From Boeing:
Rocketdyne is responsible for the end-to-end electrical power system for the International Space Station.
The system consists of power generation, energy storage and power management and distribution. The system provides 78 kw to the users with the power being generated by four photovoltaic (PV) Array Modules. Each module consists of two flexible deployable array wings of silicon solar cells supported by an extendible mast.
The station orbits the earth every 95 min. spending approximately 2/3 of the time in sunlight 1/3 in eclipse. Power is provided during sunlight by the PV Arrays. During the eclipse the 78 kw of station power is provided by Nickel-Hydrogen batteries which are charged during the sunlit part of the orbit.
The power management and distribution subsystem distributes the power at 160 volts DC around the station through a series of continuous duty, DC contactor switchgear. The switchgear has built-in microprocessors, controlled by Ada software and connected to a data bus running throughout the station. DC-DC converter units stepdown and condition the voltage from 160 to 120 volts DC to form a secondary power system to service the loads through solid-state switchgear. The converters also provide isolation of the secondary from the primary system and maintain uniform power quality throughout the station.
