“…These are insufficient because of changes in operating points during a daily cycle [Benjamin et al, 1978;Nanda et al, 1988;Das et al, 1990;Mufti et al, 2007;Nanda et al, 2006& Oysal et al, 2004 and are not suitable for all operating conditions. Therefore, variable structure controller [Benjamin et al, 1982;Sivaramaksishana et al, 1984;Tripathy et al, 1997& Shayeghi et al, 2004 has been proposed for AGC. For designing controllers based on these techniques, the perfect model is required which has to track the state variables and satisfy system constraints.…”