Power Splitting Scheme Research Articles

Unlocking the potential of electric and hybrid tractors via sensitivity and techno-economic analysis

The majority of agricultural vehicles in use today still rely on diesel-based propulsion, a major source of air pollution. Electrification is seen as a potential solution for decarbonizing these off-road vehicles but is hampered by higher upfront costs in energy storage and charging infrastructure. To better quantify these barriers, this paper proposes a techno-economic tool that can assist farmers in evaluating the total costs of ownership of electric and hybrid tractors. A pragmatic simulation model of the tractor is developed to predict the annual energy/fuel consumption and NOx emissions, while an economic model estimates the total acquisition, operation, and maintenance costs. For managing the energy in hybrid tractors, a new power split strategy based on model predictive control is developed, allowing the designer to balance energy efficiency and NOx emissions, while taking into account operational constraints of the electric powertrain. Additionally, we propose novel decision maps that allow farmers to quickly identify operating regions (in term of average load and yearly working time) where the deployment of electric/hybrid tractors is economically viable. To account for variability in the tractor’s operational conditions, we conduct both a deterministic sensitivity analysis with multi-parameter variation and a stochastic analysis of the total cost of ownership. The tool is validated with different mission profiles based on data from a California farm. The results show that, compared to diesel powertrains, electric tractors are more cost-effective for light-duty farming activities (engine loads less than 20%). On the other hand, hybrid powertrains are more economical for medium-duty tasks, where engine loads range from 20% to 60%.

Physical layer security in SWIPT-based cooperative vehicular relaying networks

The future of autonomous transportation systems depends on energy sustainability and secure information exchange from low-power vehicular sensors, hence the increased interest in vehicular sensor charging using simultaneous wireless information and power transfer (SWIPT). This study investigates the physical layer security of a SWIPT-based radio frequency energy harvesting cooperative vehicular relaying network subjected to cascade Nakagami-m and double Nakagami-m (DN) fading channels. In the considered system model, a stationary source communicates with a mobile destination through a power-splitting-based decode-and-forward relay in the presence of a mobile passive eavesdropper. Based on the Gamma-distributed first term of the Laguerre series, new statistical probability density function (PDF) and cumulative distribution function (CDF) expressions for the DN are derived to accurately model the complex cascaded fading scenario. The secrecy performance metrics analyzed are the secrecy outage probability (SOP), the probability of non-zero secrecy capacity (PNZSC), and the intercept probability (IP). In addition, the asymptotic SOP (ASOP) is investigated in the high signal-to-noise ratio (SNR) to enhance the comprehension of the secrecy performance. Based on the derived ASOP, the secrecy diversity order (SDO) of the proposed system is determined and examined. Particularly, we present analytical closed-form expressions for the secrecy performance metrics and provide a detailed understanding of the impact of the system parameters under the cascade fading scenario. Then, a power splitting (PS) optimization problem is formulated to minimize the SOP. The results demonstrate a reduction in the SOP with the proposed PS scheme compared to the equal PS scheme. The obtained analytical findings are validated using Monte Carlo simulations.

Arbitrary low-frequency power-splitting strategy in ferrite/piezoelectric magnetoelectric heterostructures: theory and experimental validation

