Velocity Adjustable Wind Turbine Simulator based onActual Wind Generator for Laboratory Use

The objective of this research is (1) to design and construct the wind turbine simulator based on the adjustable actual wind speed. (2) To investigate the wind distribution, and (3) tobe applied for testing the power output of the micro-wind turbine in the laboratory. Design and CAD drawing was applied to construct the wind turbine simulator prototype.The 3 phase induction motor with axial fan was used for the wind-generating machine. The wind speed was controlled by frequency converter drive. The anemometer, tachometer, power meter and volt/amp meter was used for wind speed, rotational and electrical data measurement. The 100-watts micro-wind turbine was applied in this study. The results showed that the adjustable wind velocity of the wind turbine simulator was realized by using axial fan with a three phase induction motor driven by an inverter which produced various wind speed at the maximum of 9.33 m/s. The distribution of air flow always covered the cross section area of the fan blade. The air flow distribution was rather constant at all frequencies. The wind turbine simulator could be applied to test the micro-wind turbine. The generated output power graph obtained from the wind turbine simulator resembled with those of the power curve of the wind turbine’s manufacturer. The open-Loop adjustable speed wind turbine simulator has a great benefit for thearchitecture and engineering laboratory use.

The idea of Prakatwutthichon.P[8] and D.S.Dolan [9]was todevelop the wind turbine tester in the open loop wind tunnel by using the axial fan as the actual wind generator. Moreover, the stack of the axial fan was applied to medium power wind turbine testing. FeiDuan [10] andWeikang Du[11] continuously developed the microwind turbine tester in the laboratory. The wind tunnel is of great importance such that it could help the researchers to design and develop the wind blade, the control techniquesand the monitoringsystem. In addition to that, the wind tunnel can be used to test the efficiency of any type of micro-scale wind turbine. The objective of this study are as follows:(1) Design and construct the wind turbine simulator based on the adjustable actual wind speed.(2) Investigate the wind distribution. (3) Apply the design to test the power output of the micro-wind turbine in the laboratory of the Faculty of Engineering and Architecture of Rajamangala University of Technology Suvarnabhumi, Thailand. Neammanee. B et al.[7] presented a wind turbine simulator which uses induction motor driven by the invertor to obtain the speed control functionality. The motor was directly coupled to the shaft of the 1 kW DC generator. They used the Van De Hoven spectrum to control the speed drive system which in turn was controlled by a DSP.

