A Multiport AC Link PV Inverter With Reduced Size and Weight for Stand-Alone Application

Abstract

In this paper, a multiport high-frequency ac link inverter is proposed as the power electronic interface between the photovoltaic (PV) modules, battery energy storage system, and three-phase ac load. In this inverter, a single-stage power conversion unit fulfills all the system requirements, i.e., inverting dc voltage to proper ac, stepping up or down the voltage, generating low harmonic ac current at the output, and input/output isolation. The ac link is formed by a parallel ac inductor/capacitor <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(LC)$</tex></formula> pair having low reactive ratings. A single-input/single-output partial resonant inverter has already been proposed by the present authors. This paper verifies the possibility of extending this topology to multiport partial resonant converters. The proposed converter is believed to overcome most of the shortcomings associated with the currently available multiport PV inverters. It is a single-stage ac link power conversion system with zero voltage turn on and soft turn off of the switches, which has very small switching losses, compact size, and light weight. The proposed converter does not contain any electrolytic capacitors at the link, which increases the reliability of this converter to a great extent. In the proposed inverter, PV side and ac side are isolated; however, if galvanic isolation is required, a single-phase high-frequency transformer can be added to the link. This converter can both step up or down the voltage, regardless of the presence of a transformer. Although this configuration is extendable to the grid-connected applications, in this paper, only the stand-alone application is considered. The performance of the proposed multiport inverter is verified through simulations and experiments.