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

Abstract

The application 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 thereof. The enhanced bidirectional converter comprises an axial double-column four-winding transformer, a switch assembly, a first rectifier assembly and a second rectifier assembly, and first and second thyristors. 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 multiple taps; the switch assembly comprises multiple switch pieces, and the switch states of the multiple switch pieces correspond to the current operation mode of the enhanced bidirectional converter with a built-in rectifier; one side of the first rectifier assembly and the second rectifier assembly is 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. Thus, by combining the advantages of a diode rectifier and an IGBT-based bidirectional converter, the problems of high cost and large occupation of the prior art and insufficient reliability of a power supply system are solved.

Description

TECHNICAL FIELD

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

[0002] Urban rail transit systems usually use uncontrolled diode rectifiers to provide DC power to drive rail traction. However, this power supply method has the disadvantages of large power supply voltage fluctuation and the need to consume braking energy through resistance during locomotive braking. Using bidirectional AC-to-DC controllable converter technology can effectively stabilize the traction DC power supply and feed energy back to the power grid in reverse during braking, thereby saving electric energy. However, bidirectional controllable converters use more electronic components, especially controllable IGBT (Insulated Gate Bipolar Transistor) devices, which have weaker impact resistance, resulting in lower overall reliability than uncontrolled diode rectifiers. Therefore, when using bidirectional AC-to-DC controllable converter technology to achieve traction power supply, a high-reliability converter circuit topology needs to be explored to solve the problem of insufficient reliability of controllable converters.

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

[0004] However, this method does not effectively solve the problem of improving the reliability of the power supply system, and needs to be improved. SUMMARY

[0005] The present application provides an enhanced bidirectional converter with built-in rectifier and a control method thereof to solve the problems of high cost and large occupation of existing technology, insufficient reliability of the power supply system, etc. Not only improves the fault ride-through capability of the equipment, enhances the reliability, but also is more economical.

[0006] To achieve the above-mentioned purpose, the first aspect of the present application provides an enhanced bidirectional converter with built-in rectifier, comprising: an axial double-column four-winding transformer, a switching assembly, a first rectifier assembly and a second rectifier assembly, 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 multiple taps;

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

[0009] One side of the first rectifier assembly and the second rectifier assembly is 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.

[0010] According to an embodiment of the present application, the axial double-column four-winding transformer comprises first to fourth taps.

[0011] According to an embodiment of the present application, the switch assembly comprises:

[0012] A first switch, one end of the first switch being connected with the third tap of the axial double-column four-winding transformer, and the other end of the first switch being connected with the first end of the first rectifier assembly;

[0013] A second switch, one end of the second switch being connected with the first tap of the axial double-column four-winding transformer, and the other end of the second switch being connected with the second end of the first rectifier assembly;

[0014] A third switch, one end of the third switch being connected with the fourth tap of the axial double-column four-winding transformer, and the other end of the third switch being connected with the second end of the second rectifier assembly;

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

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

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

[0018] According to an embodiment of the present application, the first switch, the second switch, the third switch and the fourth switch are all three-phase alternating current circuit breakers;

[0019] The fifth switch and the sixth switch are all three-phase alternating current disconnectors.

[0020] According to one embodiment of the present application, the first rectifier assembly comprises:

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

[0022] a first bidirectional converter, one end of the first bidirectional converter being 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 application, 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 the second bidirectional converter being connected to the other end of the third switch and the other end of the sixth switch, respectively.

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

[0027] According to one embodiment of the present application, the first bidirectional converter and the second bidirectional converter are both two-level full-bridge topologies or multi-level full-bridge topologies.

[0028] The enhanced bidirectional converter with built-in rectifier according to the embodiments of the present application solves the problems of high cost and large occupation of land, insufficient reliability of power supply system and the like in the prior art by combining the advantages of diode rectifiers and bidirectional converters based on IGBT, thereby not only improving the fault ride-through capability of the equipment and enhancing the reliability, but also being more economical.

[0029] To achieve the above object, the second aspect of the present application provides a control method of the enhanced bidirectional converter with built-in rectifier, which adopts the enhanced bidirectional converter with built-in rectifier according to the first aspect of the present application, wherein the method comprises the following steps:

[0030] acquiring 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, controlling the first switch, the third switch, the fifth switch and the sixth switch to be closed, and the second switch and the fourth switch to be disconnected, and detecting whether the enhanced bidirectional converter with built-in rectifier is in a fault mode;

[0032] if the enhanced bidirectional converter with built-in rectifier is in the fault mode, triggering the first thyristor and the second thyristor.

