Research On Algorithm Of Dynamic Synchronous Phasor Measurement In Power System

The power system needs to obtain high-precision real-time information of power grid frequency and phase by means of synchronous phasor measurement device.Discrete Fourier transform(DFT)algorithm is widely used in phasor measurement of power system because of its high accuracy and fast operation speed.However,DFT algorithm will produce large measurement errors under the dynamic conditions of frequency,amplitude,phase mutation,and harmonic interference,the DFT algorithm will produce large measurement error.This paper studies the phasor measurement algorithm under different dynamic conditions to improve the accuracy and response speed of phasor measurement and meet the requirements of smart grid.Firstly,the performance of existing phasor measurement algorithms is compared and analyzed.This paper introduces the basic principle of DFT,expounds and analyzes the basic principle,advantages and disadvantages of zero crossing detection method,instantaneous value method,least square method and Kalman filter algorithm used in phasor measurement,and simulates these algorithms to get the corresponding error curve.The simulation results show that the traditional DFT algorithm has a wider range of application compared with other algorithms;the traditional DFT algorithm has a better restraining effect on harmonics;the total phasor error changes regularly with frequency,and the total phasor error is the smallest when the frequency is close to the fundamental frequency.For the signal of frequency offset,the improved DFT dynamic phasor measurement algorithm is used to estimate the amplitude of the electric signal.The formula between the phase angle calculated by DFT and the actual phase angle is derived.The frequency estimation of the signal is obtained by using the phase difference of two adjacent data windows,and then the phase error is corrected.The simulation analysis based on MATLAB shows that the total phasor error of the algorithm is less than 1% when the fixed frequency offset of the signal is less than 3Hz,and the accuracy of the algorithm is high when the frequency offset is small;when the frequency offset and the frequency change linearly,the accuracy of the algorithm is higher than that of the traditional DFT algorithm,and it can meet the requirements of the relevant standards for the accuracy of the algorithm;the algorithm for harmonic The interference and noise interference have good restraining effect,and the measurement accuracy of the algorithm is improved significantly when Hamming window is added.A dynamic phasor measurement algorithm based on Taylor expansion is proposedfor dynamic signals with low frequency oscillation,amplitude and phase mutation.The phasor is expressed in the form of Taylor series,and the dynamic model of DFT is established by using Taylor expansion.The derivative of phasor is expressed by the phasor change rate of two adjacent data windows,and the DFT model is modified.The algorithm can overcome the large model error caused by the application of cosine function to approximate signal representation in traditional DFT algorithm.The simulation results show that the improved algorithm has strong anti-interference ability and high measurement accuracy in the dynamic phasor measurement of power system.Compared with the traditional DFT algorithm,the performance of the algorithm can be improved by adding Hann window.