Outer-loop Improved Damping Control Strategy for Weak Grid-tied VSC Devices

Wide frequency oscillation is an important issue in the power systems based on new energy resources. Up till now, the analysis and suppression of the oscillations are still hot topics for the researchers. First, based on the single input/single output transfer function model of the weak grid-tied voltage source converter (VSC), the impact factors and damping characteristics of the low-frequency oscillation frequency are analyzed. Then, an outer-loop improved damping control strategy based on the integrator reset control is proposed to increase the damping and the stability of the weak grid-tied VSC system by compensating the phase locked loop (PLL)'s phase delay in the weak grid condition. Also, a sensitivity analysis based parameter selection method is presented. Finally, the effectiveness of the outer-loop improved damping control is validated through the time-domain simulation and the real time digital simulation (RTDS) experiments.