A fault diagnosis method, device and equipment of an open-winding optical storage variable flow system and a storage medium

Abstract

The application discloses a kind of open-winding photovoltaic energy storage converter system fault diagnosis method, device, equipment and storage medium, is related to power electronic converter fault diagnosis technical field, the method comprises: obtaining the photovoltaic side DC bus current, energy storage side DC bus current and three-phase AC output current of open-winding photovoltaic energy storage converter system;According to three-phase AC output current, photovoltaic side DC bus current, energy storage side DC bus current obtains the current residual of photovoltaic side fault phase and the current residual of energy storage side fault phase;The current residual of photovoltaic side fault phase and the current residual of energy storage side fault phase are processed, and first diagnostic variable and second diagnostic variable are obtained;Detect the current flow direction of fault phase in open-winding photovoltaic energy storage converter system;According to the current flow direction of fault phase, first diagnostic variable and second diagnostic variable, determine fault location.The method can realize accurate fault positioning of open-winding photovoltaic energy storage converter system.

Description

Technical Field

[0001] This application relates to the field of power electronic converter fault diagnosis technology, and in particular to a fault diagnosis method, device, equipment and storage medium for an open-winding photovoltaic-storage converter system. Background Technology

[0002] The synergistic application of photovoltaic (PV) power generation and energy storage is an important form of building modern microgrids. Open-winding topologies are widely used in PV-storage converter systems due to their high voltage utilization and flexible control. This topology connects the two ends of the three-phase stator windings to two independent DC buses on the PV and energy storage sides respectively, achieving decoupled control of PV and battery energy. Power devices, as the actuators in PV-storage converter systems, are prone to open-circuit faults under long-term high-frequency switching and thermal cycling stress. This can cause distortion of the three-phase output current, abnormal DC-side voltage, and even system overcurrent shutdown. Therefore, quickly and accurately identifying and locating faulty devices is crucial for ensuring the safe operation of the system.

[0003] Existing diagnostic methods for open-circuit faults in power devices of open-winding photovoltaic-storage converter systems mainly rely on analyzing the waveform characteristics of three-phase AC current signals to identify the fault phase. Some solutions attempt to locate the fault source by adding hardware sensors or using signal injection technology, but most of them focus on common DC bus topologies and do not design strategies for the characteristics of independent DC bus photovoltaic-storage systems.

[0004] Traditional fault diagnosis methods cannot effectively decouple the fault characteristics of power devices in series bridge arms in open winding topologies, resulting in unclear fault source location. Summary of the Invention

[0005] This application provides a fault diagnosis method, apparatus, equipment, and storage medium for an open-winding photovoltaic-storage converter system, which can solve the problem of fuzzy positioning caused by the coupling of fault characteristics of power devices in series bridge arms in an independent DC bus open-winding photovoltaic-storage converter system, without the need for additional hardware.

[0006] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, this application provides a fault diagnosis method for an open-winding photovoltaic-storage converter system, the method comprising: Obtain the DC bus current on the photovoltaic side, the DC bus current on the energy storage side, and the three-phase AC output current of the open-winding photovoltaic-energy storage converter system; The fault phase is determined based on the three-phase AC output current and dynamic reference value. Based on the fault phase, the current residuals on the photovoltaic side and the energy storage side are obtained according to the DC bus current on the photovoltaic side and the DC bus current on the energy storage side. The current residuals on the photovoltaic side and the current residuals on the energy storage side are processed to obtain the first diagnostic variable and the second diagnostic variable. Obtain the current flow direction in the open-winding photovoltaic-storage converter system; The fault location is determined based on the current flow direction, the first diagnostic variable, and the second diagnostic variable.

[0007] In some possible implementations, the step of obtaining the current residuals on the photovoltaic side and the energy storage side based on the fault phase, according to the DC bus current on the photovoltaic side and the DC bus current on the energy storage side, includes: The non-fault phase is determined based on the fault phase; the current residual on the photovoltaic side is obtained based on the measured value of the DC bus current on the photovoltaic side and the measured value of the non-fault phase current; the current residual on the energy storage side is obtained based on the measured value of the DC bus current on the energy storage side and the measured value of the non-fault phase current.

[0008] In some possible implementations, determining the fault location based on the current flow direction, the first diagnostic variable, and the second diagnostic variable includes: When the current flow direction is the first direction, the first preliminary fault location is determined; if the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the first relationship, then the first preliminary fault location is determined as the first fault location. If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the second relationship, then the first preliminary fault location is determined as the second fault location; wherein, the first fault location is the upper arm power device of the photovoltaic-side inverter corresponding to the fault phase, and the second fault location is the lower arm power device of the energy storage-side inverter corresponding to the fault phase; the first noise threshold is less than the second noise threshold; and the first flow direction is the direction from the photovoltaic-side inverter to the energy storage-side inverter.

[0009] In some possible implementations, the method further includes: When the current flow direction is the second direction, the second preliminary fault location is determined; if the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the third relationship, then the second preliminary fault location is determined as the third fault location. If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the fourth relationship, then the second preliminary fault location is determined as the fourth fault location; wherein, the third fault location is the lower arm power device of the photovoltaic inverter corresponding to the fault phase, and the fourth fault location is the upper arm power device of the energy storage inverter corresponding to the fault phase; the second flow direction is the direction from the energy storage inverter to the photovoltaic inverter.

[0010] In some possible implementations, determining the fault phase based on the three-phase AC output current and the dynamic reference value includes: The sliding average of the absolute values ​​of the currents in each phase is obtained from the three-phase AC output current; the fault phase is obtained from the sliding average of the absolute values ​​of the currents in each phase, the dynamic reference value, and the fault identification threshold coefficient.

[0011] In some possible implementations, the method further includes: If, within the preset delay window, the first diagnostic variable and the second diagnostic variable consistently satisfy the amplitude characteristic condition corresponding to the fault location, then the fault location is confirmed and the fault diagnosis result is output.

[0012] In some possible implementations, the method further includes: After determining the fault location, the deviation between the first diagnostic variable and the first noise threshold, and the deviation between the second diagnostic variable and the second noise threshold are calculated; based on the deviation between the first diagnostic variable and the first noise threshold, and the deviation between the second diagnostic variable and the second noise threshold, a fault level index is generated; and a fault diagnosis result containing the fault location and the fault level index is output.

[0013] Secondly, this application provides a fault diagnosis device for an open-winding photovoltaic-storage converter system, the device comprising: The acquisition module is used to acquire the DC bus current on the photovoltaic side, the DC bus current on the energy storage side, and the three-phase AC output current of the open-winding photovoltaic-energy storage converter system; and to determine the fault phase based on the three-phase AC output current and the dynamic reference value. The calculation module is used to obtain the current residual on the photovoltaic side and the current residual on the energy storage side based on the fault phase, according to the DC bus current on the photovoltaic side and the DC bus current on the energy storage side; and to process the current residual on the fault phase on the photovoltaic side and the current residual on the fault phase on the energy storage side to obtain a first diagnostic variable and a second diagnostic variable. The diagnostic module is used to obtain the current flow direction in the open-winding photovoltaic-storage converter system; and to determine the fault location based on the current flow direction, the first diagnostic variable, and the second diagnostic variable.

[0014] Thirdly, this application provides a computing device, including a memory and a processor; The memory stores one or more computer programs, the one or more computer programs including instructions; when the instructions are executed by the processor, the computing device performs the method as described in any one of the first aspects.

[0015] Fourthly, this application provides a computer-readable storage medium for storing a computer program for performing the method as described in any one of the first aspects.

[0016] Fifthly, this application provides a computer program product comprising one or more computer instructions, wherein when the computer instructions are executed by a computer, the computer performs the method as described in any one of the first aspects.

