Investigation of the impacts of three-phase photovoltaic systems on three-phase unbalanced networks

More three-phase photovoltaic (PV) systems have been directly integrated to the electrical network at the distribution voltage level each year. Most of them are designed with balanced assumptions. In reality, under normal operating conditions distribution networks always have a certain degree of voltage imbalance, and these three-phase PV systems have already been implemented in such networks. However, their integration effects have yet to be fully identified and this should be thoroughly examined before the high PV penetration level causes serious problems in the near future. This paper studied the impacts of photovoltaic integration to an unbalanced distribution network. Using PSCAD and Matlab/Simulink softwares a three-phase photovoltaic model was built based on commonly applied balanced theories. This model was then implemented to the unbalanced IEEE 13 bus system. From simulation observation and mathematical analysis it has been determined that when voltage imbalance is within the allowable range defined by the standards the PV system achieves an approximately balanced current injection to each phase. As a result, it is suitable to implement a simplified current source model of the PV system for network analysis under such realistic operating conditions.