mppt poster

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Maximum Power Point Tracking of Photovoltaic Cells Christopher R. Poniatowski, Elizabeth Scalzetti, Kevin Xu Department of EECS, Syracuse University College of Engineering & Computer Science Overview The amount of power a solar panel produces is dependent on what the solar panel is connected to, even if the amount of sunlight does not change. If the solar panel is connected to a certain controller, that controller can make sure the panel is producing the maximum power possible for that amount of sunlight. If the amount of sunlight changes, then the maximum amount of power the panel can produce changes, as well. The Maximum Power Point Tracking (MPPT) system is able to track changes in the solar panel output with varying levels of sunlight. It adjusts the effective load to always consume the maximum power and not waste efficiency. The MPPT increases the efficiency of systems already taking advantage of solar energy. Without this addition, most systems consuming power from a solar panel are wasteful and cannot capture the maximum possible energy the solar panel is capable of producing at every point in time. Though there is an initial cost to purchase the MPPT controller, the higher efficiency it will provide results in long term saving on energy. The system will maintain its autonomy and provides a more beneficial source of renewable energy. P&O Algorithm The algorithm used must be able to manage the trade off between speed and accuracy. With this complication in mind, the Perturb and Observe (P&O) algorithm is used. In P&O, the program will check various points on the current-voltage curve that the solar panel outputs at any point in time and compares the powers of each in order to find the MPP. In the case of Incremental Conductance, the other popular algorithm, the controller can track the MPP accurately even with a rapidly changing I-V cure, by tracking the incremental conductance ( ). However, this method requires much more computational power and a very complex algorithm. The amount of light from the sun does not change extremely rapidly, so P&O is more appropriate for this system. Our P&O algorithm will check enough points of the curve in one period of time, such that it can figure out an accurate MPP, but not so much that the MPP becomes old information by the time it is obtained. Circuit Schematic The Buck Converter The converter being used is a DC-DC “Buck” converter. This converter steps down the solar panel’s voltage to achieve the maximum power. While the voltage is stepped down, the current rises. This is what creates the classic I-V curve and PV curve. With bright sunlight, the solar panel is capable of producing over 22V, which is too much for most batteries or loads to handle, requiring the use of a converter to decrease the voltage. A buck converter is especially useful because a pulse width modulated (PWM) signal can be used to control how much the voltage is scaled down. Changing the duty cycle is what changes the voltage at the output of the buck converter. The algorithm in the microcontroller is used to determine what the duty cycle should be at each point in time and update it accordingly. Efficiency Discussion With the ability to follow the MPP and operate at it, the time the system spends running at inefficient operating points significantly decreases, increasing the overall power efficiency of the system. This system’s efficiency results will be compared to those of a PWM system, the other common approach. The PWM controller holds the PWM signal to a single duty cycle and does not adjust for changes in sunlight. At full sunlight, this results in a 15% more efficient system based on our tests. Special Thanks to: Dr. Duane Marcy, Mr. William Tetley, and Dr. Tomislav Bujanovic System Block Diagram 0 0.5 1 1.5 2 2.5 0 5 10 15 20 25 Power (W) Voltage (V) Power vs Voltage Characteristic with 25Ω Load Full Sun Half Sun Low Sun MPP 70% Duty Cycle 50-55% Duty Cycle 40% Duty Cycle PWM Signal 0 0.5 1 1.5 2 2.5 3 Power (W) MPPT vs. PWM Comparison MPPT PWM Full Sun Half Sun Low Sun

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Page 1: MPPT Poster

Maximum Power Point Tracking of Photovoltaic Cells

Christopher R. Poniatowski, Elizabeth Scalzetti, Kevin Xu Department of EECS, Syracuse University

College of Engineering & Computer Science

Overview The amount of power a solar panel produces is dependent on what the solar panel is connected to, even if the amount of sunlight does not change. If the solar panel is connected to a certain controller, that controller can make sure the panel is producing the maximum power possible for that amount of sunlight. If the amount of sunlight changes, then the maximum amount of power the panel can produce changes, as well.

The Maximum Power Point Tracking (MPPT) system is able to track changes in the solar panel output with varying levels of sunlight. It adjusts the effective load to always consume the maximum power and not waste efficiency. The MPPT increases the efficiency of systems already taking advantage of solar energy. Without this addition, most systems consuming power from a solar panel are wasteful and cannot capture the maximum possible energy the solar panel is capable of producing at every point in time. Though there is an initial cost to purchase the MPPT controller, the higher efficiency it will provide results in long term saving on energy. The system will maintain its autonomy and provides a more beneficial source of renewable energy.

P&O Algorithm The algorithm used must be able to manage the trade off between speed and accuracy. With this complication in mind, the Perturb and Observe (P&O) algorithm is used. In P&O, the program will check various points on the current-voltage curve that the solar panel outputs at any point in time and compares the powers of each in order to find the MPP.

In the case of Incremental Conductance, the other popular algorithm, the controller can track the MPP accurately even with a rapidly changing I-V cure, by tracking the

incremental conductance (𝑑𝐼

𝑑𝑉). However, this method

requires much more computational power and a very complex algorithm. The amount of light from the sun does not change extremely rapidly, so P&O is more appropriate for this system. Our P&O algorithm will check enough points of the curve in one period of time, such that it can figure out an accurate MPP, but not so much that the MPP becomes old information by the time it is obtained.

Circuit Schematic

The Buck Converter The converter being used is a DC-DC “Buck” converter. This converter steps down the solar panel’s voltage to achieve the maximum power. While the voltage is stepped down, the current rises. This is what creates the classic I-V curve and PV curve.

With bright sunlight, the solar panel is capable of producing over 22V, which is too much for most batteries or loads to handle, requiring the use of a converter to decrease the voltage.

A buck converter is especially useful because a pulse width modulated (PWM) signal can be used to control how much the voltage is scaled down. Changing the duty cycle is what changes the voltage at the output of the buck converter. The algorithm in the microcontroller is used to determine what the duty cycle should be at each point in time and update it accordingly.

Efficiency Discussion With the ability to follow the MPP and operate at it, the time the system spends running at inefficient operating points significantly decreases, increasing the overall power efficiency of the system. This system’s efficiency results will be compared to those of a PWM system, the other common approach. The PWM controller holds the PWM signal to a single duty cycle and does not adjust for changes in sunlight. At full sunlight, this results in a 15% more efficient system based on our tests.

Special Thanks to: Dr. Duane Marcy, Mr. William Tetley, and

Dr. Tomislav Bujanovic

System Block Diagram

0

0.5

1

1.5

2

2.5

0 5 10 15 20 25

Po

we

r (W

)

Voltage (V)

Power vs Voltage Characteristic with 25Ω Load

Full Sun

Half Sun

Low Sun

MPP

70% Duty Cycle

50-55% Duty Cycle

40% Duty Cycle

PWM Signal

0

0.5

1

1.5

2

2.5

3

Po

wer

(W

)

MPPT vs. PWM Comparison

MPPT

PWM

Full Sun Half Sun Low Sun