HARMONIC TREATMENT IN INDUSTRIAL POWER SYSTEMS

1
HARMONIC TREATMENT IN INDUSTRIAL POWER SYSTEMS

• Presented by
• Stefanos Manias

2
CONTACT INFORMATION

• Stefanos N. Manias
• National Technical University of Athens
• Phone [phone]
• FAX [phone]
• E-mail manias_at_central.ntua.gr
• Mailing Address
• National Technical University of Athens
• Department of Electrical and Computer Engineering
• 9, Iroon Polytechniou Str, 15773 Zografou
• Athens, Greece

3
PLAN OF PRESENTATION

• DEFINITIONS
• CATEGORIES OF POWER QUALITY VARIATIONS
• HARMONIC DISTORTION SOURCES IN INDUSTRIAL POWER
  SYSTEMS
• EFFECTS OF HARMONICS ON ELECTRICAL EQUIPMENT
• HARMONIC MEASUREMENTS IN INDUSTRIAL POWER SYSTEMS
• HARMONIC STANDARDS
• HARMONIC MITIGATING TECHNIQUES
• GENERAL PASSIVE AND ACTIVE FILTER DESIGN
  PROCEDURES
• DESIGN EXAMPLES
• CONCLUSIONS

4
WHY HARMONIC ANALYSIS ?

• When a voltage and/or current waveform is
  distorted, it causes abnormal operating
  conditions in a power system such as
• Voltage Harmonics can cause additional heating in
  induction and synchronous motors and generators.
• Voltage Harmonics with high peak values can
  weaken insulation in cables, windings, and
  capacitors.
• Voltage Harmonics can cause malfunction of
  different electronic components and circuits that
  utilize the voltage waveform for synchronization
  or timing.
• Current Harmonics in motor windings can create
  Electromagnetic Interference (EMI).

5

• Current Harmonics flowing through cables can
  cause higher heating over and above the heating
  that is created from the fundamental component.
• Current Harmonics flowing through a transformer
  can cause higher heating over and above the
  heating that is created by the fundamental
  component.
• Current Harmonics flowing through circuit
  breakers and switch-gear can increase their
  heating losses.
• RESONANT CURRENTS which are created by current
  harmonics and the different filtering topologies
  of the power system can cause capacitor failures
  and/or fuse failures in the capacitor or other
  electrical equipment.
• False tripping of circuit breakers ad protective
  relays.

6
HARMONIC SOURCES
a) Current Source nonlinear load
Thyristor rectifier for dc drives,
heater drives, etc.
Per-phase equivalent circuit of thyristor
rectifier
b) Voltage source nonlinear load
Diode rectifier for ac drives, electronic
equipment, etc
Per-phase equivalent circuit of diode rectifier
7
INPUT CURRENT OF DIFFERENT NOLINEAR LOADS  
8
(No Transcript)
9
CURRENT HARMONICS GENERATED BY 6-PULSE CSI
CONVERTERS
CURRENT HARMONICS GENERATED BY 12-PULSE CSI
CONVERTERS
10
RECENT CURRENT MEASUREMENTS TAKEN IN
AN INDUSTRIAL PLANT WITH 600 KVA, 20 KV/400
V DISTRIBUTION TRANFORMER
Current waveform and its respective spectrum at
the inputs of a motor drive system
11
Current waveform and its respective spectrum at
the inputs of a motor drive system
12
Current waveform and its respective spectrum at
the secondary of the distribution transformer (
i.e. at the service entrance)
13
DEFINITIONS
f (t) Fourier Series of a periodic function f
(t)
(1)
(2)
(3)
(4)
h harmonic order
14
Percentage of the Total Harmonic Distortion of a
nonsinusoidal voltage waveform
(5)
Percentage of the Total Harmonic Distortion of a
nonsinusoidal current waveform
(6)
harmonic component of the voltage
harmonic component of the current
RMS value of the voltage distortion
15
RMS value of the current distortion
RMS value of a nonsinusoidal current
(7)

RMS value of a nonsinusoidal voltage
(8)
(9)
(10)
Harmonic Factor
16
Full load kVA rating of the Drive system
Short Circuit kVA of the distribution system
at the point of connection
SINUSOIDAL VOLTAGE NONSINUSOIDAL CURRENT
(11)
(12)
(13)
17
(14)
(15)
NONSINUSOIDAL VOLTAGE AND NONSINUSOIDAL CURRENT
(16)
(17)
18
(18)
(19)
19
(20)
(21)
(22)
(23)
20

• Harmonic sequence is the phase rotation
  relationship with respect to the fundamental
  component.
• Positive sequence harmonics ( 4th, 7th,
  10th , . (6n1) th ) have the same phase
  rotation as the fundamental component. These
  harmonics circulate between the phases.
• Negative sequence harmonics ( 2nd, 5th, 8th
  (6n-1) th ) have the opposite phase rotation
  with respect to the fundamental component. These
  harmonics circulate between the phases.
• Zero sequence harmonics ( 3rd, 6th, 9th,
  .. (6n-3) th ) do not produce a rotating field.
  These harmonics circulate between the phase and
  neutral or ground. These third order or zero
  sequence harmonics, unlike positive and negative
  sequence harmonic currents, do not cancel but add
  up arithmetically at the neutral bus.

