Your name Book report

Danny Doan

IntroductionGive an overview of the book, indicating what the focus of your book report will be. You can replace the picture on the right with a picture of the cover of the book. Simulation and Control of Wind Turbine using Hydrostatic Drive TrainAuthor: A. Nikranjbar1, A. Nazarian Sharbabaki1- Islamic Azad University/ Faculty of Engineering, Karaj, Iran. Email: a.nikranjbar@kiau.ac.ir (Corresponding author)2- Malek-Ashtar University of Technology/Mech. & Aero. Dep., Isfahan, Iran. Email: amin.nazarian@yahoo.com

AuthorOutline the authors life, focusing on the timeframe that includes the writing of this book.Main charactersCharacter OneDescribe this character.

Character TwoDescribe this character.

Character ThreeDescribe this character.

Character FourDescribe this character.

Information aubout the paperReceived March 2012 /Revised Sept. 2012 /Accepted Dec. 2012

ThemesDescribe the theme(s) of the book.EvaluationMake your main points here. Evaluate the book. Draw your conclusions.

No.TASKDEMONSTRATE & NOTE

ARTICLE

AABSTRACTI. Study about abstract1. PurposeIn paper with the demands to obtain energy from renewable energy resources, utilization of the wind turbines to convert the wind energy into the desired usable form with maximum efficiency has been faced with ever increasing research efforts. In this study taken a different approach with conventional systems, wind turbine with hydrostatic power train system is considered.2. Research Strategy/DesignHydrostatic power train system characterized with high power and torque transmission along with significant efficiency, capable of reliably controlling the performance of the system, and persistent hydraulic components, has been replaced with the conventional mechanical power train system between the vane and electric generator.3. FingdingTo explain the performance of the proposed system, a mathematical model of wind turbine with variable speed hydrostatic transmission in the MATLA/SIMULINK software has been established and the system control algorithm is presented.4. ConlusionBased on the detailed mathematical model and using the information of hydraulic equipments from famous vendors and manufacturers to make the results ever realistic, simulation results showing the great performance compared to the today's conventional wind turbines.

BKEYWORDS: Wind turbines, Hydrostatic power train, Wind turbine simulation and control.

CINTRODUCTIONII. Research Problem/Purpose1. What problem is being studied?Resounding to the industrial and technological challenge to introduce the cost-effective, reliable wind energy conversion solutions, considerable set of research efforts have been started.2. Is there a stated purpose or set of study goals?In conventional types, the wind passing over the blades exerting a turning force. The rotating blades turn a shaft inside the nacelle, which goes into a gearbox. The gearbox increases the rotation speed for the generator, which uses magnetic fields to convert the rotational energy into electrical energy. The power output goes to a transformer, which converts the electricity from the generator to the right voltage for the distribution system [2]. To overcome the drawbacks of the traditional method, specifically to eliminate the need to gearbox, the new concept of hydrostatic transmission (HST), which is characterized employing the application of continuously variable hydrostatic transmissions for wind turbines, is introduced.The author eliminate: The need to gearbox/The need for power electronicsIII. Background Literature1. What kind of articles are described?[1] http://en.wikipedia.org/wiki/History_of_wind_power # Early_Middle_Ages. [2] T. Burton, N. Jenkins, Sharpe D, and E. Bossanyi, Wind energy handbook, 2nd ed., John Wiley & Sons: West Sussex, England, pp. 2-7, 2011. [3] B. Bohlmann, Hydrostatic transmission for wind power,The National science foundation engineering research center, College of Science and Eng., Dep. of Mech. Eng., University of Minnesota. [4] J. Schmitz, N. Vatheuer, and H. Murrenhoff, Hydrostatic drive train in wind energy plants, RWTH Aachen University, IFAS Aachen, Germany. [5] X. Guo, X. J. Jibin, Z. Peng, and C. Jing, Numerical simulation and dynamic characteristics of secondary controlled hydrostatic drive,presented at theIEEE International Conf. on Mechatronics and Automation, Harbin, China, Aug. 58, 2007.[6] P. Srensen, A. D. Hansen, and P. A. C. Rosas, Wind models for simulation of power fluctuations from wind farms, Journal of Wind Engineering, Vol. 90, pp. 13811402, 2002. [7] G. Marsaglia, and W. W. Tsang, The ziggurat method for generating random variables, Journal of Statistical Software, Vol. 5, No. 8, pp.1-7, 2000. [8] E, Muljadi, and C. P. Butterfield, Pitch-Controlled Variable-Speed Wind Turbine Generation, IEEE Trans. on Industry Applications, Vol. 37, pp. 240-246, 2000. [9] B. Chitti Babu, and K. B. Mohanty, Doubly-Fed induction generator for variable speed wind energy conversion systems- modeling & simulation, International Journal of Computer and Electrical Engineering,Vol. 2, pp. 141-147, 2010. [10] S. Heier, Grid Integration of Wind Energy Conversion Systems,John Wiley & Sons Ltd. 1998. [11] K. Tan, S. Islam, Optimum control strategies in energy conversion of PMSG wind turbine system without mechanical sensors, IEE transactions on energy conversion,Vol. 19, No. 2, pp. 392399, 2004. [12] F. A., Rassul Abbas, and M. A., Abdulsada, Simulation of wind-turbine speed control by matlab, International Journal of Computer and Electrical Engineering, Vol. 2, pp. 1793-8163, 2010. [13] www.Mathworks.com/Matlab/Simulink/SimHydraulic help. [14] J. Johnson, Introduction to fluid power, 1nd ed.,Cengage Learning, 2002.By replacing the gearbox of traditional wind turbines with a continuously variable hydrostatic transmission (HST), the rotor speed could be controlled independent of the generator speed.Sim-Hydraulics is a block package under the Sim- scape in Simulink which is used to model up a hydro- static drive train system. Also used from Sim-Mechanic blocks (another block package under Simscape). The proposed model has been developed in Matlab- Simulink environment, Sim-Hyhraulics and Sim- Driveline tool boxes is used simultaneously to optimal using of rapid prototyping facility.