[0017] As can be seen from the above technical solution, this application has at least the following beneficial effects: In this application, the DC bus current on the photovoltaic side, the DC bus current on the energy storage side, and the three-phase AC output current of the open-winding photovoltaic-energy storage converter system are obtained. Based on the three-phase AC output current and a dynamic reference value, the fault phase is determined. Based on the fault phase, the current residuals of the fault phase on the photovoltaic side and the energy storage side are obtained according to the DC bus currents on the photovoltaic side and the energy storage side. The current residuals of the fault phase on the photovoltaic side and the energy storage side are processed to obtain a first diagnostic variable and a second diagnostic variable. The current flow direction of the fault phase in the open-winding photovoltaic-energy storage converter system is obtained. Based on the current flow direction of the fault phase, the first diagnostic variable, and the second diagnostic variable, the fault location is determined. In existing technical solutions, in the open-winding topology, the same phase winding is driven by the bridge arms of two inverters in series. When an open-circuit fault occurs in a power device, it is impossible to distinguish whether the fault occurred in the photovoltaic-side inverter or the energy storage-side inverter based solely on the phase current signal, resulting in a problem of series-connected bridge arm fault characteristic coupling. As can be seen, this application solves the problem of difficulty in distinguishing fault characteristic coupling in open winding topology by constructing a first diagnostic variable reflecting the active output capability of the source end and a second diagnostic variable reflecting the passive clamping absorption state of the end end, and by utilizing the essential differences in energy flow characteristics of dual inverters to achieve accurate fault location.

[0018] It should be understood that the descriptions of technical features, technical solutions, beneficial effects, or similar language in this application do not imply that all features and advantages can be achieved in any single embodiment. Rather, it is understood that the description of a feature or beneficial effect means that a specific technical feature, technical solution, or beneficial effect is included in at least one embodiment. Therefore, the descriptions of technical features, technical solutions, or beneficial effects in this specification do not necessarily refer to the same embodiment. Furthermore, the technical features, technical solutions, and beneficial effects described in this embodiment can be combined in any suitable manner. Those skilled in the art will understand that embodiments can be implemented without one or more specific technical features, technical solutions, or beneficial effects of a particular embodiment. In other embodiments, additional technical features and beneficial effects may be identified in specific embodiments that do not embody all embodiments. Attached Figure Description

[0019] Figure 1 A schematic diagram illustrating an application scenario provided in an embodiment of this application; Figure 2 A flowchart illustrating a fault diagnosis method for an open-winding photovoltaic-storage converter system provided in this application embodiment; Figure 3 A schematic diagram of a fault current flow path under forward current flow provided in an embodiment of this application; Figure 4 A schematic diagram of another fault current flow path under the forward current flow direction provided in an embodiment of this application; Figure 5 An experimental result verification diagram for a forward current flow direction provided in this application embodiment; Figure 6 Another experimental result verification diagram for the forward current flow provided in this application embodiment; Figure 7 A schematic diagram of a fault current flow path under negative current flow direction provided in an embodiment of this application; Figure 8 A schematic diagram of another fault current flow path under negative current flow provided in an embodiment of this application; Figure 9 A schematic diagram of a fault diagnosis device for an open-winding photovoltaic-storage converter system provided in an embodiment of this application; Figure 10 This is a schematic diagram of a computing device provided in an embodiment of this application. Detailed Implementation

[0020] The terms "first," "second," and "third," etc., used in this application specification and accompanying drawings are used to distinguish different objects, not to limit a specific order.

[0021] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0022] To ensure clarity and conciseness in the description of the following embodiments, a brief introduction to the related technologies is given first: Currently, open-winding photovoltaic-storage converter systems employ a topology where the photovoltaic-side inverter and the energy storage-side inverter share a three-phase open-winding load, with independent DC buses connected to both sides. Power devices are prone to open-circuit faults under long-term high-frequency switching operation and thermal cycling stress, leading to output current distortion or even system shutdown.

[0023] Existing fault diagnosis methods mainly rely on the analysis of three-phase AC current signals, such as the current averaging method and the Parker vector trajectory method. However, these methods cannot distinguish the source of faults in the series arms of the winding topology. Some solutions address the location problem by adding voltage sensors or injecting high-frequency test signals, but these have drawbacks such as high hardware costs and impact on power quality.

[0024] In view of this, embodiments of this application provide a fault diagnosis method for an open-winding photovoltaic-storage converter system. This method can be applied to a processing device, which can be a terminal or a server. Terminals include, but are not limited to, smartphones, tablets, laptops, personal digital assistants, or smart wearable devices. Servers can be cloud servers, such as central servers in a central cloud computing cluster or edge servers in an edge cloud computing cluster. Of course, servers can also be servers in a local data center. A local data center refers to a data center directly controlled by the user. Compared with existing technologies, this application does not require additional hardware sensors. It is entirely based on the existing DC-side current sensors and AC current sensors of the system, utilizing the differences in energy flow characteristics between the photovoltaic side and the energy storage side to construct diagnostic variables, achieving decoupled location of series bridge arm faults, and possessing high noise interference resistance and load adaptability.

[0025] To make the technical solution of this application clearer and easier to understand, the application scenarios of the technical solution of this application are described below with reference to the accompanying drawings. Figure 1 As shown in the figure, this figure is a schematic diagram of an application scenario provided by an embodiment of this application.

[0026] In this application scenario, the open-winding photovoltaic-storage converter system includes a photovoltaic-side inverter IN1 and an energy storage-side inverter IN2. The photovoltaic-side inverter IN1 is connected to an independent photovoltaic DC bus, and its DC bus voltage is denoted as... As the energy output terminal; the energy storage side inverter IN2 is connected to an independent energy storage DC bus, and its DC bus voltage is denoted as... As an energy buffer, the AC sides of the photovoltaic-side inverter IN1 and the energy storage-side inverter IN2 are both connected to an open-winding transformer, forming an open-winding topology. There is no direct electrical connection between the DC buses on both sides. The system is equipped with Hall current sensors to collect the DC bus current on the photovoltaic side, the DC bus current on the energy storage side, and the three-phase AC output current.

[0027] The photovoltaic-side inverter IN1 contains multiple power switching devices, among which S a11 Sa represents the power switching device on the upper arm of phase A of the photovoltaic side. 12 Indicates the power switching device of the lower arm of phase A on the photovoltaic side; Sb 11 Sb represents the power switching device on the upper arm of phase B of the photovoltaic side. 12 Indicates the power switching device of the lower arm of phase B on the photovoltaic side; Sc 11 Indicates the power switching device on the upper arm of the C-phase of the photovoltaic side, Sc 12 This refers to the power switching device of the lower arm of the C-phase on the photovoltaic side.

[0028] The energy storage-side inverter IN2 also contains multiple power switching devices, among which Sa 21 Sa represents the power switching device of the upper arm of phase A on the energy storage side. 22 Indicates the power switching device of the lower arm of phase A on the energy storage side; Sb 21 Sb represents the power switching device of the upper arm of phase B on the energy storage side. 22 Indicates the power switching device of the lower arm of phase B on the energy storage side; Sc 21 Indicates the power switching device of the upper arm of phase C on the energy storage side, Sc 22 This refers to the power switching device of the lower arm of phase C on the energy storage side.

[0029] The aforementioned power switching devices can be insulated-gate bipolar transistors or metal-oxide-semiconductor field-effect transistors. Each power switching device is connected in anti-parallel with a freewheeling diode to provide a current freewheeling path for the inductive load.

[0030] When an open-circuit fault occurs in a power device in the system, the same phase winding is driven by the bridge arms of two inverters in series. It is impossible to distinguish whether the fault occurred in the photovoltaic-side inverter or the energy storage-side inverter based solely on the phase current signal. This application's embodiment constructs a first diagnostic variable reflecting the active output capability of the source end and a second diagnostic variable reflecting the passive clamping absorption state of the end end. Utilizing the inherent differences in energy flow characteristics between the two inverters, it achieves the location of the series-connected bridge arm fault. Therefore, this scheme can solve the problem of difficulty in distinguishing fault feature coupling in open-winding topologies, while requiring no additional hardware sensors and exhibiting high noise immunity and load adaptability.

[0031] To make the technical solution of this application clearer and easier to understand, the following describes a fault diagnosis method for an open-winding photovoltaic-storage converter system provided by an embodiment of this application, in conjunction with the above application scenarios. Figure 2 As shown in the figure, this is a flowchart of a fault diagnosis method for an open-winding photovoltaic-storage converter system provided in an embodiment of this application.

