Single-sensor phase current reconstruction for fault diagnosis of three-phase voltage source inverter

Abstract

The application provides a single-sensor phase current reconstruction three-phase voltage source inverter fault diagnosis method, solves the feasibility and diagnosis time of open-circuit fault diagnosis of the single-current sensor three-phase voltage source inverter, and comprises the following steps: firstly, analyzing the existing mechanism of the direct-current bus single-sensor current unobservable area, and the voltage vector synthesis mechanism under four types of faults, i.e. single-tube open circuit, different-phase same-side double-tube open circuit, different-phase different-side double-tube open circuit and same-phase double-tube open circuit; then, replacing the zero vector with two complementary effective voltage vectors, realizing reliable reconstruction of the fault phase current in the current unobservable area; finally, the inverter fault diagnosis method composed of three diagnosis criteria, i.e. the current vector phase angle, the average current vector modulus and the phase angle, realizes the fault diagnosis of the three-phase voltage source inverter under the single-current sensor. The application realizes the open-circuit fault diagnosis under the single-sensor phase current reconstruction, and the method can effectively and quickly locate the fault power tube.

Description

Technical Field

[0001] This invention relates to the field of inverter fault diagnosis technology, and in particular to a fault diagnosis method for a three-phase voltage source inverter with single-sensor phase current reconstruction. Background Technology

[0002] Single-sensor three-phase voltage source inverters can reduce system cost and size, and also eliminate the impact of parameter differences from multiple current sensors on control system performance. However, when its core component, the power switch, operates under high voltage and high current conditions, it may break due to thermal effects under overvoltage or overcurrent, leading to open-circuit faults. Therefore, conducting research on inverter fault diagnosis based on single-sensor phase current reconstruction to achieve rapid fault diagnosis and location is of great significance for improving inverter reliability.

[0003] Three-phase current information is an important parameter for inverter fault diagnosis. The core problem of single-sensor phase current reconstruction is to eliminate the influence of the unobservable current region. Existing research methods include vector pulse insertion method, phase shift method, complementary non-zero vector method, etc. The literature [Shen Yongpeng, Zheng Zhufeng, Yang Xiaoliang, et al. DC bus current sampling voltage space vector pulse width modulation[J]. Journal of Electrical Engineering, 2021, 36(08):1617-1627.] proposed a hybrid pulse width modulation method to ensure that the reconstructed current stably follows the actual current and improves the current distortion problem. The literature [GU YIKUN, NI FENGLEI, YANGDAPENG, et al. Switching-state phase shift method for three-phase-current reconstruction with a single DC-link current sensor[J]. IEEE Transactions on Industrial Electronics, 2011, 58(11):5186-5194.] used the phase shift method to increase the sampling time under non-zero voltage vector, but the asymmetry of PWM waveform in the unobservable region will lead to current distortion. References [SHEN Yongpeng, LIU Di, LIU Pu, et al. Error Self-calibration of Phase Current Reconstruction Based on Random Pulse Width Modulation[J]. IEEE Journal of Emerging and Selected switchable viewer in Power Electronics, 2022.] propose a hybrid pulse width modulation method with error self-calibration function, which realizes self-detection and self-calibration of current zero-point drift while eliminating the unobservable current region. The literature [Xiao Fei, Xu Guanda, Lian Chuanqiang, et al. Three-phase current reconstruction strategy of single current sensor system for permanent magnet synchronous motor [J]. Journal of Electrical Engineering, 2022, 37(7): 1609–1617.] proposes a single current sensor vector control strategy based on adaptive observer, which reduces the total harmonic distortion of current and torque error, but increases the computational burden of the processing unit.The literature [SHEN Yongpeng, LIU Di, LIANG Weihua, et al. Current Reconstruction of Three-phase Voltage Source Inverters Considering Current Ripple[J].IEEE Transactions on Transportation Electrification, 2022.] proposes a midpoint value random space vector pulse width modulation phase current reconstruction strategy to address the impact of current ripple on reconstruction accuracy. This method does not require the insertion of redundant voltage vectors and a large amount of computation, thus improving the current reconstruction accuracy.

