Solid-state DC circuit breaker based on composite power electronic switches and its control method

Abstract

This invention discloses a solid-state DC circuit breaker based on a composite power electronic switch and its control method. It includes a main current-carrying branch, a transfer branch, and an energy-absorbing branch, which are connected in parallel. The main current-carrying branch includes a withstand voltage power electronic switch module and a turn-off power electronic switch module, used for current flow under normal DC grid conditions, buffering current during short-circuit faults, and diverting the current to the transfer branch. The withstand voltage power electronic switch module and the turn-off power electronic switch module are connected in series. The transfer branch includes a capacitor for receiving the current diverted from the main current-carrying branch during short-circuit faults and transferring the current to the energy-absorbing branch. The energy-absorbing branch includes an energy-absorbing MOV for absorbing the current diverted from the transfer branch during short-circuit faults. This significantly reduces the number of components, lowers costs, facilitates maintenance, and ensures the safe and reliable operation of the DC grid.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of direct current power grid, in particular to a solid-state direct current circuit breaker based on composite power electronic switch and a control method thereof. BACKGROUND

[0002] The direct current circuit breaker is a key equipment indispensable in the direct current power grid, which can cut off the fault current caused by short circuit in a very short time to ensure the safe and reliable operation of the direct current system. Since the direct current power grid has small damping, the fault current caused by short circuit has a very high rising rate, and the direct current circuit breaker needs to complete fault isolation in a very short time.

[0003] Compared with the mechanical direct current circuit breaker and the hybrid direct current circuit breaker, the solid-state direct current circuit breaker has a faster breaking speed and can break the fault current in hundreds of microseconds to complete fault isolation. Meanwhile, it has the advantages of simple structure, arcless breaking and displacement-free structure, so that the solid-state direct current circuit breaker is applied more and more widely in the direct current power grid. However, in the application scenario of high voltage and large current, the solid-state direct current circuit breaker has a large number of devices, high cost and is not convenient to maintain. SUMMARY

[0004] In view of the defects of the prior art that the solid-state direct current circuit breaker has a large number of devices, high cost and is not convenient to maintain, the present application is made, and through the specific embodiments, a solid-state direct current circuit breaker based on composite power electronic switch and a control method thereof are provided.

[0005] The present application provides a solid-state direct current circuit breaker based on composite power electronic switch, which is applied in a direct current power grid, and comprises:

[0006] A main current passing branch, a transfer branch and an energy absorbing branch are connected in parallel.

[0007] The main current passing branch comprises a voltage-withstanding power electronic switch module and a turn-off power electronic switch module, which are connected in series and used for passing current in normal condition of the direct current power grid and buffering current in short circuit fault condition, and the current is commutated to the transfer branch.

[0008] The transfer branch comprises a capacitor, which is used for receiving the current commutated from the main current passing branch in the short circuit fault condition and transferring the current to the energy absorbing branch.

[0009] The energy absorbing branch comprises an energy absorbing MOV, which is used for absorbing the current transferred from the transfer branch in the short circuit fault condition.

[0010] Specifically, in the short-circuit fault case, when the capacitor voltage in the transfer branch reaches the operating voltage of the energy-absorbing MOV, the current is transferred from the transfer branch to the energy-absorbing branch.

[0011] Specifically, the voltage-resistant power electronic switch module comprises at least one group of power electronic switch circuits.

[0012] Specifically, the connection structure between each group of power electronic switch circuits in the voltage-resistant power electronic switch module is an anti-series structure, an anti-parallel structure, a diode bridge structure, or a full-bridge structure.

[0013] Specifically, the off power electronic switch module comprises at least one group of power electronic switch circuits.

[0014] Specifically, the connection structure between each group of power electronic switch circuits in the off power electronic switch module is an anti-series structure, an anti-parallel structure, a diode bridge structure, or a full-bridge structure.

[0015] Specifically, each group of power electronic switch circuits comprises a power electronic switch, a buffer RC circuit, and an MOV.

[0016] Specifically, when the MOV voltage in the off power electronic switch module reaches the operating voltage of the MOV in the off power electronic switch module, the current is transferred from the buffer RC circuit to the MOV in the off power electronic switch module.

