Wave-by-wave current limiting control method, device, system, medium and program product

Abstract

This application provides a wave-by-wave current limiting control method, apparatus, system, medium, and program product. The method is applied to a converter based on an ANPC-2 topology, which includes multiple inner tubes, multiple outer tubes, and multiple clamping tubes. The method includes: detecting the current index of the converter's bridge arms; and when the current index is greater than or equal to a preset current threshold, sequentially turning off the inner tubes, outer tubes, and clamping tubes in that order. This application solves the problem of the lack of applicable wave-by-wave current limiting technology in ANPC-2 topologies by sequentially turning off the inner tubes, outer tubes, and clamping tubes when an ANPC-2 topology converter experiences overcurrent, thus ensuring the reliable operation of the converter.

Description

Technical Field

[0001] This application relates to the field of converter technology, and in particular to a wave-by-wave current limiting control method, device, system, medium and program product. Background Technology

[0002] Cycle-by-cycle current limiting (CBC) is a commonly used real-time circuit protection method in the field of power electronics. Its core is to monitor and limit the current in the circuit to prevent overcurrent faults and ensure the stable operation of devices and systems.

[0003] Existing wave-by-wave current limiting technology is widely used in NPC1 and ANPC-1 topologies. Based on the fast turn-off characteristics of active switching transistors, it detects current in real time and shuts down some switching transistors according to set logic when an overcurrent occurs, thereby suppressing the overcurrent. However, this wave-by-wave current limiting technology is not applicable to ANPC-2 topologies. When applied to this topology, improper turn-off sequence can easily lead to ineffective overcurrent suppression, and may even cause device damage or system shutdown. Summary of the Invention

[0004] This application provides a wave-by-wave current limiting control method, device, system, medium, and program product. For converters based on the ANPC-2 topology, the inner tube, outer tube, and clamping tube are turned off sequentially during overcurrent, solving the problem that there is no applicable wave-by-wave current limiting technology in the ANPC-2 topology.

[0005] In a first aspect, embodiments of this application provide a wave-by-wave current limiting control method applied to a converter based on an ANPC-2 topology. The converter based on the ANPC-2 topology includes multiple inner tubes, multiple outer tubes, and multiple clamping tubes. The method includes: detecting the current index of the bridge arm of the converter; when the current index is greater than or equal to a preset current threshold, turning off the inner tubes, outer tubes, and clamping tubes in sequence.

[0006] In one possible implementation, the inner tube, outer tube, and clamping tube are turned off sequentially, including: detecting the voltage and current status of the converter; determining the target inner tube, target outer tube, and target clamping tube from multiple inner tubes, multiple outer tubes, and multiple clamping tubes according to the voltage and current status; turning off the target inner tube; and if the current index detected in the next cycle is greater than or equal to a preset current threshold, then turning off the target clamping tube after turning off the target outer tube.

[0007] In one possible implementation, the inner tube, outer tube, and clamping tube are turned off sequentially, including: detecting the voltage and current status of the converter; determining the target inner tube from multiple inner tubes based on the voltage and current status, and turning off the target inner tube; if the current index detected in the next cycle is greater than or equal to a preset current threshold, determining the target outer tube and the target clamping tube from multiple outer tubes and multiple clamping tubes respectively based on the voltage and current status; and turning off the target outer tube and then turning off the target clamping tube.

[0008] In one possible implementation, the voltage and current states include voltage polarity and current polarity; the plurality of inner tubes include a first inner tube and a second inner tube, the first inner tube being located between the positive terminal of the converter and the bridge arm of the converter, and the second inner tube being located between the negative terminal of the converter and the bridge arm of the converter; if the voltage polarity and the current polarity are both positive in the voltage and current states, then the target inner tube is the first inner tube; if the voltage polarity and the current polarity are both positive in the voltage and current states, then the target inner tube is the second inner tube; if the voltage polarity and the current polarity are both negative in the voltage and current states, then the target inner tube is the second inner tube; if the voltage polarity and the current polarity are both negative in the voltage and current states, then the target inner tube is the first inner tube.

[0009] In one possible implementation, the plurality of outer tubes include a first outer tube and a second outer tube, the first outer tube being connected to a first inner tube and the second outer tube being connected to a second inner tube; the plurality of clamping tubes include a first clamping tube and a second clamping tube, the first clamping tube being connected to the first inner tube and the second clamping tube being connected to the second inner tube; if the voltage polarity is positive and the current polarity is positive in the voltage and current state, then the target outer tube is the first outer tube and the target clamping tube is the second clamping tube; if the voltage polarity is positive and the current polarity is negative in the voltage and current state, then the target outer tube is the first outer tube and the target clamping tube is the second clamping tube; if the voltage polarity is negative and the current polarity is negative in the voltage and current state, then the target outer tube is the second outer tube and the target clamping tube is the first clamping tube; if the voltage polarity is negative and the current polarity is positive in the voltage and current state, then the target outer tube is the second outer tube and the target clamping tube is the first clamping tube.

[0010] In one possible implementation, the converter is equipped with a temperature sensor, and the method further includes: detecting the temperature of the converter through the temperature sensor; and adjusting a preset current threshold according to the temperature.

