International Journal for Research and Development in Engineering (IJRDE)
www.ijrde.com
ISSN: 2279-0500
Special Issue: pp- 270-277
Design of Wind Driven PMSG Based Z-Source Inverter
fed Three Phase load for Stand-Alone Applications
G.Arthiraja1, M. Ammal Dhanalakshmi2, Dr. M. Sasikumar3
1,2
PG Scholar, 3Professor,Head of the Department EEE
Jeppiaar Engineering College, Chennai.
Abstract—This paper presents the development of design,
modeling and simulation for variable speed wind turbine
coupled PMSG based ZSI are simulated through
computer software tool using MATLAB/SIMULINK. A
variable wind speed turbine coupled Permanent Magnet
Synchronous Generator with power electronics interface
is modeled for dynamic simulation analysis. The
MATLAB/SIMULINK is provided to implements the
wind driven PMSG based ZSI for stand-alone application
components models and equations. Controllable
Impedance source inverter strategies are intended for
capturing the maximum power under variable speed
operation and maintaining reactive power generation at a
pre-determined level for constant power factor control or
voltage regulation control. Control schemes for both wind
turbine and Permanent Magnet Synchronous Generator
are constructed by user-define function provided in the
simulation. Simulation case studies provide the variable
speed wind Permanent Magnet Synchronous Generator
dynamic performance for changes in different wind speed.
This control scheme of this model can be employed to
regulate the real power, reactive power, generated voltage
and generated speed at different wind speed in the power
system. Simulation results of this model can be validate
the real power, reactive power, generated voltage and
generated speed at different wind speeds in the power
system. Its simulations results are presented.
Index Terms—Wind turbine, variable speed, Permanent
Magnet Synchronous Generator, Impedance source
inverter, Power electronics interface, Reactive power
control.
generators including speed control. Many works have
been proposed for studying the behavior of PMSG
based wind turbine system connected to the load. Most
existing models widely use PWM technique for three
phase PWM inverter and the output of the inverter is
fed to load here Induction motor is acting as a load.
Wind electrical power system are recently getting lot of
attention, because they are cost competitive,
environmental clean and safe renewable power sources,
as compared fossil fuel and nuclear power generation
capability of design, modeling, simulating and
analyzing the dynamic performance of a variable speed
wind
energy
conversion
system
using
MATLAB/SIMULINK. The modeled system includes a
fixed-pitch type wind blades, a direct-drive Permanent
Magnet Synchronous Generator without a gear-box,
and a controllable power electronics system, which
consists of a six-diode rectifier and three phase inverter.
The entire schematic diagram of the modeled wind
generation is shown in Fig. 1. Models of the elements
and the system control scheme are proposed in the form
of mathematical equations and graphical control blocks
and implemented in MATLAB/SIMULINK [2]. The
simulation results demonstrate the modeling work
provide a reliable and useful simulation tool for
evaluating the dynamic performance of a variable speed
wind turbine integrated into power system.
I. INTRODUCTION
Wind energy generation equipment is most
often installed in remote, rural areas. Wind energy has
been the subject of much recent research and
development. In order to maximize the wind energy
capture, many new wind farms will employ variable
speed wind turbine. PMSG (Permanent Magnet
Synchronous Generator) is one of the components of
Variable speed wind turbine system. PMSG offers
several advantages when compared with fixed speed
Fig. 1 Schematic representation of modeled VSWT coupled
Permanent Magnet Permanent Magnet Synchronous Generator.
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International Journal for Research and Development in Engineering (IJRDE)
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ISSN: 2279-0500
Special Issue: pp- 270-277
II. MATLAB/SIMULINK BASED
MODELING
(2)
The variable speed wind turbine model consists of the
following components.
- Wind model
- Wind turbine and control
- Permanent Magnet Synchronous Generator
- Rectifier and inverter
(3)
(4)
Where λ = tip speed ratio
M = blade angular speed [mechanical rad/s]
R = blade radius [m]
VWIND = wind speed [m/s]
PM = mechanical power from wind blades [kW]
l = air density [kg/m3]
CP = power coefficient
TM = mechanical torque from wind blades [N-m]
Fig. 2 Components of a VSWT coupled Permanent Magnet
Synchronous Generator MATLAB/SIMULINK simulation model.
Fig.2 depicts the component blocks Components of a
VSWT coupled Permanent Magnet Synchronous
Generator Matlab/Simulink simulation model. For
modeling the shaft and Permanent Magnet Synchronous
Generator, models provided by the Matlab/Simulink are
used, and models of the wind speed, the wind turbine,
power electronics block and the control block are built
into the Matlab/Simulink.
