40220140503005

International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME
34
STATCOM BASED POWER QUALITY IMPROVEMENT IN GRID
CONNECTED RENEWABLE ENERGY SYSTEMS
K M Mamatha1
, Nalini.S2
1
4th
Semester, M.Tech(Power Electronics)
2
Associate Professor
Department of Electrical and Electronics Engineering,
Dr. Ambedkar Institute of Technology, Bangalore, India
ABSTRACT
The power quality of the system is affected when it is connected to a renewable energy
sources like wind, solar etc. Hence the power injected by such sources degrades the system
performance. The scheme used in this paper tells about maintaining the unity power factor at the
source side, reactive power support only from STATCOM to wind Generator and Load and a simple
bang-bang controller for STATCOM to achieve fast dynamic response.
Key-words: IGBT (Insulated Gate Bipolar Transistor), IG (Induction Generator), FACTS (Flexible
Alternating Current Transmission System).
1. INTRODUCTION
With increase in the demand for Electricity due to increase in population and
industrialization, the Generation of power is really a challenge now a days. If we want to increase the
power generated in the conventional way i.e., by means of non-renewable energy sources like coal,
diesel, natural gases and similar fossil fuels, the pollution increases which degrades the Environment
and human life style.
Compared to the non-renewable energy sources these have the advantages of the following:
1. The sun, wind, geothermal, ocean energy are available in the abundant quantity and free to
use.
2. The non-renewable sources of energy that we are using are limited and are bound to expire one
day.
INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING &
TECHNOLOGY (IJEET)
ISSN 0976 – 6545(Print)
ISSN 0976 – 6553(Online)
Volume 5, Issue 3, March (2014), pp. 34-42
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35
3. Renewable sources have low carbon emissions, therefore they are considered as green and
environment friendly.
4. Renewable helps in stimulating the economy and creating job opportunities.
5. Renewable sources can cost less than consuming the local electrical supply. In the long run,
the prices of electricity are expected to soar since they are based on the prices of crude oil, so
renewable sources can cut your electricity bills.
But even though they have their advantages, they are not preferred due to economic criteria
of investing huge funds. Also the problems that we face when we integrate these energy sources to
the grid are quite many like power quality maintenance.In this paper we consider Wind power that can
be utilized for generation of electrical power using Wind farms with FACTS device STATCOM to
compensate the disturbances that occur due to the fluctuating nature of the wind.
2. METHODOLOGY
In this proposed scheme a FACTS device STATIC COMPENSATOR (STATCOM) is
connected at a point of common coupling with a battery energy storage system (BESS) to reduce the
power quality problems. The battery energy storage system is integrated to support the real power
source under fluctuating wind power [6]. The FACTS Device (STATCOM) control scheme for the
grid connected wind energy generation system to improve the power quality.
The STATCOM is acompensatingdevice whichis usedtocontrolthe flow ofactive and reactive power
required to the Induction Generator of the wind turbine. It is a custom power device which is gaining
a fast publicity during these days due to its exceptional features like it provides fast response,
suitable for dynamic load response or voltage regulation and automation needs, Both leading and
lagging VARS can be provided, to correct voltage surges or sags caused by reactive power
demands pulse STATCOM can be applied on wide range of distribution and transmission voltage,
overload capability of this provides reserve energy for transients from the BESS [1]. The pulse
STATCOM is controlled using the PI controller.
3. TYPES OF POWER QUALITY PROBLEM
The power quality problems are listed below:
1. Transients
2. Long Duration Voltage Variations
2.1 over voltage
2.2 under voltage
2.3 sustained interruptions
3. short duration voltage variations
3.1 interruptions
3.2 sags (dips)
3.3 swells
4. voltage and current imbalance
5. voltage fluctuation
6. power frequency variations
7. waveform distortion
7.1 harmonics
7.2 inter harmonics
7.3 noise

