Zero-loss current limiting device based on artificial zero-crossing technology and device monitoring and maintenance method

Abstract

The invention provides a zero-loss current limiting device based on an artificial zero-crossing technology and a device monitoring and maintenance method, and relates to a transformer fault current limiting technology, the device comprises a main switch branch, an energy absorption branch and an artificial zero-crossing branch; the main switch branch comprises a vacuum fast switch, the vacuum fast switch is connected in series between a bus of the power distribution system and the input end of the main transformer, and the vacuum fast switch is connected in parallel with a current limiting reactor; a modulation inductor is connected in series between the main switch branch and the artificial zero-crossing branch, and the energy absorption branch is connected in parallel to the artificial zero-crossing branch; the energy absorption branch comprises a plurality of zinc oxide resistors, and a nonlinear resistor module is formed by the plurality of zinc oxide resistors; the artificial zero-crossing branch comprises an energy storage unit and a trigger switch, the energy storage unit at least comprises a zero-crossing energy storage capacitor, and the zero-crossing energy storage capacitor and the trigger switch are connected in series. The zero-crossing energy storage capacitor releases electric energy to artificially produce a zero-crossing point, so that rapid opening of the vacuum rapid switch is facilitated, and short-circuit fault current limiting is realized.

Description

Technical Field

[0001] This invention relates to the field of transformer fault current limiting technology, and more specifically, to a zero-loss current limiting device based on artificial zero-crossing technology and a device monitoring and maintenance method. Background Technology

[0002] Transformers are the hub of the power grid for transmitting electrical energy and are the main equipment for grid operation. When a power transformer winding is short-circuited, especially when the load is short-circuited, the huge electromagnetic force generated by the fault current can cause great damage to the transformer winding.

[0003] Generally, a fast-acting switch is connected in series between the busbar and the output terminal of the transformer in a power distribution system, and a current-limiting reactor is connected in parallel with the fast-acting switch. During normal operation of the power distribution system, the fast-acting switch remains closed. When a short-circuit fault occurs in the power distribution system, the fast-acting switch is opened, allowing the current-limiting reactor to connect between the busbar and the transformer, thereby limiting the short-circuit fault current.

[0004] However, during the opening process of a fast switch, it is necessary to wait for the current on the fast switch to pass through the natural zero-crossing point in order to reduce the electric arc generated during the opening. The waiting time for the current to naturally cross the zero-crossing point increases the time for the power distribution system and transformer to bear the short-circuit fault current, thereby increasing the possibility of damage to the transformer, power distribution system lines and loads. Summary of the Invention

[0005] In order to enable the fast switch to close quickly after a short circuit fault, allowing the current-limiting reactor to be connected between the power distribution system bus and the transformer, this application provides a zero-loss current-limiting device based on artificial zero-crossing technology and a device monitoring and maintenance method.

[0006] Firstly, this application provides a zero-loss current limiting device based on artificial zero-crossing technology, employing the following technical solution: A zero-loss current limiting device based on artificial zero-crossing technology, the device comprising a main switch branch, an energy-absorbing branch, and an artificial zero-crossing branch; The main switch branch includes a vacuum fast switch, which is connected in series between the busbar of the power distribution system and the input terminal of the main transformer, and a current-limiting reactor is connected in parallel to the vacuum fast switch; A modulation inductor is connected in series between the main switch branch and the artificial zero-crossing branch, and the energy-absorbing branch is connected in parallel to the artificial zero-crossing branch; The energy-absorbing branch includes multiple zinc oxide resistors, and the multiple zinc oxide resistors constitute a nonlinear resistor module; The artificial zero-crossing branch includes the energy storage unit and the trigger switch. The energy storage unit includes at least a zero-crossing energy storage capacitor, and the zero-crossing energy storage capacitor and the trigger switch are connected in series.

[0007] Optionally, the energy storage unit is connected in series with the trigger switch, and the energy storage unit includes a first zero-crossing subunit and a second zero-crossing subunit, which are connected in parallel. The first zero-crossing subunit includes a zero-crossing energy storage capacitor and a first switching transistor, wherein the zero-crossing energy storage capacitor and the first switching transistor are connected in series; The second zero-crossing subunit includes a storage capacitor and a second switching transistor, which are connected in series.

