Reliability Evaluation of an Aggregate Battery Energy Storage System Under Dynamic Operation

Distributed generators in a microgrid (MG) mostly are renewable energy sources. A system with multiple battery energy storage devices should be used in the MG to improve power supply reliability of these renewable energy sources. This system is defined as an aggregate battery energy storage system (ABESS). To demonstrate the significance of the ABESS in the MG, its operation reliability will be analyzed in this paper. A systematic method is proposed to evaluate reliability performance of the ABESS under different failure operation cases. Besides the used-time-dependent failure rates, voltage-dependent failure rates (VDFR) of critical components in the ABESS such as DC/DC converters, DC/AC inverters, battery modules, and battery charger/controller are also formulated and incorporated in the reliability evaluation. According to differently dynamic operation cases of a microgrid with the ABESS and photovoltaic generation systems, the VDFR of the ABESS will be affected. This paper uses an analytic approach based on Markov models to assess the operation reliability of the whole ABESS. Simulation results are presented and discussed to validate that the operation reliability of the ABESS in the microgrid significantly depends on variously dynamic operating strategies along with the voltage stress.