21
EXAMPLE 1
SINUSOIDAL VOLTAGE-NONSINIMUSOIDAL CURRENT
A periodic, sinusoidal voltage of instantaneous
value
Is applied to a nonlinear load impedance. The
resulting instantaneous current is
given by
Calculate the components P, Q, D of the apparent
voltamperes and hence calculate the displacement
factor, the distortion factor and the power
factor.
Solution
The presence of the nonlinearity causes frequency
components of current (i.e. the
second and third harmonic terms) that are not
present in the applied voltage.
The rms voltage and current at the supply are
22
The apparent voltamperes at the input is
therefore given by
In this example only the fundamental frequency
components are common to both voltage and
current. Therefore, the real power P and the
apparent power Q are
displacement angle between the fundamental of
the voltage and the fundamental of the current
23

Displacement factor
Distortion factor
Therefore, the power factor is
24
EXAMPLE 2
NONSINUSOIDAL VOLTAGE-RL LOAD
A periodic, sinusoidal voltage given by
is applied to a series, linear,
resistance-inductance load of resistance 4O and
fundamental frequency reactance 10O.
Calculate the degree of power factor improvement
realizable by capacitance
Compensation when
Solution. The rms terminal voltage is given
by
Therefore
25
The instantaneous load current is given by
The rms load current
is therefore given by
26
Apparent voltamperes
at the load terminals in the absence of
capacitance is
therefore
Average power
In this case is
The power factor before compensation is therefore
27
EXAMPLE 3
NONSINUSOIDAL VOLTAGE AND NONSINIMUSOIDAL CURRENT
A periodic, nonsinusoidal voltage with
instantaneous value given by
is applied to a nonlinear impedance.
The resulting current has an instantaneous value
given by
Calculate the components
of the load apparent voltamperes
and compare thee with the classical values
respectively.
Solution.
Note that the presence of the load nonlinearity
causes a frequency component of load current
(I.e. the third harmonic term) that is not
present in the supply voltage.
28
The rms voltage and current at the supply are
given by
The load apparent voltamperes
therefore has a value defined in terms
and
Instantaneous expressions of the hypothetical
currents
are given by
29
Note that current components
contain only those harmonic terms which
are common to both voltage and current. These are
therefore consistent with the
terms.
The rms load current components
are found, as expected to sum
to the total rms load current
Components
of the apparent voltamperes can now be obtained
30
The component voltamperes are seen to sum to the
total apparent voltamperes
Components
of
are found as follows
31
From the possible compensation viewpoint it is
interesting to note that
and
differ by significant amount.
could be defined as that component of the load
apparent voltamperes that
Is obtained by the combination of supply voltage
harmonics with quadrature
Components of corresponding frequency load
current harmonics.
32
Similarly the definition of active voltamperes
could be given by that
component of the load apparent voltamperes that
is obtained by the combination
of supply voltage harmonics with in-phase
components of corresponding
frequency load current harmonics.
Both
and
are entirely fictitious and non-physical. The
active
voltamperes
Is not to be compares in importance with the
average power
which is a real physical property of the circuit.
Term
Is merely the
analytical complement of term
the energy-storage reactive voltamperes, is that
component
Term
of the load apparent voltamperes that can be
entirely compensated (for sinusoidal
supply voltage) or minimized (for nonsinusoidal
supply voltage) by energy-storage
methods.
33
Voltage and current profiles in a commercial
building
34
HARMONIC STANDARDS

• International Electrotechnical Commission (IEC)
  European Standards.
• - EN 61000-3-2 Harmonic Emissions standards
  were first published as IEC 55-2 1982 and applied
  only to household appliances. It was revised and
  reissued in 1987 and 1995 with the applicability
  expanded to include all equipment with input
  current 16A per phase. However, until January
  1st, 2001 a transition period is in effect for
  all equipment not covered by the standard prior
  to 1987.
• - The objective of EN 61000-3-2 (harmonics) is
  to test the equipment under the conditions that
  will produce the maximum harmonic amplitudes
  under normal operating conditions for each
  harmonic component. To establish limits for
  similar types of harmonics current distortion,
  equipment under test must be categorized in one
  of the following four classes.

