Power Transmission Characteristics Research Articles

Modeling and analysis of magnetic resonance wireless transmission coil

Wireless transmission technology is a new type of power transmission technology with electric and magnetic fields as the medium. It has more advantages in transmission direction, transmission characteristics, security, and penetration. The model of a magnetically coupled resonant radio energy transmission system is designed. The main parameters such as resonance frequency and mutual inductance are considered comprehensively. The model is designed using the equivalent topological circuit structure of mutual inductance coupling. The equivalent parameters in the circuit topology can be affected by setting the size of the coil, the distance between the coils, the excitation size, and the high frequency. The structure parameters of the whole system are modeled and calculated by the Ansoft Maxwell software. At the same time, the influence on the power and efficiency of wireless power transmission is explored by several factors such as the coil diameter, the distance between the transmitting end and the receiving end, and the resonance frequency of the system, so as to achieve the purpose of verifying the technical characteristics of wireless power transmission. The key factors that may affect the transmission efficiency and power of the system are analyzed in detail by deriving the calculation model of transmission efficiency and power.

Analysis on Transmission Characteristics of Dynamic Magnetic Coupling Mechanism of Racetrack Coil with Deflection Angles

In dynamic magnetically coupled contactless power transmission, the fluctuation of mutual inductance is caused by the relative motion between transmission and receiving coils, which affects the stability of power transmission. In order to reduce the fluctuation characteristics of power transmission, the mutual inductance calculation model of transmission mechanism including a racetrack coil with deflection angle is established by using Neumann formula, and the influence of different deflection angle and layout on mutual inductance fluctuation characteristics is analyse and compare. Then the power transmission system with LCC-S compensation for the transmission mechanism is established. The transmission characteristics of the racetrack coil with deflection angle are studied. The results show that reasonable design of the deflection angle can reduce the fluctuation of the mutual inductance and the power output in dynamic transmission. The fluctuation of power output can also be reduced by changing the distance between transmission coils and the length of straight side of receiving coils.

Analysis of Power Transmission Characteristics of a Novel Secondary Side LCD Series Forward Converter

A novel secondary-side LCD series forward converter is proposed, and the power transmission characteristics of the excitation inductance of the proposed converter under different modes are analyzed. By analyzing the relationship between the transmission power of forward branch and additional branch and excitation inductance, it is concluded that when the excitation inductance Lm works in CCM (continuous conduction mode), the transmission power of forward branch and additional branch has nothing to do with the value of excitation inductance. When the excitation inductance Lm works in DCM (discontinuous conduction mode), the transmission power of forward branch increases with the increase of excitation inductance, while the transmission power of additional branch decreases with the increase of excitation inductance. At the same time, the influence of power distribution on the efficiency of transformation topology is explored, and the relationship between the transmission power of the forward branch and the current stress of the switching tube was derived, and the parameter design method of magnetic element is put forward. Finally, the circuit model of the novel secondary side LCD series Forward converter is established, and the experimental results verify the correctness of the theoretical analysis and the feasibility of the parameter design method.

Consideration of Power Transmission Characteristics in a Micro-Gear Train.

Characteristics related to power transmission in the micro-domain, based on dry rolling contact of the gears, were investigated using a 3D-printed gear train with a pitch circle diameter of 84 µm in order to experimentally compare the power transmission efficiency in the macro- and micro-domains. For a basic gear train with two intermeshing gears, it was shown that the gear train in the micro-domain was capable of transmitting power to the same extent as in the macro-domain. However, in gear trains with complex power transmission paths, assuming a planetary gear train with multiple meshing gears, it has been shown that the power transmission characteristics of micro-domain gears differ from those in the macro-domain. The use of gear trains in the micro-region necessitates consideration of the loss of transmitted torque due to contact between tooth surfaces, which is unique to the micro-region and different from its use in the macro-region.

Identification of Critical Links Based on Electrical Betweenness and Neighborhood Similarity in Cyber-Physical Power Systems.

