Analysis of transient overvoltages and Self Protection Overvoltage of PV inverters through RT-CHIL

In power systems, Single-Line-to-Ground (SLG) faults are the most common type of fault. When a three-phase four-wire system supplied by an ungrounded synchronous generator is subjected to SLG faults, the unfaulted phases are expected to exhibit significant ground-fault over-voltage (GFOV). Mitigation of this is via effective grounding, as described in IEEE Std 62.92.2. However, for inverter-based resources (IBRs), the physical mechanism that leads to GFOV in synchronous machines is not present. This paper investigates whether GFOV is a problem in IBRs, and whether conventional mitigation requirements, such as providing a grounding transformer (GTF), are suitable for IBR installations. To answer these questions, a Controller Hardware-in-the-Loop (CHIL) based performance analysis is conducted. To this end, different simulation models have been developed to analyze the IBRs control and protection response. The models are comprised of a 13.2 kV, 500 kW distribution system fed by a grid connected PV inverter which was simulated in Typhoon HIL 604 real time simulator, with a IEEE Std 1547-2018 compliant external physical controller connected in the loop. The experimental set-up and tests conducted are explained and results are analyzed, showing that effective grounding requirements are much different than those for traditional generators.