Enhanced bidirectional converter with built-in rectifier and control method thereof

Abstract

The invention relates to the technical field of urban rail transit power supply, in particular to an enhanced bidirectional converter with a built-in rectifier and a control method of the enhanced bidirectional converter. Comprising an axial double-split four-winding transformer, a switch assembly, a first rectifier assembly, a second rectifier assembly, a first thyristor and a second thyristor. The input end of the axial double-column four-winding transformer is connected with a power grid, and the output end of the axial double-column four-winding transformer comprises a plurality of taps; the switch assembly comprises a plurality of switch pieces, and the switch state of the plurality of switch pieces corresponds to the current operation mode of the enhanced bidirectional converter with the built-in rectifier; one side of the first rectifier assembly and one side of the second rectifier assembly are both connected with the switch assembly, the other side of the first rectifier assembly is connected with the first thyristor, and the other side of the second rectifier assembly is connected with the second thyristor. Therefore, by fusing the advantages of the diode rectifier and the IGBT-based bidirectional converter, the problems of relatively high cost, relatively high occupied area, insufficient reliability of a power supply system and the like in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of urban rail transit power supply, and in particular to an enhanced bidirectional converter with a built-in rectifier and a control method thereof. Background Art

[0002] Urban rail transit systems usually use uncontrolled diode rectifiers to provide DC power to drive track traction. However, this power supply method has the disadvantages of large fluctuations in power supply voltage and the need to consume braking energy through resistors during locomotive braking. The use of bidirectional AC to DC controllable converter technology can effectively stabilize the traction DC power supply and reversely feed back energy to the power grid during braking, thereby saving electricity. However, since the bidirectional controllable converter uses more electronic components, especially controllable IGBT (Insulated Gate Bipolar Transistor) devices, its ability to withstand shock is weak, resulting in overall reliability inferior to that of uncontrolled diode rectifiers. Therefore, when using bidirectional AC to DC controllable converter technology to realize traction power supply, it is necessary to explore a high-reliability converter circuit topology to solve the problem of insufficient reliability of the controllable converter.

[0003] In the related art, a traction power supply network and a traction power supply system propose a solution of connecting a diode rectifier and a PWM (Pulse Width Modulation) bidirectional converter to the traction network using a switching device. This solution realizes cold standby of the rectifier and the bidirectional converter only by switching the switch.

[0004] However, this method fails to effectively solve the problem of improving the reliability of the power supply system and urgently needs to be improved. Summary of the invention

[0005] The present invention provides an enhanced bidirectional converter with a built-in rectifier and a control method thereof to solve the problems of the prior art such as large cost and large space occupied, insufficient reliability of the power supply system, etc., which not only improves the fault ride-through capability of the equipment and enhances reliability, but is also more economical.

[0006] To achieve the above-mentioned object, the first embodiment of the present invention proposes an enhanced bidirectional converter with a built-in rectifier, comprising: an axial dual-column four-winding transformer, a switch component, a first rectifier component and a second rectifier component, a first thyristor and a second thyristor, wherein:

[0007] The input end of the axial double-column four-winding transformer is connected to the power grid, and the output end of the axial double-column four-winding transformer includes a plurality of taps;

[0008] The switch assembly includes a plurality of switch elements, and the switch states of the plurality of switch elements correspond to the current operation mode of the enhanced bidirectional converter with a built-in rectifier;

[0009] One side of the first rectifier component and the second rectifier component are both connected to the switch component, the other side of the first rectifier component is connected to the first thyristor, and the other side of the second rectifier component is connected to the second thyristor.

[0010] According to one embodiment of the present invention, the axial dual-column four-winding transformer includes first to fourth taps.

