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Determination of the Frequency Dependent Thévenin Equivalent of Inverters using Differential Impedance Spectroscopy

: Rogalla, S.; Kaiser, S.; Burger, B.; Engel, B.


Institute of Electrical and Electronics Engineers -IEEE-:
IEEE 11th International Symposium on Power Electronics for Distributed Generation Systems, PEDG 2020 : 28 Sept.-1 Oct. 2020, Dubrovnik, Croatia, Virtual event
Piscataway, NJ: IEEE, 2020
ISBN: 978-1-7281-6990-3
ISBN: 978-1-7281-6989-7
ISBN: 978-1-7281-6991-0
International Symposium on Power Electronics for Distributed Generation Systems (PEDG) <11, 2020, Online>
Fraunhofer ISE ()
Leistungselektronik; Netze und Intelligente Systeme; Wechselrichter in Netzen

This paper introduces a measurement technique that allows grid-connected inverters to be interpreted as frequency-dependent Thévenin equivalents. By means of this so-called differential impedance spectroscopy it is possible to determine the spectrum of internal harmonic voltage sources as well as the effective frequency-dependent output impedance of an inverter. Having this, one can distinguish between resonance-based and source-driven harmonics, which provides a more useful analysis of harmonic interactions between inverters and the grid. This paper presents the fundamentals and the procedure of the differential impedance spectroscopy, describes a realized test-stand for inverters up to one megawatt and gives exemplary measurement results.