Integrated battery controller for distributed energy system Vasudeo Virulkar a , Mohan Aware a , Mohan Kolhe b, * a Visvesvaraya National Institute of Technology, Electrical Engineering Department, Nagpur, MS, India b University College London, UCL School of Energy and Resources and International Energy Policy Institute, Torrens Building, 220 Victoria Square, Adelaide, SA 5000, Australia article info Article history: Received 30 July 2010 Received in revised form 14 December 2010 Accepted 13 January 2011 Available online 5 March 2011 Keywords: Battery energy storage system (BESS) Distributed power system control Active filter Load levelling Hysteresis controller abstract In this article, an improved integrated battery energy storage system (BESS) controller for distributed energy system is presented. The BESS is integrated in parallel with the full wave bridge converter into the distributed energy system network. In a normal operating mode, the BESS serves as a power conditioner as well as an active power filter in a distributed power system network. This work presents BESS controller which is designed for regulating the state of charge of the batteries and also to manage the active power in a distributed power system network. The off peak load energy is used to recover the batteries’ state of charge through the BESS controller. In this BESS controller, the constant currenteconstant voltage (CCeCV) mode is used and it helps to keep the batteries’ state of charge conditions for improving the reliability of the distributed power system system. This control strategy is incorporated into the main converter. The controller helps in managing the phase, amplitude and waveform of the current and voltage on the distributed power system network. The controller ensures the power quality and also assists in improving the power factor with respect to the utility for the intermittent distributed generation as well as the load. In this article, the test results of a prototype system are presented, which validates the proposed controller strategy of BESS in a distributed power system network. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The growing pressure to reduce the carbon emissions has fuelled global interest in developing new efficient and renewable energy technologies and already has created substantial commitment to the development and deployment of such type of systems. Traditionally power system networks were built for transferring the electrical energy generated by the high capacity centrally placed power production units. The electricity industry is on the edge of making the transformation from a centralized producer controlled network to one that is less centralized and more consumer-interactive. Smart grid management will make it possible to operate distributed energy resources in coordination with the grid. Distributed energy sources include environment friendly energy sources such as solar photo- voltaic, wind turbines, and cleaner gas-fired technologies including micro turbines and fuel cells. Investment in these areas is leading to growing the number of installations of distributed generation (e.g. micro e CHP, solar systems, fuel cells, energy storage) and the promotion of increased opportunities for effective demand management schemes and energy efficiency activities [1,2]. The most utilized energy storage system for distributed energy systems is deep-cycle lead-acid batteries. In a distributed energy system (combined with intermittent energy sources like wind or solar), the batteries provide short-term energy storage as well as reliable supply of power to serve as a backup power source or for peak shaving [2,3]. At present, lead-acid batteries are one of the most cost effective energy storage technologies. These batteries can be designed for bulk energy storage or for rapid charging e dis- charging operations. Battery technologies and their electro-chem- istry are advancing very fast and offering high energy storage density, greater chargingedischarging cycling capabilities, higher reliability, and also there is a cost reduction [3,4]. Battery Energy Storage Systems (BESS) have recently emerged as one of the most promising technologies for short-term energy storage for energy applications, offering a wide range of applications in the distributed energy systems (e.g. area regulation, area protection, spinning reserve, power factor correction/improvement, reliability, power quality etc) [4e7]. Many of the BESS systems are utilized for the load levelling, power system management, stability and frequency control [8]. Such a system can also be integrated with Flexible AC Transmission System (FACTS) power controller to improve the power system reliability, operation and control [9]. A proper power conditioning system (i.e. BESS) is required to interface the batteries in a distributed power system network. The BESS controller can have different types of converter topologies. * Corresponding author. Tel.: þ61 881109966; fax: þ61 8 8212 3039. E-mail address: m.kolhe@ucl.ac.uk (M. Kolhe). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy 0360-5442/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.energy.2011.01.019 Energy 36 (2011) 2392e2398