Flux-Weakening in IPM Motor Drives: Comparison of State-of-Art Algorithms and a Novel Proposal for Controller Design

A review and comparison of some state-of-the-art flux-weakening algorithms for Interior Permanent Magnet Synchronous Motor (IPMSM) is presented in this paper, having voltage exploitation, dynamical performances and implementation efforts as key parameters of the comparison. Moreover an original proposal for the theoretical analysis of the overall dynamics of the voltage control loop is carried out, also taking into account non-linear effects and discrete-time implementation issues. All the considered algorithms have at least one feed-back path, thus providing steady-state voltage control even in presence of parameter errors, but different strategies are adopted leading to completely different behavioral characteristics. The approaches that will be analyzed are based on the control of the synchronous reference frame currents, the torque-flux characteristics and the voltage space vector angle. The effort for improving the voltage limitation performances, aiming at increasing dc bus voltage exploitation while still maintaining reasonable dynamical performances, is gaining importance due to both the efficiency demand (i.e. reducing the phase current magnitude for the required power) and some specific application issues, like the need for widening the speed-torque range given a relatively low voltage bus (e.g. in electrical or hybrid traction applications). A motor drive system for home appliances is considered in this paper as test bench for comparing the reviewed techniques. Simulation and experimental results are included.