A control method and device of a three-phase bridge, a power conversion device and a medium

Abstract

The present disclosure provides a control method and device of a three-phase bridge, a power conversion device and a medium, and relates to the field of power electronic conversion. The method comprises: in response to a target bridge arm fault in the three-phase bridge, determining a three-phase level state of the three-phase bridge, the three-phase level state missing a fault level state, and the fault level state including a level signal corresponding to the target bridge arm; generating a modulation sequence for adjusting an output voltage of the three-phase bridge according to the three-phase level state; and updating the modulation sequence to a target modulation sequence according to a neutral point potential of the three-phase bridge and a vector combination corresponding to the modulation sequence, and the target modulation sequence being used to output a target voltage of the three-phase bridge. By determining the missing fault level state in the three-phase level state, then generating the modulation sequence, and updating the modulation sequence based on the neutral point potential and the vector combination, the output voltage of the three-phase bridge after the fault is quickly reconstructed. The output interruption caused by the fault is avoided, and the balance and stability of the output voltage of the three-phase bridge in the fault state are ensured.

Description

Technical Field

[0001] This disclosure relates to the field of power electronic conversion, and in particular to a control method and device for a three-phase bridge, a power conversion device and a medium. Background Technology

[0002] In the field of electrical energy, controlling three-level inverters is a major research direction that connects the DC power of power batteries with the AC power of drive motors, which determines the power performance, driving range and operational reliability of power equipment. Summary of the Invention

[0003] This disclosure provides a control method and device for a three-phase bridge, a power conversion device and a medium. It provides a method for generating a modulation sequence based on the three-phase level state of the missing level signal when a bridge arm fault occurs in a three-phase bridge, and updating the modulation sequence based on the neutral point potential and vector combination, so as to realize uninterrupted operation of the three-phase bridge and power quality assurance.

[0004] The first aspect of this disclosure proposes a control method for a three-phase bridge, comprising: in response to a target bridge arm fault in the three-phase bridge, determining the three-phase level states of the three-phase bridge, wherein a fault level state is missing from the three-phase level states, and the fault level state includes a level signal corresponding to the target bridge arm; generating a modulation sequence for adjusting the output voltage of the three-phase bridge based on the three-phase level states; and updating the modulation sequence to a target modulation sequence based on the neutral point potential of the three-phase bridge and a vector combination corresponding to the modulation sequence, wherein the target modulation sequence is used to output a target voltage for the three-phase bridge.

[0005] The disclosed solution, in response to a target bridge arm fault in a three-phase bridge, determines the missing fault level state in the three-phase voltage levels, generates a modulation sequence based on this level state, and finally updates the modulation sequence to the target modulation sequence based on the neutral point potential, thus achieving rapid reconstruction of the three-phase bridge output voltage after a fault. Since the fault level state directly reflects the voltage signal that the target bridge arm cannot output, the generated modulation sequence can effectively avoid the faulty bridge arm, preventing output interruption due to the fault. Furthermore, by introducing neutral point potential feedback during the modulation sequence update process, the balance and stability of the three-phase bridge output voltage under fault conditions are ensured.

[0006] In this disclosure, in response to a fault in a target arm of a three-phase bridge, determining the three-phase level state of the three-phase bridge includes: in response to the target arm being the upper arm, determining that the missing fault level state in the three-phase level state includes a positive level signal; in response to the target arm being the middle arm, determining that the missing fault level state in the three-phase level state includes a zero level signal; and in response to the target arm being the lower arm, determining that the missing fault level state in the three-phase level state includes a negative level signal.

[0007] The scheme disclosed herein determines the missing level signal based on the different positions of the faulty bridge arm. A fault in the upper bridge arm prevents the phase from outputting a positive level, a fault in the middle bridge arm prevents the phase from outputting a zero level, and a fault in the lower bridge arm prevents the phase from outputting a negative level. By establishing a mapping relationship between the fault location and the missing level signal, accurate constraints are provided for the reconstruction of the modulation sequence, avoiding modulation failure caused by blind reconstruction.

[0008] In this disclosure, generating a modulation sequence for adjusting the output voltage of a three-phase bridge based on the three-phase level states includes: determining a candidate voltage vector based on the three-phase level states; and generating a modulation sequence for synthesizing a target voltage based on the candidate voltage vector.

[0009] The scheme disclosed herein selects available candidate voltage vectors based on the three-phase level state, ensuring that each vector in the candidate voltage vector set is physically realizable; then, under the constraint of the candidate voltage vectors, a modulation sequence for synthesizing the target voltage is generated, thereby achieving accurate synthesis of the target voltage under fault constraints and ensuring the output voltage accuracy under three-phase bridge fault conditions.

[0010] In this disclosure, determining candidate voltage vectors based on three-phase level states includes: determining missing voltage vectors based on three-phase level states, wherein the missing voltage vectors correspond to fault level states; and determining candidate voltage vectors based on an initial voltage vector set and the missing voltage vectors, wherein the candidate voltage vectors are associated with sectors.

[0011] The disclosed scheme identifies missing voltage vectors corresponding to fault level states and removes them from the initial voltage vector set, using the remaining vectors to form a set of candidate voltage vectors. This filtering method can filter out all unusable vectors, avoiding omissions; at the same time, the correlation between candidate voltage vectors and sectors facilitates the selection of vector combinations within subsequent sectors, improving the efficiency of modulation sequence determination.

[0012] In this disclosure, generating a modulation sequence for synthesizing a target voltage based on candidate voltage vectors includes: determining the target sector where the target voltage is located based on the target voltage; determining a combination of target voltage vectors for synthesizing the target voltage based on the target sector and candidate voltage vectors; and determining the modulation sequence based on the combination of target voltage vectors.

[0013] The disclosed scheme first determines the target sector based on the spatial location of the target voltage, and then selects the target voltage vector combination for synthesizing the target voltage only from the candidate voltage vectors corresponding to the target sector. By limiting the sector, the vector selection range is narrowed, reducing computational complexity; at the same time, it ensures the physical realizability of the selected vectors, improving the accuracy and real-time performance of modulation sequence determination.

[0014] In this disclosure, the modulation sequence is updated to a target modulation sequence based on the neutral point potential of the three-phase bridge and the vector combination corresponding to the modulation sequence, including: determining the offset polarity of the neutral point potential; adjusting the redundant vectors in the modulation sequence according to the offset polarity, and determining the target modulation sequence.

[0015] The disclosed scheme detects the polarity of the neutral point potential offset of the three-phase bridge and updates the modulation sequence accordingly through vector combination switching. Since redundant vectors have the same amplitude but different current paths, their selection affects the charging and discharging state of the neutral point potential. By selecting the corresponding vector combination based on the offset polarity, active balance control of the neutral point potential can be achieved under fault conditions, avoiding capacitor voltage imbalance and output waveform distortion caused by neutral point potential offset after a fault.

[0016] In this disclosure, a target modulation sequence is determined by adjusting redundant vectors in the modulation sequence through vector combination switching based on the offset polarity, including: obtaining a mapping relationship between vector combination and offset polarity; determining the target modulation sequence based on a first vector combination in the mapping relationship in response to a positive offset polarity; or, determining the target modulation sequence based on a second vector combination in the mapping relationship in response to a negative offset polarity.

[0017] This disclosed solution achieves rapid and accurate adjustment of the neutral point potential under fault conditions by obtaining the mapping relationship between vector combinations and offset polarities. When a positive offset of the neutral point potential is detected, a first vector combination is used to determine the target modulation sequence; when a negative offset of the neutral point potential is detected, a second vector combination is used to determine the target modulation sequence. Compared to the method that requires real-time calculation of the action time ratio of positive and negative small vectors, by pre-configuring vector combinations corresponding to different polarities, the corresponding combination can be directly selected after the offset polarity is detected, eliminating the need for complex online calculations. This results in a fast response speed and simple and reliable control logic. Furthermore, it avoids the defect of continuous adjustment methods failing to function properly when some small vectors are missing due to faults, ensuring the feasibility and effectiveness of neutral point potential balance control under fault conditions.

[0018] In this disclosure, a modulation sequence for adjusting the output voltage of a three-phase bridge is generated based on the three-phase level states, including: switching the transmission mode from a first transmission mode to a second transmission mode in response to a missing fault level state, including a zero-level signal, in the three-phase level states; and generating the modulation sequence based on the second transmission mode.

[0019] The disclosed solution addresses the fault condition of missing zero-level signal by proactively switching the transmission mode from the first transmission mode to the second transmission mode. When the zero-level signal is missing, excessive redundancy vectors are lost. Continuing to use the first transmission mode would lead to the problem of ineffective modulation sequence generation. Switching to the second transmission mode avoids this problem, ensuring that the three-phase bridge can maintain stable operation under extreme fault conditions and improving the adaptability of fault-tolerant control.

[0020] In this disclosure, the method further includes: in response to a target arm failure in a three-phase bridge, triggering a physical isolation component connected in series with the target arm to disconnect the target arm.

[0021] The solution disclosed herein achieves rapid physical disconnection of the faulty bridge arm through physical isolation components, effectively preventing the continuous flow of fault current under short-circuit faults, avoiding damage to other devices caused by fault propagation, and improving the safety and reliability of the system under short-circuit fault scenarios.

[0022] In this disclosure, in response to a fault occurring in a target arm of a three-phase bridge, the method includes: determining the voltage across a power switching device in the target arm; determining the fault as a short-circuit fault in response to the voltage remaining at zero; or, determining the fault as an open-circuit fault in response to the voltage remaining at non-zero.

[0023] The disclosed solution determines the fault type by detecting the voltage across the power switching device. A sustained zero voltage indicates a short-circuit fault, while a sustained non-zero voltage indicates an open-circuit fault. This detection method can be directly implemented using existing voltage sampling circuits, reducing hardware costs. Furthermore, the voltage determination method is simple, reliable, and has a fast response time, meeting the real-time requirements of fault-tolerant control.