[0011] Secondly, this application provides a wave-by-wave current limiting control device applied to a converter based on an ANPC-2 topology. The converter based on the ANPC-2 topology includes multiple inner tubes, multiple outer tubes, and multiple clamping tubes. The device includes: a current index detection module for detecting the current index of the bridge arm of the converter; and a wave-by-wave current limiting module for sequentially turning off the inner tubes, outer tubes, and clamping tubes in the order of the current index being greater than or equal to a preset current threshold.

[0012] Thirdly, embodiments of this application provide a control system, including: a converter based on an ANPC-2 topology, and a control unit; the converter based on the ANPC-2 topology includes multiple inner tubes, multiple outer tubes, and multiple clamping tubes; the control unit is used to execute the method provided in the first aspect above.

[0013] Fourthly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the method provided in the first aspect above.

[0014] Fifthly, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements the method provided in the first aspect above.

[0015] The wave-by-wave current limiting control method, device, system, medium, and program products provided in this application, targeting converters based on the ANPC-2 topology, sequentially shut down the switching transistors when an overcurrent fault occurs in the bridge arm, taking into account the characteristics of the ANPC-2 topology and the switching transistors used. This achieves precise suppression of the bridge arm current, thereby improving the robustness and reliability of the converter. This application constructs a precise and efficient wave-by-wave current limiting control mechanism for converters based on the ANPC-2 topology, enabling converters based on the ANPC-2 topology to effectively suppress overcurrent and avoid device damage or system shutdown caused by overcurrent. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0017] Figure 1 A schematic diagram of a single-phase bridge arm circuit structure of a converter based on the ANPC-2 topology is provided for embodiments of this application;

[0018] Figure 2 A schematic flowchart of the wave-by-wave current limiting control method provided in the embodiments of this application;

[0019] Figure 3A flowchart illustrating another wave-by-wave current limiting control method provided in this application embodiment;

[0020] Figures 4a-4d This is a schematic diagram of the turn-off process under different voltage and current states provided in the embodiments of this application;

[0021] Figures 5a-5d This is a schematic diagram illustrating the voltage and current changes before and after wave-by-wave current limiting control under different voltage and current conditions, as provided in the embodiments of this application.

[0022] Figure 6 This is a schematic diagram of a wave-by-wave current limiting control device provided in an embodiment of this application.

[0023] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0024] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0025] Commonly used converters include those based on Active Neutral Point Clamped (ANPC) technology and those based on Neutral Point Clamped (NPC) technology. Compared to NPC-based converters, ANPC-based converters use active switching transistors and anti-parallel diodes instead of passive diodes, thus achieving bidirectional on / off control. Furthermore, ANPC-based converters have six active switching transistors per phase arm, creating multiple commutation paths. These paths can be flexibly switched by controlling the on / off state of the active switching transistors. Therefore, ANPC-based converters offer significant advantages in flexibility, loss control, and performance scalability compared to NPC-based converters.

[0026] ANPC-1 and ANPC-2 (Active Neutral-Point-Clamped-2) converters are two types of converters based on active neutral-point clamping technology. A single-phase bridge arm of the ANPC-1 converter includes six active switching transistors, which can be divided into three groups: complementary inner transistors, complementary outer transistors, and complementary clamping transistors. The six active switching transistors typically use homogeneous devices, such as silicon-based IGBTs (Insulated Gate Bipolar Transistors). The switching frequency distribution among the groups of active switching transistors is relatively balanced, and the loss distribution is relatively even.

[0027] Converters based on the ANPC-2 topology have the same hardware topology as those based on the ANPC-1 topology, differing only in the modulation strategy used. The ANPC-2 topology converter uses an inner transistor for high-frequency switching and an outer transistor and clamping transistor for power-frequency switching. To balance efficiency and cost, the active switching transistors in ANPC-2 topology converters typically employ a hybrid approach using silicon-based IGBTs and MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors).

[0028] Figure 1 This is a schematic diagram of a single-phase bridge arm circuit structure of a converter based on an ANPC-2 topology, provided as an embodiment of this application. Figure 1 As shown, the converter includes six active switching transistors and anti-parallel diodes, namely VT1 to VT6. Among them, VT2 and VT3 are internal transistors, using MOSFETs with lower switching losses; VT1 and VT4 are external transistors, and VT5 and VT6 are clamping transistors, using silicon-based IGBTs with lower cost and better conduction characteristics.

[0029] Continue to refer to Figure 1 , Figure 1 P and N are the positive and negative bus terminals on the DC side, respectively. Two capacitors (C1 and C2) are used to connect the two terminals to form a DC midpoint. Figure 1 (Point 0 in the diagram). By controlling the on / off state of six active switching transistors, three different voltage levels can be output at the AC terminal.

[0030] This application applies to the operating scenarios of converters based on the ANPC-2 topology. Specifically, in scenarios such as new energy systems, electric vehicle drive systems, energy storage converters, and industrial motor control, converters are often required to achieve efficient and reliable energy conversion. However, overcurrent faults may occur during converter operation. For example, when new energy is connected to the grid, grid voltage fluctuations may cause instantaneous overload of the converter's arm current, or sudden load changes may also trigger transient overcurrents. When an overcurrent fault occurs in the converter, current suppression is necessary to ensure the safe and stable operation of the converter and the system.

