Alternating current filter switching inrush current suppression circuit, control method thereof and converter station

Abstract

The invention relates to an AC filter closing inrush current suppression circuit and a control method thereof, and a converter station, and relates to the technical field of power systems, the AC filter closing inrush current suppression circuit comprises a circuit breaker, an AC filter bank and a controller; wherein the first end of the circuit breaker is electrically connected with an alternating current bus; the first end of the alternating-current filter bank is electrically connected with the second end of the circuit breaker, and the second end of the alternating-current filter bank is grounded; the first end of the controller is electrically connected with the AC bus, and the second end is electrically connected with the switch assembly of the breaker. And the controller is used for determining the closing moment of the switch assembly according to the specification parameters of each component in the AC filter bank and the parameters of the electric signals flowing through the AC bus, and transmitting a closing instruction to the switch assembly based on the closing moment. By adopting the circuit, the complexity can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of power systems, and in particular to a circuit for suppressing closing inrush current of an AC filter, a control method thereof, and a converter station. Background Art

[0002] In UHVDC transmission projects, the converter station operates in both rectification and inversion states, which consumes a large amount of reactive power and is accompanied by the generation of a large number of harmonics. This is usually filtered through an AC filter, and the circuit breaker can control the AC filter to input the circuit for operation. However, the frequent operation of the AC filter and the circuit breaker will cause serious closing inrush current and overvoltage problems. In related technologies, the isolation transformer method is used to suppress inrush current for filters with different parameters by adjusting the transformer. However, this method requires the addition of additional equipment such as an isolation transformer, and the transformer itself also requires maintenance and inspection. Due to the addition of equipment such as the isolation transformer, there is a problem of high complexity. Summary of the Invention

[0003] Based on this, it is necessary to provide an AC filter closing inrush current suppression circuit and its control method, converter station, control device, storage medium and equipment that can reduce complexity in order to address the above technical problems.

[0004] In a first aspect, the present application provides a circuit for suppressing an AC filter closing inrush current, comprising:

[0005] a circuit breaker, wherein a first end of the circuit breaker is electrically connected to the AC bus;

[0006] an AC filter group, wherein a first end of the AC filter group is electrically connected to a second end of the circuit breaker, and a second end of the AC filter group is grounded;

[0007] A controller having a first end electrically connected to the AC bus and a second end electrically connected to a switch assembly of the circuit breaker; the controller is configured to determine a closing moment of the switch assembly based on specification parameters of components in the AC filter group and parameters of electrical signals flowing through the AC bus, and transmit a closing instruction to the switch assembly based on the closing moment.

[0008] In one embodiment, the switch assembly includes:

[0009] an auxiliary break, a first end of the auxiliary break being electrically connected to the AC bus;

[0010] A main break, wherein the first end of the main break is electrically connected to the second end of the auxiliary break, and the second end of the main break is electrically connected to the AC filter group. The main break is used to coordinate with the auxiliary break to control the on / off between the AC filter group and the AC bus.

[0011] In one embodiment, the circuit breaker further comprises:

[0012] a closing resistor, wherein two ends of the closing resistor are electrically connected to two ends of the auxiliary break, respectively, and the closing resistor is used to suppress a closing inrush current generated by the AC filter group;

[0013] A capacitor, wherein both ends of the capacitor are electrically connected to both ends of the main break, and the capacitor is used to suppress the overvoltage generated when the circuit breaker is opened.

[0014] In one embodiment, the main breaker performs a closing action in response to the closing instruction, and the auxiliary breaker maintains an open state for a preset time period in response to the closing instruction before performing a closing action.

[0015] In one embodiment, the controller is further configured to send a tripping instruction to the switch assembly of the circuit breaker; and the switch assembly controls the main break and the auxiliary break to perform a tripping action in sequence in response to the tripping instruction.

[0016] In one embodiment, the AC filter closing inrush current suppression circuit, the AC filter group includes three AC filters;

[0017] The first end of each AC filter is electrically connected to the second end of one circuit breaker, the second end of each AC filter is grounded, and the first end of each circuit breaker is electrically connected to one AC busbar.

[0018] In one embodiment, the AC filter closing inrush current suppression circuit further includes a current transformer and a voltage transformer;

[0019] The first end of the current transformer is electrically connected to the AC bus, and the second end is electrically connected to the second end of the controller, for measuring the current data in the electrical signal parameters flowing through the AC bus; the first end of the voltage transformer is connected to the AC bus, the second end is grounded, and the third end is electrically connected to the second end of the controller, for measuring the voltage data in the electrical signal parameters flowing through the AC bus.

[0020] In a second aspect, the present application provides a method for controlling a circuit for suppressing an AC filter closing inrush current, which is applied to a controller included in the circuit for suppressing an AC filter closing inrush current in any one of the above embodiments, the method comprising the following steps:

[0021] When the AC bus needs to be connected to the AC filter group, the closing resistor is controlled to be turned on;

[0022] Obtaining parameters of the electrical signal flowing through the AC bus and specification parameters of each component in the AC filter group;

[0023] Determining a closing moment of the circuit breaker corresponding to each of the AC buses according to the electrical signal parameters and the specification parameters;

[0024] A closing instruction is generated according to the closing moment, and the closing moment and the closing instruction are sent to the switch component of the circuit breaker to instruct the switch component to perform a closing operation.

