Fault handling of inverter driven PM motor drives

Abstract

An apparatus includes a multi-phase inverter, a fault detector to indicate a detection of a fault, a sensor to provide a speed signal indicative of whether a speed of a pm motor is greater than a transition speed, and a controller. The controller is operable to apply either an open-circuit response or a short-circuit response to the multi-phase inverter. The open-circuit response is applied when the speed of the pm motor is greater less than the transition speed and a fault is detected. The short-circuit response is applied when the speed of the pm motor is less greater than the transition speed and the fault is detected. The transition speed is either a fixed predetermined speed or an adjusted predetermined speed.

Description

BACKGROUND

The present invention relates to permanent magnetic motor drives. In particular, the invention relates to procedures in such drives for handling faults when detected.

Three-phase voltage inverters are commonly employed to the control the magnitude and frequency of the motor phase currents in hybrid vehicles (including electric and fuel cell powered). When the ac motor used is of the class of interior permanent magnet (IPM) type, the reaction of the system to various inverter based faults is of concern since the fault may cause an uncontrolled breaking torque in the motor.

Drive system faults can be classified as short-circuit type faults and open-circuit type faults. The behavior of various faults in permanent magnetic motor drives has been reported in the literature for many years. Modeling and system behavior of short-circuit type faults are described in B. A. Welchko, T. M. Jahns, W. L. Soong, and J. M. Nagashima, “IPM synchronous machine drive response to symmetrical and asymmetrical short circuit faults,” IEEE Trans. Energy Conversion, vol. 18, no. 2, pp. 291-298. June 2003.

For inverter driven IPM motors, an important class of open-circuit type faults results when the control gate signals to all of the six inverter switches are turned off, or disconnected. During this condition, the motor is connected to the dc source (e.g., battery, fuel cell, etc.) via the antiparallel diodes of the inverter switches. The antiparallel diodes create a potential path for current to flow which is dependant upon the motor operating condition and dc source voltage. The fault condition where the six gate signals have been turned off has been termed an uncontrolled generator mode (UCG mode) of operation since the motor would operate during the condition as a generator converting rotational power into electric currents. Modeling and system behavior during UCG mode operation is characterized in T. M. Jahns and V. Caliskan, “Uncontrolled Generator Operation of Interior PM Synchronous Machines Following High-Speed Inverter Shutdown,” IEEE Trans. Industry Applications, vol. 35, no. 6, pp. 1347-1357, Nov./Dec. 1999.

SUMMARY OF THE INVENTION

In a method example of the invention, a method for controlling a multi-phase inverter of a PM motor includes detecting a fault, sensing whether a speed signal indicates that a speed of the PM motor is greater than a transition speed, and applying either an open-circuit or a short circuit response. The open-circuit response is applied when the speed of the PM motor is greater less than the transition speed when the fault is detected, and applying a short-circuit response is applied when the speed signal indicates that the speed of the PM motor is less greater than the transition speed when the fault is detected. The transition speed is either a fixed predetermined speed or an adjusted predetermined speed.

In a first variant of the method embodiment, the applying the open-circuit response includes controlling all switches in the multi-phase inverter drive to be open.

In a second variant of the method embodiment, the applying the short-circuit response includes controlling selected switches in the multi-phase inverter drive to connect all phases of the multi-phase inverter to a single bus and controlling all other switches in the multi-phase inverter drive to be open.

In a third variant of the method embodiment, the transition speed is the fixed predetermined speed and is defined based on parameters characteristic of the PM motor.

In a fourth variant of the method embodiment, the transition speed is the adjusted predetermined speed and is defined based on parameters characteristic of the PM motor adjusted according to either a temperature of the PM motor, or a voltage of a voltage source, or both.

In an embodiment of an apparatus, the apparatus includes am a multi-phase inverter, a fault detector to indicate a detection of a fault, a sensor to provide a speed signal indicative of whether a speed of a PM motor is greater than a transition speed, and a controller. The controller is operable to apply an open-circuit response to the multi-phase inverter when the speed signal indicates that the speed of the PM motor is greater less than the transition speed and a fault is detected. The controller is additionally operable to apply a short-circuit response to the multi-phase inverter when the speed signal indicates that the speed of the PM motor is less greater than the transition speed and the fault is detected. The transition speed is either a fixed predetermined speed or an adjusted predetermined speed.

In a first variant of the apparatus embodiment, the application of the open-circuit response by the controller controls all switches in the multi-phase inverter to be open.

In a second variant of the apparatus embodiment, the application of the short-circuit response by the controller controls selected switches in the multi-phase inverter to connect all phases of the multi-phase inverter to a single bus and controls all other switches in the multi-phase inverter to be open.

In a third variant of the apparatus embodiment, the transition speed is the fixed predetermined speed and is defined based on parameters characteristic of the PM motor.

In a fourth variant of the apparatus embodiment, the transition speed is the adjusted predetermined speed and is defined based on parameters characteristic of the PM motor adjusted according to at least one of a temperature of the PM motor and a voltage of a voltage source.

