An electrically excited doubly salient motor inverter and phase winding open circuit fault diagnosis method

Abstract

This invention discloses a method for diagnosing open-circuit faults in an electrically excited doubly salient pole motor inverter and its phase windings, relating to the field of motor fault diagnosis. The method includes: calculating the midpoint voltage of the phase bridge arm in the faulty sector to determine whether the fault is an open circuit in the upper transistor, lower transistor, or phase winding; based on different open-circuit fault types, turning on the upper power transistor, lower power transistor, or upper power transistor in the corresponding conducting state of the preceding and following sectors; calculating the midpoint voltage of the phase bridge arm in the faulty sector under different conducting states; combining the changes in the line excitation back EMF of the faulty sector; and determining whether the fault is an open-circuit fault type I or open-circuit fault type II in the upper / lower / combined transistor in the corresponding conducting state of the faulty sector, or an open circuit in the phase winding where the current in the faulty sector flows in the forward or reverse direction. This invention is based on the changing trend of the line excitation back EMF in different sectors, is unaffected by changes in inductance and speed, and achieves multiple fault location methods.

Description

Technical Field

[0001] This invention relates to the field of motor fault diagnosis, and in particular to a method for diagnosing open-circuit faults in an electrically excited doubly salient pole motor inverter and its phase windings. Background Technology

[0002] Fault diagnosis technology is a prerequisite for achieving fault-tolerant operation of electrically excited doubly salient pole motor (DSEM) drive systems. Power transistor open-circuit faults are mainly classified into two types based on their cause: Type I open-circuit faults caused by drive signal loss and Type II open-circuit faults caused by power transistor damage. Type I open-circuit faults are characterized by the power transistor not conducting while the diode is conducting, while Type II open-circuit faults are characterized by both the power transistor and the diode not conducting. Phase winding open-circuit faults share similar characteristics with power transistor open-circuit faults. Therefore, distinguishing between power transistor open-circuit fault types and phase winding open-circuit faults is of significant research importance.

[0003] The technology for distinguishing open-circuit fault types in power transistors is still in its early stages, with only one relevant paper found so far. The paper "Research on Single-Transistor Open-Circuit Fault Diagnosis of Electrically Excited Doubly Salient Pole Motor Drive Circuit Based on Back EMF Current" (Journal of Electrical Engineering, November 9, 2020, Vol. 35, No. 23, pp. 4888-4897) published by Xia Yiwen et al. proposes a fault diagnosis method based on back EMF current. This method distinguishes single-transistor open-circuit fault types by changing the operating mode of the DSEM and combining it with a specific PWM chopping method. However, this method is only applicable to single transistors and cannot be applied to distinguishing open-circuit fault types in dual transistors.

[0004] For existing diagnostic methods for phase winding open circuit faults, the location characteristics of phase winding open circuit and double tube open circuit faults under the same bridge arm are similar, and existing studies cannot distinguish between them. Summary of the Invention

[0005] To address the aforementioned problems and technical requirements, the inventors have proposed a method for diagnosing open-circuit faults in the inverter and phase windings of an electrically excited doubly salient pole motor. The technical solution of this invention is as follows:

[0006] A method for diagnosing open circuit faults in an electrically excited doubly salient pole motor inverter and its phase windings involves winding a current sensor between any two phase windings of the electrically excited doubly salient pole motor inverter. The electrically excited doubly salient pole motor inverter operates sequentially in three sectors within one electrical angle cycle, with each sector corresponding to a conduction state.

[0007] The method includes the following steps:

[0008] In the current sector, if the current value collected by the current sensor is lower than the given value, the current sector is defined as the fault sector, the sector before the fault sector is the preceding sector, and the sector after the fault sector is the following sector.

[0009] Calculate the midpoint voltage of the phase bridge arm of the faulty sector to determine whether the fault is an open circuit in the upper transistor, an open circuit in the lower transistor, or an open circuit in the phase winding. The upper and lower transistors include power transistors and diodes.

[0010] If the upper transistor is open-circuited, turn on the upper power transistors in the corresponding conducting states of the front and rear sectors, recalculate the midpoint voltage of the phase bridge arm of the faulty sector, and combine it with the change of the line excitation back EMF of the faulty sector. If the voltage meets the corresponding fault location characteristics, then the fault is determined to be an open-circuit fault type I or open-circuit fault type II of the upper transistor in the corresponding conducting state of the faulty sector, or an open-circuit fault type I or open-circuit fault type II of the composite transistor composed of the upper transistor in the corresponding conducting state of the faulty sector and the upper power transistor in the corresponding conducting state of the front sector.

[0011] If the lower transistor is open-circuited, turn on the lower power transistors in the corresponding conducting states of the front and rear sectors, recalculate the midpoint voltage of the phase bridge arm of the faulty sector, and combine it with the change of the line excitation back EMF of the faulty sector. If the voltage meets the corresponding fault location characteristics, then the fault is determined to be either open-circuit fault type I or open-circuit fault type II of the lower transistor in the corresponding conducting state of the faulty sector, or open-circuit fault type I or open-circuit fault type II of the composite transistor composed of the lower transistor in the corresponding conducting state of the faulty sector and the upper power transistor in the corresponding conducting state of the rear sector.

[0012] If the phase winding is open, turn on the upper power transistor corresponding to the conducting state of the subsequent sector, recalculate the midpoint voltage of the phase bridge arm of the fault sector, and combine it with the change of the line excitation back EMF of the fault sector. If the voltage meets the corresponding fault location characteristics, then the fault is determined to be an open circuit of the phase winding through which the fault sector current flows in the forward direction or an open circuit of the phase winding through which the fault sector current flows in the reverse direction.

[0013] The further technical solution involves calculating the midpoint voltage of the phase bridge arm in the faulty sector to determine that the fault is an open circuit in the upper transistor, including:

[0014] If the current value collected by the current sensor is not zero, the midpoint voltage of the phase bridge arm in the faulty sector satisfies:

[0015]

[0016] Among them, U x U is the voltage at the midpoint of phase x bridge arm. y Let be the midpoint voltage of phase y bridge arm, and let x be the bridge arm containing the upper transistor in the conducting state corresponding to the faulty sector, and y be the bridge arm containing the lower transistor in the conducting state corresponding to the faulty sector; i d The current value collected by the current sensor; P i P is the drive signal for the power transistor in the on state corresponding to the faulty sector. j This is the drive signal for the lower power transistor in the on state corresponding to the faulty sector;

[0017] If the current value collected by the current sensor is zero, the voltage at the midpoint of the phase bridge arm of the faulty sector satisfies:

[0018]

[0019] Among them, e xy The line excitation back EMFs of phase x and phase y are given.

