Asian Journal of Current Engineering and Maths 4:6, November – December (2015) 83 –87.
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ASIAN JOURNAL OF CURRENT ENGINEERING AND MATHS
Journal homepage: http://innovativejournal.in/ajcem/index.php/ajcem
HARMONIC ELIMINATION AND POWER FACTOR CORRECTION USING SPACE
VECTOR MODULATION
Pawan Kumar
Assistant Professor, Department of Electrical and Electronics Engineering, Jeppiaar Institute of Technology, Chennai,
T.N, India.
ARTICLE INFO
ABSTRACT
Corresponding Author
Pawan kumar
Assistant Professor, Department of
Electrical and Electronics
Engineering, Jeppiaar Institute of
Technology, Chennai, T.N, India.
pawankumars@jeppiaarinstitute.org
Key Words: Active Filter, Harmonics,
Space Vector, Simulation.
This paper analysis the harmonics elimination and improve the power
quality by using space vector modulation. The voltage
and current
harmonics are produced by nonlinear loads that increase the power losses
and a negative effect on electric utility supply systems and apparatus. This
paper presents the application of Space Vector Pulse Width Modulation for
shunt active power filters .The most important part of the active power
filters is generating of gate signal for inverters to improve the power factor
and to reduce current and voltage distortion to standard limits. The
simulation results through Matlab shows that the output of the effective
current compensation.
DOI:http://dx.doi.org/10.15520/ajce
m.2015.vol4.iss6.41.pp83-87.
©2015, AJCEM, All Right Reserved.
INTRODUCTION
Harmonics are components of a deformed periodic
waveform whose frequencies are integral multiples of the
primary frequency. The loads are mainly classified in linear
and nonlinear loads. The linear loads draw current in direct
proportion to the applied voltage. Hence they do not
contribute any considerable distortion. Unlike linear loads
nonlinear loads draw impulse current with result in
warped load current. This alteration of original shape is
become source for the Harmonic components formed due
to no linear loads, thus degrading the power system quality.
Fig.1 Block Diagram
power system normally operates at 50 or 60 Hz. Current
and voltage with elevated frequencies are called as
harmonics. The harmonics disturbances in the power
supply are caused by the non-linear behaviour of the loads.
83
Due to the benefits in effectiveness and controllability of
power electronic devices, it can be implemented in almost
all power level. Hence, power harmonics has become a
serious problem. The main problem that needs to be solved
is to reduce the harmonics level in the line current. As a
result, active power filter is used to implement in the
power system for harmonics compensation function .As
there are variety of topologies of active power filter, good
control strategy needs to be designed and must be
compatible with the proposed active power filter. Fast
response and direct closed loop control strategy is
considered in this research. After determining the suitable
control strategy to use, the related compensated techniques
have to be designed and transformed into appropriate
control algorithms. Therefore, the basic of the equations
derivation of each related techniques are study in details.
Suitable control algorithms are then
developed for the proposed active power filter
THREE PHASE SHUNT ACTIVE FILTER TOPOLOGY
The working principle of a simple VSI is extended to the
three phase active power filter. The three phase shunt
active filter have 6 semi-conductor switches (s1, s2, s3, s4,
s5, s6) with two switches on each bridge. The two switches
on any leg of the filter cannot be switched on at the same
time since this would result in a short circuit across the dc
link. of the eight valid states the first and the last (000 and
111 respectively) are called zero vectors and the remaining
six states are called active vector. The schematic of a three
phase SAF and the switching states are shown in Fig. 2 and
Fig.3
Kumar /Harmonic Elimination And Power Factor Correction Using Space Vector Modulation
Fig. 2 Three Phase
Fig.3 Switching States
Shunt Active Filter
The harmonic current extracted from the distorted
line is given as the reference to the control unit and the gate
pulses are generated. These gate pulses are given to the
switches. The shunt active filter is connected with a dc
supply. The output is generated based on the switching
pulses and this output is actual compensating current to be
injected into the distorted line. The compensating current
generated by the shunt active filter is as shown in Fig. 4.
