Power Subsystem Research Articles

Battery Manufacturing Resource Assessment to Minimise Component Production Environmental Impacts

A promising route to attain a reliable impact reduction of supply chain materials is based on considering circular economy approaches, such as material recycling strategies. This work aimed to evaluate potential benefits of recycling scenarios for steel, copper, aluminium and plastic materials to the battery manufacturing stage. Focused on this aim, the life cycle assessment (LCA) and the environmental externalities methodologies were applied to two battery study cases: lithium manganese oxide and vanadium redox flow (VRFB) batteries, based on a cradle-to-gate LCA approach. In general, the results provided an insight into the raw material handling route. Environmental impacts were diminished by more than 20% in almost all the indicators, due to the lower consumption of virgin materials related to the implemented recyclability route. Particularly, VRFB exhibited better recyclability ratio than the Li-ion battery. For the former, the key components were the periphery ones attaining around 70% of impact reduction by recycling steel. Components of the power subsystem were also relevant, reaching around 40% of environmental impact reduction by recycling plastic. The results also foresaw opportunities for membranes, key components of VRFB materials. Based on findings, recycling strategies may improve the total circularity performance and economic viability of the studied systems.

Long-Term Vehicle Speed Prediction via Historical Traffic Data Analysis for Improved Energy Efficiency of Connected Electric Vehicles

Connected and automated vehicles (CAVs) are expected to provide enhanced safety, mobility, and energy efficiency. While abundant evidence has been accumulated showing substantial energy saving potentials of CAVs through eco-driving, traffic condition prediction has remained to be the main challenge in capitalizing the gains. The coupled power and thermal subsystems of CAVs necessitate the use of different speed preview windows for effective and integrated power and thermal management. Real-time vehicle-to-infrastructure (V2I) communications can provide an accurate speed prediction over a short prediction horizon (e.g., 30 s to 60 s), but not for a long range (e.g., over 180 s). Therefore, advanced approaches are required to develop detailed speed prediction for robust optimization-based energy management of CAVs. This paper presents an integrated speed prediction framework based on historical traffic data classification and real-time V2I communications for efficient energy management of electrified CAVs. The proposed framework provides multi-range speed predictions with different fidelity over short and long horizons. The proposed multi-range speed prediction is integrated with an economic model predictive control (MPC) strategy for the battery thermal management (BTM) of connected and automated electric vehicles (EVs). The simulation results over real-world urban driving cycles confirm the enhanced prediction performance of the proposed data classification strategy over a long prediction horizon. Despite the uncertainty in long-range CAVs’ speed predictions, the vehicle-level simulation results show that 14% and 19% energy savings can be accumulated sequentially through eco-driving and BTM optimization (eco-cooling), respectively, when compared with normal driving (i.e., human driver) and conventional BTM strategy.

Hierarchical Bipartite Graph Matching Method for Transactive V2V Power Exchange in Distribution Power System

In this paper, a hierarchical bipartite graph (HBG) matching method is proposed to promote transactive vehicle-to-vehicle (V2V) power exchanges in a distribution power system. A distribution system which includes EVs is divided into a series of subsystems according to EV locations, where V2V power exchanges are optimized for scheduling charging/discharging periods among transacting EVs in each subsystem. Each subsystem's power surplus or deficit will then be regulated by power exchanges among neighboring subsystems and the utility grid. The one-to-multiple and multiple-to-one modes are adopted in the proposed HBG algorithm for the promotion of transactive V2V power exchanges. Also, individual EV's electricity trading price can track that of the subsystem by adjusting respective power exchange objectives adaptively. Several case studies are presented to validate the effectiveness of the proposed method, where transactive V2V power exchanges are improved and the energy efficiency in a distribution power system is enhanced.

NOISE REDUCTION IN POWER LINES OF DIGITAL ANALOGUE SYSTEMS WITH PULSE POWER SUPPLIES

Along with the ubiquity of digital electronics, precision analog electronic components are becoming increasingly important. In this regard, the urgent task of reducing the noise level inside digital‑analog systems is to ensure a mode of operation that does not impair the accuracy of the operation of such elements. Moreover, switching power converters are one of the main sources of noise in the device power subsystem. In order to identify factors that reduce impulse noise in the power lines of the system, a mathematical model of the output elements at various stages of the conversion of pulsed power sources was developed. The results are obtained that determine the key components and their parameters in terms of the occurrence of noise in the power lines of digital‑to‑analog systems. These results are based on an analytical study of transients in pulsed secondary power sources, in digital integrated circuits, as well as noise performance of components included in linear converters.

