Small-signal stability analysis of grid-tied inverters with positive-negative sequence control

The small-signal stability of converter-dominated power systems is of critical importance, particularly as the penetration of renewable energy sources increases. Existing studies predominantly address the conventional current control (CCC), which exhibits degraded performance under voltage unbalance and grid-impedance variations. In contrast, the positive-negative sequence control (PNSC) enables independent regulation of sequence components, thereby enhancing current quality and transient performance. However, a detailed small-signal stability analysis of the PNSC has not been fully underexplored. This paper investigates the small-signal stability of the PNSCbased grid-connected inverter under varying grid conditions (e.g., different grid strengths, balanced/unbalanced scenarios). The frequency-domain analysis employs the impedance-based modeling framework in the synchronous (dq) reference frame. The 2 × 2 impedance matrices are utilized to quantify the stability margins through Bode plot and Generalized Nyquist Criterion (GNC). Furthermore, a comparative study with the CCC under both strong and weak grid conditions is presented. Timedomain simulations conducted in MATLAB/Simulink validate the frequency-domain stability predictions. The findings provide valuable insights into dynamic behavior, control design, and stability assessment in converter-dominated power systems.