Comparison of analog-to-digital filter conversion methods in a digital flickermeter

A standard of International Electrotechnical Commission (IEC) has defined the flicker measuring specification in an analog manner. But the analog specs are inefficient when implementing a flickermeter in the real world according to the standard. Therefore, it is necessary to convert its original analog filters to the corresponding digital forms as well as applying other digital processing techniques such as data sampling, bit resolution, and filtering theory. Even though a digital flickermeter may meet the requirements of the IEC standard, its outputs will vary according to the analog-to-digital filtering conversion methods used such as bilinear transformation, impulse invariance transformation, and covariance invariant transformation. This paper presents the characteristics of various filter conversion methods and the influences on the digital implementation of a flickermeter, which are simulated by using MATLAB^®. Finally, this paper concludes with which methods are the most adequate to implement an IEC digital flickermeter, helping ultimately to avoid ambiguities from analog prototypes described in original standard.