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Application of a high efficient voltage regulation system with MPPT algorithm

Erdal Irmak ⇑, Naki Güler

Gazi University, Faculty of Technology, Electrical and Electronics Engineering Department, 06500 Teknikokullar, Ankara, Turkey

a r t i c l e i n f o

 Article history:

Received 11 February 2012

Received in revised form 6 August 2012

Accepted 9 August 2012Available online 26 September 2012

Keywords:

Voltage regulation

Maximum power point tracking

Cuk converter

dsPIC

a b s t r a c t

In this study, an integrated voltage regulation system including Maximum Power Point Tracking Algo-

rithm (MPPT) is introduced to store and efficient use of the energy produced by renewable sources. A

dsPIC is used as the main controller to obtain a rapid and stable decision-making system and to decreasethe cycle time of the MPPT operation. In order to minimize the oscillations on the output voltage, a cuk

converter is used that can be operated as both buck and boost modes. Thus, efficiency of the system has

been increased considerably by storing the energy consistently. The experimental results validates that

the system developed operates highly stable and is faster than the similar ones presented in recent

literature.

  2012 Elsevier Ltd. All rights reserved.

1. Introduction

Efficient useof the energy is an important issue in thesedays as a

result of increasing daily demand for energy and the consumption of 

energy sources. Therefore, renewable energy sources such as windenergy and solar energy have gained popularity nowadays. Storing

the energy produced by renewable sources is as important as pro-

ducing it. Although the efficiency of the solar power has been in-

creased up to 46% in laboratory conditions [1], it is less than 30%

for the most solar systems installed and used in current industrial

applications. On the other hand, storing and using the energy pro-

duced by wind turbines is more difficult than the solar systems be-

cause the mechanical speed of the turbine may alter in a short

time, and thereby voltage on the output side of the generator is usu-

ally unbalanced. Thisis a seriousissuefor loads andbatteries because

of causing such problems as the generator overloading, harmonics

and unstable system forms. Therefore, designing of a high-speed

voltage control unit for the output of the system is an indispensable

requirement. In conclusion, since natural behavior of main energysource is quite stable in solar energy systems, the output voltage of 

the system is also very stable; however, especially in wind energy

systems, the output voltage has instant oscillations because the nat-

ural behaviors of wind may alter momentarily. Therefore, it is an

indispensable requirement that designing a quite rapid voltage reg-

ulation systemfor renewableenergysystems likewind energy[2–5].

In most energy systems, converters are used for regulating the

output voltage; thus, the stability of the converter is an important

factor to improve the energy efficiency. If any power system uses

either only buck or only boost converters, the energy produced

can be stored only in certain levels. For this reason, using a cuk

converter is a better solution for this issue because it can be oper-

ated as both buck and boost modes [6]. In cuk converter based sys-

tems, if the voltage produced by the source is lower than desiredlevel, the converter operates in boost mode. Otherwise, if the volt-

age produced is higher, the converter operates in buck mode.

Therefore, the energy produced can be used without any interrupt,

and thus efficiency of the system is increased. By taking into ac-

count all these reasons, a cuk converter is preferred in the system

presented in this study.

Another important factor to increase the efficiency of the sys-

tem is design of an optimum Maximum Power Point Tracking

(MPPT) system. In most of the similar power systems presented

in the literature, DSPs, PICs and FPGAs are generally used for

achieving the MPPT system. Since the DSP is an expensive control-

ler, its usage in such systems has a disadvantage. On the other

hand, usage of PICs decreases the efficiency of the system due to

their low speed response time  [4,7,8]. Furthermore, using a lowspeed controller causes distortions on the output voltage of the

systems including instant speed variations like wind turbines. By

considering such issues, dsPIC is used in this study as the main

controller to develop an efficient solution for such problems.

Recently, several studies have been presented in the literature

to improve the efficiency of the energy produced by renewable

sources such as MPPT operation for solar panels and application

of SEPIC converter [2], design of a DC–DC resonant converter for

wind turbines [9], response analyze of the converters against the

load variations in uninterrupted operation conditions   [10],

improvement of the performances for wind energy conversion

systems   [11], dynamic power point tracking systems for solar

0142-0615/$ - see front matter     2012 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.ijepes.2012.08.011

⇑ Corresponding author. Tel.: +90 312 202 85 52; fax: +90 312 212 13 38.

