Active power filter fault diagnosis method, system, device and medium

Abstract

The invention relates to the technical field of power filters, and discloses an active power filter fault diagnosis method, system and device and a medium. According to the method, voltage signals and current signals of a plurality of preset sampling points in a target active power filter are collected in real time; determining a fault indication feature of each preset fault type, and identifying the fault type of the target active power filter by using the fault indication features, therefore, three sensor faults including a DC voltage sensor fault type, a power grid voltage sensor fault type and a current sensor fault type, and electrical faults of a switch tube open-circuit fault type and an open-phase fault type are comprehensively diagnosed, the accuracy of identifying various fault types is improved, and the error of fault type identification is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of power filters, and in particular to a method, system, equipment and medium for diagnosing faults of an active power filter. Background Art

[0002] In the field of harmonic control, parallel active power filters are widely used due to their real-time performance and safety. However, in practical applications, power electronic equipment will be affected by factors such as mechanical vibration and environmental conditions. Among them, key power semiconductor devices and sensors are very prone to failure during operation. Once a failure occurs, the parallel active power filter will not be able to effectively control the harmonics and will become a harmonic source, which will not only fail to reduce harmonics, but also aggravate the pollution of the power grid.

[0003] As a power electronic converter with dynamic compensation function, the parallel active power filter usually works at a higher switching frequency. When the power device works under high frequency and high temperature conditions for a long time, it is very easy to be damaged. A survey on device failure in power electronic circuits shows that the failure rate of the main power switch tube is high. It can be seen that the damage of the power device is the main reason for the failure of the power electronic circuit. The power device failure of the inverter can generally be divided into open circuit failure and short circuit failure. After a short circuit failure occurs, a large current will appear in the circuit in a short time, which may easily cause the circuit to burn and the equipment to stop operating. For this reason, a fuse is usually added to the switch tube to convert the short circuit failure into an open circuit failure. The destructiveness of an open circuit failure is usually less than that of a short circuit failure, and it is also more difficult to detect. This kind of failure will not cause the system to crash in a short time, but it will cause the power electronic equipment to operate abnormally, resulting in secondary failures of the converter and other drive components, thereby causing more serious damage to the system and high maintenance costs.

[0004] At the same time, as a key component that provides real-time current and voltage sampling information to the controller, the accuracy of the sensor is of vital importance to the normal operation of the system. However, due to factors such as equipment aging and mechanical vibration, the current and voltage sensors in the system are prone to failure. At this time, there is a large deviation between the measured value and the actual value, and the controller will not be able to work normally. If the inverter has an overcurrent, other components in the system will be damaged due to overcurrent or overvoltage, and may even affect the load-end equipment, resulting in more serious consequences.

[0005] In summary, in order to improve the operating reliability of the parallel active power filter, it is of great significance to conduct comprehensive fault diagnosis on the power devices and sensors therein so that the parallel active power filter can perform harmonic control work safely and stably.

[0006] In the research on inverter fault diagnosis methods, the focus is mainly on the research on open-circuit fault diagnosis methods for power switch tubes. In addition, in the fault diagnosis of active power filters, sensor faults and electrical faults are not combined for comprehensive consideration, which makes it easy for fault misdiagnosis to occur. Summary of the invention

[0007] In view of this, the present invention provides an active power filter fault diagnosis method, system, device and medium, which solves the technical problem that in the fault diagnosis of the active power filter, sensor fault and electrical fault are not comprehensively considered, which easily leads to the situation that the fault is misdiagnosed.

[0008] A first aspect of the present invention provides an active power filter fault diagnosis method, comprising:

[0009] Collecting voltage signals and current signals of a plurality of preset sampling points in a target active power filter in real time; wherein the preset sampling points are arranged on the inverter output lines in the target active power filter;

[0010] Determine the fault indication characteristics of each preset fault type according to the voltage signal and the current signal of each preset sampling point; wherein the preset fault types include a DC voltage sensor fault type, a grid voltage sensor fault type, a switch tube open circuit fault type, a current sensor fault type, and a phase loss fault type;

[0011] The fault type of the target active power filter is identified according to the fault indication characteristics of each of the preset fault types.

[0012] Optionally, the identifying the fault type of the target active power filter according to the fault indication characteristics of each preset fault type includes:

[0013] The fault type of the target active power filter is identified according to the fault indication characteristics of each preset fault type in a preset diagnostic order; wherein the preset diagnostic order is, in sequence, the DC voltage sensor fault type, the grid voltage sensor fault type, the switch tube open circuit fault type, the current sensor fault type and the phase loss fault type.

[0014] Optionally, the process of identifying the fault type of the DC voltage sensor includes:

[0015] Compare the change in the DC voltage signal collected by the DC voltage sensor within a unit time with a preset voltage change threshold;

[0016] When the variation of the DC voltage signal within a unit time is greater than the set voltage variation threshold, it is determined that the fault type of the target active power filter is the DC voltage sensor fault type.

[0017] Optionally, the process of identifying the fault type of the power grid voltage sensor includes:

[0018] Determining whether the current signal of the inverter output circuit is overcurrent;

[0019] When it is determined that the current signal of the inverter output line is overcurrent, a first phase-locked angle of the grid voltage signal is obtained through a grid voltage sensor, and a second phase-locked angle of the grid voltage signal is obtained through a grid voltage sensor that introduces a hysteresis current control link; wherein the hysteresis current control link is used to suppress overcurrent of the target active power filter;

[0020] Determining a phase lock angle deviation according to the first phase lock angle and the second phase lock angle;

[0021] Determining whether the phase-locking angle deviation is greater than a preset phase-locking angle deviation threshold;

[0022] When it is determined that the phase-locking angle deviation is greater than the preset phase-locking angle deviation threshold, it is determined that the fault type of the target active power filter is the grid voltage sensor fault type.

[0023] Optionally, the method further comprises:

[0024] Determining a mathematical model of the target active power filter in a two-phase stationary α-β coordinate system according to the topological structure of the target active power filter;

[0025] updating the mathematical model in the two-phase static α-β coordinate system according to the voltage signal and the current signal of the inverter output circuit, and determining the current trajectory on the α-β plane according to the updated mathematical model in the two-phase static α-β coordinate system;

[0026] According to the distribution area of ​​the current trajectory relative to the α-β plane, the specific fault type of the target active power filter is determined; the specific fault type includes a switch tube open circuit fault type, a current sensor fault type and a phase loss fault type.