[0008] Optionally, it also includes an energy-consuming circuit, which includes an energy-consuming thyristor one, an energy-consuming thyristor two, an energy-consuming resistor, and an energy-consuming inductor. The connection node between the zero-crossing energy storage capacitor and the first switching transistor is connected to the input terminal of the first energy-consuming thyristor; the output terminal of the first energy-consuming thyristor is connected to one of the connection terminals of the energy-consuming inductor. The connection node between the storage capacitor and the second switching transistor is connected to the input terminal of the second energy-consuming thyristor. The output terminal of the second energy-consuming thyristor is connected to one end of the energy-consuming inductor, and the output terminal of the first energy-consuming thyristor is connected to the output terminal of the second energy-consuming thyristor. The other end of the energy-consuming inductor is connected to the energy-consuming resistor, and the other end of the energy-consuming resistor is connected to the connection node between the zero-crossing energy storage capacitor and the reserve capacitor.

[0009] Optionally, it also includes a CT energy storage circuit for storing energy in the zero-crossing energy storage capacitor and the reserve capacitor; The CT energy storage circuit includes a power-supplying CT, a power-supplying transformer, a power-supplying resistor, a voltage stabilizing module, a power-supplying thyristor one, and a power-supplying thyristor two; The power-collecting CT is mounted on the busbar, and the two output terminals of the power-collecting CT are electrically connected to the two output terminals of the primary side of the power-collecting transformer, respectively. The power-collecting resistor is connected in parallel to the primary side of the power-collecting transformer. The two input terminals of the voltage stabilization module are respectively connected to the two output terminals of the power extraction transformer. The negative terminal of the voltage stabilization module is connected to the connection node between the zero-crossing energy storage capacitor and the reserve capacitor. The positive terminal of the voltage stabilization module is simultaneously connected to the input terminals of the first power extraction thyristor and the second power extraction thyristor. The output terminal of the first power-collecting thyristor is connected to the connection node between the first switching transistor and the zero-crossing energy storage capacitor, and the output terminal of the second power-collecting thyristor is connected to the connection node between the second switching transistor and the storage capacitor.

[0010] Secondly, this application provides a monitoring and maintenance method for a zero-loss current limiting device based on artificial zero-crossing technology, which is applied to the zero-loss current limiting device based on artificial zero-crossing technology described in the first aspect, and adopts the following technical solution: A monitoring and maintenance method for a zero-loss current limiting device based on artificial zero-crossing technology, the method comprising: The current value of the main switch branch fed back by the current sensor is acquired in real time, and the current operating status of the main switch branch is identified based on the current value of the main switch branch; If the main switch branch is identified as being in a short-circuit fault operation state, then mark the time of manual intervention zero crossing after the current time and generate a manual zero crossing intervention command to control the first switch tube and the trigger switch to conduct at the time of manual zero crossing. After the zero-crossing moment of the aforementioned artificial intervention: Based on the obtained main switch branch current value, generate manual zero-crossing turn-off information; If the manual zero-crossing shutdown information carries a zero-crossing continuous operation flag, a secondary zero-crossing correction command is generated.

[0011] Optionally, generating manual zero-crossing turn-off information based on the obtained main switch branch current value includes: If, within a preset time period after the manual intervention zero-crossing moment, the current value of the main switch branch is equal to zero, then a manual zero-crossing shutdown information carrying a manual zero-crossing shutdown identifier is generated. If, within a preset time period after the manual intervention zero-crossing moment, all the main switch branch current values ​​are greater than or less than zero, then a manual zero-crossing shutdown message carrying a zero-crossing continuous operation identifier is generated.

[0012] Optionally, the secondary zero-crossing correction command includes a command to turn off the first switch, a command to turn on the second switch, and a command to turn on the trigger switch.

[0013] Optionally, the method further includes: After manual intervention at the zero crossing moment and a preset waiting time, a power consumption command is generated to control the first switch to turn off and the first power consumption thyristor to turn on. When the zero-crossing energy storage voltage across the zero-crossing energy storage capacitor is less than the preset discharge voltage threshold, a primary energy storage command is generated to control the first energy-consuming thyristor to turn off and the first energy-storing thyristor to turn on. After generating the second zero-crossing correction instruction and after the waiting time interval, a second energy-consuming instruction is generated to control the second switch to turn off and the energy-consuming thyristor to turn on. When the received storage voltage across the storage capacitor is less than the discharge voltage threshold, a secondary energy storage command is generated to control the second energy-consuming thyristor to turn off and the second energy-storing thyristor to turn on.

