07-05-2013, 01:13 PM
ROLE OF POWER ELECTRONICS IN RENEWABLE ENERGY SYSTEMS
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Abstract:
The rapid increase in global energy
consumption and the impact of greenhouse gas
emissions has accelerated the transition towards
greener energy sources. The need for distributed
generation (DG) employing renewable energy sources
such as wind, solar and fuel cells has gained
significant momentum. Advanced power electronic
systems, affordable high performance devices, and
smart energy management principles are deemed to
be an integral part of renewable, green and efficient
energy systems. This paper briefly describes the
attributes of DG. An overview of wind, fuel cell, solar
based energy conversion systems has been presented.
A qualitative description of the role of power
electronics in wind, solar, and photovoltaic systems
has been presented.
INTRODUCTION
The global energy consumption has been continually
increasing over the last century. Official estimates
indicate a 44 percent increase in global energy
consumption during the period 2006 - 2030 [1]. It can be
said that fossil fuels (liquid, coal and natural gas) have
been the primary energy source for the present day
world. Sustained urbanization, industrialization, and
increased penetration of electricity have led to
unprecedented dependency on fossil fuels. Presently, the
most important concerns regarding fossil fuels are the
green house gas emissions and the irreversible depletion
of natural resources. Based on the official energy
statistics from the US Government, the global carbon
dioxide emissions will increase by 39 percent to reach
40.4 billion metric tons from 2006 to 2030 [1]. Green
house gas emissions and the related threat of global
warming and depleting fossil fuel reserves have placed a
lot of importance on the role of alternative and greener
energy sources.
WIND ENERGY SYSTEMS
Wind energy has the biggest share in the renewable
energy sector [1], [3]. Over the past 20 years, grid
connected wind capacity has more than doubled and the
cost of power generated from wind energy based systems
has reduced to one-sixth of the corresponding value in
the early 1980s [3]. The important features associated
with a wind energy conversion system are:
Available wind energy
Type of wind turbine employed
Type of electric generator and power electronic
circuitry employed for interfacing with the grid
Wind energy – Wind speeds, air pressure, atmospheric
temperature, earth surface temperature etc., are highly
inter-linked parameters. Due to the inherent complexity,
it is unrealistic to expect an exact physics based
prediction methodology for wind intensity/sustainability.
However, distribution based models have been proposed,
and employed to predict the sustainability of wind
energy conversion systems [4]. Detailed explanation of
the wind energy resources is beyond the scope of this
paper. Based on studies it has been reported that the
variation of the mean output power from a 20 year period
to the next has a standard deviation of less than 0.1 [4]. It
can be concluded with reasonable confidence that wind
energy is a dependable source of clean energy. Basics of
physics of wind energy can be summarized as below.
CONCLUSION
The importance of renewable energy, renewable energy
based energy conversion systems, and distributed power
generation has been reiterated. A brief overview of the
wind energy basics and the existing PE interface
requirements and techniques have been addressed
qualitatively. The basic electrical characteristics of fuel
cell and photovoltaic based systems have been presented.
The different methods of integrating these systems to the
grid have been briefly described. The advantage of
employing a Z-source inverter over a conventional dc-ac
VSI has been emphasized. It can be concluded that with
the advancements being made in the area of renewable
energy and distributed power generation power
electronics has a demanding and critical role in the future
of efficient power generation and distribution.