Design and Implementation of a Hybrid Real-Time State of Charge Estimation Scheme for Battery Energy Storage Systems

Abstract

In order to maximize the operating flexibility and optimize the system performance of a battery energy storage system (BESS), developing a reliable real-time estimation method for the state of charge (SOC) of a BESS is one of the crucial tasks. In practice, the accuracy of real-time SOC detection can be interfered with by various factors, such as battery's intrinsic nonlinearities, working current, temperature, and aging level, etc. Considering the feasibility in practical applications, this paper proposes a hybrid real-time SOC estimation scheme for BESSs based on an adaptive network-based fuzzy inference system (ANFIS) and Coulomb counting method, where a commercially available lead-acid battery-based BESS is used as the research target. The ANFIS allows effective learning of the nonlinear characteristics in charging and discharging processes of a battery. In addition, the'Coulomb counting method with an efficiency adjusting mechanism is simultaneously used in the proposed scheme to provide a reference SOC for checking the system reliability. The proposed estimating scheme was first simulated in a Matlab software environment and then implemented with an experimental hardware setup, where an industrial-grade digital control system using DS1104 as the control kernel and dSPACE Real-Time Interface (RTI) interface were used. Results from both simulation and experimental tests verify the feasibility and effectiveness of the proposed hybrid SOC estimation algorithm.Keywords: battery energy storage system (BESS); state of charge (SOC); adaptive network-based fuzzy inference system (ANFIS) Processes 2020, 8, 2 2 of 22 As a result, real-time SOC can be determined based on a given initial SOC value. This process can be expressed as (1):

State of charge estimation of ultracapacitor based on equivalent circuit model using adaptive neuro-fuzzy inference system

“…In their implementation, some utilize Ultracapacitor-battery hybrids to get optimal performance from both energy storage devices [13]. It is also possible to use an Ultracapacitor as the primary energy storage device in electric vehicles, for example, electric scooters and buses [14]. Fast charging capabilities make Ultracapacitor a breakthrough in battery replacement technology [15].…”