A comprehensive identification method for open-circuit faults in VIENNA rectifiers

Abstract

The present application provides a comprehensive diagnostic method for open-circuit faults of VIENNA rectifiers, and relates to the technical field of fault detection of VIENNA rectifiers. The steps of the method are: using the current sensor provided by the VIENNA rectifier to obtain the instantaneous value of the three-phase input current in real time and perform an inverse tangent function transformation. The transformed three-phase current is used to detect the zero-value platform and the 0-1 / 2 amplitude duration, and compared with the set threshold value, so as to determine the type of open-circuit fault and the fault phase. At the same time, the mean value of the three-phase current within a cycle is calculated through a sliding window, and the faulty tube is located by judging the positive and negative polarity of the current mean. This method does not require additional hardware and improves the speed of identifying single-tube open-circuit faults of rectifiers.

Description

Technical Field

[0001] The invention relates to open circuit fault diagnosis of a switch tube of a power electronic converter, and in particular to a method for comprehensive identification of open circuit faults of a VIENNA rectifier. Background Art

[0002] As a three-phase PWM rectifier, VIENNA rectifier has the advantages of high power factor, high power density, small number of switch tubes, and no bridge arm direct-through problem. It is widely used in fields with high requirements for rectifier performance. The working environment in these fields is often high frequency and high stress state, and the devices in the rectifier are very prone to failure. According to statistics, diode and power switch tube failures account for up to 47% of power converters. When the rectifier is running with a fault, the output voltage is unstable, the power factor correction cannot be achieved, the circuit operation is affected, and harmonics are generated to pollute the power grid. Early identification and location of faults are of great significance to improving system reliability.

[0003] At present, the rectifier open circuit fault diagnosis methods are roughly divided into current characteristics-based, voltage characteristics-based and artificial intelligence-based methods. The current characteristics-based diagnosis method is easily affected by the load and input current, and has the disadvantage of too long diagnosis time; the voltage characteristics-based diagnosis method often requires additional equipment, which increases the complexity of the system; the artificial intelligence-based method often requires a large amount of historical data, and the diagnosis method is complicated. Therefore, it is necessary to propose a method for online identification of open circuit faults that does not require the addition of additional sensors, has a simple algorithm, requires only a small amount of sampling signals, and can be convenient for the widely used VIENNA rectifier, so as to take necessary protection measures in time after the fault and improve the operating stability and safety of the charging device. Summary of the invention

[0004] The present application aims to provide a method for comprehensive identification of VIENNA rectifier open-circuit faults that can effectively improve the accuracy and reliability of diagnosis compared to the prior art diagnostic methods, does not require additional devices, has a simple implementation method, and has no complex control.

[0005] The technical solution adopted by the present invention is to use the current sensor of the VIENNA rectifier to detect the instantaneous value of the three-phase input current and perform an inverse tangent function transformation to determine whether there is a zero-value platform in the three-phase input current after the inverse tangent function transformation. If there is a zero-value platform in any phase input current, the phase is determined to be a power switch tube fault phase; the duration of the 0-1 / 2 amplitude of the three-phase input current after the inverse tangent function transformation is determined. If the duration of the 0-1 / 2 amplitude of any phase input current is greater than the threshold, the phase is determined to be a rectifier diode fault phase. While determining the fault type and fault phase, a sliding window is used to calculate the current cycle mean and absolute average value, and a fault feature quantity D is constructed. nk . By judging Dnk The positive and negative polarity of the fault phase is used to determine which bridge arm of the fault phase has a fault and locate the faulty device.

[0006] According to the technical solution provided in the embodiment of the present application, the steps of determining the fault type and the fault phase include: using the current sensor provided by the VIENNA rectifier to detect the instantaneous value of the three-phase input current and performing an inverse tangent function transformation. The transformation formula is:

[0007] i nk =arctan(i k )*2 / π(k=a,b,c) (1)

[0008] In the formula, i nk is the three-phase current after the inverse tangent function transformation. It can be seen from the formula that i nk The amplitude is in [-1,1], which avoids the influence of load on the diagnosis result.

[0009] Using the hysteresis comparison method, the boundary value i for detecting the zero value platform is set th , if -i th< i nk< i th , then the current can be considered to be 0. The zero value flag and amplitude flag are defined as ε k1 , ε k2 , as shown in the formula:

[0010]

[0011] When ε k1 , ε k2 When it changes from 0 to 1, the zero value platform and amplitude detection program are triggered, and the counter C k1 and C k2 Start counting. In each sampling period, if the current meets the above action conditions, C k1 and C k2 Accumulate 1. When the above conditions are not met, the counter stops counting and clears to zero. The zero value and amplitude duration of the current are t k1 ,t k2 :

[0012] t k1 =C k1 T s , k=a,b,c (4)

[0013] t k2 =C k2 T s , k=a,b,c (5)

[0014] Where T s is the current sampling period.

