Search Results (486)

Reliable pack-level battery systems capable of safely handling instantaneous high-C-rate discharge above 10C during take-off, climb, and hovering are required for the commercialization of urban air mobility (UAM) aircraft. However, pack-level studies on wide-range C-rate characteristics of battery systems for UAM applications remain very limited, and most previous studies have been restricted to single-cell experiments or battery-pack simulations. In this study, a 24S1P test battery pack using nickel–cobalt–manganese (NCM) pouch cells, with a nominal voltage of 88.8 V and a capacity of 22 Ah, was designed and fabricated. A two-level battery management system (BMS) based on the LTC6803G-4 was also developed. To evaluate the charge–discharge characteristics of the battery system, constant-current discharge tests were conducted under five conditions ranging from 0.2C (4.4 A) to 10.68C (235 A), and charging tests were performed over the range of 0.2C–2C. The discharge test results showed that the capacity retention remained within 97.5–100.0% in the 1C–5C range, confirming excellent power capability. Continuous discharge operation was confirmed at 10.68C, the maximum discharge condition considered for vertical take-off and climb. Under this condition, the capacity decreased to 16.26 Ah, corresponding to 74.2% of the rated capacity, owing to internal-resistance-induced voltage drop, electrochemical polarization, and early attainment of the cut-off voltage. The Peukert exponent was estimated to be 1.113. An apparent pack-level direct-current internal resistance (DCIR) of approximately 40.3 mΩ was estimated from the initial voltage-drop analysis under different discharge-current conditions. In addition, the maximum temperature during 10.68C discharge was measured as 55.1 °C, providing a thermal margin of 4.9 °C relative to the operational temperature limit of 60 °C adopted in this study. Finally, a 24S4P battery system with a capacity of 88 Ah, consisting of four 24S1P battery packs connected in parallel, was installed in the VS-210, a 210 kg-class maximum take-off weight (MTOW) eVTOL aircraft. An in-flight test was conducted by repeating six take-off–hovering–landing cycles during a total test session of 15 min 20 s, and a stable propulsion power supply was maintained throughout all flight cycles. This study provides experimental baseline data for the design and preliminary safety assessment of high-power battery systems for UAM applications by presenting both the electrical and thermal characteristics of a 24S NCM battery pack over a wide discharge-rate range of 0.2C–10.68C and in-flight eVTOL data. Full article

This study presents a full polymer piezoelectric flextensional energy harvester (FPPFEH) comprising a single-layer poly(vinylidene fluoride) (PVDF) film bonded to a 3D-printed polylactic acid (PLA) flextensional frame. For an arm inclination angle of $\theta =10°$, the free-body model gives a theoretical geometric force-amplification factor of $M_{\mathrm{F}}=\cot \theta \approx 5.67$; this value represents an ideal upper bound and was not independently validated by local force or strain measurements. During assembly, the film was tensioned only to remove visible slack and maintain a flat configuration. No intentional pretension was applied, and any residual tension was not measured. Off-resonance force-controlled tests showed that the generated voltage was approximately proportional to the dynamic input force and nearly independent of frequency after accounting for attenuation caused by the finite measurement-input impedance. The ideal quasi-static model overpredicted the absolute voltage by a nearly constant factor across the tested force range. This offset is consistent with a lumped reduction associated with frame compliance and the in-plane anisotropy of the PVDF film, neither of which was independently measured. At $30\mathrm{Hz}$ and $12.32{\mathrm{N}}_{\mathrm{rms}}$, the rectified output charged a $6600\mathsf{\mu }\mathrm{F}$ supercapacitor to $2.10\mathrm{V}$ in $14\min$, corresponding to $14.55\mathrm{mJ}$ of stored energy. Under base-acceleration excitation from $0.05$ g to 1 g, the voltage peak occurred between $112.88$ and $116.49\mathrm{Hz}$, close to the electrical anti-resonance near $114\mathrm{Hz}$, and reached $12.11{\mathrm{V}}_{\mathrm{peak}}$ at 1 g. Near resonance, the highest measured power among the tested resistive loads occurred between 150 and $200\mathrm{k}\Omega$; however, the exact optimal resistance could not be resolved from the four tested loads. These results demonstrate off-resonance force-driven energy storage and resonance-mode vibration energy harvesting within the tested conditions. Full article

