Analysis of Multisampled Current Control for Active Filters

This paper investigates the multisampling techniques applied to the current control in active-power-filter (APF) applications. In APF applications with digital control, the main bandwidth limitation derives from A/D conversion and computational delays and the sampling-related delay of the digital pulsewidth modulation (DPWM). Using field-programmable gate arrays and fast A/D converters for the control implementation, it is possible to minimize the former two; thus, the overall phase lag is dominated by the DPWM, which can strongly be reduced by the multiple-sampling approach, breaking bandwidth limitations of single-sampled solutions. Moreover, as the multisampling approach triggers nonlinear behaviors that can negatively impact the filter-compensating capabilities, a solution based on a simple digital filter is proposed which linearizes the system behavior and does not waste the multisampling advantages. Simulation and experimental results on a 10-kVA prototype confirm the theoretical expectations.