[0033] According to one embodiment of the present application, after the current operation mode of the enhanced bidirectional converter with built-in rectifier is acquired, further comprising:

[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 all controlled to be open, the second switch and the fourth switch are controlled to be closed, and the first thyristor and the second thyristor are both controlled to be in a triggered state.

[0035] The control method of the enhanced bidirectional converter with built-in rectifier according to the embodiment of the present application fuses the advantages of the diode rectifier and the IGBT-based bidirectional converter, designs an enhanced bidirectional converter with built-in rectifier, and solves the problems of high cost and large occupation of the prior art, and insufficient reliability of the power supply system, etc., thereby not only improving the fault ride-through capability of the equipment and enhancing the reliability, but also being more economical.

[0036] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0037] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the accompanying drawings, wherein:

[0038] Figure 1 FIG. 1 is a structural schematic diagram of an enhanced bidirectional converter with built-in rectifier according to an embodiment of the present application;

[0039] Figure 2 FIG. 4 is a schematic diagram of a 1-phase winding of an axial double-split four-winding transformer according to one embodiment of the present application;

[0040] Figure 3 FIG. 6 is a schematic diagram of a 1-phase winding of an axial double-split four-winding transformer with added taps according to one embodiment of the present application;

[0041] Figure 4 FIG. 10 is a flowchart of a control method of an enhanced bidirectional converter with built-in rectifier according to an embodiment of the present application. DETAILED DESCRIPTION

[0042] Embodiments of the present application are described in detail below with reference to the accompanying drawings, examples of which are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0043] An enhanced bidirectional converter with built-in rectifier and a control method thereof according to an embodiment of the present application are described below with reference to the accompanying drawings.

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

[0045] Before introducing the enhanced bidirectional converter with built-in rectifier according to an embodiment of the present application, the related technical background is introduced.

[0046] The urban rail transit system in China generally adopts a 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 as a centralized or decentralized external power source of the traction power supply system. The traction transformer in the traction substation (hereinafter referred to as 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 the advantages of simple structure and strong current carrying capacity, it also has the disadvantages of 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 is developed by introducing full-controlled power semiconductor devices such as insulated gate bipolar thyristors (IGBT) and advanced technologies such as pulse width modulation. The device realizes the decoupling of the AC power grid and the DC traction grid, enabling independent control of the DC voltage, and thus enabling rapid scheduling of power between traction substations. This becomes the core path to realize new energy consumption, renewable energy utilization, and reduce power grid loss.

[0048] With the transformation of the bidirectional converter from single traction substation grid operation to full line equipment, it will further become the direct executor of the full line DC voltage support and power rapid regulation on the basis of completely replacing the rectifier unit power supply. According to the analysis of the national subway demand, the bidirectional converter faces the following challenges:

[0049] (1) Challenge of short circuit fault tolerance. Since IGBT has the problem of insufficient overcurrent capacity, the IGBT-based converter performs worse than the diode converter in overcurrent capacity, so more comprehensive protection and heat dissipation mechanisms must be provided, which increases the cost and space requirement. In addition, the reliability of the flexible DC converter based on IGBT semiconductor devices and high-precision control systems has not been universally 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, bidirectional converters have improved reliability due to the introduction of fully controlled IGBTs and control circuits, which is a key to industrial application. Effective measures need to be taken from multiple angles such as technical research and development and industrial landing to ensure stable operation of the equipment.

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

[0052] Based on the above problems, the embodiment of the present application proposes an enhanced bidirectional converter with built-in rectifier, which solves the problems of high cost and large occupation of existing technology, and insufficient reliability of power supply system by integrating the advantages of diode rectifier and bidirectional converter based on IGBT. Not only improves the fault ride-through capability of the equipment and enhances the reliability, but also is more economical.

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

[0054] For example, as shown in Figure 1 , the enhanced bidirectional converter with built-in rectifier 10 includes an axial double-column four-winding transformer B1, a switch assembly 100, a first rectifier assembly 200 and a second rectifier assembly 300, a first thyristor T1 and a second thyristor T2, wherein the input end of the axial double-column four-winding transformer B1 is connected with the power grid, and the output end of the axial double-column four-winding transformer B1 includes multiple taps; the switch assembly 100 includes multiple switch pieces, and the switch state of the multiple switch pieces corresponds to the current operation mode of the enhanced bidirectional converter with built-in rectifier 10; one side of the first rectifier assembly 200 and the second rectifier assembly 300 is connected with the switch assembly 100, the other side of the first rectifier assembly 200 is connected with the first thyristor T1, and the other side of the second rectifier assembly 300 is connected with the second thyristor T2.

