Reference Flux Calculation Suitable for Inverter Overmodulation in Direct Torque Controlled PMSM Drive System

This paper proposes a method of inverter overmodulation drive of permanent magnet synchronous motor drive system based on direct torque control (DTC). It is important to operate in the overmodulation region to maximize the motor output power. In the proposed method, the transition from linear region of the pulse width modulation to the overmodulation region is achieved by suitable calculation of reference flux for the flux-weakening control in the M-T frame, which is a reference frame synchronized with the stator flux-linkage vector. Hence, the voltage and current limitations can be achieved by simple mathematical equations. In addition, the proposed system also includes DTC in the M-T frame, armature voltage estimation for stator flux estimation. The effectiveness of the proposed method is provided by both simulation and experimental results.