Power grid simulator fault diagnosis method based on voltage deviation value

Abstract

The invention discloses a power grid simulator fault diagnosis method based on a voltage deviation value, and the method comprises the steps: collecting the voltage outputted by an H-bridge circuit port of a power grid simulator in real time in an interval, and carrying out the calculation to form a voltage array and a voltage deviation value array; the method is used for diagnosing four common abnormal conditions of voltage abrupt change, voltage peak value abnormity, voltage deviation value abrupt change and long-term invariability of the voltage deviation value caused by short circuit or open circuit faults of a device, and high-efficiency diagnosis of faults of the power grid simulator is realized. According to the diagnosis method, the diagnosis time is reduced to a quarter of a period in speed; in the aspect of economy, only the existing port voltage signal is needed, and a sensor does not need to be newly added; and in the aspect of reliability, the method does not depend on high-frequency sampling data, and the physical definition of the diagnosis process is ensured.

Description

Technical Field

[0001] This invention belongs to the field of fault identification technology for power grid simulators for offshore wind power, and specifically relates to a fault diagnosis method for power grid simulators based on voltage deviation. Background Technology

[0002] As a core device in the electrical testing section of a wind power ground test platform, the power grid simulator accurately simulates power grid characteristics and tests the grid-connected performance of wind turbines. Currently, the modular multilevel power grid simulator has become a core device in ground test platforms. Through a cascaded H-bridge structure, it effectively simulates high-order harmonics of the power grid and enables independent three-phase control, providing crucial support for verifying the grid-connected performance of wind turbines. However, its modular structure contains a large number of insulated-gate bipolar transistors, significantly increasing the overall system failure probability. Once a failure occurs, it not only interrupts the testing process but may also lead to serious misjudgments of wind turbine performance due to abnormal output waveforms, directly jeopardizing the accuracy and credibility of the test conclusions. Therefore, to improve the reliability and availability of the power grid simulator and provide strong support for developing fault-tolerant strategies, it is necessary to study rapid fault diagnosis methods suitable for modular multilevel power grid simulators.

[0003] Currently, commonly used fault diagnosis methods include intelligent diagnosis methods based on neural networks and methods that diagnose faults by setting thresholds for the effective values ​​of voltage and current. However, intelligent diagnosis methods based on neural networks require a large number of fault samples, while the failure rate of equipment in actual application is low, resulting in insufficient fault samples and long fault diagnosis time. The method of setting thresholds for the effective values ​​of voltage and current is simple and efficient, but it requires at least one cycle of voltage as a criterion, making diagnosis not timely enough.

[0004] Therefore, in wind turbine testing, an application scenario with extremely high requirements for reliability and timeliness, there is an urgent need to study a new fault diagnosis scheme that balances rapid response and engineering practicality, so as to break through the bottlenecks of existing methods in terms of data dependence and diagnostic speed, and provide a solid guarantee for the accurate testing of wind power equipment and grid safety. Summary of the Invention

