Parameter identification for induction machines
A method and a control apparatus for determining parameters for controlling an electric drive having an electric machine improve the start-up of the electric drive by applying a current indicator as a signal at three-phase winding connections of the electric machine, and measuring a d-component and a q-component of the stator voltage and of the stator current at the winding connections. In a first measurement step, a rotating current indicator is applied to the three-phase winding connections and the electric machine is oriented such that an exciter current in the q-axis assumes a minimum. In a second measurement step, when the rotor of the electric machine is stationary, a field winding of the electrical machine is short-circuited and a current indicator in form of a binary noise signal is applied to the winding connections. A stator impedance is then determined as a first control parameter.
1. A method for determining control parameters for a vector control controlling an electric drive having an electric machine, comprising:
in a first measurement step, applying a rotating current indicator to the three-phase winding connections and orienting the electric machine such that an exciter current in a q-axis adopts a minimum value;
in a second measurement step, when a rotor of the electric machine is stationary, short-circuiting a field winding of the electric machine and applying to the three-phase winding connections a current indicator in form of a binary noise signal;
measuring, at three-phase winding connections, a d-component and a q-component of a stator voltage and of a stator current;
determining from the measured d-component and the q-component of the stator voltage and of the stator current as a first control parameter a stator impedance;
generating the binary noise signal using a pseudo-random number sequence produced with a feedback shift register having a shift clock, with different predeterminable frequency spectra being generated with a plurality of shift clocks.
2. The method of claim 1 , wherein the stator impedance is frequency-dependent and determined using a Fast Fourier Transformation.
3. The method of claim 1 , further comprising calculating a frequency response of the real part and the imaginary part of the stator impedance.
4. The method of claim 1 , further comprising
measuring a field current of the short-circuited field winding, and
determining from the field current and the d-component of the stator current as a second control parameter a ratio of the field current to the stator current.
5. The method of claim 4 , wherein at least one of the first and second control parameters are stored for use in the vector control.
6. A control apparatus for an electric drive configured to determine and store a control parameter for a vector control in a start-up phase, and to use the stored control parameter for the vector control after completion of the start-up phase, wherein the vector control determines the control parameter for the vector control by
applying, in a first measurement step, a rotating current indicator to the three-phase winding connections and orienting the electric machine such that an exciter current in a q-axis adopts a minimum value;
short-circuiting, in a second measurement step, when a rotor of the electric machine is stationary, a field winding of the electric machine and applying to the three-phase winding connections a current indicator in form of a binary noise signal;
measuring, at three-phase winding connections, a d-component and a q-component of a stator voltage and of a stator current;
determining from the measured d-component and the q-component of the stator voltage and of the stator current as a first control parameter a stator impedance;
generating the binary noise signal using a pseudo-random number sequence produced with a feedback shift register having a shift clock, with different predeterminable frequency spectra being generated with a plurality of shift clocks.
7. An electric drive, comprising
an electric machine,
a frequency converter, and
a voltage measuring apparatus and a current measuring apparatus arranged in an electrical connection between the frequency converter and the electric machine,
wherein the frequency converter has a control apparatus for the electric drive configured to determine and store a control parameter for a vector control in a start-up phase of the electric drive, and to use the stored control parameter for the vector control after completion of the start-up phase, wherein the vector control determines the control parameter for the vector control by
applying, in a first measurement step, a rotating current indicator to the three-phase winding connections and orienting the electric machine such that an exciter current in a q-axis adopts a minimum value;
short-circuiting, in a second measurement step, when a rotor of the electric machine is stationary, a field winding of the electric machine and applying to the three-phase winding connections a current indicator in form of a binary noise signal;
measuring with the voltage measuring apparatus and the current measuring apparatus, at three-phase winding connections, a d-component and a q-component of a stator voltage and of a stator current;
determining from the measured d-component and the q-component of the stator voltage and of the stator current as a first control parameter a stator impedance; and
generating the binary noise signal using a pseudo-random number sequence produced with a feedback shift register having a shift clock, with different predeterminable frequency spectra being generated with a plurality of shift clocks.