A combined high-voltage DC circuit breaker, fault control method and monitoring system

Abstract

The present invention provides a combined high-voltage direct current circuit breaker, a fault control method and a monitoring system, which relate to the technical field of flexible direct current transmission equipment. The combined high-voltage direct current circuit breaker includes a main disconnecting branch, an energy-consuming branch, a plurality of disconnecting branches, a plurality of auxiliary branches and a voltage commutation circuit; the voltage commutation circuit is connected in parallel to both ends of the resonant capacitor in the main disconnecting branch, and is used to adjust the voltage polarity at both ends of the resonant capacitor before the reclosing action, so as to ensure that the main disconnecting branch generates a resonant current in the opposite direction of the fault current after the reclosing action, and ensure that the combined high-voltage direct current circuit breaker can smoothly transfer and disconnect the second fault current. The combined high-voltage direct current circuit breaker monitoring system is used to monitor the temperature rise of each power electronic device, and can further generate the aging gradient information of the corresponding power electronic device according to the temperature rise, so as to realize the aging monitoring of the power electronic device.

Description

Technical Field

[0001] The present application relates to the technical field of flexible direct current transmission equipment, and in particular to a combined high-voltage direct current circuit breaker, a fault control method and a monitoring system. Background Art

[0002] With the continuous development of new energy, the flexible direct current transmission system provides an economical and reliable technical support route for the consumption of new energy. However, it has the system characteristics of rapid development and rapid increase in amplitude of fault current, and requires core equipment such as DC circuit breakers to provide reliable isolation in the event of faults to ensure its safe and stable operation.

[0003] At present, the technical solutions of high-voltage DC circuit breakers used in actual projects are mainly divided into three technical routes: mechanical, hybrid and combined. The relevant technology discloses a Chinese invention patent application with application publication number CN117674041A, a combined high-voltage DC circuit breaker and a control method thereof under multi-fault conditions. The combined high-voltage DC circuit breaker includes a main breaking branch, an energy absorbing branch, at least two breaking branches, and at least two auxiliary branches;

[0004] A control method for a combined high-voltage direct current circuit breaker under a multi-fault condition, the method comprising: when a line fault occurs, the auxiliary branch switch and the disconnecting branch switch of the faulty line are actuated simultaneously; when the auxiliary branch switch and the disconnecting branch switch have completed their actions, the electronic trigger switch is turned on, and the line fault current charges the pressure-bearing capacitor; when the voltage of the pressure-bearing capacitor reaches the point where the arrester is actuated, the arrester limits the voltage and absorbs the energy of the disconnecting current, and after the arrester finishes consuming energy, a reclosing operation is performed;

[0005] However, under the topological structure of this DC circuit breaker, in order to ensure the smooth operation of the reclosing operation, before reclosing, the disconnecting branch switch on the faulty line must be closed first, and the auxiliary branch switch must be closed, so that the pressure-bearing capacitor is discharged through inductive oscillation and the sub-module capacitor is charged at the same time. After the pressure-bearing capacitor is discharged, the voltage of the sub-module capacitor reaches a value close to the initial value, and the auxiliary branch switch corresponding to the faulty line is disconnected, meeting the conditions for disconnection again. The action logic before reclosing is complex and the control is cumbersome, and the reliability of the second fault current interruption after reclosing cannot be guaranteed.

[0006] In addition, the successful opening and closing of the DC circuit breaker depends on the reliability of the fully controlled power electronic devices in the electronic trigger switch. However, there are currently too few means of monitoring the status of power electronic devices, and it is impossible to grasp the status of the power electronic devices themselves. Summary of the invention

[0007] In order to ensure the reliability of the second interruption of the fault current after reclosing, simplify the action logic before reclosing, and effectively monitor the status of power electronic devices in the DC circuit breaker, the present application provides a combined high-voltage DC circuit breaker, a fault control method and a monitoring system.

