F6 - 2 2011 International Conference on Electrical Engineering and Informatics

17-19 July 2011, Bandung, Indonesia

Design of Electronic Load Controller for a Self

Excited Induction Generator Using Fuzzy Logic
Method Based Microcontroller
Yahya Sofian#1*, Munawar Iyas*2
#
Department of Electrical Engineering,Bandung State Polytechnic, Bandung, Indonesia
*
School of Electrical Engineering & Informatics, Bandung Institute of Technology, Bandung, Indonesia
1
sofianyahya@polban.ac.id
2
iyas@lskk.ee.itb.ac.id
Abstract— The self-excited induction generators (SEIGs) are consider economical, robust and require minimal maintenance
considered to be well suited for generating electricity by means of and are likely to be managed by un-skilled operators, because
conventional energy sources and for supplying electrical energy they are usually installed remote from any maintenance
in remote and rural areas. Induction generators have many facilities.
advantages such as cost, reduced maintenance, rugged, and The squirrel cage induction machine with capacitive self-
simple construction, brushless rotor (squirrel cage). A three- excitation, known as self-excited induction generators (SEIGs)
phase induction generator can be operated on a C-2C connection are considered as an alternative to the well-developed
for supplying single phase loads. The main disadvantage of SEIG
synchronous generators. Induction generators are widely used
has is that it poor voltage regulation, and its value depends on
the prime mover speed, capacitance, load current and power for micro-hydro powered electric generation, especially in
factor of the load. The electronic load controller (ELC) can be remote and isolated areas, because they do not need an
used for maintaining constant voltage and frequency of SEIG external power supply to produce the excitation magnetic field.
with variable consumer load driven by constant primer mover. Furthermore, induction generators have more advantages such
This paper presents the design and implementation of a digitally as low cost, reduced maintenance, rugged and simple
controlled ELC using fuzzy logic method based microcontroller construction, brushless rotor (squirrel cage), good over-speed
for an SEIG feeding single-phase load. The ELC consist of a capability, and inherent protrction against short circuit [4].
rectifier, MOSFET as a chopper switch, ATMega32 micro- Keeping the voltage and frequency of SEIG constant in spite
controller, voltage sensor, opto-coupler, and resistive dump load
of the change in load, can be done by regulating the
in which power consumption was varied through the duty cycle
of the chopper. However an ELC consist of electronics system, in capacitance value or by controlling the speed of the prime
general, has complex nonlinear model with parameter variation movers. One alternative for supplying single phase loads
problem, and the control need to be very fast. The fuzzy logic widely used in remote and rural areas is using three-phase
based controller gives nonlinear control with fast response and induction generator. It is used to supply the single phase loads
virtually no overshoot. The proposed ELC has been tested by by using the connection C-2C. If the induction generator is
step change in the consumer load. The simulated perfomance of used to supply single phase with a constant load, the ELC
the controller is supplmented by experimental results. could be applied to maintain constant power output SEIG, for
this purpose the dump load must be connected in parallel with
Keywords— Electronic load controller (ELC), Self excited the consumer load so that the total power load is generated by
induction generator (SEIG), Fuzzy logic, Microcontroller the SEIG is constant. The amount of power that flowing into
the dump load is controlled by the electronic load controller
I. INTRODUCTION
(ELC) [1-6].
Recently, most of the electricity is generated making use of Various controllers for SEIG have been reported in literature.
fossil fuels (coal, oil, and natural gas). These fossil fuels are T.Chandra Sekhar et al. [9] proposed different voltage
limited and will run out in the future. Fossil fuels are a non- regulation schemes such as power electronic controller,
renewable energy source and they have continuously degraded electronic load controller and magnetic amplifier (saturable
the environmental conditions. In such a situation researchers core reactor). Bhim Singh et al [7] has been developed an
are forced to make effort to make use of new and renewable ELC for two winding single phase SEIG. Juan M.Ramirez et
energy sources in an economical and safe way. Among al [3] proposed an ELC with antiparallel insulated-gate bipolar
electrical generation using the renewable sources, micro- transistor (IGBT) switches are used to control dump load
hydro generation systems are an attractive alternative for connection and disconnection. D.K.Palwalia et al [2] present
remote locations where an electrical grid is not available. design and implementation of Digital Signal Processor (DSP)
Furthermore, it is important to that such systems must be based induction generator controller (IGC) for single phase

