A modular de-icing and balancing control system and method for power transmission lines

Abstract

This invention discloses a modular de-icing and equalization control system and method for power transmission lines. The system includes: N A mobile ice-melting unit; an input combination control module and an output combination control module, which are connected to each mobile ice-melting unit; N A real-time measurement module is installed on the output side of each mobile ice-melting unit; an incoming line grid connection control module is connected between the power grid and the input combined control module; an ice-melting outgoing line control module is connected between the output combined control module and the line to be ice-melted; a balancing control module is used to receive the current signal from each mobile ice-melting unit, output the control signal for the on-load tap changer position of the primary side of each mobile ice-melting unit and the parallel connection signal to the input combined control module, and output the ice-melting mode control signal to the output combined control module. This invention can achieve flexible modular expansion and has the advantages of strong control capability, high control accuracy, high device utilization, and low system loss.

Description

Technical Field

[0001] This invention mainly relates to the field of power line de-icing technology, specifically to a modular de-icing equalization control system and control method for power transmission lines. Background Technology

[0002] The safe and stable operation of the power system is directly related to industrial production and the protection of people's lives. High-voltage transmission lines, such as 500kV lines, serve as the backbone of the power system, acting as crucial power transmission channels and key sections for inter-regional and inter-provincial power grid connections. They transmit large amounts of power, cover a wide area, and span long distances, often traversing complex geographical environments. They frequently cross high-altitude mountainous regions, high-humidity reservoirs and lakes, and other areas prone to icing. In winter, low temperatures and snowfall make them highly susceptible to icing on conductor surfaces, leading to serious faults such as tower collapses and line breaks, and even large-scale power outages. This reduces the power grid's supply capacity and reliability, causing significant losses to the social economy. To address the threat of ice storms, compared to traditional passive anti-icing methods for transmission lines, de-icing technology can achieve efficient and proactive removal of icing, and has become a key area of ​​research and application in the field of ice prevention.

[0003] However, existing DC de-icing technology for 500kV and other high-voltage transmission lines still faces several challenges in practical applications. To meet the demands of high-power, long-distance transmission, large-section, long-distance conductors are often used, resulting in higher de-icing current and voltage requirements, necessitating the deployment of large-capacity DC de-icing devices. Fixed DC de-icing devices have stringent site requirements, long construction periods, and investment costs several times higher than mobile de-icing devices, and can only be used for de-icing fixed lines. Using mobile DC de-icing devices is a more flexible and cost-effective solution. However, existing mobile DC de-icing devices are limited by the size and load capacity of their vehicle-mounted platforms, resulting in typically small single-unit capacities. Increasing their capacity excessively to meet the de-icing needs of 500kV transmission lines would lead to a sharp increase in size and weight, causing transportation limitations and making it difficult to reach iced sections, thus negating the core advantage of mobile de-icing devices' flexible deployment.

[0004] To address the aforementioned contradictions, multiple mobile DC de-icing devices are operated in parallel to increase overall capacity. However, practical applications face the challenge of current balancing. On one hand, the existing de-icing devices are numerous and varied, with significant differences in internal parameters between different batches and output capacities. On the other hand, even within the same batch, transformers may exhibit short-circuit impedance deviations, secondary tap setting errors, and output voltage imbalances between the two secondary windings of a three-winding transformer. Furthermore, the forward voltage drop and on-resistance of diodes in a twelve-pulse rectifier may differ, leading to current imbalances between internal rectifier bridges and external components. This current imbalance causes some devices to operate under overload, shortening equipment lifespan and even causing malfunctions, while other units operate under light loads, resulting in wasted capacity and reduced de-icing efficiency. DC de-icing devices typically employ diode rectification, which generates less heat, has lower harmonic content, and requires no complex control system or additional cost compared to thyristors. However, it cannot be regulated, necessitating alternative methods for current sharing. Adding power electronic devices for control increases equipment size and weight, raises costs, and increases harmonic content, thus negating the advantages of mobile de-icing's flexibility and transportation, and also affecting power grid quality. Therefore, developing a modular de-icing method for transmission lines that enables multi-unit balanced control without adding extra equipment is key to solving the problem of flexible and efficient de-icing of long-distance, large-section conductors. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a precise control system and method for the modular de-icing and balancing control of transmission lines.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A modular de-icing and balancing control system for power transmission lines includes: A mobile ice-melting unit connected in parallel, of which It is a positive integer greater than or equal to 2; The input combination control module is connected to the input end of each of the mobile ice-melting units and is used to control the parallel connection of each mobile ice-melting unit, the adjustment of the on-load tap changer on the primary side, and the disconnection of the input side of the faulty unit. The output combination control module is connected to the output terminal of each mobile ice-melting unit and is used to collect the output current of each mobile ice-melting unit, control the output mode of each mobile ice-melting unit, and disconnect the output side of the faulty unit. Each real-time measurement module is set on the output side of each mobile ice-melting unit to measure the output current of each mobile ice-melting unit. The incoming line grid connection control module is connected between the power grid and the input combination control module, and is used to control the overall grid connection of the system; The de-icing output control module is connected between the output combination regulation module and the line to be de-iced, and is used to control the output of the total de-icing current. The equalization control module is connected to each real-time measurement module, the input combination control module and the output combination control module. It is used to receive the current signal of each mobile ice melting unit, calculate and output the control signal of the on-load tap changer of the primary side of each mobile ice melting unit to the input combination control module based on the current deviation rate through the equalization control algorithm, and output the fault unit cut-off signal when a fault is detected.

