A Three-phase Parallel Multi-functional Converter

Power quality issues are becoming more and more serious due to the large industrial usage of power electronics equipment, including harmonics, reactive power, three phase unbalance, large difference between peak load and vale load, voltage disturbance and so on. Recent researches on the power quality improvement are mostly focused on separate compensation of a single issue, so to save the cost, research on comprehensive compensation is meaningful.This paper extends the research scope of APF, SVG and UPS, proposes a multifunctional converter. It works not only to compensate harmonics and reactive power, charge and discharge from DC load, but also as EPS when utility system is cut off.The first chapter describes the background of the project. Several issues of power quality are presented, including harmonics, reactive power, three phase unbalance, large difference between peak load and vale load, voltage disturbance and so on. Then the causes and corresponding compensation measures are introduced. We can find the possibility of comprehensive compensation using voltage sourced converter by comparison.In the second chapter, a kind of current track way using double hysteresis SVPWM is mainly studied. Distorted current compensation is based on the real-time current analysis methods and current track techniques. The third chapter presents several usual current analysis methods and mainly focuses on instantaneous reactive power(IRP) theory and methods using dq transformation. Based on the purpose of the compensation system , a comprehensive measure about the two ways is proposed and validated by MATLAB.The fourth chapter presented the principle and output voltage control strategy of the emergency power supply. Because the circuit needs current overload protect, a double loop strategy ,with current feedback of filter inductance as inner loop and output voltage as outer loop, is studied.In the fifth chapter, the multifunctional converter system is presented. And with MATLAB the effects of the functions are approved. The paper is summarized in the end.