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MICROCONTROLLER BASED MPPT SOLAR TRACKER
Transcript of MICROCONTROLLER BASED MPPT SOLAR TRACKER
LCD display unit displays the status of the battery. An inbuilt voltmeter is set up in the controller and it reads out the voltage level of the battery. The read out voltage is displayed on the LCD display.
MICROCONTROLLER BASED MPPT SOLAR TRACKER
Familiarization of various MPPT algorithms with special focus on analog implementation
Design and testing of MPPT controller for battery charger using dithering and limit cycling techniques
Solar power is an alternative technology that will hopefully lead us away from our petroleum dependent energy sources.
The major problem with solar panel technology is that the efficiencies for solar power systems are still poor and the costs per kilo-watt-hour (kwh) are not competitive.
Solar panels themselves are quite inefficient (approximately 30%) in their ability to convert sunlight to energy.
Solar panel is the fundamental energy conversion component of photovoltaic (PV) systems.
PV generation systems have two big problems, namely:
(1) the efficiency of electric power generation is very low, especially under low radiation states
(2) the amount of electric power generated by solar arrays is always changing with weather conditions, that is, irradiation.
The efficiency of solar panel being low it is necessary:
To design a Maximum Power Point Tracker (MPPT), a specific kind of charge controller that will utilize the solar panel to its maximum potential.
PV CELL MODEL
The PV cell can be considered as a two terminal device which conducts like a diode in the dark and generates a photo voltage when charged by Sun.
BLOCK DIAGRAM DESCRIPTION
It is the major part of the system. The microcontroller controls all the operations. The solar panel is aligned according to the intensity of sunlight under the control of the microcontroller.
The system consists of two sensors, each composed of LDR. One unit is made up of four LDRs. These are placed at the four corners of the solar panel. The intensity of sunlight is sensed by the LDR and the output is sent to the controller. The control unit analyzes it and decides the direction in which the panel has to be rotated, so that it gets maximum intensity of light.
The other unit of sensor is also composed of LDRs which is meant for the control of a lighting load.
Servo motor is used to rotate the panel in desired direction. It is controlled by the controller.
It is meant to control the charging of battery. It sends the status of battery to the microcontroller unit.
Load control is meant for the control of the load. It receives control signals from the controller and controls the load.
INTRODUCTION TO SUN TRACKING
As the range of applications for solar energy increases, so does the need for improved materials and methods used to harness this power source. There are several factors that affect the efficiency of the collection process. Major influences on overall efficiency include solar cell efficiency, intensity of source radiation and storage techniques. The materials used in solar cell manufacturing limit the efficiency of a solar cell. This makes it particularly difficult to make considerable improvements in the performance of the cell, and hence restricts the efficiency of the overall collection process. Therefore, the most attainable method of improving the performance of solar power collection is to increase the mean intensity of radiation received from the source.
NEED OF SUN TRACKING
Each day, the sun rises in the east, moves across the sky, and sets in the west. Whenever the sun is shining on us, it is sending energy in our direction. If there is a solar cell to turn and look at the sun all day, then it would be receiving the maximum amount of sunlight possible and converting it into the more useful energy form electricity. It is seen that the sun appears to follow a path that is nearly directly overhead. However, for locations north or south of the tropics (e.g., latitudes greater than 23.5 degrees), the sun never reaches a position that is directly overhead. Instead, it follows a path across the southern or the northern part of the sky.
OBJECTIVE OF THE WORK
If a solar cell is configured so that it faces the sun continually as it moves across the sky from east to west, the most electrical energy possible can be obtained. One way to do this, of course, is by hand. However, keeping a solar cell facing the sun throughout the day is not a very efficient use of a person’s time. Going outside to a solar cell every hour to turn it toward the sun might be possible, but this would still not be an efficient method. A photo sensor is employed to control the solar cell tracking system. For example, if the photo sensor is not aligned with sun rays, then it could turn on the motor until it is once again aligned. If the motor is attached to the frame holding the solar cell, then the solar cell could be moved to face the sun. As long as the photo sensor is in alignment with the sun, nothing happens.
