Direct-current deicing control method, system and equipment for hybrid MMC of various lines of transformer substation and medium

Abstract

The invention is suitable for the technical field of direct-current ice melting, and discloses a direct-current ice melting control method, system, equipment and medium for a hybrid MMC of various lines of a transformer substation, and the method comprises the steps: obtaining an ice melting request of an outgoing line, comparing the sum of ice melting current target values of all lines with the maximum output capability of a full-bridge and half-bridge hybrid MMC direct-current ice melting system, generating an ice melting time sequence strategy; based on the ice melting request, the system is controlled to be switched from a reactive compensation mode to a direct current ice melting operation mode, direct current side voltage and current return-to-zero control is started, then the direct current reference value return-to-zero control is quitted, and ice melting is carried out on the current line; if a fault point is detected in the ice melting process, direct current side fault ride-through is executed; and if the line to be de-iced still exists, restarting the direct current reference value return-to-zero control to de-ice until no line to be de-iced exists, and switching to a reactive compensation mode. Automatic sorting and start-stop when the plurality of outgoing lines need to be de-iced are realized, and safe and stable operation of a power distribution network is ensured.

Description

Technical Field

[0001] This invention relates to the field of DC de-icing technology, and in particular to a DC de-icing control method, system, equipment and medium for a hybrid MMC (Multi-line Control) system for multiple lines in a substation. Background Technology

[0002] Among the various natural disasters encountered by power systems, snow and ice disasters are among the most severe. Compared with other accidents, snow and ice disasters generally cause more serious damage to the power grid, ranging from minor ice flashes to tower collapses, line breaks, and even power grid paralysis.

[0003] Currently, there are various methods and equipment for de-icing and melting lines to improve the power grid's ability to withstand snow and ice disasters. Thermal de-icing has the advantages of short-time melting, simple operation, and ease of implementation. Thermal de-icing is a de-icing technology that converts electrical energy into heat energy. Generally, current is passed through the conductors to heat them and achieve the purpose of melting ice. It can be divided into AC de-icing and DC de-icing. DC de-icing systems include different technical routes based on thyristors and MMC submodules. MMC-based DC de-icing systems can achieve reactive power compensation and DC de-icing mode switching, improving the operation of MMC-based DC de-icing technology. However, MMC DC de-icing systems are technically complex and cumbersome to operate, requiring the design of DC de-icing control methods to achieve automatic de-icing technology for power grid outgoing lines, reducing manual operation and ensuring system safety. Summary of the Invention

[0004] In view of the aforementioned problems of cumbersome and unsafe existing ice-melting operations, this invention is proposed.

[0005] Therefore, this invention provides a DC de-icing control method, system, equipment, and medium for hybrid MMC systems with multiple lines in substations to solve the problems of complex operation procedures during reactive power compensation and de-icing mode switching in existing MMC DC de-icing systems; the risk of arcing from traditional on-load operation disconnect switches, threatening equipment and personnel safety; the lack of scientific de-icing timing scheduling when multiple lines are iced, making it impossible to prioritize important lines; and the easy interruption of de-icing operations when transient faults occur on the DC side.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a DC de-icing control method for a hybrid MMC (Multi-Line Control) system in a substation, comprising: Obtain the de-icing request of the outgoing line and calculate the target value of the de-icing current required for each line based on the preset line parameters; The sum of the target values ​​of the de-icing current of all lines is compared with the maximum output capacity of the full-half-bridge hybrid MMC DC de-icing system to generate a de-icing timing strategy. Based on the ice melting request, the system is controlled to switch from reactive power compensation mode to DC ice melting operation mode, and DC current reference value zeroing control is initiated. The DC side voltage and current are brought to zero by the DC current reference value zeroing control. After closing the isolation switch of the corresponding line, the DC current reference value zeroing control is exited, and the current line is de-iced according to the preset slope. If a fault point is detected during the de-icing process, a DC-side fault ride-through will be performed. If there are still lines to be melted in the ice melting timing strategy, restart the DC current reference value zeroing control to melt the ice until there are no more lines to be melted and switch to reactive power compensation mode.

