Basic Harmonics Training

8/20/2019 Basic Harmonics Training

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Basic HarmonicsOnline WEB Training Module

Revision 002


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Learning Objectives

In this training module we will learn the fundamentals of “Harmonics”.

We will focus on:

The Ideal vs. Distorted Waveform.

Definition of Harmonics

Time Domain / Frequency Domain Analysis

Calculation of THiD

Harmonic Producing Loads

Standards and Recommendations

Harmonic Mitigation Techniques

Software Tools


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The Ideal Waveform

In public power distribution networks the ideal undistorted AC electrical signal has a

typical frequency of 50Hz or 60Hz depending on the country or region.


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The Ideal Waveform

In public power distribution networks the ideal undistorted AC electrical signal has a

typical frequency of 50Hz or 60Hz depending on the country or region.

Due to the method of generation, the signal alternates between proportionally equal,positive and negative values.

In reality however these signals contain many types of disturbances.


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Power Disturbances

The power grid normally experiences huge

variations of load and reacts to changes inthe voltage waveform.

Causes of power disturbances range fromelectrical switching circuits to lightning.


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Power Disturbances




Voltage

fluctuation

Voltagedip

Power

interruption

Voltage rise

Transientover-voltage

Harmonic

distortion

Commutation

dips/notches

Frequency

fluctuation


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Power Disturbances




Harmonic distortions are repetitive and

continuous deformations of the voltage orcurrent waveforms.

All distortions result in deviations from theideal sinusoidal waveform.

Voltage

fluctuation

Voltagedip

Power

interruption

Voltage rise

Transientover-voltage

Harmonic

distortion

Commutation

dips/notches

Frequency

fluctuation



Learning Objectives




Calculation of THiD




Software Tools




In a periodic signal the primary, desired frequency is the "Fundamental Frequency“.


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A “Harmonic” refers to a component of a periodic signal, that is itself:

“a periodic s i n u s o i d a l signal , with a frequency that is an integer multiple of thefundamental frequency”.


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Therefore in public power distribution networks:

The frequency of an nth Harmonic is: f n = n X 50Hz or f n = n X 60Hz


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Therefore in public power distribution networks:

The frequency of an nth Harmonic is: f n = n X 50Hz or f n = n X 60Hz

Fundamental Freq.1st Harmonic 2nd Harmonic 3rd Harmonic 4th Harmonic

f1 = 50Hz f2 = 100Hz f3 = 150Hz f4 = 200 Hzf1 = 60Hz f2 = 120Hz f3 = 180Hz f4 = 240 Hz


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The Study of Harmonics

Harmonics appear in many fields of science and in the natural world.


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In electrical systems harmonics are primarily caused by loads that draw current

repetitively but in a non-sinusoidal manner.

Harmonics are typically regarded as an undesired, costly and sometimes dangerousbi-product of active electrical systems.


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In electrical systems harmonics are primarily caused by loads that draw current

repetitively but in a non-sinusoidal manner.

Harmonics are typically regarded as an undesired, costly and sometimes dangerousbi-product of active electrical systems.

We use a combination of “Time Domain” graphs, “Frequency Domain” graphs andmathematics to determine the extent of the problem.


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Learning Objectives



Time Domain / Frequency Domain Analysis Calculation of THiD




Software Tools


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Time Domain Graphs

In electrical engineering, "time domain" is a term used to describe the analysis of

electrical signals with respect to time.


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Time Domain Graphs



In the graph below we have an example of an ideal un-distorted alternating voltageor current signal. The values of the signal fluctuate between positive and negativeamplitudes over time.


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Time Domain Graphs



In the graph below we have an example of an ideal un-distorted alternating voltageor current signal. The values of the signal fluctuate between positive and negativeamplitudes over time.

As time progresses, the graphical representation clearly displays the variance inamplitude.


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Frequency Domain Graphs

Frequency Domain graphs allow us to see the amplitudes of the frequencies that

make up a signal.


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make up a signal.

We use Fourier Series transforms to create Frequency Domain graphs.


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make up a signal.

We use Fourier Series transforms to create Frequency Domain graphs.

Time Domain Frequency DomainFourier Series Transform


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Harmonics Illustrator Demonstration

We are now going to look at a short demonstration of transforming time domain

signals into the frequency domain using the:

Harmonic Illustrator


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Harmonics Orders

f1, f2, f3 etc. are referred to as “Harmonic Orders”.

