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A REVIEW ON ACTIVE POWER FILTERING TECHNIQUE
Vineet Kumar**, Ashish Kr. Gupta*
*S.G.I. Agra, India
**PITM, Nashik, India
Mail-id:
Abstract -Active filtering of electric
are from
rectifiers
and electric
arc
power
mature
furnaces.
Common
applications
of
technology for harmonic and reactive
rectifiers
power compensation in two-wire (single
uninterruptible power supplies (UPS).
phase), three-wire (three phase without
Systems with such loads are prime
neutral), and four-wire (three phase with
candidates to develop harmonic-related
neutral) ac power networks with nonlinear
problems and are, therefore, also prime
loads. This paper presents the comparison
candidates
of
measurement/analysis system.
has
now
different
become
modern
and
a
traditional
techniques to mitigate harmonics and
reactive power component. This paper also
presents the selection of active filters for
specific applications.
are
solid-state
for
drives
a
and
harmonic-
Conventionally passive L–C filters were
used to reduce harmonics and capacitors
were employed to improve the power
factor of the ac loads. However, passive
Index Terms - Active power filters, active power
filters
line conditioners, harmonics and reactive power
compensation, large size, and resonance
compensation, power quality.
I.
Any device with nonlinear characteristics
that derive their input power from a
electrical
system
may
be
responsible for injecting harmonic currents
and voltages into the electrical system. The
primary sources of undesired harmonics
The
demerits
of
fixed
increased
severity
of
harmonic
pollution in power networks has attracted
the attention of power electronics and
power
system
engineers
to
develop
dynamic and adjustable solutions to the
power quality problems. Such equipment,
generally known as active filters (AF’s)
International Journal of Innovative Research in Engineering and Applied Sciences.
doi:15.06.15/3/9-14/June 2015
the
[1].
INTRODUCTION
sinusoidal
have
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[2], are also called active power line
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printers, and Xerox machines behave as
conditioners
instantaneous
nonlinear loads and cause power quality
reactive power compensators (IRPC’s),
problems. Single-phase (two wire) AF’s
active power filters (APF’s), and active
are investigated in varying configurations
power quality conditioners (APQC’s). In
and control strategies to meet the needs of
recent years, many publications have also
single-phase nonlinear loads [6-7].
(APLC’s),
appeared on the harmonics, reactive
power, load balancing, and neutral current
compensation associated with linear and
nonlinear loads. This paper is also aimed
to investigate a simple shunt APF for
reactive power and harmoniccompensation
of the non-linear loads.
II.
ART OF DESIGNING ACTIVE
FILTERS
A harmonic can be defined as “a
sinusoidal component of a periodic wave
or quantity having a frequency that is an
integral multiple of the fundamental
frequency”. Harmonics can be thought of,
therefore, as voltages and/or currents
present on an electrical system at some
multiple of the fundamental frequency.
AF’s can be classified based on
topology, converter type, and the number
of phases. The converter type can be either
CSI or VSI bridge structure. The topology
can be shunt, series, or a combination of
both. The third classification is based on
the number of phases, such as two-wire
(single phase) and three- or four-wire
three-phase systems [3].
1. Topology based filter Design - AF’s
can be classified based on the topology
used as series or shunt filters and unified
power
quality
conditioners
use
a
combination of both. Combinations of
active series and passive shunt filtering are
known as hybrid filters.
Typical harmonics for a 50-Hz system are
the fifth (250 Hz), the seventh (350 Hz),
and the eleventh (550 Hz).
The AF technology is now mature for
providing compensation for harmonics,
Fig. 1 Shunt Active Filter
reactive power, and/or neutral current in ac
networks. Single-phase loads, such as
Fig 1 shows an example of an active shunt
domestic lights and ovens, TV’s, computer
filter, which is most widely used to
power supplies, air conditioners, laser
eliminate
International Journal of Innovative Research in Engineering and Applied Sciences.
doi:15.06.15/3/9-14/June 2015
current
harmonics,
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reactive
power compensation (also known as
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storage element (either inductor or dc-bus
STATCON), and balancing unbalanced
capacitor) is shared between two current
currents. It is mainly used at the load end,
source or voltage-source bridges operating
because current harmonics are injected by
as
nonlinear loads.
compensators.
active
series
and
active
shunt
Fig 2 Series Active Filter
Fig. 2 shows the basic block of a stand-
Fig 4 Hybrid filter
alone active series filter. It is connected
before the load in series with the mains,
using a transformer, to eliminate voltage
harmonics, and to balance and regulate the
terminal voltage of the load or line.It is
used to reduce negative-sequence voltage
and regulate the voltage on three-phase
systems.
Fig. 4 shows the hybrid filter, which is a
combination of an active series filter and
passive shunt filter. It is quite popular
because the solid-state devices used in the
active series part can be of reduced size
and cost (about 5% of the load size) and a
major part of the hybrid filter is made of
the passive shunt L–C filter used to
eliminate lower order harmonics. It has the
capability of reducing voltage and current
harmonics at a reasonable cost.
