A complete dynamic model of a wind turbine was found to have increasing errors as the electrical current increased. After investigation it was found to be related to an increase in the stator resistance with current. This paper presents how these changes in resistance affect the generator and wind turbine performance, while comparing the model results to field data. A model was created to predict stator resistance changes at different currents using the experimental field data.

The novel use of the Euclidean distance between consecutive pixel intensity values is presented as a solution for railway line detection and tracking. The Euclidean distance between consecutive pixel intensity values, a searching strategy and a mathematical tool, in the form of collinearity testing, are the key elements of this method of railway line detection and tracking. The Euclidean distance between consecutive pixels’ intensity values defines edges. Four points are marked where significant changes in pixel intensity values occur on two horizontal lines across an image; two on each line. These points are used for detecting and tracking railway line tracks using the collinearity test of the cross product of two vectors. The four points are also used as the control points for correcting perspective distortion in an image, better known as transforming the image into a bird’s-eye view using the Top View Transformation model. Finally, the four points are used in calculating the changes in the pitch angle as the altitude of the railway line track bed rises and falls. The changes in the pitch angle are used in a model to stabilize the transformation of the image into the bird’s-eye view. The searching strategy, which is the cornerstone of this algorithm refers to the placement of the two lines across the image. An equation is presented that governs how far apart the two lines should be based on the curvature of the railway line track.

Driver assisted and autonomous driving systems are now moving from feature to model detection using machine learning for detecting rail-road boundaries. It is ideal that these models are extracted from real world environments rather than synthetically generated models. Where possible, railroad modelling systems should be used in real-time applications that do not require much processing power. A railroad modelling systems can be used as a building block for other systems like object detection; the model serves as the region of interest to search for impending obstacles. Since the railroad modelling systems can be used for real-time and offline applications it is imperative that the railroad model be traced out as closely as possible. Most railroad modelling algorithms approximate the railroad boundaries as a linear model though this is not always the case.

Small wind turbine sites, in general, use a 0.5Hz sampling interval and a 10-minute averaging interval for a feasibility study or turbine testing. Studies have established that the calculated performance variation of small wind turbines when averaging at large time intervals. The performance variation is larger for sites with high wind variability. However, these studies are often based on low sampling frequency and high averaging intervals. In the present study, wind speed data has been measured at a high sampling frequency of 20Hz with an ultrasonic sensor. A dynamic model of a 50W Rutland wind turbine is used to analyse the simulated performance using wind speed data at a range of sampling intervals and some averaging intervals. The wind turbine and the anemometer are installed in a residential area of high wind variability. The energy is calculated and compared directly using the wind turbine model and using the IEC recommended method of bins. The direct method results show that the rise in instantaneous sampling intervals up to 20 seconds has an insignificant effect on the energy output. Whereas, for 2-seconds sampled wind data averaged over 10-minutes, energy overestimates of 19% is observed. However, where only 10-minute interval averaged wind data are available, there is a significant underestimate in energy by 45%. The energy calculated using the method of bins overestimates the energy by 19% for high resolution wind data and underestimates by 22% for 10-minute average data.

Lines play a very important role in image processing and computer vision. They are a clue or a feature that enables further processing of an image, both in the image processing and computer vision fields. It is therefore imperative that they are accurately extracted or detected. The clues obtained from an image are used to calculate the line parameters, which tends to be an efficient way to detect lines. The strength of the proposed algorithm is its ability to limit the search area simply. The context of detecting straight lines in this research is mainly for the implementation of Autonomous Driving Systems (ADS) and Driver Assisted Systems (DAS) for trains. The proposed algorithm can be implemented in many image processing and computer vision procedures that require straight line detection.

