Adaptive fuzzy hysteresis band current control for reducing switching losses of hybrid active power filter

Although hysteresis band current control is an easy to implement and robust control method for industrial power electronics converters, it has also some disadvantages like variable and high switching frequency causing high switching losses. In this study, a novel adaptive fuzzy hysteresis band current control system is proposed by making use of fuzzy expressions of both hybrid active power filter (HAPF) current and integral of its harmonic components to reduce the switching losses of three-phase three-wire two-level HAPF. To reach this aim, a relation between switching frequency and integral of filter current harmonic components is formulised and used for defining a fuzzy hysteresis band. Moreover, the magnitude of the instantaneous current switched is also correlated to the switching losses; in this way, its fuzzy expression is also used for defining hysteresis band. Those fuzzy expressions are then utilised to constitute a dynamically changing hysteresis bandwidth. The proposed control system is finally optimised using EMTDC/PSCAD simulation environment and implemented in the field. The implemented HAPF system has been shown to successfully suppress all the interharmonic and harmonic current components produced by a steel melting facility occupying three induction melting furnaces and it has provided around 9% reduction in overall losses