ELECTROMAGNETIC SWITCHING TRANSIENTS IN TRANSMISSION LINE COOPERATING WITH THE LOCAL SUBSYSTEM

The article investigates the overvoltage occurring during switching states in the line cooperating with the local subsystem. It discusses the possibilities of determining extreme values of overvoltage of all kinds by means of simulation tests. In particular, special attention was paid to the need to faithfully representation of components in power system i.e. transmission line, voltage transformer and surge arrester for correct reproduce electromagnetic waveforms on the primary as well as secondary side of voltage transformers. Overvoltages appearing in the line connected to the local subsystem during switching operations are forced by the change of network operating conditions. Electromagnetic transients in the unloaded line were tested after its sudden disconnection from the power supply. In the research, particular attention was paid to the conditions of switching off the line (moment and disconnection unity), the influence of surge protection devices, the type of the voltage transformer and the short-circuit power of the power subsystems. Simulation tests have shown that under certain conditions overvoltages with dangerously high values (e.g. 2.25x400 kV) may occur.

A novel concept of cost-effective active debris removal spacecraft system

Post Mission Disposal (PMD) alone is an insufficient solution to stabilize the orbital debris environment, but combining Active Debris Removal (ADR) with PMD and other means of debris mitigation is considered a promising remediation method. The cost reduction of ADR is essential to make it a sustainable business. The major cost driver of ADR is the ADR spacecraft and its launcher, both of which are largely influenced by the spacecraft size. A trade-off study of the ADR spacecraft system has been conducted to minimize its size, resulting in the novel concept of a cost-effective ADR spacecraft system. The authors introduce the combination of electric propulsion (EP) and air drag utilization for the debris deorbit phase so as to lower the EP requirement, thereby leading to cost reduction of the ADR spacecraft. The minimum delta-V reentry method is also considered to reduce the propellant mass for final reentry. EP performance (e.g. thrust, specific impulse, mass) is modeled as a function of power consumption, and optimum EP performance has been explored to minimize overall mass of the ADR spacecraft, including its electrical power subsystem with this EP model. Given the minimum thrust limit to satisfy the mission duration requirement, a higher thrust-to-power ratio is preferable for debris removal electric propulsion. This paper discusses the optimal EP performance requirements in detail, and the results show that a roughly 500-kg ADR satellite using a 600-W-class Hall thruster can remove about three tons of a rocket body debris from an 800-km circular orbit within 600 days.

Comprehensive design and control methodology for DC‐powered satellite electrical subsystem based on PV and battery

The design of electrical power subsystem of a satellite is challenging since it involves many components and depends on multiple parameters including mission duration, satellite orbit, eclipse times and etc. In contrast to the existing mission specific designs, we propose a generalized and comprehensive method to design and size key EPS elements: PV array and battery, which are integral for mission success. For battery, the proposed design incorporates battery cell characteristics, round trip efficiency, degradation, eclipse load profile and operating modes. The proposed design of PV array takes into account orbit inclination and altitude. In addition, structure and geometry of PV array are also considered and used for irradiance forecasting. Reliability, power margins and power fraction for summer solstice are also factored in the design. For the planning and development of operational strategy, parameter limits are determined for depth of discharge, initial state-of-charge, final state-of-charge and end-of-charge voltage of the battery. The controller design is also presented for the EPS. The effectiveness of the proposed design methodology is verified by a case study of Mysat-1, an imaging nanosatellite developed and launched by Khalifa University.

EMBEDDED SYSTEMS – CONTROL OF POWER SUBSYSTEMS

The main role of embedded system is to control the product behaviour or control of outside world. Microcontroller as embedded system obtains information through the sensors and makes adequate impact to outside world after sensor data processing. The microcontroller impact is realized through the actuators which convert the electrical energy (or different type of energy) to mechanical work. These processes are executed because of fulfil customer requirements. Microcontrollers as signal controllers work only with low power signals. This paper discusses the possibilities and application of controlling the power subsystems via using the embedded systems.