[0032] The method includes: S201. The processing equipment acquires the DC bus current on the photovoltaic side, the DC bus current on the energy storage side, and the three-phase AC output current of the open-winding photovoltaic-energy storage converter system.

[0033] An open-winding photovoltaic-energy storage converter system refers to a converter system that integrates photovoltaic power generation and energy storage using an open-winding topology. In this system, the two ends of the three-phase stator windings are connected to two independent voltage source inverters: a photovoltaic-side inverter and an energy storage-side inverter. The DC side of the photovoltaic-side inverter is connected to the photovoltaic power generation unit, and the DC side of the energy storage-side inverter is connected to the energy storage unit. The DC buses on both sides are independent and have no direct electrical connection. The power devices in the system employ insulated-gate bipolar transistors (IGBTs).

[0034] The photovoltaic-side DC bus current refers to the current at the DC bus of the inverter connected to the photovoltaic power generation unit. This current reflects the total energy output level of the photovoltaic-side inverter to the AC side. The energy storage-side DC bus current refers to the current at the DC bus of the inverter connected to the energy storage unit. This current reflects the energy absorption or release status of the energy storage-side inverter. The three-phase AC output current refers to the three-phase current on the open-winding load side, denoted as phase A current, phase B current, and phase C current, respectively. This current directly reflects the power output of the system.

[0035] The processing equipment synchronously acquires the aforementioned electrical quantities through Hall current sensors configured within the system. Specifically, within each sampling cycle of the digital controller, the processing equipment reads the output signals of the photovoltaic-side DC bus current sensor, the energy storage-side DC bus current sensor, and the three-phase AC output current sensor through the analog-to-digital conversion module, and restores the acquired digital quantities to actual physical values ​​according to the preset transformer ratio and reference voltage.

[0036] The reason for obtaining these three types of data is that the three-phase AC output current contains direct information about the distortion of the current waveform after a fault occurs, which can be used to quickly pinpoint the phase in which the fault occurs; the DC bus current on the photovoltaic side and the DC bus current on the energy storage side reflect the energy flow state of the system from the source end and the end end, respectively. The two have a definite mathematical relationship under normal operating conditions, but will show abnormal deviations under fault conditions. This deviation can be used to distinguish whether the fault occurs on the photovoltaic side or the energy storage side; the above current sensors are all standard configurations of open-winding photovoltaic-energy storage converter systems, and no additional hardware costs are required.

[0037] By simultaneously collecting DC bus currents from the photovoltaic and energy storage sides, as well as three-phase AC output currents, data for hierarchical diagnosis can be obtained. Utilizing existing sensor resources, multi-dimensional electrical information that can simultaneously reflect the global state and local fault characteristics of the system can be acquired without increasing hardware costs. Among these, the DC side current and AC side current are used in combination to construct diagnostic variables and decouple series bridge arm fault characteristics based on the differences in current flow loops.

[0038] S202. The processing equipment determines the fault phase based on the three-phase AC output current and dynamic reference value.

[0039] The fault phase refers to the load phase corresponding to an open-circuit fault in a power device in an open-winding photovoltaic-storage converter system, such as one of phases A, B, or C. The dynamic reference value is a reference value calculated in real-time based on the three-phase AC output current. This value is dynamically adjusted according to changes in system load to eliminate interference from load fluctuations in fault diagnosis.

[0040] The processing equipment first constructs a sliding window average value calculation model for each of the acquired three-phase AC output currents. Specifically, the time window width is set to one fundamental frequency cycle, and the sliding average value of the absolute value of each phase current is calculated in real time. Its expression is:

[0041] in, Let x be the moving average of the phase current at the k-th sampling time, where x = {A, B, C}. For the width of the sliding window, Let be the instantaneous value of the phase x current at the j-th sampling moment. This is the sequence number of the current sampling time. The loop variable is defined at each sampling time, and its value ranges from k. W+1 to k.

[0042] Under fault-free operation, the three-phase currents are symmetrical, and the sliding average values ​​of each phase are essentially equal. When a single-phase open-circuit fault occurs, the faulty phase current exhibits a half-wave loss, causing a significant drop in its absolute average value. To eliminate interference from sudden load changes or fluctuations in light intensity on the diagnostic process, the processing equipment calculates the arithmetic mean of the sliding average values ​​of the three-phase currents in real time, defining it as a dynamic reference value. The calculation formula is as follows:

[0043] in, As a dynamic baseline value, Let be the moving average value of the phase A current. This is the moving average value of the phase B current. This is the moving average value of the C-phase current.

[0044] The processing equipment introduces a fault identification threshold coefficient λ, which in this application ranges from 0.75 to 0.95. A phase is determined to be a faulty phase when the following logical criterion is met: the sliding average value of a phase current is less than the dynamic reference value multiplied by the fault identification threshold coefficient. .

[0045] Specifically, if If so, then phase A is determined to be faulty; if If so, then phase B is determined to be faulty; if If so, then phase C is determined to be faulty.

[0046] In some embodiments, during normal operating conditions, the moving average value of the absolute value of the three-phase current is collected. = = =6A, at this time the dynamic reference value The current is 6A. If the fault identification threshold coefficient λ is set to 0.85, then the judgment threshold is 5.1A. When an open-circuit fault occurs in phase A, its phase current exhibits a half-wave loss, leading to... The current rapidly drops below the threshold of 5.1A. Meanwhile, due to the coupling effect of the three-phase circuit, the currents in phases B and C will experience some distortion or amplitude fluctuations, but their moving average value... and It remains above the judgment threshold of 5.1A. Based on this quantification characteristic, the system can eliminate interference from phases B and C, identify phase A as the faulty phase, and trigger subsequent location procedures.

[0047] After identifying the faulty phase, the processing equipment further collects the current command value of that phase at the time of the fault. If the current command value is greater than zero, the fault interval is identified as a positive half-wave path, meaning the fault may occur in the upper arm power device of that phase on the photovoltaic side or the lower arm power device of that phase on the energy storage side. If the current command value is less than zero, the fault interval is identified as a negative half-wave path, meaning the fault may occur in the lower arm power device of that phase on the photovoltaic side or the upper arm power device of that phase on the energy storage side.

[0048] This application utilizes current mean characteristic analysis based on a sliding window to quickly pinpoint the fault phase after a fault occurs. By employing a comparison strategy of dynamic reference values ​​and fault coefficients, the influence of load variations and three-phase coupling effects on fault identification is effectively eliminated, improving the accuracy and robustness of fault detection. While pinpointing the fault phase, this method can also preliminarily determine the possible half-wave interval of the fault based on the current command value, narrowing the search range for location and improving diagnostic efficiency.

[0049] S203. The processing equipment, based on the fault phase, obtains the current residual on the photovoltaic side and the current residual on the energy storage side according to the DC bus current on the photovoltaic side and the DC bus current on the energy storage side.

[0050] Current residual refers to the deviation between the measured value of the DC-side current and the theoretical value obtained based on the reconstruction of the current of the non-faulty phase. The current residual on the photovoltaic side characterizes whether the energy output capability of the photovoltaic inverter is abnormal on the faulty phase; the current residual on the energy storage side characterizes whether the energy absorption or release capability of the energy storage inverter is abnormal on the faulty phase. Under normal, fault-free operation, since Kirchhoff's current law holds strictly, and the sum of the product of the switching function and the current of the non-faulty phase can accurately reconstruct the equivalent current component of the faulty phase on the DC side, the values ​​of the current residual on both the photovoltaic and energy storage sides are close to zero. In actual systems, affected by factors such as current sensor measurement noise, analog-to-digital conversion quantization error, and switching ripple, the residual will fluctuate slightly near zero, but the fluctuation amplitude is usually limited to a preset noise threshold range, and this state is considered normal. When an open-circuit fault occurs in the power device corresponding to one side of the inverter, the current flow path of the faulty phase is disrupted. This prevents the measured value of the DC bus current on that side from being correctly reconstructed from the current of the non-faulty phases, resulting in a significant positive or negative deviation in the current residual on that side, with its absolute value significantly exceeding the corresponding noise threshold. Simultaneously, the inverter on the other side, which is not experiencing a fault, maintains its energy flow path, and its corresponding current residual remains within the noise threshold. This state, where the residual significantly deviates from zero on one side while remaining close to zero on the other, is considered abnormal. The larger the magnitude and the longer the duration of the abnormal residual, the more significant the fault characteristics.

