Mechanisms and strategies of power regulation in wind turbines

The modelling and simulation of wind turbines is becoming more important as the penetration levels of wind turbines are increasing. This means that the effects the various types of wind turbines have on electrical grids and possible ways to control power output quality should be understood in order to facilitate wind energy expansion and to ensure minimal negative effects on local and wider area grids. Chapter 2 provides a literature review of the current research related to constant speed turbines (both passive and active stall) and the variable speed DFIG turbine. Although the latter is not examined further in this thesis, it is mentioned to provide a point of comparison with the constant speed technology. The literature review also enabled to results of previous simulation and the results of this thesis to be successfully validated. The Chapter 3 deals with the constant speed turbine as a steady state simulation. The steady state simulation showed that the chosen turbine characteristic would have a power generation design point of 2MW, and was designed for optimum output at an average wind velocity of 15m/s. The steady state simulations also showed that effect a change in frequency would have on the power output. Comparing the simulations of the passive stall of Chapter 4 and the active stall control of Chapter 5 it was shown that with the addition of pitch control there was still a significant overshoot of design output power of 0.06-0.08p.u, along with a high frequency variation of 0.05p.u. While the pitch actuators were engaged, this did not provide any significant reduction in design point overshoot or turbine behaviour The advantage of the active stall control was explored in Chapter 6, demonstrating the active stall control turbine can be used successfully in providing primary, secondary and high frequency support. A new set point could be reached within the required 10sec, and the output remained relatively steady. Though this power output is of course still reliant, and varies slightly depending on the wind velocity behaviour