[0008] In a first aspect, the present application provides a combined high-voltage DC circuit breaker, which adopts the following technical solution:

[0009] A combined high-voltage direct current circuit breaker comprises a main breaking branch, an energy consumption branch, a plurality of breaking branches, and a plurality of auxiliary branches, and the combined high-voltage direct current circuit breaker further comprises a voltage commutation circuit;

[0010] A plurality of the disconnecting branches are arranged on a plurality of DC lines of the flexible DC power grid;

[0011] The plurality of auxiliary branches are connected in series with the main disconnecting branch, and the series-connected auxiliary branches and the main disconnecting branch are connected in parallel to the corresponding disconnecting branch;

[0012] The energy consumption branch is connected in parallel to the main disconnecting branch;

[0013] The voltage switching circuit is connected in parallel to the two ends of the resonant capacitor in the main disconnecting branch, and is used to adjust the voltage across the two ends of the resonant capacitor before the reclosing action.

[0014] Optionally, the disconnecting branch includes a fast-opening mechanical switch and an isolating switch, and the fast-opening mechanical switch is connected in series with the isolating switch.

[0015] Optionally, the main disconnect branch includes a plurality of H-bridge sub-modules connected in series, and a resonant inductor and a resonant capacitor connected in series with the plurality of H-bridge sub-modules.

[0016] Optionally, the voltage commutation circuit includes a bidirectional thyristor conduction module, an energy dissipation inductor and an energy dissipation resistor, and the bidirectional thyristor conduction module, the energy dissipation inductor and the energy dissipation resistor are connected in series in sequence;

[0017] The bidirectional thyristor conduction module adopts a bidirectional thyristor parallel connection form and is used to adjust the current flow direction in the voltage commutation circuit.

[0018] Optionally, the H-bridge submodule is composed of fully-controlled power electronic devices, and each of the fully-controlled power electronic devices is configured with a zero-crossing monitoring triggering and disconnecting module, and the zero-crossing monitoring triggering and disconnecting module is connected to a control and protection system in the combined high-voltage DC circuit breaker.

[0019] Optionally, the auxiliary switch in the auxiliary branch is a fast closing mechanical switch.

[0020] Optionally, the auxiliary switch in the auxiliary branch is a power electronic device switch.

[0021] In a second aspect, the present application provides a combined high-voltage DC circuit breaker fault control method, which adopts the following technical solution:

[0022] A combined high-voltage direct current circuit breaker fault control method, the breaking strategy of the combined high-voltage direct current circuit breaker comprising:

[0023] Monitor the circuit operation status of multiple lines in real time, and when a target DC line fault is detected, control the fast-disconnecting mechanical switch on the disconnecting branch to start opening, and control the auxiliary switch on the auxiliary branch to start closing;

[0024] When the auxiliary switch is in the closed position, the H-bridge submodule of the main disconnected branch is triggered to turn on, and the main disconnected branch begins to generate an oscillating current that is opposite to the fault current and has the same amplitude;

[0025] The upper and lower bridge arms of the H-bridge submodule are triggered to alternately conduct. The oscillating current generated by the main disconnected branch increases continuously until it is opposite to the fault current and has the same amplitude. The current of the fast-opening mechanical switch in the disconnected branch passes through zero, achieving arc extinguishing and disconnection.

[0026] The H-bridge submodule remains turned on until the voltage across the resonant capacitor is charged to the threshold voltage of the energy-consuming device in the energy-consuming branch. At this time, the energy-consuming branch is turned on, the absorption of the fault current energy is completed, and the breaking process ends.

[0027] Optionally, after the energy consumption branch is turned on, the energy absorption of the fault current is completed, and the breaking process is completed, the method further includes:

[0028] Controlling the auxiliary switch of the auxiliary branch to open;

[0029] The bidirectional thyristor conduction module on the voltage commutation circuit is turned on, the resonant capacitor is discharged through the energy-consuming resistor and the energy-consuming inductor in the voltage commutation circuit, the voltage polarity on the resonant capacitor is reversed, and the voltage meets the next reclosing charging voltage adjustment, waiting for reclosing;

[0030] After reclosing, if the target DC line fault is identified again, the breaking strategy of the combined high-voltage DC circuit breaker is repeated; if the target DC line fault is not identified, the operation of the DC line is restored.