Exploring low-frequency (LF) arbitrary power-splitting technologies to address the independent excitation issues of LF/VLF mechanical antennas (MA) with random distributions is challenging due to unidentified device construction and operation mechanism. In light of this, a device construction strategy for three-port magnetoelectric (ME) arbitrary power splitter in composite of ferrite/piezoelectric heterostructure, as well as theoretical model was developed. To validate the feasibility and effectiveness of the strategy, three size-tailored ME samples with length ratio of split PZT segments in 1:1, 2:1, and 3:2 were modeled, fabricated and comparatively characterized. Experimental results show that the achievable maximum power conversion efficiencies (PE) reach 52%, 71%, and 59% for three tailored ME samples, respectively, and as expected the power-splitting ratios are directly proportional to the square ratio of ME voltage coefficient (MEVC) from each port of the tailored ME samples, which are in coincidence with theory under desired operation stability and favorable experiment repeatability evaluated by uncertainties of 0.25854 V cm−1 Oe−1 and 0.32979 V cm−1 Oe−1 for each port. Therefore, a prediction of evolutionary tendency for arbitrary power splitter realization was expanded in view of our experimental observations, and a great flexibility for device future design and further optimization was also provided. Therefore, the presented LF power-splitting strategy paves the ways for arbitrary power splitter realization and enriches the multi-functional ME power electronics families, as well as enables potential applications for efficient excitations of MAs in high-permeable military underwater and civilian emergency rescue distribution long-wave communication system for practical scenarios of submarine, underground railways, tunnels and collapsed residential buildings.

A regulatory power split strategy for energy management with battery and ultracapacitor

Electric vehicle batteries face fast degradation due to the high frequency of charging/discharging cycles and great peak power demands. Lifetime, continuity of supply and power density of these batteries affect the performance of electric vehicles (EVs). Hybrid energy storage systems (HESS) offers a feasible solution by incorporating other energy storage elements like ultra-capacitor (UC) along with battery. Their combination provides higher efficiency and better performance in terms energy/power density. UC can behave like a power buffer when the EV is accelerating and regenerating. The HESS needs a controller that can split the available power between different sub systems as per demand. This paper presents a regulatory control strategy useful in HESS with battery and UC for the speed regulation of a brushless DC (BLDC) motor using a 3-port bidirectional DC-DC converter. The regulatory control strategy monitors the state of charge (SOC) of UC and a fuzzy logic controller regulates the power flow between HESS and the motor. Simulation in MATLAB validates the efficacy of the strategy. Simulation results and hardware evaluation confirm that the regulatory control scheme is effective in splitting the available power according to the load demand and achieves better energy efficiency.

Transmitter design and AE–AR region characterization for NOMA-SLIPT UWOC systems with uniformly distributed message and Imp-SIC

This paper investigates simultaneous lightwave and information transfer (SLIPT) based non-orthogonal multiple access (NOMA) in underwater optical wireless communication (UWOC) systems. At the user signal separation (SS) based SLIPT scheme is employed. Imperfect successive interference cancellation (SIC) at the near user is considered. Firstly, we derive the maximum allowable electrical power for message symbols at the transmitter, ensuring input to the laser diode lies within the linear region and. A novel linearity-constrained transmitter design is proposed for the uniformly distributed message, followed by calculations of instantaneous data rate and instantaneous harvested energy for both users. Then, closed-form expressions for average data rates (AR) and average energy harvested (AE) under weak turbulence-induced fading channels using Holtzman’s approximation are derived. The tightness of the approximation is confirmed by Monte-Carlo simulations. AE–AR boundaries for both users show an initial rise and subsequent decline in data rates with increased harvested energy, owing to higher bias values restricting transmitter power. The study also examines trade-offs between AE and AR across various system parameters including beam divergence angles, imperfection of SIC, power allocation coefficients, and water types, is conducted. We observe shifting and shrinking/expansion of the AE–AR region depending upon the variation of the various system parameters. We also show that the discussed SS scheme is general and encompasses time-switching (TS), and power-splitting (PS) schemes as special cases. We also briefly discuss as to how the developed framework could be extended to more than two users. In summary, the overall effective energy consumption deduces owing to the adoption of SLIPT at the users, making the considered setup more energy-efficient.

Optimal Sizing and Analysis of Hybrid Battery Packs for Electric Racing Cars

The electrification trend is spreading not only in the field of traditional vehicles, but also in the racing one, with challenging power and range demands. As an example, the next generation of Formula E will increase power up to 600 kW, almost triplicating the actual standards. In this paper, we investigate the potential benefits of hybrid battery packs in a racing scenario. Hybrid battery packs combine different cell technologies aiming at exploiting their respective high-power and high-energy densities. To this purpose, we formulate a co-design optimization problem that finds the optimal hybrid battery pack configuration to minimize the race time, on a given circuit. As a case study, the next generation of Formula E on the 2021 Rome Formula E ePrix is considered. Results show a significant gain in terms of race time, compared to a single cell chemistry battery pack. Moreover, the analysis points out interesting results on the optimal power split strategy and the role of mechanical brakes.

