Comparative Performance Analysis Involving a Three-Phase UPQC Operating With Conventional and Dual/Inverted Power-Line Conditioning Strategies

This article deals with a complete evaluating and comparative analysis involving static and dynamic performances of a three-phase unified power quality conditioner (UPQC) controlled to operate using conventional and dual/inverted compensation strategies for performing active power-line conditioning. In the conventional strategy, the series converter of the UPQC operates as a nonsinusoidal voltage source, while the parallel converter operates as a nonsinusoidal current source. Differently, when the UPQC operates with a dual/inverted strategy, the series converter operates as a sinusoidal current source, while the parallel converter is controlled to act as a sinusoidal voltage source. Although, in theory, the results achieved using the mentioned strategies looks similar, in practical applications there are considerable differences in both static and dynamic performances that must be considered for choosing the best compensation strategy to be adopted. Thus, this article addresses aspects related to the mathematical modeling, control and generation of the control references applied to the UPQC, which are implemented using two three-level neutral-point clamped inverters. Furthermore, the performance of the UPQC operating under static disturbances (grid voltage harmonics/unbalances and load current harmonics), as well as dynamic disturbances (voltage sags/swells and load changes) are extensively tested by means of an experimental setup.