Event-Based Power Quality Analysis and Assessment Procedure for a PV-ESS Integrated Demonstration Facility

This study evaluates the power quality of a full-scale PV-ESS demonstration facility integrating PV generation, ESS, EV chargers, and office loads. Two field datasets were combined: 1-min VCB relay data at the high-voltage grid connection point and 1-s high-resolution measurements from eight operating events. The VCB data were used to analyze long-term active/reactive power flow, voltage, current, and frequency, while the high-resolution data were used to evaluate THD, waveforms, and transient P-Q characteristics. The grid connection point repeatedly changed between receiving and reverse power flow conditions, with reverse power flow accounting for 38.7% of the analysis period. Voltage THD remained relatively stable at an average of 1.68%, whereas current THD showed greater event-dependent variation. A temporary reactive power transition was also observed. Based on these results, an event-based assessment procedure integrating long-term operating data and high-resolution power quality measurements is proposed for monitoring and improving PV-ESS integrated facilities.