mlsa-iai-msu-lab/ru_sci_bench_zho_cite_reranking huggingface dataset:
Superconducting magnetic energy storage for stabilizing grid integrated with wind power generation systems

Due to the interconnection of various renewable energies and adaptive technologies,voltage quality and frequency stability of modern power systems are becoming erratic.Superconducting magnetic energy storage (SMES),for its dynamic characteristic,is very efficient for rapid exchange of electrical power with grid during small and large disturbances to address those instabilities.In addition,SMES plays an important role in integrating renewable sources such as wind generators to power grid by controlling output power of wind plant and improving the stability of power system.Efficient application of SMES in various power system operations depends on the proper location in the power system,exact energy and power ratings and appropriate controllers.In this paper,an effort is given to explain SMES device and its controllability to mitigate the stability of power grid integrated with wind power generation systems.
Current-limiting characteristics of saturated iron-core fault current limiters in VSC-HVDC systems based on electromagnetic energy conversion mechanism

A common method to examine the current-limiting performance of saturated iron-core fault current limiter (SI-FCL) in high-voltage direct-current transmission based on voltage source converter (VSC-HVDC) systems is to solve differential equations based on the system fault transient characteristics and the equivalent inductance calculation equation.This method analyzes the fault current of the VSC-HVDC system in the time domain.However,it is computationally complex and cannot directly reflect the relationship between parameters and the currentlimiting effect of the SI-FCL.In this paper,the relationship between the magnetic flux density and magnetic field energy of the SI-FCL is analyzed.The energy exchange between the DC capacitor and the SI-FCL in the DC short circuit fault process is analyzed.From the perspective of electromagnetic energy conversion,the criterion for determining the current-limiting ability of the SI-FCL in the transient process is given based on the parameters of the SI-FCL and VSC-HVDC system.On this basis,the characteristics of the DC side fault current and the capacitor voltage when the SI-FCL has current-limiting ability are examined.Based on the parameters of the SI-FCL and VSC-HVDC system,a method for calculating the fault current peak value and capacitor voltage drop time is given.Finally,the accuracy of the analysis of the SI-FCL in the VSC-HVDC system based on the electromagnetic energy conversion mechanism is demonstrated through a case study and simulation results of the VSC-HVDC system with different SI-FCLs.
An online maximum power point capturing technique for highefficiency power generation of solar photovoltaic systems

This paper proposes a novel high-efficiency generation technique for photovoltaic (PV) system,named maximum power point capturing (MPPC) technique.This is an aperiodic perturbation MPPC technique compared to the conventional periodic perturbation maximum power point tracking technique.Firstly,under a closed-loop circuit and an open-loop circuit,the complete I-V curves and P-V curves are defined.Secondly,the proposed MPPC technique is based on the complete I-V curves and a practical model of solar PV systems.The proposed method realizes that maximum power point (MPP) is captured online,and its control strategy is designed to set a steady operating area around MPP.The duty cycle keeps constant when the operating point is within the steady operating area,i.e.,aperiodic perturbation,and when the operating point is outside the steady operating area,MPPC is triggered to capture a new MPP with an updated steady operating area.Simulation results demonstrate that no oscillations exist in steady-state;dynamic performances are improved;and only two perturbations are required to capture the new MPP.Using the proposed MPPC method,low voltage ride through and high voltage ride through can be prevented.
Fault diagnosis of wind turbine bearing based on stochastic subspace identification and multi-kernel support vector machine

In order to accurately identify a bearing fault on a wind turbine,a novel fault diagnosis method based on stochastic subspace identification (SSI) and multi-kernel support vector machine (MSVM) is proposed.Firstly,the collected vibration signal of the wind turbine bearing is processed by the SSI method to extract fault feature vectors.Then,the MSVM is constructed based on Gauss kernel support vector machine (SVM) and polynomial kernel SVM.Finally,fault feature vectors which indicate the condition of the wind turbine bearing are inputted to the MSVM for fault pattern recognition.The results indicate that the SSI-MSVM method is effective in fault diagnosis for a wind turbine bearing and can successfully identify fault types of bearing and achieve higher diagnostic accuracy than that of K-means clustering,fuzzy means clustering and traditional SVM.
Scenario-based analysis and probability assessment of sub-synchronous oscillation caused by wind farms with direct-driven wind generators

Recently,explanations of the sub-synchronous oscillation (SSO) caused by wind farms based on directdriven wind generators (DDWGs) have been published in the literatures,in which the controller parameters of DDWGs and the system equivalent parameters play an important role.However,more than one set of parameters can cause weakly damped sub-synchronous modes.The most vulnerable and highly possible scenario is still unknown.To find scenarios that have potential oscillation risks,this paper proposes a small disturbance model of wind farms with DDWGs connected to the grid using a state-space modeling technique.Taguchi’s orthogonal array testing is introduced to generate different scenarios.Multiple scenarios with different parameter settings that may lead to SSOs are found.A probabilistic analysis method based on the Gaussian mixture model is employed to evaluate the consistency of these scenarios with the actual accidents.Electromagnetic transient simulations are performed to verify the findings.
Primary and secondary control in DC microgrids:a review