[0014] Optionally, after generating the second zero-crossing correction command, the method further includes: Based on multiple historical main switch branch current values, a zero-crossing adjustment difference is generated; The energy storage voltage adjustment value is calculated and generated based on the zero-crossing adjustment prediction difference and the pre-stored reserve voltage adjustment data.

[0015] In summary, this application includes at least one of the following beneficial technical effects: After a short circuit fault occurs, the vacuum fast switch is controlled to open. When the vacuum fast switch reaches the effective opening distance, the trigger switch is controlled to close. At this time, under the action of the zero-crossing energy storage capacitor, a high-frequency resonant current is forcibly superimposed on the power frequency fault current of the vacuum fast switch, artificially creating a zero-crossing point. This facilitates the vacuum interrupter current of the vacuum fast switch to cross zero and extinguish the arc, thus facilitating the rapid opening of the vacuum fast switch. The current-limiting reactor is connected to the main branch to achieve current limiting during short circuit faults. If the vacuum fast switch fails to generate a zero-crossing point after detecting a short-circuit fault due to the combined action of the zero-crossing energy storage capacitor, the first switching transistor, and the trigger switch, the controller quickly controls the first switching transistor to turn off, the second switching transistor to turn on, and controls the trigger switch to turn on. Then, the storage capacitor adds a high-frequency resonant current to the vacuum fast switch, which can still artificially generate a zero-crossing point, so that the vacuum arc-extinguishing chamber current of the vacuum fast switch can cross zero to extinguish the arc, thereby realizing the rapid tripping of the vacuum fast switch. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0017] Figure 1 This is a circuit diagram of a zero-loss current limiting device using artificial zero-crossing technology provided in an embodiment of this application.

[0018] Figure 2 This is a circuit diagram of a CT power supply circuit and a power consumption circuit provided in an embodiment of this application.

[0019] Figure 3 This is a flowchart illustrating a monitoring and maintenance method for a zero-loss current limiting device based on manual zero-crossing technology, provided in an embodiment of this application.

[0020] Figure 4This is a timing diagram of the operation of a zero-crossing energy storage capacitor in a zero-loss current limiting device when a short-circuit fault occurs during the positive half-cycle of the power frequency, provided in an embodiment of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the following will be described in conjunction with the appendix. Figure 1-4 The embodiments of the present invention will be described in further detail below.

[0022] This application provides a zero-loss current limiting device based on artificial zero-crossing technology. The zero-loss current limiting device based on artificial zero-crossing technology includes a main switch branch, an energy absorption branch, an artificial zero-crossing branch, and a current limiting reactor X.

[0023] The main switch branch includes a vacuum fast switch K1, which is connected in series between the bus and the input terminal of the main transformer T1. Under normal line operation, the vacuum fast switch K1 remains closed, thereby reducing the power loss between the bus and the main transformer T1.

[0024] The current-limiting reactor X is connected in parallel with the vacuum fast switch K1. When a short-circuit fault is detected in the line, the vacuum fast switch K1 is controlled to open. At this time, the fault current is transferred to the current-limiting reactor X, thereby reducing the impact of the fault current on the electrical equipment.

[0025] A modulation inductor L1 is connected in series between the main switch branch and the artificial zero-crossing branch, and the energy-absorbing branch is connected in parallel to the artificial zero-crossing branch. The energy-absorbing branch includes multiple zinc oxide resistors, which together form a nonlinear resistor module (MOV).

[0026] One end of the nonlinear resistor module MOV is connected to the modulation inductor L1, and the other end of the nonlinear resistor module MOV is connected to the vacuum fast switch K1. The other end of the modulation inductor L1 is also connected to the vacuum fast switch K1, thus forming a circuit with the nonlinear resistor module MOV, the modulation inductor L1, and the vacuum fast switch K1.

[0027] like Figure 1 As shown, the artificial zero-crossing branch is connected in parallel to the energy-absorbing branch. During the process of controlling the vacuum fast switch K1 to open, when the vacuum fast switch K1 reaches the effective opening distance, the artificial zero-crossing branch superimposes a high-frequency resonant current on the vacuum fast switch K1 to artificially create a zero-crossing point, forcing the current in the arc-extinguishing chamber of the vacuum fast switch K1 to cross zero and extinguish the arc.

[0028] The artificial zero-crossing branch includes an energy storage unit and a trigger switch K2, which are connected in series. The trigger switch K2 can be a vacuum trigger switch or a nitrogen-filled trigger switch.