[0007] As a preferred embodiment of the DC de-icing control method for a hybrid MMC (Multi-Line Controller) in a substation as described in this invention, the method involves: comparing the sum of the target de-icing current values ​​of all lines with the maximum output capacity of the full-half-bridge hybrid MMC DC de-icing system to generate a de-icing timing strategy, including: If the total target value of the de-icing current of all outgoing lines is not greater than the maximum output capacity of the system, then all lines will be aggregated and de-iced simultaneously. If the total target value of the de-icing current for all outgoing lines is greater than the maximum output capacity of the system, then all lines are grouped and sorted according to the importance of the power supply load and de-iced in sequence.

[0008] As a preferred embodiment of the DC de-icing control method for a hybrid MMC (Multi-Line Controller) in a substation according to the present invention, wherein: the starting DC current reference value zeroing control includes: The DC de-icing system controls and maintains the DC current and DC voltage at zero by adjusting the negative voltage control capability of the full-bridge submodule. Among them, the DC side electrical quantities are continuously monitored, and the disconnecting switch action command is issued only when the DC current and DC voltage are both zero.

[0009] As a preferred embodiment of the DC de-icing control method for a hybrid MMC (Multi-line Control) system in a substation according to the present invention, wherein: the execution of DC-side fault ride-through includes: When the action signal of the DC de-icing system protection device is received, the DC current reference value is zeroed out, and the DC side voltage and current are zeroed out. After the DC side voltage and current return to zero, determine whether the fault point has been cleared: if the fault point has been cleared, exit the DC current reference value zeroing control, restore current output and continue the ice melting process. If the fault point is not cleared, exit the DC ice melting operation mode and switch to reactive power compensation mode.

[0010] As a preferred embodiment of the DC de-icing control method for a hybrid MMC (Multi-line Control) system in a substation according to the present invention, wherein: the target de-icing current value required for each outgoing line includes: in, The target value for the de-icing current. For line resistance, The set melting time, The heat absorbed to melt the ice. This refers to the heat dissipated from the circuit during the de-icing process.

[0011] As a preferred embodiment of the DC de-icing control method for a hybrid MMC (Multi-line Control) system in a substation as described in this invention, the switching process between the reactive power compensation mode and the DC de-icing mode includes: In reactive power compensation mode, the DC ice melting system provides reactive power support by disconnecting the DC ice melting bus disconnecting switch and connecting only to the AC power grid. Upon receiving the de-icing start command, the reactive power output is first locked, and the DC current reference value is zeroed. After the DC current and DC voltage return to zero, the DC de-icing bus disconnect switch and the disconnect switch of the closed line are then closed.

[0012] As a preferred embodiment of the hybrid MMC DC de-icing control method for multiple lines in a substation according to the present invention, the full-half-bridge hybrid MMC DC de-icing system includes: The hybrid MMC DC de-icing system includes full-bridge sub-modules and half-bridge sub-modules, and is equipped with protection and control devices. The proportion of full-bridge submodules is configured to have the ability to output negative voltage.

[0013] Secondly, the present invention provides a hybrid MMC DC de-icing control system for multiple lines in a substation, comprising: The target current module is used to obtain the de-icing request of the outgoing line and calculate the target de-icing current value required for each line based on the preset line parameters. The timing strategy module is used to compare the sum of the target values ​​of the de-icing current of all lines with the maximum output capacity of the full-half-bridge hybrid MMC DC de-icing system to generate a de-icing timing strategy. The switching module is used to control the system to switch from reactive power compensation mode to DC ice melting operation mode based on the ice melting request, and to start DC current reference value zeroing control. The de-icing execution module is used to reduce the DC side voltage and current to zero through DC current reference value zeroing control, close the isolation switch of the corresponding line, exit the DC current reference value zeroing control, and de-ic the current line according to the preset slope. The fault detection module is used to perform DC-side fault ride-through if a fault point is detected during the ice melting process. The strategy execution module is used to restart the DC current reference value zeroing control to perform ice melting based on the fact that there are still lines to be melted in the ice melting timing strategy, until there are no more lines to be melted and switch to reactive power compensation mode.

[0014] Thirdly, the present invention provides an electronic device, comprising: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of a DC de-icing control method for a hybrid MMC of multiple lines in a substation.

[0015] Fourthly, the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the DC de-icing control method for a hybrid MMC of multiple lines in the substation.

