Due to the excellent thermal stability and high-power density in steady state, no-insulation (NI) winding technology is widely used in the application of superconducting magnets. However, current ripple and background...
Due to the excellent thermal stability and high-power density in steady state, no-insulation (NI) winding technology is widely used in the application of superconducting magnets. However, current ripple and background magnetic field fluctuations caused by relative devices result in repetitive turn-to-turn current of the NI insert magnet, which will impose a great impact on the thermal stability of the NI magnet. This paper analyzes the cylindrical and radial current distributions of NI magnet under dynamic operating conditions by 2D finite-element method. The results provide references of thermal conductive structure design and assessment of operational reliability of NI magnets in changing working conditions.
This paper provides a detailed introduction to a modular modeling approach for the transfer function of the VSC grid-connected system. The obtained results can accurately reflect the small-disturbance stability level ...
This paper provides a detailed introduction to a modular modeling approach for the transfer function of the VSC grid-connected system. The obtained results can accurately reflect the small-disturbance stability level of VSC grid-connected systems. These results are based on the VSC outer-loop reference signal and the corresponding feedback signal, constituting a two-input two-output system. The modeling process involves three steps. Initially, only the dynamic processes of the VSC inner-loop control and PLL control modules are considered. Subsequently, the relevant modules of the VSC outer-loop control are included. Finally, it is condensed into a concise form. By utilizing the basic property of linearity in systems that adhere to the superposition principle, it can be converted into an equivalent single-input single-output system. This enables the application of the Nyquist stability criterion for stability analysis. All results presented in this paper have been validated through PSCAD/EMTDC simulation.
The offshore wind farm connected modular multilevel converter (MMC)-based high-voltage direct-current (HVDC) transmission system is prone to lose transient synchronization stability under AC faults. The multi-wind tur...
The offshore wind farm connected modular multilevel converter (MMC)-based high-voltage direct-current (HVDC) transmission system is prone to lose transient synchronization stability under AC faults. The multi-wind turbine (WT) interaction can cause a great deal WTs to lose stability in quick succession. Moreover, the multiple WTs further interact with the control of MMC, making the system stability analysis complicated. In order to guarantee a reliable operation of the system, based on equal area criterion (EAC), this paper exhaustively analyzes the stability problem of such offshore wind farm. The investigated wind farm is made up of full-scale type-4 wind turbines (WTs). It is found that the injected current distribution of MMC and WT are especially predominant in such two interactions. Based on above analysis, a stability-oriented current scheme is proposed to minimize the adverse effect of interactions, enhancing the synchronization stability. Finally, above theoretical analysis and effectiveness of the proposed current scheme are verified by MATLAB/Simulink simulation results.
Security-constrained unit commitment (SCUC) is of great importance for the economic and reliable operation of the power system. The computational hardness of SCUC remains a significant issue in the power system and el...
详细信息
CS emits plasma and metal vapor towards the arc gap, which influences the interruption of VCB. In order to analyze the dynamic evolution of CS and its effect on charged particles, the observation experiments of CS and...
CS emits plasma and metal vapor towards the arc gap, which influences the interruption of VCB. In order to analyze the dynamic evolution of CS and its effect on charged particles, the observation experiments of CS and charged particles were carried out. Using cup-shaped electrode of AMF, the dynamic pictures of CS in the diffusion is shot by high-speed camera, and the distribution of CS is observed. The CS is identify by Matlab software, and the diameter, diffusion rate and quantity of the CS are obtained. The dynamic evolution of them with different breaking conditions is analyzed. The characteristic parameters of charged particles were diagnosed by colorimetric method. The 2D spatial distribution was obtained. The results indicate that the change of the quantity of CS with time is consistent with that of current waveform. The rise in the quantity of CS is related to the diffusion and split of the spots. It is observed that the evolution of CS on the electrode is not completely uniform. At the more radial outward position of the electrodes, the distance between CS is greater. The diameter and diffusion rate of CS are not constant. It is observed that charged particles density decays and fluctuates radially, and the temperature increases along the radial direction. This is related to the evolution of CS.
Currently, the restoration of energy and communication networks in post-disaster power distribution systems is often considered independently, lacking effective coordination. To address this issue, this paper proposes...
