The document discusses power quality issues caused by harmonics from non-linear loads. It provides background on the increasing use of non-linear loads and effects of harmonics. Specific sources of harmonics are outlined along with their impact on power quality including overheating, failures, and interference. Mitigation techniques are reviewed such as passive and active filtering. Active power filters are highlighted as an effective solution, with shunt active power filters discussed in detail for compensating harmonic currents and reactive power. The document concludes that active power filtering is still developing and more research is needed on techniques like controls and artificial intelligence to further improve power quality.

1. Engr. Rifat Ara
Submitted to:
Esteemed Dr. Umer Aamir Khan
CUST

2.  Various power quality problems.
 Reasons
 HARMONICS
 THD
 Single load Spectra
 Various sources of Harmonics
 Effects of harmonics on Power quality
 Mitigation techniques
 SAPF
 Conclusion
 Reference’s

3. Power quality faces severe challenges due to Electrical Noises as:
 Harmonic pollution
 Impulses
 Transients
 Excessive Neutral currents
 Interruptions
 Wiring and earthing problems
 Sags or surges.

4. It has been seen that up to 1980‟s the loads were of linear type.
 In the modern IT world extensive use of non-linear power electronic or
solid state devices as non-linear loads like diodes. power Transistors
SCR’S Microprocessor Controls etc.
 Generation and grid connection technology through power electronic-
interfaces.
 Use of diverse industrial Electronic Devices and Home Appliances.
 Use of Renewable Power Integration.
 Demands for highly efficient consumption.
 Coupling of variety of energy inputs.
 Varied Energy Conversion Technologies with inter-coupling of chemical
energy thermodynamics, electrodynamics ,etc.
 Increasing emphasis on power system efficiency, maximum utilization.
Are the main reasons of power quality pollution.

5. Severe distortion of sinusoidal waveform i,e Choppy, non –linear or non –
sinusoidal current drawn by Electronic loads actually a Fundamental frequency
component plus many integer multiples of this fundamental Frequency. These
integer multiples are just higher order frequency components.
Two Phenomena are:
CURRENT DISTORTION
VOLTAGE DISTORTION
Current distortion produces voltage distortion .when these harmonic currents flow
across the network Impedance they create a voltage drop at the same frequency
as the harmonic current.

9.  RECTIFIERS
 INVERTERS
 CHOPPERS
 UPS,SMPS,
 FLUORESCE-NTLIGHTS(CFL)
 STATIC-VAR-COMPENSATORS
 VARIABLE FREQUENCY-MOTORDRIVES(VFD)
 POWER TRANSFORMER,BALLASTINDUCTOR
 CYDOCONVERTERS
 TELEVISION SETS,
 PC’S,SYNCHRONOUS MACHINES
 INDUCTION MACHINES,WASHING ELECTRIC ARC FURNACES
 MOTOR-SOFT-START-UNITS,PULSE-BURST-HEATING
 SOLDERING EQUIPMENT,MERCURY VAPOR OR HIGH PRESSURE SODIUM LAMPS,
 BATTERYCHARGERS
 REFRIGERATORS,FREEZERS,
 MACHINES,AC’S,FAX MACHINES
 PRINTERS,HVDC-SYSTEMS

11.  SMPS generate high third harmonic ,primarily responsible for neutral currents
 Three phase loads like rectifiers/chargers, Bridges,
Controlled Bridges in Drives UPS generate
High order harmonic currents of 5,7,11,13

Voltage –source non-linear load
Diode rectifier for ac drives electronic equipment etc.
 Current distorted waveform of three phase variable
Variable speed drives ,lifts with harmonic spectrum.
 Current distorted waveform of single phase loads
Computers, phones,lighting.

12. 6-pulse rectifier with output voltage filtering 3% reactor filter
THD 40%(5,7,11,..)
6-pulse rectifier with large output inductor and
THD is 28% (5,7,11)
12-pulse rectifier with THD% of 15%
(11,13,..)

13. Lowering of Power factor leading to penalties on monthly bills ,increase in Electrical Losses, Over
heating of conductors due to increased copper loss, increased skin effect ,increased proximity effect
caused by magnetic field of harmonic currents.
In all type of harmonics the tripled harmonics are more severe, examples of triplet harmonics are 3rd
9th 15th These harmonics produce bigger problems to engineers because they produce more
distortion in voltage. The effect of triplex harmonics comes with overheating in wires, weaken
insulation in cables, windings and capacitors. overheating in transformer units also may become the
cause of end user equipment failure. Among all types of nonlinear loads which affect the system most
are power converters. Uninterrupted power system (UPS), various types of electric furnaces etc.
EFFECTS OF CURRENT HARMONICS
 Neutral Conductor Overloading ,Over-stressing of power factor correction capacitors.
 Increased Eddy current losses due to increased harmonic order resulting in over -heating,
reduced life of Transformers ,Premature Equipment failure, increased faults ultimately
increasing systems capital and maintenance cost. Due to 3rd harmonics issue that circulate in
Delta winding causing over heating due to Eddy current losses
 Tripping of circuit breakers .Tripping is 3rd harmonic phenomenon in circuit breakers which may
have reasons like high current flow in the circuit due to higher order harmonics .Peak sensing
breakers may trip needlessly due to high crest factor of distorted wave –form.
 Neutral earth potential.
 Heat loss on rotating machines due to increased resistance with the high frequency. EMI in
motor windings .Motor/generator failures. Crest factors etc. Lighting Ballast failures ,PC-monitor-
Stroboscope-effect ,Overheating and resonance with capacitors. Improper operation of
microprocessor based Equipment. Re-injectio n of harmonic currents into the utility networks.