[0025] In one embodiment, determining the closing moment of the circuit breaker corresponding to the coil on the AC side of each phase of the converter transformer according to the electrical signal parameter and each of the specification parameters includes:

[0026] Determining the equivalent impedance of the AC filter group on each of the AC busbars according to the specification parameters;

[0027] determining, based on the electrical signal parameters and the equivalent impedance, a relationship between an instantaneous current flowing through each of the AC busbars and a closing phase angle of the circuit breaker corresponding to each of the AC busbars;

[0028] The closing moment of the circuit breaker corresponding to each AC bus is determined according to the relationship between the instantaneous current flowing through each AC bus and the closing phase angle of the circuit breaker corresponding to each AC bus.

[0029] In a third aspect, the present application provides a converter station, comprising the AC filter closing inrush current suppression circuit according to any one of the above embodiments.

[0030] In a fourth aspect, the present application provides a control device for a circuit for suppressing a closing inrush current of an AC filter, comprising:

[0031] The resistance conduction module is used to control the conduction of the closing resistor when the AC bus needs to be connected to the AC filter group;

[0032] A parameter acquisition module, configured to acquire parameters of the electrical signal flowing through the AC bus and specification parameters of each component in the AC filter group;

[0033] a time determination module, configured to determine a closing time of the circuit breaker corresponding to each of the AC buses according to the electrical signal parameters and the specification parameters;

[0034] A closing instruction module is used to generate a closing instruction according to the closing moment, and send the closing moment and the closing instruction to the switch component of the circuit breaker to instruct the switch component to perform a closing operation.

[0035] In a fifth aspect, the present application provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the following steps are implemented:

[0036] When the AC bus needs to be connected to the AC filter group, the closing resistor is controlled to be turned on;

[0037] Obtaining parameters of the electrical signal flowing through the AC bus and specification parameters of each component in the AC filter group;

[0038] Determining a closing moment of the circuit breaker corresponding to each of the AC buses according to the electrical signal parameters and the specification parameters;

[0039] A closing instruction is generated according to the closing moment, and the closing moment and the closing instruction are sent to the switch component of the circuit breaker to instruct the switch component to perform a closing operation.

[0040] In a sixth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the following steps are implemented:

[0041] When the AC bus needs to be connected to the AC filter group, the closing resistor is controlled to be turned on;

[0042] Obtaining parameters of the electrical signal flowing through the AC bus and specification parameters of each component in the AC filter group;

[0043] Determining a closing moment of the circuit breaker corresponding to each of the AC buses according to the electrical signal parameters and the specification parameters;

[0044] A closing instruction is generated according to the closing moment, and the closing moment and the closing instruction are sent to the switch component of the circuit breaker to instruct the switch component to perform a closing operation.

[0045] The AC filter closing inrush current suppression circuit and its control method, converter station, control device, storage medium, and equipment described above include a circuit breaker, an AC filter group, and a controller. The circuit breaker has a first end electrically connected to an AC busbar. The AC filter group has a first end electrically connected to a second end of the circuit breaker, which is grounded. The circuit breaker is used to control the on / off connection between the AC filter group and the AC busbar, and the AC filter group is used to filter harmonics and perform reactive power compensation. The controller has a first end electrically connected to the AC busbar, and a second end electrically connected to a switch assembly of the circuit breaker. The controller is used to determine the closing moment of the switch assembly based on the specifications of the components in the AC filter group and the parameters of the electrical signal flowing through the AC busbar, and transmit a closing instruction to the switch assembly based on the closing moment. The controller's control algorithm determines the closing moment of the circuit breaker and controls the execution of the closing operation, eliminating the need for additional equipment such as an isolation transformer. This simplifies the circuit structure, reduces complexity, and reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0047] Figure 1 Schematic diagram of a circuit for suppressing closing inrush current of an AC filter in one embodiment;

[0048] Figure 2 A schematic structural diagram of a circuit for suppressing closing inrush current of an AC filter in another embodiment;

[0049] Figure 3 Schematic diagram of the structure of a circuit for suppressing closing inrush current of an AC filter in another embodiment;

[0050] Figure 4 A schematic structural diagram of a circuit for suppressing closing inrush current of an AC filter in yet another embodiment;

[0051] Figure 5 1 is a flow chart of a method for controlling a circuit for suppressing closing inrush current of an AC filter in one embodiment;

[0052] Figure 6 Schematic diagram of the equivalent circuit topology structure of an AC filter on any phase AC bus in one embodiment;

[0053] Figure 7 Schematic diagram of the relationship between instantaneous current and closing phase angle of a circuit breaker in one embodiment;

[0054] Figure 8 Schematic diagram of the peak modulus of the closing inrush current of the three phases of the branch where the filter is located in one embodiment;

[0055] Figure 9 A schematic diagram of a simulation of a closing inrush current waveform in solution 1 in an embodiment;

[0056] Figure 10 Schematic diagram of a simulation of a closing inrush current waveform in solution 2 in an embodiment;

[0057] Figure 11 A structural block diagram of a control device for a circuit for suppressing closing inrush current of an AC filter in one embodiment;

[0058] Figure 12 FIG. 1 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0059] To facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings provide embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0061] It will be understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor without departing from the scope of this application. The first resistor and the second resistor are both resistors, but they are not the same resistor.

