Method and system for diagnosing open-circuit fault and current sensor fault based on phase current spatial distribution

Abstract

The invention discloses an open-circuit fault and current sensor fault diagnosis method and system based on phase current space distribution, and the method comprises the steps: enabling six-phase current of a dual three-phase permanent magnet synchronous motor to output a pair of mutually orthogonal signals through a second-order generalized integrator, and inputting the signals into a phase-locked loop; extracting the phase of each phase current when the dual three-phase permanent magnet synchronous motor has an open-circuit fault and a current sensor fault; according to different change amplitudes of the phase of each phase of phase current after faults occur in different phases, a diagnosis variable is set, a fault positioning criterion is formulated by using the change amplitudes of the diagnosis variable when the fault phases are different, and the fault phases are positioned; identifying the fault type of the fault phase by using the zero-sequence current and a second-order difference operator; and quantitatively describing the fault degree according to the phase difference after the fault occurs. According to the diagnosis method provided by the invention, faults and open-circuit faults of a plurality of current sensors can be comprehensively diagnosed only by processing the phase current, and fault phases can be quickly and accurately positioned and fault types can be quickly and accurately distinguished under steady-state and dynamic conditions.

Description

Technical Field

[0001] The present invention belongs to the field of multi-phase permanent magnet synchronous motor drive control application, and in particular relates to an open circuit fault and current sensor fault diagnosis method of a dual three-phase permanent magnet synchronous motor based on phase current spatial distribution. Background Art

[0002] With the increasing requirements for the power level and reliability of motor speed control systems in some application fields, the limitations of traditional three-phase motors have gradually become prominent, and multi-phase motors have gradually received extensive attention and research from academia and industry. On the other hand, with the rapid development of power electronics technology and modern control theory, AC transmission systems have widely adopted power electronic converters for motor control, and the number of motor phases is no longer limited by the number of power grid phases. At present, multi-phase motors have gradually been used in some fields with relatively high requirements for reliability, power level and power density, such as aerospace, ship propulsion, rail transportation, electric vehicles, etc. Common faults of dual three-phase permanent magnet synchronous motors include open circuit faults, current sensor faults, etc. These faults will cause system performance to degrade or even cause the entire drive system to fail.

[0003] In order to improve the reliability and stability of dual three-phase permanent magnet synchronous motors, it is of great significance to study fault diagnosis strategies. Chinese patent CN110726962A discloses a method for diagnosing gain faults of current sensors of permanent magnet linear motors. The method uses an observer to obtain an estimated dq axis current and compares it with the dq axis current obtained by the actual measurement value of the current sensor, thereby achieving diagnosis and positioning. Chinese patent CN111458666A discloses a method for diagnosing open circuit faults of permanent magnet synchronous motor windings. It collects several bits of current data at equal time intervals to form the original sequence of the gray prediction model, and substitutes the original sequence into the mathematical model of gray prediction to predict the current data at the next moment, and then makes a difference between the predicted data and the original data and compares it with the set threshold value to determine whether it is a fault and feedback the fault signal. The above methods are all for a single current sensor or open circuit fault, but the characteristics of the open circuit fault and the current sensor disconnection fault are similar. In addition, the multi-phase permanent magnet synchronous motor contains a harmonic plane, which must be controlled during the operation of the drive system, otherwise it is not conducive to the performance of the motor and generates large losses. Therefore, the above method may not be applicable to the field of multi-phase permanent magnet synchronous motor control.

[0004] In order to achieve the goal of combining the open-circuit fault of a multi-phase permanent magnet synchronous motor with the current sensor fault diagnosis and further expand the scope of the current sensor fault diagnosis, relevant research is urgently needed. Summary of the invention

[0005] In view of this, the present invention provides a method for diagnosing open circuit faults and current sensor faults of a dual three-phase permanent magnet synchronous motor based on the spatial distribution of phase current. Multiple current sensor faults and open circuit faults can be comprehensively diagnosed only by processing the phase current, and the proposed fault identification method can be combined with other fault location methods for diagnosis.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A method for open circuit fault and current sensor fault diagnosis based on phase current spatial distribution:

[0008] The six-phase current of the dual three-phase permanent magnet synchronous motor outputs a pair of mutually orthogonal signals through a second-order generalized integrator, which are input into a phase-locked loop, and the phase of each phase current when an open circuit fault or a current sensor fault occurs in the dual three-phase permanent magnet synchronous motor is extracted by the phase-locked loop;

[0009] According to the different change ranges of the phase current of each phase after a fault occurs in different phases, a diagnostic variable is established, and the fault location criterion is formulated by using the change range of the diagnostic variable when the fault phase is different to locate the fault phase;

[0010] The fault type of the fault phase is identified using zero-sequence current and second-order difference operator;

[0011] The fault severity is quantitatively described based on the phase difference after the fault occurs.