[0015] Define the fault indicator value as

[0016]

[0017] Where t th1 and t th2 is the time threshold. k1 =1, indicating that the k-phase power switch tube fails; R k1 =0, indicating that the k-phase power switch is normal; R k2 =1 indicates that the k-phase diode is faulty; R k2 =0 means the k-phase diode is normal.

[0018] According to the technical solution provided in the embodiment of the present application, the zero-value platform judgment threshold t th1 According to GB14549-93 power quality standard, the total harmonic distortion rate of AC current should be less than 5%. Current threshold i th It can be obtained by formula (6).

[0019] i th =i H =5%*i1 (8)

[0020] In the formula, i H is the harmonic current, and i1 is the fundamental current amplitude.

[0021] Formula (9) is the natural zero change through -i th< i nk< i th The time required. In order to avoid the time threshold being too large or too small to affect the recognition speed and accuracy, t is calculated by formula (9).

[0022] -5%i1≤i1 sin(2πf*t)≤5%i1 (9)

[0023] Where f is the current frequency. To improve the accuracy and speed of identification, the zero-value platform judgment threshold t th1 Take 2t.

[0024] According to the technical solution provided in the embodiment of the present application, the steps of locating the faulty device include: using a sliding window to calculate the current cycle mean and the absolute average value. In order to improve the accuracy and positioning speed of the positioning method, a sliding sampling window is used for data sampling, that is, each time a data is sampled, the window slides one position to the right and updates the sampling window once. The expression for updating the sampled data is:

[0025]

[0026] From equation (1) and equation (10), we can further obtain nkThe normalized mean and absolute mean of are:

[0027]

[0028] Where k and j are sampling moments; N is the number of sampling points in one cycle.

[0029] Construct the fault location feature D based on the normalized average value and the absolute average value nk for:

[0030]

[0031] When it is determined that a rectifier diode or power switch of a phase has an open circuit fault, it is only necessary to nk The polarity of the input current can be determined by the rectifier diode or power switch tube. If the rectifier diode or power switch tube has an open circuit fault, the input current will be lost regardless of whether it is a positive half-cycle or a negative half-cycle. If the VIENNA rectifier operates normally, then D nk is 0; if the upper bridge arm fails, causing the current positive half cycle to be missing, then D nk <0; if the lower bridge arm fails, causing the current negative half cycle to be missing, then D nk >0. Then, the fault bit identification value is defined as

[0032]

[0033] Where, d nk is the error threshold; R up =1 indicates that the upper bridge arm device is faulty, R down =1 indicates a low bridge arm device failure.

[0034] According to the technical solution provided by the embodiment of the present application, it includes a current conversion module, which is used to obtain the instantaneous amplitude of the three-phase input current of the rectifier in real time, and perform an inverse tangent function transformation on the three-phase input current of the VIENNA rectifier; a fault type and fault phase identification module, which determines whether there is a zero-value platform in the three-phase input current after the inverse tangent function transformation, and if there is a zero-value platform in any phase input current, it is determined that the phase is a power switch tube fault phase; it is determined that the 0-1 / 2 amplitude duration of the three-phase input current after the inverse tangent function transformation, if the 0-1 / 2 amplitude duration of any phase input current is greater than a threshold, it is determined that the phase is a rectifier diode fault phase; the fault type and fault phase identification are completed; the fault location module, while determining the fault type and fault phase, uses a sliding window to calculate the current cycle mean and absolute average value, and constructs a fault feature quantity D nk . By judging D nk The positive and negative polarity of the fault phase is used to determine which bridge arm of the fault phase has a fault and locate the faulty device.

[0035] In summary, the present application discloses a method for comprehensive identification of open-circuit faults of VIENNA rectifiers.

[0036] Compared with the prior art, the present invention has the following outstanding substantive features and significant progress:

[0037] (1) The fault identification method proposed in the present invention can accurately locate the open circuit faults of the rectifier diode and the power switch tube, and has fast diagnosis speed and high reliability, which can provide a basis for the subsequent fault tolerance of the system.

[0038] (2) No additional detection equipment is required, and the cost is low. The three-phase current i is detected by the built-in current sensor a 、i b and i c , perform fault diagnosis at low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. 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 creative work. The present invention is further described below in combination with the drawings and embodiments.