[0029] The energy storage unit includes a first zero-crossing subunit and a second zero-crossing subunit, which are connected in parallel. The first zero-crossing subunit includes a zero-crossing energy storage capacitor C1 and a first switching transistor Q1 connected in series. The second zero-crossing subunit includes a storage capacitor C2 and a second switching transistor Q2 connected in series. The first switching transistor Q1 and the second switching transistor Q2 can be thyristors, MOSFETs, etc.

[0030] The zero-loss current limiting device based on artificial zero-crossing technology also includes a controller and multiple CT current sensors. CT current sensors are installed on the main switch branch where the vacuum fast switch K1 is located, the branch where the current limiting reactor X is located, the artificial zero-crossing branch, and the energy-absorbing branch. In addition, voltage sensors are connected in parallel to both the zero-crossing energy storage capacitor C1 and the reserve capacitor C2.

[0031] The controller receives current values ​​fed back from multiple CT current sensors. At the same time, multiple control terminals of the controller are connected to the control terminals of the first switch Q1 and the second switch Q2, respectively, so that the controller can control the first switch Q1 and the second switch Q2 to turn on or off.

[0032] When a short-circuit fault occurs in the line, the power distribution system current jumps from the rated current to the fault current. At this time, the controller can detect the short-circuit fault through the CT current sensor. Then, the controller controls the vacuum fast switch K1 to open, and at the same time controls the first switch Q1 to turn on. When the vacuum fast switch K1 reaches the effective opening distance, the controller controls the trigger switch K2 to close. At this time, under the action of the zero-crossing energy storage capacitor C1, a high-frequency resonant current is forcibly superimposed on the power frequency fault current of the vacuum fast switch K1, artificially creating a zero-crossing point, so as to facilitate the zero-crossing arc extinguishing of the vacuum interrupter current of the vacuum fast switch K1.

[0033] When the zero-crossing energy storage capacitor C1 creates a zero-crossing point on the main switch branch, the fault current is transferred to the artificial zero-crossing branch and charges the zero-crossing energy storage capacitor C1. Under the combined action of the system power supply and the modulation inductor L1, the voltage across the zero-crossing energy storage capacitor C1 reverses and increases. When the voltage reaches the conduction voltage of the nonlinear resistor module MOV, the fault current naturally flows into the energy absorption branch. The vacuum fast switch K1 of the main switch branch is extinguished and turned off. The fault current decays to the milliampere level in the form of a triangular wave under approximately constant voltage in the nonlinear resistor module MOV. Thus, the vacuum fast switch K1 is forced to open, and the current-limiting reactor X is connected to the main branch to achieve current limiting for short-circuit faults.

[0034] If, after detecting a short-circuit fault, the vacuum fast switch K1 fails to generate a zero-crossing point due to the combined action of the zero-crossing energy storage capacitor C1, the first switch Q1, and the trigger switch K2, the controller quickly controls the first switch Q1 to turn off, the second switch Q2 to turn on, and controls the trigger switch K2 to turn on. Then, the storage capacitor C2 adds a high-frequency resonant current to the vacuum fast switch K1 to artificially generate a zero-crossing point, thereby enabling the vacuum interrupter current of the vacuum fast switch K1 to cross zero and extinguish the arc.

[0035] Similarly, when the storage capacitor C2 creates a zero-crossing point on the main switch branch, the fault current is transferred to the artificial zero-crossing branch to charge the storage capacitor C2. Under the combined action of the system power supply and the modulation inductor L1, the voltage across the storage capacitor C2 reverses and increases. When the voltage reaches the conduction voltage of the nonlinear resistor module MOV, the fault current naturally flows into the energy absorption branch. The vacuum fast switch K1 of the main switch branch is extinguished and turned off. The fault current decays to the milliampere level in the form of a triangular wave under approximately constant voltage in the nonlinear resistor module MOV. Thus, the vacuum fast switch K1 is forced to open, and the current-limiting reactor X is connected to the main branch to achieve current limiting for short-circuit faults.

[0036] The zero-loss current limiting device based on artificial zero-crossing technology also includes an energy-consuming circuit, which includes an energy-consuming thyristor S1, an energy-consuming thyristor S2, an energy-consuming resistor R1, and an energy-consuming inductor L2.

[0037] Both the energy-consuming thyristor S1 and the energy-consuming thyristor S2 are bidirectional thyristors. The input terminal of the energy-consuming thyristor S1 is connected to one end of the zero-crossing energy storage capacitor C1, and the input terminal of the energy-consuming thyristor S1 is also connected to the end of the first switching transistor Q1.