Optimal power split control strategy for plug-in biofuel-electric hybrid vehicle using improvised adaptive ECMS control algorithm

Optimal power split control strategy for plug-in biofuel-electric hybrid vehicle using improvised adaptive ECMS control algorithm

System outage probability and diversity analysis of a SWIPT based two-way DF relay network under transceiver hardware impairments

This paper investigates the system outage performance of a simultaneous wireless information and power transfer (SWIPT) based two-way decode-and-forward (DF) relay network, where potential hardware impairments (HIs) in all transceivers are considered. After harvesting energy and decoding messages simultaneously via a power splitting scheme, the energy-limited relay node forwards the decoded information to both terminals. Each terminal combines the signals from the direct and relaying links via selection combining. We derive the system outage probability under independent but non-identically distributed Nakagami-m fading channels. It reveals an overall system ceiling (OSC) effect, i.e., the system falls in outage if the target rate exceeds an OSC threshold that is determined by the levels of HIs. Furthermore, we derive the diversity gain of the considered network. The result reveals that when the transmission rate is below the OSC threshold, the achieved diversity gain equals the sum of the shape parameter of the direct link and the smaller shape parameter of the terminal-to-relay links; otherwise, the diversity gain is zero. This is different from the amplify-and-forward (AF) strategy, under which the relaying links have no contribution to the diversity gain. Simulation results validate the analytical results and reveal that compared with the AF strategy, the SWIPT based two-way relaying links under the DF strategy are more robust to HIs and achieve a lower system outage probability.

Transient Solid Oxide Cell Reactor Model Used in rSOC Mode-Switching Analysis and Power Split Control of an SOFC-Battery Hybrid

Defossilization of the global energy system requires a transition towards intermittent renewable energy sources and approaches that enable efficient conversion of primary energy sources into electrical energy. Due to their high efficiency in converting chemical into electrical energy and vice versa, solid oxide cell (SOC) systems provide solutions for both of these aspects. Within this contribution, two researched cases utilizing SOC's are presented, based on simulation studies and experiments.Characteristically, SOC reactors produce hydrogen from steam in solid oxide electrolysis (SOE) mode, or electricity from reformates in solid oxide fuel cell (SOFC) mode. An application of both modes as reversible solid oxide cell (rSOC) is to balance a renewable power supply with storage and power production, leading to high utilization of the same equipment. An application in SOFC mode is the maritime transportation powertrain. In both cases, transient operation is needed whenever mode transitions occur. In particular, switching between rSOC modes implies transitioning exothermal SOFC, endothermal, thermoneutral and exothermal SOE operation. Similarly, supplying the power demand of a maritime drivetrain in SOFC mode leads to various exothermic levels, as pertinent to part or full load operation. Operating strategies are needed to suppress potentially damaging thermal stresses during these transitions in the electrochemical SOC reactors. In order to identify such operating strategies, experiments have been carried out and a transient model has been developed for the analysis of rSOC mode-switching and SOFC drivetrain power supply, which are presented in this study. The 1D+1D SOC dynamic multi-reactor model includes the individual SOC reactors, piping and insulation, and is implemented in the in-house developed transient energy process system simulation framework TEMPEST [1,2]. The model couples the transient balances of mass and energy with electrochemistry, internal reforming kinetics, heat transfer, and flow distribution. As a result, temperature and voltage characteristics at cell, stack, and module levels are obtained to analyze for e.g. unwanted thermal stress. In the EU project SWITCH [3], experiments were performed at DLR with a Large Stack Module (LSM) from SolydEra (formerly SOLIDpower) to validate the model in transient 75 kW electrolysis mode, 25 kW fuel cell mode and mode-switching operation between electrolysis and polygeneration mode. The so called polygeneration mode refers to simultaneous generation of hydrogen and electricity at partial fuel utilization with natural gas, biogas or e-methane. Simulative studies of mode-switching procedures from SOE to SOFC-mode polygeneration show that drawing fuel cell current soon after reaching open circuit voltage and sufficiently in advance of the methane ramp completion leads to a reduced temperature decrease at the inlet of the cell without reaching oxygen to carbon ratios low enough to favor carbon deposition. In the EU project NAUTILUS [4], the mismatch between the transient response possibilities of SOFC systems and the power demand of a ship is addressed by connecting Li-ion batteries to the powertrain. Batteries respond to highly transient ship load demand changes, while the SOFC’s provide base part load to full load, according to a power split control strategy. A battery model developed and parametrized by the Chair for Electrochemical Energy Conversion and Storage Systems of RWTH Aachen University [5] was added to TEMPEST and validated using DLR experiments with a 40 kWh Li-ion battery. Simulation results of the SOFC-battery hybrid in Figure 1 show that a rule-based power split control strategy [6] ensures that the power demand of the ship is met at all times while the battery state of charge (SoC) remains within specified range, and the SOFC power is drawn at one of three fixed power levels for reduced thermal stress. An experimental campaign to test this and other control strategies with a 32 kW LSM from SolydEra and the 40 kWh battery is in progress at DLR. Acknowledgements Project SWITCH has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under Grant Agreement No 875148. This Joint Undertaking receives support from the European Union’s Horizon 2020 Research and Innovation program, Hydrogen Europe and Hydrogen Europe Research. Project NAUTILUS has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 861647.

