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Design of Track Control System in PV

Jun-ming Xiao Ling-yun Jiao Hai-ming Zu Rui Zang

School of Electronic and Information EngineeringZhongyuan of Technology

Zhengzhou, P.R. China

xiaojunming528@163.com(.M .Xiao) jiaolingyun@163.com(L. Y Jiao)

Abstract-S dvlp pplct

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Keywordsphotovoltaic power; automatic track control;

controer; sun trajecto tracking; electrooptical tracking

I.

In the energy crisis and environmental highlight

of today tates have adopted a series of signicant measures to

and support the development of solar energy.

Photovoltaic power is one of the main ways of solar energy

utilization, has the characteristics of environmentally-iendly

and application range is ver wide, has now

been used in comication, transportation and other elds,

has a place in the national economy energy system [1]. At

present, the cost of photovoltaic power generation is too high,

can not be compared with the traditional forms of power

generation, the development of domestic PV power

97814446055710$6.00 010 EEE

517

In order to reduce the cost of PV power, countries

around the world are constantly exploring, at this stage the

more approach are mainly tracking method and the

light-gathering method. Tracking method that is using

model, keep light vertical irradiate photovoltaicarray to improve solar panels' ability of absorb solar

radiation. Track control system in PV using tracking

solar power generation equipment can enhance the power

generation efciency 35%, decrease cost by 25% [2].

II. THE OF TRCK YTEM PV

Fig. The block diagram of track control system in

Solar energy as one kind of clean and non-pollution energy,has very broad prospects for development however there is

the problem of low density, intermittent and space distribution

changes [3], which put forward higher requirements for the

collection and use of solar energy. At present, solar panels of

photovoltaic power generation system are basically xed, can

not make ll use of solar energy resources and generation

eciency is lower. Track control system in PV can

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automatically adjust the orientation of solar panels according

to the altitude angle and azimuth angle of sun, make the sun

light always perpendicular incident the surface of photo voltaic

array to obtain the maximum power generation efciency.

As gure I show is the block diagram of track control

system in PV, system uses modular design, mainly composedby photovoltaic array, tracker, sensors, controller, inverter and

other components. Sensors can accurately receive sunshine

within a certain angle and transform it into a measurable error

signal; tracker can handle the error signal which is measured

by sensors, then output motor triggered signals according to

the control algorithm; controller can control the motor's

running and stop according to the motor triggered signals.

III. RCKIG METHOD ND CONTROL TRTEGY DEIGN

PRICLE

A The calculation /sun angle

The sun path changes as the season changes, the

position tracking method can be divided into horizon

coordinates tracking and equatorial coordinates tracking,

horizon coordinate tracking method track the suns

angle and angle, equatorial coordinate tracking

method track the sun's declination angle and solar angle.

Since the change range of solar declination angle is no more

than 2327, its changes slowly so choose horizon coordinatetracing method.

The calculation formula of sun altitude angle a and

azimuth angle s [4]:

a 5 + 5 Bh ( 1 )

s = a - 5 / a

Or, s 5 Bh / a

Where, declination angle

5= 23.4 sin(360x284+n )

36

( 2 )

518

is installation site Bh is solar angle; n is the

days of year.

According to the geographical latitude, the declination

Angle and observation time, using equation (1) and (2) can

calculate the suns altitude angle and azimuth angle at anymoment, any area.

Tracking mode

The tracking mode that adopts at home and abroad

is very much, it can be divided into trajectory

tracking mode and electro-optical tracking according to the

different forms of tracking [5], can be divided into

tracking method and biaxial tracking method according to the

different forms of exercise [6].

trajector tracking mode and electro-optical

tracking mode have some limitations, sun trajectory tracking

mode need to positioning before running, can not

carry on automatic when sun angle calculation has

errors. Electro-optical tracking mode under the of

the weather greatly, appear not to track or wrong track

of the of the weather problem, especially in

weather conditions may occur motor reciprocating

motion result in the waste of energy. This paper

selected the biaxial tracking method of trajectory trackingmode combined with electro-optical tracking mode. In the

of strong light using light intensity detect circuit

detect ray deviation to electro-optical tracking, In case of

weather changes the system automatically turns into sun

trajectory tracking mode.

C Control mode

In photovoltaic power tracking system, control mode can

be divided into three types of open loop, closed loop and

hybrid control according to whether exist feedback while thecontrol system control the quantity control. the open

loop control mode is and easy to realize, has

the problem of tracking when the

overcast and rainy days, system will consume large amounts

of power. Therefore, this article selected the closed loop

control mode. Closed loop control mode schematic diagram is

shown as Fig.2.

