Voltage Control Approach With Dynamic Voltage Reference for PV Distributed Generation Operating Under Cloud-Induced Shading Conditions

The integration of photovoltaic generation into distribution systems can deteriorate the system voltage and the conventional voltage regulation process based on step voltage regulators. The system operation under cloud conditions is much more challenging than the operation under clear sky conditions, requiring alternative voltage control approaches. This work proposes an adaptive voltage control approach for photovoltaic distributed generation units operating under cloud conditions. The control approach employs an adaptive voltage reference to cope with the dynamic reactive power margin and limited voltage regulation capability of photovoltaic distributed generation units. The proposed volt-var control is local, coordinates with step voltage regulators, and fills a gap in voltage control approaches by simultaneously considering dynamic models and realistic cloud shading conditions. The voltage regulation margin of each distributed generation unit is determined in real-time by a straightforward formulation also proposed in this work. The proposed control effectively mitigated the voltage fluctuations caused by stochastic variations of the photovoltaic generation and system loads, outperforming the conventional control approach based on fixed voltage reference. The proposed control reduced the number of tap changes by 63% and mitigated voltage fluctuations with magnitudes higher than 3%. The formulation to determine the voltage regulation margin effectively supported the voltage regulation process by providing a feasible range of values for the voltage reference of the distributed generation units.