Josiah L. Munda

Feasibility study of a hybrid PV-micro hydro system for rural electrification

The present study investigates the possibility of using a stand-alone solar/micro hydro hybrid power system for low-cost electricity production which can satisfy the energy load requirements of a typical remote and isolated rural area. In this context, the optimal dimensions to improve the technical and economical performances of the hybrid system are determined according to the load energy requirements, the solar and water resources and the importance of supply continuity. The proposed systems installation and operating costs are simulated using the Hybrid Optimization Model for Electric Renewable (HOMER) with the stream flow, the solar radiation and the system components costs as inputs; and then compared with those of other supply options such as grid extension and diesel generation.

Economic and environmental analysis of micro hydropower system for rural power supply

This paper discusses the advantages of using renewable energy sources in the architecture of an off-grid hybrid power system in rural areas. The studied system is composed of a diesel generator to which a micro hydropower plant is added. Simulations using the Hybrid Optimization Model for Electric Renewable (HOMER) are performed for given annual values of hydro resources, power demands and hybrid system component costs. The results highlight the cost-effectiveness character and the reduction of gas pollutant emissions achieved by using such a system rather than a diesel generator to supply the same load.

Particle swarm optimized T-S fuzzy logic controller for maximum power point tracking in a photovoltaic system

A particle swarm optimized Takagi-Sugeno (T-S) fuzzy logic controller for maximum power point tracking in a photovoltaic (PV) system is presented. The method proposed automates the tuning of fuzzy logic controller (FLC) rules and membership functions as opposed to the trial-and-error approach. Expert knowledge used for tuning the FLC is extracted from an improved PV module model under varying solar radiation, temperature, and load conditions. The proposed optimized FLC provides fast and accurate tracking of the maximum power point (MPP) under varying operating conditions. The formulation, implementation, and simulation results are presented. Results obtained has shown that the optimized FLC gives a better performance compared with the conventional FLC tuned using trial and error.

The ieee 34 node radial test feeder as a simulation testbench for Distributed Generation

The advent of distributed generation introduces new challenges and possibilities of controlling reactive power and regulating voltage in distribution systems. In addition, dynamic behavior of the distribution system is influenced by the presence of Distributed Generation (DG). As a result, the impact of DG on distribution system radial feeders and laterals needs to be evaluated in terms of steady state normal and transient conditions before implementation. Several computer programs exist to carry out such simulations and this paper focuses on DigSILENT PowerFactory. Power Factory provides steady state solutions for balanced and unbalanced load flow for both transmission and distribution networks, short circuit calculations and, it also provides dynamic solutions for transient studies. The main objective of this work is to establish a test bench in PowerFactory and report steady state results. The simulation test bench is to be used in ongoing research work for analysis of the impact of various forms of DG on distribution networks. The IEEE 34 Node test feeder is modeled and results are compared with those of the IEEE distribution system analysis subcommittee.

Stability Analysis and Control of a Wind Turbine-Driven Induction Generator

This article presents the details of various methods of analysis suitable for dynamic and transient stability analysis of an induction generator-infinite bus power system, under various control strategies. The mechanical torque of the generator is obtained from a pitch-controlled wind turbine. Self-excitation of the induction generator is from a terminal capacitor, the value of which is also controlled. Step-by-step simulation studies are performed under conventional control methods. Fuzzy logic control is then introduced in the control of the terminal capacitor and the wind turbine blade pitch angle.

VSC HVDC transmission corridor: An option for PV power injection and AC network stability support

The pressure of increasing power demand and supply inequality is forcing utilities to interconnect AC systems to meet demands. High Voltage Direct Current (HVDC) schemes are becoming a more attractive solution as they have been used extensively in interconnected power systems worldwide. This paper investigates the role of voltage source converter (VSC) based HVDC transmission corridor for PV power injection and for AC network stability support. Overview of Namibia Caprivi-link interconnector a case study, potential of very large scale PV in Namibia and prospects of PV power injection on the DC-link is presented. The system is modelled simulated in Matlab/Simulink. Critical contingencies such as sudden island conditions, three-phase to ground fault are simulated with and without PV penetration. Results show the stability support on the AC side networks by PV power injection on the dc-link.

Distribution network reconfiguration using genetic algorithm and load flow

There are various ways of reducing active power losses in distribution networks. Network reconfiguration is one of the most important methods. However, it can be a very difficult optimisation problem. The proposed Genetic Algorithm with Rank Weight selection is used to search the population for the optimum solution in the network. The chromosome is represented by a string of binary numbers (zeroes, 0s and ones, 1s). By opening one switch in each loop (fundamental loop approach), almost all the solutions will be feasible (radial networks). By doing this the chromosome will only consist of the open switches (Genotype); thus reducing the computation time. Constraints are used to filter the search by means of penalty factors, which guarantees the solution found by the Genetic Algorithm to be feasible.

Input-output linearizing and decoupling control of a nonholonomic power wheelchair

While nonholonomic-powered wheelchairs (NPWs) have made advances over the past three decades, the control algorithms remain virtually unchanged since 1980s. The simple proportional-integral (PI) controller is antiquated, and does not perform well in the presence of disturbances, sensors uncertainties, nonlinearities and load variations. The practical interest is driven by the fact that todays wheelchairs need to be operated under tighter performance specifications. At the same time more and more constraints, stemming for example from environmental and safety considerations, need to be satisfied. Often these demands can only be met when nonlinearities and constraints are explicitly considered in the controller. A new approach to trajectory tracking control for wheelchair systems containing uncertain, nonsmooth nonlinearities is proposed. The method is based on decoupling theory and system input-output feedback linearization technique by which the system stability and convergence of velocity tracking errors to zero are rigorously examined. The effectiveness and efficiency of the proposed controller is demonstrated through simulation studies. The study would result in better driving performance, smoother feel, and fewer accidents or inadvertent collisions.

DC motor control via high order differential feedback control

In practice, there are many motor systems whose models are usually unknown or partially unknown. However, the majority of control schemes focus on model-dependent techniques. To cope up with unavailable dynamics, a model-free controlling problem for a DC motor system is investigated in this study. A robust higher-order differential feedback controller (HODFC), which does not depend on the model of the controlled DC motor system, is applied. The controller only utilizes the information of the measured output and the given objective as well as the extracted differentials of those via higher-order differentiator (HOD). Simulation results show that HODFC successfully controls the uncertain DC motor system, and can drive its trajectories to desired steady states subject to unknown bounded disturbance. Stability, convergence and robustness of PID, Fuzzy and HODFC control schemes for the closed-loop system behavior are compared. From the performance comparisons, the robust HODFC control system yields favorable control performance superior to that of PID and Fuzzy control systems. Moreover, it not only has a learning ability similar to that of Fuzzy control but also a simple control structure as PID control.

Residential Lighting Modelling: ANFIS Approach in Comparison with Linear Regression

Most practices applied in the development of lighting usage profile do not reflect the complexity occupants have on lighting loads in residential buildings. This study involves the use of Adaptive Neural Fuzzy Inference System (ANFIS) and regression model for residential load usage profile development, prediction and evaluation for energy and demand side management initiatives. Three variables namely natural light, occupancy (active) and income level were considered in this study. A better correlation of fit and reduced root mean square error was obtained in comparison with the regression model. The developed approach (ANFIS) has the ability to give better lighting prediction accuracy in relation to non-linearity data and behavioural tendencies.