Power Subsystem Research Articles

Observation of Sustained Arc Circuit Failure on Solar Array Backside in Low Earth Orbit

On March 12, 2010, two anomalies occurred simultaneously on NASA’s Aura spacecraft, both lasting under 1 min. There was a momentum buildup due to a persistent disturbance torque lasting 40–50 s. A system anomaly in the current and voltage telemetry of one of the power subsystem array regulator electronic modules lasted for the same duration and ended with six strings (one array group) of solar cell current loss. This paper presents the evidence gathered by the joint NASA/GSFC–Northrop Grumman investigation team that concluded that both anomalies were caused by a sustained vacuum arc on the array backside. The primary cause that triggered the sustained arc was not conclusively established.

Design and Optimization of Microsatellite Power System

In the framework of studying and Optimization of the power subsystem for a microsatellite, our purpose is to cover all aspects leading to the optimization of power which ensures accomplishment of the microsatellite mission in orbit. The power subsystem of a microsatellite is responsible to provide a necessary energy for the different operations of spacecraft under all spatial conditions that may be met during its mission, this until the end of its envisaged lifetime. It must to include the photovoltaic generator, the batteries, the battery charge regulator (BCR), power conditioning module, distribution module and protection. There are many technical problems, such as the failure of the photovoltaic panels causing a dysfunction of the satellite, for that the literature suggests solutions about the algorithms of optimization, the most important is the research of the maximum power point tracking (MPPT) when the photovoltaic generator and the load are connected through a static converter. The maximum power point varies according to several factors such as, irradiance and temperature.

An Inductive Power and Data Telemetry Subsystem With Fast Transient Low Dropout Regulator for Biomedical Implants.

This paper presents a capacitorless low-dropout (LDO) regulator with fast transient response and data reverse telemetry circuit for fully implantable wireless transmission applications. We propose a novel hybrid feedback structure using high-frequency compensation technology to achieve a rapid transient response for the LDO regulator. To reduce the size of the implant and transmit neural recordings through the same coil without interfering with power transmission, the load-shift-key (LSK) modulation technique is adopted for back data telemetry. The proposed implantable chip, fabricated using commercial 0.18 μm complementary metal oxide semiconductor technology, yielded an output power of 15 mW. Under 1.15 V operation voltage, the maximum overshoot and undershoot voltages were less than 45 mV and 55 mV, respectively, for a 15 mA full-load current whose rising and falling time were less than 100 ns. The proposed LSK transceiver uses a digitized demodulator to improve bandwidth efficiency for low carrier frequency operation.

A New Absorption–compression Refrigeration System Using a Mid-temperature Heat Source for Freezing Application

The use of an absorption refrigeration system is a promising way to utilize waste heat from industrial processes. Ammonia–water absorption refrigeration system is commonly used for freezing applications with temperatures lower than 0°C. When the refrigeration temperature is lower than -30°C, the performance dramatically decreases. We proposed a new absorption–compression refrigeration system to produce cooling energy at -30°C to -55°C. The proposed system comprised three subsystems, namely, a power generation subsystem using an ammonia–water mixture as the working fluid, an ammonia–water absorption refrigeration subsystem, and a CO2 compression refrigeration subsystem. The system utilized the heat source in a cascade manner. The power subsystem converted the high-temperature portion of heat into power to drive the CO2 compression refrigeration subsystem, thereby resulting in the generation of low-temperature cooling energy. The low-temperature portion of heat is converted into cooling energy to offer the heat sink of the CO2 compression refrigeration subsystem. A simulation study was conducted, and results showed that the coefficient of performance of the proposed system was 0.277, which was approximately 50% higher than that of a conventional two-stage absorption refrigeration system. This work may provide a new way to produce low-temperature cooling energy using mid-temperature heat source.

Anomaly detection for satellite power subsystem with associated rules based on Kernel Principal Component Analysis

The paper presents an implementable method of anomaly detection for satellite power system. Specifically, a data-driven anomaly detection method for sensor data integrated Kernel Principal Component Analysis (KPCA) and association rule mining is demonstrated. Establishing associated rules among sensor monitoring data sets, this approach analyses the structure of measure space via its Eigen matrix with KPCA, and identifies the anomaly. Especially, different anomalies from satellite system and sensors can be distinguished with the changes of association rules. The effectiveness of the method is proved on sensor data from Feng-Yun satellite power subsystem.

