| 主权项 |
1. A method for field weakening control of a three phase permanent magnet AC motor having a rotor and stator driven by a three phase current generated by a variable frequency drive, the method comprising:
inputting a target speed and a maximum drive voltage; measuring the three phase current supplied to the permanent magnet AC motor; transforming the measured three phase current signal into a two-phase signal projected onto a two-axis rotating reference frame, the phase components of the two-phase signal defining a feedback quadrature current and a feedback direct current; calculating an estimated rotor speed and estimated rotor position; calculating a speed error signal by subtracting the estimated rotor speed from the target speed; calculating, using a speed controller, a torque demand from the speed error signal; calculating a demand quadrature current using the torque demand and a demand direct current; calculating a quadrature current error signal by subtracting the feedback quadrature current from the quadrature demand current; calculating, using an Iq controller, a quadrature voltage from the quadrature current error signal; calculating the demand direct current from the maximum drive voltage, the direct voltage and the estimated rotor speed; calculating a total voltage supplied to the AC motor; calculating a voltage error signal by subtracting the total voltage supplied to the AC motor from the maximum drive voltage; calculating a field weakening offset from the voltage error signal; applying the field weakening offset to the demand direct current; calculating a direct current error signal by subtracting the feedback direct current from the demand direct current as offset by the field weakening offset; calculating, using an Id controller, a direct voltage from the direct current error signal; transforming the quadrature and direct voltages into a three phase voltage signal; and modulating a DC voltage with a three phase inverter to supply three phase current to the permanent magnet AC motor. |
