Power quality improvement in low voltage distribution network utilizing improved unified power quality conditioner.

Doctoral Degree. University of KwaZulu-Natal, Durban.The upgrade of the power system, network, and as it attained some complexity level, the voltage related problems and power loss has become frequently pronounced. The power quality challenges load at extreme end of the feeder like voltage sag and swell, and power loss at load centre due to peak load as not received adequate attention. Therefore, this research proposes a Power Angle Control PAC approach for enhancing voltage profile and mitigating voltage sag, voltage swell, and reduced power loss in low voltage radial distribution system (RDS). The amelioration of voltage sag, voltage swell, weak voltage profile, and power loss with a capable power electronics-based power controller device known as Improve Unified Power Quality Conditioner I-UPQC was conceived. Also, the same controller was optimally implemented using hybrid of genetic algorithm and improved particle swarm optimization GA-IPSO in RDS to mitigate the voltage issues, and power loss experienced at peak loading. A new control design-model of Power Angle Control (PAC) of the UPQC has been designed and established using direct, quadrature, and zero components dq0 and proportional integral (PI) controller method. The simulation was implemented in MATLAB/Simulink environment. The results obtained at steady-state condition and when the new I-UPQC was connected show that series inverter can participate actively in ameliorating in the process of mitigating sag and swell by maintaining a PAC of 25% improvement. It was observed that power loss reduced from 1.7% to 1.5% and the feeder is within the standard limit of ±5%. Furthermore, the interconnection of I-UPQC with photovoltaic solar power through the DC link shows a better voltage profile while the load voltage within the allowable range of ±5% all through the disturbance and power loss reduction is 1.3%. Lastly, results obtained by optimal allocation of I-UPQC in RDS using analytical and GA-IPSO show that reactive power injection improved the voltage related issues from 0.952 to 0.9989 p.u., and power loss was further reduced to 1.2% from 3.4%. Also, the minimum bus voltage profile, voltage sag, and power loss are within statutory limits of ±5 % and less than 2 %, respectively. The major contributions of this research are the reduction of sag impact and power loss on the sensitive load in RDS feeder.Publications on page iii

Voltage control in Smart Grids

Smart grids are slowly becoming a reality, and will soon become embedded in all aspects of society: legislation, economy, environment, etc. Voltage control and reactive power compensation are crucial for the smart grid development. This project provides a background on all these issues and focuses on determining which the best device to control voltage is. The study was carried out on the IEEE 34 Node Test Feeder using the Power Factory DIgSILENT software. It was found that StatVars, dynamic devices, keep voltage more stable and within regulated limits than capacitors, and that nodes at the end of lines or acting as sole connection for more than two segments of network, and therefore under high loading stress, are more vulnerable to voltage drops. Therfore, meshed network topologies are more favourable for stable voltage and smart grid development. Using this knowledge, smart grids will be developed. This will enable a higher penetration of renewable energies and therefore a reduction of greenhouse gas emissions, a more competitive electricity market and an overall improvement of society’s state of wellbeing.Las redes inteligentes se están transformando poco a poco en una realidad, y pronto estarán integradas en todos los aspectos de la sociedad: legislación, economía, medio ambiente, etc. El control de tensión y la compensación de potencia reactiva son cruciales para el desarrollo de la red inteligente. Este proyecto proporciona una base sobre todas estas cuestiones y se centra en determinar cuál es el mejor dispositivo para controlar la tensión. El estudio ha sido llevado a cabo sobre la red de prueba IEEE 34 usando el programa de DIgSILENT, Power Factory. Se encontró que los StatVars, dispositivos dinámicos, mantienen la tensión más estable y dentro de los límites regulados que los condensadores, y que los nodos al final de líneas o que actúan como única conexión de más de dos segmentos de la red, y por tanto bajo un alto estrés de carga, son más vulnerables a caídas de tensión. Por lo tanto, las topologías malladas son más favorables para una tensión estable y el desarrollo de la red inteligente. Usando este conocimiento, las redes inteligentes podrán desarrollarse. Esto permitirá una penetración más alta de energías renovables y por tanto una reducción de las emisiones de gases de efecto invernadero, un mercado eléctrico más competitivo y una mejora global en el estado de bienestar de la sociedad.Ingeniería de la Energí