Department of Electrical Engineeering
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Item The 3rd International Training Course in Information Technology-based for Electric Engineering Education(2009-11) Mushi, Aviti Thadei; Justo, Jackson JohnThis is a report from the representatives of Tanzania to the Third International Training Course in Information Technology-based for Electric Engineering Education. It was held at Electronic Engineering Polytechnic Institute of Surabaya (EEPIS).Item Access Authorization and Monitoring for Web Based Resources for e-Learning System for Secondary Schools in Tanzania(2007-11) Mkocha, K.; Kissaka, M. M.; Mwinyiwiwa, Bakari M. M.This paper presents the development of a mechanism for the authorization and monitoring of data for a web based e-learning system. System data as well as the different user groups accessing the data have been defined. Constraints to use the LAMP solution stack, the UML models are coded in PHP which is embedded in the HTML. These interfaces are used as doorways through which different users, as per their role, can access and work on the system data according to their clearance. On the other hand, the administrator can see different reports, from system logs by simply pressing a button.Item Application of Multipurpose Voltage Source Converter(2003) Masamila, B.; Nzali, A. H.; Mwinyiwiwa, Bakari M. M.Item An Approach for Development of a Multipurpose Power Electronics Research Facility(University of Dar es Salaam, 1999-09) Mwinyiwiwa, Bakari M. M.Item A Blue Print of a Unified Communications and Integrated Collaborations System in the Health Sector of Developing Countries: A Case of Uganda(World Academy of Science, Engineering and Technology, 2012) Excellence, F.; Mwinyiwiwa, Bakari M. M.; Haule, Damian D.; Omar, F. H.Access to information is the key to the empowerment of everybody despite where they are living. This research is to be carried out in respect of the people living in developing countries, considering their plight and complex geographical, demographic, social-economic conditions surrounding the areas they live, which hinder access to information and of professionals providing services such as medical workers, which has led to high death rates and development stagnation. Research on Unified Communications and Integrated Collaborations (UCIC) system in the health sector of developing countries comes in to create a possible solution of bridging the digital canyon among the communities. The aim is to deliver services in a seamless manner to assist health workers situated anywhere to be accessed easily and access information which will help in service delivery. The proposed UCIC provides the most immersive Telepresence experience for one-to-one or many-tomany meetings. Extending to locations anywhere in the world, the transformative platform delivers Ultra-low operating costs through the use of general purpose networks and using special lenses and track systems.Item Broadband Access Technologies for Rural Connectivity in Developing Countries(International Journal of Research and Reviews in Computer Science (IJRRCS), 2011) Simba, F.; Mwinyiwiwa, Bakari M. M.; Mjema, E. M.; Trojer, L.; Mvungi, N. H.Rural areas especially those of the developing countries provide challenging environment to implement communication infrastructure for data and Internet based services. The main challenges are the high cost of network implementation and lack of customer base, as rural areas are characterized by low income, highly scattered and low population density. This situation drives network operators to establish network infrastructures in urban/city centers leaving rural areas as underserved community. This paper surveys the available connectivity technologies with potentials to offer broadband access network to rural areas. The scope of this survey is on wireless access technologies, due to the fact that they are efficient in terms of cost, time of deployment and network management for rural environment. We provide comparison of the surveyed technologies in terms of their capacity (data rates) and coverage. We also discuss the current deployment of WiMAX and 3G technologies in Africa, which is a home to most of the developing countries. The survey results indicate potential broadband access technologies for rural areas of the developing countries.Item A Case Study Describing the Creation and Implementation of a Capacity Building Program for Mixed Mode Delivery of Academic Programmes in Developing Countries(ICCE, 2005) Howell, S.; Mwinyiwiwa, Bakari M. M.; Chadwick, C.In 2002 RMIT UNIVERSITY (RMIT) were awarded a World Bank (WB) four year contract (2003 --2006) by the AFRICAN VIRTUAL UNIVERSITY (AVU) for • Delivery of a COMPUTER SCIENCE (CS) diploma and degree to 8 AVU Learning Centres (LC) in Africa using an INFORMATION COMMUNICATIONS TECHNOLOGY (ICT) mixed-mode delivery model, and • Building capacity in the LEAD PARTNER UNIVERSITY (LPU), in this case the UNIVERSITY OF DAR ES SALAAM (UDSM) in Tanzania, so that they could take over the management & operations of the program from RMIT as from the end of the contract-Dec 2006. The inclusion of effective CAPACITY BUILDING (CB) into the program was viewed as an essential and urgent requirement that would lead to an ongoing and sustainable program. This need is particularly important in the areas of ICT, where the technology has the potential to support