[0011] According to one embodiment of the present invention, the switch assembly comprises:

[0012] a first switch, wherein one end of the first switch is connected to the third tap of the axial dual-column four-winding transformer, and the other end of the first switch is connected to the first end of the first rectifier assembly;

[0013] a second switch, wherein one end of the second switch is connected to the first tap of the axially dual-split four-winding transformer, and the other end of the second switch is connected to the second end of the first rectifier assembly;

[0014] a third switch, one end of the third switch being connected to a fourth tap of the axially dual-column four-winding transformer, and the other end of the third switch being connected to a second end of the second rectifier assembly;

[0015] a fourth switch, one end of the fourth switch being connected to the second tap of the axial dual-column four-winding transformer, and the other end of the fourth switch being connected to the first end of the second rectifier assembly;

[0016] a fifth switch, one end of the fifth switch being respectively connected to the first end of the first rectifier assembly and the other end of the first switch, and the other end of the fifth switch being respectively connected to the second end of the first rectifier assembly and the other end of the second switch;

[0017] A sixth switch, one end of which is respectively connected to the first end of the second rectifier assembly and the other end of the fourth switch, and the other end of which is respectively connected to the second end of the second rectifier assembly and the other end of the third switch.

[0018] According to one embodiment of the present invention, the first switch, the second switch, the third switch and the fourth switch are all three-phase AC circuit breakers;

[0019] The fifth switch and the sixth switch are both three-phase AC isolating switches.

[0020] According to one embodiment of the present invention, the first rectifier component comprises:

[0021] a first 6-pulse rectifier, one end of the first 6-pulse rectifier being respectively connected to the other end of the second switch and one end of the fifth switch;

[0022] A first bidirectional converter, one end of which is connected to the other end of the fifth switch and the other end of the first switch respectively.

[0023] According to one embodiment of the present invention, the second rectifier assembly comprises:

[0024] a second 6-pulse rectifier, one end of the second 6-pulse rectifier being connected to the other end of the fourth switch and one end of the sixth switch respectively;

[0025] A second bidirectional converter, one end of which is connected to the other end of the third switch and the other end of the sixth switch respectively.

[0026] According to an embodiment of the present invention, both the first 6-pulse rectifier and the second 6-pulse rectifier are three-phase full-bridge topologies formed by diodes.

[0027] According to an embodiment of the present invention, both the first bidirectional converter and the second bidirectional converter adopt a two-level full-bridge topology or a multi-level full-bridge topology.

[0028] The enhanced bidirectional converter with built-in rectifier proposed in the embodiment of the present invention solves the problems of large cost and space occupation, insufficient reliability of power supply system and the like of the prior art by integrating the advantages of diode rectifier and IGBT-based bidirectional converter. It not only improves the fault ride-through capability of the equipment and enhances reliability, but is also more economical.

[0029] To achieve the above object, a second aspect of the present invention provides a control method for an enhanced bidirectional converter with a built-in rectifier, using the enhanced bidirectional converter with a built-in rectifier as described in the first aspect of the present invention, wherein the method comprises the following steps:

[0030] Get the current operation mode of the enhanced bidirectional converter with built-in rectifier;

[0031] If the current operation mode is the bidirectional converter operation mode, the first switch, the third switch, the fifth switch and the sixth switch are controlled to be closed, the second switch and the fourth switch are disconnected, and it is detected whether the enhanced bidirectional converter with a built-in rectifier is in a fault mode;

[0032] If the enhanced bidirectional converter with a built-in rectifier is in a fault mode, the first thyristor and the second thyristor are triggered.

[0033] According to one embodiment of the present invention, after obtaining the current operation mode of the enhanced bidirectional converter with a built-in rectifier, the method further includes:

[0034] If the current operation mode is a diode rectifier operation mode, the first switch, the third switch, the fifth switch and the sixth switch are controlled to be opened, and the second switch and the fourth switch are closed, and the first thyristor and the second thyristor are controlled to be in a triggered state.

[0035] According to the control method of the enhanced bidirectional converter with built-in rectifier proposed in the embodiment of the present invention, by integrating the advantages of the diode rectifier and the IGBT-based bidirectional converter, an enhanced bidirectional converter with built-in rectifier is designed, which solves the problems of the prior art such as large cost and large space, insufficient reliability of the power supply system, etc., and not only improves the fault ride-through capability of the equipment and enhances reliability, but is also more economical.