The mechanical torque obtained from equation (4)
enters into the input torque to the Permanent Magnet
Synchronous Generator, and is driving the generator. CP
may be expressed as a function of the tip speed ratio
(TSR) λ given by equation (2) [5].
(5)
Where
A. Wind Model
A wind model selected for this study is a fourcomponent Mode l [3], and can be described by
equation (1).
VWIND = VBASE + VGUST + VRAMP + VNOISE
(1)
Where,
VBASE = base wind speed [m/s]
VGUST = gust wind component [m/s]
VRAMP = ramp wind component [m/s]
VNOISE = noise wind component [m/s]
The base component is a constant speed and wind gust
component can be usually expressed as a sine or cosine
wave function [4]. In this simulation, wind speed can be
representing the constant block in Matlab/Simulink.
B. Wind Turbine
The wind turbine is described by the following equation
(2), (3) and (4)
β
is the blade pitch angle. For a fixed pitch
type the value of
β
is set to a constant value.
C. Permanent Magnet Synchronous Generator
The Matlab/Simulink provides a fully developed
synchronous
Permanent
Magnet
Synchronous
Generator model, which is based on generalized
machine theory [2] and with this model both subtransient and transient behavior can be examined. It is
considered that the Permanent Magnet Synchronous
Generator is equipped with an exciter identical to IEEE
type 1 model [6]. The exciter plays a role of meeting
the dc link voltage requirement. Since the Permanent
Magnet Synchronous Generator is a direct drive type
with low speed and a high number of poles, the wind
turbine and the generator are rotating at the same
mechanical speed via the same shaft. Therefore, shaft
dynamics can be characterized by a swing equation on a
single mass rotating shown in equation (6). The shaft
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International Journal for Research and Development in Engineering (IJRDE)
www.ijrde.com
ISSN: 2279-0500
Special Issue: pp- 270-277
dynamics and the rotating mass can be represented by
multi-mass torsional shaft model of Matlab/Simulink,
which can be easily interfaced with the synchronous
machine model
Impedance source inverter it convert into ac and
inverter output is given to voltage load system.
(6)
Where
JM = a single rotating inertia [kg-m2]
TE = electric torque produced by generator [N-m]
D = damping [J-s/rad]
In variable speed operation, the rotating speed of the
wind generator is not consistent with the electrical
synchronous speed of the electric network and
generally much slower than the speed. The electrical
base frequency of the machine in the built-in models
must be set to a value corresponding to the rated
mechanical speed of the wind turbine specified by a
manufacturer or a designer. Equation (7) and (8) give
the value for the electrical base speed of the
synchronous machine wB..
(7)
(8)
Where
fB = electrical base frequency of the generator [Hz]
P = number of poles
RPMTUR = mechanical rated speed of the turbine [rpm]
Fig. 3 Rectifier and inverter model.
The ZSI is a voltage harmonic source in the point view
of ac system and a harmonic filter need be placed
appropriately to reduce the voltage harmonics it
generates [8]. A L-C harmonic filter consisting of a
series interconnection inductor and a parallel capacitor
is located at the ZSI terminal. Fig. 4 shows a rectifier
and ZSI system model that has been implemented in
Matlab/Simulink. The six diodes rectifier converts ac
power generated by the wind generator into dc power in
an uncontrollable way and so control has to be
implemented by the power electronics inverter.
Current-controlled ZSIs can generate an ac current
which follows a desired reference waveform so can
transfer the captured real power along with controllable
reactive power. For the modeling study, DQ control
method that is widely used for ZSI current control is
employed. Variables in the ABC three phase
coordinates may be transformed into those in the d-q
reference frame rotating at synchronous speed by the
rotational d-q transformation matrix [2]. In the threephase balanced system, the instantaneous active and
reactive power outputs, P and Q, of the wind turbine are
described by equation (9).
D. Power Electronics Control
Several types of power electronics interfaces have been
investigated [7]. In this study, system is interfaced with
a six diode rectifier and three phase Impedance source
inverter which is less expensive than others and
commonly put into industrial use, has been modeled for
AC-DC–AC conversion. . Fig. 3 shows a rectifier
model and inverter model. The six diodes rectifier
converts ac power generated by the wind generator into
dc power in an uncontrollable way and it is given to
(9)
Where
VD = d-axis voltage at the wind turbine
VQ = q-axis voltage at the wind turbine
ID = d-axis current at the wind turbine
IQ = q-axis current at the wind turbine.
Here, VQ is identical to the magnitude of the
instantaneous voltage at the wind generation system
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International Journal for Research and Development in Engineering (IJRDE)
www.ijrde.com
ISSN: 2279-0500
Special Issue: pp- 270-277
and VD is zero in the rotating d-q coordinates, so the
equation (9) may be contracted into simpler equation
(10).
