Internal and external short-circuit protection circuits and control methods for bidirectional converters in rail transit

Abstract

This invention discloses a topology and control method for internal and external short-circuit protection of a bidirectional converter in rail transit. The protection topology includes one diode module and two thyristor modules. The AC input terminal of the diode module is connected to the inductor input terminal of the bidirectional converter, and the positive terminal of its DC side is connected to the anodes of the first and second thyristor modules respectively, while the negative terminal is connected to the negative terminal of the bidirectional converter. The cathodes of the first and second thyristor modules are connected to the positive and negative terminals of the DC side of the bidirectional converter respectively. During normal operation, the first and second thyristor modules are locked; when an external short circuit occurs, only the first thyristor module is activated; when an internal short circuit occurs, only the second thyristor module is activated. The internal and external short-circuit protection topology and control method proposed in this invention can suppress the short-circuit current flowing through the bidirectional converter in the event of an internal or external short circuit, avoiding damage to the inductor caused by the strong electrodynamic force generated by the short-circuit current and damage to the electromagnetically sensitive components inside the cabinet by strong electromagnetic interference.

Description

Technical Field

[0001] This invention relates to the field of rail transit, and more particularly to internal and external short-circuit protection circuits and control methods for bidirectional converters in rail transit. Background Technology

[0002] The current urban rail transit traction power supply system uses a 24-pulse rectifier unit plus a regenerative energy feedback device. This system suffers from problems such as uncontrollable contact network voltage during train traction, large voltage fluctuations, poor traction power supply voltage quality, high line losses, and significant cross-regional power supply issues. The mainstream solution currently is to use bidirectional converters. Bidirectional converters have four-quadrant operation capabilities, enabling precise control of the contact network voltage under different operating conditions. However, because bidirectional converters use fully controlled devices, their short-circuit withstand capability is poor compared to diode units. To ensure high-reliability operation of bidirectional converters, their short-circuit withstand capability needs further improvement.

[0003] Patent CN201611116262.X proposes a scheme of paralleling rectifier devices on IGBTs. However, during normal operation, a high-frequency circulating current problem exists between the rectifier devices and the anti-parallel diodes of the IGBTs. Patent CN202211114930.0 proposes a scheme of uncontrolled rectifier bridge + common-mode inductor, which suppresses high-frequency circulating current through the common-mode inductor. However, the increase in inductance increases the size and cost of the equipment, and the circulating current is only suppressed, still occurring in small amounts. Patents CN202210756980.2 and CN202111234189.7 propose a thyristor bypass scheme and a rectifier module + single thyristor scheme, respectively, to protect against external DC-side short circuits. However, when an IGBT shoot-through or short-circuit fault occurs inside the bidirectional converter, the short-circuit current will flow through the inductors and power modules inside the cabinet, generating large electrodynamic forces and strong electromagnetic interference, damaging the equipment inside the cabinet.

[0004] To address the shortcomings of existing technologies, this invention provides an internal and external short-circuit protection circuit and control method for a bidirectional converter in rail transit, which is used to solve internal and external short-circuit faults in the bidirectional converter and prevent short-circuit current from damaging the bidirectional converter equipment.

[0005] The present invention adopts the following technical solution.

[0006] The first aspect of this invention proposes an internal and external short-circuit protection circuit for a bidirectional converter in rail transit. An AC power supply is sequentially connected to the AC side of the bidirectional converter via a first switch and a transformer, while the DC side of the bidirectional converter is connected to a second switch. The bidirectional converter consists of an inductor and power units.

[0007] The internal and external short-circuit protection circuit includes one diode module and two thyristor modules;

[0008] The AC input terminal of the diode module is connected to the inductor input terminal of the bidirectional converter.

[0009] The DC positive output terminal of the diode module is connected to the DC positive terminal of the bidirectional converter through the first thyristor module.

[0010] The DC positive output terminal of the diode module is connected to the DC negative output terminal of the diode module through the second thyristor module.

[0011] The DC negative output terminal of the diode module is connected to the DC negative terminal of the bidirectional converter.

[0012] The internal short circuit fault refers to the power device shoot-through short circuit fault occurring inside the power unit. Short circuits between the AC side of the converter and ground, the positive DC side, and the negative DC side are also considered as internal short circuits. The external short circuit fault refers to the short circuit between the power unit and the second switch and the DC side short circuit occurring in the line after the second switch.

