Chapter 5
Power Quality Improvement by using Power Active Filters
86
CHAPTER 5
POWER QUALITY IMPROVEMENT BY USING POWER ACTIVE
FILTERS
5.1 POWER QUALITY IMPROVEMENT
This chapter deals with the harmonic elimination in Power System by adopting various methods.
Due to the development of Power Electronics technology, more Power Electronics appliances
are used, which leads the serious harmonics pollutions. Using Shunt Active Filters we can
eliminate these kinds of harmonics. The development of new Shunt Active Filter is presented.
The concept of proposed Shunt Active Filter and its operating Principle, Control Theory is also
discussed. The filtering scheme provides harmonics suppression at the source so that the source
will supply high quality power to linear load. The „Power Quality‟ has become the „buzzword‟
in the last one decade due to increase in quality-sensitive load, like computers, non-linear
switched devices, which are the sources of disturbance to create poor power quality
&
awareness of implications of power quality.
5.2 INTRODUCTION
Quality means customer satisfaction, which cannot be defined absolutely. It is defined with
reference to consumer expectations. The quality of a product is thus measured by using yardstick
of consumer satisfaction. Electric power quality is satisfaction of its customer; a consumer is
satisfied if he is able to use power through his equipment and devices to serve his purpose. This
is possible only if his equipment and devices have Electromagnetic Compatibility (EMC) with
the supply quality; Thus, EMC is the measure of power quality. The SIMULINK/MATLAB is a
highly developed graphical user interface simulation tool. It has proved instrumental in
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Chapter 5
Power Quality Improvement by using Power Active Filters
87
implementing the graphical based controller. The Simulation tool has been used to perform the
modeling and simulation of the customer power controller for a wide range of operating
conditions. The Simulation results of the proposed filter are discussed.
The objective of this chapter develops the proposed new shunt active power filter for the
current harmonics suppression using SIMULINK / MATALAB for power quality
improvement.[42]
5.3 FILTERS
Filters are used to restrict the flow of harmonics current in the Power Systems. It is a LC
circuit, which passes all frequencies in its pass bands and stops all frequencies in its stop
bands. There are two basic types of filters. The simplest method of harmonics filtering is with
passive filters. It uses the reactive storage components, namely capacitors and inductors. It has
two types. Shunt passive filter is the Combination of L and C elements, which are connected in
parallel with the line. It will restrict the flow of harmonics through the line. Fig-5.1 shows the
configuration of Shunt passive Filter.
Non-linear load
L
supply
Non-linear
load
L
c
supply
c
Fig 5.1 Shunt passive filters
Fig 5.2 Series passive filters
Series passive filter is the combination of L & C in parallel, which are connected in series with
the supply as in Fig 5.2, which has the ability to eliminate harmonics amplification of shunt
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Chapter 5
Power Quality Improvement by using Power Active Filters
88
passive filter. The series active filter needs a much smaller kVA rating than a conventional
shunt active filter, and as a result, the combined system has good filtering characteristics and
high efficiency. This chapter presents a design of the shunt passive filter that makes possible a
great reduction in the required kVA rating of the series active filter. It can minimize the peak
voltage across the series active filter and reduce the required kVA rating of the filter to 60
percent. A computer simulation geared to practical applications of large three-phase. Thyristor
rectifiers are used to compare the compensation characteristics of the optimized system with
those of a combined system that uses a conventional shunt passive filter. Active Filters are
newly emerging devices for harmonics filtering, which will use Controllable Sources to cancel
the harmonics in the Power Systems. The basic principle of operation of an Active Filter is to
inject a suitable non-sinusoidal voltage and currents in to the system in order to achieve a clean
voltage and current waveforms at the point of filtering.