36
Elimination of these problems are analyzed and discussed in the paper [4] and the
STATCOM is used to overcome the power quality problems.
4. BLOCK DIAGRAM
The propose system consists of three phase AC source, Wind power generating system, non-
linear load, STATCOM with Battery energy storage system [1], PI controller. The three phase bridge
rectifier.
Figure 4.1: Block diagram of the proposed system
Is used as a non-linear load. The block diagram for proposed method is shown in Figure
4.1.The STATCOM and PI controller in order to eliminate harmonics, to compensate reactive power
demand and to maintain unity power factor at source side.
Wind generating system using induction generator. It requires reactive power for
magnetization. When the generated an active power of an induction is varied due to wind [3].
Absorbed reactive power and terminal voltage of an induction generator can be significantly
affected. A proper control scheme in wind generating system is used to product active power.
It generated power is given to the non- liner load. This nonlinear load will produce some
distortion in output waveform. Due to this input side also get affected and more losses, more power
consumption and equipment get damaged. STATCOM is used to reduce harmonic to improve
performance of system. Reference current is taken from output side is compared with input current
and is given as input to the PI controller. Its controller output is given to input of STATCOM. An
opposite harmonics from STATCOM is injected to line at point of common coupling in order to
maintain the unity power factor at the source side.
5. PROPOSED CIRCUIT DIAGRAM:
The proposed circuit diagram is as shown in the figure 5.1. The STATCOM absorbs the
power from the source and the energy is stored using the battery and also provides reactive power
support to the load and wind energy system when necessary, hence a dual power flow is indicated in
the figure 5.1.

International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976
ISSN 0976 – 6553(Online) Volume 5, Issue
Figure 5.1: Proposed circuit diagram
6. SIMULATION ENVIRONMENT
Simulation is carried out using MATLAB. The name MATLAB stands for Matrix
Laboratory. MATLAB is a software package for high performance numerical computation and
visualization. It provides an interactive
computation, graphics and animations. The combination of analysis capabilities, flexibility,
reliability and powerful graphics makes MATLAB the premier software package for electrical
engineers. Best of all, MATLAB provides easy extensibility with its own high level programming
language.
7. MODELING OF OVER ALL CIRCUIT SYSTEM
Figure: 7.1 shows the complete MATLAB model of
The power circuit as well as control
Simulink. The grid source is represented by three
connected at the load end.STATCOM is connected in shunt and it consists of PWM voltage source
inverter circuit and a DC capacitor connected at its DC bus. An IGBT
implemented using Universal bridge block from Power Electronics subset of PSB.
Fig 7.1:Over All Circuit Diagram in Simulink
Snubber circuits are connected in parallel wit
STATCOM system is carried out for linear and non
modelled using the block three-phase parallel R
6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME
37
Figure 5.1: Proposed circuit diagram [7]
SIMULATION ENVIRONMENT
visualization. It provides an interactive environment with hundreds of built-in functions for technical
Best of all, MATLAB provides easy extensibility with its own high level programming
OVER ALL CIRCUIT SYSTEM
s the complete MATLAB model of STATCOM along with control circuit.
The power circuit as well as control system are modelled using Power System Block set and
Simulink. The grid source is represented by three-phase AC source. Three-phase AC loads are
and a DC capacitor connected at its DC bus. An IGBT-based PWM inverter is
implemented using Universal bridge block from Power Electronics subset of PSB.
Over All Circuit Diagram in Simulink (MATLAB)
er circuits are connected in parallel with each IGBT for protection. Simulation of
STATCOM system is carried out for linear and non-linear loads. The linear load on the system is
phase parallel R-L load connected in delta configuration. The non
in functions for technical
Best of all, MATLAB provides easy extensibility with its own high level programming
STATCOM along with control circuit.
system are modelled using Power System Block set and
phase AC loads are
based PWM inverter is
h each IGBT for protection. Simulation of
linear loads. The linear load on the system is
L load connected in delta configuration. The non-

ISSN 0976 – 6553(Online) Volume 5, Issue
linear load on the system is modelled using R and R
rectifier. Provision is made to connect loads in parallel so that the effect of sudden load addition and
removal is studied. The feeder connected from the three
appropriate values of resistive and inductive components.
Fig 7.2: MATLAB model of controller block
The control scheme is based on injecting the currents into the grid
controller. The controller makes the use of a hysteresis current controlled technique. By using such
technique, the controller keeps the control system variable between boundaries of hysteresis area and
gives correct switching signals for STATCOM operation. The MATLA
scheme for generating the switching signals to the STATCOM is shown in the abo
8. SIMULATION RESULTS
The hybrid energy generating system is connected with grid having the nonlinear load. The
performance of the system is measured by switching the STATCOM at time 0.21 s in the system and
how the STATCOM responds to the step change command for increase in additional load at 0.21s is
shown in the simulation. When STATCOM controller is made ON, without change in any other load
condition parameters, it starts to mitigate for reactive dem
dynamic performance is also carried out by step change in a load, when applied at 0.21 s. This
additional demand is fulfil by STATCOM compensator. Thus, STATC
real power from source. The result of source current, load
respectively. While the result of injected current from S
Fig 8.1: waveform 3 phase output
0
-60
-40
-20
0
20
40
60
80
IabcinAmpere
6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME
38
stem is modelled using R and R-C circuits connected at output of the diode
removal is studied. The feeder connected from the three-phase source to load is modelled using
appropriate values of resistive and inductive components.
Fig 7.2: MATLAB model of controller block
The control scheme is based on injecting the currents into the grid [5] using hysteresis current
The controller makes the use of a hysteresis current controlled technique. By using such
gives correct switching signals for STATCOM operation. The MATLAB model for control system
scheme for generating the switching signals to the STATCOM is shown in the above fig 7.2.
measured by switching the STATCOM at time 0.21 s in the system and
condition parameters, it starts to mitigate for reactive demand as well as harmonic current.
additional demand is fulfil by STATCOM compensator. Thus, STATCOM can regulate the available
real power from source. The result of source current, load current are shown in Figure: 8.2 and 8.4
respectively. While the result of injected current from STATCOM are shown in Figure: 8.1
Fig 8.1: waveform 3 phase output current of STATCOM
0.5 1 1.5 2 2.5 3 3.5 4
x10
4Timeinsec
STATCOM3-PHASEOUTPUTCURRENT
C circuits connected at output of the diode
is modelled using
hysteresis current
The controller makes the use of a hysteresis current controlled technique. By using such
B model for control system
ve fig 7.2.
measured by switching the STATCOM at time 0.21 s in the system and
and as well as harmonic current. The
OM can regulate the available
current are shown in Figure: 8.2 and 8.4
TATCOM are shown in Figure: 8.1.

