Electro-magnetic Transient (EMT) simulation packages have been traditionally used to study a detailed representation of a small portion of system while transient stability tools employ simplified, phasor-domain representation of bulk power systems in planning and operation studies. As the number of power electronic devices such as HVDC and FACTS systems grows, there is a strong need to close the gap between EMT and transient stability studies to accurately represent complex behaviours of such devices and their interactions with the system in large-scale power systems dynamic studies. To this end, hybrid simulation is a promising approach wherein a small part of system is represented by a detailed, three-phase model while phasor-domain modeling is used for rest of system. By combining advantages of EMT and transient stability studies, hybrid simulation facilitates analyzing system-wide dynamic behaviors using high level of details which is not available in typical EMT or transient stability studies. In this regard, Powertech Labs in collaboration with Korea Electric Power Research Institute (KEPRI) and Yonsei University has developed TSAT-RTDS Interface (TRI), which is a tool for performing hybrid simulation studies using TSAT and RTDS. In TRI, user divides system into a number of islands connected through boundary branches. Each island is modeled and simulated in either TSAT or RTDS. At each transient stability integration time-step, TRI exchanges boundary injections between simulation tools. Flexible structure of TRI makes it possible to model any part of system in RTDS or TSAT, or user may use multiple TSAT instances or RTDS racks to simulate large systems. As a result, impact of low-frequency oscillations on RTDS model (which is typically ignored) may be investigated in a hybrid simulation environment.
Pouya Zadehkhost, Powertech Labs