[0024] In summary, the three-phase bridge control method proposed in this disclosure achieves comprehensive fault-tolerant control for both open-circuit and short-circuit faults by responding to a target bridge arm fault in the three-phase bridge, determining the missing fault level state in the three-phase level state in real time, and generating a modulation sequence accordingly. By adaptively reconstructing the modulation sequence based on the missing level state, the inherent redundant vector resources of the three-phase bridge are utilized, eliminating the need for additional fault-tolerant power units and reducing system cost and complexity. Furthermore, through vector combination reselection driven by the neutral point potential, active balancing of the neutral point potential under fault conditions is achieved, effectively suppressing capacitor voltage unevenness and output waveform distortion, ensuring the stable operation of the three-phase bridge under fault conditions, and improving the reliability and driving safety of the electric drive system.

[0025] The second aspect of this disclosure provides a control device for a three-phase bridge, comprising a determining module, a generating module, and a controlling module. The determining module, in response to a target bridge arm fault in the three-phase bridge, determines the three-phase level states of the three-phase bridge, where a fault level state is missing from the three-phase level states. The fault level state includes the level signal corresponding to the target bridge arm. The generating module, based on the three-phase level states, generates a modulation sequence for adjusting the output voltage of the three-phase bridge. The controlling module, based on the neutral point potential of the three-phase bridge and the vector combination corresponding to the modulation sequence, updates the modulation sequence to a target modulation sequence, which is used to output a target voltage for the three-phase bridge.

[0026] In this disclosure, the determining module is configured to: determine, in response to the target bridge arm being the upper bridge arm, that the missing fault level state in the three-phase level states includes a positive level signal; determine, in response to the target bridge arm being the middle bridge arm, that the missing fault level state in the three-phase level states includes a zero level signal; and determine, in response to the target bridge arm being the lower bridge arm, that the missing fault level state in the three-phase level states includes a negative level signal.

[0027] In this disclosure, the generation module is used to: determine candidate voltage vectors based on the three-phase level states; and generate a modulation sequence for synthesizing a target voltage based on the candidate voltage vectors.

[0028] In this disclosure, the generation module is used to: determine the missing voltage vector based on the three-phase level state, wherein the missing voltage vector corresponds to the fault level state; and determine the candidate voltage vector based on the initial voltage vector set and the missing voltage vector, wherein the candidate voltage vector is associated with the sector.

[0029] In this disclosure, the generation module is used to: determine the target sector where the target voltage is located based on the target voltage; determine the target voltage vector combination for synthesizing the target voltage according to the target sector and candidate voltage vectors; and determine the modulation sequence according to the target voltage vector combination.

[0030] In this disclosure, the control module is used to: determine the offset polarity of the neutral point potential; and adjust the redundant vector in the modulation sequence according to the offset polarity to determine the target modulation sequence.

[0031] In this disclosure, the control module is configured to: acquire the mapping relationship between vector combinations and offset polarity; determine the target modulation sequence according to the first vector combination in the mapping relationship in response to a positive offset polarity; or, determine the target modulation sequence according to the second vector combination in the mapping relationship in response to a negative offset polarity.

[0032] In this disclosure, the generation module is used to: switch the transmission mode from a first transmission mode to a second transmission mode in response to a missing fault level state, including a zero-level signal, in the three-phase level state; and generate a modulation sequence according to the second transmission mode.

[0033] In this disclosure, the control module is also configured to: in response to a target arm failure in a three-phase bridge, trigger a physical isolation component connected in series with the target arm to disconnect the target arm.

[0034] In this disclosure, the determining module is used to: determine the voltage across the power switching device in the target bridge arm; determine the fault as a short circuit fault in response to the voltage being continuously zero; or determine the fault as an open circuit fault in response to the voltage being continuously non-zero.

[0035] In summary, the three-phase bridge control device proposed in this disclosure reduces system cost and complexity by adaptively reconstructing the modulation sequence based on the missing level state, eliminating the need for additional fault-tolerant power units. Through the dynamic adjustment of redundant vectors driven by the neutral point potential offset polarity, it achieves active balancing of the neutral point potential under fault conditions, effectively suppressing capacitor voltage unevenness and output waveform distortion, ensuring the stable operation of the three-phase bridge under fault conditions, and improving the reliability and driving safety of the electric drive system.

[0036] A third aspect of this disclosure provides a power conversion device including a three-phase bridge, the three-phase bridge including three phase bridge arms, the phase bridge arms including an upper bridge arm, a middle bridge arm and a lower bridge arm, the power conversion device being configured to perform the control method described in any embodiment of the first aspect of this disclosure.

[0037] The power conversion device disclosed herein achieves stable operation of power conversion between the power supply and the motor by executing the above-described control method.

[0038] In this disclosure, each bridge arm in the phase bridge arm is connected in series with a physical isolation component, which is used to disconnect the target bridge arm that is faulty.

[0039] The power conversion device disclosed herein achieves rapid physical isolation of faulty bridge arms by connecting physical isolation components in series in each bridge arm, effectively preventing the continuous flow of fault current under short-circuit faults and ensuring system safety under fault conditions.

[0040] A fourth aspect of this disclosure provides an electronic device comprising: a processor and a memory for storing a computer program capable of running on the processor, wherein the processor, when running the computer program, performs the method described in any embodiment of the first aspect of this disclosure.

[0041] The fifth aspect of this disclosure provides a computer-readable storage medium storing computer instructions for causing a computer to perform the methods described in any embodiment of the first aspect of this disclosure.

[0042] A sixth aspect of this disclosure provides a program product including computer instructions for causing a computer to perform the methods described in any embodiment of the first aspect of this disclosure.

[0043] In summary, the control method and device, power conversion device and medium for the three-phase bridge proposed in this disclosure achieve rapid and reliable adjustment of the neutral point potential under fault conditions by updating the modulation sequence to the target modulation sequence based on the neutral point potential and vector combination of the three-phase bridge. This significantly reduces the computational burden and response delay of the control system. Furthermore, since this scheme does not rely on the continuous adjustment of the redundant vector's duration, it can still operate effectively even when a fault causes the partial loss of redundant vectors, avoiding the shortcomings of traditional continuous adjustment methods that cannot operate normally under fault conditions. This ensures the feasibility and effectiveness of neutral point potential balance control under fault conditions and improves the operational stability and reliability of the three-phase bridge under fault conditions.

[0044] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0045] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure, and are not intended to unduly limit this disclosure.

[0046] Figure 1 This is a schematic diagram of the structure of a three-phase bridge as shown in an embodiment of this disclosure; Figure 2 This is one of the flowcharts illustrating the control method for a three-phase bridge according to an embodiment of this disclosure; Figure 3 This is a second schematic flowchart illustrating the control method for a three-phase bridge according to an embodiment of this disclosure; Figure 4A This is a hardware topology diagram of a T-type three-level inverter; Figure 4B This is a spatial vector distribution map; Figure 4C This is a diagram showing the space voltage vector distribution after the loss of the P-level state. Figure 4D This is a diagram showing the space voltage vector distribution after the loss of the N-level state. Figure 4E This is a diagram showing the space voltage vector distribution after the loss of the zero-level state. Figure 5 This is a schematic diagram of the structure of a three-phase bridge control device according to an embodiment of the present disclosure; Figure 6 This is a schematic diagram of the structure of an electronic device according to an embodiment of the present disclosure. Detailed Implementation

[0047] Embodiments of this disclosure are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, and by way of example, the same or similar reference numerals denote 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 intended to explain this disclosure, and should not be construed as limiting this disclosure.

[0048] T-type three-level inverters, as a replacement for two-level and I-NPC three-level topologies, are in a rapid development stage of technological maturity, large-scale application, and reliability improvement. Compared with two-level inverters, the T-type three-level topology can reduce the voltage stress on the switching transistors to half that of the DC bus voltage, significantly reducing conduction and switching losses. As electric vehicles upgrade to high-voltage platforms, T-type three-level inverters have a larger number of components and higher system complexity. The risk of open-circuit / short-circuit faults in the power switches has become a bottleneck restricting the safe operation of the system. Therefore, fault diagnosis and fault-tolerant control technologies have become the main research directions in this field.

[0049] The main problems with fault-tolerant control technologies for T-type three-level inverters are as follows: Neutral point potential imbalance: Most solutions rely on natural balancing after modulation signal reconstruction or hardware reconstruction, lacking a dynamic correlation control strategy with neutral point potential deviation. When a large deviation occurs, rapid stabilization is impossible, easily leading to uneven capacitor voltage, output waveform distortion, and other problems affecting stable motor operation. Incomplete fault type coverage: Most related technologies only design fault-tolerant strategies for open-circuit faults in power devices, or lack effective physical isolation methods for short-circuit faults, easily leading to fault propagation, PCB burnout, and even safety accidents. Poor topology adaptability: For I-type NPC three-level inverters, the fault analysis and control logic cannot adapt to the topology and fault characteristics of T-type three-level inverters, resulting in control failure and insufficient stability under T-type topologies. High system cost and complexity: Some solutions achieve fault tolerance by adding a large number of fault-tolerant power switching devices, significantly increasing system cost, size, and topology complexity, which is not conducive to engineering applications. Insufficient driving safety and reliability, and the fact that some technical solutions are prone to problems such as power interruption and unstable control after failure, can lead to electric vehicles losing power or experiencing dangerous conditions such as shaking and stalling while driving, and in severe cases, can threaten the safety of drivers and passengers.

