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Contents:
1. Abstract
2. Introduction
3. Traditional solutions in eliminating harmonic currents
(i)Oversizing and derating of the installation
(ii)specially connected transformers
(iii)series reactors
(iv)tuned passive filter
4.Topologies of active harmonic conditioners
(i)series conditioners
(ii)parallel conditioners
(iii)hybrid conditioners
5.Parallel active conditioner:system description
(i)Operating principle
(ii)Detailed description
(iii)Points of connection of active conditioner
6.Case study:ELF Aquitaine
(i)Description of the installation
(ii)Problems experienced by ELF and site audit
(iii)Analysis of the solution
(iv)Final solution
7.Comparision of active harmonic filter and tuned passive filter
8.Active compensation of harmonics in industrial applications
9.Conclusion
1.ABSTRACT:
In little more than ten years, electricity power quality has grown from obscurityto a major
issue. converters and power electronics gave birth to numerous newapplications, offering unmatched comfort,
flexibility and efficiency to the customers. However, their proliferation during the last decade is creating a growing concern andgenerates more and more problems: not only these electronic loads pollutethe AC distribution
system with harmonic currents, but they also appear to be verysensitive to the voltage distortion. Then, electric
-ity power quality is becoming a major issue for utilities andfor their customers, and both are quickly adopting th
-e philosophy and the limitsproposed by the new International Standards (519-1992 IEEE, 61000.3-2/4 IEC). To
-day, recent advances in power electronic technology are providingan unprecedented capability for conditioning
And compensating harmonic distortiongenerated by the non-linear loads. The case study presented in this paper demonstrates the role of the power source, the load and the AC distribution system as regards power quality.
The benefitof harmonic cancellation equipment is clearly shown. Among the different technicalsolutions, a shunt –
currentinjection mode - active harmonic conditioneris evaluated, and detailed site measurements are presented
as confirmationof the unsurpassed performances. This new innovative active conditioner appears to be the easiest of use, the mostflexible, the most efficient and cost effective one.
2.INTRODUCTION:
Today, the situation on low-voltage AC systems has become a serious concern. The quality of
electrical power in commercial and industrial installations isundeniably decreasing. In addition to, such as outages, sags and spikes due toswitching and atmospheric phenomena, there are inherent, internal causes specific
to each site and resulting from the combined use of linear and non-linear loads. Untimely tripping of protection
devices, harmonic overloads, high levels of voltage and current distortion, temperature rise in conductors and all
contributeto reducing the quality and the reliability of a low-voltage AC system. The above disturbances are well
and directly related to the proliferationof loads consuming non-sinusoidal current, referred to as "non-linear loads".
This type of load is used for the conversion, variation and regulation of electrical power in commercial, industrial
and residential installations. The prospect of a rapid return to linear-load conditions is illusory. Recent studiesshow that the consumption of non-linear current will sharply increase in the years to come. However, the remarkable
progress made by power electronic devices in the recentyears, fast IGBT's, makes it possible to design self adaptable harmonic suppressors called active harmonic conditioner, known also as active filters. Active are proving
to be viable option for controlling harmonic distortion levels in many applications.
3. Traditional solutions in eliminating harmonic
currents
Today, a various panel of harmonic mitigation equipment or solutions is proposed, but all present
some disadvantages. These solutions are listed here after.
(i)oversizing or derating:
of the installation
This solution does not attempt to eliminate the harmonic currents flowingin the electrical installation,
but rather to”make do" by avoiding the consequences. When designing a new installation, the idea is to oversize all
installation Elements likely to transmit harmonic currents, namely the transformers, cables, circuitbreakers, engine
generator Sets and the distribution switchboards. The most widely implemented solution is oversizing of the neutral
conductor The result is a major increase in cost. In existing installations, the most common solution is to derate the
equipment subjected to the harmonic currents. The consequence is an installation that cannot be used to its full
potential.
(ii)specially connected:
transformers
This solution inhibits propagation of third-order harmonic currentsand their multiples. It is a centralized
solution for a set of single phase loads. However, it produces no effect on harmonic orders that are not multiples
of three (H5, H7, ...). On the contrary, this solution limits the available power fromthe source and increases line.