Final Assembly of the Helmholtz-Zentrum Berlin Series-Connected Hybrid Magnet System

The final assembly of the Series-Connected Hybrid magnet system for the Helmholtz-Zentrum Berlin for Materials and Energy (HZB) has occurred with the integration of the superconducting cold mass, cryostat, resistive Florida-Bitter coils, and the cryogenic, chilled water, power, and control subsystems. The hybrid magnet consists of a 13-T superconducting $\hbox{Nb}_{3}\hbox{Sn/CICC}$ coil and a set of 12-T resistive, water cooled coils at 4.4 MW. Much of the cryostat and cold mass functional requirements were dictated by the electromagnetic interactions between the superconducting and resistive coils. This includes the radial decentering and axial aligning forces from normal operations and a 1.1 MN fault load. The system assembly was an international achievement with the cold mass being completed at the NHMFL in the USA, cryostat to cold mass interfaces made at Criotec Impianti in Italy, and final assembly at the HZB in Germany.

Hierarchical Fuzzy-Logic-Based Electrical Power Subsystem for Pico Satellite ERPSat-1

Despite the recent advances in space technologies, electrical power systems are still challenging researchers developing small satellites for low earth orbit use. In order to supply their subsystems, these satellites can only use the power stored onboard from solar energy. Therefore, the electrical power system should ensure a maximum exploitation of energy sources and should optimize the distribution of the available electrical power. This paper introduces a new intelligent electrical power subsystem for pico satellites. It is based on fuzzy logic and hierarchical fuzzy logic algorithms allowing a faster energy storage and a better and efficient energy distribution. The developed subsystem is composed of three main blocks, which are the fuzzy maximum power point tracker, the power conditioner, and the hierarchical fuzzy subsystem controller. The intelligent electrical power subsystem was successfully integrated in ERPSat-1 pico satellite. Furthermore, the simulations and experimental data of the proposed system have shown better results compared to other architectures used for previous small satellite electrical power subsystems.

Leakage Power Reduction in 32-bit Digital Comparator Using Modified Power Gating Technique

As scaling down of CMOS transistor’s channel length is done for miniaturization, the design community primarily focuses on the high performance & power-aware design. The power consumption of any circuit solely holds the performance and the life of it. But static power consumption deteriorates them and dominates the dynamic power consumption because of its leakage components. A modified approach of pulse triggering in the Power Gating technique called MPG (Modified Power Gating) is proposed to reduce the static power consumption (leakage power) of digital subsystems. Sub threshold leakage power of MPG Inverter (INV) and 32-bit Digital Comparator (DC) is analyzed and reduced with 35% to 40% leakage savings compared with conventional and existing techniques by simulating it in Cadence GPDK.

Design of Low Power Adaptive Pulse TriggeredFlip-Flop Using Modified Clock Gating Schemeat 90 nm Technology

In this paper, a novel low power adaptive pulse triggered flip-flop (PTFF) featuring exclusive-or gate based clock gating with replica path delay scheme is proposed. Clock gating is a very accepted technique to reduce dynamic power of idle clocking subsystems. Incorporating clock gating with PTFF leads to reduction in dynamic power consumption and replica path delay pulse generator simplifies design effort and achieves robust timing characteristics as compared to the conventional PTFF. The proposed PTFF features best power delay product performance. This scheme is implemented using CMOS 90nm BSIM4 technology file in Synopsys HSPICE. Simulation results indicate that the proposed design excels conventional designs in performance metrics such as average power consumption, minimum D to Q delay, and power-delay-product. The average power consumption of the proposed design reduces by 51% as compared to replica-path pulse triggered flip-flop for 100% switching activity.

Fault-Tolerant Distributed Load/Frequency Coordination Strategies for Multi-Area Power MicroGrids

A parallel distributed fault-tolerant supervisory strategy is considered for addressing Load/Frequency set-point reconfiguration problems in multi-area power microgrids. Besides the ability to coordinate the power subsystems under nominal conditions, it is shown here that the scheme is capable of reconfiguring, to some extent and whenever necessary in response to unexpected load changes and/or faults, the current nominal equilibrium. This is achieved by changing the nominal set-points on frequency and power production in such a way that viable evolutions arise for the overall power system during the transients and a new post-fault sustainable equilibrium is reached. An example on a four-area power system is considered in order to demonstrate the effectiveness of the strategy.

Thermal analysis of multifunctional structural battery for satellite applications

Multifunctional structures combine multiple functionalities in a single structural part in order to increase performance while limiting mass and volume. Conventional satellite batteries are designed separately as a stand-alone subsystem then added to satellite host structure in the last assembly, bringing assistant containers and connectors etc. that often cause undesirable mass loading effects and consume valuable space. Power subsystem and then the whole satellite can benefit from the introduction of multi-functionality as a means of improving overall system efficiency. This paper presents the investigation of a new multifunctional structural battery (MFSB) consisting of energy storage, energy supply, and load bearing ability in a single composite structural panel for satellite applications. Thermal vacuum testing (TVT) was carried out and transient thermal analysis was performed, and the results demonstrated that the current material formula and workmanship are viable in the space. When mounted within satellites as an equipment-panel, the designed MFSB panel can keep itself retaining the required operational temperature without supplementary thermal control approaches.

