Fault-tolerant control method, device and equipment of cascaded H-bridge inverter and storage medium

Abstract

The invention discloses a fault-tolerant control method, device and equipment for a cascaded H-bridge inverter and a storage medium, and relates to the technical field of converter control, and the method comprises the steps: determining a fault single-phase H-bridge sub-module when the cascaded H-bridge inverter breaks down, and carrying out the bypass processing of the fault single-phase H-bridge sub-module; determining a fault type of a corresponding phase based on the fault single-phase H-bridge sub-module; according to the fault type, generating a corresponding zero sequence voltage; and based on the fault type and the corresponding zero sequence voltage, determining the maximum balanced line voltage which can be output by the cascaded H-bridge inverter under the condition of three-phase line voltage balance, and controlling the inverter based on the maximum balanced line voltage. Namely, through closed-loop control logic of fault type identification, zero-sequence voltage customization, maximum balance voltage solving and modulation instruction reconstruction, stable operation and three-phase balance of a motor system are ensured, meanwhile, the power potential of the inverter in the fault state is released to the maximum extent, and therefore the voltage output capacity of the inverter is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of converter control, in particular to a fault-tolerant control method, device and equipment of a cascaded H-bridge inverter and a storage medium. BACKGROUND

[0002] The cascaded H-bridge multilevel inverter has been widely used in high-power motor drive and other fields due to its unique advantages of reducing the voltage stress of switching devices, reducing the voltage and current step change rate, and reducing the total harmonic distortion of output voltage and current. However, the design structure of multiple switching devices and multiple modules also significantly increases the probability of failure of the cascaded H-bridge multilevel inverter.

[0003] The software fault-tolerant control strategy in the current fault-tolerant control strategy of the cascaded H-bridge multilevel inverter does not require additional hardware costs, and by modifying the control and modulation of the inverter, the inverter can still operate stably at maximum power after a fault occurs. However, the current fault-tolerant strategy reduces the zero sequence component required to be injected under low line voltage requirements, and cannot achieve efficient utilization of the bus voltage, thereby failing to ensure that the system can operate stably after a fault occurs and improve the output voltage capability of the inverter.

[0004] The above content is only used to assist in understanding the technical solutions of the present application and does not represent the acknowledgement of the above content as prior art. SUMMARY

[0005] The main purpose of the present application is to provide a fault-tolerant control method, device, equipment, storage medium and product of a cascaded H-bridge inverter, which aims to solve the technical problem of failing to ensure that the system can operate stably after a fault occurs and improve the output voltage capability of the inverter.

[0006] To achieve the above-mentioned purpose, the present application provides a fault-tolerant control method of a cascaded H-bridge inverter, which comprises: When a fault occurs in the cascaded H-bridge inverter, a fault single-phase H-bridge sub-module is determined, and the fault single-phase H-bridge sub-module is bypassed; Based on the fault single-phase H-bridge sub-module, the fault type of the corresponding phase is determined; According to the fault type, the corresponding zero sequence voltage is generated; Based on the fault type and the corresponding zero sequence voltage, the maximum balanced line voltage that the cascaded H-bridge inverter can output under the condition of three-phase line voltage balance is determined, and the inverter is controlled based on the maximum balanced line voltage.

[0007] In an embodiment, the fault type includes open-circuit fault of a switching tube and inverter module fault; The step of generating the corresponding zero sequence voltage according to the fault type comprises: when the fault type is a switch open-circuit fault, generating a direct-current zero sequence voltage; when the fault type is an inverter module fault, generating a fundamental frequency alternating-current zero sequence voltage.

[0008] In an embodiment, the step of generating the direct-current zero sequence voltage when the fault type is a switch open-circuit fault comprises: when the fault type is a switch open-circuit fault, counting a first total number of fault single-phase H-bridge sub-modules that lose the ability to output a positive voltage level in the fault single-phase H-bridge sub-modules; counting a second total number of fault single-phase H-bridge sub-modules that lose the ability to output a negative voltage level in the fault single-phase H-bridge sub-modules; performing a difference calculation on the first total number and the second total number to determine an amplitude value required for generating the direct-current zero sequence voltage; outputting the amplitude value as a constant value to generate the direct-current zero sequence voltage.

[0009] In an embodiment, the step of generating the fundamental frequency alternating-current zero sequence voltage when the fault type is an inverter module fault comprises: when the fault type is an inverter module fault, obtaining a three-phase reference voltage signal; based on the three-phase reference voltage signal, constructing a zero sequence voltage component synchronized with a fundamental frequency of a power grid to which the cascaded H-bridge inverter belongs; outputting the zero sequence voltage component as the fundamental frequency alternating-current zero sequence voltage.

[0010] In an embodiment, the step of determining the maximum balanced line voltage that can be output by the cascaded H-bridge inverter under a three-phase line voltage balance condition based on the fault type and the corresponding zero sequence voltage comprises: superimposing the zero sequence voltage on a preset three-phase reference modulation wave to obtain actual modulation instructions of each phase of the cascaded H-bridge inverter; determining a voltage output range currently available for each phase according to the fault type; determining a maximum amplitude of the three-phase reference modulation wave, the maximum amplitude satisfying that the actual modulation instructions of all phases do not exceed the corresponding voltage output range; based on the maximum amplitude, determining a synthesized three-phase line voltage amplitude, and determining the three-phase line voltage amplitude as the maximum balanced line voltage.

