Research On Wideband Signal Measurement Algorithm In Power-Electronized Power System

The large-scale power electronic equipment application makes the power system signal gradually show wideband characteristics of frequency.Many harmonics and interharmonics have a severe impact on the power quality,which directly endangers the safe and stable operation of the power system.Facing the power-electronized power system with changeable conditions,prominent wideband oscillation phenomenon and increasingly complex structure,the wide area measurement system with tracking fundamental phasor as the core function can not deal with a series of problems caused by wideband oscillation.In order to improve the monitoring ability of the power grid operation state,it is urgent to study the wideband signal measurement algorithm suitable for wideband oscillation.Accurate and efficient measurement of wideband signal components is also the premise of harmonic/interharmonic control,which is significant to maintaining the power grid’s safe and stable operation.Based on this,this paper aims to realize the high-precision measurement of fundamental,harmonic,and interharmonic signals in the frequency band of 2.5～2500Hz.Using the preliminary information obtained by resampling the Prony algorithm,a high-precision estimation algorithm of the wideband signal based on the wideband Taylor phasor model is proposed to realize the short-time high-resolution signal measurement of fundamental,harmonic,and interharmonic in the wideband signal.The main research results of this paper are as follows:(1)The harmonic/interharmonic phasor model and its frequency calculation method are supplemented from the perspective of actual demand.The Fourier transform theory and the root causes of spectrum leakage and fence effect in asynchronous sampling are deduced and analyzed.The windowed interpolation algorithm can effectively simulate the spectrum leakage and fence effect.The characteristics of standard window functions and the selection principle of window functions are discussed,and the focus of the bispectral interpolation algorithm and the correction formula of standard window functions are deduced.The windowed bimodal interpolation algorithm can improve the measurement accuracy of wideband signals.Still,due to the limitation of frequency resolution in a short time window,DFT algorithms can not measure signals with similar frequencies with high accuracy.(2)Aiming at the problems of signal sensing timeliness and frequency resolution in DFT algorithms,a short-time sensing method of wideband signals based on resampling Prony is proposed.The order determination method of the second-order difference sequence can effectively improve the singular value denoising performance and determine the signal fraction.The denoised signal can effectively obtain the components of high-frequency,lowfrequency,and approximate frequency signals by resampling the Prony method,which improves the short-term perception performance of the Prony Algorithm for low-frequency interharmonic signals and approximate frequency signals and has better frequency resolution in the short-term window.(3)A short-time wideband signal measurement algorithm based on the wideband Taylor model is proposed by using the perceived frequency information of wideband signal.Based on the good dynamic characteristics of the Taylor coefficient,the wideband Taylor phasor model is established,and the above wideband Taylor model is solved by the least square method to obtain each signal phasor.The short-time high-resolution measurement of wideband signal is realized,and the measurement accuracy and dynamic measurement performance of fundamental,harmonic,and interharmonic of phasor measurement algorithm under wideband oscillation conditions are improved.The simulation results show that the proposed SMAWT algorithm has high accuracy in measuring fundamental,harmonic,and interharmonic under the condition of fundamental dynamic change.The proposed algorithm can maintain the TVE value of fundamental wave measurement within 1% under various static/dynamic conditions,which meets 3% of the standard requirements;It can keep the measured TVE value of harmonic,interharmonic,and low-frequency interharmonic signals of approximate frequency signals within 5% of the standard requirements;At the same time,the measurement frequency error can be lower than 0.07 Hz under various static/dynamic conditions,which has good comprehensive measurement performance.