[0004] For three-phase voltage source inverters, a single current sensor at the DC bus can reflect the phase current under any power switch fault. Traditional inverter fault diagnosis methods mainly rely on the extraction of phase current fault characteristic values. The literature [CECATIC, TOMMASO AO D, GENDUSO F, et al. Comprehensive Modeling and Experimental Testing of Fault Detection and Management of a Nonredundant Fault-Tolerant VSI[J].IEEE Transactions on Industrial Electronics,2015,62(6):3945-3954.] proposes a fault diagnosis method based on the slope of the current vector trajectory. This method extracts the vector phase angle characteristics through the Lissajous diagram of the current vector trajectory, thereby realizing the location of the faulty power transistor. However, it detects fewer fault types and has the risk of misdiagnosis. Reference [Yu Yong, Jiang Shengcheng, Yang Rongfeng, et al. Diagnosis method for open circuit faults of IGBTs in frequency converters [J]. Proceedings of the CSEE, 2011, 31(09): 30-35.] proposes a normalized inverter open circuit fault diagnosis method based on Fourier transform. It uses Fourier transform to separate the DC component and odd harmonics of single-phase current, and locates the faulty device based on the normalized DC component. However, it is not suitable for detecting open circuit faults of dual power switches. Reference [Zhang Jianghan, Zhao Jin, Zhou Dehong, et al. High-performance fault diagnosis in PWM voltage-source inverters for vector-controlled induction motor drives [J]. IEEE Transactions on Power Electronics, 2014, 29(11): 6087-6099.] proposes a normalization method that combines current error with the average value of the fundamental period of phase current. It can locate the faulty power transistor by setting an empirical threshold, but the diagnosis time requires more than two fundamental periods. The literature [Chen Yong, Liu Zhilong, Chen Zhangyong. A rapid diagnosis and location method for open circuit faults in inverters based on current vector feature analysis [J]. Journal of Electrical Engineering, 2018, 33(04): 883-891.] states that, based on the phase angle characteristics of the current vector after Park transformation, when a power switch fails, the scanning time of the sector where the fault is located will change, thereby realizing the location of different fault locations.Reference [ESPINOZA-TREJO DR, CAMPOS-DELGADO DU, Bossio G, et al. Fault diagnosis scheme for open-circuit faults in field-oriented control induction motordrives[J]. IET Power Electronics, 2013, 6(5): 869-877.] proposes a fault diagnosis method based on a nonlinear observer, which uses the stator current and residual obtained from the nonlinear observer for fault detection and location, but the diagnostic accuracy is greatly affected by the residual. Reference [An Quntao, Sun Li, Zhao Ke, et al. Inverter open-circuit fault diagnosis method based on switching function model[J]. Proceedings of the CSEE, 2010, 30(06): 1-6.] realizes the diagnosis of single-tube open-circuit faults and single-phase open-circuit faults by performing double Fourier transform spectrum analysis on the DC side current, but the diagnosis results are affected by noise disturbance. Reference [Cui Bowen, Ren Zhang. Fault diagnosis of three-phase inverter based on spectral estimation [J]. Journal of Electrical Engineering, 2009, 24(11): 192-198.] determines the faulty switching element and its fault nature based on spectral estimation and neural network, but the computational load is large and the real-time performance is poor. Reference [Chen Chaobo, Wang Xiaxia, Gao Song, et al. Open circuit fault diagnosis method of inverter based on interval sliding mode observer [J]. Proceedings of the CSEE, 2020, 40(14): 4569-4579+4736.] estimates the current value under normal conditions through sliding mode observer and locates the fault based on the actual system and the residual of the observer, which improves the robustness of the system, but is sensitive to the residual parameter. Summary of the Invention

[0005] To address the feasibility and time constraints of open-circuit fault diagnosis in single-current-sensor three-phase voltage source inverters, this invention proposes a fault diagnosis method for single-sensor phase current reconstruction in three-phase voltage source inverters. First, the existence mechanism of the unobservable region of the DC bus current by a single sensor is analyzed, along with the voltage vector synthesis mechanism under four types of faults: single-transistor open circuit, open circuit of two transistors on the same side but different phases, open circuit of two transistors on different phases and opposite sides, and open circuit of two transistors on the same phase. Then, two complementary effective voltage vectors replace the zero vector, achieving reliable reconstruction of the fault phase current within the unobservable current region. Furthermore, an inverter fault diagnosis method is constructed, consisting of three diagnostic criteria: current vector phase angle, average current vector magnitude, and phase angle, enabling fault diagnosis of three-phase voltage source inverters under a single current sensor.

[0006] The technical solution of this invention is implemented as follows:

[0007] A fault diagnosis method for a three-phase voltage source inverter based on single-sensor phase current reconstruction comprises the following steps:

[0008] Step 1: Analyze the existence mechanism of the unobservable region of the DC bus single sensor current, and the voltage vector synthesis mechanism under four types of faults: single tube open circuit, open circuit of two tubes on the same side of different phases, open circuit of two tubes on different phases and opposite sides, and open circuit of two tubes on the same phase.

[0009] Step 2: By replacing the original zero vector with a complementary non-zero vector, two new sampling windows that meet the minimum sampling time are provided within the carrier period, eliminating the influence of the unobservable region and realizing three-phase current reconstruction;

[0010] Step 3: Calculate the current vector phase angle, average current vector magnitude, and average current vector phase angle based on the reconstructed three-phase currents, and use the current vector phase angle, average current vector magnitude, and average current vector phase angle as diagnostic criteria to locate the fault and obtain the diagnostic results.

[0011] The mechanism for the existence of the unobservable region of the DC bus single-sensor current is as follows: Under SVPWM modulation, the switching state of each phase bridge arm switching device can be determined by the variable S. p (p∈{a, b, c}) represents the upper bridge arm conducting, denoted by S. p =1 indicates that S is used when the lower bridge arm is conducting. p =0 is used to represent; space voltage vector u i (S a S b S c ), i∈{0,1,2,3,4,5,6,7} represents 8 different switching states, including 6 effective voltage vectors and 2 zero voltage vectors; the entire working area can be divided into 6 sectors, each sector containing a normal region, a sector boundary and a low modulation region, where the normal region is the observable region, and the sector boundary and low modulation region are the unobservable regions.

[0012] In step two, the specific implementation method is as follows:

[0013] When the reference voltage vector u ref When located in the observable region, taking sector I as an example, the effective voltage vectors u1, u2 and the zero vector's action times T1, T2 and T0 are respectively:

[0014]

[0015] in, To adjust the system, U dc Indicates DC bus voltage; T s θ represents the carrier period; θ represents the phase angle range of the target vector.

[0016] When the reference voltage vector uref When located in the unobservable region, the zero voltage vectors u0 and u7 are replaced by complementary non-zero vectors u3 and u6, and their duration is:

[0017]

[0018] In complementary nonzero vector compensation, let the resultant voltage vector of sector I be u' ref :

[0019] u' ref T s = u1T1 + u2T2 + u3T3 + u6T6;

[0020] because Composite vector u' ref Satisfy: u' ref T s =u1T1+u2T2=u ref T s ;

[0021] The effective voltage vector u1(100) has an action time that satisfies the minimum sampling time T. min Located within the observable area, it can generate sampling point T. sam1 u2(110) does not satisfy the minimum sampling time T min Located in the unobservable region; at this time, according to the principle of complementary non-zero vector compensation, the zero voltage vectors u0 and u7 are replaced with complementary non-zero vectors u3 and u6, both with an action time of T0 / 2, and current sampling is performed when u6 is in action, with the sampling point being T. sam2 ;T sam1 and T sam2 Obtain the current i of phase A and phase C respectively are -i bre This enables three-phase current reconfiguration.

[0022] The minimum sampling time T min The expression is:

[0023] T min =T on +T db +T rise +T sr +T con ;

[0024] Among them, T on T is the on-time of the switching device. db T is the PWM dead time. con T is the A / D conversion time. rise T is the rise time of the current in the sampling circuit. sr This represents the slew rate of the operational amplifier.

[0025] The method for calculating the current vector phase angle, average current vector magnitude, and average current vector phase angle based on the reconstructed three-phase current is as follows:

[0026] Reconstructing three-phase current i are i bre i cre The two-phase components in the αβ coordinate system can be obtained through the Park transformation:

[0027]

[0028] Among them, i α i represents the α-axis current component after Park transformation. β Represents the β-axis current component after Park transformation; i represents i α and i β The resultant current vector in a two-phase coordinate system;

[0029] i α i β Average current vector within one cycle The formula for the average current vector synthesis is as follows:

[0030]

[0031] Where v = α, β, i v (n) represents the current vector, n represents the initial summation value, and N represents the final summation value. * The number of current samples within one cycle. The average current component along the α-axis; The average current component along the β axis; This represents the synthesized average current vector;

[0032] The phase angle of the current vector can be obtained using inverse trigonometric functions. Average current vector magnitude and average current vector phase angle They are respectively:

[0033]

[0034] When a three-phase voltage source inverter is operating normally in steady state, the i after Park transformation α and i β The resultant current vector i in the two-phase coordinate system rotates along a circular trajectory, i.e. Two-phase current i α and i β Average current vector over any period The value is 0; when one or two power switches experience an open-circuit fault, because part of the effective voltage vector cannot participate in vector synthesis, the trajectory of the current vector i changes, and the average current vector... modulus and phase angle It is not always 0.

[0035] The method for fault location based on current vector phase angle, average current vector magnitude, and average current vector phase angle to obtain diagnostic results is as follows:

[0036] Calculate the phase angle of the current vector i By comparison and Determine its trajectory;

[0037] Calculate the average current vector modulus and phase angle By comparison and and Locate the fault location;

[0038] Output fault location variable S dio Obtain the diagnosis results;

[0039] in, The current vector phase angle threshold, k = 1, 2, The threshold value for the average current vector magnitude is given by k' = 1, 2, 3. Where is the average current vector phase angle threshold, p is the fault location, and S is the average current vector phase angle threshold. dio S is the variable for fault location. dio The tens digit and units digit of the value correspond to the fault location, respectively.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1) This invention ensures that the current sampling time at the DC bus is greater than T by using two complementary effective non-zero vectors instead of the zero vector. min This enables reliable reconfiguration of fault phase currents within regions where current is unobservable.

