Study On Voltage Sag Detection And Compensation Strategies Of Distribution System

In recent years, with the rapid development of information technology, sensitive load such as computer and microprocessor-based electrical equipment, their the proportions of power quality are increasing in recent years, these sensitive load on power quality demands much more demanding than the traditional electrical equipment. Voltage sag is a modern power quality problem in the central part, which resulted in increasingly serious harm, causing huge economic losses, and therefore people are paying more and more attention to it.Custom Power Technology is a new technology that based on power electronics technology, to improve power quality and increase the reliability for the purpose. Using of power electronics systems means the transformation of power system distribution network without a voltage fluctuation, non-voltage asymmetry, without intelligent distribution network harmonic pollution to meet the power system load on the system sensitive to power quality and supply reliability requirements.The application of Custom Power is quite promising in distribution system. It becomes one of the forward researches nowadays. Its objective is to reconstruct distribution system into flexible system, which has no flickers, no sag or swell, and no harmonics.Dynamic voltage restorer is an automatic voltage compensation device, based on custom power technology, which can compensate the voltage sag, swell and harmonic with good economy. When the voltage sag occurs in distribution system, DVR could control the voltage stability in side of load-sensitive.Based on previous work, this paper proposes an improved detection method for single-phase voltage based on transient voltage d-q transformation to improve demand derivatives to construct the three-phase virtual voltage, through the transient voltage d-q transformation and low-pass filter to be sag characteristics, than the traditional method a small amount, and greatly reduces the detection of sag characteristics of the delay. Then introduce DVR structure and its working principle, the current common DVR compensation method, that defects voltage compensation method, in-phase compensation method and the minimum active power compensation method are introduced, then to make an analysis of these compensation methods of characteristics and the compensation principle.In voltage sag detection and compensation strategies for a certain amount of study, structure the DVR model in MATLAB simulation platform, and its major such as the main circuit, PWM, IGBT, and LC filters for parameter setting and connection, voltage sag detection and compensation strategies simulation are based on this model. Detection method used is the d-q transformation method, it is based on instantaneous reactive power, this method which is using in-phase compensation method and the minimum active power compensation method, by these two common methods of simulation compared with their specific characteristics and the actual in the range of applications.Simulation results show that the detection and the compensation method used are correct and effective.