Session
Session XI: Advanced Technologies 3
Abstract
This paper describes the design and implementation of an advanced high-performance nanosatellite power system, with an emphasis on its battery management and peak power tracking (PPT) capabilities. This power system has been developed for the University of Toronto Institute for Aerospace Studies‘ Space Flight Laboratory (UTIAS/SFL) Generic Nanosatellite Bus (GNB), which has enabled a wide variety of new space applications on a small scale. The GNB has a 20cm cubical form factor with no deployed solar arrays, making it inherently power-limited. Consequently, the need to accommodate relatively high powered payloads for multi-year missions has dic-tated the need for maximum utilization of solar power, and with maximum efficiency. To accomplish this, the GNB power system implements an unconventional parallel-regulated Direct Energy Transfer (DET) architecture with PPT functionality using a single bi-directional digital switch-mode power converter per battery, which also permits mul-tiple redundant batteries as required. The trade space between different power system architectures is explored for missions of this class, and a parallel-regulated DET bus is shown to be the regulated topology of highest efficiency, advantageous when the range of solar array and bus voltages for a spacecraft are closely matched. The primary regu-lation device—referred to as a Battery Charge/Discharge Regulator (BCDR)—is described, and the advantages of its design are discussed. Finally, a new variant on conventional peak power tracking—referred to as Peak Current Tracking (PCT)—is discussed. The PCT algorithm is implemented using spacecraft BCDRs, and works to maximize battery charge current as well as to minimize battery discharge current. PCT operates during both sunlight and ec-lipse, and interrogates the entire system to determine the optimal voltage for battery charge management, which is an emergent property of the technique. PCT is shown to reduce battery depth-of-discharge by almost 20% compared to systems with fixed system voltages. The GNB power system design represents a significant advance over what has previously been implemented on a nanospacecraft scale, further enabling advanced missions on a power-limited platform.
Presentation Slides
Peak Power Tracking on a Nanosatellite Scale: The Design and Implementation of Digital Power Electronics on the SFL Generic Nanosatellite Bus
This paper describes the design and implementation of an advanced high-performance nanosatellite power system, with an emphasis on its battery management and peak power tracking (PPT) capabilities. This power system has been developed for the University of Toronto Institute for Aerospace Studies‘ Space Flight Laboratory (UTIAS/SFL) Generic Nanosatellite Bus (GNB), which has enabled a wide variety of new space applications on a small scale. The GNB has a 20cm cubical form factor with no deployed solar arrays, making it inherently power-limited. Consequently, the need to accommodate relatively high powered payloads for multi-year missions has dic-tated the need for maximum utilization of solar power, and with maximum efficiency. To accomplish this, the GNB power system implements an unconventional parallel-regulated Direct Energy Transfer (DET) architecture with PPT functionality using a single bi-directional digital switch-mode power converter per battery, which also permits mul-tiple redundant batteries as required. The trade space between different power system architectures is explored for missions of this class, and a parallel-regulated DET bus is shown to be the regulated topology of highest efficiency, advantageous when the range of solar array and bus voltages for a spacecraft are closely matched. The primary regu-lation device—referred to as a Battery Charge/Discharge Regulator (BCDR)—is described, and the advantages of its design are discussed. Finally, a new variant on conventional peak power tracking—referred to as Peak Current Tracking (PCT)—is discussed. The PCT algorithm is implemented using spacecraft BCDRs, and works to maximize battery charge current as well as to minimize battery discharge current. PCT operates during both sunlight and ec-lipse, and interrogates the entire system to determine the optimal voltage for battery charge management, which is an emergent property of the technique. PCT is shown to reduce battery depth-of-discharge by almost 20% compared to systems with fixed system voltages. The GNB power system design represents a significant advance over what has previously been implemented on a nanospacecraft scale, further enabling advanced missions on a power-limited platform.