The consequence is an increase in the voltage distortion due to the other harmonic orders.
(iii)series reactors:
This solution, used for variable speed drives and three phase rectifiers, consists inconnecting a reactor in
series upstream of a non-linear-load. A reactor is notexpensive, but has limited effectiveness. One must be installed
for each non-linearload. Current distortion is divided by a factor of approximately two.
(iv)tuned passive filter:
The idea is to "trap" the harmonic currents in L/C circuits tuned to the harmonicorders requiring filtering.
A filter therefore comprises a series of "stages", each corresponding to an harmonic order. Orders 5 and 7 are the
most commonly filtered. A filter may be installed for one load or a set of loads. Its design requires in-depthstudy of the
AC system and collaboration with a consulting engineer. Sizing depends on the harmonic spectrum of the load and
the impedance of the power source. Rating also must be co-ordinated with reactive power requirements of the loads,
and it is often difficult to design the filters to avoid leading power factor operation for some load conditions. This
solution is moderately effective and its design depends entirely on the given power source and the loads, i.e. it is not
flexible and is virtually impossibleto upgrade. Its application may create system resonance which are dependent on
specific system conditions. Note: when appropriately designed, this type of filter may also be used to distortion present on the electrical network of the power distributor, provided a significant overrating for harmonic absorption
from the power system.
4.Topologies of active harmonic conditioners:
The idea of active harmonic conditioners, also named active filters, is relativelyold, however the lack of an effective
technique at a competitive price slowedits development for a number of years. Today, the wide-spread use of IGBT
components, mastery of their implementation and the availability of new digital signal processing (DSP) techniques
are paving the way to a much brighter future for the active harmonic conditioner. The active harmonic conditioner
concept uses power electronics to produce harmonic components which cancel the harmonic components of the nonlinear loads. A number of different topologies are being proposed, whom some of them are described here after.
Within each topologies there are issues of required components ratings and method of rating the overall conditioner
for the loads to be compensated.
(i)series conditioners:
This type of conditioner, connected in series on the distribution network, compensates both the harmonic currents
generated by the load and the voltage distortion already present on the AC system. This solution is technically
similar to a line conditioners and must be sized for the total load rating.
(ii)parallel conditioners:
Also called shunt conditioners they are connected in parallel with the AC line andneed to be sized only for the
harmonic power (harmonic current) drawn by the nonlinearload(s). The parallel topology selected for SineWave
is in no way dependenton the load or electrical AC system characteristics. It is described in detailin the section 4.
(iii)hybrid conditioners:
This solution, combining an active conditioner and a passive filter, may be eitherof the series or parallel type. In
certain cases, it may be a cost-effective solution. Thepassive filter carries out basic filtering (5th order, for example)
and the activeconditioner, through its precise and dynamic technique, covers the other orders.
5.parallel active harmonic conditioner: system
description:
(i)operating principle:
The active conditioner is connected in-parallel with the AC line, and constantlyinjects currents that precisely
correspond to the harmonic components drawnby the load. The result is that the current supplied by the power
source remains sinusoidal.
I load = I fundamental + I harmonic
I conditioner = I harmonic
I load = I source + I conditioner
Fig. 04 - Active harmonic compensation principle
The normal power source provides the fundamental current, and the harmonic currents required by the load are
supplied by the active harmonic conditioner (AHC). The entire low-frequency harmonic spectrum (H2 to H25) is
covered. If the harmonic currents drawn by the load are greater than the rating of the active conditioner, the
conditioner automatically limits its output current to its rated one. Easy to implement, an active conditioner may
beinstalled at any point on a low voltage AC system to compensate the power drawn by one or several non-line
-ar loads, thus avoiding the circulation of harmonic currents throughout the low-voltageAC system.