To satisfy the constant-current/constant-voltage (CC/CV) charging requirements of electric-vehicle batteries, this paper investigates the extension of an established fixed-frequency reconfigurable three-coil wireless power transfer system using a modified receiver-side LCC-type network. The receiver-side shunt capacitor introduces a current-dividing path, so the receiver-coil current differs from the equivalent rectifier-load current and the strict self-resonant value of the L₂—C₂ branch no longer provides the intended CC regulation. A current-division-aware fundamental-harmonic model is established, and a closed-form correction gives C₂ = 21.950 nF instead of the strict resonant value of 22.825 nF at 85 kHz. Calculated results show that the maximum CC target error over RL = 15–35 Ω is reduced from 8.948% to 0.031%, while the calculated CC/CV transition resistance is restored from 39.25 Ω to 34.97 Ω. Comparative analytical results are provided for the series-compensated baseline, the strictly resonant LCC-type configuration, and the corrected LCC-type configuration, together with receiver-current and coupling-sensitivity assessments. At RL = 35 Ω, the retained prototype measurements give an output voltage of 109.14 V, an output current of 3.121 A, an output power of 0.341 kW, and a DC-DC efficiency of 93.120%. The prototype measurements confirm the nominal operating target of the corrected design, while the analytical and numerical results clarify the modeling, correction, and current-stress tradeoffs introduced by the modified receiver network. Full article

Battery discharging is governed by a fundamental trade-off between output power and energy conversion efficiency due to internal dissipation. In this paper, we demonstrate that such a trade-off universally yields a parabolic envelope $P\propto \eta (1-\eta )$. The efficiency at maximum power is exactly one half, mirroring the well-known half-Carnot limit in finite-time thermodynamics. To extend this bound into practical operational rules, we formulate a multistage constant-discharging (MSCD) schedule subject to simultaneous real-time load demands and a global discharging deadline. Analytical resolution via the Karush–Kuhn–Tucker conditions reveals a remarkably compact optimal policy: $I_i^{★}=\max (I_i^{\mathrm{req}},I_0)$. Under this rule, stages limited by external demand run exactly at their minimum required currents, while all remaining stages are elevated to a uniform baseline $I_0$ fixed by the deadline constraint. By tracing the dissipation–time Pareto front, we quantify how internal resistance shifts the operational boundaries and sharpens the trade-off corner. This analysis establishes a rigorous thermodynamic baseline for the scheduling layer of battery management systems, offering natural extensions to nonlinear models incorporating temperature and state-of-charge dependencies. Full article

A synchronous-Buck converter is proposed as part of a maximum power point tracking (MPPT) controller for charging a 12 V battery from a photovoltaic (PV) solar panel. This design incorporates a control module that manages energy flow from the solar panel to the battery. The novel module sequentially integrates MPPT, active current limiting (constant current, CC), and voltage regulation (constant voltage, CV), along with protection mechanisms and low-computational-complexity control. It also incorporates a synchronous-Buck converter with a current PI control loop; this differs from the strategy used in a traditional Buck converter in terms of how much switching losses are reduced. The proposal integrates these two stages and establishes a robust control scheme that enables the battery charging process in photovoltaic systems to adapt to variations in both input and output conditions. Additionally, an irradiance detection logic has been incorporated to ensure that the system operates only when there is sufficient solar radiation is available, thereby extending the system’s lifetime and improving overall energy utilization. This work focuses on the practical integration and experimental validation of a comprehensive maximum-power-point-tracking (MPPT)-based charging system. The main contributions of this study can be summarized as follows: (1) practical integration; (2) experimental validation; (3) hardware-based protection strategy and low-computational-complexity control. To validate the designed system, a 70 W prototype with 90% efficiency was implemented and tested. The experimental results verify that the implemented protection mechanism prevents the battery from discharging unnecessarily during low-irradiance or nighttime conditions. This improves the overall efficiency of the system and extends the battery’s lifetime. Full article