[0031] In a third aspect, the present application provides a combined high-voltage DC circuit breaker monitoring system, which adopts the following technical solution:

[0032] A combined high-voltage direct current circuit breaker monitoring system, the combined high-voltage direct current circuit breaker monitoring system is used to monitor power electronic devices in the combined high-voltage direct current circuit breaker, the system comprising:

[0033] Junction temperature monitoring module, used to monitor the historical junction temperature information of each power electronic device in the combined high-voltage DC circuit breaker;

[0034] Leakage current monitoring module, used to monitor the insulation aging of each power electronic device in the combined high-voltage DC circuit breaker;

[0035] The state determination module is used to generate state determination information corresponding to each power electronic device according to the historical junction temperature information and the preset temperature safety value of each power electronic device in the last breaking process of the combined high-voltage DC circuit breaker.

[0036] Optionally, the system further includes:

[0037] A data processing module, used for collecting or obtaining the ideal junction temperature information corresponding to the power electronic device under each model;

[0038] The data processing module is further used to generate a junction temperature difference according to the plurality of the ideal junction temperature information and the corresponding historical junction temperature information;

[0039] Aging gradient information corresponding to the power electronic device is generated according to the plurality of junction temperature differences and preset aging junction temperature difference gradient distribution information.

[0040] Optionally, the system further includes:

[0041] The information update adjustment module is used to update the aging junction temperature difference gradient distribution information according to the aging gradient information and actual usage time corresponding to each of the power electronic devices.

[0042] In summary, the present application includes at least one of the following beneficial technical effects:

[0043] After the combined high-voltage DC circuit breaker executes the breaking strategy and before the reclosing action, the voltage commutation circuit in the combined high-voltage DC circuit breaker triggers the bidirectional thyristor conduction module to discharge the voltage of the resonant capacitor to the energy-consuming resistor and the energy-consuming inductor, thereby adjusting the voltage polarity at both ends of the resonant capacitor, ensuring that the main breaking branch generates a resonant current in the opposite direction to the fault current after the reclosing action, ensuring that the combined high-voltage DC circuit breaker can smoothly transfer and break the second fault current;

[0044] During the long-term operation of the combined high-voltage DC circuit breaker, the junction temperature monitoring module monitors the temperature rise of each power electronic device in the combined high-voltage DC circuit breaker to quickly understand the temperature rise of the power electronic device; further, the data processing module divides the estimated aging of the power electronic device according to the ideal temperature rise and actual temperature rise of the power electronic device, so that the staff can replace the power electronic device with more serious aging in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0046] Figure 1 This is a circuit structure block diagram of a combined high-voltage DC circuit breaker provided in an embodiment of the present application.

[0047] Figure 2 This is a circuit diagram of a disconnecting branch provided in an embodiment of the present application.

[0048] Figure 3 This is a circuit diagram of a main disconnect branch provided in an embodiment of the present application.

[0049] Figure 4 This is a circuit diagram of an H-bridge submodule provided in an embodiment of the present application.

[0050] Figure 5 This is a circuit diagram of an energy consumption branch provided in an embodiment of the present application.

[0051] Figure 6 It is a circuit diagram of a voltage commutation circuit provided in an embodiment of the present application.

[0052] Figure 7 It is a circuit diagram of a combined high-voltage DC circuit breaker provided in an embodiment of the present application.

[0053] Figure 8 It is a flow chart of a combined high-voltage DC circuit breaker fault control method provided in an embodiment of the present application.

[0054] Fig. 9 This is a timing diagram of a combined high-voltage DC circuit breaker switching strategy in an embodiment of the present application. DETAILED DESCRIPTION

[0055] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below in conjunction with Figures 1-9.

[0056] An embodiment of the present application provides a combined high-voltage direct current circuit breaker. Embodiment 1

[0057] A combined high-voltage direct current circuit breaker comprises a main breaking branch, an energy consumption branch, a plurality of disconnecting branches, a plurality of auxiliary branches and a voltage reversing circuit.

[0058] like Figure 1 As shown, in the embodiment of the present application, there are two disconnecting branches and two auxiliary branches, but the figure only shows one implementation mode, and the number of disconnecting branches and auxiliary branches can be one or more.