[0012] Furthermore, the diagnostic variable is:

[0013]

[0014] Among them, θ A represents the phase of the A-phase current extracted by the phase-locked loop, θ B Indicates the phase of the B-phase current extracted by the phase-locked loop, θ C represents the phase of the C-phase current extracted by the phase-locked loop, θ D represents the phase of the D-phase current extracted by the phase-locked loop, θ E represents the phase of the E-phase current extracted by the phase-locked loop, θ F represents the phase of the F phase current extracted by the phase-locked loop, △θ1 represents the phase difference between the BC phase currents, △θ2 represents the phase difference between the AC phase currents, △θ3 represents the phase difference between the AB phase currents, △θ4 represents the phase difference between the EF phase currents, △θ5 represents the phase difference between the DF phase currents, △θ6 represents the phase difference between the DE phase currents, and the diagnostic variable Δθ n ={Δθ1,Δθ2,Δθ3,Δθ4,Δθ5,Δθ6}.

[0015] Furthermore, the fault location criterion is:

[0016] When the dual-three-phase permanent magnet synchronous motor is operating normally, Max{Δθ n}<g, and the fault flag F x of each phase is 0;

[0017] When a fault occurs in phase A of the dual-three-phase permanent magnet synchronous motor, Max{Δθ n} = Δθ1 > g, and the fault flag F A of phase A is 1;

[0018] When a fault occurs in phase B of the dual-three-phase permanent magnet synchronous motor, Max{Δθ n} = Δθ2 > g, and the fault flag F B of phase B is 1;

[0019] When a fault occurs in phase C of the dual-three-phase permanent magnet synchronous motor, Max{Δθ n} = Δθ3 > g, and the fault flag F C of phase C is 1;

[0020] When a fault occurs in phase D of the dual-three-phase permanent magnet synchronous motor, Max{Δθ n} = Δθ4 > g, and the fault flag F D of phase D is 1;

[0021] When a fault occurs in phase E of the dual-three-phase permanent magnet synchronous motor, Max{Δθ n} = Δθ5 > g, and the fault flag F E of phase E is 1;

[0022] When a fault occurs in phase R of the dual-three-phase permanent magnet synchronous motor, Max{Δθ n} = Δθ6 > g, and the fault flag F F of phase F is 1;

[0023] Among them, g represents the set threshold.

[0024] Furthermore, the fault type is determined by the fault flag F x of a certain phase of the motor, the fault type diagnosis variables Y x and Z, and the sampled phase current i x' Specifically:

[0025] When F x = 1 and Z = 0, an open circuit fault occurs in the dual-three-phase permanent magnet synchronous motor;

[0026] When F x = 1, Z = 1, Y x = 0, and i x' = 0, a current sensor disconnection fault occurs in the dual-three-phase permanent magnet synchronous motor;

[0027] When F x =1, Z=1, Y x =1, the current sensor gain fault occurs in the dual three-phase permanent magnet synchronous motor;

[0028] When F x =1, Z=1, Y x =0, i x' =C', a current sensor stuck fault occurs in the dual three-phase permanent magnet synchronous motor, where C' is a constant not equal to 0.

[0029] Furthermore, the fault type diagnosis variable Y x satisfy:

[0030]

[0031] Wherein, N is the moving average value of the phase current, which is determined based on the principle that when the current sensor fails, the zero-sequence current is not always 0, and when there is an open circuit fault, the zero-sequence current is 0; ε1 is the set threshold.

[0032] Furthermore, the Where T represents the electrical cycle, i A 、i B 、i C 、i D 、i E 、i F Indicates the phase current.

[0033] Furthermore, the fault type diagnosis variable Z satisfies:

[0034]

[0035] Among them, h is the diagnostic variable is the moving average value, and ε2 is the set threshold.