[0062] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if there is transmission of electrical signals or data between the connected circuits, modules, units, etc.

[0063] It is understood that “at least one” refers to one or more, “a plurality” refers to two or more, and “at least a portion of an element” refers to a portion or all of an element.

[0064] As used herein, the singular forms "a," "an," and "the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include," "comprising," "having," and the like specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Furthermore, the term "and / or" as used in this specification includes any and all combinations of the relevant listed items.

[0065] As described in the background art, the prior art technology for suppressing the closing inrush current of AC filters is highly complex. The inventors have discovered that this problem arises because, in UHVDC transmission projects, converter stations operate in both rectification and inversion states, which consumes a large amount of reactive power and is accompanied by the generation of a large number of harmonics. Considering the characteristics of the converter equipment and system performance requirements, an AC filter must be installed on the AC side of each converter station to compensate for reactive power and filter out harmonics. However, the frequent operation of the AC filter circuit breaker can cause serious closing inrush current and overvoltage problems, which can easily lead to malfunction of protection, shorten the life of electrical components, and even cause damage. Therefore, finding a method that can reliably suppress the closing inrush current is key to avoiding equipment damage, power fluctuations, and malfunction of protection in DC transmission systems. Methods for suppressing the closing inrush current of AC filters mainly include the isolation transformer method and the phase-selective closing device method. The isolation transformer method can suppress inrush current by adjusting the transformer for filters with different parameters. However, this method requires the addition of additional equipment such as an isolation transformer, and the transformer itself also requires maintenance and overhaul. The addition of equipment such as the isolation transformer increases the overall investment cost, resulting in the disadvantages of complex equipment and high cost. The phase-selective closing device method uses a phase-shifting transformer to control the voltage phase when the filter is closed, thereby reducing closing inrush current and overvoltage. However, the phase-selective closing device itself has a complex structure and requires a high level of technical expertise for maintenance and management. In addition, the phase-selective closing device has a high level of technical expertise, resulting in a relatively high cost of the equipment. Therefore, this method has the disadvantages of complex equipment and high cost.

[0066] Based on the above reasons, the present invention provides a circuit for suppressing the closing inrush current of an AC filter, aiming to reduce the complexity of the circuit.

[0067] In one embodiment, Figure 1 As shown, a circuit for suppressing closing inrush current of an AC filter is provided, which includes a circuit breaker 11 , an AC filter group 12 and a controller 13 .

[0068] Among them, the first end of the circuit breaker 11 is electrically connected to the AC bus 14; the first end of the AC filter group 12 is electrically connected to the second end of the circuit breaker 11, and the second end of the AC filter group 12 is grounded. The circuit breaker 11 is used to control the on and off of the connection between the AC filter group 12 and the AC bus 14, and the AC filter group 12 is used to filter out harmonics and perform reactive power compensation; the first end of the controller 13 is electrically connected to the AC bus 14, and the second end is electrically connected to the switch component 111 of the circuit breaker 11; the controller 13 is used to determine the closing time of the switch component 111 based on the specifications of each component in the AC filter group 12 and the parameters of the electrical signal flowing through the AC bus 14, and transmit a closing instruction to the switch component 111 based on the closing time.

[0069] It is understood that the specification parameters can be specific indicators that describe the electrical, physical, and performance characteristics of circuit components, such as the resistance value of a resistor, the capacitance value of a capacitor, and the inductance value of an inductor. The electrical signal parameters flowing through the AC bus 14 can be voltage data and current data flowing through the AC bus 14. The closing moment is generally the moment when the voltage phase angle of the voltage data flowing through the AC bus 14 is 0°. This embodiment controls the calculation of the moment when the voltage phase angle of the voltage data flowing through the AC bus 14 is 0° by using the specification parameters of each component in the topological structure of the AC filter group 12 and the electrical signal parameters flowing through the AC bus 14, thereby obtaining the closing moment with the minimum closing inrush current.

[0070] It should be noted that the AC bus 14 is also electrically connected to the AC side coil of the converter transformer, so that when the switch assembly 111 of the circuit breaker 11 is closed, the AC filter group 12 can filter the harmonics generated on the AC side of the converter transformer and compensate for the reactive power.

[0071] In the above-mentioned AC filter closing inrush current suppression circuit, the circuit includes a circuit breaker 11, an AC filter group 12 and a controller 13; wherein, the first end of the circuit breaker 11 is electrically connected to the AC bus 14; the first end of the AC filter group 12 is electrically connected to the second end of the circuit breaker 11, and the second end of the AC filter group 12 is grounded. The circuit breaker 11 is used to control the on and off of the connection between the AC filter group 12 and the AC bus 14, and the AC filter group 12 is used to filter harmonics and perform reactive power compensation; the first end of the controller 13 is electrically connected to the AC bus 14, and the second end is electrically connected to the switch component 111 of the circuit breaker 11; the controller 13 is used to determine the closing time of the switch component 111 based on the specifications of each component in the AC filter group 12 and the parameters of the electrical signal flowing through the AC bus 14, and transmit a closing instruction to the switch component 111 based on the closing time. The control algorithm of the controller 13 is used to determine the closing moment of the circuit breaker 11 and control the closing operation, without the need to connect additional equipment such as an isolation transformer, thereby simplifying the circuit structure and reducing complexity and cost.

