Control technique for limiting the current of an induction machine drive system
First Claim
1. A method of deriving phase voltage control signals suitable for use in controlling current flow to an induction motor, said method comprising the steps of:
- subtracting a stator phase current value from a commanded current value to obtain an error term;
converting said error term into a commanded voltage value in synchronous reference frame;
transforming said commanded voltage value into a commanded voltage vector in stationary reference frame; and
converting said commanded voltage vector into the phase voltage control signals via a pulse width modulation control.
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Abstract
A method and apparatus for deriving phase voltage control signals for use in controlling current flow to an induction motor. The method may comprise obtaining an error term; converting the error term into a commanded voltage value; transforming the commanded voltage value into a commanded voltage vector; and converting the commanded voltage vector into the phase voltage control signals via pulse width modulation control. The apparatus may comprise a Park vector converter for converting a first stator phase measurement and a second stator phase measurement into a stator phase current vector; a scalar operator for obtaining a stator phase current value; a summer for obtaining an error term; an error converter for converting the error term into a commanded voltage value; a voltage transformer for transforming the commanded voltage value into a commanded voltage vector, and pulse width modulation control for converting the commanded voltage vector into the phase voltage control signals.
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Citations
41 Claims
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1. A method of deriving phase voltage control signals suitable for use in controlling current flow to an induction motor, said method comprising the steps of:
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subtracting a stator phase current value from a commanded current value to obtain an error term;
converting said error term into a commanded voltage value in synchronous reference frame;
transforming said commanded voltage value into a commanded voltage vector in stationary reference frame; and
converting said commanded voltage vector into the phase voltage control signals via a pulse width modulation control. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of deriving phase voltage control signals suitable for use in controlling current flow to an induction motor, said method comprising the steps of:
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obtaining a first stator current measurement for a first phase of the induction motor;
obtaining a second stator current measurement for a second phase of the induction motor;
transforming said first and second stator current measurements into a stator phase current value via a Park vector transformation;
subtracting said stator phase current Park vector value from a commanded current Park vector magnitude value to obtain an error term;
operating on said error term via a regulator to obtain a terminal signal;
integrating said terminal signal to obtain a commanded voltage value in synchronous reference frame;
transforming said commanded voltage value into a commanded voltage vector in stationary reference frame; and
converting said commanded voltage vector into the phase voltage control signals via a pulse width modulation control. - View Dependent Claims (19, 20, 21)
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22. A method of deriving phase voltage control signals suitable for use in controlling current flow to an induction motor, said method comprising the steps of:
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subtracting a stator phase current Park vector value from a commanded current Park vector magnitude value to obtain an error term;
operating on said error term to obtain a terminal signal;
summing an input parameter with said terminal signal to obtain a terminal sum;
integrating said error signal to obtain a commanded voltage value in synchronous reference frame;
obtaining an electrical angle by multiplying said commanded voltage value by a constant to obtain a frequency value and integrating said frequency value;
generating a unit vector as a function of said electrical angle;
multiplying said commanded voltage value by said unit vector to yield a commanded voltage vector in stationary reference frame;
converting said commanded voltage vector into the phase voltage control signals via a pulse width modulation control;
obtaining from the induction motor a first stator current measurement for a first phase of the induction motor;
obtaining from the induction motor a second stator current measurement for a second phase of the induction motor;
transforming said first and second stator current measurements into a stator phase current Park vector in stationary reference frame;
generating a complex exponential term as a function of said electrical angle;
multiplying said stator phase current Park vector in stationary reference frame by said complex exponential term to yield a stator phase current Park vector in synchronous reference frame; and
obtaining the magnitude of said stator phase current Park vector in synchronous reference frame to yield said stator phase current Park vector magnitude value. - View Dependent Claims (23, 24)
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25. A method of deriving phase voltage control signals suitable for use in controlling current flow to an induction motor, said method comprising the steps of:
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obtaining a first stator current measurement for a first phase of the induction motor;
obtaining a second stator current measurement for a second phase of the induction motor;
obtaining a third stator current measurement for a third phase of the induction motor;
transforming said first, second, and third stator current measurements into a stator phase current Park vector in stationary reference frame;
multiplying said stator phase current Park vector in stationary reference frame by a complex exponential term to yield a stator phase current Park vector in synchronous reference frame;
obtaining the magnitude of said stator phase current Park vector in synchronous reference frame to yield a stator phase current Park vector magnitude value;
subtracting said stator phase current Park vector magnitude value from a commanded current value to obtain an error term;
operating on said error term via a proportional integral differential regulator to obtain a terminal voltage signal;
integrating said terminal voltage signal to obtain a commanded voltage magnitude value in synchronous reference frame;
transforming said commanded voltage magnitude value into a commanded voltage vector in stationary reference frame; and
converting said commanded voltage vector into the phase voltage control signals via a pulse width modulation control.
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26. A controller suitable for providing phase voltage control signals to an induction motor, said controller comprising:
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a Park vector converter for converting a first stator measurement of a first phase of the induction motor and a second stator measurement of a second phase of the induction motor into a stator phase current Park vector in stationary reference frame;
a scalar operator for obtaining the magnitude of said stator phase current Park vector to yield a stator phase current Park vector magnitude value;
a summer for subtracting said stator phase Park vector current value from a commanded current Park vector value to obtain an error term;
an error converter for converting said error term into a commanded voltage Park vector magnitude value in synchronous reference frame;
a voltage transformer for transforming said commanded voltage Park vector magnitude value into a commanded voltage vector in stationary reference frame; and
a pulse width modulation control for converting said commanded voltage vector into the phase voltage control signals. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34)
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35. An induction machine drive system comprising:
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an induction motor having a first current sensor for measuring a first stator phase current, said induction motor further having a second current sensor for measuring a second stator phase current;
an inverter for transmitting power from a DC link to said induction motor;
a controller for receiving a first stator current measurement from said first current sensor, said controller further for receiving a second stator current measurement from said second current sensor, said controller including;
a Park vector converter for converting said first stator current measurement and said second stator current measurement into a stator phase current Park vector;
a scalar operator for obtaining the magnitude of said stator phase current Park vector to yield a stator phase current value;
a voltage vector generator for producing a commanded voltage vector as a function of said stator phase current value and a commanded current value;
a space vector modulation control for producing a plurality of phase voltage control signals from said commanded voltage vector; and
a gate drive for converting said plurality of phase voltage control signals into a control signal for said inverter. - View Dependent Claims (36, 37, 38, 39, 40, 41)
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Specification