Development of Three-Phase Active Harmonic Filter with Series Capacitor Topology

Abstract

Power Quality is highly degraded due to presence of nonlinear loads in the utility system. The mains voltage should be a sinusoidal voltage with constant amplitude and frequency. But in actual condition the mains does not exist to be sinusoidal because of harmonic generation due to non-liner characteristics of power electronics converters. Harmonics are generated due to switching action of power electronics converters. Previously, the passive filters were used to tackle problem related to harmonics, but the passive filters suffer from series or parallel resonance, which makes them bulky and complex system with poor efficiency. With improvement in power electronic devices a new approach, the active harmonic filters has been proposed. Active filters for elimination of the harmonics have futures like, load regulation, control on reactive power and voltage regulation. In this project, attention has been paid to hybrid solation of the active harmonic filter which consists of passive (LC) filter and three-phase PWM inverter. In hybrid active harmonic filter, the three-phase PWM inverter and passive filter are directly connected in series with each other. The passive filter is tuned to harmonic frequency of 13th order. The hybrid filters are most preferable solution for harmonic elimination compared to conventional passive filters or active filters in terms of cost and performance. The passive is absorbs the harmonic current generated by the nonlinear load and the active filter connected in series with the passive filter is used to improving the filtering performance of the system. The active filter dc-link voltage is reduced because the fundamental component of the supply voltage drop across the filter capacitor. This resulted in reduction of the rating and the cost of the active filter.