[0036] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0038] Figure 1 A schematic diagram of the structure of an enhanced bidirectional converter with a built-in rectifier provided according to an embodiment of the present invention;

[0039] Figure 2 A schematic diagram of a one-phase winding of an axial double-split four-winding transformer according to an embodiment of the present invention;

[0040] Figure 3 A schematic diagram of a one-phase winding of an axial double-split four-winding transformer with taps added according to an embodiment of the present invention;

[0041] Figure 4 The present invention is a flow chart of a control method of an enhanced bidirectional converter with a built-in rectifier provided in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0042] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0043] The following describes an enhanced bidirectional converter with a built-in rectifier and a control method thereof according to an embodiment of the present invention with reference to the accompanying drawings.

[0044] Figure 1 It is a schematic structural diagram of an enhanced bidirectional converter with a built-in rectifier according to an embodiment of the present invention.

[0045] Before introducing the enhanced bidirectional converter with built-in rectifier proposed in the embodiment of the present invention, the relevant technical background is first introduced.

[0046] my country's urban rail transit system generally adopts 1500V or 750V DC power supply mode. The main substation is responsible for reducing the 110kV AC power of the urban power grid to 35kV or 10kV, which serves as a centralized or decentralized external power supply for the traction power supply system. The traction transformer in the traction substation (hereinafter referred to as the traction substation) further reduces the voltage, and then converts it into DC power through a 12 or 24-pulse diode rectifier unit to provide energy for the locomotive. Although the diode rectifier unit has advantages such as simple structure and strong current carrying capacity, it also has disadvantages such as unidirectional power flow, unadjustable DC voltage, large voltage drop during commutation, high DC harmonic content, and low power factor.

[0047] To solve the above problems, a bidirectional converter device was developed by introducing fully controlled power semiconductor devices such as insulated gate bipolar thyristors (IGBTs) and advanced technologies such as pulse width modulation. This device decouples the AC grid from the DC traction grid, allowing the DC voltage to be independently controlled, and thus allowing the power between traction stations to be quickly dispatched. This has become the core path to achieve new energy consumption, renewable energy utilization, and reduce grid losses.

[0048] As the bidirectional converter is transformed from single traction station grid operation to full-line equipment, it will completely replace the rectifier unit power supply and further become the direct executor of the DC voltage support and power rapid regulation of the entire line. Based on the analysis of national subway needs, the bidirectional converter faces the following challenges:

[0049] (1) Challenges in short-circuit fault tolerance. Due to the inherent insufficient overcurrent capacity of IGBT, IGBT-based converters are inferior to diode converters in terms of overcurrent capacity. Therefore, they must be equipped with more comprehensive protection and heat dissipation mechanisms, but this leads to increased costs and space requirements. In addition, the reliability of flexible DC converters based on IGBT semiconductor devices and high-precision control systems has not yet been widely recognized in the industry.

[0050] (2) Reliability challenge. The safety of urban rail transit has become the cornerstone of urban safety. Compared with traditional rectifier units, the reliability improvement of bidirectional converters has become the key to industrial application due to the introduction of fully controlled IGBTs and control circuits. Effective measures need to be taken from multiple perspectives such as technology research and development and industrial implementation to ensure the stable operation of the equipment.

[0051] (3) The challenge of adaptability of civil engineering space. Limited by the civil engineering space of underground traction stations, the size of bidirectional converters is one of the biggest obstacles to their industrial application, especially in existing lines. How to further improve power density and reduce size through more compact design will strongly promote the industrial application of bidirectional converters.

[0052] It is based on the above problems that the embodiments of the present invention propose an enhanced bidirectional converter with a built-in rectifier. By integrating the advantages of a diode rectifier and an IGBT-based bidirectional converter, it solves the problems of the existing technology, such as large cost and footprint, and insufficient reliability of the power supply system. It not only improves the fault-crossing capability of the equipment and enhances reliability, but is also more economical.

[0053] Next, the enhanced bidirectional converter with built-in rectifier will be described in detail.

