A Robust, Efficiency Optimized Flux-Weakening Control Algorithm for PM Synchronous Machines

An enhanced flux-weakening control algorithm with optimized operating efficiency of permanent magnet synchronous machines (PMSM) is presented. It is robust to variation of dc bus voltage and load level; and insensitive to machine parameters. The developed speed/flux-weakening controller (SFWC) can automatically generate the required demagnetizing current and produce torque component at high speeds based on the d-q current cross-coupling effect. By selecting a voltage constant adaptive to load level and rotor speed, the demagnetizing current is optimized, resulting in less copper losses and higher efficiency especially under light load conditions in the flux-weakening region. Moreover, the proposed control scheme is able to achieve both flux weakening and speed regulation simultaneously using only one current regulator, in contrast to the conventional two- loop (d-q-axis) control approaches. Both computer simulation and experimental results are provided to verify its feasibility and effectiveness.