Motor drive control using pulse-width modulation pulse skipping

A drive circuit for a motor of a compressor, the drive circuit comprising:

• a power factor correction converter configured to produce a DC power supply from AC input power;
• an inverter including power switching devices controlled according to voltage signals, wherein the power switching devices pulse-width modulate the DC power supply to generate a plurality of output voltages that are applied to a plurality of windings of the motor, respectively;
• a current control module configured to generate the voltage signals based on a current demand;
• a torque mapping module configured to generate the current demand based on a torque demand;
• an estimator configured to calculate an estimated speed of the motor based on measured current from at least one of the plurality of windings of the motor;
• a speed loop control module configured to calculate a closed loop torque value based on a difference between the estimated speed of the motor and a commanded speed of the motor;
• a transition module configured to generate a transition signal instructing a transition from closed loop mode to open loop mode in response to convergence of the estimator;
• a multiplexer configured to:
• from initial startup of the motor until the transition signal is generated, output an open loop torque value as the torque demand;
• and
• subsequent to the transition signal being generated, output the closed loop torque value as the torque demand;
• and
• an open loop torque module configured to:
• determine a torque limit by indexing a lookup table with both (i) a voltage of the DC power supply and (ii) a temperature of the power switching devices;
• in response to a predetermined open loop torque value being less than the torque limit, output the predetermined open loop torque value as the open loop torque value;
• and
• in response to the predetermined open loop torque value being greater than the torque limit, output the torque limit as the open loop torque value.

A method of controlling a motor of a compressor, the method comprising:

• determining an upper limit based on a voltage of a DC power supply;
• generating an open loop torque value, including applying the upper limit to the open loop torque value;
• selecting one of the open loop torque value and a closed loop torque value as a torque demand;
• generating voltage signals based on the torque demand;
• and
• controlling power switching devices of an inverter according to the voltage signals to generate output voltages from the DC power supply, wherein the output voltages are applied to windings of the motor.