Research On Recovery Technology Of Voltage Sag Compensation And Interruption Based On Dynamic Voltage Recovery Device

With the advance of Intelligent Manufacturing 2025,a variety of precision equipment and instruments have been put into use on a large scale,and the requirements for power quality of such equipment are extremely strict.Among many factors affecting power quality,voltage sag and interruption are particularly prominent.At present,the main method to solve the voltage sag and interruption problem is to install dynamic voltage restorer(DVR)on the sensitive load side.However,with the increase of the sensitive load connected to the bus,the compensation voltage output by each DVR at the same time will be different in magnitude and phase,which will affect each other on the bus,resulting in limited improvement of power quality,and the total investment and loss will also rise substantially.Therefore,in order to solve the above problems,this paper concentrates on voltage control at the grid side,and the main research work is as follows:Firstly,based on the fact that important users use double-section buses to supply power and the probability of voltage sags occurring simultaneously is very small,a new dynamic voltage recovery device is designed to centralized governance voltage sags and interruptions on the grid side.The device switches working modes according to the depth of voltage sags,and realizes centralized stability compensation for voltage sag and quickly recovery of voltage interrupt on bus.According to the input and output characteristics of the device,a cascaded 3H Bridge inverter circuit is designed as the core of the main circuit topology.The simulation results show that the output voltage level of the main circuit is large and the harmonic content is small.The harmonic characteristics of the system voltage can be effectively improved while the voltage recovery is completed.Secondly,in the voltage sag compensation operation mode,the relationship between compensation voltage and energy loss of three classical compensation strategies is compared and analyzed.A minimum energy tracking compensation strategy under voltage constraints is proposed.By setting the phase constraints,the minimum energy tracking is performed to find the optimal compensation voltage phasor,which not only ensures the voltage phase deviation after compensation is small,but also considers the energy loss of the energy storage unit during the compensation process,thereby greatly improving the device compensation durability.The simulation results show that the compensation voltage amplitude and energy loss are both lower under the proposed strategy,and the phase deviation of the voltage after compensation is small,and the compensation effect is good.Thirdly,in the voltage interrupt recovery mode,an improved droop control based on virtual impedance is proposed to achieve seamless transfer between the operation modes of the inverters during voltage interruption recovery.And QPR control is introduced to realize zero steady-state error control of the voltage.On this basis,adaptive SOGI-PLL is used to improve the precision of phase-locked,and the pre-synchronization control of grid-connected is realized by secondary frequency and voltage regulation under improved droop control.In addition,the seamless mode switching is realized by changing the droop coefficient when islands are switched.The simulation analysis shows that,this strategy not only achieve stable operation of islanding and grid-connected mode,but also achieve seamless transfer between operating modes,thus achieving fast recovery of voltage interruption.Finally,based on the above main circuit,the hardware circuit and software program of the digital control system are designed,and the experimental platform is built,which lays a foundation for the subsequent voltage sag compensation experiment and voltage interruption recovery experiment.