[0042] 2) This invention uses an inverter fault diagnosis method based on current vector phase angle, average current vector magnitude and phase angle as diagnostic criteria, with a diagnosis time of 0.5ms, to achieve rapid location of faulty power transistors. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a block diagram of the DC bus single current sensor system for a three-phase voltage source inverter according to the present invention.

[0045] Figure 2 This is a diagram showing the spatial voltage vector and its distribution in various regions according to the present invention.

[0046] Figure 3 This is a schematic diagram of the normal region phase current sampling and reconstruction principle of the present invention.

[0047] Figure 4 The present invention provides voltage vector analysis under S2 fault; (a) is the current flow diagram under the action of u3(010), (b) is the current flow diagram under the action of u3(010), and (c) is the current flow diagram under the action of u3(010). 3S2 (010) Vector composite diagram, (d) is u 5S2 (001) Vector composite diagram, (e) is the voltage vector distribution diagram under S2 fault.

[0048] Figure 5 This invention provides voltage vector analysis under fault S1S3; (a) is the current flow diagram under the action of u4(011), (b) is the current flow diagram under the action of u6(101), and (c) is the current flow diagram under the action of u4(011). 4S13 (011) Vector composite diagram, (d) is u 6S13 (101) Vector composite diagram, (e) is the voltage vector distribution diagram under S1S3 fault.

[0049] Figure 6 For the voltage vector analysis under fault S1S4 of the present invention; (a) is the current flow diagram under the action of u2(110), (b) is the current flow diagram under the action of u5(001), (c) is the current flow diagram under the action of u2(110). 2S14 (110) Vector composite graph, (d) is u 5S14 (001) Vector composite diagram, (e) is the voltage vector distribution diagram under S1S4 fault.

[0050] Figure 7 For the voltage vector analysis under the S1S2 fault of the present invention; (a) is the current flow diagram under the action of u2 (110), (b) is the current flow diagram under the action of u3 (010), (c) is the current flow diagram under the action of u5 (001), (d) is the current flow diagram under the action of u6 (101), (e) is the current flow diagram under the action of u 2S12(110) Vector composite graph, (f) is u 3S12 (010) Vector composite diagram, (g) is u 5S12 (001) Vector composite diagram, (h) is u 6S12 (101) Vector composite diagram, (i) is the voltage vector distribution diagram under S1S2 fault.

[0051] Figure 8 This is a schematic diagram of the complementary nonzero vector compensation principle of the present invention.

[0052] Figure 9 This is a PWM waveform diagram under the complementary non-zero vector compensation of the present invention.

[0053] Figure 10 This is a flowchart of the fault diagnosis process of the present invention.

[0054] Figure 11 This serves as the experimental platform for the present invention.

[0055] Figure 12 This refers to the PWM waveform and sampling time within the unobservable region of each sector in this invention.

[0056] Figure 13 The waveforms of the actual and reconstructed three-phase currents under the S2 fault of this invention are shown.

[0057] Figure 14 The actual and reconstructed three-phase current waveforms under the S1S3 fault of this invention are shown.

[0058] Figure 15 The actual and reconstructed three-phase current waveforms under the S1S2 fault of this invention are shown.

[0059] Figure 16 This is a vector diagram of the current after an open-circuit fault, as presented in this invention.

[0060] Figure 17 The fault current vector phase angle is the one specified in this invention.

[0061] Figure 18 The average current vector magnitude of the present invention

[0062] Figure 19 The average current vector phase angle of this invention

[0063] Figure 20 This is the fault diagnosis result of the present invention. Detailed Implementation

[0064] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] This invention provides a fault diagnosis method for a three-phase voltage source inverter based on single-sensor phase current reconstruction, solving the feasibility and time issues of open-circuit fault diagnosis in a single-current sensor three-phase voltage source inverter. The steps are as follows: First, the existence mechanism of the unobservable region of the DC bus single-sensor current is analyzed, along with the voltage vector synthesis mechanism under four types of faults: single-transistor open circuit, open circuit of two transistors on the same side but different phases, open circuit of two transistors on different phases and opposite sides, and open circuit of two transistors on the same phase. Second, by replacing the original zero vector with a complementary non-zero vector, two new sampling windows satisfying the minimum sampling time are provided within the carrier cycle, eliminating the influence of the unobservable region and realizing three-phase current reconstruction. Finally, the phase angle of the current vector, the magnitude of the average current vector, and the phase angle of the average current vector are calculated based on the reconstructed three-phase current, and these three parameters are used as diagnostic criteria for fault location to obtain the diagnostic results. This achieves fault diagnosis of a three-phase voltage source inverter under a single current sensor.

