US2010237817A1PendingUtilityA1
Method and Apparatus for Estimating Rotor Position in a Sensorless Synchronous Motor
Est. expiryMar 23, 2029(~2.7 yrs left)· nominal 20-yr term from priority
H02P 21/18H02P 21/26H02P 21/0007
42
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Claims
Abstract
The present invention provides a simple, robust, and universal position observer for use with sensorless synchronous machines. The observer may be implemented using an equivalent EMF model of a synchronous machine or, alternately, using a sliding mode controller based on the equivalent EMF model of the synchronous machine. The observer may be used on any type of synchronous machine, including salient or non-salient pole machines such as a permanent magnet, interior permanent magnet, wound rotor, or reluctance synchronous machine. The observer provides low sensitivity to parameter variations and disturbances or transient conditions in the machine. In addition, no knowledge of speed is required as an input to the observer and an estimated position may be calculated using a subset of the machine parameters.
Claims
exact text as granted — not AI-modified1 . A method of estimating a rotor position in a synchronous motor comprising the steps of:
determining a current drawn by and a voltage applied to the synchronous motor during operation of the synchronous motor; obtaining a motor resistance and a q axis inductance for the synchronous motor; applying the motor current and voltage as an input to a model of the synchronous motor to obtain an equivalent EMF value of the motor, the model being a function of the motor resistance and the q axis inductance and independent of motor speed and d axis inductance; and determining the estimated rotor position from the equivalent EMF value.
2 . The method of estimating the rotor position of claim 1 wherein the model of the synchronous motor is of the form:
[
v
α
v
β
]
=
[
R
+
L
q
t
0
0
R
+
L
q
t
]
·
[
i
α
i
β
]
+
[
e
α
′
e
β
′
]
3 . The method of claim 1 wherein the equivalent EMF value is in a stationary reference frame such that the equivalent EMF value has an alpha and a beta component and determining the estimated rotor position comprises the steps of:
integrating each of the alpha and beta components of the equivalent EMF value; and
calculating the arctangent of the integrated alpha component over the integrated beta component.
4 . The method of estimating the rotor position of claim 1 wherein the estimated rotor position is used to regulate the current drawn by and to determine the voltage applied to the synchronous motor.
5 . The method of estimating the rotor position of claim 1 wherein the synchronous motor is a salient pole motor.
6 . The method of estimating the rotor position of claim 1 wherein the synchronous motor is a non-salient pole motor.
7 . The method of estimating the rotor position of claim 1 wherein the q axis inductance is obtained from a table of q axis inductances that are a function of the current drawn by the synchronous motor.
8 . The method of estimating the rotor position of claim 1 wherein the motor current and voltage are transformed to a stationary reference frame such that a transformed current and voltage each have an alpha and a beta component wherein the alpha component leads the beta component by ninety degrees and the alpha component has substantially the same magnitude as the beta component.
9 . The method of estimating the rotor position of claim 8 wherein the model uses the transformed current and voltage to determine an equivalent EMF value in the stationary reference frame having an alpha and a beta component.
10 . The method of estimating the rotor position of claim 9 wherein the equivalent EMF value is integrated with respect to time to obtain a flux linkage as a complex vector in the stationary reference frame having an alpha and a beta component.
11 . The method of estimating the rotor position of claim 10 wherein the estimated rotor position is obtained by determining an arctangent of the beta component of the flux linkage over the alpha component of the flux linkage.
12 . A method of estimating a rotor position in a synchronous motor comprising the steps of:
determining a current drawn by and a voltage applied to the synchronous motor during operation of the synchronous motor; obtaining a motor resistance and a q axis inductance for the synchronous motor; applying the motor current and voltage signals as an input to a model of the synchronous motor to obtain an observed value of motor current output to the motor, the model being a function of the motor resistance, the q axis inductance, and a controller gain and independent of motor speed and d axis inductance; determining the estimated rotor position based on the difference between the observed value of motor current and the measured current signal; and
13 . The method of estimating a rotor position of claim 12 wherein the observed and measured motor currents are in a stationary reference frame having an alpha and a beta component and using a difference between the observed motor current and the measured motor current to obtain the estimated rotor position further comprises the steps of:
using a sign function on each of the alpha and beta components of the observed motor current to identify whether the difference is greater than or less than zero;
passing the output of the sign function through a low pass filter to extract an equivalent EMF value in the stationary reference frame having an alpha and a beta component; and
obtaining the estimated rotor position by negating an arctangent of the alpha component of the equivalent EMF value over the beta component of the equivalent EMF value.
14 . The method of estimating the rotor position of claim 12 wherein the model of the synchronous motor is of the form:
[
i
α
^
.
i
β
^
.
]
=
1
L
q
[
v
α
v
β
]
-
R
L
q
[
i
α
^
i
β
^
]
-
K
SM
L
q
[
sign
(
i
α
^
-
i
α
)
sign
(
i
β
^
-
i
β
)
]
15 . A motor drive system for a multi-phase synchronous motor having an input voltage source comprising:
a power conversion section to convert an input voltage to an output voltage for the synchronous motor; at least one voltage sensor providing a voltage signal corresponding to the output voltage applied to the motor; at least one current sensor providing a current signal corresponding to a current output to the motor; a processor receiving each of the voltage signals and the current signals and executing a stored program, the program performing the steps of: obtaining a motor resistance and a q axis inductance for the synchronous motor; obtaining the voltage and current signals at a predetermined time interval, the time interval being selected such that a change in speed of the synchronous motor during the time interval is approximately zero; applying the motor current and voltage signals as an input to a model of the synchronous motor to obtain an equivalent EMF value of the motor, the model being a function of the motor resistance and the q axis inductance and independent of motor speed and d axis inductance; determining the estimated rotor position from the equivalent EMF value; and providing at least one command signal to the power conversion section to control the conversion of the input voltage to the output voltage based on the estimated rotor position.
16 . A motor drive system for a multi-phase synchronous motor having an input voltage source comprising:
a power conversion section to convert an input voltage to an output voltage for the synchronous motor; at least one voltage sensor providing a voltage signal corresponding to the output voltage applied to the motor; at least one current sensor providing a current signal corresponding to a current output to the motor; a processor receiving each of the voltage signals and the current signals and executing a stored program, the program performing the steps of: obtaining a motor resistance and a q axis inductance for the synchronous motor; obtaining the voltage and current signals at a predetermined time interval, the time interval being selected such that a change in speed of the synchronous motor during the time interval is approximately zero; applying the motor current and voltage signals as an input to a model of the synchronous motor to obtain an observed value of motor current output to the motor, the model being a function of the motor resistance, the q axis inductance, and a controller gain and independent of motor speed and d axis inductance; determining the estimated rotor position based on the difference between the observed value of motor current and the measured current signal; and providing at least one command signal to the power conversion section to control the conversion of the input voltage to the output voltage based on the estimated rotor position.Cited by (0)
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