[0059] Among them, multiple disconnect branches are arranged on multiple DC lines of the flexible DC power grid, and the disconnect branches are used for the corresponding DC lines to carry current under normal working conditions and to disconnect current under fault conditions.

[0060] Multiple auxiliary branches are connected in parallel, and the input end of each auxiliary branch is connected to the output end of the main disconnecting branch. The output ends of multiple auxiliary branches are connected to multiple disconnecting branches one by one, so that the main disconnecting branch and the auxiliary branch are connected in series and then connected in parallel to the corresponding disconnecting branch. The auxiliary branch is used to achieve electrical isolation between the main disconnecting branch and the energy-consuming branch and the DC line under normal working conditions, and to achieve timely input of the main disconnecting branch and the energy-consuming branch into the DC line under fault conditions.

[0061] The energy-consuming branch is connected in parallel with the main disconnecting branch, and is used to absorb fault energy after the DC line is disconnected due to a fault.

[0062] The voltage switching circuit is connected in parallel to both ends of the resonant capacitor C of the main disconnecting branch, and the voltage switching circuit is used to adjust the voltage polarity of both ends of the resonant capacitor C before the reclosing action.

[0063] like Figure 2 As shown, the disconnecting branch includes a fast disconnecting mechanical switch and an isolating switch, and the fast disconnecting mechanical switch and the isolating switch are connected in series. The fast disconnecting mechanical switch is used to quickly reach a safe opening distance to complete the disconnecting operation under line fault conditions, and the isolating knife switch is used to disconnect the DC from the main disconnecting DC and the fault line to form electrical isolation under line fault conditions after the current on the fast disconnecting mechanical switch passes zero, thereby reducing the circuit fault caused by the fast disconnecting mechanical switch due to misclosing.

[0064] The auxiliary branch is composed of a fast closing mechanical switch, which is used in fault conditions and quickly reaches the closing position before the main disconnect branch is triggered. Under normal conditions, the fast closing mechanical switch forms an electrical isolation between the main disconnect branch and the disconnect branch.

[0065] like Figure 3 and Figure 4 As shown, the main disconnecting branch includes an H-bridge submodule, a resonant inductor L and a resonant capacitor C, and the preferred number of H-bridge submodules in this application can be three groups. Multiple groups of H-bridge submodules are connected in series with the resonant capacitor C and the resonant inductor L in sequence.

[0066] The H-bridge submodule is composed of a fully controlled power electronic device and a submodule capacitor C1. Specifically, the fully controlled power electronic device includes a switch tube T1, a switch tube T2, a switch tube 3, and a switch tube T4. Before the combined high-voltage DC circuit breaker is disconnected, the submodule capacitor C1 needs to be adjusted to a negative voltage. In the process of triggering the H-bridge submodule, multiple submodule capacitors C1, the resonant capacitor C, and the resonant inductor L generate an increasing oscillating current.

[0067] In the H-bridge submodule, the fully controlled power electronic devices of the upper and lower bridges need to be triggered to turn on and off alternately to provide an oscillating current with increasing peak value.

[0068] In the H-bridge submodule, all fully-controlled power electronic devices are equipped with zero-crossing monitoring triggering and disconnecting modules, which are connected to the control and protection system of the combined high-voltage DC circuit breaker to ensure that when multiple fully-controlled power electronic devices are triggered alternately, the conduction and shutdown of the fully-controlled power electronic devices are near the zero crossing of their current, thereby reducing the possibility of damage to the fully-controlled power electronic devices due to overcurrent.

[0069] like Figure 5 As shown, the energy consumption branch includes multiple nonlinear resistors or multiple lightning arresters, and the threshold voltage thereof is 1.2-1.5 times of the rated voltage of the line.