[0005] The main objective of this invention is to overcome the shortcomings and deficiencies of existing technologies and provide a fault diagnosis method for power grid simulators based on voltage deviation. The voltage characteristics under various faults in a power grid simulator vary significantly depending on the fault type, system parameters, and the location of the detection point. Based on fault type, there are various types, including symmetrical faults (three-phase short circuit), asymmetrical faults, and open circuit faults. Different faults also exhibit different voltage characteristics. This method collects voltage data from the H-bridge circuit and determines the fault type of the power grid simulator based on the differences in voltage characteristics under various faults.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A fault diagnosis method for a power grid simulator based on voltage deviation is proposed. This method is applied to a power grid simulator composed of four H-bridge units forming an H-bridge circuit, with an assembly voltage value of... The DC power supply provides the operating voltage for the H-bridge unit. Each H-bridge unit consists of one IGBT transistor, numbered VT1, VT2, VT3, and VT4. Each IGBT transistor is connected in parallel with a freewheeling diode, numbered VD1, VD2, VD3, and VD4, for current freewheeling and protection. In the bridge arm structure of the power grid simulator, the bridge arm closer to the positive terminal of the DC power supply is called the upper bridge arm, and the one closer to the negative terminal is called the lower bridge arm. Therefore, VT1 and VT3 form the upper bridge arm, and VT2 and VT4 form the lower bridge arm. Each pair of independent components of the upper and lower bridge arms forms a branch. The connection point between VT1 and VT2 is point a, and the connection point between VT3 and VT4 is point b. Current is drawn from points a and b as output ports. The fault diagnosis method includes the following steps: S1. Collect the single-phase output voltage of the power grid simulator under working conditions, perform differential calculation to obtain the voltage deviation, and form a voltage array and a voltage deviation array; S2. Determine the voltage sudden change threshold and use the voltage deviation array obtained from the data acquisition and calculation to determine whether the voltage has suddenly changed. S3. Determine the voltage peak abnormality standard. Determine whether the voltage peak is abnormal based on the collected voltage array and voltage deviation array. If an abnormality occurs, proceed to step S4; otherwise, proceed to step S5. S4. Determine the voltage deviation sudden change threshold, and use the voltage deviation array obtained from the data acquisition and calculation to determine whether the voltage deviation changes abruptly. S5. Determine the threshold for long-term stability of voltage deviation, and use the voltage deviation array obtained from the data acquisition and calculation to determine whether the voltage deviation remains unchanged over a long period of time.

[0007] Furthermore, step S1 is performed as follows: When the power grid simulator is running normally, it outputs a positive voltage at the output port between points a and b by controlling the on / off combinations of the IGBT elements in the H-bridge unit. negative voltage and zero voltage, where the output positive voltage The on / off combination is that VT1 and VT4 are on, and the output voltage is negative. The on / off combination is that VT2 and VT3 are on, and when VT1 and VT2 or VT3 and VT4 are on, the output port between points a and b outputs zero voltage. However, when the power grid simulator malfunctions, the port output voltage will deviate from the normal state. When any two IGBTs in VT1, VT2, VT3, and VT4 are open-circuited, the output voltage is 0 for the entire cycle or 0 for half a cycle. When any one of VT1, VT2, VT3, and VT4 is open-circuited, the output voltage waveform is asymmetrical and the peak value decreases. When any one of VT1, VT2, VT3, and VT4 is short-circuited, the output current at the output port between points a and b increases sharply and the voltage decreases sharply. Fault diagnosis can be performed based on the abnormal characteristics of voltage and current in the above-mentioned fault types. This invention determines the IGBT open-circuit fault based on the abnormal characteristics of voltage data when the IGBT is short-circuited or open-circuited.

[0008] A voltmeter is connected in parallel at the output port between points a and b to collect the single-phase output voltage during the operation of the power grid simulator. Each interval Each data acquisition is recorded, and the first recorded data point is recorded as the voltage at time 1. This process is repeated to obtain the voltage array. ,

[0009] in, For the period of the modulated wave, u i for Voltage data collected at various times, i=1,2,…,n; Define voltage deviation This is the difference between the voltage value at this moment and the voltage value collected at the previous moment, i.e.

[0010] in, Let j be the output voltage value acquired at time j. for The output voltage values ​​are collected at various times, j=2,…,n. The voltage array is thus calculated. remove The voltage deviation of the external elements is used to obtain the voltage deviation array. :

[0011] in, Let be the voltage deviation at time j.