[0066] The DC bus single-current sensor phase current reconstruction system reconstructs the three-phase current by time-division multiplexing the DC bus current information corresponding to the application of each voltage vector within one carrier cycle. Its system structure is as follows: Figure 1 As shown.

[0067] In SVPWM (Space Vector Pulse Width Modulation) modulation, the switching state of each phase bridge arm switching device can be determined by the variable S. p (p∈{a, b, c}) represents the upper bridge arm conducting, denoted by S. p =1 indicates that S is used when the lower bridge arm is conducting. p =0 is used to represent this. For example Figure 2 As shown, the space voltage vector u i (S a S b S c The $i \in {0, 1, 2, 3, 4, 5, 6, 7}$ represents 8 different switching states, containing 6 effective voltage vectors and 2 zero voltage vectors. The entire operating region can be divided into 6 sectors, each containing a normal region, a sector boundary, and a low-modulation region. The normal region is the observable region, while the sector boundary and low-modulation region are the unobservable regions. Figure 2 As shown.

[0068] Let the carrier period be T s Taking sector I as an example, in the normal region, the reference voltage vector u ref It can be synthesized from effective voltage vectors u1 and u2 and zero voltage vectors u0 and u7. For example... Figure 3 As shown, based on the effective voltage vectors u1 and u2, T is respectively... sam1 and T sam2 DC bus current i dc By sampling, the two-phase current i can be obtained. are and -i cre The third phase current i bre This can be derived from Kirchhoff's current law.

[0069] Based on the above method, the DC bus current under different voltage vectors in each sector is sampled, and the sampling results shown in Table 1 are obtained, thereby realizing phase current reconstruction.

[0070] Table 1 Voltage Vector and DC Bus Current

[0071]

[0072] In actual circuits, due to the on-time T of the switching device... on PWM dead time T db Due to the presence of this, the DC bus cannot immediately exhibit phase current under vector action. Simultaneously, it is affected by the AD conversion time T. con The current rise time T in the sampling circuit rise Operational amplifier voltage slew rate T sr Due to limitations, bus current sampling results typically require a certain amount of time to stabilize. Therefore, the shortest time required to accurately complete DC bus current sampling is defined as the minimum sampling time T. min ,

[0073] T min =T on +T db +T rise +T sr +T con (1)

[0074] In sectors where current is unobservable, such as sector boundaries and low-modulation regions, at least one effective voltage vector does not satisfy T. min Inaccurate current sampling is impossible. Therefore, the key to single-sensor phase current reconstruction is to ensure that there are two or more signals that meet the T signal in each carrier cycle. min Different effective voltage vectors.

[0075] Common open-circuit faults in three-phase voltage source inverters include single-tube open-circuit fault, open-circuit fault of two tubes on the same side but different phases, open-circuit fault of two tubes on different phases and different sides but different phases, and open-circuit fault of two tubes on the same phase, totaling 4 categories and 21 fault states, as shown in Table 2.

[0076] Table 2 Inverter Fault Types and Fault Locations

[0077]

[0078] (1) Single tube open circuit fault

[0079] Taking an open-circuit fault in phase S2 as an example, the voltage drop across phase b is U. dc / 2, the partial voltage of phase c is -U dc / 2. Under specific load conditions, the current flow direction under fault conditions is as follows: Figure 4 As shown in (a) and 4(b). At this time, u1, u2, u6, u0 and u7 are unaffected; u3(010) becomes like Figure 4 As shown in (c); u5(001) becomes like Figure 4 As shown in (d); u4(011) becomes a zero vector. Under this fault condition, only u1, u2, u6, and u... 3S2 and u 5S2 Synthesize the target vector, such as Figure 4 As shown in (e).

[0080] (2) Open circuit fault of two tubes on the same side of the opposite direction

[0081] Taking an open-circuit fault (S1S3) as an example, under a specific load, the current flow direction under the fault condition is as follows: Figure 5 As shown in (a) and 5(b). At this time, u5, u0, and u7 are unaffected; u4(011) becomes like Figure 5 As shown in (c); u6(101) becomes like Figure 5 As shown in (d); u1(100), u2(110), and u3(010) become zero vectors. Under this fault condition, only u5 and u... 4S13 and u 6S13 Synthesize the target vector, such as Figure 5 As shown in (e).

