MIMO identification techniques in online measurement of bus impedance of interconnected power-electronics systems

Bus impedance is an important parameter for stability analysis and control design of interconnected power-electronics systems that consist of multiple power converters. This paper presents an online multi-input-multi-output (MIMO) measurement method to monitor the bus impedance of a medium-voltage DC (MVDC) distribution system on an all-electric ship. The method is based on Fourier techniques and simultaneous injection of orthogonal perturbations using existing converters. The method overcomes limitations of previously presented measurement techniques, which require several measurement cycles to obtain the bus impedance in order to avoid crosstalk among measurements. The presented approach can be used for system state monitoring and for control adaptation. Experimental results are presented and used to demonstrate the effectiveness of the proposed method.