Power grid iced line on-line ice melting method and system based on HDT transformer

Abstract

The invention belongs to the technical field of online ice melting, and particularly relates to a power grid ice-coated line online ice melting method and system based on an HDT transformer, and the method comprises the steps: controlling one HDT transformer to input a first ice melting current to the head end of an ice-coated line, the current phase of the first ice melting current being 90 degrees ahead of the grid-connected point voltage phase of the first ice melting current, and the HDT transformer externally presents a capacitance characteristic; meanwhile, the other HDT transformer is controlled to input a second ice melting current to the tail end of the icing line, the current phase of the second ice melting current lags behind the grid-connected point voltage phase by 90 degrees, the HDT transformer shows the inductance characteristic outwards, the current amplitude of the first ice melting current is equal to that of the second ice melting current, and the ice melting current flows on the icing line between the two HDT transformers; only reactive interaction exists between the HDT transformer and the icing line, and the sum of power interaction is zero, so that on-line ice melting of the icing line is realized under the condition that the normal power supply voltage of the icing line is not influenced.

Description

Technical Field

[0001] The present invention belongs to the technical field of online ice melting, and in particular relates to an online ice melting method, system, equipment and medium for ice-covered power line based on HDT transformer. Background Art

[0002] In recent years, various natural disasters, such as ice disasters, earthquakes, floods, and wildfires, have occurred frequently, posing a huge threat to the safe and stable operation of the power system. Among the various natural disasters suffered by the power system, ice disasters are one of the most serious disasters for the power system. Compared with other accidents, ice disasters often cause more serious losses to the power grid, ranging from ice flash to tower (pole) collapse, line breakage, and even large-scale paralysis of the power grid. Therefore, how to solve the problem of power grid icing during engineering operation has become an important research topic.

[0003] At present, deicing methods at home and abroad can be roughly divided into three categories: natural deicing, mechanical deicing and high-current deicing. The natural deicing method refers to a method of deicing and anti-icing that does not require external energy supply but relies solely on natural forces. This method requires less equipment investment and is simple and easy to operate, but the deicing effect is poor and the efficiency is low. The mechanical deicing method refers to the use of various mechanical forces to cause stress damage to the ice layer and cause it to fall off the wire; it mainly includes external force beating method, pulley rolling and scraping method and electromagnetic pulse deicing method. The external force beating method is handled on-site by the operator. Although this method is simple and easy to operate, it can only remove a small part of the ice, and the deicing speed is slow, the safety is poor, the workload is large, and the economy is poor; the pulley rolling method mainly uses the force applied to the pulley to bend the wire, generate stress to cause the ice to crack and fall off, but it is easy to accidentally damage the power equipment; the electromagnetic pulse deicing method is to apply a trigger pulse to the rectifier, so that the capacitor generates a strong magnetic field discharge through the coil to excite the electric pulse, thereby generating eddy currents in the wire, and the ice on the surface of the wire expands and falls under the action of the eddy current magnetic field and the coil magnetic field. This method is not mature enough and has not been put into practical application. The large current ice melting method uses the existing equipment and transmission capacity of the power grid to thermally melt the ice of the line through appropriate technical measures. The large current ice melting method includes overcurrent ice melting method, AC short-circuit current ice melting method, and DC current ice melting method. These methods have many limitations and disadvantages such as practical operation difficulties. For example: the overcurrent ice melting method requires increasing the load current of the ice-covered line, which will be limited by the system capacity and operation mode, and cannot melt the ice on the lightning protection line and overhead ground wire; the AC short-circuit current ice melting method consumes a lot of power and needs to modify the protection setting value. It is also necessary to ensure the safety of the system and the power supply of important users in the case of a short circuit. The operation process is complicated and cumbersome, and it has high requirements for dispatchers; the DC current ice melting method requires a special DC ice melting device, which has high construction and maintenance costs.

[0004] The invention patent with application number CN202210760795 provides a non-stop ice-melting device and method for distribution lines. The ice-melting device is composed of two cascaded H-bridge converters (CHBCs). One end of the two CHBCs is connected to the ground, and the other ends are respectively connected to the neutral points of two grounding transformers. The two grounding transformers are respectively connected to the beginning and end of the three-phase ice-covered line; this method requires the addition of a grounding transformer and the connection to the neutral point of the grounding transformer, which increases the cost.

