This thesis aims to simulate and find out more about the electrical dynamics of a six-phase exciter for hydropower generators. Because ordinary electric circuit-based simulation software only simulate three-phase electrical systems, a FEM-based software is used for the electrical dynamics simulations of the six-phase system. The objective is to analyse the pulsation behaviour of the rectified electrical output on the six-phase system and compare it to the three-phase system. The three-phase system is also simulated with filters with the aim of decreasing the amplitude of the pulsations on the electrical output. It is expected that an upgraded system from a three-phase system to a six-phase system should double the pulsation frequency on the rectified electrical output. However, the result shows that the rectified electrical output of the six-phase system consists of pulsations with unexpected frequencies. The simulated RL-filter on the three-phase system shows only insignificantly small changes on the rectified electrical pulsation amplitude.

This thesis aims to simulate and find out more about the electrical dynamics of asix-phase exciter for hydropower generators. Because ordinary electric circuit-basedsimulation software only simulate three-phase electrical systems, a FEM-basedsoftware is used for the electrical dynamics simulations of the six-phase system. Theobjective is to analyse the pulsation behaviour of the rectified electrical output on thesix-phase system and compare it to the three-phase system. The three-phase systemis also simulated with filters with the aim of decreasing the amplitude of the pulsationson the electrical output.It is expected that an upgraded system from a three-phase system to a six-phasesystem should double the pulsation frequency on the rectified electrical output.However, the result shows that the rectified electrical output of the six-phase systemconsists of pulsations with unexpected frequencies. The simulated RL-filter on thethree-phase system shows only insignificantly small changes on the rectified electricalpulsation amplitude.

The power transfer capability of long high voltage transmission lines is often limited by the inductive reactance of the transmission line. Series compensation is in some instances employed to lower the inductive reactance of the transmission line which increases the transmission line power transfer capability. Numerous methods have been employed to provide series compensation of a transmission line. One such method is to use a thyristor controlled series capacitor (TCSC). A thyristor controlled senes capacitor (TCSC) belongs to the flexible altemating CUlTent transmission systems (FACTS) family of devices. It is a variable capacitive and inductive reactance device that can be used to provide series compensation in high voltage transmission lines. One of the significant advantages that a TCSC has over other series compensation devices is that the TCSC's reactance is instantaneously and continuously variable. This means that the TCSC can be used not only to provide series compensation but can also be used to enhance the stability of the power system. However accurate control of the TCSC is challenging due to its highly non-linear variable reactance characteristic. The TCSC consists of back to back thyristors that control the reactance of the TCSC. By changing the trigger angle of these back to back thyristors it is possible to vary the reactance of the TCSC. The reactance characteristic becomes highly non linear at higher levels of compensation; at such operating points the trigger angle of the thyristors needs to be accurately controlled to avoid small variations in the thyristor trigger angle causing significant variation in the reactance of the TCSC. Literature has shown that there is an acceptable limit to the resolution of the thyristor trigger angle based on the parameters of the components used in the TCSC. If a controller is developed to meet this acceptable level of thyristor trigger angle resolution, then the operation of the TCSC will also be acceptable and its operation will not result in unwanted fluctuations in the transmission line variables. This thesis details the development of such a controller for use in a laboratory-scale TCSC. The thesis then goes on to present the practical results obtained from laboratory experiments on the laboratory-scale TCSC with the TCSC triggering controller being used to control the operation of the laboratory-scale TCSC. For purposes of comparison and benchmarking, a detailed simulation model of the laboratory-scale TCSC is developed to take into account the non-ideal properties of the components used in make-up of the laboratory-scale TCSC since the theoretical model is derived assuming ideal conditions. The detailed simulation model is also used to aid in the redesign the power circuit of the laboratory-scale TCSC in an attempt to improve the perfonnance of the laboratory-scale TCSC by obtaining better agreement between the theoretical and practical results. The redesigned laboratory-scale TCSC is used to obtain practical results to COnfill11 the findings of the simulation studies. Finally, the TCSC triggering controller is tested using a real time digital simulator (RTDS). The simulation model developed on the RTDS consisted of a two area, four generator power, with the TCSC connected between the two areas. The RTDS simulation model is used to study the ability of the TCSC to damp inter-area mode oscillations and hence the RTDS simulation model incorporated a power oscillation controller. The input of TCSC triggering controller was "connected" to the power oscillation damping controller and the output of the TCSC triggering controller was "connected" to the thyristors of the TCSC. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.