[0013] Preferably, the diode module topology is a three-phase bridge structure;

[0014] The sum of the equivalent on-resistance of the rectifier circuit diode in the diode module and the on-resistance of the first thyristor module is less than the on-resistance of the anti-parallel diode of the bidirectional converter power unit IGBT.

[0015] The sum of the equivalent on-resistance of the rectifier circuit diode in the diode module and the on-resistance of the second thyristor module is less than the on-resistance of the anti-parallel diode of the bidirectional converter power unit IGBT.

[0016] Preferably, the sum of the equivalent on-resistance of the rectifier circuit diode and the on-resistance of the first thyristor module, R1, is equal to the on-resistance of the IGBT anti-parallel diode, R... D The ratio is no greater than one-tenth;

[0017] The sum of the equivalent on-resistance of the rectifier circuit diode in the diode module and the on-resistance of the second thyristor module, R2, and the on-resistance of the IGBT anti-parallel diode, R... D The ratio is no greater than one-tenth.

[0018] Preferably, the first thyristor module 1 contains at least one thyristor. The number of thyristors is selected according to the magnitude of the external short-circuit current of the bidirectional converter, and the thyristors are connected in parallel.

[0019] The second thyristor module 2 contains at least one thyristor. The number of thyristors is selected according to the magnitude of the short-circuit current inside the bidirectional converter, and the thyristors operate in parallel.

[0020] Preferably, the control terminals of the first thyristor module and the second thyristor module are both connected to the bidirectional converter control device, and the bidirectional converter control device independently controls the conduction and blocking of the first thyristor module and the second thyristor module.

[0021] A second aspect of this invention provides a method for internal and external short-circuit protection control of a bidirectional converter for rail transit based on the protection topology described in the first aspect of this invention, comprising:

[0022] The bidirectional converter control device detects short-circuit faults in the bidirectional converter in real time, and both the first thyristor module and the second thyristor module are in a locked state.

[0023] When the bidirectional converter control and protection device detects a short circuit fault outside the bidirectional converter, it immediately controls the first thyristor module to conduct and keeps the second thyristor module locked.

[0024] If an external short-circuit fault is detected and cleared within a preset time T, the first thyristor module is locked out; otherwise, the thyristor module 1 remains on and a trip command is sent to the first and second switches. The first thyristor module 1 is locked out after the first and second switches trip.

[0025] When the bidirectional converter control and protection device detects a short circuit fault inside the bidirectional converter, it immediately controls the second thyristor module to conduct, keeps thyristor module 1 locked, and sends a trip command to the first and second switches. After the first and second switches trip, the second thyristor module is locked.

[0026] When the bidirectional converter control and protection device detects a short circuit fault both inside and outside the bidirectional converter, it immediately controls the first and second thyristor modules to conduct and sends a trip command to the first and second switches. After the first and second switches trip, the first and second thyristor modules are locked out.

[0027] Preferably, the condition for determining that a short circuit fault has occurred outside the bidirectional converter is: the DC side voltage of the bidirectional converter is less than the set DC voltage threshold Udcset or the DC side current of the bidirectional converter is greater than the set DC current threshold Idcset.

[0028] Preferably, the current-voltage threshold Udcset is set to 0.3 times the rated voltage V, and the DC current threshold Idcset is set to 1.5 times the rated current of the DC circuit.

[0029] Preferably, the preset time T is 80ms to 200ms.

[0030] Preferably, the condition for determining that a short circuit has occurred inside the bidirectional converter is:

[0031] The bidirectional converter's AC side current exceeds the AC threshold Iac_set, or the power module experiences an IGBT drive failure, or the voltage imbalance of the upper and lower capacitors on the DC side of the bidirectional converter exceeds the set imbalance threshold.

[0032] Preferably, the AC threshold Iac_set is 1.5 times the rated AC current;

[0033] The unbalance threshold is set to ensure that the capacitor voltage deviation does not exceed 15% of the rated voltage.

[0034] The beneficial effects of this invention are that, compared with the prior art, it considers both internal and external short-circuit faults. By controlling the thyristor module, in the event of an internal short-circuit fault, the fault short-circuit current is confined within the diode module, preventing excessive short-circuit current from flowing through the normal power module and the connected inductor, thus preventing the generation of strong electrodynamic forces and electromagnetic interference, and damage to inductors and other equipment. In the event of an external short-circuit fault, it can protect the power module inside the cabinet, continuously providing short-circuit current for the feeder switch to correctly clear the fault.

