Research And Implementation Of Fault Detection Method For Power Grid

When the grid voltage is short-circuited,the system is accompanied by odd-order harmonics and high-frequency noise.At this time,it is necessary to filter the harmonics to obtain a pure fundamental signal,locate the fault,and detect the characteristic information of grid quickly and effectively.So,the speed response of the wind turbine to the grid fault is accelerated,and corresponding measures are taken in time to avoid huge economic losses.Therefore,he short-circuit fault of grid voltage system is taken as the research object,and the harmonic detection algorithm of single-phase voltage and the fast detection algorithm of phase and frequency of three-phase system are deeply studied in this paper.First of all,the overall design scheme of the single-phase voltage harmonic detection and grid voltage short-circuit fault phase-locking method is presented.The commonly used harmonic detection algorithm and phase frequency detection algorithm are analyzed,and the working principle and process of each method are explained.The advantages and disadvantages of each method are summarized,and the harmonic detection and grid voltage frequency phase detection algorithms adopted in this paper are proposed.Secondly,in order to solve the problem that the existing grid voltage harmonic detection algorithm has insufficient detection precision and complicated algorithm calculation,based on the wavelet packet algorithm and two-stage method theory,a detection algorithm based on wavelet packet transform is proposed.The threshold comparison method is proposed based on wavelet transform algorithm,and the proposed algorithm is modeled and analyzed.According to the simulation results,the detection algorithm can effectively filter the harmonics to obtain a complete fundamental wave,and the obtained fundamental waveform satisfies the user’s requirements,and can quickly locate the voltage fluctuation of the single-phase power grid beyond the specified range.Thirdly,the principle of the extended Kalman algorithm is explained in detail,and the mathematical model of the complex extended Kalman filter phase-locked algorithm is analyzed and simulated.However,when using this algorithm to detect short-circuit faults,phase detection is distorted and frequency oscillations are large.To this end,an improved extended Kalman filter detection algorithm is proposed,and the algorithm is simulated using S-function.By comparing and analyzing the simulation results of the two methods,it is obtained that the improved algorithm has higher accuracy in detecting phase and frequency.Finally,In order to verify the effect of the algorithm of extended Kalman Filter,an experimental platform with EP4CE30F23C7 as the computing chip was established.The phase detection experiment of improved and extended Kalman is completed,and the experimental results are analyzed to verify the feasibility and effectiveness of the proposed algorithm.