The present invention relates to control systems for a combined cycle power plant and systems which optimize the performance of such power plants.
Combined cycle power plants are typically used to generate electrical power delivered to a power grid. The power is distributed by the grid to consumers, such as residences, businesses and other consumers of electrical power. Combined cycle power plants are paid for the power delivered to the grid.
The price paid for power delivered to the grid varies based on the demand for power. The price may be higher for power delivered during normal business hours than for power delivered in the middle of the night. Similarly, the price may be higher during summer and winter than during fall and spring. Typically the prices are set periodically, such as each day, week or month. The prices are given to the power plants.
The operators of the plants use the prices to determine how much power to generate and deliver to the power grid. The operators also consider the cost to generate power by their power plants. The difference between the price for power and the cost to generate the power is a measure of the profitability of the power plant. The profitability of the power plant is an important indicator to the economic viability of the plant.
Determining the cost to generate power involves several factors, such as the cost of fuel and ambient conditions, such as outside temperature and humidity. The operating state of the gas and steam turbines in the power plant are also factors influencing the cost to generate power. Other factors affecting the cost to generate power and the power output capacity of the plant include the costs introduced by power augmentation devices, such as a chiller to cool the air entering a gas turbine and a duct firing system to supplement the generation of steam for the steam turbines. The relationship between these factors is complex. It has long been difficult to operate a combined cycle power plant with power augmentation devices in a manner that minimizes the cost of generating power and maximizes the profitability of the plant.
Similarly, the long term and short term variations in the demand for power are factors influencing the setting of the loads on the steam turbines and gas turbines in a combined cycle power plant. Steam turbines typically operate at a steady state to generate a constant amount of power. Gas turbines are well suited to produce varying amounts of power, such as for peak power during certain hours of a day.
Due to the complexities in determining the cost to generate power, variations in the price of power and variations in fuel cost, there is a long felt need for systems and methods to assist operators in controlling combined cycle power plants and in determining optimal operational settings for the power plant. The optimal operational settings would be useful to increase the profitability of the power plant and increase the effectiveness of the power plant in meeting a need for power by a power grid. The complexities in determining the optimal operational settings are greatly expanded when power augmentation equipment, such as air chillers and duct firing devices, are added to the power plant.