Method for controlling a synchronous electrical machine, corresponding system and motor vehicle comprising the system

A method for controlling a synchronous electrical machine with a permanent magnet powered by a battery delivering a power supply voltage at its terminals, the method comprising:

• computing an initial direct voltage component and of an initial quadratic voltage component in a revolving reference frame comprising a plurality of axes;
• verifying a saturation condition in which it is verified, in an orthogonal reference frame having the direct voltage components for X-axis and the quadratic voltage components for Y-axis, that point of coordinates Vdc and Vqc is outside of a range dependent on Vbat and delimited by a contour, Vdc denoting the initial direct voltage component, Vqc denoting the initial quadratic voltage component, and Vbat denoting a power supply voltage at terminals of the battery, and, if the saturation condition is verified;
• computing an angle
• α
• =
• arctan
• 
• (
• Vqc
• Vdc
• )
• ;
• generating voltages to be applied to the electrical machine if α varies negatively and Vdc is positive or if α varies positively and Vdc is negative, by determining a point of intersection between the contour and a straight line passing through the origin of the orthogonal reference frame and the point of coordinates Vdc and Vqc, the direct voltage component to be applied then being the X-axis of the intersection and the quadratic voltage component to be applied then being the Y-axis of the intersection, whereas, if these conditions on the angle α and the voltage Vdc are not verified, then the voltages already applied in the preceding implementation of the method are applied.

A system for controlling a synchronous electrical machine with permanent magnet powered by a battery having a voltage at its terminals, the system comprising:

• first computation means configured to deliver, at an instant, an initial direct voltage component and an initial quadratic voltage component in a revolving reference frame comprising a plurality of axes;
• second computation means configured to verify a saturation condition in an orthogonal reference frame having the direct voltage components for X-axis and the quadratic voltage components for Y-axis, and to verify a saturation condition being configured to verify that a point of coordinates Vdc and Vqc is outside of a range dependent on Vbat and delimited by a contour, Vdc denoting the initial direct voltage component, Vqc denoting the initial quadratic voltage component, and Vbat denoting a power supply voltage at terminals of the battery, and, if the saturation condition is verified,
• third computation means configured to compute an angle
• α
• =
• arctan
• 
• (
• Vqc
• Vdc
• )
• if the saturation condition is verified;
• means for generating voltages to be applied to the electrical machine configured to determine, if the saturation condition is verified and if α varies negatively and Vdc is positive or if α varies positively and Vdc is negative, a point of intersection between the contour and a straight line passing through the origin of the orthogonal reference frame and the point of coordinates Vdc and Vqc, the direct voltage component to be applied being the X-axis of the intersection and the quadratic voltage component to be applied being the Y-axis of the intersection, whereas, if the saturation condition is verified but these conditions on the angle α and the voltage Vdc are not verified, then the voltages to be applied are the voltages applied at the preceding instant by the control system.