[0020] A further technical solution involves calculating the midpoint voltage of the phase bridge arm in the faulty sector to determine that the fault is an open circuit in the lower transistor, including:

[0021] If the current value collected by the current sensor is not zero, the midpoint voltage of the phase bridge arm in the faulty sector satisfies:

[0022]

[0023] Among them, U x U is the voltage at the midpoint of phase x bridge arm. y U is the midpoint voltage of the y-phase bridge arm, where x is the bridge arm containing the upper transistor in the conducting state corresponding to the faulty sector, and y is the bridge arm containing the lower transistor in the conducting state corresponding to the faulty sector; dc The bus DC voltage; i d The current value collected by the current sensor; P i P is the drive signal for the power transistor in the on state corresponding to the faulty sector. j This is the drive signal for the lower power transistor in the on state corresponding to the faulty sector;

[0024] If the current value collected by the current sensor is zero, the voltage at the midpoint of the phase bridge arm of the faulty sector satisfies:

[0025]

[0026] Among them, e xy The line excitation back EMFs of phase x and phase y are given.

[0027] A further technical solution involves calculating the midpoint voltage of the phase bridge arm in the faulty sector to determine that the fault is an open circuit in the phase winding, including:

[0028] The phase bridge arm midpoint voltage of the faulty sector satisfies:

[0029]

[0030] Among them, U x U is the voltage at the midpoint of phase x bridge arm. y U is the midpoint voltage of the y-phase bridge arm, where x is the bridge arm containing the upper transistor in the conducting state corresponding to the faulty sector, and y is the bridge arm containing the lower transistor in the conducting state corresponding to the faulty sector; dc The bus DC voltage; i d The current value collected by the current sensor; P iP is the drive signal for the power transistor in the on state corresponding to the faulty sector. j This is the drive signal for the lower power transistor in the on state corresponding to the faulty sector.

[0031] The further technical solution is to determine the fault as either open-circuit fault type I or open-circuit fault type II of the upper transistor corresponding to the conducting state of the faulty sector, including:

[0032] If the upper transistor is open-circuited, turn on the upper power transistor corresponding to the conducting state in the previous sector, recalculate the midpoint voltage of the phase bridge arm of the faulty sector, and combine it with the change of the line excitation back EMF of the faulty sector. When the voltage meets the first fault location characteristic: when P m When = 1, U x =U y =U dc Then the fault is determined to be an open circuit of the upper power transistor corresponding to the on state of the faulty sector; when the voltage meets the second fault location characteristic: when P m When = 1, U x >U dc U y =U dc If the fault is determined to be that the upper power transistor and upper diode in the corresponding conducting state of the faulty sector are simultaneously open;

[0033] Among them, P m U is the drive signal for the upper power transistor in the corresponding on state of the front sector. x U is the voltage at the midpoint of phase x bridge arm. y U is the midpoint voltage of the y-phase bridge arm, where x is the bridge arm containing the upper transistor in the conducting state corresponding to the faulty sector, and y is the bridge arm containing the lower transistor in the conducting state corresponding to the faulty sector; dc This is the DC voltage of the bus.

[0034] A further technical solution is to determine the fault as an open-circuit fault type I or open-circuit fault type II of a composite transistor consisting of the upper power transistor in the on-state of the faulty sector and the upper power transistor in the on-state of the preceding sector, including:

[0035] If the voltage does not meet the first or second fault location characteristics, disconnect the conducting transistor in the front sector and turn on the corresponding conducting transistor in the rear sector. Recalculate the midpoint voltage of the phase bridge arm in the faulty sector. Combined with the change in the line excitation back EMF of the faulty sector, when the voltage meets the third fault location characteristic: when P... m When = 1, U y ≠U dc And when P k When = 1, U x =U z =U dcThe fault is determined to be a composite transistor consisting of the power transistor in the corresponding conducting state of the faulty sector and the power transistor in the corresponding conducting state of the previous sector, both of which are simultaneously open-circuited; when the voltage meets the fourth fault location characteristic: when P m When = 1, U y ≠U dc And when P k When = 1, U x >U dc U z =U dc If the fault is determined to be that the composite transistor consisting of the upper power transistor and the upper diode in the corresponding conducting state of the faulty sector and the upper power transistor in the corresponding conducting state of the previous sector are all open.

[0036] Among them, P k This is the drive signal for the upper power transistor in the subsequent sector, corresponding to its on-state. U z Let z be the voltage at the midpoint of phase z arm, where z is the remaining phase arm excluding phases x and y.

[0037] The further technical solution is to determine the fault as either open-circuit fault type I or open-circuit fault type II of the lower transistor corresponding to the conducting state of the faulty sector, including:

[0038] If the lower power transistor is open-circuited, turn on the lower power transistor corresponding to the conducting state in the subsequent sector, recalculate the midpoint voltage of the phase bridge arm of the faulty sector, and combine it with the change in the line excitation back EMF of the faulty sector. When the voltage meets the fifth fault location characteristic: when P n When = 1, U x =U y =0, then the fault is determined to be an open circuit in the lower power transistor corresponding to the conduction state of the faulty sector; when the voltage meets the sixth fault location characteristic: when P n When = 1, U x =0,U y If the value is less than 0, the fault is determined to be that the lower power transistor and the lower diode in the corresponding conducting state of the faulty sector are both open.

[0039] Among them, P n This is the drive signal for the lower power transistor in the following sector, corresponding to its on state. U x U is the voltage at the midpoint of phase x bridge arm. y Let x be the voltage at the midpoint of the y-phase bridge arm, and let x be the bridge arm containing the upper transistor in the conducting state corresponding to the faulty sector, and y be the bridge arm containing the lower transistor in the conducting state corresponding to the faulty sector.

