Alternating current ice melting reactive compensation control method considering impedance change of ground wire

Abstract

The invention relates to an alternating current ice melting reactive compensation control method considering ground wire impedance change, which belongs to the technical field of alternating current ice melting, and comprises the following steps: S1, connecting a reactive compensation device into an ice melting loop, and injecting ice melting current into an overhead ground wire through an alternating current power supply; s2, measuring the length and the temperature of the ground wire in the ice melting process through a sag and temperature sensing and monitoring assembly; s3, on the basis of the ground wire impedance change model in the ice melting process, ground wire impedance change is calculated according to the ground wire length and the ground wire temperature; s4, substituting the ground wire impedance value into the heat effect theoretical model, and calculating the required reactive compensation capacity in combination with the temperature rise and the current effective value; and S5, based on the optimal array algorithm, controlling the reactive power compensation device to switch the switching capacitor bank array combination of the corresponding reactive power compensation capacity.

Description

Technical Field

[0001] This invention belongs to the field of AC de-icing technology and relates to an AC de-icing reactive power compensation control method that takes into account changes in ground wire impedance. Background Technology

[0002] Ice accumulation on overhead ground wires poses serious safety hazards, making the application and development of de-icing technology a highly valued issue. Traditional DC de-icing methods involve large, costly devices that are often difficult to move and require energizing the entire ground wire to achieve Joule heating, resulting in high power consumption and poor flexibility. In contrast, AC de-icing methods have lower equipment costs and can draw AC power directly from the grid, significantly simplifying the equipment. Relatively small AC de-icing devices can be moved flexibly to de-ic the ground wire by section, potentially significantly reducing power consumption during de-icing.

[0003] However, existing AC de-icing technology faces challenges in current regulation compared to DC de-icing, particularly in precise current control. This results in AC de-icing devices providing a large effective de-icing current even in areas with mild icing, leading to energy waste or excessive ground wire temperature rise exceeding operating requirements. AC de-icing control methods primarily rely on impedance adjustment of the de-icing circuit to alter the effective value of the de-icing current and the active power responsible for ground wire temperature rise. Some studies propose adjustable control of AC de-icing through distributed power flow controllers, utilizing bypass switches to alter the equivalent impedance of the coupling transformer for flexible regulation. However, most research focuses on increasing AC de-icing power, and current methods have insufficient research on expanding the adjustable range and controllability of the de-icing current. Furthermore, changes in conductor temperature and sag (line length) during overhead ground wire de-icing cause variations in the equivalent impedance of the de-icing circuit, making AC de-icing current regulation and line impedance matching even more difficult.

[0004] AC de-icing technology, with its flexible and adjustable de-icing current and ability to adapt to changes in loop impedance during the de-icing process, can significantly reduce de-icing power consumption. It is suitable for distributed de-icing strategies that adjust the de-icing output based on the actual icing conditions of different grounding segments. Therefore, designing a reliable AC de-icing impedance feedback control method is of great significance. Summary of the Invention In view of this, the purpose of the present invention is to provide an AC de-icing reactive power compensation control method that takes into account changes in grounding impedance.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A reactive power compensation control method for AC de-icing considering ground wire impedance changes includes the following steps: S1: Connect the reactive power compensation device to the de-icing circuit and inject de-icing current into the overhead ground wire through AC power supply; S2: Measure the ground wire length and ground wire temperature during the ice melting process using sag and temperature sensing monitoring components; S3: Based on the ground wire impedance change model during the ice melting process, the ground wire impedance change is calculated according to the ground wire length and ground wire temperature; S4: Substitute the grounding impedance value into the thermal effect theoretical model and combine it with the temperature rise and the effective value of the current to calculate the required reactive power compensation capacity; S5: Based on the optimal array algorithm, control the switching of the capacitor bank array combination of the corresponding reactive power compensation capacity of the reactive power compensation device.

[0006] Furthermore, the temperature sensing and monitoring component is based on optical fiber temperature sensing and identification, detects the characteristic quantity of light to realize ground wire temperature monitoring, and uses composite optical cable ground wire to transmit optical signals and thermal information.

[0007] Furthermore, the sag sensing and monitoring component uses an accelerometer to detect the acceleration information of the ground wire in various directions, calculates the displacement and tilt angle of the conductor through mechanical calculations, and then depicts the sag trajectory of the ground wire, and further calculates the length of the ground wire.