(10)
where |VO| is the instantaneous voltage magnitude of
the wind turbine system. Since the voltage remains at a
level of the load AC voltage and the voltage variation is
very small compared to changes in the magnitude of IQ
and ID, P and Q are mainly subject to the d-axis current
and q-axis current respectively. Fig. 4 illustrates DQ
control decouples real and reactive components and
enables real power and reactive power to be separately
controlled by specifying the respective reference values
of PREF and QREF for the both power outputs and
independently adjusting the magnitude of the d-axis
current IQ and that of the q-axis current ID. The
reference values PREF and QREF of the wind
generation are specified by what ZSI’s control
strategies are taken for real and reactive power output.
The firing signals are generated by the sine pulse width
modulation (SPWM) technique. The desired current
vector IABC_REF and the actual output current vector
IABC_WT of the wind system are compared and
The maximum aerodynamic power available from wind
energy can be described by equation (11) . This simply
means that the maximum power may be achieved by
varying the turbine speed with varying wind speed such
that at all times it is on the track of the maximum power
curve [1], [9]. One way of enabling the maximum
power capture is to specify the reference value of real
power for the inverter control as the available
maximum power multiplied by the inverter efficiency,
as shown in equation (12).
(11)
(12)
Where CP MAX= the maximum power coefficient
λ OPT = value of λ where CP MAX= CP ( λ OPT)
η = electrical loss in generator and inverter
F. Reactive Power Control
Various control modes can be used for determining the
amount of reactive compensation to provide. Possible
control modes include power factor, Kvar, current and
voltage. Constant power factor mode and voltage
regulation mode are implemented in this analysis. In
constant power factor control (PFC) mode, the
reference value of the reactive power of the wind
turbine, QREF, may be specified by equation (13).
(13)
Where PF is power factor and PREF is the reference
value of real power output of the VSWT.
Fig. 4 Current control scheme of a Impedance source inverter
The error signal vector IERR is compared with a
triangle waveform vector to create the switching
signals.
E. Capturing the maximum power
In voltage regulation (VR) mode, reactive
power compensation is controlled in such a manner that
the voltage magnitude of the VSWT-connected bus
being kept constant at a specified level. The reference
magnitude of the voltage to be regulated must be set as
the nominal voltage of the AC load where the wind
turbine is considered as being interconnected. Whether
the mode controls constant power factor or voltage, the
reactive power capability of a VSWT is limited. Such a
limitation is required to be considered in the modeling
Methods Enriching Power and Energy Development (MEPED) 2014
273 | P a g e
International Journal for Research and Development in Engineering (IJRDE)
www.ijrde.com
ISSN: 2279-0500
Special Issue: pp- 270-277
study. The reactive capability limits of the wind turbine
used in this study are determined by MVA rating of the
inverter which may be described by equation (14).
Continuous
powergui
signalrms
(14)
Where QLIMITS, PINV and SINV are the reactive power limits,
thereal power output and MVA rating of the inverter
respectively.
RMS
signalrms
RMS 5
Display 8
Scope 6
+
v
-
M4
Scope 2
g
D
P6
M3
S
Subsystem
Conn1
P4
S
M1
g
D
g
D
P2
Volt1
S
L2
III. MATLAB/SIMULINK STUDIES OF
PROPOSED SYSTEM
Display
Tm
c1
A
c2
m
B
+
v
-
Conn2
C
Asynchronous Machine
SI Units
Out1
p5
M7
Scope 11
Gain
P3
g
D
g
D
P5
S
L1
-K-
<Rotor speed (wm)>
<Electromagnetic torque Te (N*m)>
g
D
M5
Scope 10
S
S
M6
Fig.6.Simulink Model of PMSG based Three phase ZSI fed Induction
motor load.
Fig. 5 Matlab/Simulink model of VSWT coupled Permanent Magnet
Synchronous Generator interfaced with power electronics
The proposed model is implemented into
Matlab/Simulink computer software tool and simulated
for analyzing the dynamic behaviors of a wind turbine
with varying wind conditions. Fig. 5 shows a VSWT
based PMSG model implemented in Matlab/Simulink.
It indicates wind turbine model, Permanent Magnet
Synchronous Generator model, power electronics
model with power load system and control blocks. The
generated voltage of the Permanent Magnet
Synchronous Generator is step up the voltage using step
up transformer (0.6kv/2.5k). The step up voltage is
given to the power electronics interface of the load
system which consists of rectifier and inverter. The
inverter output is again step up to 130kv using step up
transformer. The detailed explanation of each
component of the proposed system was already
discussed in section II.
