A flexible AGC algorithm for the Hellenic interconnected system

A flexible automatic generation control (AGC) algorithm is described that has been developed for the Hellenic interconnected system. The algorithm includes the three well-known load frequency control (LFC) types (flat frequency, flat tie-line, and tie-line bias) and introduces four operating modes that depend on the magnitude of the measured area control error (ACE). These modes are the steady-state operating mode, the normal operating mode, and two distinct emergency modes. The LFC stability margins are calculated for the case of slow-acting, flat frequency control. The effects of integral feedback are also considered and analyzed. An approximate economic dispatch algorithm is presented that makes use of a predetermined table of the economic loading of units. Simulation results are reported that demonstrate satisfactory operation of the AGC system. Detailed transient stability program simulations demonstrate that a number of ACE measurements per measuring period are necessary to avoid dangerous false emergencies