30 results on '"Abdelsalam, Ibrahim"'
Search Results
2. Standalone PV-based single-phase split-source inverter using model-predictive control
- Author
-
Elthokaby, Youssuf, Abdelsalam, Ibrahim, Abdel-Rahim, Naser, and Mohamed, Islam
- Published
- 2023
- Full Text
- View/download PDF
3. Discrimination between normal and cancer white blood cells using holographic projection technique
- Author
-
Rania M. Abdelazeem and Dahi Ghareab Abdelsalam Ibrahim
- Subjects
Medicine ,Science - Abstract
White blood cells (WBCs) play a vital role in the diagnosis of many blood diseases. Such diagnosis is based on the morphological analysis of blood microscopic images which is performed manually by skilled hematologist. However, this method has many drawbacks, such as the dependence on the hematologist’s skill, slow performance, and varying accuracy. Therefore, in the current study, a new optical method for discrimination between normal and cancer WBCs of peripheral blood film (PBF) images is presented. This method is based on holographic projection technique which is able to provide an accurate and fast optical reconstruction method of WBCs floating in the air. Besides, it can provide a 3D visualization map of one WBC with its characterization parameters from only a single 2D hologram. To achieve that, at first, WBCs are accurately segmented from the microscopic PBF images using a developed in-house MATLAB code. Then, their associated phase computer-generated holograms (CGHs) are calculated using the well-known iterative Fourier transform algorithm (IFTA). Within the utilized algorithm, a speckle noise reduction technique, based on temporal multiplexing of spatial frequencies, is applied to minimize the speckle noise across the reconstruction plane. Additionally, a special hologram modulation is added to the calculated holograms to provide a 3D visualization map of one WBC, and discriminate normal and cancer WBCs. Finally, the calculated phase-holograms are uploaded on a phase-only spatial light modulator (SLM) for optical reconstruction. The optical reconstruction of such phase-holograms yields precise representation of normal and cancer WBCs. Moreover, a 3D visualization map of one WBC with its characterization parameters is provided. Therefore, the proposed technique can be used as a valuable tool for interpretation and analysis of WBCs, this in turn could provide an improvement in diagnosis and prognosis of blood diseases.
- Published
- 2022
4. A hybrid half‐bridge submodule‐based DC–DC modular multilevel converter with a single bidirectional high‐voltage valve.
- Author
-
Elserougi, Ahmed, Abdelsalam, Ibrahim, and Massoud, Ahmed
- Subjects
- *
VALVES , *POWER electronics , *CAPACITORS - Abstract
Modular Multilevel Converters (MMCs) are promising candidates for high‐voltage high‐power applications. The main challenge of the MMCs is the zero‐frequency operation. To achieve a successful DC–DC conversion process with balanced capacitors' voltages with limited voltage ripple, this paper suggests the employment of the conventional two‐leg half‐bridge submodule‐based MMC structure in conjunction with a single bidirectional high‐voltage (HV) valve across the low‐voltage side. In the suggested structure, the HV valve is controlled on and off to ensure energy equalization for the MMC arms. In addition, soft‐switching for the HV valve is proposed to reduce the switching losses. Detailed illustration and design of the proposed concept are presented. Simulation and experimentation results are elucidated to show the effectiveness of the proposed DC–DC hybrid MMC. The results showed efficient performance of the suggested converter. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
5. Discrimination between normal and cancer white blood cells using holographic projection technique.
- Author
-
Abdelazeem, Rania M. and Ghareab Abdelsalam Ibrahim, Dahi
- Subjects
- *
LEUCOCYTES , *SPECKLE interference , *MICROSCOPY , *SPATIAL light modulators , *HOLOGRAPHY - Abstract
White blood cells (WBCs) play a vital role in the diagnosis of many blood diseases. Such diagnosis is based on the morphological analysis of blood microscopic images which is performed manually by skilled hematologist. However, this method has many drawbacks, such as the dependence on the hematologist's skill, slow performance, and varying accuracy. Therefore, in the current study, a new optical method for discrimination between normal and cancer WBCs of peripheral blood film (PBF) images is presented. This method is based on holographic projection technique which is able to provide an accurate and fast optical reconstruction method of WBCs floating in the air. Besides, it can provide a 3D visualization map of one WBC with its characterization parameters from only a single 2D hologram. To achieve that, at first, WBCs are accurately segmented from the microscopic PBF images using a developed in-house MATLAB code. Then, their associated phase computer-generated holograms (CGHs) are calculated using the well-known iterative Fourier transform algorithm (IFTA). Within the utilized algorithm, a speckle noise reduction technique, based on temporal multiplexing of spatial frequencies, is applied to minimize the speckle noise across the reconstruction plane. Additionally, a special hologram modulation is added to the calculated holograms to provide a 3D visualization map of one WBC, and discriminate normal and cancer WBCs. Finally, the calculated phase-holograms are uploaded on a phase-only spatial light modulator (SLM) for optical reconstruction. The optical reconstruction of such phase-holograms yields precise representation of normal and cancer WBCs. Moreover, a 3D visualization map of one WBC with its characterization parameters is provided. Therefore, the proposed technique can be used as a valuable tool for interpretation and analysis of WBCs, this in turn could provide an improvement in diagnosis and prognosis of blood diseases. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
6. Generalized Active Power Flow Controller for Multiactive Bridge DC–DC Converters With Minimum-Current-Point-Tracking Algorithm.
