Recently high-frequency common magnetic-links with cores of advanced magnetic materials, such as nanocrystalline and amorphous materials, have been considered as viable candidates for the development of medium-voltage power converters. This offers a new route of step-up-transformer-less compact and lightweight direct grid integration of renewable generation systems. Most importantly, it minimizes the voltage imbalance and common mode issues of the converter systems. However, the electromagnetic design of high-frequency common magnetic-links is a multi-physics problem and thereby affects the system efficiency and cost. In this paper, an optimization technique is proposed and verified by prototype magnetic-links. The design optimization, implementation, test platform, and experimental test results are analyzed and discussed.