Research On Power Quality Monitoring Method Of Distributed Generator Based On Virtual Instrument

With the large-scale centralized power supply shortcomings emerged increasingly,distributed generator has gradually come into people’s view with its features of economy,flexibility and environmental protection.But the access of distributed generator to the grid will cause a lot of power quality problems.Meanwhile,with the increasing number of sensitive equipment,power quality problem needs more accurate,comprehensive,timely monitoring and analysis,so it is urgent to develop more powerful monitoring devices and methods to cope with it.First of all,this thesis explains the significance and status of the research,introducts the power quality problem in detail,analyzes the algorithm of various power quality indicators and the requirements of national standards.Then we study the influence of distributed generator on power quality,laying the foundation for the construction of each detection module in the monitoring system.Secondly,aiming at power quality detection and noise pollution,in combination with complete ensemble empirical mode decomposition with adaptive noise(CEEMDAN),permutation entropy(PE),wavelet threshold denoising based on undecimated wavelet transform(UWT)and hilbert-huang transform(HHT),we propose a time-frequency power quality detection method based on CEEMDAN-UWT denoising.CEEMDAN decomposes the disturbance signal into a series of intrinsic mode function with single-component characteristics,UWT denoising is used to deal with the noise components screened out by PE and reconstruction to obtain the original signal after denoising,the hilbert-huang transform is used to get the characteristic information.The method is implemented in Lab VIEW and simulated independently,the results show that the method studied in this thesis improves the SNR of the disturbance signal by 41.9%.Therefore,our method has good denoising effect and can accurately detect time-frequency information such as the instantaneous frequency and hilbert spectrum of the disturbance,verify the effectiveness of the proposed method.In the end,based on the previous research,this thesis builts a power quality monitoring system based on virtual instrument,which has greater advantages in scalability and maintainability than traditional systems.We combine power quality monitoring and new signal processing method with virtual instrument technology,PXI equipment is used to build the hardware,and the software is not programed with MATLAB,but only with G language to complete the entire power quality monitoring system programming,so it’s more intuitive and convenient.By means of modularization,data acquisition,signal generator,basic measurement,harmonic analysis,voltage fluctuation,three-phase unbalance,time-frequency analysis module and data storage module are designed.After simulation verification,the test results of each module meet the design requirements,the measurement error is small,the effect is relatively ideal.It has a good application prospect and provides new ideas and methods for the development of modern distributed generator power quality detection instruments and systems.