ISSN 2319-8885
Vol.03,Issue.50
December-2014,
Pages:10141-10148
www.ijsetr.com
Power Quality in Grid Connected Wind Energy under Fixed and Varying
Wind Speed
K.V.BHADANE1, M.S.BALLAL2, R.M.MOHARIL3
1
Ph.D Scholar, RTM Nagpur, MS, India, E-mail: kishor4293@yahoo.co.in.
2
RTM Nagpur, MS, India & 3RTM Nagpur, MS, India.
Abstract: Maharashtra peoples face the problem of load shedding because of the power deficiency and huge gap between
availability and requirement of power. Hence to overcome this problem the use of more renewable wind energy in rural area
has been used as solution in high wind potential region. Due to heavy penetration of grid connected wind energy, the power
quality of electric system gets affected. Hence the aim of the research is to investigate the Power Quality issues and its analysis,
causes responsible for PQ issues, etc in grid connected wind farm .Increase in grid connected Induction generators, the
requirement of reactive power is high, the system power factor get affected. The effect of wind speed on power quality of grid
connected wind farm has been analyzed. The electric power system has been analyzed under constant speed, variable speed and
gust speed in terms of PQ effect on system and its management. The reactive power management has been described. Sudden
change in wind i.e. random nature of wind velocity will affect the electric power system performance has been identified.
Keywords: PQ Power Quality, Wind Farm, Reactive Power, Power Factor, Grid System Wind Velocity.
I. INTRODUCTION
In North Maharashtra of India, peoples face load
shedding problem because there is huge gap between
requirement and availability of electric power. In summer,
this power gap is rises tremendous and to solve this problem
temporary heavy load shedding is implemented. The system
is affected by the heavy load shedding. The used of
conventional power plant in Maharashtra state is more and
due to this the pollution is more and it also affect to
environmental aspects. The maximum power generation is
done through the thermal power system but day by day the
quality of coal used is not so good, old power plant and their
maintenance, efficiency of plant, calorific value of coal, old
transmission and distribution lines and their losses ,etc.
factors affect the generation capacity of the plant and also
quality of electric power. This attempt is consider to
creating the awareness about the more used of renewable
energy such as wind energy, solar energy, etc in rural area
of north Maharashtra region [1, 11]. The renewable energy
is available in free of cost though initial investment is high
.ones the renewable plant is erected small regular
maintenance is required and running cost is tremendously
reduced. The wind energy is pollution free and it protect to
our environment and also to the nature. Hence the wind
energy is also called as green energy [5] The heavy
penetration of wind power to the grid system is responsible
for exploiting the power quality of the system; hence more
attention is required for power quality of the system. The
aim of this paper is to Study the heavy penetrated grid
connected wind farm, Investigations of power quality issues,
power quality analysis of grid connected wind farm at
different wind velocity such as constant, variable and gust
speed, study of reactive power requirement and its
management, PQ analysis with power output with respect to
different wind velocity, power factor and its management,
performance analysis of grid connected wind farm at
various nature of wind velocity has been done [2].
II. WIND POWER IN NORTH MAHARASHTRA
A. Overview
The wind potential in north Maharashtra region is high
which is illustrated in Fig.1.
Fig.1. Location of case
Panchpatta, India [3].
Copyright @ 2014 IJSETR. All rights reserved.
study
in
Maharashtra,
K.V.BHADANE, M.S.BALLAL, R.M.MOHARIL
and renewable energy installed capacity in India illustrated
big generator is sensed by sensor and the selected generators
are active to generate the power in proportional with wind
in Fig.2.
velocity. The power is generate at 690V and step up to
33KV which is utilized further for distribution line. Further
it is step up to 132KV/220KV for feeding the power to the
grid system.
Fig.2.Renewable energy installed capacity in India [4].
The different renewable energy contribution of different
state in India is illustrated in Fig.3.
Fig.3.Renewable energy installed capacity in India [4].
The seasonable penetration of high power to grid is
between the months of May to September, medium between
November to February month and low at remaining months.