2. Can you tell from the literature why the authors are doing this study?Thus, by replacing the gearbox in a wind turbine with an HST, the reliability of the machine could be increased.This research aims to present a fixed speed wind turbine simulation with constant blade pitch angle and a typical variable speed hydrostatic system as a drive train. For the purpose of this research a specific drive train system with a secondary control unit in hydrostatic transmissions with a variable- displacement motor is developed [5]. The secondary control unit is used to control hydro motor swash plate movements and consequently the motor instantaneous displace- ment, output shaft angular velocity and amount of entered torque to the generator.3. Is the study important?Yes, it is. Because in this study taken a different approach with conventional systems which help decrease the high cost and increase the effection.IV. Research question/Hypothesis1. Does the research question (hypothesis) follow logical from the literature review? Yes, it does.2. Is there a clear rationable for the hypothesis?This new concept also provides the generators rotational speed to be matched exactly to the frequency of the power network by continuously varying the transmission ratio, thus omitting the need for frequency converters and providing higher current quality. At the same time, the rotational speed of the wind turbine can be controlled. Positive side effects are the good damping characteristics of the hydraulic drive train as well as the high power to weight ratio which results in a significantly reduced weight of the nacelle. Due to a modular design the transmission can also be adapted to a wide power range by switching off several parts of the system and virtually maintenance-free, which drastically reduces the operating and maintenance costs with ease of access to critical components [4].

DMAIN IDEA

EMETHODV. If sampling was used/identify (Nu c s dng phng php ly mu)1. Who was studied?2. How were they selected?3. Name the sampling strategy?4. Is the sample appropriate; would you suspect that any bias was introduced into the study because of the sampling strategy?

VI. Procedures/established methoda. WIND MODEL[6] P. Srensen, A. D. Hansen, and P. A. C. Rosas, Wind models for simulation of power fluctuations from wind farms, Journal of Wind Engineering, Vol. 90, pp. 13811402, 2002. 1. What is the implementation procedure?The wind speed is calculated as an average value of the fixed-point wind speed over the whole rotor, and it takes the tower shadow and the rotational turbulences into account.2. What ideas were used into the study?Wind models for simulation of power fluctuations from wind farms.3. Is the study design appropriate for answering the question?

[7] G. Marsaglia, and W. W. Tsang, The ziggurat method for generating random variables, Journal of Statistical Software, Vol. 5, No. 8, pp.1-7, 2000. 1. What is the implementation procedure?A main component in this model is the normally distributed white noise generator. Therefore, in order to obtain the same wind time series in all considered simulation tools used in the Simulation Platform some investigations have been done. It has been found that the built in white noise generator from different simulation tools uses a different algorithm and thus a different wind time series is obtained. A new normally distributed white noise generator has been implemented using a 'C' S-Function based on the Ziggurat Algorithm developed by G. Marsaglia [7]. The general structure of wind Simulink model is shown in Fig. 2.

