FPGA-based Centralized Controller for Multiple PV Generators Tied to the DC Bus

Ahmed, Ashraf,Ganeshkumar, Pradeep,Park, Joung-Hu,Lee, Hojin The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.4

The integration of photovoltaic (PV) energy sources into DC grid has gained considerable attention because of its enhanced conversion efficiency with reduced number of power conversion stages. During the integration process, a local control unit is normally included with every power conversion stage of the PV source to accomplish the process of maximum power point tracking. A centralized monitoring and supervisory control unit is required for monitoring, power management, and protection of the entire system. Therefore, we propose a field-programmable gate array (FPGA) based centralized control unit that integrates all local controllers with the centralized monitoring unit. The main focus of this study is on the process of integrating many local control units into a single central unit. In this paper, we present design and optimization procedures for the hardware implementation of FPGA architecture. Furthermore, we propose a transient analysis and control design methodology with consideration of the nonlinear characteristics of the PV source. Hardware experiment results verify the efficiency of the central control unit and controller design.

Inelastic large deflection analysis of space steel frames consisting of I-shaped cross section

Ashraf ElSabbagh,Ahmed Hanefa,Ahmed Zubydan,Mohamed ElGhandour,Tarek Sharaf 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.6

This paper presents a simplified model to capture the nonlinear behavior of steel frames depending on the spread of plasticity method. New interaction formulae were derived to evaluate the plastic strength for I-shaped steel sections under uniaxial bending moment and axial compression load. Also, new empirical formulae were derived to evaluate the tangent stiffness modulus of steel I-shaped cross-sections considering the effect of the residual stresses suggested by the specifications in European Convention for Construction Steelworks (ECCS). The secant stiffness which depends on the tangent modulus is used to evaluate the internal forces. Based on stiffness matrix method, a finite element analysis program was developed for the nonlinear analysis of space steel frames using the derived formulae. Comparison between the proposed model results with those given by the fiber model shows very good agreement. Numerical examples were introduced to verify, check the accuracy, and evaluate the efficiency of the proposed model. The analysis results show that the new proposed model is accurate and able to minimize the solution time.

An Efficient Single-Sourced Asymmetrical Cascaded Multilevel Inverter With Reduced Leakage Current Suitable for Single-Stage PV Systems

Ahmed, Ashraf,Sundar Manoharan, Mohana,Park, Joung-Hu IEEE 2019 IEEE transactions on energy conversion Vol.34 No.1

<P>An isolated single sourced multi-output dc/dc converter with a high-frequency link was proposed before to feed different cells of the Asymmetrical Cascaded H-bridge (ACHB) inverter. One of the fundamental advantages of the ACHB is that the main H-bridge is commutated with fundamental frequency, passing the majority of the inverter power. However, the isolated dc/dc converter needs to be connected to the main voltage source with high-voltage/high-frequency switches, which limits the power capability and the efficiency of the converter. In this paper, a switching pattern based on nearest level modulation method is proposed to command all the power to be transferred through the main H-bridge. Therefore, the power circulates between the auxiliary H-bridges with no need for high-voltage switches. As a result, a single-input single-output auxiliary converter is needed with only 5% of the power rating. This solution reduces cost and size while it improves the efficiency of the converter. Furthermore, the architecture makes the inverter more suitable for high power and high-voltage applications. The inverter switching strategy is based on programmable firing angles. The main dc-link of the grid connected inverter is controlled to achieve maximum power point tracking, while the dc/dc isolated converter is controlled to regulate the auxiliary dc-links. The proposed topology is verified by simulation and experimental results using a 1.5 kW hardware prototype.</P>

Precise Detection and Elimination of Grid Injected DC from Single Phase Inverters

Ashraf Abdel hafeez Ahmed Mahm,Ran Li 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.

