Wind energy has become the fastest growing form of energy among many other power generation application systems the world over. To date, over 60,000 MW of wind generation application systems have been installed. This energy source is projected to contribute a 2.91% of the world’s electricity power come the year 2030 and a 5.1% plus in the year 2050. Harnessing this source of electric power generation has raised so much research interest with the focus being, the cost effective utilization of this energy with the sole aim of quality and reliability in its delivery.
In the last decade, wind turbine sizes have been developed from 20KW to 2MW. At the moment larger wind turbines are being developed. Wind turbine size has led to the emergence of different concepts being developed and tested. The one idea that surpasses the rest is the development of a variable speed wind energy conversion system that allows the tracking of wind speed through a shaft speed that ensures optimal power generation. However, since this variable speed wind energy conversion system employ the use of aerodynamic controls it becomes more expensive and complex as turbines become large in size.
This situation provides an incentive to consider control approaches while ensuring that the tip speed ratio is maintained at its optimum value, not withstanding wind variations. One such approach is the use of a permanent magnet synchronous generator that uses a maximum power point tracking control scheme. Ideally, squirrel caged induction generators are used as wind turbine generators because of their compactness, light weight and low cost. However, since the induction generator is supplied with exciting current from power system and fixed speed operation, the generated power is always fluctuating with change in wind speed thus affecting the electrical power quality.T
o counter this, a variable speed wing generator system has been widely adopted since it can reduce this output fluctuations. In addition, there is a specific turbine rotational speed that generates maximum power. In this way, the maximum power point tracking for each wind speed increases the energy generation. Permanent magnet synchronous generator has a simple structure and high efficiency thus many large sized wind turbine generators have adopted its use. It uses an AC-DC-AC method which needs no synchronization of the rotational speed of the wind turbine engine with frequency of power system. To do this, a chopper circuit is connected in parallel with a filter capacitor in DC link circuit. This configuration ensures the avoidance of over voltage through the consumption of energy from wind turbine generator’s resistance.(Fig 1).
The permanent synchronous generator is connected to the power system through two power converters namely; generator-side converter and grid- inverter. Generator side converter controls the permanent synchronous generator’s rotational speed so as to achieve variable speed operation with maximum power point tracking control. A vector control scheme is used as shown in fig 8 (b).
The increased use of wind as a source of power has led to numerous challenges in the design and development of stable wind power generation systems. This has led to deviation from traditional wind turbine generators that are driven by squirrel – cage induction generators to more advanced use of variable speed generation systems that employ the use of permanent synchronous generators that have maximum power point tracking control.
According to Yaoqin, the aerodynamical characteristic of the wind turbine, a maximum power point tracking is necessary to get high efficiency for wind power conversion, which means that the rotating speed of wind turbine should be adjusted in the real time to capture maximum wind power. Because of the fast variation of wind speed and the heavy inertia of generator, the maximum power point tracking control of wind generation is much challengeable.
Thogman J.S, alludes that a new maximum power point tracking control scheme be developed for permanent magnetic generator that is driven by a three-phase inverter to generate 350 V direct current power to the DC bus line. The main differences between the method used in the proposed maximum power point tracking system and other techniques used in the past are as follows:(1) The tracking step is variable according to the change of wind speed; (2) In order to avoid the dead time effect of the inverter the control is synchronized to the rotating speed of the generator; (3) A low pass filter is used at the output of the maximum power point tracking controller to decrease the fluctuation of the rotating speed reference. The resulting system has high-efficiency, lower-cost and fast, stable tracking speed.
The problems presented by an uncontrolled wind power generation is the loss of large wind power which would otherwise would have been used up as electrical power for driving and powering other electrical applications. Thus, in a way the use of a maximum power point tracking control in permanent synchronous generator reduces this loss significantly. My proposal therefore would be the adoption of more computer based control tracking systems as this will not only ease the accuracy in the control but will also simplify the design and even compact the design the more.
The use of filter capacitors in itself is temporal because capacitors tend to leak after some time thus also compromising on the quality of smoothing of the DC voltage. The use of chopper circuit is also not as effective as they start losing their inductance values with time that is why an improved and microcontroller based circuit is handy in eliminating this setbacks.
This paper will take into account other scholars work on the same subject. The conversion system dynamic comes up from modelling the dynamic behavior due to the main subsystems of this system: the variable speed wind turbine, the mechanical drive train, and the PMSG and power electronic converters. The mechanical drive train dynamic will be considered using three different model approaches, respectively, one mass, two-mass or three-mass model approaches in order to discuss which of the approaches are more appropriated in detaining the behavior of the system.
The power electronic converters will be modeled for three different topologies, respectively, two-level, multilevel or matrix converters. The electric network will be modeled by a circuit consisting a series of a resistance and inductance with a voltage source, respectively, considering two hypotheses: without harmonic distortion or with distortion due to the third harmonic, in order to show the influence of this third harmonic in the converter output electric current. Two types of control strategies will be considered through the use of classical control or fractional-order control.