[0070] like Figure 6 As shown, the voltage commutation circuit includes a bidirectional thyristor conduction module, an energy dissipation inductor and an energy dissipation resistor, and the bidirectional thyristor conduction module, the energy dissipation inductor and the energy dissipation resistor are connected in series in sequence;

[0071] The power electronic module adopts the parallel connection of bidirectional thyristors to adjust the current flow direction in the voltage commutation circuit and effectively deal with the fault current types in different directions of the system;

[0072] Energy-consuming inductor, used to prevent the voltage commutation circuit from changing too much when the current changes instantaneously;

[0073] The energy dissipation resistor is used to consume the voltage across the resonant capacitor C. Embodiment 2

[0074] The second embodiment of the present application is different from the first embodiment only in the auxiliary branch. In the second embodiment, the auxiliary switch of the auxiliary branch is composed of a power electronic device.

[0075] like Figure 8 and Fig. 9 As shown, based on the above content, the present application also discloses a combined high-voltage DC circuit breaker fault control method, which is applied to the above-mentioned combined high-voltage DC circuit breaker. The execution subject of the combined high-voltage DC circuit breaker fault control method can be a control and protection system in the combined high-voltage DC circuit breaker. The breaking strategy of the combined high-voltage DC circuit breaker includes:

[0076] Step 1: Monitor the circuit operation status of multiple lines in real time, and when a target DC line fault is detected, control the fast-tripping mechanical switch on the disconnecting branch to start opening, and control the auxiliary switch on the auxiliary branch to start closing.

[0077] In implementation, the control and protection system in the combined high-voltage DC circuit breaker monitors the circuit operation status of multiple DC lines in real time. Specifically, each DC line is equipped with a current transformer. The control and protection system identifies and determines the operation status of the DC circuit by receiving the DC circuit current signal fed back by the current transformer.

[0078] When the control and protection system detects that one of the DC lines has a fault, the DC line detected here can be called the target DC line. That is, when the control and protection system detects that the current of the target DC line is greater than the set current threshold, the control and protection system controls the fast opening mechanical switch on the disconnecting branch corresponding to the target DC line to start opening, and controls the fast closing mechanical switch on the corresponding auxiliary branch to start closing. Here, the auxiliary switch in the auxiliary branch is regarded as a fast closing mechanical switch for explanation. When the auxiliary switch is a power electronic device switch, it is the same as the fast closing mechanical switch, and no excessive elaboration is given.

[0079] like Fig. 9 As shown in the figure, at time t1, each switch receives the command and starts to operate. The fast opening mechanism K1 starts to open, and the fast closing switch K3 of the auxiliary branch closes at the same time.

[0080] Step 2: When the auxiliary switch is in the closed position, the H-bridge submodule of the main disconnected branch is triggered to turn on, and the main disconnected branch begins to generate an oscillating current that is opposite to the fault current and has the same amplitude.

[0081] During implementation, at time t2, the fast closing mechanical switch K3 is in the closing position, which is less than 2ms from time t1. The control protection system triggers the switch tube T1, the switch tube T4, the submodule capacitor C1, the resonant capacitor C, and the resonant inductor L to resonate. At this time, the main disconnecting branch begins to generate an oscillating current with an amplitude equal to that of the fault circuit and in the opposite direction.

[0082] Step 3: Trigger the alternating conduction of the upper and lower arms of the H-bridge submodule. The oscillating current generated by the main disconnected branch increases continuously until it is opposite to the fault current and has the same amplitude. The current of the fast-opening mechanical switch in the disconnected branch passes through zero, achieving arc extinguishing and disconnection.

[0083] In the implementation, when the resonant current passes through zero, the switch tubes T1 and T4 are turned off, and then the switch tubes T2 and T3 are triggered, and the resonant capacitor C and the resonant inductor L resonate; at t3, the line current I k When it reaches zero, the quick-disconnect switch K1 extinguishes the arc.

[0084] Step 4: The H-bridge submodule remains turned on until the voltage across the resonant capacitor is charged to the threshold voltage of the energy-consuming device in the energy-consuming branch. At this time, the energy-consuming branch is turned on, the fault current energy is absorbed, and the breaking process ends.