[0040] The further technical solution is to determine the fault as an open-circuit fault type I or open-circuit fault type II of a composite transistor consisting of the lower power transistor in the on-state of the faulty sector and the lower power transistor in the on-state of the subsequent sector, including:

[0041] If the voltage does not meet the fifth or sixth fault location characteristic, disconnect the downstream sector's conducting transistor, turn on the corresponding downstream power transistor in the upstream sector, and recalculate the midpoint voltage of the phase bridge arm of the faulty sector. Combined with the change in the line excitation back EMF of the faulty sector, when the voltage meets the seventh fault location characteristic: when P... n When = 1, U x ≠0, and when P q When = 1, U y =U z =0, then the fault is determined to be the simultaneous open circuit of the composite transistor consisting of the lower power transistor in the corresponding conducting state of the faulty sector and the lower power transistor in the corresponding conducting state of the subsequent sector; when the voltage meets the eighth fault location characteristic: when P n When = 1, U x ≠0, and when P q When = 1, U y <0,U z =0, then the fault is determined to be that the composite transistor consisting of the lower power transistor and the lower diode in the corresponding conducting state of the fault sector and the lower power transistor in the corresponding conducting state of the subsequent sector are all open.

[0042] Among them, P q U is the drive signal for the lower power transistor in the preceding sector, corresponding to its on state. z Let z be the voltage at the midpoint of phase z arm, where z is the remaining phase arm excluding phases x and y.

[0043] A further technical solution is that, if the voltage meets the corresponding fault location characteristics, the fault is determined to be an open circuit in the phase winding through which the fault sector current flows in the forward direction or an open circuit in the phase winding through which the fault sector current flows in the reverse direction, including:

[0044] When the voltage meets the ninth fault location characteristic: when P k When = 1, U x =U dc / 2, then the fault is determined to be an open circuit in the phase winding through which the fault sector current flows in the forward direction; when the voltage meets the tenth fault location characteristic: when P k When = 1, U x =U dc If so, the fault is determined to be an open circuit in the phase winding through which the fault sector current flows in reverse.

[0045] Among them, P k This is the drive signal for the upper power transistor in the subsequent sector, corresponding to its on-state. U x U is the midpoint voltage of phase x bridge arm, where x is the bridge arm containing the upper transistor in the conducting state corresponding to the faulty sector. dc This is the DC voltage of the bus.

[0046] The further technical solution is that the conduction states corresponding to each sector are as follows:

[0047] Define 0°-120° as sector one: G1=1, G2=0, G3=0, the upper power transistor of phase A bridge arm and the lower power transistor of phase C bridge arm are turned on, the remaining power transistors are turned off, the current in phase A winding is positive and the current in phase C winding is negative, |i d |=i _fd ;

[0048] Define 120°-240° as sector two: G1=0, G2=1, G3=0, the upper power transistor of phase B bridge arm and the lower power transistor of phase A bridge arm are turned on, the remaining power transistors are turned off, the current in phase B winding is positive and the current in phase A winding is negative, |i d | / 2=i _fd ;

[0049] Define 240°-360° as sector three: G1=0, G2=0, G3=1, the upper power transistor of phase C and the lower power transistor of phase B are turned on, the remaining power transistors are turned off, the current in phase C winding is positive, and the current in phase B winding is negative, |i d |=i _fd ;

[0050] Among them, G s Let i be the position signal of sector s. d i is the current value collected by the current sensor. _fd For i d Phase current feedback value obtained through phase current construction strategy.

[0051] The beneficial technical effects of this invention are:

[0052] The fault diagnosis method proposed in this application, by changing the traditional position of the current sensor, determines which of the three major fault types is met when the collected current value is lower than a given value by calculating the midpoint voltage of the phase bridge arm of the faulty sector. To further pinpoint the specific fault belonging to that type, depending on the fault type, the upper / lower power transistors corresponding to the conducting state of the preceding or following sector are turned on, or only the upper power transistor corresponding to the conducting state of the following sector is turned on. The midpoint voltage of the phase bridge arm of the faulty sector is calculated again. Combined with the change in the line excitation back EMF of the faulty sector, the corresponding fault location characteristics of the relevant voltages are obtained. Based on the satisfied fault location characteristics, fault location can be achieved. The system distinguishes between open-circuit fault types I and II for the upper and lower transistors in the faulty sector, and identifies open-circuit phase windings through which current flows in both directions in the faulty sector, unaffected by changes in inductance or rotational speed. Further, it shuts off the conduction state of the previous step and turns on the corresponding upper / lower power transistors in the subsequent or preceding sector. Using the same method as the previous step, it obtains the corresponding voltage fault location characteristics. Based on these fault location characteristics, it can distinguish between open-circuit fault types I and II for the composite transistor formed by the upper and lower transistors of the faulty sector and the conducting transistor of the previous step. For the distinction of open circuits in two transistors within the same bridge arm, the same method can be used to locate faults in different sectors. Attached Figure Description

[0053] Figure 1 (a) is a topology diagram of the DSEM inverter provided in this application.

[0054] Figure 1 (b) is a topology diagram of the current sensor provided in this application.

[0055] Figure 2 (a) is the inductance change curve under one electrical angle period provided in this application.

[0056] Figure 2 (b) is the power transistor turn-on logic under an electrical angle cycle provided in this application.

[0057] Figure 3 This is a control block diagram of the DSEM drive system provided in this application.

[0058] Figure 4 This is a flowchart of the inverter and phase winding open circuit fault diagnosis method provided in this application.

[0059] Figure 5 This is the curve showing the change in the back electromotive force of the linear excitation of sector one provided in this application.

[0060] Figure 6 (a) is the circuit state of the open-circuit fault type I of the upper transistor corresponding to the conduction state of the fault sector provided in this application.

[0061] Figure 6(b) is the circuit state of the open-circuit fault type II of the upper tube corresponding to the conduction state of the fault sector provided in this application.

[0062] Figure 7 (a) is the circuit state of the composite transistor consisting of the upper transistor in the on state corresponding to the fault sector and the upper power transistor in the on state corresponding to the previous sector, provided in this application, for open-circuit fault type I.

[0063] Figure 7 (b) is the circuit state of the composite transistor consisting of the upper transistor in the on state corresponding to the fault sector and the upper power transistor in the on state corresponding to the previous sector, provided in this application, for open-circuit fault type II.

