Improving the Solution Range in Selective Harmonic Mitigation Pulse Width Modulation Technique for Cascaded Multilevel Converters

Mohammad Najjar,Hossein Iman-Eini,Amirhossein Moeini,Shahrokh Farhangi 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

This paper proposes an improved low frequency Selective Harmonic Mitigation-PWM (SHM-PWM) technique. The proposed method mitigates the low order harmonics of the output voltage up to the 50<SUP>th</SUP> harmonic well and satisfies the grid codes EN 50160 and CIGRE-WG 36–05. Using a modified criterion for the switching angles, the range of the modulation index for non-linear SHM equations is improved, without increasing the switching frequency of the CHB converter. Due to the low switching frequency of the CHB converter, mitigating the harmonics of the converter up to the 50<SUP>th</SUP> order and finding a wider modulation index range, the size and cost of the passive filters can be significantly reduced with the proposed technique. Therefore, the proposed technique is more efficient than the conventional SHM-PWM. To verify the effectiveness of the proposed method, a 7-level Cascaded H-bridge (CHB) converter is utilized for the study. Simulation and experimental results confirm the validity of the above claims.

Increasing the Range of Modulation Indices with the Polarities of Cells and Switching Constraint Reliefs for the Selective Harmonic Elimination Pulse Width Modulation Technique

Mohammad Najjar,Hossein Iman-Eini,Amirhossein Moeini 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4

In this paper an improved low frequency selective harmonic elimination-PWM (SHE-PWM) technique for Cascaded H-bridge (CHB) converters is proposed. The proposed method is able to eliminate low order harmonics from the output voltage of the converter for a wide range of modulation indices. To solve SHE-PWM equations, especially for low modulation indices, a modified method is used which employs either the positive or negative voltage polarities of H-bridge cells to increase the freedom degrees of each cell. Freedom degrees of the switching angles are also used to increase the range of available solutions for non-linear SHE equations. The proposed SHE methods can successfully eliminate up to 25<SUP>th</SUP> harmonic from a 7-level output voltage by using just nine switching transitions or a 150 Hz switching frequency. To confirm the validity of the proposed method, simulation and experimental results have been presented.

Increasing the Range of Modulation Indices with the Polarities of Cells and Switching Constraint Reliefs for the Selective Harmonic Elimination Pulse Width Modulation Technique

Najjar, Mohammad,Iman-Eini, Hossein,Moeini, Amirhossein The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4

In this paper an improved low frequency selective harmonic elimination-PWM (SHE-PWM) technique for Cascaded H-bridge (CHB) converters is proposed. The proposed method is able to eliminate low order harmonics from the output voltage of the converter for a wide range of modulation indices. To solve SHE-PWM equations, especially for low modulation indices, a modified method is used which employs either the positive or negative voltage polarities of H-bridge cells to increase the freedom degrees of each cell. Freedom degrees of the switching angles are also used to increase the range of available solutions for non-linear SHE equations. The proposed SHE methods can successfully eliminate up to $25^{th}$ harmonic from a 7-level output voltage by using just nine switching transitions or a 150 Hz switching frequency. To confirm the validity of the proposed method, simulation and experimental results have been presented.

Improving the Solution Range in Selective Harmonic Mitigation Pulse Width Modulation Technique for Cascaded Multilevel Converters

Najjar, Mohammad,Iman-Eini, Hossein,Moeini, Amirhossein,Farhangi, Shahrokh The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

This paper proposes an improved low frequency Selective Harmonic Mitigation-PWM (SHM-PWM) technique. The proposed method mitigates the low order harmonics of the output voltage up to the $50^{th}$ harmonic well and satisfies the grid codes EN 50160 and CIGRE-WG 36-05. Using a modified criterion for the switching angles, the range of the modulation index for non-linear SHM equations is improved, without increasing the switching frequency of the CHB converter. Due to the low switching frequency of the CHB converter, mitigating the harmonics of the converter up to the $50^{th}$ order and finding a wider modulation index range, the size and cost of the passive filters can be significantly reduced with the proposed technique. Therefore, the proposed technique is more efficient than the conventional SHM-PWM. To verify the effectiveness of the proposed method, a 7-level Cascaded H-bridge (CHB) converter is utilized for the study. Simulation and experimental results confirm the validity of the above claims.