Demonstration of Prognostics-Enabled Decision Making Algorithms on a Hardware Mobile Robot Test Platform


 
 
 Prognostics-enabled Decision Making (PDM) is an emerging research area that aims to integrate prognostic health information and knowledge about the future operating conditions into the process of selecting subsequent actions for the system. Previous work developing and testing PDM algorithms has been done in simulation; this paper describes the effort leading to a successful demonstration of PDM algorithms on a hardware mobile robot platform. The hardware platform, based on the K11 planetary rover prototype, was modified to allow injection of selected fault modes related to the rover’s electrical power subsystem. The PDM algorithms were adapted to the hardware platform, including development of a software module framework, a new route planner, and modifications to increase the algorithms’ robustness to sensor noise and system timing issues. A set of test scenarios was chosen to demonstrate the algorithms’ capabilities. The modifications to run with a hardware platform, the test scenarios, and the test results are described in detail. The results show a successful use of PDM algorithms on a hardware test platform to optimize mission planning in the presence of electrical system faults.
 
 

Cell Equalization System for Li-Ion Battery Management Based on Fly-Back DC/AC Convertor

Cell equalization acts an important role on the battery life preserving for space application. This paper describes a lithium ion battery cell equalization method for spacecraft that employs innovative design features in power subsystem. The scheme proposed for balancing the battery pack relies on energy conversion devices as it uses transformers to move energy from high voltage cells to low voltage cells without energy loss. The method employs bi-directional forward DC-AC converters, plus a unique common node to provide autonomous charge distribution. It also supports individual cell voltage monitoring, telemetry data. Multisim is used to analyze the function and performance, experimental result proves that the method is effective for Lithium Ion battery equalization.

Holographic diffraction-through-aperture spectrum splitting for increased hybrid solar energy conversion efficiency

A holographic module is designed to split light into two spectral bands for hybrid solar energy conversion. Incoming light is either transmitted to a large subsystem receiver or diffracted through an aperture in this receiver toward a second subsystem receiver. The holographic element is simulated using rigorous diffraction and ray-tracing methods. Two applications of the design are described and simulated. A photovoltaic/thermal system with 93% optical efficiency and adjustable subsystem power output ratio is designed to address solar intermittency and provide energy storage. A photovoltaic system added to an alga biofuel operation significantly increases energy output while maintaining 92% of the original algae yield. The energy return on investment of this photovoltaic/biofuel system is 2.4× greater than that of the biofuel system alone, leading to economically viable operation. Modifications to the standard holographic lens provide additional increases in spectrum-splitting capability, optical efficiency, and energy conversion efficiency. The diffraction-through-aperture concept is demonstrated as a successful approach to spectrum splitting for hybrid solar applications. Copyright © 2014 John Wiley & Sons, Ltd.

A Framework for Visual Dynamic Analysis of Ray Tracing Algorithms

Abstract A novel approach is presented for recording high volume data about ray tracing rendering systems' runtime state and its subsequent dynamic analysis and interactive visualization in the algorithm computational domain. Our framework extracts light paths traced by the system and leverages on a powerful filtering subsystem, helping interactive visualization and exploration of the desired subset of recorded data. We introduce a versatile data logging format and acceleration structures for easy access and filtering. We have implemented a plugin based framework and a tool set that realize all ideas presented in this paper. The framework provides data logging API for instrumenting production-ready, multithreaded, distributed renderers. The framework visualization tool enables deeper understanding of the ray tracing algorithms for novices, as well as for experts.

A feasible system integrating combined heating and power system with ground-source heat pump

A system integrating CHP (combined heating and power) subsystem based on natural gas and GSHP (ground-source heat pump subsystem) in series is proposed. By help of simulation software-Aspen Plus, the energy performance of a typical CHP&GSHP-S (S refers to ‘in series’) system was analyzed. The results show that the system can make a better use of waste heat in flue gas from CHP (combined heating and power subsystem). The total system energy efficiency is 123% and the COP (coefficient of performance) of GSHP (ground-source heat pump) subsystem is 5.3. A referenced CHP&GSHP-P (P refers to ‘in parallel’) system is used for comparison; its total system energy efficiency and COP of GSHP subsystem are 118.6% and 3.5 respectively. Compared with CHP&GSHP-P system with different operating parameters, the CHP&GSHP-S system can increase total system energy efficiency by 0.8–34.7%, with related output ratio of heat to power (R) from 1.9 to 18.3. Furthermore, the COP of GSHP subsystem can be increased between the range 3.6 and 6, which is much higher than that in conventional CHP&GSHP-P system. This study will be helpful for other efficient GSHP systems integrating if there is waste heat or other heat resources with low temperature.