education and contribute meaningfully to the development of economic and sustainable industries. To be effective, CB would need to be seen as a holistic process involving the whole organisation. This paper describes: • the complexities and key issues involved in developing a CB program with the primary objective being “To ensure that UDSM is “operationally ready” to take over the management and the delivery of CS Program from RMIT.by Dec 2006" • the 'organisational mirroring' planning approach created to develop the CB program and • the specific strategies and activities that formed the CB program. Finally the paper reflects on the strategies and activities adopted and discusses key issues arising during implementation and lessons learned to date.Item Challenges of Deploying Unified Communications and Integrated Collaborations System in the Health Sector of Developing Countries: A Case of Uganda(2013) Excellence, F.; Mwinyiwiwa, Bakari M. M.Access to information holds the key to the empowerment of everybody despite where they are living. This research is to be carried out in respect of the people living in developing countries, considering their plight and complex geographical, demographic, social-economic conditions surrounding the areas they live, which hinder access to information and of professionals providing services such as medical workers, which has led to high death rates and development stagnation. Research on Unified Communications and Integrated Collaborations (UCIC) system in the health sector of developing countries comes in to create a possible solution of bridging the digital canyon among the communities. The system is meant to deliver services in a seamless manner to assist health workers situated anywhere to be accessed easily and access information which will help in service delivery. The proposed UCIC provides the most immersive telepresence experience for one-to-one or many-to-many meetings. Extending to locations anywhere in the world, the transformative platform delivers Ultra-low operating costs through the use of general purpose networks and using special lenses and track systems. The aim is to identify challenges anticipated in the deployment of the UCIC system in the health sector of developing countries and recommend possible solutions. These recommendations once adopted and implemented correctly will bring enhancement to the speed and quality of services offered by health workers. The capacities of UCIC will help health workers shorten decision cycles, accelerate service delivery and save lives by speeding access to information and by making it possible for all health workers and patients to collaborate everywhere.Item Comparison of On-Line Partial Discharge Detection Techniques for High Voltage Power Cable Joints and Terminations(College of Engineering and Technology, University of Dar es Salaam, 2023-02-28) Chambela, Prisca Paul; Mushi, Aviti ThadeiCable joints and terminations play a vital role in providing dependable electrical connection, mechanical support and physical safeguard. These provide electrical stress control to shielded power cables. Despite their usefulness, they suffer from partial discharges (PD) because of enhanced voltage stress, moisture ingress and poor workmanship (during installation). Therefore, it is necessary to undertake on-line PD detection to determine their state. Some of these techniques are capacitive coupler (CC); acoustic emission (AE); and high frequency current transducer (HFCT). This article presents a literature review of these techniques based on the cost, availability, and applicability. The comparative analysis is also provided on location of their sensors, quantification and detection ability. The CC technique involves the quantification of the coupler sensor input measured in mV/pC by realizing the time of flight between two sensors for which the results are used to estimate location of the PD. Meanwhile, the AE technique has an advantage of high immunity to electrical noise, with a caveat that acoustic signals are highly attenuated within the cable joints. Additionally, the combination of the acoustic sensors and PD electrical couplers can be used to discriminate PDs from electrical noise. The HFCT has two methods – with denoising (HFCT-WiD) and without denoising (HFCT-WoD). The HFCT-WiD technique can significantly reduce the sensor’s detection sensitivity due to its high value of noise to signal ratio (NSR). Comparatively, the HFCT has the best results of quantification and detection ability for PDs among all three techniques investigated. However, in places where electrical noise is severe, PD activities may be detected effectively with AE technique. Further work is needed to statistically map these methods and establish their correlation with experimental data.Item Conceptual Synthesis of Multi-Source Renewable Energy Based Microgrid(World Academy of Science, Engineering and Technology, 2013-12) Mwinyiwiwa, Bakari M. M.; Manyahi, Mighanda J.; Gregory, Nicodemu; Kyaruzi, Alex LMicrogrids are increasingly being considered to provide electricity for the expanding energy demand in the grid distribution network and grid isolated areas. However, the technical challenges associated with the operation and controls are immense. Management of dynamic power balances, power flow, and network voltage profiles imposes unique challenges in the context of microgrids. Stability of the microgrid