Discrete Nonlinear Control based on a double dq Transform of a Multi-Cell UPQC

A Discrete Nonlinear Control with a double dq Transform of a Multi-Cell Unified Power Quality Conditioner (UPQC) based on Single-Phase Power Cells is presented. The UPQC is a back-to-back connection of active filters; combining a shunt and a series topology but maintaining the features of both units, where the main objective is to improve the power quality. The multivariable, nonlinear and coupled nature of the UPQC makes the control a difficult task. In this work, a discrete nonlinear control of a multilevel UPQC based on Single-Phase power cells is proposed, where the controlled variables are decoupled to improve both dynamic and static system responses. In this scheme, two different Park Transforms are used to conveniently synchronize each compensator allowing a dedicated control regulator for every output variable. This paper shows that the DC link voltage of every power cell can be controlled in a wider range as compared to a traditional control strategy, thus improving robustness for several types of loads.