Quantization Effects on Digital-PR-Controlled Active Power Filter

Digital proportional-resonant (PR) controllers have proven effective when used with an active power filter (APF) to compensate for nonlinear load harmonics. Their performances may, however, degrade significantly when implemented with a low-end microcontroller due to coefficient quantization errors. The extent of the degradation depends on the chosen operator, form of the second-order resonant module, and the structure for implementing the PR controller. These three factors are now comprehensively evaluated to find suitable schemes for implementing an example sixth-order PR controller for an APF. The target is to retain accurate tracking even when realized with a low bit count. Furthermore, to quantify the analysis, the sensitivity of poles and zeros (SPZ) and the sensitivity of gain (SG) have been defined to index quantization influences on different implementations. The computed SPZ and SG trends have then been borrowed for explaining the simulation and experimental results presented in this article, and identifying three suitable realization forms with lower coefficient sensitivities.