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Impedance estimator for multi-source DC microgrids with islanding detection capabilities

DC microgrids with integrated distributed generators (DGs) require island detection in all converters. This work proposes an impedance estimation strategy to detect the grid connection status among all active participants in the DC microgrid. The method is based on a pulse signal injection (PSI) combined with the recursive least squares (RLS) algorithm to estimate the equivalent parallel resistance and capacitance of the components connected to the DC bus (both active and passive). This technique allows to detect islanding conditions by using the estimated capacitance value as a reliable metric. Compared with the existing DC island detection technology, this method: 1) does not have a non-detection region; 2) has a little impact on the DC bus voltage; 3) provides simultaneous islanding detection for all converters of the DC microgrid and 4) avoids using a dedicated communication layer. The method is verified in single and multi-converter scenarios.