[0008] Furthermore, the model for the change in ground wire impedance during the ice melting process described in step S3 is constructed as follows: After the injection of AC de-icing current into the overhead ground wire covered with ice, the heat balance equation during the establishment of thermal steady state satisfies the following formula:

[0009] In the formula, I rms This is the effective value of the power frequency AC current. R D For the dynamic resistance of the overhead ground wire, d a , d b These are the conductor layer and the ice layer along the gradient direction, respectively. z Length, m a , m b These represent the total mass of the conductor layer and the ice layer, respectively. C a , C b The specific heat capacities of the conductor layer and the ice layer are respectively. , These represent the temperature gradients of the conductor layer and the ice layer, respectively. h The convective heat transfer coefficient characterizes heat convection transfer. and These are the surface emissivity and the Stefan-Boltzmann constant, respectively, characterizing thermal radiation transfer. S Area of ​​contact with air. T 0、 T c These are the average temperatures of the air contact surface and the external environment, respectively. During the ice melting process R D The change is primarily affected by temperature conditions, satisfying the formula:

[0010] In the formula, R D The resistance at any temperature R 20 The resistance value at 20℃ T a The average temperature of the conductor. α It is the temperature coefficient of resistance; Changes in the sag of the overhead ground wire result in changes in the conductor length, and the conductor length satisfies the formula:

[0011] In the formula, L D The actual dynamic inner length of the span is calculated to take into account the sag condition. l s For gear distance, H The difference in height; For the specific load of the wire, The minimum point stress is related to the mass of the overhead ground wire itself and the load force; under arbitrary temperature conditions, the dynamic resistance of the conductor considering the dynamic length of the conductor is considered. R D Satisfying the formula:

[0012] In the formula, For any temperature, the length direction of the line is... x Equivalent resistivity of the conductor cross-section at that location. and These represent the resistivity of the steel core and aluminum layer of aluminum-clad steel strand at any temperature. A steel ( x ), A Al ( x ) respectively represent x The cross-sectional area of ​​the steel core and aluminum layer is used to calculate the dynamic resistance of the overhead ground wire during the ice melting process. R D ; I rms The adjustment is based on switching reactive power compensation capacitors, while the line reactance in the de-icing compensation circuit is... X D It also changes dynamically with the degree of sag during the melting process, satisfying the formula:

[0013] In the formula, The power frequency is 50Hz. is the vacuum permeability constant. d ij The geometric mean distance between any two lines of an overhead transmission line. d m GMR is the overall geometric mean distance parameter, and GMR is the average geometric radius of the ground wire, which is related to the stranded wire structure and deformation.

[0014] Furthermore, in step S4, the melting circuit adjusts the circuit impedance by switching the reactive power compensation capacitor, thereby changing the effective value of the AC melting current. The method of matching the switching of the reactive power compensation capacitor with the change in the melting circuit impedance is to adjust the effective value of the circuit melting current so that the conductor temperature rise meets the AC melting temperature control constraint. The effective range of AC current required to be injected during the de-icing process of the overhead ground wire is calculated based on the temperature constraint boundary conditions. The control range of reactive power compensation capacity is obtained by inversion of the current control range, satisfying the formula:

[0015] In the formula, Q com For reactive power compensation, C com For reactive power compensation capacity, V rms and I rms To connect to the power frequency AC voltage and current RMS values Q line For line reactive power, P The active power of the line; the voltage across the capacitor. V com Satisfying the formula: .

[0016] Furthermore, in step S5, the optimal array algorithm is used to match the combination of the switched capacitor bank arrays with the required reactive power compensation capacity. First, initialize the circuit array, then add any capacitor C in the array. i Make any combination; Preset voltage Assign to any array combination and detect the array output current. And calculate the array capacitance. C m and through formula The difference was calculated. ; Find the minimum value among the N array combinations. The absolute value and the new optimal result obtained by repeating the above steps The values ​​are compared to determine whether the absolute value of the difference satisfies the condition that it is less than a threshold. Q If the conditions are met, then... hour, If the matching capacitance value and the reactive power compensation scheme corresponding to the capacitor switching array are used, then the process will proceed to the step of randomly generating N schemes according to the preset algorithm until the threshold condition is met.

[0017] Furthermore, it also includes the following steps: Collect real-time temperature, humidity, wind speed, and line sag; determine whether the specific work requirement is rapid de-icing or preventative antifreeze; determine the icing situation through acceleration and tension sensors, as well as image recognition. Matches a pre-defined constraint library, including maximum de-icing current, minimum effective de-icing current, and conductor temperature rise limits; Perform multi-objective optimization calculations: dynamically adjust the output voltage range on the transformer side, and simultaneously match the optimal reactive power compensation switching position based on the line impedance characteristics.

[0018] Furthermore, a fully graphical programming technology is adopted to perform logic programming according to requirements, meeting users' requirements for simple boundary manipulation.

[0019] The beneficial effects of this invention are as follows: Based on the research and analysis of the application conditions of overhead ground wire de-icing technology, this method adopts the following solutions to the key technical problems existing in current de-icing methods: 1) To address the issues of high power consumption and low efficiency in traditional de-icing technologies, this method proposes a flexible and portable AC de-icing device. The designed control method enables segmented de-icing by adjusting the output of the overhead ground wire according to the icing status of the section.

[0020] 2) In view of the difficulty in precise current control of AC de-icing technology compared with DC de-icing technology, this method proposes a multi-level reactive power compensation control adjustment method to change the impedance of the de-icing circuit as needed, thereby changing the effective value of the de-icing current.