[0027] Optionally, determining the specific fault type of the target active power filter according to the distribution area of ​​the current trajectory relative to the α-β plane includes:

[0028] Dividing the α-β plane into six sectors according to the current trajectories corresponding to the specific fault types;

[0029] Discretizing the current trajectory according to sampling moments to obtain a plurality of current sampling points;

[0030] Counting the number of current sampling points falling into each of the sectors, and comparing the number of current sampling points in each of the sectors with a preset number threshold;

[0031] Determine a six-bit binary number according to a comparison result between the number of current sampling points of each sector and the preset number threshold; wherein, when the number of current sampling points of the sector is greater than the preset number threshold, the binary number of the corresponding bit of the sector is assigned a value of 1; when the number of current sampling points of the sector is not greater than the preset number threshold, the binary number of the corresponding bit of the sector is assigned a value of 0;

[0032] The six-bit binary number is matched with the preset standard binary numbers corresponding to each of the specific fault types to obtain the specific fault type that matches the six-bit binary number.

[0033] Optionally, the method further comprises:

[0034] Disconnecting any phase bridge arm of the inverter and obtaining the current value of the remaining non-fault phase that is not disconnected;

[0035] Comparing the absolute value of the current value of the remaining non-fault phase that has not been disconnected with a preset current threshold;

[0036] If the absolute value of the current value of the remaining non-fault phase that is not disconnected is greater than the preset current threshold, it is determined that the fault type of the target active power filter is a current sensor fault type;

[0037] If the absolute value of the current value of the remaining non-faulty phase that has not been disconnected is not greater than the preset current threshold, it is determined that the fault type of the target active power filter is a phase loss fault type.

[0038] In a second aspect, the present invention further provides an active power filter fault diagnosis system, comprising:

[0039] A signal acquisition module, used for real-time acquisition of voltage signals and current signals of a plurality of preset sampling points in a target active power filter; wherein the preset sampling points are arranged on the inverter output lines in the target active power filter;

[0040] A fault characteristic determination module, used to determine the fault indication characteristics of each preset fault type according to the voltage signal and the current signal of each preset sampling point; wherein the preset fault types include a DC voltage sensor fault type, a grid voltage sensor fault type, a switch tube open circuit fault type, a current sensor fault type and a phase loss fault type;

[0041] The fault type identification module is used to identify the fault type of the target active power filter according to the fault indication characteristics of each preset fault type.

[0042] In a third aspect, the present invention further provides an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the active power filter fault diagnosis method as described in the first aspect.

[0043] In a fourth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed, implements the steps of the active power filter fault diagnosis method as described in the first aspect.

[0044] It can be seen from the above technical scheme that the present invention collects voltage signals and current signals of multiple preset sampling points in the target active power filter in real time, determines the fault indication characteristics of each preset fault type according to the voltage signals and current signals, and identifies the fault type of the target active power filter by using the fault indication characteristics, thereby comprehensively diagnosing three types of sensor faults of DC voltage sensor fault type, grid voltage sensor fault type and current sensor fault type, as well as electrical faults of switch tube open circuit fault type and phase loss fault type, thereby improving the accuracy of identifying various fault types and reducing the error of fault type identification. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0046] Figure 1 An application environment of an active power filter fault diagnosis method provided by an embodiment of the present invention;

[0047] Figure 2 A flowchart of an active power filter fault diagnosis method provided by an embodiment of the present invention;

[0048] Figure 3 A schematic diagram of a phase failure of an active power filter provided by an embodiment of the present invention;

[0049] Figure 4 A schematic diagram of a fault diagnosis process provided by an embodiment of the present invention;

[0050] Figure 5 It is a schematic diagram of the topological structure of a parallel active power filter;

[0051] Figure 6 It is the control principle diagram of APF;

[0052] Figure 7 It is a schematic diagram of the output current trajectory under a phase failure;

[0053] Figure 8a Schematic diagram of the current trajectory area of ​​the upper and lower switch failures of phase A;

[0054] Figure 8b Schematic diagram of the current trajectory area of ​​the upper and lower switch failures of phase B;

[0055] Figure 8c Schematic diagram of the current trajectory area of ​​the upper and lower switch failures of phase C;

[0056] Fig. 9 This is a schematic diagram of the output current trajectory in the case of a current sensor failure;

[0057] Fig.10 It is a schematic diagram of the sector division of the α-β plane;

[0058] Fig.11 A schematic structural diagram of an active power filter fault diagnosis system provided by an embodiment of the present invention;

[0059] Fig.12 A schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0060] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] The active power filter fault diagnosis method provided in the embodiment of the present application can be applied to Figure 1In the application environment shown. Among them, the terminal 101 communicates with the server 102 through the network. The data storage system can store the data that the server 102 needs to process. The data storage system can be integrated on the server 102, or it can be placed on the cloud or other network servers. The terminal 101 or the server 102 collects the voltage signals and current signals of multiple preset sampling points in the target active power filter in real time; wherein the preset sampling points are set on the inverter output line in the target active power filter; according to the voltage signals and current signals of each preset sampling point, the fault indication characteristics of each preset fault type are determined; wherein the preset fault types include DC voltage sensor fault type, grid voltage sensor fault type, switch tube open circuit fault type, current sensor fault type and phase loss fault type; according to the fault indication characteristics of each preset fault type, the fault type of the target active power filter is identified.

[0062] The terminal 101 may be a computer, a mobile terminal, or the like.

[0063] The server 102 may be an independent physical server, a server cluster or a distributed system composed of multiple physical servers, or a cloud server that provides cloud computing services.

[0064] like Figure 2 As shown, the embodiment of the present application provides an active power filter fault diagnosis method, which is applied to Figure 1 The terminal 101 or the server 102 in the example is used to illustrate, and the steps include the following steps S1 to S3. Among them:

[0065] Step S1, collecting voltage signals and current signals of a plurality of preset sampling points in a target active power filter in real time; wherein the preset sampling points are set on the inverter output lines in the target active power filter.

[0066] Among them, the embodiment of the present application is explained by taking a three-phase three-wire parallel voltage-type active power filter (APF) as an example. The preset sampling points can be set on the A phase, B phase and C phase of the inverter output line in the target APF to collect the voltage signals and current signals of the A phase, B phase and C phase in real time respectively.

[0067] Step S2, determining the fault indication characteristics of each preset fault type according to the voltage signal and current signal of each preset sampling point; wherein the preset fault types include DC voltage sensor fault type, grid voltage sensor fault type, switch tube open circuit fault type, current sensor fault type and phase loss fault type.

[0068] It is understandable that in the embodiments of the present application, we focus on the fact that the fault indication characteristics exhibited by different fault types are different. In order to accurately identify the fault type occurring in the target active power filter, this embodiment proposes a method for analyzing the changes in voltage signals and current signals based on preset sampling points. By carefully monitoring and analyzing the changes in these signals at specific sampling points, we can effectively determine the fault indication characteristics corresponding to each preset fault type. In this way, when a fault occurs in the target active power filter, we can accurately determine the specific type of the fault based on these change characteristics.