[0085] In practice, after the arc of the quick-disconnect switch is extinguished, the switch tubes T1 and T4 in the H-bridge submodule remain on, and the fault current charges the resonant capacitor. At t4, the voltage across the arrester on the energy-consuming branch reaches the threshold voltage, the switch tubes T1 and T4 are disconnected, and the fault current is transferred to the energy-consuming branch to consume energy. At t5, the energy absorption is completed, and the combined high-voltage DC circuit breaker breaking process ends.

[0086] Optionally, after step 4, there is also a reclosing process for the combined high-voltage DC circuit breaker, so that the combined high-voltage DC circuit breaker can execute the next breaking strategy. The specific operation process is as follows:

[0087] Step 5: Control the auxiliary switch of the auxiliary branch to open.

[0088] In implementation, after the combined high-voltage DC circuit breaker is disconnected, an opening command is issued to the fast closing mechanical switch of the auxiliary branch circuit, so that the fast opening mechanical switch is opened.

[0089] Step 6: Turn on the bidirectional thyristor conduction module on the voltage commutation circuit, the resonant capacitor is discharged through the energy-consuming resistor and the energy-consuming inductor in the voltage commutation circuit, the voltage polarity on the resonant capacitor is reversed, and the voltage meets the charging voltage condition for the next reclosing, waiting for reclosing.

[0090] During implementation, the control and protection system issues a trigger command to turn on the bidirectional thyristor conduction module, so that the voltage of the resonant capacitor is discharged to the energy-consuming resistor and the energy-consuming inductor, and then the voltage polarity at both ends of the resonant capacitor is adjusted to ensure that the main branch generates a resonant current in the opposite direction of the fault current after the reclosing action, ensuring that the combined high-voltage DC circuit breaker can smoothly transfer and disconnect the second fault current.

[0091] Step 7: After reclosing, if the target DC line fault is identified again, the breaking strategy of the combined high-voltage DC circuit breaker is repeated; if the target DC line fault is not identified, the operation of the DC line is restored.

[0092] In implementation, after the combined high-voltage DC circuit breaker is reclosed, if the control and protection system determines and identifies that the target DC line is still in a faulty condition through the current transformer, it is identified that the current target DC line still has a fault, and the above steps 1 to 5 are overlapped to perform the breaking strategy of the combined high-voltage DC circuit breaker. If the control and protection system determines and identifies that the target DC line is in a normal condition through the current transformer, it is identified that the current target DC line fault is cleared, and the normal operation of the combined high-voltage DC circuit breaker is restored.

[0093] Based on the above content, the present application also discloses a combined high-voltage DC circuit breaker monitoring system, which is applied to the combined high-voltage DC circuit breaker. The combined high-voltage DC circuit breaker monitoring system is used to monitor the power electronic devices in the combined high-voltage DC circuit breaker. The system includes:

[0094] Junction temperature monitoring module, used to monitor the historical junction temperature information of each power electronic device in the combined high-voltage DC circuit breaker;

[0095] Leakage current monitoring module, used to monitor the insulation aging of each power electronic device in the combined high-voltage DC circuit breaker;

[0096] The state identification module is used to generate state identification information corresponding to each power electronic device according to the historical junction temperature information and the preset temperature safety value of each power electronic device in the last breaking process of the combined high-voltage DC circuit breaker.

[0097] In implementation, the junction temperature monitoring module of the power electronic monitoring system monitors the stability of each power electronic device in the combined high-voltage DC circuit breaker in real time and records the temperature rise of each power electronic device, which can be referred to as historical junction temperature information. The power electronic device here can be a fully controlled power electronic device of the H-bridge submodule in the main breaker branch, or a bidirectional thyristor conduction module in the voltage commutation circuit.

[0098] The state identification module in the power electronic monitoring system identifies the state of the power electronic device based on the historical junction temperature information corresponding to each power electronic device during the last disconnection process of the combined high-voltage DC circuit breaker. Specifically, one of the power electronic devices is taken as an example, which is referred to as the target power electronic device. The highest temperature value in the historical junction temperature information corresponding to the target power electronic device is captured, and then the highest temperature value is compared with the preset temperature safety value. When the highest temperature value is less than the temperature safety value, it is called a normal temperature rise state, and when the highest temperature value is greater than or equal to the temperature safety value, it is called an abnormal temperature rise state.

