(De-)stabilising effect of power electronic interfaced DG units in distribution networks

An increasing number of distributed generation (DG) units is being connected to the distribution network. This introduces a large number of power electronic converters. Due to the output capacitance of these and other converters there is a risk on harmonics, badly damped transients and so on. In this paper it has been investigated whether the DG unit converters can contribute to the damping in the grid. The analysis showed that for converters with conventional control this contribution is limited, and in some cases even negative. Additional controllers on the DG unit converter are proposed that will significantly increase the damping in the network to which it is connected