Power Reserve Control for Gas Turbines in Combined Cycle Applications

In order to be able to optimally operate a combined cycle power plant in a liberalized electricity market, knowledge of the plant’s maximum exportable power generation capacity is vital. However, the maximum power output of a power plant is affected by numerous variable factors, such as the ambient conditions at the plant site. In addition, the allowable plant operating range might be narrowed by a compulsory reserve margin, if the power plant is participating in a frequency regulation program. In this paper, a power reserve controller is derived, which facilitates the optimal operation of a combined cycle gas turbine power plant subject to a reserve margin requirement. The power reserve controller is based on a mathematical description of the power plant and uses an adaptation mechanism to predict on a real-time basis the maximum allowable plant load limit. Based on tests on a single shaft combined cycle power plant, the operation of the power reserve controller is demonstrated and its performance is assessed. The test results prove that the controller predicts the maximum power output of the plant with high accuracy and that it is able to maintain a desired reserve capacity for frequency response as specified.