A Synchronized Measurement Method For Wide Frequency Bandwidth Signals In Renewable Areas

Recently,with the centralized and distributed grid-connection of large-scale renewable energy and the application of DC transmission technologies,a large number of power electronic devices have been deployed in power systems.The mechanism characteristics of power systems have changed,and power signals are showing wider frequency bandwidth,faster dynamic processes and higher noise level.Thus,new requirements,such as monitoring frequency bandwidth and response time,are put forward.The existing synchrophasor measurement units(PMUs)can only measure the fundamental phasor,and cannot realize the monitoring of signals with wide-frequency bandwidth.Therefore,a method for wide-frequency bandwidth measurement in renewable areas must be studied.The existing measurement methods are difficult to take into account both response speed and frequency resolution.To this end,the characteristics of the wide-frequency bandwidth signals in renewable areas and the limitations of traditional spectrum clustering methods are analyzed.Based on the analysis results,a K-ESPRIT based method for wide-frequency bandwidth measurement is proposed,which can realize the fast and high-precision measurement of the wide-frequency bandwidth signals.Then,to improve the algorithm stability and measurement accuracy under the condition of high noise level,a kurtosis based method is proposed to estimate the number of frequency components in signals.Under fault conditions,the phasor accuracy may be affected by decaying DC components.To this end,a signal model for complex situations(such as frequency deviation,harmonics,and decaying DC components)is constructed.After analyzing the limitations of the Discrete Fourier transform(DFT)to solve the model parameters,a phasor measurement method for complex signals is proposed.This method can suppress the influence of decaying DC components on the fundamental phasor,and improve the phasor accuracy under fault conditions.Then,the structure of wide-frequency measurement device is designed.Based on.this,the hardware selection and.software.development.are performed to develop a prototype of wide-frequency measurement.A laboratory testing platform is built to test the measurement performance of the prototype.In addition,the field-recorded data is also used to verify the validity of the methods.The test results demonstrate that the proposed method can monitor the wide-frequency signals precisely and quickly.