| ’IEC 61000-4-15: 2010 Electromagnetic compatibility(EMC)-Part 4-15: Testing and measurement techniques-Flickermeter-Functional and design specifications’ Standard requires different types of flicker signals to be measured under complex environments,such as fundamental frequency change,harmonics,phase jumps,noise impact,etc.However,most of the existing flicker measurement methods are not enough to solve such a complex flicker measurement problem,and the flicker measurement method recommended by IEC only gives the measurement principle blocks diagram to measure the flicker severity parameters,without specific design details.Therefore,aiming at the complex measurement environment and signal types(especially square wave modulation signal)noticed by IEC standard,this paper attempts to use a digital algorithm based on Taylor Fourier transform,which is applied to dynamic phasor measurement,to carry out fast and accurate voltage flicker measurement.The main researchs of this paper includes two parts: the first part is to study the algorithm of Taylor Fourier Transform and the algorithms based on dynamic phasor model including the Taylor Fourier Transform;the second part is to study the application of Taylor Fourier Transform and its derivative and improved algorithms to voltage flicker measurement.In the reaserch of the algorithms based on dynamic phasor model,this paper presents a simplified dynamic synchrophasor estimator based on the Sinc interpolation function with using weighted least squares(SWLS).The expressions of SWLS-based phasor estimator for either complex-valued or real-valued variables are derived.Especially,the SWLS-based phasor estimator is expressed as the sum of the weighted discrete-time Fourier transform(WDTFT)of the analyzed signal.It is proved that the SWLS has the similar characteristics as the Tylor weighted least squares method.The relationship between the SWLS and the WDTFT of the analyzed signal is then specifically analyzed in case of the 2nd order Taylor model.The simplified SWLS(S2WLS)for phasor estimation is achieved with a reduced computational burden by appropriating the SWLS-based phasor estimator for real-valued variables.The S2 WLS can be attractive in practical dynamic synchrophasor estimation because of its low computational burden and high accuracy.Simulation results show that the phasors estimated by the proposed method fulfill the requirement of the M-class if a proper number of signal cycles is adopted.In the reaserch of the application of Taylor Fourier Transform to voltage flicker measurement,this paper proposes a method for dynamic voltage flicker measurement based on Taylor-Fourier Filter(TFF).Firstly,the envelope of voltage flicker is extracted by TFF.The envelope can be expressed by the Taylor coefficients,and the estimation of the modulation depth,modulation frequency,the identify of the modulation types and detection of the envelope transients can thus be achieved.Secondly,the TFF of the extracted envelop is performed to estimate the time and frequency domain information of each flicker component.Finally,based on the estimated envelope parameters,the flicker values are calculated according to the definitions of IEC(International Electro technical Commission).The proposed method is compared with the Teager energy operator + S transform which can also realize the measurement of dynamic voltage flicker.Simulation results show that the proposed method has higher accuracy and less computation than that of the S transform based on the Teager energy operator.The proposed method can achieve the measurement of time-varying voltage flicker.The practical application results confirmed accuracy and usefulness of the proposed method. |