Identifying critical links is of great importance for ensuring the safety of the cyber-physical power system. Traditional electrical betweenness only considers power flow distribution on the link itself, while ignoring the local influence of neighborhood links and the coupled reaction of information flow on energy flow. An identification method based on electrical betweenness centrality and neighborhood similarity is proposed to consider the internal power flow dynamic influence existing in multi-neighborhood nodes and the topological structure interdependence between power nodes and communication nodes. Firstly, for the power network, the electrical topological overlap is proposed to quantify the vulnerability of the links. This approach comprehensively considers the local contribution of neighborhood nodes, power transmission characteristics, generator capacity, and load. Secondly, in communication networks, effective distance closeness centrality is defined to evaluate the importance of communication links, simultaneously taking into account factors such as the information equipment function and spatial relationships. Next, under the influence of coupled factors, a comprehensive model is constructed based on the dependency relationships between information flow and energy flow to more accurately assess the critical links in the power network. Finally, the simulation results show the effectiveness of the proposed method under dynamic and static attacks.

Basic Study of a Wireless Power Transmission System Using Superconducting Coil as a Ground-Side Coil for Electric Vehicles

We proposed a large-capacity wireless power transmission (WPT) system for the electric vehicle in which a high-temperature superconducting (HTS) coil is installed only on the ground side. On the other hand, the design guideline of the 100 kW class WPT system using the HTS and the copper coils for EVs has not been sufficiently discussed. Therefore, we analyzed the electric power transmission characteristics of the 100 kW class proposed WPT system using the HTS coil and the copper coil by an electromagnetic field analysis using the finite element method (FEM) and an equivalent circuit analysis. Also, we investigated the effect of a cooling temperature of the HTS coil on the receiving power and the transmission efficiency of the proposed WPT system for EVs. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">As a result, we found that the proposed WPT systems using the high-inductance primary and secondary coils are suitable for a low-frequency operation around 1 kHz. On the other hand, the proposed WPT systems with high-frequency operation above 10 kHz are suitable for reducing the weight of the secondary coil. In addition, although the system efficiency considering the cryocooler power loss is reduced by decreasing an operating temperature of the primary HTS coil, it is possible to realize a large-capacity WPT system with the receiving power of more than 100 kW.

Investigation of HTS Coil Structure Robustness Against Misalignment Between Coils in a Wireless Power Transmission System for Railway Vehicles

A wireless power transmission (WPT) system using high-temperature superconducting (HTS) coils has been investigated. However, it is difficult to precisely match the positions of the primary and secondary coils. Thus, the HTS coil structure with high misalignment tolerance is required. In this paper, we investigated the non-circular HTS coil structure with a high quality factor for the WPT system, such as a rectangular coil and a racetrack coil. Also, we evaluated the power transmission characteristics of the WPT system using the non-circular HTS coils. As a result, the quality factor of the non-circular HTS coils was maximum when the radial gap between turns was almost the same as the HTS wire width, and increased with increasing coil length in a rail longitudinal direction. Also, the receiving power and the system efficiency using the non-circular HTS coils were more robust against misalignment between coils than those using the circular HTS coils. On the other hand, the receiving power decreased with increasing the coil length of the non-circular HTS coils in the rail longitudinal direction due to thermal radiation from normal temperature. From the above, the receiving power of the WPT system with small lateral misalignments can be improved by using the rectangular coils with a short coil length in the rail longitudinal direction in parallel. Moreover, the system efficiency of the WPT system with large lateral misalignments can be improved by using the rectangular coils or the racetrack coils with a long coil length in the rail longitudinal direction.

Research on Double LCC Compensation Network for Multi-Resonant Point Switching in Underwater Wireless Power Transfer System

This paper introduces a control method suitable for AUVs to transmit underwater radio energy that improves the stability of AUV charging under water based on double LCC compensation. The coupling coefficient decreases with the rise of the coil offset in the underwater wireless power transfer system, such that the power transmission capability is reduced. To solve the above-mentioned problem, a double LCC resonant compensation network impedance characteristic is proposed in this study through the analysis of the double LCC resonant compensation network. To be specific, the wireless power transmission method for multi-resonant point switching of the LCC compensation network is developed. The multiple resonance points of the developed method are not correlated with the load impedance in the double LCC resonance compensation network, and the multiple resonance points are consistent with the power transmission characteristics. Moreover, the appropriate resonance frequency is matched based on different coupling coefficients, and the multi-resonance points are switched to each other to increase the system’s transmission power and transmission efficiency. As revealed by the results of the simulation and experimental studies, the double LCC compensation network with multi-resonance point switching is capable of achieving the output characteristics of constant-voltage/constant-current of the wireless power transfer system, reducing the system current harmonics effectively, and enhancing the power transmission capability and anti-offset capability.

