Suggested grid code modifications to ensure wide-scale adoption of photovoltaic energy in distributed power generation systems

Current grid standards seem to largely require low power (e.g. several kilowatts) single-phase photovoltaic (PV) systems to operate at unity power factor with maximum power point tracking, and disconnect from the grid under grid faults. However, in case of wide-scale penetration of single-phase PV systems in the distributed grid, the disconnection under grid faults can contribute to: a) voltage flickers, b) power outages, and c) system instability. In this paper, grid code modifications are explored for wide-scale adoption of PV systems in the distribution grid. More recently, Italy and Japan, have undertaken a major review of standards for PV power conversion systems connected to low voltage networks. In view of this, the importance of low voltage ride-through for single-phase PV power systems under grid faults along with reactive power injection is studied in this paper. Three reactive power injection strategies are discussed in detail. Simulations are presented for a PV power system with low voltage ride-through capability and ancillary services. An example of a full-bridge single-phase grid-connected system is tested experimentally to demonstrate the potential benefits.