Non-linear loads
Nonlinear
loads
source
source
Active
filter
Active
filter
Fig 5.3 Shunt active filters
Fig 5.4 Series active filters
Shunt Active Filter is connected in parallel to the load. The system configuration is shown in
Fig 5.3. It consists of a Voltage Source Inverter and a filter inductor connected in series. It
performs a harmonics current suppression to the line. Where as series active filter shown in Fig
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Chapter 5
Power Quality Improvement by using Power Active Filters
89
5.4, is connected in series with the load. The major advantages of the Series Active Filter are, it
maintains the output voltage waveform as sinusoidal and balances the three-phase voltage.[43]
5.4 HARMONICS MEASUREMENT
5.4.1 Importance of monitoring PQ
In a case study where the end-user equipment knocked off-line 30 times in 9 months but there
were only five operations on the utility substation breaker. There were so many events, which
will result in end-user problems that never show up in the utility statistics. One example is
capacitor switching, which is quite common and normal on the utility system, but can cause
transient over-voltage that disrupt manufacturing of machinery. Another is a momentary fault
any where in the system that causes voltage to sag briefly at the location of the customer,
which might cause an adjustable-speed drive or a distributed generator to trip off, but the utility
will have no indication that anything will miss on the feeder unless it has power quality
monitor installed.
5.4.2 Harmonics study
If a case study is conducted with two transformers, in which first transformer is supplying nonlinear load and there are 4 feeders on this transformer, whose rating is 2MVA which were
supplying the non-linear loads. The harmonics distortion can be observed from Fig 5.5.
Fig 5.5 Current Harmonics
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Chapter 5
Power Quality Improvement by using Power Active Filters
Current
Time
Fig 5.6 Current waveform
Table 5.1 Current Harmonic
Amp
A
B
C
N
THD%f
15.2
16.0
13.2
20.6
H3%f
0.8
1.4
0.7
5.0
H5%f
14.5
15.1
12.6
4.6
H7%f
14.1
4.8
3.5
4.3
H9%f
0.8
0.4
0.5
17.8
H11%f
0.6
0.9
0.8
2.9
H13%f
0.9
0.9
0.9
2.7
H15%f
0.1
0.1
0.1
1.9
Harmonics
Voltage ↑
Time →
Fig 5.7 Voltage waveform
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90
Chapter 5
Power Quality Improvement by using Power Active Filters
Voltage
↑
Harmonics
Time →
Fig 5.8 Voltage Harmonics
Table 5.2 Voltage Harmonic
Volt
A
B
C
N
THD%f
4.1
4.4
4.2
67.6
H3%f
0.2
0.2
0.2
6.0
H5%f
4.0
4.2
4.0
59.5
H7%f
0.8
0.9
0.8
20.0
H9%f
0.3
0.2
0.3
21.6
H11%f
0.3
0.3
0.2
8.2
H13%f
0.2
0.3
0.3
4.4
H15%f
0.1
0.0
0.1
1.3
Harmonics
Table 5.3 Power & Energy
P/V/I/pf
kW
kVA
kVAr
pf
A
0.53
0.55
0.15
0.96
B
0.43
0.45
0.13
0.96
C
0.56
0.58
0.15
0.97
Irms
Vrms
2.2
244.1
1.9
243.9
2.4
243.9
Total
1.52
1.58
0.43
0.96
(least)
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Chapter 5
Power Quality Improvement by using Power Active Filters
92
It can be observed from the above waveforms and tables that the transformer contains current
harmonics of around 16% and voltage harmonics of 4%. Major harmonics in Current
waveform are 5th and 7th harmonics. Hence it is strongly recommended to mitigate the 5th and
7th harmonics in current waveform.
