Switched reluctance motor power converter fault diagnosis method based on phase current average value analysis

Abstract

The invention provides a switched reluctance motor power converter fault diagnosis method based on phase current average value analysis, relates to the field of motor driving system fault diagnosis, and mainly researches the diagnosis of an open-circuit fault and a short-circuit fault of a switched reluctance motor power converter. The method comprises the following steps: firstly, calculating an average value of each phase current in the same rotor rotation period in real time, taking the average value of the phase current as an open-circuit fault characteristic value, calculating a ratio of the average values of two adjacent phases as a short-circuit fault characteristic value, defining an asymmetry degree as a short-circuit fault phase judgment basis, and designing a corresponding diagnosis rule; a fault phase is positioned according to each value of the matrix; according to the method, fault detection can be accurately realized on the premise of reducing the operand and the number of sensors, fault detection can be performed on the electric driving system in real time, targeted maintenance can be performed on the system, the cost is reduced, and the method is suitable for the electric driving system consisting of switched reluctance motors with various phase numbers and power converters with various topological structures.

Description

Technical field:

[0001] The present invention relates to the field of motor drive system fault diagnosis, and in particular to a method for diagnosing faults of a switched reluctance motor used in electric vehicles. Background technology:

[0002] Switched reluctance motors (SRMs) have the advantages of a simple structure, a wide speed regulation range, and high starting torque, and have been widely used in electric vehicles and other industrial fields. Driven by advances in electronic power devices, digital control, and sensor technology, SRM drive systems now boast simple control methods, high operating efficiency, good fault tolerance, and low cost. In SRM drive systems, the power converter provides energy to the motor and is a key link in energy transmission. Furthermore, the power transistors in the power converter are constantly alternating between on and off during system operation, resulting in significant component losses and a high risk of failure. Therefore, the power converter is a key weak link in motor drive systems, and research on fault diagnosis of power converters is of great significance.

[0003] Existing fault diagnosis methods often require complex signal processing and multiple sensors, resulting in high computational complexity and high cost. Therefore, a simple and efficient fault diagnosis method is needed that reduces the computational complexity and the number of sensors while ensuring accurate diagnosis of open or short circuit faults in power converters. Summary of the invention:

[0004] In order to address the shortcomings of the above technical methods and accurately realize fault diagnosis and positioning while reducing the amount of calculation and the number of sensors, the present invention provides a switched reluctance motor power converter fault diagnosis method based on phase current average value analysis.

[0005] The present invention is implemented using the following design scheme: a switched reluctance motor power converter fault diagnosis method based on phase current average value analysis, which includes:

[0006] A fault diagnosis method for switched reluctance motor power converters based on phase current average analysis primarily includes a motor module, a power converter module, a controller module, a sensor module, a calculation module, and a fault diagnosis module. The diagnostic process involves collecting the stator winding phase currents within one rotor rotation cycle and calculating the average current value of each phase in real time. When the average current value falls below an open-circuit fault threshold, an open-circuit fault is determined in the power converter. Short-circuit faults require simultaneous analysis of the current characteristics of each phase. The asymmetry P is determined by comparing the ratio of the average current values ​​of two adjacent phases with the fault threshold. The position of the "1" in the asymmetry P can be used to determine a short-circuit fault in the power converter and pinpoint the location of the faulty phase.

[0007] Beneficial effects of the present invention:

[0008] 1. The present invention is not limited by the number of motor phases and the topology of the power converter, and can effectively perform fault diagnosis on switched reluctance motor systems with various phases.

[0009] 2. The fault diagnosis method proposed in the present invention does not require the addition of additional sensors during the fault information collection process, which can effectively reduce the complexity and cost of the diagnostic system.

[0010] 3. The present invention only needs to calculate the average value of each current, which has a small amount of calculation and is suitable for real-time diagnosis. It can perform targeted maintenance on the motor drive system in a timely manner and reduce loss costs.