[0007] Preferably, the mobile ice-melting unit includes: An adaptive current distribution voltage regulating transformer has an on-load tap changer configured on its primary winding and an off-load tap changer configured on its first and second secondary windings. The primary winding is connected to the input combination control module. The twelve-pulse rectifier includes a first six-pulse rectifier bridge and a second six-pulse rectifier bridge, which are respectively connected to the two secondary windings of the adaptive current distribution voltage regulating transformer. A dynamic current balancing device is connected between the output terminals of the first six-pulse rectifier bridge and the second six-pulse rectifier bridge to achieve current balancing between the two rectifier bridges. The switch module has its input side connected to the DC output terminal of the twelve-pulse rectifier and its output side connected to the output combination control module. It is used to reconstruct the connection topology between the DC output and the three-phase conductors of the line to be melted.

[0008] This invention also discloses a control method based on the above-described modular de-icing equalization control system for transmission lines, comprising the following steps: Calculate the required de-icing voltage and current range based on the parameters of the line to be de-iced, and determine the target de-icing voltage. With the target de-icing current The number of mobile de-icing units connected in parallel is determined based on the rated parameters of each mobile de-icing unit. ; Based on the target de-icing voltage Adjust the no-load voltage regulation position of the secondary side of the transformer in each mobile ice-melting unit to the preset position, and configure the parameters of the dynamic current balancing device in each mobile ice-melting unit to achieve current balance inside the mobile ice-melting unit. The target current is balanced by allocating it to each mobile ice-melting unit according to its capacity ratio. For the on-load tap changer position Initial pre-adjustment was performed, and all mobile ice-melting units were started up in a balanced manner; The system is started and connected to the grid for de-icing. The output current of the mobile de-icing unit is monitored by the real-time measurement module, and the current deviation rate of each mobile de-icing unit is calculated. If the current deviation rate exceeds the preset threshold, the on-load tap changer of the primary side of the transformer in the corresponding mobile de-icing unit is adjusted by the equalization control module until the current deviation rate of all mobile de-icing units is lower than the preset threshold and the total de-icing current reaches the target value.

[0009] Preferably, each mobile ice-melting unit balances the target current. The calculation formula is:

[0010] in, For the first k Rated current of each ice-melting unit; For the first i Rated current of each ice-melting unit; On-load tap changer position The calculation formula is:

[0011] This refers to the voltage of the power grid bus. Gear; When rectifiers are connected in parallel, the first k The conduction voltage of the diode in the ice-melting unit AC equivalent voltage; When rectifiers are connected in parallel, the first The AC equivalent voltage of the diode forward voltage of each ice-melting unit; The AC equivalent resistance of the wire to be melted when the rectifiers are connected in parallel; This is the equivalent de-icing voltage; When rectifiers are connected in parallel, the first i On-resistance of diodes in each ice-melting unit AC equivalent resistance; When rectifiers are connected in parallel, the first k The AC equivalent resistance of the diode conduction resistance of each ice-melting unit; For the first k The equivalent impedance of the primary and secondary windings of a transformer; For the first The equivalent impedance of the primary and secondary windings of a transformer.

[0012] Preferably, during the de-icing process, the total de-icing current and the current of each mobile de-icing unit are continuously monitored. If the current deviation rate exceeds the preset threshold again, or if the total de-icing current needs to be adjusted, the on-load tap changer of the primary side of each mobile de-icing unit is dynamically adjusted through a combination of inner and outer loop control to maintain current balance. If an overcurrent is detected in a mobile de-icing unit or the total de-icing current exceeds the limit, and the problem cannot be resolved by voltage adjustment, the faulty de-icing unit will be identified and disconnected, and the remaining de-icing units will be rebalanced.

[0013] Preferably, the control method combining inner and outer loops specifically includes: The outer ring calculates the adjustment amount of the total de-icing current based on environmental changes and updates the total target de-icing current. ; The inner loop recalculates the reference current for each ice-melting unit. Based on the deviation between the measured current of each ice-melting unit and the recalculated reference current, the on-load tap changer on the primary side of the transformer of the corresponding ice-melting unit is adjusted step by step. And the magnitude of a single adjustment Within the preset range, the specific adjustment formula is as follows:

[0014] in, This is the equivalent current deviation.

[0015] Preferably, the adjustment amount of the total de-icing current The calculation formula is:

[0016] in, For environment variables, , , For the outer loop control coefficient: New overall target de-icing current for: .

[0017] Preferably, the target de-icing voltage is determined. The process is as follows: Calculate the allowable range of the de-icing voltage and take the intersection of this range with the output voltage ranges corresponding to multiple taps on the secondary side of the transformer in each de-icing unit. Select the voltage closest to the median value of the allowable range of the de-icing voltage from this intersection as the target de-icing voltage. .

[0018] Preferably, the parameters of the dynamic current balancing device in each mobile ice-melting unit are inductance. The calculation formula is:

[0019] in, f For the power grid AC frequency, U k1 , U k2 These are the output voltages of the two six-pulse rectifier bridges in the twelve-pulse rectifier.

[0020] Preferably, the current deviation rate The calculation formula is:

[0021] in For the first The DC current of each ice-melting unit; For the first Rated current of each ice-melting unit; For the first Rated current of each ice-melting unit.

[0022] Preferably, after the ice has completely melted, the incoming grid control module, the ice-melting outgoing control module, the input combination control module, and the output combination control module are disconnected in sequence, and each mobile ice-melting unit is cut off to complete the ice melting process.

[0023] Compared with the prior art, the advantages of the present invention are as follows: This invention enables flexible expansion of the capacity of de-icing units. After solving the problem of parallel balancing of modular de-icing, the number of de-icing units can be increased or decreased more flexibly according to the different lengths and cross-sections of the lines to be de-iced. A single de-icing unit can be used for de-icing small-capacity lines, while a balanced combination can meet the de-icing needs of large-capacity lines, greatly improving the utilization rate and applicability of de-icing units.

[0024] This invention can achieve dual current balance between the device and the external current. By using on-load tap changer on the primary side of the transformer, it compensates for the external current deviation between different ice-melting devices. At the same time, by using the circulating current suppression component at the parallel output of the twelve-pulse rectifier, it suppresses the internal current imbalance between the two six-pulse rectifier bridges. The two are independent of each other and can be adjusted flexibly, forming a dual control mechanism that coordinates internal and external current, so that the overall output current can achieve high-precision and highly controllable balance.

