Wireless charging is a technology of transmitting power through an air gap to electrical devices for the purpose of energy replenishment. The recent progress in wireless charging techniques and development of commercial products have provided a promising alternative way to address the energy bottleneck of conventionally portable battery-powered devices. However, the incorporation of wireless charging into the existing wireless communication systems also brings along a series of challenging issues with regard to implementation, scheduling, and power management. In this paper, we present a comprehensive overview of wireless charging techniques, the developments in technical standards, and their recent advances in network applications. In particular, with regard to network applications, we review the static charger scheduling strategies, mobile charger dispatch strategies and wireless charger deployment strategies. Additionally, we discuss open issues and challenges in implementing wireless charging technologies. Finally, we envision some practical future network applications of wireless charging.

Wireless Charging Technologies: Fundamentals, Standards, and Network Applications

Optimal energy management of a renewable-based isolated microgrid with pumped-storage unit and demand response

The increasing share of renewables in the power generation mix makes the power system volatile to uncertain meteorological conditions. The stochastic nature of renewables demands energy storage systems (ESS) to maintain the stability of the grid. Among various ESS, pumped hydro storage (PHS) is a technically matured and economically viable option for large scale energy storage. However, it has not gained much attention from researchers due to its technical maturity and site-specific nature. Lately, the focus is shifting towards the development of variable speed PHS and different reservoir schemes to realize PHS with the existing infrastructure. Nevertheless, the development of variable speed PHS necessitates a proper selection of power converter topology with a suitable control technique. Thus, the principal objective of this paper is to present a critical review of different levels of control of the variable speed PHS. Firstly, a state of the art comparison between PHS and other ESS is presented through critical data analysis using Tableau software. Secondly, the control strategies are categorized into a hierarchical structure and reviewed based on a bottom-up approach. Towards the end, a synoptic review is presented to elucidate the dominating strategy at each level of the control hierarchy. Finally, the domains which require further attention are distinctively reported to leverage the future research of PHS.

Variable speed pumped hydro storage: A review of converters, controls and energy management strategies

Detection of the power lines in UAV remote sensed images using spectral-spatial methods

Transformer oil-based nanofluid: The application of nanomaterials on thermal, electrical and physicochemical properties of liquid insulation-A review

This paper discusses the analysis, design, and experimental validation of a modular isolated matrix converter (MIMC), including modulation, commutation, and control. The MIMC topology is a single-stage high power density ac–ac converter, which is attractive for traction applications and space-restricted low voltage (LV) or medium voltage (MV) future distribution networks. The topology under study utilizes bidirectional switches based dual-active-bridge cells as basic building blocks. A single cell would have limited practical application as the output frequency is locked to the input one. On the contrary, the repetition of single cells proposed in the MIMC extending the matrix converter concept, achieves variable frequency operation while also providing a modular structure. However, the presence of medium frequency transformers in each cell poses additional challenges for modulation and safe commutation that are discussed and solved in this paper. Experimental results from a proof-of-concept 6 kW laboratory scale prototype validate the practical feasibility and the operation of the MIMC.

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A Three-Phase Modular Isolated Matrix Converter

Power electronic converters play a vital role in a power system and the most commonly used type of DC/DC converters is buck converter. This is due to the fact that buck converters are widely used to step down the voltage as well as they provide good voltage regulation in critical applications including power supplies for data centers. Therefore, designing a buck converter that gives a regulated output, acceptable for switch mode power supplies is still challenging task. A closed loop buck converter mitigates the problems such as input voltage unstability or variation. This paper discusses the effects of input voltage variations on the open loop and closed loop models of buck converter. Voltage Mode Control (VMC) has been proposed to develop an efficient closed loop system in order to avoid voltage fluctuations at the output of the buck converter.

Voltage mode controlled buck converter under input voltage variations

Today, variable speed pumped storage (VSPS) system is an emerging technique, being used in hydro powered plants to increase the efficiency, quality and control of the power of the grid The doubly fed induction machine (DFIM) based VSPS systems are gaining more importance because of the cheap price of the converter ie back to back power electronics converter This paper discuses an efficient method for the rotor side converter (RSC) to control the active and reactive power flowing through the stator of DFIM while the grid side converter (GSC) has been used to maintain the DC voltage level This paper also discusses the VSPS systems Worldwide and its comparison with hydro powered projects which are recently developed in Pakistan This paper suggests the use of VSPS systems in Pakistan to increase the efficiency of the conventional hydro power projects

Active and reactive power control of a variable speed pumped storage system

The aim of project is to design an automated speed detection system which can detect the speed of vehicles and if over-speeding occurs, extract the license number of vehicle and send it via email to Toll Plaza to charge fine. The system is designed for Punjab license plates which are currently implemented in Pakistan. Doppler effect phenomenon is used for the speed measurement. If over-speeding is detected, a camera automatically captures the picture of the vehicle and Digital Image Processing (DIP) techniques are applied to extract the license number. MATLAB is used for image processing. Afterwards, the extracted license plate number is sent via email to Toll Plaza. The results show that the proposed system successfully detects over speeding, extracts the license plate, has high performance and can be deployed on roads to check for over speeding.

Automated over speeding detection and reporting system

This paper proposes a generalized commutation strategy suitable for matrix-based isolated ac/ac conversion stages in solid-state transformers for use whenever there is nonnegligible leakage inductance in the isolation transformer. The standard 4-step commutation used in matrix converters can no longer be applied when transformer leakage inductance is present, as overrated switching devices or dissipative snubbers would be necessary, reducing the attractiveness of the topologies that include matrix-based isolated ac/ac stages. A case study of a single-phase ac/ac converter has been investigated in detail to demonstrate the application of the proposed commutation method to a topology that has recently been identified as the potential building block for future multimodular ac/ac converters for grid applications. The proposed leakage-inductance-tolerant commutation strategy is based on the definition of a current decoupling phase in the commutation sequence and only needs suitable timing of the commutation steps, without high bandwidth voltage or current measurements. Matching simulations and experimental results from a 3-kW laboratory scale prototype are presented to support the effectiveness of the proposed strategy.

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Usman Nasir

Papers

A Three-Phase Modular Isolated Matrix Converter

Voltage mode controlled buck converter under input voltage variations

Active and reactive power control of a variable speed pumped storage system

Automated over speeding detection and reporting system

A Leakage-Inductance-Tolerant Commutation Strategy for Isolated AC/AC Converters