TIDUF77 June 2024 MSPM0G1507
This is the most important transformation in the FOC. In fact, this projection modifies a 2-phase orthogonal system (α, β) in the (d, q) rotating reference frame. Considering the d axis aligned with the rotor flux, Figure 2-12 shows the relationship for the current vector from the two reference frame.
The flux and torque components of the current vector are determined by Equation 8.
where
These components depend on the current vector (α, β) components and on the rotor flux position; if the right rotor flux position is known then, by this projection, the d,q component becomes a constant. Two phase currents now turn into dc quantity (time-invariant). At this point the torque control becomes easier where constant isd (flux component) and isq (torque component) current components controlled independently.