Markus Beukenberg

Design and Operational Aspects of Gas and Steam Turbines for the Novel Solar Hybrid Combined Cycle SHCC

Solar hybrid power plants are characterized by a combination of heat input both of high temperature solar heat and heat from combustion of gaseous or liquid fuel which enables to supply the electricity market according to its requirements and to utilize the limited and high grade natural resources economically. The SHCC® power plant concept integrates the high temperature solar heat into the gas turbine process and in addition — depending on the scheme of the process cycle — downstream into the steam cycle. The feed-in of solar heat into the gas turbine is carried out between compressor outlet and combustor inlet either by direct solar thermal heating of the pressurized air inside the receivers of the solar tower or by indirectly heating via interconnection of a heat transfer fluid. Thus, high shares of solar heat input referring to the total heat input of more than 60% in design point can be achieved. Besides low consumption of fossil fuels and high efficiency, the SHCC® concept is aimed for a permanent availability of the power plant capacity due to the possible substitution of solar heat by combustion heat during periods without sufficient solar irradiation. In consequence, no additional standby capacity is necessary. SHCC® can be conducted with today’s power plant and solar technology. One of the possible variants has already been demonstrated in the test field PSA in Spain using a small capacity gas turbine with location in the head of the solar tower for direct heating of the combustion air. However, the authors present and analyze also alternative concepts for power plants of higher capacity. Of course, the gas turbine needs a design which enables the external heating of the combustion air. Today only a few types of gas turbines are available for SHCC® demonstration. But these gas turbines were not designed for solar hybrid application at all. Thus, the autors present finally some reflections on gas turbine parameters and their consequences for SHCC® as basis for evaluation of potentials of SHCC® .Copyright

Design of Reduced Order State Space Controllers With Adaptive Limiting Functions for Industrial Twin Shaft Gas Turbines

The designs of model-based state space controllers for industrial twin shaft gas turbines, presented at last year’s conference [1], were enhanced by a limiting function for selected state variables. In order to avoid the disadvantages of common controller concepts involving abrupt structural changes, the limitation was realised by a parameter-variant state space controller. To reduce the sensitivity of the full state space controller to parameter changes, a reduced order controller was developed, taking into account only the dominant state variables of the system. As in previously presented designs, a PI state space controller was designed for the reduced system using the pole placement method. Subsequently, this reduced controller was adapted to the original nonlinear system. With appropriate pole placements for the reduced order state space controller, a high quality of control, comparable to the behaviour of a full state space controller, can be obtained. The resulting controller also shows a reduced sensitivity to variations of the feedback parameters. The intended state variable limitation of the original nonlinear system to defined thresholds has been achieved by applying floating functions between different controller parameter sets.© 2006 ASME

Design of State Space Controllers for Industrial Twin Shaft Gas Turbines

This paper depicts the development of a new control strategy for industrial gas turbines to improve the control accuracy in the entire operating range. In the first step, a complex mathematical model has been developed, which is implemented into the controller dynamic simulation. An automatic operating point dependent linearization process permits the model to be displayed in a linear state space description. Three established controller design procedures have been applied to the process. In the past, only a small number of state space control designs have been presented for industrial gas turbines. These approaches use low order mathematical descriptions, which often do not describe the system behavior in detail. This paper presents a controller design for a more detailed mathematic model of the 15th order. It is indicated, that certain controller designs are difficult to realize or even fail. These effects result from unfavourable numerical conditions (depending on the operating point) in combination with the high order of the approximated linear system description. The tested pole placement designs show favorable closed loop system dynamic behavior and were improved by adding an integrating part to the controller.Copyright