The 5th PSU-UNS International Conference on Engineering and Technology (ICET-2011), Phuket, May 2-3, 2011

Prince of Songkla University, Faculty of Engineering Hat Yai, Songkhla, Thailand 90112

Abstract: This paper describes the design and

experiment testing of energy management system for a

handmade permanent magnet generator. The generator

which use in this experiment is the handmade permanent

magnet generator which can generate the electrical

energy at low speed. The generator generates 3 phase

AC power then must be conversed to DC by a rectifier

circuit and sent to a BUCK converter. The BUCK

converter controls work during an appropriate input

voltage for decreasing the generator staring torque. An

energy from a generator is charged to battery. From the

experiment, the designed energy management system can

be controlled and applied to use in a small scale sea

wave power generation system. The system can generate

the electrical power during 0.2- 0.5 kW.

Keywords: Permanent magnet generator /DC-DC

converter / Sea wave power generator

1. INTRODUCTION

The electrical energy is important for daily living,

including an economical development and a stability of

the country. The electrical energy consumption in

Thailand tends to go up all the time. The electrical

energy from fossil fuel such as petroleum, natural gas

and coal cause a pollution. A renewable energy using is a

solution to solve the problem form fossil fuel. An aim of

this research is to study and test the handmade permanent

magnet generator which can be easily built in houses and

develop the energy management system which can be

manage the generated power for the handmade

permanent magnet generator to appropriate and

efficiently to use.

2. THE SYSTEM COMPONENTS

The system is consits of the handmade permanent

magnet generator and the electrical power management

circuit. The details of each part are as follow:

2.1. Handmade Permanent Magnet Generator

The generator in this experiment is an axial flux

permanent magnet generator. The stator consists of 9

winding sets, connected to the winding in series 3

windings per phase and poured the polyester resin on it

to form the stator body. (see figure 1a, 1b) The stator

winding can be connected in wye or delta connection.

Fig.1. The component of handmade PMG.

The generator have 2 sets of rotor, each rotor body is

also made from the polyester rasin, consists of the

permanent magnet 12 pieces per set arrange in circle.

(see figure 1c) The stator winding connection and the

rotor arrangment are shown in figure 2.

1

2

3

Fig.2. The stator winding connection.

Energy Management Systems for a

Handmade Permanent Magnet Generator

Jensak Eakburanawat1*

, Chaiyan Thongsongyod2

Department of Electrical Engineering, Faculty of Engineering, Rajamangkala University of

Technology Rattanakosin, Thailand

*Authors to correspondence should be addressed via email: jensak@hotmail.com

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The generator assembly is installing the stator and

rotor on the same shaft. The stator is fixed and the rotor

can move. (see figure 1d)

2.2 Energy Management System

Figure 3 shown a block diagram of permanent

magnet generator and the enegy management system.

The energy from the generator is the 3 phase AC and it is

depended on the mechanical source. The mechanical

source is an unstable source such as wind, sea wave or

other renewable energies. The output of generator maybe

unstable as well. Therefore, the system must convert the

AC power to DC power and store the energy to the

battery then use the continue power from the battery

again. The purposes of energy management system are

Fig.3 Diagram of PMG and energy management system.

• The 3 phase rectifier is used for converting the AC

power output of generator to DC power and sent to

the buck converter circuit.

• The buck converter circuit is used for controling a

properly for battery charging.

• The battery is used for storage the energy and

supplied the power to load.

2.3 Buck Converter

The DC converter which is used in the purpose

system is the Buck converter. Because of the output AC

voltage of generator is high, so when the rectifier

converts the output voltage to DC voltage, the output of

rectifier will be higher than the battery terminal voltage.

It’s necessary to reduce the output voltage of rectifier to

be proper to charge the battery. The output voltage of

Buck converter is lower than input voltage. The output

voltage of circuit can be controlled by the duty cycle.

The ratio of the output voltage to the input voltage and

the duty cycle are defined as:

( ) ( )d o on o s onV V t V T t− = − (1)

o on

d s

V tD

V T= = (2)

.o dV V D= (3)

Where Vd is the input voltage, Vo is the output voltage, ton

is during the on stage, Ts is the period, D is the duty

cycle.

2.4 Control Circuit

In a small renewable energy system, when the

permanent magnet generator supply the power to load,

cogging force occures. In this time, the generator

requires many torques from the source. Most renewable

energy sources can not be maintain the continue power

supply to the load. The cogging force make the generator

speed reduced until the generator can not build up the

power.

The control circuit is designed to operate in the

period of time. The Buck converter is controlled by an

On-Off hysteresis control circuit which can turn on and

off the Buck converter by DC bus voltage level. From

figure 4, the control circuit is detected the output voltage

level of rectifier. If the voltage build up to the upper set

point, the controller will turn on the converter. The

system operates in cut-in mode, the energy will be

charged into the battery. If the voltage decrease untill

lower set point, the controller will turn off the converter

and the system will operate in cut-out mode, the

generator is a free load. It can build up the speed and

supply the power agian. The upper and lower set point

can be setted by variable resistor. The function of the

control circuit is sent the from supply voltage to TL494

for generating the gate drive signal to control the buck

converter.

