Optimization to controllability measure of the POD in DFIG-integrated power systems to improve small-signal stability margin considering the impact of pre-fault slip

The power oscillation damper (POD) at the doubly-fed induction generator (DFIG) helps to damp the low-frequency oscillation (LFO) in the power system, but the damping effect is affected by the pre-fault slip (s_|0|) under the overspeed mode. This paper investigates the relationship among the damping effect of the POD, the transfer function (TF) of the POD, and s_|0|, and proposes a new optimization scheme to extend the allowable range of s_|0|. At first, the controllability measure (CM) is introduced to quantify the damping effect of the POD, and the sensitivity model of the CM is newly derived to analyze the influence of s_|0| and the TF on the damping effect. Then, the small-signal stability margin (SSSM) is defined by the allowable range of s_|0| and applied to quantify the system stability influenced by both s_|0| and the POD. By adding a new constraint to the eigenvalue sensitivity, the sensitivity model of the SSSM is derived. Lastly, based on the proposed sensitivity model, the interior point method is applied to solve the proposed optimization scheme to POD’s parameters and extend the allowable range of s_|0|. Simulation results show that the CM of the POD is more sensitive to s_|0| than the TF of the POD. Compared with the existing eigenvalue sensitivity-based optimization scheme, the proposed scheme has a better effect on the SSSM.