- Author
-
Hebala, Osama M., Aboushady, Ahmed A., Ahmed, Khaled H., and Abdelsalam, Ibrahim
- Subjects
ELECTRICAL load ,DC-to-DC converters ,REACTIVE power ,ALGORITHMS ,MAXIMUM power point trackers ,BRIDGE circuits ,VOLTAGE control - Abstract
This article proposes a new active power flow controller for dc–dc multiactive bridge (MAB) converters with minimum current point tracking (MCPT) to minimize conductive losses. Unlike recent efforts in this area, the proposed controller does not require look-up table for implementation nor complex nonlinear converter modeling and is not circuit parameter dependent. The proposed control scheme is also generalized for MAB converters with any number of ports and is derived in per unit form to enable standard implementation for buck/boost/unity-gain operating modes. The proposed MCPT algorithm is based on an innovative adaptive perturb and observe tracking of the minimum current point (MCP) on the MAB converter current characteristic plane. This MCP is tracked while active power regulation is simultaneously achieved based on a new phase shift decoupler to enable direct regulation of individual port active power. Detailed design procedure of the proposed controller is presented and extensive simulation is carried out to validate the effectiveness of the proposed MCPT closed loop controller. Experimental implementation is also provided to substantiate the simulation results. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
7. An isolated‐boost‐converter‐based unidirectional three‐phase off‐board fast charger for electric vehicles.
- Author
-
Elserougi, Ahmed, Abdelsalam, Ibrahim, and Massoud, Ahmed
- Subjects
- *
ELECTRIC vehicles , *BATTERY chargers , *ELECTRIC vehicle batteries , *ELECTRIC current converters , *DC-to-DC converters - Abstract
In this work, a novel three‐phase unidirectional off‐board Electric Vehicles (EVs) fast charger is proposed. Each phase of the proposed converter consists of a two‐stage converter. The first stage is an AC–DC front‐end converter with power factor correction (PFC) control. The front‐end AC–DC converter is based on an isolated boost converter, which has a boosting capability and provides galvanic isolation. In this stage, parallel‐in parallel‐out isolated boost converter modules are employed in each phase. This enables sharing the current among modules to avoid implementing one module with a high current rating to meet the fast‐charging requirements. The multimodule option provides fault‐ride through capability for the proposed charger. The DC outputs of involved phases, that is, three isolated DC voltages, are fed to three cascaded DC–DC unidirectional buck converters. The charging terminals are used to charge the EV battery through a filter inductor with a charging current controller's aid. A detailed illustration of the suggested closed‐loop controllers is presented to ensure a successful operation for the proposed architecture. A simulation case study for a 25‐kW charger is presented. Finally, a 1‐kW prototype is implemented for experimental validation. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
8. Modular Multilevel Converter With Self-Energy Equalization for Medium Voltage AC Drive Applications.
- Author
-
Elserougi, Ahmed A., Abdelsalam, Ibrahim, Massoud, Ahmed, and Ahmed, Shehab
- Subjects
- *
VOLTAGE , *SEMICONDUCTOR devices , *AC DC transformers , *PASSIVE components , *ENERGY consumption , *CAPACITORS - Abstract
The modular multilevel converter (MMC) is a promising candidate for high-/medium-voltage high-power applications such as medium voltage ac drives due to its modularity, reliability, and scalability. The main challenge of a conventional MMC is low-frequency operation. Capacitor voltage ripple is inversely proportional to the operating frequency. Hence, operating at low frequency necessitates employing large submodule capacitances to limit voltage ripple or the utilization of energy equalization modules (EEMs). The first option negatively affects converter lifetime, and the second option requires a large number of semiconductor devices and isolating transformers. In this article, a modified MMC topology with self-energy equalization is proposed to ensure converter operation with balanced capacitor voltages with low ripple during zero-/low-frequency conditions. Operating with balanced capacitor voltages with low ripple is achieved by maintaining the same energy level in the involved upper and lower arms. A low device count alternative to the EEMs approach is proposed in this work. Detailed illustration of the operational concept and design of the associated passive components is presented. The performance of the proposed medium voltage ac drive is elucidated through simulation and experimental results. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
