Real-Time Simulators (RTS) of electrical networks are one of the major tools used for testing of functional applications, as it provides close reproduction of how the equipment or product will behave in the real field. This presentation focuses on hardware-in-the-loop (HIL) real-time simulation, where the device under test interfaces with the simulator platform through I/O terminals, including filtering, signal conversion (analog-to-digital, digital-to-analog), signal processing. microgrid applications present a particularly interesting study case for HIL testing, due to their specificities and constraints:

• Existence of a regulatory framework (for instance, IEEE P2030.7 and P2030.8 microgrid controller functional and test standards), which justifies the requirement to create a validation platform in order to verify and demonstrate compliance to the standards.
• Challenge of the implementation of seamless transitions between the steady-state modes (grid-connected mode and islanded mode): particularly, a seamless islanding transition requires to implement a very fast coordination between the islanding detection, the operating mode commands of the generators and other actions of the protection scheme.
• Wide range of the microgrid control timeframes - primary control, secondary control and tertiary control. The testing needs to validate not only the fast response to individual events, but also the performance of the controls on mid-term and long-term scales.
• Variety of the characteristics of microgrids: even considering only AC microgrids, they can differ significantly one from the other, with differentiators such as market segment, topology, area, perimeter of responsibility (within public distribution network or private installation).

The session describes the use of digital real-time simulators in the context of microgrid applications, focusing on controller hardware-in-the-loop (CHIL), whereby the power system is entirely modelled inside the simulator. The approach is illustrated with a real project use case where the CHIL validation of the microgrid controller functionalities and the protection scheme was the last step before implementation in the field within a community-scale microgrid.

Key Lerning Points:

• Microgrid control solutions present significant challenges in design and testing due to their complexity and wide range of possible configurations.
• Comprehensive testing is required both for pre-packaged microgrid products and bespoke solutions.
• Hardware-In-the-Loop testing using real-time simulators is highly beneficial for improving the reliability of microgrids.
• Seamless transitions between various Microgrid modes and states (grid-connected, islanded, resynchronization, black-start, planned/unplanned islanding) require careful upfront design and subsequent validation. Consideration should also be given to grid-forming vs. grid-following capabilities of the primary assets (battery storage systems, inverter-connected renewable energy sources, conventional generators), as well as their proprietary controls.

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