[0099] Furthermore, the leakage current monitoring module in the power electronic monitoring system can also monitor the leakage current, voltage overload, etc. of multiple electronic components in the combined high-voltage DC circuit breaker to extend the service life of the combined high-voltage DC circuit breaker and reduce the probability of failure.

[0100] Optionally, the monitoring system also includes:

[0101] A data processing module, used for collecting or obtaining the ideal junction temperature information corresponding to each model of power electronic device;

[0102] The data processing module is further used to generate a junction temperature difference value according to a plurality of ideal junction temperature information and corresponding historical junction temperature information;

[0103] According to the multiple junction temperature differences and the preset aging junction temperature difference gradient distribution information, aging gradient information of the corresponding power electronic device is generated.

[0104] In implementation, the data processing module obtains the ideal junction temperature information of the power electronic devices of each model in the combined high-voltage DC circuit breaker from the Internet, manufacturers or user experiments. The ideal junction temperature information is used to reflect the relationship between temperature rise and flowing current.

[0105] Then the data processing module compares the historical junction temperature information with the ideal junction temperature information under the same model to obtain the junction temperature difference between the historical junction temperature information and the ideal junction temperature information for the same current flow line.

[0106] The data processing module is preset with aging junction temperature difference gradient distribution information, which is used to reflect the corresponding relationship between the junction temperature difference and the aging degree. The aging degree here can be understood as the service life and the remaining service life of the power electronic device under ideal conditions.

[0107] Furthermore, the data processing module has the currently acquired temperature difference value and acquires the aging gradient information of each power electronic device, so as to timely replace the power electronic devices with more serious aging.

[0108] Optionally, the monitoring system also includes:

[0109] The information update adjustment module is used to update the aging junction temperature difference gradient distribution information according to the aging gradient information corresponding to each power electronic device and the actual use time.

[0110] During implementation, the information update module of the power electronic monitoring system counts the aging gradient information and actual usage time corresponding to each power electronic device, and then calculates the estimated usage time under each aging gradient based on the aging gradient information and actual usage time of the power electronic devices of the same model, and then updates the aging junction temperature difference gradient distribution information based on the estimated usage time under each aging gradient. Therefore, the aging of the power electronic devices in the current combined high-voltage DC circuit breaker is evaluated through the actual operation of the power electronic devices, thereby increasing the accuracy of the aging evaluation.

[0111] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

[0112] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A combined high-voltage DC circuit breaker, comprising a main breaking branch, an energy consumption branch, a plurality of breaking branches, and a plurality of auxiliary branches, characterized in that: The combined high-voltage DC circuit breaker also includes a voltage commutation circuit; A plurality of the disconnecting branches are arranged on a plurality of DC lines of the flexible DC power grid; The plurality of auxiliary branches are connected in series with the main disconnecting branch, and the series-connected auxiliary branches and the main disconnecting branch are connected in parallel to the corresponding disconnecting branch; The energy consumption branch is connected in parallel to the main disconnecting branch; The voltage reversing circuit is connected in parallel to the two ends of the resonant capacitor in the main breaking branch, and by adjusting the voltage polarity at the two ends of the resonant capacitor, it is ensured that the main breaking branch generates a resonant current in the opposite direction to the fault current after the reclosing action, so as to ensure that the combined high-voltage DC circuit breaker can smoothly transfer and break the second fault current; The breaking strategies of combined high-voltage DC circuit breakers include: Monitor the circuit operation status of multiple lines in real time, and when a target DC line fault is detected, control the fast-disconnecting mechanical switch on the disconnecting branch to start opening, and control the auxiliary switch on the auxiliary branch to start closing; When the auxiliary switch is in the closed position, the H-bridge submodule of the main disconnected branch is triggered to turn on, and the main disconnected branch begins to generate an oscillating current that is opposite to the fault current and has the same amplitude; The upper and lower bridge arms of the H-bridge submodule are triggered to alternately conduct. The oscillating current generated by the main disconnected branch increases continuously until it is opposite to the fault current and has the same amplitude. The current of the fast-opening mechanical switch in the disconnected branch passes through zero, achieving arc extinguishing and disconnection. The H-bridge submodule remains turned on until the voltage across the resonant capacitor is charged to the threshold voltage of the energy-consuming device in the energy-consuming branch. At this time, the energy-consuming branch is turned on, the fault current energy is absorbed, and the breaking process ends; After the energy consumption branch is turned on, the energy absorption of the fault current is completed, and the breaking process is completed, the method further includes: Controlling the auxiliary switch of the auxiliary branch to open; The bidirectional thyristor conduction module on the voltage commutation circuit is turned on, the resonant capacitor is discharged through the energy-consuming resistor and the energy-consuming inductor in the voltage commutation circuit, the voltage polarity on the resonant capacitor is reversed, and the voltage meets the next reclosing charging voltage adjustment, waiting for reclosing; After reclosing, if the target DC line fault is identified again, the breaking strategy of the combined high-voltage DC circuit breaker is repeated; if the target DC line fault is not identified, the operation of the DC line is restored.

