Novel control for small-scale three-phase wind generation systems in high wind speed regions

Abstract

This Ph.D. research focuses on control methods for performance improvement for small-scale three-phase wind generation systems particularly when operating in high wind speed regions. For small-scale wind generation systems, the generated torque and power as well as the rotation speed fluctuate violently with changing wind conditions. And these fluctuations would easily result in over-rated operation. Many attempts in regulating the system have been presented in recent literature which can be summarized by adding additional regulation devices, such as: pitch control units, yaw control units; and by advanced control algorithms. The additional regulation components will lead to an increase in system cost and size which make the use of the advanced control algorithm more promising in the practical applications. In order to overcome the drawbacks of the control methods in recent literature, a novel control algorithm called “High Wind Power Regulator (HWPR)” is designed as a major part of this dissertation to perform electrical stall regulation of the small-scale wind generation system when operating in high wind speed regions. Meanwhile, in a typical wind generation system, a DC-link is used to balance the power difference and to decouple the control between the wind generator-side converter and the grid-side inverter, which plays a critical part in the system. However, as the HWPR algorithm regulates the wind generation system in high wind speed regions, the power flow from the wind generator to the power grid changes violently due to rapid wind power changes. And this rapid power transition may cause severe DC-link voltage fluctuations. In order to reduce this DC-link voltage fluctuation, observer-based DC-link voltage control algorithms featured in fast DC-link voltage regulation are also developed in this Ph.D. research. The proposed algorithms estimate the power value fed into the DC-link and integrates with a Proportional-Integral (PI) controller combining the advantages of a fast-transient response offered by the observer and control robustness from the PI controller. The effectiveness of the proposed control methods for small-scale wind generation have been verified through both the computer simulation on a MATLAB/SIMULINK platform and laboratory experiments on a wind turbine testbed with a prototype wind generation system.