[0021] 3) In view of the problem that existing research focuses on improving the power of AC ice melting but does not fully expand the adjustable range and controllability of ice melting current, this method proposes a feedback regulation method for matching the current and the dynamic impedance of the circuit during the ice melting process, and combines it with the method of increasing the number of switching capacitor banks to improve the control range and accuracy.

[0022] 4) To address the problem of matching difficulties caused by changes in circuit impedance during the ice melting process, this method proposes a calculation model for dynamic impedance and reactive power compensation capacity matching during the ice melting process, forming a sensor monitoring feedback design to enable dynamic matching of reactive power compensation capacitor capacity switching control with circuit impedance during the ice melting process.

[0023] This method offers the following advantages, providing a more precise and flexible method for controlling the de-icing current in overhead ground wire AC de-icing technology: 1) The control accuracy of AC de-icing current is relatively high. The complexity and control accuracy are balanced by the design of switching capacitor banks and control algorithms. 2) The theoretical model for the change in ground wire loop impedance during ice melting and the dynamic matching of reactive power compensation capacity fully considers the influence of changes in ground wire temperature and sag (line length) caused by ice melting. Simulation and experimental verification show that the calculation results of the established model are relatively accurate. 3) The impedance sensing and monitoring of the overhead ground wire and the feedback control of the switching of the multi-stage reactive power compensation capacitor can achieve the required temperature rise effect with appropriate current according to the actual icing situation of the de-icing ground wire section, thereby reducing the power consumption of de-icing.

[0024] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 Overall block diagram of AC reactive power compensation control method for de-icing considering ground wire impedance changes; Figure 2 A schematic diagram showing the impedance change of the overhead ground wire during the AC de-icing process; Figure 3 This is a schematic diagram of the switching of reactive power compensation capacitors under impedance feedback control. Figure 4 Schematic diagram of fiber optic composite cable and impedance sensing; Figure 5 To communicate the intelligent feedback control block diagram for reactive power compensation during ice melting; Figure 6 A simulation calculation model for the impedance variation of overhead ground wires; Figure 7 The calculation results for reactive power compensation of multi-stage control for double-sided aluminum-clad steel stranded circuits; Figure 8 The calculation results are for reactive power compensation in multi-stage control of aluminum-clad steel stranded wire + OPGW circuit. Figure 9 The ground wire temperature rise curves under AC de-icing current for reactive power compensation capacity regulation are shown, where (a)-(c) are the ground wire temperature rise curves under target currents of 300A, 350A, and 400A, respectively. Detailed Implementation

[0026] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0027] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0028] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0029] Example 1: This invention provides an AC de-icing reactive power compensation control method that considers ground wire impedance changes. This method injects de-icing current into the overhead ground wire via an AC power supply. The resulting de-icing loop adjusts the loop impedance by switching reactive power compensation capacitors, thereby changing the effective value of the AC de-icing current. The temperature rise of the overhead ground wire caused by the injected AC current is calculated based on a thermal effect model, and the temperature rise is constrained by the critical de-icing current and the maximum de-icing current. Considering the changes in conductor impedance caused by variations in conductor temperature and ice thickness during the ice melting process, to improve the accuracy and reliability of the control, the topology of the AC de-icing reactive power compensation method that considers impedance changes is as follows: Figure 1 As shown.

[0030] The switching of reactive power compensation capacitors is matched with the impedance changes of the de-icing circuit to achieve flexible control while improving the accuracy of AC de-icing technology regulation based on actual line conditions. The method of matching reactive power compensation with ground wire impedance changes involves adjusting the effective value of the de-icing current in the circuit to ensure that the conductor temperature rise meets the AC de-icing temperature rise regulation constraints. Specifically, the intelligent feedback control module matches the switching of reactive power compensation capacitors with the impedance changes of the de-icing circuit. The proposed theoretical model of the overhead ground wire de-icing process shows that the changes in sag and line length caused by the increase in conductor temperature and the change in ice layer can correspond to the calculation of the line's dynamic impedance. Based on the temperature constraint boundary conditions of the overhead ground wire, the effective value range of the AC current injected during the conductor de-icing process can be calculated, further improving the non-electrical quantity control and protection method of the AC de-icing system. In summary, this method, through dynamic impedance sensing and monitoring of the overhead ground wire and feedback regulation of the switching of multi-stage reactive power compensation capacitors, can achieve the required temperature rise effect with an appropriate current according to the actual icing conditions of the de-icing ground wire section, thereby achieving more precise control and reducing de-icing power consumption.

[0031] First, a theoretical model of ground wire impedance change and reactive power compensation control method during the ice melting process is presented. Utilizing a flexible and portable AC ice melting device, an adjustable AC ice melting current is injected according to the actual icing conditions of different line sections. This reduces unnecessary overhead ground wire ice melting power consumption, offering advantages over conventional large-scale DC ice melting devices. The AC current control is based on reactive power capacity compensation; however, the ice melting process involves changes in the temperature and length of the overhead ground wire, leading to impedance changes in the compensation circuit and increasing the complexity of current regulation and matching. Figure 2 As shown.