[0036] Further, taking phase A as an example:

[0037] When an open circuit fault occurs in phase A of a dual three-phase permanent magnet synchronous motor, the phase current of phase B Phase current of phase C

[0038] When the current sensor of phase A of the dual three-phase permanent magnet synchronous motor is disconnected, the current of each phase is expressed as:

[0039]

[0040]

[0041] Among them, i qrepresents the q-axis current of the dual three-phase permanent magnet synchronous motor in the rotating coordinate system, θ e represents the rotor position angle;

[0042] When a current sensor gain fault occurs in phase A of a dual three-phase permanent magnet synchronous motor, the phase current of each phase is expressed as:

[0043]

[0044] Among them, k represents the gain coefficient, the intermediate quantity θ f Satisfy |θ B -θ C |=2θ f ,θ B Indicates the phase of the B-phase current extracted by the phase-locked loop, θ C Indicates the phase of the C-phase current extracted by the phase-locked loop;

[0045] When the current sensor of phase A of the dual three-phase permanent magnet synchronous motor is stuck, the phase current of each phase is expressed as:

[0046]

[0047] Wherein, C represents the hysteresis coefficient.

[0048] Furthermore, when a gain fault occurs in phase A, the relationship between the gain coefficient k and the phase difference between the phase currents of phases B and C is:

[0049]

[0050] The magnitude of the gain coefficient k describes the extent of the gain failure.

[0051] A system for diagnosing open circuit faults and current sensor faults based on phase current spatial distribution, comprising:

[0052] The integral average module is used to integrate the fault identification factor. When the integral value is greater than the set threshold, the fault identification factor is set to 1.

[0053] The fault diagnosis and positioning module is used to diagnose and locate open circuit faults and current sensor faults.

[0054] The beneficial effects of the present invention are:

[0055] 1) The present invention sets up diagnostic variables according to the different change amplitudes of the phase currents of each phase after a fault occurs in different phases, and formulates fault location criteria by using the change amplitudes of the diagnostic variables at different fault phases to locate the fault phase; uses zero-sequence current and a second-order differential operator to identify the fault type of the fault phase; after locating the fault phase and identifying the fault type, quantitatively describes the fault degree according to the phase difference after the fault, which can better meet the requirements of fault detection in dynamic conditions.

[0056] 2) The present invention analyzes the current conditions of each phase after an open circuit fault and a current sensor fault, formulates a fault location criterion, and provides the real current after the fault, which can be used for subsequent fault-tolerant control of the motor.

[0057] 3) The present invention can distinguish between faults only by analyzing the phase current and can effectively locate the faults, and the implementation method is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a structural block diagram of the control and open circuit and current sensor fault diagnosis of the dual three-phase permanent magnet synchronous motor drive system of the present invention;

[0059] Figure 2 This is a structural block diagram of the drive system under fault conditions described in the present invention;

[0060] FIG3( a ) is a spatial distribution diagram of currents of each phase when the A phase current sensor is disconnected according to the present invention;

[0061] FIG3( b ) is a spatial distribution diagram of currents of each phase under a positive gain fault of the A-phase current sensor according to the present invention;

[0062] FIG3( c ) is a spatial distribution diagram of currents of each phase under a negative gain fault of the phase A current sensor according to the present invention;

[0063] FIG3( d ) is a spatial distribution diagram of currents of each phase under a stuck fault of the A-phase current sensor according to the present invention;

[0064] Figure 4 This is the structural diagram of the SOGI of the present invention;

[0065] Figure 5 This is a structural diagram of the phase-locked loop of the present invention;

[0066] Figure 6 This is a flow chart of the current sensor and open circuit fault diagnosis of the present invention;

[0067] FIG. 7( a ) is an experimental diagram of the A-phase open circuit fault diagnosis result of the present invention;

[0068] FIG7( b ) is an experimental diagram of the A-phase current sensor disconnection fault diagnosis result of the present invention;

[0069] FIG. 7( c ) is an experimental diagram of the diagnosis result of the gain fault (k=2) of the phase A current sensor according to the present invention;

[0070] FIG. 7( d ) is an experimental diagram of the diagnosis results of the A-phase current sensor stuck fault (C=2) according to the present invention. DETAILED DESCRIPTION

[0071] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0072] The present invention proposes a method for diagnosing open circuit fault and current sensor fault of a dual three-phase permanent magnet synchronous motor based on the spatial distribution of phase current. Figure 1 The structure shown includes system hardware and system software. The system hardware includes dual three-phase permanent magnet synchronous motors, SVPWM modules, inverters, position sensors, and current sensors. The system software includes speed controllers, current controllers, coordinate transformation modules, integral average modules, and fault diagnosis and positioning modules.