The above simulink model describes that the
generated voltage is fed with the impedance source
network and the inverter output voltage is given to the
three phase induction motor. Here the impedance
source inverter does both buck and boost operation. The
inductor and capacitances design is chosen depend
upon the application. The induction motor rotor speed
and torque is observed.
IV. SIMULATION RESULTS ANALYSIS OF
VSWT BASED PMSG.
The rating capacity is chosen to be 1.5 MVA and real
power 1.5 MW. The rated speed of the rotor is chosen
to be 40 rpm. The rated wind speed is 8 m/s. the cut-in
and cut-out speeds are 4 m/s and 16 m/s respectively.
The switching frequency of the load interface inverter is
1.040 kHz. The capacitor value of load interface
rectifier is 2500uF and d.c link voltage is 2.5 kv. The
generated voltage of Permanent Magnet Synchronous
Generator is 0.6kv. The transformer rating of load
connected side is 2.5k/130kv. The p.u voltage
magnitude of primary of the transformer is 0.99 p.u.
The maximum value of Cp is 1.2. the proposed system
operate the unity power factor control.
Methods Enriching Power and Energy Development (MEPED) 2014
274 | P a g e
International Journal for Research and Development in Engineering (IJRDE)
www.ijrde.com
ISSN: 2279-0500
Special Issue: pp- 270-277
Fig.10.Simulation results of VSWT based PMSG generated speed.
Fig.7.Simulation results of VSWT based PMSG generator voltage.
V. SIMULATION RESULTS ANALYSIS OF
ZSI FED INDUCTION MOTOR LOAD
The Impedance source inverters (ZSI) are used to
regulate the speed of three-phase squirrel cage motors
by changes the frequency and the voltage and consist of
input rectifier, DC link and output converter. They are
available for low voltage range and medium voltage
range. The value of inductance L1 and L2 is chosen
depend upon the application. In this project the value is
chosen for inductor is L1 = L2 = 2MH and the value for
capacitor C1 = C2 = 2200µf. the operating frequency is
10Khz. The parameters of three phase induction motor
load are 5HP horse power, voltage is 420V, current is
8Amps, frequency is 60Hz and rotor type is squirrel
cage.
Fig.8. Simulation results of VSWT based PMSG generated three
phase current
Fig.11. simulation results of three phase ZSI output
Voltage.
The fig.11. shows the three phase ZSI output voltage of
the three phase impedance source inverter fed
induction motor. The output voltage value is 380V AC
Fig.9. Simulation results of VSWT based PMSG generated three
(peak voltage). The fig.12. shows the simulation results
phase voltage.
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International Journal for Research and Development in Engineering (IJRDE)
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ISSN: 2279-0500
Special Issue: pp- 270-277
of speed of Induction motor. The rotating speed of
induction motor is 1500RPM which is achieved by the
output voltage of an impedance source inverter. The
fig.13. shows the simulation results of generated torque
of an Induction motor. The generated electromagnetic
torque for three phase impedance source inverter fed
induction motor achieved is 40 Tm. The fig.14. shows
the simulation results of switching pulses of ZSI. The
value of pulse amplitude is 1V and the value of pulse
width is 33.3% of period, and the time period is 0.02
sec.
Fig.14. simulation results of switching pulses of ZSI.
VI. CONCLUSIONS
Fig.12.simulation results of speed of Induction motor.
Fig.13. simulation results of generated torque of an Induction motor.
A dynamic model of a variable speed wind generation
with power electronic interface was proposed for
computer software tool simulation study and
implemented in Matlab/Simulink. Component models
of a VSWT and its control scheme have been built by
using matlab function block and control block provided
in the software. A wind model was integrated into the
modeling to see the wind impact. Dynamic responses of
the wind turbine to varying wind speeds and under
different reactive control schemes were simulated and
analyzed based on the modeled system. In the view
point of electric utilities, load interface of intermittent
generation sources such as wind turbines has been a
challenge that can cause lower power quality in power
systems. So comprehensive impact studies are
absolutely necessary before wind turbines being added
to real networks. Also, users who intend to install wind
turbines in networks must ensure their systems meet the
requirements for load connection. Therefore, the work
done in this study provides a reliable tool for evaluating
the performance of variable speed wind turbines and
their impacts on power networks in terms of dynamic
behaviors as a preliminary analysis for their actual
integrations and operations.
VII. REFERNCES
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and AliYazdianVarjani, “ A new variable speed wind
energy conversion system Using permanent magnet
synchoronus generator and Z-source inverter”. IEEE
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September 2009.
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276 | P a g e
International Journal for Research and Development in Engineering (IJRDE)
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ISSN: 2279-0500
Special Issue: pp- 270-277
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