[0035] The short-circuit protection circuit only includes diode modules and thyristor modules. The number of first and second thyristors is selected according to the magnitude of the internal and external short-circuit currents of the bidirectional converter. This saves costs and reduces size while ensuring high reliability of the bidirectional converter. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the internal and external short-circuit protection circuit of the bidirectional converter for rail transit in this invention;

[0037] Figure 2 This is a schematic diagram of the control method for the internal and external short-circuit protection circuit of the bidirectional converter for rail transit according to the present invention;

[0038] Figure 1 Explanation of the designations: 1. Bidirectional converter; 2. Inductor; 3. Power unit; 4. Internal and external short-circuit protection circuit; 5. Diode module; 6. First thyristor module; 7. Second thyristor module; 8. Transformer; 9. First switch; 10. Second switch. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0041] like Figure 1 As shown, Embodiment 1 of the present invention provides an internal and external short-circuit protection circuit for a bidirectional converter in rail transit. An AC power supply is connected to the AC side of the bidirectional converter via a first switch and a transformer in sequence, while the DC side of the bidirectional converter is connected to a second switch. The bidirectional converter consists of an inductor and power units.

[0042] The internal and external short-circuit protection circuit includes one diode module and two thyristor modules;

[0043] The AC input terminal of the diode module is connected to the inductor input terminal of the bidirectional converter.

[0044] The DC positive output terminal of the diode module is connected to the DC positive terminal of the bidirectional converter through the first thyristor module.

[0045] The DC positive output terminal of the diode module is connected to the DC negative output terminal of the diode module through the second thyristor module.

[0046] The DC negative output terminal of the diode module is connected to the DC negative terminal of the bidirectional converter.

[0047] The internal short circuit fault refers to the power device shoot-through short circuit fault occurring inside the power unit. Short circuits between the AC side of the converter and ground, the positive DC side, and the negative DC side are also considered as internal short circuits. The external short circuit fault refers to the short circuit between the power unit and the second switch and the DC side short circuit occurring in the line after the second switch.

[0048] Preferably, the diode module topology is a three-phase bridge structure;

[0049] The sum of the equivalent on-resistance of the rectifier circuit diode in the diode module and the on-resistance of the first thyristor module is less than the on-resistance of the anti-parallel diode of the bidirectional converter power unit IGBT.

[0050] The sum of the equivalent on-resistance of the rectifier circuit diode in the diode module and the on-resistance of the second thyristor module is less than the on-resistance of the anti-parallel diode of the bidirectional converter power unit IGBT.

[0051] Preferably, the sum of the equivalent on-resistance of the rectifier circuit diode and the on-resistance of the first thyristor module, R1, is equal to the on-resistance of the IGBT anti-parallel diode, R... D The ratio is no greater than one-tenth;

[0052] The sum of the equivalent on-resistance of the rectifier circuit diode in the diode module and the on-resistance of the second thyristor module, R2, and the on-resistance of the IGBT anti-parallel diode, R... D The ratio of 'bar' is no more than one-tenth.

[0053] Specifically, in this embodiment, both of the above-mentioned ratios are one-tenth.

[0054] Preferably, the first thyristor module contains at least one thyristor. The number of thyristors is selected according to the magnitude of the external short-circuit current of the bidirectional converter, and the thyristors are connected in parallel.

[0055] The second thyristor module contains at least one thyristor. The number of thyristors is selected according to the magnitude of the short-circuit current inside the bidirectional converter, and the thyristors operate in parallel.

[0056] Preferably, the control terminals of the first thyristor module and the second thyristor module are both connected to the bidirectional converter control device, and the bidirectional converter control device independently controls the conduction and blocking of the first thyristor module and the second thyristor module.

[0057] The bidirectional converter control and protection device is connected to the first thyristor module and the second thyristor module via optical fiber.

[0058] like Figure 2 As shown, Embodiment 2 of the present invention provides a method for internal and external short-circuit protection control of a bidirectional converter for rail transit based on the protection topology described in Embodiment 1, comprising:

[0059] The bidirectional converter control device detects short-circuit faults in the bidirectional converter in real time, and both the first thyristor module and the second thyristor module are in a locked state.

[0060] When the bidirectional converter control and protection device detects a short circuit fault outside the bidirectional converter, it immediately controls the first thyristor module to conduct and keeps the second thyristor module locked.