Only loads such as half wave rectifiers drawing current with a DC componentgenerate even numbered Harmonic Orders.


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Harmonics Orders



Single Phase AC harmonic generating loads, generate odd numbered harmonics.


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Harmonics Orders



Single Phase AC harmonic gernerating loads, generate odd numbered harmonics.

Ideal three phase AC harmonic generating loads, generally draw current equally fromeach phase so the harmonic numbers divisible by 3 are cancelled.


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Tools for Frequency Domain Analysis

The most common tools used in industry to display such graphs in electricalengineering are “Spectrum Analyzers”.

Spectrum Analyzer


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Modern oscilloscopes typically have a simple spectrum analyzer included as standard.

Spectrum Analyzer


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More sophisticated analyzers can measure a very wide range of frequencies that can

be useful in electronics and high frequency analysis of electrical disturbances.

Spectrum Analyzer


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More sophisticated analyzers can measure a very wide range of frequencies that can

be useful in electronics and high frequency analysis of electrical disturbances.

Others can contain dedicated functions to measure electrical distortions such asharmonics in three phase systems and can be called “Power Quality Analyzers”.

Spectrum Analyzer Power Quality Analyzer


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Learning Objectives




Calculation of THiD




Software Tools


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“Fundamental Current” refers to the current carried in the fundamental frequency.

I(h1) (Example: f1 = 100 A)

“Total harmonic current distortion” refers to the ratio of all harmonic currents to thefundamental current.

Total Harmonic Current Distortion – THiD


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Total Harmonic Current Distortion – THiD


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Other Measurements of Harmonic Distortion

RMS Current of the distorted signal.

Peak Values for Current and Voltage.

THvD – Total Harmonic Voltage Distortion.

TDD – Total Demanded Distortion relating to Maximum Load Current.

PWHD – Partial Weighted Harmonic Distortion relating to specific harmonic ranges.


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Learning Objectives




Calculation of THiD




Software Tools


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Harmonics are primarily caused by loads that draw current repetitively but in anon-sinusoidal manner.


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Examples of Harmonic Loads include: Ballast / Fluorescent Lighting & Computer power supplies Uninterruptable Power Supplies (UPS’) & Variable Speed Drives Charging circuits incorporating rectifiers

Arc Welders & 3 phase machines


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Examples of Harmonic Loads include: Ballast / Fluorescent Lighting & Computer power supplies Uninterruptable Power Supplies (UPS’) & Variable Speed Drives Charging circuits incorporating rectifiers

Arc Welders & 3 phase machines

Examples of load current waveforms with harmonics.


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Current vs. Voltage Distortion Current distortion relates to load level

performance

I*Z=V


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Current vs. Voltage Distortion Current distortion relates to load level

performance

I*Z=V

Voltage distortion relates tosystem level performance.

Harmonic currents of the non-linearload AND the system short-circuitimpedance are required to calculatevoltage distortion. It is NOT possible topredict the voltage distortion knowingonly the load performance.


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Current vs. Voltage Distortion

Current distortion relates to load level performance

I*Z=V

Voltage distortion relates tosystem level performance.

Harmonic currents of the non-linearload AND the system short-circuitimpedance are required to calculatevoltage distortion. It is NOT possible topredict the voltage distortion knowingonly the load performance.

Background voltage distortion is alsorelated to system level performance.Same as secondary transformer sidevoltage distortion. Backgrounddistortion can be caused by energyconsumers far away and is alwayspresent to some extent (0.5 - 3%).


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Problems caused by current distortion Transformer overload and audible noise.

Tripping of serial relays and circuit breakers.

Stressing of Power Factor correction capacitors.

Premature aging of serially installed equipment.

Overheating of cables and insulation stress. Overheating of transformers and insulation stress.

Current Distortion


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Problems caused by voltage distortion Malfunction of electronic equipment

Breakdown of electronic equipment

Increased Electromagnetic Interference (EMI)

Increased losses at direct online motors

Torque ripples from direct online motors

Erratic operation

Voltage Distortion


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Learning Objectives




Calculation of THiD




Software Tools


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The EMC directive

RadiatedEN61000-4-3( 80–1000MHz)

Conducted emission

EN55011(0,15-30MHz)

Radiated

emissionEN55011

(30 -1000MHz )

100Hz 1 kHz 10 kHz 100 kHz 1 MHz 10 MHz10Hz 100 MHz

Working

area

Harmonic

disturbance

Conducted

interference

Radiated

interference

1 GHz

Conducted RF-CMEN61000-4-6(0,15-80MHz)

Harmonicdistortion

EN61000-3-2/4/12

Emissions /

Immunity

Electromagnetic compatibility (EMC)

Harmonic Norms are a part of EMC group ofNorms in IEC 61xxx-x-x.

