Medium-Voltage Impedance Measurement Unit for Assessing the System Stability of Electric Ships

This paper describes the design and implementation of the first medium-voltage impedance measurement unit (IMU) capable of characterizing in situ source and load impedances of dc and ac networks (4160 V ac, 6000 V dc, 300 A, 2.2 MVA) in the frequency range of 0.1 Hz-1 kHz. The IMU comprises three power electronics building blocks (PEBBs), each built using 10-kV SiC MOSFET H-bridges. The modularity of the PEBBs allows for both series and shunt perturbation injection modes to be realized, as both injection modes are needed to accurately predict the stability of the electrical system. The effectiveness of the proposed impedance identification approach is experimentally verified on medium voltage power grid.