35

• CLASS-A Balanced three-phase equipment and
  all other equipment
• except that stated in one
  of the remaining three classes.
• CLASS-B Portable electrical tools, which are
  hand held during normal
• operation and used for a
  short time only (few minutes)
• CLASS-C Lighting equipment including dimming
  devices.
• CLASS-D Equipment having an input current
  with special wave shape
• ( e.g.equipment with
  off-line capacitor-rectifier AC input
• circuitry and switch Mode
  power Supplies) and an active
• input power 600W.
• - Additional harmonic current testing,
  measurement techniques and instrumentation
  guidelines for these standards are covered in IEC
  1000-4-7.

36

• IEEE 519-1992 United States Standards on
  harmonic limits
• IEEE limits service entrance harmonics.
• The IEEE standard 519-1992 limits the level of
  harmonics at the customer service entrance or
  Point of Common Coupling (PCC).
• With this approach the costumers current
  distortion is limited based on relative size of
  the load and the power suppliers voltage
  distortion based on the voltage level.
• IEEE 519 and IEC 1000-3-2 apply different
  philosophies, which effectively limit harmonics
  at different locations. IEEE 519 limits harmonics
  primarily at the service entrance while IEC
  1000-3-2 is applied at the terminals of end-user
  equipment. Therefore, IEC limits will tend to
  reduce harmonic-related losses in an industrial
  plant wiring, while IEEE harmonic limits are
  designed to prevent interactions between
  neighbors and the power system.

37
POWER QUALITY STANDARDS IEEE 519-1992
STANDARDS
TABLE I CURRENT DISTORTION LIMITS FOR GENERAL
DISTRIBUTION SYSTEMS (120-69000 V)
38
TABLE II LOW VOLTAGE SYSTEM CLASSIFICATION AND
DISTORTION LIMITS IEEE 519-1992 STANDARTS
39
TABLE III LIMITS OF THD IEEE 519-1992 STANDARDS
40
TABLE IVPROPOSED IEC 555-2 CLASS D STANDARDS for
power from 50 to 600W
41
METHODOLOGY FOR COMPUTING DISTORTION

• Step 1 Compute the individual current harmonic
  distortion at each dedicated bus using different
  Software programs (i.e. SIMULINK, SPICE, e.t.c.)
  or tables that provide the current distortion of
  nonlinear loads.
• Step 2 Compute the voltage and current
  harmonic content at the Point of Common Coupling
  (PCC) which is located at the input of the
  industrial power system.
• - Each individual harmonic current
  at the PCC is the sum of harmonic current
  contribution from each dedicated bus.
• - The load current at PCC is the
  sum of the load current contribution from each
  dedicated bus.
• - The maximum demand load current
  at PCC can be found by computing the load
  currents for each branch feeder and multiply by a
  demand factor to obtain feeder demand. Then the
  sum of all feeder demands is divided by a
  diversity factor to obtain the maximum demand
  load current.

42

• Step 3 Choose a base MVA and base KV for the
  system use the following equations in order to
  compute individual and total current and voltage
  harmonic distortions at PCC and any other point
  within the power system.

Ib Base current in Amps
(24)
(25)
System impedance
MVAb Base MVA, MVAsc short circuit MVA at
the point of interest
VH Percent individual harmonic voltage
distortion
(26)
43
(27)
h harmonic order
(28)
IH Percent individual harmonic distortion
Isc Short Circuit current at the point under
consideration.
IL Estimated maximum demand load current
S.C. Ratio Short circuit Ratio
(29)
MVAD Demand MVA
44
K Factor Factor useful for transformers design
and specifically from
transformers that feed
Adjustable Speed Drives
(30)
ONCE THE SHORT CIRCUIT RATIO IS KNOWN, THE IEEE
CURRENT HARMONIC LIMITS CAN BE FOUND AS SPECIFIED
IN TABLE I OF THE IEEE 519-1992 POWER QUALITY
STANDARDS
USING THE ABOVE EQUATIONS VALUES OF IDIVINDUAL
AND TOTAL VOLTAGE AND CURRENT HARMONIC DISTORTION
CAN BE COMPUTED AND COMPARED WITH THE IEEE LIMITS
45

• Step 4 If the analysis is being performed for
  CSI-type drives then the area of the voltage
  notch AN should also be computed.
• At this point an impedance diagram of the under
  analysis industrial power system should be
  available.
• The Notch Area AN at the PCC can be calculated
  as follows.