[0073] The two sets of three-phase windings of the dual three-phase permanent magnet synchronous motor have a spatial phase difference of 30°; the inverter is a six-phase two-topology structure, the input end of the inverter is connected to the DC current source, the signal end of the inverter is connected to the SVPWM module, and the output end of the inverter is connected to the A, B, C, D, E, and F phases of the dual three-phase permanent magnet synchronous motor, which is responsible for converting the PWM signal into the six-phase sinusoidal alternating current required to drive the motor; the position sensor uses a resolver transformer, which is coaxially connected to the dual three-phase permanent magnet synchronous motor to collect the mechanical angular velocity of the motor; the current sensor is connected to the inverter, which is responsible for collecting the six-phase current of the dual three-phase permanent magnet synchronous motor.

[0074] The speed controller is controlled by PI to obtain the dq-axis reference current required by the dual three-phase permanent magnet synchronous motor; the current controller is controlled by PI to obtain the dq-axis voltage and the xy-axis reference voltage; the coordinate conversion module is used to convert the six-phase current in the natural coordinate system into the current in the rotating coordinate system to achieve decoupling control; the integral average module is used to integrate the fault identification factor, and when its integral value is greater than the set threshold, the fault identification factor is set to 1; the fault diagnosis and positioning module is used to diagnose and locate open circuit faults and current sensor faults.

[0075] The specific implementation steps of the proposed open circuit fault and current sensor fault diagnosis method of a dual three-phase permanent magnet synchronous motor based on phase current spatial distribution include:

[0076] Step 1) According to the VSD matrix and Kirchhoff's law, the spatial distribution of phase current when different faults occur in each phase of the dual three-phase permanent magnet synchronous motor is derived.

[0077] Step 1.1) Use the VSD coordinate transformation method to decompose the various vector spaces of the dual three-phase permanent magnet synchronous motor into three mutually orthogonal subspaces, namely the α-β subspace, the xy subspace, and the zero-sequence subspace. The vector space decomposition (VSD) matrix can be expressed as:

[0078]

[0079] Step 1.2) The six-phase current of the dual three-phase permanent magnet synchronous motor collected by the current sensor is expressed as the current in the α-β subspace in the form of two sets of coordinates, the two sets of coordinates are α1-β1 and α2-β2, and the relationship between the coordinates α1-β1, α2-β2 and α-β, xy subspace is as follows:

[0080]

[0081] Among them, i A 、i B 、i C 、i D 、i E 、i F are the phase currents of the dual three-phase permanent magnet synchronous motor, i α1 represents the α1-axis current in the α subspace, i β1 represents the β1-axis current in the β subspace, i α2 represents the α2-axis current in the α subspace, i β2 represents the β2-axis current in the β subspace, i α represents the α-axis current in the α-subspace, i β represents the β-axis current in the β subspace, i x represents the x-axis current in the harmonic subspace, i y represents the y-axis current of the harmonic subspace;

[0082] It should be noted that in the healthy state of the motor, each three-phase winding of the dual three-phase permanent magnet synchronous motor contributes half of the power. Therefore, the relationship between the α-β and xy subspaces can be rewritten as follows:

[0083]

[0084] Step 1.3) Take phase A as an example. When an open circuit fault occurs in phase A, the feedback of the current sensor of phase A is zero, and the current in the winding is also zero. Using Kirchhoff's law, the relationship between the phase currents of the dual three-phase permanent magnet synchronous motor can be derived as follows:

[0085] i B +i C =0 (5)

[0086] i D +i E +i F =0 (6)

[0087] In the case of an open-circuit fault in phase A, the expression between the α1-β1 subspace derives i α1= 0, i is derived from the transformation matrix from dq to α-β α2 =-i q sinθ e +i d cosθ e Then, combining the relationship between α1-β1, α2-β2, α-β, and xy subspaces, the i of the dual three-phase permanent magnet synchronous motor can be derived. x , as shown below:

[0088] i x =i q sinθ e -i d cosθ e (7)

[0089] Among them, i q represents the q-axis current of the dual three-phase permanent magnet synchronous motor in the rotating coordinate system, i d represents the d-axis current of the dual three-phase permanent magnet synchronous motor in the rotating coordinate system, θ e represents the rotor position angle;

[0090] Under normal circumstances, the voltage on the xy plane of the dual three-phase permanent magnet synchronous motor can be expressed as the line voltage:

[0091]

[0092] Among them, u x represents the voltage on the x-plane, u AB Indicates the AB phase line voltage, u BC Indicates BC phase line voltage, u DE Indicates DE phase line voltage, u EF Indicates ED phase line voltage, u y represents the voltage on the y plane;

[0093] It can be seen from equation (8) that the abnormal terminal voltage under open circuit fault will cause obvious voltage components to appear on the xy plane, which in turn will cause obvious current components to appear on the xy plane. When the A phase has an open circuit fault, the actual value of the AB phase line voltage u AB_rel can be regarded as its correct value u AB_cot and error u AB_err The superposition of, that is: u AB_rel =u AB_cot +u AB_err .