[0011] In an embodiment, before the step of determining the maximum amplitude of the three-phase reference modulation wave, the method further comprises: based on the time-varying characteristics of the zero sequence voltage and the voltage output range of each phase, determining a maximum modulation amplitude of the actual modulation instructions of each phase within the corresponding voltage output range; The step of determining the maximum amplitude of the three-phase reference modulation wave includes: The minimum value is selected from each of the maximum modulation amplitudes to determine the maximum amplitude of the three-phase reference modulation wave.

[0012] In one embodiment, the step of determining the fault type of the corresponding phase based on the faulty single-phase H-bridge submodule includes: If the faulty single-phase H-bridge submodule has one or more open-circuit switches, then the faulty single-phase H-bridge submodule shall be handled. If the power grid to which the faulty single-phase H-bridge submodule belongs loses its ability to output positive or negative levels after the fault is handled, then the fault type corresponding to the faulty single-phase H-bridge submodule is determined to be an open circuit fault of the switching transistor. If multiple switching transistors of the faulty single-phase H-bridge submodule are open-circuited and disconnected by a bypass switch, then the fault type corresponding to the faulty single-phase H-bridge submodule is determined to be an inverter module fault.

[0013] Furthermore, to achieve the above objectives, this application also proposes a fault-tolerant control device for a cascaded H-bridge inverter, the fault-tolerant control device for the cascaded H-bridge inverter comprising: The processing module is used to identify the faulty single-phase H-bridge sub-module when a fault occurs in the cascaded H-bridge inverter, and to bypass the faulty single-phase H-bridge sub-module. The determination module is used to determine the fault type of the corresponding phase based on the faulty single-phase H-bridge submodule; A generation module is used to generate a corresponding zero-sequence voltage based on the fault type. The control module is used to determine the maximum balanced line voltage that the cascaded H-bridge inverter can output under the condition of three-phase line voltage balance based on the fault type and the corresponding zero-sequence voltage, and to control the inverter based on the maximum balanced line voltage.

[0014] In addition, to achieve the above objectives, this application also proposes a fault-tolerant control device for a cascaded H-bridge inverter, the device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the fault-tolerant control method for the cascaded H-bridge inverter as described above.

[0015] In addition, to achieve the above objectives, this application also proposes a storage medium, which is a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the steps of the fault-tolerant control method for the cascaded H-bridge inverter as described above.

[0016] One or more technical solutions proposed in this application have at least the following technical effects: Upon fault detection, the faulty single-phase H-bridge submodule is first bypassed and isolated to ensure the safety of the motor system containing the inverter. Then, a customized zero-sequence voltage is generated based on the specific fault type of the faulty single-phase H-bridge submodule, instead of using a general or conservative zero-sequence injection strategy. Therefore, the zero-sequence voltage not only compensates for phase voltage asymmetry caused by module loss but also serves as an optimization variable in the process of determining the maximum output balanced line voltage. Furthermore, using three-phase line voltage balance as a hard constraint, the maximum balanced line voltage achievable by the motor system under fault conditions is determined, and the modulation command is reconstructed based on the maximum balanced line voltage to control the inverter. In other words, this application, through closed-loop control logic of fault type identification, zero-sequence voltage customization, maximum balanced voltage calculation, and modulation command reconstruction, ensures stable operation and three-phase balance of the motor system while maximizing the power potential of the inverter under fault conditions, thereby improving the inverter's output voltage capability. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating the first embodiment of the fault-tolerant control method for the cascaded H-bridge inverter in this application; Figure 2 This is a flowchart illustrating Embodiment 2 of the fault-tolerant control method for the cascaded H-bridge inverter in this application. Figure 3 This is a flowchart illustrating Embodiment 3 of the fault-tolerant control method for the cascaded H-bridge inverter in this application. Figure 4 This is a schematic diagram of the module structure of the fault-tolerant control device for the cascaded H-bridge inverter in an embodiment of this application; Figure 5 This is a schematic diagram of the equipment structure of the hardware operating environment involved in the fault-tolerant control method of the cascaded H-bridge inverter in the embodiments of this application.

[0020] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] It should be understood that the specific embodiments described herein are merely illustrative of the technical solutions of this application and are not intended to limit this application.

[0022] It should be noted that the executing entity in this embodiment can be a computing service device with data processing, network communication, and program execution functions, such as a tablet computer, personal computer, or mobile phone, or an electronic device or power dispatching platform capable of performing the above functions. The following description uses a power dispatching platform as an example to illustrate this embodiment and the subsequent embodiments.

[0023] Based on this, the embodiments of this application provide a fault-tolerant control method for a cascaded H-bridge inverter, referring to... Figure 1 , Figure 1 This is a flowchart illustrating the first embodiment of the fault-tolerant control method for the cascaded H-bridge inverter of this application.