2. What ideas were used into the study?The ziggurat method for generating random variables3. Is the study design appropriate for answering the question?A wind time series for 50 sec with 0.05 sec sample time, an average wind speed of 9 (m/sec) and (16 m/sec) and 12% turbulence intensity has been generated for the model as shown in Fig. 3.

b. WIND TURBINE ROTOR MODEL[8] E, Muljadi, and C. P. Butterfield, Pitch-Controlled Variable-Speed Wind Turbine Generation, IEEE Trans. on Industry Applications, Vol. 37, pp. 240-246, 2000. 1. What is the implementation procedure?Models for the power producing capabilities of a wind turbine rotor have been previously developed [8]. The block diagram of the wind turbine rotor is presented in Fig. 4.

According to (1), the output mechanical power of the wind turbine (PT) is given by the usual cube law equation [9].

Where, PT is mechanical output power of the turbine (W), CP is the power coefficient, is the air density (kg/m3), A is the wind turbine rotor swept area (m2) and V is the wind speed (m/s). Equation (2) present a generic equation i.e. used to model up CP. This equation, based on the modeling turbine characteristics of [10] is presented below.

Where is tip speed ratio ( is shown as (4)), is blade pitch angle and the coefficients C1to C6 are; C1=0.5176, C2=116, C3=0.4, C4=5, C5= 21 and C6=0.0068. The power coefficient for proposed model of wind turbine rotor with various pitch angles versus tip speed ratio is presented in Fig. 5. According to shown figure, the maximum value of Cp (CPmax= 0.48) is achieved for =0 degree and for =8.1. This particular value of is defined as the nominal value (nom). Some relationship between CP, various and various wind speeds are presented in [11], [12].

Where T is the mechanical angular velocity of the generator (rad/s), R is the radius of the rotor (m) and V is wind speed (m/s).

The wind turbine power characteristics for zero pitch angle (=0) with average wind speed of 12 (m/s) and different values of the pitch angle are illustrated as Fig. 6.

The wind turbine rotor has been developed in Matlab-Simulink simulator software. The simulink model is presented in Fig. 7.

2. What ideas were used into the study?Pitch-Controlled Variable-Speed Wind Turbine Generation3. Is the study design appropriate for answering the question?Fig. 5. Power coefficient versus tip speed ratio with various pitch angles Fig. 6. The turbine power characteristics for zero pitch angle Fig. 7. The Simulink model for the fixed speed wind turbine rotor c. HYDROSTATIC DRIVE TRAIN SYSTEMIn this paper, the system demonstrates usage of the so-called ''secondary control'' in hydrostatic transmissions with a variable-displacement motor. The drive train system consists of a hydrostatic transmission built of a pressure compensated variable-displacement pump, a variable- displacement motor, a fixeddisplacement pump as a booster pump, pressure relief valves, check valves, the secondary control unit and so on. The block diagram of closed circuit hydrostatic transmition system is presented in Fig. 8.

4.1. Hydraulic Pump[13] www.Mathworks.com/Matlab/Simulink/SimHydraulic help. 1. What is the implementation procedure?A variable displacement pressure-compensated pump has been used in hydrostatic drive train simulation. This kind of pump tries to maintain preset pressure at its outlet by adjusting its delivery flow in accordance with the drive train system requirements. The flow rate equation for the main pump is presented in (5).

Where, q is pump flow rate (m3/s), D is pump instantaneous displacement (m3/rad), is pump angular velocity (rad/s), kleak is pump leakage coefficient and P is the pressure differential across the pump (Pa) [13], [14]. Torque at the pump driving shaft for the main pump is presented in (6).

Where, mechis pump/motor mechanical efficiency. Pump instantaneous displacement (D), is proportional to the Pressure differential across the pump, Proportion of the pressure and displacement is defined as (7) [13].

Where, Pmaxis maximum pressure (Pmax=Pset+Preg), Pset is pump setting pressure, Preg is pump pressure regulation range, Dmax is pump maximum displacement and k coefficient is defined as (8) [13].

Leakage coefficient of pump/motor (kleak) and Hagen-Poiseuille coefficient of pump/motor (kHP) are defined as (9).

Where, is fluid kinematic viscosity (cst), is fluid density (kg/m3), nom is pump/motor nominal angular velocity (rad/s), V is pump/motor volumetric efficiency, nom is nominal fluid kinematic viscosity (cst) and Pnom is pump and motor nominal pressure (Pa) [13]. The pump/motor leakage flow is determined based on the assumption that it is linearly proportional to the pressure differential across the pump/motor and can be computed by using the Hagen-Poiseuille formula as (10).

