Shivarudrappa Biradar, IJRIT-84
International Journal of Research in Information Technology (IJRIT)
www.ijrit.com ISSN 2001-5569
Sub-Module Distributed Maximum Power Point Tracking For Solar Photo Voltaic Applications
Shivarudrappa Biradar1, Marina Chandy2
1M.tech 4th sem , Digital Electronics, Srinivas Institute of Technology, Mangaluru, India
2Associate Professor, Electronics and communication, Srinivas Institute of Technology, Mangaluru, India
Abstract
This project will explores the advantage of power electronics in solar photovoltaic applications by using integrated maximum power point tracking (MPPT).We are proposing a system that will provides the increase in captured energy during shading conditions also, during the same time reduction in overall cost. This is achieved by direct integrating, MPPT power converters that are from DC to DC into existing junction boxes. We are now going to the designing and implementation of a very high-efficiency (>98%) buck converter MPPT, along with MPPT control techniques that uses both local and global maximum power point extraction. Through the detailed experimental measurements under real-world conditions and we are going to verify the captured energy will be increased and list the benefits of the architecture.
KEYWORDS—MPPT algorithms, Solar energy, Review, Classification, Comparison
1. Introduction
With rising world-wide energy demands and soaring prices of fossil fuels, need of renewable energy sources has increased. Among these, solar photovoltaic (PV) energy has seen a rapid growth in the last few years, resulting in decreased prices of PV panels as production capacity increases at a fast pace. As the PV panel prices decrease, the cost of the power electronics required to extract the maximum power of the PV modules and to interface the PV system to the grid is becoming a larger part of the overall system cost. Much attention has therefore been given to the development of power electronics that enable a cost reduction of the overall system. In addition, much research is focused on increasing the efficiency of the power processing stage, as well as on improving the power yield of the overall system.
Shivarudrappa Biradar, IJRIT-85 Many PV installations suffer from current mismatch between two panels, due to non-uniform shading of the cell array, dirt accumulation, or manufacturing variability. Ensuring uniform illumination is particularly challenging in residential PV applications, where large current mismatch can be accure due to some of the objects that cause shading. In this proposed system, any shading or other source of cell current mismatch will cause the overall system output power has to be reduced, since the current in the string is reduced by the weakest panel. While all today panel employ bypass diodes that help protect the panels and limit the negative effect of partial shading, any partial shading can still have a significant negative effect on a solar installation.
The micro-inverter (also known as panel-level inverter) concept has been proposed to address this problem by operating each panel at its maximum power point, and perform DC to AC conversion for each and every panel. and this technique will helps to increase in overall energy capturing of the proposed system, inverters typically suffer from low efficiency where as high-voltage inverters having more efficiency, this leads to the large voltage transformation is required to interface the two different panel voltage ( 20-40 V) to the grid (e.g. 120-240 V rms ) as well as the need for the low cost. In single-phase micro-inverters, the twice line-frequency power ripple also introduces another challenge; this must be buffered at each micro inverter stage, which results in large panel-voltage capacitors and complicated converter topologies that employ high voltage capacitors.
One of the big issues in the power sector is the increasing the demand for power but the availability of the resources is very less, Demand has increased for renewable sources to be utilized. We use conventional technique to meet the energy demand. Renewable energy sources for EX solar energy and wind energy are the primary energy sources which can be utilized in this issue. The continuous use of fossil fuels has affected the environment depleting the biosphere and to global warming.
Solar energy is freely available in nature it can be used properly. Solar energy is used as energy generating unit. Thus it can be used to provide the power to the rural areas where the availability of power grids is very less or nil. Advantage of using solar energy is that it can be used for portable operation.
2. Modeling of solar cell
The solar cell is considered as the building block of a solar panel. A PV module is constructed by connecting two or more number of solar cells in parallel and series. by Considering only one single solar cell; it can be constructed by using a current source, two resistors and a diode. This model is commonly known as a single diode model. Different models are also available but here we are mainly considering only single diode model
Shivarudrappa Biradar, IJRIT-86
Figure 1: Single diode model
2.1 Irradiation effect
The P-V and I-V curves of a solar cell are totally dependent on the solar irradiation values. The solar irradiation value changes keeps on fluctuating, due to the environmental condition but we can use control mechanisms which are available to track this change and we can change the working of the solar cell according to the our requirements and load demands. If higher the solar irradiation that is irradiation coming from sun, higher the solar input is applied to the solar panel and hence magnitude of the power will increase for the same voltage value.
