Current controller for low switching frequency by means of increasing the null vectors time application

This paper presents a new software-implemented current regulator for three phase loads based on orthogonal two-phase /spl alpha/-/spl beta/ system. The controller uses the module of the error for defining two control situations, called of steady state and transitory, which depend on the position of the current error inside or outside of the hysteresis margin. In the steady state, a new active vector voltage application strategy is used for assuring the nearest trajectory to the diameter of the current error within the circular boundary hysteresis when a null vector is applied. Moreover, this null vector is chosen between V(0) and V(7) for reducing the number of inverter's switches commutations. On the other hand, in the transitory zone the control applies only active vectors, for reducing quickly the error inside the hysteresis margins. Computer simulations were carried out in order to investigate the performance of the regulator, and results show the effectiveness of the proposed control scheme.