1,721,023 research outputs found
Fast Calculation of Shielding Effectiveness in Wireless Power Transfer Systems
No full textThis paper proposes a fast analytical procedure to evaluate the shielding effectiveness (SE) of conductive shields in wireless power transfer (WPT) systems. The methodology exploits the current image method combined with a compact SE calculation formulation, which can also be extended to multilayered shields. A standard case study is considered, and the results are validated through finite-element method (FEM) simulations
Standing Wave Pattern and Distribution of Currents in Resonator Arrays for Wireless Power Transfer
Full text linkThe possibility of increasing the transmission efficiency in mid-range wireless power transfer (WPT) applications can be achieved by inserting resonant relay coils between the transmitting and receiving sides of the device, forming an array of magnetically coupled resonant circuits, over which a receiver can be placed. This is a very cheap solution for improving the performance of the WPT apparatus, even if the complexity of the system increases, requiring a complete and detailed investigation for a smart design and control of the apparatus. The presented study investigates the current distribution in the coils of the array, which revealed strong peaks in magnitude depending on the load and receiver position. The analysis is carried out with the transmission line (TL) theory and it is performed for different positions of the receiver, as well as for different load conditions. Furthermore, a real application is considered and discussed, which includes the presence of a power converter as power supply and a battery charging system as load. Each resonant circuit resonates at 150 kHz and the whole apparatus is capable to transmit power up to 1 kW with an efficiency around 70%. The theoretical results have been validated with experimental measurements
Magnetic near Field Investigation and Shielding Effectiveness Evaluation of an Inductive Power Transfer System with a Resonator Array
No full textThis paper presents a study of the magnetic near field produced by an inductive power transfer (IPT) system composed of an array of magnetically coupled resonators that may be embedded in a table for powering desktop electronic devices. The analysis is performed considering different positions of the receiver circuit, namely different structures of the system, that lead to very different behaviour in terms of the generated magnetic field. Significant peaks of the magnetic field have been detected in correspondence of certain resonators of the array for different positions of the receiver, thereby making shield actions necessary. An estimation of the shielding effectiveness of a shield used to reduce human exposure to the generated magnetic field is carried out. The theoretical results have been validated with experimental measurements
Input Current of H-bridge Inverters with Asymmetric Switch Parameters for Wireless Power Transfer Applications
No full textIn modern DC distribution networks both consumer and prosumer devices are interfaced to the grid via power converters equipped with suitable filtering circuitry to mitigate conducted electromagnetic interference (EMI), also referred to as conducted emissions (CE). However, the presence of asymmetries in the converter, such as the deviation of the component parameters from the designed ones and possible device failure, can significantly alter the input current and voltage waveforms while the device still works satisfactorily. This inevitably leads to an increase in the harmonic pollution in the power grid, being the EMI filters designed for acting on different waveforms. This paper investigates the effect that non-idealities of power switches have on the input current of an H-bridge inverter
Conducted Emission Analysis of a Near-Field Wireless Power Transfer System
No full textIn modern inductive power transfer (IPT) systems, especially if devoted to electric vehicle (EV) charging, the alignment between the transmitter and receiver coils still represents one of the most relevant issues. Besides a well-known drop in the efficiency and transferred power, operating in a misalignment condition also affects the conducted emissions towards the grid, that increase as the coupling between the transmitter and receiver weakens. This paper investigates the conducted emissions of an IPT system for different alignment conditions. The system is supplied by a full-bridge inverter and feeds an equivalent load of 5 Ω through a full-bridge diode rectifier. The inductive coupling is realized with two identical square coils, that resonate with lumped capacitors connected in series at the resonant frequency of 147 kHz. A simple model has been used for the prediction of the differential-mode conducted emissions and the results have been compared with experiments. The measurements have been performed with the general setup for conducted emissions described in IEC standards and the disturbance voltages have been processed to assess the highest emission level which defines the worst case scenario for electromagnetic compatibility
Simple Formula for the Calculation of Shielding Effectiveness of Finite Width Conductive Shields
No full textIn this paper, a fast and simple analytical formulation for the calculation of the shielding effectiveness of finite width conductive shields at extremely low frequency is proposed. The magnetic field generated by a current loop is analysed considering a conductive shield of various widths and for different distances of the source from the shield and from the field point. The effect of the system parameters on the shielding effectiveness is investigated. A formula for the shielding effectiveness of finite width conductive shields at extremely low frequency is derived from the values of the magnetic field in absence of the shield and in presence of a shield of infinite extension
Surface Current Analysis in a 2D Metamaterial
No full textThis paper investigates the distribution of the currents in a 2D metamaterial realized with coupled-resonant circuits, when it is excited by a voltage source in an arbitrary cell. Possible different models for the analysis of these structures are illustrated and the effect of the approximations they introduce on the current values are shown for a 5× 5 array. Furthermore, the matching of the boundaries of the metamaterial is discussed and possible values for the matching impedances have been numerically calculated for arrays with a small number of resonators
Deep-Learning Based Transient Identification in Switched-Mode Power Supplies Conducted Emissions
No full textConducted emissions (CE) caused by Switched-Mode Power Supplies (SMPSs) present harmonic and interharmonic distortion that occur in a wide range of frequencies and usually reveal a nonstationary behaviour. This requires long and complicated measures to ensure all the transient components to be correctly assessed. The analysis and classification of SMPS CE is addressed by employing an artificial neural network (ANN), with the aim of discriminate the part of the measured disturbance that is strongly affected by transient components and highlight the most relevant features of the CE spectrum. Thus, the subsequent frequency analysis can be performed on a smaller data set, allowing savings in time and computational efforts
Two-port network compact representation of resonator arrays for wireless power transfer with variable receiver position
Full text linkThis paper presents an equivalent circuit characterization of an array of resonators for wireless power transfer (WPT) applications. These apparatuses are composed of magnetically coupled resonant coils acting as a transmitter which feeds a receiver coil that can be placed over them at any position, allowing the tolerance of the system to the receiver misalignment to be dramatically enhanced. This advantage makes resonator arrays a suitable solution for both low- and high-power applications. The latter usually involve battery charging, with the resonator array acting as a transformer stage, ensuring galvanic isolation. An equivalent two-port network can be defined for any receiver position, allowing the array to be treated as a traditional transformer. Thereby, the simulation of the system can be simplified, as it is required in the design steps of a converter and control strategy. Analytical expressions of the two-port network parameters are proposed for arrays of any size and length. The formulas have been numerically and experimentally validated
Variability of Conducted Emissions of EV Chargers due to Mutual Effects on a DC Grid
No full textDC grids are becoming a popular choice to cope with highly dynamic and distorting loads, such as electric vehicle chargers that feature significant conducted emissions in the supraharmonic range, on/off load profiles and large power levels (especially for fast charging mode, enabled by connection to a DC grid). One major factor affecting the reliable assessment of emissions in the supraharmonic frequency interval (2 kHz to 150 kHz) is the definition of the supply conditions namely the feeding impedance; in addition, emissions in this frequency range are a mix of differential- and common-mode emissions, with prevalence of the former. It is demonstrated that supply impedance values at the EV charger connection may be highly variable depending on network loading and location of the other connected EV chargers: some scenarios of small and medium extension of the DC network are evaluated, showing peculiar frequency intervals where emissions could vary by as much as 20 dB simply as the consequence of connection and disconnection of other EVs
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