[0012] Furthermore, step S2 is as follows: A voltage surge refers to a dramatic change in the output voltage at the output ports between points a and b within a very short period of time. This is caused by overvoltage generated when a short circuit occurs in the H-bridge circuit and when the short-circuit current is turned off. Therefore, a short-circuit fault can be identified. Since the acquisition of output voltage data between points a and b involves time intervals, a voltage surge threshold should be determined to determine whether a voltage surge has occurred at a specific moment. This serves as the boundary for voltage surges. Determine the voltage change threshold The definition is as follows:

[0013] in, The DC current and voltage values ​​connected to the power grid simulator are used to determine whether a voltage surge occurs in the H-bridge circuit of the power grid simulator during the acquisition period based on the collected voltage data, and the voltage deviation is then arrayed. middle With voltage change threshold Compare the values ​​to determine if the deviation is too large or if a short circuit has occurred in the circuit. when , At time j, the voltage deviation is determined. If the value is too large, a short-circuit fault occurs in the H-bridge structure of the power grid simulator; when When, the voltage deviation at time j is determined. Normal, no voltage surge occurred, proceed to step S3 for fault diagnosis of abnormal voltage peak.

[0014] Furthermore, step S3 is as follows: Voltage peak anomaly refers to the instantaneous output voltage value of the port of the H-bridge circuit exceeding the designed normal operating range at a certain moment, reaching an amplitude that may endanger the normal operation of the system. This anomaly is usually caused by an open circuit fault. The inductance in the circuit generates a huge induced voltage when the current is interrupted. The induced voltage is superimposed on the power supply voltage, which will lead to voltage peak anomaly. This can be used to determine whether an open circuit fault has occurred in the H-bridge circuit.

[0015] Take voltage array and voltage deviation array The elements and criteria for abnormal voltage peak values. The comparison was performed to determine whether a fault had occurred in the power system at the time the data was collected. when When the voltage deviation is small, meaning the voltage is close to the peak value, and the instantaneous output voltage value of the output port between points a and b at this moment j deviates from the peak voltage value when the H-bridge circuit is operating normally, it indicates that the peak voltage is too low or the voltage is asymmetrical, which meets the voltage peak abnormality standard and is judged as a fault. Then, proceed to step S4 to diagnose the fault of sudden change in voltage deviation. when When the voltage deviation is small, meaning the voltage is close to its peak value, the deviation between the output voltage at points a and b at time j and the peak voltage during normal operation is within the normal range, indicating that the peak voltage is normal at this time. Therefore, the voltage deviation is small and the growth rate is large, which does not meet the condition of sudden change in voltage deviation. So, the fault diagnosis of sudden change in voltage deviation in step S4 is skipped, and the process proceeds to step S5 to diagnose the fault of long-term unchanged voltage deviation.

[0016] Furthermore, step S4 is as follows: Sudden voltage deviation refers to a drastic change in the output voltage of the H-bridge circuit within a very short period of time, exceeding the normal fluctuation range. This will affect the normal operation of the H-bridge circuit in the power grid simulator and should be judged as a fault. Because the data collection occurs at time intervals, a threshold for determining sudden changes in voltage deviation needs to be established to assess this. This serves as the boundary for sudden changes in voltage deviation. If the voltage waveform is considered as a sine wave, then the maximum value of the voltage deviation is: However, in actual production, the threshold should have a safety margin to account for the impact of uncertainties. Here, let the threshold for sudden changes in voltage deviation be... Retain a margin of 1.2 times.

[0017] From voltage deviation array Elements and thresholds Compare the values ​​to determine whether the H-bridge circuit has experienced a sudden voltage deviation fault at that moment. when When the voltage deviation changes abruptly, it is considered an abnormal voltage deviation change; when If the voltage deviation at that moment is considered to be within the normal range, proceed to step S5 for fault diagnosis of a long-term unchanged voltage deviation.

[0018] Furthermore, step S5 is as follows: A voltage deviation that remains constant over a long period means that the voltage deviation value remains basically constant within the period during which it should change normally. It loses its dynamic characteristics and is a hidden fault mode that poses a huge hidden danger to the operation of the H-bridge circuit. It should be judged as a fault. To diagnose faults where the voltage deviation remains constant over a long period, a threshold for determining the long-term stability of the voltage deviation should be established, taking into account the time interval between data acquisitions. This serves as the boundary for the voltage deviation to remain constant over a long period. Define the threshold for determining whether the voltage deviation remains constant over a long period of time.