The 600 wind turbines are erected with different power
capacity such as 1MW, 1.25MW, etc. the total installed
capacity of wind farm is approximately 600MW. The two
fixed induction generators are used for generating the
power. Whenever the wind velocity is between 3 m/sec to 8
m/sec, small generator is sensed by sensor and it generates
power proportional with magnitude of wind velocity.
Whenever wind velocity is between 9 m/sec to 24 m/sec, the
B. Impact of High Penetrated Wind Farm
In a wind farm, 3-ø Induction motor is used as 3-ø
Induction generator with the help of high gearbox ratio but
due to large number of Induction generators are used, the
requirement of reactive power is more and this is fulfill
from the supply utility side [6]. Hence the reactive power
management is big issue and due to this the system power
factor gets affected. In short, it’s created additional Burdon
on the system [7]. The soft starter which contains the
thyristors with varying the firing angle is used for starting of
induction generators. In this case, because of power
electronics used as non-linear load, the harmonics are
generated [8]. The switching of induction generators from
small generator to big generators and vice-versa is occurred
in two fixed speed induction motor as induction generator.
This continues switching is responsible for generation of
harmonics [9]. Voltage dip/sag is occurred due to starting of
high capacity induction motors, overload, short circuit, etc.
The load which causes the significant variation in current,
especially reactive component can cause the voltage flicker.
Large capacitors are utilized for reactive power
compensation is responsible voltage swell and also sudden
switching off the large load. System faults are creating the
voltage swell [10]. The system power factor is affected due
to huge requirement of reactive power and this is because of
induction motor worked as induction generator. In short,
there is limitation for penetration of wind power to the grid
system because the system power quality is get affected and
it is not so economical [11].
C. Importance of Power Quality In Large Wind Farm
The electric power quality is defined as the degree of
any deviation from the nominal values the voltage
magnitude and frequency. Power quality has become very
important issue over the last decade. A key reason for
increasing the importance is rapid spread of the use of
equipments sensitive to power system disturbances and the
widespread use of non-linearity behaving power electronic
converters and equipments [12].The wind turbines can have
significant effect and increases the complexity of this
problem. Depending on the grid configuration and type of
wind turbines used, the different power quality problems are
arises. Due to increase the awareness of power quality
issues by the end users. The utility customers are becoming
better informed about such issues as interruptions, sag and
switching transient which are challenging the utilities to
improve quality of power developed [13]. In the wind farm,
the use of automated and integrated processes which are
more sensitive to the power quality problems. Due to poor
power quality of wind farm it affects the system in technical
and economic manner [14].
International Journal of Scientific Engineering and Technology Research
Volume.03, IssueNo.50, December-2014, Pages: 10141-10148
Power Quality in Grid Connected Wind Energy under Fixed and Varying Wind Speed
Inductance(L) pu 0.0125 0.039 H
III. SYSTEM DEVELOPMENT
A. Case Study
Parameters for PI section transmission line
Actual case study consists of 20 feeders and each feeder
having capacity of 30 wind turbines. The wind power
Parameters Positive Sequence Zero Sequence
density is illustrated in Fig. 4. Hence the total 600 wind
turbines are connected together with total installed capacity
Resistance(/Km) 0.1153 0.413 Ω
of 600 MW. The case study system is developed for the
wind farm. Out of 600 wind turbines, the wind farm consist
Inductance(mH/Km) 1.05 3.32 mH
of 52 numbers of wind turbines having capacity of each is
1.25MW &1.5 MW respectively Because of limitations to
Capacitance(μF/Km) 11.33 5.01 μF [7].
consider the total 600 wind turbines. The wind turbines are
connected through four feeders of 33 KV lines which are
The simulations are used to compute power quality of a
feeding the power to 220 KV Substation with certain
wind turbine i.e. active power, reactive power, maximum
kilometers of length of lines. The model is developed in the
power, V,I , etc. The applied computation method is
MATLAB/SIMULINK [17] as shown in Fig.5. The
reflecting the international power quality standards of wind
parameters used for the simulation of the above model of an
turbine IEC 61400-21 [20]. The system of home meter
Induction Generator based wind turbine are as follows:
reading is composed of control terminal in distance, GPRS
Induction Generator- fixed speed and variable speed type.
module and user metering module.
