W. Mielczarski et al., REDUCTION OF HARMONIC CURRENTS GENERATED BY DISCHARGE LAMP SYSTEMS, IEE proceedings. Generation, transmission and distribution, 145(4), 1998, pp. 363-368
The paper presents a novel scheme for minimising harmonic currents gen
erated by 3-phase systems of discharge lamps. The main idea is to inst
all in the neutral conductor a filter with characteristics which allow
s the first harmonic component to flow with minimum attenuation while
higher harmonic components of the neutral current are attenuated. For
filter design, a 3-phase system of fluorescent lamps is substituted by
a Thevenin equivalent seen from the common point of a lamp connection
and the ground point of the supply system. It leads to nonlinear Thev
enin equivalents when an internal impedance and an equivalent voltage
are dependent on the current flowing in the neutral conductor. The equ
ivalent circuits developed are subsequently used for filter design and
simulation. Rosenbrock's optimisation procedure is implemented to com
pute filter parameters. The assumed objective function aims at the sma
ll impedance for the first harmonic to allow asymmetrical current flow
and large impedance for higher harmonics to reduce harmonic distortio
n in the supply and neutral currents. The equivalent models developed
are applied for simulation of filter working conditions in the neutral
conductors. Simulations are verified by laboratory tests, showing goo
d agreement.