DC-bus capacitorless rectifier-inverter motor drive with online optimized harmonic controlled PWM

A dc-bus capacitorless rectifier-inverter motor drive is discussed in this paper. Two three-phase, two-level voltage-source converters (VSCs) are connected back-to-back to form an AC-AC regenerative converter. Only the motoring operation of the regenerative converter is studied in this paper. The lack of a dc-bus capacitor results in low-frequency dc voltage ripple following the rectification of the ac utility source and such ripple would cause low-order harmonics being fed to the motor. These harmonics are eliminated by a method based on selective harmonic elimination pulse-width modulation (SHE-PWM) being further optimized online. Simulations and experimental results are presented in order to confirm the validity of the proposed motor drive.