[0064] Figure 8 (a) is the circuit state of the phase winding with the fault sector current passing in the forward direction as provided in this application.

[0065] Figure 8 (b) is the circuit state of the phase winding with the fault sector current flowing in reverse, as provided in this application. Detailed Implementation

[0066] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0067] like Figure 1 As shown in (a), the three-phase windings of the DSEM in this application are connected in a star configuration. The three-phase windings are phase A, phase B, and phase C. The inverter adopts a bridge drive and includes a bus DC power supply U. dc Filter capacitor C1, power transistors T1-T6 (first to sixth), diodes D1-D6 (first to sixth).

[0068] The collectors of the first to sixth power transistors T1-T6 are connected to the cathodes of the corresponding first to sixth diodes D1-D6, and the emitters are connected to the anodes of the corresponding first to sixth diodes D1-D6.

[0069] The emitter of the first power transistor T1 is connected to the collector of the fourth power transistor T4, and one end of the A-phase winding is connected between them. The emitter of the third power transistor T3 is connected to the collector of the sixth power transistor T6, and one end of the B-phase winding is connected between them. The emitter of the fifth power transistor T5 is connected to the collector of the second power transistor T2, and one end of the C-phase winding is connected between them. Therefore, the first power transistor T1 and the first diode D1 form the upper transistor of the A-phase bridge arm, the fourth power transistor T4 and the fourth diode D4 form the lower transistor of the A-phase bridge arm, and so on for the other phase bridge arms.

[0070] Bus DC power supply U dcThe diodes are connected in parallel across the filter capacitor C1, with the positive terminal of the power supply connected to the cathodes of the first diode D1, the third diode D3, and the fifth diode D5, respectively, and the negative terminal of the power supply connected to the anodes of the fourth diode D4, the sixth diode D6, and the second diode D2, respectively.

[0071] The current sensor LEM1 is wound between any two phase windings of the DSEM inverter. In this example, the current sensor LEM1 is wound around the A and B phase windings. Figure 1 As shown in (b). Here, P represents the positive direction of the current, N represents the negative direction of the current, and the current value measured by current sensor LEM1 is i. d =i ab , then i ab With phase current i p The relationship (p = a, b, c) is: i ab =i a -i b .

[0072] The DSEM inverter of this application operates sequentially in three sectors within one electrical angle cycle, with each sector corresponding to a different conduction state. Figure 2 As shown in (a) and (b), the current i in different sectors under one electrical angle period of the DSEM is obtained through analysis. ab with i _fd The relationships and conduction states are as follows:

[0073] Define 0°-120° as sector one: G1=1, G2=0, G3=0, the upper power transistor T1 of phase A bridge arm and the lower power transistor T2 of phase C bridge arm are turned on, the remaining power transistors are turned off, the current in phase A winding is positive and the current in phase C winding is negative, |i ab |=i _fd .

[0074] Define 120°-240° as sector two: G1=0, G2=1, G3=0, the upper power transistor T3 of phase B bridge arm and the lower power transistor T4 of phase A bridge arm are turned on, the remaining power transistors are turned off, the current in phase B winding is positive and the current in phase A winding is negative, |i ab | / 2=i _fd .

[0075] Define 240°-360° as sector three: G1=0, G2=0, G3=1, the upper power transistor T5 of phase C bridge arm and the lower power transistor T6 of phase B bridge arm are turned on, the remaining power transistors are turned off, the current in phase C winding is positive and the current in phase B winding is negative, |i ab |=i _fd .

[0076] Among them, G s Let i be the position signal of sector s. _fd For i abPhase current feedback value obtained through phase current construction strategy.

[0077] The DSEM drive system of this application adopts a dual closed-loop control method of speed and current, such as Figure 3 As shown, if the current sensor uses a winding method with phases A and B, then |i ab |、|i ab | / 2、|i ab | These are respectively used as the current loop feedback values ​​i in sector one, sector two, and sector three. _fd This enables the motor to operate normally within one electrical angle cycle.

[0078] Since the working principle of the three sectors in one electrical angle cycle of DSEM is equivalent and the winding method of the three current sensors is equivalent to each other, this embodiment takes the fault occurring in sector one and using the A and B phase winding method as an example for fault analysis. The sector before the faulty sector is called the front sector and the sector after the faulty sector is called the rear sector. It is assumed that the system uses the upper transistor cut-off control.

[0079] Based on the above DSEM inverter structure and sector division, this embodiment provides a method for diagnosing open-circuit faults in electrically excited doubly salient pole motor inverters and phase windings. The flowchart of this method is as follows: Figure 4 As shown, the specific steps include the following:

[0080] Step 1: If the current value collected by the current sensor is lower than the given value, calculate the midpoint voltage of the phase bridge arm of the faulty sector to determine whether the fault is an open circuit of the upper tube, an open circuit of the lower tube, or an open circuit of the phase winding. The upper and lower tubes include power transistors and diodes.

[0081] Step 11: If the current value collected by the current sensor is not zero, and the voltage at the midpoint of the phase bridge arm of the faulty sector satisfies equation (1), then the fault is determined to be an open circuit of the upper tube, including T1 open circuit (corresponding to open circuit fault type I), T1D1 (corresponding to open circuit fault type II), composite tube T1 T5 open circuit (corresponding to open circuit fault type I), and composite tube T1D1 T5 (corresponding to open circuit fault type II).

[0082]

[0083] Among them, U a U is the voltage at the midpoint of phase A bridge arm. c U is the voltage at the midpoint of the C-phase bridge arm. D4_on U is the forward voltage of D4. T2_on P1 is the forward voltage of T2. Since the forward voltage drop of the power transistor and the diode is relatively small, approximately zero, it can be ignored. P1 is the drive signal of the upper power transistor T1, and P2 is the drive signal of the lower power transistor T2.

[0084] If the current value collected by the current sensor is zero, and the voltage at the midpoint of the phase bridge arm of the faulty sector satisfies equation (2), then the fault is determined to be an open circuit in the upper tube.

[0085]

[0086] Among them, e ac The line excitation back EMF of phases A and C.

