%0 Journal Article
%T Analysis of a Three-Phase Grid-Connected PV Power System Using a Modified Dual-Stage Inverter
%A Denizar Cruz Martins
%J ISRN Renewable Energy
%D 2013
%R 10.1155/2013/406312
%X This paper presents a grid-connected PV system in a centralized configuration constructed through a three-phase dual-stage inverter. For the DC-DC stage the three-phase series resonant converter is chosen thanks to the advantages that it exhibits. However, it is inadequate for the accomplishment of MPPT, due to its efficiency strongly depending on the implemented deadtime and switching frequency. Then, this paper proposes a conceptual modification, that is, a modified dual-stage inverter in which the inverter stage is responsible for both the MPPT and the grid-current control. In addition, the DC-DC converter operates with constant duty cycle and frequency. Such configuration requires a new concept, introduced as Behavior Matching. It serves as a fundamental feature for the DC-DC converter to reproduce the PV array I¨CV characteristic when they are connected, without control action. The maximum power operating point is found by maximizing the direct axis current, obtained by Park's transformation from the inverter, through the perturbation and observation algorithm. Any specific measurement to realize the MPPT is needed. The galvanic isolation is achieved by using a high-frequency transformer. The structure is appropriate for high power applications, above 10£¿kW. 1. Introduction The photovoltaic solar energy represents an emergent technology in function of the continuous fall in the production costs and in the technological progress of the PV modules. This alternative energy can significantly contribute with the reduction in the emission of greenhouse gases in the atmosphere, which attack the environment deeply. Around 75% of the PV systems installed in the world are grid connected [1]. In the grid-connected PV system, DC-AC converters (inverters) need to realize the grid interconnection, inverting the dc current that comes from the PV array into a sinusoidal waveform synchronized with the utility grid [2, 3]. Besides, the DC-AC converter is used to stabilize the dc-bus voltage to a specific value, because the output voltage of the PV array varies with temperature, irradiance, and the effect of MPPT (maximum power point tracking) [4¨C23]. The DC-AC conversion systems, depending on its topology, can be classified as presented as follows [24, 25]. (i)Single-stage inverter: in one processing stage, MPPT and grid-current control are handled (Figure 1).(ii)Dual-stage inverter: a DC-DC converter performs the MPPT and a DC-AC one is responsible for the grid-current controlling (Figure 2).(iii)Multistage inverter: various DC-DC converters are used for the MPPT
%U http://www.hindawi.com/journals/isrn.renewable.energy/2013/406312/