[0032] Among them, after the injection of AC de-icing current into the ice-covered overhead ground wire, the heat balance equation during the establishment of thermal steady state satisfies the following formula: (1) In the formula, I rms This is the effective value of the power frequency AC current. R D For the dynamic resistance of the overhead ground wire, d a , d b These are the conductor layer and the ice layer along the gradient direction, respectively. z Length, m a , m b These represent the total mass of the conductor layer and the ice layer, respectively. C a , C b The specific heat capacities of the conductor layer and the ice layer are respectively. , These represent the temperature gradients of the conductor layer and the ice layer, respectively.h The convective heat transfer coefficient characterizes heat convection transfer. and These are the surface emissivity and the Stefan-Boltzmann constant, respectively, characterizing thermal radiation transfer. S Area of ​​contact with air. T 0、 T c These represent the average temperatures of the air contact surface and the external environment, respectively.

[0033] The effective value boundary conditions for the injected AC current need to be constrained by the critical de-icing current (the ground wire temperature reaches the ice melting point of 0℃ within 60 minutes) and the maximum de-icing current (not exceeding the allowable ground wire temperature of 90℃ in steady state) to ensure reliable de-icing while keeping the overhead ground wire under safe operating conditions. Flexible control of the de-icing current requires constant monitoring of the dynamic resistance of the ground wire during the establishment of thermal steady state. R D The changes, and adjust the effective value of the de-icing current to a suitable value constrained by boundary conditions. I rms During the ice melting process R D The change is primarily affected by temperature conditions, satisfying the formula: (2) In the formula, R D The resistance at any temperature R 20 The resistance value at 20℃ T a The average temperature of the conductor. α The resistance temperature coefficient is taken as a standard value of 0.0036. Ideally, when the ice layer has not completely melted, the ice temperature gradually approaches the critical melting temperature of 0°C from the ambient temperature. Furthermore, as the ice melts, the equivalent mass of the conductor decreases, and the sag of the overhead ground wire also decreases. This change in sag leads to a change in the conductor length. The conductor length satisfies the formula: (3) In the formula, L D The actual dynamic inner length of the span is calculated to take into account the sag condition. l s For gear distance, H This is due to the height difference. For the specific load of the wire, The minimum point stress is related to the mass of the overhead ground wire itself and the load (weight of the ice layer). The dynamic resistance of the conductor considering the dynamic length is given under arbitrary temperature conditions. R D Satisfying the formula: (4) In the formula, For any temperature, the length direction of the line is... x Equivalent resistivity of the conductor cross-section at that location. and These represent the resistivity of the steel core and aluminum layer of aluminum-clad steel strand at any temperature. A steel ( x ), A Al ( x ) respectively represent x The cross-sectional area of ​​the steel core and aluminum layer is used to calculate the dynamic resistance of the overhead ground wire during the ice melting process. R D .also, I rms The adjustment is based on switching reactive power compensation capacitors, while the line reactance in the de-icing compensation circuit is... X D It will also change dynamically with the change in the degree of sag during the melting process, satisfying the formula: (5) In the formula, The power frequency is 50Hz. is the vacuum permeability constant. d ij The geometric mean distance between any two lines of an overhead transmission line. d m The overall geometric mean distance parameter is denoted as GMR. GMR is the average geometric radius of the ground wire, which is related to the stranded wire structure and deformation. Therefore, a model for the change in line impedance parameters caused by ice during the de-icing process can be established.

[0034] This method injects de-icing current into the overhead ground wire via AC power. The resulting de-icing circuit adjusts its impedance by switching on and off a reactive power compensation capacitor, thereby changing the effective value of the AC de-icing current. Matching the switching of the reactive power compensation capacitor with the impedance change of the de-icing circuit improves the accuracy of AC de-icing technology in adjusting the current according to actual line conditions. The method of matching reactive power compensation with ground wire impedance change involves adjusting the effective value of the circuit de-icing current so that the conductor temperature rise meets the temperature rise constraint for AC de-icing control. Based on the temperature constraint boundary conditions of the overhead ground wire, the effective value range of the AC current required for conductor de-icing can be calculated. The control range of the reactive power compensation capacity can be derived from the current control range, satisfying the formula: (6) In the formula, Q com For reactive power compensation, C com For reactive power compensation capacity, Vrms and I rms To connect to the power frequency AC voltage and current RMS values Q line For line reactive power, P This represents the active power of the line. In the above formula, the voltage across the capacitor is... V com Satisfying the formula: (7) By establishing a feedback control calculation model for impedance changes, the reactive power compensation capacity during the ice melting process can be optimized. C com It allows for flexible adjustment and dynamic matching. This method controls the switching of compensation capacitors based on the specific requirements of the overhead ground wire with varying impedance for reactive power compensation capacity, thereby improving the controllability of the AC de-icing current. The feedback switching control of the reactive power compensation capacitors is as follows: Figure 3 As shown.

