Control of Transient Overvoltage for Inverter Only Based Microgrids in Power Distribution System

Transient overvoltage (TOV) is an important design consideration for interconnecting inverter-based generation resources to a four-wire distribution system. Past studies investigated temporary overvoltage resulting from ground fault overvoltage (GFOV) and load rejection overvoltage (LROV) for photovoltaic (PV) inverters in a grid-following mode of operation. Grid forming mode of operation for inverters has gained increased attention since it helps to increase power system resiliency. An inverter's response during faults depends on its control methodology, which can impact the overvoltage observed in the system during an unbalanced ground fault. A methodology is proposed to control the negative sequence impedance during a ground fault to help mitigate the potential of transient overvoltage. An electromagnetic transient simulation is performed using PSCAD on a small system to validate the inverter characteristics and effectiveness of the proposed method.