[0072] In one embodiment, Figure 2 As shown, the switch assembly 111 includes an auxiliary break 1111 and a main break 1112;

[0073] Among them, the first end of the auxiliary break 1111 is electrically connected to the AC bus 14; the first end of the main break 1112 is electrically connected to the second end of the auxiliary break 1111, and the second end of the main break 1112 is electrically connected to the AC filter group 12. The main break 1112 is used to coordinate with the auxiliary break 1111 to control the on and off between the AC filter group 12 and the AC bus 14.

[0074] It is understood that main break 1112 is the primary conductive path of circuit breaker 11, responsible for carrying the rated current of the circuit when closed. During opening, main break 1112 rapidly opens, severing the current path and preventing the arc from continuing to burn. Auxiliary break 1111 is typically used to connect a closing resistor in parallel. Closing auxiliary break 1111 during the initial closing phase allows the closing resistor to connect to the circuit, limiting the closing inrush current and overvoltage generated by AC filter bank 12 at the moment of closing. During the opening process, the delayed opening of auxiliary break 1111 reduces the energy of the arc at main break 1112, protecting the main contacts.

[0075] In this embodiment, the switch assembly 111 of the circuit breaker 11 is provided with a main break 1112 and an auxiliary break 1111. The main break 1112 is responsible for switching large currents, and the auxiliary break 1111 shares arc energy, which can extend the life of the circuit breaker 11. The auxiliary break 1111 introduces a closing resistor to suppress the closing inrush current. In addition, the main break 1112 and the auxiliary break 1111 are operated in stages to avoid mechanical shock and improve the stability of the system.

[0076] In one embodiment, continue to refer to Figure 2 , the circuit breaker 11 further includes a closing resistor 112 and a capacitor 113;

[0077] Among them, the two ends of the closing resistor 112 are respectively electrically connected to the two ends of the auxiliary breaker 1111, and the closing resistor 112 is used to suppress the closing inrush current generated by the AC filter group 12; the two ends of the capacitor 113 are respectively electrically connected to the two ends of the main breaker 1112, and the capacitor 113 is used to suppress the overvoltage generated when the circuit breaker 11 is opened.

[0078] The resistance of the closing resistor 112 may be in the range of 400 to 1500Ω, and the phase angle of the closing resistor 112 when exiting may be in the range of -180° to 180°.

[0079] It should be noted that the main disconnect 1112 immediately closes in response to the closing instruction, and the auxiliary disconnect 1111 remains in the open state for a period of time according to a preset time period in response to the closing instruction before closing. Therefore, when there is a need to connect the AC filter bank 12 to the circuit, the main disconnect 1112 is immediately closed, and then the auxiliary disconnect 1111 is kept open, so that the closing resistor 112 connected in parallel at both ends of the auxiliary disconnect 1111 can be connected to the circuit first to suppress the closing inrush current generated by the AC filter bank 12 at the moment the main disconnect 1112 is closed. After the closing resistor 112 has been connected to the circuit for a preset time period, the auxiliary disconnect 1111 is closed to fully connect the AC filter bank 12.

[0080] It is understandable that when circuit breaker 11 opens, the sudden interruption of current can cause high voltage to be generated in the inductive element. Connecting capacitor 113 in parallel with main break 1112 absorbs the energy released by the inductive element, slowing the rate of voltage rise and preventing breakdown of the equipment insulation. Controller 13 calculates the corresponding closing moment for circuit breaker 11 and sends a closing command to the switch assembly 111 of each phase circuit breaker 11 at the corresponding moment, causing circuit breaker 11 to close at the selected voltage phase angle, thereby reducing the impact of the closing inrush current on the circuit breaker 11 itself and the system. Furthermore, due to the discrete mechanical action of circuit breaker 11, the actual closing moment deviates from the ideal closing moment. This deviation can result in an excessively large closing inrush current. The provision of closing resistor 112 can mitigate this error by limiting the current and suppressing the formation of a closing inrush current. During closing, the charge stored in capacitor 113 needs to be released through the circuit. This charge flow causes a momentary increase in current, generating an inrush current. However, due to the existence of the resistance of the closing resistor 112, the current will not increase indefinitely, but will be limited by the resistance and gradually increase until it reaches a balanced state, thereby improving the suppression effect of the closing inrush current.

[0081] In one embodiment, continue to refer to Figure 2 The controller 13 is further configured to send a tripping instruction to the switch assembly 111 of the circuit breaker 11; the switch assembly 111 responds to the tripping instruction and controls the main break 1111 and the auxiliary break 1112 to perform the tripping action in sequence.

[0082] It should be noted that the generation of the trip command can be initiated by the user, or it can be initiated by the controller 13 based on the monitoring circuit conditions to meet the conditions for initiating the trip command. The user-initiated situation is generally when the equipment is maintained or repaired, and the circuit breaker 11 needs to be disconnected to ensure safety, or when a planned power outage is made to adjust the grid structure, a trip command also needs to be initiated. The situation in which the controller 13 automatically initiates the trip command is generally when the controller 13 detects abnormal conditions such as short circuit, overload, ground fault, etc., and the protection relay automatically triggers the trip condition. In addition, when the controller 13 detects abnormal conditions in the grid such as voltage instability and frequency deviation exceeding the preset range, the trip condition will also be triggered, thereby ensuring the safety of the grid and the timeliness of abnormal maintenance.