Where, qleakis pump/motor leakage flow (m3/s), d and L are geometric parameters of the leakage path, is fluid dynamic viscosity (= ) [13].2. What ideas were used into the study?SimHydraulic for Hydraulic Pump3. Is the study design appropriate for answering the question?4.2. Hydraulic Motor[13] www.Mathworks.com/Matlab/Simulink/SimHydraulic help. [14] J. Johnson, Introduction to fluid power, 1nd ed.,Cengage Learning, 2002.1. What is the implementation procedure?The hydraulic motors flow equation is presented as bellow.

Where, q is flow rate through the motors (m3/s), D is motor displacement (m3/rad), is output shaft angular velocity (rad/s), kleak is motor leakage coefficient and P is the pressure differential across the motors (Pa) [13], [14]. The torque at the motor output shaft (N.m) is defined as (12) [13], [14].

2. What ideas were used into the study?SimHydraulic for |Hydraulic MotorIntroduction to fluid power3. Is the study design appropriate for answering the question?4.3. Secondary control unit 1. What is the implementation procedure?In a hydrostatic transmission, the displacement of its variable-displacement hydro-motor is often regulated by the swash plate angle using a hydraulic servo-mechanism. Therefore, the swash plate dynamics play an important role in the dynamics of the hydrostatic transmission. The secondary control unit simulation in presented in Fig. 9.

This unit is essentially a servo-cylinder controlled by a proportional 4-way valve. The servo-cylinder drives the control member of a variable-displacement motor represented in the model with mass, spring, and damper. The model is designed as a closed-loop control system with an angular velocity feedback. Dynamic compensator PD is installed in the secondary control unit to improve system stability. The hydrostatic drive train with secondary control unit system has been developed by Sim-Hydraulicsimulator environment (Fig.10). The variable displacement pressure compensated pump, variable displacement hydraulic motor and fixed displacement pump (booster pump) parameters are presented in Table_1. The model is developed by two main flexible pipelines with 30 (m) length and 0.05 (m2) cross-sectional areas.

2. What ideas were used into the study?

3. Is the study design appropriate for answering the question?Fig. 9. The Sim-Hydraulic model for hydro-motor control unitFig. 10. The Sim-Hydraulic model for the proposed hydrostatic drive train system in Matlab environmentTable 1.The main hydraulic pump (MP), hydraulic motor (HM) and booster pump (BP) parametersd. WIND TURBINE DEVELOPMENT 1. What is the implementation procedure?The wind turbine development in Matlab-Simulink software environment is shown in Figure 11. The model consists of three main subsystems; a) wind model simulation, b) wind turbine rotor, c) hydrostatic drive train with sensors and a simple gearbox.

2. What ideas were used into the study?3. Is the study design appropriate for answering the question?Fig. 11. The wind turbine development in Matlab- Simulink software environment

FSIMULATION & EXPERIMENTAL RESULTVII. SIMULATION RESULTS1. Was the statistic used to test the hypothesis appropriate for the scale of measurement and study design? Yes, it was.The output results according to various input, are presented in two sections, some different inputs are considered as bellow; a. The average wind speed of 9 (m/s) & 16 (m/s) with unit step input of secondary control unit.b. The average wind speed of 9 (m/s) with unit step and unit ramp input of secondary control unit signals.2. Were the study finding clearly presented? Yes, they were.3. Did the statistical test support or fail to support the study hypothesis?Yes, it support to the hypothesis aubout simulation 4. Did the figure effective display the study results?6.1. Section 1The power coefficient, torque and power of wind turbine rotor, torque and mechanical rotation of hydromotors (with unit step signal of secondary control unit) in the average wind speed of 9(m/s) and 16(m/s) are presented in Fig. 12 to Fig. 16.

6.2. Section 2 The simulation results of the hydro-pump flow rate, the servo-cylinder displacement in motor swash plate control mechanism, hydraulic motor torque and mechanical rotation with unit step and unit ramp signal of secondary control unit and the average wind speed of 12 (m/s) are presented in Fig. 17 to Fig. 20

5. Can the results be used to answer the research question?

GCONLUSIONVIII. Conlusion1. Did the author offer a strong explanation of their findings?2. What do the study findings mean for theory?3. How do the study findings build upon previous research?IX. Discussions1. Did the authors present their view of study limitation

Page 1

Page 4