[0016] Compared with existing technologies, the beneficial effects of this invention are as follows: Utilizing the negative voltage output capability of the full-bridge submodule, the DC voltage and current are forcibly reduced to zero before the disconnecting switch operates, achieving arc-free opening and closing under zero electrical quantity conditions, eliminating the risk of operational overvoltage and arc damage to equipment; when transient faults such as ice flashover are detected, the AC circuit breaker is not tripped, but rather deionized through rapid voltage reduction, and de-icing automatically resumes after the fault is cleared, avoiding frequent shutdowns and restarts, and significantly improving de-icing efficiency; it can automatically calculate target values ​​based on line parameters and generate optimal timing strategies based on system capacity and load importance, realizing automated full-process management of multi-line de-icing; it achieves automatic sorting, automatic start and stop when multiple outgoing lines need de-icing, automatic disconnection and continued de-icing when a DC-side fault occurs, while reducing human intervention and ensuring the safe and stable operation of the new energy distribution network. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the overall process of a DC de-icing control method for a hybrid MMC (Multi-line Control) system in a substation according to an embodiment of the present invention.

[0019] Figure 2This is a schematic diagram of a DC de-icing system for a hybrid MMC (Multi-line DC de-icing control) method for multiple lines in a substation, as described in an embodiment of the present invention.

[0020] Figure 3 This is a negative pressure control schematic diagram of a DC de-icing control method for a hybrid MMC (Multi-line Controller) in a substation according to an embodiment of the present invention.

[0021] Figure 4 This is a schematic diagram illustrating the specific process of a DC de-icing control method for a hybrid MMC (Multi-line Control) system in a substation according to an embodiment of the present invention. Detailed Implementation

[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0023] Example 1, referring to Figure 1 As an embodiment of the present invention, a DC de-icing control method for a hybrid MMC (Multi-Line Control) system in a substation is provided, comprising: S100: Obtain the de-icing request of the outgoing line and calculate the target value of the de-icing current required for each line based on the preset line parameters; S200: Compare the sum of the target values ​​of the de-icing current of all lines with the maximum output capacity of the full-half-bridge hybrid MMC DC de-icing system to generate a de-icing timing strategy; S300: Based on the ice melting request, control the system to switch from reactive power compensation mode to DC ice melting operation mode, and start DC current reference value zeroing control; S400: By controlling the DC current reference value to zero, the DC side voltage and current are reduced to zero. After closing the isolation switch of the corresponding line, the DC current reference value to zero control is exited, and the current line is de-iced according to the preset slope. S500: If a fault point is detected during the de-icing process, DC-side fault ride-through will be performed; S600: If there are still lines to be melted in the ice melting timing strategy, restart the DC current reference value zeroing control to melt the ice until there are no more lines to be melted and switch to reactive power compensation mode.

[0024] It should be noted that the DC de-icing system of a substation operates under high voltage and high current conditions, and its operating mode switching is complex. During icing disasters, line operating parameters fluctuate drastically with ice thickness and ambient temperature, making it difficult for traditional open-loop control to accurately match the de-icing current. Furthermore, the full-half-bridge hybrid MMC contains numerous submodules; if residual voltage or induced current exists on the DC side during mode switching or line rotation, it can easily generate a high-energy arc at the moment the disconnecting switch operates, causing equipment damage or even grid oscillation. In addition, improper handling of transient faults such as ice flashover can interrupt the entire de-icing process. Therefore, the need for a control strategy that can achieve precise zeroing of electrical quantities, rapid fault ride-through, and automatic timing management of multiple lines is particularly urgent.

[0025] Therefore, to address the aforementioned problems, steps S100-S600 are used to collect line icing data and calculate the target de-icing current value for each line using the heat balance formula. By determining whether the total demand current exceeds the device's maximum capacity, a strategy for simultaneous or grouped de-icing is determined. When preparing for de-icing, the negative voltage control capability of the full-bridge submodule is used to control the DC voltage and current to 0. Once it is confirmed that there is no power, the switch is closed, and the de-icing current is output according to the slope to begin de-icing. If a fault occurs during de-icing, DC side fault ride-through is initiated, and negative voltage control is performed again. If there are still lines to be de-iced, the DC current reference value zeroing control is restarted to continue de-icing until there are no more lines to be de-iced and the system switches to reactive power compensation mode.

[0026] Example 2, refer to Figures 1-4 As an embodiment of the present invention, based on the above embodiment, a DC de-icing control method for a hybrid MMC of multiple lines in a substation is provided.

