Faculty of Engineering and Built Environment
Permanent URI for this communityhttp://ir-dev.dut.ac.za/handle/10321/9
Browse
4 results
Search Results
Item Stability analysis of the Namibian power grid with integration of large offshore wind farms using a VSC-HVDC scheme(2022-05-13) Mbaimbai, Nicky K.; Davidson, Innocent EwaenThe use of the wind for electrical power production has seen a meteoric increase due to the wind being a free and abundantly available resource, especially when the site is offshore. The wind resource along the Namibian coastline could therefore be implemented to develop offshore wind farms that would enable Namibia to meet its steadily increasing power demand. The efficient transmission of bulk power from offshore sites to the onshore AC grid is widely achieved through voltage source converter-based high voltage direct current (VSC-HVDC) schemes. This study aims to investigate the power system stability response of the Namibian network, particularly in terms of rotor angle stability, to the integration of large offshore wind farms. A single machine infinite bus (SMIB) model developed in DIgSILENT PowerFactory was used as a test bed for the study. Transient and small-signal stability analysis in relation to different fault scenarios on the main transmission lines were then carried out after doubly-fed induction generators (DFIGs) representing offshore wind farms were integrated into the SMIB model. The same methodology was applied on a reduced model of the NamPower network. DigSILENT PowerFactory’s VSC-HVDC offshore wind farm template model was integrated to a reduced model of the NamPower network. The entire network was then subjected to different fault scenarios along backbone transmission lines, major busbars and the HVDC link at different penetration levels of offshore wind power. The study established that the integration of large offshore wind farms using a VSC-HVDC scheme to the reduced NamPower network negatively affected the network's transient and small-signal stability. However, there was a positive impact on the voltage levels of the network due to the reactive power compensation supplied by the VSC-HVDC link. The VSC-HVDC link also maintained low-voltage ride-through of the offshore wind farms during faults that comply with the Namibian transmission grid code.Item 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 KayodeThe 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.Item Power flow and faults analysis of a hybrid DC Microgrid : PV system and wind energy(2021-12-01) Zulu, Musawenkosi Lethumcebo Thanduxolo; Ojo, Evans E.; Akinrinde, Ajibola O.Rural electrification has become a very important means of improving the standard of living of rural dwellers, a process which also helps in the electrification of remote and isolated regions. Presently, the electrification of such regions can be achieved through the use of renewable energy. The use of renewable energy sources such as PV and wind energy is gaining popularity as the solution to achieving the electrification of rural areas, such as the use of the microgrid, which can be in the form of an AC or DC microgrid. The DC microgrid can be used to connect distributed energy resources and its energy storage is considered to be an economical system to meet consumer demand due to its benefits, namely environmental friendliness, reliability and good performance in load distribution. The power system may experience many faults when transferring power via overhead transmission lines to the load. When these faults occur, it is important to detect the location and isolate the part that had experienced the fault quickly, without de-activating the whole microgrid. The main aim of this study was to conduct a power flow and faults analysis on a hybrid DC microgrid model with battery storage. The hybrid energy sources for the DC microgrid are the PV system and wind energy system. Firstly, this research conducted a power flow analysis for the hybrid DC microgrid. Secondly, a fault analysis was carried out on the system and both the power flow and the fault analysis were formulated through implementation in a MATLAB/Simulink environment under various conditions in order to ascertain the stability and reliability of the system. Various MATLAB/Simulations were carried out, including the DC single-line-ground fault and DC line-line fault and are analysed in a designed hybrid DC microgrid power system. The results showed that DC line-to-line and DC line-to-ground faults lead to the imbalance of DC voltage, which is difficult to re-balance and stabilize in the system after the existence of these faults. When these faults occurred in the system, there was immense fluctuation and unsteadiness of output load power delivered to consumers. Moreover, wind-generated power on the generation side was severely affected. Based on the results and analysis of those results, the hybrid DC microgrid is seen as a satisfactory and optimum concept for the generation and transmission of power for rural and isolated area electrification, i.e. it can provide power to remote areas that cannot be reached by the national grid. The study revealed, based on the analysis of results, that it has an effective response under fault conditions. Results for a hybrid DC microgrid revealed that high quality of power is experienced in load distribution. Also based on the results, when DC faults occurs there is disturbance to output.Item Design and simulation of an optimized small wind turbine(2021-12-01) Sanjimba, Norberto Fernando Soares; Tabakov, Pavel Y.The volatility of fossil fuel's price, pollution, and emission associated with converting fos- sil fuel into a useful type of energy led man to search for more sustainable energy sources that are pollution-free and renewable. Today, renewable energy technologies, such as solar and large wind turbines, are developed to a stage of maturity, having the cost of produc- ing electricity dropping signicantly in the last decade, therefore making these technologies competitive with the traditional counterpart. The cost of producing electricity through small wind turbines is still high compared to large wind turbines or photovoltaic technology. For small wind turbines to successfully compete with other technologies and contribute to the diversication of o-grid technology, further research is needed to reduce the levelised cost of energy (LCOE). Therefore, this study aims to reduce the levelised cost of energy (LCOE) of small wind turbines. To achieve the ob- jective, a 10 kW wind turbine operating at a site of an average wind speed of 7.5 m/s was designed, optimized, and simulated. With low LCOE in mind, the turbine components were designed as simple as possible to reduce manufacturing costs. The blades are made of uniform cross-sectional area, which made possible to use aluminum as the blade material, and the blade cross-sectional area is made out of a high lift airfoil. The hub is made of aluminum and modelled and designed as a disc with holes to bolt the blades and attach the main shaft. The mainframe is treated as a thick plate with a proper arrangement to connect the generator, the main and yaw bearings, the tail support, and any other ancillaries needed. An octal tapered tower with a height of 20 m made of steel was designed and optimized for low weight. The electrical power is to be produced by a direct drive variable speed permanent magnet synchronous generator. The control system is designed in such a way that allows the turbine to operate in maximum power eciency for any speed below the rated speed, and to increase reliability, a sensorless control system is suggested. The research started with a broad review of the relevant literature on wind turbines in general and small wind turbines. The turbine blades design began by analysing the aero- dynamic performance of the blade. To accomplish that, XFoil was used to generate the aerodynamic parameters of the airfoil, the Blade Element Momentum (BEM) method was used to estimate the blades' aerodynamic performance, and Qblade was employed to com- pare the results, and Computational Fluid Dynamics (CFD) was used to verify the results. The preliminary design was done using standard IEC 61400-2 to obtain the load cases, and general engineering formulas, CFD and Finite Element Analysis (FEA) was used to analyse the load in the components according to IEC 61400-2, FAST-V7 was used to simulate the turbine's overall performance, standard formulas were used to evaluate the economic perfor- mance of the design, MatLab was used to perform all needed calculations. In this study, it is evident that using standard IEC 61400-2 to estimate the load, gyroscopic load components dominate the design, and the control system must be used to limit those loads. The designed turbine has relatively high eciency and low LCOE.