5.4.3 Power Quality Evaluation
Transform rating: 2 MVA
Electrical System = 415V,50 Hz, 3 Ph 3 Wires (With capacitor bank switched ON)
Apparent Power, S = 860.23 kVA
Real Power,
P = 700 kW
Reactive Power, Q = 500 kVAR
Power Factor, pf = 0.97(lagging)
(5.1)
Source Voltage, V
(Phase-A), VA = 243 Vrms THDVfund, A = 4.1%
(Phase-B), VB = 243 Vrms THDVfund, B = 4.4%
(Phase-C), VC = 243 Vrms THDVfund, C = 4.2%
(5.2)
Load Current, IL
(Phase-A), IL, A = 1500 A
THDIfund, A = 15.2%
(Phase-B), IL, B = 1260 A
THDIfund, B = 16.0%
(Phase-C), IL, C = 1560 A
THDIfund, C = 13.2%
(Neutral), IL, N = 120 A
THDIfund, N = 20.6%
Power & Current are calculated by using CT Ratio 400:1
The total harmonic current for each phase is calculated as follows
IH = THDIfund × (iL÷
(1+THDIfund2))
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Chapter 5
Power Quality Improvement by using Power Active Filters
IH, A = 0.152 × (1500÷
(1+0.1522)) =
IH, B = 0.160 × (1260÷
(1+0.162))
IH, C = 0.132 × (1560÷
(1+0.1322)) =
204.14A
IH, N = 0.206 × (120÷
(1+0.2062)) =
242.10 A
=
93
225.41A
199.06A
(5.4)
Hence from the above calculation it is observed that the transformer contains a harmonics
current of 200A per phase. Hence it is strongly recommended to reduce harmonics currents.
THD results are obtained by FFT test.
5.5 HARMONIC ANALYSIS
The case study conducted on 3 transformers in which one of them is of 1.5MVA, which drives
a load of 50 kW with variable frequency. It is observed from Fig 5.1 that, the transformer is
supplying a highly non-linear load current of 25% THD. In which major harmonics are 5th and
7th.
5.5.1 Power Quality Evaluation
Transformer rating :(1.5MVA)
Electrical System = 415 V, 50 Hz, 3 Phase 3 Wires
Apparent Power, S = 834 kVA
Real Power, P = 815 kW
Reactive Power, Q =180 kVAr
Power Factor, p f = 0.98(lagging)
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Chapter 5
Power Quality Improvement by using Power Active Filters
94
Source Voltage, V
(Phase-A), V = 399.2 Vrms THDVfund, A = 4..5%
(Phase-B), VB = 397.5 Vrms THDVfund, B = 4.2%
(Phase-C), VC = 397.1 Vrms THDVfund, C = 4.3%
(5.6)
Load Current, IL
(Phase-A), IL, A = 1260 A THDIfund, A = 25.2%
(Phase-B), IL, B = 1260 A THDIfund, B = 24.5%
(Phase-C), IL, C = 1140 A THDIfund, C = 25.0%
(5.7)
Power & Current are calculated by using CT Ratio 600:1
The total harmonic current for each phase is calculated as follows
IH = THDIfund × (iL÷
(1+THDIfund2)
IH, A= 0.252 × (1260÷
(1+0.2522)) = 307.89A
IH, B = 0.245 × (1260÷
(1+0.2452)) = 299.83A
IH, C = 0.25 × (1140÷
(1+0.252)) = 276.49A
(5.8)
Hence from the above calculation it is observed that the transformer contains a harmonics
current of 300A per phase. Hence it is strongly recommended to reduce harmonic currents
[44].THD results are obtained by FFT test.
5.6 MECHANISM OF ACTIVE HARMONIC FILTER
A 100 Amp Active Harmonics filter may be installed in PDB2 of Plant III supplied by Tx1.
The Plant III has got 30 Ring frames, each ring frame having VFD (Variable Frequency Drive)
of 50 kW rating. 30 Ring frames have been grouped into four groups. A Power Distribution
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Chapter 5
Power Quality Improvement by using Power Active Filters
95
Board (PDB) supports each group. PDB2 supports 8 numbers of ring frames. Single line
diagram of the same installation is given below in Fig 5.9. They were facing a Problem of high
current harmonics more than 25% in PDB2. Tripping of the Circuit breaker and higher
temperature of cable and transformer (Tx1). The 100 Amp APF Units may be installed across
the load of PDB2.
