PWM Current Source Inverters

Abstract

This chapter focuses on the pulse‐width‐modulated (PWM) current source inverter (CSI) technologies for high‐power medium voltage drives. It analyses three modulation techniques for the CSI, which include trapezoidal pulse width modulation (TPWM), selective harmonic elimination (SHE), and space vector modulation (SVM). The SVM scheme has the lowest DC current utilization due to its bypass operation. The SHE scheme features superior harmonic performance. The inverters used in medium voltage (MV) drives can be generally classified into voltage source inverter (VSI) and CSI. The dwell time for the stationary vectors essentially represents the duty‐cycle time of the chosen switches during a sampling period. To increase the power rating of a CSI fed drive, two or more CSIs can operate in a parallel manner. One of the well‐known CSI topologies is the load‐commutated inverter (LCI). The LCI employs SCR thyristors whose commutation is assisted by the load with a leading power factor.