  Transmission and distribution dynamic co-simulation is a practical and
effective approach to leverage existing simulation tools for transmission and
distribution systems to simulate dynamic stability and performance of
transmission and distribution systems in a systematic manner. Given that these
tools are developed as stand-alone programs and there are inherent differences
between them, interface techniques become critical to bridge them. Two
important unsolved questions are: 1) which interface technique is better and
should be used, and 2) how the modeling and simulation capabilities in these
tools that are available and can be exploited for co-simulation should be
considered when selecting an interface technique. To address these questions,
this paper presents a comparative study for different interface techniques that
can be employed for T and D dynamic co-simulation. The study provides insights
into the pros and cons of each interface technique, and helps researchers make
informed decisions on choosing the interface techniques.