39
Fig 8.2: waveform of source current
Fig 8.3: Source Active and reactive power
Fig 8.4: Load Current in Amps
It is observed that the source current on the grid is affected due to the effects of nonlinear
load and wind generator, thus purity of waveform may be lost on both sides in the system. The
inverter output voltage under STATCOM operation with load variation is shown in Figure: 8.9 and
8.6. The dynamic load does affect the inverter output voltage. The source current with and without
STATCOM operation is shown in Figure: 8.2. This shows that the unity power factor is maintained
for the source power when the STATCOM is in operation.
Fig 8.5: STATCOM Active and reactive power
0 0.5 1 1.5 2 2.5 3 3.5 4
x10
4
-60
-40
-20
0
20
40
60
Time insec
IasinAmpere
SourceCurrent
0 0.5 1 1.5 2 2.5 3 3.5 4
x 10
4
-2000
0
2000
4000
6000
8000
10000
12000
14000
16000
Time in sec
Activepower(W)andReactivepower(VAR)
ACTIVE POW ER (W) AND REACTIVE POWER (VAR) DELIVERED BY SOURCE
0 0.5 1 1.5 2 2.5 3 3.5 4
x 10
4
-80
-60
-40
-20
0
20
40
60
80
Time in sec
LoadcurrentinAmp
LOAD CURRENT
0 0.5 1 1.5 2 2.5 3 3.5 4
x 10
4
-2000
0
2000
4000
6000
8000
10000
Time in sec
Activepower(W)andReactivepower(VAR)
ACTIVE POW ER(W) AND REACTIVE POWER(VAR) DELIVERED BY STATCOM

40
Fig 8.6: STATCOM Output Current
Fig 8.7: 3 phase of voltage wind energy system
Fig 8.8: 3 phase current of wind energy system
The average power flow is measured at the point of common coupling, with and without
controller operation in the grid is shown in Figure: 8.3. The controller is operated for power quality
mode to inject the power at t = 0.21 s, during this operation source reactive power is reduced to zero.
0 0.5 1 1.5 2 2.5 3 3.5 4
x 10
4
-60
-40
-20
0
20
40
60
80
Time in sec
outputcurrentinAmps
STATCOM OUTPUT CURRENT(Ia1)
0 0.5 1 1.5 2 2.5 3 3.5 4
x 10
4
-400
-300
-200
-100
0
100
200
300
400
3 PHASE VOLTAGE OF WIND ENERGY SYSTEM
VOLTAGEINVOLTS
TIME IN SEC
0 0.5 1 1.5 2 2.5 3 3.5 4
x 10
4
-4
-3
-2
-1
0
1
2
3
4
3 PHASE CURRENT OF WIND ENERGY SYSTEM
TIME IN SEC
CURRENTINAMPS

