The Research Of Power Quality Monitoring System Based On Virtual Instrument

Various impact and non-linear loads are growing rapidly together with the growing loads,which cause serious pollution on the power supply system. On the other hand,with social progress and development,modern industrial electrical equipment require higher power quality, so people pay close attention to power quality problems.To improve and enhance power quality,power quality problems should be detected in time and assessment accurately, therefore, research on power quality detection method and to develop the measurement instruments have a certain theoretical and practical value.This paper analyzes the domestic and international power quality monitoring device status and direction of development, introduces the basic concept of power quality, national standards, the definition of five steady-state indicators, causes and hazards and the restrictions of the corresponding indicators in national standard, a brief analysis of the current indicators of power quality measurement methods and their advantages and disadvantages associated.Among the methods to calculate three-phase voltage unbalance factor, the national standard definition and IEC definition are more complicated, the definition recommend by national standard and CIGRE can not calculate the positive sequence component and negative sequence component, the IEEE definition and NEMA definition are low accuracy computation, to solve this problem, the vector graphical procedure of positive-sequence component and negative-sequence component to calculate three-phase voltage unbalance factor is proposed. With only using the voltage amplitudes of three phases, the proposed method can calculate positive-sequence component, negative-sequence component and three-phase voltage unbalance factor accurately. New method can serve as a precise calculation of three-phase voltage unbalance algorithm.With the reduction in the number of incandescent lamps, fluorescent and LED lights are used in a large-scale, the deficiency of IEC flickermeter could not measuring interhamonic-caused voltage flickers has become increasingly apparent. In order to compensate for this shortcoming, we analyze the source of error in sine interpolation, as sine interpolation may cause errors on assessment of the flick, we propose a new approach based on sine interpolation to measure voltage flicker. The goal of new method is to promote further study on improving the flickermeter algorithm.In this paper, five steady-state module of power quality are designed based on LabVIEW environment, the function of index limit automatically write into the database is realized, database query software is redacted based on Visual Basic environment, the network communication function is initial realized, simulation, accuracy test and actual measurement on electric supply are done aim at the measurement modules, verification and measurement results indicate that the measurement modules have higher accuracy and stability, they can provide reliable support for for further experimental verification. Furthermore, the measured data can provide reference for the electricity supply user or division to control the power quality problems.