[0055] Specifically, the enhanced bidirectional converter with built-in rectifier 10 includes an axial double-column four-winding transformer B1, which is a rectifier transformer commonly used in 12-pulse rectifiers of DC traction power supply systems. In order to understand its structure more intuitively, please refer to Figure 2 , Figure 2 for a schematic diagram of a phase winding of the transformer. As Figure 2As shown, H1 and H2 represent two split windings located on the primary side, and L1 and L2 represent two windings located on the secondary side. The design feature of this transformer is that its split reactance value can be greater than 20%, which makes it possible to effectively reduce the critical current I dg that may occur during the operation of a 12-pulse rectifier unit. The reduction of the critical current I dg can reduce equipment failures and maintenance costs caused by excessive current, and is of great significance to 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, as shown in Figure 1 , the input end is used to directly connect with the power grid, thereby allowing the converter to receive alternating current from the power grid. The output end 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 also includes a switching assembly 100 composed of multiple switching elements. The switching state of these switching elements is controlled according to the current operating mode of the enhanced bidirectional converter 10 with built-in rectifier. By precisely controlling the switching state of the switching assembly 100, fine management of current flow direction and power flow can be achieved.

[0057] The first rectifier assembly 200 and the second rectifier assembly 300 are key components of the enhanced bidirectional converter 10 with built-in rectifier, responsible for converting alternating current into direct current. One side of both assemblies is connected to the switching assembly 100, ensuring that they can receive alternating current from the switching assembly 100. The other side of the first rectifier assembly 200 is connected to the first thyristor T1, while the other side of the second rectifier assembly 300 is connected to the second thyristor T2. The first thyristor T1 and the second thyristor T2 are key elements for controlling current direction and adjusting current size, ensuring that the converter can effectively operate in different modes.

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

[0059] Specifically, in one specific embodiment of the present application, improvements are made to the two secondary windings of the transformer shown in Figure 2 , and multiple taps are added. As shown in Figure 3 , Figure 3 the tap positions a1, a2, a3, and a4 correspond to the tap positions described in Figure 1 , thereby optimizing the performance of the transformer.

[0060] It is understood that in a DC traction power supply system, transformer tap parameters refer to the different voltage levels at the transformer output terminals. These levels allow the power supply system to provide different voltage values ​​as needed, which is crucial for ensuring the normal operation of the power supply system and the compatibility of 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 to K4 and fifth to sixth switches S1 to S2, wherein one end of the first switch K1 is connected to the third tap a3 of the axially dual-split 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 axially dual-split 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 axially dual-split 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 axially dual-split 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; and the fifth switch S1 and the sixth switch S2 are all three-phase AC isolating switches.

[0065] It can be understood that the three-phase AC circuit breaker is an electrical switching device used in power systems. It can cut off and connect the current in a three-phase AC circuit, mainly used to protect the circuit from overload or short circuit. Three-phase AC refers to three alternating currents with the same frequency and a phase difference of 120 degrees, and 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. Three-phase AC disconnector is a switching device used in power systems that can cut off or connect the circuit of three-phase AC, 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, preventing current from accidentally flowing into the work area.

[0066] Through this configuration, the switch assembly 100 can flexibly switch between different working modes, ensuring efficient transmission and conversion of electrical energy. The first to fourth switches K1~K4 are mainly responsible for regulating the current flow between the axial double-column four-winding transformer B1 and the first and second rectifier assemblies 200 and 300, while the fifth and sixth switches S1~S2 are used to realize current splitting and merging within 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, as shown in Figure 1 The first rectifier assembly 200 includes a first 6-pulse rectifier 201 and a first bidirectional converter 202, wherein one end of the first 6-pulse rectifier 201 is connected to the other end of the second switch K2 and one end of the fifth switch S1, respectively; one end of the first bidirectional converter 202 is connected to the other end of the fifth switch S1 and the other end of the first switch K1, respectively.

[0068] Specifically, in the embodiments of the present application, the first rectifier assembly 200 is designed to include two main parts, namely, a first 6-pulse rectifier (DIODE) 201 and a first bidirectional converter (Voltage Source Converter, VSC) 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 at the same time, 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 also can 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 at the same time, it is also connected to the other end of the first switch K1. This connection 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 alternating current into direct current and control the flow direction of the current, thereby achieving efficient operation of the power system.