[0069] Among them, the DC voltage sensor fault type refers to the inability of the DC voltage sensor to accurately measure or transmit the DC voltage signal, resulting in the inability of the active power filter to work properly. The DC voltage sensor is usually used to monitor the DC bus voltage in the active power filter. During normal and stable operation, the actual value of the DC side voltage can completely track the reference value. When the DC voltage sensor fails, its measured value will change and no longer accurately reflect the DC voltage signal. If the sensor has an instantaneous large voltage jump, it may directly cause the system to crash. When identifying the DC voltage sensor fault type, the system can monitor the changes in the DC voltage signal.

[0070] The grid voltage sensor fault type is that when the grid voltage sensor fails, the grid voltage signal it collects may be deviated or distorted, which will affect the normal operation of the active power filter. The grid voltage sensor is usually used to monitor the voltage of the grid to ensure that the active power filter can compensate according to the actual condition of the grid. If the grid voltage sensor fails, it may cause the active power filter to misjudge the grid condition, thereby performing incorrect compensation operations, and may even cause problems such as overcurrent or overvoltage in the system.

[0071] When a switch tube open circuit fault occurs, it usually causes the performance of the active power filter to degrade or fail completely. As a key component in the active power filter, the switch tube is responsible for controlling the on and off of the current to achieve filtering and compensation functions. When the switch tube has an open circuit fault, the current cannot pass normally, which will cause the active power filter to be unable to effectively suppress the harmonics in the power grid, thereby affecting the stability and power quality of the entire power system.

[0072] The current flow path of each switch tube on the inverter bridge arm under the normal state of the active power filter and the switch tube fault state. Considering different current directions and switch states, the bridge arm has four working modes.

[0073] In the normal state, the upper switch tube is turned on, the lower switch tube is turned off, and the inverter outputs a high level; the upper switch tube is turned off, the lower switch tube is turned on, and the inverter outputs a low level. When an open circuit fault occurs, the current flow path through the switch is turned off. When the output is high and the current direction is positive, the phase current flows out through the lower diode, and the current flow path changes. In this case, the inverter output is forced to change from a high level to a low level, and the current flow path in other unused switch states will not be affected. The low level state when the current direction is positive will force the forward current to drop to zero. At this time, the inverter is equivalent to operating in a phase-loss fault state until the current changes direction, the current flow path is normal, and the inverter outputs current normally. Similarly, when an open circuit fault occurs, when the inverter outputs a low level and the current direction is negative, the low level will be forced to change to a high level, and the current flowing in will flow in, while the other states are the same as normal operation. At this time, the current flows in, and the inverter high level state causes the output current of the fault phase to become zero until the current direction changes and the inverter outputs normally.

[0074] When a switch failure occurs, the inverter output voltage changes, similar to a phase failure. The difference is that a switch failure only causes the inverter to output an abnormal voltage when a specific current flows. When the upper switch is open, an incorrect voltage level is only generated when the current flows out, and when the lower switch is open, an incorrect voltage level is only output when the current flows in. Therefore, when a switch open failure occurs, the output voltage remains normal within half of the fundamental cycle, and the remaining half of the cycle outputs an incorrect voltage level.

[0075] The current sensor failure type is that when the current sensor fails, the current signal it measures may be deviated or distorted, causing the active power filter to be unable to accurately obtain the current information in the power grid, thereby affecting the filtering and compensation effects. As an important component of the active power filter, the current sensor is responsible for monitoring the current conditions in the power grid to ensure that the active power filter can accurately perform compensation operations based on the actual current conditions. If the current sensor fails, it may cause the active power filter to misjudge the current conditions in the power grid, thereby performing incorrect compensation, and may even cause problems such as overcurrent or undercompensation in the system.

[0076] The phase failure type is a fault that may occur inside the inverter or in the path between the inverter output and the grid. Figure 3 The schematic diagram of the active power filter phase failure is shown. Once a phase failure occurs, the equipment will operate in an abnormal operating state. At this time, the compensation current output by the inverter will not be able to track the reference current. Long-term operation in this state will have an adverse effect on the power electronic equipment and will also affect the effect of harmonic compensation on the grid side.

[0077] Step S3: Identify the fault type of the target active power filter according to the fault indication characteristics of each preset fault type.

[0078] It should be noted that the embodiment of the present application collects voltage signals and current signals of multiple preset sampling points in the target active power filter in real time, determines the fault indication characteristics of each preset fault type according to the voltage signals and current signals, and identifies the fault type of the target active power filter using the fault indication characteristics, thereby comprehensively diagnosing three types of sensor faults, namely, DC voltage sensor fault type, grid voltage sensor fault type, and current sensor fault type, as well as electrical faults of switch tube open circuit fault type and phase loss fault type, thereby improving the accuracy of identifying various fault types and reducing the error of fault type identification.

[0079] In some embodiments, the embodiments of the present application combine the fault indication characteristics of different fault types with the corresponding thresholds to perform comprehensive diagnosis on five types of fault types. Specifically, the fault type of the target active power filter is identified according to the fault indication characteristics of each preset fault type in accordance with the preset diagnostic sequence; wherein the preset diagnostic sequence is DC voltage sensor fault type, grid voltage sensor fault type, switch tube open circuit fault type, current sensor fault type and phase loss fault type.

[0080] like Figure 4 As shown, by combining the diagnosis processes of various preset fault types, misjudgment of the fault type is avoided through logical identification.

[0081] In the active power filter control strategy, when space vector modulation is performed normally and stably according to the capacitor voltage information provided by the DC bus voltage sensor, the actual value of the DC side voltage can completely track the reference value. When the DC voltage sensor fails, its measured value will change and no longer accurately reflect the DC voltage signal.

[0082] Therefore, in some embodiments, the process of identifying the fault type of the DC voltage sensor includes:

[0083] Step S301: compare the variation of the DC voltage signal collected by the DC voltage sensor within a unit time with a preset voltage variation threshold.

[0084] Step S302: When the variation of the DC voltage signal within a unit time is greater than a set voltage variation threshold, it is determined that the fault type of the target active power filter is a DC voltage sensor fault type.

[0085] The voltage variation threshold is preset and can be 20, 30, etc. The DC voltage signal on the inverter output line in the target active power filter is collected by the DC voltage sensor, and the variation of the DC voltage signal in unit time is compared with the preset voltage variation threshold. When the variation of the DC voltage signal in unit time is greater than the set voltage variation threshold, the fault type of the target active power filter is determined to be a DC voltage sensor fault type; when the variation of the DC voltage signal in unit time is greater than the set voltage variation threshold, the target active power filter is determined to be in normal operation or other fault types.

