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MAXIMUM POWER POINT TRACKING OF SOLAR PANELS USING SEPIC CONVERTER
SUBMITTED BY:
M.GANESH. S.SIVAKUMAR.
K.DEVARAJ. A.RAJKUMAR.
GUIDED BY:
Mr. S.BALAKRISHNAN M.E
TITLE DESCRIPTION:
Solar power is an alternative technology that will hopefully lead
us away from our
Petroleum and coal dependent energy sources. The major problem
with solar panel technology is that the efficiencies for solar power
systems are still poor and the costs per kilo-watt-hour (kW/h) are not
competitive, in most cases, to compete with petroleum energy
sources. Solar panels themselves are quite inefficient (approximately
30%) in their ability to convert sunlight to energy. However, the charge
controllers and other devices that make up the solar power system are
also somewhat inefficient and costly.
Our goal is to design a Maximum Power Point Tracker (MPPT), a
specific kind of charge controller that will utilize the solar panel to its
maximum potential. The MPPT is a charge controller that compensates
for the changing Voltage vs. Current characteristic of a solar cell. The
MPPT fools the panels into outputting a different voltage and current
allowing more power to go into the battery or batteries by making the
solar cell think the load is changing when you really are unable to
change the load. The MPPT monitors the output voltage and current
from the solar panel and determines the operating point that will
deliver that maximum amount of power available to the batteries.
If our version of the MPPT can accurately track the always-
changing operating point where the power is at its maximum, then the
efficiency of the solar cell will be increased. There are many different
applications for solar power systems, but there are also many
limitations to these applications. The cost-benefit is too low for solar
power systems to be widely used for powering homes, businesses, or
even individual products. Solar power systems are used as the main
power source for a large majority if not all of the satellites that orbit
the earth. However, the benefit of utilizing solar power in space far
outweighs the cost to implement them.
There are wide ranges of different products available to the
consumer that are solar powered, but they can be expensive or
impractical because of their limitations. Solar power systems are not
competitive on the market because consumers are familiar with the
practical, more convenient products that have more common power
sources that they are used to. Some consumer products are radios,
flashlights, motor-home trickle charging systems, outdoor solar
lighting, and laptop charging systems, and even home systems that
can be tied to their existing power grid. Some of the more practical
applications are used for remote locations such as cabins or small
villages that are located far from the closest power grid.
As a result, the cost to install a solar power system is cheaper
than the cost to send transmission lines from the power grid. Solar
powered systems are also very convenient in small applications such
as powering calculators, outdoor lighting, and even traffic lights. By
attempting to make solar panel systems more efficient altogether,
solar powered products could be used more commonly. While solar
panels are not very efficient due to their current limitations, we hope
to extract the maximum amount of possible power from the solar panel
with our MPPT device. This is just one aspect of making solar power
more efficient.
The actual manufacturing of solar panels is important and is not
something that we are able to take on in this project. There are many
important factors that determine the amount of power the solar panels
can extract from the sun including temperature, time of year,
geographic location, and positioning of the sun. These factors can be
minimized by designing a proper system that can monitor the output of
the solar cell and extract the maximum amount of possible power from
the solar panels. In order to enable us to complete this project in an
effective manner we need to understand the solar technology and the
most important aspects of it. We will look at different applications and
whether or not they are even feasible at the current state of solar
technology. After understanding more about the technology that solar
power involves and the different applications that it is used for, we can
then approach our problem for a specific application and design the
best solar panel peak power tracking system.
BLOCK DIAGRAM:
The basic block diagram of the system is shown in Figure
The solar panel will feed the SEPIC converter directly which
stores the electrical energy temporarily in an inductor and then
charges the battery. The battery then feeds the load during sunlight
hours as well as nighttime. The SEPIC converter is to be operated by a
controller. The controller will monitor the voltage and current levels
coming from the solar cell and controls the SEPIC converter
accordingly. While not shown, all active components controller will be
getting its power from the solar cell.
SEPIC CONVERTER DESCRIPTION:
The SEPIC converter is one of the most important components to
the Maximum Peak Power Tracker. To achieve maximum power from
the solar panels, we must operate the panels at their optimum power
point. By opening or closing a switch, the output of the solar panel will
either be shorted or open circuited. The switch discussed will actually
be a MOSFET. The controller will control this MOSFET. To understand
the SEPIC converter, the MOSFET is modeled with a simple ideal switch.
The switch, U1, will open and close to control the voltage level over the
SOLAR PANEL
SEPIC CONVERTER BATTERY
CONTROL CIRCUIT
inductor, which will essentially set the solar panels to their optimum
power level. The SEPIC converter is shown in Figure with the solar
panel shown as a voltage source Vs. More accurate representations of
the solar panel will be used shortly.
L1 + Vc- - Vd + I1
Io
R +
Vi S L2 I2
Vo
As the switch is closed the voltage drops as the current increases towards its
maximum short circuit current. If the switch is closed for a long enough period of time
the voltage will eventually drop to zero and thus the power at this point is zero. If the
switch is open, the voltage will rise to its open circuit voltage and no current flows out of
the solar panel. Again the power will be zero watts. Due to the inductor’s presence in the
SEPIC converter, current and voltage transients will not happen instantly but instead take
some time. Therefore the power cannot instantly move from optimum to zero, but instead
takes some time constant. By opening and closing this switch at fast speeds, it is possible
to pick a place such as the peak power point and operate close to this point. The
equivalent circuit of the solar panel is shown in the figure.
rg converter
Solar Panel
+ vi ri Load
vg
-
FUNCTION DESCRIPTION:
The input resistance of the converter and the output resistance of the
solar panel is matched by feeding the both signals to the error amplifier
The error amplifier in the control circuit compares the maximum input
ripple voltage and the attenuated switch voltage stress and generates error
signal the error signal is then superimposed with a small signal Sinusoidal
perturbation which produces the combined drive signal Vcon.
The combined signal Vcon is compared to a ramp function to generate
a PWM gate signal to the main switch the error amplifier generates a signal
so as to increase or decrease the duty cycle w.r.t input and output resistance
values of the inverter and panel
The regulatory actions cause the feedback network to adjust the duty
cycle in order to make equal of input and output resistance of converter and
solar panel Trance of converter and solar panel
ADVANTAGES:
Simple and elegant technique.
It doesn’t need any mathematical calculation.
No need of output sampling and digital signal processing.
It can be used in various meteorological condition.
APPLICATION:
Used in solar street light light traction.
Used in aero space industries.
Used in communication equipments.
Used as a power supply controller in remote areas.