Evaluation of the Impact of Grid Voltage Unbalance Severity on Reactive Power Compensation Performance and DC-Link Voltage Stability of a STATCOM

Abstract

Grid voltage unbalance is one of the major issues affecting the power quality of modern distribution systems due to uneven load distribution, the integration of distributed energy resources, and grid disturbances. This condition may reduce the reactive power compensation performance and the DC-link voltage stability of a Static Synchronous Compensator (STATCOM). This paper presents a quantitative evaluation of the impact of grid voltage unbalance severity on the performance of a three-phase STATCOM. The model is developed in the MATLAB/Simulink environment using a synchronous reference frame control method combined with PI controllers. Four voltage unbalance levels corresponding to voltage unbalance factors (VUFs) of 0%, 2%, 4%, and 6% are investigated. System performance is evaluated in terms of the reactive power of the source and the STATCOM, compensation effectiveness, power factor, and DC-link voltage fluctuation. Simulation results show that as the VUF increases, the reactive power compensation capability of the STATCOM decreases, while the reactive power supplied by the source and the DC-link voltage fluctuation increase, and the power factor decreases. The research results provide a reference for the evaluation, design, and operation of STATCOMs under unbalanced grid conditions.