Research On Dynamic Voltage Restorer And Its Application In Low-voltage Ride-through Capability For Wind Farm

With the development of technology, distribution network becomes more and more complex,and a large number of sensitive electronic devices have been widely used in it, which makespeople pay more attention on the transient power quality problems such as voltage sag. As areal-time compensation device, dynamic voltage restorer (DVR) can improve power qualitiesby eliminating these problems such as voltage sag and flicker in milliseconds.This paper firstly introduces the working principle and system structure of DVR, establishingthe mathematical model. And a control flowchart of DVR has been derived from themathematical model. Based on the flowchart, this essay analyses the stability of DVR and pointout the advantages and disadvantages of this control strategy. As to three kinds of compensationstrategy (full compensation, in-phase compensation, minimum energy compensation), a detailedanalysis of their application scope is given.There are detailed analysis and comparison of several traditional voltage detection methodsin this paper. A in-depth study on the voltage detection method based on instantaneous reactivepower theory has been done in the essay. With the corresponding simulation model, thesimulation result shows that this method can quickly and accurately detect distortion voltage, inline with the requirement of DVR voltage detection.As to the problem of low voltage ride through (LVRT), this paper elaborates the significanceand engineering meaning of LVRT. To optimize the energy and voltage in DC bus, an E-Vcontrol strategy is adopted in this paper. And the inner and outer loop control flowchart andSPLL control model are shown in this part.At the end of this paper, the DVR simulation system module is established to prove thevalidity of E-V control strategy and the possibility of using DVR in wind farm. And thesimulation results show that DVR can effectively improving the LVRT capability of windgenerator.