22-09-2014, 02:46 PM
PHOTOVOLTAIC SYSTEM
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INTRODUCTION
The PV System is becoming very common because of its usefulness in generating electricity. Here we will discuss the types of PV system and its components with circuit diagram. These systems can be used for both grid connected and off-grid (battery only) systems. A photovoltaic system offers a way to generate clean, quiet, and reliable energy. The acronym PV is a combination of two words; ‘photo’ and ‘voltaic’. The word photo represents light, and the meaning of voltaic is ‘producing electricity’. The whole word explains that it is a device that produces electricity from light.
Using maximum power point tracker (MPPT) with the intermediate converter can increase the system efficiency by matching the PV systems to the loads. This paper presents a maximum power point tracker based on Gradient Approximation (GA) and a control scheme for and a control scheme for a single-phase inverter connected to the utility grid. GA provides an adaptive nature for the system performance.
The photovoltaic (PV) generators have a nonlinear V-I characteristics and maximum power points which vary with the illumination level and temperature. Using maximum power point tracker (MPPT) with the intermediate converter can increase the system efficiency by matching the PV systems to the loads. This paper presents an irradiation level estimator and a maximum power point tracker based on support vector regression (SVR) and a control scheme for and a control scheme for a single-phase inverter connected to the utility grid. SVR provides an adaptive nature for the system performance. Also the SVR provides excellent features such as fast response, good performance and the ability to change the regression function to improve control system. The single-phase dc/dc converter is designed to control the power flow to the maximum value. The simulation results have verified the validity of the proposed estimation algorithm.
PHOTOVOLTAIC SYSTEM
A real PV array has been modeled. It consists of 30 PV modules with 36x2 mono crystalline silicon solar cells each one, connected in series and parallel. Each module can produce 106 W of DC electrical power with an area of 126.5 square centimeters. The array is configured as follows: fifteen modules are connected in series, resulting a nominal operating voltage of 325 V. Then, 2 of these series strings are connected in parallel, resulting in a current of 6A. The rated power of the PV array is 2.6 Kw (DC). In order to allow the interaction between a DC/DC converter and the PV array, a simulation model for a PV
array has been developed, including the dependence of the PV array output with the irradiance and temperature.
In general, PV modules have nonlinear voltage-current characteristics, and there is only one unique operating point for a PV with a maximum output power under particular conditions.
CONCLUSION
This paper presented two-stage energy conversion system to connect the PV array to the grid utility. Maximum power scanning algorithm is used regularly to determine the optimum duty-ratio to extract the MPP. It also presented the inverter control scheme to deliver the converter output power to the utility grid at unity power. The simulation results have shown that the advantage of this system is fast response, good transient performance, and high accuracy. By utilizing the PV array voltage and current information from both of the PV modules, the relative slope of the array V-I curve with respect the slope at
the peak power point can be found, which moves the operating point toward the peak power point.