Research On Dynamic Voltage Restorer For Low Voltage Distribution Network

With the adjustment and upgrading of China’s industrial structure,the number of sensitive loads in low-voltage distribution network is increasing,and various types of sensitive loads require higher and higher voltage quality of low-voltage distribution network.Therefore,improving the voltage quality of distribution network has become the focus of power supply departments.In view of the current situation that most sensitive loads in high-tech industry are mainly low-voltage devices,choosing Dynamic Voltage Restorer as a user-side series compensation device to solve the voltage quality problem of low-voltage distribution network is a research hotspot in recent years.Firstly,the working principle and topology of DVR are analyzed and studied,and the DC module,inverter module,filter module and access module involved in DVR topology are compared and analyzed respectively.A DVR topology suitable for low voltage distribution network is determined and the main circuit parameters are calculated.Then the voltage detection algorithm of DVR is studied,and the advantages and disadvantages of several common voltage detection algorithms are compared and analyzed.aiming at the problem that noise in the signal to be detected interferes with the detection results,based on morphological filter,derivation voltage detection algorithm and adaptive theory,an improved derivation voltage detection algorithm based on adaptive compound morphological pre-filtering is proposed.Through simulation and experiments to detect the noisy voltage drop,it is verified that the algorithm has better real-time performance and higher accuracy.The compensation strategy and control mode of DVR are also studied.Based on the comparative analysis of three commonly used compensation strategies,a compensation strategy considering sensitive load types and equipment limit is selected.The advantages and disadvantages of feedforward control and feedback control are compared and analyzed,and a compound control method based on feedforward control is selected.Through the simulation model,the compensation strategy considering the limit of DVR equipment,the compound control mode and the compensation ability of DVR in the case of three-phase voltage drop are verified respectively.Finally,a single-phase DVR physical verification platform suitable for low-voltage distribution network is designed,the drive circuit,detection circuit and other hardware parts are designed,and the relevant software control programs are designed based on TMS320F28335 digital signal processor.At the same time,a voltage sag simulation circuit is designed,and the experimental results show that the DVR suitable for low-voltage distribution network has good compensation performance for voltage sag.