Three-level bidirectional DC converter power device fault diagnosis method

Abstract

The invention discloses a three-level bidirectional direct current converter power device fault diagnosis method, and relates to the field of three-level bidirectional direct current converter state monitoring and fault diagnosis. In order to solve the defects that an existing three-level bidirectional direct-current converter has a converter fault due to an open circuit fault of a power switch tube, fault detection is lacked, and a fault point cannot be accurately found, operation state information of the three-level bidirectional direct-current converter is collected; determining a characteristic value capable of representing the running state of the three-level bidirectional direct-current converter; fault feature information of the three-level bidirectional direct-current converter is processed and judged; and carrying out fault diagnosis on the three-level bidirectional direct current converter. The method is mainly used for monitoring, diagnosing and early warning the power device open circuit problem of the neutral-point clamped three-level direct-current converter commonly used in occasions such as an energy storage power station, a ship propulsion system and a new energy power generation system.

Description

Technical Field

[0001] The invention relates to the field of state monitoring and fault diagnosis of three-level bidirectional direct current converters, and in particular to a method for diagnosing power device faults of three-level bidirectional direct current converters based on frequency analysis. Background Art

[0002] In recent years, the energy storage industry has developed rapidly. As the power level of energy storage systems continues to increase, DC converters with higher bus voltage levels and larger voltage differences on both sides are required to meet the characteristics of high voltage and high current. Therefore, multi-level technology, especially hybrid three-level technology, has become an effective means to build DC converters. It achieves multi-level output by transforming the main circuit topology, reduces the voltage stress of power devices, avoids the series connection of power devices, and is conducive to the realization of systems with larger output capacity and higher voltage levels.

[0003] However, with the improvement of multi-level technology, the number of switches has also increased, resulting in an increase in the probability of failure of the hybrid three-level converter. According to relevant statistics, most of the failures are caused by the power switch (IGBT), and will eventually manifest as a switch short circuit failure.

[0004] A short-circuit failure in the power switch tube of a multi-level converter is a fatal blow to the converter, and may even affect the harmonic level and vibration and noise performance of the energy storage system. Energy storage systems are currently increasingly tending to be unmanned or with few people on duty, which places higher requirements on the prevention and handling of such failures.

[0005] Therefore, there is a need for a three-level bidirectional DC converter power device fault diagnosis method that can detect the hybrid three-level converter's open circuit fault, provide early warning, and accurately locate the fault. Summary of the invention

[0006] In order to solve the defects of the existing three-level bidirectional DC converter, such as converter failure caused by short-circuit failure of the power switch tube, lack of fault detection, and inability to accurately find the fault point, the present invention provides a three-level bidirectional DC converter power device fault diagnosis method that can detect the short-circuit fault of the hybrid three-level converter, give early warning, and accurately locate the fault.

[0007] A method for diagnosing a fault of a power device of a three-level bidirectional DC converter according to the present invention comprises the following steps: Step 1: collecting operating status information of a three-level bidirectional DC converter; Step 2: determining a characteristic value that can characterize the operating state of the three-level bidirectional DC converter; Step 3: Process and determine the fault characteristic information of the three-level bidirectional DC converter; perform fault diagnosis on the three-level bidirectional DC converter.

[0008] Further: In S1, the operating status information includes the voltage between the midpoint of the leading bridge arm and the midpoint of the lagging bridge arm on the high-voltage side , the voltage across the leading bridge arm and the lagging bridge arm on the high-voltage side , the voltage between the midpoint of the leading bridge arm and the midpoint of the lagging bridge arm on the low voltage side and the voltage across the leading bridge arm and the lagging bridge arm on the low voltage side .

[0009] Further: in S2, the step of determining the characteristic value that can characterize the operating state of the three-level bidirectional DC converter specifically comprises the following steps: Step 21: Before the three-level bidirectional DC converter is put into operation, the voltage and current waveforms of the three-level bidirectional DC converter under rated working conditions are tested according to its working conditions, and are recorded as , as the initial value of the operating state of the three-level bidirectional DC converter; Step 22: Perform fast Fourier decomposition on the voltage initial value waveform to obtain frequency domain distribution curves of the initial voltage test waveform in different frequency bands, as follows: ; The frequency distribution diagram of the initial voltage waveform is analyzed to determine the center frequency where the frequency distribution is most concentrated, which are recorded as , , , , and use it as the voltage component characteristic value.