Transient Solid Oxide Cell Reactor Model Used in rSOC Mode-Switching Analysis and Power Split Control of an SOFC-Battery Hybrid

Defossilization of the global energy system requires a transition towards intermittent renewable energy sources and approaches that enable efficient conversion of primary energy sources into electrical energy. Due to their high efficiency in converting chemical into electrical energy and vice versa, solid oxide cell (SOC) systems provide solutions for both of these aspects. However, mode transitions in SOC operation require operating strategies to ensure that thermal gradients in the reactors are suppressed. In this study, two researched cases utilizing SOC’s are presented, based on simulation studies and experiments with an SOC multi-reactor module. The transient module model is validated in 75 kW electrolysis and polygeneration, and applied to analyze the effect of internal steam methane reforming on the temperature profile of the reactors. Subsequently, it is coupled with a validated Li-ion battery model, to test a rule-based power split control strategy suitable for a demand curve characteristic of a ship.

On the Performance of Coded Cooperative Communication with Multiple Energy-Harvesting Relays and Error-Prone Forwarding

In this paper, we consider a coded cooperative communication network with multiple energy-harvesting (EH) relays. In order to adequately address the problem of error propagation due to the erroneous decoding at the relays, as in the case of conventional decode and forward (DF) relaying protocol, we propose coded cooperative schemes with hard information relaying (HIR) and soft information relaying (SIR) strategies. The performance of the relayed communication with EH relay depends crucially on the channel decoding capability at the relay, channel gains at the source–relay and relay–destination links, and ultimately on the power-splitting ratio of the relay EH receiver. The exact closed-form expression for the outage probability performance of the coded cooperative scheme with HIR strategy and relay selection (CC-HIR-RS) is derived for both cases, namely for constant and optimal power-splitting ratios. Concerning the coded cooperative scheme with SIR strategy, a Rayleigh Gaussian log likelihood ratio-based model is used to describe the soft estimated symbols at the output of the relay soft encoder. Directives are provided to determine the model parameters, and, accordingly, the signal-to-noise ratio (SNR) of the equivalent one-hop relaying channel is derived. A closed-form expression for the outage probability performance of the proposed coded cooperative scheme with SIR and relay selection (CC-SIR-RS) is derived. In addition, a fuzzy logic-based power-splitting scheme in EH relay applying SIR is proposed. The fading coefficients of the source–relay and relay–destination links and distance between source and relay node are considered as input parameters of the fuzzy logic system to obtain an appropriate power-splitting ratio that leads to a quasi-optimal SNR of the equivalent end-to-end channel. Monte Carlo simulations are presented to demonstrate the validity of the analytical results, and a comparison between the performance of the CC-HIR-RS scheme with constant and optimized power-splitting ratios and that of the CC-SIR-RS scheme with constant and fuzzy logic-based power-splitting ratios is provided.