II. LITERATURE REVIEW
R. Ahshan et al. [12] developed a Programmable Logic Controller (PLC) controller which is able to control small-scale wind turbine simulator (WTS). The small-scale wind turbine simulator was used in the Energy System Laboratory of Memorial University of Newfoundland. The WTS used the directly coupled DC motor to drive the induction generator and connected the AC power to the low-voltage utility grid.
Weihao.Hu et al. [13] presented the wind turbine simulator by using permanent magnet synchronous motor (PMSM) driven by vector control technique. The torque of motor was controlled by a micro-controller-based module inverter. This system obtains the wind speed and calculates torque of a real wind turbine by using the wind turbine characteristics and the rotation speed of PMSM. Subsequently, the output torque of the PMSM can be regulated by controlling the stator current and frequency. The inverter driving the PMSM can work like a real wind turbine.
Moore.I et al. [14] presented the hardware of the wind turbine simulator that connects the output of the wind turbine generator to the utility grid by 2 back-to-back convertors. The 1 kW synchronous generator was applied in this hardware. The AC to DC converter was controlled via an embedded control system and driven by a DCmotor. A basic control method for the power transfer was implemented in MATLAB/Simulink and then used to drive a converter PWM via a dSPACE interface.
Paepen.S et al. [15] showed the small wind turbine simulator which was controlled by LabVIEW via the industrial invertor drive (SIEMENS). The wind energy pattern was generated by LabVIEW. The PC-based monitoring system can display torque, power, wind speed and other parameters from the wind turbine simulator. D.S. Dolan et al. [9] developed the wind tunnel for lab-scale wind turbine testing. They used the tube axial duct fan with 5 horse power (hp) induction motor driven by a Siemens inverter. The fan diameter was 42 inches driven by the belts. The test employed the use of a 400W-wind generator. The results found that the tunnel was able to generate wind speed up to 14m/s at the cross sectional area as large as 3.25× 3.25 feet 2 .  developed the wind turbine simulator by using square cage induction motor with direct coupling to the induction generator. The DSP-TMS320C33 was applied to control the torque of the motor drive and the generator produced electrical power for the utility grid. Karakasis.N et al. [4] presented the wind turbine simulator for laboratory use. The simulator comprises of a 5.5-kW induction generator which is driven by a variable speed drive AC motor and a PLC that simulates the wind turbine power speed characteristics. The motor drive is connected to the generator by shaft direct coupling method. The performance of the Wind Energy Conversion System can be tested at the laboratory in dynamic and steady-state wind condition as well as in stand-alone and grid connected configurations.
[5] applied MATLAB/Simulink to represent the model of WTS. This model can simulate the operating parameters of the DC Motor driving the induction generator. In addition to that, the model is able to identify the mechanical power and torque for varying wind velocity and identify the power flow of an induction generator into the load.
Liyong Yang et al.[16] developed the novel WTS that uses 11.5 kW PMSM to drive the generator by employing real time programming with the DSP interface. The novel WTS can control the torque of generator comparable to the natural wind.
CiprianVlad et al. [17] presented the real-time replication of a stand-alone wind energy conversion system. This system uses the 3 phase induction motor to directly drive the shaft of the 3 phase permanent magnet synchronous generator (PMSG). The load current of the generator was controlled by theDC chopper.  designed and constructed the 20 kW of WTS by using AC motor with torque control inverter to drive the wind turbine generator by coupling belt. The AC motor drove the pitch control blade of the generator. This system can simulate with comparable similarities as the 3MW wind turbine.
Fernando Martinez et al. [2] developed the open-loop wind turbine emulator (WTE). The model consists of the AC Motor drive with direct coupling to an induction generator. The speed of the DC Motor was controlled by 3 phases AC-to -DC convertor. The output of the generator is connected to the grid via a grid-tie inverter. The emulator can be adjusted to the power curve of commercial wind turbine. P. Prakatwatthchon et al. [8] developed the prototype of the wind turbine tester with variable velocity pattern. The wind generator uses 0.37kW AC motor which was driven by invertor drives. They studied the air flow pattern in different conditions which include the incorporation of honeycomb, the incorporation of the nozzle, and without both the honeycomb and nozzle. The results found that the best wind distribution and wind speed is in the case without honeycomb and nozzle.
[10] developed the wind field by setting up arrays of axial fans and investigated its uniformity and turbulence intensity. The wind field consisted of 9 independently controllable axial fans in a 3 × 3 stacked square configuration. The dimensions of the effective wind output area are 3.76×3.76 m 2 . The system can be used to generate model wind speed up to 9.53 m/s. Subsequently, the system also investigated the dynamic response of a 1:50 scale model OC3 spar floating wind turbine concept which was designed for the operational depth of 200 m. In this study, the rotor was allowed to rotate freely with the wind speed, and this approach eliminated some of the undesirable effects of controlling wind turbine rotational speed Weikang Du et al. [11] from the State Key Laboratory of Ocean Engineering in Shanghai, China investigated the 1/50th scale model wind turbine based on a NREL-5MW. The wind field generator was axial fans in a 3 × 3 stacked square configuration. The model blade was designed at zero pitch angles and further tested in FAST, a fully coupled simulation tool. A model test was conducted using the optimized blade geometry.

A. DetermineMotor and Inverter size
The author defined the wind-generating machinesuch that it can generate the maximum wind speed at 9 m/s. The fan blade diameter is 0.56 meter. The wind flow rate (Q) can be determined by equation (1). The power at the rotor disk (equation (2)) gives the maximum power available in the wind [19]. But practically, wind turbine extracts only 20% -40% of the energy from the wind. Therefore, the mechanical power developed by the wind turbine in such situations can be estimated by using equation (3). The maximum power coefficient is around 0.1 -0.4. [20] The power of motor drive could be determined by equation (4). Lastly, the overall efficiency is determined by equation (5).
ρis the air mass density(1.2 kg/m 3 at 25 )[8], A is the area of rotor disk, A = πR 2 (m 2 ), V is the wind flow speed(m/s), Q is the wind flow rate (m 3 /s),P is the wind Power (W) and P motor is the power of motor (W), P mech =mechanical power of the wind turbine(W), C p = maximum power coefficient, P out =electrical power output of the wind turbine including the rectifierand convertor(W), ɳ overall = overall efficiency of the wind turbine.
The author estimatedthat the efficiency of motor and invertor is around 50%, and the efficiency of the wind turbine generator is estimated to be 50%. This is because there are electrical losses and mechanical losses in the motor and generator. To determine the rated power of motor, equation (4) will be used. The calculation result of the motor's power is 347.12 W. The rating of motor that was used in this project was SUNTEC-MH-B3; 3 phase/220V/50Hz/375W/1450rpm. The inverter, acting as a frequency converter,was used to drive the three phase induction motor. The author chose a single phase 220V/50Hz input inverter with a 3 phase 220V output. The motor model is DELTA VFD-EL. This model is suitable to control and drive theSUNTEC-MH-B3 motor. Thespecification of the motor, the invertor and the blade of wind simulatorare as shown in Table I.  (1)to design CAD and drawing of the wind turbine simulator, and adjustable wind-generating machine.
(2)To assembly and improve the wind turbine simulator.
(3) Test the motor'soperating by using the frequency convertor drive. (4) Determine relationship between the powers of motor vs wind speed by varies the frequency. (5) Investigate the wind distribution and wind pattern of the wind-generating machine. (6) Install a 100 W micro-wind turbine generator and (7) determine the power output and efficiency of micro-wind turbine generator.