Currently, the restoration of energy and communication networks in post-disaster power distribution systems is often considered independently, lacking effective coordination. To address this issue, this paper proposes a post-disaster recovery strategy for the energy-communication network of power distribution systems that involves coordinated scheduling of drone small cell (DSC) and maintenance personnel (MP). Firstly, scheduling models of DSC and MP are established to quantitatively analyze their temporal and spatial characteristics. Then, a post-disaster recovery strategy is proposed for the energy-communication network under the coordinated scheduling of DSC and MP. The energy-communication network is restored with the objective of minimizing the operating costs of the post-disaster power distribution system. The effectiveness of the proposed strategy is verified through numerical simulations based on an improved IEEE 33-node distribution network.
To deal with the icing of overhead lines caused by frequent ice disasters, this subject proposes a new uninterruptible electric ice-melting technology for distribution network. The deicing device is composed of adjust...
To deal with the icing of overhead lines caused by frequent ice disasters, this subject proposes a new uninterruptible electric ice-melting technology for distribution network. The deicing device is composed of adjustable reactor and earthing transformer. The head end of the device is connected to the substation power supply through a transformer, and the end is short-circuited with one-phase line in the ice- covered section through a ground wire to form a zero-sequence circuit, so as to provide zero-sequence current to the line to be deiced online to make the line heat up and melt the ice to achieve deicing without power outage. After the article puts forward this scheme, the model was built in Maxwell 3D software for verification, and the ice melting test is carried out on the pilot line, which proves the feasibility of this scheme.
High temperature superconducting (HTS) cables will suffer from performance degradation at high operating temperatures, and in severe cases even quench. The cryogenic system is able to effectively regulate the temperat...
High temperature superconducting (HTS) cables will suffer from performance degradation at high operating temperatures, and in severe cases even quench. The cryogenic system is able to effectively regulate the temperature distribution of the HTS cable by setting the operating parameters in a reasonable range to ensure its performance. It is therefore necessary to investigate operation strategy for cryogenic system that take the temperature distribution along the cable into account. In this paper, the specific requirements for the safe operation of HTS cable system with regard to the operating parameters of cryogenic system are analyzed. An operation strategy for cryogenic system is proposed to achieve thermally stable operation of HTS cable.
Modeling the process of the static magnetic hysteresis accurately is essential to compute the magnetic fields of electrical devices and components, and a modified static hysteresis model based on Tellinen hysteresis m...
Modeling the process of the static magnetic hysteresis accurately is essential to compute the magnetic fields of electrical devices and components, and a modified static hysteresis model based on Tellinen hysteresis model is presented and verified in this paper. Only two measured ascending curves are needed to solve this static model, rather than the limiting loop, which is friendly to measuring device. By comparing the measured static hysteresis curves with the calculated static hysteresis curves, it is found that the static model shows good efficiency and accuracy, and the error caused by Tellinen hysteresis model itself could be negligible when the two measured curves the model demands are close to the curve to be computed.
Because poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)is water processable,thermally stable,and highly conductive,PEDOT:PSS and its composites have been considered to be one of the most promising f...
详细信息
Because poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)is water processable,thermally stable,and highly conductive,PEDOT:PSS and its composites have been considered to be one of the most promising flexible thermoelectric ***,the PEDOT:PSS film prepared from its commercial aqueous dispersion usually has very low conductivity,thus cannot be directly utilized for TE ***,a simple environmental friendly strategy via femtosecond laser irradiation without any chemical dopants and treatments was *** optimal conditions,the electrical conductivity of the treated film is increased to 803.1 S cm^(-1)from 1.2 S cm^(-1)around three order of magnitude higher,and the power factor is improved to 19.0μW m^(-1)K^(-2),which is enhanced more than 200 *** mechanism for such remarkable enhancement was attributed to the transition of the PEDOT chains from a coil to a linear or expanded coil conformation,reduction of the interplanar stacking distance,and the removal of insulating PSS with increasing the oxidation level of PEDOT,facilitating the charge *** work presents an effective route for fabricating high-performance flexible conductive polymer films and wearable thermoelectric devices.
暂无评论