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
Test and evaluation of load converter topologies used in the Space Station Freedom power management and distribution dc test bed
Power components hardware in support of the Space Station Freedom dc Electrical Power System were tested. One type of breadboard hardware tested is the dc Load Converter Unit, which constitutes the power interface between the electric power system and the actual load. These units are dc to dc converters that provide the final system regulation before power is delivered to the load. Three load converters were tested: a series resonant converter, a series inductor switchmode converter, and a switching full-bridge forward converter. The topology, operation principles, and tests results are described, in general. A comparative analysis of the three units is given with respect to efficiency, regulation, short circuit behavior (protection), and transient characteristics.
The Game Planners: Transforming Canada's Sport System.
The Game Planners studies the policy-making process in six Canadian national sports organizations, each of which deals with a different high-profile Olympic event. The authors argue that the creation of a "high-performance" sport system in Canada is due to pressure from three areas: the Canadian government, the physical education profession, and the sports community.