C. Design and CAD drawing of the wind turbine simulator
The concept idea of the author was realized into a CAD drawing and will be built to a prototype in the next step. The CAD drawing of the wind turbine simulator was developed by using SolidWorks2012.The drawings of an axial fan, an adjustable speed wind generator, a 100-Watts six blademicro-wind turbine and aluminium frame with the arcylic wall is as shown in Figure 2. Moreover, the base-plate of the micro-wind turbine canbe removed and switched to test a different one.

Start
Design and CAD drawing of the wind turbine simulator.
Assembly and improved the wind simulator.
Test the invertor to drive a motor by frequency control.
Determine relationship between of power of motor, wind speed at frequency 10 to 50 Hz.
Investigated the wind distribution wind pattern of the wind simulator.
Installed a wind turbine generator.
Determine the power output of wind turbine and rotational speed via 10 to 50 Hz of frequency driver.

D. Assem
The w theory of speed con author as thickness and the w as shown cm (W/L

E. Wind
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A. The operation of the wind simulator.
In order to test the designof the wind simulator, the author established the relationship between the power of motor, wind speed and frequency. Figure 4 shows the experimental diagram. The 3-cups anemometer was installed at the center of the motor shaft ata distance of 60cm. The actual wind speed can be adjusted by the frequency convertor drive (Invertor) which is in an intervalfrom 0Hz to 50 Hz. Figure 6 shows that the maximum wind speed which is equal to 9.33 m/s, when the frequency of the rotation of motor is at a maximum of 50 Hz. At this point the power consumed by motor is about 252 W. The wind speed can be adjusted linearly from 0 to 9.33 m/s as shown by the blue line on the graph in Figure 5. The input power of motor drive increases proportionally with the frequency of themotor.

B. Investigatingthe wind distribution.
To investigate the pattern of the wind distribution that can be generated by the actual wind simulator, the experimental setup was performed as shownin Figure 6. The anemometer set up is the same as the firstexperiment. The wind measurement position is on the XY line from -40 cm to +40 cm, with an interval step of 2 cm. The set up wind speed are at five levels from 10 Hz to 50 Hz with an interval step of 10 Hz. The result of the wind distribution for each frequency is as shown in , when the rate frequency of the motor is at 50 Hz, the wind speed was constant but with a slight fluctuation (9.33 m/s to 8.6 m/s) when XY +28to -28 cm. (the measurement position is equal to the diameter of the blade). However, the wind speed will immediately decrease at the measurement position of more than ±28 cm. For example, the wind speed was only about 2 m/s at ±40 cm measurement position. If the speed of the motor was decreased, the wind speed will be decreased as well. The graph displays the wind speed at 50Hz, 40Hz, 30Hz, 20Hz, and 10 Hz. The distribution of air flow always covered the cross section area of the fan blade. The air flow distribution is constant at all frequencies, although, the wind speed will decrease at the end of the blade diameter as shown in Figure 8. The setup has been connected as the experimental diagram shown in Figure 9. The setup disconnects the Rload to obtain the no-load test status. The speed of wind simulator was adjusted at the frequency from 10 Hz to 50 Hz (at the step interval of 10 Hz). The rotational speeds of motor and wind turbine generator were then measured. The graph of the rotational speed with respect to the frequency is as shown in Figure 10. It was shown that the rotational speed will increase linearly with the frequency. The maximum speed of the motor was 1333.2 rpm and the generator maximum speed was 469.6 rpm. When the generator takes a full-load, the speed of generator was reduced at all frequencies. The comparison of no-load and full-load speed of the wind turbine generator is as shown in Figure 11.