E-mail addresses: erdal@gazi.edu.tr (E. Irmak), nakiguler@gazi.edu.tr (N. Güler).

Electrical Power and Energy Systems 44 (2013) 703–712

Contents lists available at SciVerse ScienceDirect

Electrical Power and Energy Systems

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energy [12–14]. These systems presented in   [2,7,9–15] have used

lower switching frequencies which are usually between 2 kHz

and 50 kHz. As a difference, higher switching frequencies (about

100 kHz) are used in this study. Thus, oscillation on the output

voltage is minimized considerably. Furthermore, analysis of the

transient response time of the system against the oscillations on

the output voltage and instant variations on the input voltage have

also been analyzed in detail and the system has been verified suc-cessfully. As a result of experimental tests, it has been observed

that the system achieved has more speed response time than the

similar ones  [10,14–26].

Another superior feature of the system designed is uninterrupt-

edly storage of the energy. While only boost or only buck convert-

ers have been used in similar studies for solar energy   [7,12] and

wind energy [19,27], the cuk converter has been used in this study

which is capable to store the energy produced in both the buck and

the boost modes. Additionally, while some similar studies such as

control of fuel cells  [10,28], wind systems  [11], and MPPT opera-

tions [29] have used traditional and ready to use converters, more

flexible and original converter system and MPPT algorithm are de-

signed and carried out in this study. Moreover, the converter sys-

tem and MPPT algorithm developed can easily be adapted to new

conditions that will be appeared in future like adding new solar

panels or wind turbines to the system. Also, MPPT level can easily

be set to any desired value that will be needed as a result of these

new conditions.

In addition to novelties summarized above, a current protection

unit against overloading situations has been added to the system

because overloading to energy source may cause instant descents

on output voltage and thus any part of the system may be dam-

aged. Furthermore, software side of the system is very important

for giving a rapid decision during undesired conditions like over-

loading [30]. In this study, control software of the system is devel-

oped using a flexible programming language.

2. Design of the cuk converter 

Cuk converters are gained popularity in these days because

oscillation on the output voltage of them is less than the other

types of converters like the buck and the boost. Although using

an external filter is a solution for minimizing the oscillations

[31,32], there are some disadvantages of this method such as in-

crease of the cost and increase of the equipment used. In order

to avoid from all these problems, cuk converter has been preferred

in this study. Use of the cuk converter has made it possible to store

the produced energy continuously. If the source voltage is lower

than the system reference value, the cuk converter operates in

boost mode and if the source voltage is higher than the reference

value, the converter operates in buck mode. Thus, the energy pro-

duced can be stored without any interrupt and thereby efficiencyof the system is increased considerably.

Fig. 1 illustrates the circuit diagram of a cuk converter. Currents

of both inductances flow through the  D2 diode. Energy supplied by

the   Li  and input source energy charge the   C i   capacitor together.

Voltage of the  C i  can be determined as in the following equation:

V ci ¼ V i þ V o   ð1Þ

where V ci is the voltage of the capacitor,  V i is the input voltage, and

V o  is the output voltage.

Since the V ci is higher than the input voltage, the  iLi current de-

creases and thus the energy stored into the Lo inductance feeds the

output. While the mosfet is switched on, voltage of the C i biases the

D 2   reversely and inductance currents flow through the switching

device. Because the   V ci  is higher than the output voltage,   C i   dis-charges itself through the switching equipment by transferring

its energy to the  Lo   inductance and to the output. As a result, the

current of  Lo inductance increases. Similarly, the iLi current also in-

creases due to energy applied from the input [6]. The output volt-

age is in a reverse polarity according to the input voltage due to

discharging effect of   C o   capacitor. Ratio of the output voltage

against the input voltage can be determined as in the following

equation:

V oV i

¼  D

1 D  ð2Þ

If the losses are neglected, the output voltage is equal to the in-

put voltage. Accordingly, ratio of the output current against the in-

put current, oscillation on the output voltage and efficiency of theconverter can be derived from the following equations:

