Operating region comparison of symmetric and asymmetric Multilevel Shunt Active Power Filters

An operating region comparison is performed between a symmetric and an asymmetric CHB Multilevel Shunt Active Power Filter aimed to simultaneously compensate linear and nonlinear currents. The symmetric approach considers that all the power cells injects the same voltage; while the asymmetric case consists in the inclusion of two types of power cells; one of them meant for fundamental reactive power compensation and the other to cancel out the distortion power. Using steady state equations, the modulating signals of the H-bridges are calculated for a wide range of load conditions. This is used to identify when the converters lie in over-modulation and thus, the allowable operating region is found. Different values for the system parameters are considered in order to identify the compensation capabilities of both approaches. The presented results are supported with theoretical developments and simulated analyses.