K. Redondo

Influence of the Carrier Phase on Flicker Measurement for Rectangular Voltage Fluctuations

This paper presents an analysis of the influence of the phase relationship between the fundamental frequency and the rectangular voltage fluctuation on flicker measurements made by the International Electrotechnical Commission (IEC) flickermeter. We analytically studied the origin of the deviations for a set of significant fluctuation frequencies. We found that the nonlinear behavior of the squaring multiplier of the IEC flickermeter produces an additional dc component in instantaneous flicker sensation Pinst for several rectangular fluctuation frequencies. The value of this dc component depends on the phase relationship between the fundamental and the fluctuation frequency. The analysis of this paper has contributed to clarify the definition of some performance tests of the IEC flickermeter standard IEC 61000-4-15 ed.2. This will help develop calibration and verification methods for the flickermeters.

Type testing of a highly accurate illuminance flickermeter

The standard IEC 61000-4-15 establishes the design specifications to measure the annoyance produced by flicker. This instrument is based on the working principles and the response to input voltage variations of an incandescent lamp, which was taken as the reference lamp for the design. However, nowadays new lighting technologies are being adopted worldwide and the incandescent lamp has fallen into disuse. With the purpose of characterizing the sensitivity to voltage fluctuations of new modern lamps an adapted flickermeter has been designed. This tool uses as input the illuminance signals registered from the different lighting technologies. This paper describes the implementation of an illuminance flickermeter as well as its functional verification according to the type tests described in the new edition of the IEC 61000-4-15 standard.

Sensitivity to flicker of dimmable and non-dimmable lamps

In the last years, modern lighting technologies are being adopted worldwide. However, in terms of flicker, the incandescent lamp was the one used as the reference lamp in the design of the standards. Due to their different working principles, the new lamps may have quite a different response to input voltage variations than the response of the incandescent lamp. This paper describes the results of the study of the sensitivity of some modern lamps by means of objective tests.

Effects of digital differentiation on flicker measurements in wind turbines

Quantification of the flicker generated by wind turbines is a rather complex process requiring high-precision measurements. Based on the measurements of voltage and current time-series, the procedure uses an inductive circuit model to make the final measurements site-independent. This paper presents a study on the inaccuracy introduced by the numerical algorithms in calculating the derivative of the sampled signal when evaluating the flicker emission of wind turbines. It describes the alternatives found in the digital signal processing literature, and presents a comparative study of the results using analytically generated signals. The application of differentiation methods to the actual signal data of a wind turbine showed that depending on the implemented method, the differences in flicker emission quantification could be significant.

Case study: Flicker emission and 3P power oscillations on fixed-speed wind turbines

This paper studies the influence that the power oscillations due to the tower shadow effect and the wind shear have on the flicker emission of fixed-speed wind turbines. For three-bladed wind turbines, the frequency of this characteristic fluctuation of power is 3 times the blade rotational frequency, and it is known as 3P oscillation. This work aims to analyse real measurement data from an experimental wind farm in Northern Spain in order to extract time-frequency features related to the 3P oscillation. In the same way, the algorithm that measures the generated flicker during continuous operation of wind turbines is applied to the recorded data. Using the instantaneous flicker sensation and the short-time flicker severity, the correlation between the 3P oscillation and the flicker characteristic of a wind turbine is presented. The results demonstrate that monitoring 3P power oscillation allows obtaining an estimation of the flicker emission on wind turbines.

Revision of the standard method for statistical evaluation of flicker coefficients in wind turbines

This paper presents a comparative study of the method used for measuring the flicker emission from wind turbines as currently defined in standard IEC 61400-21 and the new proposal included in the draft version of the revised standard. The new procedure applies a different arrangement scheme to the flicker measurements, and simplifies the statistical analysis to obtain the final flicker coefficients. The study performs a comparison based on data from a wind turbine measuring campaign. The results from both methods are discussed, and the proper statistical analysis is determined. The comparison shows that it is possible to simplify the flickers statistical evaluation and obtain flicker coefficients that are consistent with the results from the standard in force. The study points out the research challenges in the validation of the assessment method that is required to comply with the technical regulations and grid codes.