Recent Advances in Electrical and Computer Engineering
General study of
self excited induction generator used in isolated
renewable energy conversion source
Mohamed. Barara, Ahmed. Abbou, Mohamed. Akherraz , Abderrahim.Bennassar and Mohamed larbi.
ELhafyani

The objective of this work is divided into two parts: in the first
part we present the experimental curve of variation speed and
capacitance with the SIEG connected to load and no load in
order to show the behavior of our machine, The relationship
between magnetizing inductance (Lm )and phase voltage for
induction machine was obtained experimentally, and in the
second part we are more interested in the control of the DC bus
voltage in order to provide an essentially constant terminal DC
voltage in spite of the presence of disturbances such as step
change in rotor speed and application of sudden AC load for
supplied an isolated DC load ,the simulation results are given
to demonstrate the effectiveness of the proposed method.
Abstract—In this paper we have present a general study of self
excited induction generator used in isolated renewable energy
conversion source ,the behavior of generated voltage under variable
load ,rotor speed and excitation capacitance is presented ,also we
have proposed a robust controller suitable in order to control the
terminal DC voltage under different speed and AC load conditions
for supplied an isolated DC load, the experimental characteristic
curve of the generator and simulation result of proposed control
scheme are presented.
Keywords—Renewable
Generator, DC link control.
energy,
Self-excited
induction
II. SYSTEM CONFIGURATION WITHOUT CONTROL SCHEME
I. INTRODUCTION
T
he energy demand around the world increases the great
opposition facing the nuclear energy in some countries
have spur researchers attentions for renewable energy.
The self excited induction generator is a very popular machine
used in isolated areas to generate electrical energy because of
its low price, mechanical simplicity, robust structure.
When capacitors are connected across the stator terminals of
an induction machine, and driven at a given speed, the voltage
will be induced from a remnant magnetic flux in the core.
The proposed system starts excitation process from
capacitors bank which are connected across the stator
terminals of an induction machine driven by unregulated
prime mover (DC motor in laboratory test) and supplying AC
load
The induced emf and current in the stator windings will
continue to rise until steady state is attained. This behavior is
influenced by the Magnetic saturation of the machine. At this
operating point the voltage and current will continue to
oscillate at a given peak value and frequency[6] , However, its
major disadvantage is the inability to control the terminal
voltage under variable load and speed conditions
Fig.1: self excited induction generator system
Mohamed . Barara , Ahmed abbou ,Mohammed Akherraz and abderrahim
bennassar are with the Electrical Department Laboratory of Power
Electronic and Control Mohamed V University , Mohammadia School of
Engineering Agdal Rabat Morocco :Mohamed-barara@hotmail.fr.
When the induction machine when used for motoring
application, it is important to determine the magnetizing
inductance at rated voltage. In the SEIG, the variation of
Mohamed,larbi Elhafyani is with Université Mohamed I, EST,LGEM. 473,
60000 Oujda, Morocco: m_elhafyani@yahoo.fr
ISBN: 978-1-61804-228-6
143
Recent Advances in Electrical and Computer Engineering
Where:
magnetizing inductance Lm is the main factor in the dynamics
of voltage build up and stabilization[3].
The relationship between magnetizing inductance (Lm) and
phase voltage for induction machine was obtained
experimentally as show in Fig 3:
𝑖𝑞𝑠
𝑖𝑠𝑑
𝐼=
𝑖𝑞𝑟
𝑖𝑑𝑟
𝐿𝑚 𝐾𝑞 − 𝐿𝑟 𝑉𝑐𝑞
𝐿𝑚 𝐾𝑑 − 𝐿𝑟 𝑉𝑐𝑑
B=
𝐿𝑚 𝑉𝑐𝑞 − 𝐿𝑠 𝐾𝑞
𝐿𝑚 𝑉𝑐𝑑 − 𝐿𝑠 𝐾𝑑
−𝐿𝑟 𝑅𝑠 − 𝐿2𝑚 𝑤𝑟
1 𝐿2𝑚 𝑤𝑟
−𝐿𝑠 𝑅𝑠
𝐴=
𝐿 𝐿𝑚 𝑅𝑠
𝐿𝑠 𝑤𝑟 𝐿𝑚
−𝐿𝑠 𝑤𝑟 𝐿𝑟
𝐿𝑚 𝑅𝑠
the magnetizing inductance is calculated by driving the
induction machine at synchronous speed and taking
measurements when the applied voltage was varied from zero
to 100% of the rated voltage.
