An impedance model of a PV grid-connected system

PV grid-connected systems are rich in nonlinear behaviors. Their operation depends on several factors such as radiation, switching algorithm and maximum power point tracking (MPPT) algorithm implemented in the grid-connected inverter which give rise to a variety of nonlinear behaviors and uncertainties. This paper proposes a passive impedance network as a model that can capture the system behaviors based on scenarios and data observed on the actual PV grid-connected system. A hardware experimental setup is created to imitate the operating characteristics of a PV grid-connected system such as current and voltage on both dc and ac sides. This work emphasizes on the salient features of the system operation and modeling strategies. Because of nonlinearity in the proposed model, the measured data and the Newton-Raphson iterative method are used to determine the model parameters. The study results show that the impedances in the proposed model have shown negative characteristics similar to that commonly found in power electronic converters. The proposed model may be integrated into a sequential, power solver for determining effects on a distribution system.