Faculty of Engineering and Built Environment

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Coordinated control of conventional power sources and plug-in hybrid electric vehicles for a hybrid power system
(2022-05) Adbul-Kader, Mohammed Ozayr; Akindeji, Timothy Kayode; Sharma, Gulshan
Globally, the requirement for renewable and clean energy technologies is becoming vastly popular. With the high implementation of solar and wind energy systems, together with plugin hybrid electric vehicle (PHEV) aggregators, energy costs can be minimised, greenhouse gas emissions decrease, and overall maintenance becomes reduced. The constant increase of load demand is becoming a challenge for the current power systems, with difficulties including stability concerns and excessive regulations by the government. Due to irradiance and wind speed fluctuations, the solar and wind energy system’s non-linearity affects the existing power system stability. The growth of the electric vehicle industry has also shed new light on potential auxiliary services that can be provided, as and when required, to the power system. Hence, this research examines the potential control strategies that are required to maintain the system in steady-state conditions after disturbances that occur with higher penetration of renewable energy systems (RESs) and PHEVs. The case study models a isolated two-area thermal type power system that is interconnected through an AC tie-line. Three scenarios are modelled, simulated and analysed. The first scenario models a isolated thermal power system with PHEVs with two areas which utilises a fractional order proportional integral derivative (FOPID) controller in each area. The resulting model is analysed to see the effects of PHEVs coupled with FOPID on the power system. The second scenario models a isolated two-area thermal power system with RES and utilises a fuzzy type-2 (FT2) FOPID controller in each area. The RES penetration istested for its non-linearity effect on the isolated power system, and the error is reduced by an advanced controller that uses artificial intelligence techniques. The third scenario is modelled as an isolated two-area thermal power system with PHEVs and RES coupled with neural network predictive controller (NNPC) in each area. The three scenarios are simulated in MATLAB/Simulink with results displayed graphically and numerically. The results show that the integration of PHEVs for load and/or storage in the multi-area power system, and the proposed control methods for each scenario, have the best dynamic response with the least error, no oscillations and the fastest response to steady state condition.
Design of control strategies for frequency stability of PV-thermal interconnected power system
(2021-02) Estrice, Milton Solomon; Sharma, Gulshan; Akindeji, Timothy Kayode
Renewable energy in particular solar energy is a viable option to meet the increasing energy demand for the modern world. The Solar resource in South Africa is among the highest in the world. With the progression of modern society, both energy demands and energy prices are increasing, which has welcomed the introduction of renewable energy resources as an alternative. However, solar radiation varies over the complete day sometimes over the season, and sometimes over the complete year. Further, the power demand is highly variable in nature. Hence, the generated power should match the customer demands over the period of twenty-four hours, and further, it should be economical for customers and electrical utilities. Hence, this study will focus on integrating PV plants with thermal plants to meet the rising customer power demand. The integration of PV with thermal power plants will bring some new challenges in the domain of power system operation & control which is the frequency of the power system should be restricted to well-defined values. Hence, suitable control strategies are to be developed for the successful and smooth operation of the power system. In this research work, an attempt is made to investigate an interlinked system comprising of a thermal and a PV generation system. The control strategies based on PID controllers and their gains tuned through effective tuning techniques are presented. In addition, the concept of fuzzy logic is used to address the problem of frequency managing of PV-Thermal via effectively designing fuzzy proportional, fuzzy integral, and fuzzy PI built control strategies to ensure the frequency regulation of the energy system. The obtained results are shown via a graphical approach, and the best control design is explore and suggested for the considered system. In addition, the scope for further improvement and possible direction areas are also explored and listed in this report.
Evaluation of grid-scale battery energy storage system as an enabler for large-scale renewable energy integration
(2022-09-29) Loji, Nomhle; Davidson, Innocent Ewaen; Akindeji, Timothy Kayode
Because of many substantial benefits over other renewable energy resources (RES), photovoltaic (PV) and wind technologies are the most important emerging renewable energy sources (RES) and they are rapidly and widely propagating. However, they are nondispatchable and, the stochastic and intermittent natures of solar irradiation and wind, are some of the fundamental barriers and challenges to their development and their large-scale deployment. As a result, power systems operators have no control over DG’s available resources and are compelled to operate conventional generators to both cater for normal changes in load demand and make provision for DG’s output variations. These concerns lead to increase the uncertainty in power systems operation as they modify both the structure and the operation of the distribution network by affecting inter alia, the voltage profile and stability, the direction of network power flow and the overall performance of the power system. Enabling PV penetration into electrical grids require a balance of supply and demand that cannot be achieved by oneself. Because of the flexibility to control their real power output, batteries are suggested as a suitable and cost effective solution to mitigate the adverse effects of intermittency and shape the fluctuation of the system’s output into relatively constant power. There is a need to quantitatively investigate and evaluate the performance of the use of BESS that adequately smoothen the output of the PV-BESS sub-system for over-voltage reduction and peak load shaving during the high PV generation – low consumption time in lieu of power curtailment or reactive power injection. Using DigSILENT™ - PowerFactory™ this research work investigated the impacts of BESS on voltage stability and power losses with the aim of increasing system loadability and enhancing stability. A modified standard IEEE 9-Bus was used to perform the studies using four cases and various scenarios and the simulation results and comparative analysis first reveal that the combined effect of the Solar PV-BESS system has a substantial positive impact on the system loadability improvement and reduction of the total power system losses. Results further confirmed the BESS’s ability to act as generator, or load, respectively during high load demand/lower PV generation and lower demand//higher Solar PV generation to contribute to the voltage regulation and power system stability, offsetting effectively the intermittency of Solar PV energy sources and subsequently enabling greater RE penetration.