[0035] The main switch is activated by closing S. 12 Disconnect S 11 The compensation device is connected to the ice-melting circuit. By sensing changes in line impedance during the ice-melting process, the switching switch S1 to S2 is adjusted accordingly. n Different combinations of these components allow for adjustment of the total compensation capacitor, thereby altering the effective value of the injected AC de-icing current. Dynamic impedance is indirectly measured via sag and temperature sensing monitoring components, and impedance changes are calculated based on the aforementioned theoretical model. The fiber-optic temperature sensing identification utilizes an optical fiber composite overhead ground wire (OPGW) to transmit optical signals and thermal information. The optical fiber is typically located at the center of the transmission line, supported by a steel core and protected by aluminum transmission wires, enabling timely and accurate reflection of the transmission line's temperature status. A schematic diagram of the impedance sensing monitoring component is shown below. Figure 4 As shown.

[0036] Fiber optic monitoring reliably monitors ground wire temperature by detecting characteristic quantities of light, which are then used in a theoretical model to calculate the impedance of the de-icing circuit. This method effectively avoids the repeated installation of temperature measurement channels, thus reducing size, and also has advantages such as high sensitivity, strong resistance to electromagnetic interference, long detection distance, and passive operation. The sag of the line is monitored using an accelerometer. Acceleration information in various directions of the ground wire is detected, and mechanical calculations are performed to determine the conductor displacement and tilt angle. This allows for the depiction of the ground wire sag trajectory and further calculation of the line length and impedance.

[0037] Subsequently, the impedance calculation value is substituted into the thermal effect theoretical model, combined with the temperature rise and the effective value of the current, to determine the required reactive power compensation capacity. Finally, the reactive power compensation device is controlled to switch on the corresponding reactive power compensation capacity. The optimal array algorithm is used to match the switching capacitor bank array combination with the required reactive power compensation capacity: first, the circuit array is initialized, then any capacitor C in the array... i Arbitrary combination. Then, the preset voltage is applied. Assign to any array combination and detect the array output current. The array capacitance value is calculated by the host computer. C m and through formula The difference was calculated. Finally, the minimum number of combinations of N arrays is determined. The absolute value and the new optimal result obtained by repeating the above steps The values ​​are compared to determine whether the absolute value of the difference satisfies the condition that it is less than a threshold. Q (Required precision). If the conditions are met, then... hour, If the matching capacitance value and the corresponding reactive power compensation power allocation scheme of the capacitor switching array are found, then the process can be adopted; otherwise, proceed to the step of randomly generating N schemes according to a preset algorithm until the threshold condition is met. The intelligent control decision-making process is as follows: Figure 5 As shown.

[0038] This method achieves safe and efficient de-icing control by dynamically balancing electrical parameters, environmental conditions, and equipment limitations. First, key input parameters are determined: environmental information (including real-time temperature, humidity, wind speed, and line sag), specific operational requirements (such as rapid de-icing or preventative antifreeze), and icing conditions (determined through a fusion of multiple technologies including acceleration and tension sensors, and image recognition). After importing the data, the host computer system matches it to a pre-defined constraint library, with the three most critical constraints being: maximum de-icing current, minimum effective de-icing current, and conductor temperature rise limit. Finally, multi-objective optimization calculations are performed: the output voltage range is dynamically adjusted on the transformer side, while the optimal reactive power compensation switching position is matched based on line impedance characteristics. This method automatically calculates reactive power compensation capacity based on line length and current impedance, and employs a segmented capacitor compensation control strategy, particularly for long lines, to improve voltage distribution and power consumption requirements. Subsequently, fully graphical programming technology can be used to program the device logic according to requirements, meeting the user's requirements for simple boundary manipulation: for example, if the protection function of the protection component needs to be replaced during use, the built-in logic diagram can be updated through the device's maintenance port, which is simple and flexible.

[0039] Based on the aforementioned theoretical model analysis, a distributed parametric impedance calculation and thermal effect model for overhead ground wires was constructed. The temperature rise of the conductors under AC de-icing current was calculated and verified, and a current control strategy was designed. Furthermore, the dynamic matching design of reactive power compensation capacity under impedance changes during the de-icing process was improved. The overhead ground wire de-icing circuit includes aluminum-clad steel stranded wire and an OPGW (Optical Optical Cable Grounding Wire) ground wire. This model sets parameters for JLB20A-240 type aluminum-clad steel stranded wire and OPGW-28B1+8B4-225 type ... Figure 6 As shown.