[0050] Therefore, to solve the aforementioned technical problems, this disclosure provides a fault-tolerant control method for T-type NPC three-level inverters. By setting different vector combinations for neutral point offset, the neutral point potential balance is achieved, effectively improving system reliability when power devices experience open-circuit / short-circuit faults. Furthermore, by timely isolating the faulty bridge arm and utilizing the redundant voltage vector characteristic of the T-type NPC three-level inverter, the T-type NPC three-level inverter can continue to operate under fault conditions.

[0051] The control method for the three-phase bridge proposed in this disclosure will now be described in detail with reference to the accompanying drawings.

[0052] The method proposed in this disclosure can be applied to the topology characteristics and fault-tolerant control of T-type three-level inverters, and can be further extended to the following technical fields: New energy power generation and storage: including medium- and high-power power conversion scenarios such as photovoltaic grid-connected power conversion devices, energy storage converters (PCS), and wind power converters, ensuring the reliability and stability of renewable energy grid connection. Industrial drive and frequency conversion: suitable for medium- and high-voltage frequency converters and industrial servo drive systems, improving the fault self-healing capability and operational safety of production line equipment. High-power charging infrastructure: applied to DC fast charging piles for electric vehicles and charging modules for battery swapping stations, ensuring that a single component failure during charging does not affect the overall output, improving the availability of charging equipment.

[0053] Figure 1 This is a schematic diagram of a three-phase bridge according to an embodiment of the present disclosure. The control method proposed in this disclosure can be used to control a three-phase bridge, such as... Figure 1 The three-phase bridge 1000 shown in (1) includes three power modules 100. The power modules can be phase bridge arms, and each phase bridge arm includes at least three bridge arms. For example, it includes an upper bridge arm, a middle bridge arm, and a lower bridge arm. The topology of the three-phase bridge can be a T-type three-level topology.

[0054] For example, a three-phase bridge arm may include phase A, phase B, and phase C. Each phase arm has the same topology.

[0055] In some embodiments, such as Figure 1The power module 100 shown in Figure (2) has at least three bridge arms, including a first bridge arm 110, a second bridge arm 120, and a third bridge arm 130. The first ends of each of the first bridge arms 110, 120, and 130 are connected to the AC output terminal AC of the power module 100. The AC output terminal AC of the power module 100 is used to connect to an external load (such as one phase winding of a motor). The second end of the first bridge arm 110 is connected to the positive terminal DC+ of the DC bus to obtain a positive voltage level from the DC bus. The second end of the second bridge arm 120 is connected to the midpoint O of the DC bus to obtain a zero voltage level from the DC bus. The second end of the third bridge arm 130 is connected to the negative terminal DC- of the DC bus to obtain a negative voltage level from the DC bus.

[0056] For example, the first bridge arm is the upper bridge arm, the second bridge arm is the middle bridge arm, and the third bridge arm is the lower bridge arm.

[0057] In this embodiment, the positive terminal DC+ of the DC bus, the midpoint O of the DC bus, and the negative terminal DC- of the DC bus together constitute the DC connection terminal group of the power module 100, which is used to connect to an external DC power supply or a DC bus capacitor bank.

[0058] In some embodiments, each phase arm of the three-phase bridge is connected in series with a physical isolation component (such as a burst tube or fuse). When a power switching device in the target arm fails, the physical isolation component connected in series with the target arm is triggered to disconnect the target arm. This achieves rapid disconnection of the faulty arm using a low-cost physical isolation component, reducing system cost and topology complexity while ensuring fault tolerance.

[0059] In some embodiments, a first physical isolation component 1101 is connected in series in the first bridge arm 110, a second physical isolation component 1201 is connected in series in the second bridge arm 120, and a third physical isolation component 1301 is connected in series in the third bridge arm 130. The physical isolation components are used to disconnect the bridge arm when a fault occurs in their respective bridge arms, preventing the fault current from spreading to other parts of the power module or external circuits.

[0060] In some embodiments, the first bridge arm 110 includes a first power switch 1102. A first end of the first power switch is connected to the positive terminal of the DC bus, and a second end of the first power switch is connected to the AC output terminal via a first physical isolation component.

[0061] In some embodiments, the second bridge arm 120 includes a second power switch 1202 and a third power switch 1203. A first end of the second power switch is connected to the positive terminal of the DC bus, and a second end of the second power switch is connected to the first end of the third power switch. The second end of the third power switch is connected to the midpoint of the DC bus. The midpoint between the second and third power switches is connected to the AC output terminal via a second physical isolation component.

[0062] In some embodiments, the third bridge arm 130 includes a fourth power switch 1302. A third physical isolation component is connected in series between the first terminal of the fourth power switch and the AC output terminal, and the second terminal of the fourth power switch is connected to the negative terminal of the DC bus. That is, the first terminal of the fourth power switch is connected to the AC output terminal via the third physical isolation component.

[0063] In some embodiments, the first bridge arm, the second bridge arm, and the third bridge arm together constitute a single-phase bridge arm structure of a T-type three-level topology, and the power module 100 can independently output one phase of AC power.

[0064] In some embodiments, the power switches may be IGBTs (Insulated Gate Bipolar Transistors), with diodes connected in anti-parallel to each power switch to provide a freewheeling path during switch-off. The first terminal of each power switch is the collector, and the second terminal is the emitter.

[0065] In other embodiments, the power switches may be SiC MOSFETs (silicon carbide metal-oxide-semiconductor field-effect transistors), and each power switch is connected in anti-parallel with a body diode or an external diode. The first terminal of the power switch is the drain, and the second terminal is the source.

[0066] In some embodiments, the physical isolation component is an explosive tube. The explosive tube is capable of rapidly detonating upon receiving a trigger signal and disconnecting the physical isolation device in its circuit path. When a target bridge arm fails, the control module sends a trigger signal to the explosive tube corresponding to that target bridge arm, causing the explosive tube to detonate and sever the circuit connection of that bridge arm.

[0067] In other embodiments, the physical isolation component is a fuse. When a short-circuit fault occurs in the target bridge arm, causing excessive current, the fuse blows and disconnects the circuit connection of that bridge arm.

[0068] In some embodiments, the power module 100 further includes a drive circuit connected to the control terminal of each power switch transistor, used to drive each power switch transistor to turn on or off in response to an external control signal.

[0069] Through the control method disclosed herein, the three-phase bridge can maintain a stable output voltage after an open-circuit or short-circuit fault occurs in the power switching device, ensuring uninterrupted operation of the load equipment and improving the reliability and safety of the system.

[0070] In this disclosure, when the upper bridge arm fails, the phase bridge arm cannot output a positive level P; when the middle bridge arm fails, the phase bridge arm cannot output a zero level O; and when the lower bridge arm fails, the phase bridge arm cannot output a negative level N. When a certain phase bridge arm cannot output a specific level signal, all voltage vectors containing that level signal in the space voltage vector diagram are unavailable, and the set of available voltage vectors for the three-phase bridge is limited.

[0071] This disclosure determines the set of available voltage vectors based on the missing level signals and generates a modulation sequence using the inherent redundant vector resources of the three-phase bridge, thereby enabling voltage output reconstruction under fault conditions without the need for additional power switching transistors.

[0072] Figure 2 This is one of the flowcharts illustrating a three-phase bridge control method according to an embodiment of this disclosure, based on Figure 1 The structure of the three-phase bridge shown is as follows: Figure 2 As shown, the method includes the following steps.

[0073] Step 201: In response to a target arm fault in the three-phase bridge, determine the three-phase level state of the three-phase bridge.

[0074] In some embodiments, a fault level state is missing from the three-phase level states, and the fault level state includes the level signal corresponding to the target bridge arm.

[0075] In some embodiments, the target arm can be any one of the three phase arms.

[0076] In some embodiments, the three-phase level state can represent the level state obtained by arranging and combining the level signals output by each phase arm.

[0077] In some embodiments, when a target bridge arm fails, the level signal originally output by the target bridge arm cannot be output normally, and the level state containing the level signal is the fault level state. The level state in the three-phase level state is missing due to the missing level signal, resulting in the absence of the fault level state.

[0078] In some embodiments, in response to a fault occurring in a target arm of the three-phase bridge, determining the three-phase level state of the three-phase bridge includes: in response to the target arm being the upper arm, determining that the missing fault level state in the three-phase level state includes a positive level signal; in response to the target arm being the middle arm, determining that the missing fault level state in the three-phase level state includes a zero level signal; and in response to the target arm being the lower arm, determining that the missing fault level state in the three-phase level state includes a negative level signal.

[0079] In some embodiments, when the target bridge arm is the upper bridge arm, the positive level signal originally output by the upper bridge arm is missing, causing the level state containing the positive level signal to be determined as a fault level state.

[0080] For example, taking a fault in the upper arm of phase A as an example, when phase A cannot output P, ​​all fault level states of phase A with level P (such as PON, PNN, POO, PPO, etc.) are unavailable.

[0081] In some embodiments, when the target bridge arm is the middle bridge arm, the zero-level signal originally output by the middle bridge arm is missing, causing the level state containing the zero-level signal to be determined as a fault level state. Since this level state is missing, the three-phase level states also lack this fault level state accordingly.

[0082] For example, taking a fault in the bridge arm of phase A as an example, phase A cannot output 0, and can only output P or N. Then the 0 level signal that should have been able to be output is missing, and all three-phase level combinations containing the 0 level of this phase are unusable.

[0083] In some embodiments, when the target bridge arm is the lower bridge arm, the negative level signal originally output by the lower bridge arm is missing, causing the level state containing the negative level signal to be determined as a fault level state. Since this level state is missing, the three-phase level states also lack this fault level state accordingly.

[0084] For example, taking a fault in the lower arm of phase A as an example, phase A cannot output N, and can only output P or O. Then the N-level signal that should have been able to be output is missing, that is, all three-phase level combinations containing the N-level of this phase are unusable.