[0040] Figure 1 It is a three-phase six-switch VIENNA rectifier topology;

[0041] Figure 2 It is the open circuit fault diagnosis flow chart;

[0042] Figure 3 YesS a1 and D a1 Three-phase input current when an open circuit fault occurs;

[0043] Figure 4 YesS a1 When there is an open circuit fault, the simulation waveform of the counting variable and the fault location variable;

[0044] Figure 5 Yes D a1 When an open circuit fault occurs, the simulation waveform of the counting variable and the fault location variable is shown. DETAILED DESCRIPTION

[0045] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0046] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0047] The present invention is described in detail below with reference to the accompanying drawings and embodiments. Figure 1 The topological structure diagram of the three-phase six-switch VIENNA rectifier is shown in Figure 1. k1 is the upper bridge arm power switch tube, S k2 D is the lower bridge arm power switch tube; k1 is the upper bridge arm rectifier diode, D k2 It is the lower bridge arm rectifier diode (k is a, b, c).

[0048] The current sensor of the VIENNA rectifier is used to detect the instantaneous value of the three-phase input current and perform an inverse tangent function transformation to determine whether there is a zero-value platform in the three-phase input current after the inverse tangent function transformation. If there is a zero-value platform in any phase input current, the phase is determined to be a power switch tube fault phase; the duration of the 0-1 / 2 amplitude of the three-phase input current after the inverse tangent function transformation is determined. If the duration of the 0-1 / 2 amplitude of any phase input current is greater than the threshold, the phase is determined to be a rectifier diode fault phase. While determining the fault type and fault phase, a sliding window is used to calculate the current cycle mean and absolute average value, and the fault feature quantity D is constructed. nk . By judging D nk The positive and negative polarity of the fault phase is used to determine which bridge arm of the fault phase has a fault and locate the faulty device.

[0049] Step 1: Determine the fault type and fault phase

[0050] The current sensor of the VIENNA rectifier is used to detect the instantaneous value of the three-phase input current and perform an inverse tangent function transformation. The transformation formula is:

[0051] i nk =actan(i k )*2 / π(k=a,b,c) (1)

[0052] In the formula, i nk is the three-phase current after the inverse tangent function transformation. It can be seen from the formula that i nk The amplitude is in [-1,1], which avoids the influence of load on the diagnosis result.

[0053] Using the hysteresis comparison method, the boundary value i for detecting the zero value platform is set th , if -i th< i nk< i th , then the current can be considered to be 0. The zero value flag and amplitude flag are defined as εk1 , ε k2 , as shown in the formula:

[0054]

[0055] When ε k1 , ε k2 When it changes from 0 to 1, the zero value platform and amplitude detection program are triggered, and the counter C k1 and C k2 Start counting. In each sampling period, if the current meets the above action conditions, C k1 and C k2 Accumulate 1. When the above conditions are not met, the counter stops counting and clears to zero. The zero value and amplitude duration of the current are t k1 ,t k2 :

[0056] t k1 =C k1 T s , k=a,b,c (4)

[0057] t k2 =C k2 T s , k=a,b,c (5)

[0058] Where T s is the current sampling period, which can be selected as 0.0001s.

[0059] Define the fault indicator value as

[0060]

[0061] Where t th1 and t th2 is the time threshold. k1 =1, indicating that the k-phase power switch tube fails; R k1 =0, indicating that the k-phase power switch is normal; R k2 =1 indicates that the k-phase diode is faulty; R k2 =0 means the k-phase diode is normal.

[0062] Zero value platform judgment threshold t th1 According to GB14549-93 power quality standard, the total harmonic distortion rate of AC current should be less than 5%. Current threshold i th It can be obtained by formula (6).

[0063] i th =i H =5%*i1 (8)

[0064] In the formula, iH is the harmonic current, and i1 is the fundamental current amplitude.

[0065] Formula (9) is the natural zero change through -i th< i nk< i th The time required. In order to avoid the time threshold being too large or too small to affect the recognition speed and accuracy. Calculate through formula (9) to get t th1 Take 2t.

[0066] -5%i1≤i1 sin(2πf*t)≤5%i1 (9)

[0067] Where f is the current frequency.

[0068] The second step is to locate the faulty device.

[0069] The sliding window is used to calculate the current cycle mean and absolute average. In order to improve the accuracy and positioning speed of the positioning method, a sliding sampling window is used for data sampling, that is, each time a data is sampled, the window slides one bit to the right and updates the sampling window. The expression for updating the sampling data is:

[0070]

[0071] From equation (1) and equation (10), we can further obtain nk The normalized mean and absolute mean of are:

[0072]

[0073] Where k and j are sampling moments; N is the number of sampling points in one cycle.