An overview of frequency‐based power split strategies in electric vehicles with battery/supercapacitor hybrid energy storage system

AbstractEnergy management in hybrid energy storage systems (HESSs) consisting of battery and supercapacitor packages has an essential role in the efficient and safe use of energy storage devices. In the mentioned HESSs, with frequency separation‐based energy management, the source with slow dynamics (eg, batteries) is supported by other sources with fast dynamics (eg, supercapacitors). To realize power sharing in the battery/supercapacitor HESS, the load current is divided into low‐ and high‐frequency components and supplied/allocated from energy storage devices. This review touches on the historical development of electric vehicles and includes extensive information about the battery and supercapacitor. It also comprehensively analyzes frequency separation‐based power allocation strategies for battery/supercapacitors HESS. These strategies were investigated in detail regarding their features, advantages, and restrictions. In addition, interconnection circuit topologies and control techniques used in frequency‐based power allocation were explained comprehensively. As a result, this study will serve as a guide on frequency‐based power separation principles in HESS.

Performance enhancement in the cell-free massive MIMO SWIPT system with active eavesdropping

This paper investigates the secure transmission for simultaneous wireless information and power transfer (SWIPT) in the cell-free massive multiple-input multiple-output (MIMO) system. To develop green communication, legitimate users harvest energy by the hybrid time switching (TS) and power splitting (PS) strategy in the downlink phase, and the harvested energy can provide power to send uplink pilot sequences for the next time slot. By in-built batteries, the active eavesdropper can send the same pilots with the wiretapped user, which results in undesirable correlations between the channel estimates. Under these scenarios, we derive the closed-form expressions of average harvested energy and achievable rates, and propose an iterative power control (PC) scheme based on max–min fairness algorithm with energy and secrecy constraints (MMF-ESC). This scheme can ensure the uniform good services for all users preserving the distributed architecture advantage of cell-free networks, while meeting the requirements of energy harvested by legitimate users and network security against active eavesdroppers. Besides, continuous approximation, bisection and path tracking are jointly applied to cope with the high-complexity and non-convex optimization. Numerical results demonstrate that MMF-ESC PC scheme can effectively increase the achievable rate and the average harvested energy of each user, and decrease the eavesdropping rate below the threshold. Moreover, the results also reveal that PS strategy is superior in harvesting energy in terms of more stringent network requirements for average achievable rates or security.

Ultracompact, polarization-independent, and highly scalable optical power splitting model employing fan-out bending metamaterials

Optical power splitters (OPSs) are essential components in the photonic integrated circuits. Considerable power splitting schemes have been reported on the silicon-on-insulator platform. However, the corresponding device lengths are enlarged, and polarization-sensitive operations are usually encountered when the splitting channels are increased from two to five. In this paper, a novel power splitting model is proposed to overcome these limitations. Here, fan-out bending subwavelength grating (FBSWG) metamaterials instead of classical straight SWGs are leveraged to expand the input TE/TM mode in an ultracompact region and further bend its wavefronts. By using N -angled tapers to match bending wavefronts, the light expanded by FBSWGs can be collected and evenly distributed into N output channels. Based on such a model, three OPSs are designed and experimentally demonstrated, which are the shortest polarization-independent 1 × 3 , 1 × 4 , and 1 × 5 OPSs reported until now to our knowledge. The characterizations show low insertion losses ( < 1.2 dB , < 1.35 dB , and < 1.65 dB ) and uniformities ( < 0.9 dB , < 1 dB , and < 1 dB ) over bandwidths of 54 nm, 49 nm, and 38 nm for the 1 × 3 , 1 × 4 , and 1 × 5 OPSs, respectively. For the first time, an ultracompact device length of < 4.3 μm and a polarization-independent operation can be maintained simultaneously as the output splitting channels are increased.