The drawbacks of passive filters are eliminated in active
filters. The industrial loads, generally being non-linear,
contribute highly to the current harmonics because of
semiconductor switching. Hence the proposed method uses
shunt active filter for harmonic compensation.
Fig 5 P-Q Transformation.
To control active filters the p-q theory is one of
several methods that can be used . It has following
characteristics, they are namely:1. It is inherently a threephase system theory 2. It can be applied to any three-phase
system either balanced or unbalanced, with or without
harmonics in both voltages and currents. 3. It is based in
instant values, producing excellent dynamic response 4. Its
calculations are relatively simple. It includes algebraic
expressions that capable to implement through standard
processors) 5. It allows two control strategies: i) Constant
instantaneous supply power ii) Sinusoidal supply current.
As the compensator will only compensate the
instantaneous reactive power, we have to set the real
power to zero. The instantaneous reactive power is set into
opposite vectors due to this it cancel the reactive element
in the line current.
The compensating current of each phase can be derived by
using the inverse orthogonal transformations which is
given by
Fig.4 Actual Compensating Current for Phase A
HARMONIC EXTRACTION TECHNIQUES
The common theory of the Instantaneous Reactive Power in
3-Phase Circuits is also called as instantaneous power
theory, or p-q theory. It depends on instantaneous values in
3-phase power systems with or without neutral wire, and is
valid for steady-state or transient operations, also for
generic voltage and current waveforms. The p-q theory
consists
of
Clarke
transformation
(algebraic
transformation) of the three-phase voltages and currents in
the a-b-c coordinates to the a-ß-0 coordinates, which
follows the method of the p-q theory instantaneous power
components:
In the case of a non-sinusoidal or unequal supply voltage,
the only variation is that the supply current will include
harmonics, but in practical cases the distortion is negligible.
The calculations presented so far are synthesized in Fig.6
The power components p and q are related to the
equivalent a-ß voltages and currents, and can be written
together:
Fig. 6 P-Q Transformation
SPACE VECTOR PULSE WIDTH MODULATION
A typical three phase active power filter consists of six
power switches S1 to S6 that shapes the output by
controlling the switching variables a, a’, b, b’, c, c’. Thus the
on and off state of the upper switches S1, S2 and S3 can be
used to obtain the compensating current. In the Fig 7 the
switching signals are represented in Cartesian coordinate
system.
Fig.5 shows the modification of the 3 phase voltages
and currents vectors in a-b-c coordinates into
orthogonal coordinates, a-ß coordinates.
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Kumar /Harmonic Elimination And Power Factor Correction Using Space Vector Modulation
Three hysteresis bands of the width δ are defined
about every reference value of the phase currents (ia; ib; ic)
as shown in Fig. 9
Fig 9 Hysteresis Band
The goal is to keep the actual value of the currents
inside their hysteresis bands every time. As the three
currents are not independent from each other, the system
is transformed into (a;ß) coordinate system. With the
transformation of the three hysteresis bands into this
coordinate construction, they result in an hysteresis
hexagon area.
Fig 7 Space Vector Plane
The relationship between the switching variable vector [a,
b, c] t and the L-L voltage vector [Vab Vbc Vca] t is
expressed by
Also, the relationship between the switching variable
vector [a, b, c] t as well as the phase voltage vector [Va Vb
Vc] t can be expressed below.
There are eight possible combinations of on and off
arrangement for the three upper power switches. The on
and off states of the lower power devices are opposite to
the upper devices and so are easily decided once the states
of the upper power transistors are determined. According
to equations given above the eight switching vectors,
output line to neutral voltage and output L-L voltages with
reference to DC-link Vdc , are given in Table 1
Fig 10 Eight Space Voltage Vectors and Regions
The reference current vector iref points towards the centre
of the hysteresis what can be seen in Fig. 11 The actual
value of the current i has to be kept within the hexagon
area. Every time when the tip of the current touches the
border of the surface move out of the hexagon, the inverter
has to be switched in sequence to force the current into the
hexagon area. The current error is defined as:
Table 1 Switching Vector Output
Space Vector PWM refers to a unique switching series of
the upper three power transistors of a three-phase power
inverter. It has been shown to produce less harmonic
deformation in the output voltage.