[0005] The document "Online Deicing Method and Simulation Research on Phase-Shifting Transformer Applied to Transmission Lines" provides a method for online deicing of transmission lines using phase-shifting transformers. It mainly utilizes the voltage difference generated at the input and output ends of the phase-shifting transformer during closed-loop operation to drive the line circulation to achieve deicing. When the phase-shifting transformer applied to the power system achieves online deicing, the reactive power consumed is proportional to the line reactance value. However, for lines below 110kV, the impedance value is too large, and the reactive power consumption is difficult to compensate. In addition, the lines are often radial and cannot be looped. Therefore, this method is only applicable to online deicing of 220kV and above lines. The phase-shifting transformer adjusts the polarity output of the excitation transformer winding and the position of the on-load tap to change the direction and size of the superimposed vector voltage to achieve leading and lagging regulation of different voltages. However, the adjustment range is limited and 90-degree voltage regulation cannot be achieved.

[0006] In summary, most of the current ice-melting methods have shortcomings and are all aimed at transmission lines. There is little research on ice-melting technology for medium and low voltage distribution lines, and there is a lack of economical and applicable online ice-melting methods. Summary of the invention

[0007] The purpose of the present invention is to provide an online ice-melting method, system, equipment and medium for ice-covered power lines based on HDT transformers, which are economical and applicable and suitable for medium and low voltage distribution lines, in view of the above-mentioned problems existing in the prior art.

[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 ice-melting method for an ice-covered line of an electric power grid based on a HDT transformer, wherein the online ice-melting method for an ice-covered line of an electric power grid is performed based on an online ice-melting network architecture, wherein the online ice-melting network architecture comprises two HDT transformers connected to the head end and the end end of the ice-covered line, wherein both HDT transformers are connected to the ice-covered line through a current compensation winding arranged on the parallel side, and are connected to the secondary line through a voltage compensation winding arranged on the series side;

[0010] The online ice-melting method for ice-covered lines of the power grid is specifically as follows: controlling the parallel converter of the HDT transformer located at the head end of the ice-covered line to input a first ice-melting current whose current phase is 90 degrees ahead of the voltage phase of the grid-connected point after the current compensation winding is isolated; at the same time, controlling the parallel converter of the HDT transformer located at the end of the ice-covered line to input a second ice-melting current whose current phase is 90 degrees behind the voltage phase of the grid-connected point after the current compensation winding is isolated; the second ice-melting current is equal to the current amplitude of the first ice-melting current.

[0011] The calculation formula of the current amplitude of the first ice-melting current or the second ice-melting current is:

[0012] I HDT =K·I min ≤I max ;

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

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

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

[0016] In a second aspect, the present invention provides an online ice-melting system for ice-covered lines of a power grid based on a HDT transformer, wherein the online ice-melting system comprises an online ice-melting network architecture and a control module;

[0017] The online ice melting network architecture includes two HDT transformers connected to the head end and the end end of the ice-covered line. Both HDT transformers are connected to the ice-covered line through the current compensation windings arranged on the parallel side and are connected to the secondary line through the voltage compensation windings arranged on the series side.

[0018] The control module is used to control the parallel converter of the HDT transformer located at the head end of the ice-covered line to input a first ice-melting current whose current phase is 90 degrees ahead of the voltage phase of its grid-connected point after the current compensation winding is isolated; at the same time, control the parallel converter of the HDT transformer located at the end of the ice-covered line to input a second ice-melting current whose current phase lags the voltage phase of its grid-connected point by 90 degrees after the current compensation winding is isolated; the second ice-melting current has the same current amplitude as the first ice-melting current.

[0019] The calculation formula of the current amplitude of the first ice-melting current or the second ice-melting current is:

[0020] I HDT=K·I min ≤I max ;

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

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

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

[0024] In a third aspect, the present invention provides an online ice-melting device for ice-covered lines of a power grid based on a HDT transformer, the online ice-melting device comprising 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 ice-melting method according to instructions in the computer program code.