LF-SWIPT: Outage Analysis for SWIPT Relaying Networks Using Lossy Forwarding With QoS Guaranteed

We analyze the outage performance of a lossy forwarding (LF) relaying system with the simultaneous wireless information and power transfer (SWIPT) capability. In the system of LF with SWIPT (LF-SWIPT), a source broadcasts its message to both a relay and a destination. A relay node with SWIPT functionality harvests energy and decodes information from the source signal. The energy is split into two parts for information processing and message forwarding, respectively. For information processing, the relay attempts to decode the incoming source signal and forms an estimate. Unlike the existing decode-and-forward SWIPT system (DF-SWIPT), the estimate is always forwarded using the harvested energy. The destination performs joint decoding to recover the message with the signals received from both the source node and the relay node. We derive the outage probability for the LF-SWIPT system based on the theorem of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">source coding with side information</i> . The simulation results demonstrate that the proposed system achieves significant gains (around 1–2 dB) compared to the DF-SWIPT system. We further evaluate the impact of the distance and the power splitting (PS) strategy on the system performance using simulations. Finally, we build an optimization algorithm on the PS ratio by maximizing the admissible region from the theoretical perspective.

Hybridization of battery and ultracapacitor for electric vehicle application with dynamic energy management and non-linear state feedback controller

• Proposed a dynamic energy management system for hybrid sources in an electric vehicle. • Buck-boost H-bridge converters are introduced for bidirectional power flow control. • System non-linearities are addressed using a nonlinear state feedback controller. • The proposed system accurately delivers instantaneous vehicle speed and torque. This paper describes a methodology to control a multi-source battery-capacitor hybrid EV incorporating a dynamic power splitting strategy. Considering the requirement for precise speed control characteristics of the EV and the non-linear behavior of traction motor with system disturbances, a non-linear state feedback controller (NLSFC) with a disturbance observer is suggested as the speed control technique for the EV traction motor. To interface a parallel configured multi-source system, a non-inverted buck-boost H-bridge is proposed as the source side converter for effective recovery of the braking energy. Detailed control design for traction motor and converter is also presented for efficient control of EV. Besides, an adaptive energy management strategy considering power profile and dynamic source characteristics is incorporated into the overall control system. The simulation results from various case studies indicate that the proposed system can follow the required vehicle speed and torque despite the sudden change in EV load torque. Furthermore, the comparative analysis between NLSFC and PI controller shows improvement with steady-state error reduction from 0.43 to 0.0014 and peak overshoot drop from 12.07% to 3.51% during acceleration of the system when proposed NLSFC is adopted. The proposed solutions will be implemented in a prototype EV system in the future.

Energy-Efficient Massive MIMO SWIPT-Enabled Systems

This study focuses on the downlink (DL) transmission of massive multiple-input-multiple-output (MIMO) with the support of simultaneous wireless information and power transfer (SWIPT) system based on a power-splitting (PS) scheme. To reach the green design target in the concept of wireless communication networks, this paper maximizes the system’s energy efficiency (EE) using joint system-level optimization. First, the closed-form expressions of the harvested energy and achievable data rate are first derived. Then, we formulated the EE maximization problem by jointly optimizing user equipment (UE) pilot transmission time allocation, the received PS ratios, a base station (BS) transmit power allocation, and a number of BS antennas while considering the minimum data rate as user’s quality-of-service (QoS) requirement and the maximum BS power transmission constraint. However, the formulated EE maximization problem is non-convex and non-linear which is difficult to solve. Hence, we propose an efficient low-complex alternative optimization (LCAO) algorithm to solve the non-convex problem iteratively with an acceptable computational complexity level. Simulation results are provided to evaluate the derived closed-form expressions and validate the proposed LCAO algorithm’s efficiency. The optimality, convergence, and complexity of the LCAO algorithm are analytically investigated. Results indicate that the proposed LCAO algorithm outperforms the equal power allocation (EPA) scheme by 15% better EE gain and 4% better than the max-min fairness scheme when the BS power transmission capacity is higher than 3 (Watt).

