Internal Power Reserve Estimation for Frequency Regulation in Storageless Photovoltaic System

Power system continuously undergoes demand-supply differences, reflected in the grid frequency. Consequently, grid tied Photovoltaic (PV) systems present a challenging research frontier. Diminishing such differences is a chief expectation from grid-interfaced PV technology, that dictates an active power reserve management mechanism to mimic generator's automatic generation control. The main theme of this work is to maintain an active power reserve by deloading a storage-less PV system. The frequency compensation feature of a 100kW photovoltaic generator is explored in microgrid containing a backup diesel generator and static resistive load. The test system is subjected to short circuit fault and subsequent islanding event is analyzed. Network frequency is regulated by a modified incremental conductance algorithm that releases or absorbs internal power reserve. Hence, reserve management requires an estimate of permissible power for a particular set of ambient source constraints of module temperature and solar irradiance. A technique called stepwise regression is used to train and develop a statistical model for reserve estimation. The modeling results are compared with an equivalent 100kW PV system's load line analysis in Simulink, and are found in considerable agreement. The significance of reserve estimation in hierarchical frequency compensation mechanism during grid faults is established with and without accurate reserve estimation.