[0019]

[0020] From voltage deviation array Elements and thresholds Compare the results to determine if the H-bridge circuit has experienced a fault where the voltage deviation remains constant over a long period of time. when When j=4,5,…,n, the voltage deviation is considered to be within If there is no significant change within a certain period, it is determined to be an abnormal situation where the voltage deviation remains unchanged for a long period of time; when When j=4,5,…,n, the H-bridge circuit is considered to be normal and without fault.

[0021] Furthermore, the fault diagnosis method also includes: S6. When the voltage and voltage deviation data of the H-bridge circuit at this moment are diagnosed through fault diagnosis, it is determined that the H-bridge circuit of the power grid simulator is operating normally at this moment. The voltage value of the output port and the calculated voltage deviation are recorded at this moment as the basis for judging whether the H-bridge circuit is normal at the next moment.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) This invention does not require a large number of difficult-to-obtain fault samples for model training. Fault diagnosis can be achieved simply by detecting the port output voltage of the power grid simulator. By calculating the voltage deviation and using theoretical formulas to accurately judge voltage fluctuations and voltage peaks, the entire diagnostic process is based on explicit algebraic operations. This not only avoids the stringent requirements of data-driven methods on the amount and quality of data, but also saves the cost and complexity of installing additional sensing equipment.

[0023] (2) This invention first determines whether a sudden change in voltage occurs through theoretical formulas, thus initially identifying potential faults; then, by calculating the voltage peak deviation, it performs secondary verification and confirmation of the anomaly. This progressive, hierarchical diagnostic logic effectively eliminates instantaneous interference, ensures the accuracy of the judgment, and significantly reduces the time required for the entire diagnostic process to less than a quarter of the power frequency cycle, which is much faster than the traditional method based on effective values, thus saving valuable time for subsequent fault-tolerant control.

[0024] (3) The voltage deviation, sudden change criterion, and peak value criterion proposed in this invention are all based on directly measurable port voltages and are expressed and calculated using simple algebraic formulas. This method has low computational requirements, low hardware computing power requirements, and is easy to implement in engineering fields. At the same time, all criteria are directly related to the physical characteristics of the output waveform of the power grid simulator, and the diagnostic conclusions are traceable and interpretable, fundamentally solving the trust problem of "black box" decision-making in intelligent diagnostic algorithms.

[0025] (4) This invention comprehensively fulfills the core requirements of fault diagnosis: in terms of speed, it reduces the diagnosis time to a quarter cycle; in terms of economy, it only requires existing port voltage signals and does not require additional sensors; in terms of reliability, it eliminates the dependence on unstable data sources and ensures the physical clarity of the diagnosis process. This provides efficient and practical key technical support for improving the reliability and availability of the power grid simulator test platform and enabling it to achieve advanced fault-tolerant operation. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the H-bridge circuit structure of the power grid simulator in an embodiment of the present invention; Figure 2 This is a flowchart of a power grid simulator fault diagnosis method based on voltage deviation in Embodiment 1 of the present invention; Figure 3 This is a flowchart of a power grid simulator fault diagnosis method based on voltage deviation in Embodiment 2 of the present invention. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort are within the scope of protection of the present application.