[0051] After locking onto the faulty phase, the processing equipment constructs an analytical model of the DC-side current based on Kirchhoff's current law. Specifically, the processing equipment uses the real-time sampled current of the non-faulty phase and the switching function of the corresponding bridge arm to reconstruct the theoretical current component of the faulty phase on the DC side. Then, it calculates the deviation between the measured value and the reconstructed theoretical value of the DC-side current, generating the photovoltaic-side current residual and the energy storage-side current residual, respectively.

[0052] The processing equipment defines the direction of the current flowing out of the positive terminal of the DC power supply as the positive direction. For the photovoltaic (PV) side inverter, which serves as the energy output terminal, the PV side DC bus current is the sum of the three-phase outflow currents. The processing equipment subtracts the algebraic sum of the products of all non-faulty phase currents and their corresponding upper bridge arm switching functions from the measured value of the PV side DC bus current to obtain the PV side current residual, expressed as:

[0053]

[0054]

[0055] in, The current residual of phase A in the photovoltaic side fault phase. This represents the current residual of phase B during a photovoltaic-side fault. This represents the current residual of phase C during a photovoltaic fault. This represents the measured value of the DC bus current on the photovoltaic side. For the switching function of the power device in the upper arm of phase B on the photovoltaic side, This is the measured value of the B-phase current in the three-phase AC output current. For the switching function of the power device in the upper arm of phase C on the photovoltaic side, This is the measured value of the C-phase current in the three-phase AC output current. For the switching function of the power device in the upper arm of phase A on the photovoltaic side, This is the measured value of phase A current in the three-phase AC output current.

[0056] For the energy storage-side inverter, which acts as an energy input or buffer, the phase current flowing into the DC bus makes a negative contribution. The processing equipment adds the measured value of the DC bus current on the energy storage side to the algebraic sum of the products of all non-faulty phase currents and their corresponding upper bridge arm switching functions, yielding the current residual on the energy storage side, expressed as:

[0057]

[0058]

[0059] in, The current residual of phase A in the fault phase on the energy storage side. The current residual of phase B in the fault phase on the energy storage side. The current residual of phase C in the fault phase on the energy storage side. This represents the measured value of the DC bus current on the energy storage side. For the switching function of the power device in the upper arm of phase B on the energy storage side, For the switching function of the power device in the upper arm of phase C on the energy storage side, This is the switching function for the power devices on the upper arm of phase A on the energy storage side.

[0060] By mapping the fault characteristics of the AC side to the DC side, the dimensionality of the fault characteristics is expanded. The theoretical current component of the fault phase is reconstructed using information from the non-faulty phase, avoiding the interference of fault phase current distortion on the residual calculation. Different residual calculation formulas are used for the photovoltaic side and the energy storage side, so that the faults on both sides exhibit different characteristic patterns in the diagnostic variables of the next step, thereby decoupling the fault characteristics of the series bridge arm in the open winding topology.

[0061] S204. The processing equipment processes the current residual on the photovoltaic side and the current residual on the energy storage side to obtain the first diagnostic variable and the second diagnostic variable.

[0062] The first diagnostic variable is a quantitative index obtained after feature extraction of the current residual on the photovoltaic side. This variable is used to characterize the ability of the photovoltaic inverter to actively output energy to the faulty phase winding. The second diagnostic variable is a quantitative index obtained after feature extraction of the current residual on the energy storage side. This variable is used to characterize the ability of the energy storage inverter to passively clamp and absorb the faulty phase current.

[0063] The instantaneous current residual signal obtained in step S203 contains a high-frequency ripple component coupled with the switching frequency. If used directly for fault diagnosis, it is easily affected by switching noise and system transient disturbances, leading to misjudgment. Therefore, the processing device performs feature extraction on the instantaneous residual signal to extract the steady-state component that reflects the average state of energy flow.

[0064] Specifically, the processing device sets the feature extraction window width to one PWM switching cycle. Within this window, the processing device performs a moving average calculation on the current residual on the photovoltaic side to obtain the first diagnostic variable, the expression of which is:

[0065] in, The first diagnostic variable at the k-th sampling time. This represents the number of sampling points contained in one PWM switching cycle. Let x be the residual current value of the photovoltaic-side fault phase x at the j-th sampling time, x={A, B, C}.

[0066] The processing equipment uses the same method to calculate the moving average of the current residual on the energy storage side within the same window width, obtaining the second diagnostic variable, whose expression is:

[0067] in, The second diagnostic variable at the k-th sampling time. This represents the number of sampling points contained in one PWM switching cycle. Let x be the current residual value of the fault phase x on the energy storage side at the j-th sampling time, x={A, B, C}.

[0068] After the above moving average processing, the original instantaneous residual signal is transformed into an eigenvector composed of two DC values. This feature vector will be used to determine the fault location.

[0069] The beneficial effects of this step are as follows: First, the moving average within the PWM switching cycle can effectively filter out high-frequency switching ripple and extract the DC component that reflects the average level of power flow, thereby improving the noise immunity of the diagnostic variables; Second, the moving average algorithm is simple to calculate and does not require complex frequency domain transformation, making it suitable for real-time execution in embedded digital controllers; Third, by converting the time-varying residual waveform into a stable DC diagnostic variable, fault logic judgment can be based on simple threshold comparison, reducing the implementation complexity of the algorithm.

[0070] This application effectively eliminates the influence of high-frequency switching noise and system transient fluctuations on the diagnostic results by performing moving average processing on the instantaneous residuals, thereby improving the robustness of fault diagnosis. It compresses complex fault waveform information into two concise diagnostic variables, significantly reducing the complexity of fault classification. The first and second diagnostic variables reflect the energy flow state of the system from the source and end, respectively. Their physical meanings are clear and independent of each other, and they are used to distinguish between photovoltaic-side faults and energy storage-side faults based on the difference in current flow loops.

[0071] S205. The processing equipment obtains the current flow direction in the open-winding photovoltaic-storage converter system, and determines the fault location based on the current flow direction, the first diagnostic variable, and the second diagnostic variable.

[0072] Current flow direction refers to the positive or negative direction of the fault phase current, reflecting the direction of energy flow between the photovoltaic (PV) inverter and the energy storage inverter. When the current flow direction is positive, it means that the current flows out of the PV inverter, through the stator winding, and into the energy storage inverter. In this case, the PV side acts as the energy output terminal, and the energy storage side acts as the energy receiving terminal. When the current flow direction is negative, it means that the current flows out of the energy storage inverter, through the stator winding, and into the PV inverter. In this case, the energy storage side acts as the energy output terminal, and the PV side acts as the energy receiving terminal. The direction of current flow from the PV inverter to the energy storage inverter is defined as the first flow direction, and the direction of current flow from the energy storage inverter to the PV inverter is defined as the second flow direction.

[0073] The fault location refers to the specific location of the power device where the open-circuit fault occurred, including the upper arm power device of the photovoltaic inverter corresponding to the fault phase, the lower arm power device of the photovoltaic inverter corresponding to the fault phase, the upper arm power device of the energy storage inverter corresponding to the fault phase, or the lower arm power device of the energy storage inverter corresponding to the fault phase.

[0074] The processing equipment collects the instantaneous current value of the faulty phase in real time through AC current sensors configured within the system. Specifically, the three-phase AC output current is detected by Hall current sensors, filtered and amplified by a signal conditioning circuit, and then converted into a digital quantity by an analog-to-digital converter before being sent to the processor. In each sampling cycle, the processor reads the instantaneous sampled value of the faulty phase current. If the instantaneous value is greater than a preset positive current threshold, the current flow direction is determined to be the first direction, from the photovoltaic inverter to the energy storage inverter; if the instantaneous value is less than a preset negative current threshold, the current flow direction is determined to be the second direction, from the energy storage inverter to the photovoltaic inverter. To prevent misjudgment of the flow direction due to noise, the processor can perform a moving average filtering process on the current values ​​of multiple consecutive sampling points, or use the current command value as an auxiliary criterion. When the instantaneous current amplitude crosses zero or approaches zero, the current command value corresponding to the current drive signal is used as the standard.