[0025] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, and the computer program implements the aforementioned online ice melting method when executed by a processor.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention discloses an online ice-melting method for an ice-covered line of a power grid based on a HDT transformer. The method controls the parallel converter of the HDT transformer located at the head end of the ice-covered line to input a first ice-melting current whose current phase is 90 degrees ahead of the voltage phase of the grid-connected point after the current compensation winding is isolated, so that the HDT transformer located at the head end of the ice-covered line presents a capacitive characteristic externally; at the same time, the parallel converter of the HDT transformer located at the end of the ice-covered line is controlled to input a second ice-melting current whose current phase is 90 degrees behind the voltage phase of the grid-connected point after the current compensation winding is isolated, so that the HDT transformer located at the end of the ice-covered line presents an inductive characteristic externally, the current amplitudes of the first ice-melting current and the second ice-melting current are equal, the first ice-melting current and the second ice-melting current flow on the ice-covered line between the two HDT transformers, so that only reactive interaction exists between the HDT transformer and the ice-covered line, and the sum of power interaction is zero, so that the online ice-melting of the ice-covered line is realized without affecting the normal power supply voltage of the ice-covered line. In addition to online ice melting, the HDT transformer itself also has multiple functions such as reactive power compensation, power factor control, three-phase current asymmetry compensation, voltage fluctuation control, etc., and has a wide range of uses. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 2 This is the simulation waveform obtained for test 1.

[0030] Figure 3 This is the simulation waveform obtained for test 2.

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

[0032] Figure 5 It is a structural block diagram of the online ice melting equipment described in the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with specific implementations and drawings.

[0034] The present invention is based on the hybrid flexible distribution transformer (HDT transformer) currently used in the distribution network. The principle is mainly to flexibly control the reactive current to generate reactive current that does not affect the normal power supply of the distribution network, and flow through the ice-covered line of the distribution network to achieve the ice melting effect. The HDT transformer controls its output current through a parallel converter, thereby increasing the reactive current flowing through the ice melting line, so that the reactive current flowing during ice melting meets the ice melting requirements.

[0035] Embodiment 1:

[0036] An online deicing method for ice-covered power lines based on HDT transformers is based on Figure 1The online ice-melting network architecture shown in the figure is carried out, and the online ice-melting network architecture includes two HDT transformers connected to the head end and the end of the ice-covered line. The HDT transformer is composed of a transformer body and a converter module. The transformer body is composed of 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 is composed of a parallel converter of a full-bridge power unit and a series converter of a full-bridge power unit. The parallel converter has the same structure as the series converter. The parallel converter and the series converter 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 the two HDT transformers are both connected to the ice-covered line. The ice-covered line The busbar of the 10kV distribution network is connected to the secondary line of the two HDT transformers, and the voltage compensation windings of the two HDT transformers are connected to the secondary line, which is a 400V transmission line. The online de-icing method of the de-icing line of the power grid is specifically as follows: the parallel converter of the HDT transformer located at the head end of the de-icing line is controlled to input a first de-icing current whose current phase is 90 degrees ahead of the phase of the grid-connected point voltage Vs to the head end of the de-icing line after the current compensation winding is isolated; at the same time, the parallel converter of the HDT transformer located at the end of the de-icing line is controlled to input a second de-icing current whose current phase lags 90 degrees behind the phase of the grid-connected point voltage Vs to the end of the de-icing line after the current compensation winding is isolated; the current amplitude of the second de-icing current is equal to that of the first de-icing current; the current amplitude of the first de-icing current or the second de-icing current is calculated as follows:

[0037] I HDT =K·I min ≤I max ;

[0038] In the above formula, I HDT is the current amplitude of the first ice-melting current or the second ice-melting current; K is the ice-melting current coefficient, K≥1, and is generally set to 1.1 to ensure the ice-melting effect; I min ,I max They are the minimum ice-melting current and the maximum ice-melting current respectively. The T / CSEE0061-2017 standard "Technical Guidelines for Current Melting of Overhead Lines" stipulates that the minimum ice-melting current and the maximum ice-melting current can be obtained by looking up the table based on the conductor model.

