Test Rig for Hybrid System Emulation: New Real-Time Transient Model Validated in a Wide Operative Range

This paper reports an entirely new simulation tool for a hybrid system emulator facility built by the Thermochemical Power Group (TPG) at the University of Genoa, Italy. This new software was developed with the following targets: realtime performance, good stability level and high calculation reliability. In details, to obtain real-time performance a new approach based on 0-D technique was chosen also for components usually analysed with 1-D or 2-D tools (e.g. the recuperator). These are essential key aspects to operate it in hardware-in-the-loop mode or to evaluate predictive results for long transient operations. This work was based on collaboration between the University of Manchester, UK and the University of Genoa, Italy. The activity was carried out with a test rig composed of the following technology: a microturbine package able to produce up to 100 kWe and modified for external connections, external pipes designed for several purposes (by-pass, measurement or bleed), and a high temperature modular vessel necessary to emulate the dimension of an SOFC stack. The real-time transient model of this facility was developed inside the Matlab-Simulink environment with the following modelling approach: a library of components allows to reach a high level of flexibility and an user-friendly approach. This model includes the machine control system as an essential device to analyse further layouts (new components in the rig) and hardware-in-the-loop operations. The experimental data collected in the laboratory by TPG were used to validate the simulation tool. The results calculated with the model were satisfactory compared with experimental data considering both steady-state and transient operations. The most important innovative aspects of this work are related to this wide validation range (not only small power steps, but the whole operative range was considered) obtaining real-time performance and considering microturbine conditions different from standard operations (additional pressure and temperature losses and unusual thermal capacitance). The modelling simplified approach used for such a complex system is an important innovative aspect, because usually the model reliability performance is obtained with more complex (and not real-time) tools. This work is based on an innovative modelling approach based on 0-D tools able to operate in real-time mode (as necessary for hardware-in-the-loop tests) with an accuracy level comparable with more complex and more time consuming software. This validated tool is an important base for future calculations to study innovative hybrid system layouts. For instance, TPG is planning to analyse the option of increasing fuel cell pressure and performance with a booster system (e.g. a turbocharger).