Transcript Battery Charge Regulator for a photovoltaic power system using

Battery Charge Regulator for a photovoltaic
power system using microcontroller
By:
Raed Wa’el Ennab & Raja Sa’ed Anabtawi
Supervised by :
Prof. Marwan Mahmoud
Introduction
Since the beginning of the oil crises, which remarkably
influenced power development programs all over the world,
massive technological and research efforts are being
concentrated in the field of renewable energy resources.
In the solar sector for electricity generation, greater
attention is being given to photovoltaic conversion.
Features
1- Charge any rechargeable battery 12V, 24V.
2- Supply any low dc load.
3- Solar-powered.
4- Displays charging status.
5- Polarity checking.
6- Current Limiting.
Advantages and Disadvantages:
The advantages are:
1- Renewable resource.
3- Non-polluting.
5- easy to install.
2- Silent.
4- Little maintenance.
6- Reliability.
And the disadvantages are:
1- Very expensive.
2- No work at night.
Block Diagram
Solar Panel
Regulator
PIC
Lead Acid
battery
Load
Photovoltaic
cells:
Solar
Panel
Regulator
PIC
Battery
In our design, the solar panels will function as a power
supply to our circuit. It will convert the sun radiation
to voltage and current.
types of photovoltaic cells :
1-mono-crystal silicon.
2-Polycrystal silicon .
3-Amorphous silicon (thin film silicon).
Load
efficiency
Material
level of efficiency in %
Mono crystalline silicon
14-17
Polycrystalline silicon
13-15
Amorphous silicon
5-7
production
number of cells
The output voltage of a module depends on the number of
cells connected in series. The module we used was 25 cell
connected in series.
solar cell I-V characteristics
A Typical Current-Voltage
Curve for a Module at
(1000)W/m^2
&
(500)W/m^2
A Typical Current-Voltage
Curve for a Module at (85)c and
(25)
Photovoltaic Arrays:
Series connection
Parallel connection
Charge
Regulator :
Regulator
The solar charge regulator main task is to charge the battery
and to protect it from overcharging and deep discharging.
Deep discharging could also damage the battery.
Kind of charge regulators:
1-Simplest switch on/off regulators.
2-PWM ( Pulse Width Modulation).
3-MPPT charge regulator (Maximum Power Point Tracking).
Lead Acid Battery
Solar
panel
Regulator
PIC
Lead acid
Battery
1- We are going to work on six-cell lead-acid batteries.
2- Voltage/cell 1.75-2.4 V.
3- Battery charge.
4- Battery efficiency.
5- Minimum Voltage.
Load
Lead acid battery
In our project, the circuit we built has two leds; red one
and green one.
Circuitry
circuitry
+S
S-
Circuitry
•
when the voltage is lower than 14.4 V the comparator
(IC3) allows a high negative output signal to switch on the
PNP transistor (Q1).
•
During charging, the battery voltage increase until it
reaches the 14.4 V value. At this voltage, the transistor
(Q1) will be switched off.
•
N1 and N2 from the IC4001 are utilized as pulse
oscillators for the purpose of testing.
•
In this short period, transistor Q2 will be switched on, and
a current will flow from the emitter to the collector of
Q2.
•
Then the comparator (IC2) compares the battery voltage
with the open-circuit voltage of the solar generator.
•
The main objective of using the pulse generator is to
control the voltage of both the solar generator and the
battery continuously.

The objective of the comparator (IC5) is to control the
battery voltage during the discharging mode
two MOSFET transistors were
utilized instead of one
- To make the prevention of the battery discharging via
the solar generator as strong as possible.
- The temperature of the two transistors, due to the
voltage drop across them, is divided equally between
them.
- Increasing the reliability of the controller since one
transistor can perform the task of the other in case of
its failure.
- This arrangement protects the controller from failure
whether it is connected to the solar generator first or
to battery.
Features of The Locally developed
Battery Control Unit (BCU)
- Protects battery against overcharging: the unit controls the
charging current via a regulated impulse, thus preventing
harmful overcharging.
- Protect the battery against deep discharging: the unit
controls battery discharge by means of bistable load relay.
- If the battery charge drops bellow a predetermined voltage threshold, the relay automatically disconnects the
load, this is indicated by a red light- emitting diode (LED).
- The unit is protected against battery reverse polarity via a
diode (D4).
PIC
Flow chart
Read the
battery
Voltage
Read the
voltage fro
the
regulator
Out to the
battery
from the
regulator
Out to the
load from
the
Regulator
Here we used the DAC to convert the digital output from
the PIC to Analog.
Results
Results
Resistance
(ohm)
0
Current
(mA)
401.7
Voltage
(V)
0
I-V Characteristic
10
384
1.92
At G=950 w/m2
20
379.2
3.85
30
370.1
5.12
40
365
6.02
50
360.3
6.9
60
353.5
7.5
70
352.2
8.61
80
351.4
10.4
90
350.8
11.3
100
305
15.4
>>
0
19.1
Results
Fill factor and efficiency:
The Imp = 350 m A and the Vmp =15 volt
So the max power point = 15*.350= 5.25 watt.
The fill Factor:
FF= (Imp*Vmp)/ (Is.c*Vo.c)
= (15*0.350)/ (19*.4) = 70%
The efficiency:
Eff= P.opt/ A.Ee
Eff=5.25/ 0.3*0.3*950 =6.1%
The results we got were:
Vpv
(V)
17.1
14.9
14.1
13.46
Ipv
(mA)
328
302
298
275
Vbatt
(V)
Ibatt
(mA)
12.6
12.9
13.01
13.27
323
296
289.6
270
Problems we have faced:
1- The output voltage was about 15 volts, and the PIC
accept only 5 V maximum.

2- The radiation from the sun was different from day to
another.

3- The wires we used first were the thin wires so when the
current passed these wires got hotter.
The applications for our
project
Conclusion and
Recommendation:
-From the technical and economical viewpoints, it can be said
that the PV technology has attained an acceptable
degree of operational efficiency and reliability.
-Module degradation seemed to be a problem in amorphous PV
technology.
-The tested amorphous PV module showed power
degradation between 16.4% and 39% at the end of the
first year testing period.
-if we have more time we could program the PIC with a
program that can drive a stepper motor and rotate
it as the max radiation from sun and that by using photo
sensors.