Impact of a Heavy-Duty Gas Turbine Operating Under Temperature Control on System Stability

Frequency drops and the high ambient temperature cause a decrease in airflow and an increase in the exhaust gas temperature of a gas turbine (GT). These two conditions significantly reduce the maximum continuous power output of GTs. Correct modeling of these conditions under heavily loaded conditions, such as in hot summer, is very important. Otherwise, the simulated maximum output of GT may be significantly higher than the real one and estimation of frequency responsive reserve and spinning reserve may be gravely erroneous. This paper describes the modeling and simulation of a heavy-duty GT operating under temperature control to study its impact on power system stability. For the practical simulation, a simple logic was added to the temperature reference parameter to represent the GT under the temperature control mode under steady-state conditions in the popular Rowen GT model, and the bumpless tracking logic was considered in the proportional-integral temperature controller. For three widely used GT models, GAST, GAST2A, and GGOV1, the effect of the temperature control loop on the transient stability is reviewed in a simple manner by applying the three-phase fault. Finally, the impact of GT under temperature control operation on frequency stability was analyzed using the proposed GT model with the determined model parameters of a practical GT system with 341 MVA during frequency drop against a six-machine, 23-bus system.