14.  Capacitor dielectric failure , dielectric stress hence destructive damage
 Torque pulsation in Motors (due to negative rotation of 5th ad 11th harmonic)
 Insulation Breakdown.
 PC monitor and power supply failure.
 Electronic Lighting failure.
 Causes linear devices to draw non-linear currents leading to current
distortion effects.
Various other effects of harmonic pollution are:
Reduction in life of incandescent lamps due to distorted power supply
Communication interference or failure experienced by computers, telephones,
radio /TV Tx /RX ,Process problems, metering errors leading to higher billing
to consumers ,Drives/Power Supplies can be affected by mis-operation due to
multiple zero crossings. Harmonics can cause failure of the commutation
circuits, found in DC drives and AC drives with silicon controlled rectifiers
(SCRs)

15.  Various Techniques to mitigate harmonics so far are:
 Isolation of harmonic loads
 Conductor spacing and sizing. Over –sizing of cables ,sources
 Non-linear transformers. Transformers with different couplings limits 3rd harmonic and its
multiples.(3rd,9th,and so on)
 K –rated Transformers
 Non-Linear Panel Boards
 Prevention or Blocking of Harmonics by using Isolation transformers ,Line-Reactors etc
Anti-harm reactors and series filters decrease Total harmonic distortion.
 Filtering like passive Filtering( De –tuned Capacitor and reactor combination can be tuned
for low impedance path to certain frequencies i.e. ,tuned filters attenuate harmonics at the
tuning frequency.
 More pulse bridge rectifiers.
 Artificial intelligence

16. Active Filtering: The main purpose of Active filtering is phase shifting.
Active power filter (APF) First developed by Japanese Akagi is
combination of an Inverter and capacitor, uses active devices Op-amp or
Transistors with passive components is one of the best compensators
that have shown good ability in harmonic elimination .Since passive filter
has draw backs of resonance, not suitable for higher order harmonics as
its performance is limited to a few harmonics. APF offers number of
advantages over passive filter like no harmful resonance, can suppress
supply current harmonics as well as reactive currents and voltage sags.
Depending upon the connection of passive components the APF can be
classified as Series APF, Shunt APF ,Hybrid APF

17.  Series APF: Connected in series with Transmission line and acts as
controlled voltage source. used to compensate harmonics in supply voltage.
 Shunt APF: Connected in parallel with T.L and acts as a controlled current
source used to compensate harmonics in the supply current.
 Unified Power Quality Controller: Combination of Passive, Series and Shunt
Active Filters.

18. ( )
POWER SOURCE
NON-LINEAR LOAD SOURCE OF HARMONICS
APF(SUPPLIES REQUIRED HARMONICS
TO THE LOAD) .THE CTS OF APF ANALYZE THE HARMONICS REQUIRED BY
THE LOAD.

19. Load current has fundamental and harmonic components both and filter current If is the
harmonic compensating current such that:
IL=Is + If or IL+Ih = Is+Ih. Or IL= Is .Hence supply current represents the fundamental
waveform input output harmonics

20.  simple control circuit and more sharp frequency response.
 Implementation cost is low.
 Do not create displacement power factor problems and utility
loading.
 Supply inductance LS, does not affect the harmonic compensation
of parallel active filter system.
 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.

21. Composite waveform
+ 180 degrees phase
Shifted harmonics.
=Fundamental-frequency

22.  Design of Shunt Active Power Filter for Improvement of Power Quality with Artificial
Intelligence Techniques.
In this Simulation an analysis and comparison of THD of the source current with
different types of controllers is performed. Here THD of source current with
conventional PI controller is compared with the artificial neural network (ANN) based
PI and Particle Swarm Optimization (PSO) based PI. Hysteresis Band Current
Controller (HBCC) is used to generate the gate pulses of the VSI of the filter
Simulations are carried out in MATLAB/SIMULINK environment using sim power
system toolbox .Here real and reactive power (P-Q) theory is used to generate
reference currents to control SAPF which is used to compensate reactive power and
harmonic currents with different types of controllers. At this level, comparative studies
between the conventional PI controller, ANN based PI controller and Particle Swarm
Optimization (PSO) based PI showed that Particle Swarm Optimization has been
proved to be better in terms of harmonic reduction in source current and
compensating the reactive power. The dc bus voltage has been maintained constant
equal to the reference voltage by all PI,ANN based PI and PSO based PI. It has been
found that these robust and nonlinear controllers prove to be better than conventional
controllers.
 Design parameters are listed in the table

