Unidirectional current interruption device and operation method thereof

Abstract

The present disclosure relates to a unidirectional DC current interruption device and an operation method thereof. According to one embodiment disclosed herein, in a unidirectional DC current interruption device comprising a first reactor, a thyristor, a second reactor, and a capacitor, a reverse current is generated by discharge of the capacitor and mutual induction between the reactors when a failure occurs in a load side circuit after the thyristor is turned on by a gate signal, and thus the thyristor can be turned off to quickly interrupt a DC current.

Description

Unidirectional current blocking device and method of operation thereof

[0001] The present disclosure relates to a unidirectional current interruption device and a method of operation thereof.

[0002] The following description merely provides background information related to the present embodiment and does not constitute prior art.

[0003] When a fault occurs in a DC system, the DC fault current rises rapidly, and the longer the interruption time, the larger the magnitude of the DC fault current that must be interrupted. Therefore, a DC circuit breaker capable of interrupting the DC fault current quickly is required.

[0004] DC circuit breakers using semiconductor devices with a turn-off function (e.g., IGBTs) have a very fast breaking speed. However, because they perform an opening operation by receiving a signal from a protective relay when a fault occurs, they cannot interrupt the DC fault current immediately upon the occurrence of the fault.

[0005] Semiconductor devices with turn-off functions (e.g., IGBTs) are expensive, and as the voltage and current increase, the size of the semiconductor device also increases, leading to higher device configuration costs. This makes it difficult to apply them to medium voltage (MV) or high voltage (HV) DC systems.

[0006] The present disclosure aims to provide a unidirectional DC current interruption device using a thyristor and a commutation circuit that operates immediately upon the occurrence of a fault, and a method of operation thereof.

[0007] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below.

[0008] According to one embodiment of the present disclosure, a unidirectional DC current blocking device comprising a first reactor, a thyristor, a second reactor, and a capacitor, wherein one end of the first reactor is connected to a power-side circuit of a DC line, the other end of the first reactor is connected to a positive terminal of the thyristor, the negative terminal of the thyristor is connected to one end of the second reactor and one end of the capacitor, one end of the second reactor is connected to a negative terminal of the thyristor and one end of the capacitor, the other end of the second reactor is connected to a load-side circuit of the DC line, and the other end of the capacitor is grounded, the thyristor is turned on by a gate signal, and the capacitor is charged with a normal operating current flowing through the DC line, and in response to a fault occurring in the load-side circuit, the capacitor is discharged, and a reverse current in the opposite direction to the normal operating current is generated by mutual induction between the first reactor and the second reactor, and the reverse current is the A unidirectional DC current blocking device is provided, which is supplied to a thyristor and turns off the thyristor.

[0009] When a fault occurs in the load-side circuit, the capacitor, the second reactor, and the ground fault path form a commutation circuit.

[0010] The change in current of the second reactor due to the discharge of the capacitor induces a voltage in the first reactor, and the reverse current is generated by the induced voltage.

[0011] The above-described unidirectional DC current cutoff device may further include a closing switch for cutting off the load current during normal operation.

[0012] The above-mentioned input switch may include an Insulated Gate Bipolar Transistor (IGBT), a Wide Band Gap (WBG) semiconductor switch, a thyristor, a mechanical switch, or a Spark Gap switch.

[0013] The above unidirectional DC current blocking device may further include a nonlinear resistance element to suppress the inrush voltage generated when the thyristor is turned off or to absorb residual energy.

[0014] The above nonlinear resistance element can be connected in parallel with the above thyristor.

[0015] According to another embodiment of the present disclosure, a method performed by a unidirectional DC current blocking device comprises: a process in which a capacitor is charged with a normal operating current flowing through a DC line while the thyristor is turned on; a process in which the capacitor is discharged in response to a fault occurring in the load-side circuit of the DC line; a process in which a reverse current in the opposite direction to the normal operating current is generated by mutual induction between a first reactor and a second reactor; and a process in which the reverse current is supplied to the thyristor so that the thyristor is turned off.