[0027] In this embodiment of the application, step S100 involves obtaining the de-icing request for the outgoing line and calculating the target de-icing current value required for each line based on preset line parameters, including the following steps A1-A3: A1: The full-semi-bridge hybrid MMC DC ice melting system; Specifically, the AC substation adopts a three-way connection configuration with multiple outgoing line bays and is equipped with a hybrid full-bridge and half-bridge MMC DC de-icing system. This system includes full-bridge submodules (FBSM) and half-bridge submodules (HBSM), and is equipped with protection and control devices. The full-bridge submodules have the capability for negative voltage output; the number of full-bridge submodules is ≥75%n, where n is the sum of the number of full-bridge and half-bridge submodules.

[0028] The number of modules required for the full-bridge submodule is calculated as follows: In the formula, This refers to the rated voltage of the power module capacitor. The rated DC voltage; The modulation ratio is (0.85~1); The peak value of the modulated wave; This represents the total number of bridge sub-modules. This represents the total number of bridge sub-modules. This represents the total number of submodules.

[0029] For example, such as Figure 2 As shown, the AC substation is configured with 7 outgoing line bays, each bay consisting of 3 circuit breakers (Q1, Q2, Q3), and the number of bays is two times the number of series circuit breakers.

[0030] A2: Obtain the de-icing request for the outgoing line; Specifically, when icing occurs on the AC outgoing line, the DC de-icing system control device monitors key status indicators such as the line temperature and line tension of the AC outgoing line in real time. When the AC outgoing line tension exceeds the set threshold and the AC outgoing line temperature is less than the set threshold (e.g., <-3℃), the DC de-icing system control device determines that the AC outgoing line is severely iced and generates a de-icing request.

[0031] Furthermore, when phases A and B of line 1 require de-icing, the DC de-icing system control device issues the first set of circuit breaker tripping commands for Q1 and Q2. When Q1 and Q2 are detected to be in the tripped state and the AC voltage... When the voltage is 0kV, the DC de-icing control device sends a de-icing command to the opposite side of the line. After receiving the command, the substation on the opposite side of the line disconnects circuit breakers Q1 and Q2 on both sides of the line. When the DC de-icing control device detects that Q1 and Q2 on the opposite side of the line are in the open state, it short-circuits the AC outgoing line. After completing the above operations, the DC de-icing control device determines that line 1 has the conditions for DC de-icing and sends K1A and K1B closing commands. When the closed state of K1A and K1B is detected, the DC de-icing control device sends F1 and F2 disconnecting switch closing commands. When the closed state of F1 and F2 is detected, the A and B phases of line 1 have the conditions for de-icing.

[0032] The steps for connecting each phase of other lines to the de-icing system are as described above; It should be noted that each outgoing line is connected to the DC de-icing positive and negative busbars via a three-phase split disconnect switch (A, B, and C phases can be operated individually using K1~Kn, and the number of n is related to the number of outgoing lines) to achieve individual de-icing of the A / B / C three-phase lines. The full-half-bridge hybrid MMC de-icing device is connected to the de-icing busbars via disconnect switches F1 and F2.

[0033] A3: The target value of the de-icing current required for each line is calculated based on the preset line parameters; Specifically, the full-bridge / half-bridge hybrid MMC de-icing system calculates the current required for de-icing each line based on the AC outgoing lines and the preset line parameters (line resistance, de-icing time) of the de-icing system: In the formula, For de-icing current, The resistance of each de-icing line, The de-icing time set for operators The heat absorbed to melt ice. This refers to all the heat that has been dissipated.

[0034] It should be noted that by using both tension and temperature as criteria, the automatic triggering of ice melting demand is achieved, avoiding the lag of manual inspection, and ensuring operational safety by first cutting off power and then short-circuiting.

[0035] In this embodiment of the application, step S200 compares the sum of the target values ​​of the de-icing current for all lines with the maximum output capacity of the full-half-bridge hybrid MMC DC de-icing system to generate a de-icing timing strategy, including: Specifically, by summing the calculated de-icing current required for each AC outgoing line, the DC de-icing device obtains the maximum de-icing current required for simultaneous de-icing of the AC lines.