[0075] Specifically, the processing equipment reads the current command value of the phase at the time of the fault. If the current command value is greater than zero, it is determined to be the first flow direction; if the current command value is less than zero, it is determined to be the second flow direction.

[0076] The processing equipment uses corresponding diagnostic logic to analyze the first and second diagnostic variables according to the different current flow directions.

[0077] When the current flow direction of the fault phase is the first direction, the processing equipment determines the first preliminary fault location, and then determines the first fault location based on the amplitude characteristics of the first diagnostic variable, the amplitude characteristics of the second diagnostic variable, the first noise threshold, and the second noise threshold. If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the first relationship, then the first preliminary fault location is determined as the first fault location. If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the second relationship, then the first preliminary fault location is determined as the second fault location. The first preliminary fault location includes the upper arm power device of the photovoltaic inverter corresponding to the fault phase and the lower arm power device of the energy storage inverter corresponding to the fault phase. The first noise threshold is less than the second noise threshold.

[0078] The specific steps are as follows: This application provides a schematic diagram of the fault current flow path in the forward current flow direction to illustrate the current flow path when an open-circuit fault occurs in the power device of the upper arm of a photovoltaic inverter. Figure 3As shown, when an open-circuit fault occurs in the power device of the upper arm of phase A of the photovoltaic inverter, the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy a first relationship. Here, the amplitude characteristics of the first diagnostic variable refer to the magnitude and polarity of the first diagnostic variable; the amplitude characteristics of the second diagnostic variable refer to the magnitude and polarity of the second diagnostic variable. The first relationship is that the amplitude characteristics of the first diagnostic variable are less than the first noise threshold, and the amplitude characteristics of the second diagnostic variable are less than the second noise threshold. This means that the active path for the photovoltaic power supply to output energy to the phase A winding is physically cut off, and the first diagnostic variable exhibits amplitude attenuation characteristics, with its value returning to zero or less than the preset zero-current noise threshold. Due to the system inductor freewheeling effect and the three-phase coupling effect, the current will form a temporary freewheeling circuit through the anti-parallel diodes of the lower arm of the photovoltaic side and the anti-parallel diodes of the lower arm of the energy storage side, resulting in intermittent weak negative pulses in the DC bus current of the energy storage side. Therefore, the second diagnostic variable exhibits an intermittent negative value with a small amplitude or close to zero, and its absolute value is less than the preset second noise threshold. Based on the above characteristics, the processing equipment determines that the first fault location is an open circuit in the upper arm power device of the corresponding fault phase of the photovoltaic inverter.

[0079] This application also provides another schematic diagram of the fault current flow path under the forward current flow direction, such as... Figure 4 As shown, when an open-circuit fault occurs in the power device of the lower arm of phase A in the energy storage inverter, the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy a second relationship. This second relationship states that the amplitude characteristic of the first diagnostic variable is greater than the first noise threshold, and the amplitude characteristic of the second diagnostic variable is much smaller than the second noise threshold. This means that the power device of the upper arm on the photovoltaic side can still respond to the drive signal and operate normally, continuously injecting energy into the phase A winding. Therefore, the first diagnostic variable remains a positive value related to the load current, and its value is greater than the first noise threshold. However, because the normal return path of the lower arm on the energy storage side is interrupted by the fault, the accumulated inductor current cannot flow back to the negative terminal of the battery through the lower diode. This forces the current to continuously open the anti-parallel diode of the upper arm on the energy storage side and flow into the positive terminal of the DC bus on the energy storage side. This passive clamping absorption state causes the DC bus current on the energy storage side to exhibit a continuous and large-amplitude negative current, resulting in a negative clamping characteristic in the second diagnostic variable. Its value is less than the negative second noise threshold, and its absolute value is much greater than that under the photovoltaic side fault condition. Based on the above characteristics, the processing equipment determines that the second fault location is an open circuit in the lower arm power device of the corresponding fault phase of the energy storage side inverter.

[0080] The fault diagnosis logic described above for forward current flow can be uniformly described by the following expression:

[0081] in, The first noise threshold, The second noise threshold, As the primary diagnostic variable, F1 is the second diagnostic variable and is a discrete scalar with positive integer values.

[0082] Both the first and second noise thresholds are preset positive numbers, determined based on the current residual fluctuation range of the open-winding photovoltaic-storage converter system under normal operating conditions. Specifically, when the system is operating normally without faults and in a steady-state condition, the current residuals of the fault phases on the photovoltaic side and the energy storage side are continuously collected, and the root mean square value or maximum absolute value fluctuation amplitude of both within a sliding window is calculated. The statistical upper limit of the current residual fluctuation amplitude on the photovoltaic side is multiplied by a preset reliability coefficient to obtain the first noise threshold; the statistical upper limit of the current residual fluctuation amplitude on the energy storage side is multiplied by a preset reliability coefficient to obtain the second noise threshold. The reliability coefficient typically ranges from 1.2 to 2.0 to ensure that the thresholds can effectively cover signal noise and measurement errors under normal operating conditions, while avoiding a reduction in fault detection sensitivity due to excessively high threshold settings.

[0083] As an optional implementation, the first and second noise thresholds can also be adaptively adjusted according to the actual operating conditions of the system. For example, when the system load current is small, the fluctuation amplitude of the current residual is correspondingly reduced, and the noise threshold can be appropriately lowered to improve the sensitivity of fault detection; when the system load current is large, the noise threshold can be appropriately increased to enhance the anti-interference capability. The processing equipment can dynamically adjust the values ​​of the first and second noise thresholds according to the real-time monitored output power or the effective value of the load current, through table lookup or linear interpolation.

[0084] As an alternative implementation, the first noise threshold and the second noise threshold can also use the same value, that is, the first noise threshold is equal to the second noise threshold. In this case, only one noise threshold parameter needs to be preset, simplifying the system configuration. In practical engineering applications, it is recommended to set the noise threshold to 1% to 5% of the DC side current value corresponding to the system's rated current. This range can effectively filter out measurement noise under normal operating conditions without excessively delaying the fault detection response time.

[0085] The fault characteristics and logic diagnosis of the above-mentioned positive current flow downward can be summarized in Table 1: Table 1: Fault Characteristics and Logic Diagnosis Table for Positive Current Flow

[0086] To verify the correctness and speed of the method for diagnosing open-circuit faults in the upper arm power devices of a photovoltaic inverter, this application provides an experimental result diagram, such as... Figure 5As shown in the figure, this is the experimental result under an open-circuit fault in the upper arm of phase A of the photovoltaic inverter. Wherein, t K The fault detection start time is the moment when the fault start flag K first changes from 0 to 1; t F The fault diagnosis is completed when the fault type flag F stably outputs the corresponding fault code; T c For the system's power frequency period, t F t K The fault diagnosis delay of this method is characterized. The time from fault occurrence to fault identification is 0.02 fundamental frequency cycles, and the time from fault occurrence to fault location is 0.06 fundamental frequency cycles. This application also provides another experimental result graph, as shown below. Figure 6 The figure shows the experimental results under an open-circuit fault in the lower arm of phase A of the energy storage-side inverter. The time from fault occurrence to fault identification was 0.02 fundamental frequency cycles, and the time from fault occurrence to fault location was 0.07 fundamental frequency cycles. Both sets of experimental results verify the correctness and speed of the above diagnostic method.

[0087] When the current flow direction of the fault phase is the second direction, the processing equipment determines the second preliminary fault location, and then makes a judgment based on the amplitude characteristics of the first diagnostic variable, the amplitude characteristics of the second diagnostic variable, the first noise threshold, and the second noise threshold: If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy a third relationship, wherein the third relationship is that the amplitude characteristics of the first diagnostic variable are less than the second noise threshold, and the amplitude characteristics of the second diagnostic variable are less than the first noise threshold, that is, the absolute value of the first diagnostic variable is less than the second noise threshold, and the absolute value of the second diagnostic variable is less than the first noise threshold, then the second preliminary fault location is determined as the third fault location; wherein the third fault location is the lower arm power device of the photovoltaic inverter corresponding to the fault phase.