[0082] (3) Open circuit fault of two tubes with different phases and sides

[0083] Taking an open-circuit fault (S1S4) as an example, under a specific load, the current flow direction under the fault condition is as follows: Figure 6 As shown in (a) and 6(b). At this time, u3, u4, u0, and u7 are unaffected; u2(110) becomes like Figure 6As shown in (c); u5(001) becomes like Figure 6 As shown in (d); u1(100) and u6(101) become zero vectors. Under this fault condition, only u3, u4, and u 2S14 and u 5S14 Synthesize the target vector, such as Figure 6 As shown in (e).

[0084] (4) Open circuit fault of in-phase dual transistors

[0085] Taking an open-circuit fault (S1S2) as an example, under a specific load, the current flow direction under the fault condition is as follows: Figure 7 As shown in (a), 7(b), 7(c), and 7(d), u0 and u7 are unaffected at this time; u2(110) becomes... like Figure 7 As shown in (e); u3(010) becomes like Figure 7 As shown in (f); u5(001) becomes like Figure 7 As shown in (g); u6(101) becomes like Figure 7 As shown in (h). Under this fault condition, only u can be used. 2S12 u 3S12 u 5S12 and u 6S12 Synthesize the target vector, such as Figure 7 As shown in (e).

[0086] As shown in Table 3, when an open-circuit fault occurs, the phase angle range θ of the target vector is as follows, and the phase angle range of the current vector is also shown in Table 3. Same as θ.

[0087] Table 3 Voltage Vector Phase Angle Range under Fault Conditions

[0088]

[0089] As shown in Table 3, the phase angle ranges of the current vectors for different open-circuit faults overlap. Therefore, using only the phase angle range as a fault diagnosis criterion is not feasible.

[0090] When the reference voltage vector u ref When located within the observable region, taking sector I as an example, such as Figure 8 As shown in (a), the effective voltage vectors u1, u2 and the zero vector's action times T1, T2 and T0 are respectively:

[0091]

[0092]

[0093] Where M represents the modulation scheme, U dc Indicates DC bus voltage; T s θ represents the carrier period; θ represents the phase angle range of the target vector.

[0094] When the reference vector u ref When located in unobservable current regions such as sector boundaries and low-modulation regions, two new vectors satisfying T are provided within the carrier period by replacing the original zero vector with a complementary non-zero vector. min The sampling window eliminates the influence of unobservable areas. For example... Figure 8 As shown in (b), by replacing the zero voltage vectors u0 and u7 with complementary non-zero vectors u3 and u6, the duration of their action is,

[0095]

[0096] In the original SVPWM cycle,

[0097]

[0098] In complementary nonzero vector compensation, let the resultant voltage vector of sector I be u' ref :

[0099] u' ref T s =u1T1+u2T2+u3T3+u6T6 (6)

[0100] Furthermore,

[0101]

[0102] Composite vector u' ref satisfy:

[0103] u' ref T s =u1T1+u2T2=u ref T s (8)

[0104] It can be seen that u' ref The size and direction remain unchanged, which conforms to the volt-second balance principle.

[0105] like Figure 9 As shown, the effective voltage vector u1(100) has an action time that satisfies the minimum sampling time T. min Located within the observable area, it can generate sampling point T. sam1 u2(110) does not satisfy the minimum sampling time T minLocated in the unobservable region; at this time, according to the principle of complementary non-zero vector compensation, the zero voltage vectors u0 and u7 are replaced with complementary non-zero vectors u3 and u6, both with an action time of T0 / 2, and current sampling is performed when u6 is in action, with the sampling point being T. sam2 ;T sam1 and T sam2 Obtain the current i of phase A and phase C respectively are -i bre This enables three-phase current reconfiguration.

[0106] Reconstructing three-phase current i are i bre i cre The two-phase components in the αβ coordinate system can be obtained through the Park transformation:

[0107]

[0108] Among them, i α i represents the α-axis current component after Park transformation. β Represents the β-axis current component after Park transformation; i represents i α and i β The resultant current vector in a two-phase coordinate system.

[0109] i α i β Average current vector within one cycle The formula for the average current vector synthesis is as follows:

[0110]

[0111] Where, v = α,β i v (n) represents the current vector, n represents the initial summation value, and N represents the final summation value. * The number of current samples within one cycle. The average current component along the α-axis; The average current component along the β axis; This represents the average current vector after synthesis.

[0112] The phase angle of the current vector can be obtained using inverse trigonometric functions. Average current vector magnitude and average current vector phase angle They are respectively:

[0113]

[0114] When a three-phase voltage source inverter is operating normally in steady state, the i after Park transformation α and i βThe resultant current vector i in the two-phase coordinate system rotates along a circular trajectory, i.e. Two-phase current i α and i β Average current vector over any period The value is 0; when one or two power switches experience an open-circuit fault, because part of the effective voltage vector cannot participate in vector synthesis, the trajectory of the current vector i changes, and the average current vector... modulus and phase angle It is not always 0.