Harnessing tidal energy for power generation in South Africa
(2020-08) Sewnarain, Shikar; Onunka, C; Akindeji, Timothy Kayode
The growth of the world population has come with an increased demand for energy since every process requires it. The most widely used source of energy for generating electricity is coal, which contributes about forty percent. However, there is a global concern about climate change, of which the use of coal- and petroleum-based fuels are stated as contributing factors. Resultantly, demand for cleaner, sustainable energy sources is on the rise. Research indicates that tidal energy is able to generate quite a significant amount of electricity. It is against this backdrop that the research presented in this thesis was undertaken, investigating the design and development of a tidal wave barrage system for South Africa. Hence, the objective of this work is to calculate, design and simulate a tidal barrage system considering the generation capacity and cost of the system. The design enabled the calculation of the potential generation of power, as well as the required size of the tidal barrage. The calculated results were used as input for the tidal wave barrage system model, which was used in the system simulation. The system functional diagram was used in developing a function Matlab®/Simulink® model, based on mathematical models of the constituent tidal barrage components. The input parameters for this model were derived from the tidal wave data and the mechanical design properties of the turbine and generator. The Simulink® simulations showed that the tidal barrage system could generate approximately 2MW per unit - the ideal generating capacity for which each generation unit was designed. However, the Simulink® simulations do not consider the hydrodynamics of the system. The hydrodynamics of the system were simulated using DTOcean® simulation software. The input for the simulation model was derived from the theoretical calculations, the tidal wave data, the site properties, and the Simulink® results. The simulations showed a lower power output compared with the Simulink® results. The system design was completed with the results indicating there is potential for generating power from tidal waves in South Africa. The economic value and costing of the tidal plant indicate that the levelised cost of energy is comparable to that of existing tidal power plants. This thesis will assist in paving the way for further studies into the utilisation of the country’s tidal energy, with a recommendation that data for specific sites is gathered for assessment of the power generation capacity.
Investigating the application of Static Synchronous Compensator (STATCOM) for mitigating power transmission line losses
(2017) Adebiyi, Abayomi Aduragba,; Akindeji, Timothy Kayode; Naidoo, Timothy Kayode
Voltage instability and increased power loss on transmission lines are major challenges in power transmission due to ever increasing load growth. This work investigates the effect of Static Synchronous Compensator (STATCOM) to mitigate power losses and enhance the voltage stability of a transmission system. STATCOM, a shunt-connected power electronic device, operate as a Voltage Source Converter (VSC) to improve power transfer capacity of transmission lines by injecting a set of three-phase balanced sinusoidal current with controllable magnitude and phase angle into the transmission lines to regulate the line voltage and compensate for reactive power at the Point of Common Coupling (PCC). To validate the capacity of STATCOM in this light, a modified model of IEEE 14 bus test system was simulated using DIgSILENT PowerFactory v15. Four different load profiles were included by increasing the base load in a step of 10%. In each case, power flow was run with and without STATCOM incorporated in the network with a view to determine the impact of STATCOM on bus voltage and transmission line losses. The simulation results are obtained were recorded and analyzed. It is noted that there was sufficient improvement in the new voltage profile obtained for the weak buses of the system, the active and reactive power losses were mitigated by 17.73% and 24.80% respectively when STATCOM was incorporated at normal load. The results showed that STATCOM could give quick voltage support to reduce the likelihood of voltage collapse and mitigate power losses along the transmission lines. Reduction of reactive power losses along the lines is higher than the active power losses resulting in the improvement of the voltage profile as the device is connected to the system.