Geoelectric field observations play a vital role in geophysical exploration, geological disaster early warning, and underground resource detection. Traditional contact non-polarisable electrodes, which require burial and electrolyte coupling, are hindered by several issues, such as limited adaptability to challenging terrain, significant electrode potential drift, and high susceptibility to environmental interference. Existing non-contact electric field sensors often exhibit insufficient coupling capacitance, poor impedance matching for ultra-weak high-impedance signals, and inadequate low-frequency noise suppression, rendering them unsuitable for the precise acquisition of natural microvolt-level geoelectric field signals. To address these challenges, this study introduces an innovative non-contact geoelectric field sensor with a three-layer composite structure. The sensor operates based on the principle of a parallel-plate capacitor, with a conductive silver paste layer at the top acting as the signal acquisition electrode plate, which forms an equivalent parallel-plate capacitance model with the ground to achieve non-contact capacitive coupling for geoelectric field detection. The intermediate layer uses lead zirconate titanate (PZT) piezoelectric ceramics as a support medium with a high dielectric constant. At the bottom is a silicon-based, flexible, sensitive ground-contacting layer with high elasticity, which allows it to adapt to micro-level surface irregularities, eliminating air gaps between the electrode plate and the ground, increasing plate-to-ground coupling capacitance, and ensuring the stability of the capacitance. The three-layer structure was created using a dry-press sintering integration approach, which eliminates interlayer bonding materials while ensuring consistent dielectric performance and efficient charge transfer. Additionally, a specialised signal-conditioning circuit was designed to match the ultra-high-impedance sensitive unit, utilising the ADA4528-2 ultra-low-noise precision operational amplifier, which achieved low-loss conversion and strong noise suppression for ultra-weak high-impedance charge signals. The circuit simulation results demonstrate that the designed circuit achieves an input impedance of no less than 10 TΩ, an effective operating bandwidth from 0.02 Hz to 20 kHz, and a voltage noise density lower than 1.5 μV/√Hz at 10 Hz, fully covering the ultra-low-frequency effective band of natural geoelectric fields. Field experiments comparing artificial and natural field signals revealed that the proposed sensor could be quickly deployed by simply attaching it to the ground without burial. Its time-domain waveform consistency and frequency-domain component matching were nearly identical to those of commercial standard solid non-polarisable electrodes, with a cross-correlation coefficient greater than 0.98, indicating no significant potential drift or power-frequency interference. By structurally eliminating the inherent electrode potential difference, the sensor offers advantages such as ease of deployment, strong environmental adaptability, high precision for weak signal acquisition, and excellent engineering substitutability. It is well suited for long-term geoelectric field observations in complex field scenarios, including deserts, Gobi areas, and frozen soil regions, and provides a high-performance, novel sensing solution for geoelectric field detection in extreme environments. Full article

An Ag|AgCl redox couple has been thought to work as a reversible reference electrode, although metal dissolution often occurs irreversibly. This report examines the kinetics by means of ac-impedance of AgCl films at the Ag electrode. A brief result is that the reaction rate for conventional voltammetric currents is totally irreversible, although it can be enhanced with the thickness of the AgCl film. According to the frequency-dependence of the imaginary admittance, the double layer capacitance is determined only by the geometrical area of the Ag-electrode to exhibit 140 μF cm⁻². This value is caused by the delocalized charge of AgCl dipoles rather than by water dipoles. The charge transfer rate of AgCl + e⁻ ↔ Ag + Cl⁻ was evaluated from the variation in the real admittance with the frequency to yield the charge transfer rate constant on the order of 10⁻⁹ cm s⁻¹. The rate constants increased with the surface density (Γ) of the deposited AgCl in proportion to Γ^0.3. The fractional power of the increase indicates that the reaction should occur not only at the geometrical area of the Ag-electrode but also at fluctuated Ag-particles in electric connection with the Ag-electrode, caused by percolation. The reversibility of Ag|AgCl can be realized at current densities smaller than 0.1 μA mm⁻², exemplified by 10 nA at a 0.3 mm disk. Then, Ag|AgCl can be used as a counter electrode in ultramicroelectrode techniques in a two-electrode system. Full article