[0038] The output terminal of the energy-consuming thyristor S1 is connected to one end of the energy-consuming inductor L2, the other end of the energy-consuming inductor L2 is connected to one end of the energy-consuming resistor R1, and the other end of the energy-consuming resistor R1 is connected to the end of the zero-crossing energy storage capacitor C1 away from the first switching transistor Q1.

[0039] The input terminal of the second energy-consuming thyristor S2 is connected to one end of the storage capacitor C2, and the input terminal of the second energy-consuming thyristor S2 is also connected to the end of the second switching transistor Q2. The output terminal of the second energy-consuming thyristor S2 is connected to the energy-consuming inductor L2, and the output terminal of the first energy-consuming thyristor S1 is also connected to the output terminal of the first energy-consuming thyristor S1.

[0040] After the zero-crossing energy storage capacitor C1 releases electrical energy, the controller controls the first switch Q1 to turn off and controls the energy-consuming thyristor S1 to turn on. At this time, the reverse voltage stored in the zero-crossing energy storage capacitor C1 is consumed by the energy-consuming resistor R1 and the energy-consuming inductor L2 in the energy-consuming circuit.

[0041] Similarly, after the storage capacitor C2 releases electrical energy, the controller controls the second switch Q2 to turn off and controls the energy-consuming thyristor S2 to turn on. At this time, the reverse voltage stored in the storage capacitor C2 is consumed by the energy-consuming resistor R1 and the energy-consuming inductor L2 in the energy-consuming circuit.

[0042] The zero-loss current limiting device based on artificial zero-crossing technology also includes a CT energy storage circuit, which includes a power-taking CT, a power-taking transformer T2, a power-taking resistor R2, a voltage stabilization module, a power-taking thyristor S3, and a power-taking thyristor S4.

[0043] The power-collecting CT is mounted on the busbar to facilitate its access to power from the busbar. The output terminals of the power-collecting CT are connected to the two output terminals of the primary side of the power-collecting transformer T2, and the power-collecting resistor R2 is connected in parallel to the primary side of the power-collecting transformer T2.

[0044] The two input terminals of the voltage stabilization module are connected to the two output terminals of the secondary side of the power extraction transformer T2, respectively. The positive terminal of the output terminal of the voltage stabilization module is connected to the input terminals of power extraction thyristor S3 and power extraction thyristor S4, respectively. The negative terminal of the output terminal of the voltage stabilization module is connected to the connection node between the zero-crossing energy storage capacitor C1 and the reserve capacitor C2.

[0045] The output terminal of the first power-taking thyristor S3 is connected to the connection node between the first switching transistor Q1 and the zero-crossing energy storage capacitor C1, and the output terminal of the second power-taking thyristor S4 is connected to the connection node between the second switching transistor Q2 and the storage capacitor C2.

[0046] When it is necessary to charge the zero-crossing energy storage capacitor C1, the controller controls the first switch Q1 to turn off and controls the power-taking thyristor S3 to turn on. When it is necessary to charge the storage capacitor C2, the controller controls the second switch Q2 to turn off and controls the power-taking thyristor S4 to turn on.

[0047] This application also provides a monitoring and maintenance method for a zero-loss current limiting device based on artificial zero-crossing technology. The method is applied to a zero-loss current limiting device based on artificial zero-crossing technology. The main body executing this method can be the controller in the zero-loss current limiting device based on artificial zero-crossing technology, and is assisted by multiple CT current sensors, a first switch Q1, a second switch Q2, a first energy-consuming thyristor S1, a second energy-consuming thyristor S2, a first power-taking thyristor S3, a second power-taking thyristor S4, and a trigger switch K2.

[0048] The following will describe the specific implementation methods. Figure 3 The processing flow shown is explained in detail below: Step S1: Obtain the current value of the main switch branch fed back by the current sensor in real time, and identify the current operating status of the main switch branch based on the current value of the main switch branch.

[0049] In practice, the controller acquires the main switch branch current value fed back by the current sensor in real time.

[0050] The controller then identifies the current operating status of the main switch branch by the current value flowing through it.

[0051] Step S2: If the main switch branch is identified as being in a short-circuit fault operation state, then mark the time of manual intervention zero crossing after the current time and generate a manual zero crossing intervention command to control the first switch Q1 and the trigger switch K2 to conduct at the time of manual zero crossing.

