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The advantages of the Modular Multilevel Converter (MMC) as a Voltage Source Converter (VSC) is well known. These includes scalability, increased reliability, lower Total Harmonic Distortion (THD) in output variables, fault tolerance and so forth. The MMC has found its most application in High Voltage DC (HVDC) systems again because of the stated advantages. In the analysis of such systems, because...
Renewable sources like solar photovoltaic (PV) are preferred to be operated at low voltages. This necessitates high voltage boosting when they have to be connected to the high voltage DC bus. Conventional DC-DC converters (eg. boost and buck-boost) offer high voltage gain at the cost of reduced efficiency. This paper proposes a novel method to integrate low voltage PV power to the high voltage DC...
Historically, Eskom South Africa produced the cheapest electricity in the world, but this position has changed over the last decade due to several factors, such as constraints in building new generation plants within the country. This has led to under frequency load shedding and the doubling of electricity prices in the country. With the ongoing electricity price increases, connection of small scale...
Historically, Eskom South Africa produced the cheapest electricity in the world, but this position has changed over the last decade due to several factors, such as constraints in building new generation plants within the country. This has led to under frequency load shedding and the doubling of electricity prices in the country. With the ongoing electricity price increases, connection of small scale...
Rising energy costs, growing public concern about environmental impacts of fossil fuel energy generating resources and energy constraints of utilities across the globe have increased the relevance and need for alternative renewable energy resources at the customers point of use. In South Africa, there is a strong interest from electricity suppliers and customers in rooftop photovoltaic systems connection...
Plug-in electric vehicles are the driving force behind a paradigm not only in the auto industry but also in the electric power sector. This paper explores the possibility of plug-in electric vehicles serving as electrical energy storage (EES) devices in a microgrid-in the so called vehicle-to-grid concept in Ghana. A vehicle-to-grid technology assisted microgrid is proposed as a solution to address...
The increased use of non-linear loads such as lighting technologies (bulbs) has led to power quality variation of distribution networks. In recent times, different lighting technologies are finding their ways into the market. As such, it is paramount to evaluate the performance characteristics of these lighting technologies and the possible effects they might have on the power network. In this paper,...
Squirrel-cage induction generator wind power plant requires the provision of reactive power for self-excitation and to sustain the generated voltage. The Katsina wind power plant comprising of several squirrel cage generators, each has a fixed capacitor bank connected in shunt to the wind turbine generator provide the needed reactive power. These capacitors are selected to enable the excitation of...
This paper sets forth the decoupling procedures for a triple-star interior permanent magnet machines where the inductances are mutually coupled between the three machine sets when the original model equations are transformed to the rotor reference frame. Dynamic and steady-state analyses based on this coupled model is complicated. It is very hard to ensure total independence of the controllers for...
This article presents an inverting Nx multilevel boost converter (Inverting Nx MBC) with continuous input current for DC link applications where several negative voltage levels are required with self-balancing such as photovoltaic (PV) multilevel inverter systems. The voltage obtains from the photovoltaic array need to boost before a feed to inverter for practical utilization or grid connect. In this...
The bidirectional DC-DC three level converter (TLC) has been proposed as a viable choice for vehicular applications due to its high efficiency, low ripple harmonics and compact size. In this study we investigate the performance of the TLC when operated in a combination of duty cycles that are not the same (d1 ≠ d4). Using the model equations of the converter derived using the switching function approach,...
This paper presents a new multiphase-multilevel inverter configuration for open-winding loads and suitable for medium power (low-voltage/high-current) applications such as ‘More Electric Aircraft’. Modular structure comprised of standard dual three-phase voltage source inverter (VSI) along with one additional bi-directional semi-conductor device (MOSFET/IGBT) per phase and two capacitors with neutral...
In this paper triple-star nine phase symmetrical and asymmetrical wound IPM machines are modeled by means of the full order coupled models which are required to predict all the possible influences of the harmonics generated due to winding distributions and the saliency of the rotor structure. A simplified model which predicts the average components behavior is also determined. Comparative computer...
This article presents the developments of a novel isolated/non-isolated quad inverter configuration for multilevel dual six-phase (twelve-phase) star-winding converter. The modular circuit consists of four standard voltage source inverters (VSIs). Each VSI is incorporated with one bi-directional switch (MOSFET/IGBT) per phase and links with the neutral line through two capacitors which allows symmetrical...
The paper presents a speed and current controller design that provides the maximum power from the wind turbine and minimizes copper loss of the generator under varying wind speed. The paper also presents a grid side inverter controller design which keeps the DC link voltage of the inverter constant and controls reactive power flow to maintain unity power factor. Additionally, an estimated frequency...
Wind power is both an efficient and reliable form of clean source of renewable energy. It can be an excellent method of harnessing renewable energy from locations where there is availability of land. The Katsina Wind Farm (WF) project was designed to be a pilot project because it is the first WF in West Africa. The project covers 200hectares (10,000m2/hectare) of land. The monthly average temperature...
This study evaluates the electrical energy use patterns of 2 Nigerian food and beverage industries (FBI) over a period of 4 years (2010–2013) with the aim of developing an index that measures the energy efficiency of producing a finished product. The data used for the study consist of monthly diesel consumption (liters), electricity consumption (kWh), the mass of finished product (kg and unit mass...
Increasing pressure from both customers and regulators to maintain and enhance service reliability, while at the same time controlling costs has put power utilities on their toes. In view of this, asset management has become an increasingly important aspect of power business strategies such that electricity companies can utilize assets to the fullest while maintaining system reliability. This paper...
This paper describes a novel proposal of double quad-inverter configuration for multilevel twelve-phase open-winding ac converter. Modular power units are developed from reconfigured eight classical three-phase voltage source inverters (VSIs). Each VSI has one additional bi-directional switching device (MOSFET/IGBT) per each phase and linked neutral with two capacitors. An original modified single...
Under-frequency load shedding, rising electricity prices, changing environmental regulations and delays in constructing new power stations have plunged South Africa into one of its greatest challenges ever in the electricity sector. This has led consumers and producers alike to explore various energy generation options to assist the sector to meet the electricity demands. Electric utilities are faced...
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