With the rapid development of power electronics technology,microgrid (MG) concept has been widely accepted in the field of electrical engineering.Due to the advantages of direct current (DC) distribution systems such as reduced losses and easy integration with energy storage resources,DC MGs have drawn increasing attentions nowadays.With the increase of distributed generation,a DC MG consisting of multiple sources is a hot research topic.The challenge in such a multi-source DC MG is to provide voltage support and good power sharing performance.As the control strategy plays an important role in ensuring MG’s power quality and efficiency,a comprehensive review of the state-of-art control approaches in DC MGs is necessary.This paper provides an overview of the primary and secondary control methods under the hierarchical control architecture for DC MGs.Specifically,inner loop and droop control approaches in primary control are reviewed.Centralized,distributed and decentralized approach based secondary control is discussed in details.Key findings and future trends are also presented at last.
Penetrating power characteristics of half-wavelength AC transmission in point-to-grid system

With the proposed concept of global energy interconnection,half-wavelength alternating current transmission (HWACT) technology becomes of more interest.HWACT lines can be adopted to establish a pointto-grid system,in which the penetrating power (PP) is produced between receiving terminals,having a significant effect on the power flow distribution.In order to investigate this phenomenon,the PP characteristics of the HWACT system are researched in this paper.First,the mathematical relationship between the transmission power and terminal bus voltages of a single HWACT line is derived using the equations of a distributed parameter model.The research indicates that the relationship between power and terminal voltages shows ‘‘reverse characteristics’’ opposite to those of regular short transmission lines.Then,the concept and definition of PP in a point-to-grid system with two receiving terminals are proposed,and the corresponding relationship between PP and the terminal bus voltages is derived.Simulations are carried out to validate the theory under different conditions,so that the accuracy and adaptiveness of the theoretical analysis can be proved.In addition,the results demonstrate that selecting the location for a HWACT system has demanding requirements in order to control the value of PP.
Constant frequency operation of parallel resonant converter for constant-current constant-voltage battery charger applications

This paper proposes a design and control approach to parallel resonant converter (PRC) based battery chargers.The proposed approach is particularly suitable for the constant-current constant-voltage (CC-CV) charging method,which is the most commonly utilized one.Since the PRC is operated at two different frequencies for each CC and CV charging modes,this approach eliminates the need for complicated control techniques such as the frequency-control and phase-shift-control.The proposed method not only simplifies the design and implementation processes of the converter unit but also simplifies the design of output filter configuration and decreases the number of the required components for the control of the charger.The proposed method is confirmed by two experimental setups.The results show that the designed charger circuit ensured a very stable constant current in CC charging phase,where the charging current is fixed to 1.75 A.Although a voltage increase in CV phase is observed,the charger circuit is able to decrease the charging current to 0.5 A in CV phase,as depicted in battery data-sheet.The efficiency of the charger is figured out to be in the range of 86%-93% in the first setup,while it is found to be in the range of 78%-88% in the second setup,where a high frequency transformer is employed.
Frequency control of future power systems:reviewing and evaluating challenges and new control methods

Integration of more renewable energy resources introduces a challenge in frequency control of future power systems.This paper reviews and evaluates the possible challenges and the new control methods of frequency in future power systems.Different types of loads and distributed energy resources (DERs) are reviewed.A model representation of a population of the water heater devices for the demand side frequency response is considered.A model representation of a population of battery energy storage system (BESS)-based DERs such as smart electric vehicles (EVs) charging,large-scale BESSs,and residential and non-residential BESSs,are highlighted.The simplified Great Britain power system and the 14-machine South-East Australian power system were used to demonstrate the effectiveness of the new methods in controlling power system frequency following a disturbance.These new methods are effective in recovering the fallen frequency response and present a great potential in controlling the frequency in future power systems.
Mitigation of power system forced oscillations based on unified power flow controller

Forced oscillations (FOs),or low-frequency oscillations (LFOs) caused by periodic,continuous,small power disturbances,threaten the security and stability of power systems.Flexible AC transmission system (FACTS) devices can effectively mitigate LFOs via stability control.We propose a novel method that mitigates FOs by shifting the resonant frequency.Based on the features of the linearized swing equation of a generator,a resonant frequency shift can be achieved by controlling the synchronous torque coefficient using a unified power flow controller (UPFC).Because of the resonance mechanism,the steady-state response of an FO can be effectively mitigated when the resonant frequency changes from the original one,which was close to the disturbance frequency.The principle is that a change in resonant frequency affects the resonance condition.Simulations are conducted in a single-machine infinite-bus (SMIB) system,and the simulation results verify that the method is straightforward to implement and can significantly mitigate FOs.The controller robustness when the resonant frequency is not accurately estimated is also analyzed in the simulations.
Modelling,parameter estimation and assessment of partial shading conditions of photovoltaic modules

