# Simple question of input of a PMSM steady state model

I am working on a control problem using a PMSM steady state model. I am not very familiar with hardware so I might need your help on some of the basic information.

The model has three states: angle speed, quadrature-axis current and direct-axis current. I saw some papers assume the the quadrature- and direct-axis stator voltage components as zero, and add only one control law input on the direct-axis current state.

So my question is, in practice, can I add two voltages to the two axis currents receptively? Will there be any difference to use one control input and two control inputs? Thank you.