Sizing of a solar/hydrogen system for high altitude long endurance aircrafts

High altitude long endurance (HALE) aircrafts are aerial platforms operating in the stratosphere, providing relay services for wireless communication networks. These platforms are an alternative to increase the effectiveness of future communication. Nevertheless, the power system is a key part that determines the implementation and feasibility of these platforms. One effective and renewable option to power an HALE aircraft is a photovoltaic system (PVS) with hydrogen storage. In this paper, the simulation of the solar/hydrogen closed loop system is carried out for a parametric combination of the subsystems power. Power consumption of the propeller was determined as a function of the aircraft weight in steady flight and in still air. In order to obtain the optimal nominal powers the efficacies are calculated at hourly intervals over the course of the year by means of an analytical energy balance. The proposed method was implemented in an algorithm, which allows fast estimation of the actual time of flight and the system efficiency. Finally, the energy system of three HALE aircrafts was analyzed in relation of their wing area and total and empty mass.

System-Level Multicriteria Modelling of Payload Operational Times for Communication Satellite Missions in LEO

The spacecraft payload operational time (SPOT) is amongst the main critical design considerations that must be optimised and validated during the system engineering analysis of a spacecraft mission. This requirement becomes more demanding for a communication satellite mission that relies on the functionality of the payload for its operation and service delivery. The design principles and performance budgets of the payload module are based on the subsubsystems and subsystems that enable the mission to be accomplished. The SPOT constraint is tied to the spacecraft size, weight and power (SWAP) limitations, operational modes of the subsystems and orbital patterns where the system is being deployed. This paper presents a system-level multicriteria optimisation of POTs for communication satellite (ComSat) missions in low-Earth orbit (LEO). The parameter space investigation (PSI) method was utilised to accomplish the multicriteria optimisation of the payload power and spacecraft mass. In the multicriteria optimisation and vector investigation (MOVI) process, 2048 tests were performed and the PSI was conservatively designed to yield 658 pareto optimal solutions vectors; a pareto optimal solution of 37.119 W for the payload module yielded highly adaptive microsatellite (HAM) mass and power margin of 97.021 kg and 23.366 W respectively. The required maximum subsystem power consumption for the power-storing mode is 25.703 W. From the analysis, the solar array capability was calculated to deliver 116.828 W for the mission; this forms the beginning-of-life design point. The prototype design for the ComSat mission yielded a maximum POT of approximately 494 minutes for the onboard payload processing and communication (downlink and uplink). The findings promise to enhance the design of a reliable and capability-based payload module for real-time digital video and broadband media, mobile services, interactive data transfer and voice communication.

Theoretical analysis of a reverse osmosis desalination system driven by solar-powered organic Rankine cycle and wind energy

The utilization of renewable energy for desalination can solve the problems of energy crisis and fresh water shortage. In this study, a reverse osmosis (RO) desalination system driven by solar-powered organic Rankine cycle (ORC) and wind energy is proposed, which is different from the current desalination system driven by single energy source. In order to ensure the continuous production, energy storage units are employed. A mathematical model is established to simulate the overall system which mainly consists of a solar collector subsystem, an ORC subsystem, a wind power subsystem and a RO desalination subsystem. The sensitive analysis of some key parameters, namely turbine inlet pressure, condenser temperature of ORC, feed water pressure and the water salinity, is conducted to determine the relationship between parameters and fresh water output. The result shows daily fresh water output increases with the increase in the turbine inlet pressure under the given conditions. The condenser temperature has a significant effect on daily fresh water output. With the increase in feed water pressure, the fresh water output and the required membrane area both decreases. The fresh water output is also sensitive to the water salinity, while the required membrane area is less sensitive to it.

Analytical Leakage-Aware Thermal Modeling of a Real-Time System

We consider a firm real-time system with a single processor working in two power modes depending on whether it is idle or executing a job. The system is equipped with dynamic thermal management through a cooling subsystem which can switch between two cooling modes. Real-time jobs which arrive to the system have stochastic properties and are prone to soft errors. A successful job is one that enters the system and completes its execution with no timing or soft error. Appropriateness of the system is evaluated based on its performance, temperature behavior, reliability, and energy consumption. It is noteworthy that these criteria have mutual interactions to each other: the stochastic nature of the system affects the success ratio of jobs beside the system dynamic power, the leakage as well as dynamic power impacts the processor temperature, this temperature affects the leakage power, the cooling subsystem power, and the soft error rate, which the latter in turn impacts the system reliability and the success ratio of jobs. This paper proposes an analytical evaluation method with a Markovian view to the system which considers these reciprocal effects. A number of simulation experiments are carried out to validate the accuracy of the proposed method.