Simulation, Design, and Analysis of Three-Level Shunt Active Harmonic Filter using T-Type NPC Topology

Abstract

Power quality at the source side deteriorates due to current harmonics which are introduced in the power system by non-linear loads, originating a vital difficulty. Rectifiers, variable speed drive, switched mode power supply, etc. types of non-linear loads create such harmonics. Conventional technique to eliminate such harmonics is use of passive filters but this technique has the disadvantage of series and parallel resonance within the network impedance, overcompensation of reactive power at fundamental frequency and poor flexibility. Shunt Active Harmonic Filters (SAHF) are generally used to reduce current harmonics. The active harmonic filters introduce remunerating currents into the source to neutralize the harmonics possessed by the load current. The compensating currents will be derived by sensing three-phase voltages at the Point of Common Coupling (PCC) and load currents. Efforts are made in this study to analyze Fast Fourier Transform (FFT) algorithm, Instantaneous Reactive Power (IRP) technique, and Synchronous Reference Frame (SRF) technique used to derive the reference compensating currents. These compensating currents act as reference currents for the fixed switching based current controllers which generate control signals for the SAHF employing three-level T-type Neutral Point Clamped (TNPC) topology of converter.