[0040] Based on theoretical analysis, changes in ground wire temperature and sag will cause changes in the dynamic impedance of the de-icing circuit. Combining the adjustable range of the actual reactive power compensation device with the aforementioned thermal effect model, the calculation results of the reactive power switching capacity corresponding to different temperatures and sag conditions (line length) of the overhead ground wire during the de-icing process are shown in Tables 1-4. Table 1 shows the calculation results of dynamic impedance and reactive power matching compensation during the de-icing process (temperature changes, range 2.6km).

[0041] Table 1

[0042] Table 2 shows the calculation results of dynamic impedance and reactive capacity matching compensation during the ice melting process (temperature change, span 3.2km).

[0043] Table 2

[0044] Table 3 shows the calculation results of dynamic impedance and reactive capacity matching compensation during the ice melting process (line length variation, span 2.6km).

[0045] Table 3

[0046] Table 4 shows the calculation results of dynamic impedance and reactive capacity matching compensation during the ice melting process (line length variation, span 3.0km).

[0047] Table 4

[0048] Calculation results show that under a span of 2.6km, as the temperature of the overhead ground wire increases from the ambient temperature of -20℃ to the ice melting temperature of 0℃ during the de-icing process, the loop resistance continuously increases. The compensation capacity required for a de-icing current of 400A under an 855V AC power output decreases from 1075.18μF to 933.71μF, consistent with theoretical analysis. The composite optical cable ground wire requires an even lower de-icing current of 380A, and the compensation capacity under a 950V AC power output decreases from 1311.75μF to 1148.01μF, also consistent with the aforementioned pattern. Under a span of 3.2km, the line impedance increases, requiring a larger AC de-icing power supply or an increased reactive power compensation capacity. Changing the AC power supply can be achieved by switching the transformer's operating mode.

[0049] Under the same span and environmental conditions, the impact of different sags on the line length during the ice melting process of overhead ground wires is shown in the table. The calculation of the varying line length parameters considers the changes in line length within the span under three conditions: maximum wind speed sag, maximum icing sag, and maximum temperature sag. For the ground wire parameters of the test section under study, the calculated line length within the span increases by a maximum of 11.6% relative to the span, with an average increase of 1.7%. When calculated per unit span length (1km), the maximum line length within the span is 1116m. The calculation process assumes that the ice layer and conductor have reached the critical melting temperature of 0℃. As the ice melts, the line load decreases, the line length shortens, and thus the loop impedance decreases. Under the same target current and AC power output voltage conditions, the required compensation capacity shows an increasing trend, consistent with theoretical analysis. Based on the aforementioned impedance calculation, an AC compensation strategy for ice melting is designed according to the optimal values ​​of the double-sided aluminum-clad steel stranded circuit or the optimal values ​​of the aluminum-clad steel stranded + OPGW circuit parameters. Without considering redundant combinations, the calculated results of the ice melting current corresponding to the switching capacitor banks at each span under different loop lengths (spans) are shown in the table. Figure 7-8 As shown.

[0050] Parameters calculated based on the dynamic impedance model enable feedback regulation with multi-level dynamic matching. The actual current regulation error of the compensation device is less than 0.25%. The capacity of the multi-level switching reactive power compensation capacitor is limited by the capacitor banks used in the compensation device. Increasing the number of capacitor banks (n) can further improve the accuracy of capacity matching, making the actual compensation capacity closer to the theoretical calculation requirements, but the complexity and size of the device will also increase accordingly.

[0051] To verify the correctness of the AC de-icing current control strategy designed by the method, on-site tests were conducted at a 10kV distribution cabinet using AC power and a transformer to measure the temperature rise and control during the AC de-icing process of the ground wire. The experimental setup, combined with the switchgear current booster, can control a maximum current of 2000A. The experimental data recorded by the sensors were processed and analyzed in real-time on-site by a host computer.

[0052] The test section's ground wire was constructed from 20.3AS aluminum-clad steel strands, while the conductive portion of the optical cable was composed of 14AS and 20.3AS aluminum-clad steel strands, with a resistance temperature coefficient α of 0.0036. A ground wire temperature probe, in conjunction with surface-distributed temperature sensing units, accurately measured the conductor temperature rise, while an ambient temperature sensor monitored experimental conditions in real time. Experimental measurements were conducted using the DS-2008 high-power line power frequency parameter inter-frequency testing system. Simultaneously, the experimental ground wire parameters were input into the theoretical dynamic impedance model to calculate the impedance of the studied ground wire segment. The comparison between the dynamic impedance calculated by the theoretical model and the impedance value measured by the standard impedance tester in the measurement system is shown below.

[0053] Table 5 compares the dynamic impedance test values ​​and theoretical model calculation values ​​of overhead ground wires.

