UDOM IR :: Browsing by Author "Mvungi, Nerey H."

Browsing by Author "Mvungi, Nerey H."

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Agents based service restoration in electrical secondary distribution network
(IEEE Xplore, 2019) Mwifunyi, Rukia J.; Mvungi, Nerey H.; Kissaka, Mussa M.
Service Restoration (SR) is one of the fundamental functionalities of distribution management system during the fault management process. Several approaches have been devised to solve the SR problem on the distribution network including centralized and distributed approaches. Most of the existing studies focused on the service restoration in the medium voltage network with very few focusing on the Secondary Distribution Network (SDN). In most countries including Tanzania, the service restoration is accomplished manually through relying on operational experiences, rated capacity of the transformers and peak hour demand for decision making. This study aimed at designing a distributed algorithm based on the multiagent system for SR in the SDN. The study has been conducted through intensive literature review together with focus group discussion with key stakeholders from the utility company, study visits to the Tanzania SDN in Dar es Salaam region and interviews with the technical people. SDN with three transformers rated at 315kVA, 200kVA and 100kVA have been chosen as the pilot site for designing the distributed algorithm. The designed algorithm includes designing of multiagent system, objective functions to be optimized and design for the equipment specifications and power system network topology to support SR. Four agents namely, Control Agent, Grid Agent, Load Agent and Switch Agent have been found to be optimal for the SR process. The designed restoration process mainly focuses on load transfer to the nearby transformer and load shedding. The future work will focus on the real implementation of the designed algorithm and consideration of the integration of the renewable distributed generations.
Assessment of non transmittable codewords enhancement to viterbi algorithm decoding
(LJS Publishing, 2014) Mrutu, Salehe I.; Sam, Anael; Mvungi, Nerey H.
Researchers have shown that practical mobile communication channels introduce errors that are concentrated in a certain locality rather than random errors. These are burst errors caused by deep fading of the wireless channel or a lightning strike. The existing Viterbi Algorithm (VA) capable of correcting random errors is inefficient in correcting burst errors and therefore resulting in unacceptable amount of residual errors. This paper presents an assessment of Non-Transmittable Codewords (NTCs) enhancement technique to VA in decoding the received signals subjected to burst errors that may occur in poor channels. A hard decision, 1/2 rate and constraint length K is equal to 3 Viterbi Algorithm decoding technique, Binary Phase-Shift Keying (BPSK) and Additional White Gaussian Noise (AWGN) are components used in MATLAB software based simulation when assessing the proposed technique. Applying 6NTCs to VA decoder enables the decoder to reduce 83.7 percent of its residual errors. However, the technique reduces the encoder’s data transmission rate from 1/2 to 1/6.
Distributed approach in fault localisation and service restoration: State-of-the-art and future direction
(Taylor and Francis, 2019) Mwifunyi, Rukia J.; Kissaka, Mussa M.; Mvungi, Nerey H.
This paper presents a survey of recent development in Fault Localisation and Service Restoration (FLSR) following electrical disturbance in Power Distribution Systems (PDS) based on distributed approaches. Distributed approaches have been found to fit well in the distribution systems as they have more than one decision-making component, and data processing can be done in parallel in individual units that makes it faster and requires less processing capabilities centrally. Recently reported distributed approaches have been studied and analysed. With ever-growing integration of the renewable distributed generation (DG) into the distribution systems, it has been realised that, the uncertainty nature of both load demand and DG need to be considered in the service restoration problems for improve defficiency. Consideration of uncertainty nature of the renewable generation and load demands in the distributed FLSR result into the increased restored customers as well as avoiding overloading and underloading after restoration. The paper starts with a general overview of the Multi Agent Systems (MAS) as the distributed control approach and approaches for forecasting load demand and DG power and then discusses different approaches used for FLSR in PDS by showing their strengths and limitations. The review is concluded by giving future research directions.
Factors influencing citizens utilisation of government websites
(Journal of Informatics and Virtual education, 2011) Mwangakala, Hilda; Mvungi, Nerey H.
The use of website for wide-ranging applications has become a reality following rapid developments in communications and information technologies. Government and their agencies have adopted and used it to communicate with and to offer services to their citizens. The approach of using information technology (IT) is conceived as being easier and more convenient. Therefore, increasingly governments and their agencies use websites to provide information and services. The problem is whether the services and information reach the intended recipients. This paper looks at different schemes to assess the utilization of such offerings, the factors and parameters that influence its acceptability. A conceptual modal to measure acceptability and use of government websites is presented based on six identified parameters: trust, usefulness, easy of use, satisfaction and demographic characteristics.
Multiagent based fault localisation and service restoration in Tanzanian secondary distribution network
(Taylor & Francis, 2021) Mwifunyi, Rukia J.; Mvungi, Nerey H.; Kissaka, Mussa M
