can be used, however, in order to modify reference values of the control loops such that performances can be adjusted to changing internal or external conditions. In the power distribution area a great number of SSPCs and some mechanical switches are to be operated (on/off commands, status acquisition), which can be extremly simplified by PINDAP. In order to support in-orbit maintenance, check-out data from the built-in test equipment (BITE) are transferred to the subsystem processor. Evaluation of these data leads e.g. to indication of equipment/life limited items which need to be replaced. Due to PINDAP, failure cases can be handled now with a clear allocation of tasks: • Failure identification and isolation is performed on equipment level. • Recovery actions, however, on subsystem and system level by giving highest priority to crew safety and mission objectives. A remarkable feature of the described hierarchy is that only processed results will routinely progress upward through the different management levels. Raw data will do this on request only. The immediate consequence is a reduced data stream to the ground station, representing an important step towards alleviated ground support requirements. It is of importance, however, that the mentioned automated control functions will be accessible to crew or ground in order to provide the possibility for manual override. The described properties clearly underline the benefits of this new power management and control approach. A chief advantage is that the entire control procedure is less rigid. It allows adaptation to changing operational conditions. This is based on the fact that due to PINDAP hardware is replaced by software. 8. Summary/Conclusions The paper describes advanced power supply and distribution systems to be used on unmanned/man-tended Columbus elements, capable of supplying 8 to 30 kW to a variety of users in low earth orbits. Emphasis has been put on new techniques and technologies which are indispensible in order to cope with the stringent COLUMBUS requirements. In this context it is to be recognized that a subsystem as the EPS which shall deliver electrical power for large-scale space activities can only use proven technologies. The challenge to the designing engineers is to make the described innovations so reliable that they can be used without any restrictions on all COLUMBUS elements. In order to achieve this, the related research and development activities have been initiated already (ESA's PSTP program). Areas receiving special attention are: • Photovoltaic power generation in the low earth orbit environment; • Energy storage devices with improved cycle-life and depth of discharge properties (NiH2 technology); • Medium voltage DC distribution systems (switching, protection); • New methods for power management and control. AEG is confident that these R&D activities in conjunction with the technical competence of all parties involved, will bridge the gap between escalating demands on technical performance and state of the art—such that the described new approaches will be realized successfully.
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