On the control and operation of the electrical power system for the International Space Station

This paper describes the latest on-orbit International Space Station (ISS) electrical power system (EPS) operational control capabilities including autonomous functions, override capabilities, operational constraints and their verification. The ISS requires the ability of the vehicle to detect, isolate and recover “functions required for 24 hour autonomous operation” without crew or ground intervention. This results in a necessity to design and develop autonomous operations without routine commanding and override of specific automation. The paper covers the autonomous tiers of control, the manual control strings provided to the flight crew and ground for operational flexibility, operation procedures and the verification of EPS flight hardware and software. It covers how the EPS operations are performed by means of hardware, software, firmware and procedures. The EPS control domains are defined by a functional decomposition of Space Station capabilities and the allocation of those functions to a particular EPS hardware, software, firmware capability or to a control tier. In the paper, all the control domains within the EPS sub-system are defined to include the autonomous, manual and system constraints providing full coverage of EPS functionality