Power Quality Enhancement in Industrial Networks Using a Transformerless Shunt Hybrid Active Power Filter with MVF-PLL: System Design and Experimental Validation

This paper proposes a transformerless Shunt Hybrid Active Power Filter (SHAPF) designed to mitigate harmonic distortion and compensate for reactive power demand induced by non-linear industrial loads. The active filter control algorithm is implemented within the Synchronous Reference Frame (SRF) framework, employing a Multi-Variable Filter (MVF) coupled with a robust Phase-Locked Loop (PLL) for precise reference current generation. The structural arrangement comprises a single 7th-harmonic tuned LC passive filter per phase directly interfaced in series with a low-power three-phase Voltage Source Inverter (VSI), eliminating the requirement for a heavy coupling transformer. Consequently, the power rating requirement of the active converter is significantly reduced compared to standard active topologies. The dynamic performance of the system and control algorithm is verified through MATLAB/Simulink modeling and validated on a 20 kVA experimental laboratory setup developed at the LIAS Laboratory, University of Poitiers. Steady-state and dynamic transient results confirm that the proposed SHAPF reduces grid current Total Harmonic Distortion (THD) from 27.38% down to 2.71% in simulation and 3.9% experimentally, fully meeting IEEE-519 standards.