Search Results (84)

A transient multibody dynamics simulation of rolling-element bearings is the basis for the design of high-speed rotating machinery; however, the established solvers are proprietary, cannot be used with automatic differentiation, and offer no built-in measure of their own physical consistency. We present OpenBEARD, an open-source, fully differentiable transient dynamics solver for angular-contact ball bearings. The solver steps a $40+13Z$-component state (inner ring, cage, and Z balls with quaternion attitude, plus guide-patch, lumped-thermal, and energy-audit states) forward in time under coupled Hertzian contact, Hamrock–Dowson and full-multigrid elastohydrodynamic lubrication, thermal–elastohydrodynamic traction, and centrifugal/press-fit clearance models, using nondimensionalized implicit stiff time integration. A built-in metriplectic conservation audit checks energy closure, the second law per dissipation channel, and the gyroscopic-power identity at every output step. OpenBEARD is cross-verified against two published ADORE references of Gupta. For a high-speed NASA angular-contact ball bearing, the quasi-static contact loads, angles, stresses, and centrifugal force match the published values to within $0.3\%$, and the ball spin and orbital velocities and the spin-axis orientation to ≤0.1%. The inner-race spin-to-roll ratio—a slip-derived secondary quantity that is the most model-sensitive metric in this class of solvers—differs from the NASA quasi-static reference by $8.8\%$. In the separate caged BallBearingTestCase benchmark, the corresponding quasi-static difference is $3.2\%$, and the transient settled value is $\approx 16\%$ above the ADORE step-100 snapshot; these bounded offsets reflect different spin-moment constitutive models. The BallBearingTestCase comparison—a caged bearing under combined thrust and radial load—matches the per-ball contact angles and loads to within $0.23\%$ RMS, and a single published dynamic snapshot (step 100) agrees with the transient contact mechanics to within a few percent. The built-in energy-closure residual stays of order ${10}^{-5}$ with no second-law violations. In the fully transient regime, race control emerges as a dynamical attractor of the coupled traction balance—ball-spin states perturbed by $\pm 12\%$ converge to a single outer-race-control solution—rather than the kinematic hypothesis assumed by quasi-static theory. OpenBEARD is released under the MIT license. Full article

To address the insufficient voltage boost capability and excessive device stress of DC–DC converters at hydrogen fuel cell output ports—issues that hinder the safe and stable operation of megawatt-level grid-connected systems—this paper proposes a two-stage, multi-unit interconnected grid-connection topology. This topology features a single-switch boost capability with a double Z-source network, accompanied by a dedicated grid-connection control strategy. First, the switching device in the quasi-Z-source converter is positioned at the front end to mitigate the device stress in the DC boost stage of the grid-connected topology. Second, the inductors in the Z-source converter are replaced with quasi-Z-source networks to form a double Z-source structure, thereby enhancing the boost capability of the front-end DC–DC Boost converter for hydrogen fuel cells, reducing the duty cycle, and suppressing inductor ripple current. Subsequently, an AC/DC grid-connection regulation strategy is designed to achieve stable power output from the hydrogen fuel cells. The results show that compared with the traditional Z-source Boost converter scheme, the proposed topology increases the output voltage by 21.2% and reduces the voltage stress of the switching device by 8.3% at the rated output power, making it highly suitable for high-power applications. Finally, the correctness of the theoretical analysis and the effectiveness of the proposed topology are verified through simulations and experiments. Full article

