Vector control system for induction motors

A vector control method for a three-phase ac induction motor driven by a pulse width modulation-type power converter comprising the steps of:

• applying an exciting current command value and a torque current command value in a rotating magnetic field coordinate system;
• detecting an actual exciting current value and torque value;
• detecting a deviation between said exciting current command value and said detected actual exciting value and a deviation between said torque current command value and said detected actual torque value;
• producing three phase ac voltage command values in a stator coordinate system tending to reduce said deviations to zero and using the same as control signals for said PWM-type power converter;
• and
• causing said power converter to determine voltages for driving said induction motor and a frequency in accordance with said three phase ac voltage command values;
• said actual exciting current value and torque current value detecting step further comprising,
• integrating a value of each of two phase ac inputs of three phase ac inputs of said induction motor and then sampling the integrated values at a predetermined period;
• subjecting each of said sampled values of the integrated two phase ac values to definite integration at said predetermined period;
• and
• transforming said definite integrated values to an actual exciting current value and torque current value in said rotating magnetic field coordinate system.

A vector control method for a three-phase ac induction motor comprising the steps of:

• applying an exciting current command value and a torque current command value in a rotating magnetic field coordinate system;
• detecting an actual exciting current value and torque current value;
• detecting a deviation between said exciting current command value and said detected actual exciting current value and a deviation between said torque current command value and said detected actual torque current value;
• producing three phase ac voltage command values in a stator coordinate system tending to reduce said deviations to zero;
• and
• determining voltages and a frequency for driving said induction motor in accordance with said three phase ac voltage command values;
• said actual exciting current value and torque current detecting step further comprising,
• transforming three phase ac inputs of said induction motor to orthogonal two phase ac currents in said stator coordinate system,
• integrating the orthogonal two phase ac currents,
• sampling the integrated value of each of said two phase ac currents at a predetermined period,
• detecting a difference between an integrated value of an nth sampled value and an integrating value of a (n+1)th sampled value (n represents a positive integer) of each said ac current value, and
• transforming said difference values to an actual exciting current value and torque current value, respectively, in said rotating magnetic field coordinate system.

A vector control method for a three-phase ac induction motor comprising the steps of:

• applying an exciting current command value and a torque current command value in a rotating magnetic field coordinate system;
• detecting an actual exciting current value and torque current value;
• detecting a deviation between said exciting current command value and said detected exciting current value and a difference between said torque current command value and said detected actual torque current value;
• producing three phase ac voltage command values in a stator coordinate system tending to reduce said deviations to zero;
• and
• determining voltages and a frequency for driving said induction motor in accordance with said three phase ac voltage command values;
• said step for detecting said actual exciting current value and torque current value further comprising,
• integrating a value of each of two phase ac inputs of three phase ac inputs to said induction motor and then sampling the integrated values at a predetermined period;
• transforming said integrated value to orthogonal two phase ac values in said stator coordinate system;
• detecting a difference between integrated values of nth and (n+1)th sampled values of each of said transformed orthogonal two phase ac values (n is a positive integer);
• and
• transforming said difference values to an actual exciting current value and torque current value, respectively, in said rotating magnetic field coordinate system.

A vector control system for a three-phase ac induction motor comprising:

• a power converter for generating three phase ac currents;
• an induction motor for receiving said three phase ac currents;
• means for detecting a value of each phase current of said three phase ac currents;
• means for receiving an exciting current command value and a torque current command value in a rotating magnetic field coordinate system for said induction motor;
• means for detecting an actual exciting current value and torque current value;
• means for detecting a deviation between said exciting current command value and said detected exciting current value and a deviation between said torque current command value and said detected torque current value;
• means for producing voltage commands in said rotating magnetic field coordinate system tending to reduce said deviations to zero;
• first coordinate transformation means for transforming said voltage commands to three phase ac voltage commands in a stator coordinate system;
• means responsive to said three phase ac command values to control said power converter;
• said actual exciting current value and torque current value detecting means including,
• means for integrating a value of each of two phase ac currents of said detected three phase ac currents and sampling said integrated value at a predetermined period;
• means for subjecting each of said sampled value of the integrated two phase ac currents to definite integration at said predetermined period;
• and
• second coordinate transformation means for transforming said definite integrated values to an actual exciting current value and torque current value, respectively, in said rotating magnetic field coordinate system.