[0085] In the above embodiments, the missing level signal is determined according to the different positions of the faulty bridge arm. A fault in the upper bridge arm prevents the phase from outputting a positive level, a fault in the middle bridge arm prevents the phase from outputting a zero level, and a fault in the lower bridge arm prevents the phase from outputting a negative level. By establishing a mapping relationship between the fault location and the missing level signal, accurate constraints are provided for the reconstruction of the modulation sequence, avoiding modulation failure caused by blind reconstruction.

[0086] In some embodiments, in response to a fault occurring in a target arm of a three-phase bridge, the method includes: determining the voltage across a power switching device in the target arm; determining the fault as a short-circuit fault in response to the voltage remaining at zero; or, determining the fault as an open-circuit fault in response to the voltage remaining at non-zero.

[0087] In some embodiments, the power switching device can be a power switching transistor in each bridge arm. The voltage across the power switching device in the target bridge arm can be determined by real-time detection of the voltage between the collector and emitter (or drain and source) of the power switching transistor, i.e., Vce or Vds, through a voltage sampling circuit.

[0088] In some embodiments, the power switching device, under normal operating conditions, alternately turns on (voltage at both ends close to 0V) and off (voltage at both ends close to the bus voltage) according to the PWM drive signal. When the device malfunctions, its terminal voltage will exhibit abnormal characteristics of being continuously zero or continuously non-zero.

[0089] In some embodiments, in response to a continuously zero voltage, a low-impedance path can be formed between the collector and emitter (or drain and source) of the power switching device, equivalent to a continuous conducting state. In this case, regardless of changes in the drive signal, the voltage across the device remains close to 0V and does not switch with the PWM cycle. If the device is short-circuited or shoot-through and cannot be turned off normally, the fault is determined to be a short circuit. If not handled promptly, this may lead to a shoot-through short circuit between the upper and lower bridge arms, causing a large current to burn out the power module or PCB board.

[0090] In some embodiments, in response to a persistently non-zero voltage, i.e., an internal open circuit in the power switching device, current cannot flow through the device regardless of changes in the drive signal. If the device were to be in a conducting state, the voltage across it would be the bus voltage or close to the bus voltage. If, over multiple consecutive detection cycles, the voltage value remains at a high DC voltage level and does not switch with the PWM cycle, it indicates that the device is open-circuited and cannot conduct normally, confirming an open-circuit fault. In this case, the output capability of that phase bridge arm is limited, requiring the faulty bridge arm to be disabled and the modulation sequence reconstructed to maintain the continued operation of the three-phase bridge.

[0091] In the above embodiment, the fault type is determined by detecting the voltage across the power switching device. A continuous zero voltage indicates a short-circuit fault, while a continuous non-zero voltage indicates an open-circuit fault. This detection method can be implemented directly using existing voltage sampling circuits, reducing hardware costs. Furthermore, the voltage determination method is simple, reliable, and has a fast response speed, meeting the real-time requirements of fault-tolerant control.

[0092] Step 202: Generate a modulation sequence to adjust the output voltage of the three-phase bridge based on the three-phase level states.

[0093] In some embodiments, a modulation sequence capable of controlling the output voltage of the three-phase bridge is generated based on the three-phase level states. This can be achieved by selecting candidate vectors from the available voltage vectors based on the level loss caused by a fault, and generating a modulation sequence (i.e., an SVPWM waveform generation sequence) accordingly. This sequence is used to control the on / off state of each power switch in the three-phase bridge, ensuring that the three-phase bridge can still output the desired voltage even under fault conditions.

[0094] In this embodiment, due to different fault locations, the missing level signals differ, resulting in different usable level states for each phase. Therefore, the modulation sequence needs to be dynamically generated based on the actual three-phase level states, rather than using a fixed transmission sequence. In each control cycle, the system recalculates and generates an adapted modulation sequence based on the current fault state and the reference / target voltage.

[0095] In this embodiment, under fault conditions, the number of available voltage vectors in the modulation sequence is less than under normal conditions. However, by reasonably selecting the remaining vectors, the required reference voltage can still be synthesized, so that the three-phase bridge can maintain a stable output voltage after the fault.

[0096] For example, taking a fault in the upper arm of phase A as an example, phase A cannot output a positive level P, and can only output O and N. In this case, all voltage vectors of phase A with a level of P (such as PON, PNN, POO, etc.) are unusable. Among the remaining usable vectors, there are still a sufficient number of small vectors, medium vectors, and zero vectors. By reselecting the vector combination, the reference voltage can still be synthesized, but the output voltage amplitude is reduced, that is, it enters the derating operation mode.

[0097] In some embodiments, generating a modulation sequence for adjusting the output voltage of a three-phase bridge based on the three-phase level states includes: determining a candidate voltage vector based on the three-phase level states; and generating a modulation sequence for synthesizing a target voltage based on the candidate voltage vector.

[0098] In some embodiments, a spatial voltage vector diagram can be reconstructed based on the three-phase voltage states. In the spatial vector diagram, each voltage vector has a corresponding combination of level signals for the three-phase voltage states (e.g., the large vector PNN corresponds to phase A P, phase B N, and phase C N). If a certain three-phase voltage state contains unusable level signals, then the voltage vector corresponding to that combination is unusable. Therefore, there is a one-to-one correspondence between missing levels and unusable vectors.

[0099] In some embodiments, based on the reconstructed spatial voltage vector map, available candidate voltage vectors can be determined. By mapping the level state to the voltage vector, fault information is transmitted to the modulation layer, so that the subsequent generated modulation sequence can be selected and arranged among the available candidate voltage vectors.

[0100] In the above embodiments, available candidate voltage vectors are selected based on the three-phase level states to ensure that each vector in the candidate voltage vector set is physically realizable; then, under the constraints of the candidate voltage vectors, a modulation sequence for synthesizing the target voltage is generated, thereby achieving accurate synthesis of the target voltage under fault constraints and ensuring the output voltage accuracy under three-phase bridge fault conditions.

[0101] In some embodiments, determining candidate voltage vectors based on three-phase level states includes: determining missing voltage vectors based on three-phase level states, wherein the missing voltage vectors correspond to fault level states; and determining candidate voltage vectors based on an initial set of voltage vectors and the missing voltage vectors, wherein the candidate voltage vectors are associated with sectors.

[0102] In some embodiments, based on the three-phase level states, a missing voltage vector corresponding to the fault level states can be determined.

[0103] For example, when a fault occurs in the upper arm of phase A, causing phase A to be unable to output a positive level P, the fault level state is all the level states of phase A when it is P. The missing voltage vector is the voltage vector corresponding to all three-phase level combinations of phase A when the level is P (such as PON, PNN, POO, PPO, etc.).

[0104] In some embodiments, the initial voltage vector set is a complete combination that includes all level signals P, O, and N. Once the missing voltage vector is determined, the missing voltage vector can be removed from the initial voltage vector set, and the remaining voltage vectors that do not contain the A-phase P level constitute the set of candidate voltage vectors.

[0105] In some embodiments, each sector corresponds to a specific set of candidate voltage vectors. The candidate voltage vectors within a sector can be combined to synthesize a corresponding reference voltage. The reference voltage synthesized by different combinations of candidate voltage vectors can be the same or different.

[0106] In the above embodiments, by identifying the missing voltage vectors corresponding to the fault level state and removing them from the initial voltage vector set, the remaining vectors form a set of candidate voltage vectors. This filtering method can filter out all unusable vectors, avoiding omissions; at the same time, the correlation between candidate voltage vectors and sectors facilitates the selection of vector combinations within subsequent sectors, improving the efficiency of determining the modulation sequence.

[0107] In some embodiments, generating a modulation sequence for synthesizing a target voltage based on candidate voltage vectors includes: determining a target sector where the target voltage is located based on the target voltage; determining a combination of target voltage vectors for synthesizing the target voltage based on the target sector and candidate voltage vectors; and determining a modulation sequence based on the combination of target voltage vectors.

[0108] In some embodiments, the target voltage may be a reference voltage vector Vref that the control system expects the three-phase bridge output to be generated by an upper-level controller (such as a current loop PI regulator) based on torque / speed commands, and has a defined amplitude and phase angle in the space voltage vector diagram.

[0109] In some embodiments, the target sector where the target voltage is located can be determined based on the target voltage, that is, the sector position of the target voltage vector Vref in the space voltage vector diagram, which is determined by the phase angle of Vref.

[0110] For example, if the phase angle is between 0° and 60°, then the target sector is the first sector.

[0111] In some embodiments, determining the target voltage vector combination based on the target sector and candidate voltage vectors may involve selecting candidate voltage vectors in the target sector as the target voltage vectors in the target voltage vector combination.

[0112] In some embodiments, within each sector, several basic voltage vectors need to be selected to synthesize a reference voltage vector Vref using the volt-second balance principle. Under normal conditions, each sector typically selects two adjacent non-zero vectors and one zero vector (or more vectors) for combination. Target voltage vector combination, under the constraint of candidate voltage vectors, selects the specific set of vectors used to synthesize Vref and their respective application times from the available vector set corresponding to the target sector.

[0113] For example, consider a fault in the upper arm of phase A (phase A lacks P): Under normal conditions, the first sector typically uses vector combinations: POO-OOO / OON-ONN-... (phase A can output P). When phase A lacks P, vectors containing P, such as POO, become unavailable. The system then reselects available vectors from the candidate vectors (e.g., OOO-OON-ONN-...) to synthesize Vref. Although the number of available vectors decreases, Vref can still be synthesized by appropriately selecting the remaining vectors, only the output voltage amplitude is reduced.