[0094] Since the correct value of the voltage in the xy plane is close to zero, the correct value of the x-axis voltage u x_cot and the correct value of the y-axis voltage u y_cot are close to zero. Then, the actual value of the x-axis voltage u x_rland the actual value of the y-axis voltage u y_rl The estimate is:

[0095]

[0096] The mathematical model of the dual three-phase permanent magnet synchronous motor in the xy plane is as follows:

[0097]

[0098] Among them, R s Indicates stator resistance, L ls Indicates leakage inductance;

[0099] According to equations (8)-(10), the i after the A phase open circuit fault is derived y is zero. As shown below:

[0100]

[0101] Combine i B +i C =0, i D +i E +i F = 0, it can be deduced that

[0102] It can be concluded that after an open-circuit fault occurs in phase A, the phase current space vectors of phases B and C differ by 180°. Because phases D, E, and F have no faults, the angle change between the phase current space vectors of phases BC is the largest. The analysis is similar when an open-circuit fault occurs in other phases.

[0103] Step 1.4) Because i x 、i y The reference value i x * 、i y * Set to zero, phase A can still carry current after the current sensor is disconnected. Due to the influence of closed-loop control, the sampled i x 、i y Tends to zero. Combining the VSD matrix, Kirchhoff's law and formulas (2) and (3), the expressions of the currents of each phase after the current sensor failure of phase A can be derived. First, the expressions of the currents of each phase of the current sensor disconnection fault and the real current of the fault phase are as follows:

[0104]

[0105] i Areal =3i d cosθ e -3i q sinθe (14)

[0106] From equations (12) and (13), the spatial distribution of the phase currents after a line break fault occurs is shown in Figure 3(a). B′ 、i C′ Represents the phase current space vectors of phases B and C after the fault. From Figure 3(a), it can be seen that after the current sensor disconnection fault occurs in phase A, the angle change between the phase current space vectors of phases BC is the largest.

[0107] The expressions of the phase currents of each phase when the current sensor gain fault occurs in phase A and the real current of the fault phase are as follows:

[0108]

[0109] Where k represents the gain coefficient;

[0110] From equations (15)-(17), the spatial distribution of the phase currents of each phase after the gain fault occurs is shown in Figure 3(b) and Figure 3(c). It can be seen from Figure 3(b) and Figure 3(c) that after the current sensor gain fault occurs in phase A, the angle between the phase current space vectors of phase BC changes the most.

[0111] The expressions of the phase currents of each phase when the current sensor of phase A is stuck and the real current of the faulty phase are as follows:

[0112]

[0113] i Areal =3(i d cosθ e -i q sinθ e )-2C (20)

[0114] Wherein, C represents the hysteresis coefficient.

[0115] From equations (18)-(20), the spatial distribution of the phase currents of each phase after the stuck fault occurs is shown in Figure 3(d). It can be seen from Figure 3(d) that after the current sensor stuck fault occurs in phase A, the angle between the phase current space vectors of phase BC changes the most.

[0116] When an open circuit fault and a current sensor fault occur, the structure diagram between the dual three-phase permanent magnet synchronous motor and the inverter is as follows Figure 2 shown.

[0117] Step 2) A second-order generalized integrator is used to eliminate current distortion caused by a fault, and a phase-locked loop is used to extract the phase of each phase current when an open circuit fault and a current sensor fault occur.

[0118] Step 2.1) Current distortion and torque ripple are also inevitable during faults. In order to accurately obtain the phasor, a second-order generalized integrator (SOGI) is used. SOGI can effectively filter out signal components with frequencies higher than the center frequency. The SOGI structure is shown in the figure. Figure 4 As shown. The transfer function of SOGI is expressed as follows:

[0119]

[0120] Among them, i x,β and i x,α is the output signal, ω is the center frequency, and s represents the integral. In the present invention, the gain coefficient k is set to 0.5, and the center frequency is selected as the fundamental frequency.

