On-line ice-melting method and system for iced power grid line based on HDT transformer

Abstract

The present application belongs to the technical field of online ice melting, and particularly relates to a power grid iced line online ice melting method and system based on HDT transformers. The method controls a first ice melting current of a HDT transformer to be 90 degrees ahead of the phase of the voltage at the grid connection point of the iced line, and the HDT transformer presents a capacitive characteristic to the outside. Meanwhile, the method controls a second ice melting current of another HDT transformer to be 90 degrees behind the phase of the voltage at the grid connection point of the iced line, and the HDT transformer presents an inductive characteristic to the outside. The current amplitudes of the first ice melting current and the second ice melting current are equal, and the ice melting current flows on the iced line between the two HDT transformers. The HDT transformers and the iced line only have reactive power interaction, and the sum of the power interaction is zero, so that the iced line online ice melting is realized without affecting the normal power supply voltage of the iced line.

Description

Technical Field

[0001] This invention belongs to the field of online de-icing technology, specifically relating to an online de-icing method, system, equipment, and medium for power grid icing lines based on HDT transformers. Background Technology

[0002] In recent years, various natural disasters, such as ice storms, earthquakes, floods, and wildfires, have occurred frequently, posing a significant threat to the safe and stable operation of the power system. Among the various natural disasters that affect the power system, ice storms are one of the most severe. Compared to other accidents, ice storms often cause more serious damage to the power grid, ranging from minor ice flashovers to tower collapses, line breaks, and even large-scale grid paralysis. Therefore, how to address the problem of power grid icing during engineering operations has become an important research topic.

[0003] Currently, de-icing methods both domestically and internationally can be broadly categorized into three types: natural de-icing, mechanical de-icing, and high-current de-icing. Natural de-icing refers to methods that rely solely on natural forces to remove and prevent icing without external energy supply. This method requires less equipment investment and is simple and easy to implement, but its de-icing effect is poor and its efficiency is low. Mechanical de-icing utilizes various mechanical forces to cause stress-induced breakage of the ice layer, causing it to detach from the conductor. It mainly includes external force knocking, pulley rolling and scraping, and electromagnetic pulse de-icing. External force knocking is handled on-site by the operator; while simple and easy to implement, it can only remove a small portion of the ice, resulting in slow de-icing speed, poor safety, large workload, and poor economy. Pulley rolling primarily utilizes the force applied to pulleys to bend the conductor, generating stress that causes the ice to crack and detach, but it can easily damage electrical equipment. Electromagnetic pulse de-icing involves applying a trigger pulse to the rectifier, causing the capacitor to generate a strong magnetic field discharge through the coil, thus generating eddy currents in the conductor. Under the influence of the eddy current magnetic field and the coil magnetic field, the ice on the conductor surface expands, cracks, and falls off. This method is currently not mature enough and has not been put into practical application. High-current de-icing utilizes existing power grid equipment and transmission capacity to thermally de-ice lines through appropriate technical measures. High-current de-icing methods include overcurrent de-icing, AC short-circuit current de-icing, and DC current de-icing. These methods all have many limitations and drawbacks, such as difficulties in practical operation. For example, overcurrent de-icing requires increasing the load current of the iced lines, is limited by system capacity and operating mode, and cannot melt ice on lightning protection wires and overhead ground wires; AC short-circuit current de-icing consumes a large amount of electricity and requires modification of protection settings, and also needs to ensure system safety and power supply to important users under short-circuit conditions, making the operation complex and cumbersome, and demanding high skills from dispatchers; DC current de-icing requires specialized DC de-icing devices, resulting in high costs for construction and maintenance.

[0004] The invention patent with application number CN202210760795 provides a power-off de-icing device and method for power distribution lines. This de-icing device consists of two cascaded H-bridge converters (CHBCs). One end of each CHBC is connected to the ground, and the other end is connected to the neutral point of two grounding transformers, which are respectively connected to the beginning and end of the three-phase icing line. This method requires the addition of a grounding transformer and connection to its neutral point, which increases the cost.

