lines should comprehensively consider numerous factors, including temperature, wind speed, convection, and radiative heat transfer. Therefore, the Burgosdorf empirical de-icing model is generally adopted. This model shows that within a specified de-icing time... Within this range, when the effective value of the line current remains at the critical de-icing current... The ice on the line will melt.

[0031] In online de-icing mode, the multi-functional rapid emergency control device generates a zero-sequence voltage at the grounding point of the split capacitor, which in turn generates a zero-sequence current. This zero-sequence current flows through the line and converges at the grounding transformer. Simultaneously, the device flexibly regulates the line current by superimposing the zero-sequence current, positive-sequence current, and line load current. This not only reduces the capacity and cost of the device but also enables time-sharing reuse, effectively improving equipment utilization efficiency.

[0032] The multi-functional rapid emergency control device generates positive sequence current flowing through the line during power flow regulation, thus producing power flow current. The positive sequence equivalent circuit is as follows: Figure 2 As shown, the two port converters can be equivalent to controllable voltage sources. and , The voltage of distribution network 1 is... and The impedance of distribution network line 1, This refers to the transmitting end current (power flow current). and For transmitting power, For the voltage of distribution network 2, and The impedance of distribution network line 2, For the receiving end current, and This represents the power at the receiving end.

[0033] For ease of analysis, we assume... , , For the voltage of distribution network 1 that leads the phase of the controlled voltage source, according to KVL:

[0034] (1)

[0035] From the power equation, the power injected by MMC can be expressed as:

[0036] (2)

[0037] Combining equations (1) and (2), it can be seen that the active power and reactive power transmitted by the multi-functional rapid emergency control device can be expressed as:

[0038] (3)

[0039] The above analysis shows that the multi-functional rapid emergency control device generates current flowing through the line requiring de-icing operations when transmitting power. However, the generated current, combined with the line current, is insufficient to meet the critical de-icing current requirement. By controlling the bridge arm voltage of the multi-functional rapid emergency control device, a zero-sequence voltage is generated at the grounding point of the split capacitor, forming a zero-sequence de-icing circuit. This allows a zero-sequence de-icing current to flow through the line, further increasing the line current to meet the critical de-icing current requirement.

[0040] Because distribution transformers generally use The wiring method eliminates the path for zero-sequence current, thus maintaining a symmetrical line voltage on the load side and not affecting normal load operation. Because the bridge arm of the multi-functional rapid emergency control device can be independently controlled, the zero-sequence current generated at the grounding point of the split capacitor can be equivalent to a controlled current source. The zero-sequence equivalent circuit formed by the multi-functional rapid emergency control device and GT is as follows: Figure 3 As shown. The resistance to ground of the distribution network is... capacitance to ground is The no-load impedance of a grounding transformer is typically 4% to 6%. Furthermore, the line-to-ground impedance is in parallel with the no-load impedance of the grounding transformer. Therefore, the influence of the line-to-ground capacitance current on circuit analysis can be ignored.

[0041] Neglecting the impact of the line on local branches, the KCL equations for the connection point can be written as follows:

[0042] (4)

[0043] Ground current of grounding transformer It can be represented as:

[0044] (5)

[0045] The entire circuit is three-phase symmetrical, and by the superposition theorem, we can obtain:

[0046] (6)

[0047] After the multi-functional rapid emergency control device actively injects de-icing current, the line current can be expressed as:

[0048] (7)

[0049] During online de-icing mode, assuming the zero-sequence de-icing current injected at the grounding point of the split capacitor of the multi-functional rapid emergency control device... Represented as:

[0050] (8)

[0051] In the formula, The angular frequency of the power grid. This represents the phase of the ice-melting current.

[0052] Step S102: Determine the line current based on the zero-sequence current, the positive-sequence current, and the line load current.

[0053] According to the superposition theorem, in the online de-icing mode, the line current consists of three parts: load current, power flow current, and zero-sequence de-icing current. The line current can be obtained from equations (1), (7), and (8). for:

[0054] (9)

[0055] In summary, the multi-functional rapid emergency control device of this application achieves online de-icing by utilizing zero-sequence de-icing current and power flow control current through the coordinated operation of back-to-back modular multilevel converters and grounding transformers. This not only reduces the capacity and cost of the multi-functional rapid emergency control device, but also realizes time-sharing reuse of the emergency control device, effectively improving equipment utilization efficiency and achieving time-sharing reuse of power electronic devices.

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

Claims

1. A multi-functional rapid emergency control device for active power distribution networks in ice storm scenarios, characterized in that: include: The multi-functional rapid emergency control device consists of a back-to-back modular multilevel converter configured at the beginning of the line, a grounding transformer module at the end of the line, and a distribution network module connected to both ends of the back-to-back modular multilevel converter. The back-to-back modular multilevel converter includes two identical first three-phase circuit topologies and second three-phase circuit topologies, as well as a DC split capacitor module. The first three-phase circuit topologies and the second three-phase circuit topologies are connected to the two ends of the DC split capacitor module. The DC split capacitor module includes a first DC split capacitor and a second DC split capacitor, with the negative terminal of the first DC split capacitor and the positive terminal of the second DC split capacitor connected to the ground terminal.

2. The apparatus according to claim 1, characterized in that, The power distribution module includes a first power distribution side and a second power distribution side with identical structures. The first power distribution side includes a first three-phase line topology, and the second power distribution side includes a second three-phase line topology. The first three-phase line topology corresponds to the first three-phase circuit topology, and the second three-phase line topology corresponds to the second three-phase circuit topology.

3. The apparatus according to claim 2, characterized in that, The first three-phase circuit topology and the second three-phase circuit topology include three identical single-phase circuit topologies. The single-phase circuit topology includes an upper bridge arm module, an upper bridge arm inductor, a lower bridge arm module, and a lower bridge arm inductor. One end of the upper bridge arm module is connected to the positive terminal of the first DC split capacitor, and one end of the lower bridge arm module is connected to the negative terminal of the second DC split capacitor.

4. The apparatus according to claim 3, characterized in that, The first three-phase line topology and the second three-phase line topology include three identical single-phase line topologies. The single-phase line topology includes line resistance and line inductance. The other end of the upper bridge arm module is connected to one end of the upper bridge arm inductor, and the other end of the lower bridge arm module is connected to one end of the lower bridge arm inductor. The other ends of the upper bridge arm inductor and the other ends of the lower bridge arm inductor are both connected to one end of the line resistance.

5. The apparatus according to claim 4, characterized in that, The grounding transformer module includes two identical grounding transformers. One end of the line inductor is connected to the other end of the line resistor, and the other end of the line inductor is connected to the grounding transformer.

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