Reactive Power Dispatch of Inverter-Based Renewable Distributed Generation for Optimal Feeder Operation

Driven by technical challenges and environmental needs, there has been significant interest towards integrating more renewable energy sources (RESs) into the electricity grid. However, the high penetration level of RESs is usually accompanied with a few operating challenges such as voltage variation, reverse power flow, and frequent operations of Volt/Var control devices. To address these challenges, this paper presents a centralized coordinated voltage and reactive power control for a medium-voltage (MV) active distribution network (DN) dominated by photovoltaic (PV) and wind power systems. The proposed model minimizes the operating cost by minimizing the real power loss and reducing the number of OLTC operations while maintaining the network voltage within the allowable limits. The objective is to determine the required reactive power from the inverter based RESs (IBRESs) and the optimal setting of the OLTC. The coordination problem is formulated as a mixed-integer nonlinear programming (MINLP) optimization problem and solved by GAMS software. The proposed model is validated by a two-feeder MV distribution system connected to a sub-transmission system via a substation transformer. The results show that the proposed model can optimize the operational cost of active DNs. Hence, utility and customer satisfaction can be met.