Fault Localisation and Service Restoration (FLSR) is a fundamental function during the distribution system’s fault management process for improved service reliability and resilience. In Tanzania, fault management in the Secondary Distribution Network (SDN) is accomplished manually through customer calls and manual-line inspections. Service restoration’s decision relies on prior experiences, rated capacity of transformers and peak hour demand, causing prolonged service restoration and load shedding. Approaches devised to solve the FLSR problem include centralised and distributed ones. The study aimed at designing and developing a distributed algorithm based on the Multiagent System (MAS) for FLSR in SDN. Data from the Tanzanian utility company, including load demand, distribution network topology, and emergency reports, enabled the development of the MAS for FLSR. An intensive literature review has also been conducted. Five agents, namely Control Agent, Grid Agent, Load Agent, Renewable Distributed Generation Agent and Switch Agent have been developed to support the FLSR process. The agents facilitated decision-making by locating faults and perform a restoration process through load transfer to the nearby transformer and shedding loads. Consideration of the stochastic nature of load demand through using the LSTM model maximised the restored load. Future work will focus on deploying and testing the developed algorithm on a real power system
Performance of binary locked convolutional codes with non-transmittable codewords in flat and slow rayleigh-fading channel
(Foundation of Computer Science, 2014) Mrutu, Salehe I.; Sam, Anael; Mvungi, Nerey H.
Communication over wireless media is vulnerable to distortion by noise. Therefore, the application of an error control mechanism is necessary to minimize the Bit Error Rate (BER). It is proposed to use locked binary convolutional code with Non-Transmittable codewords to enhance Viterbi Algorithm decoders; as one of the forward error correction mechanisms. The proposed enhancement empowers Viterbi algorithm decoders to reduce one of its inherent limitations of residual errors due to burst errors. This paper evaluates the performance of the locked (2, 1, 2) binary convolutional code with Non-Transmittable codewords enhancement technique over flat and slow Rayleigh Fading channel using a MATLAB software simulation. Simulation result shows 80.92 percent reduction of residual errors when 6 Non-Transmittable Codewords were applied to Viterbi Algorithm (VA) decoding. On the other hand, the technique lowers the encoder’s data transmission rate from 1/2 to 1/6.
Short-term load forecasting for improved service restoration in electrical power systems: A case of Tanzania
(IEEE, 2020) Mwifunyi, Rukia J.; Kissaka, Mussa M.; Mvungi, Nerey H.
Reliable operation of the power system and efficient utilization of its resources requires load demand forecasting in a wide range of time leads, from minutes to several days. Underestimation of load demand forces the power system to operate in a vulnerable region to the disturbance. In the Tanzanian electrical power distribution network, peak hour load demand values are used during service restoration resulting in prolonged load shedding. This study aims at developing a short-term load forecasting model to be used during service restoration for improved service reliability. Several methods have been devised for short-term load forecasting including conventional statistical approaches and data-driven approaches. Data-driven approaches perform well in load forecasting due to its ability in learning features for the dataset with nonlinear characteristics like load demand dataset. The study has adopted an experimental design approach in developing the short-term load foresting model using six years datasets from 2014 to 2019 with twenty minutes resolution from the Tanzania power distribution network. A total of 141,749 datasets were used and three deep learning models namely Long Short-Term Memory (LSTM), Recurrent Neural Network (RNN) and Gated Recurrent Unit (GRU) were used during the experiments. It has been observed that the LSTM outperforms the RNN and GRU with forecasting accuracy of 96.43%. The future work will be the development of a distributed algorithm for service restoration considering stochastic nature of load demand using developed forecasting load model.
Towards affordable broadband communication: a quantitative assessment of TV white space in Tanzania
(Springer Nature, 2017) Matogoro, Jabhera; Mvungi, Nerey H.; Justinian, Anatory; Karandikar, Abhay; Singh, Jaspreet
A quantitative assessment of TV White Space in Tanzania was conducted to assess the level of spectrum utilization as well as a key milestone towards the use of white space for affordable broadband communication. Two approaches have been used; pollution and protection viewpoints and experimental spectrum measurements based on energy detection principle. The study focused on 470–694 MHz UHF spectrum band which is used for digital terrestrial television in Tanzania. It was found that, more than 120 MHz is available as white space in various locations in Tanzania when pollution and protection view point was used and about 184 MHz are available as white space in Dodoma urban using experimental spectrum measurements and almost 100% of the available frequencies are not used in Dodoma rural. Both approaches revealed that there is low spectrum utilization and therefore presents a best case towards development of dynamic spectrum access technologies in Tanzania
Trellis analysis of transmission burst errors in viterbi decoding
(IJCSIS PUBLICATION, 2014) Mrutu, Salehe I.; Sam, Anael; Mvungi, Nerey H.
The Viterbi decoder is the most favorable solution to the problem of decoding codewords from a convolutional encoder. Viterbi decoder performs exceptionally well when a received codewords block contains single or multiple and scattered errors in a received codewords block. However, the formation of burst errors in data transmission due to high transmission speed and the widely varying error conditions of wireless media in fading channel creates decoding challenge for such conditions which result in unbearable amount of residual errors. By using Viterbi decoders’ trellis diagrams, this paper analyses the effects of burst errors to the decoder that lead to residual errors and proposes improvement to the encoding and decoding procedures of the existing (2, 1, 2) binary convolutional encoder. The improved version facilitate effectiveness in the decoder (Viterbi algorithm) in decoding burst errors and hence reduction of residual errors in a poor channel. The proposed enhancements improve the decoder’s operational performance by 75 percent. However, the proposed modification reduces the encoder’s data transmission rate from 1/2 to 1/6.

Browsing by Author "Mvungi, Nerey H."

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