Coordinated control of on-load tap changer and D-STATCOM for voltage regulation of radial distribution systems with DG units

This paper presents a new technique for voltage regulation of a radial medium voltage (MV) distribution grid in presence of distributed generation (DG) units. The proposed technique consists of the coordinated actions of on-load tap changer (OLTC) of transformer and reactive power compensation by distribution static synchronous compensator (D-STATCOM). Managing the system voltage using the action of OLTC is one of the most common ways for voltage regulation of MV systems. However, OLTC cannot be used for voltage regulation of long radial distribution feeders as it changes the sending point voltage of the feeder. In this study, the problem of using OLTC for the voltage regulation of a radial distribution feeder will be solved by using reactive power compensation at the DG connected bus. Simulation results reveal that the proposed control method is capable of maintaining the system voltages within the permitted range. Thanks to the coordinated control method, the drawbacks of each voltage control method are covered by the other one that results in minimization of the system losses as well.