There are two components:
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Switching and resistive losses in the inverter. The switching losses increase with higher PWM frequency, but you should not attempt to reduce it to avoid stability hazards. The resistive losses are constant for a given inverter design. For background, see this: Estimating the power dissipation of a motor controller. Overall, you are not going to be able to meaningfully alter this term.
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Reactive power in the AC link. Minimization of this term requires that the motor model as configured in the controller accurately follows the actual motor parameters. See Motor control fundamentals - Telega v1.0 Reference Manual, search for “The model of the motor is imperfect and the feedback from the sensors is imprecise, which introduces unavoidable divergence between the state of the real motor and the model maintained by the state estimator.” The most critical parameters are the flux linkage (this term dominates at high speeds) and resistance (this term dominates at high currents). You can see that from the simplified dq-frame motor state equations presented there.
The motor resistance goes up with temperature, so if the motor runs hot, you may want to take that into account by increasing the corresponding motor parameter. The flux linkage may decrease at high currents due to core saturation, which may also need to be reflected in the model settings.