A New Co-Simulation Approach of Active Power Curtailment for Voltage Optimization in PV-Rich Distribution Networks

In recent years, distribution networks have faced technical issues caused by the increasing integration of pho-tovoltaics. Voltage level violations are addressed as the main technical issue for distribution system operators. However, photo-voltaics are inverter-based sources and can participate in voltage control. The photovoltaic inverter has several modes of operation, but due to the high R/X ratio of the distribution network, the volt-watt control mode represents the most attractive for researchers. This paper presents an optimal power flow-based model for voltage optimization using active power curtailment from photovoltaics as a control variable. The optimization problem minimizes the voltage deviation. The optimal power flow-based active power curtailment model is realized using a new co-simulation approach that interconnects the computational intelligence optimization method and power system simulation software. The proposed model is applied to an unbalanced IEEE European low voltage distribution feeder test system. The optimization model has been evaluated over three case studies which differ according to the level of photovoltaic integration. Results show that the proposed optimal power flow-based active power curtailment approach improves voltage profiles in distribution feeders and mitigates voltage issues caused by photovoltaics. However, due to unbalanced power flow and the assumption of equal active power curtailment per each phase of photovoltaic, voltages are reduced even in phases where the allowable limit is not exceeded. Secondly, this objective function formulation has a shortcoming since it tries to reduce differences of voltages below the reference value and observes this as a deviation, thus increasing its value. Finally, with that approach losses in active distribution feeder are indirectly affected and reduced.