CHAPTER-7 CONCLUSIONS AND FUTURE SCOPE

Transcription

1 CHAPTER-7 CONCLUSIONS AND FUTURE SCOPE

2 7. CONCLUSIONS This chapter intends to summarize the work which has been carried out throughout this thesis, emphasizing those elements, which contribute to Maximum Power Point Tracking under partially shadowed and non uniform shadowed conditions. The thesis addresses an important technical challenge that has to be surmounted for better and increased use of solar power. In the context of Indian scenario large scale exploration of solar energy is a necessity. Policy initiatives of the government should be supplemented through better research and development in increasing the efficiency of the PV systems. Most of the renewable energy resources come from nature and the technical challenge in surmounting the environmental challenges is huge in any major initiative to tap energy from it and solar power is no alien to it. The problem is unique and complex and has many interrelated factors that add to the complexity. Unlike other renewable energy sources solar energy has other domestic and stand alone applications as well. The problems offered by these applications are entirely different from those encountered when connecting the system to the grid. To encourage investors and other stakeholders to invest large scale in solar power the efficiency and yield of the solar PV modules has to be increased. This thesis is a sincere attempt to aid in enhancing the efficiency of PV module by tracking the maximum power point under varying shadow conditions. The thesis has two main objectives like modelling and extraction of PV cell parameters and tracking of maximum power point under variable shadow conditions. In the first chapter, it has been analysed the energy scenario in India and the importance to tap the solar energy which is the vast potential being offered by the sun. The performance tests with different models like two diode model and single diode model. In chapter 3, verifies the validity of different models viz Mathematical modeling, Simulink modeling, Simscape modeling for commercial PV panels. The results exhibit the performance of these models. The proposed models were tested for 157

3 their performance, simulated in different environmental conditions, vides changing irradiance and partial shading. The primary objective of this chapter is to highlight the occurrence of multiple peaks under nonuniform shading conditions. The single diode model based on bishops model clearly helped the researcher to understand the influence of temperature and irradiance on short circuit current (I sc) and the open circuit current (I oc ). This model helped the researcher in modeling the behavior of the PV cell as a function of temperature and solar irradiance. This model also helped in studying the P-V and I-V characteristics under different conditions of insoltaion.the two diode model provided with a comprehensive analysis of influence of temperature and irradiance values on the I-V and P-V characteristics of the PV cell. The results of nonuniform shading conditions of different values of temperature and irradiance helped in studying the effects of both temperature changes and insolation changes on the characteristics of PV cells, which is an important aspect in understanding and extraction different operating parameters of the PV cells. Since the Modeling of PV cell involves the estimation of the I-V and P-V characteristic curves to emulate the real cell under various environmental conditions and it is important to have a model that is truly reflective of a real time system. The Simscape model provides one such opportunity. In this work Simscape model is used to analyze the effect of nonuniform shading on the characteristics of the PV cell. The shell SQ-175 which is having 72 solar cells connected in series is modeled and tested on nonuniform insolation conditions. The models clearly presented the occurrence of multiple peaks under non uniform shading conditions. The use of Simscape model has enhanced the flexibility in selecting the number of parameters being analyzed in regard to the solar cell. Simscape model presents a better opportunity in modeling commercially available PV Panels. In chapter 4, the researcher has used two evolutionary approaches namely Genetic Algorithm and Differential Evolution for extracting the parameters. The models are also validated for different and partially shadowed conditions. To validate the above PV array has been used, which comprising of six PV cells connected in series. For validation four panels is considered to have uniform insolation and remaining two panels having different insolation. From the results it can be observed 158

4 that both DE and GA methods converge well with the data sheet values. DE method scores over the GA method in terms of faster response and slower convergence time. The chapter 5 comprehends a detailed analysis of Maximum Power Point tracking methods. A conventional method based on short circuit and Incremental conductance with direct control are used and the proposed method is using an Artificial Neural Network(ANN) Photo Voltaic Genetic Algorithm(GA) function, are simulated and the results were presented for different insolation values including non uniform insolation of PV panels. The data needed to train the ANN was obtained using the maximum power GA function. The GA is used to optimize the input dataset of the ANN to obtain a smaller and more ejective input dataset. This method is particularly important in noisy and unimportant data, which reduces the generalization ability and electiveness of the ANN. The GA is used to keep the most decisive data and remove insignificant data. When using the new dataset, a smaller error value may result at the end of training. The solar irradiance, cell temperature values are input into the controller and the reference voltage value of the PV modules corresponding to the MPP is calculated by the GA-optimized ANN structure. When the output voltage of the PV modules is adjusted to these values, the system is assumed to operate at the MPP. Compared with the conventional methods, the proposed ANN-based method improved the transitional state and reduced the oscillations in steady state, as the maximum power point was obtained beforehand by the ANN model. Both the compared methods vary the duty cycle of the converter. As observed from the results the ANN based tracker is capable of adjusting the duty cycle even in the presence of nonuniform shading conditions to operate the PV at its Maximum Power Point. The results were presented in comparison with the ideal power, the output power and the maximum power tracked for different scenarios.. In chapter 6, the fuzzy controller feeds on the insolation as input and gives the reference current value for operating the DC to DC converter. The fuzzy controller provides a flexibility of developing the maximum power point at all the situations for better PV Module performance. The fuzzy controller tracks the operating reference current value compared to the standard Partab & Observer method enabling better 159

5 stability of the system. This feature enables the proposed system to track maximum power points under partially shading and rapidly varying insolation conditions. It is designed as a comprehensive system that has been generalized for maximum power point tracking under partially shadowed and nonuniform shadow conditions. An attempt is been made in this thesis to contribute for better maximum power point tracking. Unlike the existing methods that are based on periodically sweeping the entire I-V characteristic of the array our approach increases the optimization of this process enhancing the overall power output and efficiency. FUTURE SCOPE The present proposed algorithm will be implemented in a VLSI platform in future to have its applications extended to the real time monitoring of maximum power point under partially shadowed conditions. It is also suggested that the utility of various power electronic devices in maintaining the system stability can also be investigated in relation to the rapidly varying shadow conditions. A detailed Cost analysis can be conducted considering carbon credit to show whether it is economically viable or not. Since the performance of PV system is strongly dependent on loss factors such as shading, PCS losses, mismatch, PV array temperature rise, etc. There is a necessity for reviewing these loss factors to evaluate and analyze accurately the performance of PV system. Designing PV cells with some electrical appliances like DC DC boosters are very useful in boosting up the voltage wherever it is necessary and also for suppressing the ripples etc. DC DC choppers with variable duty cycle can be used along with filters. For direct application of DC that kind of system can be designed. Intelligent devices like microprocessors, PLC (programmable logic controller) may be added to the system to keep the operating point (maximum power point) for maximum efficiency. 160

6 A detailed performance analysis of the present system can be carried out to show its reliability as a future work. Solar PV is a technology that offers a solution for a number of problems associated with fossil fuels. It is clean decentralized, indigenous and does not need continuous import of a resource. On the above of that, India has among the highest solar irradiance in the world which makes Solar PV all the more attractive for India. 161