Reconfigurable Two-Stage Solar PV -Battery Supported– Small Hydro System Based Micro-Grid

The operation of a double stage solar photovoltaic (PV)-battery supported small hydro system in reconfigurable modes like the grid connection (GC) and an islanded mode (IM) is reported. The small hydro system consists of a permanent magnet synchronous generator (PMSG) driven by an uncontrolled hydro turbine. Whenever the GC is not present this system works at IM and if the grid is available it synchronizes and operates in GC. A multilayer harmonics compensation phase locked loop (MHC-PLL) control is presented in this work. This PLL technique is used to estimate harmonics free positive sequence grid and hydro generator voltage phase angles for accurate and timely grid synchronization. A modified complex co-efficient (MCC) based filter is implemented to extract load currents fundamental component and controls the switching signals to voltage source converter (VSC) operating in both reconfigurable modes. An improved perturb and observe (IP&O) based maximum power point tracking (MPPT) control technique is used to extract maximum power from the solar photovoltaic (SPV) array. The boost converter based two-stage solar PV generation is controlled with its output to match with the DC-link voltage. The bidirectional converter (BDC) controls the bidirectional power flow in the battery by controlling its charging\discharging current.