Design and Implementationof PV System Tracking by Microcontroller

8/20/2019 Design and Implementationof PV System Tracking by Microcontroller

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IPASJ International Journal of Electrical Engineering (IIJEE) Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm

A Publisher for Research Motivation........ Email: [email protected]

Volume 3, Issue 8, August 2015 ISSN 2321-600X

Volume 3, Issue 8, August 2015 Page 6

ABSTRACT This paper presents an automatic dual axis sun tracking system based PIC 16F877A microcontroller which is programmed by flow

code. The tracker uses four LDR (Light Dependent Resistor) to sense the position of the sun. Microcontroller order the stepper

motor and DC motor to rotate dependent on the voltage difference among the four LDR detectors. The stepper motor moves the PV

panel in the horizontal direction from east to west while the DC motor moves the PV in the vertical direction. The practical results

show that the overall output energy of tracking PV panel is increased by 20%.

Keywords: Sun Tracking, Microcontrollers, PV, LDR, Stepper motor, DC motor.

1. IntroductionThe output power produced by the PV panels depends strongly on the incident light radiation. The continuous

modification of the sun-earth relative position determines a continuously changing of incident radiation on a fixed PV

panel. The point of maximum received energy is reached when the direction of solar radiation is perpendicular on the

panel surface. Thus an increase of the output energy of a given PV panel can be obtained by mounting the panel on a

solar tracking device that follows the sun trajectory [1].

Solar tracking strategies are several types and can be classified according to several criteria. One of them, A

classification of solar tracking systems can be made depending on the orientation type. According to this criterion, we

can identify solar tracking systems that orient the PV panels based on a previously computed sun trajectory, in

comparison with panels with an on-line orientation system that reacts to the instantaneous solar light radiation. The

later solution is simpler to achieve than former and it was chosen for the solar tracking system proposed in this paper.This paper deals with the design and execution of a solar tracker system dedicated to the PV conversion panels. The

results from daily analyses show, as expected, that in clear days the dual axis tracker PV system provides the highest

performance. The results indicated that a solar tracking system with photo-sensor is the optimum system and base on

this result we can verify possibility to apply large scale system. Compared to a fixed panel, with tracker PV panel

driven by a solar tracker is kept under the best possible irradiation for all positions of the Sun, as the light falls close to

the geometric normal incidence angle. Automatic solar tracking systems (using light intensity sensing) may boost

consistently the conversion efficiency of a PV panel, thus in this way deriving more energy from the sun.

2. Sun positions and module tracking.As depicted in Figure 1, the position of the sun with respect to that of the earth changes in a cyclic manner during the

course of a calendar year. Tracking the position of the sun in order to expose a solar panel to maximum radiation at any

given time is the main purpose of a solar tracking PV system[2].

Figure 1(a) Illustration of the summer and winter solstices

Design and Implementationof PV System

Tracking by MicrocontrollerAref Y. Eliwa

1, Emad A. Sweelem

2

1Electronics Research Institute,El-Tahrir St., Dokki, Cairo, Egypt.

2Electronics Research Institute,El-Tahrir St., Dokki, Cairo, Egypt.


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Figure 1 (b) Sun Path Diagram for 400 N Latitude During Winter and Summer Solstices.

For many years, several energy companies and research institutions have been performing solar tracking for improving

the efficiency of solar energy production. A variety of techniques of solar energy production used have proven that up to

30% more solar energy can be collected with a solar tracker than with a fixed PV system1. The cost of such systems is

however still very prohibitive for the average consumer or for a small-scale application. The current work shows that a

comparable system can be designed at a much lower cost particularly for academic institutions. In addition, the solar

trackers currently available are generally not programmable for location flexibility. Moving a system from the northern

hemisphere to the southern hemisphere, coupled with latitudinal and longitudinal position changes, can result in

considerable design changes to the tracker’s control circuitry.