[0114] In some embodiments, determining the modulation sequence based on the target voltage vector combination can be achieved by arranging the vectors in the target voltage vector combination in a specific order to form a PWM waveform sequence. In three-level SVPWM, to reduce the number of switching operations and lower switching losses, the modulation sequence can adopt a five-segment or seven-segment symmetrical waveform generation method, for example: seven-segment sequence: V0-V1-V2-V3-V2-V1-V0; five-segment sequence: V0-V1-V2-V1-V0. This modulation sequence is ultimately converted into PWM drive signals for each phase power switch, determining the actual output voltage waveform of the three-phase bridge.

[0115] In the above embodiments, the target sector where the target voltage is located is first determined based on its spatial position. Then, the target voltage vector combination used to synthesize the target voltage is selected only from the candidate voltage vectors corresponding to the target sector. By limiting the sector, the vector selection range is narrowed, reducing computational complexity. At the same time, the physical realizability of the selected vector is ensured, improving the accuracy and real-time performance of the modulation sequence determination.

[0116] In some embodiments, the method further includes: in response to a target arm failure in a three-phase bridge, triggering a physical isolation component connected in series with the target arm to disconnect the target arm.

[0117] In this embodiment, when the target bridge arm fails, the target bridge arm can be isolated by triggering the physical isolation component to disconnect it, thereby avoiding interference with the status of other normal bridge arms and ensuring that the three-phase bridge can operate normally.

[0118] In the above embodiments, the faulty bridge arm is quickly physically disconnected by the physical isolation component, which effectively prevents the continuous flow of fault current under short-circuit fault, avoids damage to other devices caused by fault propagation, and improves the safety and reliability of the system under short-circuit fault scenarios.

[0119] Step 203: Update the modulation sequence to the target modulation sequence based on the neutral point potential of the three-phase bridge and the vector combination corresponding to the modulation sequence.

[0120] In some embodiments, the target modulation sequence is used to output the target voltage of the three-phase bridge.

[0121] In some embodiments, the neutral point potential can be achieved by connecting two bus capacitors in series between the positive and negative terminals of the DC bus, with the connection point of the two capacitors being the neutral point. When the voltages of the two bus capacitors are exactly equal, the neutral point potential is half of the DC bus voltage (i.e., the ideal midpoint). However, in actual operation, due to the asymmetrical charging and discharging of the two capacitors by the three-phase bridge under different switching states, the neutral point potential will shift. This shift in neutral point potential can lead to uneven capacitor voltages, output waveform distortion, and increased voltage stress on power devices, potentially damaging devices or causing system failures in severe cases. Therefore, it is necessary to monitor and suppress the neutral point potential in real time.

[0122] In some embodiments, the modulation sequence generated in step 202 can be modified according to the neutral point potential to ensure that the modified modulation sequence can control the three-phase bridge to output a stable target voltage.

[0123] In some embodiments, updating the modulation sequence to a target modulation sequence based on the neutral point potential of the three-phase bridge and the vector combination corresponding to the modulation sequence includes: determining the offset polarity of the neutral point potential; and adjusting the redundant vectors in the modulation sequence by switching the vector combination based on the offset polarity to determine the target modulation sequence.

[0124] In some embodiments, the polarity of the neutral point potential shift can be determined by detecting the voltages of the two capacitors on the DC bus side connected to the three-phase bridge, i.e., by detecting the voltage between the midpoint of the DC bus and the negative terminal of the DC bus, or by detecting the voltage difference between the first capacitor and the second capacitor. When the voltage of the first capacitor is higher than the voltage of the second capacitor, the neutral point potential is determined to be negatively shifted; when the voltage of the first capacitor is lower than the voltage of the second capacitor, the neutral point potential is determined to be positively shifted.

[0125] In this embodiment, the redundant vectors synthesize the same voltage (i.e., the output voltage vectors are equivalent), but the midpoint currents are in opposite directions, thus their influence on the neutral point potential is opposite. Space voltage vectors can be classified into four categories: large vectors, medium vectors, small vectors, and zero vectors. Among them, small vectors are divided into two groups, each corresponding to space voltage vectors with the same amplitude but opposite phases, and are redundant vectors. For example, in a three-level inverter, POO and ONN are a pair of redundant small vectors; they produce the same output voltage, but their influence on the DC-side neutral point potential is opposite.

[0126] In this embodiment, by switching vector combinations according to the offset polarity, redundant vectors in the modulation sequence can be adjusted accordingly, thereby achieving joint optimization of the synthesized target voltage and the equilibrium midpoint potential.

[0127] In this embodiment, the target modulation sequence is generated by switching vector combinations according to the offset polarity. This can be achieved by switching the type of redundant vectors and changing the direction and magnitude of the neutral point current while keeping the output voltage constant, thereby pulling the neutral point potential back to a balanced state and maintaining the stable output of the three-phase bridge.

[0128] In the above embodiment, the polarity of the neutral point potential offset of the three-phase bridge is detected, and the redundant vector in the modulation sequence is dynamically adjusted accordingly. Since the redundant vectors have the same amplitude but different current paths, their selection will affect the charging and discharging state of the neutral point potential. By selecting the corresponding redundant vector according to the offset polarity, active balance control of the neutral point potential can be achieved under fault conditions, avoiding the problems of uneven capacitor voltage and output waveform distortion caused by the neutral point potential offset after a fault.

[0129] In some embodiments, the target modulation sequence is determined by adjusting redundant vectors in the modulation sequence through vector combination switching based on the offset polarity, including: obtaining a mapping relationship between vector combination and offset polarity; determining the target modulation sequence based on a first vector combination in the mapping relationship in response to a positive offset polarity; or, determining the target modulation sequence based on a second vector combination in the mapping relationship in response to a negative offset polarity.

[0130] In some embodiments, the mapping relationship between vector combinations and offset polarities is a pre-configured correspondence. Since some small vectors are missing under fault conditions, it is impossible to continuously adjust the neutral point potential by adjusting the ratio of the action time of positive and negative small vectors in real time. Therefore, corresponding vector combinations are pre-configured for both positive and negative offset polarities of the neutral point potential. When an offset polarity is detected, the modulation sequence is updated by directly selecting the vector combination corresponding to that polarity, thus pulling the neutral point potential back to a balanced state while maintaining a constant output voltage.

[0131] In this embodiment, the first vector combination and the second vector combination are different preset vector sequences for the positive and negative offsets of the neutral point potential, respectively. The vector combination is switched by selecting the corresponding preset vector sequence after the offset polarity is detected, rather than calculating the proportion of the action time of each vector in real time.

[0132] In some embodiments, different mapping relationships can be set for different bridge arms, so that in the event of a target bridge arm failure, the mapping relationship corresponding to the target bridge arm can be obtained for updating the modulation sequence of the neutral point potential shift under the target bridge arm failure.

[0133] In this embodiment, the first vector combination and the second vector combination are different. When the offset polarity is positive, the proportion of negative small vectors in the first vector combination is greater than that in the second vector combination; when the offset polarity is negative, the proportion of positive small vectors in the second vector combination is greater than that in the first vector combination.

[0134] In this embodiment, since both the first vector combination and the second vector combination are determined based on the three-phase level state, and the type and order of redundant vectors in each combination are pre-configured, there is no need to calculate the action time of each vector in real time during the actual control process. The corresponding combination can be selected directly according to the offset polarity, which significantly reduces the calculation burden and response delay under fault conditions.

[0135] For example, taking the upper arm fault of phase A as an example, the mapping relationship between vector combination and offset polarity is shown in Table 1.

[0136] Table 1:

[0137] For example, taking a fault in the upper arm of phase A (phase A lacks P level) as an example, when the neutral point potential shifts positively, in sector II, the first vector combination (such as [OOO]-[OON]-[NON]-[O ON]-[OOO]) is selected according to the mapping relationship. In this combination, the proportion of negative small vectors (such as NON, ONN, etc.) is relatively high, causing the neutral point potential to move in the negative direction, thereby offsetting the positive shift. When the neutral point potential shifts negatively, the second vector combination (such as [O OO]-[OPO]-[OON]-[OPO]-[OOO]) is selected according to the mapping relationship. In this combination, the proportion of positive small vectors (such as OPO, POO, etc.) is relatively high, causing the neutral point potential to move in the positive direction, thereby offsetting the negative shift.

[0138] In summary, by responding to a target bridge arm fault in a three-phase bridge, the missing fault level state in the three-phase level state is determined, and then a modulation sequence is generated based on this level state. The modulation sequence is updated to the target modulation sequence by vector combination switching, which realizes the rapid and reliable adjustment of the neutral point potential under fault conditions and the rapid reconstruction of the three-phase bridge output voltage after a fault.

[0139] Figure 3 This is the second schematic flowchart illustrating the control method of a three-phase bridge according to an embodiment of this disclosure, based on Figure 2 The embodiment shown, Figure 3 right Figure 2 Step 202 in the text will be further explained, such as Figure 3 As shown, the steps include the following.

[0140] Step 301: In response to the missing fault level state in the three-phase level state, including the zero level signal, the waveform transmission mode is switched from the first waveform transmission mode to the second waveform transmission mode.

[0141] In some embodiments, the absence of a zero-level signal is caused by a fault in the middle arm of one phase of a three-phase bridge, resulting in that phase being unable to output a zero level (0V). In this case, the phase can only output a positive level P and a negative level N, that is, the phase operates in a two-level mode.

[0142] In some embodiments, the first waveform transmission method can be a three-level space vector pulse width modulation (SVPWM) method, and the second waveform transmission method can be a two-level SVPWM method. When the zero-level signal is missing, the redundant vectors among the available candidate voltage vectors are insufficient to support the neutral point potential balance control under the three-level waveform transmission method. Therefore, the waveform transmission method is switched to the two-level SVPWM method to ensure that the three-phase bridge can still maintain a stable output voltage under extreme fault conditions.

[0143] Step 302: Generate a modulation sequence according to the second transmission method.

