Effect of Voltage Unbalance on the Power Quality of Three-Phase Grid-Connected PV Inverters

Voltage unbalance has become a power quality issue of concern in the low voltage networks due to the increased penetration of photovoltaic (PV) power generation and there exists little or no standards guiding on the voltage unbalance limit at low voltage networks in some jurisdictions. This study sought to demonstrate the effects of voltage unbalance on the behavior of commercial grid-connected PV inverter in terms of DC-AC conversion efficiency, and power quality parameters such as harmonics and current unbalance at the point of connection. The experiment showed that voltage unbalance has little effect on the inverter efficiency of less than 1% reduction. An increase in current total harmonic distortion is experienced and stayed way below the 5% limit stipulated in the IEEE standard. The 3
^rd
and 9
^th
individual harmonics components exhibited a strong correlation with voltage unbalance showing an increase as voltage unbalance increases. Current unbalance has a direct proportionality relationship with voltage unbalance.