[0025] This invention enables real-time dynamic monitoring of the ice melting process. By using a high-precision real-time measurement module to monitor key parameters in real time, and combined with dynamic load voltage regulation and fault isolation mechanisms, it can quickly respond to the impact of fluctuations in parameters such as wind speed, temperature, and conductor resistance on the ice melting process, and make dynamic real-time adjustments during the ice melting process to maintain current balance throughout the process.

[0026] This invention enables precise control of the output de-icing voltage and current. The combination of on-load fine voltage regulation on the primary side and off-load voltage regulation on the secondary side increases the adjustment range of the de-icing voltage and current, improves the adjustment accuracy, and enhances the de-icing current control capability.

[0027] This invention can improve the overall efficiency of the modular ice-melting device. By controlling the current balance of each ice-melting unit, the large-capacity ice-melting unit can bear more ice-melting current output, while the small-capacity ice-melting unit outputs a smaller current, instead of all of them bearing the same amount of current. This can improve the utilization rate of the ice-melting unit, rationalize the loss distribution, reduce the total loss, extend the lifespan, and reduce the size of the heat dissipation device. Attached Figure Description

[0028] Figure 1 This is a structural block diagram of the ice-melting equilibrium control system according to an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the mobile ice-melting unit structure according to an embodiment of the present invention.

[0030] Figure 3 For the present invention N Equivalent model diagram of several mobile ice-melting units operating in parallel.

[0031] Figure 4 This is a flowchart of the ice melting equilibrium control method according to an embodiment of the present invention.

[0032] Figure 5 This is a flowchart of the real-time load control method according to an embodiment of the present invention. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0034] like Figure 1 As shown in the embodiment of the present invention, the modular de-icing balancing control system for transmission lines is used to solve the problem of current imbalance when multiple mobile de-icing units operate in parallel during de-icing of 500kV and other high-voltage transmission lines. Specifically, it includes... A mobile ice-melting unit connected in parallel, an input combination control module, and an output combination control module. The system includes a real-time measurement module, an incoming line grid connection control module, an ice-melting outgoing line control module, and a balancing control module. It is a positive integer greater than or equal to 2.

[0035] like Figure 2 As shown, the mobile ice-melting unit includes an adaptive current distribution voltage regulating transformer, a twelve-pulse rectifier, a dynamic current balancing device, and a disconnect switch module. The adaptive current distribution voltage regulating transformer consists of a primary winding equipped with an on-load tap changer, a first secondary winding equipped with an off-load tap changer, and a second secondary winding. The primary winding is connected to the input combined control module and then connected to the power grid through the incoming line grid connection control module. The secondary winding is connected to the first six-pulse rectifier bridge and the second six-pulse rectifier bridge respectively. It can realize the functions of fine on-load voltage regulation on the primary side and wide-range off-load voltage regulation on the secondary side, while meeting the wide-range regulation of de-icing output of different lines and the balanced matching between different de-icing units. The twelve-pulse rectifier includes a first six-pulse rectifier bridge and a second six-pulse rectifier bridge. The first six-pulse rectifier bridge and the second six-pulse rectifier bridge are connected in parallel through two dynamic current balancing devices, and the output current is sent to the knife switch module. The six-pulse rectifier bridge consists of six diodes and is an uncontrollable device that does not have an independent control port. The dynamic current balancing device can achieve current balancing within the ice melting unit through magnetic field coupling; The input side of the switch module is a bipolar DC connection port, which corresponds to the positive and negative poles of the DC de-icing device, respectively; the output side is a three-phase conductor connection port, which corresponds to the three-phase conductors of the transmission line to be de-iced. Through the internal combination action of the switch module, the topology reconstruction connection between the bipolar DC connection port and the three-phase conductor connection port is realized to form different de-icing circuits. Equalization control module receives N The output signal of each real-time measurement module is output through an equalization control algorithm. N The on-load modulation signal of the primary side of each ice-melting unit is sent to the input combined control module. When the current deviation rate is adjusted to <5%, it enters the dead zone and maintains the current on-load modulation signal; at the same time, the signal of the real-time measurement module can be monitored in real time, and the location of the fault unit to be cut off is output to the input combined control module and the output combined control module through the anomaly judgment algorithm. The real-time measurement module can measure the output current of each unit through Hall sensors and other means, so that the equalization control module can calculate the on-load tap change level. The input combined control module includes unit grid-connected control and equalization adjustment devices, which are connected to the primary windings of each ice-melting unit to control... N Each unit is connected in parallel; it receives the modulation signal from the equalization control module and adjusts... Each ice-melting unit transformer has an on-load tap changer on the primary side, and simultaneously receives a fault signal from the equalization control module to control the input side of the faulty unit to cut off. The output combined control module includes a busbar and a de-icing outlet control device, and... The switch module of each ice-melting unit is connected to receive the fault signal of the equalization control module and control the output side of the faulty unit to cut off. The incoming line grid connection control module includes the main grid connection switch, the incoming line reactor, and controls... All ice-melting units were connected to the grid as a whole; The de-icing control switch is in After the ice-melting units are connected in parallel and ready, the total current is controlled and output to the circuit to be melted.

[0036] like Figure 4 As shown, this embodiment of the invention also provides a control method based on the above-described modular de-icing equalization control system for transmission lines, comprising the following steps: S1. System Configuration and Parameter Presets: Specifically, based on the type and length of the conductors of the transmission lines to be melted. and ambient temperature Obtain the resistance of the wire at the current temperature and under the ice-melting method. Target de-icing current Permissible range and corresponding target de-icing voltage permissible range;

[0037]

[0038]

[0039] in, , These are the minimum and maximum ice-melting currents, respectively. , These are the minimum and maximum ice-melting voltages, respectively. This is the voltage redundancy factor, used to compensate for line voltage drop; This refers to the resistivity per unit length of the corresponding wire type; This is the de-icing method coefficient, which is used when the conductor uses a two-phase series de-icing method. =2; When using a two-in-one-series method for ice melting... =1.5.