[0029] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0030] Example 1 like Figure 3 As shown, this embodiment discloses a fault diagnosis method for a power grid simulator based on voltage deviation, which is applied to a power grid simulator, such as... Figure 1 The disclosed schematic diagram of the H-bridge circuit structure of the power grid simulator shows that the simulator consists of four H-bridge units, with an assembly voltage value of The DC power supply provides the operating voltage for the H-bridge unit. Each H-bridge unit consists of one IGBT transistor, numbered VT1, VT2, VT3, and VT4. Each IGBT transistor is connected in parallel with a freewheeling diode, numbered VD1, VD2, VD3, and VD4, for current freewheeling and protection. The H-bridge has two parts: an upper arm and a lower arm. VT1 and VT3 form the upper arm, while VT2 and VT4 form the lower arm. Each pair of independent components in the upper and lower arms forms a branch. The connection point of VT1 and VT2 is point a, and the connection point of VT3 and VT4 is point b. Current is drawn from points a and b as output ports. When the power grid simulator is running normally, it outputs a positive voltage at the port between points a and b by controlling the on / off combinations of the IGBT elements in the H-bridge unit. negative voltage and zero voltage, where the output positive voltage The on / off combination is that VT1 and VT4 are on, and the output voltage is negative. When VT2 and VT3 are turned on, the output port between points a and b outputs zero voltage when VT1 and VT2 or VT3 and VT4 are turned on. However, when the power grid simulator malfunctions, the output voltage of the port will deviate from the normal state. When any two IGBTs in VT1, VT2, VT3, and VT4 are open-circuited, the output voltage is 0 for the entire cycle or 0 for half a cycle. When any one of VT1, VT2, VT3, and VT4 is open-circuited, the output voltage waveform is asymmetrical and the peak value decreases. When any one of VT1, VT2, VT3, and VT4 is short-circuited, the current output at the output port between points a and b increases sharply, and the voltage decreases sharply. The fault characteristics of the above-mentioned fault types can be used for fault diagnosis in the power grid simulator. In this embodiment, the abnormal characteristics of the voltage data when the IGBT is short-circuited or open-circuited are used to determine the IGBT open-circuit fault.

[0031] A voltmeter is connected in parallel at the output port between points a and b to collect the single-phase output voltage during the operation of the power grid simulator. DC power supply for the H-bridge circuit in the power grid simulator. Rated frequency The period is 0.02s. Let the starting time be 1, and subsequent times be sequentially incremented from 1. The voltmeter is marked with each interval... The voltage of phase A output from ports a and b is collected once.

[0032] The collected voltage data are shown in Table 1.

[0033] Table 1. Partial Voltage Data Acquired

[0034] S1. Obtain the voltage array and voltage deviation array; A voltage array is formed from the collected port output voltage data. ,

[0035] in, For the period of the modulated wave, and They are time 1, time 2, and Voltage data collected at time 10000 and time 10000; Take voltage array elements Define voltage deviation This is the difference between the voltage value at this moment and the voltage value collected at the previous moment, i.e.

[0036] in, for The output voltage value is collected at all times. for The output voltage value is collected at all times.

[0037] The voltage array is thus calculated. remove The voltage deviation of the external elements is used to obtain the voltage deviation array. .

[0038]

[0039] in, and They are time 1, time 2, and The voltage deviation between time 10000 and time 10000.

[0040] Take voltage array and voltage deviation array The element at time 3871 and Further fault diagnosis will be conducted.

[0041] S2. Determine the voltage sudden change threshold and use the voltage deviation array obtained from the data acquisition and calculation to determine whether the voltage has suddenly changed. Determine the voltage change threshold The definition is as follows:

[0042] voltage deviation With voltage change threshold Compare the values ​​to determine if the deviation is too large or if a short circuit has occurred in the circuit. From the voltage deviation array, we can obtain Therefore The voltage deviation at time 3871 was determined. Normal, no voltage surge occurred, proceed to fault diagnosis for abnormal voltage peak. S3. Determine the abnormal voltage peak value standard by judging whether the voltage peak value is abnormal based on the collected voltage array and voltage deviation array; Take voltage and voltage deviation By comparing the data with the criteria for abnormal voltage peak values, it can be determined whether a fault has occurred in the power system at the time the data was collected.