[0054] For example, Figure 1 As shown, the enhanced bidirectional converter 10 with built-in rectifier includes: an axial dual-column four-winding transformer B1, a switch component 100, a first rectifier component 200 and a second rectifier component 300, a first thyristor T1 and a second thyristor T2, wherein the input end of the axial dual-column four-winding transformer B1 is connected to the power grid, and the output end of the axial dual-column four-winding transformer B1 includes multiple taps; the switch component 100 includes multiple switch elements, and the switching states of the multiple switch elements correspond to the current operating mode of the enhanced bidirectional converter 10 with built-in rectifier; one side of the first rectifier component 200 and the second rectifier component 300 are both connected to the switch component 100, the other side of the first rectifier component 200 is connected to the first thyristor T1, and the other side of the second rectifier component 300 is connected to the second thyristor T2.

[0055] Specifically, the enhanced bidirectional converter 10 with built-in rectifier includes an axial double-column four-winding transformer B1, which is a rectifier transformer commonly used in 12-pulse rectifiers in DC traction power supply systems. Figure 2 , Figure 2 A schematic diagram of one phase winding of the transformer is shown in FIG. Figure 2As shown in the figure, H1 and H2 represent two split windings on the primary side, and L1 and L2 represent two windings on the secondary side. The design feature of this transformer is that its split reactance value can be greater than 20%, which enables it to effectively reduce the critical current I that may appear during the operation of the 12-pulse rectifier unit. dg . Critical current I dg The reduction of can reduce equipment failure and maintenance costs caused by excessive current, which is of great significance for improving the stability and reliability of the entire power supply system. The axial double-column four-winding transformer B1 has an input end and an output end, such as Figure 1 As shown, its input terminal is used to connect directly to the grid, thereby allowing the converter to receive AC power from the grid. The output terminal of the axial double-column four-winding transformer B1 is configured with multiple taps, which can provide different voltage levels to adapt to different operating conditions and load requirements.

[0056] In addition, the enhanced bidirectional converter 10 with built-in rectifier further includes a switch assembly 100, which is composed of a plurality of switch elements. The switching states of these switch elements are controlled according to the current operation mode of the enhanced bidirectional converter 10 with built-in rectifier. By accurately controlling the switching state of the switch assembly 100, fine management of current flow and power flow can be achieved.

[0057] The first rectifier component 200 and the second rectifier component 300 are key components of the enhanced bidirectional converter 10 with built-in rectifiers, responsible for converting AC power into DC power. One side of these two components is connected to the switch component 100, ensuring that they can receive AC power from the switch component 100. The other side of the first rectifier component 200 is connected to the first thyristor T1, while the other side of the second rectifier component 300 is connected to the second thyristor T2. The first thyristor T1 and the second thyristor T2 are key components for controlling the direction of current and adjusting the current size, which can ensure that the converter can operate effectively in different working modes.

[0058] Optionally, in some embodiments, Figure 1 As shown, the axial dual-column four-winding transformer B1 includes first to fourth taps a1-a4.

[0059] Specifically, in a specific embodiment of the present invention, Figure 2 The two secondary windings of the transformer shown are improved by adding multiple taps. Figure 3 As shown, Figure 3 The taps a1, a2, a3 and a4 are Figure 1 The tap positions described in are corresponding, thereby optimizing the transformer performance.

[0060] It is understandable that in a DC traction power supply system, the transformer tap parameters refer to different voltage levels at the transformer output terminals, which allow the power supply system to provide different voltage values ​​as needed, which is essential to ensure the normal operation of the power supply system and the compatibility of the equipment. In an embodiment of the present invention, the transformer tap parameters are determined as follows:

[0061] (1) For a 1500Vdc (i.e. 1500 volts direct current) DC traction power supply system, the typical voltage value of taps a1 and a2 can be 1180V-1200Vac (i.e. 1180 to 1200 volts alternating current); the typical voltage value of taps a3 and a4 can be 900Vac (i.e. 900 volts alternating current).

[0062] (2) For a 750Vdc (i.e. 750 volts direct current) DC traction power supply system, the typical voltage value of taps a1 and a2 can be 590V-600Vac (i.e. 590 to 600 volts alternating current); the typical voltage value of taps a3 and a4 can be 450Vac (i.e. 450 volts alternating current).