Simli is a village of 450 households with a minigrid supplied solely by a 29kW microhydro system. The very weak grid performance during the dry season is presented and the interactions between energy use and grid operating practices are investigated. The results are given for eight households, trialling four types of electric cookers, in order to reduce firewood use. There is considerable interaction between the electric cookers and the power system. The effects of the power system and the electric stoves on the cooking preferences is also revealed. The addition of electric stoves during the evening cooking hours lead to an increase in the frequency of short power outages causing major interruptions while cooking.

The design process for a single phase, smart, universal charger for light electric vehicles, is presented. With a step up, power factor correction circuit, followed by a phase shifted, full bridge converter, with synchronous rectification on the secondary side. Due to the resistor-capacitor-diode snubber on the secondary side, the current peak at the start of power transfer, leads to false triggering during light load control with peak current mode control. The solution developed for light loads, is to change from peak current control to voltage control. This is achieved by limiting the maximum phase shift, instead of changing the reference value. For the power factor correction stage, measured and calculated efficiencies are compared as a function of the output power. The voltage and current waveforms are shown for the power factor correction circuit, and for the phase shifted bridge, the measured current waveform is compared with simulation.

This paper presents a review of some options for electrifying low income areas. Various reasons for non electrification are presented and the benefits of electrification are shown to be highly variable. Types of communities without electrification are described including those that may be in the midst of electrified areas. Types of electrification are described in terms of the configuration. Two case studies are presented where the electrification has not functioned well and reasons are given for this.

Filters in photovoltaic inverters play a vital role of attenuating high frequency harmonics and improving the quality of the power transferred from the photovoltaic (PV) panels to the grid. Inverter filters form part of the inverter output impedance and can be connected to the grid even if the inverter does not produce any active power. This paper focuses on the impact of inverter filters on the low voltage (LV) network impedance and assess the change in existing harmonic current and voltages. The impact of inverter filters on the network series and parallel resonance impedance assuming high proliferation of PV energy is assessed, including the resulting change in flow of harmonic current and voltage distortions.

Active power filters are required to compensate for the harmonic distortion of the supply arising from downstream nonlinear loads by identifying the distortion of the load current and injecting a compensating current into the ac system. Crucial to the compensation performance of the filter is the identification of the reference current. In the design process, explicit consideration of the elements of the reference current is necessary to achieve harmonic current cancellation, reactive power compensation, load balancing and neutral current compensation. Upstream poor quality supply voltage compromises the identification process and thus the compensation effectiveness. In this paper, a review is made of the significance of the elements that make up the reference current and their consideration or limitation in various reference identification methods.

Insulated Gate Bipolar Transistors (IGBTs) are semiconductor devices used in power modules for inverters and in many other applications. The challenge however is that these devices do not last their estimated life span of about 20 years and experience different failure mechanisms. It is of interest to study the failure mechanisms to give a better understanding of how to improve reliability of these devices as well as model and accurately predict the lifetime of IGBTs. The IGBT circuitry is encapsulated in silicone gel and the presence of this silicone gel prevents visual inspection of the type of failure mechanism that was experienced by the IGBT. When using a scanning electron microscope to examine the failed module, the sample may need to be gold plated and will be placed in a vacuum. Any silicone gel remaining on the IGBT module under investigation will vaporise and coat parts of the electron microscope thus damaging the microscope. Hence there is need to be able to remove all the silicone gel from the IGBT module before proper investigation into the mechanism that caused failure can begin. The results of these experiments show a practical approach on how to remove silicone in the laboratory from IGBT modules without causing any further corrossive damage to the modules under investigation.

Nonlinear loads draw a distorted current from the supply containing both nonzero and zero sequence harmonic amplitudes. In a three phase four wire network, such loads would also result in a high neutral current. This paper compares the design and performance of four branch shunt passive filter topologies in a three phase four wire stiff grid to selectively filter both nonzero and zero sequence harmonics. The results have shown the effectiveness of the filter to attenuate nonzero sequence harmonics and the limitation, due to system resonance, to attenuate zero sequence harmonics. A modified passive filter with a supply side neutral impedance is presented in this paper to improve filter performance. Computer simulation as well as experimental setup were implemented for the comparison and results have shown the effectiveness of the modified passive filter to selectively filter both nonzero and zero sequence harmonics.

