Recent advances on AC PV-modules for grid-connected Photovoltaic plants

Abstract

The paper provides an overview on Photovoltaic (PV) AC-modules, among typical PV-modules which only produce DC output. A novel approach for designing of a new AC PV-module is also presented and discussed, being an other goal of the paper that of introducing an innovative AC PV-module simply based on a conventional DC PV-module and on a micro and distributed energy storage system. PV-plants endowed by AC PV-modules have several advantages over conventional PV-plants: lower generation losses caused by unequal PV-module generation, higher degree of flexibility in the planning and installation of PV-modules, lower price due to the economy of mass production of AC PV-modules, lower minimum system size (and hence lower barrier to the PV market entry), superior ability to site individual modules without concerning for partial shading and other kinds of mismatching conditions; furthermore, installation is safer because there are no high-voltage DC-bus connections. Based on previous researches on distributed energy storage for grid-connected photovoltaic plants, the basic idea for introducing a new AC PV-module is that of connecting a certain number of rechargeable batteries in parallel to a specifically designed number of PV-cells, according to a criterion of maximizing the PV-module generated energy and the number of voltage levels that we want to physically get as input for a multilevel inverter that is proposed to be mounted on the backside of the new AC PV-module. The use of a multilevel inverter technology introduce many advantages with respect to conventional PWM inverters: a greater efficiency, a greater reliability, a lower harmonic pollution on the AC output voltage and so on. To confirm the effectiveness of the proposed idea, the circuit configuration of the introduced AC PV-module and its operating principle are numerically tested by means of some Pspice simulations, performed under ideal operating conditions of batteries.