Research And Implemetation Of Dynamic Voltage Restorer Based On On-Line Forecast And Grille Fractal Method

Dynamic voltage restorer (DVR) gradually becomes the main means to solve the dynamic voltage problem because of its outstanding compensation effect and low expense. This dissertation presents a systematic study on many aspects of DVR, including detection algorithm, main circuit structure and the hardware design of DVR. And it will give a help to strengthen the stability and the robust of DVR. The main work is as follows:(1) This dissertation analyzes the principle of DVR and proposes a novel detection algorithm which is based on the on-line forecast algorithm and grille fractal method. Some sample values combined with the frequency obtained by software phase locked loop (SPLL) are used to form the current fundamental voltage wave, which can replace the mathematical filters in the general DVR detection algorithm. The validity of the method was verified by the result of software emulator and device test, which means the proposed method can exactly detect the voltage disturbance in any conditions of dynamic voltage quality.(2) A new main structure of DVR with three single phase inverter is proposed. Based on the easy-control characteristic, three single phase structure can feed up the shortage of the general three phase structure which can not compensate the three phase unbalanced. The results of the unbalanced experiments caused by the unbalanced load or the unsymmetrical short circuit show that the new structure can greatly restrain the voltage unbalanced.(3) The theory of the grille fractal method is introduced to the process of the detection of the voltage interruption so as to quantify the degree of the voltage interruption by optimization of the grille and to obtain the point when voltage sag or swell to give the start of stop information to the reference wave production component by comparing it with the nominal voltage value. The results of the simulation show that the method can rapidly locates the start and stop time of the voltage interruption and use it as the start and stop information of the DVR compensation.(4) The implementation of the prototype has achieved. TMS320LF24 series DSP is used as the core of process to finish the software implementation of the proposal detection method and the hardware implementation of the DVR system. The results of the device experiments indicate that the preferred device is able to detect the voltage sags within about 3ms, which can meet the real time requirements for DVR. Compared with the general devices based on the detection algorithms which employed certain kinds of mathematic transform and lowpasses, the preferred device is much more simple and faster.