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BSI PD IEC TR 61000-4-40:2020

$167.15

Electromagnetic compatibility (EMC) – Testing and measurement techniques. Digital methods for the measurement of power quantities of modulated or distorted signals

Published By Publication Date Number of Pages
BSI 2020 38
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This part of IEC 61000, which is a Technical Report, deals with the assessment of electrical power quantities (RMS voltage, RMS current and active power). It explains and compares two digital algorithms suitable for power quantity measurements in fluctuating or non-periodic loads. The examples are from 50 Hz or 60 Hz power systems.

This document does not attempt to cover all possible digital implementations of the algorithms used for power quantity assessment in fluctuating loads, for example in the context of the EMC assessment described in several IEC documents. Rather, it compares averaging with one of the filtering algorithms. This document aims to highlight some examples of applications that illustrate how the presented algorithms work. Further, guidance is given for quantifying the accuracy of each approach.

PDF Catalog

PDF Pages PDF Title
2 undefined
5 CONTENTS
7 FOREWORD
9 INTRODUCTION
10 1 Scope
2 Normative references
3 Terms and definitions
4 General
12 5 Modulated sine waveforms used in this document to compare measurement algorithms
5.1 General
13 5.2 Half-wave rectification
5.3 Full-wave rectification
Figures
Figure 1 – Typical resistive load current and supply voltage waveform of half-wave rectification
14 5.4 Multi-cycle symmetrical control
Figure 2 – Typical full-bridge rectifier current and supply voltage waveforms
Figure 3 – Current and voltage patterns in an MCSC circuit, (left) 1/3 MCSC and (right) 2/3 MCSC
15 5.5 Random on-off control
6 Measurement algorithms
6.1 General
6.2 Averaging algorithms
6.2.1 General
Figure 4 – Amplitude of 50 Hz current with on and off periods varying within a 1 min to 2 min range
16 6.2.2 Performance of the averaging algorithm
17 Figure 5 – Step response of an algorithm in Formula (6) with a half-cycle, 1-cycle and 10-cycle measurement interval
18 Figure 6 – RMS current and active power for half-wave rectification
Figure 7 – Sliding average RMS current and active power of a device controlled with a 1/3 MCSC circuit
19 Figure 8 – Worst case 1/3 MCSC circuit active power calculation variation
Table 1 – Calculated power of 2/3 MCSC for different measurement windows
20 Figure 9 – Example of a 10 min sliding average power calculation for a load having a 92 s period
21 6.2.3 Instrumental errors of the averaging algorithm
Figure 10 – Active power of randomly fluctuating load averaged over a sliding 10 min interval
22 6.3 Smoothing filter algorithm
6.3.1 Frequency and step response
Figure 11 – Sensitivity of the full-bridge rectifier RMS current and active power measurement to time interval error of single-cycle sliding average calculation
23 Figure 12 – Comparison of the first and the 10th order filters used to estimate RMS current of a step signal
Figure 13 – Filter frequency responses
Figure 14 – Filter step responses
24 6.3.2 Verification of the smoothing filter algorithm
Figure 15 – Output of the 10th order smoothing filter used to calculate the active power of a signal with a step change
25 Figure 16 – Delay and response time of a 10th order filter used to assess the sinusoidal current of a sinusoidal waveform
Figure 17 – Measurement of the current and power of a half-wave rectified signal using a smoothing filter with a 10 Hz cut-off frequency
26 Figure 18 – Power quantities in full wave rectification assessed using a smoothing filter with 16,667 Hz cut-off frequency
Figure 19 – MCSC 1/3 pattern power quantities filtered with approximately 5,556 Hz cut-off frequency
27 Figure 20 – Active power of a load having a 92 s period measured with different algorithms
28 6.3.3 Instrumental errors of the filtering algorithm
7 Conclusions
Figure 21 – Active power of randomly fluctuating load measured using different algorithms
30 Annex A (informative)Smoothing filter studied in this document
A.1 Algorithm
34 A.2 General C++ class program code
37 Bibliography
BSI PD IEC TR 61000-4-40:2020
$167.15