ADVANTAGES OF SOLAR ENERGY
1. Need no fuel
2. Has no moving parts to wear out
3. Non-polluting & quick responding
4. Adaptable for on-site installation
5. Easy maintenance
6. Can be integrated with other renewable energy sources
7. Simple & efficient
RELEVANCE OF SOLAR TRACKERS
For people living in remote communities, often in third world countries, access to grid-connected electricity is not always possible. Often the nearest utility is a long distance from homes and the cost of developing the infrastructure that would allow for access to the grid is prohibitive. Remote communities in third world countries are of course not the only ones that suffer this dilemma. Australia is a large country with many farmers and communities that are remote from the local grid and in these cases alternative sources of electrical power must be obtained.
TYPES OF SOLAR TRACKERS
There are many different types of solar tracker which can be grouped into single axis and double axis models
SINGLE AXIS SOLAR TRACKERS
Single axis solar trackers can either have a horizontal or a vertical axle. The horizontal type is used in tropical regions where the sun gets very high at noon, but the days are short. The vertical type is used in high latitudes (such as in UK) where the sun does not get very high, but summer days can be very long. These have a manually adjustable tilt angle of 0 - 45 °and automatic tracking of the sun from East to West. They use the PV modules themselves as light sensor to avoid unnecessary tracking movement and for reliability. At night the trackers take up a horizontal position.
DUAL AXIS TRACKER
Double axis solar trackers have both a horizontal and a vertical axle and so can track the Sun's apparent motion exactly anywhere in the world. This type of system is used to control astronomical telescopes, and so there is plenty of software available to automatically predict and track the motion of the sun across the sky. Dual axis trackers track the sun both East to West and North to South for added power output (approx 40% gain) and convenience.
INTRODUCTION TO STEPPER MOTOR
The stepper motor is an electromagnetic device that converts digital pulses into mechanical shaft rotation. The shaft or spindle of a stepper motor rotates in discrete step increments when electrical command pulses are applied to it in the proper sequence. The sequence of the applied pulses is directly related to the direction of motor shafts rotation. The speed of the motor shafts rotation is directly related to the frequency of the input pulses and the length of rotation is directly related to the number of input pulses applied. Many advantages are achieved using this kind of motors, such as higher simplicity, since no brushes or contacts are present, low cost, high reliability, high torque at low speeds, and high accuracy of motion. Many systems with stepper motors need to control the acceleration/ deceleration when changing the speed.
STEPPER MOTOR CONNECTION
The wires from the Logic PCB connector to the stepper motor are as follows
Black +12V common
The ULN2003 / MC1413 is a 7-bit 50V 500mA TTL-input NPN Darlington driver. This is more than adequate to control a four phase unipolar stepper motor such as the KP4M4-001. It is recommended to connect a 12v zener diode between the power supply and VDD (Pin 9) on the chip, to absorb reverse (or "back") EMF from the magnetic field collapsing when motor coils are switched off.
CONNECTION OF THE CIRCUIT
Use Microcontroller PIC16F877A to give +5v supply to pins a, b, c, d one by one that’s:
a=5v, b=0, c=0, d=0 a=0, b=5v, c=0, d=0 a=0, b=0, c=5v, d=0 a=0, b=0, c=0,d=5v Then the motor will run.
STEPPER MOTOR ADVANTAGES AND DISADVANTAGES
1. The rotation angle of the motor is proportional to the input pulse.
2. The motor has full torque at standstill (if the windings are energized)
3. Precise positioning and repeatability of movement since good stepper motors have an accuracy of 3 – 5% of a step and this error is non cumulative from one step to the next.
4. Excellent response to starting/ stopping/reversing.
5. Very reliable since there are no contact brushes in the motor. Therefore, the life of the motor is simply dependant on the life of the bearing.
1. Resonances can occur if not properly controlled.
2. Not easy to operate at extremely high speeds.
APPLICATIONS OF STEPPER MOTOR
A stepper motor can be a good choice whenever controlled movement is required. They can be used to advantage in applications where you need to control rotation angle, speed, position and synchronism. Because of the inherent advantages listed previously, stepper motors have found their place in many different applications. Some of these include printers, plotters, high end office equipment, hard disk drives, medical equipment, fax machines, automotive and many more.
GEORGEKUTTY THOMAS (B110096EE)
J S JAYAKRISHNAN (B110516EE)
KARTHIKA M (B110242EE)
KELVIN ANTO (B110213EE)
12 volt is required.
Minimum input required for 7805= drop across IC7805+ required output voltage=3+5=8v