New voltage regulation scheme for photovoltaic systems based on Thevenin's Theorem

The distribution grid structure is expected to change in the upcoming years with the further penetration of renewable energy sources (RES). Most of the energy needs will be covered by local distributed generators (DG) responsible also for maintaining good levels of power quality and grid stability. As a consequence, measures for regulating the voltage within acceptable levels will be required as well as storage to allow proper utilization of produced energy and to ensure that the distribution grid operates in an uninterruptable and healthy way. In this work, a new voltage regulation scheme inspired by Thevenin's Theorem is developed and presented. The well-known dynamic power factor method is modified accordingly to provide a variable lower limit, which is defined by the Thevenin equivalent impedance (TEI) measured at the point of common coupling with the electricity grid. The new voltage regulation scheme is incorporated into the control circuit of a verified Photovoltaic (PV) system model for its further evaluation via computer simulations.