[0040] Based on the parameters and model of the mobile ice-melting unit, determine the voltage intersection of multiple taps on the secondary side of its voltage regulating transformer. The secondary AC voltage is rectified into DC voltage, and its intersection with the allowable range of the ice-melting voltage is then taken. and from the intersection The voltage closest to the median value of the allowable range for de-icing voltage is selected as the target de-icing voltage. In order to determine the target de-icing current .

[0041] in The calculation formula is:

[0042]

[0043] in This is the midpoint of the de-icing voltage range, specifically:

[0044] By employing the above methods, the target de-icing voltage can be reasonably selected while meeting de-icing requirements and safety constraints. and target de-icing current This ensures efficient and stable de-icing, while also preventing issues such as excessive current causing overheating and damage to wires and devices, or de-icing too quickly leading to ice detachment and jumping.

[0045] Secondly, based on the rated current of each mobile ice-melting unit Determine the number of parallel mobile ice-melting units. N , When the rated current of each mobile de-icing unit is the same, the number of de-icing units connected in parallel is... N Target de-icing current With unit rated current The ratio is rounded up, specifically:

[0046] To ensure the system continues to operate normally even if some mobile de-icing units fail, a certain amount of redundancy is provided. N r .

[0047] Hundreds of mobile ice-melting units have been deployed, with various models and varying rated current parameters. When the rated currents of different mobile ice-melting units differ, the number of units to be connected in parallel is determined based on their rated currents. Prioritizing combinations with the fewest parallel units while ensuring the total ice-melting current requirement is met, this approach reduces the complexity of parallel control, improves system reliability, and enhances on-site deployment flexibility.

[0048] Number of parallel mobile ice melting units Specifically:

[0049] in It is a temporary variable.

[0050] S2. Secondary side no-load voltage regulation setting and internal unit balancing configuration: The initial state of the on-load tap changer on the primary side of the adaptive current distribution voltage regulating transformer of each mobile ice melting unit is as follows: Based on the target de-icing voltage Adjust the no-load tap changers of the first and second secondary windings of the adaptive current distribution tap changer in each ice melting unit to the set position. Among them, gears The calculation formula is:

[0051] in, This is the voltage of the power grid bus.

[0052] Ideally, after no-load voltage regulation on the secondary side and twelve-pulse rectification, the DC output voltage of each de-icing unit reaches the preset value, achieving the target de-icing voltage. However, in reality, there are deviations in the no-load voltage regulation output of each de-icing unit, and the short-circuit impedance of the transformer winding is not completely consistent. The output voltage of each de-icing unit is not consistent, and the current is unbalanced after parallel connection. The output de-icing voltage and de-icing current deviate from the target values. Therefore, after the no-load voltage regulation setting on the secondary side, it is necessary to perform on-load balancing debugging of the de-icing units.

[0053] Before external current sharing is performed during the on-load balancing commissioning of the ice-melting unit, an internal dynamic current balancing device is configured to balance the internal current of the ice-melting unit. The two are independently controlled and do not interfere with each other, efficiently achieving simultaneous internal and external current balancing. The rectifiers in each ice-melting unit are all configured in parallel, outputting current through the dynamic current balancing device; at this point, the internal current of the unit is balanced. However, due to impedance and tap deviations in each ice-melting unit, the external current is not yet balanced. Inductance value of the dynamic current balancing device in each ice melting unit It can output voltage from two six-pulse rectifier bridges. , Maximum difference setting: ; in, f This refers to the AC frequency of the power grid.

[0054] S3. Load balancing test of the ice melting unit: Each ice-melting unit is connected in parallel to the transmission line to be melted. The target current for balancing each unit is set. The on-load tap changer on the primary side is initially adjusted so that the current deviation control threshold of each unit is less than 5%. Ice melting is started with balanced current, and the output current of each ice-melting unit is sampled in real time.

[0055] The current is allocated to each ice-melting unit according to its capacity ratio, then the... Output current deviation of each ice melting unit Current deviation rate for:

[0056]

[0057] in, The first monitoring module for real-time measurement k DC current of each ice-melting unit For the first i Rated current of each ice-melting unit; For the first k Rated current of each mobile ice-melting unit.

[0058] Specifically, when the rated current of each mobile ice-melting unit is the same, , for:

[0059]

[0060] The current deviation control threshold is set to 5%; when If the current is less than 5%, it is considered that the current of each ice-melting unit is balanced, and the total ice-melting output current reaches the target current. ; when ≥5%, triggering closed-loop regulation, adjusting the first... k The on-load tap changer on the primary side of the transformer in each ice-melting unit adjusts the output voltage on the secondary side, thereby balancing the DC current of each ice-melting unit.

[0061] To facilitate the calculation of the impact of the on-load tap changer position on the primary side of the transformer on the circulating current, the entire circuit is equivalent to the secondary side of the transformer, and the effective value is taken for calculation. Figure 3 As shown: No. k Each ice-melting unit balances the target current. Corresponding equivalent current deviation Equivalent Deviation Rate for:

[0062]

[0063]

[0064] For the first k Equivalent current on the secondary side of the transformer in the ice-melting unit.

[0065] When the rated current parameters of each mobile ice-melting unit are different, the current of each ice-melting unit is allocated differently according to the corresponding rated current ratio; when the rated current of each mobile ice-melting unit is the same, for:

[0066] Therefore Equivalent to Closed-loop regulation only requires controlling A current balance of less than 5% can be achieved by controlling the current of each ice-melting unit to be balanced, while the total ice-melting output current reaches the target current. .