978-1-4577-0752-0/11/$26.00 ©2011 IEEE

SEIG. Sarsing Gao et al [1] present analysis and the design of
a microcontroller (PIC 18F252) based SEIG-ELC. A PI
controller is used to provide proper control without steady
state errors or instability.
This paper present the design and implementation of
Electronic Load Controller (ELC) for a Self Excited Induction
Generator (SEIG). The SEIG using three phase induction
generator as a single phase SEIG feeding single phase loads.
The control technique to be used fuzzy based ATMega32
Fig. 1 Three-phase SEIG with ELC feeding single phase load
microcontroller. The mains reasons of using fuzzy logic
controller to gives nonlinear control with fast response and
virtually no overshoot. The proposed ELC will be tested under
single phase resistive load.

II. SYSTEM DESCRIPTION

The proposed as schematic diagram of ELC for SEIG using
fuzzy logic method based microcontroller is shown in Fig 1
and Fig 2 for supplying single phase loads. The ELC is
designed to operate an a delta connected three phase induction
machine with specification as follow 0.18 kW, 220 V, 1,67 A,
4 pole, 50 Hz, 1370 rpm. Two capacitors are connected C-2C
as shown in Fig 1, for facilities the single phase load of a three
phase induction generator. The ELC consists of a uncontrolled
rectifier with parallel-resonant filters, MOSFET, ATMega32 Fig.2 ELC consists of uncontrolled rectifier
microcontroller, voltage sensor, opto-coupler, and a series
dump load (resistor). The proposed uncontrolled single phase The AC voltage from SEIG terminal rectified by means of an
diode rectifier is shown in Fig 2, in which conversion of ac uncontrolled rectifier with parallel-resonant filter. The dump
power (from generator) to dc power. This rectifier with load is designed so that when the duty cycle of the switch is
parallel-resonant filter topology yields increased input power unity, an operating power of 0.12 kW diverted to dump load.
factor and power density as compared with the conventional The terminal voltage for feedback is sensed with voltage
diode rectifier [14]. A MOSFET is used as a chopper switch. transducer to achieve a DC value proportional to SEIG output
When gate pulse to MOSFET is high, the current flows voltage. This analog voltage is given to ADC input of the
through the dump load and the power is consumed. A fuzzy ATMega32 microcontroller. The sensed voltage is compared
logic controller was applied to ELC, the controller regulates with reference, which is taken as proportional to the rated
the pulse width or duty cycle of chopper is decided by terminal voltage of the SEIG and may be altered when
difference of power generation to consumer load. The required. The microcontroller is programmed in such a way
ATMega32 microcontroller is used for generation of suitable that the feedback voltage is compared with a reference value
pulse width in accordance with consumer load. Since the of 220 V for every 50 milliseconds and an error signal is
speed and hence the frequency is constant, the output power generated. A fuzzy logic controller is used to gives nonlinear
remains constant when the voltage is maintained at the rated control with fast response and virtually no overshoot. The
value. signal of PWM is fed to opto-coupler, which function as
insulation of the power circuit and the control circuit. The
III. IMPLEMENTATION signal drives the MOSFET switch an appropiate duty cycle.
The SEIG is connected in delta connection and excitation The design aspects of single phase ELC are described in
capacitors are connected in a C-2C configuration. Excitation subsequent sections.
capacitance has to provide required voltage on load at the
operating speed for the given induction machine operating as A. Rectifier Circuit
a SEIG such that it generates rated terminal voltage at full
The diode rectifier is designed using a single phase bridge
load. The output power of the SEIG is held constant at varying
parallel-resonant filter, the rectifier which will be designed
consumers loads. In order to keep SEIG output power constant,
a dump load is connected in parallel with the consumer load has the following specifications:
so the total generated power is held constant, that is
Pout = Pd + Pc Ei = 220 Vrms Pr =150 Watt
where Pout is the generated power of the generator (which Frek = 50 Hz Ripple = 5%
should be kept constant), Pc is the consumer load power, and
Pd is dump load power.
 The opto-coupler circuit that also functions as a gate driver
using the TLP 250.

