A novel filter to mitigate interharmonic problems caused by variable frequency drives

Variable frequency drive (VFD) is known to produce interharmonics (IH). These IH components can be difficult to mitigate even though their magnitudes are general small. These problems are often caused by the parallel resonance between the drive filter and the supply system. In this paper, we present a novel filtering scheme that can avoid the interharmonic resonance on one hand and that can filter the characteristic harmonics on the other, thus leading to an effective solution to mitigate VFD-produced interharmonics. Two real-life cases have been used to demonstrate the effectiveness of the scheme. The first case involves the voltage flicker caused by VFD-produced interharmonics. The second case involves a VFD related interference problem in a powerline communication (PLC).