Single-phase voltage source inverters are used for connecting small scale renewable energy sources to low voltage distribution networks. They operate to supply the network with sinusoidal current. If output transformers are not used, these inverters must prevent excessive dc current injection, which may cause detrimental effects in the network. In this study, the causes of dc current injection in a common inverter topology are analyzed. This work explains the design and test of a passive filter circuit precisely measuring the dc component in the inverter output current. The filtered dc signal is then used to control the single phase inverter for the objective to keep the dc injection low – below the standard limit. Characteristics of the proposed method are illustrated using simulation and experimental results.

Minimally Invasive Transforaminal Lumbar Interbody Fusion for the Surgical Management of Post-Discectomy Syndrome

Ahmed Bahaa Al Din AlShazli,Ashraf Yassin Amer,Ahmed Maher Sultan,Ahmed Samir Barakat,Wael Koptan,Yasser ElMiligui,Hesham Shaker 대한척추외과학회 2020 Asian Spine Journal Vol.14 No.2

Study Design: This was a prospective case series of 30 patients with post-discectomy syndrome with an average of 18 months of follow-up (level IV). Purpose: The efficacy of post-discectomy syndrome managed by minimally invasive surgery transforaminal lumbar interbody fusion (MIS-TLIF) was evaluated. Overview of Literature: In post-discectomy syndrome wherein conservative treatment had failed, the best surgical treatment modality still remains controversial. Methods: Patients were functionally assessed using the Visual Analog Scale (VAS) for low back pain (LBP) and leg pain (LP) and Oswestry Disability Index (ODI). Radiological fusion was confirmed with plain X-rays and when indicated with computed tomography scan at 12 months postoperatively. A total of 30 patients with 37 operated at lumbar levels with failed discectomy surgery who met our inclusion criteria were treated with MIS-TLIF. Results: The ODI of all patients showed significant improvement from a mean of 73.78% preoperatively to 16.67% at 1 month and 14.13% at 12 months postoperatively. The preoperative LBP VAS score (mean, 4.37) showed a significant decrease (p<0.001) to 1.90 at 1 month and 1.10 at 12 months. Preoperative LP VAS score of limb pain averaged 7.53 and showed a significant (p<0.001) decrease to 3.47 at 1 month and 1.10 at 12 months. All patients attained radiological fusion at 12 months. Conclusions: MIS-TILF constitutes a valid and effective treatment option for patients with post-discectomy syndrome.

A Cascaded-Boost Topology for Electrolyte-less Power Conditioning System Suitable for PV Residential Applications

Ashraf Ahmed,Mohammad Irfan,Joung-hu Park 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Single-phase inverters need large bulk DC link electrolyte capacitors which reduce the life time of the converter circuit. Furthermore, there is a safety need for low input voltage in photovoltaic (PV) residential applications. A new cascaded power-decoupling topology is proposed in this paper with film capacitors and high step-up ratio. The topology is based on cascaded double boost; the output of the source side boost (the auxiliary DC link) is free to oscillate in double frequency of the AC output around a controlled average voltage. Besides, the second boost controls the main DC-link voltage within a demanded ripple range. A detailed design procedure of the topology is proposed, followed by transient analysis and controller design. Finally, the proposed circuit will be verified by simulation and experimental results.

FPGA-based Centralized Controller for Multiple PV Generators Tied to the DC Bus

Ashraf Ahmed,Pradeep Ganeshkumar,Joung-Hu Park,Hojin Lee 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.4

The integration of photovoltaic (PV) energy sources into DC grid has gained considerable attention because of its enhanced conversion efficiency with reduced number of power conversion stages. During the integration process, a local control unit is normally included with every power conversion stage of the PV source to accomplish the process of maximum power point tracking. A centralized monitoring and supervisory control unit is required for monitoring, power management, and protection of the entire system. Therefore, we propose a field-programmable gate array (FPGA) based centralized control unit that integrates all local controllers with the centralized monitoring unit. The main focus of this study is on the process of integrating many local control units into a single central unit. In this paper, we present design and optimization procedures for the hardware implementation of FPGA architecture. Furthermore, we propose a transient analysis and control design methodology with consideration of the nonlinear characteristics of the PV source. Hardware experiment results verify the efficiency of the central control unit and controller design.