[0063] Optionally, in some embodiments, Figure 1 As shown, the switch assembly 100 includes: first to fourth switches K1-K4 and fifth to sixth switches S1-S2, wherein one end of the first switch K1 is connected to the third tap a3 of the axial dual-column four-winding transformer B1, and the other end of the first switch K1 is connected to the first end of the first rectifier assembly 200; one end of the second switch K2 is connected to the first tap a1 of the axial dual-column four-winding transformer B1, and the other end of the second switch K2 is connected to the second end of the first rectifier assembly 200; one end of the third switch K3 is connected to the fourth tap a4 of the axial dual-column four-winding transformer B1, and the other end of the third switch K3 is connected to the second end of the second rectifier assembly 300. one end of the fourth switch K4 is connected to the second tap a2 of the axial dual-column four-winding transformer B1, and the other end of the fourth switch K4 is connected to the first end of the second rectifier assembly 300; one end of the fifth switch S1 is respectively connected to the first end of the first rectifier assembly 200 and the other end of the first switch K1, and the other end of the fifth switch S1 is respectively connected to the second end of the first rectifier assembly 200 and the other end of the second switch K2; one end of the sixth switch S2 is respectively connected to the first end of the second rectifier assembly 300 and the other end of the fourth switch K4, and the other end of the sixth switch S2 is respectively connected to the second end of the second rectifier assembly 300 and the other end of the third switch K3.

[0064] Furthermore, in some embodiments, the first switch K1 , the second switch K2 , the third switch K3 and the fourth switch K4 are all three-phase AC circuit breakers; the fifth switch S1 and the sixth switch S2 are all three-phase AC isolating switches.

[0065] It can be understood that a three-phase AC circuit breaker is an electrical switching device used in power systems. It is capable of cutting off and connecting the current in a three-phase AC circuit, and is mainly used to protect the circuit from overload or short circuit. Three-phase AC refers to three ACs with the same frequency and a phase difference of 120 degrees. The "three-phase" of the circuit breaker means that it can handle three phases of electricity at the same time, ensuring the safety and stability of the entire power supply system. The three-phase AC isolating switch is a switching device used in power systems that can cut off or connect a three-phase AC circuit, but does not have the function of switching load current. This switch is mainly used to ensure that the circuit can be safely isolated when maintaining or repairing the circuit to prevent the current from accidentally flowing into the work area.

[0066] Through this configuration, the switch assembly 100 can be flexibly switched in different working modes to ensure efficient transmission and conversion of electric energy. The first to fourth switches K1-K4 are mainly responsible for adjusting the current flow between the axial dual-column four-winding transformer B1 and the first rectifier assembly 200 and the second rectifier assembly 300, while the fifth to sixth switches S1-S2 are used to realize the current division and merging inside the first and second rectifier assemblies. This design not only improves the stability and reliability of the system, but also significantly improves the overall efficiency of the converter.

[0067] Optionally, in some embodiments, Figure 1 As shown, the first rectifier component 200 includes: a first six-pulse rectifier 201 and a first bidirectional converter 202, wherein one end of the first six-pulse rectifier 201 is respectively connected to the other end of the second switch K2 and one end of the fifth switch S1; one end of the first bidirectional converter 202 is respectively connected to the other end of the fifth switch S1 and the other end of the first switch K1.

[0068] Specifically, in the embodiment of the present invention, the first rectifier assembly 200 is designed to include two main parts, namely, a first 6-pulse rectifier (DIODE, crystal diode) 201 and a first bidirectional converter (Voltage Source Converter, VSC for short) 202. One end of the first 6-pulse rectifier 201 is connected to the other end of the second switch K2 through a connection point, and it is also connected to one end of the fifth switch S1. Such a design ensures that the current can flow to the first 6-pulse rectifier 201 through the second switch K2, and can also flow to the first 6-pulse rectifier 201 through the fifth switch S1. On the other hand, one end of the first bidirectional converter 202 is also connected to the other end of the fifth switch S1 through a connection point, and it is also connected to the other end of the first switch K1. This connection method allows the current to flow bidirectionally between the first bidirectional converter 202 and the first switch K1. Through this structure, the first rectifier assembly 200 can effectively convert AC power into DC power, and can control the flow direction of the current, thereby achieving efficient operation of the power system.

