Stability Assessment of DFIG Subsynchronous Oscillation Based on Energy Dissipation Intensity Analysis

Concerning the subsynchronous oscillation caused by the integration of doubly-fed induction generator (DFIG) to the power grid via the series compensation circuit, a method to assess the stability of subsynchronous oscillation based on the dissipation intensity is proposed in this article. First, the transient energy that DFIG generates in one oscillation period is defined as the dynamic energy of DFIG, and the model of DFIG dynamic energy containing internal control and external networks is constructed. And then, according to the Lyapunov stability theory, the negative gradient of dynamic energy is defined as the dissipation intensity, which reflects the dissipation effect of DFIG on the energy generated during oscillation. On this basis, the effect of the series compensation degree, phase-locked loop, and converter control parameters on subsynchronous oscillation is assessed, and real-time assessment of the stability level of DFIG-integrated power system is realized. Finally, a simulation model is built in RT-LAB to verify the proposed method. Simulation results demonstrate that the stability level of the system can be assessed accurately according to the value of dissipation intensity. When the value of dissipation intensity is positive, system oscillation converges. When the dissipation intensity is zero, the system oscillates with constant-amplitude oscillation. When the value of dissipation intensity is negative, system oscillation diverges.