[0031] Currently, wave-by-wave current limiting is commonly used to suppress current in converters. This involves real-time monitoring of the current based on the fast turn-off characteristics of active switching transistors, and shutting down some transistors according to a set logic when an overcurrent occurs, thereby suppressing the overcurrent. However, existing wave-by-wave current limiting control methods are widely used in NPC1 and ANPC-1 topologies. The ANPC-2 topology, due to its hybrid active switching transistor scheme, exhibits significant differences from other topologies in terms of switching frequency and freewheeling characteristics, making existing wave-by-wave current limiting control methods unsuitable for direct application. Directly using existing wave-by-wave current limiting control methods in the ANPC-2 topology can easily lead to improper turn-off sequence, failing to effectively suppress overcurrent and potentially causing device damage or system shutdown.

[0032] The wave-by-wave current limiting control method provided in this application analyzes the characteristics of the converter based on the ANPC-2 type topology and selectively shuts off the inner tube, outer tube and clamping tube in sequence when the current in the bridge arm is overcurrent, thereby realizing the step-by-step current limiting control for the ANPC-2 type topology.

[0033] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0034] Figure 2 This is a schematic flowchart illustrating the wave-by-wave current limiting control method provided in an embodiment of this application. Figure 2 As shown, the method includes:

[0035] Step S201: Detect the current index of the bridge arm of the converter.

[0036] The method provided in this application is applied to a converter based on the ANPC-2 topology (hereinafter referred to as the converter). The converter based on the ANPC-2 topology includes multiple inner tubes, multiple outer tubes, and multiple clamping tubes.

[0037] For example, a converter based on the ANPC-2 topology can be Figure 1 The converter shown is as follows. It includes multiple inner tubes, including VT2 and VT3; multiple outer tubes, including VT1 and VT4; and multiple clamping tubes, including VT5 and VT6.

[0038] The bridge arm of a converter is the branch where the converter's output current is located. The current specification refers to the AC current output from the bridge arm of the converter, such as... Figure 1 The output current at the AC terminal.

[0039] In this step, a current sensor can be installed in the converter to collect the current index of the converter's bridge arm.

[0040] In some embodiments, the current index of the converter's bridge arm collected by the current sensor can be acquired according to a preset period.

[0041] Step S202: When the current index is greater than or equal to the preset current threshold, the tubes are turned off in sequence according to the order of inner tube, outer tube and clamping tube.

[0042] The preset current threshold is a pre-set configurable parameter. The preset current threshold can be determined based on multiple factors such as the device tolerance of the converter and load, and system safety requirements.

[0043] In this step, when the current index is greater than or equal to the preset current threshold, it indicates that there is an overcurrent fault in the converter, and the converter needs to be controlled by wave-by-wave current limiting, that is, the inner tube, outer tube and clamping tube are turned off in sequence.

[0044] In some embodiments, in practical applications, when the current index is greater than or equal to a preset current threshold, the converter can trigger an overcurrent signal. In response to the overcurrent signal, the converter sequentially shuts down the inner tube, outer tube, and clamping tube in that order.

[0045] In this embodiment, the overcurrent signal may include the voltage and current states during an overcurrent event. In response to the overcurrent signal, the converter sequentially shuts down the inner tube, outer tube, and clamping tube according to the voltage and current states.

[0046] For example, firstly, at least one inner tube is shut off from among the multiple inner tubes, putting the bridge arm into freewheeling mode, thereby reducing the absolute value of the current index of the converter's bridge arm. Then, if the reduced current index is still greater than or equal to a preset current threshold, i.e., an overcurrent fault still exists, at least one outer tube is shut off from among the multiple outer tubes. Finally, after shutting off at least one outer tube, if the current index of the converter's bridge arm is still greater than or equal to the preset current threshold, at least one clamping tube is shut off from among the multiple clamping tubes, completely closing the bridge arm.

[0047] For example, based on the voltage and current status, a target inner tube can be identified from multiple inner tubes and turned off, causing the bridge arm to enter a freewheeling state. Then, if the reduced current index is still greater than or equal to a current threshold, a target outer tube can be identified from multiple outer tubes and turned off. Finally, if the current index is still greater than or equal to a preset current threshold after turning off the target outer tube, a target clamping tube can be identified from multiple clamping tubes and turned off.

[0048] In some embodiments, if the current index is less than a preset current threshold, it indicates that there is no overcurrent fault, and there is no need to continue shutting down the inner tube, outer tube, or clamping tube.

[0049] For example, when the detected current index is greater than or equal to a preset current threshold, at least one inner tube is shut off from among multiple inner tubes. Then, if the current index after shutting off the inner tube is less than the preset current threshold, there is no need to continue shutting off the outer tube and the clamping tube.

[0050] In some embodiments, if the current index drops below a preset current threshold after some or all active switches are turned off, the bridge arm returns to normal operation. If the current index still does not drop below the preset current threshold after a preset time period after all active switches are turned off, the converter is shut down and a fault warning is sent.

[0051] In some embodiments, the preset current threshold may include a short-term current threshold and a long-term current threshold. The short-term current threshold is used to identify short-term overcurrents, and the long-term current threshold is used to identify long-term overcurrents.

