Research On Voltage Sag Detection And Compensation Technology

Voltage sag is one of the most serious power quality problems, has attractedmore and more attentions of scholar, power supply units and users both domestic andabroad. This paper focuses on the voltage sag detection methods and motioncompensation technology.The voltage sag characteristic quantities detection is the basis and foundation ofthe sag compensation control. This paper briefly introduced the basic concepts ofvoltage sag, analyzed of the real-time detection methods currently used to detectvoltage sag characteristic quantities. Then, at the basis of transformationmethod applied on single phase, this paper proposes an improved method shiftedwith an adjustable angle to construct vectors. The improved method adjusts thesize of the appropriate delay angle to guarantee real-time performance and accuracyof the detection result. In power voltage unbalanced condition negative sequencevoltage is contained, software PLL can not accurately track the fundamentalfrequency, Therefore in this paper, the phase shift method is used to eliminate thenegative sequence component instead of filtering out the second harmoniccomponent after dq transformation. Through the space vector transformation asize-adjustable angle is shifted to calculate the fundamental voltage of the positiveand negative sequence voltage. The improved SPLL is able to separate the positiveand negative sequence component, and did not affect the stability of the system. Thesimulation results show that the effectiveness of the new method and improvingSPLL is expected to be applied to the dynamic voltage restorer.Dynamic Voltage Restorer (DVR) is an effective means of voltage sagcompensation. This paper describes the basic voltage sag suppression method,systematic states the dynamic voltage restorer (DVR) device working principle andsystem composition, makes a comparative study of the control of the device,establishes the design feature of DVR. Several different compensation strategy isanalyzed to compare their advantages and disadvantages, based on depth analyzingof the DVR device output voltage and power characteristics, the paper proposes anoptimal time compensation strategy, the simulation analysis verify that thecompensation method can effectively extend the DVR compensation time.