Synthetic inertia offers the potential to increase power system stability during generation-load imbalances; particularly when conventional generation has been displaced by non-synchronous in-feed. This study is based on three frequency transients caused by the loss of 14% of the synchronous generation on the Irish system. Analysis of PMU data from power plants is used to determine the per unit displacement potential with BESS of differing delay times and ramp rates. It is observed that synchronous generators undergo a step change in power output during frequency transients. The unsuitability of a droop response for a synthetic inertia response is demonstrated and that a step change in power output is required to maximize inertial participation. The displacement results are compared to existing and proposed operating characteristics of the Irish system.

Battery energy storage systems (BESS) are being deployed to provide a range of power system services. In this paper, the voltage support capabilities of a 10 MVA, 5 MWh BESS installed at a thermal power plant are explored. The study specifically relates to the voltage dips caused by starting of large boiler feed pump motors on the 11 kV supply of the power plant. The benefits of reactive power injection from BESS are explored via simulation and validation is provided from tests on the actual plant. The likely reduction in voltage dip if the BESS can contribute its rated reactive current is quantified. As a result, the motors experience higher starting torque and peak current, however as they start more quickly, the contribution to heating is expected to reduce. The effect on provision of other services demanded from the BESS and wider opportunities to provide voltage support are discussed.