[0036] If the total target value of the de-icing current of all outgoing lines is not greater than the maximum output capacity of the system, then all lines will be aggregated and de-iced simultaneously. The simultaneous de-icing process includes: when icing occurs on the AC outgoing line, the DC de-icing system control device monitors key status indicators such as the line temperature and tension of the AC outgoing line in real time. When the tension of the AC outgoing line exceeds the set threshold and the AC outgoing line temperature is below the set threshold (e.g., <-3℃), the DC de-icing control device determines that severe icing has occurred on the AC outgoing line. The DC de-icing control device issues a shutdown command for the AC outgoing line, trips the AC circuit breakers Q1 and Q2 on both sides of the AC outgoing line, and issues a de-icing command to the substation on the opposite side of the AC outgoing line. Upon receiving the de-icing command, the substation on the opposite side of the AC outgoing line opens AC circuit breakers Q1 and Q2 on both sides of the AC outgoing line, short-circuiting the AC outgoing line. After receiving confirmation that the substation on the opposite side of the AC outgoing line has completed the short-circuit operation, the DC de-icing control device issues closing commands K1A and K1B. When Kn is detected as closed, the DC de-icing control device issues closing commands F1 and F2 disconnect switches. When F1 and F2 are detected as closed, it is determined that the AC outgoing line has entered de-icing mode. In other words, when all disconnect switches are closed, the DC de-icing system control device determines that the AC outgoing line is simultaneously de-icing.

[0037] If the total target value of the de-icing current for all outgoing lines is greater than the maximum output capacity of the system, then all lines are grouped and sorted according to the importance of the power supply load and de-iced in sequence.

[0038] The sequential de-icing process includes: determining the importance of an AC line based on its location in the AC power grid, its importance in inter-regional connections, and whether disconnecting N-1 would cause overload on other AC lines. The DC de-icing system control device aggregates and groups all lines based on their resistance and importance, and prioritizes important outgoing lines for de-icing.

[0039] In an alternative implementation, the grouping of AC lines based on their importance in step S200 can also incorporate real-time meteorological data, such as the influence of wind direction, wind speed, ambient temperature on the icing growth rate, and the physical condition of the lines themselves, to construct a weighted function, with those scoring higher receiving priority for icing.

[0040] In another optional implementation, the grouping based on the importance of AC lines in step S200 can also incorporate N-1 or even N-2 grid verification logic. When calculating the grouping, the power flow of the remaining grid is simulated to determine if it exceeds limits when several lines are disconnected for de-icing. If a grouping scheme would cause overload of the remaining lines, the grouping combination is automatically adjusted, for example, by de-icing two heavily loaded lines at different times.

[0041] In this embodiment of the application, step S300, based on the ice-melting request, controls the system to switch from reactive power compensation mode to DC ice-melting operation mode, and initiates DC current reference value zeroing control, including: Specifically, the full-half-bridge hybrid MMC ice-melting system has two operating modes: reactive power compensation mode and DC ice-melting mode. During initial operation, the system operates in reactive power compensation mode. In this mode, the full-half-bridge hybrid MMC ice-melting device disconnects F1 and F2 from the DC bus and connects only to the AC grid, providing reactive power support to maintain AC voltage stability. The reactive power compensation mode includes two operating states: constant reactive power and constant AC voltage.

[0042] Furthermore, the DC ice-melting operation mode is activated and the DC ice-melting system exits the reactive power compensation operation mode. At the same time, the DC ice-melting system control device activates the DC current reference value zeroing control (negative voltage control mode, reference value is 0). Through the negative voltage control capability of the full-bridge submodule, the DC voltage is controlled to 0kV and the DC current is 0kA.

[0043] For example, such as Figure 3The diagram shown is for negative pressure control. In reactive power compensation mode, the DC de-icing control device compares the submodule voltage with the set value 1.0pu, and the calculated difference error is used to calculate the D-axis current reference value using Kp and Ki. When a DC side fault occurs or K1~K7 are not closed, according to... (Set value is 0kV) Output DC voltage reference value. When the DC side fault ends or it is determined that the ice melting conditions are met (K1~K7 closed state, F1 and F2 closed state, AC outgoing circuit breaker Q1 / Q3 and Q2 open state), switch to constant DC current control. The DC voltage reference value is obtained by comparing the DC current reference value and the DC current and calculating the difference error through Kp and Ki. Figure 3 middle The per-unit value represents the average voltage of the submodule; PI represents the PI loop. This is a reference value for DC current. It is direct current; This is the reference value for the d-axis. This is a reference value for the q-axis. This is the DC voltage reference setting. This is a reference value for DC voltage. Modulated wave for upper bridge arm; This is the modulated wave for the lower bridge arm.

[0044] It should be noted that traditional half-bridge MMC cannot output 0 voltage on the DC side due to diode rectification effect. However, this invention utilizes the negative voltage capability of the full bridge to actively return to zero, creating the necessary and sufficient conditions for arc-free operation of the subsequent disconnecting switch and solving the risk of closing the circuit breaker under energized conditions.