[0144] In some embodiments, generating a modulation sequence according to the second transmission method can be achieved by controlling the power switches of the upper and lower bridge arms in each phase bridge arm to operate under a two-level space vector pulse width modulation mode, while turning off the power switches of all middle bridge arms, so that the three-phase bridge operates in a two-level mode.

[0145] For example, taking a fault in the middle bridge arm of phase A as an example, after detecting that phase A cannot output a zero-level signal O, the waveform output mode of the three-phase bridge is switched from three-level SVPWM to two-level SVPWM. Only the upper and lower bridge arm switches of each phase remain operational, while all middle bridge arm switches are turned off. The three-phase bridge outputs voltage in two-level SVPWM mode, which can achieve derating operation.

[0146] In this embodiment, the specific method for generating the modulation sequence according to the second wave transmission method is not limited in this disclosure. In the event of a neutral point potential shift, a DC bus voltage equalization control strategy independent of the switching state (such as a hardware voltage equalization resistor or an independent capacitor voltage equalization circuit) can be used for management.

[0147] In summary, the three-phase bridge control method proposed in this disclosure, by responding to a target bridge arm fault in the three-phase bridge, determines the missing fault level state in the three-phase voltage levels, generates a modulation sequence based on this level state, and finally updates the modulation sequence to the target modulation sequence based on the neutral point potential, thus achieving rapid reconstruction of the three-phase bridge output voltage after a fault. Since the fault level state directly reflects the voltage signal that the target bridge arm cannot output, the generated modulation sequence can effectively avoid the faulty bridge arm, preventing output interruption caused by the fault. Furthermore, by introducing neutral point potential feedback during the modulation sequence update process, the balance and stability of the three-phase bridge output voltage under fault conditions are ensured.

[0148] based on Figures 2-3 The embodiments shown below provide a specific implementation method, which can be used as... Figures 2-3 One specific implementation of the embodiment shown is illustrated.

[0149] A fault-tolerant control method for a T-type NPC three-level inverter includes the following steps: Step 1, real-time device fault detection of the T-type NPC three-level inverter to determine the location and type of the fault; Step 2, determining the lost space voltage vector under the fault state based on the fault location and fault type, and drawing a space voltage vector distribution diagram under the fault state; Step 3, based on the redrawn space voltage vector distribution diagram, redesigning the combination for synthesizing the rotating reference space voltage vector using redundant space vectors.

[0150] Figure 4A This is a hardware topology diagram of a T-type three-level inverter in a specific implementation. It is a T-type derivative structure of the midpoint clamped three-level topology. The whole consists of three main parts: DC bus-side energy storage unit, three-phase inverter bridge arm, sampling current limiting and protection device. It is used to realize the conversion of DC power to three-phase AC power, and the topology design takes into account both conduction loss optimization and fault tolerance capability.

[0151] This topology can be mainly divided into two parts: the DC bus-side energy storage unit and the three-phase inverter bridge arms. The DC bus-side energy storage unit includes a DC power supply Udc, a first DC bus capacitor C1, and a second DC bus capacitor C2. The positive output terminal of Udc is electrically connected to one end of C1, the other end of C1 is electrically connected to one end of C2, and the other end of C2 is electrically connected to the negative output terminal of Udc. The connection point of C1 and C2 constitutes the DC bus midpoint (O point), providing a zero-level reference potential for the three-phase inverter bridge arms. C1 and C2 are used to stabilize the DC bus voltage, suppress bus voltage fluctuations, and simultaneously achieve midpoint potential balance of the DC bus voltage. Three-phase inverter bridge arms (taking A, B, and C phases as an example): This topology sets up three independent inverter bridge arms for phases A, B, and C. Each phase bridge arm adopts a T-type symmetrical switch structure, specifically composed of an upper bridge arm switch group, a middle bridge arm clamping switch group, and a lower bridge arm switch group. The device configuration and connection relationship of each phase bridge arm are consistent.

[0152] Taking phase A of the bridge arm as an example: The upper bridge arm switching transistor group includes the first main switching transistor Sa1, which is an IGBT device with a reverse parallel diode. The collector of Sa1 is electrically connected to the positive side of the DC bus (the positive terminal of C1); the emitter of Sa1 is electrically connected to the AC output terminal of phase A of the bridge arm through the first exploding diode Ra1. The middle bridge arm clamping switching transistor group includes the second main switching transistor Sa2 and the third main switching transistor Sa3; both Sa2 and Sa3 are IGBT devices with reverse parallel diodes. The collector of Sa2 is electrically connected to the positive side of the DC bus (the positive terminal of C1), and the emitter of Sa2 is electrically connected to the collector of Sa3; the emitter of Sa3 is electrically connected to the DC bus (point O). The midpoint of the connection between Sa2 and Sa3 is electrically connected to the AC output terminal of phase A of the bridge arm through the second exploding diode Ra2. The lower bridge arm switching transistor group includes the fourth main switching transistor Sa4, which is an IGBT device with a reverse parallel diode. The collector of Sa4 is electrically connected to the AC output terminal of the A-phase bridge arm; the emitter of Sa4 is electrically connected to the negative side of the DC bus (C2 negative terminal) through the third explosion tube Ra3.

[0153] Based on this topology, the above steps can be described in detail as follows: In step 1, real-time device fault detection is required for the T-type NPC three-level inverter to determine the fault location and type. Fault locations include the upper arm, middle arm, and lower arm. When the real-time monitored voltage is consistently zero, a short-circuit fault is determined in the corresponding power electronic device. When the real-time monitored voltage is consistently non-zero, an open-circuit fault is determined in the corresponding power electronic device.

[0154] In step 2, the spatial vector distribution diagram under fault-free conditions is as follows: Figure 4BAs shown. A complete space vector synthesis relies on all three phases being able to provide P, O, and N voltage levels. However, when the upper bridge arm is faulted and shielded, that phase cannot provide a P level; when the middle bridge arm is faulted and shielded, that phase cannot provide an O level; and when the lower bridge arm is faulted and shielded, that phase cannot provide an N level. Figure 4B This is a spatial vector diagram under normal conditions, such as... Figure 4B As shown, a lack of voltage level will severely affect the original space vector synthesis method.

[0155] In step 3, by Figure 4B It can be seen that space voltage vectors can be divided into four categories: large vectors, medium vectors, small vectors, and zero vectors. Large vectors contain 6 three-phase output level states: PNN, PPN, NPN, NPP, NNP, and PNP. Medium vectors contain 6 three-phase output level states: PON, OPN, NPO, NOP, ONP, and PNO. Small vectors contain 12 three-phase output level states, divided into two symmetrical groups: Group 1: POO, ONN, PPO, OON, OPO, NON; Group 2: OPP, NOO, OPP, NOO, POP, ONO. Each group of small vectors corresponds to space voltage vectors with the same amplitude but opposite phase. Zero vectors contain 3 three-phase output level states: PPP, OOO, and NNN. It can be seen that both small and zero vectors have redundancy; therefore, when phase A cannot provide P level due to power device failure, redundant vectors can still be used for space vector synthesis.

[0156] Depending on the different fault conditions, the following three scenarios may exist.

[0157] Example 1: Real-time fault monitoring is performed on a T-type three-level inverter. When the voltage at the Sa1 terminal is always zero or always non-zero, it is determined that a short circuit / open circuit fault has occurred in the upper bridge arm of phase A. At this time, the explosion tube Ra1 is used to cut off the upper bridge arm of phase A to shield the faulty device. Therefore, phase A cannot output the P level state and can only output the O and N level states. Figure 4C The diagram shows the space voltage vector distribution after the loss of the P-level state. The space vectors lost due to the fault are crossed out by double lines. As can be seen from the diagram, although the small vectors lost in the second to fifth sectors can be compensated by redundant small vectors, all large vectors in the first and sixth sectors are lost, and there are no redundant large vectors. Therefore, after fault-tolerant control, the amplitude of the synthesized space vector is reduced, and the inverter is in a derating operation state.

[0158] Due to the absence of some small vectors, the T-type three-level inverter in fault condition cannot balance the neutral point potential by adjusting the duration of the positive and negative small vectors according to the neutral point potential. In order to make full use of redundant vectors and minimize the neutral point potential shift, two different vector combinations are designed for neutral point potentials of different polarities. The pulse transmission sequence is shown in Table 1 of the above embodiment.

[0159] Example 2: Real-time fault monitoring is performed on a T-type three-level inverter. When the voltage across Sa4 is always zero or always non-zero, it is determined that a short circuit / open circuit fault has occurred in the lower bridge arm of phase A. At this time, the explosion tube Ra3 is used to cut off the lower bridge arm of phase A to shield the faulty device. Therefore, phase A cannot output the N level state and can only output the P and O level states. Figure 4D The diagram shows the space voltage vector distribution after the loss of the N-level state. The space vectors lost due to the fault are crossed out by double lines. As can be seen from the diagram, although the small lost vectors in sectors 1, 2, 5, and 6 can be compensated by redundant small vectors, all large vectors in sectors 3 and 4 are lost, and these lost large vectors have no redundancy. Therefore, after fault-tolerant control, the amplitude of the synthesized space vector decreases, and the inverter operates in a derating state.

[0160] Due to the absence of some small vectors, the T-type three-level inverter under fault conditions cannot adjust the duration of the positive and negative small vectors to balance the neutral point potential based on the neutral point potential. In order to make full use of the redundant vectors and minimize the neutral point potential shift, two different vector combinations are designed for neutral point potentials of different polarities. The pulse transmission sequences are shown in Table 2 below.

