Speed control of mechanically paralleled electrical drives without intercommunication buses

A method for outputting a current demand to drive an electrical motor of paralleled electric motors driving a mechanical load, the method comprising:

• receiving a desired speed output of the electrical motor;
• measuring an actual speed output of the electrical motor;
• calculating a speed error between the desired speed output of the electrical motor and the actual speed output of the electrical motor and subtracting a first gain;
• outputting a current demand to drive the electrical motor based on (i) the speed error between the desired speed output of the electrical motor and the measured speed of the electrical motor and (ii) a feedback signal of the current demand scaled by the first gain;
• and
• varying the first gain by applying one or more gain scheduling techniques so as to apply larger gain values during speed transients and smaller gain values during steady-state operation of the electrical motor.

A system comprising:

• a first electrical motor and associated first motor drive;
• and
• a second electrical motor and associated second motor drive;
• wherein the first electrical motor comprises a first output shaft and a first speed sensor configured to measure a speed of the first output shaft;
• wherein the first motor drive comprises a first controller configured to output (i) a first current demand for the first electrical motor based on a first speed error between a desired speed of the first output shaft and the measured speed of the first output shaft and (ii) a first feedback signal of the first current demand scaled by a first gain, the first gain being subtracted from the first speed error, and wherein the first controller is further configured to vary the first gain using one or more gain scheduling techniques so as to apply larger gain values during speed transients and smaller gain values during steady-state operation of the first electrical motor;
• wherein the second electrical motor comprises a second output shaft and a second speed sensor configured to measure a speed of the second output shaft;
• wherein the second motor drive comprises a second controller configured to output (i) a second current demand for the second electrical motor based on a second speed error between a desired speed of the second output shaft and the measured speed of the second output shaft and (ii) a second feedback signal of the second current demand scaled by a second gain, the second gain being subtracted from the second speed error;
• and
• wherein the desired speed of the first output shaft is common to the desired speed of the second output shaft.