during both grid-connected and islanded mode is considered as the major challenge during its operation. Traditional control methods have been employed are based on the assumption of linear loads. For instance the concept of PQ, voltage and frequency control through decoupled PQ are some of very useful when considering linear loads, but they fall short when considering nonlinear loads. The deficiency of traditional control methods of microgrid suggests that more research in the control of microgrids should be done. This research aims at introducing the dq technique concept into decoupled PQ for dynamic load demand control in inverter interfaced DG system operating as isolated LV microgrid. Decoupled PQ in exact mathematical formulation in dq frame is expected to accommodate all variations of the line parameters (resistance and inductance) and to relinquish forced relationship between the DG variables such as power, voltage and frequency in LV microgrids and allow for individual parameter control (frequency and line voltages). This concept is expected to address and achieve accurate control, improve microgrid stability and power quality at all load conditions.Item Construction and Test of a Delta Modulated Buck Type 3 Phase Converter(McGill University, 1989) Mwinyiwiwa, Bakari M. M.A Delta Modulated, Buck Type, Three Phase PWM Converter was constructed and tested. The converter is of the current source type and can be used in conjunction with current source inverters. The d.c. current is regulated by proportional feedback control loop. By delta modulation of the voltages across the a.c. terminaIs of the converter, the a.c. source currents are "indirectly" controlled so that the fundamental components remain in a predefined phase with respect to the source voltages. Test results have shown that the converter draws near sinusoidal a.c. currents at unit y power factor, with leading power factor a possibility.Item Control Algorithm for Shunt Active Power Filter using Synchronous Reference Frame Theory(World Academy of Science, Engineering and Technology, 2009) Msigwa, C. J.; Kundy, B. J.; Mwinyiwiwa, Bakari M. M.his paper presents a method for obtaining the desired reference current for Voltage Source Converter (VSC) of the Shunt Active Power Filter (SAPF) using Synchronous Reference Frame Theory. The method relies on the performance of the Proportional-Integral (PI) controller for obtaining the best control performance of the SAPF. To improve the performance of the PI controller, the feedback path to the integral term is introduced to compensate the winding up phenomenon due to integrator. Using Reference Frame Transformation, reference signals are transformed from a − b − c stationery frame to 0 − d − q rotating frame. Using the PI controller, the reference signals in the 0 − d − q rotating frame are controlled to get the desired reference signals for the Pulse Width Modulation. The synchronizer, the Phase Locked Loop (PLL) with PI filter is used for synchronization, with much emphasis on minimizing delays. The system performance is examined with Shunt Active Power Filter simulation modelItem ĆUK Converter Based Maximum Power Point Tracking for Photovoltaic System Using Incremental Conductance Technique(International Journal of Innovative Research in Advanced Engineering (IJIRAE), 2014-11) Dunia, James; Mwinyiwiwa, Bakari M. M.; Kyaruzi, Alex LPhotovoltaic (PV) energy is one of the most important energy resources since it is clean, pollution free, and sustainable. Maximum Power Point Tracking (MPPT) is used in photovoltaic (PV) systems to maximize the photovoltaic output power, irrespective of the temperature and radiation conditions. In MPPT system, the PV output power is fed directly to dc/dc converter and the output of MPPT control is used to control the dc/dc converter in order to operate at the maximum possible power point (MPP). In this paper it is proposed to track the MPP in PV module using incremental conductance algorithm. CUK converter is used as dc/dc converter to achieve the power/voltage level conversion. The MPPT system has been simulated using MATLAB/Simulink software to track the maximum output power from PV array and charge a battery bank. Simulation results show that the proposed MPPT system is capable of maximum power tracking of the PV array as desired.Item Current Equalization in SPWM FACTS Controllers at Lowest Switching Rates(IEEE Transactions on Power Electronics, 1999) Mwinyiwiwa, Bakari M. M.; Wolanski, Z.; Ooi, B. T.This paper shows that sinusoidal pulse width modulation (SPWM) FACTS controllers can be synthesized by employing “phase shifted triangle carrier technique” to multiconverters at a switching rate of only 3 pulses. The options of parallel, series and series/parallel module connections are examined for current equalization. The paper presents simulation and experimental resultsItem DC Bus Voltage Regulator for Renewable Energy Based Microgrid Application(World Academy of Science, Engineering and Technology, 2013-12) Mwinyiwiwa, Bakari M. M.Renewable Energy based microgrids are being considered to provide electricity for the expanding energy demand in the grid distribution network and grid isolated areas. The technical challenges associated with the operation and controls are immense. Electricity generation by Renewable Energy Sources is of stochastic nature such that there is a demand for regulation of voltage output