VFD 8
Incomer
Ip
Vp
Source
point Is1
Is
VFD 2
VFD 1
Vs
Transformer
Tx1
IH
IL
PDB 2
PFC
Other
loads
Solid state
Harmonics filter
Fig 5.9 Single Line Diagram of Active Filter
Transformer: 4 MVA, 33 kV /440 V, /,
PFC: power factor correction capacitors (50 kVAr cap Bank)
Solid-state harmonics filter rating: 415 V, 50 Hz, 3-Ph-3 wire, 100 Amp AHF.
VFD Rating: Each VFD is of 50 kW, 440 V, 50 Hz
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Chapter 5
Power Quality Improvement by using Power Active Filters
96
Slight Distortion in current wave is, because of higher harmonics current presents in the
system than the rating of the AHF installed at the time of measurement. Due to variation in
load sometimes-Harmonics current exceeds rating of AHF & work in full correction mode
voltage waveform.
5.7 RELATIVE STUDY
 Easy Installation.
 Installation without affecting the Production.
 Time required to install the AHF is less than 45 Min.
 User Friendly control Panel.
 Maintenance can be done easily without disturbing load efforts.
 Current transformers are to be connected at load side for Current Sensing.
 R, Y, & B terminals of AHF to be connected In shunt with the Load point.
 Current THD: Before AHF Installed Current THD (I
THD)
was: 30-31% After AHF
Installed Current THD (I THD) brought down to: 5-6%.
 Voltage THD: Before AHF Installed Current THD (I
THD)
was: 6-7% After AHF Installed
Current THD (I THD) brought down to: 4-5%.
 Improved power factor (up to Unity) without power factor correction capacitors.[45]
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Chapter 5
Power Quality Improvement by using Power Active Filters
Table 5.4 Variation of Parameters
Parameter
Avg Amp
Avg kVA
Max kVA
kW
pf
kVAr
I THD
V THD
Voltage
Before AHF
After AHF
installation
installation
(Cap Bank ON) (Cap Bank OFF)
307.88
294.68
221.57
212.28
278
258
211.6
210.8
0 .955
0 .994
67.11
19.81
24.5%
6.5%
6.4%
5.3%
415.5
415.5
Table 5.5 Transformer Primary Side
Before AHF After
AHF
Parameter
Installation
Installation
ITHD
19.6
16.3%
VTHD
2.7%
2.4%
Voltage
33KV
33KV
PF at TX6
0.976
0.986
Max kVA
1590
1540
Table 5.6 Transformer Secondary Side
Parameter
Before AHF
After
AHF
Installation
Installation
ITHD
20.5%
16%
VTHD
4.7%
4.2%
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Chapter 5
Power Quality Improvement by using Power Active Filters
98
5.8 ACTIVE FILTER CONTROL ALGORITHM
Three phase
voltage source
ia
ib
ic
Non-linear
loads
Active filter
Fig 5.10 Block diagram of the system
isource
Source
3-ph
iload
icomp
Load
3-ph
Vsource
P
controller
Coupling
coil
Inverter
module
icomp
ref
DC bus
Vdc
iload
Shunt Active Filter
Fig 5.11 Shunt Active Filter
5.8.1 Description of System configuration
The system configuration of the proposed shunt active filter is shown in the Fig 5.10. It
consists of a three-phase source, which is connected to a three-phase non-linear diode bridge
rectifier circuit. The Shunt Active Power Filter is connected in shunt with the load. It consists
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Chapter 5
Power Quality Improvement by using Power Active Filters
99
of the voltage source inverter in series with the inductor and capacitor. The triggering for the
inverter circuit is given through the control circuit. The inverter can be implemented by IGBTs
operating in hard-switched Pulse-Width Modulation (PWM) mode to provide sufficient
bandwidth for the filtering function.
