Novel PWM controlled series-connected current-source inverter drive

A novel current-source inverter (CSI) drive is presented consisting of three single-phase CSIs connected in series. It is shown that this series-connected CSI (SCCSI) can be viewed as the dual of the three-phase full-bridge voltage-source inverter (VSI), and therefore incorporates all the flexibility needed to generate any 3-level PWM motor stator current with 180 degrees conduction patterns. As a result of the increased flexibility of the SCCSI circuit topology, it is demonstrated how more sophisticated PWM switching strategies can be generated which considerably improve the drive performance at low operating speeds. The SCCSI drive performance is investigated for both quasi-square wave and PWM operation, including harmonic elimination and minimisation PWM switching strategies, and it is compared with both the conventional CSI and Duplex CSI drive performance. Both computed and experimental results obtained from a microprocessor-controlled SCCSI drive are presented, which confirm the superior low speed performance of the SCCSI drive, thereby extending the viable range of operation of the CSI drives.<>