In this paper, some of the aspects related to the design, control, operation and protection of photovoltaic (PV) systems are presented and investigated. The photovoltaic systems under study are integrating their power to the common DC bus of a hybrid AC/DC microgird in a smart grid infrastructure, where a communication layer is allowing wide area monitoring, control and protection of the whole system. These PV systems can be mainly operated either in a voltage control mode, when the DC side of the system is disconnected from the main AC grid, or in a maximum power point tracking (MPPT) mode when connected to the DC bus. The control of the power conditioning units interfacing the PV panels to the rest of the systems in these two modes of operation is investigated. Furthermore, the protection of these converters against different types of faults will be also investigated. Simulation and experimental results are included in the paper to justify the validity of the ideas and concepts discussed.