In this paper, a wind speed estimation scheme for wind driven squirrel cage induction generator was proposed. The generator speed was regulated to extract the maximum wind power and to either in constant or variable wind/ generator speed. The generator reference speed was adjusted based on the optimum tip-speed ratio and the estimated wind speed. A new support vector regression algorithm to estimate the wind speed value based on the training data from previous off-line training was presented. The presented algorithm shows a good performance in both steady state and transient operation. This algorithm can estimate the wind speed with a slight error even if the wind speed increases or decreases. SVR algorithm featured an excellent tracing for the real value. Th
is method is based on the wind turbine characteristics and independent of the generator turbine constants or torque measurements, it results a fast estimation for the wind speed value even though the wind speed is changing continuously. It is important to mention that SV regression models deserve to be used by in control applications or short-term prediction, e. g. wind speed estimation, where they can advantageously replace traditional techniques.
- Busca C. (2010) Control of Permanent Magnet Synchronous Generators for Large Wind Turbines IEEE. Transaction on Energy Conversion. 23(1).
- Connor B.; Leithead, W.E. “Relationship of the Controllability of Power/Torque Fluctuations in the Drive-Train to the Wind Turbine Configuration.” Proceedings of the 1993 Wind Energy Conversion, Fifteenth BWEA Wind Energy Conference, York, October 6–8, 1993.
- Dingguo W. and Zhixin W. (2007) Modeling and Design of Control System for Variable Speed Wind Turbine in All Operating Region. IEEE. International Journal of Systems Applications, Engineering & Development 1(3)
- Fardoun, A.A., Fuchs, E.F.,Carlin, P.W. “A Variable Speed, Direct Drive Transmission Wind Power Plant,” Proceedings of Windpower ’93, San Francisco, CA, July 12–16, 1993, Washington, D.C.: American Wind Energy Association; pp. 134–141.
- Hansen, A. C., Users Guide to the Wind Turbine Dynamics Computer Programs YawDyn and AeroDyn for ADAMSÒ, Mechanical Engineering Department, University of Utah, Salt Lake City, UT, 1996.
- Hui J. (2001) An Adaptive Approximation Method for Maximum Power Point Tracking in Wind Energy Systems. IEEE. Transaction on Energy Conversion. 23(2), pp 551.
- Izumi Y. (2011) Control Method for Maximum Power Point Tracking of a PMSG –Based WECS Using Online Parameter Identification of Wind Turbine. IEEE PEDS . 5, pp 1125-1127.
- Lotfi S, and Sajedi M, (2012) Modelling and Application of Permanent Magnet Synchronous Generator Based Variable Speed Wind Generation Systems. IEEE. International Journal of Physical Sciences. 7(3).
- Melicio R. (2001) Wind Turbines with Permanent Magnet Synchronous Generator and Full-Power Converters: Modelling, Control and Simulation IEEE. Center for Innovation in Electrical and Energy Engineering
- Muljadi E. (1998) Control Strategy for Variable-Speed, Stall-Regulated Wind Turbines. IEEE.
- Muljadi, E.,Butterfield C.P., Migliore, P. “Variable Speed Operation of Generators with Rotor-Speed Feedback in Wind Power Applications,” Presented at the ASME Wind Energy Symposium, Houston, TX, Jan. 28-February 2, 1996.
- Muljadi, E.,Butterfield C.P.,Buhl, Jr., Marshall L.“Effect of Turbulence on Power Generation for Variable Speed Wind Turbines,” Presented at the ASME Wind Energy Symposium, Reno, NV, Jan. 6-9, 1997.
- Ramtharan, G. & Jenkins, N. (2007). Influence of rotor structural dynamics representations on the electrical transient performance of DFIG wind turbines. Wind Energy, Vol. 10, No. 4, (March 2007) pp. 293-301,
- Rojas, R., Ohnishi, T. & Suzuki, T. (1995). Neutral-point-clamped inverter with improved voltage waveform and control range. IEEE Trans. Industrial Elect., Vol. 42, No. 6, (December 1995) pp. 587-594,
- Salman, S. K. & Teo, A. L. J. (2003). Windmill modeling consideration and factors influencing the stability of a grid-connected wind power-based embedded generator. IEEE Trans. Power Syst., Vol. 16, No. 2, (May 2003) pp. 793-802,
- Senjyu, T.,Tamaki, S.,Urasaki, N. & Uezato, K. (2003). Wind velocity and position sensorless operation for PMSG wind generator, Proceedings of 5th Int. Conference on Power Electronics and Drive Systems 2003, pp. 787-792,
- Taylor and Francis (2009) Characteristic Study of Vector Controlled Direct Driven Permanent Magnet Synchronous Generator in Wind Power Generation. IEEE. Electric Power Components and Systems 37.
- Wang Q. (2004) An Intelligent Maximum Power Extraction Algorithm for Inverter-Based Variable Speed Wind Turbine System. IEEE. Transaction on Power Electronics. 19 (5).
- Yona A (2008) Operation Strategies for Stability of Gearless Wind Power Generation Systems. IEEE. Transaction on Energy Conversion.
- Wright, A., Osgood, R. O., Malcolm, D. J., 1994, “Analysis of a Two-Bladed, Teetering-Hub Turbine Using the ADAMS(R) Software.” Windpower '94,Minneapolis, Minnesota, May 9-13, 1994.
Need A Custom Paper In This Topic? Look no Further!