[0069] Optionally, in some embodiments, as shown in FIG. 2, the second rectifier assembly 300 includes a second 6-pulse rectifier 301 and a second bidirectional converter 302, wherein 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, respectively; one end of the second bidirectional converter 302 is connected to the other end of the third switch K3 and the other end of the sixth switch S2, respectively. Figure 1

[0070] That is, like the first rectifier assembly 200, the second rectifier assembly 300 includes two parts, the second 6-pulse rectifier 301 and the 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, respectively; 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. Through such a design, the second rectifier assembly 300 can effectively convert and control electric energy, ensuring efficient operation of the entire system.

[0071] Optionally, in some embodiments, the first 6-pulse rectifier 201 and the second 6-pulse rectifier 301 are both three-phase full-bridge topologies composed of diodes.

[0072] ​In other words, both the first six-pulse rectifier 201 and the second six-pulse rectifier 301 utilize a three-phase full-bridge topology constructed using diodes. A diode is an electronic component that allows current to flow in one direction. The three-phase full-bridge topology means that the enhanced bidirectional converter 10 with a built-in rectifier uses four diodes forming a "bridge" structure, capable of processing three-phase AC input and converting it into DC output. Six-pulse refers to the rectifier's ability to generate six pulses of DC power, a common rectified waveform in 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 IGBTs as core electronic switching devices, and the topology of the bidirectional converter includes various types, including but not limited to typical two-level or multi-level full-bridge topologies. Two-level full-bridge topology and multi-level full-bridge topology are common topologies in power electronic circuit design, which determine the connection method and operating principle of the internal circuit of the converter. The two-level topology is relatively simple and suitable for lower power applications; 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 accordance with an embodiment of the present invention solves the problems of existing technologies such as large cost and footprint, and insufficient power supply system reliability by integrating the advantages of diode rectifiers and IGBT-based bidirectional converters. 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, the following is a reference to the attached Figure 4 The control method of the enhanced bidirectional converter with built-in rectifier proposed in an 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 according to an embodiment of the present invention 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 application, the current operation mode of the built-in rectifier enhanced bidirectional converter is divided into a bidirectional converter operation mode (i.e. normal operation mode) and a diode rectifier operation mode (i.e. bidirectional converter failure exit), and the built-in rectifier enhanced bidirectional converter preferentially adopts the bidirectional converter operation 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 all closed, the second switch and the fourth switch are opened, and whether the built-in rectifier enhanced bidirectional converter is in a failure mode is detected.

[0081] Specifically, in combination with Figure 1 As shown in the figure, 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, while the second switch K2 and the fourth switch K4 are opened, and the first 6-pulse rectifier 201 and the first bidirectional converter 202 in parallel have an overcurrent protection function of short-circuit failure, 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, the working state of the built-in rectifier enhanced bidirectional converter can also be monitored during operation to determine whether the built-in rectifier enhanced bidirectional converter is in a failure mode, further ensuring the continuous and stable operation of the equipment.

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

[0083] That is, during the operation of the equipment, the first thyristor T1 and the second thyristor T2 are kept in an untriggered state (i.e. in a blocking state), and if the built-in rectifier enhanced bidirectional converter is in a failure mode, i.e. overcurrent or short-circuit occurs in the DC circuit, as soon as it is detected that the fault current exceeds the pre-set threshold value, the first thyristor T1 and the second thyristor T2 can be triggered immediately (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, so as to protect the IGBT device from overcurrent damage, thereby improving the fault ride-through capability of the equipment and enhancing the reliability. This triggered state will last for 300ms, and after 300ms the trigger signal will be automatically cleared, and the first thyristor T1 and the second thyristor T2 will return to the 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 case of overcurrent or short-circuit, the following conditions need to be met:

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

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

[0087] Further, in some embodiments, after obtaining the current operation mode of the enhanced bidirectional converter with built-in rectifier, if the current operation mode is the diode rectifier operation mode, the first switch, the third switch, the fifth switch and the sixth switch are all opened, the second switch and the fourth switch are closed, and the first thyristor and the second thyristor are both in the triggered state.

[0088] Specifically, when the bidirectional converter fails (which can be a permanent failure or a short-term failure, such as a failure that cannot be recovered in a day) and exits the 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 opened, and the second switch K2 and the fourth switch K4 are in the closed state. This conversion process is performed offline (i.e., 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 to ensure that the current can flow 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 provided by the embodiment of the present application, by combining 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 high cost and large occupation of the prior art, and insufficient reliability of the power supply system. The device has improved fault ride-through capability and enhanced reliability, and is more economical.

