Sliding Mode Control Scheme of a Cascaded H-Bridge Multilevel Active Front End Rectifier

In this study, a sliding mode control (SMC) scheme is proposed for the single-phase cascaded H-bridge (CHB) multilevel active front end (AFE) rectifier with LCL filter. A PI controller is employed to control the DC voltage of the rectifier modules and to obtain the amplitude for the reference grid current. The SMC based current control scheme uses the grid current and filter capacitor voltage feedbacks. The resonance of the LCL filter is damped using the voltage feedback of the capacitor. Therefore, the requirement for additional damping circuitry is removed. Simulation and experimental results are presented to verify the performance of the SMC for the CHB multilevel AFE rectifier. The overall proposed control scheme provides almost unity power factor and fast transient response. It is seen from the results that the current drawn from the grid is in sinusoidal waveform with low THD.