[0052] Specifically, when the current index of the current cycle is greater than or equal to the short-term current threshold, the inner tube, outer tube, and clamping tube are turned off sequentially. When the current index of the current cycle is less than the short-term current threshold, the current index of the previous preset number of cycles is obtained. If the current index of the current cycle and the current index of the previous preset number of cycles are both greater than or equal to the long-term current threshold, or if the statistical value (such as the average value) of the current index of the current cycle and the current index of the previous preset number of cycles is greater than or equal to the long-term current threshold, then the inner tube, outer tube, and clamping tube are turned off sequentially.

[0053] Optionally, the converter is equipped with a temperature sensor, and the method further includes: detecting the temperature of the converter through the temperature sensor; and adjusting a preset current threshold according to the temperature.

[0054] Temperature sensors are used to detect the temperature of the bridge arm of the converter.

[0055] In this embodiment, the converter acquires the temperature of the converter from a temperature sensor. Based on the temperature, a preset current threshold is dynamically adjusted.

[0056] For example, if the temperature is greater than or equal to a temperature threshold, the preset current threshold is reduced to prevent performance degradation of devices in the converter due to increased temperature, such as a decrease in their withstand current. The extent of the reduction in the preset current threshold can be determined based on the characteristics of the devices used in the converter.

[0057] For example, a correspondence between temperature and a preset current threshold can be established based on the characteristics of the components in the converter. The temperature of the converter, collected by the temperature sensor, is then substituted into this correspondence to determine the preset current threshold.

[0058] By dynamically adjusting the preset current threshold, the converter can adapt to changes in device performance under different operating conditions, thereby improving the accuracy and applicability of overcurrent fault identification.

[0059] The wave-by-wave current limiting control method provided in this application, targeting converters based on the ANPC-2 topology, sequentially shuts down the switching transistors when an overcurrent fault occurs in a bridge arm, taking into account the characteristics of the ANPC-2 topology and the switching transistors used. This achieves precise suppression of the bridge arm current, thereby improving the robustness and reliability of the converter. This application constructs a precise and efficient wave-by-wave current limiting control mechanism for converters based on the ANPC-2 topology, enabling converters based on the ANPC-2 topology to effectively suppress overcurrent and avoid device damage or system shutdown caused by overcurrent.

[0060] In one possible implementation, the inner tube, outer tube, and clamping tube are turned off sequentially, including: detecting the voltage and current status of the converter; determining the target inner tube, target outer tube, and target clamping tube from multiple inner tubes, multiple outer tubes, and multiple clamping tubes according to the voltage and current status; turning off the target inner tube; and if the current index detected in the next cycle is greater than or equal to a preset current threshold, then turning off the target clamping tube after turning off the target outer tube.

[0061] The voltage and current states refer to the output voltage and current states of the converter's bridge arms. In actual operation, by controlling the on / off switching of active switching transistors (multiple internal transistors, multiple external transistors, and multiple clamping transistors), the converter's bridge arms can output different voltages and currents in different directions. Based on the output voltage and current, the voltage and current states can be determined.

[0062] In this step, the voltage and current state of the converter can be determined by the state of the active switching transistors. Alternatively, the output voltage value and current polarity can be determined by setting voltage and current sensors, thereby determining the voltage and current state.

[0063] After determining the voltage and current status of the converter, the target inner tube, target outer tube, and target clamping tube to be turned off are determined from multiple inner tubes, multiple outer tubes, and multiple clamping tubes based on the voltage and current status.

[0064] In this step, the target inner tube, target outer tube, and target clamping tube can be pre-set for each voltage and current state. For example, the current flow direction in the converter's bridge arm is simulated under each voltage and current state. Based on the current flow direction, the freewheeling path during converter overcurrent is optimized. Based on the freewheeling path under each voltage and current state, the target inner tube, target outer tube, and target clamping tube are determined.

[0065] Specifically, first, the target inner tube is shut off, allowing the bridge arm to enter freewheeling mode. If an overcurrent fault still exists in the converter in the next cycle after shutting off the target inner tube, that is, if the current index detected in the next cycle is still greater than or equal to the preset current threshold, then the target outer tube is shut off, and after shutting off the target outer tube, the target clamping tube is shut off.

[0066] Differentiated wave-by-wave current limiting is implemented based on voltage and current conditions, enabling targeted wave-by-wave current limiting for converters based on the ANPC-2 topology. This ensures accurate and efficient execution of wave-by-wave current limiting under various operating conditions and avoids improper turn-off sequence. Furthermore, compared to a one-size-fits-all approach to wave-by-wave current limiting, this application reduces the frequent turn-off of active switching transistors, thereby improving the lifespan of components within the converter.

[0067] Figure 3 This is a flowchart illustrating another wave-by-wave current limiting control method provided in an embodiment of this application. Figure 3 As shown, when the current index is greater than or equal to a preset current threshold, the method provided in this embodiment includes:

[0068] Step S301: Detect the voltage and current status of the converter.

[0069] In this step, the voltage and current state of the converter can be determined by the state of the active switching transistors. Alternatively, the output voltage value and current polarity can be determined by setting voltage and current sensors, thereby determining the voltage and current state.