[0024] In this embodiment, the fault-tolerant control method for the cascaded H-bridge inverter includes steps S10 to S40: Step S10: When a fault occurs in the cascaded H-bridge inverter, identify the faulty single-phase H-bridge sub-module and bypass the faulty single-phase H-bridge sub-module. It should be noted that the multi-level voltage source inverter topology, composed of multiple single-phase H-bridge submodules connected in series on the output side, consists of several H-bridge units cascaded with independent DC power supplies for each phase. A single-phase H-bridge submodule is the basic power unit of a cascaded H-bridge inverter, and a faulty single-phase H-bridge submodule is one that has experienced a fault. Bypass processing, upon detecting an unrecoverable fault in a single-phase H-bridge module, involves closing its mechanical or power electronic bypass switch to electrically isolate it from the main circuit, preventing it from participating in voltage output, thus preventing fault propagation and maintaining system operation.

[0025] Understandably, by timely and accurately identifying specific faulty single-phase H-bridge submodules, the power dispatching platform can precisely locate the fault source, avoiding erroneous fault-tolerance strategies due to misjudgment or omission, thus providing the prerequisites for differentiated zero-sequence voltage injection and maximum power output calculation.

[0026] Understandably, implementing active bypass processing on a single-phase H-bridge submodule with a confirmed fault can electrically isolate it from the main power circuit, effectively block the fault current path, prevent the fault from spreading to adjacent modules or DC power supplies, and improve the fault containment capability and operational safety of the power grid system. At the same time, the bypass operation removes the module from the modulation sequence, which can also prevent its uncertain output level from interfering with the overall voltage synthesis.

[0027] Furthermore, step S10 also includes: If the faulty single-phase H-bridge submodule has one or more open-circuit switches, then the faulty single-phase H-bridge submodule shall be handled. If the power grid to which the faulty single-phase H-bridge submodule belongs loses its ability to output positive or negative levels after the fault is handled, then the fault type corresponding to the faulty single-phase H-bridge submodule is determined to be an open circuit fault of the switching transistor. If multiple switching transistors of the faulty single-phase H-bridge submodule are open-circuited and disconnected by a bypass switch, then the fault type corresponding to the faulty single-phase H-bridge submodule is determined to be an inverter module fault.

[0028] It should be noted that an open circuit in a switching transistor refers to one or more power switching devices within a single-phase H-bridge submodule of a cascaded H-bridge inverter becoming open due to reasons such as drive failure, solder joint breakage, or device aging. An inverter module failure refers to a serious fault in a single-phase H-bridge module caused by multiple switching transistors simultaneously opening, a DC-side short circuit, drive power supply failure, or thermal runaway.

[0029] It should be noted that the loss of the ability to output positive or negative levels is due to an open circuit in the switching transistor, which prevents the H-bridge submodule from forming an output circuit of the corresponding polarity. The bypass switch is a protective switching device integrated into each H-bridge submodule. It closes when an unrecoverable fault occurs in the module, directly short-circuiting the module's input / output terminals to achieve electrical isolation, prevent the fault from spreading, and maintain the system's continued operation.

[0030] Understandably, by distinguishing between open-circuit faults in switching transistors and inverter module faults, the actual current voltage output capability boundaries of each can be accurately characterized. Specifically, an open-circuit fault in a switching transistor manifests as a loss of voltage polarity but with continuously adjustable amplitude, while an inverter module fault manifests as a reduction in total voltage margin but with maintained voltage symmetry.

[0031] Understandably, common inverter faults include open-circuit faults in the switching transistors and inverter module faults. Regarding the output port voltage VjM of the H-bridge module, we can obtain:

[0032] Where Vdc is the DC voltage value of each module.

[0033] From the above formula, it can be seen that the voltage output value of a single power module is Vdc, 0, or -Vdc. When a switching device failure occurs, the voltage loss level of a single power module output is Vdc or -Vdc. When the power module fails... Figure 1After an open-circuit fault in the switch transistor shown, to prevent simultaneous turn-off of the upper and lower switches in the same bridge arm, the faulty module is handled by setting the trigger signal of the faulty switch transistor to "0" and the trigger signal of the other switch transistor in the same bridge arm to "1". After the fault handling, the trigger signals of the four switches SjM1, SjM2, SjM3, and SjM4 of the module are limited to (0110) or (0011), and the module's output level "Vdc" is lost. When a module experiences a serious fault such as multiple open-circuit faults, the fault is defined as a module fault, and the faulty module can be disconnected from the system via a bypass switch.

[0034] Step S20: Based on the faulty single-phase H-bridge submodule, determine the fault type of the corresponding phase; It should be noted that the fault types are categorized based on the failure mode of the faulty submodule and its impact on the phase voltage output capability. These fault types include open-circuit faults in switching transistors and inverter module faults.

[0035] Understandably, by further determining the fault type of the phase to which the identified faulty single-phase H-bridge submodule belongs, a refined classification of the degree of fault impact is achieved. This provides a key criterion for generating a highly adaptable and physically realizable zero-sequence voltage injection strategy, avoiding the conservatism or instability caused by a one-size-fits-all fault tolerance approach.

[0036] Step S30: Generate the corresponding zero-sequence voltage according to the fault type; It should be noted that zero-sequence voltage is a three-phase voltage component that is equal in magnitude and phase in a three-phase system, and it is zero in an ideal symmetrical system.