[0087] Equations (1) and (2) above are derived as follows: Assuming the upper power transistor T1 is open-circuited, the T1 chopper fails, and the current loop is: Phase A winding → Phase C winding → T2 → D4. When the current i ab When the current is below the given value, due to the current closed-loop effect, the driving signal P1 = P2 = 1, and the fault detection characteristics are as shown in equation (1); when the phase current drops to 0, the fault detection characteristics are as shown in equation (2). Similarly, the fault detection characteristics corresponding to the open circuit of T1D1 are the same as those in equations (1) and (2).

[0088] Step 12: If the current value collected by the current sensor is not zero, and the voltage at the midpoint of the phase bridge arm of the faulty sector satisfies equation (3), then the fault is determined to be an open circuit in the lower tube, including T2 open circuit (corresponding to open circuit fault type I), T2D2 (corresponding to open circuit fault type II), composite tube T2 T6 open circuit (corresponding to open circuit fault type I), and composite tube T2D2 T6 (corresponding to open circuit fault type II).

[0089]

[0090] If the current value collected by the current sensor is zero, and the voltage at the midpoint of the phase bridge arm of the faulty sector satisfies equation (4), then the fault is determined to be an open circuit in the lower tube.

[0091]

[0092] Step 13: If the voltage at the midpoint of the phase bridge arm of the faulty sector satisfies equation (5), then the fault is determined to be an open circuit of the phase winding, including the open circuit of phase A winding (the phase winding through which current flows in the forward direction in the faulty sector) and the open circuit of phase C winding (the phase winding through which current flows in the reverse direction in the faulty sector).

[0093]

[0094] Equation (5) above is derived from the fact that if phase A winding is open, then phases A and C windings in sector one cannot communicate with U. dc A loop is formed, making the phase current 0. According to the current closed loop effect, the driving signal P1 = P2 = 1, and the fault detection characteristics are obtained as shown in equation (5). Similarly, the fault detection characteristics of the C phase winding open circuit are the same as those in equation (5).

[0095] It should be noted that steps 11-13 are not in any particular order.

[0096] To distinguish between open circuits T1 and T1D1, this application uses a method based on the back electromotive force (EMF) of the line excitation. The back EMF of the line excitation is defined as e. ab e ac e cb Its expression is as follows:

[0097]

[0098] In the formula, e pf (p = a, b, c) represents the back electromotive force (EMF) of phase p. The curve of the linear back EMF in sector one is shown below. Figure 5 As shown, where θ1 represents e cb =0 corresponds to the rotor position angle.

[0099] Step 2: If the upper transistor is open-circuited, turn on the upper power transistor T5 corresponding to the conducting state of the previous sector, and recalculate the midpoint voltage of the phase bridge arm of the faulty sector. Combined with the change of the line excitation back EMF of the faulty sector, when the voltage meets the first fault location characteristic: when P5 = 1, U a =U c =U dc The fault is determined to be an open circuit in the upper power transistor T1 corresponding to the on-state of the faulty sector (corresponding to open circuit fault type I). When the voltage meets the second fault location characteristic: when P5 = 1, U a >U dc U c =U dc If the fault is determined to be that the upper power transistor T1 and the upper diode D1 in the corresponding conducting state of the fault sector are simultaneously open (corresponding to open circuit fault type II).

[0100] P5 is the drive signal for the power transistor T5 in the front sector, which is in the on state.

[0101] The analysis of the first and second fault location features is as follows:

[0102] Assuming T1 is open-circuited, and P5 = 1, the corresponding circuit state is as follows: Figure 6 As shown in (a), the expression for the midpoint voltage of the phase bridge arm in the faulty sector is:

[0103]

[0104] Based on the change in the line excitation back electromotive force of the faulty sector, it can be known that e ac >e bc Note e bc and Figure 5 e cb The curve is opposite. Combining this with equation (7), we can see that U... a >U b , making Figure 6 In (a), D1 is turned on, U a U in equation (7) dc +e ac Change to U dc .

[0105] Assuming T1D1 is open-circuited, and P5 = 1, the corresponding circuit state is as follows: Figure 6 As shown in (b), the voltage at the midpoint of the bridge arm still satisfies equation (7), combined with Figure 5 It can be seen that when θ∈(0°,θ1), e bc <0, U b dc D3 is not conducting, U a The value satisfies equation (7); when θ∈(θ1,120°), e bc >0, U b >U dc With D3 conducting, the voltage U can be calculated using the KVL formula for the circuit. a As shown in equation (8).

[0106]

[0107] Among them, L b L c These are the inductances of the B-phase and C-phase windings, respectively. Because e ac and e ab Both are greater than 0, therefore U a >U dc .

[0108] Combining the first and second fault location characteristics, it can be seen that the distinction between open-circuit fault types in power transistors depends on the normal operation of power transistor T5. Considering the possibility of dual-transistor faults, if a composite transistor fault occurs, the above distinction method will fail. For example, if the composite transistors T1D1T5 or T1T5 are faulty, the first and second fault location characteristics will no longer hold. To address this issue, fault location will still be achieved through line-excitation back EMF.

[0109] Step 3: If the voltage does not meet the first or second fault location characteristics, disconnect the front sector conducting transistor T5 and turn on the corresponding conducting transistor T3 in the rear sector. Recalculate the midpoint voltage of the phase bridge arm of the faulty sector. Combined with the change in the line excitation back EMF of the faulty sector, when the voltage meets the third fault location characteristic: when P5 = 1, U... c ≠U dc And when P3 = 1, U a =U b =U dc ​The fault is determined to be the simultaneous open circuit of the composite transistor consisting of the upper power transistor T1 in the corresponding conducting state of the faulty sector and the upper power transistor T5 in the corresponding conducting state of the previous sector (corresponding to open circuit fault type I). When the voltage meets the fourth fault location characteristic: when P5 = 1, U c ≠U dc And when P3 = 1, U a >U dc U b =U dc If the fault is determined to be that the composite transistor consisting of the upper power transistor T1, the upper diode D1, and the upper power transistor T5 corresponding to the conduction state of the previous sector is simultaneously open.

[0110] P3 is the drive signal for the power transistor T3 in the following sector, which is in the on state.

