Ashraf Khan

Ashraf Khan


Research Focus & Metrics

Academic Career Length

9Years (2018-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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28 February 2023 in IEEE Transactions on Industry Applications
Verified
Journal Article
Closed access
SESoroush Esmaeili
Soroush Esmaeili
MSMorteza Shekari
Morteza Shekari
MRMilad Rasouli
Milad Rasouli
SHSara Hasanpour
Sara Hasanpour
AKAshraf Khan
Ashraf Khan
Hossein HafeziHossein Hafezi
Hossein Hafezi
This article proposes, analyzes, and tests an improved high voltage gain dc-dc converter based on a single-ended primary-inductor converter (SEPIC). The proposed magnetically coupled quadratic modified SEPIC converter (MCQ-MSC) employs a coupled transformer with an optimized design to obtain a high voltage boost factor by controlling the transformer's turn ratio along with the switching duty cycle. Thanks to the unique structure of the coupled transformer, high voltage gain is obtained at low turns ratio, which is highly desirable for high voltage applications and the compact size of the converter. In addition to the coupled transformer, a voltage-boosting module is utilized to achieve a very high output voltage for a low switching duty cycle. The proposed inverter has a single switch with a wide control range of duty cycle (0<D<1), causing low conducting losses and high efficiency. Furthermore, a clamping circuit is successfully designed to remove the leakage inductance effects of the coupled transformer on the power switch. The proposed MCQ-MSC drains a continuous current from the input dc source, which makes it a suitable choice for renewable energy sources (RES). The hardware prototype of the proposed converter is tested to verify the mathematical expressions and theoretical results.

1 January 2023 in Energies
Verified
Journal Article
Open access
PDF file
HMHafiz Abdul Muqeet
Hafiz Abdul Muqeet
RLRehan Liaqat
Rehan Liaqat
Mohsin JamilMohsin Jamil
Mohsin Jamil
AKAshraf Khan
Ashraf Khan
A smart grid (SG), considered as a future electricity grid, utilizes bidirectional electricity and information flow to establish automated and widely distributed power generation. The SG provides a delivery network that has distributed energy sources, real-time asset monitoring, increased power quality, increased stability and reliability, and two-way information sharing. Furthermore, SG provides many advantages, such as demand response, distribution automation, optimized use of electricity, economical energy, real-time grid status monitoring, voltage regulation or VAR control, and electricity storage. In this survey, we explore the literature on smart Grid enabling technologies until 2022. We dig out four major systems: (1) the smart grid’s prominent features and challenges; (2) the smart grid standard system and legislations; (3) smart grid energy subsystem; and (4) the smart grid management system and protection system for new researchers for their future projects. The research challenges and future recommendations are also presented in the conclusion section to explore the new paradigm.

6 May 2019 in IEEE Journal of Emerging and Selected Topics in Power Electronics
Verified
Journal Article
Closed access
YYYanqi Yu
Yanqi Yu
RSRaed Saasaa
Raed Saasaa
AKAshraf Khan
Ashraf Khan
WEWilson Eberle
Wilson Eberle
A novel cell voltage equalizer using a series LC resonant converter is proposed for series connected energy storage devices, namely battery, or super (or ultra) capacitor cells. The proposed circuit is an active voltage equalization circuit for energy storage devices that is low cost, small in size and equalizes the voltages quickly. Compared to state of the art solutions, the proposed series LC resonant circuit eliminates the complexity of multi-winding transformers and it can balance series connected energy storage devices in a short time by transporting energy successively between the cells having highest voltage difference. The detailed circuit operation and theoretical analysis are provided. Simulation and experimental results are presented to demonstrate the voltage equalization process from an initial voltage difference of 527 mV to a final difference of 10 mV in 900 seconds for three seriesconnected super capacitor cells.