9. A modular multilevel DC‐DC converter with self‐energy equalization for DC grids.
- Author
-
Elserougi, Ahmed, Abdelsalam, Ibrahim, Massoud, Ahmed, and Ahmed, Shehab
- Subjects
DIRECT currents ,ELECTRIC power distribution grids ,RENEWABLE energy sources ,VOLTAGE-frequency converters ,BIPOLAR transistors ,CAPACITORS - Abstract
Medium‐/High Voltage DC grids are interesting for the integration of renewable energy sources. DC‐DC conversion systems are highly needed for the development of DC grids. Recently, Modular Multilevel Converter (MMC) is the most promising technology for medium‐/high‐voltage applications, but employing the conventional MMC with DC output voltage leads to diversion in the Submodule (SM) capacitor voltages, that is energy drift. This paper proposes a modified modular multilevel DC‐DC converter with self‐energy equalization, which ensures successful DC‐DC conversion with balanced capacitors voltages. In the modified topology, clamping Insulated Gate Bipolar Transistors (IGBTs) are employed in each arm to enable parallel‐connection of the capacitors in the same arm. During the operation (equalization period), the parallel‐connected upper capacitors are connected to the parallel‐connected lower capacitors in each leg through a small limiting inductor to transfer energy between the arms to ensure balanced capacitor voltages. The proposed configuration, along with the operational concepts, mathematical analysis, and design, are presented. Finally, simulation and experimental results are presented for validation. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
10. A Multiport DC–DC Converter Based on Two-Quadrant Inverter Topology for PV Systems.
- Author
-
Alajmi, Bader N., Marei, Mostafa I., and Abdelsalam, Ibrahim
- Subjects
TOPOLOGY ,ENERGY harvesting ,AC DC transformers ,DYNAMICAL systems ,INTEGRATED software ,BRIDGE circuits ,ELECTRIC inverters - Abstract
This article presents an isolated high-frequency (HF) multiport dc–dc converter for photovoltaics (PV) interfacing systems. In the proposed multiport converter, an HF transformer with multiple input windings and single output winding is utilized. Each input port is based on a proposed two-quadrant inverter topology, which connects a PV module to the HF transformer. The output port is tied to a dc bus using a rectifier. The proposed two-quadrant inverter topology prevents current flow from the ac side to the dc side. This action prevents circulating currents between different ports. Each two-quadrant inverter is controlled to harvest maximum power from its associated PV module. The analysis and operation scenarios of the proposed multiport converter are discussed. PSCAD/EMTDC software package is used to simulate the proposed PV interfacing system to investigate the operation of the proposed multiport converter topology and to examine the dynamic system behavior. In addition, an experimental prototype is developed to validate the operation scenarios of the proposed multiport dc–dc converter and to examine the performance of the presented PV interfacing system. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
11. DC–DC converter concept allowing line commutated converters and voltage source converters based HVDC systems connectivity.
- Author
-
Elgenedy, Mohamed A., Ahmed, Khaled Hani, Aboushady, Ahmed A., and Abdelsalam, Ibrahim
- Subjects
VOLTAGE-frequency converters ,INSULATED gate bipolar transistors ,IDEAL sources (Electric circuits) ,TRANSISTORS ,HIGH-voltage direct current transmission ,ELECTRIC transformers - Abstract
The most common two challenges in high-voltage direct current (HVDC) multi-terminal transmission are the DC fault isolation and the DC voltage stepping up/down. Additionally, interconnecting voltage source converter (VSC)- and line commutated converter (LCC)-based HVDC network topologies has been challenging. This study introduces a new DC–DC converter topology concept connecting both LCC- and VSC-based HVDC networks with bidirectional power flow without operation stoppage. The proposed topology is formed of two front-to-front connected bridges with an AC-link formed of a capacitor and an inductor (which can be replaced by a transformer for voltage step-up/step-down). The LCC-HVDC network bridge is formed of insulated gate commutated thyristors while the VSC-HVDC network bridge is formed of insulated gate bipolar transistors. Therefore, ON/OFF switching of both bridges and bi-directional power flow are possible. Moreover, the reactive power transfer is nullified at rated active power exchange between the proposed converter bridges. The proposed concept's detailed analysis and control equations are introduced. Different operation scenarios are simulated in addition to scaled-down experimentation to test the applicability of power transfer scenarios without operation stoppage in normal operation. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
12. Modular multilevel DC-DC converter with arm interchange concept.
- Author
-
Elserougi, Ahmed, Ibrahim Abdelsalam, Ibrahim, Massoud, Ahmed, and Ahmed, Shehab
- Subjects
- *
GRABENS (Geology) , *DENDRITIC cells , *ARCHITECTURAL design , *ARM , *CONCEPTS , *CAPACITORS - Abstract
Conventional modular multilevel converters (MMCs) are promising converters for high-voltage high-power applications. Unlike DC-AC conversion, DC-DC conversion of MMCs suffers from unbalanced capacitor voltages due to the energy drift problem. In this study, a new modular DC-DC converter is proposed, which consists of front-end half-bridge MMC with half-bridge submodules followed by full-bridge MMC with full-bridge submodules. The proposed modular multilevel DC-DC converter can be used effectively for connecting two different DC voltage levels in high-/medium-voltage DC grids. The proposed architecture provides successful DC-DC conversion with balanced capacitor voltages throughout the arm interchange concept. It also provides a high conversion ratio, bidirectional power flow, low losses, low current stresses, reduced number of submodules, and DC fault blocking capability. Detailed illustration, operational concept, and design of the proposed architecture with the arm interchange concept are presented. Simulation results for a high-voltage high-power DC-DC converter with the suggested approach are presented to demonstrate the system performance during different normal as well as abnormal operating conditions. Finally, a scaled-down prototype has been implemented for validation. The extracted simulation and experimental results elucidate the presented claims. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
13. Wind energy conversion system based on open-end winding three-phase PMSG coupled with ac−dc buck-boost converter.
- Author
-
Abdelsalam, Ibrahim, Alajmi, Bader N., Marei, Mostafa I., and Alhajri, Mohamed F.