[0037] Understandably, by generating a zero-sequence voltage with adapted form and parameters based on the determined fault type (open-circuit fault of the switching transistor or fault of the inverter module), intelligent reconstruction of the modulation reference can be achieved. In the case of an open-circuit fault of the switching transistor, a constant DC zero-sequence voltage is injected to offset the modulation wave center and compensate for the DC bias caused by the lack of positive / negative level capability. In the case of a fault in the inverter module, an AC zero-sequence voltage synchronized with the grid base frequency is injected to dynamically adjust the modulation depth of each phase, thus fully utilizing the voltage margin of the remaining sub-modules.

[0038] It is understandable that since the zero-sequence voltage is a common-mode component, it will not generate circulating current or additional losses in an ideal three-phase three-wire system. Therefore, the zero-sequence injection method does not require increasing hardware costs or introducing additional losses, and high-performance fault tolerance can be achieved by adjusting the modulation wave at the software level.

[0039] Step S40: Based on the fault type and the corresponding zero-sequence voltage, determine the maximum balanced line voltage that the cascaded H-bridge inverter can output under the condition of three-phase line voltage balance, and control the inverter based on the maximum balanced line voltage.

[0040] It should be noted that the maximum balanced line voltage is the maximum effective value or peak value of the line voltage that the cascaded H-bridge inverter can output under the current fault condition, provided that the amplitudes of the three-phase line voltages are equal and the phases are 120° apart.

[0041] Understandably, by solving for the maximum output balanced line voltage under the three-phase line voltage balance constraint, not only can the output power quality be guaranteed, but the power output capability under fault conditions can also be maximized.

[0042] Understandably, by comprehensively considering the voltage output range of each phase determined by the fault type, and based on the injection of an adaptive zero-sequence voltage, the maximum achievable line voltage amplitude under the condition of complete three-phase line voltage balance is rigorously calculated, thus realizing the theoretical limit exploration of the system's output capability within the safety boundary. The maximum balanced line voltage represents the highest effective power level that the power grid system can provide under the current fault condition, avoiding excessive derating due to conservative estimations.

[0043] This embodiment provides a fault-tolerant control method for a cascaded H-bridge inverter. Upon detecting a fault, the faulty single-phase H-bridge submodule is first bypassed and isolated to ensure the safety of the motor system containing the inverter. Then, a customized zero-sequence voltage is generated based on the specific fault type of the faulty single-phase H-bridge submodule, instead of using a general or conservative zero-sequence injection strategy. Therefore, the zero-sequence voltage is not only used to compensate for phase voltage asymmetry caused by module loss, but can also participate as an optimization variable in the process of solving for the maximum output balanced line voltage. Furthermore, using three-phase line voltage balance as a hard constraint, the maximum balanced line voltage achievable by the motor system under fault conditions is determined, and the inverter is controlled by reconstructing modulation commands based on the maximum balanced line voltage. In other words, this application, through closed-loop control logic of fault type identification, zero-sequence voltage customization, maximum balanced voltage solution, and modulation command reconstruction, ensures stable operation and three-phase balance of the motor system while maximizing the release of the inverter's power potential under fault conditions, thereby improving the inverter's output voltage capability.

[0044] Based on the first embodiment of this application, in the second embodiment of this application, the content that is the same as or similar to that in Embodiment 1 above can be referred to the above description, and will not be repeated hereafter. Based on this, please refer to... Figure 2 Step S30 also includes steps S01~S02: Step S01: When the fault type is an open-circuit fault of the switching transistor, a DC zero-sequence voltage is generated; Step S02: When the fault type is inverter module fault, generate a zero-sequence voltage of base frequency AC.

[0045] It should be noted that the zero-sequence voltage of DC is a constant common-mode voltage component injected into a three-phase system. The DC zero-sequence voltage is equal in magnitude and polarity in phases a, b, and c, and does not change with time. The zero-sequence voltage of fundamental frequency AC is a common-mode AC voltage component injected into a three-phase system with a frequency synchronized with the fundamental frequency of the power grid. Its instantaneous value is always equal in all three phases.

[0046] It is understandable that since the essence of the open circuit fault of the switching transistor is the asymmetry of the output capability of the phase level, if no compensation is made, the positive half-cycle of the modulation wave of that phase will be clipped, causing line voltage distortion. By injecting DC zero-sequence voltage, the three-phase modulation wave can be shifted down (or up) as a whole, so that the restricted phase can completely reproduce the reference waveform within its usable range, thereby restoring the line voltage symmetry. This strategy is simple, stable and has no dynamic response delay.

[0047] It is understandable that since the essence of inverter module failure is the overall reduction of the upper limit of the total amplitude of phase voltage, if only DC zero-sequence voltage is injected, although the symmetry can be improved, the full voltage margin of the remaining modules in the negative or positive half-cycle cannot be fully utilized. By injecting base frequency AC zero-sequence voltage, the three-phase modulation reference can be dynamically adjusted in each power frequency cycle, so that each phase can maximize the use of modulation depth within its own limited but symmetrical voltage window, thereby improving the output line voltage amplitude.

[0048] Furthermore, step S01 also includes: When the fault type is a switch open circuit fault, count the first total number of faulty single-phase H-bridge sub-modules that have lost the ability to output a positive level. The second total number of faulty single-phase H-bridge submodules that have lost the ability to output negative levels is counted. The difference between the first total quantity and the second total quantity is calculated to determine the amplitude required to generate the DC zero-sequence voltage. The amplitude is used as a constant output value to generate the DC zero-sequence voltage.