[0086] When the grid voltage sensor fails, the A-phase grid voltage signal collected by the grid voltage sensor deviates from the normal state, which is equivalent to the distortion of one-phase grid voltage. The rotation angle frequency signal obtained by the phase-locked loop will produce errors. When the grid voltage angle does not match the controller input phase-locked angle, the inverter will output an abnormal voltage. At this time, the inverter output voltage is not synchronized with the grid voltage, and there is a voltage difference Δu v , the emergence of this voltage difference will lead to an increase in the inverter output current.

[0087] like Figure 5 As shown, in the topology of the parallel active power filter, u sa 、u sb 、u sc is the three-phase voltage on the grid side, u dc is the DC side voltage, i ia 、i ib 、i ic is the three-phase output current of the inverter, u ia 、ui b 、u ic is the three-phase output voltage of the inverter. 1-6 is the switch tube of each phase bridge arm, L is the output inductor of each phase, and C is the DC side voltage stabilizing capacitor. At the same time, it is assumed that each switch device in the APF is an ideal device, and the line loss is not taken into account.

[0088] According to the topological structure of the parallel active power filter, the mathematical model converted to the synchronous rotating (dq) coordinate system is:

[0089]

[0090]

[0091] In the formula, , are the complex power components on the d-axis and the q-axis respectively, , are the current component on the d-axis and the current component on the q-axis respectively, , are the grid voltage component on the d-axis and the grid voltage component on the q-axis respectively. is the angular frequency.

[0092] The mathematical model in the synchronous rotating (dq) coordinate system is decoupled, and the mathematical model in the two-phase rotating coordinate system after decoupling is:

[0093]

[0094] In the formula, the superscript k represents the value corresponding to the current moment, k+1 represents the value corresponding to the next moment, and u id 、u iq are the inverter output voltage of the d-axis and the inverter output voltage of the q-axis, Δuvd, Δu vq is the voltage difference of the d-axis and the voltage difference of the q-axis.

[0095] Assume that at time k+1, the voltage difference between the grid voltage and the inverter output voltage increases suddenly, that is, the voltage difference Δu is added to the term representing the difference between the grid voltage and the inverter output voltage. v ,Right now and .

[0096] Assume that the voltage difference between the grid voltage and the inverter output voltage increases suddenly at time k+1, that is, the voltage difference Δu is added to the term representing the difference between the grid voltage and the inverter output voltage. v , while the expressions at the remaining k moments remain unchanged, the current change rate at k+1 moment will increase sharply. In the same sampling time, the current will surge, causing the inverter to output overcurrent. Therefore, when a grid voltage sensor failure occurs, it is necessary to consider limiting the inverter output overcurrent and identify the fault while ensuring the safe operation of the system.

[0097] Among them, in the process of diagnosing the fault of the grid voltage sensor, it is possible to consider introducing a hysteresis control link, which can not only effectively suppress the overcurrent phenomenon of the inverter output, but also determine whether there is a fault by comparing the difference between the voltage phase-locked angle corresponding to the hysteresis control and the phase-locked angle obtained by the grid voltage sensor. If this difference exceeds the preset threshold range, then the accurate diagnosis of the grid voltage sensor fault can be achieved accordingly. .

[0098] Among them, the hysteresis control link is to quickly constrain the output current of the inverter to the vicinity of the reference value. When the error signal exceeds the upper threshold of the hysteresis loop, the trigger signal of the inverter controls the switch tube to make its output voltage equal to the negative DC voltage. At this time, the inductor current decreases and the error decreases; when the error signal is less than the lower threshold of the hysteresis loop, the switch tube state is controlled to make the output voltage of the inverter equal to the DC side voltage. At this time, the inductor current increases and the error decreases. By repeating this process continuously, the error between the two currents is reduced, so that the output current can track the reference current.

[0099] Specifically, the identification process of the grid voltage sensor fault type includes:

[0100] Step S311, determining whether the current signal of the inverter output circuit is overcurrent.

[0101] Among them, by judging whether the current signal of the inverter output line is overcurrent, when it is judged that the current signal of the inverter output line is overcurrent, it means that the grid voltage sensor may be faulty; when it is judged that the current signal of the inverter output line is not overcurrent, it means that the target active power filter is operating normally or other faults.

[0102] Step S312: When it is determined that the current signal of the inverter output line is overcurrent, a first phase-locked angle of the grid voltage signal is obtained through a grid voltage sensor, and a second phase-locked angle of the grid voltage signal is obtained through a grid voltage sensor that introduces a hysteresis current control link; wherein the hysteresis current control link is used to suppress overcurrent of a target active power filter.

[0103] Step S313: Determine a phase locking angle deviation according to the first phase locking angle and the second phase locking angle.

[0104] The phase locking angle deviation is obtained by calculating the difference between the first phase locking angle and the second phase locking angle.

[0105] Step S314, determining whether the phase-locking angle deviation is greater than a preset phase-locking angle deviation threshold;

[0106] Step S315: When it is determined that the phase-locking angle deviation is greater than the preset phase-locking angle deviation threshold, it is determined that the fault type of the target active power filter is a grid voltage sensor fault type.

[0107] When it is determined that the phase-locking angle deviation is not greater than a preset phase-locking angle deviation threshold, it indicates that the target active power filter has other faults.

[0108] For example, when a grid voltage sensor failure occurs, Figure 6 The APF control system shown in the figure, where i la 、i lb 、i lc is the current on the load side, iia *、i ib *、i ic * is the reference current obtained after the harmonic extraction algorithm, i id *、i iq * is the reference current of the d-axis and q-axis converted to the synchronous coordinate system after coordinate transformation, i id 、i iq are the d-axis and q-axis components of the inverter output three-phase current after coordinate transformation, and u sd 、u sq is the d-axis and q-axis components of the three-phase grid voltage transformed into the two-phase rotating coordinate system, u id *、u iq * is the d-axis and q-axis components of the converter output voltage reference value, u dc is the actual value of the DC side capacitor voltage, u dc * is the DC side voltage reference value, L is the output inductance value, and ω is the grid fundamental angular frequency.

