Integrated Volt-VAr Optimization with Distributed Energy Sources to Minimize Substation Energy in Distribution System

Abstract

Volt-VAr optimization (VVO) is the tool which improves the efficiency of the distribution system by coordinating the voltage and reactive power. Due to voltage-dependence of loads, both real and reactive power will be affected by variation in voltage. Consequently, rather than minimizing active energy of the system, the focus of this article to reduce the daily apparent energy of the substation using VVO. In this, on load tap changers (OLTC), and voltage regulators (VRs) are used for voltage optimization, whereas capacitor banks (CBs) inject reactive power (VAr) into the system provided operational and system constraints satisfied. This study focuses on minimization of substation apparent energy (kVAh) by the optimal scheduling of OLTC, VRs, and CBs. The photo-voltaic (PV) and wind turbine (WT) generators are also assumed to be connected in the distribution system. Moreover, this study is extended to consider the effect of harmonics in the load current for associated loads. All the simulations are performed on modified IEEE 33-bus and IEEE 123-bus radial distribution systems. More savings in terms of substation kVAh are accomplished when DGs are connected into the system. Reductions up to 20% in substation kVAh and 37% in energy losses have been achieved.