[0083] It should be noted that during tripping, the main breaker 1111 opens first to cut off most of the current. After a certain interval, the auxiliary breaker 1112 opens to ensure that the residual current is discharged through the closing resistor and prevent the arc from reigniting. The interval between the two disconnections is determined according to the actual circuit conditions.

[0084] In one embodiment, Figure 3 As shown, the AC filter group 12 includes three AC filters (see Figure 3 AC filter 1, AC filter 2 and AC filter 3); wherein the first end of each AC filter is electrically connected to the second end of a circuit breaker 11, the second end of each AC filter is grounded, and the first end of each circuit breaker 11 is electrically connected to an AC bus 14.

[0085] It should be noted that the specific topology of the AC filter is not specifically limited, as long as it is a circuit topology that can filter out harmonics and compensate for reactive power, and can be set according to actual filtering requirements.

[0086] It is understandable that the three AC busbars 14 (as shown in the attached Figure 3 The AC busbars 1, 2 and 3 in the figure are used to transmit the AC power output by the three-phase coils on the AC side of the converter transformer, and each AC filter is used to filter the harmonics generated by the AC side of one phase of the converter transformer, and each circuit breaker 11 (as shown in the attached figure) is used to transmit the AC power output by the three-phase coils on the AC side of the converter transformer. Figure 3 Circuit breakers 1, 2, and 3 control the connection between the corresponding AC filters and the AC busbar 14 to suppress inrush current during closing. Each circuit breaker 11 is a single-phase, double-break circuit breaker. The three AC filters are connected to the three AC busbars 14 via three separate circuit breakers 11. This means that each filter independently processes the harmonics of one phase, helping to balance the three-phase system and reduce mutual interference.

[0087] In one embodiment, Figure 4As shown, the AC filter closing inrush current suppression circuit also includes a current transformer 21 and a voltage transformer 22;

[0088] Among them, the first end of the current transformer 21 is electrically connected to the AC bus 14, and the second end is electrically connected to the second end of the controller 13, and is used to measure the current data in the electrical signal parameters flowing through the AC bus 14; the first end of the voltage transformer 22 is connected to the AC bus 14, the second end is grounded, and the third end is electrically connected to the second end of the controller 13, and is used to measure the voltage data in the electrical signal parameters flowing through the AC bus 14.

[0089] Among them, the current transformer 21 is a device used to measure AC current. By converting high current into a small, manageable current, it protects measuring equipment and instruments. Its operating principle is based on electromagnetic induction: the current flowing through the main current coil generates a proportional small current for use by other equipment. The voltage transformer 22, also known as a voltage converter, is used to measure AC voltage. Its function is to convert high voltage into a lower, safely measurable voltage. It is commonly used in power system monitoring and control to ensure that measuring equipment operates within a safe voltage range. It also works based on the principle of electromagnetic induction.

[0090] It should be noted that the controller 13 obtains the current data of the AC bus 14 collected by the current transformer 21 and the voltage data collected by the voltage transformer 22. Based on the current and voltage data, the controller 13 initiates a closing command in response to requests for harmonic filtering and reactive power compensation. This allows the AC filter to be put into the circuit for filtering in a timely manner.

[0091] In one embodiment, Figure 5 As shown, a control method for a circuit for suppressing closing inrush current of an AC filter is provided, which is applied to the controller 13 included in the circuit for suppressing closing inrush current of an AC filter described in any of the above embodiments. The method comprises:

[0092] Step S502: When the AC bus needs to be connected to the AC filter group, the closing resistor is controlled to be turned on.

[0093] Optionally, when the controller detects that any AC bus needs to be connected to an AC filter group, it sends a tripping instruction to the auxiliary break in the switch assembly of the circuit breaker, thereby controlling the closing resistor to be turned on.

[0094] Step S504 , obtaining parameters of the electrical signal flowing through the AC bus and specification parameters of each component in the AC filter group.

[0095] Optionally, the controller obtains electrical signal parameters flowing through the AC bus, including current data and voltage data, through a current transformer and a voltage transformer, and obtains pre-stored specification parameters of each component in the AC filter group from a storage system.

[0096] Step S506: Determine the closing time of the circuit breaker corresponding to each AC bus according to the electrical signal parameters and various specification parameters.

[0097] Optionally, the controller calculates the moment when the voltage phase angle flowing through each AC bus is 0° based on the electrical signal parameters and specification parameters, and determines it as the closing moment of the circuit breaker corresponding to the AC bus.

[0098] Step S508: Generate a closing instruction according to the closing moment, and send the closing moment and the closing instruction to the switch component of the circuit breaker to instruct the switch component to perform the closing operation.

[0099] Optionally, the controller generates a closing instruction based on the calculated closing moment. It should be noted that the closing instruction may include the closing moment or may not include it. The controller sends the closing instruction and the closing moment to the switch component of the circuit breaker to instruct the switch component to perform the closing operation based on the closing moment. The order of the closing operation is that the main break is closed first, and the auxiliary break remains open for a preset time period before the closing operation is performed.

