21-04-2014, 03:07 PM
Sun and Maximum Power Point Tracking in Solar Array Systems Using Fuzzy Controllers Via FPGA
ABSTRACT
Solar energy is viewed as clean and renewable source of energy for the future. So the use of
Photovoltaic systems has increased in many applications. That need to improve the materials
and methods used to harness this power source. There are two major approaches; sun tracking
and maximum power point tracking. These two methods need efficient controllers. The
controller may be conventional or intelligent such as Fuzzy Logic Controller (FLC). FLCs
have the advantage to be relatively simple to design as they do not require the knowledge of
the exact model and work well for nonlinear system. To implement this controller, Field
Programmable Gate Array (FPGA) can be used. This method has many advantages over
classical microprocessors.
In this research, Two fuzzy logic controllers are fabricated on modern FPGA card (Spartan-
3AN, Xilinx Company, 2009) to increase the energy generation efficiency of solar cells. These
controllers are, sun tracking controller and maximum power point tracking controller.
Sun tracking generating power system is designed and implemented in real time. A tracking
mechanism composed of photovoltaic module, stepper motor, sensors, input/output interface
and expert FLC controller implemented on FPGA,
Introduction
Renewable energy sources play an important role in electric power generation. There are
various renewable sources which used for electric power generation, such as solar energy,
wind energy, geothermal etc. Solar Energy is a good choice for electric power generation,
since the solar energy is directly converted into electrical energy by solar photovoltaic
modules. These modules are made up of silicon cells. When many such cells are connected in
series we get a solar PV module. The current rating of the modules increases when the area of
the individual cells is increased, and vice versa. When many such PV modules are connected
in series and parallel combinations we get a solar PV arrays, that suitable for obtaining higher
power output.
The applications for solar energy are increased, and that need to improve the materials and
methods used to harness this power source. Main factors that affect the efficiency of the
collection process are solar cell efficiency, intensity of source radiation and storage
techniques. The efficiency of a solar cell is limited by materials used in solar cell
manufacturing. It is particularly difficult to make considerable improvements in the
performance of the cell, and hence restricts the efficiency of the overall collection process.
Therefore, the increase of the intensity of radiation received from the sun is the most attainable
method of improving the performance of solar power.
Background
One of the most important problems facing the world today is the energy problem. This
problem is resulted from the increase of demand for electrical energy and raised of fossil fuel
prices. Another problem in the world is the global climate change has increased. As these
problems alternative technologies for producing electricity have received greater attention.
The most important solution was in finding other renewable energy resources [23].
Renewable Energy
Renewable energy is energy which comes from natural resources such as sunlight, wind, rain,
tides, and geothermal heat, which are naturally replenished [24]. In its various forms, it derives
directly from the sun, or from heat generated deep within the earth [25]. Figure 2.1 show that
natural gas and nuclear power are expected to grow slowly over the next 40 years, at which
point natural gas will start its decline. It is also hoped that a new clean energy source of fusion
energy will be demonstrated at increasing scales from 2030 to 2070 which will then become
commercially competitive [26].
Photovoltaic Background:
Solar panels are made up of photovoltaic cells; it means the direct conversion of sunlight to
electricity by using a semiconductor, usually made of silicon [29]. The word photovoltaic
comes from the Greek meaning “light” (photo) and “electrical” (voltaic), The common
abbreviation for photovoltaic is PV [30]. Bell Laboratories produced the first solar cell in
1954. The efficiency of this cell was about 5 percent. The first cells were designed for space
applications, so the cost was not a major issue. Then solar cell efficiency increased
continuously in the following years, and costs have decreased significantly in recent decades.
The main material used in the construction of solar cells is still silicon, but other materials
have been developed, either for their potential for cost reduction or their potential for high
efficiency [30]. Over the last 20 years the world-wide demand for solar electric power systems
has grown steadily [28]. The need for low cost electric power in isolated areas is the primary
force driving the world-wide photovoltaic (PV) industry today. PV technology is simply the
least-cost option for a large number of applications, such as stand-alone power systems for
cottages and remote residences, remote telecommunication sites for utilities and the military,
water pumping for farmers, and emergency call boxes for highways and college campuses
[28].