High Voltage Pulsed Power Converters for the ESS Linear Accelerator.

Sammanfattning: Material science has become an important research area in order to fulfill today’s requirements on lighter, cheaper and more sustainable materials. The European spallation source is a research center based on the world’s most powerful neutron source, which will enable new possibilities to evaluate material properties down to an atomic level. The linear accelerator (Linac), accelerates with help of electromagnetic fields, protons to a speed of 96.2 % of the light. Due to high power and the pulsing nature of the accelerator an extremely advanced electrical supply is required. This master´s thesis comprises a concept topology for solving the impact of such pulsed power supplies on the AC grid power quality. The electrical supply consists of two series connected stages, which will be stacked in modulators. The first stage is a low voltage grid connected capacitor bank charger, the second stage converts the power to a high voltage pulsing pattern. This project comprises the first stage (the capacitor charger) which consists of an Active Front End in series with a DC/DC-converter. The main objectives are to fulfil the international standards regarding power quality, where main focus will be on flicker, low frequency harmonics emission and unitary power factor. In order to fulfill these goals with pulsating loads connected, a completely new developed power control introduced. Mathematical models have been derived in order to verify the functionality and to tune all the developed controls. A complete final implementation is done with the help of Matlab Simulink to more in-depth verify the different control parameters. This implementation is also used to check that the international standards are met. Complete calculations of power losses are also presented with evaluation of results and possible improvements. Together with the limitations, goals of the degree project and basic equations are derived in this report. The topology is shown to be extremely effective with very good results in terms of output voltage quality (capacitor charging voltage) and on flicker and low frequency harmonics impact on the grid. Almost every effects due to the pulsing output nature are totally erased seen from the grid side.