Nowadays, technology evolution and deregulation of the electric utility industry enable distributed generation (DG) to play an increasing role in locally satisfying the expanding power demand. In this paper, the islanded operation of an electrical grid supplied by wind turbines, which belong to the most rapidly expanding DG technologies, is studied. Control strategies for power electronics interface of variable speed wind turbines, ensuring fast control of frequency and voltage, are proposed.
"To overcome this drawback, gain scheduling or switching between multiple linear controllers has been proposed. In , the authors used a linearized version of the system and applied model predictive control, whereas in ,  training of neural networks and fuzzy logic techniques were used. Even if in some cases the performance of the system is satisfactory, its response to large wind variations may be unpredictable, since these methods are based on linearization and hence are valid only locally. "
[Show abstract][Hide abstract] ABSTRACT: The main contribution of this paper is the development of a nonlinear control technique for the control of individual wind turbines in a wind farm. For this purpose, a control scheme based on feedback linearization and gain scheduled linear quadratic regulator (LQR) is applied to a horizontal axis, variable speed, pitch regulated wind turbine. As a result of the physical constraints of their components, wind turbines operate at different control modes with different control objectives. To capture this hybrid nature, a flexible modeling framework based on the notion of hybrid systems is introduced, and the developed controller is designed so as to operate in all modes and over a wide range of wind speeds. The performance and the efficiency of the proposed approach is validated via simulations, and is compared with standard LQR approaches.
"Because they are not tower mounted they don't have access to the higher wind speeds that the HAWTs have and they also have the disadvantage that they possess a lower power coefficient than HAWTs. Not being able to rotate faster than the speed of the wind often means that extensive gearing is required to match the optimal speed of the rotor with that of the generator (Kanellos and Hatziargyriou, 2008; Mozammel, 1978; Mutschler and Hoffmann, 2001; Yeh and Wang, 2008; Yigang and Zhixin, 2008). "
[Show abstract][Hide abstract] ABSTRACT: The main objective of this work is to determine and design a suitable wind turbine which could be employed for rural homes or other small-scale applications. A variety of horizontal and vertical axis wind turbines exist, each possessing a number of advantages and disadvantages which needed to be taken into account before a basis for the design is selected. A small robust design which is relatively simple and cheap to construct is in essence the main criteria for wind turbine selection. A Savonius type rotor, which is a rotor based on a modification of the ‘S’ rotor, is selected as it best fitted the design criteria. A small prototype 1.5 m tall with a rotor diameter of 0.65 m is designed and built. The finished prototype is used to estimate the power obtainable under normal operating conditions.
Energy for Sustainable Development 09/2009; 13(3):159-165. DOI:10.1016/j.esd.2009.06.005 · 1.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper presents generic model of hybrid power system consisting in a combined solution one wind turbine with asynchronous generator and on hydro generator with synchronous machine. This technology was developed by to reduce the cost of supplying electricity in remote communities. The optimal wind penetration (installed wind capacity/peak electrical demand) for this system depends on the site availability of hydro energy and available wind resource. The optimal solution is evaluated first using HOMER – special design software for optimizing cost exploitation for a hybrid power systems. For the optimum solution we analyze the system by means of simulation in order to present the system behavior during normal operation.
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