Research On Voltage Sag Detection And Compensation Method Of Dynamic Voltage Restorer

With the continued growth of precision electric equipment using rate and the energy of the Internet continues to advance the process,a variety of power quality problems have emerged,in which the voltage sag is the most prominent power quality problems,enterprise users incalculable harm of voltage sag caused by the output,in order to ensure the safety and high efficiency,continuous high quality power energy compensation device for voltage sags control has achieved rapid development.As a new type of power quality regulating device,Dynamic voltage restorer(DVR)can quickly eliminate the voltage sag,solving voltage asymmetry and short-term power outages and other issues,thereby ensuring the reliable operation of the load.Due to the good dynamic compensation performance,DVR has become the most economical and effective compensation device to improve the power quality problem.This paper from the working principle of DVR,the detailed analysis of system structure of cascade multilevel DVR,comparative analysis of the advantages and disadvantages of the traditional principle of several DVR multilevel inverter circuit,inverter main circuit unit determine the design of the 2H+ bridge multilevel inverter structure.For the problem that DVR device cannot take the system stability and dynamic response speed into account,using a proportional integral based on double closed loop PI and improved proportional resonant external loop MPR controller three layer composite control strategy,so that the DVR device can further improve the harmonic characteristics of system voltage compensation while load voltage.Secondly,propose an interactive detection method combined with the improved d-q transform and aliasing wavelet transform algorithm,which is based onab change detection method,using aliasing wavelet transform harmonic signal is decomposed into different sub-band signals,so that further precise extraction of fundamental and harmonic components characteristics.The simulation results show that the method has a certain filtering noise reduction function,and has high accuracy and good real-time performance.In view of the existence of the traditional compensation control method,phase distortion problem of large active powerconsumption,put forward an optimization method based on compensation transition model,simulation results show that the compensation effect of the DVR system design is very good,can realize the system output active power and prolong the time of minimum compensation.Finally,the design of cascaded multilevel DVR digital circuit is presented,which includes the main control circuit,signal conditioning circuit,detection circuit and driving circuit.The software design is divided into three parts: A/D sampling circuit design,startup compensation program design,SPWM wave output and design.The DVR experiment platform is built,which includes the main circuit and the control circuit.In the premise of hardware and software debugging,a simple voltage sag detection and compensation control method is designed,it can be seen from the experimental results that the designed system can basically realize the dynamic response and fast compensation function of DVR.