Impedance Measurement in Dynamic Analysis of Multi-Converter Systems

Advancements in power electronics have led to the growing number of applications of DC distribution multi-converter systems in recent years. The dynamics and stability of multi-converter systems can be conveniently analyzed using methods based on the evaluation of DC network bus impedances. Therefore, efficient and fast wideband methods for measuring the frequency-responses of converter impedances as part of the bus impedance calculation are needed. The pseudo-random binary sequences (PRBS) are highly suitable broadband excitations for converter impedance identification due to many attractive properties such as easy generation, controllable frequency-domain parameters and low measurement time. The thesis work reviews the broadband methods for frequency-response measurements of a multi-converter network using PRBS, and provides studies of DC distribution systems and their stability analysis methods. A simulation approach and a practical experiments are presented in the work to verify the reviewed measurement techniques. The benefits of using binary excitations in power converter impedance estimation were successfully verified. In addition, some of the limitations and special considerations with the methods were briefly discussed. These limitations included the PRBS’s amplitude design tradeoff and its sensitivity to environment noise disturbances