A numerical analysis is performed for the three-dimensional, turbulent flow of air in a thyristor valve hall located at the Dorsey Converter Station, owned and operated by Manitoba Hydro. The goal of this analysis was to determine the configurations that result in increased air-side cooling effectiveness in the valve hall. The governing equations are solved using the Computational Fluid Dynamics (CFD) code CFX-5. This computer code uses a finite volume method of solution and is based on a finite element approach for representing the geometry. The effects of inlet and outlet opening geometry, inlet air mass flow rate, and inlet air angle on the thermal performance for the air-side cooling of the thyristor valve hall geometry are examined.

The thesis Is concerned with the development of a separately excited DC machine In which gate turn-off thyristor devices with their associated firing and protective circuits are used to provide the static commutation of armature coil current. The developed machine has Its armature winding with 24 tapping points located on the stator and Interconnected In "Lop" configuration. The Initiation of the conduction periods of armature switching devices Is defined by a digital control logic circuit. In conjunction with an Incremental rotary encoder which provides the necessary feedback Information relating to shaft speed and shaft angular position. This Is arranged such that, under normal running conditions of the machine, the axis of the radial field of the armature winding maintains the normal space-quadrature relationship with that of the main field winding, giving the optimal torque angle of 000. Provision Is made, however, within the digital control circuit for controlled departure of the armature switch tapping points from the quadrature axis positions, and the effect of this, In Improving commutation Is Investigated. The effect of Interpoles Is also explored. On the basis of the analysis carried out, a proposal Is made for the future development of the machine employing a reduced number of armature switching devices without the need for Interpole windings.

A numerical analysis is performed for the three-dimensional, turbulent flow of air in a thyristor valve hall located at the Dorsey Converter Station, owned and operated by Manitoba Hydro. The goal of this analysis was to determine the configurations that result in increased air-side cooling effectiveness in the valve hall. The governing equations are solved using the Computational Fluid Dynamics (CFD) code CFX-5. This computer code uses a finite volume method of solution and is based on a finite element approach for representing the geometry. The effects of inlet and outlet opening geometry, inlet air mass flow rate, and inlet air angle on the thermal performance for the air-side cooling of the thyristor valve hall geometry are examined.

Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 131-136). Also available via the World Wide Web.

In this thesis I will evaluate few discrete devices and their differences in structure, static and switching characteristics and also some structurall and manufacturing principles. After that I will follow up with their integration into power modules , where I will also aim on construction solutions and trends. These power moduls are today delivered as „stack“ or „system“, where for optimization and highest achievable efficiency of the whole unit the integration of protection, drive and cooloing stage is incorporated. Cooling and drive of some devices will be subject of a separate chapter. Also some of novel materials, which are very promissing, will be introduced. They show improvemnet in electrical and thermal properties. They have potential to replace the currently dominant Silicon in the near future.

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Ce travail traite de la conception de générateur alimentant une lampe DBD destinée à la production de rayonnement UV. Cette alimentation doit permettre un contrôle efficace du rayonnement, grâce aux degrés de liberté apportés par le contrôle du générateur (fréquence, amplitude du courant injecté dans la lampe). Le modèle électrique de la lampe est utilisé pour prédire l’impact des caractéristiques du générateur sur le rayonnement UV produit. Une synthèse des interrupteurs de puissance du convertisseur statique permettant le contrôle du courant injecté est proposée et des solutions d’implémentation sont étudiées. Une démarche de conception en vue de l’optimisation du transformateur haute tension est proposée, notamment en ce qui concerne la valeur de ses éléments parasites. L’ensemble de ces travaux est étayé par des réalisations expérimentales. / This work presents the concept of a generator supplying a DBD lamp for UV radiation production purpose. This supply permits effective control of radiation based on degree-of-freedom provided by generator control system (lamp current frequency and ampli-tude). Lamp electrical model is used to predict the impact of power source characteristics on the produced UV radiation. A synthesis of the switching devices of power converter for current lamp control is pro-posed and the implemented solutions are studied. A design procedure for high voltage transformer optimization is proposed in particular concerning parasitic elements. The entire work is supported by experimentations.