Three-phase Signal Model-based Dynamic Synchrophasor Estimation Algorithms

The wide-area measurement technology based on the synchronous phasor measurement device as the hardware,provides an effective method for the prediction and monitoring of the power grid.In recent years,the synchronous phasor measurement device is widely used in the transmission network and received much attention in construction of the distribution network.However,large-scale distributed power grid connection,harmonics,interharmonics,and Gaussian white noise pollution have caused the transmission and distribution network environment to become increasingly complex,which has brought great challenges to the measurement performance of synchronous phasor measurement algorithms.The paper establishes a phasor model based on three-phase signals,and proposes a dynamic phasor measurement algorithm based on the model.Considering that the frequency doubling component error will reduce the accuracy and stability of the single-phase phasor measurement algorithm,this paper first analyzes the causes of the frequency doubling error in the single-phase DFT phasor model,and then presents a phasor model based on three-phase signal.The proposed phasor model eliminates the frequency doubling component error,which can be applied to the phasor measurement algorithm of DFT class and improve the measurement accuracy.For M-class PMU applications,the phasor model based on three-phase signal is applied to the time-domain algorithm.Firstly,Taylor series is used to fit the dynamic characteristics of three-phase signals;secondly,the phasor model based on three-phase signals is used to replace the single-phase phasor model to eliminate the frequency doubling component error;secondly,the Taylor coefficient based on Phasor Model in the time domain is used to get the accurate phasor measurement value;finally,the ideal signal generated by MATLAB and the simulation signal generated by PSCAD/EMTDC are verified.Compared with the single-phase dynamic phasor measurement algorithm,the feasibility of the proposed phasor model applied to DFT algorithm and the validity and applicability of the dynamic synchronous phasor time-domain measurement algorithm based on the three-phase signal model are verified.For the comprehensive application of the phasor measurement algorithm in the P-class PMU,the phasor model based on the three-phase signal is further applied to the frequency domain algorithm.First,the Taylor series is used to fit the dynamic changes of the three-phase signal;second,the phasor model based on the three-phase signal is extended into the frequency domain;then,the frequency domain information is fully utilized to solve the phasor model Taylor in a single data window The various derivatives of the series output accurate measurement values of phasors through the steps of offline matrix calling and phase shift;finally,the verification of the ideal signal generated by the MATLAB platform and the simulation signal generated by the PSCAD/EMTDC platform: based on the three-phase signal The dynamic synchronization phasor frequency domain measurement algorithm of the model not only has the advantage of faster dynamic response of the frequency domain algorithm,but also solves the problem of insufficient measurement accuracy of the frequency domain algorithm.Considering the unbalanced fault in distribution network,it will affect the measurement accuracy of dynamic synchronous phasor measurement algorithm based on three-phase signal model.First of all,a three-phase signal model considering the imbalance factor is established;then,the problem of the decline of the algorithm phasor measurement accuracy is theoretically derived;secondly,the algorithm improvement scheme under the unbalanced condition is proposed to improve the measurement accuracy of the algorithm under the unbalanced condition;finally,the positive of the algorithm improvement scheme under the unbalanced condition is verified by the test signal generated by Matlab platform Accuracy and applicability.Theoretical studies and simulation tests made in the paper prove that the proposed phasor model based on three-phase signals can be applied to DFT-based phasor measurement algorithms.After the error of the frequency-doubling component in the phasor model is eliminated,the accuracy of the phasor measurement is obtained.Significantly improved,providing another idea for the development of synchronous phasor measurement technology.