Sub-Synchronous Modal Energy-Based Method for Locating SSO Sources in Power Systems With DFIGs

Equipment safety and system stability are increasingly threatened by sub-synchronous oscillations (SSOs) for the mounting proportion of doubly-fed induction generators (DFIGs) in power systems, which calls for accurate and timely identification of SSO sources. In this article, a sub-synchronous modal energy (SSME)-based approach is proposed for locating SSO sources in power systems with DFIGs. Firstly, the sub-synchronous modal energy balance equation of a power system with DFIGs is derived via generalized Hamiltonian theory. Then, each component of the SSME balance equation is analyzed to illustrate that the flow direction of SSME serves as a suggestive criterion for identifying SSO sources. Considering the SSME of subsystems can be easily obtained online with measurement data, a novel SSO source location method is proposed based on the SSME of subsystem. Finally, the performance of the SSME-based method is demonstrated under both forced and negative-damping SSO scenarios. Simulation results validate the effectiveness of the proposed SSO source location method as well as its improvement in accuracy compared with conventional energy-based method.