28-07-2011, 03:45 PM
Abstract:
A maximum power point tracking algorithm for single-stage converters connecting
photovoltaic panels to a single-phase grid is presented in this paper. The algorithm is
based on the processing of current and voltage low-frequency oscillations introduced in the
PV panels by the single-phase utility grid. The algorithm has been developed to allow an
array of PV modules to be connected to the grid by using a single-stage converter. This
simple structure yields higher efficiency and reliability when compared with standard solutions
based on double-stage converters configuration. The proposed maximum power point
tracking algorithm has been numerically simulated and experimentally verified by means of
a converter prototype connected to a single-phase grid. Copyright C 2005 IFAC
Keywords: Converters, Solar energy, Renewable energy systems, Efficiency, Inverters.
1. INTRODUCTION
One of the most promising candidates for the large
scale spreading of renewable energy source is the
photovoltaic technology. In particular, photovoltaic
roofs give an important share of new installations of
PV panels. For these applications the rated power is
lower than 5 kW and the PV panels are permanently
connected to a single-phase grid. The power flow between
the PV panels and the grid is controlled by a
power conditioning system (PCS), which should be
reliable and inexpensive. To obtain the maximum efficiency
of the system, the PCS must keep the power
extracted from the PV panels close to the maximum
power point (MPP). Several solutions for PCS with
maximum power point tracking (MPPT) capability
have been recently proposed, based on both singlestage
(Kuo et al., 2001) and double-stage converter
topologies (Gow et al., 2000).
This paper deals with a single-phase, single-stage PCS
configuration, using a simple and effective MPPT
embedded algorithm. The scheme of the proposed
system is shown in Fig. 1. The output of the PV panels
is directly connected to the dc-link of the single-phase
inverter (VSI type), and the output of the inverter is
connected to the grid through the ac-link inductor Lac.
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