Design of Passive Harmonic Tuned Filter for Uninterruptible Power Supply

Harmonics causes distortion in transmission and distribution system. This paper presents a study of harmonic filters to reduce harmonic distortion caused by non-linear loads such as AC/DC drives, converters, uninterruptible power supply (UPS) etc. In this paper, UPS system is considered as a non-linear load. UPS system consist of rectifier and inverter, which produces required DC or AC output using thyristor switching. Thyristor switching in rectifiers are source of harmonics. To mitigate these harmonics, passive and active filters are used. The capacitors that are used in conventional detuned passive filters carries large amount of current, while the drawback of active filters is that their rating is very close to the load and are expensive. To overcome the limitations of these filters, a simple and cost-effective tuned LC filter is proposed. This configuration avoids the resonance with system impedance. The series connected LC tank filter blocks the flow of harmonic currents and prevents them from entering into the source, which is validated from the MATLAB simulation results. The proposed system is verified by its hardware implementation.