Fig.8 Locus Traced by SVPWM and SPWM
SPACE VECTOR BASED HYSTERESIS
CONTROL
CURRENT
85
Fig 11 Hysteresis hexagon in a-ß plane
The error of each phase current is controlled by a 12 stage
hysteresis comparator, which is shown in Fig.12 A
switching logic sequence is essential because of the
coupling of three phases. When the current error vector ie
reaches the boundary of the hysteresis hexagon, the
switching sequence has to prefer next, the most favourable
switching state with respect to the following The current
difference ie should be moved back towards the middle of
the hysteresis hexagon as gradually as feasible to achieve a
low switching frequency, If the tip of the current error ie is
outer surface of the hexagon, it have to be returned in
hexagon quickly (important for dynamic computing).Each
position corresponds to a space vector. V0 is the void
voltage vector, and it normally has two
switching patterns V0 (000) and V0 (111). The remaining
six voltage vectors are labelled from V1 to V6 and are
divided into six regions.
Kumar /Harmonic Elimination And Power Factor Correction Using Space Vector Modulation
Fig 13 Simulation of SVPWM model
Fig 12 Hysteresis Comparator
The comparator which is used denote the space voltage
vectors i) the narrow band comparator ii) the inner band
comparator. The output signals of the outer band hysteresis
comparator, B ao , B bo , B co and the output signals of the
inner band hysteresis comparator, B ai ,B bi , B ci , provide
the information to a switching table in the programmable
logic array to generate appropriate gate switching
sequence signals to the three phase inverter or known as
the active power filter.
Fig 14 Harmonic Extraction Block
Fig 15 Hybrid SVM HCC modulation
WAVEFORMS:
Table 2 Hybrid SVM HCC Switching Function Table
The SVM regions are given by the upper hysteresis band as
given below.
Source Current before Compensation
The Hybrid SVM HCC technique will present a better
control technique and strategy for the active power filter.
SIMULATION
SUPPLY PARAMETERS OF THE SYSTEM
Source voltage: 220V, single phase
Source inductance: 0.5mH
Source Resistance: 0.02 ohm
Line frequency: 50Hz
NON LINEAR LOADS:
Rectifier fed R Load
Rating: 1KVA maximum
Load resistance: 100 ohms
Filter capacitor: 1000uf/250
SIMULATION OF SVPWM MODEL
Source current after compensation
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Kumar /Harmonic Elimination And Power Factor Correction Using Space Vector Modulation
method is power loss and component rating is typically
lower when compared
to other power factor correction methods. Besides the
compensation current is still a sine wave with almost unit
power factor regardless of whether the mains voltage is
distorted or non- distorted. As a conclusion, the objectives
of this project have been achieved by plummeting the
harmonic contents that exist in a power system with a
chosen nonlinear load.
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Generated pulses
Source Current, Load Current, Extracted
Harmonic Current
CONCLUSION
The Hybrid SVM HCC technique will present a better
control technique and strategy for the active power filter.
Besides that, it can realize the installation of the active
power filter to the utilities and the end user The active
power filter is a new and effective solution for harmonic
related problems. In this work a simple and efficient
control block, to generate reference current templates and
PWM switching technique for active power filters is
implemented and tested. The controller eliminates the
unwanted harmonics and correction supply power factor.
This system is capable to compensate the harmonics due to
a three phase uncontrolled diode rectifier and it produces
positive results by minimizing the quantity of THD of the
line current. This type of Active power filters provides a
cost-effective, unfailing, and feasible solution for power
quality Control. We are seeing that the APF just computing
the reactive and harmonic current. The advantage of this
How to cite this article: KUMAR, Pawan. Harmonic Elimination And Power Factor Correction Using Space Vector
Modulation. Asian Journal of Current Engineering and Maths, [S.l.], v. 4, n. 6, p. 83-87, dec. 2015. ISSN 2277-4920.
Available at: <http://innovativejournal.in/ajcem/index.php/ajcem/article/view/41>. Date accessed: 12 Dec. 2015.
doi:10.15520/ajcem.2015.vol4.iss6.41.pp83-87
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