Research Of Three-phase Blance System Saver

As the development of modern technology, a large number of sensitive electricalequipments are put into use in production and life fields, leading to higher requirements onpower quality from electricity consumers. Among all kinds of power quality problems, notonly contains the three-phase voltage unbalance, voltage harmonics, voltage quality problem, alsocontains a voltage drop, raised such as dynamic voltage quality problems, these problems in manyproblems of probability is also the most common。At present, there are corresponding measuresfor these problems: balanced devices connected by inductor and capacitor to improvethree-phase voltage imbalance; the passive or (and) active power filters to suppress voltageharmonic; and dynamic voltage restorer (DVR) to improve the voltage sag. However, theseproblems may appear simultaneously. Therefore, designing a device which can suppress thethree problems at the same time to improve the power quality is necessary.This thesis analyses and learns from principles of DVR, bringing up concept ofthree-phase balanced system saver which is composed of DC energy storage, threesingle-phase inverter and passive power filter. Real-time compensation can be made toimprove three-phase voltage distortion when problems occur.Introduce the production, harm of three voltage problems and present improvementmeasures at home and abroad. Bring up the concept of power-saver of three-phase balancedsystem;Analyze and learn from principles of DVR and the main circuit topology is composedof DC energy storage, three single-phase inverter and passive power filter. Design the mainparameters;The detection of three power quality problems aims at the fundamental positivesequence voltage detection. The thesis identifies d-q transformation method based on theinstantaneous reactive power theory; When fundamental positive sequence voltage sag occurs,three compensation methods can be chosen based on the specific requirements and devicesconditions; SPWM modulation is used to track compensation orders for inverter control;Single-phase equivalent circuit and mathematical model are made. Analyze shortcomings offeed-forward control strategy and bring up feed-forward PD closed-loop control strategy;Thefinal, proof is made for the correctness of theoretical analysis using MATLAB simulation.