Correcting current imbalances in three-phase four-wire distribution systems

This paper presents the analysis and control of a current imbalance compensator designed to eliminate upstream negative- and zero- sequence current components caused by single-phase loads in three-phase four-wire systems. The proposed compensator significantly reduces the fundamental-frequency current component in the neutral conductor and can potentially be used to eliminate harmonic currents. The Matlab/Simulink™ simulations are based on a 3-MVA radial feeder case study and a scaled-down 10-kVA test setup used to validate the proposed ideas. Three TMS320F28335 DSPs are used to implement the control system and the results of both the simulations and the prototype testing are shown and discussed. Results from testing of the prototype demonstrate the ability of the compensator to reduce the current in the neutral conductor.