(ii)recording of real current for non-linear load:
(iii)detailed description:
Fig. 08 - Active conditioner single-line diagram
The active harmonic conditioner is made up of the following elements:
FU1: ultra fast protection fuse;
R1 and contactor K1: precharge system for chemical capacitors C2 & C3;
Lf & Cf: filter intended to attenuate the effects of chopping;
L1, DC/ac converter, C2 and C3: PWM inverter leg;
CT2: sensors for inverter currents;
control electronics;
CT1: external sensor for current drawn by the load.
The converter comprises a three phase IGBT current inverter leg that chops atan average switching frequency of 16
kHz, chemical capacitor C2 and C3 providingback up power. The conditioner draws from the power source the active
powerrequired for its operation.
The control electronics comprise:
an harmonic-extraction module which generates a regulation set point proportionalto the harmonic components of
the load current;
a module that regulates inverter currents and the DC voltage;
a monitoring module which ensures filter protection in the event of overload oran internal fault;
a control module which generates the control signals necessary for inverteroperation.
To enhance the compensation capacity at a given point in the installation, it is possible to connect active conditioners
in parallel.
(iv)points of connection of the active conditioner:
The active conditioner may be installed at different points on AC distributionsystems:
close to the loads generating high level of harmonics to ensure local compensation of harmonic currents;

partial compensation of harmonic currents;
centrally, at the PCC level, for global compensation of harmonic currents. Ideally, compensation of harmonics
should take place at their point of origin.
A number of cost and technical criteria are used to make the best selection.
Mains advantages of the local compensation:
avoid dissemination of the harmonic currents in the electrical installation;
reduce Joule-effect losses in the cables, and load on the main transformer;
reduces size of the cables required in new installations;
means installation can meet applicable harmonic standards.
6. case study : ELF AQUITAINE:
(i)description of the l’installation:
A centralised UPS system supplies two buildings, each one of 4 floors. This UPSsystem as a dual feed
supply, either the utility power or a generator set. The distance from the UPS system to the building ranges from 35 m
to 150 m. In each building, distribution is provided through two main feeders; on each floor, a storey distribution
board supplies all the information technology equipment: PC, workstations servers. AC distribution system is 4 wires
(three phases + neutral), with the neutral conductorsized at 50% of the phase conductor.
(ii)problems experienced by Elf and site audit:
Elf experienced several type of disturbances:
functional problems in computers;
breakdown and failure of very sensitive IT equipment, as well as damages;
temperature rise in the neutral conductor, and excessive heat losses;
downstream the storey distribution board, voltage distortion non compatible withthe standard compatibility levels,
and the computer specifications.
● Most of the loads is single phase and non-linear. At the basement level, measuresdemonstrate a total current
harmonic distortion of 86%, and a current harmonicdistortion of 69% for the 3rd order.
● Then, the circulation of these harmonic currents in the long cables generates a highvoltage distortion at the end of
the
cables, where the critical IT equipment areconnected. At the point of use, the voltage distortion is double versus the
one at the UPS output: 8.3% vs 4.2%. When operating on the generator set andon the static by-pass of the UPS
system, during maintenance or test, voltage distortion up to 15% was noticed.
● Also, the neutral current is 140% of the phase current, creating over temperaturein the neutral conductor, and
neutral to earth voltage as high as 8 V.
The here after table summarises the voltage measures focused on the feeders F and G:
UPS output
feeder G - 4th floor
feeder G - comp. suite
feeder F - 4th floor
feeder C - 4th floor
THDU
phase / neutral
voltage
neutral / earth
4,2%
0v
8,3v
4v
4,4v
8%
8,3%
5,7%
6%
The following table gives the detailed measures of feeder G, at the basement level:
total I rms
crest factor
THDI
power factor
I harmonic rms
THDU
neutral / earth voltage
I neutral rms
66 A
2,3
86%
0,72
42 A
7,7%
7,9 V
108 A
(iii)analyse of the solutions:
Of course, the solution implemented has to eliminate the disturbances experiencedby Elf, but also must guaranty a
voltage distortion lower than 5% at the point of use, i.e. at the input of the computer equipment. Several solutions
were proposed and compared by the consultant who carried out the site audit.