This paper proposes an optimal tracking control framework for a permanent magnet synchronous motor (PMSM) drive integrated with a quasi-Z-source (QZS) inverter for all-electric aircraft applications. Two tracking control strategies are developed: (i) an online adaptive optimal control (OAC) method for tracking motor speed and (ii) a linear quadratic integral (LQI) controller for regulating the peak DC-link voltage (PDV) of the QZS. Due to the nonlinear characteristics, parameter uncertainties, and external disturbances inherent in PMSM systems, achieving accurate speed tracking and stable DC-link voltage (DCV) regulation using a PDV control strategy under varying power flow conditions remains a significant challenge. In this study, the PMSM model is represented as a nonlinear system with strict feedback. Augmented feedforward control signals are incorporated to restructure the conventional cascade control architecture into a novel optimal control framework. Based on this formulation, a saturated adaptive optimal control law is proposed, relying on a near-optimal solution to the Hamilton–Jacobi–Isaacs (HJI) equation. This solution is approximated using an online approximator combined with an integral reinforcement learning technique. Meanwhile, an LQI controller is employed to regulate the PDV and suppress voltage fluctuations in the QZS. Simulation results demonstrate that the proposed approach significantly improves speed tracking accuracy, DCV stability, and disturbance rejection capability while improving the overall performance and reliability of PMSM drive systems. The simulation results demonstrate that the proposed control strategies have strong potential for effective application in all-electric aircraft systems, meeting the requirements of high performance and energy efficiency. Full article

Passenger fuel cell vehicles (FCVs) require high-gain DC/DC converters to achieve voltage matching between the low-power fuel cell (FC) stack (50–200 V) and the vehicle DC bus (400–800 V). To address the challenges in existing step-up DC/DC converters in relation to balancing the requirements of high voltage gain, wide input voltage range, low input current ripple and voltage stress, the common ground of input–output, and high efficiency in passenger FCV applications, this paper proposes three types of high-gain DC/DC converters based on an interleaved structure, incorporating quadratic Boost, quasi-Z source, and switched-inductor impedance networks. These designs effectively balance the scenario requirements of passenger FCVs. Meanwhile, taking one of the proposed converters (Interleaved-Quadratic Boost; I-QB) as an example, its steady-state performance such as voltage gain is analyzed and compared in detail with existing voltage step-up DC/DC converters. Furthermore, a scaled-down SiC-based experimental platform is constructed. Steady-state experiments validate the converter’s maximum voltage step-up capability of ten times, wide input voltage range of 30–80 V, input current ripple of less than 0.3 A, and low voltage stress on devices (≤U_o/2), thereby confirming the feasibility of these converters and the correctness of the performance analysis. The dynamic experimental results indicated that under input voltage step changes of 50–80 V and 100–50% load step changes, the I-QB converter exhibits a minor voltage overshoot with settling time under 200 ms. The prototype achieves a peak efficiency of 94.2%, confirming these converters’ suitability for passenger FCV powertrains. Full article

The intermittent nature of photovoltaic (PV) energy, especially under nonlinear and unbalanced loading situations, has made it more difficult to ensure steady operation as it is increasingly integrated into modern power systems. The Power Quality (PQ) issues cause severe degradation of both system performance and device lifetime. A novel Neural Power Quality Network (NeuPQ-Net) controlled Unified Power Quality Conditioner (UPQC) combined with a Quasi Z-Source Lift (QZSL) converter for PV applications is presented in this research as a novel solution for addressing these issues. The QZSL converter, which is controlled by a Maximum Power Point Tracking (MPPT) algorithm based on Perturb and Observe (P&O), increases the PV source voltage to the necessary DC-link level. A Zebra Optimisation Algorithm tuned PI (ZOA-PI) controller continually adjusts PI gains for quick and accurate regulation, ensuring steady DC-link voltage. Unlike conventional Synchronous Reference Frame (SRF) or Decoupled Double Synchronous Reference Frame (DDSRF)-based reference generation, the proposed NeuPQ-Net operates directly in the abc domain, eliminating Phase-Locked Loop (PLL) dependency and reducing computational complexity. Simulation and hardware prototype validations demonstrate that the proposed system achieves significant improvements in PQ indices, including reduced Total Harmonic Distortion (THD), faster response to transients, and enhanced voltage regulation, while complying with IEEE-519 standards. Full article