41
Fig 8.9: STATCOM Output Voltage
The average power flow is measured at the point of common coupling, with and without
controller operation in the grid. The controller is operated for power quality mode to inject the
reactive power at t = 0.21 s, during this operation source reactive power is reduced to zero is shown
in Figure:8.5.
Fig 8.10: Source Current of without STATCOM and FFT of Source Current without
STATCOM
The current waveform before and after the STATCOM operation is analyzed. The Fourier
analysis of this waveform is expressed and the THD of this source current at PCC without
STATCOM is 13.28 %, as shown in Figure: 8.10.
Fig 8.11: Source Current of with STATCOM and FFT of Source Current with STATCOM
The power quality improvement is observed at point of common coupling, when the
controller is in ON condition. The STATCOM is placed in the operation at 0.21 s and source current
waveform is shown in Figure: 8.11 with its FFT. It is shown that the THD has been improved
considerably and within the norms of the standard. The above tests with proposed scheme has not
only power quality improvement feature but it also has sustain capability to support the load with the
energy storage through the batteries.
0 0.5 1 1.5 2 2.5 3 3.5 4
x 10
4
-1500
-1000
-500
0
500
1000
1500
STATCOM OUTPUT VOLTAGE
TIME IN SEC
VOLTAGEINVOLTS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
-50
0
50
Selected signal: 17.5 cycles. FFT window (in red): 2 cycles
Time (s)
0 100 200 300 400 500 600 700 800 900 1000
0
0.01
0.02
0.03
0.04
0.05
Frequency (Hz)
Fundamental (50Hz) = 55.21 , THD= 0.97%
Mag(%ofFundamental)
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
-50
0
50
Selected signal: 17.5 cycles. FFT window (in red): 2 cycles
Time (s)
0 100 200 300 400 500 600 700 800 900 1000
0
2
4
6
8
10
12
Frequency (Hz)
Fundamental (50Hz) = 49.52 , THD= 15.04%
Mag(%ofFundamental)

42
CONCLUSION
In this paper we present the FACTS device (STATCOM) -based control scheme for power
quality improvement in grid connected wind generating system and with nonlinear load. The power
quality issues and its consequences on the consumer and electric utility are presented. The operation
of the control system developed for the STATCOM in MATLAB/SIMULINK for maintaining the
power quality is to be simulated. It has a capability to cancel out the harmonic parts of the load
current. It maintains the source voltage and current in-phase and support the reactive power demand
for the wind generator and load at PCC in the grid system, thus it gives an opportunity to enhance the
utilization factor of transmission line.
Thus the integrated wind generation and FACTS device with BESS have shown the
outstanding performance in maintaining the voltage profile as per requirement. Thus the proposed
scheme in the grid connected system fulfils the power quality requirements and maintains the grid
voltage free from distortion and harmonics.
FUTURE ENHANCEMENTS
The proposed a STATCOM control scheme for grid connected hybrid wind power energy
system to improve power quality is using for conventional control of PI controller which is used to
compensate non -linear load and reactive power demand.We can also use fuzzy logic in the
controller side which will reduce the settling time and increase the response of the circuit.
REFERENCES
[1] B. S. Borowy and Z. M. Salameh, (1997), “Dynamic response of a stand-alone wind energy
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Conversion, vol. 12, no. 1, pp. 73–78, Mar.
[2] Francisco Diaz Gonzalez1, Marcela Martnez-Rojas (2011), “Strategies for Reactive Power
Control in Wind Farms with STATCOM” IREC Catalonia Institute for Energy Research.
[3] J.J.Gutierrez,J.Ruiz, L. A. Leturiondo, and A. Lazkano, (2009) “Flicker Measurement System
for Wind Turbine Certification” IEEE TRANSACTIONS ON INSTRUMENTATION AND
MEASUREMENT, VOL. 58, NO. 2, pp.375-382.
[4] Kyung soo kook and yiluliu (2006) “Mitigation of the Wind Generation Integration Related
Power Quality Issues by Energy Storage” Electrical Power Quality and Utilisation, Journal
Vol.XII, No.2, pp.77-82.7.
[5] Mukhtiar Singh, VinodKhadkikar, Ambrish Chandra, Rajiv K. Varma (2011), “Grid
Interconnection of Renewable Energy Sources at the Distribution Level With Power-Quality
Improvement Features” IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 26, NO.
1, pp.307-315.
[6] Sharad W. Mohod and Mohan V. Aware (2012) “Micro Wind Power Generator with Battery
Energy Storage for Critical Load” IEEE SYSTEMS JOURNAL, VOL. 6, NO.1, pp.118-125.
[7] Sharad W. Mohod and Mohan V. Aware (2010), “A STATCOM-Control Scheme for Grid
Connected Wind Energy System for Power Quality Improvement” IEEE SYSTEMS
JOURNAL, VOL. 4, NO. 3, pp.346-352.
[8] S.Dileep Kumar Varma and Divya Dandu, “Modelling and Simulation of Hybrid Renewable
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ISSN Online: 0976-6553.

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