[0049] It should be noted that the first total number refers to the total number of single-phase H-bridge submodules belonging to the same phase that have lost the ability to output a positive level under the current fault condition. The second total number refers to the total number of single-phase H-bridge submodules belonging to the same phase that have lost the ability to output a negative level under the current fault condition. The magnitude of the DC zero-sequence voltage is a constant common-mode offset that needs to be injected to compensate for the asymmetry in phase voltage output capability caused by the first total number not being equal to the second total number.

[0050] Understandably, by quantifying the number of modules that have lost their positive / negative level capabilities and calculating the difference between the first total number and the second total number, the required amplitude of the DC zero-sequence voltage is obtained. The zero-sequence voltage amplitude is directly correlated with the degree of physical asymmetry of the fault, thereby achieving the precision, parameterization, and calculability of the zero-sequence compensation amount, thus improving the compensation accuracy.

[0051] Furthermore, step S02 also includes: When the fault type is inverter module fault, the three-phase reference voltage signal is acquired; Based on the three-phase reference voltage signal, a zero-sequence voltage component synchronized with the base frequency of the power grid to which the cascaded H-bridge inverter belongs is constructed; The zero-sequence voltage component is used as the fundamental frequency AC zero-sequence voltage output.

[0052] It should be noted that the three-phase reference voltage signal is the original modulation command signal set by the power dispatching platform to generate the desired output waveform. The zero-sequence voltage component is a common-mode AC voltage signal with a frequency strictly consistent with the grid fundamental frequency, an adjustable phase, and an instantaneous value that is exactly the same in all three phases.

[0053] Understandably, when an inverter module fails, the number of available sub-modules for each phase decreases, resulting in an overall decrease in the maximum output phase voltage amplitude. By injecting an AC zero-sequence voltage synchronized with the grid base frequency, the common reference of the three-phase modulation wave can be dynamically shifted without changing the characteristics of the line voltage difference mode, so that each phase can maximize the use of modulation depth within its new constraint range.

[0054] It is understandable that, since the zero-sequence voltage frequency is strictly synchronized with the power grid, its waveform has a definite phase relationship in each cycle, which can be optimized in conjunction with the reference voltage signal. For example, when the reference voltage is near its peak value, adjusting the zero-sequence phase appropriately can prevent a certain phase from reaching the voltage limit first, thereby improving the overall modulation linearity and output amplitude.

[0055] Understandably, the baseband AC zero-sequence frequency better suits the physical nature of module disconnection faults, which involves the periodic change of voltage margin over time. By using the baseband AC zero-sequence frequency to dynamically adjust the three-phase modulation reference at the same frequency as the grid voltage, the periodic voltage margin limitations caused by module loss in each phase can be precisely matched. This maximizes the symmetrical output capability of the remaining sub-modules while maintaining strict line voltage symmetry, thereby increasing the maximum output line voltage amplitude under fault conditions and effectively mitigating power loss.

[0056] Based on the first and second embodiments of this application, the same or similar content as the above embodiments in the third embodiment of this application can be referred to the above description, and will not be repeated hereafter. Based on this, please refer to... Figure 2Step S40 also includes steps S1 to S4: Step S1: The zero-sequence voltage is superimposed on a preset three-phase reference modulation wave to obtain the actual modulation command of each phase of the cascaded H-bridge inverter. Step S2: Determine the available voltage output range for each corresponding fault type; Step S3: Determine the maximum amplitude of the three-phase reference modulation wave, wherein the maximum amplitude satisfies that the actual modulation command of all phases does not exceed its corresponding voltage output range; Step S4: Based on the maximum amplitude value, determine the synthesized three-phase line voltage amplitude, and determine the three-phase line voltage amplitude as the maximum balanced line voltage.

[0057] It should be noted that the three-phase reference modulation wave is the original modulation command signal set by the power control platform to generate the desired output voltage, and it is usually a three-phase symmetrical sine wave. The actual modulation command is the final drive signal obtained by superimposing the zero-sequence voltage onto the three-phase reference modulation wave, which is used to control the switching state of each H-bridge submodule. The currently available voltage output range for each phase is the maximum and minimum output voltage value that can be synthesized by all healthy submodules of a certain phase under the current fault condition.

[0058] Understandably, by jointly optimizing the zero-sequence voltage and modulation amplitude, and ensuring that all phases operate within their physical feasible domain, the maximum output capacity that satisfies the three-phase line voltage balance condition can be accurately solved, thereby achieving the leap from being able to operate to operating optimally.

[0059] Understandably, since the maximum balanced line voltage is a theoretical upper limit dynamically calculated based on the current fault state, controlling the inverter based on the maximum balanced line voltage can avoid energy waste caused by conservative derating, and can maintain the load power supply capacity to the maximum extent while ensuring power quality.

[0060] Furthermore, prior to step S3, the fault-tolerant control method for the cascaded H-bridge inverter further includes: Based on the time-varying characteristics of the zero-sequence voltage and the voltage output range of each phase, the maximum modulation amplitude of the actual modulation command of each phase within the corresponding voltage output range is determined. Optionally, step S3 further includes: The minimum value is selected from each of the maximum modulation amplitudes to determine the maximum amplitude of the three-phase reference modulation wave.

