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The objective of the research is to develop a cost-effective, dynamic grid controller called the controllable network transformer (CNT) that can be implemented by augmenting existing load tap changing (LTC) transformers with an AC-AC converter. The concept is based on using a fractionally rated direct AC-AC converter to control the power through an existing passive LTC. By using a modulation strategy based on virtual quadrature sources (VQS), it is possible to control both the magnitude and the phase angle of the output voltage of the CNT without having any inter-phase connections. The CNT architecture has many advantages over existing power flow controllers, like absence of low frequency storage, fractional converter rating, retro-fitting existing assets and independent per-phase operation making it potentially attractive for utility applications. The independent control of the magnitude and the phase angle of the output voltage allow independent real and reactive power flow control through the CNT-controlled line. In a meshed network with asymmetric network stresses this functionality can be used to redirect power from critically loaded assets to other relatively under-utilized parallel paths. The power flow controllability of CNT can thus be used to lower the overall cost of generation of power. The solid state switches in the CNT with fast response capability enable incorporation of various additional critical functionalities like grid fault ride through, bypassing internal faults and dynamic damping. This bouquet of features makes the CNT useful under both steady state and transient conditions without compromising the grid reliability.

The planning of distribution systems consists in determining the optimum site and size of new substations and feeders in order to satisfy the future power demand with minimum investment and operational costs and an acceptable level of reliability. This problem is a combinatorial, non-linear and constrained optimization problem. Several solution methods based on genetic algorithms have been reported in the literature; however, some of these methods have been reported with applications to small systems while others have long solution time. In addition, the vast majority of the developed methods handle planning problems simplifying them as single-objective problems but, there are some planning aspects that can not be combined into a single scalar objective; therefore, they require to be treated separately. The cause of these shortcomings is the poor representation of the potential solutions and their genetic operators This thesis presents the design of a genetic algorithm using a direct representation technique and specialized genetic operators for power distribution system expansion planning problems. These operators effectively preserve and exploit critical configurations that contribute to the optimization of the objective function. The constraints of the problems are efficiently handle with new strategies. The genetic algorithm was tested on several theoretical and real large-scale power distribution systems. Problems of network reconfiguration for loss reduction were also included in order to show the potential of the algorithm to resolve operational problems. Both single-objective and multi-objective formulations were considered in the tests. The results were compared with results from other heuristic methods such as ant colony system algorithms, evolutionary programming, differential evolution and other genetic algorithms reported in the literature. From these comparisons it was concluded that the proposed genetic algorithm is suitable to resolve problems of largescale power distribution system planning. Moreover, the algorithm proved to be effective, efficient and robust with better performance than other previous methods.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017. / High Voltage Direct Current (HVDC) transmission is a safe and efficient technology designed to deliver large amounts of electrical power over long distances with minimal losses and at low costs. HVDC links require converters and filters at both terminal stations. The core component of the HVDC system is the power converter that connects the DC and AC systems together. The conversion from AC to DC, and vice versa, is achieved mainly through electronic switches called thyristors. The thyristor-based Line Commutated Converter (LCC) is a mature and trusted technology for HVDC transmission throughout the world. HVDC converters are bidirectional and can function in either rectification (AC to DC) or inversion mode (DC to AC). This is achieved when the voltage polarity across the converter gets swapped by the controllers, because current cannot change its direction in thyristors. In this thesis an analytical model of the HVDC converters is developed in the frequency domain by modelling it in DIgSILENT. The objective is to study the harmonics induced to the AC side from HVDC converters. Therefore, it is important in the real world to understand the principles, what causes harmonics to be generated in HVDC and transferred to the HVAC system. The objective of this thesis is to investigate the effectiveness of mitigation techniques used, on how they reduce harmonics by keeping these harmonic levels within specified values admissible by international standards (e.g. IEEE, etc).