They are listed here after:
installation of double wound transformer on each feeder;
renewal of the overall distribution, changing also the earthing system;
increase of the size of the neutral conductor;
installation of active harmonic conditioner(s) at the basement level of each feeder.
The advantages and disadvantages of each solutions were evaluated carefully, bothon the economical and technical
viewpoints. The analyse is summarized in the following table:
transformer
renewal
advantages
elimination of voltage drops
due to harmonic current
circulation;
elimination of third
harmonic.
ease of implementation
increase of neutral
conductor size
no change of the earthing
system and mastering of
circulating neutral current.
active harmonic
conditioner
competitive price;
reduction of the voltage
distortion;
reduction of the neutral
current;
significant decrease
of the rms current.
disadvantages
high price:
derating of transformer;
influence of inrush current on
UPS.
new earthing system not
recommended;
difficulty to master the circulating
currents in the AC system;
no reduction of the voltage
distortion.
no reduction of the voltage
distortion;
slight reduction of the voltage drop
in the neutral conductor;
a lot of cabling works.
need to install 2 conditioners
on the same feeder (F & G).
The active harmonic conditioner solution was selected as it was the most competitive, and the only one to 100% meet
the customer requirements.
(iv)final solution:
To get the best benefit for the customer, one active conditioner will be connected to each feeder, at the basement
level. For feeders F & G, whose distance from UPS system is very long, one additional conditioner will be installed
at the 2nd floor level. Then, harmonic distortion at 4 th floor will be as low as possible.
(v)site results:
This section describes the waveform and the characteristics of the powerof feeder G after connection of one 30 A
active harmonic conditioner at the basement level. This is the first step of the implementation of the solution. The
measures and results presented here after gives a good idea of the improvement thanks to the active harmonic
conditioner.
Conclusion:
The benefit of the active conditioner is clearly demonstrated on the current.
reduction of 29% of the rms current (from 66 to 47 A);
crest factor decreased to 1.92 after compensation (vs 2.3);
improvement of the power factor from 0.72 to 0.92.
harmonic spectrum:
120
100
80
60
40
20
0
H1
H3
H5
H7
H9
H11
Fig. 15 - Line (load) current spectrum (% of H1) without active conditioner
120
100
80
60
40
20
0
H1
H3
H5
H7
Fig. 16 - Line (source) current spectrum (% of H1) with active conditioner
H9
H11
Conclusion:
The graphs show the impact of the SineWave active conditioner on the harmonic currents. Due to the high harmonic
current, the active conditioner operates in limitation mode and compensates partly for the harmonic currents.
THDI attenuation of 3: 86% down to 28%;
reduction of 65% of the neutral current: 108 A down to 38 A;
reduction by 70% of the harmonic rms current: 42 A down to 13 A.
7. comparison between active harmonic conditioner
and tuned passive filter:
harmonic-current control
influence of a frequency
variation
influence of a modification in
the impedance
influence of an increase in
current
added equipment (load)
harmonic control by order
modification in the fundamental
frequency
dimensions
weight
passive filter
requires a filter for each
frequency (bulky)
reduced effectiveness
active harmonic conditioner
simultaneously monitors
several frequencies
no effect
risk of resonance
no effect
risk of overload and damage
in certain cases, requires
modifications to the filte
very difficult
cannot be modified
no risk of overload, but less
effective
no problem if I_conditioner >
I_load_harmonics
possible via parameters
possible via reconfiguration
large
high
small
low
8. Active Compensation of Harmonics in Industrial
Applications:
In industrial low and medium voltage mains, passive filters and PFC capacitors have traditionally been
used to improve the supply quality. However, they cannot be rated only for the loads being. They are
affected by harmonic currents from other non-linear loads or by harmonics from the power system.
Compared with passive element compensators, an active harmonic compensator (AHC) can be used to
improve the supply quality without worrying about all the problems associated with applying passive
elements.