AN AN1 AN2 . V . microsec
(31)
AN1 , AN2 , are the notch areas contribution
of the different busses
(32)
ANDR1 Notch area at the input of the drive
46
Step 5 Determine preliminary filter design.
Step 6 Compute THDv and THDi magnitudes and
impedance versus frequency plots with filters
added to the system, one at a time. SIMULINK or
PSPICE software programs can be used for final
adjustments.
Step 7 Analyze results and specify final filter
design.
47
EXAMPLE OF A SYSTEM ONE LINE DIAGRAM
48
System impedances diagram which can be used to
calculate its resonance using PSPICE or SIMULINK
programs
49
TYPES OF FILTERS
1) Parallel-passive filter for current-source
nonlinear loads

• Harmonic Sinc
• Low Impedance
• Cheapest
• VA ratings VT (Load Harmonic current
  reactive current of the filter)

50
2) Series-passive filter for voltage-source
nonlinear loads

• Harmonic dam
• High-impedance
• Cheapest
• VA ratings Load current (Fundamental drop
  across filter Load Harmonic Voltage)

51
3) Basic parallel-active filter for current
source in nonlinear loads
52
4) Basic series-active filter for voltage-source
in nonlinear loads

53
5) Parallel combination of parallel active and
parallel passive
6) Series combination of series active and series
passive
54
7) Hybrid of series active and parallel passive
8) Hybrid of parallel active and series passive
55
9) Series combination of parallel-passive and
parallel-active
10) Parallel combination of series-passive and
series-active
56
11) Combined system of series-active and
parallel-active
12) Combined system of parallel-active and
series-active
57
A SIMPLE EXAMPLE OF AN INDUSTRIAL POWER
DISTRIBUTION SYSTEM
58
HARMONIC LIMITS EVALUATION WHEN
POWER-FACTOR-CORRECTION CAPASITORS ARE USED

• As it can be seen from the power distribution
  circuit the power-factor-correction capacitor
  bank, which is connected on the 480 Volts bus,
  can create a parallel resonance between the
  capacitors and the system source inductance.
• The single phase equivalent circuit of the
  distribution system is shown below.

Using the above circuit the following equations
hold
59
(33)
(34)
The turns ratio of the transformer at PCC
(35)
(36)
60
(37)
(38)
(39)
(40)
(41)
(42)
61
The impedance looking into the system
from the load, consists of the parallel
combination of source impedance
and the capacitor impedance
(43)
(44)
The equation for can be used to determine
the equivalent system impedance for different
frequencies. The harmonic producing loads can
resonate (parallel resonance), the above
equivalent circuit. Designating the parallel
resonant frequency by (rad/sec) or (HZ)
and equating the inductive and capacitive
reactances.
62

• Harmonic current components that are close to the
  parallel resonant frequency are amplified.
• Higher order harmonic currents at the PCC are
  reduced because the capacitors are low impedance
  at these frequencies.
• The figure below shows the effect of adding
  capacitors on the 480 Volts bus for power factor
  correction.

This figure shows that by adding some typical
sizes of power factor correction capacitors will
result in the magnification of the 5th and 7th
harmonic components, which in turns makes it even
more difficult to meet the IEEE 519-1992 harmonic
current standards . - Power factor correction
capacitors should not be used without turning
reactors in case the adjustable speed drives are
gt10 of the plant load.
63
EXAMPLE

• Let us examine an industrial plant with the
  following data
• Medium voltage 20KVLL
• Low voltage 0.4 KVLL
• Utility three phase short circuit power 250 MVA
• For asymmetrical current, the ratio of
  system impedance

The Transformer is rated 1000 KVA, 20 KV-400
Y/230 V Rpu 1, Xpu 7

• - The system frequency is fsys 50 HZ.
• - For power factor correction capacitors the
  following cases are examined
• 200 KVAR
• 400 KVAR
• 600 KVAR
• 800 KVAR

64

• The parallel resonant frequencies for every case
  of power factor correction is calculated as
  follows

65
Case a
For 200 KVAR, the harmonic order at which
parallel resonance occurs is
66
Case b
Case c
67
Case d
It is clear for the above system that in the 600
KVAR case, there exists a parallel resonant
frequency close to the 5th harmonic.
68
POWER FACTOR CORRECTION AND HARMONIC TREATMENT
USING TUNED FILTERS

• - Basic configuration of a tuned 3-f capacitor
  bank for power factor correction and harmonic
  treatment.

• Simple and cheap filter
• Prevents of current harmonic magnification

69

• IN ORDER TO AVOID HARMONIC MAGNIFICATION WE
  CHOOSE A TUNED FREQUENCY lt FITH HARMONIC (i.e
  4.7)
• The frequency characteristic of the tuned filter
  at 4.7 is shown below

• As it can be seen from the above figure
  significant reduction of the 5th harmonic is
  achieved. Moreover, there is some reduction for
  all the other harmonic components.

