Power Quality Enhancement in Medium-Voltage Distribution Grids: A Performance Evaluation of D2VC and D-STATCOM under Generation Ramps and Load Unbalance

Abstract

The quality of power in medium-voltage distribution grids has become increasingly challenging due to the growing penetration of variable renewable energy sources and the increasing presence of unbalanced loads. Variable distributed generation introduces generation ramps at the Point of Common Coupling (PCC), causing rapid voltage fluctuations and three-phase unbalances that can challenge conventional voltage regulation equipment. To address these issues, this paper compares two voltage compensation controllers: the Dynamic Direct Voltage Controller (D2VC), which directly regulates voltage magnitude and phase, and the Distribution Static Synchronous Compensator (D-STATCOM), which controls voltage through reactive power injection or absorption. The performance of both devices is assessed through time-domain simulations in PSCAD/EMTDC on a grid-connected medium-voltage distribution system under generation-ramp and unbalanced-load conditions. The comparison considers voltage regulation, settling time, apparent power requirements, and voltage unbalance mitigation. The D2VC required 0.430–0.446 MVA, versus 1.66–2.20 MVA for the D-STATCOM, and restored balanced PCC voltages. The D-STATCOM settled faster but retained a residual negative-sequence component. These results demonstrate distinct dynamic and power requirements for the two compensation approaches.