5.8.2 Operating Principle
Three-phase bridge rectifier with RL loads (non-linear loads) is connected to the three phase
three wire distribution system as shown in Fig 5.11. Due to the nature of the non-linear loads,
harmonics are injected in to the system. Shunt Active Power Filter is connected in shunt with
the load to suppress the harmonics. The Voltage Source Inverter (VSI) generates a
compensating harmonics current in to the phase conductors through the inductor and capacitor
sets connected in series with it. The generated harmonics currents cancel each other with out
affecting the fundamental part of the source current.
5.8.3 Control Strategy
There are three stages in the active filtering technology. In the first stage the essentials voltage
and current signals are sensed using power transformers and current transformers to gather
accurate system information. In the second stage, compensating commands in terms of current
or voltage levels are derived based on control methods and AF configuration. In the third stage
of control, the gating signals for the solid-state devices of the AF are generated using PWM
techniques. In this we have used the instantaneous p-q theory for deriving the compensating
signal. [46]
5.8.4 Control Algorithm
The generalized theory of the instantaneous reactive power in three phase circuits is also
known as instantaneous power theory, or P-Q theory. It is based on instantaneous values in
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Chapter 5
Power Quality Improvement by using Power Active Filters
100
three-phase power systems with or without neutral wire, and is valid for steady state or
transitory operations, as well as for generator voltage and current waveforms. The p-q theory
consists of an algebraic transformation of the three-phase voltages and currents in the a-b-c coordinates to the --0 coordinates, followed by the calculation of the
v0
= 2/3 ●
v
v
1/ 2
1/ 2
1/ 2
1
-1/2
-1/2
0
3/2
-3/2
va
●
vb
vc
(5.10)
p-q theory instantaneous power components. As explained above the first step in p-q theory is
to transfer the a-b-c frame of voltage and currents into --0 coordinates.
1/ 2
i0
i
= 2/3 ●
i
1
0
1/ 2
1/ 2
-1/2
-1/2
3/2
-3/2
ia
●
ib
ic
(5.11)
The instantaneous powers “p” and “q” are calculated using the equations given below
p0 = v0•i0
instantaneous zero sequence power.
p
= v•i+v•i
instantaneous real power.
q
= v• i-v• i
instantaneous imaginary power
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Chapter 5
Power Quality Improvement by using Power Active Filters
p
v
v
-v
v
=
q
•
101
i
i
(5.12)
Where p =p + p ~
q =q + q ~
p0 =p0 + p ~0
p0 = Mean value of the instantaneous zero sequence power –corresponds to the energy per time
unity which is transferred from the power supply to the load through the zero sequence
components of voltage and current.
p ~0 = Alternated value of the instantaneous zero sequence power. It means the energy per time
unity is exchanged between the power supply and the load through the zero sequence
components. The zero-sequence power only exists in three-phase system with neutral wire.
Furthermore, the system must have unbalanced voltages and currents and/or 3rd harmonics in
both voltage and current of at least one phase.
p = Mean value of the instantaneous real power, corresponds to the energy per time unity,
which is transferred from power supply to the load, through a-b-c coordinates, in a balanced
way (it is the desired power component).
p ~ = Alternated value of the instantaneous real power, it is the energy per time unity, that is
exchanged between the power supply and the load, through a-b-c coordinates.
q = Instantaneous imaginary power, corresponds to the power that is exchanged between the
phases of the load. This component does not imply any transference or exchange of energy
between the power supply and the load, but is responsible for the existence of undesirable
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Chapter 5
Power Quality Improvement by using Power Active Filters
102
currents, which circulates between the system phases. In the case of a balanced sinusoidal
voltage supply and a balanced with or without harmonics, q(the mean value of the
instantaneous imaginary power) is equal to the conventional reactive power (q=3.V.I1.sin)
Vc
Linear loads
Balanced
unbalanced
Non-linear loads
Balanced
unbalance
120
120
Vb
Va
Power
supply
N
Shunt Active
power filter
C
Vdc
Fig 5.12 Shunt Active Filters with Linear Loads
As in Fig 5.12 ,
is usually desirable p-q theory power component. The other quantities can
be compensated using a shunt active filter.
