Power ramp limitation and frequency support in large scale PVPPs without storage

Photovoltaic (PV) power generation started to become a mature technology and large scale PV Power Plants (PVPPs) operating in Maximum Power Point Tracking (MPPT) are not a solution anymore. During changes in the meteorological conditions, PVPPs output is directly influenced creating high power ramps inducing short-term voltage and frequency instabilities into the power system. System operators in countries with increased PV penetration started to become more and more conservative regarding their operation creating strict Grid Codes (GCs). As a proven fact European Network of Transmission System Operators for Electricity (ENTSO-E) pushed the limit one step forward involving PVPPs to contribute with ancillary services even to frequency support. The goal of the paper is to present PVPPs with power ramp limitation and frequency support capabilities without involving any storage equipment. This is achieved by setting the PVPP under its MPP and ensuring a certain amount of reserve. The nature of the reserve has a dynamic character, being released during transients in irradiance and frequency. The entire components of the system are modeled in RSCAD and the performance evaluated on a Real Time Digital Simulator (RTDS).