[0017] Optionally, the transfer branch further comprises a voltage-limiting element, and the voltage-limiting element is connected in series with the capacitor.

[0018] Specifically, the voltage-limiting element comprises an MOV and / or a discharge gap.

[0019] Specifically, the rated voltage of the voltage-limiting element is lower than the rated voltage of the MOV in the off power electronic switch module.

[0020] Optionally, the energy-absorbing branch further comprises an energy-absorbing branch switch connected in series with the energy-absorbing MOV, which is used to disconnect the energy-absorbing branch when the DC power grid is normal and to turn on the energy-absorbing branch when a short-circuit fault occurs.

[0021] Specifically, the energy-absorbing branch switch comprises a power electronic switch and / or a discharge gap.

[0022] Specifically, the power electronic switch is a controllable power electronic switch.

[0023] Specifically, the controllable power electronic switch comprises an IGCT, an IGBT, an IEGT, and a thyristor.

[0024] Based on the same inventive concept, the embodiment of the present application also provides a control method of a solid-state DC circuit breaker based on a composite power electronic switch, which is connected to a DC power grid, and when a short-circuit fault occurs in the DC power grid, the solid-state DC circuit breaker is used to cut off the short-circuit fault current in the DC power grid.

[0025] The above technical solution provided by the embodiment of the present application has at least the following beneficial effects:

[0026] For the DC power grid, the advantages of different power electronic devices are effectively utilized, and for the application scenario of high voltage and large current, a low-cost solid-state DC circuit breaker solution is proposed, which greatly reduces the number of devices, is convenient to maintain, and ensures the safe and reliable operation of the DC power grid.

[0027] Other features and advantages of the present application will be described in the following description, and some will become apparent from the description, or will be understood by those skilled in the art. The purpose and other advantages of the present application can be achieved and obtained by the structure specifically pointed out in the written description, claims, and drawings.

[0028] The technical solution of the present application will be further described in detail below by means of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings are used to provide a further understanding of the present application, and constitute a part of the specification, together with the embodiments of the present application, to explain the present application, and do not constitute a limitation of the present application. In the drawings:

[0030] Figure 1 is a structural schematic diagram of a solid-state DC circuit breaker based on a composite power electronic switch in the embodiment of the present application;

[0031] Figure 2 is a specific structural schematic diagram of a solid-state DC circuit breaker based on a composite power electronic switch in the embodiment of the present application;

[0032] Figure 3a is a schematic diagram of current flowing through the main current path under normal conditions of a DC power grid in the embodiment of the present application;

[0033] Figure 3b is a schematic diagram of current charging a capacitor through a buffer RC branch under a short-circuit fault condition in the embodiment of the present application;

[0034] Figure 3c is a schematic diagram of current commutation to a transfer branch under a short-circuit fault condition in the embodiment of the present application;

[0035] Figure 3dA schematic diagram for current diversion to the energy absorption branch under short-circuit fault condition in the embodiment of the present application. DETAILED DESCRIPTION

[0036] Exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it is understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure can be more thoroughly understood, and the scope of the present disclosure can be accurately conveyed to those skilled in the art.

[0037] To solve the problems in the prior art, the embodiment of the present application provides a solid-state DC circuit breaker based on a composite power electronic switch and a control method thereof.

[0038] The embodiment of the present application provides a solid-state DC circuit breaker based on a composite power electronic switch, which is applied in a DC power grid, and the structure thereof is shown in the figure. Figure 1 As shown in the figure, the solid-state DC circuit breaker comprises:

[0039] A main current branch, a diversion branch and an energy absorption branch, which are connected in parallel; as shown in the figure, the number of devices in the three branches is significantly reduced compared with the number of devices in the DC circuit breaker in the prior art, thereby reducing the cost and facilitating maintenance and management. Figure 1

[0040] The main current branch comprises a voltage-withstanding power electronic switch module and a turn-off power electronic switch module, which are used for current flow under normal conditions of the DC power grid and current buffering under short-circuit fault conditions, and the current is commutated to the diversion branch, and the voltage-withstanding power electronic switch module and the turn-off power electronic switch module are connected in series.