Photovoltaic (PV) systems are prone to different types of faults, primarily electrical faults such as line-to-ground (L-G) and line-to-line (L-L) faults, which can significantly reduce system performance, efficiency, and lead to increased power losses. Moreover, mechanical damage caused by environmental stressors (such as wind, hail, or temperature variations), aging, or improper installation also contribute to system degradation. This study specifically focuses on electrical faults and proposes a method that not only enables the isolation of faulty modules but also ensures the uninterrupted operation of the remaining healthy modules and also assists in the localization of faults. Unlike benchmarked techniques-based boost converters, the Quasi-Z-Source Boost Converter (QZBC) topology offers improved voltage boosting with high gain values, reduced component stress, and enhanced reliability when the PV system is undergoing fault identification and localization algorithms. A 600-watt PV system connected with a Quasi-Z-Source Boost Converter was implemented and tested under different fault conditions using a hardware-in-the-loop (HIL) setup with Typhoon HIL. All the component values of the QZBC were calculated based on the system requirements rather than assumed, ensuring both practical feasibility and design accuracy. The experimental results show that the converter achieved an efficiency of over 96% under electrical-fault conditions, confirming the effectiveness of the quasi-Z-source boost converter in maintaining a stable power output when the PV system is undergoing fault identification and localization algorithms. The study further highlights the benefits of HIL-based testing for evaluating PV-system resilience and fault-handling capabilities in real-time conditions using a Typhoon HIL 404 environment. Full article

This publication investigates the control of output voltage-boosting in a Quasi-Z-Source direct matrix converter operating as part of a PMSM drive system with an RLC grid filter. The structure and control algorithms enabling regulation of the converter’s output voltage in both step-down and step-up modes are presented. These methods are based on the $dq$ transformation, which provides a measurement signal for a linear PI-type controller. The article includes simulation results obtained using Matlab Simulink 2019a, which facilitated the preliminary verification of the applied structures and methods. The obtained model revealed the presence of nonlinearities in the Quasi-Z-Source voltage control system, which were subsequently confirmed through experimental verification. The system is stable but exhibits oscillatory behavior, with its parameters dependent on the amplitude of the step of the voltage gain coefficient. The voltage control system regulates the output voltage at least 10 times faster than a single period of the grid voltage sine wave. To enhance voltage control, a tunable controller with optimized parameters was proposed. The conducted studies demonstrated a 16.5% improvement in the IAE index and faster settling time for Quasi-Z-Source voltage control using the proposed controller compared to the reference controller. Full article

Z-source/quasi-z-source inverters can make up for some limitations of traditional voltage-/current-source inverters. In recent years, more and more research has been carried on z-source/quasi-z-source inverters, but most of them are unable to realize input/output galvanic isolation. The proposal of high-frequency isolated z-source/quasi-z-source inverters greatly enriches the topological family of this type of converter but places relatively high voltage stress on the capacitors. In this paper, a novel circuit topology of a quasi-z-source inverter with a high-frequency AC link of a new high-proportion power system is proposed. The operating principle and abnormal operating states, such as discontinuous-conduction mode (DCM) operation and abnormal states caused by component failures, are analyzed. The double closed-loop control strategy is analyzed and designed, and a grid-connected photovoltaic system based on the inverter is designed. The experimental results verify that the presented inverter has advantages such as high-frequency electrical isolation, bi-directional power flow, lower voltage stress on the capacitors, etc. Full article

Large-scale photovoltaic (PV) systems are being widely deployed to meet global environmental goals and renewable energy targets. Advances in PV technology have driven investment in the electric sector. However, as the size of PV arrays grows, more obstacles and challenges emerge. The primary obstacles are the occurrence of direct current (DC) faults and shading in a large array of PV panels, where any malfunction in a single panel can have a detrimental impact on the overall output power of the entire series-connected PV string and therefore the PV array. Due to the abrupt and frequent fluctuations in power, beside the low-PV systems’ moment of inertia, various technical problems may arise at the point of common coupling (PCC) of grid-connected PV generations, such as frequency and voltage stability, power efficiency, voltage sag, harmonic distortion, and other power quality factors. The majority of the suggested solutions were deficient in several crucial transient operating features and cost feasibility; therefore, this paper introduces a novel power electronic DC–DC converter that seeks to mitigate these effects by compensating for the decrease in current on the DC side of the system. The suggested solution was derived from the dual-source voltage-fed quasi-Z-source inverter (VF-qZSI), where the PV generation power can be supported by an energy storage element. This paper also presents the system architecture and the corresponding power switching control. The feasibility of the proposed method is investigated with real field data and the PSCAD simulation platform during all possible weather conditions and array faults. The results demonstrate the feasibility and capability of the proposed scheme, which contributes in suppressing the peak of the transient power-to-time variation (dP/dt) by 72% and reducing its normalized root-mean-square error by about 38%, with an AC current total harmonic distortion (THD) of only 1.04%. Full article