Inverter filters are used to attenuate high frequency harmonics and improve power quality in grid connected inverters. In some basic grid connected inverters, inverter filters can be left connected to the grid when the inverter is not producing any active power. This paper focuses on the effect of grid connected inverter filters on a power system particularly on low voltage networks. It will assess the effects of inverter filters connected to the grid, assuming a high proliferation of photovoltaic energy systems on a low voltage distribution network that is designed to meet South African standards.

Examples are given of differing techniques of non-destructive imaging of semiconductor devices in order to detect faults which may affect their lifetime. Images are shown from optical microscopy and also X-ray systems to illustrate the visibility of faults under differing visualisation techniques. The techniques also include three dimensional visualisation. Issues with the silicone gel are described and separation of the silicon and aluminium cross sections.

Single phase induction motors typically require 7 times their rated current to provide the necessary starting torque. This provides a challenge in weak electrical systems. The work presented in this paper illustrates that starting a refrigerator compressor motor from a non-zero frequency supply with v/f ratio changing and a suitable ramp time a reduction in starting current is observed while being able to provide starting torque required.

A novel polarization based optical fibre sensor for monitoring the frequency as well as the plane of vibrations in renewable energy wind turbines is presented. We successfully demonstrate operation for vibrations from 57-117 Hz, with simultaneous sensing in two orthogonal planes.

This paper gives the results of an investigation on the use of exhaustive block matching techniques in detecting railway-line tracks in a video sequence with the view of implementing the outcome in a real-time system. The main focus of the research is to implement the exhaustive search block matching algorithm optimally and resolve any implementation problems that may arise. The algorithm is implemented on a video sequence that has undergone inverse perspective mapping. The second highlight of this research is to eliminate many video processing techniques, this is done in order to compensate for the computational expense for which the exhaustive search block matching algorithm is known for. The procedure entails traversing a very small block from the previous frame on the top and bottom ends of the current frame and marking the coordinates where the cost function is the minimum.

Informal settlements are often temporary settlements which exist without the usual residential infrastructure, including no electricity. This paper presents a case study for a particular informal settlement in terms of 3 possibilities of a styles of electrification, consisting of grid connection, photovoltaic systems for large household solar and small household solar systems. The effect of no land tenure is shown to be an overriding factor.

When photovoltaic systems are used as the energy source to start motors, the resultant voltage drop can be too large to enable effective starting. An active filter circuit using inductor energy storage is described, which can be used to maintain the output voltage. Simulation and experimental results are shown

Constant voltage and frequency can be generated by a Self-Excited Induction Generator (SEIG) driven with a fixed-speed low-head hydro-turbine when a constant electrical load is maintained by an Electronic Load Controller (ELC). In the Conventional-ELC (C-ELC), usually a chopper with a dump load is used in parallel with the consumer loads to provide regulation of voltage and control of frequency. In the C-ELC configuration a high degree of stress can be experienced by stator windings and excitation capacitors resulting from chopper operation, since in each chopping period the dump load is connected to the stator winding for a short period then disconnected. A new ELC topology is proposed to reduce this stress. Compared with the C-ELC, the main dump load has been divided into two separated parts. A part of the dump load can be connected in parallel with the consumer loads, resulting in less variation in the total load seen by the SEIG and less stress on the stator windings and excitation capacitors. This proposed topology can be utilized per-phase using bi-directional power switches, hence it can operate with unbalanced consumer loads. Simulation results demonstrate that even with unbalanced three-phase loads (assisted with bi-directional switches per-phase), the proposed topology has the capability to regulate voltage from no-load to full load. Moreover, the Total Harmonic Distortion (THD) analysis for output (stator) current shows a 9% improvement compared with the most recent results in the literature.