Analysis and control of a multi-string photovoltaic (PV) system interfaced with a utility grid

This paper focuses on the study of a two-stage, multi-string photovoltaic (PV) system connected by a common DC bus to a centralized inverter, interfaced with a utility grid. The distribution network model, load model and DC bus model are used for simulation. PV system exhibits non-linear v-i characteristics and an intermediate boost converter is employed to operate the PV array at its maximum power point. An incremental conductance algorithm is employed to control the boost converter. A centralized inverter is controlled via a decoupled current control method and interfaced to the utility grid through a distribution transformer. The control of inverter is completely independent of maximum power point control of boost converter. Finally system stability is assessed with respect to variation in solar radiation of the PV and distribution network parameters.