[0161] Table 2:

[0162] Example 3: Real-time fault monitoring is performed on a T-type three-level inverter. When the voltage across Sa2 or Sa3 is always zero or always non-zero, it is determined that a short circuit / open circuit fault has occurred in the bridge arm of phase A. At this time, the explosion tube Ra2 is used to cut off the lower bridge arm of phase A to shield the faulty device. Therefore, phase A cannot output a zero level state and can only output two levels, P and N. Figure 4E The diagram shows the space voltage vector distribution after the loss of the zero-level state. The double-lined areas represent the space vectors lost due to the fault. As can be seen, although all negative small vectors are lost in the first and second sectors, leaving only positive small vectors, if redundant vectors are still selected for fault-tolerant control in this situation, the neutral point potential offset cannot be compensated. Therefore, in this state, it is necessary to directly switch to the more mature traditional two-level inverter drive strategy.

[0163] The specific real-time measures are as follows: upon detecting a fault in the middle bridge arm, the faulty middle bridge arm is promptly shielded using an explosion tube. At this time, Sa1, Sa4, Sb1, Sb4, Sc1, and Sc4 all operate under the two-level SVPWM wave propagation drive signal, and all remaining switching devices are turned off.

[0164] In summary, this solution, in the fault-tolerant control process, for the T-type three-level inverter when a fault occurs, accurately identifies the neutral point potential offset state of different polarities and designs a corresponding matching space vector combination strategy to achieve dynamic balance control of the neutral point potential under fault conditions. This effectively reduces the total harmonic distortion (THD) of the inverter output phase current, reduces the torque pulsation of the motor load, ensures the stability of load operation, and improves the control accuracy of the system.

[0165] When a T-type three-level inverter experiences a zero-level loss fault, given that this fault leads to excessive loss of system redundant small vectors, the limp-point strategy cannot achieve neutral point potential balance control, and its operational reliability is poor, this technical solution actively switches to a more reliable two-level SVPWM waveform mode to replace the limp-point strategy. This not only solves the problem of neutral point potential imbalance under zero-level loss faults but also ensures that the inverter can maintain a stable and efficient operating state under fault conditions, avoiding system shutdown due to fault expansion.

[0166] Furthermore, this solution does not rely on faulty power devices to achieve freewheeling operation. From the control logic level, it avoids the risks of freewheeling abnormalities and secondary faults caused by the performance degradation and failure of faulty power modules. This significantly improves the reliability and stability of the T-type three-level inverter under fault conditions, extends the fault-free operation cycle of the equipment, and reduces operation and maintenance costs.

[0167] Figure 5 This is a schematic diagram of the structure of a three-phase bridge control device 500 according to an embodiment of the present disclosure. The three-phase bridge includes three phase bridge arms, which include an upper bridge arm, a middle bridge arm, and a lower bridge arm, as shown below. Figure 5 As shown, the device includes: a determining module 510, a generating module 520, and a control module 530.

[0168] The determination module is used to respond to a target bridge arm fault in the three-phase bridge by determining the three-phase level state of the three-phase bridge. The fault level state is missing from the three-phase level state, and the fault level state includes the level signal corresponding to the target bridge arm. The generation module is used to generate a modulation sequence to adjust the output voltage of the three-phase bridge based on the three-phase level state. The control module is used to update the modulation sequence to the target modulation sequence based on the neutral point potential of the three-phase bridge and the vector combination corresponding to the modulation sequence. The target modulation sequence is used to output the target voltage of the three-phase bridge.

[0169] In some embodiments, the determining module is configured to: determine, in response to the target bridge arm being the upper bridge arm, that the missing fault level state in the three-phase level states includes a positive level signal; determine, in response to the target bridge arm being the middle bridge arm, that the missing fault level state in the three-phase level states includes a zero level signal; and determine, in response to the target bridge arm being the lower bridge arm, that the missing fault level state in the three-phase level states includes a negative level signal.

[0170] In some embodiments, the generation module is configured to: determine candidate voltage vectors based on the three-phase level states; and generate a modulation sequence for synthesizing a target voltage based on the candidate voltage vectors.

[0171] In some embodiments, the generation module is used to: determine the missing voltage vector based on the three-phase level state, wherein the missing voltage vector corresponds to the fault level state; and determine the candidate voltage vector based on the initial voltage vector set and the missing voltage vector, wherein the candidate voltage vector is associated with the sector.

[0172] In some embodiments, the generation module is configured to: determine the target sector where the target voltage is located based on the target voltage; determine a target voltage vector combination for synthesizing the target voltage according to the target sector and candidate voltage vectors; and determine a modulation sequence according to the target voltage vector combination.

[0173] In some embodiments, the control module is used to: determine the offset polarity of the neutral point potential; and, based on the offset polarity, adjust redundant vectors in the modulation sequence by vector combination switching to determine the target modulation sequence.

[0174] In some embodiments, the control module is configured to: obtain a mapping relationship between vector combinations and offset polarity; determine a target modulation sequence based on a first vector combination in the mapping relationship in response to a positive offset polarity; or, determine a target modulation sequence based on a second vector combination in the mapping relationship in response to a negative offset polarity.

[0175] In some embodiments, the generation module is configured to: switch the transmission mode from a first transmission mode to a second transmission mode in response to a missing fault level state in the three-phase level states, including a zero-level signal; and generate a modulation sequence according to the second transmission mode.

[0176] In some embodiments, the control module is further configured to: in response to a target arm failure in a three-phase bridge, trigger a physical isolation component connected in series with the target arm to disconnect the target arm.

[0177] In some embodiments, the determining module is configured to: determine the voltage across the power switching device in the target arm; determine the fault as a short circuit fault in response to the voltage being continuously zero; or, determine the fault as an open circuit fault in response to the voltage being continuously non-zero.

[0178] In summary, this device reduces system cost and complexity by adaptively reconstructing the modulation sequence based on the missing level state, eliminating the need for additional fault-tolerant power units. Through the dynamic adjustment of redundant vectors driven by the neutral point potential offset polarity, it achieves active balancing of the neutral point potential under fault conditions, effectively suppressing capacitor voltage unevenness and output waveform distortion, ensuring the stable operation of the three-phase bridge under fault conditions, and improving the reliability and driving safety of the electric drive system.

[0179] This disclosure proposes a power conversion device, which includes a three-phase bridge, the three-phase bridge including three phase bridge arms, the phase bridge arms including an upper bridge arm, a middle bridge arm and a lower bridge arm, and the power conversion device is configured to perform the control method described in the above embodiments of this disclosure.

[0180] In some embodiments, each bridge arm in the phase bridge arm is connected in series with a physical isolation component, which is used to disconnect the target bridge arm that is faulty.

[0181] The power conversion device disclosed herein achieves rapid physical isolation of faulty bridge arms by connecting physical isolation components in series in each bridge arm, effectively preventing the continuous flow of fault current under short-circuit faults and ensuring system safety under fault conditions.

[0182] Figure 6 This is a schematic diagram of the structure of an electronic device 600 for implementing the above-described three-phase bridge control method, according to an exemplary embodiment.

[0183] Reference Figure 6 The electronic device 600 may include one or more of the following components: a processing component 602, a memory 604, a power supply component 606, a multimedia component 608, an audio component 610, an input / output (I / O) interface 612, a sensor component 614, and a communication component 616.

[0184] Processing component 602 typically controls the overall operation of electronic device 600, such as operations associated with display, telephone calls, data communication, camera operation, and recording operations. Processing component 602 may include one or more processors 620 to execute instructions to perform all or part of the steps of the methods described above. Furthermore, processing component 602 may include one or more modules to facilitate interaction between processing component 602 and other components. For example, processing component 602 may include a multimedia module to facilitate interaction between multimedia component 608 and processing component 602.

[0185] Memory 604 is configured to store various types of data to support the operation of electronic device 600. Examples of such data include instructions for any application or method operating on electronic device 600, contact data, phonebook data, messages, pictures, videos, etc. Memory 604 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.

[0186] Power supply component 606 provides power to various components of electronic device 600. Power supply component 606 may include a power management system, one or more power supplies, and other components associated with generating, managing, and distributing power to electronic device 600.

[0187] Multimedia component 608 includes a screen that provides an output interface between electronic device 600 and user. In some embodiments, the screen may include a liquid crystal display (LCD) and a touch panel (TP). If the screen includes a touch panel, the screen may be implemented as a touchscreen to receive input signals from the user. The touch panel includes one or more touch sensors to sense touches, swipes, and gestures on the touch panel. The touch sensors may sense not only the boundaries of touch or swipe actions but also the duration and pressure associated with the touch or swipe operation. In some embodiments, multimedia component 608 includes a front-facing camera and / or a rear-facing camera. When electronic device 600 is in an operating mode, such as a shooting mode or video mode, the front-facing camera and / or rear-facing camera may receive external multimedia data. Each front-facing camera and rear-facing camera may be a fixed optical lens system or have focal length and optical zoom capabilities.

[0188] Audio component 610 is configured to output and / or input audio signals. For example, audio component 610 includes a microphone (MIC) configured to receive external audio signals when electronic device 600 is in an operating mode, such as call mode, recording mode, and voice recognition mode. The received audio signals may be further stored in memory 604 or transmitted via communication component 616. In some embodiments, audio component 610 also includes a speaker for outputting audio signals.

[0189] I / O interface 612 provides an interface between processing component 602 and peripheral interface modules, such as keyboards, click wheels, buttons, etc. These buttons may include, but are not limited to, home buttons, volume buttons, power buttons, and lock buttons.

[0190] Sensor assembly 614 includes one or more sensors for providing state assessments of various aspects of electronic device 600. For example, sensor assembly 614 may detect the on / off state of electronic device 600, the relative positioning of components such as the display and keypad of electronic device 600, changes in position of electronic device 600 or a component of electronic device 600, the presence or absence of user contact with electronic device 600, orientation or acceleration / deceleration of electronic device 600, and temperature changes of electronic device 600. Sensor assembly 614 may include a proximity sensor configured to detect the presence of nearby objects without any physical contact. Sensor assembly 614 may also include a light sensor, such as a CMOS or CCD image sensor, for use in imaging applications. In some embodiments, sensor assembly 614 may also include an accelerometer, gyroscope, magnetometer, pressure sensor, or temperature sensor.

