An optimization based design method for harmonic filters in unbalanced utility AC systems

This paper presents a novel design technique for harmonic filters in AC unbalanced power systems. The design methodology is based on nonlinear minimization of a composite objective function depicting the three filter requirements of low harmonic injection into the AC host utility grid, maximum absorption by the harmonic filter, and minimum harmonic voltage distortion, with the avoidance of any parallel resonance or harmonic intensification condition on the AC network. The design methodology relies on harmonic scans and phase impedance measurements and the system curve fitted equivalent impedance/admittance transfer function within the harmonic band of interest. The min-max optimization is performed over a specified set of discrete dominant “offending” harmonics for given filter inequality constraints using newly defined equivalent system dynamic impedance equivalents