Using Power Hardware-in-the-Loop Simulation to Explore Uninterrupted Power Service of a Converter for Microgrid

In this paper, the control strategy for a grid-connected inverter to seamlessly transition from grid following to grid forming operation with minimal interruption was proposed and verified with power hardware-in-the-loop (PHIL) simulation. The system verification included a scenario in which the main generator trips offline in a microgrid, which is difficult to verify in the real environment. In this PHIL system, the hardware of interest is a reduced-scale prototype battery inverter, while the model of interest, implemented on a real-time simulator, comprises the rest of the microgrid, including the generator, constant-power and constant-impedance loads. The power converter is interfaced to the microgrid system and the energy storage system through PHIL interfaces, providing closed-loop interaction with the simulated system. PHIL simulation of this event presents stability challenges due to the large changes in impedance in the model of interest and the hardware of interest when the generator is taken offline and the control mode of the inverter transitions. In this work, stable operation of the system is achieved using a new PHIL interface approach, and operation of the system is demonstrated using the flexibility afforded by the PHIL simulation approach.