70
The single phase equivalent circuit of the power
distribution system with the tuned filter is
shown below
Using the above circuit the following equations
hold
71
(45)
Resonant frequency of the series filter
(46)
The new parallel combination is having resonant
frequency when
(parallel resonance)
resonance frequency of the equivalent
distribution circuit
(47)
Also
(48)
72
(49)
(50)
(51)
73
or 4.7 th harmonic
As it was discussed before Selecting
With KVcap 0.4 , KVARcap 600
The new parallel combination is having resonant
frequency
with
we have
(without Lf was 4.76)
74
The following table shows the variation of
Parallel resonant frequency With and without
resonant inductor
75
SIMULATED RESULTS USING MATLAB/SIMULINK
76
SIMULINK RESULTS
77
SIMULINK RESULTS
78
ACTIVE FILTERING
Parallel type
Series type
79
RESULTS OF ACTIVE FILTERING
Input current of a 6-pulse Rectifier driving a DC
machine without any input filtering
Input current with Active Filtering
80
Typical 6-pulse drive voltage waveform
Voltage source improvement with active filtering
81
SHUNT ACTIVE FILTERS

• By inserting a parallel active filter in a
  non-linear load location we can inject a harmonic
  current component with the same amplitude as that
  of the load in to the AC system.

C
Equivalent circuit
82
ADVANTAGES OF THE SHUNT OR PARALLEL ACTIVE FILTER

• Low implementation cost.
• Do not create displacement power factor problems
  and utility loading.
• Supply inductance LS, does not affect the
  harmonic compensation of parallel active filter
  system.
• Simple control circuit.
• Can damp harmonic propagation in a distribution
  feeder or between two distribution feeders.
• Easy to connect in parallel a number of active
  filter modules in order to achieve higher power
  requirements.
• Easy protection and inexpensive isolation
  switchgear.
• Easy to be installed.
• Provides immunity from ambient harmonic loads.

83
WAVEFORMS OF THE PARALLEL ACTIVE FILTER
Source voltage
Load current
Source current
A. F. output current
84
PARALLEL ACTIVE FILTER EQUATIONS
(52)
(53)
(54)
(55)
If
Then the above equations become
(56)
(57)
85
(58)
Equation (55) is the required condition for the
parallel A.F. to cancel the load harmonic
current. Only G can be predesign by the A.F.
while Zs and ZL are determined by the system.
For pure current source type of harmonic source
and consequently equations (53) and (55) become
(59)
(60)
Source impedance
Is the equivalent harmonic current source
Equivalent load impedance
equivalent transfer function of the active
filter
Equation (59) shows that the compensation
characteristics of the A.F. are not influenced by
the source impedance, Zs. This is a major
advantage of the A.F. with respect to the passive
ones.
86

• The DC bus nominal voltage, , must be
  greater than or equal to line voltage peak in
  order to actively control
• The selection of the interface inductance of the
  active filter is based on the compromise of
  keeping the output current ripple of the inverter
  low and the same time to be able to track the
  desired source current.
• The required capacitor value is dictated by the
  maximum acceptable voltage ripple. A good initial
  guess of C is

Also
peak line-neutral voltage
DC voltage of the DC bus of the inverter
Line phase current
maximum acceptable voltage ripple,
Phase current of the inverter
87
P-Q THEORY
For identifying the harmonic currents in general
the method of computing instantaneous active and
reactive power is used. Transformation of the
three-phase voltages and and
the three-phase load currents and
into a-ß orthogonal coordinate.
88
Then according to theory, the
instantaneous real power and the
instantaneous imaginary (reactive) power
are calculated.
where
DC low frequency comp. high freq. comp.
DC low frequency comp. high freq. comp.
89
The conventional active power is corresponding to
, the conventional reactive power to
and the negative sequence to the 2 f components
of and .
The commands of the three-phase compensating
currents injected by the shunt active
conditioner, , and are
given by
Instantaneous real power command
Instantaneous reactive power command
90
Substituting
Current Harmonics compensation is achieved
Current Harmonics and low frequency
variation Components of reactive power
compensation
Current Harmonics and low frequency
variation Components of active and reactive power
compensation
91
HARMONIC DETECTION METHODS

• Load current detection iAF iLh
• It is suitable for shunt active filters
  which are installed near one or more non-linear
  loads.

ii) Supply current detection iAF KS iSh
Is the most basic harmonic detection method
for series active filters acting as a voltage
source vAF.
iii) Voltage detection It is suitable
for shunt active filters which are used as
Unified Power Quality Conditioners. This type of
Active Filter is installed in primary power
distribution systems. The Unified Power Quality
Conditioner consists of a series and a shunt
active filter.
92
SHUNT ACTIVE FILTER CONTROL
a) Shunt active filter control based on voltage
detection
93
Using this technique the three-phase voltages,
which are detected at the point of installation,
are transformed to and on the dq
coordinates. Then two first order high-pass
filters of 5HZ in order to extract the ac
components and from
and . Next the ac components are applied
to the inverse dq transformation circuit, so that
the control circuit to provide the three-phase
harmonic voltages at the point of installation.
Finally, amplifying each harmonic voltage by a
gain Kv produces each phase current reference.
The active filter behaves like a resistor 1/KV
ohms to the external circuit for harmonic
frequencies without altering the fundamental
components. The current control circuit compares
the reference current with the actual current
of the active filter and amplifies the error
by a gain KI . Each phase voltage detected at the
point of installation, v is added to each
magnified error signal, thus constituting a feed
forward compensation in order to improve current
controllability. As a result, the current
controller yields three-phase voltage references.
Then, each reference voltage is compared
with a high frequency triangular waveform to
generate the gate signals for the power
semiconductor devices.
94
b) Reference current calculation scheme using
source currents (is), load currents (iL) and
voltages at the point of installation (vS).
95
3-f HYBRID ACTIVE-PASSIVE FILTER
Compensation of current harmonics and
displacement power factor can be achieved
simultaneously.
96
In the current harmonic compensation mode, the
active filter improves the filtering
characteristic of the passive filter by imposing
a voltage harmonic waveform at its terminals with
an amplitude
97
If the AC mains voltage is pure sinusoidal, then

