Study of a grid connected wave power plant – synchronization to the grid
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
A wave power plant is being developed at the division of electricity at Uppsala universitet. What makes this wave power plant different from other designs is that they use a linear generator. The linear generator has both positive and negative properties. On the positive side is the high reliability and high efficiency in a wave power plant application. On the negative side is the none sinusoidal output of the linear generator that requires additional power electronic devices, in this case a rectifier and a inverter, to reach the required quality for grid connection. The wave power plants are connected to a shared DC-bus and the maximum amplitude of this DC-bus is dependent on the wave climate. The line to line voltage output of the inverter cannot be higher than 1.56 times the level of the DC-bus. So in order for the inverter output to remain at 1kV even if the DC level falls to low, a variable transformer is used. To increase the amount of power that can be extracted from the waves the DC level has to be set to a level that is wave climate dependent. This is due to that power is only extracted when the output of the linear generators are higher than the DC level. In this project a model of a wave power plant is constructed in Simulink. This model contains wave energy converters, rectifiers, inverter, inverter controller, a variable transformer and a strong grid. The inverter controller is based on dq-0 transformation and a PI controller. The model is used to see how the inverter can be synchronized to the grid and how the inverter controller and the variable transformer can be used to control the DC level and maintain a stable inverter output. The results show that the DC level can be controlled by the inverter controller and the variable transformer. Due to losses in the AC filter and cables, the amount of power that can be produced in the inverter is maximized when the variable transformer is the highest level the DC level can sustain.
Place, publisher, year, edition, pages
2009. , 51 p.
UPTEC ES, ISSN 1650-8300 ; 09 023
Engineering and Technology
IdentifiersURN: urn:nbn:se:uu:diva-113293OAI: oai:DiVA.org:uu-113293DiVA: diva2:290370
Master Programme in Energy Systems Engineering
Leijon, MatsTengblad, Ulla