I have an interior permanent magnet BLDC motor and I want to plot the torque speed curve considering maximum torque per ampere (MPTA). With usual model of BLDC motor which is based on DC machine equations, it is difficult to consider reluctance torque and achieve flux weakening region of the torque speed curve.

Is there any other model which I can use? Is it possible to use dq model? If yes, how? Because dq model is used for sinusoidal excitation, but BLDC motor is excited with six-step inverter. In other words, the motor is excited with quasi-square pulses rather than sinusoidal waveform. Using the fundamental component of the waveform seems to be inaccurate. So what is the solution?

Note that I look for an analytical model not FEA software.