in order to satisfy the standard loads’ requirements. In a renewable energy based microgrid, the energy sources give stochastically variable magnitude AC or DC voltages. AC voltage regulation of micro and mini sources pose practical challenges as well as unbearable costs. It is therefore practically and economically viable to convert the voltage outputs from stochastic AC and DC voltage sources to constant DC voltage to satisfy various DC loads including inverters which ultimately feed AC loads. This paper presents results obtained from SEPIC converter based DC bus voltage regulator as a case study for renewable energy microgrid application. Real-Time Simulation results show that upon appropriate choice of controller parameters for control of the SEPIC converter, the output DC bus voltage can be kept constant regardless of wide range of voltage variations of the source. This feature is particularly important in the situation that multiple renewable sources are to be integrated to supply a microgrid under main grid integration or isolated modes of operation.Item DC Drive System Using Delta Modulated CS Delta Modulated PWM Converter(ANSTI EE, 1991-11) Mwinyiwiwa, Bakari M. M.Item DC Voltage Regulation of Solar PV/Wind and Biofuel System Incorporating Battery Storage(University of Dar es Salaam, 2021-11-12) Juma, Mwaka Ismail; Mwinyiwiwa, Bakari Mohammedi Mfaume; Msigwa, Consalva Joseph; Mushi, Aviti ThadeiTanzania has several places which lack the access to grid. These areas can be powered by utilizing hybrid energy systems (HES) such as solar photovoltaic, wind, and biodiesel. However, such a system produces voltage control challenges at the DC bus due to stochastic nature of those sources, if battery is not coupled. Therefore, this paper first proposes a HES that is coupled to a battery. Secondly, it proposes a control that can regulate the three sources of energy such that the DC bus is maintained at 750 V. Simulation results have shown that a conventional proportional and integral controller can achieve DC bus voltage regulation for the system proposed in this paper regardless of irradiance variation, wind speed variation, or the load variation. This type of energy sources is feasible for use in rural arrears of Tanzania.Item Delta Modulated Buck Type PWM Converter(IEEE Transactions on Industry Applications, 1992) Mwinyiwiwa, Bakari M. M.; Birks, P. M.; Ooi, B. T.A delta-modulated, current-source, three-phase pulsewidth modulation (PWM) rectifier is described. The rectifier is intended to be used in conjunction with controlled current inverters. An outer proportional feedback loop regulates the unidirectional output current flowing through the DC link. An inner feedback loop maintains near sinusoidal waveform currents at unity or leading power factor from the utility power supply. The inner loop controls the current indirectly by delta modulation of the voltage across the AC terminals of the converter. The converter has been conceived as the circuit dual of the hysteresis current-controlled boost-type rectifier. Experimental results from a laboratory model are presentedItem Design and Construction of a Multipurpose Voltage Source Converter(University of Dar es Salaam, 2001) Masamila, B.; Nzali, A. H.; Mwinyiwiwa, Bakari M. M.Item Design and simulation of hybrid renewable energy sources for Mwanza International Airport(University of Dar es Salaam, 2022-10-21) Minja, Monyiaichi Nelson; Mushi, Aviti ThadeiThis paper presents the design and simulation of hybrid renewable energy sources utilizing both solar energy and wind energy sources with a backup generator. The demand for reliable electric energy in support of investments in large social and economic developmental activities such as airport operations has been an agenda worldwide. In Tanzania, Mwanza International Airport (MIA) consumes about 18 MVA annually of electricity power in support of its operations. About 78–80% of the world commercial energy comes from fossil fuels. Non-renewable fuels apart from other negative effects contribute to the global warming through destruction of ozone layer. Additionally, most of centralized conventional methods of generation require transmission systems, add complexity of the system and poor power quality. Therefore, the proposal to use a mixed coupled hybrid renewable energy source to power the airport is necessary. The considered energy mix are solar photovoltaic, wind, diesel generator and a battery. There is an average solar irradiation of 5.38 kWh/m2 and wind speed average of 4.20 m/s that is able to be converted to electricity by installation of 10 kW wind turbine. The intermittency is taken care of by the diesel generator and the battery designed at 40 kVA and 400 Ah respectively. The project will be in operational for a period of 25 years hence its costs are reasonable and the justification is the potential of the estimated energy. Some mathematical computations were performed and, in the end simulation results displayed different techno-economic HRES configurations. The complete design of the selected system would include 78.48 kW PV system comprising 314 pieces of 200 W poly-crystalline modules, 608 batteries of 83.4 Ah, 12V rating, load following dispatch strategy, 140 kVA diesel generator, and 41.64kVA bidirectional converter. The net present cost of the selected design was $357,780.8, cost of energy $0.93/kW, and minimum renewable fraction of 40.2%.