Power Conversion Technologies for High-Performance AC Micro-grid

Abstract

Increasing electrical energy demand in tandem with the requirement to ensure good levels of load power quality is a growing need. Traditionally, power electronics-based static uninterruptable power supplies and diesel gensets have been employed to ensure continuity of power supply to tackle power interruptions. AC micro-grids (MG) have attracted significant attention recently owing to their ability to address these issues on a macro-scale with the aid of clusters of on-site heterogeneous micro-sources along with suitable energy storage systems. However, these systems are not necessarily large and complex networks, and it is observed that even simpler systems of smaller ratings functionally qualify as AC micro-grids. To meet the objectives of achieving high performance at low cost, three types of power conversion technologies are proposed for AC micro-grids: (1) reconfigurable battery/grid-tied inverter (RBGTI); (2) dual-mode converter (DMC); and (3) active-phase converter (APC), which enhance power quality and efficiency of energy access. RBGTI and DMC are photo-voltaic (PV) inverter-based MG technologies that ensure efficient solar energy utilization even in the absence of the power grid, unlike conventional PV grid-tied inverters. APC is a motor-drive technology that enables safe interconnection of three-phase motors on single-phase grids or micro-grids while ensuring high levels of efficiency and load power quality when compared to the conventional double-conversion drive systems. These technologies are particularly relevant in the Indian scenario, where there are grid power quality and availability are significantly different from that of other parts of the world. A high-performance General-Purpose Inverter Stack platform developed in the laboratory is employed to realize and verify the performance of the proposed power conversion technologies.