Real-time software-in-the-loop EMT models of wind turbine and power plant controller: applicability and experiences

As the penetration of wind turbine generators (WTG) and other inverter-based resources increase in the system, offline electromagnetic transient simulations (EMT) using black-box user-defined controls are becoming widely available and used in the industry for stability and grid compliance studies. Nonetheless, there are certain challenges when using offline EMT models for tasks that involve large system simulation, testing of protection and control devices (i.e., protection relays), or interoperability analysis of different OEMs and other equipment such as HVDC, STATCOM, etc, mainly posed by simulation time. In this sense, real-time EMT simulations are emerging as important solutions for such challenges, where traditionally, hardware-in-the-loop (HiL) is used, incorporating control and protection hardware and, more recently, real-time software-in-the-loop (RTSiL). This paper gives an overview of RTSiL, illustrating different alternative development approaches of real-time SiL models. The paper starts by defining the domain of applicability of offline EMT models, real-time SiL, and HiL, highlighting the importance and differences between each method. It then proceeds to explain the different methodologies available for black-boxing controls and simulating SiL in different real-time simulators and the advantages and disadvantages of different methods. The paper shows results for the implementation of the real-source code of Type IV offshore wind turbines and power plant control (PPC) in both offline and online platforms, utilizing PSCAD and the SiL solutions from Real-Time Digital Simulator (RTDS) with GTSOC. The paper ends by discussing important differences between offline and online and the fact that RTSiL, as a new technology, still needs more maturation and verification.