Bidirectional multiport microinverter and grid-multimode-operation control for a non-linear load

Abstract

Micro-inverters usually are used to connect photovoltaic panels (PV) to the electricity grid. If the energy provided by the panel is not enough to satisfy the demands, the system becomes dependent exclusively of the grid. This constraint demands the use of a battery bank, therefore it is necessary to add a third port to the micro-inverter to connect this energy backup. In this paper, a two stage micro-inverter is proposed, the first stage is a DC/DC Triple Active Bridge (TAB) converter that integrates a back-up battery and works in soft switching; and the second stage is a Voltage Source Inverter (VSl) that operates in both grid-connected mode (GCM) and Stand Alone Mode (SAM). The grid-multimode operation controller developed detects the islanding fault and maintains the energy quality for a typical nonlinear load. Reliability and robustness of Uninterrupted Power Supplies (UPS) are increased by the proposed control.