Can be compensated without the need of any
power supply in the shunt active filter. This quantity is delivered from the power supply to the
load through the active filter. This means that the energy previously transferred from the
source to the load through the zero sequence components of voltage and current, is now
delivered in a balanced way from the source phases. It is also concluded from Fig 5.12 that the
active filter DC Bus is necessary to compensate input power Pi and out put power po, since
these quantities must be stored in this component at one moment to be later delivered to the
load. The instantaneous imaginary power (q), which includes the conventional reactive power,
is compensated without the contribution of the DC Bus. This means that, the size of the DC
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Chapter 5
Power Quality Improvement by using Power Active Filters
103
Bus does not dependent on the amount of reactive power to be compensated. The
compensation reference currents in --0 components can be calculated by using the equations
(4.13) & (5.14)
ic
ic

1
=
v
- v
v
v
________________
v2+v2
p -p0

q
(5.13)
Since zero sequence current must be compensated, the reference compensation current in the 0
coordinate is i0 itself. ic0 = i0, In order to get the compensating currents in a-b-c reference
frame the inverse transformation of --0 to a-b-c is applied.
ica
icb
icc
= 2/3 ●
1/ 2
1
1/ 2
-1/2
1/ 2
-1/2
ic0
0
3/2
-3/2
●
ic
ic
(5.14)
Fig 5.13 Active & Reactive power control
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Chapter 5
Power Quality Improvement by using Power Active Filters
104
5.8.5 Features of p-q theory
The above Fig 5.13 synthesizes the reference current calculations of instantaneous p-q theory
 It is inherently a 3-phase system theory
 It is based on instantaneous values, allowing excellent dynamic response
 Its calculations are relatively simple (it only includes algebraic expressions that can be
Implemented using standard processors).
 It can be applied to any three-phase system (balanced or unbalanced, with or without
Harmonics in both voltages and currents) [47]
5.9 SIMULATION RESULTS
The SIMUINK/MATLAB (version 7) is a highly developed graphical user interface simulation
tool. It has proved instrumental in implementing the graphical based controller. The Simulation
tool has been used to perform the modeling and simulation of the custom power controller for a
wide range of operating conditions. The Simulation results of the proposed filter are discussed
in this chapter. The Proposed scheme of Shunt Active Filter is shown in Fig 5.14. For both
with and without filter. The active filter is connected in parallel with the 3 phase supply. The
load taken for the simulation is Diode and Thyristor bridge rectifier with RL load. The Tables
5.7 & 5.8 show the values of R and L for both diode and thyristor bridge rectifiers respectively.
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Power Quality Improvement by using Power Active Filters
105
Table 5.7 Parameters for Diode Bridge Load
Load parameters
Active filter parameters
Resistance =2 ohms
IGBT Inverter DC Bus = 900V
Inductance =1.5mH
Inverter Coupling Inductance/Phase =1.5mH
Ripple Filter Parameters Rect./phase = 4 ohms
Cap/phase =36 µf
Cap/phase =72 µf
Table 5.8 Parameters For Thyristor Bridge Rectifier Load
Load parameters
Active filter parameters
Resistance =2 ohms
IGBT Inverter DC Bus = 900V
Inductance =1.5mH
Inverter Coupling Inductance/Phase =1.5mH
Ripple Filter Parameters Rect./phase = 4 ohms
Cap/phase =36 µf
Cap/phase =72 µf
As explained in the control algorithm, there are basically three main steps in instantaneous p-q
theory.
First step is converting the voltage and currents in ABC reference (stationary) frame into alpha
beta zero sequence (which is also stationary) frame as shown in Fig 5.15.