A typical solar tracking PV system must be equipped with two essential features:

a) Azimuth tracking for adjusting the tilt angle of the surface of the PV array during changing seasons; and

b) Daily solar tracking for maximum solar radiation incidence to the PV array.The Tilt Angle θ (as shown in Figure 2) of a PV system required at any given time in the year can be expressed as

afunction of the seasonal Sun’s Altitude φ as follows [3,4]:

Tilt Angle θ = 90 – φ

Figure 2 Tilt Angle θ of a PV array

3. PV Tracking System DesignThe dual axis tracking technique is design [5,6]to track the sun in both azimuth and altitude angles to enable the PV

panel perpendicular to the illumination of the sun:i-The PV panel used in this system amorphous silicon solar cell, the maximum output power is 60W, open circuit

voltage is 22V, short circuit current is 3.4A and its dimensions 315*925 mm and its weight 7.1 Kg (Figure 3)


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Figure 3 PV panel.

ii- The mechanical mechanism as shown in Figure 4 includes a stepper motor and DC motor. The system consists of

PV panel, frame, stepper motor, DC motor, sensor circuit and driver circuits.

Pv module support

Figure 4 PV tracking mechincal mechanism.

a- Stepper Motor.

Stepper motors (Figure5)[7] provide a means for precise positioning and speed control without the use of feedback

sensors. The basic operation of a stepper motor allows the shaft to move a precise number of degrees each time a pulse

of electricity is sent to the motor. Since the shaft of the motor moves only the number of degrees that it was designed

for when each pulse is delivered, you can control the pulses that are sent and control the positioning and speed. The

rotor of the motor produces

Figure5 Stepper Motor used

torque from the interaction between the magnetic field in the stator and rotor. The strength of the magnetic fields is

proportional to the amount of current sent to the stator and the number of turns in the windings.The stepper motor uses the theory of operation for magnets to make the motor shaft turn a precise distance when a

pulse of electricity is provided. You learned previously that like poles of a magnet repel and unlike poles attract. Fig 6

shows a typical cross-sectional view of the rotor and stator of a stepper motor. From this diagram you can see that the

stator (stationary winding) has eight poles, and the rotor has six poles (three complete magnets). The rotor will require


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24 pulses of electricity to move the 24 steps to make one complete revolution. Another way to say this is that the rotor

will move precisely 15° for each pulse of electricity that the motor receives. The number of degrees the rotor will turn

when a pulse of electricity is delivered to the motor can be calculated by dividing the number of degrees in one

revolution of the shaft (360°) by the number of poles (north and south) in the rotor. In this stepper motor 360° isdivided by 24 to get 15°.

When no power is applied to the motor, the residual magnetism in the rotor magnets will cause the rotor to detent or

align one set of its magnetic poles with the magnetic poles of one of the stator magnets. This means that the rotor will

have 24 possible detent positions. When the rotor is in a decent position, it will have enough magnetic force to keep the

shaft from moving to the next position. This is what makes the rotor feel like it is clicking from one position to the next

as you rotate the rotor by hand with no power applied.

.

Figure6 Diagram that shows the position of the six-pole rotor and eight-pole stator of a typical steppermotor

Stepper Motor Advantages[8]:1.

The rotation angle of the motor is proportional to the input pulse.

2.

The motor has full torque at standstill (if the windings are energized)

3. Precise positioning and repeatability of movement since good stepper motors have an accuracy of 3 – 5% of a step

and this error is non-cumulative from one step to the next.

4. Excellent response to starting/stopping/reversing.

5. Very reliable since there are no contact brushes in the motor.

6. Therefore the life of the motor is simply dependent on the life of the bearing.

7. The motors response to digital input pulses provides open-loop control, making the motor simpler and less costly to

control.

8. It is possible to achieve very low speed synchronous rotation with a load that is directly coupled to the shaft.

9. A wide range of rotational speeds can be realized as the speed is proportional to the frequency of the input pulses.

The center taps are connected to a positive voltage while the coil ends are alternately grounded to cause a reversal of

the field direction in that winding and Phase motor. The number of phases is equal to two times the number of coils.

The motor is rotated by applying power to the windings in a sequence as shown in table 1.


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Table 1: Four positions of stepper motor operation.

S1 S2 S3 S4 Result

1 0 0 1 Motor moves

right

0 1 1 0 Motor moves left

0 0 0 0 Motor free runs

0 1 0 1 Motor brakes

1 0 1 0 Motor brakes

1 1 0 0 Shoot-through

0 0 1 1 Shoot-through

Figure7 Bridge drives motor.

An H bridge (Figure7) is built with four switches (solid-state or mechanical). When the switches S1 and S4 (according

to Figure7) are closed (and S2 and S3 are open) a positive voltage will be applied across the motor. By opening S1 and

S4 switches and closing S2 and S3 switches, this voltage is reversed, allowing reverse operation of the motor.