[0039] The method of the present invention realizes online ice melting of ice-covered lines by injecting reactive current into the lines through two HDT transformers, and can flexibly adjust the ice melting time according to the ice melting demand. In the process of ice melting, there is no need to cut off the load and line, which does not affect the normal operation of the distribution network and ensures the reliability of power supply of the power grid. After the ice melting is completed, the HDT transformer exits the ice melting mode and enters the normal working mode with functions such as reactive compensation, three-phase unbalanced compensation, and voltage fluctuation suppression.

[0040] To verify the effectiveness of the method described in the present invention, the following tests are performed:

[0041] Test 1:

[0042] Assume that the three-phase ice-covered line model is JL / G1A-50, the ice thickness is 8mm, the ambient temperature is minus 5 degrees, and the wind speed is 5m / s. According to the Technical Guidelines for Current De-icing of Overhead Lines, the maximum de-icing current I in this case can be obtained. max The minimum ice melting current is 405.63A. min is 206.31A, based on which the ice melting current amplitude of the HDT transformer I HDT Set to 226.91A.

[0043] During ice melting, at 0.05s, one HDT transformer injects the first ice-melting current at the head end of the ice-covered line, that is, the first ice-melting current with a phase leading of 90 degrees is injected at the head end, and the other HDT transformer injects the second ice-melting current with equal amplitude and opposite phase at the end of the ice-covered line, that is, the second ice-melting current with a phase lagging of 90 degrees is injected at the end, thereby realizing simultaneous ice melting of the three-phase ice-covered lines.

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

[0045] Test 2:

[0046] The model of the three-phase ice-covered line is JL / G1A-120, the ice thickness is 15mm, the ambient temperature is minus 3 degrees, and the wind speed is 3m / s. According to the Technical Guidelines for Current De-icing of Overhead Lines, the maximum de-icing current I can be obtained under this condition. max The minimum ice melting current is 611.17A. min is 274.31A, K is set to 1.4, and the ice melting current amplitude of the HDT transformer is I HDT Set to 384A.

[0047] During ice melting, at 0.05s, one HDT transformer injects the first ice-melting current at the head end of the ice-covered line, that is, the first ice-melting current with a phase leading of 90 degrees is injected at the head end, and the other HDT transformer injects the second ice-melting current with equal amplitude and opposite phase at the end of the ice-covered line, that is, the second ice-melting current with a phase lagging of 90 degrees is injected at the end, thereby realizing simultaneous ice melting of the three-phase ice-covered lines.

[0048] The simulation results are as follows Figure 3 As shown, it can be seen that the peak value of the normal working current I_line flowing through the line before 0.05s is 20A, and the effective value is 14A. After the ice-melting current is injected, the working current I_line peak value is 564A, and the effective value is about 398A; and the load working current I_load before and after the ice-melting current is injected remains unchanged. It can be seen that the sum of power interactions during the ice-melting process is zero. Ice melting does not affect the normal 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] Embodiment 2:

[0050] See also Figure 4 , an online ice-melting system for ice-covered power lines based on HDT transformers, the online ice-melting system comprising an online ice-melting network architecture and a control module; the online ice-melting network architecture comprises two HDT transformers connected to the head end and the end end of the ice-covered line, the two HDT transformers are connected to the ice-covered line through current compensation windings arranged on the parallel side, the ice-covered line is a 10kV distribution network bus, the two HDT transformers are connected to the secondary line through voltage compensation windings arranged on the series side, the secondary line is a 400V transmission line; the control module is used to control the The parallel converter of the HDT transformer at the head end of the ice-covered line is isolated by the current compensation winding, and the input current phase of the first ice-melting current of the first end of the ice-covered line is 90 degrees ahead of the voltage phase of the grid-connected point; at the same time, the parallel converter of the HDT transformer at the end of the ice-covered line is controlled to input the second ice-melting current of the current phase of the end of the ice-covered line after the current compensation winding is isolated; the current amplitude of the second ice-melting current is equal to that of the first ice-melting current; the calculation formula of the current amplitude of the first ice-melting current or the second ice-melting current is:

[0051] I HDT =K·I min ≤I max ;

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

[0053] Embodiment 3:

[0054] See also Figure 5, an online ice-melting device for ice-covered lines of a power grid based on a HDT transformer, the online ice-melting device comprising a memory and a processor, the memory being used to store computer program codes and transmit the computer program codes to the processor, the processor being used to execute the online ice-melting method as described in Example 1 according to instructions in the computer program codes.