Fig.3 Rectifier with parallel-resonant filter topology

A based on the calculation of the following component values

Fig.4 Opto-coupler circuit with TLP 250
obtained [14]:
D. Fuzzy Logic Controller
Lr = 0,319 H ; Cr = 3,52 uF ; C0 = 58,39 uF
A fuzzy logic controller consists of four main components as
fuzzification, rule base, inference mechanism and
B. Specifications MOSFET and Dummy Load
defuzzification. The fuzzification converts its inputs into
fuzzy values with membership functions in the form of
The voltage rating of the uncontrolled rectifier and the triangle, trapezoid, bell or other appropriate forms expressed
chopper switch (MOSFET) is calculated based on rms value by the fuzzy linguistic variables. The rule base contains the
ac input voltage (VL) to the diode bridge and the average expert’s linguistic descriptions expressed in the form of
value of dc voltage. The average value of the output dc logical implications such as IF x is positive THEN y is big.
calculated based on the following equation: The inference mechanism evaluates fuzzy information to
activate and apply control rules. The defuzzification that uses
2 methods such as centre of gravity, maximum and weighted
Vdc = 2 VL = 0,9 VL = 0,9 x 220 = 198 V
π mean converts the inference mechanism into the crisp values
applied to the actual system.
With estimates of 10% more voltage than the voltage rating The proposed schematic of an ELC is shown in Fig. 2.
for the transient state, the rms voltage to 242 V (220 +22) and There are two inputs and one output of the fuzzy controller.
the peak voltage is thus, calculated as : The first input is the error between reference value that is
desired output value and generator output value. The second
input is the derivative of the error. The inputs are given by:
Vdc = 2 x 242 = 342,2 V
e(k) = r(k) – y(k)
Current rating of single phase uncontrolled rectifier and the ∆e(k) = e(k) – e(k-1)
chopper switch is calculated as :
The design of the fuzzy controller depends on information
P 150 about the system behavior or experience of a human expert.
I ac = = = 0,68 A
VL 220 The fuzzification stage is determined by the choice of the
I peak = ( Iac x 2) / 0,9 = (0,68 x 2) / 0,9 =1,51 A range, shape and number of the membership functions. The
input membership functions for the error and the delta error to
the fuzzy controller, the positioning universe was divided into
From the calculation above, the maximum voltage is 342.2 V seven domains which are negative big (NB), negative medium
and maximum current 1.51 A. (NM), negative small (NS), zero (Z), positive small (PS),
The rating of dump load resistance, Rd is calculated as: positive medium (PM), and positive big (PB). The output
membership functions are chosen to be nonuniformly
distributed seven singletons functions. The output
(Vdc ) 2 (198) 2 membership function processed by the fuzzy logic algorithm
RD = = = 261,36 Ω produces the PWM singletons taken as output assignments for
P 150
the control dump load.
C. Opto-coupler Circuit
 Fig.5 Membership functions of error and the delta error

Fig.6 Membership functions output

The set of rules for fuzzy controller is shown in Table I.