Natural disasters can split distribution networks into isolated microgrids, and the remaining local storage is often not enough to keep critical loads supplied until repairs start. Mobile emergency power vehicles (MEPVs) are useful in bridging this gap, but their dispatch is easily distorted when travel time is treated as static and battery charging is treated as constant-rate. This paper studies MEPV routing and load restoration under scenario-based road degradation and non-linear constant-current/constant-voltage (CC-CV) charging. A limited-communication setting is also stated explicitly, since post-disaster information is usually intermittent rather than fully real-time. The resulting scheduling problem is solved by an Improved Adaptive Harmony Search (IAHS) algorithm. IAHS keeps the harmony–memory structure but moves binary load decisions through a continuous latent space before threshold decoding, so that the differential update can use population differences without repeatedly disturbing load variables that have already become stable. Tests on a six-area system show higher average recovery and lower dispersion than HS, AHS, GHS, and AHS with standard BDE. Additional road-degradation sensitivity tests and single-MEPV scale-up tests show that the method remains feasible under stronger road deterioration and that computation time grows in a manageable way as the number of load variables increases. Full article

Electric vehicle (EV) charging has a large, spatially clustered, schedulable load whose vehicle-to-grid flexibility can be sold back to the power system. That flexibility has grid value only when the committed quantity can be reliably delivered under uncertainty. Open forecasting benchmarks operators rely on report-only point predictions. The dispatch models that turn forecasts into firm commitments assume a constant round-trip efficiency, so the committed flexibility is systematically over-scheduled. This study contributes two complementary modules, validated separately on public data. The first is a calibrated probabilistic charging forecaster that provides, to our knowledge, the first prediction intervals with reported empirical coverage on the UrbanEV benchmark. It is a gradient-boosted quantile-regression model that combines each zone’s own-history lags with adjacency-weighted neighbor-mean features and exogenous price and calendar inputs. It is calibrated by conformalized quantile regression and scored over thirty zones across a 120-day hourly window. The second is a deliverable-flexibility envelope whose returnable-energy bounds are set by measured, state-of-charge- and rate-dependent vehicle-to-grid (V2G) discharge efficiency rather than a constant round-trip number. These bounds are fit to the measured discharge traces of three V2G-capable vehicles in the Esser bidirectional-charging dataset. Chosen as a lightweight, reproducible baseline, the forecaster keeps its prediction intervals within a five-percentage-point coverage tolerance at both the 80% and 90% nominal levels. Measured coverage is 0.823 and 0.911. It also improves on the continuous ranked probability score of its conformalized-point counterpart at matched point accuracy. This calibration holds across the hyperparameter neighborhood and under data deficiency. On the delivery side, a leave-one-vehicle oracle shows the efficiency-aware envelope short-delivers less than the constant-average-efficiency aggregator on held-out vehicles. Its residual shortfall is 1.21% against the aggregator’s 2.03% at the conservative operating point. The margin widens as commitments grow more aggressive and discharges reach the lowest states of charge. Each of these two measured properties, calibrated demand-side uncertainty and state-dependent discharge physics, imposes a material, separately validated constraint on how much contracted EV flexibility can be delivered, a constraint the point-forecasting frontier leaves unaddressed. Full article