[0067] No. k The equivalent output voltage of the secondary side of the ice-melting unit transformer for:

[0068] in, This is the voltage of the power grid bus.

[0069] No. k Equivalent current on the secondary side of the transformer in the ice-melting unit for:

[0070] in, This is the equivalent de-icing voltage. For the first k The equivalent impedance of the primary and secondary windings of a transformer When rectifiers are connected in parallel, the first k On-resistance of diodes in each ice-melting unit The AC equivalent resistance. When rectifiers are connected in parallel, the first k The conduction voltage of the diode in the ice-melting unit The AC equivalent voltage.

[0071] Equivalent de-icing voltage for:

[0072] in, The AC equivalent resistance of the wire to be melted when the rectifiers are connected in parallel; For the first Equivalent output voltage of the secondary side of the transformer in the ice-melting unit; When rectifiers are connected in parallel, the first The conduction voltage of the diode in the ice-melting unit AC equivalent voltage; For the first The equivalent impedance of the primary and secondary windings of the transformer; When rectifiers are connected in parallel, the first On-resistance of diodes in each ice-melting unit The AC equivalent resistance.

[0073] Therefore, the first k Equivalent current on the secondary side of the transformer in the ice-melting unit It can be expressed as about The function, and The larger, The smaller the value, the more likely the ice melt will begin, which can be determined by the following formula. Perform initial setup to enable and With an equivalent deviation of less than 5%, each ice-melting unit can start up evenly.

[0074] No. k The equivalent impedance of the primary and secondary windings of the transformer It can be determined by the transformer's rated voltage. Rated power Percentage of short-circuit impedance of primary winding Percentage of short-circuit impedance of the first secondary winding Percentage of short-circuit impedance of the second secondary winding The calculation yields the following results:

[0075] AC equivalent resistance of the wire to be melted when rectifiers are connected in parallel When rectifiers are connected in parallel, the first k On-resistance of diodes in each ice-melting unit AC equivalent resistance When rectifiers are connected in parallel, the first k The conduction voltage of the diode in the ice-melting unit AC equivalent voltage for:

[0076]

[0077]

[0078] The output combination control module will The switchgear modules of each mobile ice-melting unit are uniformly switched to the same ice-melting mode, and the output terminals of each ice-melting unit are connected in parallel to the busbar; the input combination control module controls the primary side of each ice-melting unit transformer to be connected in parallel, and controls the on-load tap changer position of the primary side. Initial pre-adjustment is performed; the de-icing outgoing control module is closed, connecting the busbar to the transmission line to be de-iced; the incoming grid connection control module is closed, and the system draws power from the grid busbar and starts de-icing. Pre-adjustment achieves initial equalization control, effectively suppressing the output current deviation of each unit, while ensuring that the total output current of the ice-melting process matches the target current. Basic match. When <5%, it is assumed that the output current of each ice-melting unit is distributed proportionally to the capacity of each ice-melting unit, the current of each ice-melting unit is balanced, and the total output current of ice-melting reaches the target current. Maintain the current number of turns and only perform periodic sampling monitoring; when If the value is ≥5%, dynamic equilibrium control needs to continue.

[0079] S4. Dynamic equilibrium control of the ice melting process: A dual-closed-loop balanced control strategy is constructed. During the ice-melting process, current changes are continuously monitored. Based on the deviation between the output current of each ice-melting unit and its corresponding reference current, when changes in conductor parameters or environmental conditions cause the current deviation to exceed a preset threshold, the on-load tap changer on the primary side of the transformer in each ice-melting unit is dynamically adjusted. This gradually converges the output current of each ice-melting unit to a current deviation rate of <5%, maintaining current balance in the parallel system. The outer loop adjusts the control input by monitoring environmental parameters. Inner ring according to (Δ N ≤Δ N max Step-by-step adjustment By setting Δ N max Limiting the range of gear adjustment can prevent current surges and frequent fluctuations in the number of turns caused by rapid gear changes.

[0080] Specifically, environmental parameters and total DC de-icing current are monitored through a real-time measurement module. and the output current of each ice melting unit The total de-icing current and the equalization control module are controlled to balance the total de-icing current and The current of each branch is controlled by a dual closed-loop system.

[0081] If the resistance of the wire is affected by the melting of ice during the de-icing process or changes in environmental parameters... Changes in parameters such as the equivalent impedance of the de-icing unit can cause the de-icing current to deviate from the target value or the current deviation rate of each de-icing unit. If the value exceeds 5%, the equalization control module immediately adjusts the on-load tap changer on the primary side of the corresponding ice-melting unit transformer step by step to maintain the balance and stability of the DC parallel system.

[0082] If environmental parameters change during the de-icing process, it is necessary to adjust the total DC de-icing current. The equalization control module can also make overall adjustments to the on-load tap changers on the primary side of each ice-melting unit transformer, adjusting the total current. Simultaneously, maintain current balance across all de-icing units. The outer layer's total current closed-loop output determines the total target de-icing current. This yields a new reference current for each ice-melting unit. The inner branch current closed loop is in Adjust the on-load tap changer position of each unit's primary side based on the above.

[0083] Outer loop calculation of total current adjustment Output total target de-icing current The new reference current for each unit can be obtained from the formula in S3:

[0084] in, For environment variables, , , For the outer loop control coefficient:

[0085] The on-load tap changer positions of the primary side transformers of each ice-melting unit in the inner loop output are as follows: To avoid current surges caused by rapid changes in gear position in a single operation, a setting is used... Limit the range of the gear adjustment, and adjust the gear of the on-load tap changer on the original side by Δ. N ( Adjustments are made step by step, using the following formula:

[0086] To avoid frequent fluctuations in the number of turns, a dead zone can be set. When the current deviation rate is less than 5%, on-load tap changer should be paused. .

