System Identification of Low Voltage DC Sources

Nowadays low voltage DC distribution systems show considerable advantages in many significant aspects in comparison to AC systems. At consumption level photovoltaic systems are the prevalent type of DC sources. That is why, in this paper the process of system analysis is demonstrated by modelling of a photovoltaic module. Depending on the pre-existing knowledge of the system under study the modelling process is a rather theoretical or a rather experimental approach. Additionally, in case of complex systems the experimental model is easier to determine. The experimental system analysis is also termed identification. After the determination of the system boundary the equivalent circuits of both the static DC behavior and the dynamic AC small-signal behavior are build up based on the pre-existing knowledge about the module. Subsequently, the beforehand defined experiments are performed. To identify the AC small-signal behavior, impedance spectroscopy is used. On the basis of the determined static and dynamic nonparametric models the values of the parameters of both equivalent circuits are identified and evaluated.