Unit commitment (UC) is to determine the optimal unit
status and generation level during each time interval of the scheduled period.
The purpose of UC is to minimize the total generation cost while satisfying
system demand, reserve requirements, and unit constraints. Among the UC
constraints, an adequate provision of reserve is important to ensure the
security of power system and the fast-response reserve is essential to bring
system frequency back to acceptable level following the loss of an online unit
within a few seconds. In this paper, the authors present and solve a UC problem
including the frequency-based reserve constraints to determine the optimal FRR
requirements and unit MW schedules. The UC problem is solved by using Lagrangian
Relaxation-based approach and compared with the actual system schedules. It is
observed that favorable reserve and unit MW schedules are obtained by the
proposed method while the system security is maintained.