[0061] If an external short-circuit fault is detected and cleared within a preset time T, the first thyristor module is locked out; otherwise, the thyristor module 1 remains on and a trip command is sent to the first and second switches. The first thyristor module 1 is locked out after the first and second switches trip.

[0062] When the bidirectional converter control and protection device detects a short circuit fault inside the bidirectional converter, it immediately controls the second thyristor module to conduct, keeps thyristor module 1 locked, and sends a trip command to the first and second switches. After the first and second switches trip, the second thyristor module is locked.

[0063] When the bidirectional converter control and protection device detects a short circuit fault both inside and outside the bidirectional converter, it immediately controls the first and second thyristor modules to conduct and sends a trip command to the first and second switches. After the first and second switches trip, the first and second thyristor modules are locked out.

[0064] Preferably, the condition for determining that a short circuit fault has occurred outside the bidirectional converter is: the DC side voltage of the bidirectional converter is less than the set DC voltage threshold Udcset or the DC side current of the bidirectional converter is greater than the set DC current threshold Idcset.

[0065] Preferably, the current-voltage threshold Udcset is set to 0.3 times the rated voltage, and the DC current threshold Idcset is set to 1.5 times the rated DC circuit current.

[0066] Preferably, the preset time T is 80ms to 200ms.

[0067] Specifically, in this embodiment, the preset time is selected as 120ms.

[0068] Preferably, the condition for determining that a short circuit has occurred inside the bidirectional converter is:

[0069] The bidirectional converter's AC side current exceeds the AC threshold Iac_set, or the power module experiences an IGBT drive failure, or the voltage imbalance of the upper and lower capacitors on the DC side of the bidirectional converter exceeds the set imbalance threshold.

[0070] Preferably, the AC threshold Iac_set is 1.5 times the rated AC current;

[0071] The unbalance threshold is set to ensure that the capacitor voltage deviation does not exceed 15% of the rated voltage.

[0072] The beneficial effects of this invention are that, compared with the prior art, it considers both internal and external short-circuit faults. By controlling the thyristor module, in the event of an internal short-circuit fault, the fault short-circuit current is confined within the diode module, preventing excessive short-circuit current from flowing through the normal power module and the connected inductor, thus preventing the generation of strong electrodynamic forces and electromagnetic interference, and damage to inductors and other equipment. In the event of an external short-circuit fault, it can protect the power module inside the cabinet, continuously providing short-circuit current for the feeder switch to correctly clear the fault.

[0073] The short-circuit protection circuit only includes diode modules and thyristor modules. The number of first and second thyristors is selected according to the magnitude of the internal and external short-circuit currents of the bidirectional converter. This saves costs and reduces size while ensuring the high reliability of the bidirectional converter.

[0074] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0075] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0076] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0077] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. An internal and external short-circuit protection circuit for a bidirectional converter in rail transit, wherein the AC power supply is connected to the AC side of the bidirectional converter sequentially through a first switch and a transformer, and the DC side of the bidirectional converter is connected to a second switch; the bidirectional converter is composed of inductors and power units, characterized in that, The internal and external short-circuit protection circuit includes one diode module and two thyristor modules; The AC input terminal of the diode module is connected to the inductor input terminal of the bidirectional converter. The DC positive output terminal of the diode module is connected to the DC positive terminal of the bidirectional converter through the first thyristor module. The DC positive output terminal of the diode module is connected to the DC negative output terminal of the diode module through the second thyristor module. The DC negative output terminal of the diode module is connected to the DC negative terminal of the bidirectional converter. Internal short circuit faults are power device shoot-through short circuit faults occurring within the power unit. Short circuits on the AC side of the converter to ground, to the positive DC side, and to the negative DC side are also considered internal short circuits. External short circuit faults are short circuits between the power unit and the second switch, and DC side short circuits occurring in the lines after the second switch. When the bidirectional converter control and protection device detects a short circuit fault outside the bidirectional converter, it immediately controls the first thyristor module to conduct and keeps the second thyristor module locked. When the bidirectional converter control and protection device detects a short circuit fault inside the bidirectional converter, it immediately controls the second thyristor module to conduct, keeps the first thyristor module locked, and sends a trip command to the first and second switches. After the first and second switches trip, the second thyristor module is locked.