[0111] The analysis of the third and fourth fault location features is as follows:

[0112] Assuming the composite pipe T1T5 is faulty, its fault detection characteristics still satisfy equations (1) and (2). If the above method is used, the U corresponding to P5=1 will be obtained. c ≠U dc This indicates that T5 is open-circuited. To further distinguish the open-circuit fault type, the line excitation back EMF e is used at this time. ab To perform the diagnosis, let P3 = 1, and the corresponding circuit state is as follows: Figure 7 As shown in (a), the expression for the midpoint voltage of the phase bridge arm in the faulty sector is:

[0113]

[0114] Based on the change in the line excitation back electromotive force of the faulty sector, it can be known that e ab >0 and e ab >e cb Therefore, D1 is on, U a byU dc +e ab Change to U dc .

[0115] Similarly, assuming T1D1T5 is open-circuited, and P3 = 1, the corresponding circuit state is as follows: Figure 7 As shown in (b), the voltage at the midpoint of the bridge arm still satisfies equation (9), combined with... Figure 5 It can be seen that the final result is U a >U dc .

[0116] Step 4: If the lower transistor is open-circuited, turn on the lower power transistor T4 corresponding to the conducting state in the subsequent sector, and recalculate the midpoint voltage of the phase bridge arm of the faulty sector. Combined with the change in the line excitation back EMF of the faulty sector, when the voltage meets the fifth fault location characteristic: when P4 = 1, Ua =U c =0, then the fault is determined to be an open circuit in the lower power transistor T2 corresponding to the on state of the faulty sector. When the voltage meets the sixth fault location characteristic: when P4 = 1, U a =0,U c If <0, the fault is determined to be that the lower power transistor T2 and the lower diode D2 in the corresponding conducting state of the faulty sector are both open.

[0117] P4 is the drive signal for the lower power transistor T4 in the following sector, which is in the on state.

[0118] The analytical principles for the fifth and sixth fault location features are similar to those for the first and second fault location features, and will not be elaborated upon here.

[0119] Step 5: If the voltage does not meet the fifth or sixth fault location characteristic, disconnect the downstream sector conducting transistor T4 and turn on the corresponding downstream power transistor T6 in the upstream sector. Recalculate the midpoint voltage of the phase bridge arm of the faulty sector. Combined with the change in the line excitation back EMF of the faulty sector, when the voltage meets the seventh fault location characteristic: when P4 = 1, U... a ≠0, and when P6=1, U c =U b =0, then the fault is determined to be the simultaneous open circuit of the composite transistor consisting of the lower power transistor T2 in the corresponding conducting state of the faulty sector and the lower power transistor T6 in the corresponding conducting state of the subsequent sector. When the voltage meets the eighth fault location characteristic: when P4 = 1, U a ≠0, and when P6=1, U c <0,U b =0, then the fault is determined to be that the composite transistor consisting of the lower power transistor T2 and the lower diode D2 in the corresponding conducting state of the fault sector and the lower power transistor T6 in the corresponding conducting state of the subsequent sector are all open.

[0120] P6 is the drive signal for the lower power transistor T6 in the first sector, which is in the on state.

[0121] The analytical principles for the seventh and eighth fault location features are similar to those for the third and fourth fault location features, and will not be elaborated upon here.

[0122] Step 6: If the phase winding is open, turn on the upper power transistor T3 corresponding to the conducting state of the subsequent sector, and recalculate the midpoint voltage of the phase bridge arm of the faulty sector. Combined with the change in the line excitation back EMF of the faulty sector, when the voltage meets the ninth fault location characteristic: when P3 = 1, U a =U dc / 2, then the fault is determined to be an open circuit in phase A winding (a phase winding in which current flows in the forward direction in the fault sector); when the voltage meets the tenth fault location characteristic: when P3 = 1, U a =U dcIf so, the fault is determined to be an open circuit in phase C winding (a phase winding in which current flows in reverse through the fault sector).

[0123] The analysis of the ninth and tenth fault location characteristics is as follows:

[0124] Similar to the analysis principle of the above fault location characteristics, in order to distinguish between open circuits in phase A and phase C windings, the method based on the line excitation back EMF e is also adopted. ab The method. Assuming phase A winding is open-circuited, let P3 = 1, the corresponding circuit state is as follows. Figure 8 As shown in (a); assuming the C-phase winding is open-circuited, and P3 = 1, the corresponding circuit state is as follows: Figure 8 As shown in (b), U is obtained according to the circuit state. a with U dc The relationship is shown in the ninth and tenth fault location features, thus allowing for differentiation.

[0125] Similarly, if sector two and sector three fail, their fault diagnosis methods are similar to those for sector one. Therefore, based on the sector where the rotor is located, we can obtain the expressions for the fault detection characteristics and fault location characteristics of the three sectors throughout the entire electrical angle cycle. The definitions of the variables for different sectors are shown in Table 1.

[0126] Table 1 Definitions of Variables for Different Sectors

[0127] <![CDATA[G1=1]]> <![CDATA[G2=1]]> <![CDATA[G3=1]]> x a b c y c a b i 1 3 5 j 2 4 6 m 5 1 3 n 4 6 2 k 3 5 1 z b c a q 6 2 4

[0128] The fault diagnosis scheme proposed in this invention has the following three advantages:

[0129] (1) It can distinguish the open circuit fault type of the power transistor and is not affected by changes in inductance or speed;

[0130] (2) It can realize the diagnosis of open circuit faults in composite pipes;

[0131] (3) It can distinguish between open circuits in phase windings and open circuits in two tubes under the same bridge arm. For the distinction between open circuits in two tubes under the same bridge arm, the same method can be used to locate the fault of a single tube in different sectors. After polling the three sectors, the faulty tube is combined to determine whether it belongs to the same bridge arm.