[0052] In implementation, the controller can use the collected main switch branch current value, referred to here as the historical main switch branch current value, to plot a current variation curve that follows a sinusoidal wave, such as... Figure 4 As shown.

[0053] Then, when the current value of the main switch branch collected by the controller in real time deviates significantly from the current change curve, that is, at a certain moment, the difference between the current value of the main switch branch collected by the controller and the current value in the current change curve is greater than the preset current threshold, the current main switch branch is marked as a short circuit fault operation state.

[0054] Furthermore, the controller marks the zero-crossing moment of manual intervention after the current moment. Specifically, after detecting a short-circuit fault operation, the controller controls the vacuum fast switch K1 to open, and then within 1.5ms, the vacuum fast switch K1 reaches the effective opening distance. Therefore, the controller can mark the zero-crossing moment of manual intervention 1.5ms after issuing the command to open the vacuum fast switch K1.

[0055] After the moment of artificial intervention at zero: Step S3: Generate manual zero-crossing turn-off information based on the obtained main switch branch current value.

[0056] In practice, after the zero-crossing moment is manually intervened, the controller still acquires the main switch branch current value in real time, and uses the main switch branch current value acquired after the zero-crossing moment to identify whether the vacuum fast switch K1 has been opened after the zero-crossing moment is manually intervened.

[0057] Specifically, if the current value of the main switch branch is equal to zero within a preset time after the manual intervention zero crossing moment, then a manual zero crossing shutdown information carrying a manual zero crossing shutdown identifier is generated. If, within a preset time period after the manual intervention at the zero-crossing point, the current values ​​of all main switch branches are greater than or less than zero, then a manual zero-crossing shutdown message carrying a zero-crossing continuous operation indicator will be generated.

[0058] During implementation, the controller will monitor the changes in the main switch branch current value within a preset time after the moment of manual intervention at the zero crossing. Scenario 1: If the main switch branch current value still does not return to zero within the preset time after manual intervention at the zero-crossing moment, then a manual zero-crossing turn-off message carrying a zero-crossing continuous operation flag will be generated. Scenario 2: If the current value of the main switch branch returns to zero within a preset time after the manual zero-crossing moment, then a manual zero-crossing turn-off message carrying a manual zero-crossing turn-off flag will be generated.

[0059] Step S4: If the manual zero-crossing shutdown information carries a zero-crossing continuous operation flag, then a secondary zero-crossing correction instruction is generated.

[0060] In practice, when the controller generates a manual zero-crossing shutdown information that includes a zero-crossing continuous operation flag, the controller generates a secondary zero-crossing correction command to take the zero-crossing energy storage capacitor C1 out of operation and put the reserve capacitor C2 into operation.

[0061] Specifically, the secondary zero-crossing correction instructions include the instruction to turn off the first switch Q1, the instruction to turn on the second switch Q2, and the instruction to turn on the trigger switch K2.

[0062] Optionally, the following processing also exists in this application, and the specific process is as follows: After manual intervention at the zero-crossing moment and a preset waiting time, a primary energy dissipation command is generated to control the first switch Q1 to turn off and the energy-consuming thyristor S1 to turn on.

[0063] In practice, after the controller manually intervenes at the zero-crossing moment and after a preset waiting time, the voltage across the zero-crossing energy storage capacitor C1 rises in the reverse direction to a certain value. Then, the controller generates an energy dissipation command to control the first switch Q1 to turn off and the energy dissipation thyristor S1 to turn on, so that the reverse voltage stored in the zero-crossing energy storage capacitor C1 can be dissipated through the energy dissipation inductor L2 and the energy dissipation resistor R1.

[0064] When the zero-crossing energy storage voltage across the zero-crossing energy storage capacitor C1 is less than the preset discharge voltage threshold, a primary energy storage command is generated to control the energy-consuming thyristor S1 to turn off and the energy-storing thyristor S1 to turn on.

[0065] In implementation, a voltage sensor is connected in parallel with the zero-crossing energy storage capacitor C1 to detect the voltage value across C1. When the controller receives a zero-crossing energy storage voltage across C1 that is less than a preset discharge voltage threshold, the controller generates another energy storage command to turn off the energy-consuming thyristor S1 and turn on the energy storage thyristor S1, so that the CT energy storage circuit can charge the zero-crossing energy storage capacitor C1.