[0061] It should be noted that the time-varying characteristics of zero-sequence voltage include the time-varying characteristics of DC zero-sequence voltage and the time-varying characteristics of fundamental frequency AC zero-sequence voltage. The time-varying characteristics of DC zero-sequence voltage are constant, while the time-varying characteristics of fundamental frequency AC zero-sequence voltage are sinusoidal changes synchronized with the fundamental frequency of the power grid.

[0062] Understandably, by independently calculating the maximum modulation amplitude of each phase based on the time-varying characteristics of zero-sequence voltage and the voltage boundaries of each phase, a refined model of the capability of each phase is achieved; and by taking the minimum value as the global amplitude, it is ensured that the performance of the power grid system is determined by the weakest phase.

[0063] It should be noted that the above examples are only for understanding this application and do not constitute a limitation on the fault-tolerant control method of the cascaded H-bridge inverter in this application. Any simple modifications based on this technical concept are within the protection scope of this application.

[0064] This application also provides a fault-tolerant control device for a cascaded H-bridge inverter; please refer to [reference needed]. Figure 4 The fault-tolerant control device for the cascaded H-bridge inverter includes: The processing module 10 is used to identify the faulty single-phase H-bridge sub-module when a fault occurs in the cascaded H-bridge inverter, and to bypass the faulty single-phase H-bridge sub-module. The determination module 20 is used to determine the fault type of the corresponding phase based on the faulty single-phase H-bridge submodule; The generation module 30 is used to generate a corresponding zero-sequence voltage according to the fault type; The control module 40 is used to determine the maximum balanced line voltage that the cascaded H-bridge inverter can output under the condition of three-phase line voltage balance based on the fault type and the corresponding zero-sequence voltage, and to control the inverter based on the maximum balanced line voltage.

[0065] Optionally, the fault types include open-circuit faults of switching transistors and inverter module faults; The generation module 30 is also used to generate a DC zero-sequence voltage when the fault type is a switch open-circuit fault, and to generate a base frequency AC zero-sequence voltage when the fault type is an inverter module fault.

[0066] Optionally, the generation module 30 is further configured to, when the fault type is a switch open circuit fault, count the first total number of faulty single-phase H-bridge sub-modules that have lost the ability to output a positive level; count the second total number of faulty single-phase H-bridge sub-modules that have lost the ability to output a negative level; calculate the difference between the first total number and the second total number to determine the amplitude required to generate the DC zero-sequence voltage; and output the amplitude as a constant value to generate the DC zero-sequence voltage.

[0067] Optionally, the generation module 30 is further configured to acquire a three-phase reference voltage signal when the fault type is an inverter module fault; construct a zero-sequence voltage component that is synchronized with the base frequency of the power grid to which the cascaded H-bridge inverter belongs based on the three-phase reference voltage signal; and output the zero-sequence voltage component as the base frequency AC zero-sequence voltage.

[0068] Optionally, the control module 40 is further configured to superimpose the zero-sequence voltage onto a preset three-phase reference modulation wave to obtain the actual modulation command of each phase of the cascaded H-bridge inverter; determine the currently available voltage output range of each phase according to the fault type; determine the maximum amplitude of the three-phase reference modulation wave, wherein the maximum amplitude satisfies that the actual modulation command of all phases does not exceed its corresponding voltage output range; and determine the synthesized three-phase line voltage amplitude based on the maximum amplitude, and determine the three-phase line voltage amplitude as the maximum balanced line voltage.

[0069] Optionally, the control module 40 is further configured to determine the maximum modulation amplitude of the actual modulation command of each phase within the corresponding voltage output range based on the time-varying characteristics of the zero-sequence voltage and the voltage output range of each phase; and select the minimum value from each maximum modulation amplitude to determine the maximum amplitude of the three-phase reference modulation wave.

[0070] Optionally, the processing module 10 is further configured to: if the faulty single-phase H-bridge submodule has one or more open-circuit switches, perform fault handling on the faulty single-phase H-bridge submodule; if the power grid to which the faulty single-phase H-bridge submodule belongs loses the ability to output a positive or negative level after fault handling, determine the fault type corresponding to the faulty single-phase H-bridge submodule as an open-circuit switch fault; if the faulty single-phase H-bridge submodule has multiple open-circuit switches and is disconnected by a bypass switch, determine the fault type corresponding to the faulty single-phase H-bridge submodule as an inverter module fault.

[0071] The fault-tolerant control device for cascaded H-bridge inverters provided in this application adopts the fault-tolerant control method for cascaded H-bridge inverters in the above embodiments, which can solve the technical problem of not being able to guarantee the stable operation of the system after a fault while improving the inverter's output voltage capability. Compared with the prior art, the beneficial effects of the fault-tolerant control device for cascaded H-bridge inverters provided in this application are the same as those of the fault-tolerant control method for cascaded H-bridge inverters provided in the above embodiments, and other technical features in the fault-tolerant control device for cascaded H-bridge inverters are the same as those disclosed in the methods of the above embodiments, and will not be repeated here.

[0072] This application provides a fault-tolerant control device for a cascaded H-bridge inverter. The fault-tolerant control device for the cascaded H-bridge inverter includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the fault-tolerant control method for the cascaded H-bridge inverter in the above embodiment 1.