[0016] According to an embodiment of the present disclosure, a fault current can be quickly interrupted.

[0017] According to an embodiment of the present disclosure, the design of a DC current interruption device can be simplified and the configuration cost reduced.

[0018] According to an embodiment of the present disclosure, a DC current interruption device can be easily applied to a medium voltage or high voltage DC system.

[0019] The effects of the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description below.

[0020] FIG. 1 is a diagram showing the configuration of a unidirectional DC current blocking device according to one embodiment of the present disclosure.

[0021] FIGS. 2a to 2c are drawings for explaining the operation of a unidirectional DC current blocking device according to one embodiment of the present disclosure.

[0022] FIG. 3 is a diagram showing the configuration of a unidirectional DC current blocking device according to another embodiment of the present disclosure.

[0023] FIG. 4 is a flowchart of a method performed by a unidirectional DC current blocking device according to one embodiment of the present disclosure.

[0024] Some embodiments of the present disclosure are described in detail below with reference to exemplary drawings. It should be noted that in assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the present disclosure, if it is determined that a detailed description of related known components or functions could obscure the essence of the present disclosure, such detailed description is omitted.

[0025] In describing the components of the embodiments according to the present disclosure, symbols such as first, second, i), ii), a), b), etc., may be used. These symbols are intended only to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by the symbols. When a part in the specification is described as 'comprising' or 'having' a component, this means that, unless explicitly stated otherwise, it does not exclude other components but may include additional components. Furthermore, terms such as 'part' or 'module' described in the specification refer to a unit that processes at least one function or operation, and this may be implemented in hardware, software, or a combination of hardware and software.

[0026] The description of the invention disclosed below, together with the accompanying drawings, is intended to describe exemplary embodiments of the invention and is not intended to represent the only embodiment in which the invention may be practiced.

[0027] In this specification, the term 'turn-on' may be used interchangeably with 'closed' or 'closed pole', and the term 'turn-off' may be used interchangeably with 'open' or 'open pole'.

[0028] In this specification, if one end of a specific element or circuit is the right end of the specific element or circuit, the other end of the specific element or circuit may be the left end of the specific element or circuit. If one end of a specific element or circuit is the left end of the specific element or circuit, the other end of the specific element or circuit may be the right end of the specific element or circuit.

[0029] In this specification, the term "one side" refers to the power source side in a DC system, and the term "other side" refers to the load side. However, this is for the convenience of explanation and the present disclosure is not limited thereto.

[0030] The present disclosure relates to a unidirectional DC current interruption device and a method of operation thereof. Specifically, it provides a unidirectional DC current interruption technology using a thyristor and a commutation circuit that operates immediately upon the occurrence of a fault.

[0031] A unidirectional DC current blocking device according to embodiments of the present disclosure is configured based on a thyristor, which is a turn-on element, and implements the turn-off of the thyristor using a commutation circuit composed of a capacitor and a reactor and a ground fault path created when a fault occurs in a DC system.

[0032] Since the thyristor is turned on by a gate signal and turned off immediately upon the occurrence of a fault such as a ground fault, the magnitude of the fault current to be interrupted is equal to the load current. Therefore, compared to DC interruption devices based on Insulated Gate Bipolar Transistors (IGBTs) that interrupt fault currents larger than the load current, there is an advantage in being able to keep the capacity of the device that absorbs switching surge voltage and residual energy of the DC system small.

[0033] In addition, thyristors have the advantage of being suitable for application in medium-voltage (MV) or high-voltage (HV) systems and high-current systems because they offer greater voltage and current capacity per unit compared to IGBTs.

[0034] FIG. 1 is a diagram showing the configuration of a unidirectional DC current blocking device according to one embodiment of the present disclosure.

[0035] Referring to FIG. 1, a unidirectional DC current blocking device (100) according to one embodiment of the present disclosure includes a thyristor (110), a capacitor (120), a first reactor (131), a second reactor (132), and a making switch (140). The unidirectional DC current blocking device (100) may further include a control unit (not shown) that controls the overall operation of the components. For example, the control unit may generate a gate signal for turning on the thyristor (110) and / or a signal for controlling the operation of the making switch (140).