[0109] In the APF control system, if the rotation angular frequency calculated based on the sensor information is different from the actual rotation angular frequency of the power grid, the inverter will have an overcurrent. Whether the two rotation angular frequencies are out of sync and whether the inverter output current exceeds the threshold is used as the fault characteristics, and the hysteresis current control link is used to suppress the overcurrent of the APF. At the same time, the corresponding voltage signal is obtained under this control method. This signal is in phase with the actual voltage of the power grid. Its phase information is calculated through a phase-locked loop and compared with the phase information obtained by the power grid voltage sensor. In the event of a sensor failure, there is a difference in the phase information obtained by these two methods. The embodiment of the present application will locate the fault based on this principle. Suppose the phase-locked angle obtained by the power grid voltage sensor is The phase-locked angle obtained by the voltage corresponding to the hysteresis current control link is , under the premise of normal operation of APF, the difference between the two phase-locked angles is close to zero, but in the case of voltage sensor failure, the difference will be offset. Based on this feature, the fault indicator variable is defined for:

[0110]

[0111] In the formula, It indicates the phase-locked angle calculated by the grid voltage sensor at the current moment. Indicates the phase-locked angle obtained by hysteresis control at the current moment. In order to ensure the rapidity of diagnosis and avoid misdiagnosis, the fault indication variable The threshold is set to 2rad. When the fault indicator variable of the grid voltage sensor is greater than 2rad, it means that the sensor has failed.

[0112] It is understandable that, in response to possible fault problems of the grid voltage sensor, the embodiment of the present application proposes a fault diagnosis method based on hysteresis control. This method has a dual function. On the one hand, it can effectively suppress the overcurrent phenomenon of the inverter output through the hysteresis current control link, thereby protecting the inverter from damage; on the other hand, the method can also accurately diagnose the fault of the grid voltage sensor by comparing and analyzing the difference between the voltage phase-locking angle and the phase-locking angle provided by the grid voltage sensor. Through this method, the fault of the grid voltage sensor can be discovered and handled in time to ensure the stable operation of the entire power system. .

[0113] In the case of a phase failure, the active power filter is analyzed under the phase failure state. The voltage on the α-β plane in the two-phase stationary (α-β) coordinate system is expressed as the three-phase voltage:

[0114]

[0115] In the formula, , They are the voltage component of the α-axis and the voltage component of the β-axis respectively.

[0116] Taking the phase failure of phase A as an example, the output voltage of the faulty phase is zero. Combining Kirchhoff's law, the voltage component of the α-β plane can be obtained as follows:

[0117]

[0118] In the formula, u ib is the output phase voltage of the non-fault phase. According to the above formula, the actual voltage trajectory of the α-β plane under the phase failure is a straight line parallel to the β axis, that is, the actual value u α 、u β There is a linear relationship between them. According to the APF mathematical model in the two-phase stationary coordinate system, the actual current trajectory of the α-β plane is also a straight line. Similarly, the current trajectory of the α-β plane after a phase failure occurs in different phases can be obtained as follows: Figure 7 shown.

[0119] After a switch failure occurs, the inverter output voltage changes, similar to a phase failure. The difference is that a switch failure only causes the inverter to output an abnormal voltage when a specific current flows. When the upper switch is open, an incorrect voltage level is only generated when the current flows out, and when the lower switch is open, an incorrect voltage level is only output when the current flows in. Therefore, when a switch open failure occurs, the output voltage remains normal within half of the fundamental cycle, and the remaining half of the cycle outputs an incorrect voltage level.

[0120] When a switch tube open circuit fault occurs, the switch tube S on phase A A1Take the inverter output current trajectory as an example. When the current flows out, the inverter output voltage will become low level, and when the current flows in, the output will be normal. The output voltage of the fault phase is:

[0121]

[0122] According to the mathematical model in the two-phase stationary coordinate system, the output current is:

[0123]

[0124] Transforming it to the α-β coordinate system, we can see that the value on the α axis is non-positive, and the output current trajectory of the inverter will move in the left half plane bounded by the β axis. Similarly, the current trajectories of different switch tube open circuit faults can be derived. They are bounded by different straight line equations and distributed in different areas according to the different fault locations, such as Figure 8a~Figure 8c shown.

[0125] Exemplarily, the current trajectory process of different switch tube open circuit faults is derived as follows:

[0126] After a switch failure occurs, the inverter output voltage changes. The output voltage remains normal within half of the fundamental wave cycle, and outputs an incorrect level in the remaining half cycle.

[0127] Take the switch failure on phase B as an example. B =0, in the two-phase stationary coordinate system, U a =U α , substituting into the mathematical model of APF in the α-β plane, the voltage trajectory U in the α-β plane is obtained β = *Uα, and the current trajectory is obtained in the same way.

[0128] When the upper switch is open, only the current flows out (i.e., i B >0), an error level is generated, and the remaining half fundamental wave period is output normally. B >0, -1 / 2i α + i β >0, i.e. i β - *i α >0 (the corresponding area is a line with a slope of The upper half of the straight line). In this case, the error level causes the output voltage and current to be 0. The current trajectory at this time is a line with a slope of The output current is normal in the remaining half of the fundamental cycle, corresponding to the lower half of the straight line (i β - *iα<0), therefore, the current trajectory under this fault condition is as follows: Figure 8b Medium S B1 area shown.

[0129] In the case of current sensor failure, the current sensor failure may cause zero output, gain error and noise error. The sensor measurement value after the failure can be regarded as the superposition of the actual value and the error value. Since the APF is a three-phase symmetrical system, the three-phase bridge arm analysis method is the same. This article will take the case of phase A failure as an example to analyze the output current of the inverter phase A current sensor failure. At this time, the inverter output phase A current measurement value i ia_fdk_os is the actual value of phase A current i ia_real_os and A phase current error i ia_err_os sum:

[0130] i ia_fdk_os =i ia_real_os +i ia_err_os

[0131] Considering the situation where the current sensor signal is completely lost, that is, when zero output occurs, the current error can be obtained as:

[0132]

[0133] Combining the above formula with Kirchhoff's current law, we can get the measured values ​​of the three-phase output current at this time:

[0134]

[0135] Substituting the above equation into the equation, we can obtain the current trajectory of the output current in the α-β plane when the phase A current sensor fails:

[0136]

[0137] It can be seen that in i α 、i β In the current trajectory diagram drawn with α as the horizontal and vertical coordinates, its motion trajectory is a straight line parallel to the β axis. Similarly, the current trajectory of the output current in the α-β plane can be obtained after the other two-phase current sensors fail, as shown in Fig. 9 shown.

[0138] The linear slope of the motion trajectory in the case of current sensor failure is the same as the slope of the current trajectory in the phase failure state. Therefore, if only the current trajectory method is used to diagnose the current sensor failure, it will not be possible to accurately identify the current sensor failure and the phase failure. In order to identify each fault separately, it is necessary to further distinguish between the two faults.

