7. Power Management and Control The area of EPS control, check-out and operation is strongly influenced by the new COLUMBUS scenario. For the power system the following goals are of primary importance: • EPS autonomy to be enhanced. —Reduced dependence on ground stations. —High degree of functional independence from the DHS to be achieved. • In-orbit maintenance shall be facilitated. —Self check capability/failure diagnostics. • Interface complexity between subsystems to be reduced. —Simplification of design/development/test/integration. • Decentralization. —Tasks shall be shared such that a high degree of functional modularity is obtained (increased reliability). By clearly recognizing the significance of these topics, much study effort has been spent in order to develop new ideas in the area of power management and subsystem control. As a result AEG has proposed the Power system ZMernal DAta Processing (PINDAP) assembly. PINDAP is a data acquisition and processing system taylored to the specific EPS needs. Hardwarewise it is in line with the present COLUMBUS baseline, i.e. it makes use of presently defined building blocks as: • STAUs (Standard Acquisition Units) as data interface to the individual EPS equipment; • system LAN for data transfer between the equipment dedicated STAUs and the EPS subsystem processor; • subsystem processor as PINDAP Kernel. Automated systems must be structured hierarchically. For COLUMBUS the following three levels are to be distinguished with respect to the on-board intelligence hierarchy: • System Level (Level 1): On-board management. • Subsystem Level (Level 2): Subsystem management. • Equipment Level (Level 3): Local management. PINDAP's role and position in the frame of this hierarchy is shown in Fig. 8. It provides a centralized interface to the DMS such that interactions between both subsystems are performed at highest feasible level. Interactions between DMS and PINDAP are required for activation/deactivation of the EPS or in the case of EPS reconfiguration (e.g. switch-over to back-up buses, load shedding etc.). On the other hand PINDAP coordinates and supervises all subsystem internal functions. Therefore, it performs thorough status monitoring, command generation and management of redundancies. In this context special attention is to be paid to the energy storage system. According to the present baseline, NiH2 batteries shall be used for the IOC version. Hence, hundreds of cells must be supervised individually which will result in a fairly high data stream to the central processor. The task of closed loop control of currents and voltages, as frequently encountered in all kind of power conditioning equipment, will not be transferred to PINDAP. It
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