[0069] Optionally, in some embodiments, Figure 1 As shown, the second rectifier component 300 includes: a second six-pulse rectifier 301 and a second bidirectional converter 302, wherein one end of the second six-pulse rectifier 301 is respectively connected to the other end of the fourth switch K4 and one end of the sixth switch S2; one end of the second bidirectional converter 302 is respectively connected to the other end of the third switch K3 and the other end of the sixth switch S2.

[0070] That is to say, similar to the first rectifier assembly 200, the second rectifier assembly 300 includes two parts, namely, a second 6-pulse rectifier 301 and a second bidirectional converter 302. One end of the second 6-pulse rectifier 301 is connected to the other end of the fourth switch K4 and one end of the sixth switch S2 through a connection point; at the same time, one end of the second bidirectional converter 302 is also connected to the other end of the third switch K3 and the other end of the sixth switch S2 through a connection point. This design enables the second rectifier assembly 300 to effectively perform power conversion and control, ensuring efficient operation of the entire system.

[0071] Optionally, in some embodiments, both the first six-pulse rectifier 201 and the second six-pulse rectifier 301 are three-phase full-bridge topologies formed by diodes.

[0072] That is, the first 6-pulse rectifier 201 and the second 6-pulse rectifier 301 are both three-phase full-bridge topology structures formed by diodes. A diode is an electronic component that allows current to flow in one direction, and the three-phase full-bridge topology structure means that the enhanced bidirectional converter 10 with built-in rectifiers is composed of four diodes forming a "bridge" structure, which can process three-phase AC input and convert it into DC output. Six pulses means that the rectifier can generate six pulses of DC, which is a more common rectification waveform in the case of three-phase AC.

[0073] Optionally, in some embodiments, the first bidirectional converter 202 and the second bidirectional converter 302 both adopt a two-level full-bridge topology or a multi-level full-bridge topology.

[0074] It should be noted that, in the embodiment of the present invention, the first bidirectional converter 202 and the second bidirectional converter 302 mainly use IGBT as the core electronic switching device, and the topology of the bidirectional converter includes various types, including but not limited to the typical two-level or multi-level full-bridge topology. The two-level full-bridge topology and the multi-level full-bridge topology are common topologies in power electronic circuit design, which determine the connection method and working principle of the internal circuit of the converter. The two-level topology is relatively simple and suitable for lower power applications; while the multi-level topology is more complex and can handle higher voltage and higher power power conversion, while having better power quality.

[0075] The enhanced bidirectional converter with built-in rectifier proposed in the embodiment of the present invention solves the problems of large cost and space occupation, insufficient reliability of power supply system and the like of the prior art by integrating the advantages of diode rectifier and IGBT-based bidirectional converter. It not only improves the fault ride-through capability of the equipment and enhances reliability, but is also more economical.

[0076] To facilitate those skilled in the art to further understand the enhanced bidirectional converter with built-in rectifier proposed in the embodiment of the present invention, Figure 4 The control method of the enhanced bidirectional converter with built-in rectifier proposed according to the embodiment of the present invention is further described.

[0077] like Figure 4 As shown, the control method of the enhanced bidirectional converter with built-in rectifier adopts Figure 1 The enhanced bidirectional converter with a built-in rectifier of the embodiment, wherein the method comprises the following steps:

[0078] In step S401, the current operation mode of the enhanced bidirectional converter with a built-in rectifier is obtained.

[0079] It can be understood that, in the embodiment of the present invention, the current operating mode of the enhanced bidirectional converter with a built-in rectifier is divided into a bidirectional converter operating mode (i.e., a normal operating mode) and a diode rectifier operating mode (i.e., a bidirectional converter fault exit), and the enhanced bidirectional converter with a built-in rectifier preferentially adopts the bidirectional converter operating mode.

[0080] In step S402, if the current operation mode is the bidirectional converter operation mode, the first switch, the third switch, the fifth switch and the sixth switch are controlled to be closed, and the second switch and the fourth switch are opened, and it is detected whether the enhanced bidirectional converter with a built-in rectifier is in a fault mode.

