Performance of a Series Connected Multicell Li-Ion Storage in a Solar DC Nano-Grid
Syed Aun Abbas, Omer Pervaiz, SM Arman Mahboob , M Azhar Iqbal
National University of Computer and Emerging Sciences, Lahore, Pakistan

Nowadays uninterrupted power supply is becoming an inevitable need for various residential and commercial applications. This requirement can be fulfilled either through utility grid or by the use of alternate power sources at times when grid is not available. The conventional mean to produce electricity during the absence of main grid is through expensive, maintenance hungry and non-environment friendly diesel/petrol generators. However in recent years this trend has been shifted towards the use of ecofriendly renewable resources such as wind and solar for electricity generation. Electricity generation through these sustainable resources is highly intermittent in nature and is dependent on the environmental and climatic conditions. Storage is used with these resources to maintain generation stability during environmental variations. Moreover, storage becomes indispensable when Nanogrid operates in an islanded mode or during hours when utility grid is not present (much prevalent situation in developing countries). In this paper, the focus is mainly on the implementation of PV based DC Nanogrid system with series connected Lithium ion batteries as storage device. The behavior of series connected batteries with unmatched characteristics (due to manufacturing tolerances) under random discharge profiles and its impact on overall system in terms of reduction in its back up time is investigated. For this purpose simulation model of a Nanogrid is developed having maximum solar generation of 3KWp with a storage capacity of 40AH. Four series connected batteries of lithium iron phosphate are connected to generate a DC bus of 51.2V nominal. A random load is connected to the DC bus and performance of battery bank is simulated against different operating scenarios.