A vector control system for a three phase ac induction motor comprising:

• a pulse width modulation-type power converter for generating three phase ac currents;
• an induction motor for receiving said three phase ac currents;
• means for detecting a value of each of said three phase ac currents;
• means for receiving an exciting current command value and a torque current command value in a rotating magnetic field coordinate system for said induction motor;
• means for detecting an actual exciting current value and torque current value;
• means for detecting a deviation between said exciting current command value and said detected exciting current value and a deviation between said torque current command value and said detected torque current value;
• means for producing voltage commands in said rotating magnetic field coordinate system tending to reduce said deviations to zero;
• first coordinate transformation means for transforming said voltage commands to three phase ac voltage commands in said stator coordinate system;
• and
• means responsive to said three phase ac voltage command values to control said power converter;
• said actual exciting current value and torque current value detecting means including,
• means for integrating a value of each of two phase ac currents of said detected phase currents and sampling the integrated value at a predetermined period;
• means for subjecting each of said sampled value of the integrated two phase ac currents to definite integration at said predetermined period;
• second coordinate transformation means for transforming said definite integrated values to an actual exciting current value and torque current value, respectively, in said rotating magnetic field coordinate system.

A vector control system for a three-phase ac induction motor comprising:

• a power converter for generating three phase ac currents;
• an induction motor for receiving said three phase ac currents;
• means for detecting a value of each of said three phase ac currents;
• means for receiving an exciting current command value and a torque current command value in a rotating magnetic field coordinate system for said induction motor;
• means for detecting an actual exciting current value and torque current value;
• means for detecting a deviation between said exciting current command value and said detected exciting current and a deviation between said torque current command value and said detected torque current value;
• means for producing voltage commands in said rotating magnetic field coordinate system tending to reduce said deviations to reduce;
• first coordinate transformation means for transforming said three phase voltage commands to three phase ac voltage commands in a stator coordinate system;
• and
• means responsive to said three phase ac voltage command values to control said power converter;
• said actual exciting current value and torque current value detecting means comprising,
• 3phase-2 phase converting means for converting said detected three phase currents to orthogonal two phase ac currents in said stator coordinate system;
• means for integrating a value of each of said orthogonal two phase ac currents and sampling the integrated value at a predetermined period;
• means for detecting a difference between an integrated value of an nth sampled value and an integrated value of a (n+1)th sampled value (n is a positive integer);
• and
• second coordinate transformation means for transforming said differential values to an actual exciting current value and torque current value, respectively, in said rotating magnetic field coordinate system.

A vector control system for a three-phase ac induction motor comprising:

• a power converter for generating three phase ac currents;
• an induction motor for receiving said three phase ac currents;
• means for detecting a value of each of said three phase ac currents;
• means for receiving an exciting current command value and a torque current command value in a rotating magnetic field coordinate system for said induction motor;
• means for detecting an actual exciting current value and torque current value;
• means for detecting a deviation between said exciting current command value and said detected exciting current value and a deviation between said torque current command value and said detected torque current value;
• means for producing voltage commands in said rotating magnetic field coordinate system tending to reduce said deviations to zero;
• first coordinate transformation means for transforming said voltage commands to three phase ac voltage commands in said stator coordinate system;
• and
• means responsive to said three phase ac voltage command values to control said power converter;
• said actual exciting current value and torque current value detecting means including;
• means for integrating a value of each of two phase ac currents of said detected three phase ac currents and sampling the integrated value at a predetermined period;
• phase converting means for converting said integrated values to orthogonal two phase ac values in said stator coordinate system;
• means for detecting a difference between an integrated value of an nth sampled value and an integrated value of a (n+1)th sampled value of each of said converted orthogonal two phase ac values (n is a positive integer);
• and
• second coordinate transformation means for transforming said differential values to an actual exciting current value and torque current value, respectively, in said rotating magnetic field coordinate system.