A novel voltage and Var control model in distribution networks considering high penetration of renewable energy sources

Traditionally, distribution systems were designed as a central generation to provide load consumption. However, by restructuring in power systems and integration of Distributed Energy Resources (DERs), especially Renewable Energy Sources (RESs) in the MV/LV level, distribution system operators (DSOs) are encountering decentralized feed-in issue. This can lead to new operational issues in the distribution systems, such as interaction between the different mechanisms of Voltage and Var control (VVC) which full coordination between them is necessary. On the other hand, private distribution companies (DISCOs) prefer to supply the demand from their DERs instead of purchasing power from the grid to the extent possible to achieve the maximum profit. To address these challenges, this paper proposes a new model for operation of the distribution networks. The objective function of this model is the profit of DISCO to be maximized while all operation constraints, such as bus voltage limits, are satisfied. In this model the decision variables are the amount of power bought from the grid, the output power of RESs, steps of shunt capacitor banks as well as the set point of the On Load Tap Changers (OLTCs) in the subtransmission substations. To assess the effectiveness of the proposed method, this model is implemented on a test system. The numerical results show that the DISCO can significantly increase its profit by simultaneous managing the amount of bought power from upper utility and optimal scheduling of RESs, switching of shunt capacitor banks and OLTCs.