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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Conceptual Consequences of the SI
摘要： The SI and its forerunners were largely developed in response to the confusion of multiple electromagnetic unit systems at the start of the 20th century. More than 100 years later, the success of the SI is evidenced by its almost universal acceptance. The adoption of the ampere as the fourth base unit has proved to be a beneficial way of simplifying electromagnetic units. However, an unintended consequence of adopting this system has been the development of several misconceptions regarding the physics of electromagnetic quantities. The anticipated educational activities associated with the upcoming SI redefinition offer an ideal opportunity to resolve this concern.
关键词： CGS,Permeability of Free Space,SI,Ampere,Magnetic Constant,Electrical Units
更新于2025-09-23 15:22:29
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Apparent delocalization of the current density in metallic wires observed with diamond nitrogen-vacancy magnetometry
摘要： We report on a quantitative analysis of the magnetic field generated by a continuous current running in metallic microwires fabricated on an electrically insulating diamond substrate. A layer of nitrogen-vacancy (NV) centers engineered near the diamond surface is employed to obtain spatial maps of the vector magnetic field, by measuring Zeeman shifts through optically detected magnetic resonance spectroscopy. The in-plane magnetic field (i.e., parallel to the diamond surface) is found to be significantly weaker than predicted, while the out-of-plane field also exhibits an unexpected modulation. We show that the measured magnetic field is incompatible with Ampère’s circuital law or Gauss’s law for magnetism when we assume that the current is confined to the metal, independent of the details of the current density. This result was reproduced in several diamond samples, with a measured deviation from Ampère’s law by as much as 94(6)% (i.e., a 15σ violation). To resolve this apparent magnetic anomaly, we introduce a generalized description whereby the current is allowed to flow both above the NV sensing layer (including in the metallic wire) and below the NV layer (i.e., in the diamond). Inversion of the Biot-Savart law within this two-channel description leads to a unique solution for the two current densities that completely explains the data, is consistent with the laws of classical electrodynamics, and indicates a total NV-measured current that closely matches the electrically measured current. However, this description also leads to the surprising conclusion that in certain circumstances the majority of the current appears to flow in the diamond substrate rather than in the metallic wire, and to spread laterally in the diamond by several micrometers away from the wire. No electrical conduction was observed between nearby test wires, ruling out a conventional conductivity effect. Moreover, the apparent delocalization of the current into the diamond persists when an insulating layer is inserted between the metallic wire and the diamond or when the metallic wire is replaced by a graphene ribbon. The possibilities of a measurement error, a problem in the data analysis, or a current-induced magnetization effect are discussed, but do not seem to offer a more plausible explanation for the effect. Understanding and mitigating this apparent anomaly will be crucial for future applications of NV magnetometry to charge transport studies.
关键词： diamond magnetometry,nitrogen-vacancy centers,Biot-Savart law,Ampère's law,magnetic field imaging,current density
更新于2025-09-19 17:15:36
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Model Predictive Control Via PV-Based VAR Scheme for Power Distribution Systems With Regular and Unexpected Abnormal Loads
摘要： This paper develops a model predictive controller (MPC) via photovoltaic (PV)-based volt-ampere reactive scheme to minimize the power loss and stabilize voltage ?uctuation when PV cells are connected to the power distribution line. The nominal power load data from California independent system operator is used to simulate dynamics of the system with DistFlow equations. Since power consumptions in fact may deviate from nominal values, an estimator is further developed to reconstruct the state variables and power loads from measurements. The integration of the MPC and estimator forms a closed-loop control framework and enables the system to quickly recover from undesired disturbances by effectively changing the real and reactive powers provided by PV cells. We use a bidirectional, single branch distribution circuit to demonstrate the performance of proposed scheme. The results show that our MPC indeed reduces power loss and keeps the voltage within a desired bound. Additionally, the estimator successfully detects and correctly estimates the abnormal change of power consumption and directs the MPC to compensate such unexpected power loads promptly.
关键词： Model predictive control (MPC),power distribution system,volt-ampere reactive (VAR) control,photovoltaic (PV)-cell
更新于2025-09-10 09:29:36
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[IEEE 2018 7th International Conference on Renewable Energy Research and Applications (ICRERA) - Paris, France (2018.10.14-2018.10.17)] 2018 7th International Conference on Renewable Energy Research and Applications (ICRERA) - Application of Model Predictive Control in Modular Multilevel Converters for MTPA Operation and reduced Switching Losses
摘要： In this paper, a one-step Model Predictive Control system is executed in the Multilevel modular converter (MMC) to control the speed of an Interior Permanent Magnet (IPM) machine. Maximum Torque per Ampere (MTPA) and Field Weakening (FW) control technique is utilized for the greatest yield torque. The proposed Control strategy tracks the reference produced by MTPA and FW calculation by freely directing voltages from the MMC modules. The proposed method also studies the relation between the switching losses of MOSFETs and sampling frequency, cost function and a number of modules in an MMC. Finally, simulation results are provided to demonstrate the appropriateness of this control procedure.
关键词： Model Predictive Control,Modular Multilevel Converter (MPC),Maximum Torque per Ampere (MTPA),Interior Permanent Magnet motor (IPM),Switching losses,Field Weakening (FW)
更新于2025-09-04 15:30:14