This paper proposes a method for assessing the effect that different features of partial shading conditions (PSC) may have on the operation of a photovoltaic (PV) system.Simulation studies,based on an experimentally validated model of a PV system,are used to assess the influence of PSC.Three classifications of PSC are defined based on the timescale of their influence on the irradiance experienced by the PV module and the relative location of the voltage at which the global maximum power point occurs is assessed.Sample case studies are presented to illustrate the application of the proposed PSC assessment method.The results have implications for the design of future maximum power point tracking methods.
Stability analysis of high power factor Vienna rectifier based on reduced order model in d-q domain

For a DC distributed power system,system stability can be predicted by dividing it into source and load subsystems,and then applying the Nyquist criterion to the impedance interaction between the source and load model.However,the generalized Nyquist criterion is extremely complicated and cannot directly reveal effective control strategies to reduce interaction problems of cascade threephase AC systems.Specifically,as a current force rectifier,this characteristic makes it difficult to judge the stability of a cascade three-phase Vienna AC system.To deal with the aforementioned problems,a simplified small signal stability criterion is presented for an AC distributed power system.Based on the criterion,the small signal model and impedance based on the reduced order model in the dq domain are studied theoretically.For the instability issue,an impedance regulator design method is presented.The correctness of the simplified stability criterion and the effectiveness of the proposed impedance regulator method are validated by extensive simulation and experiment.
Improved virtual synchronous control for grid-connected VSCs under grid voltage unbalanced conditions

This paper presents an improved virtual synchronous control (VSynC) for the grid-connected voltage source converter (VSC) so as to continuously operate under the grid voltage with steady unbalance.The improved VSynC introduces the negative sequence power controls on basis of conventional VSynC.The improved VSynC is capable of regulating the negative sequence internal voltage to reduce the negative-sequence injected currents and oscillated powers of the VSC aroused by the negative-sequence grid voltage.Three alternative local control objectives for the VSC itself under steady state unbalanced grid conditions and their corresponding power references are deduced and computed.Simulated and experimental results are presented to validate the correctness and effectiveness of the proposed improved VSynC to enhance the continuous operation performance of VSynC-based VSCs during grid voltage steady-state unbalance.
Growth inhibition and oxidative stress in two species of marine diatoms exposed to 1-phenylethanol

1-phenylethanol (1-PEA) is a flavor extensively used in the production of cosmetics,beverages,and food.The release of 1-PEA into coastal environments has aroused great concern.However,its potential effects on marine organisms are still unknown.In order to provide a better understanding of the ecological risks of 1-PEA in marine environments,this study determined the toxic effects of 1-PEA on two marine diatoms (Phaeodactylum tricornutum and Skeletonema costatum).The diatoms were grown in culture medium containing different concentrations of 1-PEA for 96 h.The contents of chlorophyll a,chlorophyll c,glutathione (GSH),malondialdehyde (MDA),and the activities of superoxide dismutase (SOD),catalase (CAT) and glutathione peroxidase (GPx),were measured at the end of the exposure period.1-PEA was shown to significantly inhibit the growth of diatoms,with 96-h EC_(50) values of 257.14 mg/L and 126.46 mg/L in P.tricornutum and S.costatum,respectively.In P.tricornutum,the levels of SOD,CAT,GPx,GSH,and MDA were stimulated only when 1-PEA concentrations were close to or greater than the 96-h EC_(50) value.However,in S.costatum,the activities of SOD and CAT,and the syntheses of two chlorophylls were inhibited even at an exposure concentration below the 96-h EC_(50) value.Taken together,these findings indicate a potential ecological risk by discharging 1-PEA into coastal areas and its species-specific toxic effects on marine organisms.
The transcription of iodothyronine deiodinase genes is regulated by thyroid hormone receptor in the Pacific oyster Crassostrea gigas