Modelling and simulation of the power subsystem of a low earth orbit CubeSat

Modelling and simulating power subsystems of CubeSats are important tools in research and satellite design. To enhance the reliability of a CubeSat, a power subsystem simulator has been furnished. Statistical process control (SPC) is used to perform post-simulation analysis to detect faults in the system. This paper presents an architectural template for a simple power subsystem of CubeSat missions. The simulator has a modular structure with mathematical models of batteries, solar arrays, and the power control unit (PCU). This simulation helps with preliminary sizing and configuration of selected electrical components in an unregulated bus voltage scenario. The solar arrays, batteries, and PCU are modelled using a current–voltage lookup table, a voltage-capacity lookup table, and repeating sequences, respectively. The design is adapted to simulate the power subsystem of ManitobaSat-1, a student CubeSat built as part of the Canadian CubeSat Project. Batteries and solar cells are well sized to supply the necessary power during daylight and eclipse period using lookup tables and conditional switches. Outputs from this model will be used by the SPC module to detect out of control conditions as the simulation will describe the baseline or “normal” behaviour. Its application with the SPC module in automating satellite communications is discussed. This simulator is easily applicable to any satellite mission by modifying a few design parameters. It provides a feasible, user-friendly, simple and easily modifiable interface to perform complex analysis.

Theoretical energy storage system sizing method and performance analysis for wind power forecast uncertainty management

Forecasting uncertainties limit the widespread adoption of wind power generation. Energy storage systems (ESSs) are essential for managing uncertainty, and ESS sizing determines the availability of uncertainty management. However, most ESS sizing studies utilize heuristic approaches. Therefore, research on the determination of ESS sizing related to uncertainty management performance is needed. This paper proposes a theoretical ESS sizing method that considers the stochastic properties of the uncertainty. In the proposed method, the power subsystem (PS) and energy subsystem (ES) capacities, which are related to the instantaneous and accumulated uncertainty characteristics of the ESS, respectively, are determined in terms of the confidence interval of the uncertainty statistic. They are presented as simple formulas by applying the extreme value theory. Furthermore, to demonstrate the uncertainty management performance of ESS sizing, the mean absolute error (MAE) is analyzed, as the variance and absolute errors of the uncertainty determine the MAE of the PS and ES, respectively. A numerical study using real wind power generation and its forecasting data verifies that the proposed method suitably reflects the characteristics of the uncertainty, with an analysis gap between the analyzed MAE and the actual measured value of less than 1%. This study can act as a reference for the expected performance when using ESS and can be extended to the theoretical economic evaluation of ESS usage.

Downsizing an orbital space robot: A dynamic system based evaluation

Small space robots have the potential to revolutionise space exploration by facilitating the on-orbit assembly of infrastructure, in shorter time scales, at reduced costs. Their commercial appeal will be further improved if such a system is also capable of performing on-orbit servicing missions, in line with the current drive to limit space debris and prolong the lifetime of satellites already in orbit. Whilst there have been a limited number of successful demonstrations of technologies capable of these on-orbit operations, the systems remain large and bespoke. The recent surge in small satellite technologies is changing the economics of space and in the near future, downsizing a space robot might become be a viable option with a host of benefits. This industry wide shift means some of the technologies for use with a downsized space robot, such as power and communication subsystems, now exist. However, there are still dynamic and control issues that need to be overcome before a downsized space robot can be capable of undertaking useful missions. This paper first outlines these issues, before analyzing the effect of downsizing a system on its operational capability. Therefore presenting the smallest controllable system such that the benefits of a small space robot can be achieved with current technologies. The sizing of the base spacecraft and manipulator are addressed here. The design presented consists of a 3 link, 6 degrees of freedom robotic manipulator mounted on a 12U form factor satellite. The feasibility of this 12U space robot was evaluated in simulation and the in-depth results presented here support the hypothesis that a small space robot is a viable solution for in-orbit operations.