[0041] The diversion branch comprises a capacitor, which is used for receiving the current commutated from the main current branch under short-circuit fault conditions and diverting the current to the energy absorption branch; optionally, the diversion branch can further comprise a voltage limiting element, or the voltage limiting element can not be used, thereby reducing the number of devices.

[0042] ​The voltage limiting element is connected in series with the capacitor, and the voltage limiting element includes MOV and / or discharge gap, which can be selected according to actual conditions, so as to reduce cost and effectively utilize the advantages of different power electronic devices. The MOV refers to a metal oxide voltage limiter (MOV), which is a capacitor overvoltage protection device composed of a resistor with a nonlinear relationship between resistance and voltage, and can be used as a key component of a series resonant fault current limiter. The longer the short-circuit fault time, the more energy the MOV needs to absorb; and the length of the closing time of the fast switch determines the size of the energy absorbed by the MOV in a short time. The discharge gap, also known as a protection gap, is generally composed of two metal rods exposed to the air with a certain gap, one of which is connected to the power supply line or zero line of the device to be protected, and the other is connected to the ground line. When a transient overvoltage attacks, the gap is broken down, and part of the overvoltage charge is introduced into the ground, preventing the voltage on the protected device from rising.

[0043] The energy absorption branch includes an energy absorption MOV for absorbing the current transferred from the transfer branch in a short-circuit fault condition. The energy absorption MOV refers to a MOV for absorbing circuit energy.

[0044] Specifically, in a short-circuit fault condition, when the capacitor voltage in the transfer branch reaches the action voltage of the energy absorption MOV, the current is transferred from the transfer branch to the energy absorption branch.

[0045] Specifically, the voltage-resistant power electronic switch module includes at least one group of power electronic switch circuits.

[0046] Specifically, the connection structure between each group of power electronic switch circuits in the voltage-resistant power electronic switch module is an anti-series structure, or an anti-parallel structure, or a diode bridge structure, or a full-bridge structure.

[0047] Specifically, the off power electronic switch module includes at least one group of power electronic switch circuits.

[0048] Specifically, the connection structure between each group of power electronic switch circuits in the off power electronic switch module is an anti-series structure, or an anti-parallel structure, or a diode bridge structure, or a full-bridge structure, etc.

[0049] Specifically, each group of the power electronic switch circuit includes a power electronic switch, a buffer RC circuit and a MOV. The buffer RC circuit is composed of a resistor and a capacitor connected in series.

[0050] Specifically, when the MOV voltage in the off power electronic switch module reaches the action voltage of the MOV in the off power electronic switch module, the current is transferred from the buffer RC circuit to the MOV in the off power electronic switch module.

[0051] Specifically, the rated voltage of the voltage limiting element is lower than the rated voltage of the MOV in the off power electronic switch module.

[0052] Optionally, the energy absorbing branch further comprises an energy absorbing branch switch connected in series with the energy absorbing MOV, for opening the energy absorbing branch when the DC power grid is normal and closing the energy absorbing branch when a short-circuit fault occurs. The energy absorbing branch can also not be provided with an energy absorbing branch switch, thereby reducing the number of devices and helping to reduce costs and facilitate maintenance.

[0053] Specifically, the energy absorbing branch switch comprises a power electronic switch and / or a discharge gap.

[0054] Specifically, the power electronic switch is a controllable power electronic switch.

[0055] Specifically, the controllable power electronic switch comprises IGCT, IGBT, IEGT and thyristor, etc., which can be selected according to actual conditions, helping to reduce costs and effectively utilize the advantages of different power electronic devices. IGCT (Integrated Gate-Commutated Thyristor) refers to an integrated gate-commutated thyristor, which combines the stable off ability of a transistor and the low on-state loss advantage of a thyristor, and exhibits the performance of a thyristor in the on phase and the characteristics of a transistor in the off phase, with the characteristics of large current, high voltage, high switching frequency, high reliability, compact structure, low loss, etc., and low cost and high yield; IGBT (Insulated Gate Bipolar Transistor) refers to an insulated gate bipolar transistor, which has the advantages of high input impedance of a metal oxide semiconductor field effect transistor and low on voltage of a power transistor, with small driving power and low saturation voltage; IEGT (Injection Enhanced Gate Transistor) is an IGBT series power electronic device with a withstand voltage of 4KV or more, with the characteristics of low loss, high speed, high voltage, active gate drive intelligence, and self-current sharing characteristics of trench structure and multi-chip parallel connection; SCR (Silicon Controlled Rectifier) refers to a silicon controlled rectifier, also known as a thyristor, with the advantages of small size, fast reaction, opening and closing in microseconds, contactless operation, no spark, no noise, high efficiency, and low cost.

