Effectiveness of damping control implemented by an energy storage system as affected by the line loading conditions

In order to understand how an energy storage system (ESS) based supplementary damping control (stabilizer) suppresses power system inter-area oscillations, this paper proposes a tie-line power variation related ESS linearized dynamic model. This model describes the direct contribution from the ESS control to the small-signal variations (oscillations) of the tie-line power. Based on the model, a general conclusion is established to assess the capability of the ESS based stabilizer to affect the damping of inter-area power oscillations. Analysis based on the general conclusion explains how the effectiveness of the ESS stabilizer changes with the variations of loading conditions of tie line. It is concluded that the ESS based stabilizer is more robust to the variations of tie-line loading conditions when it is implemented by regulating the active power exchange between the ESS and the power system. In the paper, results of computation and simulation of an example power system installed with a battery energy storage system (BESS) are presented.