Research On Power Parameters Detector Based On Improved FFT Algorithm

In the power system,the large amount of power electronic equipment and nonlinear,interfering loads exist,which make the harmonic pollution more serious.In order to reduce the pollution and harm of harmonics,it is necessary to detect harmonics accurately.In addition,the capacitive type equipment in the power system will be damaged by the environment.The dielectric loss angle can reflect the insulation damage degree of the capacitive type equipment.According to the value of dielectric loss angle,the performance and service life of insulating material of capacitive equipment can be reasonably evaluated and forecasted.Therefore,accurate detection of harmonic,dielectric loss angle and other power parameters is an important prerequisite to maintain the security and stability of power system.Fast Fourier transform algorithm is widely used to detect harmonics and dielectric loss angle because of its high computational efficiency and easy implementation in embedded system.However,influenced by asynchronous sampling,FFT algorithm has some problems,such as spectrum leakage and fence effect,which reduce the accuracy of parameter detection.At present,the method of windowing function is commonly used to suppress spectrum leakage.In this paper,based on the classical window function,the weighted summation and convolution operations are used to construct a new NBH combinatorial self-convolution window.The window function has better sidelobe characteristics,can effectively suppress spectrum leakage,and improve the detection accuracy of FFT algorithm.In order to improve the real-time performance of the algorithm,an improved three-spectral line interpolation algorithm is derived based onthe phase difference relationship between spectral lines.The improved three-line interpolation FFT harmonic analysis algorithm based on NBH combined self-convolution window is studied.Based on the fourth order NBH combined self-convolution window,using the phase difference correction algorithm which does not need to solve the higher order equation and the amount of calculation is small.A phase difference correction FFT dielectric loss angle measurement algorithm for the 4th order NBH combination self-convolution window is proposed.The simulation results of MATLAB show that the proposed algorithm is much better than the conventional algorithm in measuring accuracy and real-time performance.Finally,based on the algorithm studied,a power parameter detector with hardware structure of ADC+DSP+ARM is designed.