𝐿𝑚 𝑅𝑟 − 𝐿𝑚 𝑤𝑟 𝐿𝑟
𝐿𝑚 𝑤𝑟 𝐿𝑟
𝐿𝑚 𝑅𝑟
−𝐿𝑠 𝑅𝑟 − 𝐿𝑠 𝑤𝑟 𝐿𝑟
− 𝐿𝑠 𝑤𝑟 𝐿𝑟
−𝐿𝑠 𝑅𝑟
experimental
0.33
(1)
magnetizing inductance(H)
0.31
0.29
L= 𝐿𝑟 𝐿𝑠 − 𝐿2𝑚
Where
0.27
Modeling of The excitation system model:
0.25
𝑉𝑐𝑞 = 1/𝑐
0.23
0.21
0.19

𝑉𝑐𝑑 = 1/𝑐
0.17
30
60
90
120 150
voltage (V)
180
210
240
Fig.2: Variation of magnetizing inductance with phase voltage
(2)
(𝑖𝑑𝑠 _ 𝑖𝑟𝑙𝑑 _𝑖𝑟𝑑 ) 𝑑𝑡
(3)
The instantaneous amplitude of the magnetizing current of
the SEIG, which is computed as:
The variation of magnetizing inductance, increases until it
reaches a peak value and decreases until it attains saturated
value as shown n Fig.2
2
2
𝑖𝑚 = 𝑠𝑞𝑟𝑡 ((𝑖𝑞𝑠 + 𝑖𝑞𝑟 ) + (𝑖𝑑𝑠 +𝑖𝑑𝑟 ) )
(4)
B. Experimental results of variation speed and
capacitance while the SIEG is connected to load and no load
A. Self Excited induction Generator
The state-space form of the induction generator in the q-d
synchronously rotating reference frame is given by[3]:
In the laboratory test rig, a three phase squirrel cage
induction machine was coupled to a DC motor operating as the
prime mover.
The experimental setup includes the variation of rotor speed
with capacitance bank respectively with no load and load, in
this investigation for have a fixed generated voltage of 400V
and 250 V as show in Fig.4 and Fig.5 respectively.
Fig.3: d-q model of SEIG at no load
PI = 𝐴𝐼 + 𝐵
ISBN: 978-1-61804-228-6
_ 𝑖𝑟𝑙𝑞 _ 𝑖𝑟𝑞 ) 𝑑𝑡
Where ir d , ir q are input currents of three-phase diode
bridge rectifier and 𝑖𝑟𝑙𝑞 , 𝑖𝑟𝑙𝑑 are the AC load current
0.15
0

(𝑖𝑞𝑠
144
speed(rpm)
Recent Advances in Electrical and Computer Engineering
1
0.5
1800
1760
1720
1680
1640
1600
1560
1520
1480
1440
1400
1360
1320
1280
1240
1200
must provide a control system capable of controlling the
output voltage for a good functioning .
No load
320 Ohm
160 Ohm
106.66 Ohm
0
20
40
60
0
80
100
capacitance(µF)
120
140
160
Recently the application of semiconductor devices, controlled
converter circuits, and control algorithms has resulted in
suitable and good regulating schemes for SIEG.In literature
many researchers have proposed numerous control for
regulating the terminal voltage[2 4 5 7 10 15 17]. Since this
paper present a simple and uncomplicated control scheme.
The motivation of this work is to study the feasibility of this
system by providing a detailed transient and steady-state
analysis in order to keeps the DC bus voltage at a constant
value even the rotor speed change and application of sudden
AC load. Detailed Matlab/Simulink-based simulation studies
are carried out to demonstrate the effectiveness of the scheme.
180
speed(rpm)
Fig.4: Variation of capacitance with different speed and
loads for constant terminal voltage of 400V
1
0.5
0
1180
1160
1140
1120
1100
1080
1060
1040
1020
1000
980
960
940
920
900
60
No load
320 Ohm
160 Ohm
106.66 Ohm
Fig.6: Proposed control of self excited induction generator
70
80
90
100 110 120
Cpacitance (µF)
130
140
150
160
The variable output voltage from the generator is first rectified
using diode bridge rectifier and then controlled by dc-dc buck
converter as shown in Fig 6.
Fig.5 :Variation of capacitance with different speed and
loads for constant terminal voltage of 250V
From these figure is well observed
that the variation of
output voltage is affected
by the application of Load,
variation of speed and excitation capacitance.
A. Three Phase Diode Rectifier
Three phase diode bridge rectifier is used to convert
variable magnitude, variable frequency voltage at the
induction generator terminal into DC voltage the circuit
consists of 6 diodes, a top group of 3 diodes and a bottom
group of 3 diodes
When the generator runs at the speed of 1087 rpm, the
necessary value of capacitance will be at 80 µF for no load
connected ,in order to have a fixed terminal voltage of 250V.
In the same condition with load connected of 320 ohm the
rotor speed will be increased at 1105 rpm for maintain the
same value of the terminal voltage ,Similar analysis will be
followed to track different value of speed ,capacitance with
load and no load as summarized in Fig.5,Fig.4.