Application of knowledge engineering in spacecraft overall design

This paper proposes an advanced technology in spacecraft overall design based on knowledge engineering. Knowledge engineering is a branch of artificial intelligence. Applying knowledge engineering technology to improve the efficiency and quality of overall design process and enhance the automation of overall design, moreover focusing on solving overall spacecraft design knowledge representation, knowledge evaluation, knowledge acquisition, knowledge inference and related issues. Unlike the existing methods, this paper uses ontology technology to build a pint-sized spacecraft overall design knowledge base under protégé software environment, which achieves a better performance. Finally, simulations for the designed power subsystem based on the knowledge base are performed, and the simulation results validate the effectiveness, reliability, of the power subsystem designed by the method of spacecraft overall design based on knowledge engineering.

Electric Vehicle Battery Performance Investigation Based on Real World Current Harmonics

Electric vehicle (EV) powertrains consist of power electronic components as well as electric machines to manage the energy flow between different powertrain subsystems and to deliver the necessary torque and power requirements at the wheels. These power subsystems can generate undesired electrical harmonics on the direct current (DC) bus of the powertrain. This may lead to the on-board battery being subjected to DC current superposed with undesirable high- and low- frequency current oscillations, known as ripples. From real-world measurements, significant current harmonics perturbations within the range of 50 Hz to 4 kHz have been observed on the high voltage DC bus of the EV. In the limited literature, investigations into the impact of these harmonics on the degradation of battery systems have been conducted. In these studies, the battery systems were supplied by superposed current signals i.e., DC superposed by a single frequency alternating current (AC). None of these studies considered applying the entire spectrum of the ripple current measured in the real-world scenario, which is focused on in this research. The preliminary results indicate that there is no difference concerning capacity fade or impedance rise between the cells subjected to just DC current and those subjected additionally to a superposed AC ripple current.

Benchmark model for multi‐orbital transient analysis of satellite electrical power subsystem

In this study, an efficient multi-orbital simulation model is presented for satellite Electrical Power Subsystem (EPS) which is integral to the success of the mission. The model integrates converter models, PV array model, DC bus model, and a numerical battery model according to a generalised EPS architecture to form one unified model of the entire EPS. The proposed model reduces simulation complexity, enhances speed, and enables multi-orbit analysis capability. Dynamic interaction among the elements is modelled through a coordinated control containing maximum power point tracking (MPPT), voltage regulation, battery charge/discharge control and management. Practical concerns of digital control implementation for PI controllers and MPPT are also incorporated in the model. Anti-windup is implemented to avoid latency in controller action after the eclipse. Additionally, a robust MPPT algorithm ensures fast immediate action after eclipse. Efficient component models and practical attention-to-detail enable the developed model to simulate multiple orbits with eclipse periods. The superior speed of the model, ability to simulate multiple orbits, and test different control strategies are demonstrated with a practical case study of Mysat-1, an imaging satellite launched by the Khalifa University. The model can be used as a proof-of-concept tool for predicting the operational behaviour of EPS during the development of a satellite.

How do checkpoint mechanisms and power infrastructure failures impact on cloud applications

With the growth of cloud computing usage by commercial companies, service providers are looking for ways to improve the quality of their services. Failures in the power subsystem represent a major risk of cloud data centre unavailability at the physical level. At same time, software-level mechanisms (such as application checkpointing) can be used to maintain the application consistency after a downtime and also improve its availability. This paper analyses the impact of power subsystem failures on cloud applications availability, as well as the impact of having checkpoint mechanisms to recover the system from software-level failure. We propose stochastic models to represent the cloud power subsystem, the cloud application, and also the checkpoint-based retrieval mechanisms. The results show that the selection of a given type of checkpoint mechanism does not present a significant impact on the observed metrics. On the other hand, improving the power infrastructure implies gains in performance and availability.

Software Controlled Low Cost Thermoelectric Energy Harvester for Ultra-Low Power Wireless Sensor Nodes

General hardware architecture of an energy-harvested wireless sensor network node (EH-WSN) can be divided into power, sensing, computing and communication subsystems. Interrelation between these subsystems in combination with constrained energy supply makes design and implementation of EH-WSN a complex and challenging task. Separation of these subsystems into distinct hardware modules simplifies the design process and makes the architecture and software more generic, leading to more flexible solutions. From the other hand, tightly coupling these subsystems gives more room for optimizations at the price of increased complexity of the hardware and software. Additional engineering effort could be justified by a smaller, cheaper hardware, and more energy-efficient a wireless sensor node. The aim of this paper is to push further technical and economical boundaries related to EH-WSN by proposing a novel architecture which – by tightly coupling software and hardware of power, computing, and communication subsystems – allows the wireless sensor node to be powered by a thermoelectric generator working with about 1.5°C temperature difference while keeping the cost of all electronic components used to build such a node below 9 EUR (in volume).