[0055] Embodiment 4:

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

[0057] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0058] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0059] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0060] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0061] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. An online ice-melting method for ice-covered power lines based on HDT transformers, characterized in that: The online ice-melting method for the ice-covered line of the power grid is performed based on an online ice-melting network architecture, which includes two HDT transformers connected to the head end and the end end of the ice-covered line. Both HDT transformers are connected to the ice-covered line through a current compensation winding arranged on the parallel side, and are connected to the secondary line through a voltage compensation winding arranged on the series side. The online ice melting method for ice-covered power grid lines is specifically as follows: The parallel converter of the HDT transformer located at the head end of the ice-covered line is controlled to input a first ice-melting current whose current phase is 90 degrees ahead of the voltage phase of the grid-connected point after the current compensation winding is isolated; at the same time, the parallel converter of the HDT transformer located at the end of the ice-covered line is controlled to input a second ice-melting current whose current phase lags the voltage phase of the grid-connected point by 90 degrees after the current compensation winding is isolated; the second ice-melting current is equal to the current amplitude of the first ice-melting current.

2. The method for online ice melting of ice-covered power lines based on HDT transformer according to claim 1 is characterized in that: The calculation formula of the current amplitude of the first ice-melting current or the second ice-melting current is: IHDT=K·I min ≤I max ; In the above formula, I HDT is the current amplitude of the first ice-melting current or the second ice-melting current; K is the ice melting current coefficient, K≥1; I min ,I max They are the minimum ice-melting current and the maximum ice-melting current respectively.

3. The method for online ice melting of ice-covered power lines based on HDT transformer according to claim 1 is characterized in that: The ice-covered line is a 10kV distribution network bus.

4. The method for online ice melting of ice-covered power lines based on HDT transformers according to claim 3 is characterized in that: The secondary line is a 400V transmission line.

5. The online ice melting system for ice-covered power lines based on HDT transformers is characterized by: The online ice melting system includes an online ice melting network architecture and a control module; The online ice melting network architecture includes two HDT transformers connected to the head end and the end end of the ice-covered line. Both HDT transformers are connected to the ice-covered line through the current compensation windings arranged on the parallel side and are connected to the secondary line through the voltage compensation windings arranged on the series side. The control module is used to control the parallel converter of the HDT transformer located at the head end of the ice-covered line to input a first ice-melting current whose current phase is 90 degrees ahead of the voltage phase of its grid-connected point after the current compensation winding is isolated; at the same time, control the parallel converter of the HDT transformer located at the end of the ice-covered line to input a second ice-melting current whose current phase lags the voltage phase of its grid-connected point by 90 degrees after the current compensation winding is isolated; the second ice-melting current has the same current amplitude as the first ice-melting current.

6. The online ice melting system for ice-covered power lines based on HDT transformer according to claim 5 is characterized in that: The calculation formula of the current amplitude of the first ice-melting current or the second ice-melting current is: IHDT=K·I min ≤I max ; In the above formula, I HDT is the current amplitude of the first ice-melting current or the second ice-melting current; K is the ice-melting current coefficient; I min ,I max They are the minimum ice-melting current and the maximum ice-melting current respectively.

7. The online ice melting system for ice-covered power lines based on HDT transformer according to claim 5 is characterized by: The ice-covered line is a 10kV distribution network bus.

8. The online ice melting system for ice-covered power lines based on HDT transformer according to claim 7 is characterized in that: The secondary line is a 400V transmission line.

9. Online ice melting equipment for ice-covered power lines based on HDT transformers, characterized by: 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 used to execute the online ice melting method according to any one of claims 1 to 4 according to the instructions in the computer program code.

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

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