I oI i¼

1 D

D  ð3Þ

DV ci ¼  1

C i

Z   ð1DÞT s

0

iLidt    ð4Þ

%g ¼P oP i 100 ¼

V o I oV i I i

100   ð5Þ

where I o   is the output current,  I i   is the input current,  D  is the duty

cycle, DV ci  is the oscillation on the output voltage,  C i is the capaci-

tance of capacitor, T s is the switching period,  iLi is the current flow-

ing through the input inductance, %g   is the efficiency of theconverter, P o is the output power, and  P i  is the input power.

Since the use of a high capacity capacitor causes a high level

starting current for the system and then increases the time spent

to reach steady state condition, a low capacity capacitor is used

on the output of the system. Using the low capacity capacitor has

not damaged the output voltage because high switching frequency

is used in the system. As seen in Eq.  (4), switching time directly af-

fects to charging–discharging times of the capacitor. Thus, by using

a high switching frequency, charging of the capacitor is decreased.

Also, size of the circuit and cost of the system are decreased by

using a small capacitor.

Input power of an ideal converter is equal to its output power,

but it is not valid for real applications. Therefore, the ratio between

output and input powers is determined as the efficiency. The calcu-lations in the equations given above are performed by considering

both output power and charging time of the batteries. Then the

converter is designed by taking into account the results obtained

from these calculations. The converter is firstly designed and tested

in simulation environment. After obtaining stable responds from

simulation, the converter is prototyped.

3. dsPIC microcontroller 

dsPIC is a powerful microcontroller which can be operated un-

der high speed processes and especially designed for applications

that are needed high performance such as voice recognition, heart

sound acquisition, edge detection, and modems   [33–36]. In this

study, dsPIC is preferred for such requirements as generating theswitching signals of converters, measuring the analogue data of Fig. 1.   Circuit diagram of the cuk converter.

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system, achieving MPPT operation and regulating the output

voltage.

Since MPPT operation is mainly based on the ratio between in-

put and output powers, sensing current and voltage data in a

speed, stable and high-resolution way is very important for energy

conversion systems [17]. Especially in voltage regulation systems,

the controller should have high response time against the instant

voltage changes to keep the output voltage on a stable level  [37–40]. Taking into consideration all these issues, dsPIC is used as

the main controller in this study. In order to explain more clearly

the reason why dsPIC is preferred in this study,  Table 1  presents

a short comparison between dsPIC and other similar types of con-

trollers like DSP, PIC and PLC.

As seen in Table 1, although DSP controller has some advanta-

ges like operational speed, CPU speed and PWM pin channels, its

cost and socket type are serious disadvantages especially in indus-

trial applications. On the other hand, analog channels and speed of 

dsPIC controller are adequate for the system presented in this pa-

per. Therefore, it is decided that dsPIC is more suitable for the sys-

tem compared with DSP. Similarly, as compared with PLC and PIC,

dsPIC has more superior features in terms of cost, operation speed

and the number of channels.

4. Development of MPPT scheme

The maximum power point refers to a special point where the

derivative of the ratio between the power variation and the voltage

variation is equal to zero (Eq. (6)). Maximum Power Point Tracking

(MPPT) operation is required to efficiently use the energy produced

by several energy sources [45,46]. Solar panels provide the output

energy in direct proportion to the quantity of sunrays rebounding

on the panel.

MPP  ¼ dP 

dV  ffi 0   ð6Þ

The output power can be calculated by multiplying the currentand the voltage (Eq.   (7)) similarly to direct current circuits. The

maximum power point is computed by using Eq.  (8). During the

MPPT operation, the output voltage is fixed to its optimum value

(V mpp) by measuring and sensing the alterations on input voltage.

Thus, output power of the system is maximized continuously.

