Vector Synchronization Stabilizer to Enhance Small-signal Stability of VSC-dominant Power System in DC-voltage Control Timescale

This paper proposes a vector synchronization stabilizer (VSS) to enhance small signal stability of the power system dominant by voltage source converters (VSCs) in DC voltage control (DVC) timescale. In this paper, the small signal instability of grid-tied VSCs is recognized from the perspective of the point of common coupling (PCC) voltage vector $U_{\mathrm{t}}$. Then the principle and control structure of the proposed VSS are presented. In the proposed VSS, a brief vector synchronization unit is designed, and the vector error signal of the vector synchronization unit is employed to produce additional current compensation for VSC. And the physical mechanism of VSS based on the two-dimension damping is illustrated. Moreover, the analysis for the stability enhancement performance of VSS is studied based on the complex torque coefficients theory. With the proposed VSS utilized, the additional damping/synchronous power is adaptively provided for the VSC with different grid strength, operation conditions, control modes and control parameters. Furthermore, the recommended VSS parameter setting is presented based on the analysis of the effect of parameters. Simulation is presented to validate the correctness and effectiveness of the proposed VSS to adaptively suppress the small signal instability of grid-tied VSC. Finally, the advantages of VSS-based two-dimension damping for stability enhancement are discussed and analyzed.