Thyroid hormones (THs) are indispensable for each phyla in Chordata,while their functions in the non-chordate invertebrates are indistinct.Studies on the TH system in non-chordate invertebrates are important for understanding the evolution of TH system and may be applied in aquaculture or biofouling control at the same time.Iodothyronine deiodinases are keys to studying the TH system,as they are critical enzymes in maintaining TH homeostasis by catalyzing the initiation and termination of the effects of thyroid hormone in vertebrates.Here,we report the primary physiological effects of T4,the outer ring deiodinase activity,and a similar transcription regulation of two oyster deiodinases by TH receptor (CgTR) in an invertebrate,Pacific oyster Crassostrea gigas.L-thyroxine (T4) may have an important physiological function in the oyster,suggested by the growth retardation effect of excessive T4 in umbo larvae stage.The outer ring deiodinase activity transforming T4 to T3 (3,3′,5-triiodothyronine) was then detected in the Pacific oyster in vivo,which may be conducted by two oyster deiodinases (CgDx and CgDy).Transcription regulation of CgTR onto these two deiodinase genes was also verified by electrophoretic mobility shift assay and dual luciferase reporter assay in mammalian cells.These results contribute to a better understanding of the evolution of the TH system.
3D Eddy Current and Temperature Field Analysis of Large Hydro-generators in Leading Phase Operations

1 Abstract—As a common practice, a large hydro-generator will operate in leading phase conditions to absorb the reactive power of the power grid. However, the accurate and precise prediction of the leading phase operation capacity of a large hydro-generator has always been a formidable challenge to engineers and academicians because it is extremely hard to compute the eddy currents and losses as well as the local overheating in the pressure plate and finger. To address this problem, a full three dimensional (3D) finite element model and method of the coupled eddy current and temperature fields in the end region of a large hydro-generator are developed. The equivalent medium parameters used in the computations are comprehensively discussed. Moreover, some numerically based solution methodologies for accurate computation of the field and armature currents under different leading phase conditions are proposed. Numerical results on the coupled eddy current and temperature fields in the end regions of a 250 MW hydro-generator confirm positively the feasibility of the present work.
Novel Rotors with Low Eddy Current Loss for High Speed Permanent Magnet Machines

Due to the large rotor eddy current loss and low thermal conductivity of carbon fiber sleeve, the high temperature usually occurs in high speed permanent magnet machines (HSPMMs) at the rated operation condition, resulting in irreversible demagnetization of the permanent magnet (PM). To obtain low rotor temperature, two novel rotor structures with low rotor eddy current loss are proposed in this paper. With the output torque and air gap flux density unchanged, the performance of HSPMMs with the two proposed rotor structures are analyzed based on finite element algorithm (FEA), including eddy current loss and temperature. Finally, the appropriate parameters of the proposed rotor structures are selected, and the electromagnetic (EM) performance, rotor stress and temperature are compared with those of the conventional rotor structure.
Performance Evaluation of a 60kW IPM Motor for Medium Commercial EV Traction Application

This paper presented the design and performance analysis of a 60kW interior permanent-magnet (IPM) synchronous motor used as traction drive in a medium commercial electric vehicle (EV), according to the traction requirements of the electric vehicle under the rated operating conditions and overload conditions. The key dimensions were calculated on the basis of the permanent-magnet (PM) motor theory, and the 2D finite element method (FEM) simulation model of the IPM motor was built by using 2D Maxwell software. The influence geometric structures of the IPM motor including the PM dimensions and skewed PMs on electromagnetic torque were investigated, and the temperature distribution of the motor under rated operating condition and the condition of maximum speed were calculated. Finally, the simulation results of the IPM motor running in various operating modes were compared with the experimental results, which demonstrated that the designed IPM motor can match all requirements of the medium commercial electric vehicle driving applications.
Development of a Consequent Pole Transverse Flux Permanent Magnet Linear Machine with Passive Secondary Structure

Transverse-flux machines have the advantage of high force density owing to the peculiarity of decoupling of electric loading and magnetic loading. In this paper, a novel consequent-pole transverse-flux permanent magnet linear machine (CP-TFPMLM) is proposed and investigated. The origination of the proposed machine is from an existing transverse-flux flux-reversal linear machine (TF-FRLM), by partially replacing permanent magnet poles with soft magnetic iron for further reducing the cost of magnets. The fundamental structure and operating principle are introduced at first. The electromagnetic performance, including back EMF, detent force, and thrust force, are investigated with the finite element method. The proposed machine can achieve similar performance as compared to the TF-FRLM but with half of the magnets are used.
Optimal Split Ratio in Small High Speed PM Machines Considering Both Stator and Rotor Loss Limitations

The split ratio which is defined as the ratio between rotor and stator outer diameters is critical for permanent magnet (PM) machines. In this paper, the split ratio in small high speed PM machines is optimized analytically by considering both stator and rotor loss limitations. By this way, the thermal constrains in both stator and rotor parts can be taken into account. It shows that both losses can significantly affect the optimal split ratio and the machine performance. By considering the influence of rotor losses, especially the rotor eddy current loss, the optimal split ratio is increased significantly in certain scenarios. The output torque is calculated analytically and the influences of several key design parameters on the optimal split ratio, i.e. slot/pole combinations and magnet materials, are also investigated in details. Finally, finite element (FE) analyses are carried out for validating of the analytical model.