Research On DVR Based On AC-AC Conversion

Dynamic Voltage Restorer (DVR) is a serial compensation device which will compensate the voltage-sag and improve the quality of power supply of sensitive load. Its fine dynamic function and relative lower cost make it the most operative and cost-effective method in nowadays voltage sag solvent methods.In this thesis, the auther investigates the various DVR electric structures and analyzes the advantages and disadvantages of each method. Based on AC-AC conversion theory and high speed switching technique of IGBT, the writer makes a study of the theory and structure of a certain DVR that can work continuously, then calculates and gets the conclusion of the relationship between the duty (D) and the serial transformer ratio (a), and simulates the conclusion with the software MATLAB and ORCAD. After the comparison of various detecting methods of DVR and analyzing the defect and disadvantage of them, a new voltage sag dectecting method was brought up. This new method reacts quickly towards the voltage sag, the dectecting result shows the occurence and the end of the voltage sag synchronously. The dectecting speed is so quick that the precise result can be achieved with half circle, whether harmonic is included or not.both the analysis and the simulation result show that the value got by this method can be the compensation evidence of the DVR continuously worked based on AC-AC conversion can be achieved within half circle, whether harmonic included or not. With this quick detecting method, the writer designs the voltage-sag detecting device composed of analog elements, then constructs an experimental voltage-sag detecting device of small capacity, and gets the experiment result. The simulation, as well as the experiment result verifies that the method can weaken the disadvantage effect of voltage-sag towards the sensitive load effectively. Thus it is one of the well-worked methods in improving power quality.