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US 6,788,024 B2Granted
Position-sensorless motor control method and apparatus
AssigneeHitachi, Ltd.
InventorsSatoru Kaneko, Ryoso Masaki, Takefumi Sawada
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AssigneeHitachi, Ltd.
InventorsSatoru Kaneko, Ryoso Masaki, Takefumi Sawada
Estimating the term…
A provide a position-sensorless motor control apparatus comprises a salient-pole AC motor 2, a PWM inverter 3 for applying voltage to the AC motor 2, and a controller 1 for controlling the PWM inverter 3 by means of PWM signals, wherein the controller 1 has a position estimation means 11 which detects motor inductance in the pre-determined direction to the vector direction of the current that flows through the AC motor 2 and estimates the AC motor's rotor position based on the motor inductance.
A position-sensorless motor control method of controlling a PWM inverter for applying voltage to a salient-pole AC motor and controlling said AC motor, wherein vector control of said AC motor is performed by detecting motor inductance in the pre-determined direction to the detected current vector direction of said AC motor and estimating said AC motor's rotor position based on said detected motor inductance.
A position-sensorless motor control apparatus comprising a PWM inverter for applying voltage to a salient-pole AC motor and a controller for controlling said PWM inverter, wherein said controller comprises a means for applying a position detection voltage signal in the pre-determined direction to said AC motor's detected current vector direction and detecting the current fluctuation condition caused by said position detection voltage, a means for detecting said motor inductance from said detected current fluctuation, and a position estimation means for estimating said AC motor's rotor position based on said detected motor inductance, thereby performing vector control of said AC motor.
A position-sensorless motor control apparatus comprising a PWM inverter for applying voltage to a salient-pole AC motor and a controller for controlling said PWM inverter, wherein said controller comprises a position estimation means for detecting motor inductance in the direction 45 degrees to the magnetic flux axis and estimating said AC motor's rotor position based on said detected motor inductance.
Dependencies are inferred from the claim text.
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Estimation or adaptation of machine parameters, e.g. flux, current or voltage: estimation of constants, e.g. the rotor time constant
Control or regulation of electric motors, electric generators or dynamo-electric converters
Term ended 18 Mar 2023 (estimated)
1. Field of the Invention
The present invention relates to an AC (alternating current) motor control apparatus and specifically to a position-sensorless motor control method and apparatus that estimates and detects a magnetic pole position of a synchronous motor's rotor without needing a sensor thereby controlling the AC motor.
2. Description of Prior Art
FIG. 1 is a schematic diagram that illustrates a motor control apparatus which is a first embodiment of the present invention.
FIG. 2 shows the relation between the rotating coordinate system (d- and q-axes) and the coordinate system at rest (α-β axes).
FIG. 3 shows the inductance characteristic of the motor.
1: Controller, 2: AC motor, 3: PWM inverter, 4: Current command generator, 5: Current control section, 6: Three-phase converter, 7: PWM signal generator, 8u, 8v, 8w: Current sensor, 9: Current detector, 10: dq converter, 11: Position estimation means, 12: Speed calculator, 13: Application direction switching means, 15: Voltage signal calculator, 16: Current fluctuation calculator, 20: Reference current fluctuation determination section, 21: Position identifier
Hereafter, an embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a schematic diagram that illustrates a motor control apparatus which is a first embodiment of the present invention. First, configuration of a motor control system will be described. A controller 1 inputs torque command Tr* and outputs a signal sent by a PWM signal generator 7 to a PWM inverter 3 so that an AC motor 2 can generate torque specified by the command. At this point, a current command generator 4 located in the controller 1 inputs torque command Tr* and motor speed ωm{circumflex over ( )} to determine the current commands iq* and id* so that maximum efficiency can be obtained at the current operating point. Herein, id* denotes a current command for the direction (d-axis) of the motor rotor's magnetic flux and iq* denotes a current command for the direction (q-axis) perpendicular to the motor rotor's magnetic flux direction.
The above-mentioned d- and q-axis coordinates are rotating coordinate systems as shown in FIG. 2. The coordinate systems rotate at motor angular speed ω to the coordinate system at rest α-β axes (two-phase coordinates converted from U, V, and W phases). Herein, let the phase from the reference α-axis towards the direction (d-axis) of the motor rotor's magnetic flux be rotor position (magnetic pole position) θ. As shown in FIG. 1, in this embodiment, a current control section 5 performs current control calculation on the rotating coordinate d- and q-axes to determine voltage commands Vdc and Vqc on the d- and q-axes. Thus, the current control of the d- and q-axis coordinates makes it possible to accurately control both the magnetic flux direction current and the current (acting on torque) perpendicular to the magnetic flux direction current, thereby enabling control of the motor torque and magnetic flux.