Unified fuzzy-logic based controller for dual function 4-leg shunt APF with predictive current control

Due to the rapid increase of nonlinear and unbalanced reactive loads in 4-wire distribution systems, various power quality issues such as harmonics current, unbalanced load currents, neutral current and low power factor occur. The need for green and renewable energy sources increases daily due to increase in demand for electrical power. Photovoltaic (PV) energy is an important renewable technology that requires an inverter to interface with the electrical distribution systems. Conventionally, shunt active power filter (APF) is connected in parallel to perform power conditioning tasks such as harmonic elimination, reactive power compensation, load balancing, and neutral current elimination. This paper presents a unified Fuzzy-Logic based Controller for a 4-leg APF preforming as a dual-function converter. The presented system achieves power quality tasks like: (i) reactive power compensation, (ii) harmonics current elimination, (iii) neutral current mitigation and (iv) system line-currents balance in addition to transfer locally generated renewable energy to the grid utilizing only one power electronic based converter.