[0070] Step S302: Based on the voltage and current status, determine the target inner tube from among multiple inner tubes and turn off the target inner tube.

[0071] In this step, the current flow direction in the bridge arm of the converter is simulated under various voltage and current conditions. Based on the current flow direction, the freewheeling path during overcurrent in the converter is optimized. Based on the freewheeling path under various voltage and current conditions, the target inner tube is determined.

[0072] Optionally, the voltage and current states include voltage polarity and current polarity; the multiple inner tubes include a first inner tube and a second inner tube, the first inner tube being located between the positive terminal of the converter and the bridge arm of the converter, and the second inner tube being located between the negative terminal of the converter and the bridge arm of the converter; if the voltage polarity is positive and the current polarity is positive in the voltage and current states, then the target inner tube is the first inner tube; if the voltage polarity is positive and the current polarity is negative in the voltage and current states, then the target inner tube is the second inner tube; if the voltage polarity is negative and the current polarity is positive in the voltage and current states, then the target inner tube is the first inner tube.

[0073] Voltage and current states include voltage polarity and current polarity. When the voltage is greater than 0, the voltage polarity is positive; when the voltage is less than 0, the voltage polarity is negative. When the current is greater than 0, the current polarity is positive; when the current is less than 0, the current polarity is negative.

[0074] Specifically, the voltage and current states include voltage polarity being positive and current polarity being positive (V>0, I>0), voltage polarity being positive and current polarity being negative (V>0, I<0), voltage polarity being negative and current polarity being negative (V<0, I<0), and voltage polarity being negative and current polarity being positive (V<0, I>0).

[0075] by Figure 1 For example, VT2 is located between point P (the positive terminal of the converter) and AC (the bridge arm of the converter), and is the first inner tube. VT3 is located between point N (the negative terminal of the converter) and AC, and is the second inner tube.

[0076] If the voltage polarity is positive and the current polarity is positive (V > 0, I > 0) in the voltage and current state, then the target inner tube is the first inner tube, i.e. Figure 1 VT2 in the context; if the voltage polarity is positive and the current polarity is negative (V > 0, I < 0) in the voltage and current state, then the target inner tube is the second inner tube, i.e. Figure 1 VT3 in the context; if the voltage polarity is negative and the current polarity is negative (V < 0, I < 0) in the voltage and current state, then the target inner tube is the second inner tube, i.e. Figure 1 VT3 in the context; if the voltage polarity is negative and the current polarity is positive (V < 0, I > 0) in the voltage and current state, then the target inner tube is the first inner tube, i.e. Figure 1 VT2 in the middle.

[0077] Figures 4a-4d This is a schematic diagram of the turn-off process under different voltage and current states provided in the embodiments of this application. Figure 4aThis describes the turn-off process of an active switching transistor when both the voltage and current polarities are positive. For example... Figure 4a As shown, in the voltage and current state, when both the voltage and current polarities are positive (V > 0, I > 0), the arrow points to the current flow direction of the bridge arm. If the current index of the bridge arm increases, leading to overcurrent, the target inner tube is identified as VT2 (the first inner tube), and VT2 is turned off, causing the current flow direction to change (e.g., ...). Figure 4a (The arrow points to the direction after the inner tube is turned off), the bridge arm enters freewheeling mode, and the current index decreases.

[0078] Figure 4b This describes the turn-off process of an active switching transistor when the voltage polarity is positive and the current polarity is negative in a voltage-current state. For example... Figure 4b As shown, in the voltage and current state, when the voltage polarity is positive and the current polarity is negative (V > 0, I < 0), the arrow points to the current flow direction of the bridge arm. If the current index of the bridge arm increases, causing overcurrent, the target inner tube is identified as VT3 (the second inner tube), and VT3 is turned off, causing the current flow direction to change (e.g., ...). Figure 4b (The arrow points to the direction after the inner tube is turned off), the bridge arm enters freewheeling mode, and the current index decreases.

[0079] Figure 4c This describes the turn-off process of an active switch when both the voltage and current are negative. For example... Figure 4c As shown, in the voltage and current state, when both the voltage and current polarities are negative (V < 0, I < 0), the arrows point to the current flow direction of the bridge arm. If the current index of the bridge arm increases, leading to overcurrent, the target inner tube is identified as VT3 (the second inner tube), and VT3 is turned off. The current flow direction changes (e.g., Figure 4c (The arrow points to the direction after the inner tube is turned off), the bridge arm enters freewheeling mode, and the current index decreases.

[0080] Figure 4d This describes the turn-off process of an active switch when the voltage polarity is negative and the current polarity is positive under voltage and current conditions. For example... Figure 4d As shown, in the voltage and current state, when the voltage polarity is negative and the current polarity is positive (i.e., V < 0, I > 0), the arrow points to the current flow direction of the bridge arm. If the current index of the bridge arm increases, causing overcurrent, the target inner tube is identified as VT2 (the first inner tube), and VT2 is turned off, causing the current flow direction to change (e.g., ...). Figure 4d (The arrow points to the direction after the inner tube is turned off), the bridge arm enters freewheeling mode, and the current index decreases.

