Active filter for high order harmonics
elimination in traction system
Supervisor Dr:Robin Lisner
Hany Daoud
Associate Supervisor: Prof.:R.E.Morrison
Principle of the current injection method
The fundamental principle of this method of reducing
harmonic currents is to modify the power line waveforms
which contain different kinds of harmonics so that those
harmonics are reduced.
Current waveforms are modified by injecting equal in
magnitude but opposite in phase compensating currents.
Figures 1 & 2 show the principle. Curve A is the power
line waveforms and curve B is a waveform containing all
the harmonics of the power line waveforms. If the current
of curve B with an opposite phase is injected with the line
current curve A, a sinusoidal waveform is obtained as
shown in curve C.
C
C
B
A
A
B
Fig.1. Principle of active filtering
C
A
B
Fig.2. Active filtering principle illustrated in
the time and frequency domain.
• The purpose of the design of the shunt active filter is to inject
Fig3. Design of the active filter for 25KV traction system
QSW with current boosting to eliminate high order harmonic
currents.
• The magnitude of the filter current is controlled by DC/DC
converter.
• The phase of the filter current is controlled by DC/AC
inverter.
• 50 Hz - 400V (415V) - 225A power module
• Up to 20, programmable up to the 50th harmonic
• Individually programmable per harmonic.
• Less than 7 KW per module at full load.
• Better than 97% filtering efficiency.
• Power factor programmable from 0.6 inductive to
0.6 capacitive.
Fig. 4. Configuration of the power quality filter.
Electrical and Computer Systems Engineering
Postgraduate Student Research Forum 2001