Modeling and recognition of faults in smart distribution grid using maching intelligence technique
(2018) Onaolapo, Adeniyi Kehinde; Akindeji, Timothy Kayode; Adetiba, Emmanuel
Electrical power systems experience unforeseen faults attributable to diverse arbitrary reasons. Unanticipated failures occurring in power systems are to be prevented from propagating to other parts of the protective system to enhance economic efficacy of electric utilities and provide better service to energy consumers. Since most consumers are directly connected to power distribution networks, there is an increasing research efforts in distribution network fault recognition and fault-types identifications to solve the problem of outages due to faults. This study focuses on fault recognition and fault-types identification in electrical power distribution system based on the Design Science Research (DSR) approach. Diverse simulations of fault types at different locations were applied to the IEEE 13 Node Test Feeder to produce three phase currents and voltages as data set for this study. This was realized by modelling the IEEE 13-node benchmark test feeder in MATLAB-Simulink R2017a. In order to achieve intelligent fault recognition and fault-type identification, different Multi-layer Perceptron Artificial Neural Networks (MLP-ANN) models were designed and subsequently trained using the generated dataset with the Neural Network toolbox in MATLAB R2017a. The fault recognition task verifies if a fault occurs or not while the fault-types identification task determines the fault class as well as the faulty phase(s). Results obtained from the various MLP-ANN models were recorded and statistically analyzed. Acceptable performances were obtained for fault recognition with the 6-25-20-15-1 MLP-ANN architecture, for fault-types identification with the 6-40-4 MLP-ANN architecture and for fault location with the 6-30-15-5-4 MLP-ANN architecture. Given the result obtained in this study, MLP-ANN is adjudged suitable for intelligent fault recognition and fault-types identification in power distribution systems. The trained MLP-ANNs in this study could ultimately be incorporated in power distribution networks within South Africa and beyond in order to enhance energy customers’ satisfaction.
Modelling and performance analysis of doubly fed induction generator wind farm
(2018) Aluko, Anuoluwapo Oluwatobiloba; Akindeji, Timothy Kayode; Dorrell, D.G.; Sewchurran, Sanjeeth
Power generation from renewable sources like wind and sun have increased substantially owing to various challenges such as government regulations, environmental pollution and depletion of non-renewable energy sources over the past few decades. Of all renewable energy sources, wind appears to be the foremost of choice due to economies of scale. Due the intermittent nature of wind, the increase in the penetration of wind power to the grid gives rise to several challenges in which power quality is the most critical. The mitigation of power quality challenges to grid-connected wind energy systems and other renewable energy plants led to the development of the renewable energy grid code. This research focuses on voltage quality as one of the power quality issues affecting connection of renewable energy plants to the grid. This research models and performs analysis of a grid-connected doubly fed induction generator (DFIG) wind farm. Using the IEEE 9 bus system as a base case for the study, the modelled wind farm is then integrated into the base case. Steady state performance and performance during faults are analyzed using load flow study and transient stability studies respectively. The load flow study is carried out to comparatively evaluate the steady state stability of the base case and the wind farm integrated network with respect to the NRS 048 South Africa standard. The transient stability study is carried out on the wind farm integrated network with compliance to the South Africa renewable energy grid code (SAREGC) which allows the wind farm to reduce active power production during a continuous low voltage event below 85% at the point of common coupling. This work compensates the wind farm with a static synchronous compensator (STATCOM) to keep the voltage at the point of common coupling above the set point, thereby keeping the wind farm connected to the grid and supplying maximum active power during a low voltage event. The results show that the static synchronous compensator allows the wind farm ride through a low voltage event without disconnection and reduction in active power supply and the wind farm increases the transient stability of the network.
Numerical and experimental investigations of the impacts of the integration of wind energy into distribution network
(2021-12-01) Behara, Ramesh Kumar; Ojo, Evans E.; Akindeji, Timothy Kayode
The growing needs for electric power around the world has resulted in fossil fuel reserves to be consumed at a much faster rate. The use of these fossil fuels such as coal, petroleum and natural gas have led to huge consequences on the environment, prompting the need for sustainable energy that meets the ever increasing demands for electrical power. To achieve this, there has been a huge attempt into the utilisation of renewable energy sources for power generation. In this context, wind energy has been identified as a promising, and environmentally friendly renewable energy option. Wind turbine technologies have undergone tremendous improvements in recent years for the generation of electrical power. Wind turbines based on doubly fed induction generators have attracted particular attention because of their advantages such as variable speed, constant frequency operation, reduced flicker, and independent control capabilities for maximum power point tracking, active and reactive powers. For modern power systems, wind farms are now preferably connected directly to the distribution systems because of cost benefits associated with installing wind power in the lower voltage networks. The integration of wind power into the distribution network creates potential technical challenges that need to be investigated and have mitigation measures outlined. Detailed in this study are both numerical and experimental models to investigate these potential challenges. The focus of this research is the analytical and experimental investigations in the integration of electrical power from wind energy into the distribution grid. Firstly, the study undertaken in this project was to carry out an analytical investigation into the integration of wind energy in the distribution network. Firstly, the numerical simulation was implemented in the MATLAB/Simulink software. Secondly, the experimental work, was conducted at the High Voltage Direct Centre at the University of KwaZulu-Natal. The goal of this project was to simulate and conduct experiments to evaluate the level of penetration of wind energy, predict the impact on the network, and propose how these impacts can be mitigated. From the models analysis, the effects of these challenges intensify with the increased integration of wind energy into the distribution network. The control strategies concept of the doubly fed induction generator connected wind turbine was addressed to ascertain the required control over the level of wind power penetration in the distribution network. Based on the investigation outcomes we establish that the impact on the voltage and power from the wind power integration in the power distribution system has a goal to maintain quality and balance between supply and demand.