[0081] By determining the target inner tube based on the polarity of voltage and current, the current-carrying path can be accurately determined for different operating conditions, thus making the wave-by-wave current limiting control method more accurate and effective.

[0082] Step S303: If the current index detected in the next cycle is greater than or equal to the preset current threshold, then based on the voltage and current state, the target outer tube and the target clamping tube are determined from multiple outer tubes and multiple clamping tubes respectively.

[0083] In this step, if the current index detected in the next cycle is still greater than or equal to the preset current threshold, the overcurrent fault still exists. That is, the overcurrent fault is not resolved by turning off the target inner tube. Based on the voltage and current status, the target outer tube is determined from multiple outer tubes, and the target clamping tube is determined from multiple clamping tubes.

[0084] For example, the current flow in the bridge arm of the converter is simulated under various voltage and current conditions. Based on the active switching transistors through which the current flows, the target external transistor and the target clamping transistor are determined.

[0085] In some embodiments, if the current index detected in the next cycle is less than a preset current threshold, the converter is restored to normal operation in the next cycle, i.e., the target inner tube is restored to conduction. If an overcurrent fault still exists during the subsequent rise of the current index of the bridge arm, the target inner tube is turned off again, and the bridge arm is put back into freewheeling mode. If the target inner tube is turned off for N consecutive cycles, the target outer tube and the target clamping tube are determined from multiple outer tubes and multiple clamping tubes based on the voltage and current status.

[0086] Step S304: Shut down the target external pipe.

[0087] Step S305: After shutting off the target outer tube, shut off the target clamping tube.

[0088] Optionally, the multiple outer tubes include a first outer tube and a second outer tube, the first outer tube being connected to a first inner tube, and the second outer tube being connected to a second inner tube; the multiple clamping tubes include a first clamping tube and a second clamping tube, the first clamping tube being connected to a first inner tube, and the second clamping tube being connected to a second inner tube; if the voltage polarity is positive and the current polarity is positive in the voltage and current state, then the target outer tube is the first outer tube, and the target clamping tube is the second clamping tube; if the voltage polarity is positive and the current polarity is negative in the voltage and current state, then the target outer tube is the first outer tube, and the target clamping tube is the second clamping tube; if the voltage polarity is negative and the current polarity is negative in the voltage and current state, then the target outer tube is the second outer tube, and the target clamping tube is the first clamping tube; if the voltage polarity is negative and the current polarity is positive in the voltage and current state, then the target outer tube is the second outer tube, and the target clamping tube is the first clamping tube.

[0089] by Figure 1 For example, VT1 is connected to VT2, and VT1 is the first outer tube. VT4 is connected to VT3, and VT4 is the second outer tube. VT5 is connected to VT2, and VT5 is the first clamping tube. VT6 is connected to VT3, and VT6 is the second clamping tube.

[0090] If the voltage polarity is positive and the current polarity is positive (V > 0, I > 0) in the voltage and current state, then the target outer tube is the first outer tube, i.e. Figure 1 VT1 in the diagram refers to the second clamping transistor, i.e. Figure 1 VT6 in the context; if the voltage polarity is positive and the current polarity is negative (V > 0, I < 0) in the voltage and current state, then the target outer tube is the first outer tube, i.e. Figure 1 VT1 in the diagram refers to the second clamping transistor, i.e. Figure 1 VT6 in the context; if the voltage polarity is negative and the current polarity is negative (V < 0, I < 0) in the voltage and current state, then the target outer tube is the second outer tube, i.e. Figure 1 VT4 in the diagram refers to the first clamping transistor, i.e. Figure 1 VT5 in the context; if the voltage polarity is negative and the current polarity is positive (V < 0, I > 0) in the voltage and current state, then the target outer tube is the second outer tube, i.e. Figure 1 VT4 in the diagram refers to the first clamping transistor, i.e. Figure 1 VT5 in the middle.

[0091] Continue to refer to Figure 4a After VT2 is turned off, if the current index detected in the next cycle is still greater than or equal to the preset current threshold, then when the voltage polarity is positive and the current polarity is positive in the voltage-current state, VT1 is determined to be the target external transistor and VT6 is determined to be the target clamping transistor. VT1 and VT6 are turned off in sequence.

[0092] Continue to refer to Figure 4b After VT3 is turned off, if the current index detected in the next cycle is still greater than or equal to the preset current threshold, then when the voltage polarity is positive and the current polarity is negative in the voltage-current state, VT1 is determined to be the target external transistor and VT6 is determined to be the target clamping transistor. VT1 and VT6 are turned off in sequence.

[0093] Continue to refer to Figure 4c After VT3 is turned off, if the current index detected in the next cycle is still greater than or equal to the preset current threshold, then when the voltage polarity is negative and the current polarity is negative in the voltage-current state, VT4 is determined to be the target external transistor and VT5 is the target clamping transistor. VT4 and VT5 are turned off sequentially.

[0094] Continue to refer to Figure 4d After VT2 is turned off, if the current index detected in the next cycle is still greater than or equal to the preset current threshold, then when the voltage polarity is negative and the current polarity is positive in the voltage-current state, VT4 is determined to be the target external transistor and VT5 is determined to be the target clamping transistor. VT4 and VT5 are then turned off sequentially.

