Stability Testing and Analysis of a PMAD DC Test Bed for the Space Station Freedom
ABSTRACT The Power Management and Distribution (PMAD) DC Test Bed at the NASA Lewis Research Center is introduced. Its usefulness to the Space Station Freedom Electrical Power System (EPS) development and design are discussed in context of verifying system stability. Stability criteria developed by Middlebrook and Cuk are discussed as they apply to constant power DC to DC converters exhibiting negative input impedance at low frequencies. The utility-type Secondary Subsystem is presented and each component is described. The instrumentation used to measure input and output impedance under load is defined. Test results obtained from input and output impedance measurements of test bed components are presented. It is shown that the PMAD DC Test Bed Secondary Subsystem meets the Middlebrook stability criterion for certain loading conditions. INTRODUCTION The Space Station Freedom (SSF) Electrical Power System (EPS) is a multi-kilowatt DC power system. The eventual goal is to provide 56kW (75kW peak) of power through six (6) 9.3kW (12.5kW peak) channels. Each channel is comprised of a source subsystem, a 16OVdc (nominal) primary distribution system, and a 120Vdc secondary distribution system. The source subsystem generates and regulates the 16OVdc primary power. The primary distribution power is converted to 120Vdc by DC to DC Converters (DDCUs). The secondary distribution system then distributes the 120Vdc power to the SSF users. A Power Management and Distribution (PMAD) DC Test Bed has been developed at the NASA Lewis Research Center to provide early component and systems level data to support the development of flight hardware and EPS design. The PMAD DC Test Bed consists of breadboard hardware, configured as a single EPS channel, from power sources to user loads[l]. The Space Station Freedom Electrical Power System is unique in many ways. It will be the first space-based power system that will not have clearly defined loading conditions. Over the life of the power system hundreds
Operation of high power converters in parallel
High power converters that are used in space power subsystems are limited in power handling capability due to component and thermal limitations. For applications, such as Space Station Freedom, where multi-kilowatts of power must be delivered to user loads, parallel operation of converters becomes an attractive option when considering overall power subsystem topologies. TRW developed three different unequal power sharing approaches for parallel operation of converters. These approaches, known as droop, master-slave, and proportional adjustment, are discussed and test results are presented.
Climate change, disasters and electricity generation
Abbrevia ons Foreword 1. Introduc on 8 2. The impacts of changing climate pa erns and changing disaster risks on energy 9 op ons and electricity genera on infrastructure 2.1 The rela onship between climate change and disaster risks 10 2.2 The impact of changing climate pa erns and changing disaster risks on electricity 11 genera on from fossil fuels 2.3 The impact of changing climate pa erns and changing disaster risks on electricity 14 from nuclear power 2.4 The impact of changing climate pa erns and changing disaster risks on electricity 17 genera on from renewable energy 2.4.1 Hydropower 17 2.4.2 Wind Energy 19 2.4.3 Bioenergy 22 2.4.4 Solar Energy 24 3. Climate change and changing disaster risks: implica ons for energy policy and 26 planning