Using the nomenclature above, the switches S1 and S2 should never be closed at the same time, as this would cause a

short circuit on the input voltage source. The same applies to the switches S3 and S4. This condition is known as shoot-

through

Operation

Figure8 The two basic states of an H bridge


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The H-bridge arrangement (Figure8) is generally used to reverse the polarity of the motor, but can also be used to

'brake' the motor, where the motor comes to a sudden stop, as the motor's terminals are shorted, or to let the motor 'free

run' to a stop, as the motor is effectively disconnected from the circuit.

b- DC motorA DC motor [8] used in this work to move the pv panel in azimuth direction is shown in Figure9 and disk drives, or in

large sizes to operate steel rolling mills and paper machines. Modern DC motors are nearly always operated in

conjunction with power electronic devices.

Figure9 DC motor used.

c- LDR

A photo resistor or light dependent resistor (Figure10a) [9,10]is a component that is sensitive to light. When light falls

upon it then the resistance changes. Values of the resistance of the LDR may change over many orders of magnitude

the value of the resistance falling as the level of light increases (Figure10b). It is not uncommon for the values of

resistance of an LDR or photo resistor to be several megohms in darkness and then to fall to a few hundred ohms in

bright light. With such a wide variation in resistance, LDRs are easy to use and there are many LDR circuits available

(Figure10c). LDRs are made from semiconductor materials to enable them to have their light sensitive properties.

Many materials can be used, but one popular material for these photo resistors is cadmium sulphide (CdS).

(a) LDR photo. (b) LDR circuit.

(c) Variation of resistance with light.

Figure10 LDR sensor


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4. Experimental Work and System Tracking CircuitThe solar panel is moved in two axis by The Light Detector Resistance LDR are mounted on the solar panel. This

senses the position of the sun with respect to the position of the photovoltaic panel.The tracker should be has

microprocessor controlled, to be able to calculate optimum sunlight position and drive the motors in order to positionthe photovoltaic panel directly to the optimum sunlight. To control the tracker and solar movement, PIC 16877A were

used by using the C programming language. The block diagram of the system is shown in Figure11. This research is

designed with solar panels, LDR, Microcontroller, DC Motor and stepper motor and its driving circuit as shown in

Figures 12&13.

Figure11 The block diagram of PV system tracker

Figure12 Stepper Motor Driving circuit


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Figure13 DC motor Driving Circuit

In this research LDR are fixed on the solar panel at a distinct point. LDR varies the resistance depending upon the light

fall. The varied resistance is converted into an analog voltage signal. The analog voltage signal is then fed to an

Analogue to Digital Converter ADC inside the PIC 16F877A. ADC is nothing but analog to digital converter whichreceives the LDR voltage signals and converts them to corresponding digital signal. Then the converted digital signal is

given as the input of the microcontroller. Microcontroller receives the digital signals from the ADC and compares

them. The LDR signals are not equal except for normal incidence of sunlight. When there is a signal at LDR voltage

levels the microcontroller program drives the DC or stepper motor towards optimal incidence of sunlight. The voltage

regulator module is used to protect PIC and other connected sensors / actuators from over voltage. This is because PIC

and all other connected sensors, actuators all support 5V DC only. Over voltage will cause any of the module burn. The

practical circuit drivers and Thepv tracker is shown in Figures 14&15.

Figure14 The practical circuits of circuit drivers


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Figure15Photo of two axis tracking system.

5. Flow Chart Of the Control CircuitThe flow chart of the control system is shown in Figure 16. If the difference between the value of LDR1 and LDR4 is

less than a certain value (e), the microcontroller generates no control signals because that means that the PV panels are

perpendicular to the source light. When the difference between LDR1 and LDR4 is more than (e), the microcontroller

generates control signals to drive stepper motor 1 to the left. When the difference between LDR4 and LDR1 is more

than e, the microcontroller generates control signals to drive stepper motor 1 to the right [1][4]. The same test is done

for LDR2 and LDR3 in order to control DC motor 2 up and down. The system is programmed so that after sunset the

PV panels are directed to east waiting the sunrise. The microcontroller has been programmed using Flow code

software.

Figure 16 Flow chart of the control system.


