Sliding-Mode Flux-Weakening Control With Only Single Current Regulator for Permanent Magnet Synchronous Motor

A sliding-mode scheme using only a single current regulator for both speed and flux-weakening control has been proposed for permanent magnet synchronous motor. The scheme is simple and can effectively resolve problems faced by conventional flux-weakening control with dual current regulation loops. However, with only a single current regulator, the scheme still needs an additional mechanism for either maximizing electromagnetic torque or optimizing efficiency. As for reinforcing its immunity and robustness towards changing operating conditions, sliding-mode speed control complemented by an equivalent load-torque observer during flux-weakening has been proposed and designed accordingly. Effectiveness of the eventual scheme, in terms of widening load capacity or improving light-load efficiency of the motor, has been verified in simulations and experiments.