Table I. Fuzzy Associative Memories (FAM)

Error Fig. 7 Flow chart of fuzzy logic program

dError NB NM NS Z PS PM PB
The controller is designed to keep the operating point at
NB PB PB PM PS PS Z NS these conditions. The dump load is set as 0.12 kW in order to
NM PB PM PM PS Z NS NM consume the entire consumer load when the chopper duty
cycle is 100% i.e., when the consumer load is zero.
NS PB PM PS Z Z NS NM
First test is experiment open loop transient response of the
Z PB PM PS Z NS NM NB generator without load. The results are shown in Fig 8, the
generator is rotated by prime movers with a constant speed
PS PM PS Z Z NS NM NB
1510 rpm. The second test is still in open loop condition by
PM PM PS Z NS NM NM NB giving the load directly to the generator at a certain power
PB PS Z NS NS NM NB NB value, with initial voltage generator always at ± 231 volts.

E. Design of Fuzzy Logic Program

The software used to program ATMega32 microcontroller is

CodeVisionAVR by using C language. The program has
designed based on the flow chart as shown in the figure 7.

IV. EXPERIMENTAL RESULTS

Experimentation has carried out on a three-phase SEIG-ELC
system feeding a single-phase load with ATMega32
microcontroller has been developed and tested in laboratory
under various operating conditions. A single phase 0.18 kW,
220 V, 1.67 A, 4 pole, 50 Hz, 1370 rpm squirrel cage
induction machine is used as a single phase self-excited
Fig 8. Open loop transient response of generator
induction generator. The SEIG is driven by 220 V, 1.5 kW,
1500 rpm shunt wound DC machine used as a prime mover.
To generate 0.12 kW at 220 V and rated speed, 20μF and
10μF capacitors of 400 V are connected as C1 and C2 across
the delta winding terminals of the SEIG.
 survive on the voltage 228 volts for 4 seconds, after which it
shows an unstable response that resulted in loss of voltage
generator.
The test of load adding gradually has performed in the range
of 0 to 122 watt of power. Fig 12 shows the voltage response
when given a load of 122 watts (101.6%), the settling time is
5.5 seconds with 212 volt voltage value, -7.01% steady state
error, and error -3.63% against the reference voltage.

Fig 9. Graph of V = f(Pload) direct load open loop

Fig 9 is shows the graph based on the results of experimental
by giving direct loads. Fig 10 is shows the open loop transient
response when a load generator 80 watt (66.66%) is given
directly. The graph and open loop transient response of the
test generator with direct loading shows that the direct voltage
drops quickly when the load is given.

Fig 12. Close loop transient response of load 122 watt

(101.6%) adding gradually

V. CONCLUSIONS
Based on the design and testing electronic load controller for a
self excited induction generator using fuzzy logic method
based microcontroller has obtained conclusions. When testing
the generator without controller with the single phase loads
Fig 10. Open loop transient response when a load generator 80 directly, the generator is only able to loaded 67 watt with 147
volt terminal voltage and frequency of 42.7 Hz. While with
watt (66.66%) is given directly load gradual, the same generator could only load 67 watt with
Closed loop response experiment is conducted to test the 167 volt terminal voltage and frequency of 42.9 Hz. The ELC
performance of a induction genenerator controlled using of self excited induction generator can supply the single phase
fuzzy logic method based ATMega 32 microcontroller. Closed resistive loads up to 122 watts or 66.77% of the rating as the
loop response testing with different loading conditions, i.e the motor, with ±3.63% voltage regulation, frequency error of -
direct loading and gradual loading. Set point on a closed loop 2.6% to -3.6%, voltage THD average of 2.28%, and unity
testing is 228 volts, 3.63% of the planned reference voltage of power factor.
220 volts.
REFERENCES