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6. ResultThe output power versus time characteristic is shown in Figure17, indicate that there is an overall increase of output

energy about 20% for the two axis sun tracking system compared to the fixed PV system as shown in Figure18. The

tracking mechanism is capable of tracking the sun according to the direction of beam propagation of solar radiation andit has a provision in the software for adjustment of the system in case of seasonal variation if necessary. The power

consumption by the system is very low because of low energy consumption devices are used like as COMS digital IC’s

and other low power consuming solid state electronic components. Also, consumes a small amount of energy because it

rotates only for a fraction of every interval of time.

Figure17 Power-TIME variation comparison of fixed and tracking system.

Figure 18 Energy variation comparison of fixed and tracking system.

7. ConclusionThis paper introduced the design and implementation of PV system sun tracking using microcontroller. Sun tracking

system allows the pv panel perpendicular to the sun light. To minimize the energy consumption due to the panel

movement, the microcontroller test the output voltage difference of LDR’s sensors every a constant time (about half

hour) and sent pulse to the drivers circuit of the motors. The output energy reported for tracking system is about 20 %

over the that for fixed pv panel.


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References

[1]

Byeong-Ho Jeong, Ju-Hoon Park, Seung-Dai Kim, Jong-Ho Kang, “Performance Evaluation of Dual Axis Solar

Tracking System with Photo Diodes”, 2013 International Conference on Electrical Machines and Systems, Oct. 26-

29, 2013, Busan, Korea.

[2] http://wattsun.com/resources.html.

[3] XC95108 properties at http://xilinx.com/xlnx/xil_prodcat_product.jsp?title=xc9500_page

[4] Xilinx ISE 8.1i Foundation in depth tutorial at http://www.xilinx.com/ise/logic_design_prod/foundation.htm.

[5] OkamBingol, Ahmet Altintas, YunusOner, “Microcontroller based solar-tracking system and its implementation”,

Journal of Engineering Sciences, Vol 2, No. 12, pp. 243-248, 2006.

[6] M.R.I. Sarker, Md. Riaz Pervez and R.A. Beg, “Design, fabrication and experimental study of a novel two-axis sun

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[7] Nasir Ahmed Filfil, DeiaHalbootMohussen and Dr. Khamis A. Zidan, “Microcontroller based sun path tracking

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[8]

Jing-Min Wang and Chia-Liang Lu, “Design and implementation of a sun tracker with adDual-axis single motor

for an optical sensor-based photovoltaic system”, Sensors, pp. 3157-3168, 2013.[9]

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AUTHOR

A. Y. Eliwa: I had born in Cairo on Sept. 1964. June 2000, Ph.D was awarded from , Faculty ofEngineering, Ain Shams University in the field of solar cells technology. Bachelor of Electrical

Engineering, (very good with honor degree) from Faculty of Engineering (Shoubra), Zagazig

University (May 1987). Since 1989 , I'm working at Electronics Research Institute, PV Department

in the field of Technology and Applications of Solar. I shared in some projects ; "“New

Antireflection Coating Material for Solar Cells" 1992-1997, "Design and Implementation of an

Optimum Solar Pumping System”, 1996-1998, “Study and Selection of the Available Technology

for Mass Production of Solar Cell Modules” Final report 1996-1998, “Researches in the Technology of Production of

Electronic Components”, 1998-2002.

E. A. Sweelem: I had born in Cairo on Aug. 1969. Feb. 2003 PhD in Electrical Engineering, Cairo

University, EgyptThesis: A New Development for Modeling and Control of PV Hybrid Energy System. A

Government Fellowship in Cottbus-Germany (Technical University of Cottbus), where the experimental part

of my PhD were done there (from 18/11/2000 to 17/11/2002). Nov. 1997 M.Sc. in Electrical Engineering

Cairo University, Egypt Thesis: A Modified Air Cooling for Photovoltaic System. A Scholarship from

DAAD(German Authority) in Kassel-German (Solar Energy Institute ISET), Where experimental part of my

M.Sc. were done there (from 1/11/1995 to 31/12/1996). July 1991 B.Sc. in Electrical Engineering Cairo

University, Egypt Grade: very good with honors Graduation project grade: distinction. I am working now in

Electronics Research Institute, PV Department and my position is Researcher Since 2003 till now. I have published more than 14

papers in the field of solar cells and take shared in more than 5 research projects.

Documents

Design and Implementationof PV System Tracking by Microcontroller