- Subjects
CONVERTERS (Electronics) ,WIND power ,ENERGY conversion ,ELECTRIC inverters ,IDEAL sources (Electric circuits) - Abstract
This study proposes a new back-to-back (BTB) current source converter (CSC) configuration and presents its application for variable speed wind energy conversion system. The proposed configuration consists of three cascaded ac−dc non-inverting buck-boost converter. The ac side of each converter is connected to an open-end winding of the three-phase permanent magnet synchronous generator and the dc sides are connected in parallel to a current source inverter (CSI) without the need for a dc-side capacitor. Ac−dc converters operate under discontinuous conduction mode, and they draw sinusoidal input currents at the unity power factor from fixed or variable magnitude and frequency supply. In addition, the proposed BTB CSC addresses one of the main drawbacks of the conventional CSI which is the over-voltage experienced by switches during commutation. Moreover, the switching losses of the proposed CSI are eliminated. The ElectroMagnetic Transients including DC (EMTDC)/Power System Computer Aided Design (PSCAD) software is used to assess the feasibility of the proposed topology during normal operating conditions and during low voltage ride through. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
14. Generic Closed-Loop Controller for Power Regulation in Dual Active Bridge DC–DC Converter With Current Stress Minimization.
- Author
-
Hebala, Osama M., Aboushady, Ahmed A., Ahmed, Khaled H., and Abdelsalam, Ibrahim
- Subjects
CASCADE converters ,ELECTRIC power transmission ,PHASE shift (Nuclear physics) ,CLOSED loop systems ,PARTICLE swarm optimization - Abstract
This paper presents a comprehensive and generalized analysis of the bidirectional dual active bridge (DAB) dc–dc converter using triple phase shift (TPS) control to enable closed-loop power regulation while minimizing current stress. The key new achievements are a generic analysis in terms of possible conversion ratios/converter voltage gains (i.e., Buck/Boost/Unity), per unit based equations regardless of DAB ratings, and a new simple closed-loop controller implementable in real time to meet desired power transfer regulation at minimum current stress. Per unit based analytical expressions are derived for converter ac rms current as well as power transferred. An offline particle swarm optimization (PSO) method is used to obtain an extensive set of TPS ratios for minimizing the rms current in the entire bidirectional power range of –1 to 1 per unit. The extensive set of results achieved from PSO presents a generic data pool, which is carefully analyzed to derive simple useful relations. Such relations enable a generic closed-loop controller design that can be implemented in real time avoiding the extensive computational capacity that iterative optimization techniques require. A detailed Simulink DAB switching model is used to validate the precision of the proposed closed-loop controller under various operating conditions. An experimental prototype also substantiates the results achieved. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
15. A Self-Balanced Bidirectional Medium-/High-Voltage Hybrid Modular DC–DC Converter With Low-Voltage Common DC-Link and Sequential Charging/Discharging of Submodules Capacitors.
- Author
-
Elserougi, Ahmed A., Massoud, Ahmed, Abdelsalam, Ibrahim, and Ahmed, Shehab
- Subjects
DC-to-DC converters ,HIGH voltages ,SEMICONDUCTOR equipment ,CAPACITORS ,ELECTRIC potential measurement - Abstract
This paper proposes a medium-/high-voltage high-power hybrid modular dc–dc converter to interconnect two different dc-voltage levels in medium-/high-voltage dc grids. The converter consists of half-bridge submodules (SMs) rated at a moderate voltage level, i.e., series connection of semiconductor devices is avoided while connecting two high dc-voltage levels. The proposed architecture provides self-balancing operation, i.e., unlike conventional modular converters, no need for capacitor voltage measurement, which enhances the system reliability and simplicity. Sequential charging/discharging of SMs capacitors is adopted in the proposed approach to ensure a self-balanced operation. The proposed architecture can provide a high conversion ratio as well as power transfer in both directions, i.e., bidirectional dc–dc converter. Detailed illustration of the proposed approach operational concept, design, and overall control system is presented. Simulation and experimental results are presented to show the viability of the proposed configuration and validate the claims. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