[0073] The following is for reference. Figure 5This document illustrates a structural schematic diagram of a fault-tolerant control device suitable for implementing the cascaded H-bridge inverters of this application. The fault-tolerant control device for the cascaded H-bridge inverters in this application can include, but is not limited to, mobile terminals such as mobile phones, laptops, digital radio receivers, PDAs (Personal Digital Assistants), PADs (Portable Application Description), PMPs (Portable Media Players), and in-vehicle terminals (e.g., in-vehicle navigation terminals), as well as fixed terminals such as digital TVs and desktop computers. Figure 5 The fault-tolerant control device for the cascaded H-bridge inverter shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of this application.

[0074] like Figure 5 As shown, the fault-tolerant control device of the cascaded H-bridge inverter may include a processing unit 1001 (e.g., a central processing unit, a graphics processing unit, etc.), which can perform various appropriate actions and processes according to a program stored in read-only memory (ROM) 1002 or a program loaded from storage device 1003 into random access memory (RAM) 1004. RAM 1004 also stores various programs and data required for the operation of the fault-tolerant control device of the cascaded H-bridge inverter. The processing unit 1001, ROM 1002, and RAM 1004 are interconnected via bus 1005. Input / output (I / O) interface 1006 is also connected to the bus. Typically, the following systems can be connected to I / O interface 1006: input devices 1007 including, for example, touchscreens, touchpads, keyboards, mice, image sensors, microphones, accelerometers, gyroscopes, etc.; output devices 1008 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; storage devices 1003 including, for example, magnetic tapes, hard disks, etc.; and communication devices 1009. Communication device 1009 allows the fault-tolerant control equipment of the cascaded H-bridge inverter to communicate wirelessly or wiredly with other devices to exchange data. Although the figure shows fault-tolerant control equipment for a cascaded H-bridge inverter with various systems, it should be understood that it is not required to implement or have all the systems shown. More or fewer systems can be implemented alternatively.

[0075] Specifically, according to the embodiments disclosed in this application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments disclosed in this application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via a communication device, or installed from storage device 1003, or installed from ROM 1002. When the computer program is executed by processing device 1001, it performs the functions defined in the methods of the embodiments disclosed in this application.

[0076] The fault-tolerant control device for cascaded H-bridge inverters provided in this application adopts the fault-tolerant control method for cascaded H-bridge inverters in the above embodiments, which can solve the technical problem of not being able to guarantee the stable operation of the system after a fault while improving the inverter's output voltage capability. Compared with the prior art, the beneficial effects of the fault-tolerant control device for cascaded H-bridge inverters provided in this application are the same as those of the fault-tolerant control method for cascaded H-bridge inverters provided in the above embodiments, and other technical features in the fault-tolerant control device for cascaded H-bridge inverters are the same as those disclosed in the previous embodiment method, and will not be repeated here.

[0077] It should be understood that the various parts disclosed in this application can be implemented using hardware, software, firmware, or a combination thereof. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0078] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0079] This application provides a computer-readable storage medium having computer-readable program instructions (i.e., a computer program) stored thereon, the computer-readable program instructions being used to execute the fault-tolerant control method for the cascaded H-bridge inverter in the above embodiments.

[0080] The computer-readable storage medium provided in this application may be, for example, a USB flash drive, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to: electrical connections having one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this embodiment, the computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, system, or device. The program code contained on the computer-readable storage medium may be transmitted using any suitable medium, including but not limited to: wires, optical cables, RF (Radio Frequency), etc., or any suitable combination thereof.

[0081] The aforementioned computer-readable storage medium may be included in the fault-tolerant control device of the cascaded H-bridge inverter; or it may exist independently and not be assembled into the fault-tolerant control device of the cascaded H-bridge inverter.

[0082] The aforementioned computer-readable storage medium carries one or more programs, which, when executed by the fault-tolerant control device of the cascaded H-bridge inverter, enable the fault-tolerant control device of the cascaded H-bridge inverter to implement the aforementioned fault-tolerant control method of the cascaded H-bridge inverter.

[0083] Computer program code for performing the operations of this application can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a Local Area Network (LAN) or a Wide Area Network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0084] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0085] The modules described in the embodiments of this application can be implemented in software or hardware. The names of the modules do not necessarily limit the functionality of the unit itself.

[0086] The readable storage medium provided in this application is a computer-readable storage medium that stores computer-readable program instructions (i.e., a computer program) for executing the fault-tolerant control method of the cascaded H-bridge inverter described above. This solves the technical problem of failing to guarantee stable system operation after a fault while improving the inverter's output voltage capability. Compared with the prior art, the beneficial effects of the computer-readable storage medium provided in this application are the same as those of the fault-tolerant control method of the cascaded H-bridge inverter provided in the above embodiments, and will not be elaborated upon here.

[0087] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the fault-tolerant control method for a cascaded H-bridge inverter as described above.

[0088] The computer program product provided in this application can solve the technical problem of improving the inverter's output voltage capability while ensuring stable system operation after a fault. Compared with the prior art, the beneficial effects of the computer program product provided in this application are the same as those of the fault-tolerant control method for cascaded H-bridge inverters provided in the above embodiments, and will not be elaborated here.