[1] Sarsing Gao, S. S. Murthy, G. Bhuvaneswari, and M. Sree Lalitha

Gayathri, “Design of a Microcontroller Based Electronic Load
Controller for a Self Excited Induction GeneratorSupplying Single-
Phase Loads,” Journal of Power Electronics, Vol. 10, No. 4,pp.444-
449, 2010.
[2] Palwalia, D.K.; Singh, S.P.; , “Design and implementation of induction
generator controller for single phase self excited induction
generator,” Industrial Electronics and Applications, 2008. ICIEA 2008.
3rd IEEE Conference on , vol., no., pp.400-404, 3-5 June 2008.
[3] Juan M. Ramirez and Emmanuel Torres M., “An electronic load
controller for self excited induction generators” in IEEE PES General
Meeting, June 24-28, 2007.
[4] R. C. Bansal, “Three-Phase Self-Excited Induction Generators: An
Fig 11. The generator transient response, when tested with a Overview,” IEEE Transactions on Energy Conversion, Vol. 20, No. 2,
load of 112 watts (93.3%). pp. 292-299 June 2005.
[5] B. Singh, S.S.Murthy and Sushma Gupta, “Analysis and implement-
Fig 11 shows the generator transient response, when tested tation of an electronic load controller for a self excited induction
with a load of 112 watts (93.3%). The generator is only able to
 generator” IEE Proc.-Gener. Transm. Distrib., vol. 151, no. 1, pp. 51-
60, January 2004.

[6] Bhim Singh, S.S. Murthy & Sushma Gupta, "Transient Analysis of
Self-Excited Induction Generator with Electronic Load Controller
(ELC) Supplying Static and Dynamic Loads", IEEE Transactions on
Industry Applications , pp .1194-1204,Sept-Oct. 2005.
[7] Bhim Singh, S.S. Murthy & Sushma Gupta ,”An Electronic Voltage
and Frequency Controller for Single-Phase Self-Excited Induction
Generators for Pico Hydro Applications”,IEEE PEDS, pp 240-
245,2005.
[8] B. Singh, S. S. Murthy and S. Gupta, “Analysis and Implementation of
an Electronic Load Controller for a Self- Excited Induction Generator,”
IEE Proceedings Generation Transmission and Distribution, Vol. 151,
No.1, pp. 51-60,January 2004.
[9] Chandra, T.S., Bishnu, P.M., Voltage Regulators for Self Excited
Induction Generator, IEEE Transactions on Energy Conversion,
Vol.20, no. 4, , pp 460÷463,April 2004.
[10] J.B. Ekanayake, “Induction generators for small hydro schemes”,
Power Engineering Journal, Vol. 16, Issue 2, pp.61 –67,2002.
[11] T. F. Chan, “Single phase operation of a three phase induction
generator with the Smith connection”, EEE Trans. on EC, vol.17, No.1,
pp 47-54,March. 2002.
[12] Li Wang, Chang-Min Cheng, “Excitation capacitance required for an
isolated three-phase induction generator supplying a single-phase load,”
in Proc. IEEE Power Engineering Society Winter Meeting, Vol. 1, pp.
299-303, 2000.
[13] Alolah, A.I., Alkanhal, M.A. Excitation requirements of three phase
selfexcited induction generator under single phase loading with
minimum unbalance. u: Power Engineering Society winter meeting,
IEEE, vol. 1,pp. 257-259,2000.
[14] A.R. Prasad, P.D. Ziogas and S.N. Manias, “A Novel Passive Wave
shaping method for single phase Diode Rectifiers”, IEEE Transactions
on Industrial Electronics, Vol. IE-37, No.6, pp. 521-530,Dec. 1990.
[15] Simoes,M.Godoy dan Farret,Felix.A.,”Alternative Energy System :
design and Analysis with Induction Generator,”, 2nd ed, CRC
Press,2008.
[16] Wekhande, Shashank. dan Agarwal, Viviek., “A New Varibale Speed
Constant Voltage Controller for Self-excited Induction Generator,”
Electric Power Systems Research, Elseiver, 59, 157-164,2001.
[17] L. Zadeh, “Outline of a new approach to the analysis of complex
systems and decision processes,” IEEE Trans. Syst., Man Cybem., vol.
28, pp.28-44, 1978.