Directional Triplen Hybrid Active Filter for radial systems

Increasing use of non linear loads in residential distribution systems can cause significant growth in neutral to earth voltages and false ground relay trips. Since it is impractical to enforce the residential and other small commercial customers to limit harmonics, utilities need an effective low cost harmonic filtering solution to limit 3^rd harmonic propagation. This paper presents a Directional Triplen Hybrid Active Filter (DTHAF) for 3-ph 4-wire multi grounded radial distribution systems. The directionality feature enables isolating downstream triplen harmonic current from the system and blocking upstream triplen harmonic currents even with source voltage distortion. This feature restricts filter size to that of the harmonic load downstream. Hybrid active filter approach enables using a fractionally rated active filter and thereby reducing the cost of the filter. Existing power factor correction capacitors (PFC) on the system can be utilized for retrofit applications.