[0139] When the APF has a phase failure in phase A, the actual current i ia_real_op = zero, the actual current i output by phase B ib_real_op Equal to the current i of phase B under normal operating conditions ib , combined with Kirchhoff's current law, the actual value of the three-phase output current can be obtained as:

[0140]

[0141] Different from the phase failure, when the current sensor has a zero output failure, the actual current i output by phase A is ia_real_os It is not equal to zero. Combined with Kirchhoff's current law, the actual values ​​of the three-phase output currents are:

[0142]

[0143] It can be seen from the actual values ​​of the three-phase output current that the main difference between the two faults lies in the difference in the actual value of the A-phase output current.

[0144] Based on the above analysis of the fault process of the switch tube open circuit fault type, the current sensor fault type and the phase loss fault type, in the embodiment of the present application, the method further includes:

[0145] Step S321: Determine a mathematical model of the target active power filter in a two-phase stationary α-β coordinate system according to the topological structure of the target active power filter.

[0146] Among them, the mathematical model of the target active power filter in the two-phase stationary (α-β) coordinate system is:

[0147]

[0148] In the formula, , They are the voltage component of the α-axis and the voltage component of the β-axis respectively.

[0149] Step S322: update the mathematical model in the two-phase static α-β coordinate system according to the voltage signal and the current signal of the inverter output circuit, and determine the current trajectory on the α-β plane according to the updated mathematical model in the two-phase static α-β coordinate system.

[0150] Step S323: determining a specific fault type of the target active power filter according to a distribution area of ​​the current trajectory relative to the α-β plane; the specific fault type includes a switch tube open circuit fault type, a current sensor fault type, and a phase loss fault type.

[0151] It is understandable that after a phase failure, switch failure, or current sensor failure occurs, the output current of the inverter will form an inherent current trajectory in the α-β plane. At the same time, the slope and movement position of the current trajectory of these types of faults are significantly different. The characteristics of the current trajectory of each specific fault type are determined by combining the characteristics of these current trajectories. By comparing the current trajectories, different faults can be identified.

[0152] Specifically, according to the distribution area of ​​the current trajectory relative to the α-β plane, the specific fault type of the target active power filter is determined, including:

[0153] Step S3231, dividing the α-β plane into six sectors according to the current trajectories corresponding to each specific fault type.

[0154] Among them, the current trajectory moving on the α-β plane is composed of the current points collected at each sampling moment. Under different fault conditions, these points are located in different positions on the α-β plane, thus forming trajectories moving in different areas. From the analysis, it can be seen that when the APF has a phase failure, a switch tube failure, and a current sensor failure, although the current trajectory distribution area is different, the dividing line slope of each trajectory is the same. Based on this feature, the α-β plane can be divided into six sectors based on the different current trajectories after a phase failure, a switch tube failure, and a current sensor failure, such as Fig.10 shown.

[0155] Step S3232: discretize the current trajectory according to the sampling time to obtain multiple current sampling points.

[0156] It can be understood that the current trajectory is composed of the current at each sampling moment, and a plurality of current sampling points are obtained by discretizing the current trajectory according to the sampling moments.

[0157] Step S3233: Count the number of current sampling points falling into each sector, and compare the number of current sampling points in each sector with a preset number threshold.

[0158] Step S3234: Determine a six-bit binary number according to the comparison result between the number of current sampling points of each sector and the preset number threshold; wherein, when the number of current sampling points of the sector is greater than the preset number threshold, the binary number of the corresponding bit of the sector is assigned a value of 1; when the number of current sampling points of the sector is not greater than the preset number threshold, the binary number of the corresponding bit of the sector is assigned a value of 0;

[0159] Step S3235: Match the six-bit binary number with the preset standard binary numbers corresponding to each specific fault type to obtain a matching specific fault type.

[0160] For example, the current trajectories of the three types of faults, namely, the switch open circuit fault type, the current sensor fault type, and the phase loss fault type, correspond to different sector combinations. In order to facilitate fault diagnosis, the number of current points in each sector is counted, and the number of points greater than 5 in each sector is recorded as 1, and the number of points less than 5 is recorded as 0. Thus, a six-bit binary number Y can be obtained, which reflects the characteristics of the current trajectory. According to the value of Y, the corresponding faults of different fault types can be matched by looking up the table. Therefore, according to the different number of points in each area, the current trajectory of the system in the current state can be depicted, and the type of fault that has occurred can be deduced.

[0161] When the APF is operating normally, the sampling points in one fundamental cycle are evenly distributed in six sectors, and the binary number Y is (111111). When one of the phase failure, switch failure, and output current sensor failure occurs, a 0 element will appear in the six bits of Y, so this can be used as an indicator of the occurrence of these three types of faults. In the process of multi-type fault diagnosis based on current trajectory, it is first necessary to determine whether these faults have occurred. This goal is achieved by real-time monitoring whether a 0 element appears in Y in each fundamental cycle. After determining that a fault has occurred, the binary number Y obtained in one fundamental cycle is matched one by one with each fault state to determine the fault type.

[0162] For example, when a switch failure occurs on phase A, according to the analyzed current trajectory, all sampling current points will be distributed in the left half plane of the α-β coordinate system. Fig.10 In this case, there will be current points in sectors 2, 3, 4, and 5, which are assigned a value of 1, and the remaining sectors are assigned a value of 0. Therefore, the Y value is as shown in Table 1 when the fault type is a switch failure on phase A.

[0163] Table 1 Binary numbers corresponding to different faults

[0164]

[0165] As can be seen from Table 1, the binary numbers of phase failure and current sensor failure are similar, making it difficult to distinguish between the two. The main difference between the two types of faults is the actual current of the faulty phase. Taking the A phase fault as an example, when the APF has a phase failure, the actual output current value of the A phase is i ia_real_op When the output current sensor fails, the actual current i ia_real_os is a non-zero time variable.

[0166] To this end, in an embodiment of the present application, the method further includes:

[0167] Step S331, disconnecting any phase bridge arm of the inverter, and obtaining the current value of the remaining non-fault phase that is not disconnected;

[0168] Step S332, comparing the absolute value of the current value of the remaining non-fault phase that has not been disconnected with a preset current threshold;

[0169] Step S333: if the absolute value of the current value of the remaining non-fault phase that has not been disconnected is greater than the preset current threshold, it is determined that the fault type of the target active power filter is a current sensor fault type;

[0170] Step S334: If the absolute value of the current value of the remaining non-fault phase that has not been disconnected is not greater than the preset current threshold, it is determined that the fault type of the target active power filter is a phase loss fault type.

