Dynamic ramp-rate control to smooth short-term power fluctuations in large photovoltaic plants using battery storage systems

The changeability in the power produced by utility-scale PV plants caused by passing clouds can compromise power quality and reliability. Hence, some kind of energy storage systems (ESS) are required to reduce power variations below the limits imposed by new grid codes regulations. Here, we propose a novel control strategy to smooth out the fluctuations by using an energy storage system, namely dynamic ramp-rate control, which provides simultaneously a simple state of charge (SOC) control and 30 % less cycling degradation than classic ramp-rate control, as only is triggered when a fluctuation takes place. In addition, the strategy parameters can be tuned in order to reduce the capacity requirements by only modifying the SOC band values wherein the strategy is active. The novel techinque has been shown to work effectively with 5-s real power measurements recorded at the Amareleja PV plant (45.6 MWp, Portugal).