A 3-phase squirrel cage induction generator with a nominal
power of 1250w, 690V (f-f), 50 HZ is used for the above
system with the parameters shown below.
Induction generator parameters
IV. POWER QUALITY ANALYSIS
As per the modeling and simulation of a case study, the
power quality of the grid connected wind farm has been
investigated at different wind velocity [24] as shown in
Fig.6.
Parameter Unit
Stator Resistance R1=0.004843 Ω
Stator Leakage Reactance X1= 0.0513 Ω
Magnetizing Reactance Xh= 2.2633 Ω
Rotor Reactance (referred to Stator) X’=2 0.066 Ω
Rotor Resistance (referred to Stator) R’=2 0.004 Ω
Magnetizing Inductance=6.77h
Three Phase Transformer: A Yg/ . (D1) configuration of
three phase (2-winding) transformer is used with a nominal
power of 1MVA [7, 18]
Grid: A three-phase source with internal R-L impedance is
used to implement a grid which is connected to the wind
Generator through a T-Line & Transformer. The three phase
Short-circuit Level at base voltage of 33KV is 25MVA with
X/R ratio of 10 [7,19]
Load: A 3-Phase resistive load of 675KW/400 kvar is used
which is connected at the terminals of wind turbine. Simple
wind farm based on fixed speed wind turbines is connected
to a grid through a T-Line at Point of Common Connection
(PCC). WG transformer parameters
Parameters Primary Winding Secondary Winding
Voltage (f-f) rms (KV) 3KV 0.690V
Resistance(R) pu 0.0125 0.039 Ω
Fig.4. Network of case study consists of 600 wind
turbines in Maharashtra, India.
International Journal of Scientific Engineering and Technology Research
Volume.03, IssueNo.50, December-2014, Pages: 10141-10148
K.V.BHADANE, M.S.BALLAL, R.M.MOHARIL
Fig.6 MATLAB based heavy penetrated variable speed
wind energy system of a case study in .India [21].
A. At Constant Wind Speed IE Rated Wind Speed Of 12
M/Sec
At this stage of constant rated speed, power generation is
increased because of its rated speed, the maximum cut of
wind by the wind turbine. [25].The power generation is
stable at constant voltage level and requirement of reactive
power is less and maintained constant. This is illustrated in
Fig.7, 8.
Fig.5. Matlab/Simulink based heavy penetrated fixed
speed wind energy system of a case study in M.S. India.
Fig.7. PQ at constant speed with respect to time in X
axis.
International Journal of Scientific Engineering and Technology Research
Volume.03, IssueNo.50, December-2014, Pages: 10141-10148
Power Quality in Grid Connected Wind Energy under Fixed and Varying Wind Speed
Hence the power factor at this stage is Fig.8 rated wind
B. At Variable Wind Speed
speed 12 m/sec w r to time
If wind speed is change ie not const. and varies from
2,4,6,8,10,12,14,16,18,20,22,24 m/sec. In this stage , due to
variable nature and continuously increased of wind speed,
the requirement of reactive power is suddenly increased, the
voltage is collapse and due to the same, the system power
factor is decreased. In fact, at the middle rated wind speed,
the power generation is maximum but at initial and last end
position, the system power quality parameters are changed
& get affected. [26,28].Due to the variable nature of wind
speed, the said power quality issues are some things deviate
from their rated and get pollute the electric power system.
[29,30]. This is illustrated in Fig.9,10.
Fig.8. rated wind speed 12 m/sec w r to time [22] in X
axis.
improved.[27]. Initially the power generation and power
feeding to the grid system and their synchronization is very
critical. The starting of each waveform contains transient
condition and from this the electrical power system situation
is understood. In addition to the previous case , the nature of
the wind speed is also playing very important role .In this
case the two fixed speed is act as constant speed and hence
there effect on electric power system is moderate.
Fig.10. PQ at Gust wind speed With respect to time in x
axis.
The random or sudden change in wind speed is affecting
the voltage level, power factor, active power, etc. The
stabilization of variable wind power is big issue and more
concentration is required for the same.
