Generalized one-cycle current controller for improved SAPF power quality management

Abstract

Current controllers are used in shunt active power filters to enhance the performance of electrical power systems by improving power quality and energy efficiency. Nonlinear current controllers are preferred in systems with nonlinear and dynamic loads due to their robust and rapid tracking of varying reference currents. Within this category, reference-based one-cycle current controllers feature fixed switching frequency and quasi-instantaneous reference current tracking. When compared to implementations based on classical one-cycle controllers (OCC), they enable tracking any desired reference current while maintaining cycle-by-cycle control. They are suitable for selective harmonic filtering, as well as source current balancing and reactive current compensation. However, these controllers have shown stability problems caused by the switching function alignment – even when symmetrical centred alignment is employed. To address these challenges, this work proposes a generalized reference-based one-cycle current controller. This new controller algorithm introduces two degrees of freedom in the formation of the switching signal and achieves stability, zero integral-current-error, and the selection of the final current value at the end of each switching cycle. The effectiveness of the proposed algorithm is validated through simulations and experimental results obtained from a three-leg four-wire shunt active power filter setup. A performance comparison is made between the new algorithm and previous approaches. The results demonstrate that the proposed controller achieves superior power quality indices by reducing the current harmonic distortion and approaching unity power factor.