One Step Ahead Adaptive Control with modification for application to Aero-derivative Gas Turbine

摘要

The feasibility of the application of One Step Ahead Adaptive (OSAA) Control technique applied to a single shaft Gas Turbine power plant has been already investigated by the authors. The OSAA technique is a control algorithm especially suitable for non-linear and time-varying systems. This technique uses the Least Square algorithm to estimate in realtime a linear model of the controlled system, and, uses the estimated linear model to evaluate the feedback control variables. The OSAA control does not require the knowledge of the dynamic characteristics (e.g. state space systems or transfer functions) in order to design the control system. In the present paper, the OSAA control system is applied to an Aero-derivatives Gas Turbine. Such a Gas turbine power plant consists in a multi-shaft configuration. In the present paper a double shaft configuration has been considered. The Gas generator is composed by the high pressure turbine connected to the compressor. On the other hand the low pressure turbine drives the electric generator. Due to the complex structure of the plant layout, the double shaft Gas Turbine presents high time constants. The OSAA control system has been conveniently modified considering in the linear estimated model also the angular acceleration. This modification makes the OSAA control technique fully aware of the dynamic equilibrium conditions of the low pressure shaft and therefore it is able to promptly react to the variations of the disturbance variables. The proposed control technique, conveniently modified, has been tested in Single Input Single Output (SISO) mode to control the low pressure shaft rotational speed, starting from a steady-state condition. The power plant has been supposed to undergo to a complex variation of the electric load. The results show that the OSAA control technique effectively counteracts the load variations with limited overshoots in the controlled variables and a negligible static error.