Advancing HVDC Control & Protection Systems: The Role of Software-in-the-Loop Approaches

Traditionally the Control & Protection (C&P) system for every High Voltage Direct Current (HVDC) project is first tested through a method called FST (Factory System Test). FST is done to ensure verification of control and protection functions, testing of equipment to meet design specifications, verifying control and protection system supervision and to reduce interruptions in AC systems. As the transition to renewable energy accelerates, the demand for HVDC systems continues to rise, prompting a need to reevaluate conventional approaches to their design, procurement, and testing. This growing complexity calls for alternatives to the traditional hardware-in-the-loop (HIL) methods typically used for developing HVDC C&P systems. Emerging hardware independent technologies present compelling benefits, including enhanced interoperability, scalability, and cost-effectiveness, while maintaining high standards of quality. These strengths make it timely to assess how such innovations can ease current limitations in HVDC project deployment and support the future vision of a flexible, multi-vendor, and multi-terminal grid infrastructure. This paper investigates how software-in-the-loop (SIL) approaches-specifically non-real-time SIL (NRT-SIL) and real-time SIL (RT-SIL)-can streamline the engineering and verification processes for HVDC C&P systems. It provides an overview of existing SIL tools and simulation platforms, mapping their application across the HVDC C&P development lifecycle. Practical insights are shared from real-world HVDC implementations, demonstrating the effectiveness of SIL frameworks. The study concludes with guidance on the optimal use cases for each SIL variant.