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Power Quality Improvement by using Power Active Filters
106
Second step is to calculate the instantaneous real and reactive powers and extracting reference
compensating currents for compensating the harmonic currents and reactive power at the
source side of the system as shown in Fig 5.16
Third step is to generate the reference compensating current by using an IGBT based voltage
source inverter as shown in Fig 5.14
The results waveform will depict the effectiveness of the active filtering algorithm. It can be
observed from Fig 5.17 that the source current has become a pure sinusoidal wave and it has
been observed form POWER GUI tool that source current THD has been reduced from 24% to
2%. This can be observed from Fig 5.18 that, load power oscillations are reduced with active
filtering.
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Chapter 5
Power Quality Improvement by using Power Active Filters
Fig 5.14 Simulated Diagram of Active Harmonic filter
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Chapter 5
Power Quality Improvement by using Power Active Filters
Fig 5.15 Simulated Diagram for ABC to Alpha Beta ZeroTransforamtion
Fig 5.16 Simulated Diagram for Reference current calculation
Ph.D Thesis submitted to Jawaharlal Nehru Technological University Anantapur
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Fig 5.17 Source and load current waveforms (Time on x-axis, Vs & IL on y-axis)
Fig 5.18 Source and load power waveforms (Time on x-axis, Ps & PL on y-axis)
The same active filter is connected to thyristor based bridge rectifier which is containing more
harmonics in current compared to the diode bridge rectifier as mentioned in Fig 5.15. The
current THD is reduced from around 44% to 3% hence the designed active filter is effective
with high percentage of THD. The designed active filter is capable of reducing around 50 amps
of harmonics current in load. The simulation diagram for Active harmonics filter with thyristor
based bridge rectifier load is shown in Fig 5.19
Ph.D Thesis submitted to Jawaharlal Nehru Technological University Anantapur
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Power Quality Improvement by using Power Active Filters
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Fig 5.19 Simulated diagram of Active harmonic filter with thyristor bridge load
Fig 5.20 Shows that the load current waveform has been improved and the source becomes a
pure sinusoidal current waveform. It can also be observed from Fig 2.21 that the power
variation at the load side is reduced compared to source side, in addition to this the active
harmonics filter is capable of supplying the reactive power to the load and power factor at the
source side is also increased.
Ph.D Thesis submitted to Jawaharlal Nehru Technological University Anantapur
Chapter 5
Power Quality Improvement by using Power Active Filters
Fig 5.20 Source and load current waveforms (Time on x-axis, Is & IL on y-axis)
Fig 5.21 Source voltage and power waveforms (Time on x-axis, Vs & P on y-axis)
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5.10 CONCLUSION
The purpose of this chapter is to review the results obtained during the present work before
proceeding with the conclusions of the work done, the objective of the thesis stated in the first
chapter are recalled. The primary objective of this chapter is to model and develop the
proposed new Shunt Active Power Filter for the current harmonics suppression using
SIMULINK/MATLAB (Version 7) simulation tool.
The model of the proposed new Shunt Active Power Filter is realized. The developed new
Shunt Active Power Filtering technology is implemented for a system feeding a non-linear
load. It is simulated using the highly developed graphic tool SIMULINK available in
MATLAB. The results reveal that the proposed new Shunt Active Filtering technology is
simple and effective and is suitable for practical applications.
Table 5.9 Harmonic Distortion of Load Voltage
Dead
Vab_50Hz
THD
HS
H7
8kHz
Time(µs)
V(rms)
(%)
(%)
(%)
(%)
0
380
1.27
0.21
0.13
0.74
5
354.6
2.13
1.43
0.79
0.82
From Table 5.10, it is observed that by the suppression of voltage and current harmonics using
new active filtering technology, the power quality can be improved as discussed in the various
chapters.
Ph.D Thesis submitted to Jawaharlal Nehru Technological University Anantapur