[0054] Table 5

[0055] In Table 5, f t , U t , I t , , Z t These include the test frequency, ground voltage, ground current, line impedance angle, and line impedance value. R c , X c , L c These are the corresponding calculated impedance values. The experiment was conducted using a ground loop measurement, therefore the measured impedance values ​​include both ground wire impedance and grounding impedance. Test results show that the error between the impedance values ​​calculated from the original experimental values ​​and the test data obtained from the impedance tester is less than 0.0002, which meets expectations and demonstrates the correctness of the theoretical model. Based on the impedance calculation model, an experiment was conducted to regulate the AC de-icing current and temperature rise using reactive power compensation capacity. Between each experiment, the stranded wire temperature was allowed to drop to within 1°C of the ambient temperature. The temperature rise results of the AC de-icing current regulated by reactive power compensation capacity are shown below. Figure 9 As shown in (a)-(c).

[0056] Experimental results show that reactive power compensation capacity regulation of AC de-icing current can be achieved. During the experiment, wind speed varied significantly in certain time periods, leading to discrepancies between the stranded wire temperature rise and the expected results. Analysis of data intervals with relatively stable wind speed variations, combined with the use of thermal paste such as silicone grease for filling, revealed that the ground wire temperature rise at the target currents of 300A, 350A, and 400A met theoretical expectations. The designed method achieves capacity switching of the reactive power compensation device based on impedance change feedback, resulting in more precise and reliable AC de-icing current regulation. Adding a capacitor bank switching switch will further improve control accuracy.

[0057] Example 2: An electronic device, comprising a memory and a processor; The memory is used to store computer programs; The processor is configured to implement the method described in Embodiment 1 when executing the computer program.

[0058] Example 3: A computer-readable storage medium storing a computer program that, when executed by a processor, implements the method described in Embodiment 1.

[0059] Example 4: A computer program product includes a computer program that, when executed by a processor, implements the method described in Example 1.

[0060] In the above embodiments, the reference to "this embodiment" in the specification indicates that a specific feature, structure, or characteristic described in connection with the embodiment is included in at least some embodiments, but not necessarily all embodiments. Multiple appearances of "this embodiment" do not necessarily refer to the same embodiment.

[0061] In the above embodiments, although the invention has been described in conjunction with specific embodiments thereof, many substitutions, modifications, and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory structures (e.g., dynamic RAM (DRAM)) may be used with the embodiments discussed. The embodiments of the invention are intended to cover all such substitutions, modifications, and variations falling within the broad scope of the appended claims.

[0062] As will be understood by those skilled in the art, the computer-readable storage medium described in this embodiment allows for the implementation of all or part of the steps in the above method embodiments by computer program-related hardware. The aforementioned computer program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0063] The electronic terminal provided in this embodiment includes a processor, a memory, a transceiver, and a communication interface. The memory and the communication interface are connected to the processor and the transceiver and complete communication between them. The memory is used to store computer programs, the communication interface is used to perform communication, and the processor and the transceiver are used to run the computer programs, so that the electronic terminal performs the steps of the above method.

[0064] In this embodiment, the memory may include random access memory (RAM) and may also include non-volatile memory, such as at least one disk storage device.

[0065] The processors mentioned above can be general-purpose processors, including central processing units (CPUs), network processors (NPs), etc.; they can also be digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0066] This invention can be used in a wide range of general-purpose or special-purpose computing system environments or configurations. Examples include: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, and distributed computing environments including any of the above systems or devices, etc.

[0067] This invention can be described in the general context of computer-executable instructions, such as program modules, that are executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform a specific task or implement a specific abstract data type. This invention can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An alternating current de-icing reactive power compensation control method considering ground impedance variation, characterized in that: Comprise the following steps: S1: connect the reactive power compensation device to the ice-melting circuit, and inject ice-melting current into the overhead ground wire through the AC power supply; S2: measure the length of the ground wire and the temperature of the ground wire during the ice-melting process through the sag and temperature sensing monitoring assembly; S3: based on the ground wire impedance change model during the ice-melting process, calculate the change of the ground wire impedance according to the length of the ground wire and the temperature of the ground wire; S4: input the ground wire impedance value into the thermal effect theoretical model to calculate the required reactive power compensation capacity combined with the temperature rise and current effective value; S5: based on the optimal array algorithm, control the switching of the corresponding reactive power compensation capacity of the switched capacitor array combination.

2. The AC de-icing reactive power compensation control method considering ground impedance variation according to claim 1, characterized in that: The temperature sensing monitoring assembly based on optical fiber temperature sensing identification detects the characteristic quantity of light to realize the monitoring of the temperature of the ground wire, and utilizes the composite optical cable ground wire to transmit optical signal and thermal information.

3. The AC de-icing reactive power compensation control method considering ground impedance variation according to claim 1, characterized in that: The sag sensing monitoring assembly utilizes an acceleration sensor to detect the acceleration information of the ground wire in each direction, obtains the conductor displacement and inclination through mechanical calculation, further depicts the sag trajectory of the ground wire, and further calculates the length of the ground wire.

