Unit Commitment Considering the malfunctioned Operation of Hybrid Energy Storage Systems in Frequency Stability Support

Using security-constrained unit commitment as a preventative method of supplying power system frequency response can increase the penetration of renewable energy sources while maintaining frequency response parameters within their allowable range. Moreover, it can reduce the need for corrective actions such as under-frequency load shedding and can prevent power blackouts. So far, there have been two views about the virtual inertia of grid-connected energy storage units, pessimistic (lack of virtual inertia) and optimistic (failure-free frequency response). However, in reality, the frequency response supply system may experience malfunction and incorrect operation, which is modeled and analyzed in this paper from a techno-economic standpoint. False sensor detection, control system malfunction, wrong power injection of energy storage, inverter failure, improper parameter setting, etc., can all be considered disruptive factors. However, in order to have a more general model, the article avoids dealing with the reason behind the poor performance of the storage system and focuses only on its effects, i.e., the possibility of the storage system not participating correctly. The proposed model takes into account the system's frequency stability by linearly integrating the nadir frequency and the rate of change of frequency limits to the robust mixed-integer linear programming model with YALMIP and MOSEK solvers. The results of implementing this model in the IEEE-RTS96 network show that neglecting energy storage system malfunctions can lead to violations of frequency constraints that must be compensated by increasing costs and keeping more online units with more free headroom.