[0088] If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy a fourth relationship, wherein the fourth relationship is that the amplitude characteristics of the first diagnostic variable are much smaller than the second noise threshold, and the amplitude characteristics of the second diagnostic variable are greater than the first noise threshold, that is, the first diagnostic variable is much smaller than the negative second noise threshold, and the second diagnostic variable is greater than the first noise threshold, then the second preliminary fault location is determined as the fourth fault location; wherein, the fourth fault location is the upper bridge arm power device of the energy storage side inverter corresponding to the fault phase.

[0089] The specific steps are as follows: This application provides a schematic diagram of the fault current flow path in the second direction to illustrate the current flow path when an open-circuit fault occurs in the power device of the upper arm of the energy storage-side inverter. Figure 7 As shown, when an open-circuit fault occurs in the upper arm power device of the faulty phase in the energy storage-side inverter, the amplitude characteristics of the first diagnostic variable, the first noise threshold, and the amplitude characteristics and second noise threshold of the second diagnostic variable satisfy the third relationship. That is, the energy storage-side circuit, which serves as the energy output source for the negative half-cycle, is cut off, and the energy storage DC bus cannot inject current into the faulty phase winding, resulting in a temporary source-end interruption. At this time, the amplitude of the second diagnostic variable characterizing the energy storage-side state rapidly decays and returns to zero or is less than the preset first noise threshold. Affected by this, the entire faulty phase circuit loses its driving energy. Although the photovoltaic side has an intact path, no current flows in. Therefore, the first diagnostic variable characterizing the photovoltaic side state also returns to zero or exhibits extremely weak induced noise, the absolute value of which is less than the preset second noise threshold. Based on the characteristic that the second diagnostic variable returns to zero and the first diagnostic variable has no significant negative value, the processing equipment determines that the third fault location is an open circuit in the upper arm power device of the corresponding faulty phase in the energy storage-side inverter.

[0090] This application also provides another schematic diagram of the fault current flow path under negative current flow, such as... Figure 8 As shown, when an open-circuit fault occurs in the lower arm power device of the faulty phase of the photovoltaic inverter, the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the fourth relationship. That is, the upper arm power device on the energy storage side can still conduct normally and output energy. Therefore, the second diagnostic variable remains a positive value related to the load current, and its value is greater than the first noise threshold. However, when the current flows to the photovoltaic side, because the normal return path of the lower arm on the photovoltaic side is cut off by the fault, the inductor freewheeling forces the current to open the anti-parallel diode of the upper arm on the photovoltaic side and passively feed back into the positive terminal of the photovoltaic DC bus. This forced passive feedback current is opposite to the specified photovoltaic output direction, causing an abnormal reverse flow of the photovoltaic DC bus current, resulting in the first diagnostic variable showing a negative clamping characteristic, and its value is less than the negative second noise threshold. Based on the above characteristics, the processing equipment determines that the fourth fault location is an open circuit in the lower arm power device of the corresponding faulty phase of the photovoltaic inverter.

[0091] The fault diagnosis logic for the negative current flowing downwards described above can be uniformly described by the following expression:

[0092] in, The first noise threshold, The second noise threshold, As the primary diagnostic variable, It is the second diagnostic variable.

[0093] The fault characteristics and logic diagnosis of the above-mentioned negative current flow downward can be summarized in Table 2: Table 2: Fault Characteristics and Logic Diagnosis Table for Negative Current Flow

[0094] By detecting the current flow direction and combining the amplitude characteristics of the first and second diagnostic variables, it is possible to accurately distinguish whether the fault occurs in the photovoltaic-side inverter or the energy storage-side inverter, and specifically whether it is the upper or lower bridge arm power device. This solves the problem of difficulty in distinguishing the coupled fault characteristics of series bridge arms in open winding topologies. The diagnostic logic based on threshold comparison is simple and efficient, and can quickly locate the faulty device after the fault occurs. Experimental verification shows that the fault identification time is about 0.02 fundamental frequency cycles, and the fault location time is about 0.06 to 0.07 fundamental frequency cycles. This diagnostic method is entirely based on the existing current sensor of the system, without adding additional hardware costs, and has high engineering practical value.

[0095] In some embodiments, if the first diagnostic variable and the second diagnostic variable always satisfy the amplitude characteristic condition corresponding to the fault location within a preset delay window, the fault location is confirmed and the fault diagnosis result is output; if the first diagnostic variable or the second diagnostic variable fails to satisfy the amplitude characteristic condition within the preset delay window, the fault location is determined to be invalid.

[0096] Specifically, in this embodiment, in order to prevent misdiagnosis of faults caused by factors such as instantaneous sensor noise, transient system disturbances or sudden load changes, the processing device does not immediately output the fault result after initially determining the fault location, but introduces a delayed confirmation mechanism.

[0097] After initially determining the fault location based on the current flow direction of the fault phase, the first diagnostic variable, and the second diagnostic variable, the processing device triggers the timing unit to start timing. The processing device sets a preset delay window, the width of which can be configured according to the dynamic response characteristics of the system, typically set to 1 to 5 fundamental frequency cycles or 10 to 50 PWM switching cycles.

[0098] Within the preset delay window, the processing device continuously collects the values ​​of the first diagnostic variable and the second diagnostic variable, and determines in real time whether both consistently meet the amplitude characteristic condition corresponding to the fault location. The amplitude characteristic condition refers to the magnitude relationship between the diagnostic variable and the noise threshold as specified in the fault judgment logic determined based on the current flow direction. For example, when the fault location with forward current flowing downward is initially determined to be an open circuit in the upper arm power device on the photovoltaic side, it is necessary to verify whether the first diagnostic variable is consistently less than the first noise threshold and whether the absolute value of the second diagnostic variable is consistently less than the second noise threshold.

[0099] If the first diagnostic variable and the second diagnostic variable always satisfy the amplitude characteristic condition in every sampling moment or every diagnostic cycle within the delay window, the processing device will finally confirm that the fault location is established and output the corresponding fault information, including the phase in which the fault occurred, the inverter side (photovoltaic side or energy storage side) where the fault is located, and the specific location of the faulty device (upper arm or lower arm).

[0100] If, at any moment or during any diagnostic cycle within the delay window, the first diagnostic variable or the second diagnostic variable fails to meet the amplitude characteristic condition, the processing device determines that the fault location is invalid, identifies it as a transient disturbance event, clears the initially determined fault location information, and the system continues to operate normally without triggering a fault alarm.

[0101] The beneficial effects of this embodiment are as follows: by introducing a delayed confirmation mechanism, false diagnoses caused by sensor noise, electromagnetic interference, or system transient processes are effectively avoided, thereby improving the reliability and accuracy of fault diagnosis. The width of the delay window can be flexibly configured according to the actual application scenario, achieving a balance between diagnostic response speed and anti-interference capability.

[0102] In some embodiments, after determining the fault location, the deviation between the first diagnostic variable and the first noise threshold and the deviation between the second diagnostic variable and the second noise threshold are calculated; a fault level index is generated based on the deviation between the first diagnostic variable and the first noise threshold and the deviation between the second diagnostic variable and the second noise threshold; and a fault diagnosis result containing the fault location and the fault level index is output.

[0103] Specifically, in this embodiment, after determining the fault location, the processing device not only outputs the fault location information, but also quantitatively assesses the severity of the fault and generates a fault level index.

[0104] After the processing equipment finally confirms the fault location based on the current flow direction of the fault phase, the first diagnostic variable, and the second diagnostic variable, it further calculates the degree of deviation between the first diagnostic variable and the first noise threshold, as well as the degree of deviation between the second diagnostic variable and the second noise threshold.