[0011] 4. The fault diagnosis method proposed in the present invention can accurately diagnose the fault type and fault phase at different speeds. The modular design of each function is more concise and has a certain degree of robustness. Description of the drawings:

[0012] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0013] Figure 1 A schematic diagram of a fault diagnosis method for a switched reluctance motor power converter according to an embodiment of the present invention;

[0014] Figure 2 A simplified structural diagram of a switched reluctance motor drive system according to an embodiment of the present invention;

[0015] Figure 3 A topological structure diagram of a four-phase asymmetric half-bridge power converter of a switched reluctance motor drive system according to an embodiment of the present invention;

[0016] Figure 4 A flow chart of fault diagnosis of a switched reluctance motor power converter according to an embodiment of the present invention;

[0017] Figure 5 is the average value of the open-circuit fault current of phase A of the power converter when the motor speed is 600 r / min and 1200 r / min respectively in one embodiment of the present invention;

[0018] Figure 6 is the short-circuit fault characteristic value λ of the power converter phase A when the motor speed is 1200 r / min in one embodiment of the present invention. AB ;

[0019] Figure 7is the short-circuit fault characteristic value λ of the power converter phase A when the motor speed is 1200 r / min in one embodiment of the present invention. AC ;

[0020] Figure 8 is the short-circuit fault characteristic value λ of the power converter phase A when the motor speed is 1200 r / min in one embodiment of the present invention. AD ;

[0021] Figure 9 is the short-circuit fault characteristic value λ of the power converter phase A when the motor speed is 1200 r / min in one embodiment of the present invention. BC ;

[0022] Figure 10 is the short-circuit fault characteristic value λ of the power converter phase A when the motor speed is 1200 r / min in one embodiment of the present invention. BD ;

[0023] Figure 11 is the short-circuit fault characteristic value λ of the power converter phase A when the motor speed is 1200 r / min in one embodiment of the present invention. CD . Specific implementation method:

[0024] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0025] The purpose of the present invention is to provide a fault diagnosis method for a switched reluctance motor power converter based on the average value of the phase current. By real-time acquisition of the stator winding phase current, the average value of each phase current and the corresponding fault characteristic value are calculated, and open circuit faults and short circuit faults are diagnosed based on the comparison of the fault characteristic value with the fault threshold; the asymmetry P of the average current of two adjacent phases is calculated, and the short circuit fault phase is located according to the value of the asymmetry P.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1FIG. 1 is a schematic diagram of a fault diagnosis method for a switched reluctance motor power converter according to an embodiment of the present invention, comprising: step S100: collecting the current of each phase and calculating the average current value of each phase; step S200: after obtaining the average current value of each phase, obtaining the fault characteristic value; step S300: obtaining the asymmetry P by comparing the short-circuit fault characteristic value with the fault threshold; step S400: based on the fault characteristic value and the designed fault diagnosis criteria, jointly diagnosing the fault type and locating the fault phase by each phase.

[0028] like Figure 2 The figure shows a switched reluctance motor drive system that uses a current chopping control method. Figure 3 The figure shows the topological structure of a four-phase asymmetric half-bridge power converter, including switches, diodes, and windings. A, B, C, and D represent the four-phase windings; 3001 and 3002 are switches for phase A, 3003 and 3004 are switches for phase B, 3005 and 3006 are switches for phase C, and 3007 and 3008 are switches for phase D; 3009, 3010, 3011, 3012, 3013, 3014, 3015, and 3016 are all power converter diodes; 3017 is a power supply; and 3018 is a capacitor. The fault diagnosis method proposed by the present invention is shown in the following figure. Figure 4 shown.

[0029] In step S100, the current value of each phase winding of the switched reluctance motor is collected in real time by the current sensor, and the average value of the phase current after steady state is calculated. The current average value i is calculated according to formula 1.1. av :

[0030]

[0031] Where i av is the average value of the phase current; T is the phase current period, i is the phase current, and t represents time.

[0032] In step S200, when an open circuit fault occurs, the phase current quickly drops to zero, and the average value of the phase current also drops to zero. The average value of each current is used as the characteristic value of the open circuit fault; when i av =0, it is preliminarily judged that an open circuit fault occurs in this phase; if i av > 0, the short-circuit fault characteristic value is calculated; after a short-circuit fault occurs, the average current of the fault phase will be much larger than the average current of the other phases; taking the short circuit of phase A as an example, the short-circuit fault characteristic value λ is calculated according to formula 1.2 xy :

[0033]

[0034] Where λ AB is the short-circuit fault characteristic value, i ava is the average current of phase A, iavb is the average current of phase B, and the other phases are represented in the same way. xy The value is always greater than or equal to 1.

[0035] In step S300, the matrix E is defined according to formula 1.3. When the electric drive system operates normally, the values ​​of the matrix E are theoretically approximately equal to 1. When a short circuit fault occurs in phase A, the λ associated with the fault phase is AB ,λ AC ,λ AD It will increase significantly and be greater than the short-circuit fault threshold ε; while the other values ​​in E will increase slightly but not exceed the fault threshold ε; the analysis of other phases is similar.

