Studies on Photovoltaic Power system for Charging the Power Sources

Abstract

The Recent increase in the demand of PV system is due to the fact that they produce electric newlinepower without hampering the environment by directly converting the solar radiation into newlineelectric power. In this photovoltaic (PV) system plays a vital role. PV arrays consist of newlineparallel and series combination of PV cells that are used to generate electric power newlinedepending on the atmospheric conditions. (i.e. solar irradiance and temperature). To store newlinethe energy that is generated through their PV arrays one needs battery since batteries are the newlinepower tank of the renewable power system. newlineThese batteries play the vital role of the power supply when the renewable energy newlinepower source is not available. In this part a design has to be made to use solar energy for newlinebattery charging purpose in general and for lead acid battery charging in particular. In this newlineaspect it is necessary to couple the PV array with a boost conversion and towards this a newlinesystem has to be designed in such a way that with variation in load, the change in input newlinevoltage power fed in units, and the conversion follows the open circuit characteristics of the newlinePV array. Thus a suitable charger, especially solar charger has to developed that would newlineprovide 12 V or multiples of 12V to charge the lead acid or any other batteries for storing newlinepower as the solar battery charger cannot be used during night time. Even in this newlinedevelopment of solar charger using solar panel available in the market a controller has to be newlinedesigned based on a novel maximum power point tracking (MPPT) technique, as the power newlinefrom the sun is not going to provide maximum power all the time during the day and the newlinebattery or any power source will not get charged unless maximum power is provided. newlineA five parameter model of PV Modules has been implemented in Matlab/Simulink. newlineThe parameters of the model are determined by an approximation method using data sheet newlinevalues. Inputs to the model include light intensity and ambient temperature. The outputs are newlineany measurements of interests as well as power, cell temperature and voltage. Effects of newlinevarying the model parameters are demonstrated. A maximum power point tracking newlinealgorithm is used to keep the voltage at the maximum power point at all times. newlineA battery model based on discharge curve fitting is implemented. The model is based newlineon a fundamental battery cell which can be modified to construct many different Module newlineconfigurations. Power smoothing algorithms which average the input over a set time, are newlineused to provide a power reference to the battery system. newlinevi newlineThe PV model power output is compared to in-situ measurements by giving the newlinemodel inputs of measured irradiance profile and ambient temperature. Measurements of two newlinedifferent days, one with little variation in irradiance and one with a lot of variation, are used newlineto shed light on different effects. The difference between the output of the simulation and newlinethe measured values is very small, in the range of a few percent, especially when there is newlinelittle variation in irradiance. Large peaks indifference is probably caused by the maximum newlinepower point tracking not being able to follow rapidly changing conditions. newlineThe approximation used in the modeling of cell temperature deviates significantly newlinefrom the measured cell temperature. This is confirmed as one of the largest causes of newlinedeviations by running simulations with actual measured cell temperature. newlinePower smoothing efficiency is demonstrated with different battery Module sizes. newlineChanging the power smoothing algorithm parameters to suit the battery capacity is shown to newlinebe effective in providing as good smoothing as possible within battery constraints. newlineFor the novel MPPT techniques several algorithms are available to have the optimized newlineirradiance from the panel newlineThe proposed controller should utilize a smart multi-stage charging algorithm and this is newlineneeded to minimize the charging time of the batteries as this will be the demand for a future newlineelectric vehicle that is going to replace the existing vehicle which uses fossil fuels. For the newlineabove requirements a new controller is to be modeled for PV assisted solar charger using newlineMATLAB/Simulink simulation. Of the various algorithms available P and O and INC are the newlinetwo most extensively used algorithms employed for tracking and these will be effectively newlineemployed in the present attempt to achieve global Maximum power point. newlineThus in the present thesis an attempt is made on two aspects newline(i) MPPT is achieved through Matlab /Simulink simulations newline(ii) Control is affected through Lab view newline