Recent technology of Small scale renewable energy systems

( Ashraf Ahmed ) 한국공업화학회 2012 한국공업화학회 연구논문 초록집 Vol.2012 No.-

Allelic variation of melanocortin-1 receptor locus in Saudi indigenous sheep exhibiting different color coats

Mahmoud, Ahmed H.,Mashaly, Ashraf M.,Rady, Ahmed M.,Al-Anazi, Khalid M.,Saleh, Amgad A. Asian Australasian Association of Animal Productio 2017 Animal Bioscience Vol.30 No.2

Objective: This study was designed to characterize the DNA polymorphisms of the melanocortin-1 receptor (MC1R) gene in indigenous Saudi Arabian sheep breeds exhibiting different color coats, along with individuals of the Sawaknee breed, an exotic sheep imported from Sudan. Methods: The complete coding region of MC1R gene including parts of 3' and 5' untranslated regions was amplified and sequenced from three the indigenous Saudi sheep; Najdi (generally black, n = 41), Naeimi (generally white with brown faces, n = 36) and Herri (generally white, n = 18), in addition to 13 Sawaknee sheep. Results: Five single nucleotide polymorphisms (SNPs) were detected in the MC1R gene: two led to nonsynonymous mutations (c.218 T>A, p.73 Met>Lys and c.361 G>A, p.121 Asp>Asn) and three led to synonymous mutations (c.429 C>T, p.143 Tyr>Tyr; c.600 T>G, p.200 Leu>Leu, and c.735 C>T, p.245 Ile>Ile). Based on these five SNPs, eight haplotypes representing MC1R $E^d$ and $E^+$ alleles were identified among the studied sheep breeds. The most common haplotype (H3) of the dominant $E^d$ allele was associated with either black or brown coat color in Najdi and Sawaknee sheep, respectively. Two other haplotypes (H6 and H7) of $E^d$ allele, with only the nonsynonymous mutation A218T, were detected for the first time in Saudi indigenous sheep. Conclusion: In addition to investigating the MC1R allelic variation in Saudi indigenous sheep populations, the present study supports the assumption that the two independent nonsynonymous Met73Lys and Asp121Asn mutations in MC1R gene are associated with black or red coat colors in sheep breeds.

Interferon-γ and Interleukin-10 Gene Polymorphisms are not Predictors of Chronic Hepatitis C (Genotype-4) Disease Progression

Bahgat, Nermine Ahmed,Kamal, Manal Mohamed,Abdelaziz, Ashraf Omar,Mohye, Mohamed Ahmed,Shousha, Hend Ibrahim,ahmed, Mae Mohamed,Elbaz, Tamer Mahmoud,Nabil, Mohamed Mahmoud Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.12

Immunoregulatory cytokines have an influence on hepatitis C virus (HCV) infection outcome. This study aimed to determine whether single nucleotide polymorphisms (SNP) in IFN- ${\gamma}$ and IL-10 genes are associated with susceptibility and/or are markers of prognosis regarding chronic hepatitis C outcomes. IFN ${\gamma}$ (+874T/A) and IL-10 (-1082G/A) genotypes were determined in 75 HCV genotype 4 patients with different disease severities (chronic hepatitis, n=25, liver cirrhosis and hepatocellular carcinoma (HCC) on top of liver cirrhosis, n=50) and 25 healthy participants using allele-specific polymerase chain reaction. No statistical differences in allele or genotype distributions of IFN ${\gamma}$ and IL-10 genes were detected between patients and controls or between patientgroups. No significant difference in the frequency of IL-10 SNP at position -1082 or IFN-${\gamma}$ at position +874T/A was found between chronic HCV genotype 4 and with progression of disease severity in liver cirrhosis or HCC. In conclusion; interferon-${\gamma}$ and interleukin-10 gene polymorphisms are not predictors of disease progression in patients with chronic hepatitis C (Genotype-4).