• THDi decreases if K increases.
• The larger the voltage harmonics generated by the
  active filter a better filter compensation is
  obtained.
• A high value of the quality factor defines a
  large band width of the passive filter, improving
  the compensation characteristics of the hybrid
  topology.
• A low value of the quality factor and/or a large
  value in the tuned factor increases the required
  voltage generated by the active filter necessary
  to keep the same compensation effectiveness,
  which increases the active filter rated power.

98
Displacement power factor correction is achieved
by controlling the voltage drop across the
passive filter capacitor.
Displacement power factor control can be achieved
since at fundamental frequency the passive filter
equivalent impedance is capacitive.
99
HYBRID ACTIVE-PASSIVE FILTER
Single-phase equivalent circuit for 5th Harmonic
Single-phase equivalent circuit
100
This active filter detects the 5th harmonic
current component that flows into the passive
filter and amplifies it by a gain K in order to
determine its voltage reference which is given by
As a result, the active filter acts as a pure
resistor of K ohms for the 5th harmonic voltage
and current. The impedance of the hybrid filter
at the 5th harmonic frequency, Z5 is given by
The active filter presents a negative resistance
to the external Circuit, thus improving the Q of
the filter.
101
CONTROL CIRCUIT
The control circuit consists of two parts a
circuit for extracting the 5th current harmonic
component from the passive filter iF and a
circuit that adjusts automatically the gain K.
The reference voltage for the active filter
HARMONIC-EXTRACTING CIRCUIT
The extracting circuit detects the three-phase
currents that flow into the passive filter using
the AC current transformers and then the a-ß
coordinates are transformed to those on the d-g
coordinates by using a unit vector (cos5?t,
sin5?t) with a rotating frequency of five times
as high as the line frequency.
102
SERIES ACTIVE FILTERS

• By inserting a series Active Filter
  between the AC source and the load where the
  harmonic source is existing we can force the
  source current to become sinusoidal. The
  technique is based on a principle of harmonic
  isolation by controlling the output voltage of
  the series active filter.

Equivalent Circuit
103
- The series active filter exhibits high
impedance to harmonic current and consequently
blocks harmonic current flow from the load to the
source.
(61)
(62)
Equivalent transfer function of the detection
circuit of harmonic current, including delay time
of the control circuit.
(63)
104
A gain in pu ohms
The voltage distortion of the input AC source
is much smaller than the current distortion.
If
and
(64)
Then
(65)
(66)
105
HYBRID SERIES AND SHUNT ACTIVE FILTER

• At the Point of Common Coupling provides
• Harmonic current isolation between the sub
  transmission and the distribution system (shunt
  A.F)
• Voltage regulation (series A.F)
• Voltage flicker/imbalance compensation (series
  A.F)

106
SELECTION OF AF S FOR SPECIFIC APPLICATION
CONSIDERATIONSAF Configuration with higher
number of is more preferred
107
CONCLUSIONS

• Solid State Power Control results in harmonic
  pollution above the tolerable limits.
• Harmonic Pollution increases industrial plant
  downtimes and power losses.
• Harmonic measurements should be made in
  industrial power systems in order (a) aid in the
  design of capacitor or filter banks, (b) verify
  the design and installation of capacitor or
  filter banks, (c) verify compliance with utility
  harmonic distortion requirements, and (d)
  investigate suspected harmonic problems.
• Computer software programs such as PSPICE and
  SIMULINK can be used in order to obtain the
  harmonic behavior of an industrial power plant.
• The series LC passive filter with resonance
  frequency at 4.7 is the most popular filter.
• The disadvantages of the the tuned LC filter is
  its dynamic response because it cannot predict
  the load requirements.
• The most popular Active Filter is the parallel or
  shunt type.
• Active Filter technology is slowly used in
  industrial plants with passive filters as a
  hybrid filter. These filters can be used locally
  at the inputs of different nonlinear loads.
• Active Filter Technology is well developed and
  many manufactures are fabricating Active filters
  with large capacities.
• A large number of Active Filters configurations
  are available to compensate harmonic current,
  reactive power, neutral current, unbalance
  current, and harmonics.
• The active filters can predict the load
  requirements and consequently they exhibit very
  good dynamic response.
• LC tuned filters can be used at PCC and the same
  time active filters can be used locally at the
  input of nonlinear loads.