Neighboring Cage Fish Farming Affecting Water and Seabed Quality of the Jordanian Northern Gulf of Aqaba, Red Sea

Mohammad, Al-Zibdah,Firas, Oqaily,Tariq, Al-Najjar,Riyad, Manasrah The Korean Society of Oceanography 2008 Ocean science journal Vol.43 No.1

Environmental qualities of coastal water and bottom sediment were assessed at Jordan's northernmost tip of Gulf of Aqaba to evaluate possible impacts of the bordering fish pen cages in Eilat. Results showed significant differences between surface and bottom water in the chemical and physical variables in the different months of the year (2004-2005). Chlorophyll a was also significantly higher in bottom water when compared to that of the offshore water. Nitrate and ammonia were significantly higher in bottom water than the surface water at each individual station. The upper 2 cm of sediment sample recorded higher values of total phosphorus and organic matter. Seasonality affected the content of total phosphorus, organic matter, redox potential and color especially at the sediment layer below 3 cm of the sediment core. The present investigation showed slight modification of water and sediment qualities but no clear sign of eutrophication was observed. However, to maintain sustainability of healthy environmental conditions at the northern tip of Gulf of Aqaba potentials of any possible environmental risks arising from the fish farms or any other coastal investment should be carefully considered.

Assessing Metal Content in Halophila stipulacea Seagrass as an Indicator of Metal Pollution in the Northern Gulf of Aqaba, Red Sea

Tariq Al-Najjar,Mohammad Wahsha,Mwaffaq Al-Khushman,Maroof Khalaf,Kyle Hardage,Wissam Hayek,Khalid Abu Khadra,Adina Paytan 한국해양과학기술원 2021 Ocean science journal Vol.56 No.4

To assess the utility of the seagrass (Halophila stipulacea) for biomonitoring of metal pollution, seagrass samples were collected from four sites along the Jordanian coast of the Gulf of Aqaba between April and July 2017. Concentrations of trace metals (Cr, Mn, Fe, Ni, Zn, and Pb) in leaves, rhizomes, and roots were compared to published data on sediment trace metal and organic carbon content at the same sites to assess the degree of their fidelity in recording local trace metal pollution. The results of this study indicated that the roots of the seagrass H. stipulacea accumulated higher metal concentrations of Cd, Pb, Cr, Ni, Zn, Mn, and Fe than rhizomes and leaves. Concentrations in H. stipulacea varied significantly between sites for Mn, Fe, Zn, Cd, and Pb but not for Cr and Ni. Higher levels of seagrass trace metals in the Hotels Area and Old Phosphate Port sampling sites compared to other sampled sites are likely related to the sites' proximity to tourist and boating activity and city infrastructure which may contribute to metals accumulating in the tissues of this seagrass. In contrast to other studies, when all the data are considered, no clear trend between sediment metal concentration and seagrass metals is observed, suggesting physiological control on metal uptake by H. stipulacea and thus limiting the utility of H. stipulacea for biomonitoring of pollution.

Seasonal Changes of Water Properties and Current in the Nothernmost Gulf of Aqaba, Red Sea

Riyad Manasrah,Mohammad Zibdah,Firas Al-Ougaily,Najim Yusuf,Tariq Al-Najjar 한국해양과학기술원 2007 Ocean science journal Vol.42 No.2

Seasonal changes of tide signal(s), temperature, salinity and current were studied during the years 2004-2005 in the northernmost Gulf of Aqaba, which is under developmental activities, to obtain scientific bases for best management and sustainability. Spectrum analysis revealed permanent signals of tide measurements during all seasons, which represented semidiurnal and diurnal barotropic tides. The other signal periods of 8.13, 6.10-6.32, 4.16 and 1.02-1.05 h were not detected in all seasons, which were related to shallow water compound and overtides of principle solar and lunar constituent and to seiches generated in the Red Sea and the Gulf of Aqaba. Spatial and temporal distribution of temperature, salinity and density showed significant differences between months in the coastal and offshore region and no significant differences among the coastal sites, between the surface and bottom waters and between coastal and offshore waters. Therefore, the temporal and spatial variation of water properties in the northernmost Gulf of Aqaba behave similarly compared to other parts. The coastal current below 12 m depth was weak (3-6 cms-1) and fluctuated from east-northeastward to west-southwestward (parallel to the shoreline), which may be related to the effect of bottom topography and/or current density due to differential cooling between eastern and western parts in the study area, and wind-induced upwelling and downwelling in the eastern and western side, respectively. The prevailing northerly winds and stratification conditions during summer were the main causes of the southward current at 6 and 12 m depths with average speed of 28 and 12 cms-1, respectively.