[0087] S5. Abnormal intervention resection: If the DC current output of a certain ice-melting unit is detected to exceed 120% of the rated DC current, or the total ice-melting DC current is... Exceeding the maximum de-icing current Immediately adjust the on-load tap changer on the primary side based on the coupling formula in step S3; if the adjustment is ineffective, the equalization control module identifies the location of the faulty unit. The faulty unit is disconnected through the input and output combined control modules, and the remaining ice-melting units continue to operate in DC parallel. Simultaneously, the balancing control module recalculates the target value of the distributed current, adjusts the on-load tap changer on the primary side, and repeats step S3 to balance the current of the remaining ice-melting units. S4~S5 real-time on-load control is as follows: Figure 5 As shown.

[0088] S6. The ice has completely melted, and the melting process is complete. After the ice has completely melted, the infrared thermometer shows that the ice on the conductor has completely melted. The equalization control module triggers the shutdown procedure, sequentially disconnecting the incoming grid control module, the ice-melting outgoing control module, the input combination control module, and the output combination control module, cutting off each ice-melting unit, and completing the ice melting process.

[0089] This invention enables flexible expansion of the capacity of de-icing units. After solving the problem of parallel balancing of modular de-icing, the number of de-icing units can be increased or decreased more flexibly according to the different lengths and cross-sections of the lines to be de-iced. A single de-icing unit can be used for de-icing small-capacity lines, while a balanced combination can meet the de-icing needs of large-capacity lines, greatly improving the utilization rate and applicability of de-icing units.

[0090] This invention can achieve dual current balance between the device and the external current. By using on-load tap changer on the primary side of the transformer, it compensates for the external current deviation between different ice-melting devices. At the same time, by using the circulating current suppression component at the parallel output of the twelve-pulse rectifier, it suppresses the internal current imbalance between the two six-pulse rectifier bridges. The two are independent of each other and can be adjusted flexibly, forming a dual control mechanism that coordinates internal and external current, so that the overall output current can achieve high-precision and highly controllable balance.

[0091] This invention enables real-time dynamic monitoring of the ice melting process. By using a high-precision real-time measurement module to monitor key parameters in real time, and combined with dynamic load voltage regulation and fault isolation mechanisms, it can quickly respond to the impact of fluctuations in parameters such as wind speed, temperature, and conductor resistance on the ice melting process, and make dynamic real-time adjustments during the ice melting process to maintain current balance throughout the process.

[0092] This invention enables precise control of the output de-icing voltage and current. The combination of on-load fine voltage regulation on the primary side and off-load voltage regulation on the secondary side increases the adjustment range of the de-icing voltage and current, improves the adjustment accuracy, and enhances the de-icing current control capability.

[0093] This invention can improve the overall efficiency of the modular ice-melting device. By controlling the current balance of each ice-melting unit, the large-capacity ice-melting unit can bear more ice-melting current output, while the small-capacity ice-melting unit outputs a smaller current, instead of all of them bearing the same amount of current. This can improve the utilization rate of the ice-melting unit, rationalize the loss distribution, reduce the total loss, extend the lifespan, and reduce the size of the heat dissipation device.

[0094] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0095] Ice melting operations were carried out on a 500kV high-voltage transmission line. The line parameters were as follows: conductor type 2×JL / G1A-630, length L=50km, ambient temperature T=-5℃. Calculations showed that the conductor resistance per unit length r at 20℃ was 0.0225Ω / km, and the total resistance R after environmental factor correction was 1.125Ω. Based on the line parameters and ice melting requirements, the allowable ice melting voltage range was calculated to be 2.48kV~4.05kV, with a midpoint of 3.26kV.

[0096] Based on the existing secondary-side settings of the ice-melting units, the fifth setting is selected, where the output voltage is closest to the midpoint of the ice-melting voltage range. With an AC voltage of 2.4kV, the ice-melting requirements are met, and the target ice-melting voltage is determined to be 3.24kV, with a target ice-melting current of 2880A. Mobile ice-melting units from the same batch are selected and connected in parallel, with each unit having a rated power of 4MW and a rated current of [missing information]. I RATE =1100A, with a redundancy of 1, 4 units were ultimately selected ( N =4); The primary side of the adaptive current distribution voltage regulating transformer has a rated voltage of 10kV, and the secondary side has 8 no-load voltage regulating positions (voltage range 1.2~3.6kV) and 33 on-load voltage regulating positions; the twelve-pulse rectifier consists of two three-phase bridge six-pulse rectifier bridges; the real-time measurement module uses a Hall current sensor with a measurement accuracy of 0.2 class and a sampling frequency of 1kHz; the equalization control module uses a PLC controller with an operation cycle of 10ms. According to the secondary side AC voltage requirement corresponding to the target de-icing voltage, the no-load voltage regulating switches of the first and second secondary sides of the four de-icing unit transformers are adjusted to the 5th position. According to historical test results, the maximum difference in secondary side voltage is 227V. The inductance value of the dynamic current balancing device is 0.08mH, and the measured internal current deviation of each de-icing unit is ≤0.5%.

[0097] Calculations by the balancing control module indicate that, initially, the on-load tap changer positions on the primary side of each ice-melting unit should be set to 17, 19, 17, and 12, respectively. The output combined control module controls the switching modules of the four ice-melting units to switch to a two-parallel-one-series ice-melting mode. The input combined control module controls the parallel connection of the primary sides of the four ice-melting units and uniformly sets the on-load tap changer positions on the primary side of each ice-melting unit to 17, 19, 17, and 12, respectively. The ice-melting outgoing line control module connects the total output of the ice-melting unit to the line, and the incoming line grid connection control module closes the main grid connection switch, connecting to the 10kV grid bus, and initiating ice melting with current sharing. After the ice melting operation starts, the real-time measurement module monitors the output current of each ice-melting unit as: I=695A, I=729A, I=722A, I=718A, and the reference current I=2880A / 4=720A, with deviation rates all <5%.