16. Hybrid converter topologies for dc transmission systems.
- Author
-
Adam, Grain Philip, Alsokhiry, Fahad, Abdelsalam, Ibrahim, Fletcher, John, Lie Xu, and Al-Turki, Yusuf
- Subjects
DIRECT currents ,CONVERTERS (Electronics) ,INDEPENDENT system operators ,HYBRID systems ,ELECTRIC circuits - Abstract
This study presents types 1 and 2 hybrid converters with reduced power circuit complexity compared with the mixed cell modular multilevel converter (MC-MMC). The type 1 converter is formed by replacing the director switches of the alternate arm converter by high-voltage (HV) half-bridge (HB) cells rated for half of the dc-link voltage. Also, it resembles special case of MC-MMC, where the entire HB cells of each arm are lumped into a single HV HB cell, with both capacitors of the half- and fullbridge cells are exposed to fundamental current as in the conventional MMC. The upper and lower arms of the type 2 converter resemble a front-to-front connection of two three-phase hybrid cascaded two-level converters, where the cell capacitors of the three-phase two-level converters that act as director switches do not experience fundamental currents. Therefore, the type 2 converter offers compact design compared with type 1 converter and the MC-MMC. The technical viabilities of the proposed hybrid converters are assessed using simulations, with both converters modelled in MATLAB-Simulink using electromagnetic transient simulation approach, considering normal and transient conditions. Experimental results obtained from single-phase type 1 converter confirm the practical viability of the proposed converters. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
17. Modular multilevel converter with modified half-bridge submodule and arm filter for dc transmission systems with dc fault blocking capability.
- Author
-
Ahmed, Khaled H., Adam, Grain P., Abdelsalam, Ibrahim A., and Aboushady, Ahmed A.
- Subjects
DIRECT currents ,ELECTRIC potential ,HIGH-voltage direct current transmission ,ENERGY storage ,ELECTRIC transformers - Abstract
Although a modular multilevel converter (MMC) is universally accepted as a suitable converter topology for the highvoltage dc transmission systems, its dc fault ride performance requires substantial improvement in order to be used in critical infrastructures such as transnational multi-terminal dc (MTDC) networks. Therefore, this study proposes a modified submodule circuit for MMC that offers an improved dc fault ride through the performance with reduced semiconductor losses and enhanced control flexibility compared to that achievable with full-bridge submodules. The use of the proposed submodules allows MMC to retain its modularity; with semiconductor loss similar to that of the mixed submodules MMC, but higher than that of the halfbridge submodules. Besides dc fault blocking, the proposed submodule offers the possibility of controlling ac current in-feed during pole-to-pole dc short-circuit fault, and this makes such submodule increasingly attractive and useful for continued operation of MTDC networks during dc faults. The aforesaid attributes are validated using simulations performed in MATLAB/ SIMULINK and substantiated experimentally using the proposed submodule topology on a four-level small-scale MMC prototype. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
18. Self‐balanced non‐isolated hybrid modular DC–DC converter for medium‐voltage DC grids.
- Author
-
Elserougi, Ahmed A., Massoud, Ahmed M., Abdelsalam, Ibrahim, and Ahmed, Shehab
- Abstract
Here, a new bi‐directional hybrid modular non‐isolated DC–DC converter is proposed where it consists of a boost converter (BC) fed from the high‐voltage (HV) side. At the BC output stage, a certain number of half bridge submodules (HB‐SMs) is connected across the BC switch. During the turn‐on period of BC switch, the HB‐SMs are connected sequentially to the low‐voltage (LV) side, which results in charging/discharging their capacitors from/into the LV side. While, during the turn‐off period, the LV side is bypassed and the HB‐SMs capacitors are connected in series across the BC output stage, which results in discharging/charging them into/from the HV side. The power flow is controlled in both directions by controlling the duty cycle. The proposed configuration provides self‐balancing operation thanks to the sequential connection of HB‐SMs capacitors, and it also provides the ability to operate with high conversion ratios. Illustration and analysis of the proposed converter and its closed‐loop controller are presented. A full design of the values and ratings of the involved components are presented. Simulation study for a 2.5 MW (25 kV/10 kV) DC–DC converter is presented. Finally, experimental results for a downscaled prototype are presented for validation. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
19. Multi-tasking dc–dc and dc–ac converters for dc voltage tapping and power control in highly meshed multi-terminal HVDC networks.
- Author
-
Adam, Grain Philip, Abdelsalam, Ibrahim, Lie Xu, Fletcher, John, Burt, Graeme, and Williams, Barry
- Subjects
HIGH-voltage direct current transmission ,VOLTAGE control ,COMPUTER multitasking ,ELECTRIC current converters ,ELECTRIC power transmission - Abstract
This study extends a recently proposed dc auto-transformer to a true multi-port converter that can function simultaneously as dc auto-transformer and a dc/ac converter for dc voltage matching and tapping, and power control in highly meshed multi-terminal dc grids. The presented multi-port converter can generate multiple adjustable dc voltages from a fixed or variable input dc voltage, or from an active ac grid. Theoretical discussions and simulations indicate that when the proposed multi-port converter is used as a hybrid dc and ac hub to manage congestions and resolve loop flow issues in a highly meshed multi-terminal dc network, large dc power can be fed to the lower dc terminal, without exposing the switching devices of the lower subconverter to excessive current stress. Its increased control flexibility and response to dc faults at high and low dc terminals are validated using simulations and experiments. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
20. Full-Bridge Modular Multilevel Submodule-Based High-Voltage Bipolar Pulse Generator With Low-Voltage DC, Input for Pulsed Electric Field Applications.