Achievable Rate Maximization for Multi-Relay AF Cooperative SWIPT Systems with a Nonlinear EH Model.

In this paper, the maximization of the achievable information rate is proposed for the multi-relay amplify-and-forward cooperative simultaneous wireless information and power transfer communication systems, where the nonlinear characteristic of the energy harvesting (EH) circuits is taken into account for the receivers of the relay nodes. The time switching (TS) and power splitting (PS) schemes are considered for the EH receivers and the achievable rate maximization problems are formulated as convex and non-convex optimization problems, respectively. The optimal TS and PS ratios for the relay nodes along with the maximum achievable rates for the system are obtained, respectively, by solving the optimal problems with efficient algorithms. The asymptotic maximum achievable rates at low and high input signal-to-noise ratios (SNRs) for both the PS and TS schemes are also analyzed. It is demonstrated that the PS scheme is more susceptible to the variation of the relays’ location and the channel parameters than TS scheme, whereas the TS scheme is more susceptible to the mismatch of the resource allocation than PS scheme. Specifically, compared to the linear EH model, the nonlinear EH model achieves significant performance gain for the TS scheme, whereas inconspicuous performance improvement is achieved for the PS scheme.

Performance evaluation of multiuser Internet of Things wireless‐powered relaying networks with transceiver hardware imperfections over Nakagami‐m fading channels

SummaryWe investigate the performance of multiuser Internet of Things (IoT) relay networks in the presence of transceiver hardware impairments. In particular, IoT users communicate with a destination via a simultaneous wireless information and power transfer (SWIPT) amplify‐and‐forward relay. We exploit both time‐switching (TS) and power‐splitting (PS) protocols at the SWIPT‐aided relay terminal. Specifically, we derive the exact outage probability (OP) expressions for both TS and PS schemes under transceiver hardware imperfections over Nakagami‐m fading channels. In addition, we derive the asymptotic OP expressions for both TS and PS schemes in the high signal‐to‐noise ratio regime. From which, the diversity order of can be achieved, where denotes the fading severity parameter for the channel between IoT users and relay. Furthermore, we present a tight upper bound for the ergodic capacity (EC) under both TS and PS schemes with transceiver hardware impairments over Nakagami‐m fading channels. Moreover, our results demonstrate the impact of number of IoT users, fading severity parameters, TS factor, PS factor, and energy conversion efficiency, on the system performance. We also validate our analytical findings via numerical and simulation results.

Two-Stage Optimization Method for Sizing Stack and Battery Modules of a Fuel Cell Vehicle Based on a Power Split Control

Currently, hybrid and battery electric vehicles are the best-selling green cars commercially available. However, there is a growing interest in fuel cell electric vehicles (FCVs). Nevertheless, due to the unidirectional nature of energy transformation in an FCV, an auxiliary energy storage system (ESS) is required to cope with peak power demand and recover braking energy. In this paper, we propose a joint algorithm for sizing both the fuel cell (FC) stack and an auxiliary storage system, taking into account the power split strategy between the two energy sources. Moreover, a novel power split method is introduced based on the lumped resistance of both the FC stack and lithium-ion battery modules. Several simulation results implementing different driving cycles prove that the proposed sizing procedure is able to reduce the fuel consumption of the FCV and increase the expected lifetime of both the FC stack and lithium-ion battery modules according to a given power split strategy.