Analysis of VSC-HVDC support capability for power grids with large-scale renewable energy and multi-infeed HVDC links

Henan Power Grid is located in the north of Central China Power Grid. During its energy transition, thermal power units will be decommissioned on a large scale. Therefore, the scale of the new energy grid connection and regional external power will be further greatly increased to match the load growth demand. Under this background, Henan Power Grid plans to introduce the third HVDC (High Voltage Direct Current). Based on the actual data and the current operation status of Henan Power Grid, this paper proposes an analysis strategy about VSC-HVDC (Voltage Source Converter HVDC) to improve the support capability of the receiving power grid with multi-infeed HVDC. In recent years, VSC-HVDC technology has emerged with the strengths of flexible power regulation and strong voltage support. This paper firstly analyzes the VSC-HVDC power transmission characteristics and clarifies the mechanism of the VSC-HVDC power regulation. Then, based on the actual planning of Henan power grid, the influence of two feed-in schemes (LCC-HVDC (Line Commutated Converter HVDC) and VSC-HVDC) on the voltage stability of power grid and the number of subsequent commutation failures of other conventional DC are compared and analyzed under the three-phase short-circuit fault of AC lines near HVDC terminal location by using PSD-BPA simulation software. The results show that the VSC-HVDC scheme can effectively alleviate the voltage fluctuation (duration within 1 s and fluctuation number within 2 times) after the fault and restrain the number of subsequent commutation failures of conventional DC(with 2 times and even none).

Optical design and stray RF investigation of ITER EC H&CD equatorial launcher using mockup

The aim of this study is to assess power transmission characteristics of ITER EC H&CD equatorial launcher (EL) which will deliver 20 MW of millimeter wave power to the ITER tokamak. A precise optical mockup of the launcher is fabricated in order to experimentally verify the characteristics of 170 GHz beam transmission. To observe the intensity distribution of output beams, a mobile high-sensitivity power detection system is used for millimeter wave monitoring, which is in good agreement with quasi-optical calculations. Internal stray RF generation presents an additional concern regarding heat load inside the launcher especially in case of deteriorated input mode purity. Therefore, firstly, the stray RF power is quantified by observation after the beam duct (i.e., launcher exit) of the mockup. The results show that a significant portion of stray RF (>20%) is emitted and does not contribute to the heat load. For another approach to estimate the heat load, geometric optics is performed with various degrees of scattering. This approach indicates that nearly half of the stray RF power is emitted from the launcher exit. Thus, the internal heat load due to stray RF is calculated 44 kW/m2, which is an important result in relaxing the design conditions of the EL.

A Phase-Shift Control Method of Triple-Active-Bridge Converter for Reducing Power Loss Under Light Load Condition

This paper presents a phase-shift control method of a triple-active-bridge converter for distributed power supply systems with multiple batteries. The experimental results show that the reactive power through the transformer can be suppressed under a wide range of conditions. The proposed phase-shift control method improves the light load loss at 500W by approximately 30% compared to the conventional method. In addition, according to the power-transmission characteristics of the proposed method, for applications in which a voltage source connected to an input port is attached and detached, the power supply and demand can be adjusted between each output port while gradually lowering the charge of the input port by utilizing the characteristics of the charging operation. Therefore, the converter can continue to operate regardless of the attachment and detachment of the input port-voltage source.

Two-stage robust optimal operation of AC/DC distribution networks with power electronic transformers

Power electronic transformers (PET) are a new type of power electronic equipment with a multi-port flexible dispatch function, which can play the role of a power hub in a system composed of multiple AC-DC hybrid distribution grids for interactive sharing of power in multiple regions. In this study, a two-stage robust optimization operation model of a hybrid AC-DC distribution network with PET is proposed based on PET power transmission and transformation characteristics. The stochastic uncertainty of the distributed renewable energy output in the AC-DC grid is handled by a two-stage robust optimization method to determine the minimum total system operation cost under the worst case of distributed renewable energy output. Finally, a constrained column generation algorithm is used to solve the two-stage robust optimization model in the min-max-min form and verifies the validity of the model in this study.