Dynamic Wireless Power Transfer (DWPT) is attracting increasing interest as a promising solution to extend the operating range of battery electric vehicles while reducing stationary charging needs. In this study, a DWPT system for Electric Vehicle charging is investigated through a comparative simulation-based case study focused on the Italian A4 highway, a strategic transport corridor characterized by high traffic intensity and long-distance mobility demand. The proposed system is based on a segmented magnetic coupling architecture with planar circular coils installed along the roadway and a vehicle-side pickup coil. Under common roadway, vehicle, and magnetic coupling assumptions, a benchmark Tesla Model 3 Long Range traveling at a constant speed of 90 km/h and characterized by an estimated energy consumption of 0.129 kWh/km is considered. Two compensation solutions are comparatively assessed, namely the Series–Series (SS) topology and the Inductor-Capacitor-Capacitor (LCC) topology. The methodology evaluates the two topologies under the same benchmark conditions in terms of peak power, average transferred power, transferred energy per kilometer, and effect on vehicle State Of Charge (SOC). The SS topology provides a peak power of 22.52 kW, an average power of 12.30 kW, and an energy transfer of 0.14 kWh/km, whereas the LCC topology reaches a peak power of 20.44 kW, an average power of 13.47 kW, and an energy transfer of 0.15 kWh/km. Starting from an initial SOC of 30%, the final SOC after traveling through the usable electrified highway section reaches 37.48% with SS compensation and 44.28% with LCC compensation. The results show that both topologies enable effective dynamic charging, with the LCC solution exhibiting better energy transfer capability and higher operational stability, while the SS topology delivers higher instantaneous power peaks. From a comparative simulation perspective, the study supports the technical feasibility of DWPT deployment in highway environments and provides useful design insights for selecting compensation topologies in dynamic electric vehicle charging applications. Full article

Continouous unmanned aerial vehicle (UAV) missions are fundamentally limited by Lithium-Polymer (LiPo) battery endurance under intermittent and power-constrained renewable energy conditions. This paper proposes an integrated energy management and charging framework for a photovoltaic (PV)-powered mobile station equipped with a hybrid energy storage system (HESS) and an automated battery replacement (ABR) mechanism. A lexicographic priority-based allocator sequentially serves ABR actuation, multi-slot LiPo charging, and Brushless DC (BLDC) propulsion, while the HESS compensates for PV intermittency. At the charging level, a constraint-aware constant current–constant voltage (CC–CV) strategy is enhanced by an adaptive neuro-fuzzy inference system (ANFIS) trained on optimization-derived labels using battery temperature and its rate of change, thus enabling anticipatory thermal current derating with smooth, discontinuity-free control action. Anti-windup proportional–integral (PI) regulation and bumpless mode transfer ensure stable CC-to-CV transitions. An event-triggered emergency mode accelerates battery readiness via a max-first selection policy. Comparative simulations against a PSO/DE-optimized PID benchmark over a full diurnal PV cycle demonstrate that the ANFIS controller reduces the CC-mode current tracking root-mean-square error (RMSE) by up to 96.9%, delivers higher charge throughput, and lowers battery degradation proxies, including SOC-weighted thermal dose and equivalent full cycles (EFC). The proposed framework reliably sustains continuous charge–swap–recharge logistics under fluctuating renewable generation. Full article

Energy storage systems (ESSs) installed alongside traditional photovoltaic (PV) power plants are primarily used to track planned output, which often results in low utilization rates and extended payback periods. Moreover, existing research inadequately addresses actual grid frequency fluctuation characteristics and lacks multi-timescale optimization frameworks. To address these issues, this paper proposes a day-ahead and intraday multi-market coordinated rolling optimization strategy that integrates energy market trading with Automatic Generation Control (AGC) frequency regulation services through a zone-based frequency regulation control strategy. The strategy first defines distinct regulation zones based on regional control deviations, enabling a dynamic power allocation approach for the energy storage system. Recognizing that conventional constant power control can lead to battery overcharging, over-discharging, and reduced cycle life, the strategy introduces state of charge (SOC)-based variable power charging and discharging constraint coefficients. These constraints ensure the battery operates safely within its optimal range. Furthermore, an electrochemical energy storage life decay model is developed to quantify battery degradation. To accommodate the uncertainty in PV output, Latin hypercube sampling is employed. A day-ahead dispatch model is established to maximize the system’s total daily operating revenue, and rolling optimization is applied during the intraday phase to correct deviations from the day-ahead forecast. Finally, simulation studies using actual data from a PV power plant demonstrate that the proposed strategy achieves a total daily revenue of 107,477 ¥, representing a 24.6% improvement over energy market-only participation; battery aging costs are reduced by 11.1% compared to the scenario without zone-based frequency regulation control. Results indicate that the proposed strategy effectively balances battery life degradation against market revenue, significantly improving the overall operational efficiency and economic viability of PV-storage hybrid systems. Full article