[0098] After 0.5 hours of ice melting, the ambient temperature rises, and the outer loop adjustment target ice melting current decreases to 2800A. The total current adjustment is I = 2800 - 2880 = -80A, and the output reference current adjustment of each ice melting unit is ΔI = -20A. The new reference current for each ice melting unit is 700A. Simultaneously, due to the melting of ice, the wire resistance drops to 1.025Ω, and the total current rises to 2930A. The real-time measured currents of each ice melting unit become I = 712A, I = 745A, I = 744A, and I = 729A, with a current deviation rate of... δ =1.7%, δ =6.4%, δ=6.3%, δ =4.1%, the current deviation of the 2nd and 3rd ice-melting units exceeded the 5% threshold, triggering closed-loop regulation. The inner loop adjusted the primary speed settings of the 2nd and 3rd ice-melting units step by step according to the current deviation of each unit until the corresponding deviation rate was <5%. Ultimately, the primary speed setting of ice-melting unit 2 was adjusted to level 21, and that of ice-melting unit 3 to level 19. During the adjustment process, due to changes in the total voltage and current caused by the adjustment of other ice-melting units, the current of ice-melting unit 4 increased, and its deviation rate also began to exceed 5%. Dynamic adjustment continued, and finally, ice-melting unit 4 was adjusted to level 19. After adjustment, the speed settings of each ice-melting unit were 17, 21, 19, and 19, respectively. The measured currents were I=720A, I=711A, I=709A, and I=693A, with a total current of 2833A. The deviation rates were all <5%, restoring the equilibrium state and maintaining the current speed setting.

[0099] After 0.7 hours of ice melting, the current of the fourth ice melting unit suddenly surged to 787A, δ=12.4%>5%. Inner loop adjustment was executed, increasing the speed range to level 25, and the current dropped to 725A, restoring the deviation rate to normal. After another 0.7 hours of ice melting, the current of the third ice melting unit suddenly surged to 1492A, exceeding the 120% overcurrent threshold of the device's rated current. The speed range was increased to level 33, but the current still exceeded the limit. The equalization control module identified the faulty unit at location 3 and sent a fault signal to the input and output combination control modules, disconnecting the input and output terminals of the faulty unit. The remaining ice melting units continued DC parallel operation. The real-time measured current of each ice melting unit became I=937A, I=902A, and I=965A, respectively. Simultaneously, the equalization control module recalculated the target current value for each ice melting unit to 955A, and the current deviation rate... δ =1.9%, δ =5.5%, δ =1.0%. The original setting of the ice melting unit 2 was adjusted to setting 18. After adjustment, the current of each ice melting unit was I=928A, I=940A, and I=957A, with a deviation rate of less than 5%. The equilibrium state was restored, and the current setting was maintained.

[0100] After 1 hour of de-icing, the infrared thermometer showed that the ice on the conductor had completely melted. The equalization control module triggered the shutdown procedure, sequentially disconnecting the incoming grid control module, the de-icing outgoing control module, the input combination control module, and the output combination control module, thus cutting off each de-icing unit and completing the operation.

[0101] This embodiment achieves efficient ice melting on a 500kV line by operating four small-capacity mobile ice melting units in parallel. During the ice melting process, the current deviation rate of each ice melting unit can be controlled to less than 5%, meeting the current sharing requirements. The ice melting efficiency is high, saving energy compared to traditional single large-capacity devices. The abnormal response time is ≤100ms, and the remaining ice melting units can still maintain current sharing after a fault is cleared, demonstrating high system reliability. This verifies the effectiveness of the invention in current sharing, dynamic control, and fault adaptation of multiple ice melting units operating in parallel.

[0102] This invention is applicable to power transmission line de-icing scenarios where multiple mobile DC de-icing units operate in parallel, including... N Mobile ice-melting unit, input / output combination control module, N This modular ice-melting system, composed of real-time measurement modules and equalization control modules, employs a combination of off-load voltage regulation on the secondary side and on-load voltage regulation on the primary side, along with internal and external current sharing. This achieves balanced control of the internal and external currents of the ice-melting units while meeting the voltage and current requirements for ice melting. By sampling the output current of each ice-melting unit in real time, a closed-loop equalization control strategy is constructed based on the current deviation to adjust the on-load voltage regulation level of the primary side transformer in each ice-melting unit, thereby suppressing current imbalance caused by factors such as unit parameter deviations and model differences. This invention achieves dual current sharing both inside and outside the ice-melting unit without the need for additional power electronic regulation devices. It boasts advantages such as flexible capacity expansion, high control accuracy, and strong engineering adaptability, making it suitable for DC ice melting operations on large-section, long-distance transmission lines.

[0103] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A modular de-icing and balancing control system for transmission lines, characterized in that, include: A mobile ice-melting unit connected in parallel, of which It is a positive integer greater than or equal to 2; The input combination control module is connected to the input end of each of the mobile ice-melting units and is used to control the parallel connection of each mobile ice-melting unit, the adjustment of the on-load tap changer on the primary side, and the disconnection of the input side of the faulty unit. The output combination control module is connected to the output terminal of each mobile ice-melting unit and is used to collect the output current of each mobile ice-melting unit, control the output mode of each mobile ice-melting unit, and disconnect the output side of the faulty unit. Each real-time measurement module is set on the output side of each mobile ice-melting unit to measure the output current of each mobile ice-melting unit. The incoming line grid connection control module is connected between the power grid and the input combination control module, and is used to control the overall grid connection of the system; The de-icing output control module is connected between the output combination regulation module and the line to be de-iced, and is used to control the output of the total de-icing current. The equalization control module is connected to each real-time measurement module, the input combination control module and the output combination control module. It is used to receive the current signal of each mobile ice melting unit, calculate and output the control signal of the on-load tap changer of the primary side of each mobile ice melting unit to the input combination control module based on the current deviation rate through the equalization control algorithm, and output the fault unit cut-off signal when a fault is detected.

