Open-End Unidirectional Topologies With Reduced Controlled Switch Count

Three three-phase unidirectional open-end topologies with reduced active switch count are investigated in this paper. These configurations arise from the replacement of controlled switches by diodes, in order to reduce the system complexity. Furthermore, the costs are also reduced once less driver circuitry is needed. The proposed topologies make the ac-dc conversion of the power delivered by a permanent magnet synchronous machine operating at unity power factor. Each configuration is made out of two converters in which at least one is derived from the substitution of active switches in two-level legs or three-level neutral-point clamped legs. The proposed configurations have less switches, making it possible to obtain the same number of voltage levels (in relation with the conventional configurations) with half or quarter of the number of active switches. Also, the topologies are compared in terms of semiconductor power losses and harmonic distortion. The control strategy of the systems as well as a detailed model, simulation, and experimental results are presented.