2. The combined high-voltage DC circuit breaker according to claim 1, characterized in that: The disconnecting branch includes a fast-opening mechanical switch and an isolating switch, and the fast-opening mechanical switch is connected in series with the isolating switch.

3. The combined high-voltage DC circuit breaker according to claim 1, characterized in that: The main disconnecting branch includes a plurality of H-bridge submodules connected in series, and a resonant inductor and a resonant capacitor connected in series with the plurality of H-bridge submodules.

4. The combined high-voltage DC circuit breaker according to claim 3, characterized in that: The voltage commutation circuit comprises a bidirectional thyristor conduction module, an energy dissipation inductor and an energy dissipation resistor, wherein the bidirectional thyristor conduction module, the energy dissipation inductor and the energy dissipation resistor are sequentially connected in series; The bidirectional thyristor conduction module adopts a bidirectional thyristor parallel connection form and is used to adjust the current flow direction in the voltage commutation circuit.

5. The combined high-voltage DC circuit breaker according to claim 3, characterized in that: The H-bridge submodule is composed of fully controlled power electronic devices, and each of the fully controlled power electronic devices is configured with a zero-crossing monitoring triggering and breaking module, and the zero-crossing monitoring triggering and breaking module is connected to the control and protection system in the combined high-voltage DC circuit breaker.

6. The combined high-voltage DC circuit breaker according to claim 1, characterized in that: The auxiliary switch in the auxiliary branch is a fast closing mechanical switch.

7. The combined high-voltage DC circuit breaker according to claim 1, characterized in that: The auxiliary switch in the auxiliary branch is a power electronic device switch.

8. A combined high-voltage DC circuit breaker monitoring system, characterized in that: Applied to the combined high-voltage DC circuit breaker according to any one of claims 1 to 7, characterized in that the combined high-voltage DC circuit breaker monitoring system is used to monitor power electronic devices in the combined high-voltage DC circuit breaker, and the system comprises: Junction temperature monitoring module, used to monitor the historical junction temperature information of each power electronic device in the combined high-voltage DC circuit breaker; Leakage current monitoring module, used to monitor the insulation aging of each power electronic device in the combined high-voltage DC circuit breaker; The state determination module is used to generate state determination information corresponding to each power electronic device according to the historical junction temperature information and the preset temperature safety value of each power electronic device in the last breaking process of the combined high-voltage DC circuit breaker.

9. The combined high-voltage DC circuit breaker monitoring system according to claim 8, characterized in that: The system further comprises: A data processing module, used for collecting or obtaining the ideal junction temperature information corresponding to the power electronic device under each model; The data processing module is further used to generate a junction temperature difference according to the plurality of the ideal junction temperature information and the corresponding historical junction temperature information; Aging gradient information corresponding to the power electronic device is generated according to the plurality of junction temperature differences and preset aging junction temperature difference gradient distribution information.

10. The combined high-voltage DC circuit breaker monitoring system according to claim 9, characterized in that: The system further comprises: The information update adjustment module is used to update the aging junction temperature difference gradient distribution information according to the aging gradient information and actual usage time corresponding to each of the power electronic devices.

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