Variable speed drive control

A non-transitory computer-readable storage medium comprising instructions which, when executed by at least one hardware processor, cause the at least one hardware processor to perform a method for controlling a variable speed drive driving a three-phase electric motor, the variable speed drive comprising a pulse width modulation (PWM) controller, an inverter, and a DC-link adapted to supply the inverter with a significantly continuous voltage, wherein:

• the inverter comprises three legs connected to three windings of the electric motor, each of the three legs being connected on a first side to a positive bus of the significantly continuous voltage and on a second side to a negative bus of the significantly continuous voltage, each of the three legs comprising a top switch and a bottom switch;
• wherein
• each of the top switch and the bottom switch comprises two components, a first component being an Insulated Gate Bipolar Transistor (IGBT) controlled by a PWM signal output by the PWM controller based on a control law of the electric motor, and a second component being a freewheeling diode connected in parallel with the IGBT;
• and
• the method comprising:
• measuring current signals in the three windings of the electric motor;
• determining a current parameter associated with the electric motor based on the current signals,
• wherein the current parameter comprises a current offset of at least one of the three windings of the electric motor in relation to a zero-current value;
• or
• wherein the current parameter comprises a current misbalance between at least two windings of the electric motor;
• determining an amended control law of the electric motor for decreasing the current parameter, wherein the determining comprises determining a proportional factor and an integral factor of a proportional-integer (PI) regulator for canceling the current parameter;
• and
• outputting PWM signals to at least one of the IGBTs based on the amended control law.

A system comprising:

• a variable speed drive configured to drive a three-phase electric motor having three windings;
• an inverter comprising three legs connected to the three windings of the electric motor, each of the three legs being connected on a first side to a positive bus of a significantly continuous voltage and on a second side to a negative bus of the significantly continuous voltage, each of the three legs comprising a top switch and a bottom switch, each of the top switch and the bottom switch comprises two components, a first component being an Insulated Gate Bipolar Transistor (IGBT) controlled by a pulse width modulation (PWM) signal output by a PWM controller based on a control law of the electric motor, and a second component being a freewheeling diode connected in parallel with the IGBT;
• a DC-link adapted to supply the inverter with the significantly continuous voltage;
• and
• the PWM controller configured to execute a method comprising:
• measuring current signals in the three windings of the electric motor;
• determining a current parameter associated with the electric motor based on the current signals,
• wherein the current parameter comprises a current offset of at least one of the three windings of the electric motor in relation to a zero-current value;
• or
• wherein the current parameter comprises a current misbalance between at least two windings of the electric motor;
• determining an amended control law of the electric motor for decreasing the current parameter, wherein the determining comprises determining a proportional factor and an integral factor of a proportional-integer (PI) regulator for canceling the current parameter;
• and
• outputting PWM signals to at least one of the IGBTs based on the amended control law.