Study On Subsynchronous Harmonic Detection And Suppression Methods In Power System

China has a vast territory.New energy sources in the northwest region,especially wind power resources,are abundant.However,electricity demand is mainly concentrated in the central and eastern coastal areas where advanced industrial energy consumption is strong.This kind of imbalance in production resources and demand requires long-range large-scale production.Power transmission.However,with the large-scale grid-connected access of wind power,series compensation technology and various power electronic devices are widely used,and the stability of the power system ushered in new challenges.How to effectively detect and suppress subsynchronous resonance(SSR)has important significance for the stability of power system,the service life of power system equipment,and the reduction of failure rate.In this paper,the harmonic signal and noise signal interference in the actual situation of the subsynchronous resonance detection of the power system have caused the detection result to be difficult to observe clearly.Simulations of four common types of sub-synchronous resonances are simulated: interharmonic interference,noise signals,exponentially decaying signals,and amplitude-frequency characteristic distortions.These four analog signals are first detected using conventional parallel FFT and wavelet transforms,respectively.Based on this analysis,a novel hybrid wavelet transform and parallel FFT algorithm based on singular spectrum and detrended fluctuations was proposed to optimize the detection of subsynchronous harmonics.In order to verify the validity of the proposed method,the simulation results were verified and analyzed and compared with parallel FFT and wavelet transform simulation results.The superiority of the proposed method in the time-frequency detection of complex mutated harmonic signals is verified.For the situation that the dynamic conditions of the power grid are constantly changing,it is difficult to suppress the situation of the SSR after the double-fed fan is connected to the grid at different wind speeds.A self-adaptive controller(SAC)was added to the control loop of the doubly-fed blower to deal with the SSR suppression of the doubly-fed blower under different wind speeds and working modes.Then,the parameters of the doubly-fed blower were adjusted and adjusted.The SAC controller model was designed and the stability of the SAC control loop module itself after SAC was added was evaluated and optimized.In order to verify the effectiveness of the proposed SAC controller in suppressing SSR,the method was used to simulate the SSR effect of a doubly-fed wind farm with 350 MW capacity in three different operation modes of a doubly-fed fan and PI control and controller-free suppression.For comparison,it is verified that the proposed SAC control has a good effect on SSR suppression under different wind speeds and operating modes.