M.Ing. / Traditionally, the Electricity Supply Industry (ESI) organisational structure consisted of generating plant, transmission and distribution networks, a regulating authority and network control, all vertically integrated into single organisational structure. The result of the vertically integrated organisational structure, in other words an organisation where all the functions belong to a single organisation, and some of the organisation's functions are not the sole responsibility of one specific functional area, has been a captive market for the industry. No real market forces existed to control the industry. The responsibility for the industry was traditionally left in the hands of a single organisation, accountable only to the regulating authority. However, the industry has recently been subjected to incredible pressure to reform. The incentive to reform is based on various factors, ranging from sound business decisions, the need to reduce government debt, reduction of primary energy cost for key industries to political pressure. A common thread throughout the reform exercise is the requirement that competition must be introduced into the ESI to ensure market forces on the industry. To introduce competition into the industry, the authorities often start by unbundling the different functions in the industry. The second step is to identify the functions that can only operate effectively as a monopoly. The authorities then need to determine the optimum balance between regulatory rules and requirements and market forces on the. industry. By introducing the optimum balance between industry regulation, market forces and the specific needs of each country, the changes in the industry may result in long term gain for the industry's host country. The gains are often measured in reduced electricity cost and growth in industries dependant on the ESI as a primary energy source. The study incorporates a wide range of issues, starting with the drivers behind the deregulation effort through management tools to regulatory rules and requirements in the deregulated environment. The study evaluates the risks and benefits of the deregulated market, and examines the tools adopted from the financial markets and used in the new electricity markets. The requirement for regulatory rules will be evident throughout the dissertation, and will be discussed in detail in the final chapter. The study is concluded with the message that the common factors and resultant solutions are of such a nature that it would not be necessary to develop a new set of rules, regulations and management tools for a country starting down the road of deregulation. It would however be required to determine the needs of the industry's host country and to adapt the current tools and regulatory rules to the country it is implemented in. The final outcome of the dissertation is that the post-deregulated industry has only just started operating under the new regulatory regime and using the newly developed electricity markets. The industry is still subject to a severe learning curve, adapting and developing daily to satisfy the needs of a deregulated industry. There are sections of the industry that still need to be examined and optimised. However, the success of some of the deregulation efforts in the industry, and especially the deregulation in the UK confidently underwrite any equivalent exercise in the ESI.

Current trends in electric power consumption indicate an increasing use of dc in end-user equipment, such as computers and other electronic appliances used in households and offices. With a dc power system, ac/dc conversion within these loads can be avoided, and losses reduced. AC/DC conversion is instead centralized, and by using efficient, fully controllable power-electronic interfaces, high power quality for both ac and dc systems during steady state and ac grid disturbances can be obtained. Connection of back-up energy storage and small-size generation is also easier to realize in a dc power system. To facilitate practical application, it is important that the shift from ac to dc can be implemented with minimal changes. Results from measurements carried out on common household appliances show that most loads are able to operate with dc supply without any modifications. Furthermore, simple, and yet sufficiently accurate, load models have been derived using the measurement results. The models have been used for further analysis of the dc system, both in steady state and during transients. AC microgrids have gained research interest during the last years. A microgrid is a part of power systems which can operate both connected to the ac grid, and autonomously in island mode when the loads are supplied from locally distributed resources. A low-voltage dc microgrid can be used to supply sensitive electronic loads, since it combines the advantages of using a dc supply for electronic loads, and using local generation to supply sensitive loads. An example of a commercial power system which can benefit from using a dc microgrid is data center. The lower losses due to fewer power conversion steps results in less heat which need to be cooled, and therefore the operation costs are lowered. To ensure reliable operation of a low-voltage dc microgrid, well-designed control and protection systems are needed. An adaptive controller is required to coordinate the different resources based on the load-generation balance in the microgrid, and status of the ac grid. The performance of the developed controller has been studied and evaluated through simulations. The results show that it is possible to extend use of the data center dc microgrid to also support a limited amount of ac loads close to the data center, for example an office building. A protection-system design for low-voltage dc microgrids has been proposed, and different protection devices and grounding methods have been presented. Moreover, different fault types and their impact on the system have been analyzed. The type of protection that can be used depends on the sensitivity of the components in the microgrid. Detection methods for different components have been suggested in order to achieve a fast and accurate fault clearing. An experimental small-scale dc power system has been used to supply different loads, both during normal and fault conditions. A three-phase two-level voltage source converter in series with a Buck converter was used to interconnect the ac and the dc power systems. Together the converters have large controllability, high power quality performance, and allow bi-directional power flow. This topology can preferably be used together with energy storage. The tests confirm the feasibility of using a dc power system to supply sensitive electronic loads. / QC 20100908

