Analysis Of Current Controlled Three-phase Voltage Source Inverter(VSI) Using Hysteresis Controller For Renewable Energy Sources

Ranging from simple converting of battery power or from renewable energy sources(DC)to sinusoidal AC waveform to high power HVDC transmission of electricity for a very large scale worldwide,inverter serves variety of applications.It is irreplaceable need in variable frequency drives which makes inverter invaluable on a very large scale worldwide.There is much scope left for improvement in the inverting technology,which is the reason they have been a well researching topic across academics.The output voltage of an inverter is of three types:square wave,quasi-square wave or low distorted sine wave.Quasi-square wave and square wave are restrcited for low and medium power applications because they have high value of Total Harmonic Distortion(THD),but better quality waveform for high power application is desired.Power quality of an AC waveform(sine wave)is probably more important than quantity.Recently Voltage source inverters using hysteresis controller are getting popular and are becoming more attractive to researchers.By adjusting the hysteresis width,Total harmonic distortions can be reduced drastically.This technique is preferable for many renewable energy sources,Thus research has been carried on in proposing new techniques for the controller.Harmonics are present whenever output voltage of the inverter is not purely sinusoidal.Thus to reduce these harmonics,suitable controlling techniques are applied and proposed.Literature review suggests that to reduce the distrotions and improve the inverter output voltage and current,there exists a space.As no specific controlling technique can suite for all the applications,there exists a dire need to study and compare different techniques for hysteresis controller.Thus using suitable hysteresis technique,an effort is made in this thesis work to enhance the output voltage and minimize total harmonic distortions of the inverter.Two different techniques for the hysteresis controller will be studied and compared for single phase VSI and then better one will be applied for three phase system for the analysis.This thesis contains the comparison of two hysteresis controller techniques implemented on single phase voltage source inverter and the better will be analyzed for three phase system.The simulation of both systems is done in MATLAB/SIMULINK.The methods and benefits of different controlling techniques,including the reducing of Total Harmonic Distortions,increase the DC bus utilization and such factors are also discussed.Furthermore,a comparison between two techniques for the Hysteresis Controller is done.The better one is chosen based on lower total harmonic distortions,reduced switching complexity and gate trigger circuitry,thereby to ensure minimum switching losses,switching complexity and gate trigger circuitry.The effect of hysteresis width(h)on the output voltage and current is also analyzed.