[0089] The above description is only a part of the embodiments of this application and does not limit the scope of protection of this application. All equivalent structural transformations made under the technical concept of this application and using the content of this application specification and drawings, or direct / indirect applications in other related technical fields, are included in the scope of protection of this application.

Claims

1. A fault-tolerant control method for a cascaded H-bridge inverter, characterized in that, The method includes: When a fault occurs in the cascaded H-bridge inverter, the faulty single-phase H-bridge submodule is identified and bypassed. Based on the faulty single-phase H-bridge submodule, the fault type of the corresponding phase is determined; Based on the fault type, a corresponding zero-sequence voltage is generated; Based on the fault type and the corresponding zero-sequence voltage, the maximum balanced line voltage that the cascaded H-bridge inverter can output under the condition of three-phase line voltage balance is determined, and the inverter is controlled based on the maximum balanced line voltage.

2. The method as described in claim 1, characterized in that, The fault types include open-circuit faults in switching transistors and faults in inverter modules; The step of generating the corresponding zero-sequence voltage according to the fault type includes: When the fault type is an open-circuit fault of the switching transistor, a DC zero-sequence voltage is generated; When the fault type is inverter module fault, a zero-sequence voltage of base frequency AC is generated.

3. The method as described in claim 2, characterized in that, The step of generating a DC zero-sequence voltage when the fault type is an open-circuit fault of the switching transistor includes: When the fault type is a switch open circuit fault, count the first total number of faulty single-phase H-bridge sub-modules that have lost the ability to output a positive level. The second total number of faulty single-phase H-bridge submodules that have lost the ability to output negative levels is counted. The difference between the first total quantity and the second total quantity is calculated to determine the amplitude required to generate the DC zero-sequence voltage. The amplitude is output as a constant value to generate the DC zero-sequence voltage.

4. The method as described in claim 2, characterized in that, The step of generating a zero-sequence voltage of baseband AC when the fault type is inverter module fault includes: When the fault type is inverter module fault, the three-phase reference voltage signal is acquired; Based on the three-phase reference voltage signal, a zero-sequence voltage component synchronized with the base frequency of the power grid to which the cascaded H-bridge inverter belongs is constructed; The zero-sequence voltage component is used as the fundamental frequency AC zero-sequence voltage output.

5. The method as described in claim 1, characterized in that, The step of determining the maximum balanced line voltage that the cascaded H-bridge inverter can output under three-phase line voltage balance conditions based on the fault type and the corresponding zero-sequence voltage includes: The zero-sequence voltage is superimposed on a preset three-phase reference modulation wave to obtain the actual modulation command for each phase of the cascaded H-bridge inverter. Determine the available voltage output range for each corresponding fault type; Determine the maximum amplitude of the three-phase reference modulation wave, wherein the maximum amplitude satisfies that the actual modulation command of all phases does not exceed its corresponding voltage output range; Based on the maximum amplitude, the synthesized three-phase line voltage amplitude is determined, and the three-phase line voltage amplitude is determined as the maximum balanced line voltage.

6. The method as described in claim 5, characterized in that, Before the step of determining the maximum amplitude of the three-phase reference modulation wave, the method further includes: Based on the time-varying characteristics of the zero-sequence voltage and the voltage output range of each phase, the maximum modulation amplitude of the actual modulation command of each phase within the corresponding voltage output range is determined. The step of determining the maximum amplitude of the three-phase reference modulation wave includes: The minimum value is selected from each of the maximum modulation amplitudes to determine the maximum amplitude of the three-phase reference modulation wave.

7. The method as described in claim 1, characterized in that, The step of determining the fault type of the corresponding phase based on the faulty single-phase H-bridge submodule includes: If the faulty single-phase H-bridge submodule has one or more open-circuit switches, then the faulty single-phase H-bridge submodule shall be handled. If the power grid to which the faulty single-phase H-bridge submodule belongs loses its ability to output positive or negative levels after the fault is handled, then the fault type corresponding to the faulty single-phase H-bridge submodule is determined to be an open circuit fault of the switching transistor. If multiple switching transistors of the faulty single-phase H-bridge submodule are open-circuited and disconnected by a bypass switch, then the fault type corresponding to the faulty single-phase H-bridge submodule is determined to be an inverter module fault.

8. A fault-tolerant control device for a cascaded H-bridge inverter, characterized in that, The device includes: The processing module is used to identify the faulty single-phase H-bridge sub-module when a fault occurs in the cascaded H-bridge inverter, and to bypass the faulty single-phase H-bridge sub-module. The determination module is used to determine the fault type of the corresponding phase based on the faulty single-phase H-bridge submodule; A generation module is used to generate a corresponding zero-sequence voltage based on the fault type. The control module is used to determine the maximum balanced line voltage that the cascaded H-bridge inverter can output under the condition of three-phase line voltage balance based on the fault type and the corresponding zero-sequence voltage, and to control the inverter based on the maximum balanced line voltage.

9. A fault-tolerant control device for a cascaded H-bridge inverter, characterized in that, The device includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the fault-tolerant control method for a cascaded H-bridge inverter as described in any one of claims 1 to 7.

10. A storage medium, characterized in that, The storage medium is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by a processor, it implements the steps of the fault-tolerant control method for the cascaded H-bridge inverter as described in any one of claims 1 to 7.

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