Method and apparatus for controlling permanent magnet synchronous motor by using pulse width modulation

Claim 1

A method of controlling a permanent magnet synchronous motor by using pulse width modulation, comprising the steps of: (a) comparing a reference carrier wave with differences between detected armature currents and command signals for respective phase armature windings to obtain pulse width modulation signals; (b) controlling an inverter with the pulse width modulation signals (c) detecting a degree of saturation of voltage signals representing differences between the detected armature currents and the current command signals and determined by a peak value of the reference carrier wave; and (d) shifting phases of respective phase current command signals from those which provide an orthogonal relation between a resultant armature current and a main flux of a magnetic field, in accordance with the detected degree of saturation.

Claim 2

A method of controlling a permanent magnet synchronous motor by using pulse width modulation, comprising the steps of: (a) comparing a reference carrier wave with differences between detected armature currents and command signals for respective phase armature windings to obtain pulse width modulation signals; (b) controlling an inverter with the pulse width modulation signals (c) detecting a degree of saturation of voltage signals representing differences between the detected armature currents and the current command signals and determined by a peak value of the reference carrier wave; and (d) shifting phases of respective phase current command signals from those which provide an orthogonal relation between a resultant armature current and a main flux of a magnetic field, in accordance with the detected degree of saturation.

Claim 5

An apparatus for controlling a permanent magnet synchronous motor having a rotor, by using pulse width modulation, comprising: means for detecting a position of the rotor of the permanent magnet synchronous motor; first storage means for storing a first armature current command signal group of respective phases consisting of first armature current command signals which have values for providing an orthogonal relation between a resultant armature current and a main flux of a magnetic field, and which correspond to rotor positions; means for detecting the armature currents of the respective phases; means for comparing a reference carrier wave with difference signals representing differences between values of the first armature current command signals, read out from said first storage means in accordance with the detected rotor position, and values of the detected armature currents, and for generating pulse width modulation signals for the respective phases; an inverter for controlling the armature currents of the respective phases in response to the pulse width modulation signals; saturation detecting means for generating a saturation signal having a predetermined saturation value given in accordance with a peak value of the reference carrier wave and having a value as a predetermined function of the difference signals; second storage means for storing a second armature current command signal group of the respective phases consisting of second armature current command signals which have values for providing a relation shifted by a predetermined angle from the orthogonal between the resultant armature current and the main flux of the magnetic field, and which correspond to the rotor positions; correction signal generating means for converting values of the second armature current command signals of the respective phase windings read out from said second storage means in accordance with the rotor position, into correction signals, each having a value corresponding to a value of the saturation signal; and means for correcting the first armature current command signals in accordance with the correction signals to shift the phases of the difference signals.

Claim 6

An apparatus for controlling a permanent magnet synchronous motor having a rotor, by using pulse width modulation, comprising: means for detecting a position of the rotor of the permanent magnet synchronous motor; first storage means for storing a first armature current command signal group of respective phases consisting of first armature current command signals which have values for providing an orthogonal relation between a resultant armature current and a main flux of a magnetic field, and which correspond to rotor positions; means for detecting the armature currents of the respective phases; means for comparing a reference carrier wave with difference signals representing differences between values of the first armature current command signals, read out from said first storage means in accordance with the detected rotor position, and values of the detected armature currents, and for generating pulse width modulation signals for the respective phases; an inverter for controlling the armature currents of the respective phases in response to the pulse width modulation signals; saturation detecting means for generating a saturation signal having a predetermined saturation value given in accordance with a peak value of the reference carrier wave and having a value as a predetermined function of the difference signals; second storage means for storing a second armature current command signal group of the respective phases consisting of second armature current command signals which have values for providing a relation shifted by a predetermined angle from the orthogonal between the resultant armature current and the main flux of the magnetic field, and which correspond to the rotor positions; correction signal generating means for converting values of the second armature current command signals of the respective phase windings read out from said second storage means in accordance with the rotor position, into correction signals, each having a value corresponding to a value of the saturation signal; and means for correcting the first armature current command signals in accordance with the correction signals to shift the phases of the difference signals.