Damping performance analysis of battery energy storage system, ultracapacitor and shunt capacitor with large-scale photovoltaic plants Rakibuzzaman Shah ⇑ , N. Mithulananthan, R.C. Bansal School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD-4072, Australia article info Article history: Received 15 July 2011 Received in revised form 6 September 2011 Accepted 22 September 2011 Available online 1 November 2011 Keywords: BESS Electromechanical mode Inter-area mode PV generator Ultracapacitor Trajectory sensitivity abstract As large-scale photovoltaic (PV) generation reaches higher penetration levels, there is a greater need to meet the certain grid code requirements for interconnection. Ultracapacitor, battery energy storage sys- tem (BESS) or shunt capacitor have recently been used as auxiliary devices for large-scale PV generator system to meet the grid code requirements for interconnection. Although the individual auxiliary devices are well documented, a comparative study of these devices impact on the damping of electromechanical (EM) modes and oscillatory instability problem has not been reported so far. This paper aims to fill in the gap, and provides a comparative analysis of these auxiliary devices performance along with PV plant on the damping of EM modes. The oscillation problem is analyzed by considering different types of synchro- nous generator (e.g. hydro, thermal) as the non-electrical components of hydro and thermal units have major influences on system dynamics. The comparisons are based on the results obtained from two-area test system and New England–New York test system (16 machine 68 bus system), which are the bench- mark systems for angular stability analysis. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Grid connected large-scale PV plants are currently being widely installed in many of the developed and developing coun- tries around the world. In addition to their environmental bene- fits, they have a number of technical concerns such as power system stability, reliability and power quality. Recently, the increasing penetration level of PV systems is raising the concerns of utilities due to the possible negative impacts on power system stability [1]. Low frequency oscillation problems have been ob- served in many power systems worldwide [2,3]. Thus, prior to grid connection of large-scale PV, low frequency oscillatory insta- bility should be addressed. In order to make sure that the integra- tion of large-scale PV plant does not endanger system security and reliability, a comprehensive simulation studies are needed based on appropriate and credible approximation of PV plant and its auxiliary devices. A grid connected PV generation system includes photovoltaic array, DC/AC converter and the associated controllers. The dynamics of the PV system are completely different from that of the conventional generator, though both of them have almost identical P–Q characteristics. In the last couple of years, a num- ber of publications have been devoted to study the power elec- tronic converters for PV grid interface. However, the power system stability impact of large-scale PV has not been covered in details. Due to the given dynamics of PV, higher PV penetra- tion levels could cause possible instability problems when a large percentage of the system load is supplied by PV, as highlighted in the case studies [4–12]. Low frequency oscillatory stability studies of power systems with large-scale PV advocate that depending on penetration levels, positions and the control approaches, large-scale PV systems could have adverse effect on the critical EM modes [11,12]. However, due to slow response of PV generator controller and intermittent input to the PV, it is recommended to have some auxiliary devices in PV system such as BESS, ultracapacitor or shunt capacitor to meet the certain grid code requirements for interconnection [13]. But, none of the aforementioned studies have considered these auxiliary de- vices impact on low frequency oscillation damping. In this respect in our previous work [14], we have analyzed the impact of PV and ultracapacitor on the damping of inter-area mode. It is shown that the PV plant tends to increase the damping of the inter-area mode in presence of ultracapacitor at PV. Conversely, BESS has been recognized as a useful and powerful device for smoothing output power fluctuations of variable gener- ator like PV. During the past few years, a number of studies focused on analyzing the different aspects of integrating BESS systems with PV systems, especially standalone PV systems [15,16]. Other stud- ies focused on using BESS systems with small grid connected PV systems [17,18]. Recently, few studies investigated the use of BESS to bridge power fluctuations and fault ride-through capabilities of 0306-2619/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.apenergy.2011.09.035 ⇑ Corresponding author. Tel.: +61 (0)7 3365 1654. E-mail address: md.shah@uq.edu.au (R. Shah). Applied Energy 96 (2012) 235–244 Contents lists available at SciVerse ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy