Reduction of harmonic currents in fluorescent lighting systems: design and realisation

Large installations of fluorescent lights, such as those found in commercial buildings, can lead to distorted line currents as well as high neutral currents due to the nonlinear characteristics of the fluorescent lights. This paper describes a simple, passive filtering scheme for minimising the harmonic current in the neutral. The double tuned filter has been designed using Rosenbrock's optimisation procedure in order to maximise the third harmonic impedance of the filter and minimise the filter impedance to fundamental frequencies. The filter performance has been confirmed by field tests. The new scheme leads to a significant reduction in neutral current as well as improving the line current waveshape.