[0005] The paper "Application of Phase-Shifting Transformers in Online De-icing Methods and Simulation Research of Transmission Lines" presents a method for online de-icing of transmission lines using phase-shifting transformers. This method primarily utilizes the voltage difference generated at the input and output terminals of the phase-shifting transformer during loop operation to drive the circulating current in the line, thus achieving de-icing. When applying phase-shifting transformers to power systems for online de-icing, the reactive power consumed is proportional to the line reactance. However, for lines below 110kV, the impedance is too high, making reactive power consumption difficult to compensate for. Furthermore, the lines are often radial, making loop formation impossible. Therefore, this method is only suitable for online de-icing of 220kV and above lines. Phase-shifting transformers can also adjust the polarity output of the excitation transformer windings and the position of the on-load tap change the direction and magnitude of the superimposed vector voltage, achieving lead and lag regulation of different voltages. However, the adjustment range is limited, and 90-degree voltage regulation cannot be achieved.

[0006] In summary, most current de-icing methods have shortcomings and are all designed for transmission lines. There is limited research on de-icing technology for medium and low voltage distribution lines, and there is a lack of economical and applicable online de-icing methods. Summary of the Invention

[0007] The purpose of this invention is to address the aforementioned problems in the prior art by providing an economical and applicable method, system, equipment, and medium for online de-icing of grid icing lines based on HDT transformers, which is suitable for medium and low voltage power distribution lines.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] In a first aspect, the present invention provides an online de-icing method for power grid icing lines based on HDT transformers. The online de-icing method for power grid icing lines is based on an online de-icing network architecture, which includes two HDT transformers connected to the beginning and end of the icing line. Both HDT transformers are connected to the icing line through a current compensation winding set on the parallel side and to the secondary line through a voltage compensation winding set on the series side.

[0010] The online de-icing method for the icy power grid line is as follows: The parallel converter of the HDT transformer at the beginning of the icy line is controlled to input a first de-icing current with a phase 90 degrees ahead of the phase of its grid connection voltage after isolation via a current compensation winding. Simultaneously, the parallel converter of the HDT transformer at the end of the icy line is controlled to input a second de-icing current with a phase 90 degrees behind the phase of its grid connection voltage after isolation via a current compensation winding. The amplitudes of the second de-icing current and the first de-icing current are equal.

[0011] The formula for calculating the amplitude of the first or second de-icing current is as follows:

[0012] I HDT =K·I min ≤I max ;

[0013] In the above formula, I HDT I is the amplitude of the first or second de-icing current; K is the de-icing current coefficient, K≥1; min I max These are the minimum and maximum de-icing currents, respectively.

[0014] The icing-covered line is a 10kV distribution network bus.

[0015] The secondary line is a 400V power transmission line.

[0016] Secondly, the present invention provides an online de-icing system for power grid icing lines based on HDT transformers, the online de-icing system including an online de-icing network architecture and a control module;

[0017] The online de-icing network architecture includes two HDT transformers connected to the beginning and end of the icing line. Both HDT transformers are connected to the icing line through a current compensation winding on the parallel side and to the secondary line through a voltage compensation winding on the series side.

[0018] The control module is used to control the parallel converter of the HDT transformer located at the beginning of the icing line to input a first de-icing current whose phase leads the phase of its grid-connected voltage by 90 degrees after being isolated by the current compensation winding; at the same time, it controls the parallel converter of the HDT transformer located at the end of the icing line to input a second de-icing current whose phase lags the phase of its grid-connected voltage by 90 degrees after being isolated by the current compensation winding; the current amplitude of the second de-icing current is equal to that of the first de-icing current.

[0019] The formula for calculating the amplitude of the first or second de-icing current is as follows:

[0020] I HDT=K·I min ≤I max ;

[0021] In the above formula, I HDT I is the amplitude of the first or second de-icing current; K is the de-icing current coefficient, K≥1; min I max These are the minimum and maximum de-icing currents, respectively.

[0022] The icing-covered line is a 10kV distribution network bus.

[0023] The secondary line is a 400V power transmission line.

[0024] Thirdly, the present invention provides an online de-icing device for power grid icing lines based on HDT transformers. The online de-icing device includes a memory and a processor. The memory is used to store computer program code and transmit the computer program code to the processor. The processor is used to execute the aforementioned online de-icing method according to the instructions in the computer program code.