M.Com. (Informatics) / Critical Infrastructure is the term used to describe assets that are of utmost importance, or in other words, essential in the functioning of an environment. Societies depend on their critical infrastructure in order to maintain and continuously improve on their population’s standard of living. The creation of more self-sustainable methods of energy consumption and generation drives towards the creation of a better and more efficient evolution of the power grid critical infrastructure, named the smart grid. The introduction of the smart grid brought in a paradigm shift towards the practices used to manage the generation and distribution of electric power. The introduction of highly capable information systems to intrinsically work with current power grid technologies provided the ability to enhance economic and environmental efficiency of power systems. Although providing a wide variety of benefits, such information systems also created new points of vulnerabilities, which if exploited, place the smart grid at risk of disruptions. In order to address the security issues that occur at the application and data exchange level of smart grid information systems, the dissertation proposed the use of a security model to protect the smart grid. The Multi-Agent Smart Grid Security (MA-SGS) model is based on the use of multiple autonomous intelligent software agents which attempt to create operational stability and efficiency in the smart grid...

The objective of this research is to assess the impact to the Nelson Mandela Bay Municipality due to ongoing Electricity Distribution Industry Restructuring in South Africa as directed by the Electricity Distribution Industry Holdings on behalf of the Department of Minerals and Energy’s adopted Electricity Distribution Blue Print Report of 2001. Literature review of scholarly literature was conducted on privatisation of public utilities that offered an international perspective on experiences of other countries that has undergone similar experiences of restructuring of public assets, the state of Electricity Supply Industry in South Africa with the demonstration of structural financial and physical flows and historical background of the restructuring, proposed future model and strategic plans to achieve the future goals. Research methodology and design was done through combination of the four-research types classification in their order of sophistication except the predictive research, namely exploratory, descriptive, and analytical or explanatory researches with a further inclusion of deductive research. The compilation of data through questionnaires was also employed. Perceptions on internal impact to the NMBM due to electricity services restructuring were solicited from the sample of the top management of the NMBM, the intention was to ensure the economies of scale, greater transparency and competition in terms of service delivery were sustained during and beyond Regional Electricity Distributor establishment. Financial position of NMBM as a critical instrument for its progress has to be protected to ensure it fulfils its constitutional development mandate. The findings of the research were in strong support of ensuring operational financial viability; to meet the legitimate employment, economic and social interest of all employees; development and implementation of change management strategies; and NMBM assuming leading role in the process.

Cellular networks in Africa have grown exponentially over the past 10 years and their data centres (DCs) on average consume 3 MW of electrical power. They require a reliable electrical power supply and can have a downtime loss of over a million dollars per hour. Power quality, reliability and availability have emerged as key issues for the successful operation of a data centre. Investigations are carried out into emerging technologies and their application in data centre power distribution systems for cellular networks in Africa. Best practices are applied to develop a power distribution system (PDS) with the objective of achieving optimal reliability and availability. Analytical techniques are applied to determine and compare the reliability and availability of various power systems. Minimal cut set simulations identify system weak points and confirm component selection. Components’ inherent characteristics (CIC) and system connectivity topology (SCT) are key factors in the improvement of data centre availability. The analysis practices can be used by engineers and managers as a basis for informed decision making in determining power system reliability and the availability of an existing or a new data centre design. Weak points in the PDS of a data centre causing downtime are identified through analysis, and accurate solutions can be determined to prevent or minimise downtime. System connectivity topology (SCT) techniques were identified that could increase the reliability and availability of data centres for cellular networks in Africa. These techniques include multiple incomers from the utility company, redundancy levels of critical equipment and parallel distribution paths. Two case studies were carried out on data centres for a cellular network, one in Nigeria and one in Cameroon. The reliability and availability of both data centres was improved, with substantial reduction in downtime per year. The outcome of the case studies shows the importance of designing and implementing the power distribution system with sufficient levels of redundancy for critical equipment, and parallel distribution paths. / MSc (Engineering Sciences in Nuclear Engineering), North-West University, Potchefstroom Campus, 2014