[0081] Specifically, combined Figure 1 As shown, when the current operation mode is the bidirectional converter operation mode, the first switch K1, the third switch K3, the fifth switch S1 and the sixth switch S2 can be placed in a closed state, and the second switch K2 and the fourth switch K4 can be disconnected. The first 6-pulse rectifier 201 and the first bidirectional converter 202 connected in parallel have an overcurrent protection function for short-circuit faults, so that the current can flow along a predetermined path, while ensuring that the operation of the entire system is more efficient and stable. In addition, during the operation process, the working state of the enhanced bidirectional converter with a built-in rectifier can also be monitored to determine whether the enhanced bidirectional converter with a built-in rectifier is in a fault mode, further ensuring the continuous and stable operation of the equipment.

[0082] In step S403, if the enhanced bidirectional converter with built-in rectifier is in a fault mode, the first thyristor and the second thyristor are triggered.

[0083] That is to say, during the operation of the device, the first thyristor T1 and the second thyristor T2 are both kept in an untriggered state (i.e., in a blocked state). If the enhanced bidirectional converter with built-in rectifier is in a fault mode, i.e., an overcurrent or short circuit occurs in the DC circuit, once the fault current is detected to exceed a preset threshold, the first thyristor T1 and the second thyristor T2 can be immediately triggered (i.e., in a conducting state), so that the fault current is quickly transferred from the IGBT to the bidirectional converter and the 6-pulse rectifier branch to protect the IGBT device from overcurrent damage, thereby improving the fault ride-through capability of the device and enhancing reliability. This triggering state will last for 300ms, and the triggering signal will be automatically cleared after 300ms, so that the first thyristor T1 and the second thyristor T2 will be restored to an untriggered state so that the circuit can continue to work normally.

[0084] It should be noted that in order to ensure that the fault current can be completely transferred from the bidirectional converter branch to the 6-pulse rectifier branch in the event of overcurrent or short circuit, the following conditions must be met:

[0085] (VThy +V DIODE )+RI S <V VSC ;

[0086] Among them, V Thy is the thyristor conduction voltage drop, V DIODE is the diode (6-pulse rectifier) ​​conduction voltage drop, V VSC is the conduction voltage drop of the anti-parallel diode of the IGBT in the bidirectional converter, R is the sum of the on-resistance of the diode and the thyristor, I S is the short-circuit current flowing through the device.

[0087] Furthermore, in some other embodiments, after obtaining the current operating mode of the enhanced bidirectional converter with a built-in rectifier, it also includes: if the current operating mode is a diode rectifier operating mode, controlling the first switch, the third switch, the fifth switch and the sixth switch to be disconnected, and closing the second switch and the fourth switch, and controlling the first thyristor and the second thyristor to be in a triggered state.

[0088] Specifically, when the bidirectional converter fails (it may be a permanent fault or a short-term fault, such as one day of operation that cannot be restored) and exits operation, the current operation mode can be switched from the bidirectional converter operation mode to the diode rectifier operation mode, that is, the first switch K1, the third switch K3, the fifth switch S1 and the sixth switch S2 are disconnected, and the second switch K2 and the fourth switch K4 are closed. This conversion process is performed offline (that is, the system is in a power-off state), the first thyristor T1 and the second thyristor T2 are not triggered, and after the first to sixth switches are switched, the first thyristor T1 and the second thyristor T2 are triggered again, so that the current can pass smoothly, ensuring that the power supply system can continue to operate when the converter fails.

[0089] According to the control method of the enhanced bidirectional converter with built-in rectifier proposed in the embodiment of the present invention, by integrating the advantages of the diode rectifier and the IGBT-based bidirectional converter, an enhanced bidirectional converter with built-in rectifier is designed, which solves the problems of the prior art such as large cost and large space, insufficient reliability of the power supply system, etc., and not only improves the fault ride-through capability of the equipment and enhances reliability, but is also more economical.

[0090] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0091] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0092] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. An enhanced bidirectional converter with a built-in rectifier, characterized in that: include: Axial dual-column four-winding transformer, a switch component, a first rectifier component and a second rectifier component, a first thyristor and a second thyristor, wherein: The input end of the axial double-column four-winding transformer is connected to the power grid, and the output end of the axial double-column four-winding transformer includes a plurality of taps; The switch assembly includes a plurality of switch elements, and the switch states of the plurality of switch elements correspond to the current operation mode of the enhanced bidirectional converter with a built-in rectifier; One side of the first rectifier component and the second rectifier component are both connected to the switch component, the other side of the first rectifier component is connected to the first thyristor, and the other side of the second rectifier component is connected to the second thyristor.