[0036]

[0037] The current asymmetry P of each phase is defined according to formula 1.3:

[0038]

[0039] The value in formula 1.4 is determined by the relationship between the values ​​of formula 1.3 and the fault threshold, and the value is determined according to formula 1.5:

[0040]

[0041] In step S400, each phase is diagnosed independently based on the open circuit fault value obtained in step S200, and a short circuit fault simulation is performed on phase A. The simulation is performed at motor speeds of 600 r / min and 1200 r / min, respectively, with the fault occurring at 0.5s, to obtain the simulation results. Figure 5 As shown in the figure, the average current of the open-circuit fault of phase A of the power converter is when the motor speed is 600r / min and 1200r / min respectively. After the open-circuit fault occurs at different speeds, the average current value drops rapidly to below the open-circuit fault threshold in a short period of time, and the open-circuit fault of phase A is diagnosed.

[0042] The occurrence of the short-circuit fault and the location of the faulty phase are determined based on the phase current asymmetry P obtained in step S300. The diagnosis of the short-circuit fault requires a joint comparison of each phase. In order to prevent misjudgment, short-circuit diagnosis should be performed based on the various values ​​within the asymmetry P, under the premise that the current value of each phase is greater than or equal to the open-circuit fault threshold. When the electric drive system operates normally, the average current value of each phase has a symmetrical characteristic, and the values ​​in the asymmetry P are all "0". After a short-circuit fault occurs in phase A, each fault characteristic value will change to varying degrees. A short-circuit fault simulation is performed on phase A, with a rotation speed of 1200r / min and a fault set to occur at 0.5s to obtain the simulation results. Figures 6 to 11 As shown, it is the fault characteristic value λ when the motor speed is 1200r / min and phase A is short-circuitedAB ,λ AC ,λ AD ,λ BC ,λ BD and λ CD The characteristic value changes significantly in a short time after the fault occurs, and the characteristic values ​​related to phase A are all greater than the fault threshold ε. The other terms are greater than 1 and less than the fault threshold ε. According to formula 1.5, P AB 、P AC 、P AD The value of all is "1", and the rest are "0", which means that a short circuit fault occurs in phase A. The diagnosis of the other phases or multiple phases is similar. Equation 1.6 is the asymmetry P when phase A is short-circuited in a four-phase power converter. A :

[0043]

[0044] Through the above steps, the fault phase of the power converter can be quickly and accurately located, and the fault diagnosis of the switched reluctance motor power converter can be realized.

[0045] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A fault diagnosis method for a switched reluctance motor power converter based on phase current average value analysis, characterized in that: The method comprises: The current sensors of each phase are used to detect the current of each phase winding in real time and calculate the average current of each phase for subsequent calculation of fault characteristic values; After obtaining the average value of the phase current, the fault characteristic value is calculated and the corresponding fault judgment criteria are designed to realize the diagnosis and location of open circuit faults and short circuit faults.

2. The method for fault diagnosis of a switched reluctance motor power converter based on phase current average value analysis according to claim 1, wherein: After obtaining the current of each phase winding, the average phase current is calculated according to Formula 1, which includes: Where i av is the average phase current, T is the phase current period, i is the phase current, and t represents time.

3. The method for fault diagnosis of a switched reluctance motor power converter based on phase current average value analysis according to claim 1, wherein: The open circuit fault characteristic value is the average value of the phase current. If the average value of a phase current is lower than the set open circuit fault threshold, it is determined that an open circuit fault has occurred.

4. The method for fault diagnosis of a switched reluctance motor power converter based on phase current average value analysis according to claim 1, wherein: The ratio of the average current values ​​of each phase is calculated as the short-circuit fault characteristic value, which is calculated using Formula 2. Formula 2 includes: Where λ xy is the short-circuit fault characteristic value, i avx 、i avy and represent the average current of phase x and phase y respectively.

5. The method for fault diagnosis of a switched reluctance motor power converter based on phase current average value analysis according to claim 1, wherein: Construct an upper triangular matrix and define it as an asymmetric matrix. The values ​​of each matrix item are determined by formula 3, which includes: Where, P xy Represents the value in the asymmetry matrix, λ xy is the fault characteristic value, and ε is the short-circuit fault threshold.

6. The method for fault diagnosis of a switched reluctance motor power converter based on phase current average value analysis according to claim 5, characterized in that: When a short circuit fault occurs in different phases of the asymmetry matrix, all asymmetry values ​​related to the faulty phase are "1", while the other values ​​are "0", thereby locating the faulty phase.

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