[0043] Depend on If the voltage deviation is small, meaning the voltage is close to the peak value, and the deviation between the output voltage at points a and b at time 3871 and the peak voltage during normal operation is within the normal range, it indicates that the peak voltage is normal at this time. Therefore, skip the fault diagnosis of sudden change in voltage deviation in step S4 and proceed to step S5 for fault diagnosis of long-term unchanged voltage deviation. S4. Determine the voltage deviation sudden change threshold; use the voltage deviation array obtained from the data acquisition and calculation to determine whether the voltage deviation has a sudden change: Since the voltage deviation at time 3871 is small and the growth rate is large, it does not meet the condition of a sudden change in voltage deviation. Therefore, the fault diagnosis of a sudden change in voltage deviation in step S4 is skipped, and the fault diagnosis of a long-term unchanged voltage deviation in step S5 is entered.

[0044] S5. Determine the threshold for long-term stability of voltage deviation; use the voltage deviation array obtained from the data acquisition and calculation to determine whether the voltage deviation remains constant over a long period. Define the threshold for voltage deviation to remain constant over a long period of time. ,

[0045] From voltage deviation array elements and With threshold By comparison, it can be determined whether the H-bridge circuit has experienced an abnormal situation where the voltage deviation remains unchanged for a long period of time; Comparison yields The voltage deviation can be considered to be within If there is no significant change within a certain period, it is determined to be an abnormal situation where the voltage deviation remains unchanged for a long period of time.

[0046] Therefore, the voltage deviation caused by the open circuit fault in the H-bridge circuit of the power grid simulator remains unchanged for a long period of time.

[0047] Example 2 This embodiment continues to disclose a method for locating and identifying fault modules in a power grid simulator, applied to a power grid simulator. Step S1 is the same as step S1 in embodiment 1. The following describes the subsequent steps S2 to S6.

[0048] S2. Determine the voltage sudden change threshold and use the voltage deviation array obtained from the data acquisition and calculation to determine whether the voltage has suddenly changed. Take voltage array and voltage deviation array Elements with a time value of 500 and Perform fault diagnosis; The voltage surge threshold can be determined by the calculation in step S2 of Example 1. Voltage deviation With voltage change threshold Compare the values ​​to determine if the deviation is too large or if a short circuit has occurred in the circuit. From voltage deviation array achievable Therefore Determine the voltage deviation at time 500. Normal, no voltage surge occurred, proceed with fault diagnosis for abnormal voltage peak. S3. Determine the abnormal voltage peak value standard by judging whether the voltage peak value is abnormal based on the collected voltage array and voltage deviation array; Take voltage and voltage deviation By comparing the data with the criteria for abnormal voltage peak values, it can be determined whether a fault has occurred in the power system at the time the data was collected.

[0049] Depend on If the voltage deviation is considered small, meaning the voltage is close to the peak value, and the deviation between the output voltage at points a and b at time 500 and the peak voltage during normal operation is within the normal range, it indicates that the peak voltage is normal at this time. Therefore, skip the fault diagnosis of sudden change in voltage deviation in step S4 and proceed to step S5 for fault diagnosis of long-term unchanged voltage deviation. S4. Determine the voltage deviation sudden change threshold; use the voltage deviation array obtained from the data acquisition and calculation to determine whether the voltage deviation has a sudden change: Since the voltage deviation at time 500 is small and the growth rate is large, it does not meet the condition of sudden change in voltage deviation. Therefore, the fault diagnosis of sudden change in voltage deviation in step S4 is skipped, and the fault diagnosis of long-term unchanged voltage deviation in step S5 is entered.