P  ¼ V   I    ð7Þ

P max ¼ V mpp I mpp   ð8Þ

It is an important issue for all energy sources that the maximum

power level of the source should be known continuously and the

system should always be controlled according to this level. Other-

wise, all parts of the system can be damaged because of over cur-

rents caused by overloading. In the renewable energy resources,the power produced can be used at 100% efficiency by adjusting

the current and the voltage values. Another important factor is

the controller used in the system. Whereas the MPPT operation

can be achieved by continuously controlling the input and the out-

put powers, a powerful microcontroller is required for MPPT oper-

ations that have such features as high resolution and high response

time. In this study, a dsPIC is used as main controller which pro-

vides such requirements.

In solar energy systems, there is a direct proportion between

the output power and the voltage produced as seen in  Fig. 2, inwhich power versus voltage graphic of a 50 W solar panel is pre-

sented [47]. On the other hand, the output power does not increase

direct proportionally with the voltage. To achieve the MPPT oper-

ation for solar panels, firstly the power is assigned to the controller

as a function of the voltage, and then it is re-calculated according

to the input voltage.

In wind turbines, wind energy is used as energy source. The

power produced by the turbine depends on the torque of the gen-

erator.  Fig. 3 illustrates the power–voltage graphic of a wind tur-

bine  [27]. Output voltage of the turbine depends on the speed of 

the generator. The wind turbines generate sinusoidal output volt-

age (AC voltage) and sinusoidal voltage is converted to direct cur-

rent (DC) type of voltage using rectifiers. Then, the DC voltage is

stored into several types of batteries. Because the speed of wind

may change rapidly, all hardware and software units used in any

wind energy system should have fast response time. Otherwise,

generator, loads and/or batteries may be damaged due to over volt-

age and over current effects. This issue is another reason of why

the dsPIC is preferred as the main controller of the system pre-

sented in this study.

In accordance with all conditions mentioned above, the MPPT

algorithm developed in this study has been achieved by consis-

tently keeping control on the current and voltage values of the sys-

tem. The output voltage of the system is controlled by adjusting

the duty cycle of the switching component in the cuk converter.

The duty cycle periods applying to the system are determined

according to the results of maximum power calculation. Thus,

the power is kept under control since current of load will depends

on the voltage applied. A simplified flowchart of the MPPT algo-rithm is depicted in Fig. 4.

5. Application of the system

In this study, application of a high efficient voltage regulation

system including MPPT operation has been achieved for renewable

energy sources. Two main renewable energy sources are dealt with

in the study as the solar and the wind energies. Experimental stud-

ies on both systems are given below. In general, the voltages of 

renewable energy sources are applied to converters and value of 

the voltages are measured by a controller at the same time to ob-

tain voltage and current information required for calculating the

maximum power point. Then, duty cycle periods of the converterare determined using the calculated values and PWM signals gen-

erated are applied to the switching component in the converter.

 Table 1

A comparison between dsPIC and other controllers  [41–44].

dsPIC30F4011 Siemens S7 400 PLC PIC18F452 TMS320F2812 DSP

Maximum operation speed 8.33-ns cycle time 0.03-ls cycle time 25-ns cycle time 6.67-ns cycle time

CPU speed 30 MIPS 14 MIPS 10 MIPS Up to 120 MIPS

I/O Pins 30 Pins Expandable with external modules 28 Pins 56 Pins

Analog input 9 Channels Expandable with external modules 5 Channels 16 Channels

Resolution 10 Bit 13 Bit 10 Bit 12 Bit

PWM pins 6 Channels Expandable with external modules 2 Channels 16 Channels

Socket type DIP/SMD – DIP/SMD SMD

Architecture 16 Bit 16 Bit 8 Bit 32 Bit

Cost   €7.1   €5865   €7.39   €33

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the output voltage of the generator may be closed to zero when the

wind speed is decreased immediately.

The system presented in this study has high efficient operating

conditions. According to Figs. 7 and 8, efficiency of the system can

be analyzed as follows:

Efficiency of the system for buck mode:

P in ¼ V in I in ¼ 24 1:288 ¼ 30:9 W

P out  ¼ V out  I out  ¼ 16:96 1:75 ¼ 29:68 W

g ¼P out P in

100 ¼29:68

30:98 100 ¼ 96%

Efficiency of the system for boost mode:

P in ¼ V in I in ¼ 10 1:13 ¼ 11:3 W

P out  ¼ V out  I out  ¼ 16:48 0:59 ¼ 9:72 W

g ¼P out P in

100 ¼9:72

11:3 100 ¼ 86%

Fig. 4.   Simplified flowchart of the MPPT algorithm.

