08-08-2012, 11:35 AM
Trends of power electronics on renewable energy systems
Trends_of_power_electronics_on_RES.pdf (Size: 441.47 KB / Downloads: 158)
Abstract
The paper focuses on the power electronics used in renewable energy
systems and especially in wind and photovoltaic (PV) applications. During the last years
there was a broad development in the field of power electronics which led to more
efficient systems and reduction of the cost per installed kW. The inverters became more
efficient and reached efficiencies in excess of 98%, while commercial solar modules
reached almost 17% efficiency. Furthermore, the wind turbines use inverters of
improved efficiency, reliability and regulation capabilities. In this paper the recent trends
of power electronics topologies used in such systems are presented.
Introduction
Photovoltaic and wind energy systems
The Kyoto agreement renewed interest in renewable energy systems worldwide.
Many renewable energy technologies today are well developed, reliable, and cost
competitive with conventional generators. The cost of renewable energy
technologies is on a falling trend and is expected to fall further as demand and
production increases [1], [4]. There are many renewable energy sources such as
biomass, solar, wind, mini-hydro, and tidal power [6]. Power electronics find
applications in most RES technologies, solar and wind energy systems being the
most important applications.
Power Electronics for PV applications
The PV modules and the power electronics that convert the produced electric power
by the PV modules are the basic parts of a PV installation. The PV modules
comprise several solar cells which convert the energy of the sunlight directly into
electricity, and are connected in a proper way (typically in series), to provide desired
levels of DC current and voltage. They produce electricity due to a quantummechanic
process known as the “photovoltaic effect” [1]. A presentation of this
conversion is shown on Figure 1a. There are many semiconductor materials
suitable for solar cells manufacturing. The most commonly used are monocrystalline
Si cells, polycrystalline Si cells and amorphous Si cells, although several other thin
film technologies exist in the market.
Conclusion
In this paper the main trends of the power electronics used in PV and WT
applications are presented. Due to the high demand for renewable energy sources
applications, there is a continuing research for improving the total efficiency of
these applications and by improving each electronic part included. As far as the PV
systems are concerned the inverter’s efficiency is continuously improving and ways
to minimize the weight of the devices are tested so as to decrease transportation
costs and ease the installation. Moreover, the power and voltage range of the string
and central inverters is increased, so that more efficient and cheaper PV
installations can be realized using a relatively low number of inverters. The power
electronics for WT systems are subject to extensive R&D, especially about more
efficient control concepts and even more efficient converters.
References