Neighboring Cage Fish Farming Affecting Water and Seabed Quality of the Jordanian Northern Gulf of Aqaba, Red Sea

Al-Zibdah Mohammad,Oqaily Firas,Al-Najjar Tariq,Manasrah Riyad1 한국해양과학기술원 2008 Ocean science journal Vol.43 No.1

Environmental qualities of coastal water and bottom sediment were assessed at Jordan’s northernmost tip of Gulf of Aqaba to evaluate possible impacts of the bordering fish pen cages in Eilat. Results showed significant differences between surface and bottom water in the chemical and physical variables in the different months of the year (2004-2005). Chlorophyll a was also significantly higher in bottom water when compared to that of the offshore water. Nitrate and ammonia were significantly higher in bottom water than the surface water at each individual station. The upper 2 cm of sediment sample recorded higher values of total phosphorus and organic matter. Seasonality affected the content of total phosphorus, organic matter, redox potential and color especially at the sediment layer below 3 cm of the sediment core. The present investigation showed slight modification of water and sediment qualities but no clear sign of eutrophication was observed. However, to maintain sustainability of healthy environmental conditions at the northern tip of Gulf of Aqaba potentials of any possible environmental risks arising from the fish farms or any other coastal investment should be carefully considered.

Seasonal Changes of Water Properties and Current in the Northernmost Gulf of Aqaba, Red Sea

Manasrah, Riyad,Zibdah, Mohammad,Al-Ougaily, Firas,Yusuf, Najim,Al-Najjar, Tariq The Korean Society of Oceanography 2007 Ocean science journal Vol.42 No.2

Seasonal changes of tide signal(s), temperature, salinity and current were studied during the years 2004-2005 in the northernmost Gulf of Aqaba, which is under developmental activities, to obtain scientific bases for best management and sustainability. Spectrum analysis revealed permanent signals of tide measurements during all seasons, which represented semidiurnal and diurnal barotropic tides. The other signal periods of 8.13, 6.10-6.32, 4.16 and 1.02-1.05 h were not detected in all seasons, which were related to shallow water compound and overtides of principle solar and lunar constituent and to seiches generated in the Red Sea and the Gulf of Aqaba. Spatial and temporal distribution of temperature, salinity and density showed significant differences between months in the coastal and offshore region and no significant differences among the coastal sites, between the surface and bottom waters and between coastal and offshore waters. Therefore, the temporal and spatial variation of water properties in the northernmost Gulf of Aqaba behave similarly compared to other parts. The coastal current below 12 m depth was weak $(3-6\;cms^{-1})$ and fluctuated from east-northeastward to west-southwestward (parallel to the shoreline), which may be related to the effect of bottom topography and/or current density due to differential cooling between eastern and western parts in the study area, and wind-induced upwelling and downwelling in the eastern and western side, respectively. The prevailing northerly winds and stratification conditions during summer were the main causes of the southward current at 6 and 12 m depths with average speed of 28 and $12cms^{-1}$ respectively.

Using ANN to predict post-heating mechanical properties of cementitious composites reinforced with multi-scale additives

Hashem K. Almashaqbeh,Mohammad R. Irshidat,Yacoub Najjar 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.2

This paper focuses on predicting the post-heating mechanical properties of cementitious composites reinforced with multi-scale additives using the Artificial Neural Network (ANN) approach. A total of four different feed-forward ANN models are developed using 261 data sets collected from 18 published sources. The models are optimized using 12 input parameters selected based on a comprehensive literature review to predict the residual compressive strength, the residual flexural strengths, elastic modulus, and fracture energy of heat-damaged cementitious specimens. Furthermore, the ANN is employed to predict the impact of several variables including; the content of polypropylene (PP) microfibers and carbon nanotubes (CNTs) used in the concrete, mortar, or paste mix design, length of PP fibers, the average diameter of CNTs, and the average length of CNTs. The influence of the studied parameters is investigated at different heating levels ranged from 25°C to 800°C. The results demonstrate that the developed ANN models have a strong potential for predicting the mechanical properties of the heated cementitious composites based on the mixing ingredients in addition to the heating conditions.