2. The modular de-icing and balancing control system for transmission lines according to claim 1, characterized in that, The mobile ice-melting unit includes: An adaptive current distribution voltage regulating transformer has an on-load tap changer configured on its primary winding and an off-load tap changer configured on its first and second secondary windings. The primary winding is connected to the input combination control module. The twelve-pulse rectifier includes a first six-pulse rectifier bridge and a second six-pulse rectifier bridge, which are respectively connected to the two secondary windings of the adaptive current distribution voltage regulating transformer. A dynamic current balancing device is connected between the output terminals of the first six-pulse rectifier bridge and the second six-pulse rectifier bridge to achieve current balancing between the two rectifier bridges. The switch module has its input side connected to the DC output terminal of the twelve-pulse rectifier and its output side connected to the output combination control module. It is used to reconstruct the connection topology between the DC output and the three-phase conductors of the line to be melted.

3. A control method based on the modular de-icing and balancing control system for transmission lines as described in claim 1 or 2, characterized in that, Including the following steps: Calculate the required de-icing voltage and current range based on the parameters of the line to be de-iced, and determine the target de-icing voltage. With the target de-icing current The number of mobile de-icing units connected in parallel is determined based on the rated parameters of each mobile de-icing unit. ; Based on the target de-icing voltage Adjust the no-load voltage regulation position of the secondary side of the transformer in each mobile ice-melting unit to the preset position, and configure the parameters of the dynamic current balancing device in each mobile ice-melting unit to achieve current balance inside the mobile ice-melting unit. The target current is balanced by allocating it to each mobile ice-melting unit according to its capacity ratio. For the on-load tap changer position Initial pre-adjustment was performed, and all mobile ice-melting units were started up in a balanced manner; The system is started and connected to the grid for de-icing. The output current of the mobile de-icing unit is monitored by the real-time measurement module, and the current deviation rate of each mobile de-icing unit is calculated. If the current deviation rate exceeds the preset threshold, the on-load tap changer of the primary side of the transformer in the corresponding mobile de-icing unit is adjusted by the equalization control module until the current deviation rate of all mobile de-icing units is lower than the preset threshold and the total de-icing current reaches the target value.

4. The control method according to claim 3, characterized in that, Equalize the target current of each mobile de-icing unit The calculation formula is: in, For the first k Rated current of each ice-melting unit; For the first i Rated current of each ice-melting unit; On-load tap changer position The calculation formula is: This refers to the voltage of the power grid bus. Gear; When rectifiers are connected in parallel, the first k The conduction voltage of the diode in the ice-melting unit AC equivalent voltage; When rectifiers are connected in parallel, the first The AC equivalent voltage of the diode forward voltage of each ice-melting unit; The AC equivalent resistance of the wire to be melted when the rectifiers are connected in parallel; This is the equivalent de-icing voltage; When rectifiers are connected in parallel, the first i On-resistance of diodes in each ice-melting unit AC equivalent resistance; When rectifiers are connected in parallel, the first k The AC equivalent resistance of the diode conduction resistance of each ice-melting unit; For the first k The equivalent impedance of the primary and secondary windings of a transformer; For the first The equivalent impedance of the primary and secondary windings of a transformer.

5. The control method according to claim 3, characterized in that, During the de-icing process, the total de-icing current and the current of each mobile de-icing unit are continuously monitored. If the current deviation rate exceeds the preset threshold again, or if the total de-icing current needs to be adjusted, the on-load tap changer of the primary side of each mobile de-icing unit is dynamically adjusted through the control method of inner and outer loops to maintain current balance. If an overcurrent is detected in a mobile de-icing unit or the total de-icing current exceeds the limit, and the problem cannot be resolved by voltage adjustment, the faulty de-icing unit will be identified and disconnected, and the remaining de-icing units will be rebalanced.

6. The control method according to claim 5, characterized in that, The control method combining inner and outer loops is specifically as follows: The outer ring calculates the adjustment amount of the total de-icing current based on environmental changes and updates the total target de-icing current. ; The inner loop recalculates the reference current for each ice-melting unit. Based on the deviation between the measured current of each ice-melting unit and the recalculated reference current, the on-load tap changer on the primary side of the transformer of the corresponding ice-melting unit is adjusted step by step. And the magnitude of a single adjustment Within the preset range, the specific adjustment formula is as follows: in, This is the equivalent current deviation.

7. The control method according to claim 6, characterized in that, Adjustment amount of total de-icing current The calculation formula is: in, For environment variables, , , For the outer loop control coefficient: New overall target de-icing current for: 。 8. The control method according to any one of claims 3-7, characterized in that, Determine the target de-icing voltage The process is as follows: Calculate the allowable range of the de-icing voltage and take the intersection of this range with the output voltage ranges corresponding to multiple taps on the secondary side of the transformer in each de-icing unit. Select the voltage closest to the median value of the allowable range of the de-icing voltage from this intersection as the target de-icing voltage. .

9. The control method according to any one of claims 3-7, characterized in that, The parameters of the dynamic current balancing device in each mobile ice-melting unit are inductance. The calculation formula is: in, f For the power grid AC frequency, U k1 , U k2 These are the output voltages of the two six-pulse rectifier bridges in the twelve-pulse rectifier.

10. The control method according to any one of claims 3-7, characterized in that, Current deviation rate The calculation formula is: in For the first The DC current of each ice-melting unit; For the first Rated current of each ice-melting unit; For the first Rated current of each ice-melting unit.

11. The control method according to any one of claims 3-7, characterized in that, After the ice has completely melted, the incoming grid control module, the ice-melting outgoing control module, the input combination control module, and the output combination control module are disconnected in sequence, and each mobile ice-melting unit is cut off to complete the ice melting process.

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