System aspects of large scale implementation of a photovoltaic power plant

Abstract: In this thesis the static and dynamic behavior of large scale grid connected PV power plants are analyzed. A model of a 15 MW power plant is developed and implemented in DIgSilent Power Factory. The model considers all the panels operating at the MPP of the V-I characteristic with cos- = 1. The static behavior of this PV power plant connected to the grid is analyzed. To perform this analysis, the 15 MW power plant model is connected to a realistic grid. Two different static aspects are studied by using the U-Q curves of the PV power plant: variations of the injected active power of the PV power plant and variations of the short circuit power of the grid. As the injected active power is very dependent on the sun’s irradiation, the first analysis is performed in order to analyze the behavior of the PV power plant when the injected power is reduced. The second analysis is performed is to determine the influence of lower short circuit power at the PCC where the PV power plant can be connected in order to maintain a reasonable voltage level. Spain and Germany have started to develop a grid code which will be applied to these large scale power plants. Spain is one of the European countries which has a better potential of PV solar electricity and the government is giving a lot of subsidies to develop this technology. German government is also giving a lot of subsidies to develop PV technology. An analysis of the requirements of both grid codes is made concerning to the voltage dips and how the developed model of the PV power plant fulfills these requirements. Finally, as wind power technology is one of the most common renewable energy resources that is being developed in these days, a comparison between the model of the PV power plant and a model of a wind power farm of the same nominal power is made. The differences in steady state condition and dynamic condition of both technologies will be discussed and how both technologies fulfill the grid codes’ requirements mentioned before. During the fault, the behavior of both technologies is very different. The LVRT behavior of both technologies will be compared, when a pure three phase fault at the PCC occurs.