[0010] Further: in S3, the processing and judging of the fault characteristic information of the three-level bidirectional DC converter is for the three-level bidirectional DC converter put into operation, and its operating status is periodically sampled and judged, and the collected data of the above-mentioned monitoring voltage probe, monitoring current sensor, etc. are analyzed every X time, and the above-mentioned processing process is repeated to obtain the fault characteristic value of the three-level bidirectional DC converter obtained by the x-th sampling processing.

[0011] Further: the fault characteristic value of the three-level bidirectional DC converter includes the center frequency related to the voltage frequency domain parameter, including the center frequency of the voltage waveform between the midpoint of the leading bridge arm and the midpoint of the lagging bridge arm on the high-voltage side obtained by the x-th sampling , the xth sampling obtains the center frequency of the voltage waveform at both ends of the leading bridge arm and the lagging bridge arm on the high-voltage side , the center frequency of the voltage waveform between the midpoint of the leading bridge arm and the midpoint of the lagging bridge arm on the low voltage side is obtained by the xth sampling The center frequency of the voltage waveform at both ends of the leading bridge arm and the lagging bridge arm on the low-voltage side is obtained by sampling at the xth time .

[0012] Further: in S3, the processing and determining the fault characteristic information of the converter specifically includes the following steps: In S3, the processing and determining of the fault characteristic information of the converter specifically includes the following steps: Step 31: Analyze the change of the voltage frequency domain parameters of the three-level bidirectional DC converter to obtain the center frequency change value as follows: , y=ab, cd, ef, gh; Step 32: By comparing and analyzing the characteristic values ​​of the three-level bidirectional DC converter, determine the specific location where the short circuit fault occurs in the three-level bidirectional DC converter.

[0013] Further: in S32, when the electric energy is transmitted from the left side to the right side, the specific steps of comparing and analyzing the characteristic values ​​of the three-level bidirectional DC converter are: when >0.1, <0.1, and <0.1, <0.1, the circuit breaker fault only occurs in the first bridge arm on the left; when <0.1, >0.1, and <0.1, <0.1, the circuit breaker fault only occurs in the second bridge arm on the left; when <0.1, <0.1, and >0.1, <0.1, the circuit breaker fault only occurs in the first bridge arm on the right; when <0.1, <0.1, and <0.1, >0.1, the circuit breaker fault only occurs in the second bridge arm on the right.

[0014] Further: the first bridge arm on the left side includes a switch tube , switch tube , switch tube And switch tube The left second bridge arm includes a switch tube , switch tube , switch tube And switch tube The first right bridge arm includes a switch tube And switch tube The second right bridge arm includes a switch tube And switch tube .

[0015] Further: in S32, when the electric energy is transmitted from the right side to the left side, the judgment basis of the converter circuit breaker fault will be partially changed, and the adjusted judgment basis is as follows: when >0.5, <0.5, and <0.1, <0.1, the circuit breaker fault only occurs in the right leading bridge arm; when <0.5, >0.5, and <0.1, <0.1, the circuit breaker fault only occurs in the right lagging bridge arm; when <0.5, <0.5, and >0.1, <0.1, the circuit breaker fault only occurs in the first bridge arm on the left; when <0.5, <0.5, and <0.1, >0.1, the circuit breaker fault only occurs in the second bridge arm on the left.

[0016] Further: the first bridge arm on the left side includes a switch tube , switch tube , switch tube And switch tube The left second bridge arm includes a switch tube , switch tube , switch tube And switch tube The right leading bridge arm includes a switch tube And switch tube The second right bridge arm includes a switch tube And switch tube .

