1、.Notes on Harmonics StandardsZainal Salam: Power Electronics and DrivesNOTES ON HARMONICS EMISSION STANDARDS: IEC 1000-3-21.0Goal of implementing the StandardLimitation of harmonic components of the input current impressed on the public low-voltage supply system, for equipment with input currents of

2、 less than 16A per phase.Extend the previous standard IEC 555-32.0Classification of Equipment:· Class A: Balanced 3-phase equipment and all other equipment except those in one of the following classes.· Class B: Portable tools· Class C: Lighting equipment including dimming devices wit

3、h input active power above 25W.· Class D: Equipment having an input current with “special wave shape” and a fundamental input active power between 75 and 600W. This is the “high crest factor” waveform; e.g. single-phase rectifier input current waveform.3.0Harmonic LimitsThe limits of harmonics

4、for each phase of the line current are shown in Table 1. Note that the limits are absolute, i.e. not related to power ratings of equipment. The limits are applicable to steady state harmonic currents.Table 1Harmonic order (n)Class A max permissible harmonic current (A)Class B max permissible harmoni

5、c current (A)Odd harmonics32.303.4551.141.7170.771.15590.400.60110.330.495130.210.31515<=n<=392.25/n3.375/nEven harmonics21.081.6240.430.64560.300.458<=n<=401.84/n2.76/n4.0Impact of IEC 1000-3-2· Equipment-level compliance; cost is directly borne by end user· Cost increase: USD

6、 0.1/W to 0.3/W.· Size increase: 10 to 30%· High quality (i.e. low harmonic) rectification is required.5.0 Solutions to meet IEC 1000-3-2 StandardsPassive solution:· Using passive components i.e. line inductance and/or DC link choke. · It is quiet (not generating much EMI) and re

7、liable. · Too heavy and bulky for most applications. · They might also not be able to satisfy future Standard revisions.Active solution · Using electronics/control of switches (e.g. unity power factor correction)· Generate too much EMI.· Less reliable· Significant incre

8、ased in cost.6.0Origin of harmonic pollution.Mostly from uncontrolled/controlled rectifiers. 7.0Example (related to our design):A. Three phase bridge rectifier without line filter. Source inductance is neglected. Circuit is shown in Figure 1.Shape of line current is shown in Figure 1(a). As can be s

9、een, it is somewhat horrible.Figure 1(a)The spectra of the line current waveform are shown in Figure 1(b).Figure 1(b)The harmonic shown in Figure 1(b) is tabulated as follows. Note that the magnitude of the harmonics shown in Figure 1(b) and the ones shown in the “FOURIER COMPONENT” below is slightl

10、y different because of the “PHASE” factor. HARMONIC FREQUENCY FOURIER NORMALIZED PHASE NORMALIZED NO (HZ) COMPONENT COMPONENT (DEG) PHASE 1 5.000E+01 1.200E+01 1.000E+00 1.745E+02 0.000E+00 2 1.000E+02 3.455E+00 2.879E-01 1.731E+02 -1.372E+00 3 1.500E+02 3.851E+00 3.210E-01 -8.495E+01 -2.594E+02 4 2

11、.000E+02 2.907E+00 2.423E-01 2.758E+01 -1.469E+02 5 2.500E+02 1.019E+01 8.497E-01 2.951E+01 -1.450E+02 6 3.000E+02 1.261E+00 1.051E-01 -7.861E+01 -2.531E+02 7 3.500E+02 7.581E+00 6.319E-01 -1.670E+02 -3.415E+02 8 4.000E+02 6.827E-01 5.690E-02 -1.682E+02 -3.427E+02 9 4.500E+02 3.662E+00 3.052E-01 -7.