[0074] Construct the fault location feature D based on the normalized average value and the absolute average value nk for:

[0075]

[0076] When it is determined that a rectifier diode or power switch of a phase has an open circuit fault, it is only necessary to nk The polarity of the input current can be determined by the rectifier diode or power switch tube. If the rectifier diode or power switch tube has an open circuit fault, the input current will be lost regardless of whether it is a positive half-cycle or a negative half-cycle. If the VIENNA rectifier operates normally, then D nk is 0; if the upper bridge arm fails, causing the positive half cycle of current to be missing, then D nk <0; if the lower bridge arm fails, causing the current negative half cycle to be missing, then D nk >0. Then, the fault bit identification value is defined as

[0077]

[0078] Where, d nk is the error threshold; R up =1 indicates that the upper bridge arm device is faulty, R down =1 indicates a low bridge arm device failure.

[0079] In a specific application scenario, the fault is set to 0.02s for S a1 and D a1 open circuit.

[0080] Please refer to Figure 4 The simulation results of the fault type and fault phase location obtained according to the above method are shown in FIG. 1. At 0.02s, the fault occurs and a zero value platform appears. The counter C a1 Rapidly increases, and after reaching the set threshold, that is, after the diagnosis time shown in the figure, R a1 If it is 1, it is determined that the power switch tube of phase A is open circuit fault.

[0081] Please refer to Figure 4 The simulation results of faulty device location obtained by the above method are shown in FIG. The fault occurs at 0.02s, and the fault location feature value D na Decreases rapidly. After reaching the set threshold, that is, after the diagnosis time shown in the figure, R up =1, the upper bridge arm power switch tube is open circuit fault.

[0082] In summary, in the first-level identification results, S a1 An open circuit fault has occurred.

[0083] Please refer to Figure 5 The simulation results of the fault type and fault phase location obtained according to the above method are shown in FIG. The fault occurs at 0.02s, and the counter C that detects the duration of the 0 to 1 / 2 amplitude is a2 Rapidly increases, and after reaching the set threshold, that is, after the diagnosis time shown in the figure, R a2 If it is 1, it is determined that the a-phase rectifier diode is open-circuit fault.

[0084] Please refer to Figure 5 The simulation results of faulty device location obtained by the above method are shown in FIG. The fault occurs at 0.02s, and the fault location feature value D na Decreases rapidly. After reaching the set threshold, that is, after the diagnosis time shown in the figure, R up =1, the upper bridge arm rectifier diode is open circuit fault.

[0085] In summary, in the first-level identification results, D a1 An open circuit fault has occurred.

[0086] In combination with the above specific application scenarios, it can be seen that the online identification method provided by this embodiment can realize reliable and timely identification of single-tube open-circuit faults occurring in VIENNA rectifiers, and is very suitable for popularization and use.

[0087] The above is only a specific embodiment 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 person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for comprehensive online identification of open circuit faults in VIENNA rectifiers, characterized by: The current sensor of the VIENNA rectifier is used to detect the instantaneous value of the three-phase input current and perform an inverse tangent function transformation. The open circuit fault type and fault phase are identified by using the transformed three-phase current detection amplitude information, and the fault side is located by combining it with the positive and negative polarity of the current mean value calculated by the sliding window. Determine whether there is a zero-value platform in the three-phase input current after the inverse tangent function transformation. If there is a zero-value platform in any phase input current, determine that the phase is a power switch tube fault phase; determine the duration of the 0-1 / 2 amplitude of the three-phase input current after the inverse tangent function transformation. If the duration of the 0-1 / 2 amplitude of any phase input current is greater than the threshold, determine that the phase is a rectifier diode fault phase; so far, the fault type and fault phase are identified; While determining the fault type and fault phase, a sliding window is used to calculate the current cycle mean and absolute average value, and the fault feature quantity D is constructed. nk ; By judging D nk The positive and negative polarity of the fault phase is used to determine which bridge arm of the fault phase has a fault and locate the faulty device.

2. The VIENNA rectifier open circuit fault comprehensive online identification method according to claim 1 is characterized in that: Performing arc tangent function transformation on the instantaneous value of the three-phase input current; The current sensor of the VIENNA rectifier is used to detect the instantaneous value of the three-phase input current and perform an inverse tangent function transformation; the transformation formula is: i nk =arctan(i k )*2 / π(k=a,b,c) (1) In the formula, i nk is the three-phase current after the inverse tangent function transformation; from the formula we can see that i nk The amplitude is in [-1,1], which avoids the influence of load on the diagnosis result.