[0095] By determining the target outer tube and the target clamping tube based on the polarity of voltage and current, the path for closing the bridge arm can be accurately determined for different operating conditions, thus making the wave-by-wave current limiting control method more accurate and effective.

[0096] By first identifying and shutting down the target inner tube, if the overcurrent fault is resolved after shutting down the inner tube, there is no need to continue identifying and shutting down the target outer tube and target clamping tube. This simplifies the process, avoids redundant identification of the target outer tube and target clamping tube, and improves the efficiency of the wave-by-wave current limiting control method. In addition, it avoids directly blocking the bridge arm and reduces the risk of direct converter shutdown.

[0097] To more clearly demonstrate the effect of the wave-by-wave current limiting control method, this application also compares the changes in voltage and current before and after wave-by-wave current limiting control under various voltage and current conditions. Figures 5a-5d This is a schematic diagram showing the voltage and current changes before and after wave-by-wave current limiting control under different voltage and current conditions, as provided in the embodiments of this application.

[0098] Figure 5a This diagram illustrates the voltage and current changes before and after wave-by-wave current limiting control when both the voltage and current are positive. Figure 5a As shown, in the current index I AC When the preset current threshold is exceeded, the target internal tube is shut off. After the target internal tube is shut off, I... AC Decrease, causing I AC The current falls below a preset current threshold. In the next cycle after the current falls below the preset current threshold, the target inner tube is restored. In subsequent cycles, when the current index I... AC If the current exceeds the preset current threshold again, repeat the above steps. Based on the current curves before and after wave-by-wave current limiting control, it can be seen that the current after wave-by-wave current limiting control did not exceed the preset current threshold, indicating no overcurrent fault. Simultaneously, through wave-by-wave current limiting control, the voltage V before and after the control is... AC Basically the same.

[0099] Figure 5b This is a schematic diagram showing the changes in voltage and current before and after wave-by-wave current limiting control when the voltage polarity is positive and the current polarity is negative. Figure 5c This is a schematic diagram showing the changes in voltage and current before and after wave-by-wave current limiting control when both the voltage and current polarities are negative. Figure 5d This diagram illustrates the voltage and current changes before and after wave-by-wave current limiting control when the voltage polarity is negative and the current polarity is positive. (Example:) Figures 5b-5d As shown, the current after wave-by-wave current limiting control did not exceed the preset current threshold, indicating no overcurrent fault. Simultaneously, through wave-by-wave current limiting control, the voltage V before and after the current limit was... ACBasically the same.

[0100] Figure 6 This is a schematic diagram of a wave-by-wave current limiting control device provided in an embodiment of this application. The device is applied to a converter based on an ANPC-2 topology, which includes multiple inner tubes, multiple outer tubes, and multiple clamping tubes. Figure 6 As shown, the wave-by-wave current limiting control device provided in this embodiment includes a current index detection module 601 and a wave-by-wave current limiting module 602.

[0101] The current index detection module 601 is used to detect the current index of the bridge arm of the converter; the wave-by-wave current limiting module 602 is used to turn off the current in sequence according to the inner tube, outer tube and clamping tube when the current index is greater than or equal to the preset current threshold.

[0102] Optional, wave-by-wave current limiting module 602, specifically used for:

[0103] When the current index is greater than or equal to the preset current threshold, the voltage and current status of the converter is detected; based on the voltage and current status, the target inner tube, target outer tube, and target clamping tube are determined from multiple inner tubes, multiple outer tubes, and multiple clamping tubes respectively; the target inner tube is turned off; if the current index detected in the next cycle is greater than or equal to the preset current threshold, the target clamping tube is turned off after the target outer tube is turned off.

[0104] Optional, wave-by-wave current limiting module 602, specifically used for:

[0105] Detect the voltage and current status of the converter; based on the voltage and current status, determine the target inner tube from multiple inner tubes and turn off the target inner tube; if the current index detected in the next cycle is greater than or equal to the preset current threshold, then based on the voltage and current status, determine the target outer tube and target clamping tube from multiple outer tubes and multiple clamping tubes respectively; after turning off the target outer tube, turn off the target clamping tube.

[0106] Optionally, the voltage and current states include voltage polarity and current polarity; the multiple inner tubes include a first inner tube and a second inner tube, the first inner tube being located between the positive terminal of the converter and the bridge arm of the converter, and the second inner tube being located between the negative terminal of the converter and the bridge arm of the converter; if the voltage polarity is positive and the current polarity is positive in the voltage and current states, then the target inner tube is the first inner tube; if the voltage polarity is positive and the current polarity is negative in the voltage and current states, then the target inner tube is the second inner tube; if the voltage polarity is negative and the current polarity is positive in the voltage and current states, then the target inner tube is the first inner tube.

