OPTIMIZATION IN GENERATION FROM A HORIZONTAL AXIS WIND TURBINE VIA BLADE PITCH CONTROL AND STRUCTURE MORPHING

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1 OPTIMIZATION IN GENERATION FROM A HORIZONTAL AXIS WIND TURBINE VIA BLADE PITCH CONTROL AND STRUCTURE MORPHING PROJECT REFERENCE NO. : 37S1312 COLLEGE : SIDDAGANGA INSTITUTE OF TECHNOLOGY, TUMKUR BRANCH : ELECTRICAL AND ELECTRONICS ENGINEERING GUIDE : DR. K.P.SHIVAMURTHY STUDENTS : JAINENDRA MISHRA MAHENDRA SINGH SENWAR SINDHU RAVINDRA B SOURABH KUMAR Introduction: The world is at an energy-crisis where the fossil fuels are depleting rapidly and there is a dire need to find alternate sources of energy. The rate of energy demand has increased exponentially during the last decade. Wind power is known to be the most widely used renewable energy source. It is currently responsible for about 1.5% of the world s electricity use. Due to this major reason, it has become important for the world to develop technologies in order to maximise the harnessing of wind power. Keeping this in mind, this project aims at producing electricity for the low wind speed rate of Tumkur. This wind turbine has been specifically localized since the winds at Tumkur usually are at a speed of 3 5 m/s. The wind turbine that is being developed is set to rotate at around125 rpm. The generator rotates due to the constant motion of the blades of the wind turbine. Since the rpm of the blades are going to be low, the speed is increased by the use of a gear mechanism. Since commercially available generators are not suitable for the requirements of the project, the generator has been customdesigned. The generator used in this project is an Axial Flux generator. This is set to run at nearly twice the speed of the blades. The blades are designed in such a way that they have a unique twist, which enables maximum wind to be harnessed when in running condition. The non-uniform alternating current is then rectified to direct current. This is finally converted into alternating current, appropriate voltage of 230V using power inverters of 1450VA rating and step-up transformers. The output power of the generator is expected to be close to 1.5kW.

2 Project Description A wind turbine extracts kinetic energy from the wind and converts it into mechanical energy. This mechanical energy is then converted into electrical energy by the means of a generator. A wind turbine extracts maximum amount of energy when operating at optimal rotor speed. Since the wind is variable by nature, the optimal rotor speed also is. The speed range is expanded mainly to lower speeds, making it possible to track the optimal rotor speed starting from a lower wind speed. This will result in higher energy capture. The range of variable speed is limited and hence, in order to increase the speed of the generator, the possibility of using either controlled variable transmission or gearbox, is explored. These will help control the wind turbine over wide speed ranges in comparison to the conventional systems controlled by the generator torque. The important aspects of the project are as follows: Blade optimization: The kinetic energy of the wind should be optimally absorbed by the blades of a wind turbine. Variable pitch wind turbine (changing the angle of blades with respect to the incoming wind)will be designed and installed, which will solve this problem.wind turbine pitch control system can change incidence of rotor blades in a wind power generation system based on real-time wind speed for the purpose of adjusting output power, achieving higher utilization efficiency of wind power and providing protection for rotor blades. When wind speed is not higher than the rated speed, the blade incidence stays near the angle 0 (highest power point), which is similar to that of a generator with constant pitch, generating an output power that changes along with wind speed. Generator: The available commercial generators run at very high speeds, which is not desirable for this particular project. The generator that is designed is an Axial Flux generator. The Axial Flux generator is also a permanent magnet generator. Due to the high field strength, rare-earth magnets viz., Neodymium magnets were chosen. The field strength is 1.2T. The generator is double sided rotor which has permanent magnets embedded in the rotors and the stator containing coils is stationary.

Stator Rotor Complete generator Using bearings, it is mounted on a shaft and coupled with the hub of the turbine.

The number of coils used in the stator was 9 coils, having 208 turns each, placed at 40 degrees to each other.

The generator is made small in size in order to prevent overloading at the hub, and on the shaft.

Hence, variable alternating current is expected as output.

3 Stator Rotor Complete generator Using bearings, it is mounted on a shaft and coupled with the hub of the turbine. It is a 3phase, star connected generator containing 9 coils and 12 poles on each rotor. The number of coils used in the stator was 9 coils, having 208 turns each, placed at 40 degrees to each other. Coils The generator was found to produce a voltage around 48V, running at a speed of 250 rpm. The generator is made small in size in order to prevent overloading at the hub, and on the shaft. Power Electronics Module: Since wind is a variable entity, it cannot be controlled. Hence, variable alternating current is expected as output. The entire module involves a complete AC to AC conversion, which basically has a variable AC to variable DC conversion. Bridge rectifiers are used to suit this purpose. A variable DC to fixed DC conversion which is carried out by a Buck-Boost Converter and then fixed DC to fixed AC conversion, taken care of by 2 inverter units having a rating of 725VA each.. In order to keep the frequency at a constant value of 50 Hz, the

4 frequency modulator is used and made sure that it remains constant. The voltage is stepped up to 230V from 48V. Results: The simulation of the airfoil to be fabricated, yielded the following results: Analysis shows that for a marginally low wind at Tumkur, the preferable airfoils are NACA 2412 and NACA 5518, and on comparison, NACA 5518 is best suited. Proposed Airfoil The final Wind turbine blade design parameters

5 Wind turbine output simulation analysis

6 Design of a DC AC inverter using Multisim Generator output of single phase at constant 100 RPM Inverter output (modified sine) when generator is at 100 RPM

7 Future Scope Human Monitor Interfacing The speed of the blades, the speed of the generator and the voltage produced can be monitored at a remote location with the help of HMI. This helps the user to know the instantaneous voltages and speed. Pneumatic Drive In case of winds with a speed of less than 3 m/s, the pneumatic drive which will consist of an air compressor-blower, can be used to rotate the winds in order to provide the necessary speed of the blade and hence produce the required voltage

CHAPTER 4 MODELING OF PERMANENT MAGNET SYNCHRONOUS GENERATOR BASED WIND ENERGY CONVERSION SYSTEM

47 CHAPTER 4 MODELING OF PERMANENT MAGNET SYNCHRONOUS GENERATOR BASED WIND ENERGY CONVERSION SYSTEM 4.1 INTRODUCTION Wind energy has been the subject of much recent research and development. The only negative