[0017] The beneficial effects of the present invention are: The three-level bidirectional DC converter power device fault diagnosis method based on frequency analysis described in the present invention can determine the operating status and fault location of the multi-level DC converter commonly used in the energy storage system, and through frequency analysis, it can realize real-time monitoring of the state of the switch tube in the converter, and more accurately and quickly reflect the problem of midpoint voltage imbalance.

[0018] The method for diagnosing power device faults of a three-level bidirectional DC converter based on frequency analysis of the present invention can quickly identify and judge the beginning of the short circuit fault of the power switch tube by combining continuous online monitoring and intelligent diagnosis, and can also warn of the occurrence of the fault. The method for diagnosing power device faults of three-level bidirectional DC converters based on frequency analysis described in the present invention can realize the monitoring, diagnosis and early warning of power device short circuit problems that often occur in midpoint clamped three-level DC converters commonly used in energy storage power stations, ship propulsion systems and new energy power generation systems, and effectively reduce the probability of problems such as converter bridge arm direct conduction and continuous damage to power devices caused by the continuous deepening and spread of short circuit faults. At the same time, the present invention combines continuous online monitoring and intelligent diagnosis to quickly diagnose and locate device short circuit fault problems at the beginning of their occurrence, prevent the spread and aggravation of the fault, and help improve the safe operation performance of multi-level DC converters in facilities such as energy storage power stations, ship propulsion systems and new energy power generation systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the implementation of a method for diagnosing power device faults of a three-level bidirectional DC converter based on frequency analysis; Figure 2 The figure shows the driving waveform and midpoint voltage waveform of the three-level bidirectional DC converter during actual operation. DETAILED DESCRIPTION

[0020] The following are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a technician familiar with the technical field within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The embodiments described below are only used to explain the present invention and cannot be interpreted as limitations on the present invention. The protection scope of the present invention should be based on the protection scope of the claims. The embodiments of the present invention are described in detail below. In order to facilitate the description of the present invention and simplify the description, the technical terms used in the specification of the present invention should be interpreted in a broad sense, including but not limited to conventional replacement schemes not mentioned in this application, and also including direct implementation methods and indirect implementation methods.

[0021] Example 1 Combination Figure 1 and Figure 2This embodiment describes a method for diagnosing a power device fault in a three-level bidirectional DC converter based on frequency analysis, so as to achieve real-time monitoring of the state of a switch tube in a three-level bidirectional DC converter, including the following steps (electric energy flows from the left side to the right side): Step 1: collecting operating status information of a three-level bidirectional DC converter; The monitoring voltage probes a, b, c, d, e, f, g, and h at the key positions of the three-level bidirectional DC converter are connected to respectively test the voltage Vab between the midpoint of the leading bridge arm and the midpoint of the lagging bridge arm on the high-voltage side, the voltage Vcd at both ends of the leading bridge arm and the lagging bridge arm on the high-voltage side, the voltage Vef between the midpoint of the leading bridge arm and the midpoint of the lagging bridge arm on the low-voltage side, and the voltage Vgh at both ends of the leading bridge arm and the lagging bridge arm on the low-voltage side. The voltage waveforms within N cycles are recorded and recorded as , , , ,in: ; Where t is the time of the sampled voltage waveform, is the time domain value, is the operating frequency of the three-level bidirectional DC converter, is the single working cycle time of the power device of the three-level bidirectional DC converter; Step 2: determining a characteristic value that can characterize the operating state of the three-level bidirectional DC converter; Step 21: Before the three-level bidirectional DC converter is put into operation, the voltage and current waveforms at various positions of the three-level bidirectional DC converter under rated working conditions are tested according to its working conditions, and are recorded as , , , , as the initial value of the operating state of the three-level bidirectional DC converter; Step 22: Perform fast Fourier decomposition on the voltage initial value waveform to obtain frequency domain distribution curves of the initial voltage test waveform in different frequency bands, as follows: ; The frequency distribution diagram of the initial voltage waveform is analyzed to determine the center frequency where the frequency distribution is most concentrated, which are recorded as , , , , and use it as the voltage component characteristic value; Step 3: Processing and judging fault characteristic information of the three-level bidirectional DC converter; For the three-level bidirectional DC converter put into operation, its operating status is periodically sampled and judged, and the collected data of the above-mentioned monitoring voltage probe, monitoring current sensor, etc. are analyzed every X time. X can be set as needed, and the above-mentioned processing is repeated to obtain the fault characteristic value of the three-level bidirectional DC converter obtained by the x-th sampling process: including the voltage frequency domain parameter related , , , wait; Step 31, analyzing the change of the voltage frequency domain parameters of the three-level bidirectional DC converter, and obtaining the center frequency change value Δfy as follows: , y=ab, cd, ef, gh; Step 32: By comparing and analyzing the characteristic values ​​of the three-level bidirectional DC converter, determine the specific location where the open circuit fault occurs in the three-level bidirectional DC converter: when >0.1, <0.1, and <0.1, <0.1, the circuit breaker fault only occurs in the first bridge arm on the left (S1, S2, S3, S4); when <0.1, >0.1, and <0.1, <0.1, the circuit breaker fault only occurs in the second bridge arm on the left (S5, S6, S7, S8); when <0.1, <0.1, and >0.1, <0.1, the circuit breaker fault only occurs in the first bridge arm on the right (Q1, Q2); when <0.1, <0.1, and <0.1, >0.1, the circuit breaker fault only occurs in the second bridge arm on the right (Q3, Q4).

