Analysis of limit of the constant power speed range of the permanent magnet synchronous machine driven by dual mode inverter

The objective of this work is to show that the theoretical limit of the constant power speed range of the recently proposed dual mode inverter control (DMIC) driving the permanent synchronous machine is infinite. To reach such goal, the average value of the voltages and currents in the dq rotating reference frame are used to model the DMIC/PMSM system. The principle is shown to be the same of the vector control with field weakening operation (VCFW). However, in VCFW the voltage limit circle is given by the maximum output voltage of the VFI and therefore shrinks fast as speed increases. In the DMIC, on the other hand, the voltage limit circle is a result of the contribution of DC link voltage, the back emf, and the induced voltage provided by the derivative of the on-phase currents and it shrinks slower as speed increases compared to VCFW. The conclusion is that there is no inherent speed limit of CPOR when PMSM/DMIC control scheme is used because the voltage constraint is eliminated.