Regenerative current limiting of synchronous motor drives

A method of controlling operation of an electric machine, comprising:

• calculating a voltage-based torque limit corresponding to a voltage limit constraint of a direct current bus;
• calculating a current-based torque limit corresponding to a regenerative current limit of the direct current bus using an equation relating a total electrical power with a measured supply voltage of the direct current bus and the regenerative current limit of the direct current bus;
• calculating a final torque limit defined by a lesser one of the current-based torque limit and the voltage-based torque limit;
• commanding a plurality of switches within an inverter to cause the electric machine to produce an output torque corresponding to a torque demand and according to the final torque limit;
• and
• commanding the plurality of switches to regulate a direct-axis current not to exceed a maximum d-axis current, the maximum d-axis current defined by one of a demagnetization current limit of the electric machine or a peak d-axis current that corresponds to a solution of the equation relating the total electrical power with the supply voltage of the direct current bus and the regenerative current limit of the direct current bus.

A method of controlling operation of an electric machine, comprising:

• calculating a voltage-limited direct-axis current of the electric machine corresponding to a voltage limit constraint of a direct current bus;
• calculating a current-limited direct-axis current of the electric machine corresponding to a regenerative current limit of the direct current bus;
• calculating a final direct-axis current limit as a largest one of the voltage-limited direct-axis current and the current-limited direct-axis current;
• calculating a current-based torque limit corresponding to the regenerative current limit of the direct current bus using an equation relating a total electrical power with a measured supply voltage of the direct current bus and the regenerative current limit of the direct current bus;
• commanding a plurality of switches within an inverter to cause the electric machine to produce an output torque corresponding to a torque demand and according to the current-based torque limit;
• and
• commanding the plurality of switches to regulate a direct-axis current not to exceed the final direct-axis current limit or a peak d-axis current that corresponds to a solution of the equation relating the total electrical power with the supply voltage of the direct current bus and the regenerative current limit of the direct current bus.