[0025] Fourthly, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the aforementioned online ice-melting method.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention discloses an online de-icing method for grid icing lines based on HDT transformers. The method controls the parallel converter of the HDT transformer at the beginning of the icing line to input a first de-icing current with a phase 90 degrees ahead of its grid connection voltage after isolation via a current compensation winding. This causes the HDT transformer at the beginning of the icing line to exhibit capacitive characteristics. Simultaneously, the parallel converter of the HDT transformer at the end of the icing line is controlled to input a second de-icing current with a phase 90 degrees behind its grid connection voltage after isolation via a current compensation winding. This causes the HDT transformer at the end of the icing line to exhibit inductive characteristics. The first and second de-icing currents have equal amplitudes and flow along the icing line between the two HDT transformers. This results in only reactive power interaction between the HDT transformers and the icing line, with the sum of power interactions being zero. Online de-icing of the icing line is achieved without affecting its normal power supply voltage. In addition to online de-icing, HDT transformers also have multiple functions such as reactive power compensation, power factor control, three-phase current asymmetry compensation, and voltage fluctuation control, making them widely applicable. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the online ice melting network architecture described in this invention.

[0029] Figure 2 The simulation waveform obtained for test 1.

[0030] Figure 3 The simulation waveform obtained from test 2 is shown.

[0031] Figure 4 This is a structural block diagram of the online ice melting system described in this invention.

[0032] Figure 5 This is a structural block diagram of the online ice-melting device described in this invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0034] This invention is based on the hybrid flexible distribution transformer (HDT transformer) currently used in distribution networks. Its principle primarily involves flexibly regulating reactive current to generate reactive current that does not affect the normal power supply of the distribution network. This reactive current flows through the icing lines of the distribution network, achieving a de-icing effect. The HDT transformer regulates its output current through a parallel converter, thereby increasing the reactive current flowing through the de-icing lines, ensuring that the reactive current flowing during de-icing meets the de-icing requirements.

[0035] Example 1:

[0036] An online de-icing method for power grid icing lines based on HDT transformers, based on... Figure 1The online de-icing network architecture shown includes two HDT transformers connected to the beginning and end of the icing line. Each HDT transformer consists of a transformer body and a converter module. The transformer body comprises a main transformer, a current compensation winding on the parallel side (10kV high-voltage side), and a voltage compensation winding on the series side (400V low-voltage side). The converter module consists of a parallel converter with one full-bridge power unit and a series converter with one full-bridge power unit. The parallel and series converters have identical structures and share a high-voltage DC bus capacitor. The parallel converter is connected to the current compensation winding, and the series converter is connected to the voltage compensation winding. The current compensation windings of both HDT transformers are connected to the icing line. For a 10kV distribution network busbar, the voltage compensation windings of two HDT transformers are connected to the secondary line, which is a 400V transmission line. The online de-icing method for the icing line is as follows: The parallel converter of the HDT transformer at the beginning of the icing line is controlled to input a first de-icing current with a phase 90 degrees ahead of its grid connection voltage Vs after isolation via the current compensation winding. Simultaneously, the parallel converter of the HDT transformer at the end of the icing line is controlled to input a second de-icing current with a phase 90 degrees behind its grid connection voltage Vs after isolation via the current compensation winding. The amplitudes of the second de-icing current and the first de-icing current are equal. The formula for calculating the amplitude of the first or second de-icing current is:

[0037] I HDT =K·I min ≤I max ;

[0038] In the above formula, I HDT I is the amplitude of the first or second de-icing current; K is the de-icing current coefficient, K≥1, and is generally set to 1.1 to ensure de-icing effect; min I max These are the minimum and maximum de-icing currents, respectively. The T / CSEE0061-2017 standard "Technical Guidelines for De-icing of Overhead Lines" stipulates that the minimum and maximum de-icing currents can be obtained by referring to a table based on the conductor type.

[0039] The method described in this invention achieves online de-icing of iced lines by injecting reactive current into the lines using two HDT transformers. The de-icing time can be flexibly adjusted according to the de-icing requirements. During the de-icing process, there is no need to disconnect loads or lines, thus not affecting the normal operation of the distribution network and ensuring the reliability of power supply. After de-icing is completed, the HDT transformers exit the de-icing mode and enter a normal operating mode with functions such as reactive power compensation, three-phase imbalance compensation, and voltage fluctuation suppression.

