Real-time Electrical Emulation of Li-ion Battery Storage Using Power-Hardware-in-the-Loop

Li-ion batteries have become increasingly important in several engineering fields of technology. The batteries play a crucial role, for example, in renewable energy applications in which battery storages are used to balance the power fluctuations caused by continuously varying weather conditions. Another good example is electric vehicles whose operation is most often dependent on Li-ion batteries. The ever-increasing applications of Li-ion batteries have set new challenges in battery analysis. In order to know when the battery must be replaced and in which application it might still be utilized, knowing the age of the battery is crucial. The battery state of health (SoH) is used to estimate the aging and degradation of the battery. The SoH can be estimated by measuring the battery internal impedance since it is highly dependent on the aging processes. Studying the battery aging is time-consuming because of the slow aging mechanisms and charging or discharging the battery to the desired operating state. This thesis studies methods for emulating the battery aging in real time using power-hardware-in- the-loop environment. The methods make it possible to analyze the SoH of Li-ion batteries within a short time without utilizing the actual aging process. This thesis presents the modeling of Li-ion battery impedance and the implementation of battery emulation. The battery impedance model parameters are extracted from real data using a complex nonlinear least squares algorithm. Battery aging models are used to vary the battery SoH in real time. The operation of the emulation setup is verified by impedance measurements using wideband-identification techniques