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.<>