[0040] To verify the effectiveness of the method described in this invention, the following tests were conducted:

[0041] Test 1:

[0042] Assume a three-phase icing line, model JL / G1A-50, with an icing thickness of 8mm, an ambient temperature of -5°C, and a wind speed of 5m / s. Referring to the "Technical Guidelines for Ice Melting of Overhead Lines," the maximum ice-melting current I under these conditions can be obtained. max The minimum de-icing current is 405.63A. min The value is 206.31A. Based on this, the de-icing current amplitude I of the HDT transformer is... HDT Set to 226.91A.

[0043] During the de-icing process, at 0.05s, one HDT transformer injects the first de-icing current at the beginning of the iced line, which is a first de-icing current with a phase leading by 90 degrees. Another HDT transformer injects the second de-icing current with the same amplitude and opposite phase at the end of the iced line, which is a second de-icing current with a phase lagging by 90 degrees, thereby achieving simultaneous de-icing of the three-phase iced lines.

[0044] Simulation results are as follows Figure 2 As shown, the peak value of the normal operating current I_line flowing through the iced line before 0.05s is 20A, and its effective value is 14A. After the de-icing current is injected, the peak value of the operating current I_line is 336A, and its effective value is about 237A. The load operating current I_load remains unchanged before and after the de-icing current is injected. It can be seen that the sum of power interaction during the de-icing process is zero. De-icing does not affect the normal power supply voltage of the distribution network and does not affect the normal operation of the load.

[0045] Test 2:

[0046] The three-phase icing line is model JL / G1A-120, with an icing thickness of 15mm, an ambient temperature of -3 degrees Celsius, and a wind speed of 3m / s. Referring to the "Technical Guidelines for Ice Melting of Overhead Lines," the maximum ice melting current I under these conditions can be obtained. max The minimum de-icing current is 611.17A. min The current is 274.31A, and K is set to 1.4. Based on this, the de-icing current amplitude I of the HDT transformer is... HDT Set to 384A.

[0047] During the de-icing process, at 0.05s, one HDT transformer injects the first de-icing current at the beginning of the iced line, which is a first de-icing current with a phase leading by 90 degrees. Another HDT transformer injects the second de-icing current with the same amplitude and opposite phase at the end of the iced line, which is a second de-icing current with a phase lagging by 90 degrees, thereby achieving simultaneous de-icing of the three-phase iced lines.

[0048] Simulation results are as follows Figure 3 As shown, the peak value of the normal operating current I_line flowing through the line before 0.05s is 20A, and the effective value is 14A. After the de-icing current is injected, the peak value of the operating current I_line is 564A, and the effective value is about 398A. The load operating current I_load remains unchanged before and after the de-icing current is injected. It can be seen that the sum of power interaction during the de-icing process is zero. De-icing does not affect the normal power supply voltage of the distribution network, does not affect the normal operation of the load, and the entire network load does not need to be shut down.

[0049] Example 2:

[0050] See Figure 4 An online de-icing system for power grid icing lines based on HDT transformers is disclosed. The online de-icing system includes an online de-icing network architecture and a control module. The online de-icing network architecture includes two HDT transformers connected to the beginning and end of the icing line. Both HDT transformers are connected to the icing line via current compensation windings on their parallel sides. The icing line is a 10kV distribution network bus. Both HDT transformers are connected to a secondary line via voltage compensation windings on their series sides. The secondary line is a 400V transmission line. The control module is used to control the system located at... The parallel converter of the HDT transformer at the beginning of the icing line, after isolation by the current compensation winding, inputs a first de-icing current to the beginning of the icing line, whose phase leads the phase of its grid-connected voltage by 90 degrees. Simultaneously, the parallel converter of the HDT transformer at the end of the icing line, after isolation by the current compensation winding, inputs a second de-icing current to the end of the icing line, whose phase lags the phase of its grid-connected voltage by 90 degrees. The amplitudes of the second de-icing current and the first de-icing current are equal. The formula for calculating the amplitude of the first or second de-icing current is as follows:

[0051] I HDT =K·I min ≤I max ;

[0052] In the above formula, I HDT I is the amplitude of the first or second de-icing current; K is the de-icing current coefficient, K≥1; min I max These are the minimum and maximum de-icing currents, respectively.