[0090] In addition, the terms "first", "second", "third", "fourth", "fifth", "sixth", "seventh" and "eighth" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implying a specific number of the technical features indicated. Therefore, the features defined as "first", "second", "third", "fourth", "fifth", "sixth", "seventh" and "eighth" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0091] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean 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 do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

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

Claims

1. An enhanced bidirectional converter with built-in rectifier, characterized by, The application relates to an internal rectifier enhanced bidirectional converter. The axial double-column four-winding transformer comprises a first split winding and a second split winding on a primary side and a third split winding and a fourth split winding on a secondary side, an input end of the axial double-column four-winding transformer is connected with a power grid, and an output end of the axial double-column four-winding transformer comprises a plurality of taps. The switch assembly comprises a plurality of switches, and switch states of the plurality of switches correspond to a current operation mode of the internal rectifier enhanced bidirectional converter. The first rectifier assembly comprises a first 6-pulse rectifier and a first bidirectional converter, and the second rectifier assembly comprises a second 6-pulse rectifier and a second bidirectional converter. The axial double-column four-winding transformer comprises first to fourth taps.

2. The enhanced bidirectional converter with built-in rectifier according to claim 1, characterized in that, The switch assembly comprises:

3. The enhanced bidirectional converter with built-in rectifier according to claim 2, characterized in that, A first switch, one end of the first switch is connected with the third tap of the axial double-column four-winding transformer, and the other end of the first switch is connected with a first end of the first rectifier assembly and one end of the first bidirectional converter respectively; A second switch, one end of the second switch is connected with the first tap of the axial double-column four-winding transformer, and the other end of the second switch is connected with a second end of the first rectifier assembly and one end of the first 6-pulse rectifier respectively; A third switch, one end of the third switch is connected with the fourth tap of the axial double-column four-winding transformer, and the other end of the third switch is connected with a second end of the second rectifier assembly and one end of the second bidirectional converter respectively; A fourth switch, one end of the fourth switch is connected with the second tap of the axial double-column four-winding transformer, and the other end of the fourth switch is connected with a first end of the second rectifier assembly and one end of the second 6-pulse rectifier respectively; A fifth switch, one end of the fifth switch is connected with the first end of the first rectifier assembly, the other end of the first switch and one end of the first bidirectional converter respectively, and the other end of the fifth switch is connected with the second end of the first rectifier assembly, the other end of the second switch and one end of the first 6-pulse rectifier respectively; A sixth switch, one end of the sixth switch is connected with the first end of the second rectifier assembly, the other end of the fourth switch and one end of the second 6-pulse rectifier respectively, and the other end of the sixth switch is connected with the second end of the second rectifier assembly, the other end of the third switch and one end of the second bidirectional converter respectively.

4. The internal rectifier enhanced bidirectional converter according to claim 3, wherein ​ 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 all three-phase AC disconnectors.

5. The enhanced bidirectional converter with built-in rectifier according to claim 4, characterized in that, The first 6-pulse rectifier and the second 6-pulse rectifier are both three-phase full-bridge topologies formed by diodes.

6. The enhanced bidirectional converter with built-in rectifier according to claim 4, characterized in that, The first bidirectional converter and the second bidirectional converter both adopt two-level full-bridge topologies or multi-level full-bridge topologies.

7. A control method of an enhanced bidirectional converter with built-in rectifier, characterized by, An enhanced bidirectional converter with built-in rectifiers, according to any one of claims 1-6, wherein the method comprises the following steps: obtaining the current operation mode of the enhanced bidirectional converter with built-in rectifiers; if the current operation mode is the bidirectional converter operation mode, controlling the first switch, the third switch, the fifth switch and the sixth switch to be closed, and the second switch and the fourth switch to be opened, and detecting whether the enhanced bidirectional converter with built-in rectifiers is in a fault mode; if the enhanced bidirectional converter with built-in rectifiers is in the fault mode, triggering the first thyristor and the second thyristor.

8. The control method of the enhanced bidirectional converter with built-in rectifier according to claim 7, characterized in that, After obtaining the current operation mode of the enhanced bidirectional converter with built-in rectifiers, further comprising: if the current operation mode is the diode rectifier operation mode, controlling the first switch, the third switch, the fifth switch and the sixth switch to be opened, and the second switch and the fourth switch to be closed, and controlling the first thyristor and the second thyristor to be in the triggered state.

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