Optimal Voltage Feed-Back Flux-Weakening Control of IPMSM

A voltage feed-back flux-weakening (FW) control scheme for vector-controlled Interior Permanent Magnet Synchronous Motor (IPMSM) drive is considered in this paper. The voltage controller is based on the difference between the amplitude of the reference voltage space vector and a proper limit value, related to the feeding inverter limitations, and adopts the phase angle of reference current space vector as the control variable. A novel 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. The design of the controller can therefore be optimized for each operating condition, allowing to fix stability properties and to maximize bandwidth of the loop. A simple but effective scheduling of the voltage controller gains is proposed to address this. Maximization of the dynamical performance provides the main advantage of the proposed approach, i.e. allows a lower voltage (control) margin to be considered with respect to standard approaches, leading to a higher torque and system efficiency and/or a reduced value of the dc-bus capacitance. A motor drive system for home appliances is considered as a test bench to prove the effectiveness and importance of the proposal.