- Author
-
Abdelsalam, Ibrahim, Elgenedy, Mohamed A., Ahmed, Shehab, and Williams, Barry W.
- Subjects
- *
PULSE generators , *HIGH voltages , *ELECTRIC fields , *TOPOLOGY , *WAVE analysis - Abstract
High-voltage (HV) pulse generators (PGs) are the core of pulsed electric field applications. Applying HV pulses produces electrical pores in a biological cell membrane, in which if the size of the pores increases beyond a critical size, the cell will not survive. This paper proposes a new HV-PG based on the modular multilevel converter with full-bridge submodules (FB-SMs). In order to alleviate the need of complicated sensorless or sensor-based voltage balancing techniques for the FB-SM capacitors, a dedicated self-regulating charging circuit is connected across each FB-SM capacitor. The individual capacitor charging voltage level is obtained from three successive stages, namely, convert the low-voltage dc input voltage to a high-frequency square ac voltage, increase the ac voltage level via a nanocrystalline step-up transformer, and rectify the secondary transformer ac voltage via a diode FB rectifier. The HV bipolar pulses are formed across the load in a fourth stage through series connected FB-SMs. The flexibility of inserting and bypassing the FB-SM capacitors allows the proposed topology to generate different pulse-waveform shapes, including rectangular waveforms with specifically reduced dv/dt and ramp pulses. The practical results, from a scaled-down experimental rig with five FB-SMs and a 1-kV peak-to-peak pulse output, validate the proposed topology. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
- Full Text
- View/download PDF
21. New Efficient Submodule for a Modular Multilevel Converter in Multiterminal HVDC Networks.
- Author
-
Adam, Grain Philip, Abdelsalam, Ibrahim, Fletcher, John Edward, Burt, Graeme M., Holliday, Derrick, and Finney, Stephen Jon
- Subjects
- *
CONVERTERS (Electronics) , *HIGH-voltage direct current converters , *ELECTRIC potential , *POWER electronics , *HARMONIC analysis (Mathematics) , *ELECTRIC power systems - Abstract
In high-voltage applications, the magnitude of total semiconductor losses (on-state and switching) determines the viability of modular-type multilevel converters. Therefore, this paper presents a new cell arrangement that aims to lower total semiconductor loss of the modular multilevel converter (MMC) to less than that of the half-bridge modular multilevel converter (HB-MMC). Additional attributes of the proposed cell are: it eliminates the protective thyristors used in conventional half-bridge cells that deviate part of the dc-fault current away from the antiparallel diode of the main switch when the converter is blocked during a dc short-circuit fault, and it can facilitate continued operation of the MMC during cell failures without the need for a mechanical bypass switch. Thus, the MMC that uses the proposed cell retains all advantages of the HB-MMC such as full modularity of the power circuit and internal fault management. The claimed attributes of the proposed cell are verified using illustrative simulations and reduced scale experimentations. Additionally, this paper provides brief and critical discussions that highlight the attributes and limitations of popular MMC control methods and different MMC cells structures proposed in the literature, considering the power electronic system perspective. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
22. A Full-Bridge Submodule-Based Modular Unipolar/Bipolar High-Voltage Pulse Generator With Sequential Charging of Capacitors.
- Author
-
Elserougi, Ahmed A., Abdelsalam, Ibrahim, Massoud, Ahmed M., and Ahmed, Shehab
- Subjects
- *
ELECTRIC field strength , *PULSE generators , *CAPACITORS , *FIELD-effect transistors , *ELECTROMAGNETIC pulses - Abstract
Repetitive high pulsed electric field (PEF) is an effective method to kill microorganisms and bacteria in water treatment applications. The PEF can be generated by applying high-power electromagnetic pulse across the sample to be treated. There are two main types of high-voltage pulse generators, namely, unipolar and bipolar. In this paper, a full-bridge submodule-based modular high-voltage pulse generator, having the ability to generate unipolar and bipolar high-voltage pulses with different shapes from a relatively low-voltage input dc supply, is proposed. In the proposed configuration, relatively low-voltage insulated gate bipolar transistors (IGBTs) are required to generate the high-voltage bipolar pulses. A thyristor rated at the level of the pulsed output voltage is required in the proposed configuration to bypass the load during the charging process of capacitors. In the proposed approach, a thyristor is used instead of the self-commutated high-voltage switch (e.g., series-connected IGBTs), as thyristors are available with high-voltage ratings and possess inherent reverse voltage blocking capability. A detailed illustration of the proposed configuration and its operational concept are introduced in this paper. Simulation and experimental results are presented to validate the proposed approach. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
23. Current source back-to-back converter for wind energy conversion systems.
- Author
-
Abdelsalam, Ibrahim, Adam, Grain Philip, and Williams, Barry W.
