Current Distortion Effects on Front End of Variable Frequency Drive Under Shunt Active Filter Connected Grid

This paper investigates the pre-distortion effects of Shunt Active Filter (SAF) on Variable Frequency Drive (VFD) front end devices like diode bridge rectifier, DC link inductor and capacitor. SAF is connected at point of common coupling (PCC) to overcome harmonic effects of connected VFD in that grid. Active filter generally operates in different conditions including voltage imbalance up to 3% and varying rated load. Although harmonic mitigation is the focus point of SAF use, impedance seen by diode bridge rectifier is significantly reduced, resulting in larger DC filter capacitor ripple current, increased losses in DC link inductor and larger peak current on diode bridge rectifier. Effects of these parameter variations (including frequency range of 2-9 kHz), predominantly, are DC link inductor core loss, reduction in DC filter capacitor life time and increased conduction losses of diode bridge rectifier. A system with SAF is connected to grid driving a six-pulse rectifier VFD is studied under specified load conditions. Simulation studies are done in MATLAB
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followed by experimental test measurements. Reliability variation in front end rectifier utilities such as VFD with special emphasis on DC filter capacitor and DC link inductor is discussed in detail.