[0066] After generating the secondary zero-crossing correction instruction and waiting for a certain period of time, a secondary energy dissipation instruction is generated to control the second switch Q2 to turn off and the energy dissipation thyristor S2 to turn on.

[0067] In implementation, after the controller generates a secondary zero-crossing correction command and waits for a preset time interval, the voltage across the storage capacitor C2 rises in reverse to a certain value. Then, the controller generates a secondary energy dissipation command to control the second switch Q2 to turn off and the energy dissipation thyristor S2 to turn on, so that the reverse voltage stored in the storage capacitor C2 can be dissipated through the energy dissipation inductor L2 and the energy dissipation resistor R1.

[0068] When the received storage voltage across the storage capacitor C2 is less than the discharge voltage threshold, a secondary energy storage command is generated to control the turn-off of the energy-consuming thyristor S2 and the turn-on of the energy-storing thyristor S2.

[0069] In implementation, a voltage sensor is connected in parallel with the storage capacitor C2 to detect the voltage across C2. When the controller receives a value indicating that the storage voltage across C2 is less than a preset discharge voltage threshold, the controller generates a secondary energy storage command to turn off the energy-consuming thyristor S2 and turn on the energy-storing thyristor S2, so that the CT energy storage circuit can charge the zero-crossing energy storage capacitor C1.

[0070] Optionally, in this application, after generating the second zero-crossing correction instruction, the following processing flow also exists: The zero-crossing adjustment difference is generated based on multiple historical main switch branch current values.

[0071] In implementation, after generating the secondary zero-crossing correction command, the controller generates a zero-crossing adjustment difference based on the current value of the main switch branch at that moment. Here, the current of the main switch branch is referred to as the historical current value of the main switch branch. Moreover, the current difference here refers to the minimum current flowing in the main switch branch during the operation of the zero-crossing energy storage capacitor C1, that is, during the conduction of the first switch Q1 and the trigger switch K2.

[0072] The energy storage voltage adjustment value is calculated and generated based on the zero-crossing adjustment prediction difference and the pre-stored reserve voltage adjustment data.

[0073] In practice, the controller stores reserve voltage adjustment data, which is used to reflect the correspondence between the zero-crossing regulation difference and the voltage adjustment value.

[0074] After generating the zero-crossing adjustment difference, the controller matches the corresponding voltage adjustment value in the reserve voltage adjustment data with the zero-crossing adjustment difference, which is referred to here as the energy storage voltage adjustment value. This is so that after the zero-crossing energy storage capacitor C1 has completed its operation, the voltage across the zero-crossing energy storage capacitor C1 can be adjusted to create a zero-crossing point on the main switch branch during the next operation.

Claims

1. A zero-loss current limiting device based on artificial zero-crossing technology, characterized in that: The device includes a main switch branch, an energy absorption branch, and a manual zero-crossing branch; The main switch branch includes a vacuum fast switch, which is connected in series between the busbar of the power distribution system and the input terminal of the main transformer, and a current-limiting reactor is connected in parallel to the vacuum fast switch; A modulation inductor is connected in series between the main switch branch and the artificial zero-crossing branch, and the energy-absorbing branch is connected in parallel to the artificial zero-crossing branch; The energy-absorbing branch includes multiple zinc oxide resistors, and the multiple zinc oxide resistors constitute a nonlinear resistor module; The artificial zero-crossing branch includes the energy storage unit and the trigger switch. The energy storage unit includes at least a zero-crossing energy storage capacitor, and the zero-crossing energy storage capacitor and the trigger switch are connected in series.

2. The method according to claim 1, characterized in that: The energy storage unit is connected in series with the trigger switch. The energy storage unit includes a first zero-crossing subunit and a second zero-crossing subunit, and the first zero-crossing subunit and the second zero-crossing subunit are connected in parallel. The first zero-crossing subunit includes a zero-crossing energy storage capacitor and a first switching transistor, wherein the zero-crossing energy storage capacitor and the first switching transistor are connected in series; The second zero-crossing subunit includes a storage capacitor and a second switching transistor, which are connected in series.

