Power quality and stability analysis during islanded mode operation in a microgrid based on master-slave configuration

The current energy trend is the hybrid system projection in which renewable sources and storage systems provide a high percentage of energy needs, leaving the use of conventional system for emergency cases. Hence, microgrids represent a viable solution for the electricity demands in isolated or non-electrified areas. Only diesel generators were previously used in this kind of applications. Their efficiency is reduced during its performance, the operation and maintenance (O & M) is high cost and they present a short lifetime, when they operate in a low load operating mode. Microgrids can reduce these problems and build on the existing territory renewable energy resources, comprising a viable and favorable option. The aim of this paper is the analysis during islanded mode operation in a microgrid based on master-slave configuration. The study was conducted in the ATENEA microgrid premises in CENER (National Renewable Energy Center of Spain). The installation consists of a photovoltaic system, a diesel generator and a storage system (Lead-acid batteries). Concerning the proposed configuration, the systems that define the voltage and frequency setpoints during islanded operation can be the lead-acid batteries converter or the diesel generator. Thus, during this mode operation, concepts related to power quality and grid stability are analyzed. The study concludes with a comparison between the two systems that can operate as the master of the installation, showing the advantages and disadvantages of the diesel genset in respect with the power electronics related to the storage system or vice versa. Finally, conclusions about the most suitable system configuration for the islanded microgrid operation are obtained.