Measuring Flickers

The LabVIEW Electrical Power Toolkit complies with Class A of IEC 61000-4-15:2010 for measuring flickers. The Electrical Power Toolkit provides flicker measurement for the following systems:

• 60 W 120 V 50 Hz
• 60 W 230 V 50 Hz
• 60 W 120 V 60 Hz
• 60 W 230 V 60 Hz

A flickermeter consists of several function blocks that simulate an incandescent lamp and the eye-brain response of the human perception system. The flickermeter standard has replaced the use of flicker curves in the evaluation of voltage fluctuations. Flickermeters calculate the short-term and long-term flicker for a voltage fluctuation waveform. Refer to IEC 61000-4-15:2010 for details about the filtering parameters of the function blocks. Using a flickermeter contains the following five stages:

1. Voltage adaptation — Scale the input voltage so that the RMS output voltage maintains at a constant long-term average. While preserving voltage fluctuations on the waveform, voltage adaptation enables flicker calculation to be independent of the input voltage.
2. Square multiplier — Extract the amplitude modulation, m(t), from the input voltage waveform. The following equation defines the input voltage waveform:
   $v\left(t\right)=\sqrt{2}V\times [1+m(t\left)\right]\times \cos \left(2\pi f_{0}t\right)$
   Square the previous equation to calculate the squared voltage waveform, as shown in the following equation:
   ${v\left(t\right)}^2={2V}^2\times [1+2m(t)+{m\left(t\right)}^2]\times \left(\frac{1}{2}+\frac{1}{2}\cos \left(4\pi f_{0}t\right)\right)$

3. Weighting filters — Weighting filters include a lowpass filter, a highpass filter, and a bandpass filter with a center frequency of 8.8 Hz. The lowpass filter, highpass filter, and square multiplier work together as a demodulator. The lowpass filter first removes the double-frequency term from the squared voltage waveform. The highpass filter then eliminates the DC components. The following equation describes the filtered voltage: v(t) = 2V²m(t) + V²m(t)²

   Because m(t) ≤ 1 for small voltage fluctuations, you can ignore the second term V²m(t)² in the previous equation. You can approximate a voltage signal for small fluctuations as 2V²m(t).The bandpass filter simulates the frequency response of the eyes and brain. This bandpass filter returns the following scaled and phase-shifted modulation signal:

   $m^{\text{'}}\left(t\right)=2{\nu }^{2}MF\left(f_M\right)\cos (2\pi f_{M}t+{{\phi }^{\text{'}}}_M)$

4. Squaring and smoothing — Use squaring and smoothing to simulate the storage effect in the brain and to obtain the instantaneous flicker value. The squaring multiplier returns the following squared modulation signal:
   ${\left(m^{\text{'}}\left(t\right)\right)}^2=2{\nu }^4{\left[MF\right(f_M\left)\right]}^2+2{\nu }^4{\left[MF\right(f_M\left)\right]}^2\cos (4\pi f_{M}t+2{{\phi }^{\text{'}}}_M)$
   The lowpass filter removes the second term in the previous equation and returns the instantaneous flicker value:
   $P=2V^4{\left[MF\right(f_M\left)\right]}^2$
   The instantaneous flicker value is normalized because of the voltage adaptation and different minimum human perception of fluctuations at different modulation frequencies. An instantaneous flicker value of 1.0 represents the threshold above which 50% of observers can notice the flickering of a 60 W and 230 V incandescent lamp.
5. Statistical analysis — Perform statistical processing on the instantaneous flicker value to calculate the short-term and long-term flicker values. Refer to IEC 61000-4-15:2010 for details about calculating short-term and long-term flicker values. You can use the short-term flicker value to evaluate the degree of irritation for voltage fluctuations. A short-term flicker value of 1.0 represents the level below which complaints about flicker are unlikely to arise. A short-term flicker value greater than 1.0 indicates that voltage fluctuations are observable and likely to lead to complaints. You can use the long-term flicker value to evaluate the combined effect of flicker-causing loads over long periods. A long-term flicker value of 0.8 represents the level below which complaints about flicker are unlikely to arise.

You can apply the flickermeter standard to other types of lamps by separating the lamp response from the eye-brain response. You can modify the bandpass filters in Stage 3 to simulate different types of lamps, without modifying other stages.