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As the gure shown, closed loop control mode is using

sensor detect the deviation of the incident light rays of sun

and system optical axis, when the deviation over the threshold,

drive machine part tu to move through motor, reduce the

deviation until the sun ray and system optical axis afresh

parallelism, realize the tracking of the solar altitude angles

and azimuth Angle.

Fig.2 Closed loop control schematic diagram

IV. EIGN OF YTEM HD

A The basic composition ofhardwarePV tracking controller is a power plant that can make the

solar panel track the orientation of at any time and

the light vertical irradiates to the solar panel. It's mainly

compose with sensor, light intensity detect

temperature detect circuit, current/voltage detect circuit,

stepping motor, motor driver and other the hardware

is shown as Fig.3.

Fig.3 Controller hardware block diagram

Light intensi detect circuit

The 14 parameters that PV tracking system can detect are

the output of PV arrays, battery chargingelectric current/voltage, AC current and AC voltage of

inverter, environment battery PV

arrays environment light intensity, tracking light

intensity, sun altitude angle, angle and wind velocity.

Light intensity detect circuit schematic is shown as Fig,

is mainly consisted by photosensitive sensor, integrated

operational amplier, triode, resistance, capacitance and other

519

elements. Phototransistor and tu on aer accept

sunshine, triode ampli the electrical signals. The voltage

across the voltage follower is equal, avoid the mutual

inuence of ont and back electric circuit, differential

amplier amplify two voltage's dierence value.

Comparator's voltage VDID2 compared with reference

voltage Vref, if the co-rotating voltage larger than the

reverse input voltage, the output is high-level, else is

low-level. The motor run while the compare result VI is

low-level.

FigA Light intensity detect circuit schematic

C Stepping motor driver circuit

Stepping motor is one kind of that converts

electric into displacement, in the tracking

control system the controller's output signal as stepping

motor driver's input control signal, in order to control

stepping motor's positive inversion of longitudinal direction

and horizontal direction. As Fig.5 shown is one of the

stepping motor drive circuits, the system totally have

stepping motor drive respectively drive steppingoto's postve veso o decto ad

horizontal direction.

Control goes into transistor after 74LS 14 reverse

phase, the amplied by the transistor, then control

photoelectric switch. Aer photoelectric isolation, carry on

the voltage and amplication by power then

drive each phase windings of stepping motor, make stepping

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motor do forward, backward, speed up, slow down or stop

movement. As Fig.5 shown L is one phase winding of

stepping motor, RL is winding internal resistance, R IS

exteal resistors, has the nction of limit current and

improves the circuit time constant, the shunt capacitance

across the exteal resistors can enhance the high equency

performance of stepping motor, D is y-wheel diode, avoid

power tuber's damage because of the back electromotive force

that produced by motor winding.

+25V

Fig.S tepping motor driver circuit

V. YTEM OFTWRE DEIGN

0

Fig.6 ystem operating procedures

The soware part of PV tracking control system mainly

include ma program, data acquisition

monitoring subroutine, electro-optical tracking subroutine,

trajectory tracking batter charge and

discharge subroutine, and so on, control ow is shown as

Fig.6. The system can detect signal acquisition,

display, query, etc, can carry on real-time or historical data's

graphics image processing and print for the

information stored in the database, has the nction of

self-calibration, self-diagnosis and self-test. At the same time,

the system can adjust the position of PV array

according to test in order to achieve real-time tracking

target.

VI.

and of solar energy is one of the

effective solutions of energy crisis and the effective

means of reducing environmental pollution, solar photovoltaic

cell array's power generation has relation with the incidence

angle of the generation is the largest when ray

to the PV array. PV tracking control system

using light automatic tracking mode to make solar battery

always perpendicular to this method can greatly

enhance the capacity of solar array, reuce the overall cost ofPV power generation, create high economic eciency, meet

the of setting the environmental protection

economy energy type social, has the theory research meaning

and application prospect of promotion.

REFERENCES

X.K.Li. "Photovoltaic power development and policy analysis, un

[2] F. and P. "Design of controller for lltracking solar, Foreign electronic components, volA, pp. 4-6, 2007.

[3] J. L. Li and . B Zhou. "Design of a new kind of solar photovoltaicpower tracking system, Electrical applications, vo.28, pp.68-71, 2009.

[4] P and Y F hen " powe ytem aed on ntellgentsun tracking with low power cost, Measurement and controltechnology, vo.27, pp.36-39, 2008.

[5] X. H. Wang. "Design and research of multiple plane mirrorcondensation solar tracking system, Hefei, Hefei university, 2007.

[6] B X. Zhang. "Research of solar energy utilization tracking and gathersystem, Hefei, Hefei university, 2006.