[0050] S5. Determine the threshold for long-term stability of voltage deviation; use the voltage deviation array obtained from the data acquisition and calculation to determine whether the voltage deviation remains constant over a long period. The voltage surge threshold can be determined by the calculation in step S5 of Example 1. Array the voltage deviation elements and With threshold Compare the results to determine if the H-bridge circuit has experienced a fault where the voltage deviation remains constant over a long period of time. Depend on The H-bridge circuit can be considered normal and without fault. S6. When the voltage and voltage deviation data of the H-bridge circuit at this moment are determined to be normal after fault diagnosis, record the original data as the criterion for the next moment. It can be seen that after the fault diagnosis in steps S2 to S5, the voltage and voltage deviation at time 500 are determined to be normal operation of the H-bridge circuit of the power grid simulator at that time. The voltage value of the output port at time 500 and the calculated voltage deviation are recorded as the basis for judging whether the H-bridge circuit is normal at the next time.

[0051] In summary, traditional fault diagnosis methods, such as neural network-based intelligent diagnosis, require a large number of fault samples and are time-consuming, while methods that set thresholds for effective voltage and current values ​​require at least one cycle, resulting in insufficient timeliness. The fault diagnosis method based on voltage deviation proposed in this patent can quickly and effectively identify faults by calculating the voltage deviation and setting reasonable thresholds. This method only requires acquiring the port output voltage, eliminating the need for additional sensors. It uses algebraic formulas to determine voltage spikes, peak deviations, and deviation changes in real time, thus completing fault diagnosis within a quarter of a cycle. Compared to artificial intelligence methods, this significantly improves fault identification speed without relying on a large number of fault samples, rapidly locating fault modules and types, reducing equipment failure duration, and ensuring the reliable operation and production efficiency of the power grid simulator.

[0052] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0053] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A fault diagnosis method for a power grid simulator based on voltage deviation, applied to a power grid simulator consisting of an H-bridge circuit composed of four H-bridge units, with an assembly voltage value of... The DC power supply provides the operating voltage for the H-bridge unit. Each H-bridge unit consists of one IGBT transistor, numbered VT1, VT2, VT3, and VT4. Each IGBT transistor is connected in parallel with a freewheeling diode, numbered VD1, VD2, VD3, and VD4, for current freewheeling and protection. The power grid simulator includes an upper bridge arm and a lower bridge arm. VT1 and VT3 form the upper bridge arm, and VT2 and VT4 form the lower bridge arm. Each pair of independent components in the upper and lower bridge arms forms a branch. The connection point between VT1 and VT2 is point a, and the connection point between VT3 and VT4 is point b. Current is drawn from points a and b as output ports. Its characteristic is... The fault diagnosis method includes the following steps: S1. Collect the single-phase output voltage of the power grid simulator under working conditions, perform differential calculation to obtain the voltage deviation, and form a voltage array and a voltage deviation array; S2. Determine the voltage sudden change threshold and use the voltage deviation array obtained from the data acquisition and calculation to determine whether the voltage has suddenly changed. S3. Determine the voltage peak abnormality standard. Determine whether the voltage peak is abnormal based on the collected voltage array and voltage deviation array. If an abnormality occurs, proceed to step S4; otherwise, proceed to step S5. S4. Determine the voltage deviation sudden change threshold, and use the voltage deviation array obtained from the data acquisition and calculation to determine whether the voltage deviation changes abruptly. S5. Determine the threshold for long-term stability of voltage deviation, and use the voltage deviation array obtained from the data acquisition and calculation to determine whether the voltage deviation remains unchanged over a long period of time.

2. The fault diagnosis method for a power grid simulator based on voltage deviation according to claim 1, characterized in that, The process of step S1 is as follows: A voltmeter is connected in parallel at the output port between points a and b to collect the single-phase output voltage during the operation of the power grid simulator. Each interval Each data acquisition is recorded, and the first recorded data point is recorded as the voltage at time 1. This process is repeated to obtain the voltage array. , in, For the period of the modulated wave, u i for Voltage data collected at various times, i=1,2,…,n; Define voltage deviation This is the difference between the voltage value at this moment and the voltage value collected at the previous moment, i.e. , in, Let j be the output voltage value acquired at time j. for The output voltage values ​​are collected at various times, j=2,…,n. The voltage array is thus calculated. remove The voltage deviation of the external elements is used to obtain the voltage deviation array. : ,in, Let be the voltage deviation at time j.