The proposed active harmonic compensation AHC for industrial networks can be
successfully used with nonlinear loads and consumers with rapid fluctuations of reactive and active power to
improve the supply quality of other loads supplied from the same mains. Clear reduction of the voltage wave
form distortion and the voltage changes (flicker effects) as well as the stabilisation of the mains voltage are the
main advantages of the proposed AHC. These all make the application of the power electronics to improve the
supply voltage quality in industrial networks more effective in comparison to passive filters and PFCcapacitors.
AHC advantages:
The use of active mains compensation holds a number of advantages compared to the passive.
The AHC:
- Is easy to size to the application as the design is independent of line impedance
- Does not generate resonance
- Actively controls both harmonic and reactive currents.
AHC solutions become more relevant:
Despite the advantages, AHC’s have a limited market share mainly due to high cost. However, a number of
trends and factors indicate that this is about to change.
New developments enable the use of mass produced hardware in the active filter, which significantly will
reduce the cost.
Due to the large amount of cobber and steel used in passive filter, the increase of material cost has a higher
impact on passive solutions than on active solutions
Fig 1. Electrical diagram of the Active Harmonic Compensator connected to industrial plant.
Fig.1 shows the block diagram of the AHC. The three-phase voltage source inverters is connected to (see.1)
the industrial network.
An industrial plant may include different types of electrical loads, divided into linear loads (regenerative power
units, resistive loads, ac-machines) and non-linear loads (Adjustable Speed Drives, arcing devices, etc.)
The Active Harmonic Compensator has to detect the current harmonics and generate a compensation current that
cancels the harmonic component, leaving mainly the fundamental current to be drawn from the power supply.
The control of the AHC consists of a closed loop control for regulation of the inverter current and dc voltage, and the
detection and generation of compensation current reference. Thus, depending on applications, the AHC may include
harmonic compensation, reactive current or flicker mitigation.
Control system :
Fig.2 shows a block diagram of the control unit of the AHC. The control scheme is based on a cascade control
with a current control in the inner loop without mains voltage sensors. The current controller sets the output
voltage of the voltage source inverters for each sampling period of the control system so that the line current
has a reference value. The voltage controller allows the dc voltage to have an almost constant value. The
output signal of the dc-link voltage controller determines the value of the active current of the mains load and
losses of the power unit of the restoring system . The reactive current is calculated by the reactive power and
flicker estimation module of the control unit (see Fig.2).
Fig.2: Block diagram of the control unit
To reduce the high-frequency switching-ripple of the AHC line current, a high frequency LCL filter is connected in
between the mains and the AHC.
Current control:
The control value of the current control loop is the supply current. This current is a
result of the sum of the load current (see Fig.1) and the ac current of voltage inverter. These two three-phase
system currents are added are transformed to a signal of the two-phase quantities i Sa ,b . In Fig.2 this current
is represented as i Sa and i Sb .The reference value for the current controller i
the stationary frame a −b . The transformation of the vector i
, to
refd q
ref d ,q
(d and q components) is to
the vector i1a b, is executed by ejw1t, derived
from a phase locked loop PLL (see Fig.2).
The selection of the switching sequence for every switching operation of the both voltage source inverters is
achieved through the use of a sliding mode controller.
The selection of the switching sequence for every switching operation through the use of the sliding mode is
discussed in detail in [4-6]. This makes it possible to control the active filter without mains voltage sensors [7].
It significantly simplifies the hardware configuration of the active mains compensator, especially for medium
and high voltage applications. The output signals of two P-controllers with saturation represent two compone
-nts of the mains voltage vector u
Wa ,
u Wb which are used to detect the position of the voltage vector by PLL.
To control harmonic amplitudes in the network, the harmonic calculator is used. The principle of the operation
is based on the direct harmonic control method. This method is briefly described in [2,3].
DC-link Control :
With non-sinusoidal mains current of the voltage inverter, the dc-link voltage contains not only a ripple from transistor
switching operations, but also a low frequency voltage ripple like the dc voltage at the dc link of the diode rectifier.
This low frequency voltage ripple must be filtered in the control loop by feeding back the dc voltage otherwise this
ripple would be increased by the proportional part of the voltage controller and it would be passed on to the line
control loop. Therefore the line currents would be distorted [8].