Simultaneously enabling wireless charging for multiple electronic devices is a distinctive advantage of wireless power transfer (WPT). Nevertheless, the development of dual-receiver WPT systems is constrained by several challenges, including undesired cross-coupling effects, suboptimal spatial utilization, complex control strategies, and insufficient system stability. To overcome the limitations, this article develops a multipolarity decoupled four-coil WPT system with constant voltage (CV) and constant current (CC). The proposed system suppresses undesired cross-coupling to negligible levels, thereby reducing the system complexity. In addition, the compensation network can be designed in a straightforward manner, providing improved design flexibility. A detailed mathematical derivation is presented to rigorously demonstrate the load-independent CV and CC output characteristics. Meanwhile, the inverter can achieve zero phase angle (ZPA), thereby improving the power factor of the WPT system. In addition, the multipolarity decoupled mechanism of the four-coil magnetic coupler is analyzed in detail theoretically. Finally, an experimental prototype is built and tested. The experimental results demonstrate a strong agreement with the theoretical analysis, ensuring load-independent CV and CC outputs of 68 V and 3.5 A, respectively. The system achieves a measured peak efficiency of 85.97%. Full article

Constant current/voltage (CC/CV) output of wireless power transfer (WPT) systems deviates due to increased load resistance during charging and mutual inductance variations caused by misalignment. Dynamically regulating the DC input voltage can maintain a stable output at the preset value, and predicting the mutual inductance and load resistance can help monitor charging status. However, joint prediction of characteristics and regulation degree can be nonlinear and complicated. This work proposes a data-driven method for characteristic prediction and output optimization for WPT systems based on the current waveform from only the transmitter side. A Multi-Scale Parallel Convolutional (MSPC) neural network is applied to simultaneously predict the load resistance, mutual inductance, output deviation factor and regulation coefficient. By leveraging its multi-scale feature extraction capabilities, it can accurately estimate the aforementioned parameters based on only the AC current waveform at the transmitter side. To improve the model’s generalizability under practical conditions, transfer learning (TL) is utilized to minimize the discrepancy between simulated and physical data. Finally, a 140 W prototype of the series-series (SS)-compensated WPT system is built to validate the effectiveness of the proposed method. Full article

This paper presents a primary side model predictive control (MPC) strategy for wireless power transfer (WPT) based charging of light electric vehicle (LEVs). A battery simulator develops a model to accurately reproduce constant-current (CC) charging profile from Open Ciruit Voltage (OCV) and State of Charge (SoC) parameters of the battery. This model forms the foundation of the predictive control design, allowing accurate prediction of the charging trajectory while avoiding reliance on secondary-side feedback signals. The WPT system employs a phase-shifted full-bridge (PSFB) inverter with S-S compensation, where the primary-side controller regulates the secondary-side charging current using only primary-side current measurements. In contrast to conventional secondary side control, which is tuned around nominal coupling, requires explicit feedback, and degrades under coil misalignment and parameter variations, the proposed MPC leverages integrated system and battery models to predict future states and optimally adjust the phase shift for robust charging operation. Simulation and experimental validation on a real-time LEV charging prototype under aligned, lateral, and angular misalignment conditions demonstrate significant reduction in current-settling time compared to fixed-gain proportional-integral (PI) and known adaptive feedback controllers for same system, with lower RMS current and reduced current spikes at the battery. On the embedded controller, the proposed MPC executes within approximately 1 µs per 85 kHz PWM cycle, corresponding to less than 10% CPU utilization, confirming its practical real-time feasibility. Full article