A Modified Aalborg Inverter Extracting Maximum Power From One PV Array Source

Abstract

Distributed Photovoltaic Generation (DPVG) systems have become more important in recent years because of energy pinch and air pollution. Grid-tied inverters, as the indispensable parts of the DPVG systems, have drawn a lot of research attentions. Among various constructors, the Aalborg inverter was proposed as a candidate for the interface between the PV arrays and the power grid for some potential advantages, such as the wide range of input DC voltages, high efficiency, low cost and no leakage current. For a conventional Aalborg inverter, however, in order to gain a symmetrical gird-injected current, when the input DC voltages generated by the PV arrays are not equal, part of the input DC energy has to be discarded, which will reduce the conversion efficiency of the whole system. In this paper, a modified Aalborg inverter with a single input DC source is proposed to extract the maximum DC energy of PV arrays. The operating principle is illustrated via equivalent circuits. The control strategy is designed to balance the capacitor voltages and smooth the gridinjected current. A 110 V/50 Hz/800 W prototype has been built to verify the validity of the proposed inverter together with the effectiveness of the control strategy. Index Terms-Aalborg inverter, Buck-Boost, maximum power piont tracking (MPPT), photovoltaic system, voltage balance. I. IntroductIonW ITH the development of global economy and the increase of population, environmental pollution and energy shortage are becoming increasingly serious. Distributed Photovoltaic Generation (DPVG), as one of the most important renewable energy resources, has experienced dramatic growth worldwide due to its environmental friendliness [1]-[3]. The grid-tied inverters, connecting the power grid with PV arrays, play an integral role in DPVG systems and have been investigated [4]-[6]. Owning to the advantages of low cost,

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