[0056] Taking IGCT as the power electronic switch on the main path, SCR as the power electronic switch on the energy absorbing branch, and MOV as the voltage limiting element on the transfer branch as an example, one of the topological structures of the solid-state DC circuit breaker is introduced, and the specific topological structure is as follows: Figure 2As shown. Since the embodiments of the application disclose that the transfer branch can include a voltage limiting element, and can also not use a voltage limiting element, the energy absorbing branch can be provided with an energy absorbing branch switch, or can not be provided, the connection structure between each group of power electronic switch circuits in the off power electronic switch module is a reverse series structure, or a reverse parallel structure, or a diode bridge structure, or a full bridge structure, etc., so the solid-state DC circuit breaker can have various topological structures or connection structures.

[0057] As shown in Figure 3a , under normal circumstances of the DC power grid, the power electronic switch on the energy absorbing branch is off, and the current flows through the power electronic switches V-IGCT and I-IGCT. Among them, multiple groups of V-IGCT circuits constitute a voltage-resistant power electronic switch module, and V-IGCT represents an IGCT power electronic switch used in the voltage-resistant power electronic switch module. Multiple groups of I-IGCT circuits constitute an off power electronic switch module, and I-IGCT represents an IGCT power electronic switch used in the off power electronic switch module. In Figure 3a , 3b , 3c and 3d, in order to make the current flow lines introduced in different stages more clear, the current flow lines introduced in this stage are represented by black straight lines, and the other lines are represented by light straight lines. When a short-circuit fault occurs in the DC power grid, the I-IGCT in the off power electronic switch module is off, and the power electronic switch on the energy absorbing branch is turned on. As shown in Figure 3b , in the off power electronic switch module, the fault current is commutated from the I-IGCT to the buffer RC branch composed of the resistor R2 and the capacitor C2, and the capacitor C2 is charged. When the voltage reaches the operating voltage of the clamping MOV2, the current is transferred from the buffer branch to the MOV2. Clamping refers to limiting the potential of a point to a specified potential to prevent the overvoltage protection object from being damaged, thereby improving the working stability of the entire circuit, which is an overvoltage protection technology. For example, the MOV2 is protected from overvoltage damage. The operating voltage refers to the threshold voltage for turning on or off the overvoltage protection of the MOV. At the same time, as shown in Figure 3c , since the rated voltage of the MOV3 on the transfer branch is lower than the rated voltage of the I-IGCT clamping MOV2, the current will be commutated towards the transfer branch due to the voltage difference. When all the current of the main current flow branch is commutated to the transfer branch, the V-IGCT devices in the voltage-resistant power electronic switch module on the main current flow branch are off without current, and start to withstand voltage. After the current is commutated to the transfer branch, the current charges the capacitor C f . As shown in Figure 3d , when the C f voltage reaches the operating voltage of the energy absorbing MOV4 in the energy absorbing branch, the current is transferred from the commutation branch to the energy absorbing branch. Finally, the energy absorbing branch absorbs the energy of the circuit, and completes the short-circuit fault current extinction in the DC power grid.

[0058] The solid-state DC circuit breaker in the embodiment effectively utilizes the advantages of different power electronic devices for a DC power grid, and proposes a low-cost solid-state DC circuit breaker scheme for a high-voltage and large-current application scenario, greatly reduces the number of devices, is convenient to maintain, and guarantees safe and reliable operation of the DC power grid.

[0059] Based on the same inventive concept, the embodiment of the present application also provides a control method of a solid-state DC circuit breaker based on a composite power electronic switch, which is used to connect a solid-state DC circuit breaker based on a composite power electronic switch to a DC power grid, and use the solid-state DC circuit breaker to cut off a short-circuit fault current in the DC power grid when a short-circuit fault occurs in the DC power grid.

