A voltage source inverter controller for controlling an inverter electrically connected to an electric machine includes a current command generator, a six-step flux controller and a current regulator. The six-step flux controller generates a flux modifier to regulate flux in a flux-weakening speed/load operating region of the electric machine when operating the electric machine in a six-step mode. The current command generator converts a desired torque to three-phase desired currents that are input to a dq0-dq transformer and combined with the flux modifier to determine a modified-flux direct-quadrature (dq) current request. The current regulator includes a proportional-integral feedback controller, anti-windup elements, a dq voltage limit element and a voltage magnitude limiter. The proportional-integral feedback controller and the anti-windup elements perform closed-loop current control on the modified-flux dq current request to determine commanded dq voltages.