[0115] The diagnostic criterion intervals shown in Table 4 can be obtained by calculating the average current vector under each fault condition. Analysis reveals that the average current vector... modulus It can be used as a diagnostic criterion to distinguish fault types, and its phase angle The fault location range was further subdivided.

[0116] Table 4 Average Current Vector Diagnostic Criterion Interval

[0117]

[0118] The specific fault diagnosis process is as follows: Figure 10 As shown. First, calculate the phase angle of the current vector i. By comparison and First, determine its trajectory; second, calculate the average current vector. modulus and phase angle By comparison and and Locate the fault location; finally, output the fault location variable S. dio The diagnosis results were obtained. Among them, The current vector phase angle threshold, k = 1, 2, The threshold value for the average current vector magnitude is given by k' = 1, 2, 3. Where is the average current vector phase angle threshold, p is the fault location, and S is the average current vector phase angle threshold. dio S is the variable for fault location. dio The tens digit and units digit of the value correspond to the fault location, respectively.

[0119] Experiment and Results Analysis

[0120] Experimental platform such as Figure 11As shown in Table 5. In the experiment, the PWM carrier frequency was set to 10kHz. During three-phase current reconstruction, the sampling signal was sampled twice per cycle at a sampling frequency of 20kHz. The experiment used a three-phase induction motor MODVK48T17D200K, whose parameters are shown in Table 5. Experimental data were acquired using an A150 current probe and an MDA805A electric drive analyzer.

[0121] Table 5 Parameters of Three-Phase Induction Motor

[0122]

[0123] PWM signals and sampling pulses for each sector are as follows Figure 12 As shown in (a)-(f), it can be seen that under different voltage vectors at the sector boundary, the position of the sampling point dynamically changes with the current observation window, and the sampling window satisfies T min Require.

[0124] To verify the phase current reconstruction effect after a fault, open-circuit faults were set up in S2, S1S3, and S1S2 respectively in the experiment. The experimental results are as follows: Figure 14 , 15 As shown in Figure 16, the reconstructed three-phase current after a fault can still accurately track the actual current changes.

[0125] To more intuitively represent the phase angle range of the current vector, such as Figure 16 As shown in (a), the Park transformation is performed on the reconstructed three-phase current after the fault to obtain the current vector in the two-phase coordinate system, where the subscript of the current vector i is the fault location. It can be found that the current vector rotates within the corresponding phase angle range.

[0126] Figure 17 The figure shows the vector phase angles under various faults obtained by inverse trigonometric functions. When the current vector is located at the coordinate axis boundary, it will cause errors in the inverse trigonometric function calculation, i.e. It can only be used as a diagnostic criterion for the trajectory of current vector motion.

[0127] Will Figure 16 (a) The average current vector diagram can be obtained by averaging the current vector with a period of 0.067s, as shown below. Figure 16 As shown in (b). Average current vector magnitude and phase angle like Figure 18 , 19 As shown, both can respond to and distinguish fault types, and can be used as diagnostic criteria.

[0128] Set the occurrence time t of various faults in the experiment. on =0.067s, fault diagnosis results are as follows Figure 20As shown, the system responded to the fault at t = 0.0675s and correctly identified the fault type, with a diagnosis time of 0.5ms.

[0129] To address the feasibility and time constraints of single-sensor open-circuit fault diagnosis in three-phase voltage source inverters, this embodiment proposes a fault diagnosis strategy based on complementary non-zero vector compensation and average current vector single-sensor phase current reconstruction. Experimental verification demonstrates the effectiveness of the proposed strategy in the following ways: (1) By using two complementary effective non-zero vectors instead of a zero vector, the current sampling time at the DC bus is ensured to be greater than T. min (2) By adopting the inverter fault diagnosis method with current vector phase angle, average current vector magnitude and phase angle as diagnostic criteria, the diagnosis time is 0.5ms, and the fault power tube is quickly located.

