Design Of Power Quality Monitoring System Based On Virtual Instrument

With the rapid upgrading of the national economy,power quality problems make more and more attention.Power quality is getting worse,causing by more harmonics which produced by the growing number of DG in power system and electrical equipment.The traditional power quality monitor cannot monitor power quality on-line and power quality parameters monitored are limited,also it is different to achieve network interconnection.Therefore,designing new power quality monitoring system is of great significance.In this paper,a new power quality monitoring system with virtual instrument as the core is designed.This paper summarizes the power quality parameter definition,the theoretical basis of the measurement method and the realization process.This paper introduces the FFT method used in harmonic analysis of power system.In order to suppress the phenomenon of spectrum leakage of FFT,FFT with a windowing algorithm is proposed.In voltage flicker measurement,IEC flicker filter uses digital filters,compared with the traditional flicker,reducing the measurement error.In order to reduce the calculation error and improve the efficiency of the program,the symmetric component method and the IEC simplification method are used in the calculation of the imbalance degree.The HHT transform is introduced in the transient energy analysis,which can get the accurate position and amplitude of the short-time voltage disturbance.On this basis,this paper designs and realizes the power quality monitoring system based on virtual instrument.It can monitor the voltage and current RMS,power,three-phase imbalance,power grid harmonics,voltage fluctuations and flicker,short-time voltage disturbance monitoring,and can alarm in the abnormal state;it can achieve real-time data preservation,waveform preservation;can query data,update and delete data;can playback historical waveform,print report;can achieve remote access and other functions.Compared with the traditional monitor system,it has the advantages of friendly human-computer interaction,simple operation,strong data processing ability,small error,easy expansion and so on.Finally,the simulation and running test of the power quality monitoring system are carried out in terms of the accuracy of the relevant indicators.The results show that the measurement error of the virtual instrument is small,therefore the hardware error of the system is mainly considered in the actual measurement process.Aiming at the three-phase electrical of the laboratory,a hardware circuit of data acquisition is constructed.The system is used to monitor the quality of the laboratory.The results show that the system has good real-time processing performance and stays in stable operation,therefore it has practical application value.