In an embodiment of a machine-readable medium, the machine-readable medium includes sets of instructions operable in a controller to cause the controller to perform operations. The sets of instructions are operable to cause the controller to apply an open-circuit response to a multi-phase inverter when a speed signal from a sensor indicates that a speed of a PM motor is greater less than a transition speed when the fault is detected. The sets of instructions are further operable to cause the controller to apply a short-circuit response to the multi-phase inverter when the speed signal indicates that the speed of the PM motor is less greater than the transition speed when the fault is detected. The transition speed is either a fixed predetermined speed or an adjusted predetermined speed.

In a first variant of the machine-readable medium, the operator of applying the open-circuit response includes controlling all switches in the multi-phase inverter drive to be open.

In a second variant of the machine-readable medium, the operation of applying the short-circuit response includes controlling selected switches in the multi-phase inverter drive to connect all phases of the multi-phase inverter to a single bus and controlling all other switches in the multi-phase inverter drive to be open.

In a third variant of the machine-readable medium, the transition speed is the fixed predetermined speed and is defined based on parameters characteristic of the PM motor.

In a fourth variant of the machine-readable medium, the transition speed is the adjusted predetermined speed and is defined based on parameters characteristic of the PM motor adjusted according to at least one of a temperature of the PM motor and a voltage of a voltage source.

Having described preferred embodiments of a novel method, apparatus and media for handling faults of inverter driven PM motor drives (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the invention disclosed which are within the scope of the invention as defined by the appended claims.

Having thus described the invention with the details and particularity required by the patent laws, what is claimed and desired protected by Letters Patent is set forth in the appended claims.

Claims

1. A method for controlling a multi-phase inverter of a pm motor comprising:

detecting a fault: ;

sensing whether a speed signal indicates that a speed of the pm motor is greater than a transition speed;

applying an open-circuit response when the speed of the pm motor is greater less than the transition speed when the fault is detected; and

applying a short-circuit response when the sped of the pm motor is less greater than the transition speed when the fault is detected,

wherein the transition speed is one of a fixed predetermined speed and an adjusted predetermined speed.

2. A method according to claim 1, wherein the applying the open-circuit response includes controlling all switches in the multi-phase inverter drive to be open.

3. A method according to claim 1, wherein the applying the short-circuit response includes controlling selected switches in the multi-phase inverter drive to connect all phases of the multi-phase inverter to a single bus and controlling all other switches in the multi-phase inverter drive to be open.

4. A method according to claim 1, wherein the transition speed is the fixed predetermined speed and is defined based on parameters characteristic of the pm motor.

5. A method according to claim 1, wherein the transition speed is the adjusted predetermined speed and is defined based on parameters characteristic of the pm motor adjusted according to at least one of a temperature of the pm motor and a voltage of a voltage source.

6. An apparatus comprising:

a multi-phase inverter;

a fault detector to indicate a detection of a fault;

a sensor to provide a speed signal indicative of whether a speed of a pm motor is greater than a transition speed; and

a controller operable to apply an open-circuit response to the multi-phase inverter when the speed of the pm motor is greater less than the transition speed and a fault is detected, and additionally operable to apply a short-circuit response to the multi-phase inverter when the speed of the pm motor is less greater than the transition speed and the fault is detected, wherein the transition speed is one of a fixed predetermined speed and an adjusted predetermined speed.

7. An apparatus according to claim 6, wherein the application of the open-circuit response by the controller controls all switches in the multi-phase inverter to be open.

8. An apparatus according to claim 6, wherein the application of the short-circuit response by the controller controls selected switches in the multi-phase inverter to connect all phases of the multi-phase inverter to a single bus and controls all other switches in the multi-phase inverter to be open.

9. An apparatus according to claim 6, wherein the transition speed is the fixed predetermined speed and is defined based on parameters characteristic of the pm motor.

10. An apparatus according to claim 6, wherein the transition speed is the adjusted predetermined speed and is defined based on parameters characteristic of the pm motor adjusted according to at least one of a temperature of the pm motor and a voltage of a voltage source.

11. A machine-readable medium comprising sets of instructions operable in a controller to cause the controller to perform operations comprising:

applying an open-circuit response to a multi-phase inverter when a speed signal from a sensor indicates that a speed of a pm motor is greater less than a transition speed when a fault is detected; and

applying a short-circuit response to the multi-phase inverter when the speed signal indicates that the speed of the pm motor is less greater than the transition speed when the fault is detected,

wherein the transition speed is one of a fixed predetermined speed and an adjusted predetermined speed.

12. A machine-readable medium according to claim 11, wherein the operation of applying the open-circuit response includes controlling all switches in the multi-phase inverter drive to be open.

13. A machine-readable medium according to claim 11, wherries the operation of applying the short-circuit response includes controlling selected switches in the multi-phase inverter drive to connect all phases of the multi-phase inverter to a single bus and controlling all other switches in the multi-phase inverter drive to be open.

14. A machine-readable medium according to claim 11, wherein the transition speed is the fixed predetermined speed and is defined based on parameters characteristic of the pm motor.

15. A machine-readable medium according to claim 11, wherein the transition speed is the adjusted predetermined speed and is defined based on parameters characteristic of the pm motor adjusted according to at least one of a temperature of the pm motor and a voltage of a voltage source.