[0045] In this embodiment of the application, step S400 involves zeroing the DC side voltage and current through DC current reference value zeroing control, closing the disconnecting switch of the corresponding line, exiting the DC current reference value zeroing control, and de-icing the current line according to a preset slope, including: Specifically, when the DC voltage is detected to be 0kV and the DC current is 0kA, the control device issues a command to close the disconnect switches K1~K7 of the current group line and the disconnect switches F1 and F2 of the de-icing bus.

[0046] Furthermore, after detecting that all relevant disconnect switches K1~K7 have been closed, the system exits the DC current reference value zeroing control, increases the DC voltage and outputs the de-icing current according to the preset slope (e.g., 1pu / 0.1s), and starts the de-icing timer.

[0047] It should be noted that zero-voltage and zero-current switching operation is achieved, preventing the equipment from being burned by electric arcs during the operation of the disconnecting switch. At the same time, the ramp-up soft start of the current avoids the impact on the weak AC power grid.

[0048] In this embodiment of the application, if a fault point is detected during the de-icing process in step S500, a DC-side fault ride-through is performed, including: Specifically, during the de-icing process, if the DC de-icing system protection device detects an abnormality, it will simultaneously transmit an action signal to the DC de-icing system control device, and the system will perform DC side fault ride-through.

[0049] Furthermore, without tripping the AC circuit breaker, the DC current reference value zeroing control is restarted, and the negative voltage control capability of the full-bridge submodule is used to control the DC voltage to 0kV and the DC current to 0kA.

[0050] After the DC de-icing system protection device detects that the DC voltage and current have switched to 0, it opens the Kn isolating switch of the faulty AC line, isolating the faulty line from the DC de-icing system. The DC de-icing system then disconnects the fault point. If the fault point has been disconnected, the de-icing system protection device transmits the fault disconnection to the de-icing control device. The DC de-icing system control device then exits the DC side fault crossing and continues de-icing until the de-icing time is reached. If the fault point has not been disconnected, the de-icing control device switches to reactive power compensation mode to provide reactive power support to the AC system. After the DC de-icing control system detects that the fault point has been disconnected (by operation and maintenance personnel), it switches back to the de-icing operation mode.

[0051] In an optional implementation, fault point feature extraction in step S500 can be achieved by detecting the rate of change of DC current and the waveform characteristics of voltage drops. Faults such as ice flashover are typically accompanied by high-frequency oscillations and the voltage does not completely drop to zero; while a metallic ground fault is characterized by an instantaneous drop in voltage to zero and a linear increase in current.

[0052] In another alternative implementation, the fault detection in step S500 can be achieved by combining bridge arm current differential protection to distinguish between internal and external faults, such as distinguishing between internal MMC submodule faults (which need to be immediately blocked) and external line faults (which can be bypassed).

[0053] In this embodiment of the application, step S600, based on the fact that there are still lines to be melted in the ice-melting timing strategy, restarts the DC current reference value zeroing control to melt the ice, until there are no more lines to be melted and switches to reactive power compensation mode, includes: Specifically, when the first set of de-icing time reaches t, the de-icing ends, and the DC current reference value zeroing control is activated, controlling the DC voltage to 0kV and the DC current to 0kA. When the de-icing control device detects that the DC voltage and DC current are 0, it issues a command to open the disconnect switches K1~K7 (all lines are grouped and sorted according to the importance of the power supply load and de-iced in sequence) connecting the AC outgoing lines and the DC de-icing bus. After detecting that K1~K7 has been opened, the DC voltage is increased according to the preset slope (e.g., 1pu / 0.1s) and the de-icing current is output, and the de-icing timer begins. When all AC outgoing lines have completed de-icing, the command to open the disconnect switches F1 and F2 of the de-icing system is issued. After detecting that the disconnect switches of the de-icing system have been opened, the system switches to reactive power compensation mode to provide reactive power support to the AC system.

[0054] In an optional implementation, the step S600, where the de-icing time expires and the de-icing process ends, can be transformed from a single time control to a multi-sensor fusion judgment, such as an online monitoring line tension sensor. When the tension value is detected to return to the baseline value of the ice-free state and remain there for a certain period of time, the de-icing is considered complete, and the de-icing process is terminated early.