28. So far multiple compensation techniques have been operated co-orperatively
used for ensuring a friendly power quality .Many advanced control signal
processing techniques have been applied like Mode Control ,Fuzzy Logic
Control ,NN-theories, Adaptive signal processing etc. but still the progress is in
infancy stage.
 The PWM converter acts additionally as an active power filter for power
factor correction but drawback is it does not talk about THD[18]
 Shuffled Frog Leaping Algorithm was used to calculate switching angles
for eleven level inverter. Optimal solution for the selective harmonic
elimination problem was obtained at low modulation indices. The advantage
of meta-heuristic SFLA includes fewer control parameters, great capability
in global search and easy implementation. The disadvantage is that it is an
offline method and separate lookup table is required[15}
 Composite observer Method was used to reduce voltage harmonics in
single phase inverter ,though this method reduces THD but it can not
reduce selective harmonics[16]
 Single tuned passive harmonic filters were used to reduce voltage distortion
but this method fails due to resonance issue and insufficient capacitor
buses[5]

29.  Notch-Filter Inserted Current Reference plus Load Current Feed-Forward Scheme
(NF CR+LCFFS) was proposed to reduce Second Harmonic Current and improve the
dynamic response of two stage single phase inverter The method gives superior
dynamic performance under transient conditions and effectively reduces the second
order harmonics. The drawback of this method is that it fails to reduce harmonics
other than second order and THD parameter was not discussed[6].
 For selective harmonic elimination in multilevel converters with unbalanced dc
voltage source Optimum Pulse Width Modulation is used. The advantage of this
method is that solving higher order non-linear equations are not necessary, so
advanced algorithms are not required. In other methods, the number of equation
grows non-linearly with switching angles whereas here number of equations
increases linearly. The disadvantage is that it uses lookup table to calculate switching
angles.[7]
 Fuzzy logic method was used to reduce harmonics in current source converter, the
advantage is reduction of lower order harmonics and distortion factor to great extent
but is not suitable for higher order harmonic reduction and lookup tables are used [8]
 Real-time implementation of Selective Harmonic Pulse Width Modulation in single
phase inverter using Generalized Hopfield Neural Network was designed. The
method eliminates 5th, 7th, 11thand 13thorder harmonics while retaining the
fundamental component. The method was simulated using MATLAB and hardware
implementation is done using ARM processor MOSFET acted as a switching device.
On-line calculation of switching angle was done.[9]

30.  For reduction of Harmonics in Inverters Walsh waveform analytic technique
used linear algebra equations to get optimized switching angles using
straight -line curve fitting method. This method applies for both unipolar as
well as bipolar switching and the advantage is that there is on-line
calculation of switching angles without using lookup tables.[10]
 The homotopy method effectively reduces the lower order harmonics but it
did not give any information about total harmonic distortion[11]
 Using radail -basis function neutral network method harmonics are
eliminated in 7-level diode clamped inverter. Using modulation index of .78
.Simulation was done using SIMULINK of MATLAB .Accuracy, real time
control with quick determination of switching angles are the key features of
this method but the drawback is that it eliminated lower order harmonics
only in specific modulation region.[12]
 BFA (Bacterial Foraging Algorithm ) was for better than Genetic Algorithm
in terms of running time. This method was used for harmonic elimination of
stepped voltage of a 13- level Inverter. This method significantly eliminates
lower order harmonics.{13]

31.  Particle Swarm Optimization (PSO) algorithm has been utilized to
selectively eliminate harmonics of 11-level H-bridge inverter with unequal dc
source volt-ages. The method eliminates the specific harmonics with lower
total harmonic distortion. This method solves the asymmetry of the
transcendental equations. In hardware implementation FPGA produced
gating signals for the MOSFET switching device. The probability of optimal
finding of the switching angles decreases with increase in the number of
switching which can be due to increase in the harmonic order[14]

32.  Active power filters are emerging devices and new technology and can perform the
job of harmonic elimination properly . Passive filters have the drawbacks of fixed
compensation, resonance problem of L-C filters and are bulky. In active filters first
using transducers the harmonic disturbances are detected from the power line and
then harmonic waveform is separated from the fundamental sine wave using
reference signal estimation technique. 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. Most
popular active filter is shunt type for improving power quality and reactive power
compensation. But still APF is in its infancy stage there is still a need for further
research and development to make this technology well established.
 There is need of understanding the Power dynamics Load modeling Techniques
using a mathematical model including differential equations with controls. Techniques
required for linearization of non-linear devices .A Dynamic device or passive element
is required that can be compared to the dynamic nature of electrical energy ,
 Techniques to save electrical Energy and to smartly deliver discrete Electrical power
as per consumers requirements and Demand need to be established.
 Use of Artificial intelligence and controls in filters needs vast research further.

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36. THANK YOU
ANY QUESTION ?