[0100] In this embodiment, the closing time is determined by real-time monitoring of the circuit's electrical signal parameters and the component specification parameters of the AC filter group, which can adapt to different working conditions, improve adaptability, and timely suppress the closing inrush current. The phase-splitting closing technology and the closing resistor are combined to jointly suppress the generation of the closing inrush current, thereby improving the suppression effect of the closing inrush current.

[0101] In one embodiment, step S506 determines the closing time of the circuit breaker corresponding to each AC bus according to the electrical signal parameters and various specification parameters, including:

[0102] Based on various specification parameters, the equivalent impedance of the AC filter group on each AC bus is determined; based on the electrical signal parameters and the equivalent impedance, the relationship between the instantaneous current flowing through each AC bus and the closing phase angle of the circuit breaker corresponding to each AC bus is determined; based on the relationship between the instantaneous current flowing through each AC bus and the closing phase angle of the circuit breaker corresponding to each AC bus, the closing moment of the circuit breaker corresponding to each phase coil is determined.

[0103] Among them, equivalent impedance can refer to simplifying multiple components in the circuit (such as resistors, inductors, and capacitors) into an equivalent impedance to facilitate the analysis of circuit characteristics. In AC circuits, equivalent impedance not only takes into account the size of the resistor, but also includes the phase changes caused by the inductor and capacitor.

[0104] The closing phase angle refers to the phase relationship between current and voltage when the circuit breaker is reclosed in the power system.

[0105] Among them, instantaneous current refers to the current value at a specific moment.

[0106] Optionally, the controller converts the specification parameters of each component in the equivalent circuit of the AC filter group on each AC bus into frequency domain parameters using Laplace transform, and obtains the equivalent impedance of the equivalent circuit based on the frequency domain parameters. The controller also converts the voltage data flowing through each AC bus into an equivalent power supply. Based on the equivalent power supply corresponding to the equivalent impedance and electrical signal parameters, as well as the resonant frequency of the equivalent circuit, it obtains an expression for the relationship between the instantaneous current flowing through each AC bus and the closing phase angle of the circuit breaker corresponding to each AC bus, thereby obtaining a waveform corresponding to the expression. Furthermore, the controller determines the moment when the voltage phase angle is 0° based on the waveform, and uses this moment as the closing moment of the circuit breaker corresponding to each AC bus.

[0107] For example, Figure 6 As shown, a schematic diagram of the equivalent circuit topology of an AC filter on any phase AC bus is provided. The topology includes: a first inductor L1, a second inductor L2, a third inductor L3, a first capacitor C1, a second capacitor C2, a third capacitor C3, a first resistor R1, and a second resistor R2;

[0108] In which, the first end of the first capacitor C1 is electrically connected to the second end of the circuit breaker, the second end of the first capacitor C1 is connected in series with the first inductor L1, the second inductor L2 and the third inductor L3, the end of the third inductor L3 away from the second inductor L2 is grounded, the second capacitor C2 is connected in parallel with both ends of the second inductor L2, the third capacitor C3 is connected in parallel with both ends of the third inductor L3, the first resistor R1 is connected in parallel with both ends of the first inductor L1, and the second resistor R2 is connected in parallel with both ends of the second inductor L2.

[0109] According to this topology, the expression of equivalent power supply Us is: Among them, U m is the peak voltage on the AC bus, ω is the resonant frequency, t is the time variable, and θ is the initial phase angle.

[0110] Converting this expression into frequency domain parameters, the frequency domain equivalent impedance expression of the equivalent circuit is obtained as follows:

[0111]

[0112] Among them, Z sis the equivalent impedance, s is the frequency domain s parameter, L1, L2 and L3 are the inductance values ​​of the first inductor L1, the second inductor L2 and the third inductor L3 respectively, R1 and R2 are the resistance values ​​of the first resistor R1 and the second resistor R2 respectively, C 1、 C2 and C3 are the capacitance values ​​of the first capacitor C1, the second capacitor C2, and the third capacitor C3 respectively.

[0113] After simplifying the equivalent resistance expression, we can get:

[0114]

[0115] in:

[0116]

[0117] Furthermore, the mapping of the equivalent power supply in the frequency domain when the circuit breaker is closed is:

[0118]

[0119] So the expression of the current i in the circuit can be obtained as:

[0120]

[0121] Taking the resonant frequency ω as 648.634 Hz, we can get the relationship diagram between the instantaneous current flowing through each AC bus and the closing phase angle of the circuit breaker corresponding to each AC bus, as shown in the figure below: Figure 7 shown.

[0122] In one embodiment, a converter station is provided, comprising the AC filter closing inrush current suppression circuit described in any one of the above embodiments.