[0107] Optionally, the multiple outer tubes include a first outer tube and a second outer tube, the first outer tube being connected to a first inner tube, and the second outer tube being connected to a second inner tube; the multiple clamping tubes include a first clamping tube and a second clamping tube, the first clamping tube being connected to a first inner tube, and the second clamping tube being connected to a second inner tube; if the voltage polarity is positive and the current polarity is positive in the voltage and current state, then the target outer tube is the first outer tube, and the target clamping tube is the second clamping tube; if the voltage polarity is positive and the current polarity is negative in the voltage and current state, then the target outer tube is the first outer tube, and the target clamping tube is the second clamping tube; if the voltage polarity is negative and the current polarity is negative in the voltage and current state, then the target outer tube is the second outer tube, and the target clamping tube is the first clamping tube; if the voltage polarity is negative and the current polarity is positive in the voltage and current state, then the target outer tube is the second outer tube, and the target clamping tube is the first clamping tube.

[0108] Optionally, the converter is equipped with a temperature sensor, and the wave-by-wave current limiting control device also includes a threshold adjustment module, which is used for:

[0109] The temperature of the converter is detected by a temperature sensor; the preset current threshold is adjusted according to the temperature.

[0110] The wave-by-wave current limiting control device provided in this embodiment can execute the method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0111] This application also provides a control system, including: a converter based on an ANPC-2 topology, and a control unit; the converter based on the ANPC-2 topology includes multiple inner tubes, multiple outer tubes, and multiple clamping tubes; the control unit is used to execute the method provided in the above embodiments.

[0112] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0113] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0114] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0115] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0116] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0117] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0118] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0119] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0120] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0121] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A wave-by-wave current limiting control method, characterized in that, The method, applied to a converter based on an ANPC-2 topology, wherein the converter includes multiple inner tubes, multiple outer tubes, and multiple clamping tubes, comprises: Detect the current parameters of the bridge arms of the converter; When the current index is greater than or equal to the preset current threshold, the tubes are turned off sequentially in the order of inner tube, outer tube, and clamping tube.

2. The method according to claim 1, characterized in that, The sequential shut-off of the inner tube, outer tube, and clamping tube includes: Detect the voltage and current status of the converter; Based on the voltage and current states, the target inner tube, the target outer tube, and the target clamping tube are determined from the plurality of inner tubes, the plurality of outer tubes, and the plurality of clamping tubes, respectively. Shut down the target inner tube; If the current index detected in the next cycle is greater than or equal to the preset current threshold, then the target clamping tube will be turned off after the target outer tube is turned off.

3. The method according to claim 1, characterized in that, The sequential shut-off of the inner tube, outer tube, and clamping tube includes: Detect the voltage and current status of the converter; Based on the voltage and current state, determine the target inner tube from the plurality of inner tubes and turn off the target inner tube; If the current index detected in the next cycle is greater than or equal to the preset current threshold, then based on the voltage and current state, the target outer tube and the target clamping tube are determined from the plurality of outer tubes and the plurality of clamping tubes, respectively. After shutting off the target outer tube, shut off the target clamping tube.

4. The method according to claim 2 or 3, characterized in that, The voltage and current states include voltage polarity and current polarity; the plurality of inner tubes include a first inner tube and a second inner tube, the first inner tube being located between the positive terminal of the converter and the bridge arm of the converter, and the second inner tube being located between the negative terminal of the converter and the bridge arm of the converter; If both the voltage and current polarities are positive, then the target inner tube is the first inner tube; if both the voltage and current polarities are negative, then the target inner tube is the second inner tube; if both the voltage and current polarities are negative, then the target inner tube is the second inner tube; if both the voltage and current polarities are negative, then the target inner tube is the first inner tube.

5. The method according to claim 4, characterized in that, The plurality of outer tubes include a first outer tube and a second outer tube, the first outer tube being connected to the first inner tube, and the second outer tube being connected to the second inner tube; the plurality of clamping tubes include a first clamping tube and a second clamping tube, the first clamping tube being connected to the first inner tube, and the second clamping tube being connected to the second inner tube; If both the voltage and current polarities are positive, then the target outer tube is the first outer tube, and the target clamping tube is the second clamping tube; if both the voltage and current polarities are negative, then the target outer tube is the first outer tube, and the target clamping tube is the second clamping tube; if both the voltage and current polarities are negative, then the target outer tube is the second outer tube, and the target clamping tube is the first clamping tube; if both the voltage and current polarities are negative, then the target outer tube is the second outer tube, and the target clamping tube is the first clamping tube.

6. The method according to any one of claims 1-3, characterized in that, The converter is equipped with a temperature sensor, and the method further includes: The temperature of the converter is detected by the temperature sensor. Adjust the preset current threshold according to the temperature.

7. A wave-by-wave current limiting control device, characterized in that, An apparatus for use in a converter based on an ANPC-2 topology, wherein the converter comprises multiple inner tubes, multiple outer tubes, and multiple clamping tubes, the apparatus comprising: A current index detection module is used to detect the current index of the bridge arm of the converter; The wave-by-wave current limiting module is used to turn off the current sequentially in the order of inner tube, outer tube and clamping tube when the current index is greater than or equal to a preset current threshold.

8. A control system, characterized in that, include: A converter based on the ANPC-2 topology, and its control unit; The converter based on the ANPC-2 topology includes multiple inner tubes, multiple outer tubes, and multiple clamping tubes; The control unit is used to perform the method according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the method as described in any one of claims 1-6.

10. A computer program product, characterized in that, Includes a computer program that, when executed by a processor, implements the method of any one of claims 1-6.

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