Optimisation of hybrid micro-grid system for LTE base station
(2020) Leholo,Sempe Thom; Owolawi, Pius Adewale; Akindeji, Timothy Kayode
This study explores the prospect of powering a Long-Term Evolution (LTE) base transceiver station (LTE BTS) with a Hybrid Renewable Energy System (HRES) in the rural areas of South Africa. The focus of the study is on harnessing the inherent advantage in HRES which in return reduces the Greenhouse Gas (GHG) emissions and operational costs associated with a Diesel Generator (DG) used to power LTE BTS in the rural areas. Moreover, the HRES will help with enhancing stability, reliability, and sustainability of electric power supply to fulfil the required LTE BTS loads. Hence, the proposed HRES consists of Photovoltaic (PV) system, Wind Turbine (WT), a Fuel Cell (FC), Hydrogen Tank (HT), electrolyser, converter, and a Battery Storage (BS) back-up. In addition, the Hybrid Optimisation of Multiple Energy Resources (HOMER) software coupled with Matrix Laboratory (MATLAB) software tool were selected for the simulation processes of the HRES. There are two sensitive variables that were inputted into the written codes and available HOMER tool. This was done in order to achieve an optimal result. The two sensitive variables are the PV tilt angle and the WT hub height. Hence, the effects of the PV tilt angle and WT hub height from the PV and WT systems have been infused into the system. By having knowledge of the load requirements of the selected LTE BTS site, two distinct configurations (PV/WT/FC/BS) and (DG/BS) simulation results have been compared, respectively. The simulation results clearly showed that in comparison to the DG/BS system, the proposed PV/WT/FC/BS HRES reduced the Net Present Cost (NPC), and GHG emissions by values of 40% and 100%, respectively. It was observed that the Capacity Shortage Fraction (CSF) was less than 1%, while the other important indicator such as the Renewable Fraction (RF) was increased by 100%. It is clear that the proposed HRES would improve the electric power supply to the LTE BTS at a reduced NPC and acceptable GHG emissions, which in-turn, alleviates excessive costs and environmental effects from GHG emissions.
Voltage stability in distribution network
(2020-09) Masikana Sboniso Brutus; Sharma, Gulshan; Akindeji, Timothy Kayode
Voltage stability studies and to maintain the flat voltage profile is quite important in order to maintain the healthy operation of electric power network as well as to provide the quality and cheap electric energy to the modern power users. Further with the advancement of power electronics technologies and its application to design flexible alternating current transmission devices (FACTS) have made it easier to alleviate the voltage stability problem in a quicker and cheaper way in the modern DNs. Therefore, this research work shows an attempt to investigate and solve the problem of voltage instability in the distribution network (DN) with the help of FACTS. All buses and lines are calculated in terms of voltage stability index (VSI) and to identify the optimal location of FACTS. The bus or line with minimum voltage profile in terms of VSI are more sensitive to the voltage collapse and it may further lead to blackouts. Hence, the FACTS are permanently installed at the weakest point to enhance voltage profile and improve the voltage stability in the DN. The present study is tested on standard IEEE-15 bus DN and application results are shown to verify the feasibility of the present studies for DN. The beauty and future promise of UPFC in power quality improvement was authenticated on the IEEE-15 bus DN carried out using MATLAB software tool, five different scenarios were considered by increasing the load up to 40% at an interval of 10% from its nominal operating load. With the aim of determining the impact of UPFC on bus voltage and system losses, the load flow analysis was contributed on each scenario with and without UPFC placement in the DN. After UPFC placement there was a significant enhancement of voltages of all busses as well as weakest bus voltage jump from 0.5750 to 0.9750 p.u. and shifting that bus as well as system from voltage instability to stable zone. The active and reactive power loses were decrease by 9.83% and 27.27% that fulfil the beauty of the UPFC installation in the DNs as well as it promise to mitigate the voltage instability problem of the modern DNs