Analysis of High Frequency Impact on the DC Link Inductor of VFD Under the Influence of Shunt Active Filter

Abstract

This paper investigates the high frequency effects (2-9 kHz) on the DC link inductor of Variable Frequency Drive (VFD) connected to the grid with Shunt Active Filter (SAF) for harmonic mitigation at common point of coupling (PCC). Active filter generally operates in different conditions including voltage imbalance up to 3% and varying rated load. Most of available active filters in market operate efficiently with switching frequency in the range of 3-5 kHz. Although harmonic mitigation is the focus point of SAF use, impedance seen by diode bridge rectifier is significantly reduced which in turn increases stresses on DC link inductor and DC filter capacitor ripple current. Effects of these parameter variations in frequency range of 2–9 kHz predominantly are DC link inductor core loss, DC filter capacitor life time and increased conduction losses of diode bridge rectifier. 130 Amperes SAF connected to grid driving 132 kW VFD under different operating conditions is analyzed through MATLAB simulation and practical test measurements. Reliability variation in front end rectifier utilities such as variable frequency drives with special emphasis on DC link inductor is discussed in detail.