Sizing and operation of hybrid energy storage systems to perform ramp-rate control in PV power plants

This paper proposes a methodology for optimal sizing of a Hybrid (battery and ultracapacitors) Energy Storage system for ramp-rate control in PV plants. Frequency stability events can appear in power systems high non-dispatchable renewable energy generation due to sharp power output fluctuations. This has caused TSOs in several countries to require PV and wind plants to implement some method for limiting the pace at which the power injection to the grid is allowed to vary (ramp-rate control). Due to its quick response, properly controlled energy storage consisting of batteries and ultracapacitors can perform this task by dampening quick increases/decreases in the power injection to the grid by absorbing/injecting power at the point of common coupling. In this work, a techno-economic model is presented that can be used to calculate the Net Present Cost over the project life of different energy storage devices used for ramp-rate control by simulating their operation. A real case is studied for a PV power plant is presented. Results are reported comparing different configurations of the energy storage system.