- Subjects
WIND power ,ENERGY conversion ,ELECTROMAGNETISM ,PERMANENT magnets ,COMPUTER-aided design - Abstract
This study proposes a new back-to-back current source converter (BTB-CSC) suitable for medium-voltage high power wind energy conversion systems (WECSs). It employs a dual three-phase permanent magnet synchronous generator and two current source inverters with a phase-shift transformer at the grid side. The proposed BTB-CSC has the following advantages: reduced power circuit and control complexity; low switching losses (zero switching losses at the inverter side); and independent control of active and reactive powers. Power system computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) simulations are used as to assess the steady state and dynamic behaviour of the proposed system under different operating conditions. It is shown that the proposed WECS can ride-through ac faults. Experimental results from scaled prototype of the proposed WECS are used to validate the simulations. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
24. Three‐phase ac–dc buck–boost converter with a reduced number of switches.
- Author
-
Abdelsalam, Ibrahim, Adam, Grain P., Holliday, Derrick, and Williams, Barry W.
- Abstract
A single‐switch, single‐stage, three‐phase ac–dc buck–boost converter suitable for medium‐voltage applications is proposed. Basic relations that govern steady‐state converter operation are established, confirmed using PSCAD/EMTDC simulations, and substantiated experimentally. Simulation and experimental results establish that the proposed converter has good dynamic performance in buck and boost modes, with near unity input power factor. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
25. Hybrid Multilevel Converter With Cascaded H-bridge Cells for HVDC Applications: Operating Principle and Scalability.
- Author
-
Adam, G. P., Abdelsalam, Ibrahim Abdallah, Ahmed, Khaled Hani, and Williams, Barry W.
- Subjects
- *
CASCADE converters , *HIGH-voltage direct current transmission , *SCALABILITY , *PERFORMANCE evaluation , *SEMICONDUCTORS , *SHORT circuits - Abstract
Hybrid multilevel converters are contemplated in an attempt to optimize the performance of voltage source converters in terms of magnitude of semiconductor losses and converter footprint, and to achieve additional features such as dc short circuit proof, which is essential for a high integrity multiterminal HVDC grid. Therefore, this paper considers an emerging hybrid cascaded converter that offers the dc side short circuit proof feature at reduced loss and footprint compared to the existing multilevel and other hybrid converters. Its operating principle, modulation, and capacitor voltage balancing strategies are described in detail. Furthermore, hybrid converter scalability to high voltage applications is investigated. The validity of the modulation and capacitor voltage strategy presented are confirmed using simulation and experimentation. The hybrid cascaded converter is extendable to a large number of cells, making it applicable to high voltage applications, and operation is independent of modulation index and power factor. On these ground, the converter is expected to be applicable for both real and reactive power applications. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
26. Modified back-to-back current source converter and its application to wind energy conversion systems.
- Author
-
Abdelsalam, Ibrahim, Adam, Grain Philip, Holliday, Derrick, and Williams, Barry W.
- Subjects
WIND energy conversion systems ,IDEAL sources (Electric circuits) ,CASCADE converters ,UNINTERRUPTIBLE power supply ,HIGH voltages - Abstract
The back-to-back (BTB) converter is used in power conversion applications such as machine drives, wind energy conversion systems (WECS), uninterruptible power supplies and high-voltage, direct current transmission systems. Various topologies have evolved around voltage source converters and current source converters (CSCs) in an attempt to meet various design and reliability constraints. This paper proposes a new CSC-based BTB converter suitable for WECS application. The proposed configuration addresses the main drawbacks of the conventional BTB CSCs, such as the over-voltage frequently experienced by switches during commutation. The inverter side converter has zero switching losses. The proposed WECS offers the following advantages: simple and easy control, reduced switching frequency and maximum power point tracking with controllable grid active and reactive power. A low-voltage ride-through (LVRT) solution is also provided in the proposed WECS. PSCAD/EMTDC simulation is used to assess the steady-state and dynamic behaviours of the proposed system under different operating conditions and during LVRT. Experimental results allow steady-state and dynamic behaviour assessment of the proposed system under different operating conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
27. Single-stage, single-phase, ac-dc buck-boost converter for low-voltage applications.
- Author
-
Abdelsalam, Ibrahim, Adam, Grain P., Holliday, Derrick, and Williams, Barry W.
- Subjects
SINGLE-stage accelerators ,AC DC transformers ,CASCADE converters ,LOW voltage systems ,COMPUTER-aided design - Abstract
The suitability of a single-stage ac-dc buck-boost converter for low-voltage applications is investigated. In-depth discussion and analysis of the converter's operating principle, basic relationships that govern converter steady-state operation and details of the necessary control structures needed to comply with the grid code are provided. The validity of the proposed system is confirmed using power system computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) simulations, and is substantiated experimentally. The buck-boost converter under investigation has good dynamic performance in both buck and boost modes, and ensures near unity input power factor over the full operating range, whilst having fewer devices and passive elements than other published versions of the buck-boost converter. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
28. Modified Variable Step-Size Incremental Conductance MPPT Technique for Photovoltaic Systems.
- Author
-
Owusu-Nyarko, Isaac, Elgenedy, Mohamed A., Abdelsalam, Ibrahim, and Ahmed, Khaled H.
