Impact of Negative-Sequence Voltage on Inverter in an Islanded Microgrid

Southern California Edison (SCE) is in the development stages on various microgrid (MG) projects aimed at improving resiliency while maintaining grid reliability and safety during planned and unplanned outages, including Public Safety Power Shutoffs (PSPS). This paper aims to recognize the impact of negative-sequence voltage on an inverter for a photovoltaic (PV) based distributed generation connected in an islanded MG. A comprehensive mathematical model of the inverter along with the PV and boost converter is proposed to perform the analytical simulation in Matlab environment. It is established that the inverter design capacity is required to be significantly higher in order to meet the imbalance current caused by only a 2% negative-sequence voltage. Thus, an adequate design of the inverter that meets SCE’s needs is crucial; otherwise, the inverter will shut down prematurely due to the imposed design constraint by the manufacturer. This will hinder the success of current and future SCE-led MG projects.