3. The VIENNA rectifier open circuit fault comprehensive online identification method according to claim 2 is characterized in that: Identify the open circuit fault type and fault phase by detecting amplitude information; The hysteresis comparison method is used to set the boundary value i for detecting the zero value platform. th , if -i th< i nk< i th , the current can be considered to be 0 at this time; the zero value flag and amplitude flag are defined as ε k1 , ε k2 , as shown in the formula: When ε k1 , ε k2 When it changes from 0 to 1, the zero value platform and amplitude detection program are triggered, and the counter C k1 and C k2 Start counting; in each sampling period, if the current meets the above action conditions, C k1 and C k2 Accumulate 1; when the above conditions are not met, the counter stops counting and clears to zero; the zero value and amplitude duration of the current are t k1 ,t k2 : t k1 =C k1 T s , k=a,b,c (4) t k2 =C k2 T s , k=a,b,c (5) Where T s is the current sampling period; Define the fault indicator value as Where t th1 and t th2 is the time threshold; R k1 =1, indicating that the k-phase power switch tube fails; R k1 =0, indicating that the k-phase power switch is normal; R k2 =1 indicates that the k-phase diode fails; R k2 =0 means the k-phase diode is normal.

4. The VIENNA rectifier open circuit fault comprehensive online identification method according to claim 1 is characterized in that Zero value platform judgment threshold t th1 Determination of: According to GB14549-93 power quality standard, the total harmonic distortion rate of AC current should be less than 5%; the current threshold i th It can be obtained by formula (8); and th =i H =5%*i1 (8) In the formula, i H is the harmonic current, i1 is the fundamental current amplitude; Formula (9) is the natural zero change through |i th1 |The time required; In order to avoid the time threshold being too large or too small to affect the recognition speed and accuracy; t is calculated by formula (9); -5%i1≤i1 sin(2πf*t)≤5%i1 (9) Where f is the current frequency. To improve the accuracy and speed of identification, the zero-value platform judgment threshold t th1 Take 2t.

5. The VIENNA rectifier open circuit fault comprehensive online identification method according to claim 2 is characterized in that: The sliding window is used to calculate the current cycle mean and absolute average value; In order to improve the accuracy and speed of the positioning method, a sliding sampling window is used for data sampling, that is, each time a data is sampled, the window slides one position to the right and updates the sampling window once; the expression for updating the sampling data is: From equation (1) and equation (10), we can further obtain nk The normalized mean and absolute mean of are: Where k and j are sampling moments; N is the number of sampling points in one cycle.

6. The VIENNA rectifier open circuit fault comprehensive online identification method according to claim 5 is characterized in that: Fault characteristic quantity D nk Build: Construct the fault location feature D based on the normalized average value and the absolute average value nk for: When it is determined that a rectifier diode or power switch of a phase has an open circuit fault, it is only necessary to nk The polarity can be judged; after the rectifier diode or power switch tube has an open circuit fault, the input current will be missing regardless of the positive half-cycle or the negative half-cycle; If the VIENNA rectifier operates normally, then D nk is 0; if the upper bridge arm fails, causing the positive half cycle of current to be missing, then D nk <0; if the lower bridge arm fails, causing the current negative half cycle to be missing, then D nk >0; further, the fault location identification value is defined as Where, d nk is the error threshold; R up =1 indicates that the upper bridge arm device is faulty, R down =1 indicates a low bridge arm device failure.

7. The VIENNA rectifier open circuit fault comprehensive online identification method and device according to claim 1, characterized in that: The current conversion module is used to obtain the instantaneous amplitude of the three-phase input current of the rectifier in real time and perform an inverse tangent function transformation on the three-phase input current of the VIENNA rectifier; The fault type and fault phase identification module determines whether there is a zero-value platform in the three-phase input current after the inverse tangent function transformation. If there is a zero-value platform in any phase input current, the phase is determined to be a power switch tube fault phase; the duration of the 0-1 / 2 amplitude of the three-phase input current after the inverse tangent function transformation is determined. If the duration of the 0-1 / 2 amplitude of any phase input current is greater than the threshold, the phase is determined to be a rectifier diode fault phase; the fault type and fault phase identification are completed; The fault location module uses a sliding window to calculate the current cycle mean and absolute mean value while determining the fault type and fault phase, and constructs the fault feature quantity D nk ; By judging D nk The positive and negative polarity of the fault phase is used to determine which bridge arm of the fault phase has a fault and locate the faulty device.

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