108
REFERENCES

• RECOMMENDED PRACTICES ON HARMONIC TREATMENT
• 1 IEEE Std. 519-1992, ??IEEE Recommended
  Practices and Requirements for Harmonic Control
  in Electric Power Systems??, 1993.
• 2 IEC Sub-Committee 77B report,
  ??Compatibility Levels in Industrial Plants for
  Low Frequency Conducted Disturbances??, 1990.
• 3 IEC Sub-Committee 77A report, ??Disturbances
  Caused by Equipment Connected to the Public
  Low-Voltage Supply System Part 2 Harmonics ??,
  1990 (Revised Draft of IEC 555-2).
• 4 UK Engineering Recommendation G.5/3
  ??Limits for Harmonics in the UK Electricity
  Supply System??, 1976.
• 5 CIRGE WG 36.05 Report, ??Equipment producing
  harmonics and Conditions Governing their
  Connection to the Mains power Supply??, Electra,
  No. 123, March 1989, pp. 20-37.
• 6 Australian Standards AS-2279.1-1991,
  ??Disturbances in mains Supply Networks-Part 2
  Limitation of Harmonics Caused by Industrial
  Equipment??, 1991.

109

• DEFINITIONS
• 7 J. Arriilaga, D.A. Bradley, and P.S. Bodger,
  ??Power System Harmonics??,New York Wiley, 1985.
• 8 N. Shepherd and P. Zand, ??Energy flow and
  power factor in nonsinusoidal circuits??,
  Cambridge University Press, 1979.
• EFFECTS OF HARMONICS
• 9 J.M. Bowyer, ??Three-Part Harmony System
  Interactions Leading to a Divergent Resonant
  System??, IEEE Trans. on Industry Applications,
  Vol. 31, No. 6, Nov/Dec 1995, pp. 1341-1349.
• 10 R.D. Hondenson and P.J. Rose, ??Harmonics
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• 11 J.S. Subjak and J. S. McQuilkin,
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• 12 P.Y. Keskar, ??Specification of Variable
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110

• 13 T.S. Key, ??Cost and Benefits of Harmonic
  Current Reduction for Switch-Mode Power Supplies
  in a Commercial Building??, IEEE Trans. on
  Industry Applications, Vol. 32, No. 5,
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• PASSIVE HARMONIC TREATMENT TECHNIQUES
• 14 M.F. McGranaghan and D.R. Mueller,
  ??Designing Harmonic Filters for Adjustable-Speed
  Drives to comply with IEEE-519 Harmonic limits??,
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  2, March/April 1999, pp. 312-18.
• 15 F.Z. Peng, ??Harmonic Sources and filtering
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  Magazine, July/August 2001, pp. 18-25.
• 16 J.K. Phipps, ??A transfer Function Approach
  to Harmonic Filter Design??, IEEE Industry
  Applications Magazine March/April 1997.
• 17 S.M. Peeran, ??Application, Design, and
  Specification of Harmonic Filters for Variable
  frequency Drives??, IEEE Trans. on Industry
  Applications, Vol. 31, No. 4, July/August 1995,
  pp. 841-847.

111

• 18 J. Lai and T.S. Key, ??Effectiveness of
  Harmonic Mitigation Equipment for Commercial
  Office Buildings??, IEEE Trans. on Industry
  Applications, Vol. 33, No. 4, July/August 1997,
  pp. 1104-1110.
• 19 D.E. Rice,??A Detailed Analysis of
  Six-Pulse Converter harmonic Currents??, IEEE
  Trans. on Industry Applications, Vol. 30, No. 2,
  March/April 1994, pp. 294-304.
• 20 R.L. Almonte and Ashley, ??Harmonics at the
  Utility Industrial Interface A Real World
  Example??, IEEE Trans. on Industry Applications,
  Vol. 31, No. 6, November/December 1995, pp.
  1419-1426.
• 21 K. A. Puskarich, W.E. Reid and P. S. Hamer,
  ??Harmonic Experiments with a large
  load-Commutated inverter drive??, IEEE Trans. on
  Industry Applications, Vol. 37, No. 1, Jan/Feb.
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• 22 L.S. Czarnecki and O. T. Tan, ??Evaluation
  and Reduction of Harmonic Distortion Caused by
  Solid State Voltage Controller of Induction
  Motors??, IEEE Trans. on Energy Conversion, Vol.
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112

