A Generalized Carrier-Based PWM Technique for Multi-Level Back-to-Back Converters

This paper proposes a generalized carrier-based pulse width modulation (GCB-PWM) technique suitable for multi-level back to back (BTB) converters. The objective of GCB-PWM technique is to produce a pulse pattern in such a way that the first non-eliminated harmonic contentof the output voltage is eliminated or reduced below its permitted value without increasing the switching frequency. This is achieved by fixing the amplitude modulation index in some special values but changing the intermediate dc link voltages instead; leading to salient advantages such as the total harmonic distortion (THD) improvement and output filter size reduction. The proposed GCB-PWM technique has been applied on a seven-level BTB cascaded H-bridge (CHB) system. Simulation results show the superiority of this technique over the conventional CB-PWM from the THD and filter size points of view.