Design And Research Of Power Quality Analyzer Based On Virtual Instrument

The integration of new power to the grid and the variety of power load have brought about many problems of power quality.At the same time,the intelligent industrial production and social life make more power devices and instruments become sensitive to the power quality,and the power quality requirements of users are increasingly high.Nowadays,the traditional power quality monitors widely used can measure the power quality parameters single,function is limited,most of them do not have the convenient data transmission function,and can not well meet the measurement requirements.With the development of virtual instrument technology,it is possible to monitor power quality using virtual instrument.Therefore,this paper uses Lab VIEW software,combined with the corresponding hardware circuit and acquisition equipment,to develop a new power quality analyzer with virtual instrument as the core.The main work of this paper is as follows:(1)In-depth analysis of the power quality analysis and measurement methods.In the algorithm used by the analyzer,the voltage and current are calculated according to the definition;the classical Fast Fourier Transform method is used for harmonic analysis,and the Hanning Window is inserted to suppress the spectrum leakage;the three-phase unbalance is calculated using the IEC recommended algorithm;In voltage flicker measurement,using the algorithm given by IEC flicker,replace the analog filter with a digital filter.(2)For the detection and classification of transient disturbances,the S-transform is mainly studied.A disturbance classification method based on improved incomplete Stransform and decision tree is proposed,which can reduce the computational workload and improve the real-time performance of the classification algorithm.The simulation results show that the algorithm can distinguish 13 transient disturbances including composite disturbances and maintain high resolution under noise.(3)On the foundation of theoretical research,a power quality analyzer based on virtual instrument is designed.The developed analyzer is building block design,has a good humanmachine interaction interface and a secure login module,has the function of recording and storage,and is convenient to expand and upgrade the measuring system.(4)A simulation signal generator based on virtual instrument is designed,which can simulate any steady-state and transient power quality signal,and can change the signal-tonoise ratio at will,so as to facilitate the power quality analysis and classification test.(5)Using the designed simulation signal generator to simulate the power quality analyzer,and verify the measuring function of the analyzer.The basic steady-state parameters of power quality are measured in noisy environment,and 13 kinds of transient disturbances are monitored and classified in real time using the incomplete S-transform algorithm and decision tree classifier.The accurate analysis,identification and classification of power quality signals are achieved.(6)At last,the power quality analyzer is tested in practice.The signal source is used to simulate the steady-state and transient power quality signals generated by the power grid.The signal is collected by the data acquisition card,and then input to the developed power quality analyzer for detection and analysis.The test results show that the system has small measurement error,and can monitor and analyze the steady-state and transient signals in real time.The measurement indexes are in line with the national standard and the system is stable in operation,and has good practical application value.