[0171] For example, in order to accurately reflect the difference between the two types of faults, the bridge arm of one phase without a sensor is actively disconnected. According to Kirchhoff's current law, the current information of the faulty phase can be obtained by monitoring the current sensor data of the remaining healthy phase. In this example, the bridge arm of phase C is disconnected, and the output current measurement value i of the remaining non-faulty phase B is ib_fdk is the actual output current i of the fault phase ia_real The opposite of , that is:

[0172]

[0173] Therefore, we only need to observe the measured value of the output current of phase B, i ib_fdk A phase loss fault can be distinguished from a current sensor fault.

[0174] When a phase failure occurs in the APF, since the output current of the faulty phase A is zero, after disconnecting the C phase bridge arm, the output current measurement value of the B phase is i ib_fdk Theoretically, it is also close to zero; when the APF current sensor fails, the output current of the faulty phase A is iia, so after disconnecting the C phase bridge arm, the output current measurement value of the B phase is its opposite, which is a non-zero time variable. Based on this feature, the absolute value of the measured value of the B phase output current is defined as |i ib_fdk | is a fault indicator variable. In order to make a quick diagnosis and prevent misdiagnosis, set |i ib_fdk The current threshold of | is 1.5A. When the absolute value of the measured value of the output current of phase B |i ib_fdk | is greater than 1.5A, indicating that current is actually flowing through the fault phase at this time, and the fault is a current sensor failure. ib_fdk | is smaller than the current threshold, indicating that the current flowing through the faulty phase is very small, and the current value is abnormal due to the phase failure.

[0175] It is understandable that in the embodiments of the present application, we propose a fault diagnosis method of active intervention. The core of this method is that when the system detects a potential fault, it will take an active measure, that is, to further analyze the problem by disconnecting the non-fault phase bridge arm. In this way, the system can more accurately determine whether the output current of the remaining healthy phase exceeds the predetermined threshold. If the output current does exceed the threshold, the system can confirm the existence of the fault. This method effectively avoids the misdiagnosis of faults and improves the accuracy and reliability of fault diagnosis. .

[0176] Based on the same inventive concept, an embodiment of the present application further provides an active power filter fault diagnosis system for implementing the active power filter fault diagnosis method mentioned above.

[0177] The implementation scheme for solving the problem provided by the system is similar to the implementation scheme recorded in the above method, so the specific limitations in one or more active power filter fault diagnosis system embodiments provided below can refer to the limitations on the active power filter fault diagnosis method in the above text, and will not be repeated here.

[0178] like Fig.11 As shown, an embodiment of the present application provides an active power filter fault diagnosis system, comprising:

[0179] The signal acquisition module 100 is used to collect voltage signals and current signals of a plurality of preset sampling points in the target active power filter in real time; wherein the preset sampling points are set on the inverter output line in the target active power filter;

[0180] The fault characteristic determination module 200 is used to determine the fault indication characteristics of each preset fault type according to the voltage signal and the current signal of each preset sampling point; wherein the preset fault types include the DC voltage sensor fault type, the grid voltage sensor fault type, the switch tube open circuit fault type, the current sensor fault type and the phase loss fault type;

[0181] The fault type identification module 300 is used to identify the fault type of the target active power filter according to the fault indication characteristics of each preset fault type.

[0182] In some embodiments, the fault type identification module 300 is used to identify the fault type of the target active power filter according to the fault indication characteristics of each preset fault type in a preset diagnostic order; wherein the preset diagnostic order is DC voltage sensor fault type, grid voltage sensor fault type, switch tube open circuit fault type, current sensor fault type and phase loss fault type.

[0183] In some embodiments, the process of identifying the fault type of the DC voltage sensor includes:

[0184] Compare the change in the DC voltage signal collected by the DC voltage sensor within a unit time with a preset voltage change threshold;

[0185] When the variation of the DC voltage signal within a unit time is greater than a set voltage variation threshold, it is determined that the fault type of the target active power filter is a DC voltage sensor fault type.

[0186] In some embodiments, the process of identifying the fault type of the grid voltage sensor includes:

[0187] Determine whether the current signal of the inverter output circuit is overcurrent;

[0188] When it is determined that the current signal of the inverter output line is overcurrent, a first phase-locked angle of the grid voltage signal is obtained through a grid voltage sensor, and a second phase-locked angle of the grid voltage signal is obtained through a grid voltage sensor that introduces a hysteresis current control link; wherein the hysteresis current control link is used to suppress overcurrent of a target active power filter;

[0189] Determining a phase locking angle deviation according to the first phase locking angle and the second phase locking angle;

[0190] Determine whether the phase-lock angle deviation is greater than a preset phase-lock angle deviation threshold;

[0191] When it is determined that the phase-locking angle deviation is greater than a preset phase-locking angle deviation threshold, it is determined that the fault type of the target active power filter is a grid voltage sensor fault type.

[0192] In some embodiments, the system further includes: a first fault identification module, configured to:

[0193] According to the topological structure of the target active power filter, a mathematical model of the target active power filter in a two-phase stationary α-β coordinate system is determined;

[0194] updating a mathematical model in a two-phase stationary α-β coordinate system according to a voltage signal and a current signal of an inverter output line, and determining a current trajectory on an α-β plane according to the updated mathematical model in the two-phase stationary α-β coordinate system;

[0195] According to the distribution area of ​​the current trajectory relative to the α-β plane, the specific fault type of the target active power filter is determined; the specific fault type includes a switch tube open circuit fault type, a current sensor fault type and a phase loss fault type.

[0196] In some embodiments, the first fault identification module is used to:

[0197] The α-β plane is divided into six sectors according to the current trajectories corresponding to each specific fault type;

[0198] Discretize the current trajectory according to the sampling time to obtain multiple current sampling points;

[0199] Counting the number of current sampling points falling into each sector, and comparing the number of current sampling points in each sector with a preset number threshold;

[0200] According to the comparison result of the number of current sampling points of each sector and the preset number threshold, a six-bit binary number is determined; wherein, when the number of current sampling points of the sector is greater than the preset number threshold, the binary number of the corresponding bit of the sector is assigned a value of 1; when the number of current sampling points of the sector is not greater than the preset number threshold, the binary number of the corresponding bit of the sector is assigned a value of 0;

[0201] The six-bit binary number is matched with the preset standard binary number corresponding to each specific fault type to obtain a specific fault type that matches the same.

[0202] In some embodiments, the system further includes: a second fault identification module, configured to:

[0203] Disconnect any phase bridge arm of the inverter and obtain the current value of the remaining non-fault phase that is not disconnected;

[0204] comparing the absolute value of the current value of the remaining non-fault phase that has not been disconnected with a preset current threshold;

[0205] If the absolute value of the current value of the remaining non-fault phase that has not been disconnected is greater than the preset current threshold, it is determined that the fault type of the target active power filter is a current sensor fault type;

[0206] If the absolute value of the current value of the remaining non-fault phase that has not been disconnected is not greater than the preset current threshold, it is determined that the fault type of the target active power filter is a phase loss fault type.