[0121] Step 2.2) The six-phase current outputs a pair of mutually orthogonal signals through SOGI, which are input into the phase-locked loop. Based on the spatial distribution of phase current after different faults analyzed in step 1), the phase of each phase current is extracted using the phase-locked loop for subsequent fault location. The phase-locked loop structure is shown in Figure 2. Figure 5 As shown, Represents the estimated phasor of the phase current, K p Represents the proportionality coefficient, K i represents the integral coefficient, represents the estimated electrical angular velocity, and ε represents the difference.

[0122] Step 3) Formulate a fault location criterion based on the different fault phases and the different spatial variations of phase currents after the fault.

[0123] Step 3.1) According to the different change amplitudes of the phase currents extracted by the phase-locked loop after the fault occurs in different phases, the diagnostic variables are set as follows:

[0124]

[0125] Δθ n ={Δθ1,Δθ2,Δθ3,Δθ4,Δθ5,Δθ6} (24)

[0126] Among them, θ A represents the phase of the A-phase current extracted by the phase-locked loop, θ B Indicates the phase of the B-phase current extracted by the phase-locked loop, θ C represents the phase of the C-phase current extracted by the phase-locked loop, θ D represents the phase of the D-phase current extracted by the phase-locked loop, θ E represents the phase of the E-phase current extracted by the phase-locked loop, θ Frepresents the phase of the F phase current extracted by the phase-locked loop, △θ1 represents the phase difference between the BC phase currents, △θ2 represents the phase difference between the AC phase currents, △θ3 represents the phase difference between the AB phase currents, △θ4 represents the phase difference between the EF phase currents, △θ5 represents the phase difference between the DF phase currents, and △θ6 represents the phase difference between the DE phase currents.

[0127] Step 3.2) The fault location criteria are formulated by using the different change ranges of the established diagnostic variables at different fault phases, as shown in Table 1.

[0128] Table 1 Fault phase location accuracy

[0129]

[0130]

[0131] Table 1 F x Represents the fault flag of each phase. Because the phase difference between the currents of each phase is (2π) / 3 under normal circumstances, considering that the actual phase difference may fluctuate within a very small range of (2π) / 3, the threshold g is set here to be π / 48.

[0132] Step 4) At the same time, the zero-sequence current and the differential operator are used to identify the specific fault type;

[0133] Step 4.1) First, identify the open circuit fault and current sensor fault based on the zero-sequence current after the fault occurs. Because when the current sensor fails, the fault phase current still exists and the amplitude changes, causing the phase current to be no longer symmetrical, and the zero-sequence current is no longer constant to 0. The current in the phase with the open circuit fault of the winding is 0, and the phase currents of the other phases are still symmetrical, so the zero-sequence current is 0. Based on this principle, the moving average of the phase current is calculated as follows:

[0134]

[0135] Where, T represents the electrical period;

[0136] The differential operator can reflect the changes between discrete quantities. When the current signal does not fluctuate, the value of the differential operator is zero. Therefore, the volatility of the current signal can be judged by the differential operator, and the diagnostic variable can be obtained by using the second-order differential operator. (n=A, B, C, D, E, F), and calculate its moving average as follows:

[0137]

[0138] Among them, i n (k), i n (k-1) and i n(k-2) are the n-phase currents at the current sampling point, the previous sampling point, and the previous two sampling points respectively;

[0139] Step 4.2) Define two fault type diagnostic variables Y x and Z, as shown below:

[0140]

[0141] ε1 and ε2 are two thresholds. ε1 is used to distinguish between open circuit fault and current sensor fault. In the case of open circuit fault, N1 is approximately 0. In the case of current sensor fault, N1 fluctuates. Therefore, the value of N is much greater than 0 in the case of current sensor fault. ε2 is used to distinguish between gain fault and other current sensor faults. is fluctuating, when other current sensors fail They are all approximately 0, so the value of h in the case of gain failure is greater than the value of h in the case of other current sensor failures. Based on the above analysis, ε1 = 0.3 and ε2 = 0.2 are set. The phase current is 0 in the case of a line break fault, while the phase current is a non-zero constant C' in the case of a stuck fault. This feature can be used to distinguish between a line break fault and a stuck fault.

[0142] Step 4.3) Based on the above analysis, three variables (F x , Y x , Z) combined with the sampling phase current i x' The fault type is located and identified by the current sensor. Table 2 shows the fault identification results, where T x The value indicates the fault type.

