Analysis of Small Signal Stability on Wind Power Integration to Integrated Nepal Power System (INPS)

Bishwas Pokhrel, Assoc. Prof. Dr. Shreeraj Shakya, Assoc. Prof. Dr. Nawraj Bhattarai

Wind Turbine Generation, Small Signal Stability, Integrated Nepal Power System.

With large wind energy integration into power systems, wind farms begin to influence power systems in a much more significant manner. As wind energy systems utilize different generator technologies from the one utilized in the conventional power plants, the steady-state, transient and small-signal dynamics, as well as, power system stability will thus be significantly affected. The impact of wind energy systems on the power system dynamics and stability is thus of practical importance.

As there is a significant increase in installation of wind turbines equipped with doubly-fed induction generator (DFIG) in recent years, a dynamic model of the DFIG wind turbine is firstly developed in this study. The model is validated against field measurement data, and the validation gives confidence about the accuracy and applicability of the developed model. DFIG wind farms consist of tens to hundreds of identical DFIG wind turbines increasing the complexity of the wind farm model and simulation time.

In this study, the steady-state behavior of the DFIG is examined. Comparison is made with the conventional synchronous generators (SG) and squirrel-cage induction generators to highlight the differences between the machines. The initialization of the DFIG dynamic variables and other operating quantities is then discussed. Various methods are briefly reviewed and a step-by-step procedure is taken to avoid the iterative computations in initial condition.

The dynamical behavior of the DFIG is studied with eigen value analysis. Modal analysis is performed for both open-loop and closed-loop situations. The effect of parameters and operating point variations on small signal stability is observed. Financial analysis has been done using CREST model tool, which shows that the project is feasible in case of Nepalese subsidiaries.