Novel integrated three-port DC/DC converter for different operating modes between renewable energy, electrolyser and fuel cell/battery

AbstractDue to the slow dynamic power-regulation characteristics of the electrolyser (EL), a novel integrated three-port DC/DC converter topology based on a phase-shifted full-bridge converter and dual active-bridge converter is proposed in this paper. Especially, the proposed converter can achieve a fast auxiliary response to the EL. This topology has the features of single-stage conversion, high system integration and compatibility with multiple operation modes. The operational principles and a hybrid modulation scheme of the proposed converter are analysed in detail. In addition, the power-transmission characteristics of each port and the soft-switching range are researched. On these bases, six operation modes suitable for a hydrogen energy-storage system are designed. The simulation and a 2-kW scaled-down experimental prototype are established to verify the feasibility and effectiveness of the proposed topology in different operation modes.

Power Transmission Characteristics in Commercial Frequency of Wireless Power Transfer System for Railway Vehicles Using High Temperature Superconducting Coil

This study investigated experimentally and analytically the power transmission characteristics of High Temperature Superconducting (HTS) coils at commercial power supply frequency (50 Hz) to realize highly efficient power transmission in wireless power transfer systems for railway vehicles. We proposed a solenoidal coil with a thin magnetic core as an HTS coil structure suitable for lower frequencies and investigated its effectiveness by finite element analysis. The analysis results showed that the proposed coil can significantly suppress the current increase due to the low frequency of the wireless power transfer system. We also investigated the core shape to reduce the losses of the proposed coil and found that the loss in the coil can be reduced by increasing the length and thickness of the magnetic core. Furthermore, we compared the power transmission characteristics between the proposed coil and the conventional spiral coil and showed that the proposed coil could improve the overall efficiency by about 10 %. The power transmission characteristics at 50 Hz were also measured using the scaled-down model coil. As a result, we demonstrated that highly efficient power transmission could be achieved at 50 Hz by using the proposed solenoidal coil with a magnetic core.

Basic Coil Structure for Rapid Charge in a Low-Frequency and High-Efficiency Wireless Power Transmission System Using High-Temperature Superconducting Coil for Railway Vehicle

We have been investigating the possibility of a low-frequency and high-efficiency wireless power transmission (WPT) system for the railway vehicle using a high-temperature superconducting (HTS) coil. We investigated a basic HTS coil structure having a low ac loss and a high coupling coefficient between the primary and secondary coils by adjusting a radial gap between turns. The devised HTS coil was configured to have a radial gap approximately equal to the HTS tape width and increase the number of turns while reducing the inner diameter of the coil. Also, we analyzed the power transmission characteristics in the 40 kW class WPT system using the devised HTS coils operated at a low frequency around 1 kHz for the railway vehicle. Furthermore, we fabricated the 1 kW class WPT model system at an operating frequency of 0.92 kHz using the devised HTS coil and demonstrated the effectiveness of the low-frequency and high-efficiency WPT system using the devised HTS coil structure. As a result, we clarified that the low-frequency WPT system using the devised HTS coil for the railway vehicle can perform more rapid charging and the high-efficiency transmission than that using the copper coils.

Fast Recovery Studies on Thermal Window based Dielectric for HTS Cable

High Temperature Superconducting (HTS) cables have remarkable electric power transmission characteristics compared to conventional power cables. Thus, HTS cables are suitable for the sustainable electrical grids of the future. Electric faults of various origins and durations are inevitable in a commercial electric power transmission network. The integration of HTS cables to these networks requires reliable cable operation under fault conditions. However, it was found that HTS cables require a long recovery interval after the fault and subsequent quench. It is primarily attributed to the high thermal resistance of the cable dielectric layer. An innovative dielectric design is proposed in this article to improve the thermal performance of HTS cables and the results are compared with that of a conventional HTS cable. Transient thermal analysis was carried out to determine the recovery interval and the electric insulation characteristics were studied using an electrostatic analysis. Both studies were performed using Finite Element Analysis (FEA). It was found that a reduction in the recovery interval is possible without deterioration in the electric insulation level.

