Method for the field-oriented control of an induction motor
First Claim
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1. Method for indirect field-oriented control of an induction motor by means of a frequency converter incorporating control mean, the method comprising the steps of:
- (a) measuring rotor position of the motor,(b) calculating a slip frequency,(c) determining a transformation angle (δ
) from the measured rotor position (Θ
r) and the calculated slip frequency (ω
s) by summation,(d) making a first correction of the transformation angle (δ
) based on a fixed dead time,(e) measuring motor current,(f) determining a field-oriented voltage reference value (Usdref) given by the control means,(g) estimating a field-orientated actual voltage value (Usdpred) employing the magnetizing component of the measured motor current and taking into consideration a voltage drop proportional to the measured current,(h) calculating a voltage difference (ed) between the voltage reference value (Usdref) and the actual voltage value Usdpred),(i) determining an error angle (ε
) between a voltage reference vector (Uso) and an actual voltage vector (U'"'"'so) employing the voltage difference (ed), assuming an approximately equal amplitude and a known phase angle of the voltage reference vector (Uso) and the actual voltage vector (U'"'"'so),(j) making a second correction of the transformation angle (δ
) employing the determined error angle (ε
).
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Abstract
A method for the field-oriented control of an induction motor (2) by means of a frequency converter (1) is disclosed, in which method a transformation angle (δ) is determined by estimation and is corrected in dependence on a rotational speed (ωmR) of a rotor flux vector (imR) or of the induction motor (2) and/or in dependence on a delay time (Tdel). In this connection it is desirable to improve the control behavior. To that end, the transformation angle (δ) is corrected a second time to compensate for a phase shift in the frequency converter (1).
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Citations
19 Claims
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1. Method for indirect field-oriented control of an induction motor by means of a frequency converter incorporating control mean, the method comprising the steps of:
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(a) measuring rotor position of the motor, (b) calculating a slip frequency, (c) determining a transformation angle (δ
) from the measured rotor position (Θ
r) and the calculated slip frequency (ω
s) by summation,(d) making a first correction of the transformation angle (δ
) based on a fixed dead time,(e) measuring motor current, (f) determining a field-oriented voltage reference value (Usdref) given by the control means, (g) estimating a field-orientated actual voltage value (Usdpred) employing the magnetizing component of the measured motor current and taking into consideration a voltage drop proportional to the measured current, (h) calculating a voltage difference (ed) between the voltage reference value (Usdref) and the actual voltage value Usdpred), (i) determining an error angle (ε
) between a voltage reference vector (Uso) and an actual voltage vector (U'"'"'so) employing the voltage difference (ed), assuming an approximately equal amplitude and a known phase angle of the voltage reference vector (Uso) and the actual voltage vector (U'"'"'so),(j) making a second correction of the transformation angle (δ
) employing the determined error angle (ε
). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. Method for field-oriented control of an induction motor by means of a frequency converter, comprising determining a transformation angle by estimation, correcting the transformation angle a first time in dependence on one of I) the rotational speed of a rotor flux vector of the induction motor;
- II) the rotational speed of the induction motor;
III) a time delay; and
combinations of I), II) and III), and correcting the transformation angle a second time by determining an error angle (e) between a voltage reference vector (Uso) and an actual voltage sector (U'"'"'so) employing a voltage difference (ed), and adding this error angle to the corrected transformation angle. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
- II) the rotational speed of the induction motor;
Specification