[0132] The above descriptions are merely preferred embodiments of this application, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A method for diagnosing open-circuit faults in an electrically excited doubly salient pole motor inverter and its phase windings, characterized in that, The current sensor is wound between any two phase windings of the electrically excited doubly salient pole motor inverter. The electrically excited doubly salient pole motor inverter operates sequentially in three sectors in one electrical angle cycle, with each sector corresponding to a conduction state. The method includes: In the current sector, if the current value collected by the current sensor is lower than a given value, the current sector is defined as a faulty sector, the sector before the faulty sector is called the preceding sector, and the sector after the faulty sector is called the following sector. The fault is determined by calculating the midpoint voltage of the phase bridge arm of the faulty sector, which indicates whether the fault is an open circuit in the upper transistor, an open circuit in the lower transistor, or an open circuit in the phase winding. The upper and lower transistors include power transistors and diodes. If the upper transistor is open-circuited, then the upper power transistors in the corresponding conducting states of the front and rear sectors are turned on, and the midpoint voltage of the phase bridge arm of the faulty sector is calculated again. Combined with the change of the line excitation back EMF of the faulty sector, if the voltage meets the corresponding fault location characteristics, then the fault is determined to be open-circuit fault type I or open-circuit fault type II of the upper transistor in the corresponding conducting state of the faulty sector, or open-circuit fault type I or open-circuit fault type II of the composite transistor composed of the upper transistor in the corresponding conducting state of the faulty sector and the upper power transistor in the corresponding conducting state of the front sector. If the lower transistor is open-circuited, then the lower power transistors in the corresponding conducting states of the front and rear sectors are turned on, and the midpoint voltage of the phase bridge arm of the faulty sector is calculated again. Combined with the change of the line excitation back EMF of the faulty sector, if the voltage meets the corresponding fault location characteristics, then the fault is determined to be open-circuit fault type I or open-circuit fault type II of the lower transistor in the corresponding conducting state of the faulty sector, or open-circuit fault type I or open-circuit fault type II of the composite transistor composed of the lower transistor in the corresponding conducting state of the faulty sector and the upper power transistor in the corresponding conducting state of the rear sector. If the phase winding is open, the upper power transistor corresponding to the conducting state of the subsequent sector is turned on, and the midpoint voltage of the phase bridge arm of the faulty sector is calculated again. Combined with the change of the line excitation back EMF of the faulty sector, if the voltage meets the corresponding fault location characteristics, the fault is determined to be an open circuit of the phase winding through which the faulty sector current flows in the forward direction or an open circuit of the phase winding through which the faulty sector current flows in the reverse direction.

2. The method for diagnosing open-circuit faults in the inverter and phase windings of an electrically excited doubly salient pole motor according to claim 1, characterized in that, Calculating the phase bridge arm midpoint voltage of the faulty sector to determine that the fault is an open circuit in the upper transistor includes: If the current value collected by the current sensor is not zero, the midpoint voltage of the phase bridge arm of the faulty sector satisfies: Among them, U x U is the voltage at the midpoint of phase x bridge arm. y Let be the midpoint voltage of phase y bridge arm, and let x be the bridge arm containing the upper transistor in the conducting state corresponding to the faulty sector, and y be the bridge arm containing the lower transistor in the conducting state corresponding to the faulty sector; i d The current value collected by the current sensor; P i P is the drive signal for the power transistor in the on state corresponding to the faulty sector. j This is the drive signal for the lower power transistor in the on state corresponding to the faulty sector; If the current value collected by the current sensor is zero, the midpoint voltage of the phase bridge arm of the faulty sector satisfies: Among them, e xy The line excitation back EMFs of phases x and y are given.

3. The method for diagnosing open-circuit faults in the inverter and phase windings of an electrically excited doubly salient pole motor according to claim 1, characterized in that, Calculating the midpoint voltage of the phase bridge arm of the faulty sector to determine that the fault is an open circuit in the lower transistor includes: If the current value collected by the current sensor is not zero, the midpoint voltage of the phase bridge arm of the faulty sector satisfies: Among them, U x U is the voltage at the midpoint of phase x bridge arm. y U is the midpoint voltage of the y-phase bridge arm, where x is the bridge arm containing the upper transistor in the conducting state corresponding to the faulty sector, and y is the bridge arm containing the lower transistor in the conducting state corresponding to the faulty sector; dc The bus DC voltage; i d The current value collected by the current sensor; P i P is the drive signal for the power transistor in the on state corresponding to the faulty sector. j This is the drive signal for the lower power transistor in the on state corresponding to the faulty sector; If the current value collected by the current sensor is zero, the midpoint voltage of the phase bridge arm of the faulty sector satisfies: Among them, e xy The line excitation back EMFs of phases x and y are given.

4. The method for diagnosing open-circuit faults in the inverter and phase windings of an electrically excited doubly salient pole motor according to claim 1, characterized in that, Calculating the phase bridge arm midpoint voltage of the faulty sector to determine that the fault is an open circuit in the phase winding includes: The voltage at the midpoint of the phase bridge arm of the faulty sector satisfies: Among them, U x U is the voltage at the midpoint of phase x bridge arm. y U is the midpoint voltage of the y-phase bridge arm, where x is the bridge arm containing the upper transistor in the conducting state corresponding to the faulty sector, and y is the bridge arm containing the lower transistor in the conducting state corresponding to the faulty sector; dc The bus DC voltage; i d The current value collected by the current sensor; P i P is the drive signal for the power transistor in the on state corresponding to the faulty sector. j This is the drive signal for the lower power transistor in the on state corresponding to the faulty sector.

5. The method for diagnosing open-circuit faults in an electrically excited doubly salient pole motor inverter and its phase windings according to claim 1, characterized in that, The fault is determined to be either open-circuit fault type I or open-circuit fault type II of the upper transistor corresponding to the conduction state of the faulty sector, including: If the upper transistor is open-circuited, turn on the upper power transistor corresponding to the conducting state of the previous sector, and recalculate the midpoint voltage of the phase bridge arm of the faulty sector. Combined with the change in the line excitation back EMF of the faulty sector, when the voltage meets the first fault location characteristic: when P m When = 1, U x =U y =U dc Then the fault is determined to be an open circuit of the upper power transistor corresponding to the conduction state of the faulty sector; when the voltage meets the second fault location characteristic: when P m When = 1, U x >U dc U y =U dc If the fault is determined to be that the upper power transistor and upper diode in the corresponding conducting state of the faulty sector are simultaneously open; Among them, P m U is the drive signal for the upper power transistor in the corresponding on state of the front sector. x U is the voltage at the midpoint of phase x bridge arm. y U is the midpoint voltage of the y-phase bridge arm, where x is the bridge arm containing the upper transistor in the conducting state corresponding to the faulty sector, and y is the bridge arm containing the lower transistor in the conducting state corresponding to the faulty sector; dc This is the DC voltage of the bus.