[0022] In addition, the present invention can also achieve the following functions: When the electric energy is transmitted from the right side to the left side, the judgment basis of the three-level bidirectional DC converter circuit breaker fault will be partially changed. The adjusted judgment basis is as follows: when >0.5, <0.5, and <0.1, <0.1, the circuit breaker fault only occurs in the right leading bridge arm (Q1, Q4); when <0.5, >0.5, and <0.1, <0.1, the circuit breaker fault only occurs in the right lagging bridge arm (Q2, Q3); when <0.5, <0.5, and >0.1, <0.1, the circuit breaker fault only occurs in the first bridge arm on the left (S1, S2, S3, S4); when <0.5, <0.5, and <0.1, >0.1, the circuit breaker fault only occurs in the second bridge arm on the left (S5, S6, S7, S8).

Claims

1. A method for diagnosing a fault in a power device of a three-level bidirectional DC converter, characterized in that: The steps include: Step 1: collecting operating status information of a three-level bidirectional DC converter; Step 2: determining a characteristic value that can characterize the operating state of the three-level bidirectional DC converter; Step 3: Process and determine the fault characteristic information of the three-level bidirectional DC converter; Perform fault diagnosis on three-level bidirectional DC converter.

2. A three-level bidirectional DC converter power device fault diagnosis method according to claim 1, characterized in that: In S1, the operating status information includes the voltage between the midpoint of the leading bridge arm and the midpoint of the lagging bridge arm on the high-voltage side. , the voltage across the leading bridge arm and the lagging bridge arm on the high-voltage side , the voltage between the midpoint of the leading bridge arm and the midpoint of the lagging bridge arm on the low voltage side and the voltage across the leading bridge arm and the lagging bridge arm on the low voltage side .

3. A three-level bidirectional DC converter power device fault diagnosis method according to claim 1, characterized in that: In S2, determining the characteristic value that can characterize the operating state of the three-level bidirectional DC converter specifically includes the following steps: Step 21: Before the three-level bidirectional DC converter is put into operation, the voltage and current waveforms of the three-level bidirectional DC converter under rated working conditions are tested according to its working conditions, and are recorded as , as the initial value of the operating state of the three-level bidirectional DC converter; Step 22: Perform fast Fourier decomposition on the voltage initial value waveform to obtain frequency domain distribution curves of the initial voltage test waveform in different frequency bands, as follows: ； The frequency distribution diagram of the initial voltage waveform is analyzed to determine the center frequency where the frequency distribution is most concentrated, which are recorded as , , , , and use it as the voltage component characteristic value.

