Effective digital torque control systems for permanent magnets converter fed sinusoidal synchronous machines

A description is given of two fully digital, two-current loop structures. The first is an extrapolation of the classical strategy which consists of direct control of the phase currents with independent loops; in steady state, EMF (electromotive force) feedforward terms and phase and gain correction terms partially compensate for the digital loop´s low bandwidth. The second structure is based on the fact that the steady-state current´s phase lag and attenuation are canceled by working in the d-q frame because references and disturbances are constant. Moreover, whatever the machine, the equations are simple, and good dynamic performances are possible with simple d-q loops, EMF feedforward terms, and i/sub d/,i/sub q/ decoupling terms.<>