Tomas Petru

Modeling of wind turbines for power system studies

The modeling of wind turbines for power system studies is investigated. Complexities of various parts of a wind turbine model, such as aerodynamic conversion, drive train, and generator representation, are analyzed. The results are verified by field measurements made on a stall-regulated fixed-speed wind turbine. The modeling focuses on deriving a representation that is suitable for use in grid simulation programs.

Modeling and experimental verification of grid interaction of a DFIG wind turbine

The response of the doubly fed induction generator (DFIG) wind turbine system to grid disturbances is simulated and verified experimentally. The results are compared to the response that a fixed-speed wind turbine would have given. A voltage sag to 80% (80% remaining voltage) is handled very well, which is not the case for a fixed-speed wind turbine. A second-order model for prediction of the response of DFIG wind turbines is derived, and its simulated performance is successfully verified experimentally. The power quality impact by the DFIG wind turbine system is measured and evaluated. Steady-state impact, such as flicker emission, reactive power, and harmonic emission, is measured and analyzed. It is found that the flicker emission is very low, the reactive power is close to zero in the whole operating range, and the current THD is always lower than 5%.

Flicker contribution from wind turbine installations

In this paper, the flicker emission from a wind park connected to a grid with a high wind energy penetration is evaluated. The influence of wind speed, turbulence intensity, grid voltage quality, grid types, and number of turbines operating in the same group is measured and analyzed. The investigated wind turbines are of constant-speed stall-regulated type. It is found that the voltage quality of the grid to which the turbines are connected strongly influences the flicker emission of the turbines. Moreover, it is found that the formula used in IEC-61400-21 for determining the flicker contribution from a whole wind park gives too low total flicker value.

Grid disturbance response of wind turbines equipped with induction generator and doubly-fed induction generator

This panel paper presents measured and simulated grid disturbance responses of fixed-speed wind turbines equipped with induction generator and variable-speed wind turbines equipped with double-fed induction generator. The measured response of the fixed-speed turbine agrees very well with simulations, while the response of a double-fed induction generator cannot be assessed without detailed knowledge of the control system.