C. At Gust Wind Speed
At this GUST & SUDDEN GUST wind speed, the effect
on voltage level is suddenly point out. The voltage is
suddenly collapsed and that required the online capacitor
bank to ON/OFF as per the online required reactive power
because at this stage reactive power requirement is
tremendous and falling of power factor with maximum
Fig.9. PQ at variable wind speed with respect to time in
X axis.
International Journal of Scientific Engineering and Technology Research
Volume.03, IssueNo.50, December-2014, Pages: 10141-10148
K.V.BHADANE, M.S.BALLAL, R.M.MOHARIL
power quality parameters are get affected. Here is point out
Sometimes we have to stop our power generation at this
the challenge to generate effective power by maintaining the
moment and chances of affecting the grid parameters and
all power quality issues because of this sudden change of
their smooth operation. If the wind speed is more than the
wind speed, it is very difficult to control the situation. This
25 m/sec , for safety point of view, we have to stop the wind
is illustrated in Fig.11,12.
generator along with their grid operation. This is also one
important issue. But ultimately there is wastage of available
wind velocity. In case of constant/fixed wind turbine, the
power quality is too good because they are maintained their
speed is constant even though their wind velocity is
variable.
Fig.11. simulation waveforms at Gust wind speed.
Fig.12. Simulations waveforms at variable wind speed
With respect to time in x axis.
In fixed speed turbine, torque is variable according
variable wind velocity by maintain the induction generator
speed is constant. but in case of variable wind speed
generator, the power quality parameters are get exploited.
Because of variable wind, the induction generator will
generate the power at variable nature and this fluctuating
nature of power will affect the power quality issues. Hence
the power quality nature of variable speed induction
generator is not too good as compared to fixed
speed.[30,31]. The MATLAB/SIMULINK based subsystem
of grid connected wind farm is analyzed and there
simulation waveform has been investigated.[32]. A sharp
increase is seen in reactive power requirements from grid
when machines are switched in simultaneously.[33,34]. A
higher current harmonics distortion is seen in the lines
which are lightly loaded. [35].Therefore there is necessity to
keep the load perfectly balanced. No significant change is
seen in frequency and voltage variations. Power factor also
drops to significantly with more number of grid connected
induction generators in the grid.[36]. When the capacity of
wind farm is increased or doubled, the power quality of
electric power system is get affected. The simulated results
are analyzed and validated with the real time results of case
study considered.
V. CONCLUSION
In this case, it has been observed that the increase in grid
connected wind generation is affected the power quality of
power system. The above discussion shows that whenever
the wind velocity is rated i.e. 12m/s in fixed speed wind
turbine the power generation is maximum & as per rated
capacity of the system. but whenever the wind velocity is
greater than rated wind system i.e.>12m/s, then proportional
with 12m/s only the maximum power is generated. Actually,
we expected more power from more than rated wind grid
but there is wastage of wind power by pitching of blade
angle of wind turbine .Here we satisfied only from 12 m/s
rated wind speed and their proportional power generation
but actually they could generate more than the same. Due to
increase the number of IG, the requirement of reactive
power is increase and power factor is decrease. In this case
the variable wind are produced more power as per more
wind velocity is available i.e optimization is obtained but
due to variable wind velocity there is a direct impact on
voltage, frequency of electric power system. Hence the
stabilization of voltage and frequency through the power
electronics is very critical issue. Due to use of power
International Journal of Scientific Engineering and Technology Research
Volume.03, IssueNo.50, December-2014, Pages: 10141-10148
Power Quality in Grid Connected Wind Energy under Fixed and Varying Wind Speed
electronics there is a direct impact on P.Q of power system.
[12] Kishor .v.Bhadane , Dr.M.S.Ballal ,.Dr.R.M.Moharil1,
Smoothing of variable output power is critical task has been
Power quality study and its analysis of grid Connected wind
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energy, ICEAR2013, international conference, IIT Bombay,
is very difficult to maintain all the grid code at the
Pawai Mumbai.
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VI. ACKNOWLEDGEMENTS
[17] Mr. Dipesh M Patel, Application of Static Compensator
The authors would like to thank Hon. Mr. Sunil Raisoni,
to improve the power Quality of Grid Connected Induction
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