Electric power system for controlling an electric machine

An electric power system, comprising:

• a front-end converter electrically connected to an electric inverter electrically connected to an electric machine via a high-voltage DC bus;
• a capacitor electrically connected between positive and negative conductors of the high-voltage DC bus;
• a high-voltage DC power source disposed to supply electric power to the front-end converter;
• a controller in communication with the front-end converter, the electric inverter, the electric machine, and the high-voltage DC power source, and operatively connected to the front-end converter and the electric inverter, the controller including an instruction set, the instruction set executable to:
• monitor operation of the electric machine;
• determine a reference current based upon a magnitude of electric power supplied from the high-voltage DC power source;
• determine a motor current based upon the operation of the electric machine;
• determine a feed-forward current based upon the motor current and the operation of the electric machine;
• determine a first duty cycle based upon the reference current, the motor current and the feed-forward current;
• determine a feed-forward duty cycle based upon the monitoring of the electric machine, including the instruction set executable to:
• determine an average motor current,
• determine a rate limiter term associated with a command to operate the front-end converter in one of a linear mode and a six-step mode, and
• determine the feed-forward current based upon the motor current, the average motor current and the rate limiter;
• determine a second duty cycle based upon the feed-forward duty cycle and the first duty cycle;
• and
• control operation of the front-end converter based upon the second duty cycle.