978-1-5386-0517-2/18/$31.00 ©2018 IEEE Optimal Planning of PV Inverter in the Presence of Capacitor Bank in Medium-Voltage Distribution Networks Abdelfatah Ali 1,2 1 Department of Electrical Engineering Faculty of Engineering South Valley University 83523 Qena, Egypt E-mail: abdelfatah.mohamed@vet.bme.hu David Raisz 2 2 Department of Electric Power Engineering Faculty of Electrical Engineering and Informatics Budapest University of Technology and Economics 1111 Budapest, Hungary E-mail: raisz.david@vet.bme.hu Karar Mahmoud 3 3 Department of Electrical Engineering Faculty of Engineering Aswan University 81542 Aswan, Egypt E-mail: karar.alnagar@aswu.edu.eg Abstract—As the penetration level of the photovoltaic (PV) system increases over the coming decades, reverse power flows on the distribution feeder will happen and the associated voltage rise might lead to violations of voltage limits. The severity of the voltage regulation problem depends on the relative size and location of PV system, loads, and the distribution feeder topology. This paper proposes an approach to solve the voltage rise problem associated with PV system and to improve the total voltage deviation by optimally increasing the capacity of the PV inverter over the capacity of the PV modules in the presence of capacitor banks. An optimization model is constructed to calculate the optimal inverter capacity with minimizing the cost of PV inverter as well as the total voltage deviation on the distribution network. The overall system constraints are considered in the optimization model. The proposed approach is tested using the IEEE 119-node distribution network. The effectiveness of the proposed approach is demonstrated by calculating the optimal capacity of the PV inverter for mitigating the voltage rise problem and reducing the total voltage deviation. Index Terms-- Distribution networks, photovoltaic (PV), optimal inverter capacity, voltage rise, capacitor bank, reactive power capability. I. INTRODUCTION Supplying electrical power to consumers was typically based on centralized generation stations connected at the transmission system level. Recently, small-size distributed generations have been interconnected at the distribution network level to supply electricity locally. This modification in the infrastructure of the power system has many benefits, including: reducing losses, increasing supply reliability, and improving voltage profile in distribution networks [1]–[6]. Photovoltaic (PV) is one of the most common types of DG, and its cost is being dramatically decreased. PV units are distributed in low-voltage (LV) and medium-voltage (MV) distribution networks beside load centers. One of the major concerns about PV is voltage regulation problems, i.e., voltage rise/drop. Such voltage deviations from the nominal values have a negative impact on the domestic/industrial loads and affect their functionality [6]–[12]. The traditional voltage control devices, e.g., capacitors, often face many operational problems when employed to solve the voltage regulation problems with PV. The reason for this behavior is that the output power of PV is highly fluctuated and so the shunt capacitors are required to be switched frequently with high rate. The inverters of PV systems are often recommended to work at unity power factor, in other words, to supply only active power to the distribution system. However, several recent research studies have investigated the case when the PV inverter is allowed to inject/absorb reactive power [13]– [18]. It is demonstrated that the latter control scheme of the inverter can greatly solve the voltage regulation locally at the point of common connection (PCC). As a result, the stress on the conventional devices of voltage control will be significantly reduced. However, the spare capacity of the PV inverter during high generation occasions (i.e., sunny conditions) may not be sufficient to supply reactive power. To release the capacity of PV inverter during such event, a common practice is to increase the capacity of the interfaced inverter over the capacity of the modules of PV systems. As a result, the cost of the PV system will be increased. Therefore, an optimal capacity of the PV inverter has to be determined during the planning stage with considering the cost as well as the benefits. In addition, the capacity of capacitors must be considered in the optimization problem. In this paper, the capacity of PV inverter is optimally planned in the presence of capacitor banks in MV distribution networks. To do so, an optimization model is constructed in which the total voltage deviation and the cost of the capacity