[0105] The degree of deviation can be calculated using various mathematical forms. As an optional implementation, the degree of deviation can be expressed as a difference:

[0106]

[0107] in, The degree of deviation of the primary diagnostic variable. This represents the degree of deviation of the second diagnostic variable. When the absolute value of the diagnostic variable is greater than the corresponding noise threshold, the degree of deviation is positive, indicating that the fault characteristics are significant; when the absolute value of the diagnostic variable is less than or equal to the corresponding noise threshold, the degree of deviation is non-positive, indicating that the fault characteristics are weak or have not yet become apparent.

[0108] As another optional implementation, the degree of deviation is expressed as a ratio:

[0109]

[0110] in, This is the ratio of the first diagnostic variable to the corresponding noise threshold. This is the ratio of the second diagnostic variable to the corresponding noise threshold. A ratio greater than 1 indicates that the fault characteristics are significant, and the larger the ratio, the more severe the fault.

[0111] The processing device generates a fault level index based on the aforementioned deviation. The fault level index can be a continuous numerical value or a discrete level identifier. For example, the processing device can classify the fault level into three levels: minor fault, general fault, and severe fault: when the deviation is less than a first preset threshold, it is determined to be a minor fault; when the deviation is between the first and second preset thresholds, it is determined to be a general fault; and when the deviation is greater than the second preset threshold, it is determined to be a severe fault.

[0112] The processing equipment ultimately outputs a fault diagnosis result containing fault location and fault severity indicators. This diagnosis result can be uploaded to the host computer monitoring system via a communication interface to guide maintenance personnel in developing differentiated handling strategies: for minor faults, the system can be allowed to continue operating until the next maintenance cycle for further processing; for general faults, planned shutdown maintenance can be arranged; for severe faults, emergency shutdown protection should be implemented immediately.

[0113] The beneficial effects of this embodiment are as follows: by quantifying the deviation between diagnostic variables and noise thresholds, an objective assessment of the severity of faults is achieved; the combined output of fault level indicators and fault location information enables maintenance personnel to have a more comprehensive understanding of the system's health status and optimize the allocation of maintenance resources; the calculation method for the degree of deviation is flexible and diverse, and the difference method, ratio method, or other more complex evaluation models can be selected according to actual application needs, which has good scalability.

[0114] The above text combined Figures 1 to 8 The fault diagnosis method for the open-winding photovoltaic-storage converter system provided in the embodiments of this application has been described in detail. The apparatus and equipment provided in the embodiments of this application will be described below with reference to the accompanying drawings.

[0115] This application also provides a fault diagnosis device for an open-winding photovoltaic-storage converter system, such as... Figure 9 As shown in the figure, this is a schematic diagram of a fault diagnosis device for an open-winding photovoltaic-storage converter system provided in an embodiment of this application. The device includes: The acquisition module 901 is used to acquire the DC bus current on the photovoltaic side, the DC bus current on the energy storage side, and the three-phase AC output current of the open-winding photovoltaic-energy storage converter system; and to determine the fault phase based on the three-phase AC output current and the dynamic reference value. The calculation module 902 is used to obtain the current residual on the photovoltaic side and the current residual on the energy storage side based on the fault phase, according to the DC bus current on the photovoltaic side and the DC bus current on the energy storage side; and to process the current residual on the fault phase on the photovoltaic side and the current residual on the fault phase on the energy storage side to obtain a first diagnostic variable and a second diagnostic variable. The diagnostic module 903 is used to obtain the current flow direction in the open-winding photovoltaic-storage converter system; and to determine the fault location based on the current flow direction, the first diagnostic variable, and the second diagnostic variable.

[0116] In some possible implementations, the calculation module 902 is specifically used to determine the non-fault phase based on the fault phase; to obtain the current residual on the photovoltaic side based on the measured value of the DC bus current on the photovoltaic side and the measured value of the non-fault phase current; and to obtain the current residual on the energy storage side based on the measured value of the DC bus current on the energy storage side and the measured value of the non-fault phase current.

[0117] In some possible implementations, the diagnostic module 903 is specifically used to determine the first preliminary fault location when the current flow direction is a first direction; If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the first relationship, then the first preliminary fault location is determined as the first fault location. If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the second relationship, then the first preliminary fault location is determined as the second fault location. Wherein, the first fault location is the upper arm power device of the photovoltaic-side inverter corresponding to the fault phase, and the second fault location is the lower arm power device of the energy storage-side inverter corresponding to the fault phase; the first noise threshold is less than the second noise threshold; and the first flow direction is the direction from the photovoltaic-side inverter to the energy storage-side inverter.

[0118] In some possible implementations, the diagnostic module 903 is further configured to determine a second preliminary fault location when the current flow direction is a second flow direction; if the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy a third relationship, then the second preliminary fault location is determined as a third fault location; If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the fourth relationship, then the second preliminary fault location is determined as the fourth fault location; wherein, the third fault location is the lower arm power device of the photovoltaic inverter corresponding to the fault phase, and the fourth fault location is the upper arm power device of the energy storage inverter corresponding to the fault phase; the second flow direction is the direction from the energy storage inverter to the photovoltaic inverter.

[0119] In some possible implementations, the acquisition module 901 is specifically used to obtain the sliding average of the absolute values ​​of the currents of each phase based on the three-phase AC output current; and to obtain the fault phase based on the sliding average of the absolute values ​​of the currents of each phase, the dynamic reference value, and the fault identification threshold coefficient.

[0120] In some possible implementations, the device further includes: The judgment module is used to confirm the fault location and output the fault diagnosis result if the first diagnostic variable and the second diagnostic variable always satisfy the amplitude characteristic condition corresponding to the fault location within a preset delay window.

[0121] In some possible implementations, the device further includes: The output module is used to calculate the deviation between the first diagnostic variable and the first noise threshold, and the deviation between the second diagnostic variable and the second noise threshold, after determining the fault location; generate a fault level index based on the deviation between the first diagnostic variable and the first noise threshold, and the deviation between the second diagnostic variable and the second noise threshold; and output a fault diagnosis result containing the fault location and the fault level index.

[0122] The fault diagnosis device for the open-winding photovoltaic-storage converter system according to the embodiments of this application can correspondingly execute the method described in the embodiments of this application, and the other operations and / or functions of each module / unit of the fault diagnosis device for the open-winding photovoltaic-storage converter system are respectively for realizing Figure 2 For the sake of brevity, the corresponding processes of each method in the illustrated embodiments will not be described in detail here.

[0123] This application also provides a computing device. For example... Figure 10As shown in the figure, this is a schematic diagram of a computing device provided in an embodiment of this application. The computing device 400 includes a bus 401, a processor 402, a communication interface 403, and a memory 404. The processor 402, the memory 404, and the communication interface 403 communicate with each other via the bus 401.

[0124] Bus 401 can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of representation, Figure 10 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0125] Processor 402 can be any one or more of the following processors: central processing unit (CPU), graphics processing unit (GPU), microprocessor (MP), or digital signal processor (DSP).

[0126] Communication interface 403 is used for communication with external devices.

[0127] Memory 404 may include volatile memory, such as random access memory (RAM). Memory 404 may also include non-volatile memory, such as read-only memory (ROM), flash memory, hard disk drive (HDD), or solid state drive (SSD).

[0128] The memory 404 stores executable code, and the processor 402 executes the executable code to perform the aforementioned fault diagnosis method for the open-winding photovoltaic-storage converter system.

[0129] Specifically, in achieving Figure 9 In the case of the illustrated embodiment, and Figure 9 When the modules or units of the fault diagnosis device for the open-winding photovoltaic-storage converter system described in the embodiment are implemented by software, the following steps are performed: Figure 9The software or program code required for the functions of each module / unit can be partially or entirely stored in memory 404. Processor 402 executes the program code corresponding to each unit stored in memory 404 to perform the aforementioned fault diagnosis method for open-winding photovoltaic-storage converter system.

[0130] This application also provides a computer-readable storage medium. The computer-readable storage medium can be any available medium that a computing device can store, or a data storage device such as a data center containing one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state drive). The computer-readable storage medium includes instructions that instruct the computing device to execute the fault diagnosis method for the open-winding optical-storage converter system described above.

[0131] This application also provides a computer program product comprising one or more computer instructions. When the computer instructions are loaded and executed on a computing device, all or part of the processes or functions described in this application are generated.