4. The AC de-icing reactive power compensation control method considering ground impedance variation according to claim 1, characterized in that: The ice-melting process ground wire impedance change model in step S3 is constructed as follows: After the overhead ice-coated ground wire injects AC ice-melting current, the thermal equilibrium equation in the thermal steady state establishment process satisfies the formula: In the formula, I rms is the effective value of the power frequency alternating current, R D is the dynamic resistance of the overhead ground wire, d a , d b are the lengths of the conductor layer and the ice layer along the gradient direction, z m a , m b are the total masses of the conductor layer and the ice layer, C a , C b are the specific heat capacities of the conductor layer and the ice layer, , are the temperature variation gradients of the conductor layer and the ice layer; h is the coefficient of convective heat transfer representing the convective heat transfer, and are the surface emissivity and the Stefan-Boltzmann constant respectively representing the radiative heat transfer, S is the air contact area, T 0、 T c are the average temperatures of the air contact surface and the external environment respectively;​ During the ice melting process R D The change is first affected by the temperature condition, satisfying the formula: wherein R D R is the resistance at any temperature, R 20 R20 is the resistance at 20°C, T a T is the average temperature of the conductor, α R is the resistance temperature coefficient; The change of the overhead ground wire sag degree causes the change of the conductor length, and the conductor length satisfies the formula: wherein, L D Dynamic actual in-catenary length calculated taking sag into account, l s span, H height difference; wire specific load, minimum point stress, related to the mass of the overhead ground wire itself and the load forces; dynamic wire resistance taking dynamic line length into account at any temperature condition R D satisfies the formula: In the formula, is the equivalent resistivity of the conductor cross section at the arbitrary temperature, x and are the resistivity of the steel core and the aluminum layer of the aluminum-clad steel stranded wire at the arbitrary temperature, respectively, A steel x A Al x x represent the cross-sectional area of the steel core and the aluminum layer at the arbitrary temperature, respectively; thus the dynamic resistance of the overhead ground wire during the ice-melting process is calculated as R D I rms The adjustment of the reactive power compensation capacitor is based on the switching of the reactive power compensation capacitor, and the line reactance in the ice-melting compensation loop X D also dynamically changes with the change of the sag degree during the ice-melting process, satisfying the formula:​​​​​​ wherein, is the power frequency 50 Hz, is the vacuum permeability constant, d ij is the geometric mean distance between any two lines of the overhead transmission line, d m is the overall geometric mean distance parameter, GMR is the geometric mean radius of the ground wire, and is related to the strand structure and deformation conditions.

5. The AC de-icing reactive power compensation control method considering ground impedance variation according to claim 1, characterized in that: In step S4, the ice-melting circuit adjusts the loop impedance through the switching of the reactive power compensation capacitor, and further changes the effective value of the AC ice-melting current; the method of matching the switching of the reactive power compensation capacitor and the change of the ice-melting loop impedance is to adjust the effective value of the loop ice-melting current, so that the conductor temperature rise satisfies the AC ice-melting control temperature rise constraint; Based on the temperature constraint boundary condition of the overhead ground wire, the effective value range of the injected AC current during the ice-melting process of the conductor is calculated; through the current control range inversion, the control range of the reactive power compensation capacity is obtained, which satisfies the formula: wherein Q com Qcomp is the reactive compensation power, C com Qcomp is the reactive compensation power, V rms V is the voltage, I rms V is the voltage, V is the voltage, Q line Q is the line reactive power, P Q is the line reactive power; V is the capacitor voltage V com the formula: 。 6. The AC de-icing reactive power compensation control method considering ground impedance variation according to claim 1, wherein: In step S5, the optimal array algorithm is used to realize the matching of the switched capacitor array combination and the required reactive power compensation capacity: The circuit array is first initialized and set, and then any capacitor C i in the array is combined in any combination; The preset voltage is distributed to any array combination The array output current is detected , and the array capacity is calculated C m , and the difference is calculated by the formula ;​ The N array combination schemes are compared with the minimum The absolute values of the new round of optimal values obtained by repeating the above steps are compared with the absolute values of the previous round of optimal values to determine whether the absolute values of the differences satisfy the threshold condition Q ; if the condition is satisfied, i.e. , the matched capacitance value and the reactive power compensation power distribution scheme corresponding to the capacitance switching array can be used; otherwise, jump to the step of randomly generating N schemes according to the preset algorithm until the threshold condition is satisfied.

7. The AC de-icing reactive power compensation control method considering ground impedance variation according to claim 1, characterized in that: Further comprising the following steps: Collect real-time temperature, humidity, wind speed and line sag; determine whether the specific work requirement is rapid ice-melting or preventive anti-freezing; determine the icing condition through acceleration, tension sensor and image recognition; Match the preset constraint condition library, including the maximum ice-melting current, the minimum effective ice-melting current and the conductor temperature rise limit; Perform multi-objective optimization calculation: dynamically adjust the output voltage range at the transformer side, and match the best reactive power compensation switching switch gear position combined with the line impedance characteristics.

8. The AC de-icing reactive power compensation control method considering ground impedance variation according to claim 1, wherein: Use full graphical programming technology, perform logic programming according to requirements, and meet the requirements of simple boundary operation of users.

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