[0123] In one embodiment, another method for controlling a circuit for suppressing a closing inrush current of an AC filter is provided, comprising:

[0124] When an AC filter is required, a closing resistor is first put into operation, connected in parallel across the auxiliary terminals of the circuit breaker. A closing command is then sent to the controller, which calculates the corresponding closing times for each of the three-phase circuit breakers and sends the closing commands to the closing coils of each phase breaker at the corresponding times. This allows each phase breaker to close at the selected voltage phase angle, thereby reducing the impact of closing inrush current on the circuit breaker itself and the system. Furthermore, due to the discrete mechanical operation of the three-phase circuit breaker, the actual closing time deviates from the ideal closing time. This deviation can result in excessive closing inrush current. The pre-installed closing resistor mitigates this error by limiting the current and suppressing the formation of closing inrush current. During closing, the charge stored in the capacitor must be released through the circuit. This charge flow causes a momentary increase in current, generating an inrush current. However, due to the resistance of the parallel resistor, the current does not increase indefinitely. Instead, it is limited by the resistor and gradually increases until equilibrium is reached. The optimal solution of using closing resistors and phase-splitting closing technology can not only effectively suppress the closing inrush current, but also maintain a high level of suppression of the closing inrush current even if the actual closing moment deviates from the ideal moment due to the discreteness of the circuit breaker.

[0125] For example, Figure 6 Taking the filter in as an example, in an ideal state, the circuit breaker is closed at the voltage zero point, and 400-1500Ω closing resistors are respectively input to it. The phase angle when the closing resistor is removed is -180°-180° respectively. The peak modulus of the closing inrush current of the three phases of the branch where the filter is located is as follows: Figure 8 shown.

[0126] Depend on Figure 8 It can be seen that when the closing phase angle is constant, the peak modulus of the closing inrush current in the three-phase line will increase with the increase of the closing resistance; when the closing resistance is constant, the peak modulus of the closing inrush current will change periodically with the change of the closing resistance exit phase angle, and as the closing resistance increases, the inflection point of its change will shift backward.

[0127] From the overall test results, we can see that in Scheme 1, when the closing resistance is 1500Ω and the closing resistance exit phase angle is -135°, the closing inrush current reaches the maximum value of all schemes, which is 1.3251kA. In Scheme 2, when the closing resistance is 400Ω and the closing phase angle is -63°, the closing inrush current reaches the minimum value of all schemes, which is 0.4588kA. The closing inrush current waveforms of the above two schemes are shown as follows: Figure 9 Shown and Figure 10 shown.

[0128] Under the maximum inrush current scheme, the use of a high-resistance 1500Ω closing resistor effectively suppresses the closing inrush current when the closing resistor is activated. However, a large closing inrush current is generated the moment the closing resistor is removed, reaching its peak value very quickly and being significantly affected by harmonics. Compared to the maximum scheme, the minimum scheme does not suppress the closing inrush current as strongly when the closing resistor is activated. However, when the closing resistor is removed, the closing inrush current generated by the minimum scheme is similar to the current during branch stability, and reaches its peak value more gradually, indicating that the overall closing inrush current is less affected by harmonics.

[0129] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0130] Based on the same inventive concept, embodiments of the present application further provide a control device for an AC filter closing inrush current suppression circuit, for implementing the aforementioned control method for an AC filter closing inrush current suppression circuit. The solution provided by this device is similar to the solution described in the aforementioned method. Therefore, the specific limitations of one or more embodiments of the control device for an AC filter closing inrush current suppression circuit provided below can be found in the aforementioned limitations of the control method for an AC filter closing inrush current suppression circuit, and will not be further elaborated here.

[0131] In one embodiment, Figure 11 As shown, a control device 110 for suppressing a closing inrush current of an AC filter is provided, comprising: a resistance conduction module 1101, a parameter acquisition module 1102, a time determination module 1103, and a closing indication module 1104, wherein:

[0132] The resistance conduction module 1101 is used to control the closing resistor to conduct when the AC bus needs to be connected to the AC filter group.

[0133] The parameter acquisition module 1102 is used to acquire the parameters of the electrical signal flowing through the AC bus and the specification parameters of each component in the AC filter group.

[0134] The time determination module 1103 is used to determine the closing time of the circuit breaker corresponding to each AC bus according to the electrical signal parameters and various specification parameters.

[0135] The closing instruction module 1104 is configured to generate a closing instruction according to the closing moment, and send the closing moment and the closing instruction to the switch component of the circuit breaker to instruct the switch component to perform the closing operation.

[0136] Furthermore, in one embodiment, the time determination module 1103 is further configured to determine the equivalent impedance of the AC filter group on each AC bus based on various specification parameters; determine the relationship between the instantaneous current flowing through each AC bus and the closing phase angle of the circuit breaker corresponding to each AC bus based on the electrical signal parameters and the equivalent impedance; and determine the closing time of the circuit breaker corresponding to each AC bus based on the relationship between the instantaneous current flowing through each AC bus and the closing phase angle of the circuit breaker corresponding to each AC bus.

[0137] Each module in the control device 110 for the AC filter closing inrush current suppression circuit may be implemented in whole or in part via software, hardware, or a combination thereof. Each module may be embedded in or independent of a processor in a computer device in the form of hardware, or may be stored in a memory in the computer device in the form of software, so that the processor can call and execute the corresponding operations of each module.

[0138] In one embodiment, a computer device is provided. The computer device may be a server, and its internal structure diagram may be as follows: Figure 12 As shown. The computer device includes a processor, memory, and a network interface connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The database of the computer device is used to store data such as specification parameters and electrical signal parameters. The network interface of the computer device is used to communicate with an external terminal via a network connection. When the computer program is executed by the processor, it implements a control method for a circuit that suppresses the closing inrush current of an AC filter.