[0191] Communication component 616 is configured to facilitate wired or wireless communication between electronic device 600 and other devices. Electronic device 600 can access wireless networks based on communication standards, such as WiFi, 2G or 3G, 4G LTE, 5G NR (NewRadio), or combinations thereof. In one exemplary embodiment, communication component 616 receives broadcast signals or broadcast-related information from an external broadcast management system via a broadcast channel. In one exemplary embodiment, communication component 616 also includes a near-field communication (NFC) module to facilitate short-range communication. For example, the NFC module may be implemented based on radio frequency identification (RFID) technology, Infrared Data Association (IrDA) technology, ultra-wideband (UWB) technology, Bluetooth (BT) technology, and other technologies.

[0192] In an exemplary embodiment, the electronic device 600 may be implemented by one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), controllers, microcontrollers, microprocessors, or other electronic components to perform the methods described above.

[0193] In an exemplary embodiment, a non-transitory computer-readable storage medium including instructions is also provided, such as a memory 604 including instructions, which can be executed by a processor 620 of an electronic device 600 to perform the above-described method. For example, the non-transitory computer-readable storage medium may be a ROM, random access memory (RAM), CD-ROM, magnetic tape, floppy disk, and optical data storage device, etc.

[0194] Embodiments of this disclosure also provide a computer-readable storage medium storing computer instructions, wherein the computer instructions are used to cause a computer to execute the three-phase bridge control method described in the above embodiments of this disclosure.

[0195] Embodiments of this disclosure also provide a computer program product, including a computer program that is executed by a processor using the three-phase bridge control method described in the above embodiments of this disclosure.

[0196] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses, systems, and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0197] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0198] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of preferred embodiments of this disclosure includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the function involved, as will be understood by those skilled in the art to which embodiments of this disclosure pertain.

[0199] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processing module, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (control method), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which programs can be printed, because programs can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0200] It should be understood that various parts of the embodiments of this disclosure can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0201] Those skilled in the art will understand that all or part of the steps of the methods described in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0202] Furthermore, the functional units in the various embodiments of this disclosure can be integrated into a single processing module, or each unit can exist physically separately, or two or more units can be integrated into a single module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. The aforementioned storage medium can be a read-only memory, a hard disk, or an optical disk, etc.

[0203] Although embodiments of the present disclosure have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A control method for a three-phase bridge, characterized in that, The method includes: In response to a target bridge arm fault in the three-phase bridge, the three-phase level states of the three-phase bridge are determined, wherein a fault level state is missing from the three-phase level states, and the fault level state includes the level signal corresponding to the target bridge arm; Based on the three-phase level states, a modulation sequence is generated to adjust the output voltage of the three-phase bridge; Based on the neutral point potential of the three-phase bridge and the vector combination corresponding to the modulation sequence, the modulation sequence is updated to a target modulation sequence, which is used to output the target voltage of the three-phase bridge.

2. The method according to claim 1, characterized in that, The step of determining the three-phase level state of the three-phase bridge in response to a fault in a target arm of the three-phase bridge includes: In response to the target bridge arm being the upper bridge arm, it is determined that the missing fault level state in the three-phase level states includes a positive level signal; In response to the target bridge arm being the middle bridge arm, it is determined that the missing fault level state in the three-phase level states includes a zero-level signal; In response to the target bridge arm being the lower bridge arm, it is determined that the missing fault level state in the three-phase level states includes a negative level signal.

3. The method according to claim 1, characterized in that, The step of generating a modulation sequence to adjust the output voltage of the three-phase bridge based on the three-phase level states includes: Based on the three-phase level states, determine the candidate voltage vector; Based on the candidate voltage vector, the modulation sequence for synthesizing the target voltage is generated.

4. The method according to claim 3, characterized in that, The step of determining the candidate voltage vector based on the three-phase level states includes: Based on the three-phase level states, a missing voltage vector is determined, and the missing voltage vector corresponds to the fault level states; Based on the initial set of voltage vectors and the missing voltage vectors, candidate voltage vectors are determined, and the candidate voltage vectors are associated with sectors.

5. The method according to claim 3, characterized in that, The step of generating the modulation sequence for synthesizing the target voltage based on the candidate voltage vector includes: Based on the target voltage, determine the target sector where the target voltage is located; Based on the target sector and the candidate voltage vectors, a target voltage vector combination for synthesizing the target voltage is determined; The modulation sequence is determined based on the target voltage vector combination.

6. The method according to claim 1, characterized in that, The step of updating the modulation sequence to the target modulation sequence based on the neutral point potential of the three-phase bridge and the vector combination corresponding to the modulation sequence includes: Determine the polarity of the neutral point potential offset; Based on the offset polarity, the redundant vectors in the modulation sequence are adjusted by vector combination switching to determine the target modulation sequence.

7. The method according to claim 6, characterized in that, The step of adjusting redundant vectors in the modulation sequence by vector combination switching based on the offset polarity to determine the target modulation sequence includes: Obtain the mapping relationship between the vector combination and the offset polarity; In response to a positive offset, the target modulation sequence is determined according to a first vector combination in the mapping relationship; or, in response to a negative offset, the target modulation sequence is determined according to a second vector combination in the mapping relationship.

8. The method according to any one of claims 1 to 7, characterized in that, The step of generating a modulation sequence to adjust the output voltage of the three-phase bridge based on the three-phase level states includes: In response to the absence of a fault level state, including a zero-level signal, in the three-phase level states, the transmission mode is switched from the first transmission mode to the second transmission mode. The modulation sequence is generated according to the second transmission method.

9. The method according to claim 1, characterized in that, The method further includes: In response to a fault in the target arm of the three-phase bridge, a physical isolation component connected in series with the target arm is triggered to disconnect the target arm.

10. The method according to claim 1, characterized in that, The method, in response to a fault in a target arm of the three-phase bridge, includes: Determine the voltage across the power switching device in the target bridge arm; In response to the voltage remaining at zero, the fault is determined to be a short-circuit fault; or, in response to the voltage remaining at non-zero, the fault is determined to be an open-circuit fault.

11. A control device for a three-phase bridge, characterized in that, The control device includes a determining module, a generating module, and a control module. The determining module is used to determine the three-phase level state of the three-phase bridge in response to a target bridge arm fault in the three-phase bridge. The three-phase level state is missing a fault level state, and the fault level state includes the level signal corresponding to the target bridge arm. The generation module is used to generate a modulation sequence for adjusting the output voltage of the three-phase bridge based on the three-phase level states; The control module is used to update the modulation sequence to a target modulation sequence based on the neutral point potential of the three-phase bridge and the vector combination corresponding to the modulation sequence. The target modulation sequence is used to output a target voltage for the three-phase bridge.

12. The apparatus according to claim 11, characterized in that, The determining module is used for: In response to the target bridge arm being the upper bridge arm, it is determined that the missing fault level state in the three-phase level states includes a positive level signal; In response to the target bridge arm being the middle bridge arm, it is determined that the missing fault level state in the three-phase level states includes a zero-level signal; In response to the target bridge arm being the lower bridge arm, it is determined that the missing fault level state in the three-phase level states includes a negative level signal.

13. The apparatus according to claim 11, characterized in that, The generation module is used for: Based on the three-phase level states, determine the candidate voltage vector; Based on the candidate voltage vector, the modulation sequence for synthesizing the target voltage is generated.

14. The apparatus according to claim 13, characterized in that, The generation module is used for: Based on the target voltage, determine the target sector where the target voltage is located; Based on the target sector and the candidate voltage vectors, a target voltage vector combination for synthesizing the target voltage is determined; The modulation sequence is determined based on the target voltage vector combination.

15. The apparatus according to claim 11, characterized in that, The control module is used for: Determine the polarity of the neutral point potential offset; Based on the offset polarity, the redundant vectors in the modulation sequence are adjusted by vector combination switching to determine the target modulation sequence.

16. The apparatus according to claim 15, characterized in that, The control module is used for: Obtain the mapping relationship between the vector combination and the offset polarity; In response to the offset polarity being a positive offset, the target modulation sequence is determined according to the first vector combination in the mapping relationship; Alternatively, in response to the offset polarity being a negative offset, the target modulation sequence is determined according to the second vector combination in the mapping relationship.

17. The apparatus according to any one of claims 11 to 16, characterized in that, The generation module is used for: In response to the absence of a fault level state, including a zero-level signal, in the three-phase level states, the transmission mode is switched from the first transmission mode to the second transmission mode. The modulation sequence is generated according to the second transmission method.

18. The apparatus according to claim 11, characterized in that, The control module is used for: In response to a fault in the target arm of the three-phase bridge, a physical isolation component connected in series with the target arm is triggered to disconnect the target arm.

19. A power conversion device, characterized in that, The power conversion device includes a three-phase bridge, the three-phase bridge includes three phase bridge arms, the phase bridge arms include an upper bridge arm, a middle bridge arm, and a lower bridge arm, and the power conversion device is configured to perform the control method according to any one of claims 1 to 10.

20. The power conversion device according to claim 19, characterized in that, Each bridge arm in the phase bridge arm is connected in series with a physical isolation component, which is used to disconnect the target bridge arm that is faulty.

21. An electronic device, characterized in that, include: A processor and a memory for storing a computer program capable of running on the processor, wherein the processor, when running the computer program, performs the method of any one of claims 1 to 10.

22. A computer-readable storage medium storing computer instructions, characterized in that, The computer instructions are used to cause the computer to perform the method according to any one of claims 1 to 10.

23. A program product, characterized in that, Includes computer instructions for causing a computer to perform the method of any one of claims 1 to 10.

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