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AN IMPROVED HYBRID ACTIVE POWER FILTER FOR POWER QUALITY IMPROVEMENT IN THREE PHASE FOUR WIRE SYSTEM

This paper presents a hybrid active power filter for a three phase four wire distribution system. The scheme consists of a zigzag transformer, single phase active power filter connected in series with the utility neutral and a coupling capacitor connected in series with a voltage source converter of the active power filter (APF). The addition of coupling capacitor permits the reduction in DC link voltage requirement. This hybrid approach reduces the overall rating of the compensator. The model of topology is developed in the MATLAB / Simulink environment to simulate the performance characteristics. A proportional controller followed by a positive sequence detector is used to generate a reference signal for the VSC. Experimental studies are carried out on the prototype of three-phase four wires active power filter (APF) to validate the simulated response.