Hybrid Expert System for Computer-Aided Design of Ship Thruster Subsystems

The article presents an expert system supporting the design of ship’s power subsystems, in particular the thruster subsystem. The proposed hybrid expert system uses the results of simulation tests as the additional source of knowledge. The results of system operation are collated in a report which can be used as part of ship design description. The work oriented on developing the expert system is the continuation of the research carried out in cooperation with the shipyard’s design office, the main aim of which was to automate selected stages of the ship’s design process. The hybrid expert system for computer-aided design of ship thruster subsystems can support designers by creating part of the technical description of the thruster subsystem, evaluation of static and dynamic properties, and by checking if design solutions have met the requirements of classification societies. Additionally, the expert system supports collecting and providing information about the elements and structures of the thruster subsystem. Finally, the system provides a document with the description of the thruster structure and elements used in it. The proposed expert system is dedicated to the initial design stages.

Study on the control method about improving piezoelectric actuated photoelectric precision tracking system

Fast steering mirrors (FSM) driven by Piezoelectric transducer (PZT) are widely used in various precision stable tracking systems. Aiming to counteract the hysteresis and non-linear interference in PZT, this work applies a radial basis function (RBF) neural network to approximate its nonlinearity. Adaptive backstepping sliding mode (ABSM) controller combinewith a sliding mode control method and backstepping control is designed. Combining the characteristics of PZT and voice coil motors (VCM), the FSM driven by VCM is designed as the power sub-system to ensure that the large-angle deflection of the FSM can match a wider field of view. The FSM driven by PZT is designed as a correction sub-system, which can adjust the system error within a small range. Finally, the power sub-system and the correction sub-system are combined into a two-level precision tracking system. The simulation results show that the maximum steady-state error of the system is about 15 μrad, and the root mean square error is about 10 μrad. Compared with the traditional PI controller, the error is reduced by about 75%, the response speed is up to 10 ms, and the output is smooth without some serious viberation.

Analyzing the impact of power subsystem failures and checkpoint mechanisms on availability of cloud applications

The widespread adoption of cloud computing has been driven by technological advantages, such as pay-as-you-go plan, scalability and high availability. From cloud service providers point-of-view, managing all these high customer expectations is a growing and critical challenge. This paper examines the relationship among energy infrastructure architectures, checkpoint mechanisms, and availability of software applications in a cloud data center. We consider four power architectures, three checkpoint mechanisms (cold, warm, and hot) with different sizes of files, and two applications (Video on Demand and digital library). For that, we propose a set of stochastic models (based on Petri Net and Reliability Block Diagram) and perform sensitivity and availability analysis. From results, we note that the power architecture has a great impact on application availability while the checkpoint mechanism only impacts with the application has a low mean time to failure value.

Steady-State Power Flow Analysis of Cold-Thermal-Electric Integrated Energy System Based on Unified Power Flow Model

The integrated energy system includes various energy forms, complex operation modes and tight coupling links, which bring challenges to its steady-state modeling and steady-state power flow calculation. In order to study the steady-state characteristics of the integrated energy system, the topological structure of the cold-thermal-electric integrated energy system is given firstly. Then, the steady-state model of the power subsystem, the thermal subsystem, the cold subsystem and the distributed energy station are established, the unified power flow model is established, and the Newton Raphson algorithm is used to solve the unified power flow model. Finally, the influence of the key technical parameters on the steady-state power flow of the integrated energy system is analyzed. Research results show that the photovoltaic power generation plays a supporting role in the voltage of each bus; with the increase of electric load power, the unit value of bus voltage decreases continuously; the water supply temperature of the source node has a greater impact on the steady-state flow in the pipeline and the water supply temperature of each node; the pipeline length of the heat network has a greater impact on the end temperature of the pipeline, the water supply temperature, and the return water temperature of each node. The analysis results can support the planning, design, and optimal operation of the integrated energy system.