[0036] The thyristor (110) is a semiconductor switching element that maintains a turned-on state in a normal state and allows normal operating current to flow. Turn-off for blocking fault current is implemented through a commutation circuit to be described later. The thyristor (110) is installed between the first reactor (131) and the second reactor (132) in the DC line. The anode of the thyristor (110) is connected to the other end of the first reactor (131), and the cathode is connected to one end of the second reactor (132) and one end of the capacitor (120).

[0037] The capacitor (120) can be charged with normal operating current. That is, the normal operating current supplied to the DC line can be supplied to the capacitor (120) through the first reactor (131) and the thyristor (110), and the capacitor (120) can be charged by the normal operating current. The capacitor (120) is installed between the contact point where the thyristor (110) and the second reactor (132) are connected and ground. One end of the capacitor (120) is connected to the negative terminal of the thyristor (110) and one end of the second reactor (132), and the other end is grounded.

[0038] When an accident such as a ground fault occurs in the load-side circuit of the DC line, the ground fault path, the capacitor (120), and the second reactor (132) form a commutation circuit, and the capacitor (120) is discharged.

[0039] When the capacitor (120) is discharged, a current in the opposite direction to the normal operating current (hereinafter referred to as 'reverse current') is induced through interaction such as mutual induction between the first reactor (131) and the second reactor (132). Specifically, a change in current in the second reactor (132) occurs due to the discharge of the capacitor (120). The change in current in the second reactor (132) generates an induced voltage in the first reactor (131). The reverse current is generated by the induced voltage and supplied to the thyristor (110). Due to the reverse current, the current flowing between the positive and negative electrodes of the thyristor (110) becomes zero, and the thyristor (110) is turned off.

[0040] The first reactor (131) is installed between the power supply circuit and the thyristor (110) in the DC line. One end of the first reactor (131) is connected to the power supply circuit, and the other end is connected to the positive terminal of the thyristor (110).

[0041] A second reactor (132) is installed between the thyristor (110) and the load-side circuit in the DC line. One end of the second reactor (132) is connected to the negative terminal of the thyristor (110) and one end of the capacitor (120), and the other end is connected to the load-side circuit and one end of the switch (140).

[0042] The first reactor (131) and the second reactor (132) are closely coupled to each other, so that magnetic or electrical interaction is possible between the two reactors.

[0043] The input switch (140) can cut off the load current during normal operation. The input switch (140) maintains a turned-off state during normal operation, but can be turned on according to a control signal to cut off the load current. The input switch (140) is installed between the other end of the second reactor (132) and ground. One end of the input switch (140) is connected to the other end of the second reactor (132) and the load-side circuit, and the other end is grounded. The input switch (140) may include various forms such as an IGBT, a WBG (Wide Band Gap) semiconductor switch, a thyristor, a mechanical switch, a spark gap switch, etc., but is not limited thereto.

[0044] The operation of a unidirectional DC current blocking device according to embodiments of the present disclosure will be explained with reference to FIGS. 2a to 2c.

[0045] First, a charging process for the capacitor (120) is required.

[0046] Referring to FIG. 2a, in the normal state, the thyristor (110) remains in a turned-on state and allows the normal operating current (IN) and capacitor charging current (IC) to flow. The capacitor (120) is charged with the capacitor charging current (IC).

[0047] FIG. 2b illustrates a situation in which an accident, such as a ground fault, occurs in the load-side circuit of a DC line. Referring to FIG. 2b, as the capacitor (120) discharges, a discharge current (IC) flows through the commutation circuit. As the discharge current (IC) flows, a reverse current (IMI) is induced due to interaction, such as mutual induction between the first reactor (131) and the second reactor (132). Due to the reverse current, the current flowing between the positive and negative electrodes of the thyristor (110) becomes zero, and the thyristor (110) is turned off.