[0060] As to the control method in the above embodiment, the specific operation of the solid-state DC circuit breaker to perform short-circuit fault current cutting has been described in detail in the embodiment of the solid-state DC circuit breaker based on the composite power electronic switch, and will not be described in detail here.

[0061] The control method in the embodiment of the present application effectively utilizes the advantages of different power electronic devices for a DC power grid, and proposes a low-cost solid-state DC circuit breaker scheme for a high-voltage and large-current application scenario, greatly reduces the number of devices, is convenient to maintain, and guarantees safe and reliable operation of the DC power grid.

[0062] Any modification, supplement, and equivalent replacement, etc. within the principle range of the present application shall still belong to the patent coverage range of the present application.

Claims

1. A solid-state DC circuit breaker based on a composite power electronic switch, applied in a DC power grid, characterized in that, include: The system includes a main flow branch, a transfer branch, and an energy-absorbing branch, which are connected in parallel. The main current-carrying branch includes a withstand voltage power electronic switch module and a shutdown power electronic switch module, used for current flow under normal DC grid conditions, buffering current under short-circuit fault conditions, and diverting current to the transfer branch. The withstand voltage power electronic switch module and the shutdown power electronic switch module are connected in series. The withstand voltage power electronic switch module includes at least two sets of power electronic circuits. Each set of power electronic circuits includes a power electronic switch v-IGCT connected in parallel, an R1C1 circuit connected in parallel with the power electronic switch v-IGCT, and a metal oxide voltage limiter MOV1 connected in parallel with the resistor-capacitor circuit. The shutdown power electronic switch module includes a power electronic switch i-IGCT connected in parallel, a buffer R2C2 circuit connected in parallel with the power electronic switch i-IGCT, and a metal oxide voltage limiter MOV2 connected in parallel with the buffer R2C2 circuit. The transfer branch includes a voltage limiting element and a capacitor C connected in series. f An inductor is used to receive the current commutated from the main current-carrying branch under short-circuit fault conditions and transfer the current to the energy-absorbing branch; the rated voltage of the voltage limiting element is lower than the rated voltage of the metal oxide voltage limiter MOV2 in the power electronic switch module. The energy-absorbing branch includes an energy-absorbing branch switch and a metal oxide voltage limiter MOV4 connected in series, used to absorb the current transferred from the transfer branch in the event of a short-circuit fault; the energy-absorbing branch switch is used to disconnect the energy-absorbing branch when the DC grid is normal, and to open the energy-absorbing branch when a short-circuit fault occurs. In the event of a short-circuit fault, when the capacitor C in the transfer branch... f When the voltage reaches the operating voltage of the metal oxide voltage limiter MOV4, the current is transferred from the transfer branch to the energy absorption branch.

2. A solid-state DC circuit breaker based on a composite power electronic switch as described in claim 1, characterized in that, The connection structure between each group of power electronic switch circuits in the withstand voltage power electronic switch module is an anti-series structure, or an anti-parallel structure, or a diode bridge structure, or a full-bridge structure.

3. A solid-state DC circuit breaker based on a composite power electronic switch as described in claim 1, characterized in that, When the voltage of the metal oxide voltage limiter MOV2 in the power-off switch module reaches the operating voltage of the metal oxide voltage limiter MOV2 in the power-off switch module, the current is transferred from the buffer R2C2 circuit to the metal oxide voltage limiter MOV2 in the power-off switch module.

4. A solid-state DC circuit breaker based on a composite power electronic switch as described in claim 1, characterized in that, The voltage limiting element includes a metal oxide voltage limiter MOV3 and / or a discharge gap.

5. A solid-state DC circuit breaker based on a composite power electronic switch as described in claim 1, characterized in that, The energy-absorbing branch switch includes a power electronic switch and / or a discharge gap.

6. A control method for a solid-state DC circuit breaker based on a composite power electronic switch, characterized in that, A solid-state DC circuit breaker based on a composite power electronic switch, as described in any one of claims 1-5, is connected to a DC power grid. When a short-circuit fault occurs in the DC power grid, the solid-state DC circuit breaker is used to cut off the short-circuit fault current in the DC power grid.

Images