Study On The Single-phase Dynamic Voltage Restorer

Nowadays,a great deal of the electrical equipment controlled by the computer and digital signal processor has put into use in the life and production,and these devices are very sensitive to the fluctuations and various disturbances in power supply.So the more stringent requirements for the power quality of the power supply are puts forward.In this context,it is necessary to research the power quality compensation devices and methods to improve the power quality.Dynamic voltage restorer(DVR)is a series voltage compensation device based on the power electronic device,which is connected in series between the supply voltage source and the sensitive load.When the voltage quality problems of the power supply voltage occur,such as the voltage sag,swell,flicker,and harmonic distortion,by injecting the compensation voltage to the power line,DVR can effectively improve the voltage quality of sensitive loads,and ensure the stability of the load terminal voltage.In this paper,for the single-phase DVR,the dynamic voltage detection technology,the DVR system control method and the double DVR coordinated control methods are analyzed and studied in details.Firstly,a real-time detection method for single-phase dynamic voltage sag is introduced.In this method,a three-phase virtual voltage is constructed by reducing the single phase delay angle and use the relationship between the voltage of each phase,so that the detection algorithm can be applied to the detection of the any distortion single-phase voltage,and effectively reduces the delay of the traditional method.At the same time,this paper analyzes and studies the problem of large delay of filter in traditional method,points out that the single filter has a large delay due to the low cutoff frequency,and presents a double filter link with high cut-off frequency,improving the detection speed further.The simulation results show that the proposed method can effectively improve the real-time detection.Secondly,the DVR control method to improve the voltage quality of power supply system is studied.According to the DC side voltage fluctuation of the voltage converter in the practical DVR system,the DC fluctuation voltage is seen as a state variable,and then the DC voltage is detected in real-time by the feed-forward loop and the gain of inverter bridge is compensated for,so the influence of the unstable quantity of the DC input voltage on the compensatory output of the DVR system is offset.At the same time,according to the deficiency of the traditional proportional integral(PI)control strategy in the DVR,a genetic PI algorithm combining with repetitive controlalgorithm is proposed.Theoretical analysis testifies that the compound control algorithm can effectively improve the dynamic and static performance of the system output.The simulation results verify that the proposed compound control method can improve the response speed of the DVR system and compensation accuracy,greatly reduce the harmonic contents of the load voltage,and effectively improve the voltage quality of the sensitive load.Thirdly,aiming at the deficiency of the reliability and flexibility of the single DVR in the voltage compensation system,a double DVR series connection coordinated control system is proposed,in which a independent coordinated controller is adopted to control each DVR,and the system structure and control method of dual DVR in series are analyzed and studied further.A hybrid control method based on the fuzzy PI control which can adjust the control parameters online and repetitive control that can improve control accuracy is proposed.At the same time,according to the harmonic content and the voltage drop,three different operating modes are proposed.By setting certain control rules,the control system can choose one operation mode in the three operation modes according to the capacity amplitude limit of DVR1 and DVR2,the average compensation amount of DVR1 and DVR2,or according to the harmonic quantity compensated by DVR1 and the fundamental quantity compensated by DVR2.A double DVR system model is built in the simulation environment,and the results show that the proposed dual DVR multiple operating modes can effectively improve the reliability and flexibility of the compensation system.Finally,the paper summarizes the works of this paper.On the basis of the present results,the deficiencies of the research work are discussed and the research directions in the further are analyzed.