Fig. 5.   Block diagram of the experimental setup for solar energy system.

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As seen in the calculations above, the efficiency of the system is

equal to 96% for the buck mode and 86% for the boost mode. The

efficiency of the system has different values for each mode due

to the architecture and structure of the converter.

6. Experimental results

Once the sub-parts of the system are designed and all parts are

integrated to make it ready for operation, the system is tested un-

der several experimental studies. These are evaluating the system

performance by an analytical test of transition time for steady-

state condition, analyzing the oscillations on the output voltage;

and analyzing the response time of the system against the instant

changes occurred on the input side. It has been observed from test

results that the system operates with an optimum performance for

both the wind and the solar energy systems.

6.1. Analysis of transient time for steady-state condition

Most converters do not directly operate as steady-state whenthey started to operation first. On the other hand, so many instant

spikes are occurred on the current and voltage signals of the con-

verter if the response time of the first-time operation is decreased.

In the study presented, in order to operate the converter with the

optimum performance, the capacity value of the output capacitor,

which regulates the oscillations on the output current and the volt-

age, has been determined by performing many simulations and

calculations.

Fig. 9  illustrates the elapsed time to steady-state condition of 

the converter. As clearly seen on that figure, the elapsed time is

around 320 ls, which is an adequate time for the system.

6.2. Analysis of response time of the converter against the instant 

voltage variations

During the design stage of the system, it is especially taken into

consideration that the system can operate steadily even though it

is subjected to unsteady external operating conditions like instant

variation of the input voltage, which usually occurs in wind energy

systems. It has been observed after the experimental analyses that

the system presented has a very short response time. Thus, the sys-tem is capable of handling those problems mentioned above. In or-

Fig. 6.   Block diagram of the experimental setup for wind energy system.

Fig. 7.   Signal waveforms while the system is in buck mode (Ch1: input voltage ( V i), Ch2: output voltage (V o), Ch3: PWM signal).

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der to test the response time of the converter against the instant

voltage variations, a DC power supply with several voltage levels

has been connected to the input side of the system, and the power

supply has been switched from one level to another level suddenly

to change the voltage level on the input instantaneously. The re-

sults obtained from the experimental tests have been found con-

siderably persuasive.

Fig. 10 illustrates the time that is elapsed to re-regulate the out-

put voltage after an instant decrease on the input side and  Fig. 11depicts the elapsed time for regulation of the output voltage after

an instant increase on the input. As obviously seen in both figures,

response time of the converter is quite short as compared with the

similar ones in the literatures   [7,10,12,14–26]. Therefore, the

energy produced can be used with maximum efficiency by using

the system presented in the study.

6.3. Analysis of voltage tracking capability

In order to prevent the batteries and loads from over voltagevalues, the output voltage of the converter is kept in certain limits

Fig. 8.   Signal waveforms during the boost mode (Ch1: input voltage (V i), Ch2: output voltage (V o), Ch3: PWM signal).

Fig. 9.   Analysis of the transition time for steady-state condition (Ch1: output voltage (V o)).

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by regulating the duty cycle of PWM signals applied to the con-

verter. PWM signal and the output voltage graphics which have

been measured under a high-level input voltage are shown in

Fig. 12, where Ch1 represents the input voltage, Ch2 represents

the output voltage, and Ch3 represents the PWM signal. As seen

in figure, while the input voltage is around 20 V, the system de-

creases the output voltage to about 12 V by setting the duty cycle

of the PWM signals as 37%; hence, the converter acts as a buck con-

verter. Experimental analysis of the converter during the boost

mode is also given in   Fig 13, in which Ch1 represents the input

voltage, Ch2 represents the output voltage, and Ch3 represents

the PWM signal. As seen in figure, while the input voltage is around

6 V, the system increases the output voltage to about 12 V by set-

ting the duty cycle of the PWM signals as 67%; thus, the output

voltage is kept at the certain level both for the buck and the boost

modes to obtain a steady operation under all conditions.