3. The apparatus according to claim 2, characterized in that: It also includes a power consumption circuit, which includes a power consumption thyristor one, a power consumption thyristor two, a power consumption resistor and a power consumption inductor; The connection node between the zero-crossing energy storage capacitor and the first switching transistor is connected to the input terminal of the first energy-consuming thyristor; the output terminal of the first energy-consuming thyristor is connected to one of the connection terminals of the energy-consuming inductor. The connection node between the storage capacitor and the second switching transistor is connected to the input terminal of the second energy-consuming thyristor. The output terminal of the second energy-consuming thyristor is connected to one end of the energy-consuming inductor, and the output terminal of the first energy-consuming thyristor is connected to the output terminal of the second energy-consuming thyristor. The other end of the energy-consuming inductor is connected to the energy-consuming resistor, and the other end of the energy-consuming resistor is connected to the connection node between the zero-crossing energy storage capacitor and the reserve capacitor.

4. The method according to claim 3, characterized in that: It also includes a CT energy storage circuit for storing energy in zero-crossing energy storage capacitors and reserve capacitors; The CT energy storage circuit includes a power-supplying CT, a power-supplying transformer, a power-supplying resistor, a voltage stabilizing module, a power-supplying thyristor one, and a power-supplying thyristor two; The power-collecting CT is mounted on the busbar, and the two output terminals of the power-collecting CT are electrically connected to the two output terminals of the primary side of the power-collecting transformer, respectively. The power-collecting resistor is connected in parallel to the primary side of the power-collecting transformer. The two input terminals of the voltage stabilization module are respectively connected to the two output terminals of the power extraction transformer. The negative terminal of the voltage stabilization module is connected to the connection node between the zero-crossing energy storage capacitor and the reserve capacitor. The positive terminal of the voltage stabilization module is simultaneously connected to the input terminals of the first power extraction thyristor and the second power extraction thyristor. The output terminal of the first power-collecting thyristor is connected to the connection node between the first switching transistor and the zero-crossing energy storage capacitor, and the output terminal of the second power-collecting thyristor is connected to the connection node between the second switching transistor and the storage capacitor.

5. A monitoring and maintenance method for a zero-loss current limiting device based on artificial zero-crossing technology, applied to the zero-loss current limiting device based on artificial zero-crossing technology as described in any one of claims 1-4, characterized in that, The method includes: The current value of the main switch branch fed back by the current sensor is acquired in real time, and the current operating status of the main switch branch is identified based on the current value of the main switch branch; If the main switch branch is identified as being in a short-circuit fault operation state, then mark the time of manual intervention zero crossing after the current time and generate a manual zero crossing intervention command to control the first switch tube and the trigger switch to conduct at the time of manual zero crossing. After the zero-crossing moment of the aforementioned artificial intervention: Based on the obtained main switch branch current value, generate manual zero-crossing turn-off information; If the manual zero-crossing shutdown information carries a zero-crossing continuous operation flag, a secondary zero-crossing correction command is generated.

6. The method according to claim 5, characterized in that, The step of generating manual zero-crossing turn-off information based on the obtained main switch branch current value includes: If, within a preset time period after the manual intervention zero-crossing moment, the current value of the main switch branch is equal to zero, then a manual zero-crossing shutdown information carrying a manual zero-crossing shutdown identifier is generated. If, within a preset time period after the manual intervention zero-crossing moment, all the main switch branch current values ​​are greater than or less than zero, then a manual zero-crossing shutdown message carrying a zero-crossing continuous operation identifier is generated.

7. The method according to claim 5, characterized in that: The secondary zero-crossing correction instructions include a control instruction to turn off the first switch, a control instruction to turn on the second switch, and a trigger instruction to turn on the switch.

8. The method according to claim 7, characterized in that, The method further includes: After manual intervention at the zero crossing moment and a preset waiting time, a power consumption command is generated to control the first switch to turn off and the first power consumption thyristor to turn on. When the zero-crossing energy storage voltage across the zero-crossing energy storage capacitor is less than the preset discharge voltage threshold, a primary energy storage command is generated to control the first energy-consuming thyristor to turn off and the first energy-storing thyristor to turn on. After generating the second zero-crossing correction instruction and after the waiting time interval, a second energy-consuming instruction is generated to control the second switch to turn off and the energy-consuming thyristor to turn on. When the received storage voltage across the storage capacitor is less than the discharge voltage threshold, a secondary energy storage command is generated to control the second energy-consuming thyristor to turn off and the second energy-storing thyristor to turn on.

9. The method according to claim 9, characterized in that, After generating the second zero-crossing correction command, the process also includes: Based on multiple historical main switch branch current values, a zero-crossing adjustment difference is generated; The energy storage voltage adjustment value is calculated and generated based on the zero-crossing adjustment prediction difference and the pre-stored reserve voltage adjustment data.

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