To decrease the influence of the dc-link voltage ripple on the current control loop, the cut-off frequency of the
feedback low-pass filter must be f0=50÷75Hz. The low cut-off frequency of the feedback filter causes the large
delay time in the dc-voltage measurement and therefore the dc-link voltage control has a low dynamic.
To improve the time response of the dc-link voltage control, an adaptive control system is used, whose values
of the feedback filter and PI controller are changed in accordance with the value of the dc voltage error [8].
Simulation results :
The simulation of AHC control shows very high dynamics. This is justified first by the high dynamic of the
current controller, which is characteristic to the sliding mode control. Second, due to the implemented adaptive
dc-voltage controller the AHC can overcome much faster the transient during the connection/disconnection of
the AHC or the harmonic load change.
A simulation result is available in Fig. 3 (only a single phase is shown).
The harmonic current is generated by a typical three phase diode rectifier Adjustable Speed Drive. Since the
displacement power factor is close to unity there is no requirement of reactive power compensation in this
case, but only harmonic current mitigation. At time 0.16 the AHC is connected to the power system and starts
mitigating the harmonic currents from the ASD. The transient takes almost one fundamental period, until the
source current resembles sinusoid waveform.
Fig.3. Simulation results of AHC start-up.
Due to its high dynamics the AHC is able to compensate the harmonic currents within one fundamental period.
The current distortion of the non-linear load has a THD of 34 % while the source current reaches a THD of 4 %
.
Application examples:
The AHC operates as a highly dynamically controlled reactive current source and, thanks to special control
algorithms, the compensating reactive current is delivered at exactly the right moment. Thereby the load of
the mains is decreased and the mains voltage changes and distortions are reduced to a safe value.
Mitigation of harmonics:
In industrial mains, passive filters are traditionally used to absorb harmonics generated by non-linear loads,
primarily due to their low cost. This is a good approach when power factor correction is needed too. As they
have a lot of drawbacks, the industrial application of passive filters is limited. Compared with a passive filter,
an active filter can be used to reduce harmonics in industrial mains without worrying about all the problems
associated with applying passive filters [1].
The AHC unit enables a controlled compensation of harmonics and reactive currents like active filters, of the
mains- and current load configuration and without risk of compensator overload. The AHC unit can also be
sized for the compensating load requirement only, leading to a reduction of the installation costs of the
compensation unit.
The following experimental wave forms show the high efficiency of the AHC system for mitigation of harmonics.
These wave forms have been created by testing the AHC unit with the power rating 800 kVAr on an industrial.
The AHC unit was connected to 10 kV network by the 10/0.4 kV step-down transformer. It was estimated that
the active filter would adequately compensate five ac drives supplied by a 12-pulse current source inverter up
to 1.0 MW.
Fig. 4 shows the wave forms of the line current (one phase) of the ac drive (only one drive) and the phase (the
same phase) of the AHC. These currents were measured on the 10kV side of the transformer.
The network current is presented in Fig.5. It is the sum current which is calculated by the oscilloscope from the
measured currents from Fig. 4.
From Fig. 5 it is seen that the sum network current has practically sinusoidal and periodical wave form. The
harmonics of the ac drive current are practically eliminated as you can see from the Spectra of the ac drive
current and spectra of network current (see Fig.6).
Fig.4: The wave forms of the AHC current and the ac drive current (10kV mains, 20A/div)
:
Fig.4: The wave forms of the AHC current and the ac drive current (10kV mains, 20A/div)
Fig.5: The currents sum of the measured non-linear load current and of the AHC current (20A/div
Fig.6: Spectra of the ac drive current (lines) and the sum current (dots); the amplitude of the fundamental
harmonic is not shown. K represents the number of harmonics.
Flicker Mitigation :
Flicker, caused by large fluctuating loads, is one of the power quality problems that include interruption, voltage
sags and dips. SCR controlled Static Var Compensators (SVC) are usually used to compensate reactive and
to reduce the flicker. As it operates at the fundamental frequency, the capability of the SVC is limited [9].
Thanks to a delay time of only 2ms the AHC is highly suitable for the flicker compensation.
