Modelling and Control of Modular DC-Nanogrids Based on Loss-Free Resistors

This paper proposes a modular photovoltaic (PV) dc-Nanogrid (dc-NG) architecture for residential applications. The proposed architecture is based on the Loss-Free Resistor (LFR) concept. The dc distribution bus is supplied by PV panels, ac utility and a storage battery. The storage battery is connected to the main dc bus through a dc-dc bidirectional converter (BDC). This battery has also an important role to ensure uninterruptible power supply to the critical loads and controls the power flow in the dc-NG. A mathematical model of the system is first derived and a stability analysis is carried out showing that the stability is guaranteed under certain mild conditions. Numerical simulations of a case study for two PV panels corroborate the theoretical predictions which have been finally confirmed by experimental measurements.