• 23 R.G. Ellis, ??Harmonic Analysis of
  Industrial power Systems??, IEEE Trans. on
  Industry Applications, Vol. 32, No. 2,
  March/April 1996, pp. 417-421.
• 24 D. Adrews et al, ?? Harmonic Measurements,
  Analysis and Power factor Correction in a Modern
  Steel Manufacturing Facility??, IEEE Trans. on
  Industry Applications, Vol. 32, No. 3, May/June
  196, pp. 617-624.
• 25 D. Shipp and W. S. Vilcheck, ??Power Quality
  and Line Considerations for Variable Speed AC
  Drivers??, IEEE Trans. on Industry Applications,
  Vol.32, No.2, March/April 1996, pp. 403-410.
• 26 J. A Bonner et al, ??Selecting ratings for
  Capacitors and Reactors In Applications Involving
  Multiple Single-Tuned Filters??, IEEE Trans. on
  Power Delivery, Vol. 10, No. 1, Jan. 1995, pp.
  547-555.
• 27 E. J. Currence, J.E Plizga, and H. N.
  Nelson, ??Harmonic Resonance at a medium-sized
  Industrial Plant??, IEEE Trans. on Industry
  Applications, Vol. 31, No. 4, July/August 1995,
  pp. 682-690.

113

• 28 G. Lemieux, ??Power system harmonic
  resonance. A document case??, IEEE Trans. on
  Industry Applications, Vol. 26, No. 3, pp.
  483-487, May/June 1990.
• 29 D. D. Shipp, ??Harmonic Analysis and
  Suppression for electrical systems??, ?EEE Trans.
  on Industry Applications Vol. 15, No. 5,
  Sept./Oct. 1979.
• ACTIVE HARMONIC TREATMENT TECHNIQUES
• 30 H. Akagi, ??New trends in active filters for
  Power conditioning??, IEEE Trans. on Industry
  Applications, Vol. 32, Nov/Dec. 1996, pp.
  1312-1322.
• 31 Bhim Singh et al, ??A Review of Active
  Filters for Power Quality Improvement??, IEEE
  Trans. on Industrial Electronics, Vol. 46, No. 5,
  Oct. 1999, pp. 960-971.
• 32 F. Z. Peng, ??Application Issues of Active
  Power Filters??, IEEE Industry Applications
  Magazine, Sep./Oct. 1998, pp. 22-30.
• 33 S. Bhattacharga et al, ??Active Filter
  Systems Implementation??, IEEE Industry
  Applications Magazine, Sep./Oct. 1998, pp. 47-63.

114
34 S. Bhattacharya et al, ??Hybrid Solutions
for improving Passive Filter Performance in high
power Applications??, IEEE, Trans. on Industry
Applications, Vol. 33, No. 3, May/June 1997, pp.
732-747. 35 H. Akagi, ??Control Strategy and
site selection of a shunt active filter for
damping of harmonies propagation in power
distribution systems ??, IEEE Trans. on Power
Delivery, Vol. 12, Jan. 1997, pp.354-363. 36
H. Fujita, T. Yamasaki, and H. Akagi, ??A Hybrid
Active Filter for Damping of Harmonic Resonance
in Industrial Power Systems??, IEEE Trans. on
Power Electronics, Vol. 15, No. 2, March 2000,
pp. 215-222. 37 H. Akagi et al, ?? ? shunt
Active Filter Based on Voltage Detection for
Harmonic Termination of a Radial power
Distribution Line??, IEEE Trans. on Industry
Applications, Vol. 35, No. 3, May/June 1999, pp.
638-645. 38 D. Rivas et al, ?? A simple
control scheme for hybrid Active Power Filter??,
IEE PESC-00, pp. 991-996.
115

• 39 L. Zhou and Zi Li, ??A Novel Active Power
  filter Based on the Least compensation Current
  Control Method??, IEEE Trans. on Power
  Electronics, Vol. 15, No. 4, July 2000, pp.
  655-659.
• MODELING
• 40 IEEE Task Force on Modeling and Simulation,
  ??Modeling and Simulation of the propagation of
  harmonies in electric power networks, Part I
  Concepts, models, and simulation techniques??,
  IEEE Trans. on Power Delivery, Vol. 11, No. 1,
  Jan. 1996, pp. 452-465.
• 41 IEEE Task Force on Modeling and Simulation
  ??Modeling and Simulation of the propagation of
  harmonies in electric power networks, Part II
  Sample systems and examples??, IEEE Trans. on
  Power Delivery, Vol. 11, No. 1, Jan. 1996, pp.
  466-474.
• 42 W. Jewel et al, ??Filtering Dispersed
  harmonic Sources on Distribution??, IEEE Trans.
  on Power Delivery, Vol. 15, No. 3, July 2000, pp.
  1045-1051.
• 43 N.K. Madora and A. Kusko, ??Computer-Aided
  Design and Analysis of Power-Harmonic Filters??
  IEEE Trans. on Industry Applications, Vol. 36,
  No. 2, March/April 2000, pp.604-613.