Harmonics and unbalanced load compensation by a modular multilevel cascaded converter active power conditioner

This paper presents a novel control scheme for a modular multilevel cascaded converter (MMCC) functioning as an active power conditioner (APC) to control the reactive power, eliminate the current harmonics, and compensate unbalanced load current simultaneously. This combines a modified predictive current controller with the inter-cluster and intra-cluster voltage balance control for MMCC sub-module capacitors. Simulation studies of this MMCC-APC for a power network containing both an unbalanced thyristor controlled rectifier and a reactive load are performed and results verifying its performance under varying degrees of load current distortion measured by THD levels are presented.