Fig. 10.   Converter response against the instant voltage decrease (Ch1: output voltage (V o), Ch2: input voltage (V i)).

Fig. 11.   Converter response against the instant voltage increase (Ch1: output voltage (V o), Ch2: input voltage (V i)).

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7. Conclusion

In this study, a powerful voltage regulation system has been de-

signed for renewable energy systems to obtain the best perfor-

mance from the energy produced by them. For this, a dsPIC

based cuk converter circuit with MPPT algorithm has been devel-

oped. Buck, boost and buck–boost modes of the designed converter

have been examined experimentally under various switching fre-

quencies. Initial response of the system and elapsed time for the

steady state conditions have been tested and quite successful re-

sults have been obtained. Especially, it has been observed that

the system has eliminated the most of spikes on both the current

and voltage signals, which usually occurs in the initial times of 

the operation. Efficiency of the system has been calculated 86%

for boost mode and 96% for buck mode, which are considerable lev-

els for renewable energy systems. Analysis of the response time of 

Fig. 12.   Analysis of the voltage tracking operation during the buck mode (Ch1: input voltage (V i), Ch2: output voltage (V o), Ch3: PWM signal).

Fig. 13.   Analyze of the voltage tracking operation during the boost mode (Ch1: input voltage (V i), Ch2: output voltage (V o), Ch3: PWM signal).

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the system against instant voltage variations on the input side has

also been realized and it has been observed that the system has a

very short response time.

Furthermore, it has been revealed that if the system operates

under low frequencies, many oscillations may occur on the output

voltage. Therefore, the system presented in the study has been

operated with high frequency levels to minimize those oscillations.

Accordingly, as high level frequencies have been selected to oper-ation, dimensions of some components like coil and capacitor have

been decreased. In addition, negative situations which may be oc-

curred for the batteries or the loads have been minimized because

the output voltage has been regulated significantly.

Since the microcontroller used in the system has a fast detec-

tion time and very short response time, the system has regulated

the output power in a very short time when an instant variation

has been occurred on the input side. Thus, efficiency of the energy

produced by the system has been increased considerably.

In conclusion, all results obtained from the experimental stud-

ies show that the system operates with the best performance. Be-

sides, thanks to its low cost design, usage of the system has been

increased for industrial applications including renewable energy

sources.

References

[1] Green M. <http://www.unsw.edu.au/news/pad/articles/2009/aug/New_Solar_Record.html> [accessed 15.02.11]

[2] Darla RB. Development of maximum power point tracker for PV panels usingSEPIC converter. In: Proceeding of the 29th international conference ontelecommunications energy conference, Rome, 30 September–4 October 2007.

[3] Wang X, Yuvarajan S, Lingling F. MPPT control for a PMSG-based grid-tiedwind generation system. In: Proceedings of the annual conference on NorthAmerican power symposium, Missouri, 29 September–2 October 2010.

[4] Mazouz N, Midoun A. Control of a DC/DC converter by fuzzy controller for asolar pumping system. J Electr Power Energy Syst 2011;33(10):1623–30.

[5] Ramasamy M, Thangavel S. Photovoltaic based dynamic voltage restorer withpower saver capability using PI controller. J Electr Power Energy Syst2012;36(1):51–9.

[6] Mohan N, Robbin WP, Undeland T. Power electronics: converters, applications,and design. John Wiley & Sons; 1995.

[7] Demirtas M, Sefa I, Irmak E, Colak I. Microcontroller based DC/DC boostc onve rte r f or solar e ne rg y syste ms. J Fac Eng A rc h Gaz i U niv2007;23(3):271–7.

[8] Messai A, Mellit A, Massi PA, Guessoum A, Mekki H. FPGA-basedimplementation of a fuzzy controller (MPPT) for photovoltaic module.Energy Convers Manage 2011;52(7):2695–704.

[9] Annamalai M, Kumar MV. Design simulation of CII resonant DC-to-DCconverter for standalone wind energy system. J Comput Electric Eng2010;2(5):1793–8.