Photovoltaic (PV) energy has been a preferable choice with the rise in global energy demand, as it is a sustainable, efficient, and cost-effective source of energy. Optimizing the power generation is necessary to fully utilize the PV system. Harvesting more power uses cascading of impedance source converters taking input from low-voltage PV arrays which requires multiple maximum power point tracking (MPPT) controllers. To solve this problem, a three-level inverter topology with a proposed PV arrangement, offering higher voltage boosting and a smaller size with a lower cost suitable for low-voltage panels, is designed in this article. The design criteria for parameters are discussed with the help of the small signal analysis. In this paper, three PV arrays are used to harvest maximum energy, which require only one MPPT controller and employ an extended perturb and observe (P&O) algorithm, being faster, highly efficient, and reducing the computational burden of the controller. Moreover, a three maximum power points tracker algorithm, which perturbs one parameter and observes six variables, is designed for the selected converter topology. Finally, the designed 1.1 kVA grid-connected PV system was simulated in MATLAB (R2023a) which shows that the MPPT algorithm offers better dynamics and is highly efficient with a conversion efficiency of 99.2% during uniform irradiance and 97% efficiency during variable irradiance conditions. Full article

We report the results of time series analysis of blazar PKS 1440-389, observed by the Transiting Exoplanet Survey Satellite (TESS) in two sectors. We find that the source has a quasi-periodic oscillation (QPO) of about 3.1 days for sector 11 and around 3.7 days for sector 38 in the optical band. We use two methods to assess the QPO and its confidence level: Lomb–Scargle periodogram and weighted wavelet Z-transforms. We explore various potential explanations for these rapid quasi-periodic variations and propose that their source most likely resides within the innermost region of the accretion disk. Within this framework, we estimate the mass of the central black hole of this blazar. We obtain black hole masses of 6.65 × 10⁸${\mathrm{M}}_{\odot }$ (Schwarzschild black hole) and 4.22 × 10⁹${\mathrm{M}}_{\odot }$ (maximally rotating Kerr black hole), with a main period of 3.7 days. Finally, we utilize the kink instability model to explain the QPO. Full article

To address problems that traditional two-stage inverters suffer such as high cost, low efficiency, and complex control, this study adopts a quasi-Z-source cascaded multilevel inverter. Firstly, the quasi-Z-source inverter utilizes a unique impedance network to achieve single-stage boost and inversion without requiring a dead zone setting. Additionally, its cascaded multilevel structure enables independent control of each power unit structure without capacitor voltage sharing problems. Secondly, this study proposes a current-predictive control strategy to reduce current harmonics on the grid side. Moreover, the feedback model of current and system state is established, and the fast control of grid-connected current is realized with the deadbeat control weighted by the predicted current deviation. And a grid-side inductance parameter identification is added to improve control accuracy. Also, an improved multi-carrier phase-shifted sinusoidal PWM method is adopted to address the issue of switching frequency doubling, which is caused by the shoot-through zero vector in quasi-Z-source inverters. Finally, the problems of switching frequency doubling and high harmonics on the grid side are solved by the improved deadbeat control strategy with an improved MPSPWM method. And a seven-level simulation model is built in MATLAB (2022b) to verify the correctness and superiority of the above theory. Full article