2. The internal and external short-circuit protection circuit for the bidirectional converter of rail transit according to claim 1, characterized in that: The diode module topology is a three-phase bridge structure; The sum of the equivalent on-resistance of the rectifier circuit diode in the diode module and the on-resistance of the first thyristor module is less than the on-resistance of the anti-parallel diode of the bidirectional converter power unit IGBT. The sum of the equivalent on-resistance of the rectifier circuit diode in the diode module and the on-resistance of the second thyristor module is less than the on-resistance of the anti-parallel diode of the bidirectional converter power unit IGBT.

3. The internal and external short-circuit protection circuit for the bidirectional converter of rail transit according to claim 1, characterized in that: The sum of the equivalent on-resistance of the rectifier circuit diode in the diode module and the on-resistance of the first thyristor module. On-resistance of the diode connected in anti-parallel with the IGBT The ratio is no greater than one-tenth; The sum of the equivalent on-resistance of the rectifier circuit diode in the diode module and the on-resistance of the second thyristor module. On-resistance of the diode connected in anti-parallel with the IGBT The ratio is no greater than one-tenth.

4. The internal and external short-circuit protection circuit for the bidirectional converter of rail transit according to claim 1, characterized in that: The first thyristor module contains at least one thyristor. The number of thyristors is selected according to the magnitude of the external short-circuit current of the bidirectional converter, and the thyristors are connected in parallel. The second thyristor module contains at least one thyristor. The number of thyristors is selected according to the magnitude of the short-circuit current inside the bidirectional converter, and the thyristors operate in parallel.

5. The internal and external short-circuit protection circuit for the bidirectional converter of rail transit according to claim 1 or 4, characterized in that: The control terminals of the first thyristor module and the second thyristor module are both connected to the bidirectional converter control device, which independently controls the conduction and blocking of the first thyristor module and the second thyristor module.

6. A method for internal and external short-circuit protection control of a bidirectional converter for rail transit based on the protection circuit described in any one of claims 1-4, characterized in that, The method includes: The bidirectional converter control device detects short-circuit faults in the bidirectional converter in real time, and both the first thyristor module and the second thyristor module are in a locked state. When the bidirectional converter control and protection device detects a short circuit fault outside the bidirectional converter, it immediately controls the first thyristor module to conduct and keeps the second thyristor module locked. If an external short-circuit fault is detected and cleared within a preset time T, the first thyristor module is locked; otherwise, the first thyristor module remains on and a trip command is sent to the first and second switches. The first thyristor module is locked after the first and second switches trip. When the bidirectional converter control and protection device detects a short circuit fault inside the bidirectional converter, it immediately controls the second thyristor module to conduct, keeps the first thyristor module locked, and sends a trip command to the first and second switches. After the first and second switches trip, the second thyristor module is locked. When the bidirectional converter control and protection device detects a short circuit fault both inside and outside the bidirectional converter, it immediately controls the first and second thyristor modules to conduct and sends a trip command to the first and second switches. After the first and second switches trip, the first and second thyristor modules are locked out.

7. The method for internal and external short-circuit protection control of a bidirectional converter for rail transit according to claim 6, characterized in that: The conditions for determining that a short circuit fault has occurred outside the bidirectional converter are: the DC side voltage of the bidirectional converter is less than the set DC voltage threshold Udcset or the DC side current of the bidirectional converter is greater than the set DC current threshold Idcset.

8. The method for internal and external short-circuit protection control of a bidirectional converter for rail transit according to claim 7, characterized in that: The DC voltage threshold Udcset is set to 0.3 times the rated voltage, and the DC current threshold Idcset is set to 1.5 times the rated DC circuit current.

9. The method for internal and external short-circuit protection control of a bidirectional converter for rail transit according to claim 6, characterized in that: The preset time T is 80ms to 200ms.

10. The method for internal and external short-circuit protection control of a bidirectional converter for rail transit according to claim 6 or 7, characterized in that: The conditions for determining if a short circuit has occurred inside a bidirectional converter are: The bidirectional converter's AC side current exceeds the AC threshold Iac_set, or the power module experiences an IGBT drive failure, or the voltage imbalance of the upper and lower capacitors on the DC side of the bidirectional converter exceeds the set imbalance threshold.

11. The method for internal and external short-circuit protection control of a bidirectional converter for rail transit according to claim 10, characterized in that: The AC threshold Iac_set is 1.5 times the rated AC current.

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