iMOV – An Active Surge Protection Device for Inverter-Dominated Systems

As the penetration of inverter-based resources (IBRs) in the grid increases, classical overvoltage protection schemes should be reconsidered. A grid-connected inverter integrated with semiconductor switches is significantly more prone to failures during high-energy, overvoltage transients, such as lightning strikes, compared to existing infrastructure in the electromagnetic/mechanical grid. Although they have worked well for passive devices, such as transformers, conventional metal oxide varistor (MOV)- based overvoltage clamping methods may not provide the desired voltage protection due to their inability to achieve tight overvoltage clamping ratios. In this paper, the concept of an intelligent-MOV (iMOV) is presented. The proposed iMOV uses a combination of controlled semiconductor devices and MOVs to provide tighter voltage clamping during overvoltage scenarios. Moreover, the unique design of the iMOV ensures that the semiconductor devices do not experience the surge stress. The design considerations to realize the iMOV design for overvoltage protection are explored to build a hardware prototype. A laboratory-scale setup is created to emulate lightning impulses and test the concept. Finally, hardware results from 2 kV, 350 A voltage surge tests demonstrate the iMOV's feasibility.