[0055] In another optional implementation, the step S600, where the ice melting time expires and the melting process ends, can be transformed from a single time control to a multi-sensor fusion judgment. For example, it can combine cameras on substations or towers and use a CNN convolutional neural network to identify the diameter of the conductor wrapping. When ice layer detachment or the thickness is less than a threshold is detected, an end command is issued.

[0056] For example, such as Figure 4 The diagram shown is a schematic representation of the specific process.

[0057] Further, check if there are any remaining ice-melting groups in the generated ice-melting timing strategy: if there are, close the second group of line disconnect switches and repeat the startup steps in S400, cycling in sequence; if there are no remaining groups, after confirming that the DC voltage and DC current have returned to zero, open the ice-melting bus disconnect switches F1 and F2. Finally, the system switches back to reactive power compensation mode to continue providing voltage support to the power grid.

[0058] In summary, this invention solves the scheduling challenge of multi-line de-icing through thermal balance calculation and timing strategy generation; it addresses the operational safety issue of high-voltage DC-side disconnect switches through the "zero-voltage / zero-current switching" logic implemented by the negative voltage control of the full-bridge module; and it resolves the pain point of easy interruption in the de-icing process through DC-side fault ride-through logic. This invention achieves automatic sequencing and automatic start / stop when multiple outgoing lines need de-icing, and automatic disconnection and continuation of de-icing in the event of a DC-side fault, while reducing human intervention and ensuring the safe and stable operation of the new energy distribution network.

[0059] Example 3 illustrates a schematic scheme for a DC de-icing control method using a hybrid MMC (Multi-Line Control) system for multiple lines in a substation. It should be noted that the technical solution of this hybrid MMC system for multiple lines in a substation is based on the same concept as the aforementioned hybrid MMC method for multiple lines in a substation. Details not described in detail in this example can be found in the description of the aforementioned hybrid MMC method for multiple lines in a substation.

[0060] This embodiment also provides a hybrid MMC DC de-icing control system for multiple lines in a substation, including: The target current module is used to obtain the de-icing request of the outgoing line and calculate the target de-icing current value required for each line based on the preset line parameters. The timing strategy module is used to compare the sum of the target values ​​of the de-icing current of all lines with the maximum output capacity of the full-half-bridge hybrid MMC DC de-icing system to generate a de-icing timing strategy. The switching module is used to control the system to switch from reactive power compensation mode to DC ice melting operation mode based on the ice melting request, and to start DC current reference value zeroing control. The de-icing execution module is used to reduce the DC side voltage and current to zero through DC current reference value zeroing control, close the isolation switch of the corresponding line, exit the DC current reference value zeroing control, and de-ic the current line according to the preset slope. The fault detection module is used to perform DC-side fault ride-through if a fault point is detected during the ice melting process. The strategy execution module is used to restart the DC current reference value zeroing control to perform ice melting based on the fact that there are still lines to be melted in the ice melting timing strategy, until there are no more lines to be melted and switch to reactive power compensation mode.

[0061] This embodiment also provides an electronic device applicable to DC de-icing control of hybrid MMC for multiple lines in a substation, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the DC de-icing control method for hybrid MMC for multiple lines in a substation as proposed in the above embodiment.

[0062] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements the DC de-icing control method for hybrid MMC of multiple lines in a substation as proposed in the above embodiment.

[0063] The storage medium proposed in this embodiment and the DC de-icing control method for realizing hybrid MMC of multiple lines in substation proposed in the above embodiment belong to the same inventive concept. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0064] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0065] 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 technical solutions 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. A DC de-icing control method for a hybrid MMC (Multi-line Control) system in a substation with multiple lines, characterized in that, include: Obtain the de-icing request of the outgoing line and calculate the target value of the de-icing current required for each line based on the preset line parameters; The sum of the target values ​​of the de-icing current of all lines is compared with the maximum output capacity of the full-half-bridge hybrid MMC DC de-icing system to generate a de-icing timing strategy. Based on the ice melting request, the system is controlled to switch from reactive power compensation mode to DC ice melting operation mode, and DC current reference value zeroing control is initiated. The DC side voltage and current are brought to zero by the DC current reference value zeroing control. After closing the isolation switch of the corresponding line, the DC current reference value zeroing control is exited, and the current line is de-iced according to the preset slope. If a fault point is detected during the de-icing process, a DC-side fault ride-through will be performed. If there are still lines to be melted in the ice melting timing strategy, restart the DC current reference value zeroing control to melt the ice until there are no more lines to be melted and switch to reactive power compensation mode.