[10] Ramos-Paja CA, Romero A, Giral R, Calvente J, Martinez-Salamero L.Mathematical analysis of hybrid topologies efficiency for PEM fuel cellpower systems design. J Electr Power Energy Syst 2010;32(9):1049–61.

[11] Ghedamsi K, Aouzellag D. Improvement of the performances for wind energyconversions systems. J Electr Power Energy Syst 2010;32(9):936–45.

[12] Esram T, Kimball JW, Krein PT, Chapman PL, Midya P. Dynamic maximumpower point tracking of photovoltaic arrays using ripple correlation control.IEEE Trans Power Electron 2006;21(5):1282–91.

[13] Sait HH, Daniel SA. New control paradigm for integration of photovoltaic

energy sources with utility network. J Electr Power Energy Syst2011;33(1):86–93.

[14] Tse KK, Ho MT, Chung HS, Hui SY. A novel maximum power point tracker forPV panels using switching frequency modulation. IEEE Trans Power Electron2002;17(6):980–9.

[15] Vijayakumari A, Devarajan AT, Devarajan N. Design and development of amodel-based hardware simulator for photovoltaic array. J Electr Power EnergySyst 2012;43(1):40–6.

[16] Cirrincione M, Pucci M, Vitale G. Growing neural gas based MPPT of variablepitch wind generators with induction machines. In: Proceedings of the IEEEenergy conversion congress and exposition, Atlanta, 12–16 September 2010.

[17] Bayindir R, Irmak E, Colak   _I, Bektas A. Development of a real time energymonitoring platform. J Electr Power Energy Syst 2011;33(1):137–46.

[18] Algazar MM, AL-monier H, Abd EL-halim H, Salem MEEK. Maximum powerpoint tracking using fuzzy logic control. J Electr Power Energy Syst2012;39(1):21–8.

[19] Das Dulal Ch, Roy AK, Sinha N. GA based frequency controller for solarthermal–diesel–wind hybrid energy generation/energy storage system. J ElectrPower Energy Syst 2012;43(1):262–79.

[20] Altas IH, Sharaf AM. A novel maximum power fuzzy logic controller forphotovoltaic solar energy systems. Renew Energy 2008;33(3):388–99.

[21] Kaito T, Koizumi H, Goshima N, Kawasaki M, Kurokawa K. Development of MPPT algorithm for a digital controlled PV inverter. In: 14th Int proc tech digPVSEC-14, Bangkok, 26–30 January 2004.

[22] Gnanasaravanan A, Rajaram M. Artificial neural network for monitoring theasymmetric half bridge DC–DC converter. J Electr Power Energy Syst2012;43(1):788–92.

[23] Kitano T, Matsui M, De-hong Xu. Power sensor-less MPPT control schemeutilizing power balance at DC link-system design to ensure stability and

response. In: The 27th annual conference of the IEEE Industrial ElectronicsSociety IECON ’01, USA, 29 November–2 December 2001.

[24] Mei Q, Shan M, Liu L, Guerrero JM. A novel improved variable step-sizeincremental-resistance MPPT method for PV systems. IEEE Trans Ind Electron2011;58(6):2427–34.

[25] Pandey A, Dasgupta N, Mukerjee AK. High-performance algorithms for driftavoidance and fast tracking in solar MPPT system. IEEE Trans Energy Conver2008;23(2):681–9.

[26] Sangsoo P, Sang-Yong K, Seong-Jae J, Gyeong-Hun K, Hyo-Ryong S, Minwon P,In-Keun Y. Hardware implementation of optimization technique basedsensorless MPPT method for grid-connected PV generation system. In:International conference on electrical machines and systems ICEMS 2009,

 Japan, 15–18 November 2009.[27] Lo KY, Chang YR, Chen YM. Battery charger with MPPT function for stand-alone

wind turbines. In: Proceedings of the power electronics conference, Sapparo,21–24 June 2010.

[28] Hajizadeh A, Golkar MA. Intelligent power management strategy of hybriddist ribute d g eneration syste m. J Ele ctr Power Ene rg y S yst2007;29(10):783–95.