[0048] Referring to FIG. 2c, the thyristor (110) is turned off, thereby blocking the fault current. That is, the power side circuit and the load side circuit can be separated by turning off the thyristor (110). The residual energy caused by the discharge current (IC) is removed over time.

[0049] Meanwhile, when the switching surge voltage of the thyristor (110) is large and the residual energy of the DC system is large after the fault current is cut off, it is necessary to absorb the residual energy. To this end, the unidirectional DC current cutoff device may further include a separate energy absorption element.

[0050] FIG. 3 is a diagram showing the configuration of a unidirectional DC current blocking device according to another embodiment of the present disclosure.

[0051] Referring to FIG. 3, a unidirectional DC current blocking device (100) according to another embodiment of the present disclosure includes a thyristor (110), a capacitor (120), a first reactor (131), a second reactor (132), an insertion switch (140), and a non-linear resistance element (150). That is, a unidirectional DC current blocking device (100) according to another embodiment of the present disclosure includes all the same components as FIG. 1 and further includes a non-linear resistance element (150).

[0052] The thyristor (110), capacitor (120), first reactor (131), second reactor (132), and input switch (140) shown in FIG. 3 are identical to the components shown in FIG. 1.

[0053] A nonlinear resistor element (150) is connected in parallel to a thyristor (110) and serves to protect the system from transient inrush voltage (TIV) that occurs when the thyristor (110) is turned off and to absorb residual energy. The nonlinear resistor element (150) may include a metal oxide surge arrester (MOSA) or a metal oxide varistor (MOV).

[0054] According to embodiments of the present invention, a unidirectional DC current interruption device (100) can immediately turn off the thyristor (110) when a fault occurs, thereby rapidly interrupting the fault current. At this time, by rapidly turning off the thyristor (110), the magnitude of the fault current is limited to the same level as the load current, thereby interrupting the DC fault current. Through this, the design of the DC current interruption device can be simplified and the configuration cost reduced. In addition, since it operates based on a thyristor, it can be easily applied to medium-voltage or high-voltage DC systems.

[0055] FIG. 4 is a flowchart of a method performed by a unidirectional DC current blocking device according to one embodiment of the present disclosure.

[0056] Referring to FIG. 4, the capacitor (120) is charged through the normal operating current flowing through the DC line while the thyristor (110) is turned on (S410).

[0057] When a fault such as a ground fault occurs in the load-side circuit of the DC line, a ground fault path is created and the capacitor (120) is discharged (S420).

[0058] When the capacitor (120) is discharged, a reverse current is generated through mutual induction and interaction between the first reactor (131) and the second reactor (132), and the fault current is canceled out by the reverse current (S430). That is, the current flowing between the positive and negative electrodes of the thyristor (110) becomes zero.

[0059] The DC current blocking operation is completed as the thyristor (110) is turned off (S440).

[0060] Each component of the device or method according to the present invention may be implemented in hardware or software, or in a combination of hardware and software. Additionally, the function of each component may be implemented in software, and a microprocessor may be implemented to execute the function of the software corresponding to each component.

[0061] Various embodiments of the systems and techniques described herein may be realized as digital electronic circuits, integrated circuits, field programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include being implemented as one or more computer programs executable on a programmable system. A programmable system comprises a storage system, at least one input device, and at least one programmable processor (which may be a special-purpose processor or a general-purpose processor) coupled to receive data and instructions from at least one output device and to transmit data and instructions to them. Computer programs (which are also known as programs, software, software applications, or code) include instructions for the programmable processor and are stored on a "computer-readable recording medium."

[0062] Computer-readable recording media include all types of recording devices in which data that can be read by a computer system is stored. Such computer-readable recording media may be non-volatile or non-transitory media such as ROM, CD-ROM, magnetic tape, floppy disk, memory card, hard disk, magneto-optical disk, and storage device, and may also include transitory media such as data transmission media. Additionally, computer-readable recording media may be distributed across networked computer systems, and computer-readable code may be stored and executed in a distributed manner.

