Voltage Control of a Three-Phase Distribution Grid using a DC Microgrid-Fed STATCOM

Abstract

With the increasing penetration of microgrids in distribution systems, the possibility for voltage variations increases. This paper proposes the use of a static synchronous compensator (STATCOM) fed by a DC microgrid to control the voltage of a 3-phase AC distribution grid and provide bidirectional active power transfer from the AC grid to the DC microgrid and vice versa. A simplified control is applied to this system to manage the magnitude and angle of the system voltage at the point of common coupling. With the use of a PI controller and pulse width modulation, the proposed control was able to modify the active and reactive power compensation. The control approach is characterized by its simplicity and rapid response to system changes, such as fault occurrences or load variations. The proposed control system is applied after converting the 3-phase system into a dq system to simplify the voltage regulation process. The PSCAD package is used to perform the simulation. Results demonstrate that it is possible to control STATCOM to offset reactive power and regulate grid voltage. The results validated the ability of active power transfer through the line by injecting negative and positive active power. The transfer of active and reactive power from the AC grid to the DC microgrid, and vice versa, is examined in this study following the STATCOM rating and the energy management demands.