Improved SVM Pattern for Single-Stage CSI With Discharge Path in Electric Drives Applications

A recently proposed single-stage current source inverter (CSI) with discharge path exhibits the ability to control the drive from zero speed without the insertion of an additional pre-stage converter to control the input dc current. The size of the dc input inductor can be reduced to minimize the volume and weight of the power converter. With this choice, the output currents exhibit large distortion for the entire discontinuous conduction mode (DCM). The present work proposes a novel modulation pattern specific for the low-speed region in terms of reduction of the total harmonic distortion (THD). A fair comparison between the proposed pattern and the classical one is obtained, considering the same number of commutations per time unit. Simulations and experimental results confirm the validity and the considerable THD decrease of the proposed space vector modulation (SVM) pattern for the single-stage CSI with discharge path topology. In particular, the advantage is clear under DCM condition where the base pattern exhibits a large THD up to 15%, while the proposed one has an overall lower THD, with a maximum value of 8%.