III. PROPOSED CONTROL SCHEME OF SIEG
For proper operation of the use for this machine in standalone
renewable energy Source, cases (Wind-, micro hydro) we
ISBN: 978-1-61804-228-6
145
Recent Advances in Electrical and Computer Engineering
Fig. 7.Three-phase diode bridge rectifier
B. Buck Converter
The DC-DC converter inputs are generally unregulated DC
voltage input and the required outputs should be a constant or
fixed voltage. Application of a voltage regulator is that it
should maintains a constant or fixed output voltage under
variation of input voltage.
.
Fig. 9.Block diagram of control scheme
IV. SIMULATION RESULTS AND DISCUSSION
MATLAB/Simulink® modelling is used to observe the
proposed control. The residual magnetism in the machine is
taken into account in simulation process without which it is not
possible for the generator to self excite.
The induction generator is rated at 3 kw and the system
parameters approximation are given in Table I.
The SIEG is tested during 7 s, when the system is subjected
to step change in the rotor speed and sudden application AC
load. The proposed system starts excitation process from AC
capacitors bank of 100µF and variation rotor speed between
1500rpm, 1096rpm to 1296rpm, respectively at 0s,3s,4s, as
shown in Fig.3
Fig. 8.Buck converter circuit
The mathematical model of the buck type dc-dc converter with
the control input d are given by following equation :
di L
dt
dVc
dt
=
Vd
=
iL
L
C
(d) −
−
Vc
Vc
R∗C
in his section, for investigate the response of the system with
sudden application of AC load the generator is initially
excited at no-load and suddenly a AC load of Rac=80 Ω
applied at t = 6sec
(6)
L
(7)
170
Where R= resistive load
160
Current-mode control is a dual loop control method, including
current and voltage control loops[8]. In this method, the error
signal between output voltage Vdc and reference voltage
Vdc_ref is used to generate reference current iref. Then, this
reference current is compared with sensed inductor current iL
to control the duty cycle As show in Figure 9
150
rotor speed
C. Control scheme
140
130
120
110
100
0
1
2
3
4
t(s)
Fig.10: Rotor speed (rad/s)
ISBN: 978-1-61804-228-6
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5
6
7
Recent Advances in Electrical and Computer Engineering
4
300
3
input currents of rectifier
stator voltage
200
100
0
-100
2
1
0
-1
-2
-3
-200
-4
-300
0
1
2
3
4
5
6
t(s)
2
3
4
5
6
7
Fig.14: input current of three phases rectifiers
Any variation in rotor speed of the SEIG is directly
indicated by the variation in the terminal voltage and current of
the generator as shown in Fig.11, Fig.12
15
After connecting the AC load at t = 6s, we see the
generated current increases during this time and then decreases
to its initial value then the terminal voltage dropped ,the load
current is created as shown in Fig.12, Fig.11 Fig.813
respectively.
10
5
stator current
1
t(s)
Fig.11: generate voltage of the SIEG
0
.
500
-10
400
0
1
2
3
4
5
6
7
t(s)
Fig.12:generate current of the SIEG
4
3
uncontrolled DC voltaget
-5
-15
0
7
300
200
100
AC load current
2
0
1
0
1
2
3
4
5
t(s)
0
Fig.15: Uncontrolled DC link voltage
-1
-2
-3
-4
0
1
2
3
4
5
6
7
t(s)
Fig .13: AC load current
ISBN: 978-1-61804-228-6
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6
7
Recent Advances in Electrical and Computer Engineering
350
300
DC voltage
250
200
150
100
50
0
0
1
2
3
4
5
6
7
t(s)
Fig.16: controlled DC link voltage
The value of the DC bus voltage is maintained at constant
value of 300 V even if the rotor speed changes at 3s , 4s and
application of AC load at 6s . The controller provides a rapid
and accurate response for the reference as shown in Fig.16 it
has been demonstrated that the system is able to feed an
isolated DC loads with a robust regulated voltage.
ACKNOWLEDGMENT
This work has been developed within the framework of the
Activities of the Project: "analysis, application and advanced
control of self excited induction generator used in isolated
renewable energy source» and has been carried out for the
Electrical Department Laboratory of Power Electronic and
Control Mohamed V University , Mohammadia School of
Engineering Agdal Rabat Morocco The authors wish to place
on record its deep sense of gratitude to Mr driss Deppagh and
Mr Mohamed moutchou, of, for their valuable assistance in
this work .
V. CONCLUSION
This paper presents a general studies of SIEG include
dynamic behavior ,the variation of magnetizing inductance
are considered, also we propose a simple and uncomplicated
control scheme in order to provide a regulated DC voltage
The controller has been tested for different transient conditions
such as, sudden application for both three-phase loads , and
variable rotor speed. The simulated results show a good
performance and efficiency of the global SEIG conversion
system.
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APPENDIX
Table I: Generator and buck converter Parameters
designation
[3]
value
Rs
2.2Ω
Rr
2.68Ω
ls , lr
12 mH
C
600µF
L
50mH
Rdc
120 Ω
[4]
[5]
[6]
ISBN: 978-1-61804-228-6
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