Dynamic Synchrophasor Estimation And Harmonic Phasor Measurement Considering Frequency Deviation

Phasor measurement units are wildely employed in power systems with the appliacation of wide area measurement system.The existing commercial synchronous phasor measurement algorithm can perform well under static condition,while it cannot statisfy the requirements of practical application of phasor measurement when the system frequency and the amplitude change over time,especially when the system frequency deviate from the nominal frequency largely.Therefore,this thesis focuses on the dynamic synchronous phasor measurement algorithm considering frequency deviation,and studies its application inharmonic measurement.As large frequency deviation will lead to great errors on Taylor approximation,the accuracy can be improved by expanding the dynamic characteristics in form of Taylor series near theoretical fundamental frequency of supplied signals instead of nominal frequency(50/60Hz).The corresponding coefficient against the different frequency estimations is applied to the dynamic phasor estimator to yield accurate synchrophasor estimation with the consideration of large frequency deviation.Firstly,raw phasors attained by STFT(Short Time Fourier Transform),are employed to provide the frequency estimation.Then,according to the frequency estimation,the coefficient matrix calculated off-line in form of lookup table is selected to calculate phasor estimation at the center of data window.Finally,a shift process is taken to give phasor estimation at report time.Simulated signals,PSCAD-generated signal,RTDS-generated data and field data are employed to evaluate the performance of the proposed algorithm.The results show that the proposed algorithm can get more accurate phasor estimations than our previous work at most of the time with the cost of minor increase of computational power.In order to reduce the responce time in protection application,the frequency deviation is applied into the dynamic fundamental phasor in frequency-domain.Firstly,raw phasors attained by STFT in frequency domain are employed to provide the frequency estimation.Then,according to the frequency estimation,the coefficient matrix calculated off-line in form of lookup table is selected to calculate phasor estimation at the center of data window.Finally,a shift process is taken to give phasor estimation at report time.Simulated signalsand field data are employed to evaluate the performance of the proposed algorithm.The results prove that the proposed algorithm can get accurate phasor estimations and shorter response time with the cost of minor increase of computational power.Considering the power system's dynamic characteristics and frequency deviation,a dynamic harmonic phasor measurement algorithm is proposed based on Taylor series to attain harmonic phasor estimations.Firstly,the frequency of fundamental phasor is accurately attained by dynamic phasor estimation algorithm and the frequency deviation of harmonic phasor can be calculated according to the frequency estimation of fundamental phasor.Then,the corresponding coefficient matrix of the harmonic phasor calculated off-line in form of lookup table is selected to modify the initial harmonic phasor estimation attained via discrete Fourier transform.Simulated signals and filed data are employed to evaluate the performance of the proposed algorithm.The results show that the proposed algorithm provides more accurate harmonic phasor estimation under various conditions such as frequency deviation,frequency ramping and power oscillation,compared to that of DFT at the cost of minor computational burden increase.Compared with windowed and interpolated algorithms,the computational complexity of the proposed algorithm is dramatically reduced,so that it is more favorable to be adopted in field applications.The theoretical analysis and simulation results show that,it is scientifically rational to apply frequency deviation to the fundamental and harmonic model.The results are more suitable to actual situation,and it can provide important theoretical basis for operation planning in synchrophasor measurement in future.