[0143] Table 2 Fault identification criteria

[0144] Fault type <![CDATA[F x ]]> Z <![CDATA[Y x ]]> <![CDATA[i x' ]]> <![CDATA[T x ]]> Open circuit fault 1 0 / / 1 Disconnection failure 1 1 0 0 2 Gain Failure 1 1 1 / 3 Stuck fault 1 1 0 C' 4

[0145] Figure 6 The process of fault location and identification is demonstrated.

[0146] Step 5) After locating the fault phase and identifying the fault type, the fault extent is quantitatively described based on the phase difference after the fault.

[0147] Taking phase A as an example, according to the phase current expression under the gain fault of phase A current sensor derived in step 1.3), the relationship between the gain coefficient k and the phase difference between phase currents of phases B and C can be derived as follows:

[0148] |θ B -θ C |=2θ f (30)

[0149]

[0150] The magnitude of the gain coefficient k describes the degree of gain failure. At the same time, according to formula (31), it can be found that as k increases, the phase difference between BC increases. Correspondingly, as k decreases, the phase difference between BC also decreases. Therefore, the change in the phase difference between BC can be used to determine whether the current sensor has a positive gain or negative gain failure.

[0151] In order to verify the effectiveness of the fault diagnosis method proposed in the present invention, an experiment was conducted with a fault in phase A as an example. The dual three-phase permanent magnet synchronous motor is operated at 100 r / min and 60 N·m. Figures 7(a), (b), (c), and (d) respectively show the diagnosis results when various faults occur in phase A. a The real current of the fault phase is obtained by sampling with a current clamp. As can be seen from Figure 7(a), N1 tends to 0 before and after the fault, and T A and F A From 0 to 1, it indicates that an open circuit fault occurred in phase A. As can be seen from Figure 7(b), after the fault occurs, N1 changes from a constant value of 0 to a fluctuating value. From the fluctuation value to 0, T A From 0 to 2, it indicates that the current sensor of phase A is disconnected. As shown in Figure 7(c), is a dynamic value. After a fault, due to the change in the amplitude of the A-phase current signal, its maximum value will also change. After a fault, N1 changes from a value close to 0 to a fluctuating value. A It changes from 0 to 4, indicating that a current sensor gain fault occurs in phase A. As can be seen from Figure 7(d), before and after the fault occurs Always equal to 0, after the fault, N1 changes from 0 to a fluctuating value, T A Changing from 0 to 3 indicates that a current sensor stuck fault occurs in phase A. The above diagnosis results are consistent with the location and type of the actual fault, which shows the correctness of the fault diagnosis method of the present invention.

[0152] The embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. A method for diagnosing open circuit faults and current sensor faults based on phase current spatial distribution, characterized in that: The six-phase current of the dual three-phase permanent magnet synchronous motor outputs a pair of mutually orthogonal signals through a second-order generalized integrator, which are input into a phase-locked loop, and the phase of each phase current when an open circuit fault or a current sensor fault occurs in the dual three-phase permanent magnet synchronous motor is extracted by the phase-locked loop; According to the different change ranges of the phase current of each phase after a fault occurs in different phases, a diagnostic variable is established, and the fault location criterion is formulated by using the change range of the diagnostic variable when the fault phase is different to locate the fault phase; The fault type of the fault phase is identified using zero-sequence current and second-order difference operator; The fault severity is quantitatively described based on the phase difference after the fault occurs.

2. The open circuit fault and current sensor fault diagnosis method according to claim 1, characterized in that: The diagnostic variables are: Among them, θ A represents the phase of the A-phase current extracted by the phase-locked loop, θ B represents the phase of the B-phase current extracted by the phase-locked loop, θ C represents the phase of the C-phase current extracted by the phase-locked loop, θ D represents the phase of the D-phase current extracted by the phase-locked loop, θ E represents the phase of the E-phase current extracted by the phase-locked loop, θ F represents the phase of the F phase current extracted by the phase-locked loop, △θ1 represents the phase difference between the BC phase currents, △θ2 represents the phase difference between the AC phase currents, △θ3 represents the phase difference between the AB phase currents, △θ4 represents the phase difference between the EF phase currents, △θ5 represents the phase difference between the DF phase currents, △θ6 represents the phase difference between the DE phase currents, and the diagnostic variable Δθ n ={Δθ1,Δθ2,Δθ3,Δθ4,Δθ5,Δθ6}.

