Mid-and High-frequency Oscillation Detection Method And Development Of Wide-band Phasor Measurement Unit Device

With the development and application of power electronic technology,the power system is showing a clear development trend of power electronization,and its harmonic pollution and mid-and high-frequency oscillation problems are increasingly emerging,which seriously threaten the safe and stable operation of the power system.Accurate detection of the parameters of mid-and high-frequency oscillation is essential to effective suppress mid-and highfrequency oscillation,online wide-band measurement is helpful to monitor the dynamics of power grid wide-band signals,and can provide effective data support for the analysis of midand high-frequency oscillations.In addition,the power electronics dominated power system contains a large number of wide-band signals containing high-order harmonics and interharmonics.How to identify mid-and high-frequency oscillations from wide-band signals containing a lot of information is a difficult point.To this end,this article has carried out the following research work around the detection of mid-and high-frequency oscillation:(1)In order to ensure the accuracy of wide-band signal detection while increasing the detection speed as much as possible,a fast detection method of wide-band signal suitable for online wide-band measurement is proposed.First,divide the frequency band according to the detection requirements and adjust the sampling frequency through secondary sampling.Then,the window is selected according to the characteristics of different frequency bands.Finally,use the windowed interpolation fast Fourier transform for each frequency band to obtain the parameters of each frequency component of the signal.The proposed method is verified by two methods,namely,the simulation of the wide-band signal model containing harmonics and interharmonics and the dynamic simulation test of the broadband synchronous phasor measurement unit developed in this paper,and compared with the traditional method.The results show that the proposed method not only improves the detection speed of the algorithm,but also maintains high detection accuracy for steady-state signals.(2)In order to accurately identify mid-and high-frequency oscillation signals from wideband signals with rich information and obtain accurate oscillation parameters,a detection method for mid-and high-frequency oscillation based on transient feature identification is proposed.First,the generalized S transform is used to obtain the modal time-frequency matrix of the signal.According to the signal transient characteristics of the amplitude,the signal is judged to be steady-state,time-varying harmonics,and mid-and high-frequency oscillation signals.Then,the band-pass finite impulse response filter corresponding to each frequency band is designed,and the band-pass filter of the corresponding frequency band is used to obtain the oscillation frequency band and eliminate the interference of other frequency components for the signal containing mid-and high-frequency oscillation components,and then use the improved Hilbert-Huang transform obtains the instantaneous parameters of the oscillation component.Finally,three experimental schemes are used to verify the proposed method:mathematical simulation signal model,simulink electromagnetic transient simulation model and dynamic simulation test model based on the developed wide-band PMU device,and compared with the traditional method.The results show that the proposed method can accurately identify mid-and high-frequency oscillation signals based on signal characteristics adaptively and obtain high-precision oscillation parameters.(3)In order to solve the problem that the traditional PMU device in the wide area measurement system is difficult to apply to the wide-band measurement of the power system,a wide-band PMU device has been developed.The wide-band PMU device has high sampling frequency,high precision and high stability synchronous sampling performance,high communication bandwidth and powerful data analysis and processing capabilities.The module architecture and work flow of the developed device are introduced in detail from two aspects of hardware design and software design.Based on the real-time simulation system,the developed wide-band PMU device was tested and compared with the detection effect of the power quality analyzer.The test results show that the developed wide-band PMU device can well meet the requirements of online wide-band measurement and can provide effective data support for real-time monitoring of mid-and high-frequency oscillation.