3. The fault diagnosis method for a power grid simulator based on voltage deviation according to claim 2, characterized in that, The process of step S2 is as follows: Determine the voltage change threshold The definition is as follows: ,in, The DC current and voltage values ​​connected to the power grid simulator are used to determine whether a voltage surge occurs in the H-bridge circuit of the power grid simulator during the acquisition period based on the collected voltage data, and the voltage deviation is then arrayed. middle With voltage change threshold Compare the values ​​to determine if the deviation is too large or if a short circuit has occurred in the circuit. when , At time j, the voltage deviation is determined. If the value is too large, a short-circuit fault occurs in the H-bridge structure of the power grid simulator; when When, the voltage deviation at time j is determined. Normal, no voltage surge occurred, proceed to step S3 for fault diagnosis of abnormal voltage peak.

4. The fault diagnosis method for a power grid simulator based on voltage deviation according to claim 3, characterized in that, The process of step S3 is as follows: Take voltage array and voltage deviation array The elements and criteria for abnormal voltage peak values. The comparison was performed to determine whether a fault had occurred in the power system at the time the data was collected. when When the voltage deviation is small, meaning the voltage is close to the peak value, and the instantaneous output voltage value of the output port between points a and b at this moment j deviates from the peak voltage value when the H-bridge circuit is operating normally, it indicates that the peak voltage is too low or the voltage is asymmetrical, which meets the voltage peak abnormality standard and is judged as a fault. Then, proceed to step S4 to diagnose the fault of sudden change in voltage deviation. when When the voltage deviation is small, meaning the voltage is close to its peak value, and the deviation between the output voltage at points a and b at time j and the peak voltage during normal operation is within the normal range, it indicates that the peak voltage is normal at this time. Therefore, the fault diagnosis of sudden change in voltage deviation in step S4 is skipped, and the process proceeds to step S5 for fault diagnosis of long-term unchanged voltage deviation.

5. The fault diagnosis method for a power grid simulator based on voltage deviation according to claim 4, characterized in that, The process of step S4 is as follows: If the voltage waveform is considered as a sine wave, then the maximum value of the voltage deviation is: The threshold for sudden changes in voltage deviation Retain a margin of 1.2 times. From voltage deviation array Elements and thresholds Compare the values ​​to determine whether the H-bridge circuit has experienced a sudden voltage deviation fault at that moment. when When the voltage deviation changes abruptly, it is considered an abnormal voltage deviation change; when If the voltage deviation at that moment is considered to be within the normal range, proceed to step S5 for fault diagnosis of a long-term unchanged voltage deviation.

6. The fault diagnosis method for a power grid simulator based on voltage deviation according to claim 5, characterized in that, The process of step S5 is as follows: Define the threshold for determining whether the voltage deviation remains constant over a long period of time. : From the voltage deviation array Elements and thresholds Compare the results to determine if the H-bridge circuit has experienced a fault where the voltage deviation remains constant over a long period of time. when When j=4,5,…,n, the voltage deviation is considered to be within If there is no significant change within a certain period, it is determined to be an abnormal situation where the voltage deviation remains unchanged for a long period of time; when When j=4,5,…,n, the H-bridge circuit is considered to be normal and without fault.

7. The fault diagnosis method for a power grid simulator based on voltage deviation according to claim 6, characterized in that, The fault diagnosis method further includes: S6. When the voltage and voltage deviation data of the H-bridge circuit at this moment are diagnosed through fault diagnosis, it is determined that the H-bridge circuit of the power grid simulator is operating normally at this moment. The voltage value of the output port and the calculated voltage deviation are recorded at this moment as the basis for judging whether the H-bridge circuit is normal at the next moment.

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