The Quasi-Impedance-Source Inverter (Quasi-Z inverter) is an interesting DC-AC converter topology that can be used in applications such as fuel cells and photovoltaic generators. This topology allows for both boost capability and DC-side continuous input current. Another very interesting feature is its reliability, as it limits the current when two switches on one leg are conducting simultaneously. This is due to an extra conduction state, specifically the shoot-through state. However, the shoot-through state also causes a loss of performance, increasing electromagnetic interference and harmonic distortion. To address these issues, this work proposes a modified carrier-based control method for the T-Type single-phase quasi-Z inverter. The modified carrier-based method introduces the use of two additional states to replace the standard shoot-through state. The additional states are called the upper shoot-through and the lower shoot-through. An approach to minimize the number of switches that change state during transitions will also be considered to reduce switching losses, improving the converter efficiency. The proposed modified carrier-based control strategy will be tested using computer simulations and laboratory experiments. From the obtained results, the theoretical considerations are confirmed. In fact, through the presented results, it is possible to understand important improvements that can be obtained in the THD of the output voltage and load current. In addition, it is also possible to verify that the modified carrier method also reduces the input current ripple. Full article

This paper investigates the development of pulse width modulation (PWM) schemes for three-phase quasi-Z-source inverters (qZSIs). These inverters are notable for their voltage boost capability, built-in short-circuit protection, and continuous input current, making them suitable for low-voltage-fed applications like photovoltaic or fuel cell-based systems. Despite their advantages, qZSIs confront challenges such as increased control complexity and a larger number of passive components compared to traditional voltage source inverters (VSIs). In addition, most existing PWM schemes for qZSIs lack the capability for independent control of the amplitude modulation index and duty cycle, which is essential in closed-loop applications. This study introduces innovative space-vector PWM (SVPWM) schemes, addressing issues of independent control, synchronization, and unintentional short-circuiting in qZSIs. It evaluates several established continuous and discontinuous PWM schemes, and proposes two novel decoupled SVPWM-based schemes that integrate dead time and in which the shoot-through occurrence is synchronized with the beginning of the zero switching state. These novel schemes are designed to reduce switching losses and improve qZSI controllability. Experimental validation is conducted using a custom-developed electronic circuit board that enables the implementation of a range of PWM schemes, including the newly proposed ones. The obtained results indicate that the proposed PWM schemes can offer up to 6.8% greater efficiency and up to 7.5% reduced voltage stress compared to the closest competing PWM scheme from the literature. In addition, they contribute to reducing the electromagnetic interference and thermal stress of the related semiconductor switches. Full article

This paper reports on the location of sources contributing to a point flux measurement in the southern taiga, Russia. The measurement tower is surrounded by a coniferous forest with a mean aerodynamically active height of 27 m (h). Aerodynamical parameters of the forest, such as displacement height d and aerodynamic roughness $z_0$, derived from wind speed profile measurements for 2017–2019, were used to estimate the seasonal and daily behavior of the flux footprint. Two analytical footprint models driven by d and z₀ were used to estimate the footprint for canopy sources. The Lagrangian simulation (LS) approach driven by flow statistics from measurements and modeling was used to estimate the footprint for ground-located sources. The Flux Footprint Prediction (FFP) tool for assessing canopy flux footprint applied as the option in the EddyPro v.7 software was inspected against analytical and LS methods. For model comparisons, two parameters from estimated footprint functions were used: the upwind distance (fetch) of the peak contribution in the measured flux (X_max) and the fetch that contributed to 80% of the total flux (CF₈₀). The study shows that X_max varies slightly with season but relies on wind direction and time of day. All methods yield different X_max values but fall in the same range (60–130 m, around 2–5 h); thus, they can estimate the maximum influence distance with similar confidence. The CF₈₀ values provided by the FFP tool are significantly lower than the CF₈₀ values from other methods. For instance, the FFP tool estimates a CF₈₀ of about 200 m (7 h), whereas other methods estimate a range of 600–1100 m (25–40 h). The study emphasizes that estimating the ground source footprint requires either the LS method or more complex approaches based on Computational Fluid Dynamics (CFD) techniques. These findings have essential implications in interpreting eddy-flux measurements over the quasi-homogeneous forest. Full article