12、422E+01 -2.487E+02 10 5.000E+02 1.224E+00 1.020E-01 1.286E+02 -4.589E+01 11 5.500E+02 5.280E+00 4.401E-01 6.361E+01 -1.109E+02 12 6.000E+02 1.218E+00 1.015E-01 -5.395E+01 -2.284E+02 13 6.500E+02 2.537E+00 2.115E-01 -1.470E+02 -3.215E+02 14 7.000E+02 1.173E+00 9.776E-02 3.492E+01 -1.396E+02 15 7.500E

13、+02 2.011E+00 1.676E-01 -5.510E+01 -2.296E+02 16 8.000E+02 1.734E+00 1.445E-01 1.765E+02 2.070E+00 17 8.500E+02 1.721E+00 1.434E-01 9.745E+01 -7.702E+01 18 9.000E+02 1.218E+00 1.015E-01 -5.304E+01 -2.275E+02 19 9.500E+02 7.458E-01 6.217E-02 -1.436E+02 -3.180E+02 20 1.000E+03 1.074E+00 8.951E-02 5.94

14、5E+01 -1.150E+02 TOTAL HARMONIC DISTORTION = 1.354160E+02 PERCENTDC COMPONENT = -8.077051E-01B. Rectifier with source inductance. To illustrate the problem of “l(fā)ine voltage distortion” due to harmonic currents. Circuit is shown in Figure 2.Source voltage at the voltage at point of common coupling (p

15、cca) is shown in Figure 2(a). Note the distortion that occurs. If the latter is connected to other users, i.e. the line is commonly used, the input voltage for those users are appear to be distorted.Figure 2(a)C. Line current harmonics improvement: Passive method i.e. using line filter and DC link c

16、hoke. Case: source inductance = 1mH, line inductance = 10mH, DC choke = 40mH. Results: Line current harmonic spectra are shown in Figure 3(a). Note that, however, the system does not meet the IEC 1000-3-2 Limits (5th harmonics is bigger than 1.14A).Figure 3(a)To improve the line current harmonics, w

17、e increased the line inductance filter to 20mH. The resulting spectra are shown in Figure 3(b).Figure 3(b).The harmonics shown in Figure 1(b) are tabulated as follows. None of the harmonics exceed the limits imposed by IEC 1000-3-2 Standards. HARMONIC FREQUENCY FOURIER NORMALIZED PHASE NORMALIZED NO

18、 (HZ) COMPONENT COMPONENT (DEG) PHASE 1 5.000E+01 7.761E+00 1.000E+00 -1.818E+01 0.000E+00 2 1.000E+02 1.449E-01 1.868E-02 1.593E+02 1.775E+02 3 1.500E+02 3.890E-01 5.012E-02 1.495E+02 1.677E+02 4 2.000E+02 8.743E-02 1.127E-02 1.429E+01 3.247E+01 5 2.500E+02 1.107E+00 1.427E-01 8.109E+01 9.927E+01 6

19、 3.000E+02 1.601E-01 2.063E-02 4.294E+00 2.247E+01 7 3.500E+02 3.920E-01 5.050E-02 4.865E+01 6.683E+01 8 4.000E+02 7.494E-02 9.656E-03 5.378E+01 7.196E+01 9 4.500E+02 9.148E-02 1.179E-02 -1.688E+02 -1.506E+02 10 5.000E+02 8.792E-02 1.133E-02 6.767E+01 8.585E+01 11 5.500E+02 1.352E-01 1.743E-02 1.299

20、E+02 1.480E+02 12 6.000E+02 7.831E-02 1.009E-02 4.942E+01 6.760E+01 13 6.500E+02 3.187E-02 4.106E-03 5.156E+01 6.974E+01 14 7.000E+02 4.773E-02 6.150E-03 9.785E+01 1.160E+02 15 7.500E+02 1.982E-02 2.554E-03 -1.322E+02 -1.140E+02 16 8.000E+02 3.518E-02 4.533E-03 9.910E+01 1.173E+02 17 8.500E+02 4.524

21、E-02 5.829E-03 1.085E+02 1.267E+02 18 9.000E+02 2.510E-02 3.234E-03 2.652E+01 4.470E+01 19 9.500E+02 2.347E-02 3.024E-03 9.151E+01 1.097E+02 20 1.000E+03 1.546E-02 1.992E-03 -1.746E+01 7.183E-01 TOTAL HARMONIC DISTORTION = 1.649845E+01 PERCENTDC COMPONENT = -2.059094E-02The line current waveshape fo

22、r Figure 3 is shown in Figure 3(c). The shape has somewhat improved from the case without filter, but still not “perfect”. Note also that the high “current peaks” vanishes. This is good for the rectifier diode.Figure 3(c).Improved current waveform can be obtained by increasing values of line inductance filter and choke filter. Figure 3(d) shows an example with line inductance filter = 50mH and DC choke = 80mH. Note that th