[0053] Example 3:

[0054] See Figure 5An online de-icing device for power grid icing lines based on HDT transformers is disclosed. The online de-icing device includes a memory and a processor. The memory is used to store computer program code and transmit the computer program code to the processor. The processor is used to execute the online de-icing method as described in Example 1 according to the instructions in the computer program code.

[0055] Example 4:

[0056] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the online ice-melting method as described in Example 1.

[0057] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0058] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0059] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0060] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0061] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. An online de-icing method for power grid icing lines based on HDT transformers, characterized in that: The online de-icing method for the icing power grid line is based on an online de-icing network architecture, which includes two HDT transformers connected to the beginning and end of the icing line. Both HDT transformers are connected to the icing line through a current compensation winding set on the parallel side and to the secondary line through a voltage compensation winding set on the series side. The online de-icing method for the power grid icing lines is as follows: The parallel converter of the HDT transformer located at the beginning of the icing line is controlled to input a first de-icing current whose phase leads the phase of its grid-connected voltage by 90 degrees after being isolated by the current compensation winding; at the same time, the parallel converter of the HDT transformer located at the end of the icing line is controlled to input a second de-icing current whose phase lags the phase of its grid-connected voltage by 90 degrees after being isolated by the current compensation winding; the current amplitudes of the second de-icing current and the first de-icing current are equal.

2. The online de-icing method for power grid icing lines based on HDT transformers according to claim 1, characterized in that: The formula for calculating the amplitude of the first or second de-icing current is as follows: I HDT = K I min ≤ I max ; In the above formula, I HDT is the current amplitude of the first or second ice-melting current; K is the melting current coefficient, K≥1; I min I max These are the minimum and maximum de-icing currents, respectively.

3. The online de-icing method for power grid icing lines based on HDT transformers according to claim 1, characterized in that: The icing-covered line is a 10kV distribution network bus.

4. The online de-icing method for power grid icing lines based on HDT transformers according to claim 3, characterized in that: The secondary line is a 400V transmission line.

5. An online de-icing system for power grid icing lines based on HDT transformers, characterized in that: The online ice-melting system includes an online ice-melting network architecture and a control module; The online de-icing network architecture includes two HDT transformers connected to the beginning and end of the icing line. Both HDT transformers are connected to the icing line through a current compensation winding on the parallel side and to the secondary line through a voltage compensation winding on the series side. The control module is used to control the parallel converter of the HDT transformer located at the beginning of the icing line to input a first de-icing current whose phase leads the phase of its grid-connected voltage by 90 degrees after being isolated by the current compensation winding; at the same time, it controls the parallel converter of the HDT transformer located at the end of the icing line to input a second de-icing current whose phase lags the phase of its grid-connected voltage by 90 degrees after being isolated by the current compensation winding; the current amplitude of the second de-icing current is equal to that of the first de-icing current.

6. The online de-icing system for power grid icing lines based on HDT transformers according to claim 5, characterized in that: The formula for calculating the amplitude of the first or second de-icing current is as follows: I HDT =K·I min ≤I max ; In the above formula, I HDT I represents the amplitude of the first or second de-icing current; K is the de-icing current coefficient; I min I max These are the minimum and maximum de-icing currents, respectively.

7. The online de-icing system for power grid icing lines based on HDT transformers according to claim 5, characterized in that: The icing-covered line is a 10kV distribution network bus.

8. The online de-icing system for power grid icing lines based on HDT transformers according to claim 7, characterized in that: The secondary line is a 400V transmission line.

9. An online de-icing device for power grid icing lines based on HDT transformers, characterized in that: The online ice-melting device includes a memory and a processor; The memory is used to store computer program code and transmit the computer program code to the processor; The processor is configured to execute the online ice melting method as described in any one of claims 1 to 4 according to instructions in the computer program code.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program that, when executed by a processor, implements the online ice-melting method as described in any one of claims 1 to 4.

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