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fault diagnosis method for a three-phase voltage source inverter with single-sensor phase current reconstruction, characterized in that, The steps are as follows: Step 1: Analyze the existence mechanism of the unobservable region of single sensor current on DC bus, and the voltage vector synthesis mechanism under four types of faults: single tube open circuit, open circuit of two tubes on the same side of different phases, open circuit of two tubes on different sides of different phases, and open circuit of two tubes on the same phase. Step 2: By replacing the original zero vector with a complementary non-zero vector, two new sampling windows that meet the minimum sampling time are provided within the carrier period, eliminating the influence of the unobservable region and realizing three-phase current reconstruction; Step 3: Calculate the current vector phase angle, average current vector magnitude, and average current vector phase angle based on the reconstructed three-phase currents, and use the current vector phase angle, average current vector magnitude, and average current vector phase angle as diagnostic criteria to locate the fault and obtain the diagnostic results. The method for calculating the current vector phase angle, average current vector magnitude, and average current vector phase angle based on the reconstructed three-phase current is as follows: Reconstructing three-phase current i are i bre i cre The two-phase components in the αβ coordinate system can be obtained through the Park transformation: ； Among them, i α i represents the α-axis current component after Park transformation. β Represents the β-axis current component after Park transformation; i represents i α and i β The resultant current vector in a two-phase coordinate system; i α i β Average current vector over one period The formula for the average current vector synthesis is as follows: ； in, , Represents the current vector. N represents the termination value of the summation. * The number of current samples within one cycle. The average current component along the α-axis; The average current component along the β axis; This represents the synthesized average current vector; The phase angle φ of the current vector and the magnitude of the average current vector can be obtained using inverse trigonometric functions. and average current vector phase angle They are respectively: ； When a three-phase voltage source inverter is operating normally in steady state, the i after Park transformation α and i β The resultant current vector i in the two-phase coordinate system rotates along a circular trajectory, i.e., φ∈[-180°]. ° 180 ° Two-phase current i α and i β Average current vector over any period The value is 0; when one or two power switches experience an open-circuit fault, because part of the effective voltage vector cannot participate in vector synthesis, the trajectory of the current vector i changes, and the average current vector... modulus and phase angle It is not always 0.

2. The fault diagnosis method for a three-phase voltage source inverter based on single-sensor phase current reconstruction according to claim 1, characterized in that, The mechanism for the existence of the unobservable region of the DC bus single-sensor current is as follows: Under SVPWM modulation, the switching state of each phase bridge arm switching device is determined by the variable S. p Let p∈{a, b, c}, and S be the signal when the upper arm is conducting. p =1 indicates that S is used when the lower bridge arm is conducting. p =0 is used to represent the space voltage vector u. i (S a S b S c ), i∈{0,1,2,3,4,5,6,7} represents 8 different switching states, including 6 effective voltage vectors and 2 zero voltage vectors; the entire working area is divided into 6 sectors, each sector contains a normal region, a sector boundary and a low modulation region, where the normal region is the observable region, and the sector boundary and low modulation region are the unobservable regions.

3. The fault diagnosis method for a three-phase voltage source inverter based on single-sensor phase current reconstruction according to claim 2, characterized in that, In step two, the specific implementation method is as follows: When the reference voltage vector u ref When located in the observable region, taking sector I as an example, the effective voltage vectors u1, u2 and the zero vector's action times T1, T2 and T0 are respectively: ； in, In order to adjust the system, Indicates the DC bus voltage; T s θ represents the carrier period; θ represents the phase angle range of the target vector. When the reference voltage vector u ref When located in the unobservable region, the zero voltage vectors u0 and u7 are replaced by complementary non-zero vectors u3 and u6, and their duration is: ； In complementary nonzero vector compensation, let the resultant voltage vector of sector I be u' ref : ； because , synthesized vector u' ref satisfy: ; The effective voltage vector u1(100) has an action time that satisfies the minimum sampling time T. min Located within the observable area, it can generate sampling point T. sam1 u2(110) does not satisfy the minimum sampling time T min Located in the unobservable region; at this time, according to the principle of complementary non-zero vector compensation, the zero voltage vectors u0 and u7 are replaced with complementary non-zero vectors u3 and u6, both with an action time of T0 / 2, and current sampling is performed when u6 is in action, with the sampling point being T. sam2 ;T sam1 and T sam2 Obtain the current i of phase A and phase C respectively are -i bre This enables three-phase current reconfiguration.

4. The fault diagnosis method for a three-phase voltage source inverter based on single-sensor phase current reconstruction according to claim 3, characterized in that, The minimum sampling time T min The expression is: ； Among them, T on T is the on-time of the switching device. db T is the PWM dead time. con T is the A / D conversion time. rise T is the rise time of the current in the sampling circuit. sr This represents the slew rate of the operational amplifier.

5. The fault diagnosis method for a three-phase voltage source inverter based on single-sensor phase current reconstruction according to claim 1, characterized in that, The method for fault location based on current vector phase angle, average current vector magnitude, and average current vector phase angle to obtain diagnostic results is as follows: Calculate the phase angle φ of the current vector i by comparing φ with φ pk Determine its trajectory; Calculate the average current vector modulus and phase angle By comparison and , and Locate the fault location; Output fault location variable S dio Obtain the diagnosis results; Where, φ pk The current vector phase angle threshold, k=1,2, The threshold value for the average current vector magnitude. , Where is the average current vector phase angle threshold, p is the fault location, and S is the average current vector phase angle threshold. dio S is the variable for fault location. dio The tens digit and units digit of the value correspond to the fault location, respectively.

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