[29] Walker GR, Xue J, Sernia P. Pv string per-module maximum power pointenabling converters. In: Proceedings of the Australasian universities powerengineering conference, Christchurch, 28 September–1 October 2003.

[30] Matsui M, Xu D, Kang L, Yang Z. Limit cycle based simple MPPT control schemefor a small sized wind turbine generator system-principle and experimentalverification. In: Proceedings of the 4th international conference on powerelectronics and motion control, China, 14–16 August 2004.

[31] Kurokawa K, Ishibashi T. Dynamic characteristics of digitally controlled buck–boost DC–DC converter. In: Proceedings of the 8th international conference onpower electronics and drive systems, Taipei, 2–5 November 2009.

[32] Kurokawa F, Okamatsu M. Dynamic characteristics of DC–DC converters usingdigital filters. In: International conference on power electronics, Daegu, 22–26October 2007. p. 261–5.

[33] Siddiqui RA, Amer W, Ahsan Q, Grosvenor RI, Prickett PW. Multi-band infiniteimpulse response filtering using microcontrollers for e-Monitoringapplications. Microprocess Microsyst 2007;31(6):370–80.

[34] Xian-ting T, Zhi-dong Z. Heart sound acquisition based on PDA and bluetooth.In: Proceedings of the 4th international conference on biomedical engineering

and informatics, vol. 2, Shanghai, China, 15–17 October 2011. p. 773–6.[35] Premaratne P, Ajaz S, Monaragala R, Bandara, N, Premaratne M. Design and

implementation of edge detection algorithm in dsPIC embedded processor. In:Proceedings of the 5th international conference on information andautomation for sustainability, Sri Lanka, 17–19 December 2010.

[36] Negishi Y, Kawaguchi N. Instant learning sound sensor: flexible environmentalsound recognition system. In: 4th international conference on networkedsensing systems, Germany, 6–8 June 2007.

[37] Hlaing NK, Oo LL. Microcontroller-based single-phase automatic voltageregulator. In: 3rd IEEE international conference on computer science andinformation technology, China, 9–11 July 2010.

[38] De Silva WR, Munasingha R, Munindradasa A. Low cost voltage regulator formicro scale hydro electricity generators. In: International conference oninformation and automation, Sri Lanka, 15–17 December 2006.

[39] Jiang Z, Dougal RA. A compact digitally controlled fuel cell/battery hybridpower source. IEEE Trans Ind Electron 2006;53(4):1094–104.

[40] Chen YM, Chen CW, Chen YL. Development of an autonomous distributedmaximum power point tracking PV system. In: Energy conversion congressand exposition, Arizona, 17–22 September 2011.

[41] dsPIC30F4011. <http://tr.farnell.com/microchip/dspic30f4011-30i-p/mcu-dsp-16bit-30mips-48k-flsh-dip/dp/1439598> [accessed 15.02.11]

[42] TMS320F2812DSP. <http://tr.farnell.com/texas-instruments/tms320f2812zhhs/dsc-32bit-128k-flash-179bga/dp/1962187> [accessed 15.02.11]

[43] PIC18F452. <http://tr.farnell.com/jsp/search/browse.jsp?N=2030+203063&Ntk=gensearch&Ntt=18f452&Ntx=mode+matchallpartial> [accessed15.02.11]

[44] Siemens S7 400 PLC – CPU 416F-2DP. <http://www.megaelektrikshop.net/urunler_4208_kategori_6517.html> [accessed 15.02.11]

[45] Hohm DP, Ropp ME. Comparative study of maximum power point trackingalgorithms. In: Proceeding of 4th international conference on photovoltaicspecialists, Anchorage, 15–22 September 2000.

[46] Durán E, Cardona MS, Enrique JM, Bohórquez MA, Carretero JE, Andújar JM.New I –V  photovoltaic curves tracer based on DC–DC converters with coupled-inductors. In: Proceeding of 20th international conference on Europeanphotovoltaic solar energy, Barcelona, 6–10 June 2005.

[47] Dolara A, Faranda R, Leva S. Energy comparison of seven MPPT techniques forpv systems. J Electromagn Anal Appl 2009;1(3):152–62.

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