An assessment approach of Sub-Synchronous Oscillation in VSG-controlled DFIG Based on Elasticity Mechanics Analogy

This paper proposes an Elastic Energy Equivalent Circuit (EEEC) for analyzing the sub-synchronous control interaction (SSCI) in the power system integrated with power electronics. The EEEC can analyze the dynamic energy propagation between the series compensation capacitors and the converter controller, and quantitatively assess the effect for SSCI induced by converter controller from the view of elastic energy. First, according to the similarity between the vibration of spring system and the electromagnetic oscillation of circuit, the equivalent elastic energy circuit (EEEC) and corresponding elastic energy function of the power system integrated with DFIG are derived. Second, the energy composition of the elastic energy function is analyzed, wherein the controllable dissipated energy can reveal the effect for SSCI induced by the grid-side converter controller of DFIG. Finally, the simulation model of the power system integrated with virtual synchronous generator controlled DFIG is built to verify the correctness and feasibility of the proposed approach.