With increase in the solar irradiation value which results the increase in the open circuit voltage. This is because of the fact that, when maximum amount of sunlight incidents on to the solar cell, the electrons will get higher excitation energy, which results the increasing the electron mobility and hence maximum amount of power is generated [7]
Figure 2: solar irradiation effect on P-V curve.
2.2 Temperature effect
While writing the code in Embedded MATLAB functions increasing the temperature around the solar cell will provide the negative impact for power generating technique. When increase the temperature which results in decrease in the open circuit voltage. Temperature increasing effect results the band gap will also increased. Thus maximum amount of energy is required to cross this barrier. Hence solar system efficiency is reduced [7] and [10].
Shivarudrappa Biradar, IJRIT-87
3. Boost converter
The Boost converter helps to steps up the input voltage level to a required output voltage level without using the transformer. The important components of a boost converter are diode, inductor and a high frequency switch that is MOSFET. These all together supply the power to the load at a voltage higher than the input voltage level. The control strategy depends on the manipulation of the duty cycle in the switch.
which is responsible for change in voltage[11]
Figure 3: Boost converter circuit
The boost converter is having two modes of operation.
(I)Charging Mode of operation, (II) Discharging Mode of operation
4. Maximum power point tracking
The solar cell efficiency is very low. While increasing the efficiency, different methods are considered to match the source and load. One method is called Maximum Power Point Tracking (MPPT). This method is used to obtain the maximum power from a varying source. the I-V curve is non-linear in nature, making it difficult to use to in certain power load. This is achieved by using a boost converter having duty cycle is changed by using Maximum Power Point Tracking (MPPT) algorithm. There are different algorithm few out of them are listed below [3], [4], [5] and [8].At the load side boost converter is used and the solar panel is used to power this converter. There are different approaches are used for maximum power point tracking (MPPT) a few of them are listed below.
(I)
Perturb and Observe method. (II) Incremental Conductance methodShivarudrappa Biradar, IJRIT-88
5. Simulation
Figure 4: Boost converter with solar cell and MPPT system Model
5.1 Ilg Generator Unit
Figure 5: The Eg generator unit
6. Simulation results
The simulation of solar cell is done using MATLAB and SIMULINK. The IV and PV curves from the practically obtained results are shown below. The parameters are considered is a generalized solar cell. The graph is similar to the theoretically graph of
Shivarudrappa Biradar, IJRIT-89 the solar cell current and voltage. The peak power is represented by a circle in the graph. Here only one solar cell connected in series is considered, hence the output of solar voltage is less in this case
Figure 6: solar output voltage (78V)
Figure 7: output voltage of the boost converter (550V)
Shivarudrappa Biradar, IJRIT-90 Figure8: Power across Boost converter circuit (600W) & Power across MPPT circuit (700W).
Figure 9: When solar panel is tracking maximum irradiation at the LDR1 side
Figure 10: When solar panel is tracking maximum irradiation at the LDR2 side
Shivarudrappa Biradar, IJRIT-91
7. Conclusion and future work
500 ohms resistive load is used with the boost converter to make the output voltage and current are similar. This operation is carried out at the frequency of 10 KHz which is set with the help of a repeating sequence pulse generator. This same generator is used for producing the pulse, these pulse signal compared with the signal generated at the MPPT unit is applied to the switch for gating action. When we use the MPPT there is no need apply duty cycle as input, the algorithm itself decides and iterates the duty cycle. But if MPPT is not been used, then the user manually would have to feed the input the duty cycle to the system. Whenever solar irradiation changes in the maximum power point (MPP) changes and hence the required duty cycle for the specific operation of the system also changes. But if we use constant duty cycle then maximum power point (MPP) cannot be tracked and hence the system is less efficient.
Improvement of this project can be done by tracking the maximum power point (MPP) in changing environmental conditions. Change in Environmental condition can cause the change in ambient temperature or change in solar irradiation or even both. This can be done by writing the code in Embedded MATLAB functions, instead of Simulink models to carry out MPPT. In the Simulink models the temperature and solar irradiation can be given as variable inputs but writing the code in Embedded MATLAB functions constant values of temperature and solar irradiation can be applied.
MPPT technique can be carried out without using the controllers in order to reduce the implementation complexity and cost of hardware can be reduced.
ACKNOWLEDGMENT
We are very thankful to our beloved HOD Prof. Bhima Shastri Dept. of electronics and communication Engineering SIT Mangalore. For providing all the facility for completing this project
References
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