Addressing IEC Flickermeter Deficiencies by Digital Filtration Inside a Sliding Window

Although globally deployed for flicker assessment, the flickermeter presented by International Electrotechnical Commission (IEC) Standard 61000-4-15 has been proved to suffer from some deficiencies regarding voltage rectangular modulation and interharmonics. The latter results in flickermeter inability to accurately measure flicker for non-incandescent lamps, which are ubiquitous nowadays. The flickermeter inaccuracies tend to arise from its demodulator. So far, few solutions have been provided. Furthermore, the existing solutions deal with only the interharmonic case. This paper introduces a method to address IEC flickermeter deficiencies by developing a digital signal processing block that demodulates the voltage in a real-time manner for voltages that include interharmonics or are affected by rectangular modulation. The suggested demodulator implements discrete Fourier transform inside a sliding window. For rectangular modulation, this approach is used to demodulate the voltage. Meanwhile, for the interharmonics problem, this approach provides the interharmonic frequency. Using the measured frequency, least error squares technique is then employed inside another sliding window to find the interharmonics amplitude. On this basis, a modified flickermeter is devised. Performance of the modified flickermeter is evaluated and its effectiveness is verified using the results obtained from an experimental set-up. The contribution of this paper is not limited to IEC flickermeter modification; the proposed method can be employed for any application requiring interharmonic measurement.