Central kontra distribuerad tillståndsuppskattning för hybrida AC/DC nät

Abstract

State estimation enables for values throughout a power transmission grid to be known with a higher level of certainty. New technologies for bulk power transmission and power grid measuring enables for new possibilities in the energy sector and it is required that state estimation algorithms are developed to adapt to these new technologies. This project aims to develop a state estimator (SE) that is modified for hybrid AC/HVDC grids with voltage source converters (VSC) and phasor measurement units (PMU). Two different sets of architectures are tested. The centralized architecture where one common SE is implemented for both AC and DC grids or the distributed where a separate SE for every grid is used. The method used for the SE is the weighted least square (WLS) method. The SE will be developed based on the power grid model ’The CIGRE B4 DC Grid Test System’, designed by the International Council on Large Electric Systems (CIGRE) as a benchmark system. The SE is subject to four different scenarios in order to evaluate the quality of the SE, benefits of added phasor measurements and choice of architecture for the SE. The results of the tests show that the developed SE improves the accuracy of state values on the DC grid. However, regarding the AC state values of the converters the results of the test are ambiguous. Furthermore the distributed architecture offered slightly less accurate AC values than the centralized. The addition of PMU measurements improved the error of the estimated values.