4. A three-level bidirectional DC converter power device fault diagnosis method according to claim 1, characterized in that: In S3, the processing and judging of the fault characteristic information of the three-level bidirectional DC converter is to perform periodic sampling and judgment on the operating status of the three-level bidirectional DC converter that has been put into operation, analyze the collected data of the above-mentioned monitoring voltage probe, monitoring current sensor, etc. every X time, repeat the above-mentioned processing process, and obtain the fault characteristic value of the three-level bidirectional DC converter obtained by the x-th sampling processing.

5. A three-level bidirectional DC converter power device fault diagnosis method according to claim 4, characterized in that: The fault characteristic value of the three-level bidirectional DC converter includes the center frequency related to the voltage frequency domain parameter, and includes the center frequency of the voltage waveform between the midpoint of the leading bridge arm and the midpoint of the lagging bridge arm obtained by the xth sampling. , the xth sampling obtains the center frequency of the voltage waveform at both ends of the leading bridge arm and the lagging bridge arm on the high-voltage side , the center frequency of the voltage waveform between the midpoint of the leading bridge arm and the midpoint of the lagging bridge arm on the low voltage side is obtained by the xth sampling The center frequency of the voltage waveform at both ends of the leading bridge arm and the lagging bridge arm on the low-voltage side is obtained by sampling at the xth time .

6. A three-level bidirectional DC converter power device fault diagnosis method according to claim 5, characterized in that: In S3, the processing and determining of the fault characteristic information of the converter specifically includes the following steps: Step 31: Analyze the change of the voltage frequency domain parameters of the three-level bidirectional DC converter to obtain the center frequency change value as follows: ,y=ab、cd、ef、gh! Step 32: By comparing and analyzing the characteristic values ​​of the three-level bidirectional DC converter, determine the specific location where the short circuit fault occurs in the three-level bidirectional DC converter.

7. A three-level bidirectional DC converter power device fault diagnosis method according to claim 6, characterized in that: In S32, when the electric energy is transmitted from the left side to the right side, the specific steps of comparing and analyzing the characteristic values ​​of the three-level bidirectional DC converter are: when >0.1, <0.1, and <0.1, <0.1, the circuit breaker fault only occurs in the first bridge arm on the left; when <0.1, >0.1, and <0.1, <0.1, the circuit breaker fault only occurs in the second bridge arm on the left; when <0.1, <0.1, and >0.1, <0.1, the circuit breaker fault only occurs in the first bridge arm on the right; when <0.1, <0.1, and <0.1, >0.1, the circuit breaker fault only occurs in the second bridge arm on the right.

8. A three-level bidirectional DC converter power device fault diagnosis method according to claim 7, characterized in that: The left first bridge arm includes a switch tube , switch tube , switch tube And switch tube The left second bridge arm includes a switch tube , switch tube , switch tube And switch tube The first right bridge arm includes a switch tube And switch tube The second bridge arm on the right side includes a switch tube And switch tube .

9. A three-level bidirectional DC converter power device fault diagnosis method according to claim 6, characterized in that: In S32, when the electric energy is transmitted from the right side to the left side, the judgment basis of the converter circuit breaker fault will be partially changed, and the adjusted judgment basis is as follows: when >0.5, <0.5, and <0.1, <0.1, the circuit breaker fault only occurs in the right leading bridge arm; when <0.5, >0.5, and <0.1, <0.1, the circuit breaker fault only occurs in the right lagging bridge arm; when <0.5, <0.5, and >0.1, <0.1, the circuit breaker fault only occurs in the first bridge arm on the left; when <0.5, <0.5, and <0.1, >0.1, the circuit breaker fault only occurs in the second bridge arm on the left.

10. A three-level bidirectional DC converter power device fault diagnosis method according to claim 9, characterized in that: The left first bridge arm includes a switch tube , switch tube , switch tube And switch tube The left second bridge arm includes a switch tube , switch tube , switch tube And switch tube The right leading bridge arm includes a switch tube And switch tube The second right bridge arm includes a switch tube And switch tube .

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