2. The DC de-icing control method for hybrid MMC of multiple lines in a substation as described in claim 1, characterized in that, The sum of the target de-icing current values ​​for all lines is compared with the maximum output capacity of the full-half-bridge hybrid MMC DC de-icing system to generate a de-icing timing strategy, including: If the total target value of the de-icing current of all outgoing lines is not greater than the maximum output capacity of the system, then all lines will be aggregated and de-iced simultaneously. If the total target value of the de-icing current for all outgoing lines is greater than the maximum output capacity of the system, then all lines are grouped and sorted according to the importance of the power supply load and de-iced in sequence.

3. The DC de-icing control method for hybrid MMC of multiple lines in a substation as described in claim 2, characterized in that, The starting DC current reference value zeroing control includes: The DC de-icing system controls and maintains the DC current and DC voltage at zero by adjusting the negative voltage control capability of the full-bridge submodule. Among them, the DC side electrical quantities are continuously monitored, and the disconnecting switch action command is issued only when the DC current and DC voltage are both zero.

4. The DC de-icing control method for hybrid MMC of multiple lines in a substation as described in claim 3, characterized in that, The execution of DC-side fault ride-through includes: When the action signal of the DC de-icing system protection device is received, the DC current reference value is zeroed out, and the DC side voltage and current are zeroed out. After the DC side voltage and current return to zero, determine whether the fault point has been cleared: if the fault point has been cleared, exit the DC current reference value zeroing control, restore current output and continue the ice melting process. If the fault point is not cleared, exit the DC ice melting operation mode and switch to reactive power compensation mode.

5. The DC de-icing control method for hybrid MMC of multiple lines in a substation as described in claim 1, characterized in that, The target de-icing current value required for each outgoing line includes: in, The target value for the de-icing current. For line resistance, The set melting time, The heat absorbed to melt the ice. This refers to the heat dissipated from the circuit during the de-icing process.

6. The DC de-icing control method for hybrid MMC of multiple lines in a substation as described in claim 1, characterized in that, The switching process between the reactive power compensation mode and the DC ice melting mode includes: In reactive power compensation mode, the DC ice melting system provides reactive power support by disconnecting the DC ice melting bus disconnecting switch and connecting only to the AC power grid. Upon receiving the de-icing start command, the reactive power output is first locked, and the DC current reference value is zeroed. After the DC current and DC voltage return to zero, the DC de-icing bus disconnect switch and the disconnect switch of the closed line are then closed.

7. The DC de-icing control method for hybrid MMC of multiple lines in a substation as described in claim 2, characterized in that, The full-half-bridge hybrid MMC DC ice melting system includes: The hybrid MMC DC de-icing system includes full-bridge sub-modules and half-bridge sub-modules, and is equipped with protection and control devices. The proportion of full-bridge submodules is configured to have the ability to output negative voltage.

8. A hybrid MMC DC de-icing control system for multiple lines in a substation, using the method as described in any one of claims 1-7, characterized in that, include: The target current module is used to obtain the de-icing request of the outgoing line and calculate the target de-icing current value required for each line based on the preset line parameters. The timing strategy module is used to compare the sum of the target values ​​of the de-icing current of all lines with the maximum output capacity of the full-half-bridge hybrid MMC DC de-icing system to generate a de-icing timing strategy. The switching module is used to control the system to switch from reactive power compensation mode to DC ice melting operation mode based on the ice melting request, and to start DC current reference value zeroing control. The de-icing execution module is used to reduce the DC side voltage and current to zero through DC current reference value zeroing control, close the isolation switch of the corresponding line, exit the DC current reference value zeroing control, and de-ic the current line according to the preset slope. The fault detection module is used to perform DC-side fault ride-through if a fault point is detected during the ice melting process. The strategy execution module is used to restart the DC current reference value zeroing control to perform ice melting based on the fact that there are still lines to be melted in the ice melting timing strategy, until there are no more lines to be melted and switch to reactive power compensation mode.

9. An electronic device, characterized in that, include: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of the DC de-icing control method for the hybrid MMC of multiple lines in the substation as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, It includes the steps of storing computer-executable instructions that, when executed by a processor, implement the DC de-icing control method for a hybrid MMC of multiple lines in a substation as described in any one of claims 1 to 7.

Images