_

+

+VCC

-VCC

_

+

+VCC

-VCC

_

+

+VCC

-VCC

_

+

+VCC

-VCC

10k

+VCC

2.5k

TL494TLP250

741741

741741

0 0 0

0

0 0 0

0

0

0

1

+VEE

750

1.5k10nF

0

Battery48V

L1

L3

L2From PM

Generator

10k

10k10k

10k

10k

10k

10k

10k

10k10k

10k

Fig. 4 Buck converter and control circuit.

3. THE EXPERIMENTAL AND RESULTS

The experiment are divided into 2 parts, the first

experiment is the generator efficiency test and the second

is the energy management system test. The details and

steps of the test are as follow:

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3.1 The Generator Efficiency Test

In the experiment, we use the 1 phase 1 HP split type

induction motor is used as a prime mover. The prime

mover is coupling to the generator by pullay and belt

ratio 2:1. The generator stator winding circuit is

connected in Delta. The output terminal of generator is

connected to the 3 phase rectifier circuit and load. The

Load is a group of incandescent lamps. Start the motor

and varied speed in step. The speed of motor is varied by

inverter. Measured the input power of prime mover

motor and the output power of the rectifier. Figure 6

shown the power output of generator measure in DC

power at the load. The overall efficiency is 27%

Fig.5 The permanent magnet generator test set.

0

50

100

150

200

250

300

350

400

450

250 350 450 550 650 750

Ou

tpu

t p

ow

er

(W)

Speed (rpm)

Fig.6 The power output curve of the PMG generator.

3.2 The Energy Management System Test

In the experiment, the upper set point is setted at

175V and generator speed is 500 rpm. When the circuit

cut-in, the speed of generator is reduces, the control

circuit is held the operating status and cut-off when the

voltage equal to the lower set point. The charging period

of the system be in line with the operate time. The output

signal of control circuit and the gate drive signal are

shown in the figure 7. (measured by YOKOGAWA

oscilloscope model DL1620)

Fig. 7 The charging time of system and gate drive signal

When the system operates in cut-in mode, the

measured voltage and current at the battery terminal are

49V and 0.5A, respectively. The control operation is

tested by increasing the speed of the prime mover by

inverter until the generator build the voltage up to the

upper set point then decrease the speed down to the

lower set point and repeat the experiment continually.

Measured the electrical energy charging into battery by

power meter FLUKE model 43B, the profile of the

energy charge shown in figure 8.

Fig. 8 Output power of buck converter for battery

charging.

Fig. 9 The voltage and current input of buck converter.

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Fig. 10 The voltage and current output of buck converter.

Fig. 11 The gate-source drive signal and inductor current

of buck converter.

Figure 9. shown an input voltage and input current of

buck converter. From figure 4, there is a output voltage

signal leaving from inverting amplifier when input

voltage of converter is higher than set point voltage of

hysteresis control. The inverting amplifier is connected

to a totem pole. The totem pole is a source for PWM or

IC TL494 for generating signal for driving switch. Then,

the signal is sent to optoisolator (IC TLP250) for

bringing PWM to drive the switch. Therefore, there is a

current flow into buck converter as shown in figure 9.

The input voltage is 176V and the average input current

is 114.574mA.

Figure 10. shown an output voltage and output

current. The output voltage depends on a duty cycle. If

the duty cycle is increasing and then decreasing, the

output voltage would increase and decrease respectively.

A change of duty cycle causes a change of battery’s

input current. In figure, the output voltage is 46.612V

which is a battery’s voltage. A 319.345mA is charged to

the battery.

Figure 11. shown driving switch signal and a current

through an inductance. The current through the

inductance operates in discontinuous current mode

(DMC). The driving switch signal has 25% of duty cycle.

4. CONCLUSION

The PMG Generator requires a great number of

staring torque for defeating the cogging force when the

generator is on load. Then, the system can be operated in

continuously by using the big prime mover and more

power. When using the system with the small renewable

plant, will be not fully operate. The porpose of energy

management system is to solve this problem because the

system can continuously generated the power when the

source is strong and can be operated in period when the

source is weak then the sum of energy is more than the

uncontrol system. In this paper, The generator has a few

efficiency (about 27%). The auther will develop the

generator to more efficiency by reducing the iron loss

and copper loss in the future.

5. REFERENCES

[1] Anubhav Sinha, Devesh Kumar, Paulson Samuel,

and Rajesh Gupta, “Performance analysis of

converter based variable speed wind energy

conversion system”, Third International Conference

on Power Systems, ICPS 2009, IEEE, pp. 1-6.

[2] Bumby J.R., Stannard N., Dominy J., and McLeod

N., “A permanent magnet generator for small scale

wind and water turbines”, International Conference

on Electrical Machines, ICEM 2008, IEEE, pp. 1-6.

[3] Jensak Eakburanawat and Itsda Boonyaroonate,

“Development of a thermoelectric battery charger

with microcontroller-based maximum power point

tracking technique”, 2006, Journal of Applied

Energy.

[4] Jensak Eakburanawat and Itsda Boonyaroonate, A

Thermoelectric Battery Charger System with

Maximum Power Point Tracking Technique, ECTI

2005, May 12-13 Pattaya, Chonburi, Thailand,

2005.

[5] A. Parviainen and P. Kontkanen, “Axial Flux

Permanent Magnet Generator with Concentrated

Winding for Small Wind Power Applications”,

Electric Machines and Devices, IEMDC 2005,

IEEE, pp. 1187-1191.

[6] D.M. Whaley, W.L. Soong and N. Ertugrul,

“Investigation of Switched-Mode Rectifier for

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2849-2856.

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