2. Converter based filter design –
Fig 3 Unified power quality conditioner
Fig. 3 shows a unified power quality
conditioner (also known as a universal
AF), which is a combination of active
shunt and active series filters. The dc-link
Fig 5 Voltage-Fed Type APF
International Journal of Innovative Research in Engineering and Applied Sciences.
doi:15.06.15/3/9-14/June 2015
(2015) 9-14
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phase. Two-wire (single phase) AF’s are
used in all three modes as active series
active shunt and a combination of both as
unified line conditioners. Both converter
configurations,
current-source
PWM
bridge with inductive energy storage
element and voltage-source PWM bridge
with capacitive dc-bus energy storage
elements, are used to form two-wire AF
circuits.
Fig 6 Current-Fed Type APF
There are two types of converters used in
the development of AF’s. Fig. 6 shows the
current-fed
(PWM)
pulse-width
inverter
bridge
modulation
structure.
It
behaves as a non-sinusoidal current source
to meet the harmonic current requirement
of the nonlinear load. A diode is used in
series with the self commutating device
(IGBT) for reverse voltage blocking.The
Fig 7 Single Phase series AF with current-source
other converter used as an AF is a voltage-
converter
fed PWM inverter structure, as shown in
Fig. 5. It has a self-supporting dc voltage
bus with a large dc capacitor. It has
become more dominant, since it is lighter,
cheaper, and expandable to multilevel and
multistep
versions,
performance
with
to
enhance
lower
the
switching
frequencies.
Fig 8 Single Phase shunt AF with current-source
converter
1. Supply based filter design –AF’s can
be classified in two ways according to
supply based are single phase and three
International Journal of Innovative Research in Engineering and Applied Sciences.
doi:15.06.15/3/9-14/June 2015
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Three-phase three-wire nonlinear loads,
such as ASD’s, are major applications of
solid-state power converters. Three phase
active filters are classified in three modes.
These are capacitor midpoint four-wire
shunt AF, four-pole four-wire shunt AF,
andthree-bridge four-wire shunt AF. A
Fig 9 Single Phase series AF with Voltage-source
large number of single-phase loads may be
Converter
supplied from three-phase mains with
neutral conductor. They cause excessive
neutral current, harmonic and reactive
power burden, and unbalance. To reduce
these problems, four-wire AF’s have been
attempted.
Fig 10 Single Phase shunt AF with Voltagesource converter
Fig 9 and 10 configurations of active
series, active Shunt with a voltage-source
bridge, using capacitive storage elements.
In the case of a series AF with voltage-fed
converter, sometimes the transformer is
Fig 11 capacitor midpoint four-wire shunt AF.
removed and load is shunted with passive
L–C components [5]. The series AF is
normally
used
to
eliminate
voltage
harmonics, spikes, sags, notches, etc.,
while the shunt AF is used to eliminate
current harmonics and reactive power
compensation.
Fig. 12. Four-pole four-wire shunt AF.
International Journal of Innovative Research in Engineering and Applied Sciences.
doi:15.06.15/3/9-14/June 2015
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The first configuration of a four-wire shunt
overview,” IEEE Trans. Power App. Syst., vol.
AF is known as the capacitor midpoint
PAS-102, pp. 2455–2460, Aug. 1983.
type shown in fig 11, used in smaller
[3] B. Singh, K. Al-Hadded, “ A Review of Active
ratings. Here, the entire neutral current
Filter for Power Quality Improvement” IEEE
flows through dc-bus capacitors which are
Transactions on Industrial Electronics, vol. 46,
of a large value [4]. Fig. 12 shows another
NO. 5, pp. 960-970, Oct. 1999.
configuration known as the four-pole
[4] C. A. Quinn and N. Mohan, “Active filtering of
switch type, in which the fourth pole is
harmonic
AF
three-phase,
four-wire
loads,” in Proc. IEEE APEC’92, 1992, pp. 829–
836.
III CONCLUSION
present,
in
systems with three-phase, single-phase nonlinear
used to stabilize the neutral of the AF.
At
currents
technology is
well
[5] J. Nastran, R. Cajhen, M. Seliger, and P. Jereb,
“Active power filter for nonlinear AC loads,” IEEE
developed, and many manufacturers are
Trans. Power Electron., vol. 9, pp. 92–96, Jan.
fabricating AF’s with large capacities. The
1994.
utilities in the long run will induce the
[6] L. R. Limongi, R. Bojoi, G. Griva and A.
consumers with nonlinear loads to use the
Tenconi, “New Control Scheme for Single-Phase
AF’s for maintaining the power quality at
ActivePower Filters”, IEEE 2008.
acceptable levels. A large number of AF
[7] HL Jou, JC Wu, YJ Chang, YT Feng, “A novel
configurations are available to compensate
active power filter for harmonic suppression”,
harmonic current, reactive power, neutral
Power Delivery, IEEE Transactions on, 2005
current, unbalance current, and harmonics.
The consumer can select the AF with the
required features. It is hoped that this
survey on AF’s will be a useful reference
to the users and manufacturers.
REFERENCES
[1] Active Filters: Technical Document, 2100/1100
Series, Mitsubishi Electric Corp., Tokyo, Japan,
1989, pp. 1–36.
[2] IEEE Working Group on Power System
Harmonics,
“Power
system
harmonics:
An
International Journal of Innovative Research in Engineering and Applied Sciences.
doi:15.06.15/3/9-14/June 2015
(2015) 9-14