- Subjects
MAXIMUM power point trackers ,PHOTOVOLTAIC power systems ,ALGORITHMS - Abstract
A highly efficient photovoltaic (PV) system requires a maximum power point tracker to extract peak power from PV modules. The conventional variable step-size incremental conductance (INC) maximum power point tracking (MPPT) technique has two main drawbacks. First, it uses a pre-set scaling factor, which requires manual tuning under different irradiance levels. Second, it adapts the slope of the PV characteristics curve to vary the step-size, which means any small changes in PV module voltage will significantly increase the overall step-size. Subsequently, it deviates the operating point away from the actual reference. In this paper, a new modified variable step-size INC algorithm is proposed to address the aforementioned problems. The proposed algorithm consists of two parts, namely autonomous scaling factor and slope angle variation algorithm. The autonomous scaling factor continuously adjusts the step-size without using a pre-set constant to control the trade-off between convergence speed and tracking precision. The slope angle variation algorithm mitigates the impact of PV voltage change, especially during variable irradiance conditions to improve the MPPT efficiency. The theoretical investigations of the new technique are carried out while its practicability is confirmed by simulation and experimental results. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
29. Analysis and Design of a Multi-Port DC-DC Converter for Interfacing PV Systems.
- Author
-
Alajmi, Bader N., Marei, Mostafa I., Abdelsalam, Ibrahim, AlHajri, Mohamed F., and Flicker, Jack
- Subjects
MAXIMUM power point trackers ,COMPUTER-aided design ,PHOTOVOLTAIC power systems ,COMPUTER systems ,BUILDING performance ,ARTIFICIAL satellite tracking - Abstract
A high-frequency multi-port (HFMP) direct current (DC) to DC converter is presented. The proposed HFMP is utilized to interface a photovoltaic (PV) system. The presented HFMP is compact and can perform maximum power point tracking. It consists of a high-frequency transformer with many identical input windings and one output winding. Each input winding is connected to a PV module through an H-bridge inverter, and the maximum PV power is tracked using the perturb and observe (P&O) technique. The output winding is connected to a DC bus through a rectifier. The detailed analysis and operation of the proposed HFMP DC-DC converter are presented. Extensive numerical simulations are conducted, using power system computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) software, to evaluate the operation and dynamic behavior of the proposed PV interfacing scheme. In addition, an experimental setup is built to verify the performance of the HFMP DC-DC converter. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
30. First-line paclitaxel and cisplatin used sequentially or in combination in metastatic breast cancer: A phase II randomized study.
- Author
-
Elserafi MM, Zeeneldin AA, Abdelsalam IM, Nassar HR, Moneer MM, and Buhoush WH
- Subjects
- Adult, Antineoplastic Combined Chemotherapy Protocols adverse effects, Breast Neoplasms mortality, Cisplatin administration & dosage, Combined Modality Therapy, Drug Administration Schedule, Female, Humans, Middle Aged, Neoplasm Metastasis, Neoplasm Staging, Paclitaxel administration & dosage, Survival Analysis, Treatment Outcome, Antineoplastic Combined Chemotherapy Protocols therapeutic use, Breast Neoplasms drug therapy, Breast Neoplasms pathology, Cisplatin therapeutic use, Paclitaxel therapeutic use
- Abstract
Introduction: Breast cancer (BC) is the commonest cancer among females worldwide. Some patients present initially at advanced stages and more than 50% of them will develop metastasis (MBC) at some point. Compared to single agents, combination chemotherapy produces higher response rates (RR), longer progression-free survival (PFS) than single agents. This is associated with remarkably higher toxicities. At the same time, overall survival (OS) is comparable. This study aimed to compare safety and efficacy of combination and sequential chemotherapy., Patients and Methods: Forty-six MBC patients were randomized to receive 6 cycles of the combination of paclitaxel (175 mg/m
2 ) and cisplatin (70 mg/m2 ) (combination PC) or paclitaxel for 3 cycles followed by cisplatin for 3 cycles (sequential PC). Endpoints were RR, PFS, OS and safety., Results: Both combination and sequential PC produced similar RR (52% in both arms) and disease control rates (78.3% vs. 73.9%, p = .652). Responses were faster in the combination arm. Median PFS was 8.2 months in the combination compared to 5.0 months in the sequential arm (p = .064). The median OS was 16.5 and 18.8 months in the combination and sequential arms, respectively (p = .866). The combination was more toxic than sequential PC. Grade 3 toxicities were higher with combination PC than to sequential PC (48% vs. 4.3%; p < .001)., Conclusion: Sequential agent chemotherapy may provide similar response rate and overall survival to combination chemotherapy with much lower toxicities. The former can be considered the standard practice in most instances., (Copyright © 2018 National Cancer Institute, Cairo University. Production and hosting by Elsevier B.V. All rights reserved.)- Published
- 2018
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.