3. The open circuit fault and current sensor fault diagnosis method according to claim 2, characterized in that: The fault location criteria are: When the dual-three-phase permanent magnet synchronous motor is operating normally, Max{Δθ n}<g, and the fault flag bit F x of each phase is 0; When a fault occurs in phase A of the dual three-phase permanent magnet synchronous motor, Max{Δθ n }=Δθ1>g, the fault flag of phase A is F A =1; When a fault occurs in phase B of the dual three-phase permanent magnet synchronous motor, Max{Δθ n }=Δθ2>g, the fault flag of phase B is F B =1; When a fault occurs in phase C of the dual three-phase permanent magnet synchronous motor, Max{Δθ n }=Δθ3>g, the fault flag of phase C is F C =1; When the D phase of the dual three-phase permanent magnet synchronous motor fails, Max{Δθ n }=Δθ4>g, the fault flag of phase D is F D =1; When the E phase of the dual three-phase permanent magnet synchronous motor fails, Max{Δθ n }=Δθ5>g, the fault flag of phase E is F E =1; When the R phase of the dual three-phase permanent magnet synchronous motor fails, Max{Δθ n }=Δθ6>g, the fault flag of phase F F =1; Wherein, g represents the set threshold.

4. The open circuit fault and current sensor fault diagnosis method according to claim 3, characterized in that: The fault type is determined by the fault flag F of a phase of the motor. x , Fault type diagnostic variable Y x and Z, sampling phase current i x' Identify, specifically: When F x =1, Z=0, an open circuit fault occurs in the dual three-phase permanent magnet synchronous motor; When F x =1, Z=1, Y x =0, i x' =0, the current sensor of the dual three-phase permanent magnet synchronous motor is disconnected; When F x =1, Z=1, Y x =1, the current sensor gain fault occurs in the dual three-phase permanent magnet synchronous motor; When F x =1, Z=1, Y x =0, i x' =C', a current sensor stuck fault occurs in the dual three-phase permanent magnet synchronous motor, where C' is a constant not equal to 0.

5. The open circuit fault and current sensor fault diagnosis method according to claim 4, characterized in that: The fault type diagnostic variable Z satisfies: Wherein, N is the moving average value of the phase current, which is determined based on the principle that when the current sensor fails, the zero-sequence current is not always 0, and when there is an open circuit fault, the zero-sequence current is 0; ε1 is the set threshold.

6. The open circuit fault and current sensor fault diagnosis method according to claim 5, characterized in that: Said Where T represents the electrical cycle, i A 、i B 、i C 、i D 、i E 、i F Indicates the phase current.

7. The open circuit fault and current sensor fault diagnosis method according to claim 4, characterized in that: The fault type diagnostic variable Y x satisfy: Among them, h is the diagnostic variable is the moving average value, and ε2 is the set threshold.

8. The open circuit fault and current sensor fault diagnosis method according to claim 1, characterized in that: Take phase A as an example: When an open circuit fault occurs in phase A of a dual three-phase permanent magnet synchronous motor, the phase current of phase B Phase current of phase C When the current sensor of phase A of the dual three-phase permanent magnet synchronous motor is disconnected, the current of each phase is expressed as: Among them, i q represents the q-axis current of the dual three-phase permanent magnet synchronous motor in the rotating coordinate system, θ e represents the rotor position angle; When a current sensor gain fault occurs in phase A of a dual three-phase permanent magnet synchronous motor, the phase current of each phase is expressed as: Among them, k represents the gain coefficient, the intermediate quantity θ f Satisfy |θ B -θ C \=2θ f ,θ B represents the phase of the B-phase current extracted by the phase-locked loop, θ C Indicates the phase of the C-phase current extracted by the phase-locked loop; When the current sensor of phase A of the dual three-phase permanent magnet synchronous motor is stuck, the current of each phase is expressed as: Wherein, C represents the hysteresis coefficient.

9. The open circuit fault and current sensor fault diagnosis method according to claim 8, characterized in that: When a gain fault occurs in phase A, the relationship between the gain coefficient k and the phase difference between phase currents B and C is: The magnitude of the gain coefficient k describes the extent of the gain failure.

10. A system for implementing the open circuit fault and current sensor fault diagnosis method according to any one of claims 1 to 9, characterized in that: include: The integral average module is used to integrate the fault identification factor. When the integral value is greater than the set threshold, the fault identification factor is set to 1. The fault diagnosis and positioning module is used to diagnose and locate open circuit faults and current sensor faults.

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