28 June 2022 in Energies
Verified
Journal Article
Open access
PDF file
AAAmad Ali
Amad Ali
DSDr. Rabia Shakoor
Dr. Rabia Shakoor
ARAbdur Raheem
Abdur Raheem
HMHafiz Abdul Muqeet
Hafiz Abdul Muqeet
QAQasim Awais
Qasim Awais
Mohsin JamilMohsin Jamil
Mohsin Jamil
The popularity of electric vehicles (EVs) is increasing day by day due to their environmentally friendly operation and high milage as compared to conventional fossil fuel vehicles. Almost all leading manufacturers are working on the development of EVs. The main problem associated with EVs is that charging many of these vehicles from the grid supply system imposes an extra burden on them, especially during peak hours, which results in high per-unit costs. As a solution, EV charging stations integrated with hybrid renewable energy resources (HREs) are being preferred, which utilize multi-energy systems to produce electricity. These charging stations can either be grid-tied or isolated. Isolated EV charging stations are operated without any interconnection to the main grid. These stations are also termed standalone or remote EV charging stations, and due to the absence of a grid supply, storage becomes compulsory for these systems. To attain maximum benefits from a storage system, it must be configured properly with the EV charging station. In this paper, different types of the latest energy storage systems (ESS) are discussed with a comprehensive review of configurations of these systems for multi-energy standalone EV charging stations. ESS in these charging stations is applied mainly in three different configurations, named single storage systems, multi-storage systems, and swappable storage systems. These configurations are discussed in detail with their pros and cons. Some important expectations from future energy storage systems are also highlighted.

16 December 2021 in Energies
Verified
Journal Article
Open access
PDF file
HJHaseeb Javed
Haseeb Javed
HMHafiz Abdul Muqeet
Hafiz Abdul Muqeet
MSMoazzam Shehzad
Moazzam Shehzad
Mohsin JamilMohsin Jamil
Mohsin Jamil
AKAshraf Khan
Ashraf Khan
Josep M. GuerreroJosep M. Guerrero
Josep M. Guerrero
An energy management system (EMS) was proposed for a campus microgrid (µG) with the incorporation of renewable energy resources to reduce the operational expenses and costs. Many uncertainties have created problems for microgrids that limit the generation of photovoltaics, causing an upsurge in the energy market prices, where regulating the voltage or frequency is a challenging task among several microgrid systems, and in the present era, it is an extremely important research area. This type of difficulty may be mitigated in the distribution system by utilizing the optimal demand response (DR) planning strategy and a distributed generator (DG). The goal of this article was to present a strategy proposal for the EMS structure for a campus microgrid to reduce the operational costs while increasing the self-consumption from green DGs. For this reason, a real-time-based institutional campus was investigated here, which aimed to get all of its power from the utility grid. In the proposed scenario, solar panels and wind turbines were considered as non-dispatchable DGs, whereas a diesel generator was considered as a dispatchable DG, with the inclusion of an energy storage system (ESS) to deal with solar radiation disruptions and high utility grid running expenses. The resulting linear mathematical problem was validated and plotted in MATLAB with mixed-integer linear programming (MILP). The simulation findings demonstrated that the proposed model of the EMS reduced the grid electricity costs by 38% for the campus microgrid. The environmental effects, economic effects, and the financial comparison of installed capacity of the PV system were also investigated here, and it was discovered that installing 1000 kW and 2000 kW rooftop solar reduced the GHG generation by up to 365.34 kg CO2/day and 700.68 kg CO2/day, respectively. The significant economic and environmental advantages based on the current scenario encourage campus owners to invest in DGs and to implement the installation of energy storage systems with advanced concepts.

22 May 2019 in IEEE Transactions on Power Electronics
Verified
Journal Article
Closed access
AKAshraf Khan
Ashraf Khan
YLYun W. Lu
Yun W. Lu
WEWilson Eberle
Wilson Eberle
LWLiwei Wang
Liwei Wang
UKUsman Ali Khan
Usman Ali Khan
HCHonnyong Cha
Honnyong Cha
This paper presents novel single-phase single-stage buck-boost inverters. The proposed inverters provide buck-boost operation for a wide variation of the input dc voltage. In addition, the proposed inverters are bidirectional and therefore can provide reactive power. Further, they require only one inductor. The proposed inverters also eliminate the common-mode leakage current problem by connecting output neutral to the midpoint of capacitors or directly to input voltage sources. Therefore, they are well suitable for photovoltaic applications. Although six switches are required, two switches are working at line frequency resulting in negligible switching loss. Of the four remaining switches, only two are switching under high frequency at a time depending on the half cycle of the output voltage. The circuit operations are demonstrated through the analysis of the proposed inverters. A 120 Vrms/ 60 Hz/ 400 W hardware prototype was constructed and tested. The experimental results verify the theoretical analysis.