[0139] Those skilled in the art will understand that Figure 12 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0140] In one embodiment, a computer device is further provided, including a memory and a processor. The memory stores a computer program, and the processor implements the steps in the above method embodiments when executing the computer program.

[0141] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0142] In one embodiment, a computer program product is provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0143] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the above-mentioned embodiments. In particular, any reference to memory, database, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided herein may be, but are not limited to, general-purpose processors, central processing units (CPUs), graphics processing units (GPUs), digital signal processors (DSPs), programmable logic devices (PLDs), data processing logic devices based on quantum computing, and the like.

[0144] Throughout this specification, references to terms such as "some embodiments," "other embodiments," and "desired embodiments" indicate that a particular feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. Although these terms are used interchangeably throughout this specification, they do not necessarily refer to the same embodiment or example.

[0145] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0146] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A circuit for suppressing inrush current during closing of an AC filter, characterized in that: include: a circuit breaker, wherein a first end of the circuit breaker is electrically connected to the AC bus; an AC filter group, wherein a first end of the AC filter group is electrically connected to a second end of the circuit breaker, and a second end of the AC filter group is grounded; A controller having a first end electrically connected to the AC bus and a second end electrically connected to a switch assembly of the circuit breaker; the controller is configured to determine a closing moment of the switch assembly based on specification parameters of components in the AC filter group and parameters of electrical signals flowing through the AC bus, and transmit a closing instruction to the switch assembly based on the closing moment.

2. The AC filter closing inrush current suppression circuit according to claim 1, characterized in that: The switch assembly comprises: an auxiliary break, a first end of the auxiliary break being electrically connected to the AC bus; A main break, wherein the first end of the main break is electrically connected to the second end of the auxiliary break, and the second end of the main break is electrically connected to the AC filter group. The main break is used to coordinate with the auxiliary break to control the on / off between the AC filter group and the AC bus.

3. The AC filter closing inrush current suppression circuit according to claim 2, characterized in that: The circuit breaker further comprises: a closing resistor, wherein two ends of the closing resistor are electrically connected to two ends of the auxiliary break, respectively, and the closing resistor is used to suppress a closing inrush current generated by the AC filter group; A capacitor, wherein both ends of the capacitor are electrically connected to both ends of the main break, and the capacitor is used to suppress the overvoltage generated when the circuit breaker is opened.

4. The AC filter closing inrush current suppression circuit according to claim 3, characterized in that: The main breaker performs a closing action in response to the closing instruction, and the auxiliary breaker maintains an open state for a preset time period in response to the closing instruction and then performs a closing action.

5. The AC filter closing inrush current suppression circuit according to claim 3, characterized in that: The controller is further configured to send a tripping instruction to the switch assembly of the circuit breaker; the switch assembly controls the main break and the auxiliary break to perform a tripping action in sequence in response to the tripping instruction.

6. The AC filter closing inrush current suppression circuit according to claim 1, characterized in that: The AC filter group includes three AC filters; The first end of each AC filter is electrically connected to the second end of one circuit breaker, the second end of each AC filter is grounded, and the first end of each circuit breaker is electrically connected to one AC busbar.

7. The AC filter closing inrush current suppression circuit according to claim 1, characterized in that: Also includes current transformers and voltage transformers; The first end of the current transformer is electrically connected to the AC bus, and the second end is electrically connected to the second end of the controller, for measuring the current data in the electrical signal parameters flowing through the AC bus; the first end of the voltage transformer is connected to the AC bus, the second end is grounded, and the third end is electrically connected to the second end of the controller, for measuring the voltage data in the electrical signal parameters flowing through the AC bus.

8. A control method for a circuit for suppressing closing inrush current of an AC filter, characterized in that: The controller included in the circuit for suppressing closing inrush current of the AC filter according to any one of claims 1 to 7, wherein the method comprises the following steps: When the AC bus needs to be connected to the AC filter group, the closing resistor is controlled to be turned on; Obtaining parameters of the electrical signal flowing through the AC bus and specification parameters of each component in the AC filter group; Determining a closing moment of the circuit breaker corresponding to each of the AC buses according to the electrical signal parameters and the specification parameters; A closing instruction is generated according to the closing moment, and the closing moment and the closing instruction are sent to the switch component of the circuit breaker to instruct the switch component to perform a closing operation.

9. The control method for the AC filter closing inrush current suppression circuit according to claim 8, characterized in that: Determining the closing moment of the circuit breaker corresponding to each AC bus according to the electrical signal parameter and each of the specification parameters includes: Determining the equivalent impedance of the AC filter group on each of the AC busbars according to the specification parameters; determining, based on the electrical signal parameters and the equivalent impedance, a relationship between an instantaneous current flowing through each of the AC busbars and a closing phase angle of the circuit breaker corresponding to each of the AC busbars; The closing moment of the circuit breaker corresponding to each AC bus is determined according to the relationship between the instantaneous current flowing through each AC bus and the closing phase angle of the circuit breaker corresponding to each AC bus.

10. A converter station, characterized in that: The invention comprises a circuit for suppressing closing inrush current of an AC filter according to any one of claims 1 to 7.

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