[0132] The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions may be transmitted from one website, computer, or data center to another website, computer, or data center via wired (e.g., coaxial cable, fiber optic) or wireless (e.g., infrared, wireless, microwave, etc.) means.

[0133] When the computer program product is executed by a computer, the computer performs any of the aforementioned fault diagnosis methods for the open-winding photovoltaic-storage converter system. The computer program product can be a software installation package; when any of the aforementioned fault diagnosis methods for the open-winding photovoltaic-storage converter system needs to be used, the computer program product can be downloaded and executed on the computer.

[0134] The descriptions of the processes or structures corresponding to the above figures each have their own emphasis. For parts of a process or structure that are not described in detail, please refer to the relevant descriptions of other processes or structures.

[0135] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be covered within the scope of protection of this application.

Claims

1. A fault diagnosis method for an open-winding photovoltaic-storage converter system, characterized in that, The method includes: Obtain the DC bus current on the photovoltaic side, the DC bus current on the energy storage side, and the three-phase AC output current of the open-winding photovoltaic-energy storage converter system; The fault phase is determined based on the three-phase AC output current and dynamic reference value. Based on the fault phase, the current residuals on the photovoltaic side and the energy storage side are obtained according to the DC bus current on the photovoltaic side and the DC bus current on the energy storage side. The current residual on the photovoltaic side is calculated by moving average to obtain the first diagnostic variable, and the current residual on the energy storage side is calculated by moving average to obtain the second diagnostic variable. Obtain the current flow direction in the open-winding photovoltaic-storage converter system; When the current flow direction is the first direction, the first preliminary fault location is determined; If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the first relationship, then the first preliminary fault location is determined as the first fault location. If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the second relationship, then the first preliminary fault location is determined as the second fault location. The first relationship is that the amplitude characteristic of the first diagnostic variable is less than the first noise threshold, and the amplitude characteristic of the second diagnostic variable is less than the second noise threshold; The second relationship is that the amplitude characteristic of the first diagnostic variable is greater than the first noise threshold, and the amplitude characteristic of the second diagnostic variable is less than the second noise threshold; wherein, the amplitude characteristic of the first diagnostic variable refers to the numerical magnitude and polarity of the first diagnostic variable; the amplitude characteristic of the second diagnostic variable refers to the numerical magnitude and polarity of the second diagnostic variable. The first fault location is the upper arm power device of the photovoltaic inverter corresponding to the fault phase, and the second fault location is the lower arm power device of the energy storage inverter corresponding to the fault phase; the first noise threshold is less than the second noise threshold; the first flow direction is the direction from the photovoltaic inverter to the energy storage inverter. When the current flow direction is the second direction, the second preliminary fault location is determined; if the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the third relationship, then the second preliminary fault location is determined as the third fault location. If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the fourth relationship, then the second preliminary fault location is determined as the fourth fault location. The third relationship is that the amplitude characteristic of the first diagnostic variable is less than the second noise threshold, and the amplitude characteristic of the second diagnostic variable is less than the first noise threshold. The fourth relationship is that the amplitude characteristic of the first diagnostic variable is less than the second noise threshold, and the amplitude characteristic of the second diagnostic variable is greater than the first noise threshold; wherein, the third fault location is the lower bridge arm power device of the photovoltaic-side inverter corresponding to the fault phase, and the fourth fault location is the upper bridge arm power device of the energy storage-side inverter corresponding to the fault phase; the second flow direction is the direction from the energy storage-side inverter to the photovoltaic-side inverter.

2. The method according to claim 1, characterized in that, The process of obtaining the current residuals on the photovoltaic side and the energy storage side based on the fault phase, according to the DC bus current on the photovoltaic side and the DC bus current on the energy storage side, includes: Determine the non-fault phase based on the fault phase; The residual current on the photovoltaic side is obtained based on the measured value of the DC bus current on the photovoltaic side and the measured value of the non-fault phase current. The residual current on the energy storage side is obtained based on the measured value of the DC bus current on the energy storage side and the measured value of the non-fault phase current.

3. The method according to claim 1, characterized in that, The determination of the fault phase based on the three-phase AC output current and dynamic reference value includes: The moving average of the absolute values ​​of the currents in each phase is obtained based on the three-phase AC output current. The fault phase is obtained based on the sliding average of the absolute values ​​of the currents in each phase, the dynamic reference value, and the fault identification threshold coefficient.

4. The method according to claim 1, characterized in that, The method further includes: If, within the preset delay window, the first diagnostic variable and the second diagnostic variable consistently satisfy the amplitude characteristic condition corresponding to the fault location, then the fault location is confirmed and the fault diagnosis result is output.

5. The method according to claim 1, characterized in that, The method further includes: After determining the fault location, the deviation between the first diagnostic variable and the first noise threshold is calculated, and the deviation between the second diagnostic variable and the second noise threshold is also calculated. Based on the degree of deviation between the first diagnostic variable and the first noise threshold, and the degree of deviation between the second diagnostic variable and the second noise threshold, a fault level index is generated; The output includes the fault location and the fault level index.

6. A fault diagnosis device for an open-winding photovoltaic-storage converter system, characterized in that, The device includes: The acquisition module is used to acquire the DC bus current on the photovoltaic side, the DC bus current on the energy storage side, and the three-phase AC output current of the open-winding photovoltaic-energy storage converter system; and to determine the fault phase based on the three-phase AC output current and the dynamic reference value. The calculation module is used to obtain the current residual on the photovoltaic side and the current residual on the energy storage side based on the fault phase, according to the DC bus current on the photovoltaic side and the DC bus current on the energy storage side; to perform a moving average calculation on the current residual on the photovoltaic side to obtain a first diagnostic variable; and to perform a moving average calculation on the current residual on the energy storage side to obtain a second diagnostic variable. The diagnostic module is used to obtain the current flow direction in the open-winding photovoltaic-storage converter system; When the current flow direction is the first direction, the first preliminary fault location is determined; If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the first relationship, then the first preliminary fault location is determined as the first fault location. If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the second relationship, then the first preliminary fault location is determined as the second fault location. The first relationship is that the amplitude characteristic of the first diagnostic variable is less than the first noise threshold, and the amplitude characteristic of the second diagnostic variable is less than the second noise threshold; The second relationship is that the amplitude characteristic of the first diagnostic variable is greater than the first noise threshold, and the amplitude characteristic of the second diagnostic variable is less than the second noise threshold; wherein, the amplitude characteristic of the first diagnostic variable refers to the numerical magnitude and polarity of the first diagnostic variable; the amplitude characteristic of the second diagnostic variable refers to the numerical magnitude and polarity of the second diagnostic variable. The first fault location is the upper arm power device of the photovoltaic inverter corresponding to the fault phase, and the second fault location is the lower arm power device of the energy storage inverter corresponding to the fault phase; the first noise threshold is less than the second noise threshold; the first flow direction is the direction from the photovoltaic inverter to the energy storage inverter. When the current flow direction is the second direction, the second preliminary fault location is determined; if the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the third relationship, then the second preliminary fault location is determined as the third fault location. If the amplitude characteristics of the first diagnostic variable, the first noise threshold, the amplitude characteristics of the second diagnostic variable, and the second noise threshold satisfy the fourth relationship, then the second preliminary fault location is determined as the fourth fault location. The third relationship is that the amplitude characteristic of the first diagnostic variable is less than the second noise threshold, and the amplitude characteristic of the second diagnostic variable is less than the first noise threshold. The fourth relationship is that the amplitude characteristic of the first diagnostic variable is less than the second noise threshold, and the amplitude characteristic of the second diagnostic variable is greater than the first noise threshold; wherein, the third fault location is the lower bridge arm power device of the photovoltaic-side inverter corresponding to the fault phase, and the fourth fault location is the upper bridge arm power device of the energy storage-side inverter corresponding to the fault phase; the second flow direction is the direction from the energy storage-side inverter to the photovoltaic-side inverter.

7. A computing device, characterized in that, Including memory and processor; The memory stores one or more computer programs, the one or more computer programs including instructions; when the instructions are executed by the processor, the computing device performs the method as described in any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store a computer program for performing the method as described in any one of claims 1 to 5.

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