2. The enhanced bidirectional converter with built-in rectifier according to claim 1, characterized in that: The axially dual-split four-winding transformer includes first to fourth taps.

3. The enhanced bidirectional converter with built-in rectifier according to claim 2, characterized in that: The switch assembly comprises: a first switch, wherein one end of the first switch is connected to the third tap of the axial dual-column four-winding transformer, and the other end of the first switch is connected to the first end of the first rectifier assembly; a second switch, wherein one end of the second switch is connected to the first tap of the axially dual-split four-winding transformer, and the other end of the second switch is connected to the second end of the first rectifier assembly; a third switch, one end of the third switch being connected to a fourth tap of the axially dual-column four-winding transformer, and the other end of the third switch being connected to a second end of the second rectifier assembly; a fourth switch, one end of the fourth switch being connected to the second tap of the axial dual-column four-winding transformer, and the other end of the fourth switch being connected to the first end of the second rectifier assembly; a fifth switch, one end of the fifth switch being respectively connected to the first end of the first rectifier assembly and the other end of the first switch, and the other end of the fifth switch being respectively connected to the second end of the first rectifier assembly and the other end of the second switch; A sixth switch, one end of which is respectively connected to the first end of the second rectifier assembly and the other end of the fourth switch, and the other end of which is respectively connected to the second end of the second rectifier assembly and the other end of the third switch.

4. The enhanced bidirectional converter with built-in rectifier according to claim 3, characterized in that: The first switch, the second switch, the third switch and the fourth switch are all three-phase AC circuit breakers; The fifth switch and the sixth switch are both three-phase AC isolating switches.

5. The enhanced bidirectional converter with built-in rectifier according to claim 4, characterized in that: The first rectifier assembly comprises: a first 6-pulse rectifier, one end of the first 6-pulse rectifier being respectively connected to the other end of the second switch and one end of the fifth switch; A first bidirectional converter, one end of which is connected to the other end of the fifth switch and the other end of the first switch respectively.

6. The enhanced bidirectional converter with built-in rectifier according to claim 5, characterized in that: The second rectifier assembly comprises: a second 6-pulse rectifier, one end of the second 6-pulse rectifier being connected to the other end of the fourth switch and one end of the sixth switch respectively; A second bidirectional converter, one end of which is connected to the other end of the third switch and the other end of the sixth switch respectively.

7. The enhanced bidirectional converter with built-in rectifier according to claim 6, characterized in that: The first six-pulse rectifier and the second six-pulse rectifier are both three-phase full-bridge topologies formed by diodes.

8. The enhanced bidirectional converter with built-in rectifier according to claim 6, characterized in that: The first bidirectional converter and the second bidirectional converter both adopt a two-level full-bridge topology or a multi-level full-bridge topology.

9. A control method for an enhanced bidirectional converter with a built-in rectifier, characterized in that: An enhanced bidirectional converter with a built-in rectifier according to any one of claims 1 to 8, wherein the method comprises the following steps: Get the current operation mode of the enhanced bidirectional converter with built-in rectifier; If the current operation mode is the bidirectional converter operation mode, the first switch, the third switch, the fifth switch and the sixth switch are controlled to be closed, the second switch and the fourth switch are disconnected, and it is detected whether the enhanced bidirectional converter with a built-in rectifier is in a fault mode; If the enhanced bidirectional converter with a built-in rectifier is in a fault mode, the first thyristor and the second thyristor are triggered.

10. The control method of the enhanced bidirectional converter with built-in rectifier according to claim 9, characterized in that: After obtaining the current operating mode of the enhanced bidirectional converter with built-in rectifier, it also includes: If the current operation mode is a diode rectifier operation mode, the first switch, the third switch, the fifth switch and the sixth switch are controlled to be opened, and the second switch and the fourth switch are closed, and the first thyristor and the second thyristor are controlled to be in a triggered state.

Images