[0207] like Fig.12 As shown, an embodiment of the present application provides an electronic device, the electronic device 10 includes a memory 20 and a processor 30, the memory 20 stores a computer program, and when the computer program is executed by the processor 30, the processor 30 executes the steps of the active power filter fault diagnosis method in the above embodiment.

[0208] An embodiment of the present application provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed, the steps of the active power filter fault diagnosis method in the above embodiment are implemented.

[0209] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system, electronic device and computer storage medium can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0210] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0211] In several embodiments provided by the present invention, it is understood that each box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and a part of a module, a program segment or a code includes one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved.

[0212] In the several embodiments provided by the present invention, it should be understood that the disclosed systems, electronic devices, computer storage media and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0213] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0214] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0215] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for executing all or part of the steps of the method described in each embodiment of the present invention through a computer device (which can be a personal computer, server, or network device, etc.). The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (full name in English: Read-Only Memory, English abbreviation: ROM), random access memory (full name in English: Random Access Memory, English abbreviation: RAM), disk or optical disk and other media that can store program codes.

[0216] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for diagnosing faults of an active power filter, characterized in that: include: Collecting voltage signals and current signals of a plurality of preset sampling points in a target active power filter in real time; wherein the preset sampling points are arranged on the inverter output lines in the target active power filter; Determine the fault indication characteristics of each preset fault type according to the voltage signal and the current signal of each preset sampling point; wherein the preset fault types include a DC voltage sensor fault type, a grid voltage sensor fault type, a switch tube open circuit fault type, a current sensor fault type, and a phase loss fault type; The fault type of the target active power filter is identified according to the fault indication characteristics of each of the preset fault types.

2. The active power filter fault diagnosis method according to claim 1, characterized in that: The step of identifying the fault type of the target active power filter according to the fault indication characteristics of each preset fault type includes: The fault type of the target active power filter is identified according to the fault indication characteristics of each preset fault type in a preset diagnostic order; wherein the preset diagnostic order is, in sequence, the DC voltage sensor fault type, the grid voltage sensor fault type, the switch tube open circuit fault type, the current sensor fault type and the phase loss fault type.

3. The active power filter fault diagnosis method according to claim 1 or 2, characterized in that: The process of identifying the fault type of the DC voltage sensor includes: Compare the change in the DC voltage signal collected by the DC voltage sensor within a unit time with a preset voltage change threshold; When the variation of the DC voltage signal within a unit time is greater than the set voltage variation threshold, it is determined that the fault type of the target active power filter is the DC voltage sensor fault type.

4. The active power filter fault diagnosis method according to claim 1 or 2, characterized in that: The process of identifying the fault type of the power grid voltage sensor includes: Determining whether the current signal of the inverter output circuit is overcurrent; When it is determined that the current signal of the inverter output line is overcurrent, a first phase-locked angle of the grid voltage signal is obtained through a grid voltage sensor, and a second phase-locked angle of the grid voltage signal is obtained through a grid voltage sensor that introduces a hysteresis current control link; wherein the hysteresis current control link is used to suppress overcurrent of the target active power filter; Determining a phase lock angle deviation according to the first phase lock angle and the second phase lock angle; Determining whether the phase-locking angle deviation is greater than a preset phase-locking angle deviation threshold; When it is determined that the phase-locking angle deviation is greater than the preset phase-locking angle deviation threshold, it is determined that the fault type of the target active power filter is the grid voltage sensor fault type.

5. The active power filter fault diagnosis method according to claim 1 or 2, characterized in that: Also includes: Determining a mathematical model of the target active power filter in a two-phase stationary α-β coordinate system according to the topological structure of the target active power filter; updating the mathematical model in the two-phase static α-β coordinate system according to the voltage signal and the current signal of the inverter output circuit, and determining the current trajectory on the α-β plane according to the updated mathematical model in the two-phase static α-β coordinate system; According to the distribution area of ​​the current trajectory relative to the α-β plane, the specific fault type of the target active power filter is determined; the specific fault type includes a switch tube open circuit fault type, a current sensor fault type and a phase loss fault type.

6. The active power filter fault diagnosis method according to claim 5, characterized in that: Determining the specific fault type of the target active power filter according to the distribution area of ​​the current trajectory relative to the α-β plane includes: Dividing the α-β plane into six sectors according to the current trajectories corresponding to the specific fault types; Discretizing the current trajectory according to sampling moments to obtain a plurality of current sampling points; Counting the number of current sampling points falling into each of the sectors, and comparing the number of current sampling points in each of the sectors with a preset number threshold; Determine a six-bit binary number according to a comparison result between the number of current sampling points of each sector and the preset number threshold; wherein, when the number of current sampling points of the sector is greater than the preset number threshold, the binary number of the corresponding bit of the sector is assigned a value of 1; when the number of current sampling points of the sector is not greater than the preset number threshold, the binary number of the corresponding bit of the sector is assigned a value of 0; The six-bit binary number is matched with the preset standard binary numbers corresponding to each of the specific fault types to obtain the specific fault type that matches the six-bit binary number.

7. The active power filter fault diagnosis method according to claim 1, characterized in that: Also includes: Disconnecting any phase bridge arm of the inverter and obtaining the current value of the remaining non-fault phase that is not disconnected; Comparing the absolute value of the current value of the remaining non-fault phase that has not been disconnected with a preset current threshold; If the absolute value of the current value of the remaining non-fault phase that is not disconnected is greater than the preset current threshold, it is determined that the fault type of the target active power filter is a current sensor fault type; If the absolute value of the current value of the remaining non-faulty phase that has not been disconnected is not greater than the preset current threshold, it is determined that the fault type of the target active power filter is a phase loss fault type.

8. An active power filter fault diagnosis system, characterized in that: include: A signal acquisition module, used for real-time acquisition of voltage signals and current signals of a plurality of preset sampling points in a target active power filter; wherein the preset sampling points are arranged on the inverter output lines in the target active power filter; A fault characteristic determination module, used to determine the fault indication characteristics of each preset fault type according to the voltage signal and the current signal of each preset sampling point; wherein the preset fault types include a DC voltage sensor fault type, a grid voltage sensor fault type, a switch tube open circuit fault type, a current sensor fault type and a phase loss fault type; The fault type identification module is used to identify the fault type of the target active power filter according to the fault indication characteristics of each preset fault type.

9. An electronic device, characterized in that: The electronic device includes a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of the active power filter fault diagnosis method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the steps of the active power filter fault diagnosis method according to any one of claims 1 to 7 are implemented.

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