Fig.7 shows the measured voltage changes at the 11kVnetwork during a test of an engine without a unit. The
maximum mains voltage change was approximately 1.2%, a number which, for this frequency, is already over
the standard limit value for the flicker. The measured value of the short-time flicker Pst equals 1.5.
In Fig.8 the measured voltage changes is shown at the same test of the motor but this time using the AHC.
The mains voltage change is approximately 0.3% and lies clearly under the standard limit value. The
measured value of the short-time flicker Pst = 0.5.
Fig.7: Voltage changes at a 11kV- mains network without AHC (1V/div)
Fig.8: Voltage changes at a 11kV- mains network with AHC (1V/div)
Compensation unbalanced current from a welding machine:
Welding machines are well known to draw a high non sinusoidal current in short periods. Even unbalanced line
current, where only 2 phases are loaded are common. An example hereof is shown in Fig. 9, where only ‘t’ and
s’ are loaded with a peak current of 1200A, while phase ‘r’ remains unloaded.. Note also the non sinusoidal of
the current. The AHC will compensate the harmonic distortion as well as the unbalance between the phases
as shown in Fig 10. As a result of that load is shared by all three phases, the peak current is significant lower,
also improves voltage quality. The peak current of above 1200A in phase s’ is reduced to 400 A in all three
phases.
Fig.9: The wave forms of the welding machine line currents without AHC
Fig.9: The wave forms of the welding machine line currents without AHC
Fig.10: The wave forms of the welding machine line currents with AHC
9.conclusion:
A 30 Amp "shunt topology" active harmonic conditioner was successfully developed, and is being marketed.
All the installations equipped with the SineWave active harmonic conditionerdemonstrate excellent performances in a
wide range of applications. Regarding computer type loads, the presented case study is a clear demonstration of the
highlevel of harmonic current compensation that the conditioner can achieve. As a consequence of the compensation
of the 3rd harmonic current, the activeconditioner also reduces the neutral (harmonic) current. These results gives
very good reasons to expect in a very short time the development of active harmonic conditioner to compensate
harmonic distortion in the commercial applications, but also in the industrial sector.
9.References:
● G W Massey, "Power Distribution System Design for Operation Under Nonsinusoidal Load Conditions", IEEE
Trans.
Ind.Applic., vol.31 n° 3, may/june 1995.
● S Fukuda and T Endoh, "Control Method for a Combined Active Filter SystemEmploying a Current source
Converter",
● T Deflandre, C Courty, C Greiveldinger, EDF, "Impact des Harmoniques sur lesRéseaux Publics Français", PPRD,.
● T Key and J S Lai, "Costs and benefits of Harmonic Current reduction for SwitchmodePower Supplies in a
Commercial Building", sept. 1995.
● W Russell, "Hardening data Lines to IEC 1000-4-2, Compliance European Edition",jan./feb. 1996.
● J Moravek, "Benefits of Using a harmonic monitoring Program", EC&M, sept. 1994.
● L Lachaume and JM Vialars, "Electric Energy Metering in Presence of Harmonics",EDF study, nov. 1994.
● R Waggoner, "Beware of Single-phase Harmonic interactions", EC&M, june 1994.
● P N Enjeti, W Shiren, P Packebush, I Pitel, "Analysis and Design of a new active Power Filter to Cancel Neutral
Current harmonics in Three-phase Four-wire Electric Distribution Systems", IEE Trans. Ind. Applic., vol. 30 n°6, dec.
1994.
● S Bernard, G Trochain, "A New High Performance Active Harmonic Conditioner Based on the Current Injection
Mode", Power Quality 95, nov. 1995.
● M Mc Granaghan, L Tang, S Beranrd, S Papoz, "Evaluation of Active Filter Design and performance Using a
H Akagi, "New Trends in Active Filters", EPE 95, sept. 1995.
● T Key, JS Lai, "Comparison of Standards and Power Supply Design Options for Limiting Harmonic Distortion in
Power Systems", IEEE Trans. Ind. Applic., vol 29 n°4, jul./aug. 1993.