A Series Resonant Three-Port DC–DC Converter With Decoupling Function and Magnetic Integration

In this article, a new resonant three-port dc–dc converter with dual half bridges plus one full bridge is proposed, which can realize bidirectional power flow between each port. The resonant capacitor has three functions in the circuit: the resonant capacitor can improve the magnetic bias of half bridge converter, and therefore, the transformer saturation can be avoided; the resonant capacitor is introduced to make the inductor current close to sine wave, so that the eddy current loss of the transformer can be reduced; by setting the resonant frequency of one of the three ports equal to the switching frequency, the mutual interference between the other two ports can be reduced, so that the hardware decoupling effect is achieved. First, the operation principle of the three-port converter is analyzed. Second, the steady-state model of the converter is established, and the power transmission characteristics and soft-switching characteristics are analyzed. Third, the cause of the power coupling between ports is analyzed and the hardware decoupling method is proposed. Finally, the number of magnetic elements is reduced through magnetic integration, and the correctness of the theoretical analysis is verified by simulation and prototype experiments.

Stability Analysis and Design of Common Phase Shift Control for Input-Series Output-Parallel Dual Active Bridge With Consideration of Dead-Time Effect

Input-series output-parallel (ISOP) connected dual-active-bridge (DAB) converters allow the use for occasions requiring high input voltage and galvanic isolation with bidirectional power capability. However, when DAB converters are ISOP connected, the traditional analysis without consideration of the dead time cannot effectively explain the reason why the ISOP converter system is stable under common phase shift control (CPSC) when parameters are mismatched. In this article, it is first revealed that the stability of the ISOP DAB converter under common phase ratio control can be ensured by consideration of the dead time. Based on the analysis of the DAB power transmission characteristics with consideration of dead time, a new model is derived for the ISOP DAB converter, which can reveal the reason why the converter can operate stably under CPSC when the design parameters of the individual module are mismatched. Then, based on the derived model, the stability analysis and the parameters design are further performed. Finally, the effectiveness of the working principle and analysis is verified through results from a two-module ISOP experimental prototype.

Basic Study on Power Transmission Characteristics for High-Temperature Superconducting Cable Termination Applying a Wireless Power Transmission System

We devised an HTS cable termination applying a wireless power transmission (WPT) system. The WPT system for the HTS cable termination can mechanically separate the HTS cable (low temperature part) from the copper cable (normal temperature part). In order to clarify the feasibility and design guidelines of the WPT system for the HTS cable termination, it is necessary to investigate the power transmission characteristics of the WPT system using the HTS and copper coils. In this study, we analyzed the power transmission characteristics of the simple WPT model system for the HTS cable termination by an equivalent circuit model and a finite element method analysis, and investigated the basic coil structure for the HTS cable termination applying the WPT system. As a result, the high-efficiency WPT system for the HTS cable termination can be realized by increasing the transport current of the HTS coil more than that of the copper coil. Also, we found that the HTS-Cu system using the primary-side HTS coil and the secondary-side copper coil is suitable for the HTS cable termination applying the WPT system.

Modeling and Characteristic Analysis of Magnetic Coupling Mechanism in Seawater Environment

The electrical conductivity and dielectric constant of seawater are quite different from those of air, so it is necessary to explore the differences between wireless power transmission characteristics in the air and seawater. The equivalent circuit model of the magnetic coupling mechanism is of great significance to the analysis of the transmission characteristics. In this article, a more accurate model analyzing the wireless power transmission in seawater environment is proposed, in which all parameters of the model can be obtained by specific expressions. First, by establishing the electromagnetic field analysis model in the seawater environment, the distribution laws of underwater electric field intensity and magnetic induction intensity are obtained. Then, the equivalent self- and mutual resistances of eddy current loss are introduced based on electromagnetic field model, and the analytical solutions of them are given. The lumped parameter equivalent circuit model of the underwater magnetic coupling mechanism is further derived, and the influencing factors of eddy current loss equivalent resistances are explored, which can provide theoretical guidance for multi-objective system optimization. Finally, an underwater platform was built to verify the accuracy of the equivalent circuit model.