6. The method for diagnosing open-circuit faults in an electrically excited doubly salient pole motor inverter and its phase windings according to claim 5, characterized in that, The fault is determined to be an open-circuit fault type I or open-circuit fault type II of a composite transistor consisting of the upper power transistor in the on-state of the faulty sector and the upper power transistor in the on-state of the preceding sector, including: If the voltage does not meet the first or second fault location characteristics, disconnect the conducting transistor in the front sector, turn on the upper power transistor in the corresponding conducting state of the rear sector, and recalculate the midpoint voltage of the phase bridge arm of the faulty sector. Combined with the change in the line excitation back EMF of the faulty sector, when the voltage meets the third fault location characteristic: when P... m When = 1, U y ≠U dc And when P k When = 1, U x =U z =U dc The fault is determined to be the simultaneous open circuit of the composite transistor consisting of the upper power transistor in the on-state of the faulty sector and the upper power transistor in the on-state of the previous sector; when the voltage meets the fourth fault location characteristic: when P m When = 1, U y ≠U dc And when P k When = 1, U x >U dc U z =U dc If the fault is determined to be that the composite transistor consisting of the upper power transistor and upper diode in the corresponding conducting state of the fault sector and the upper power transistor in the corresponding conducting state of the previous sector are all open; Among them, P k This is the drive signal for the upper power transistor in the subsequent sector, corresponding to its on-state. U z Let z be the voltage at the midpoint of phase z arm, where z is the remaining phase arm excluding phases x and y.

7. The method for diagnosing open-circuit faults in an electrically excited doubly salient pole motor inverter and its phase windings according to claim 1, characterized in that, The fault is determined to be either open-circuit fault type I or open-circuit fault type II in the lower transistor corresponding to the conduction state of the faulty sector, including: If the lower transistor is open-circuited, turn on the lower power transistor corresponding to the conducting state in the subsequent sector, and recalculate the midpoint voltage of the phase bridge arm of the faulty sector. Combined with the change in the line excitation back EMF of the faulty sector, when the voltage meets the fifth fault location characteristic: when P n When = 1, U x =U y =0, then the fault is determined to be an open circuit in the lower power transistor corresponding to the conduction state of the faulty sector; when the voltage meets the sixth fault location characteristic: when P n When = 1, U x =0,U y If the value is less than 0, the fault is determined to be that the lower power transistor and the lower diode in the corresponding conducting state of the fault sector are simultaneously open. Among them, P n U is the drive signal for the lower power transistor in the following sector, corresponding to its on state. x U is the voltage at the midpoint of phase x bridge arm. y Let x be the voltage at the midpoint of phase y bridge arm, and let x be the bridge arm containing the upper transistor in the conducting state corresponding to the faulty sector, and let y be the bridge arm containing the lower transistor in the conducting state corresponding to the faulty sector.

8. The method for diagnosing open-circuit faults in an electrically excited doubly salient pole motor inverter and its phase windings according to claim 7, characterized in that, The fault is determined to be an open-circuit fault type I or open-circuit fault type II of a composite transistor consisting of the lower power transistor in the on-state of the faulty sector and the lower power transistor in the on-state of the subsequent sector, including: If the voltage does not meet the fifth or sixth fault location characteristic, then disconnect the downstream sector conduction transistor, turn on the corresponding downstream power transistor of the upstream sector, and recalculate the midpoint voltage of the phase bridge arm of the faulty sector. Combined with the change in the line excitation back EMF of the faulty sector, when the voltage meets the seventh fault location characteristic: when P... n When = 1, U x ≠0, and when P q When = 1, U y =U z =0, then the fault is determined to be that the composite transistor consisting of the lower power transistor in the on-state of the faulty sector and the lower power transistor in the on-state of the subsequent sector is simultaneously open; when the voltage meets the eighth fault location characteristic: when P n When = 1, U x ≠0, and when P q When = 1, U y <0,U z =0, then the fault is determined to be that the composite transistor consisting of the lower power transistor and lower diode in the corresponding conduction state of the fault sector and the lower power transistor in the corresponding conduction state of the subsequent sector are all open. Among them, P q U is the drive signal for the lower power transistor in the preceding sector, corresponding to its on state. z Let z be the voltage at the midpoint of phase z arm, where z is the remaining phase arm excluding phases x and y.

9. The method for diagnosing open-circuit faults in an electrically excited doubly salient pole motor inverter and its phase windings according to claim 1, characterized in that, If the voltage meets the corresponding fault location characteristics, then determining the fault as an open circuit in the phase winding through which the fault sector current flows in the forward direction or an open circuit in the phase winding through which the fault sector current flows in the reverse direction includes: When the voltage meets the ninth fault location characteristic: when P k When = 1, U x =U dc / 2, then the fault is determined to be an open circuit in the phase winding through which the current in the fault sector flows in the forward direction; when the voltage meets the tenth fault location characteristic: when P k When = 1, U x =U dc If the fault is determined to be an open circuit in the phase winding where the current in the faulty sector is flowing in the reverse direction; Among them, P k This is the drive signal for the upper power transistor in the subsequent sector, corresponding to its on-state. U x U is the voltage at the midpoint of phase x bridge arm, where x is the bridge arm containing the upper transistor in the conducting state corresponding to the faulty sector. dc This is the DC voltage of the bus.

10. The method for diagnosing open-circuit faults in an electrically excited doubly salient pole motor inverter and its phase windings according to any one of claims 1-9, characterized in that, The conduction states corresponding to each sector are as follows: Define 0°-120° as sector one: G1=1, G2=0, G3=0, the upper power transistor of phase A bridge arm and the lower power transistor of phase C bridge arm are turned on, the remaining power transistors are turned off, the current in phase A winding is positive and the current in phase C winding is negative, |i d |=i _fd ; Define 120°-240° as sector two: G1=0, G2=1, G3=0, the upper power transistor of phase B bridge arm and the lower power transistor of phase A bridge arm are turned on, the remaining power transistors are turned off, the current in phase B winding is positive and the current in phase A winding is negative, |i d | / 2=i _fd ; Define 240°-360° as sector three: G1=0, G2=0, G3=1, the upper power transistor of phase C and the lower power transistor of phase B are turned on, the remaining power transistors are turned off, the current in phase C winding is positive, and the current in phase B winding is negative, |i d |=i _fd ; Among them, G s Let i be the position signal of sector s. d i is the current value collected by the current sensor. _fd For i d Phase current feedback value obtained through phase current construction strategy.

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