[0063] Although the flowcharts in this specification describe each process as being executed sequentially, this is merely an illustrative explanation of the technical concept of one embodiment of the present disclosure. In other words, a person skilled in the art to which one embodiment of the present disclosure belongs may modify and adapt the flowcharts in this specification in various ways, such as by changing the order described therein or executing one or more of the processes in parallel, without departing from the essential characteristics of one embodiment of the present disclosure; therefore, the flowcharts in this specification are not limited to a chronological order.

[0064] The above description is merely an illustrative explanation of the technical concept of the present embodiment, and a person skilled in the art to which the present embodiment belongs would be able to make various modifications and variations within the scope of the essential characteristics of the present embodiment. Accordingly, the present embodiments are intended to explain, not limit, the technical concept of the present embodiment, and the scope of the technical concept of the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present embodiment.

[0065] (Explanation of symbols)

[0066] 110: Thyrister

[0067] 120: Capacitor

[0068] 131: Reactor 1

[0069] 132: Second Reactor

[0070] 140: Input switch

[0071] 150: Non-linear resistor element

[0072] Statements regarding sponsored research or development

[0073] This invention is the result of research conducted in 2024 with funding from the Ministry of Science and ICT and support from the National Research Council on Science and Technology (Project No.: 2710019781, Project Title: Development of Core LPIT Technology for 170kV GIS).

[0074] CROSS-REFERENCE TO RELATED APPLICATION

[0075] This patent application claims priority to Korean patent application No. 10-2024-0156937 filed on November 7, 2024, the entire contents of which are incorporated into this patent application by reference.

Claims

1. A unidirectional DC current blocking device comprising a first reactor, a thyristor, a second reactor, and a capacitor, One end of the first reactor is connected to the power side circuit of the DC line, and the other end of the first reactor is connected to the positive terminal of the thyristor, and The negative electrode of the above thyristor is connected to one end of the above second reactor and one end of the above capacitor, and One end of the second reactor is connected to the negative electrode of the thyristor and one end of the capacitor, and the other end of the second reactor is connected to the load-side circuit of the DC line, and The other end of the above capacitor is grounded, and The above thyristor is turned on by a gate signal, and the capacitor is charged with the normal operating current flowing through the DC line, and A unidirectional DC current blocking device in which, in response to a fault occurring in the load-side circuit, the capacitor is discharged, a reverse current opposite to the normal operating current is generated by mutual induction between the first reactor and the second reactor, and the reverse current is supplied to the thyristor to turn off the thyristor.

2. In Paragraph 1, A unidirectional DC current blocking device in which, when a fault occurs in the load-side circuit, the capacitor, the second reactor, and the ground fault path form a commutation circuit.

3. In Paragraph 1, A unidirectional DC current blocking device in which a change in current of the second reactor due to the discharge of the capacitor induces a voltage in the first reactor, and the reverse current is generated by the induced voltage.

4. In Paragraph 1, It further includes a closing switch for interrupting the load current during normal operation, and A unidirectional DC current interruption device in which the above-mentioned input switch is installed between the other end of the second reactor and ground, and is turned on according to a signal for interrupting the load current.

5. In Paragraph 4, The above-mentioned input switch is a unidirectional DC current blocking device comprising an Insulated Gate Bi-polar Transistor (IGBT), a Wide Band Gap (WBG) semiconductor switch, a thyristor, a mechanical switch, or a Spark Gap switch.

6. In Paragraph 1, It further includes a non-linear resistor element for suppressing the inrush voltage generated during the turn-off of the above thyristor or absorbing residual energy, and A unidirectional DC current blocking device in which the above nonlinear resistance element is connected in parallel to the above thyristor.

7. A method performed by a unidirectional DC current interruption device, The process of charging a capacitor with the normal operating current flowing through the DC line while the thyristor is turned on; A process in which the capacitor discharges in response to a fault occurring in the load-side circuit of the above DC line; A process in which a reverse current opposite to the normal operating current is generated through mutual induction between the first reactor and the second reactor; and A method comprising the process of supplying the reverse current to the thyristor and turning off the thyristor.

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