Lowfrequency

EN61000-2-2/4


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The EMC directive

RadiatedEN61000-4-3( 80–1000MHz)

Conducted emission

EN55011(0,15-30MHz)

Radiated

emissionEN55011(30 -1000MHz )

100Hz 1 kHz 10 kHz 100 kHz 1 MHz 10 MHz10Hz 100 MHz

Working

area

Harmonic

disturbance

Conducted

interference

Radiated

interference

1 GHz

Conducted RF-CMEN61000-4-6(0,15-80MHz)

Harmonicdistortion

EN61000-3-2/4/12

Emissions /

Immunity

Electromagnetic compatibility (EMC)

Harmonic Norms are a part of EMC group ofNorms in IEC 61xxx-x-x.

There are no sharp lines between thedifferent disturbance/interference bands.

Amplitudes of harmonics are highest in the

lower frequency range.

We need to understand the entire frequencyrange, as some mitigation equipment tendsto move the problem from low frequenciesto higher frequenciesLow

frequencyEN61000-2-

2/4

Note: Only IEC norms is mentioned here! Others are

sometime to be fulfilled


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M M

M

At utility level

EN 50160 System Voltage Requirements

Standards & Recommendations


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M M

M

At utility level


At customer/system Level

IEEE519G5/4 = “EN61000-3-2/12


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M M

M

At utility level



IEEE519G5/4 = “EN61000-3-2/12


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M M

M

At utility level



IEEE519G5/4 = “EN61000-3-2/12


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Learning Objectives




Calculation of THiD




Software Tools


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Passive:

DC-Inductors

18-pulse

Advanced Harmonic

Filters

Active:

///

Active Front End with PWM-rectifier

/// /

/ /

Active filter & Low Harmonic Drive

D

d

y

D

-20%

+20%

0%

12-pulse

AC-Inductors

Harmonic Mitigation Techniques for Drives


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AC & DC Inductors

DC-Inductors are typically built-in asstandard.

Overlapping of magnetic fields in the inductorreduces distortion.

Offers moderate mitigation performance.

Great RMS current reduction.

Practical / Easy production.

Cost efficient.

AC-Inductors

DC-Inductors


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12 & 18 Pulse Rectifiers

Well-known technology.

The power coming into the rectifier sectionsis phase shifted by a special transformer tocause cancellation of harmonics.

Offers fair mitigation performance

Dependant on high load and grid stability

Optimal for step-down / step-up solutions

Robust

12-pulse rectifier

18-pulse rectifier


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12 & 18 Pulse Rectifiers

12p aims to reduce 5th & 7th harmonics, andmultiples.

18p aims to reduce 5th, 7th, 11th & 13thharmonics, and multiples.

12-pulse rectifier

18-pulse rectifier


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Passive Filters

Offers medium mitigation performance

Reduces all harmonics, not just low orders

Best cost of ownership in low power

installations

Specialized Danfoss Products designed forDanfoss drives include:

Advanced Harmonic Filter AHF 010 - THiD 10%

Advanced Harmonic Filter AHF 005 - THiD 5%

Passive Filter(Also called Harmonic Trap Filter)


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Active Filters

Offers high performance mitigation

The fi lter cancels the distortion by sensing itand inserting an equal signal with theopposite phase.

Tolerant with load and grid imbalances

Expensive

Customer / System level PCC installationpossible. Group compensation, power factorcorrection and load balance correction)

New Danfoss Products include:

Active Filter – AAF

Low Harmonic Drive - LHD

Active Filter


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Active Front End

Utilizes Pulse Width Modulation (PWM) in therectifier section.

Offers highest mitigation performance

Tolerant with of load and grid imbalances

Good for regeneration of power

Very compact and light

Expensive

Active Front End - AFE


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Cost comparison

Cost

Performance

AC or DC Coils

DC+AC Coils

No Coils

12 Pulse18 Pulse

Active Filter / Low harmonic Drive

Harm. trap

Active Front end

10% THiD Passive Filters

5% THiD Passive Filters


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Passive:

DC-Inductors

AC-inductors

Advanced Harmonic

Filters

Active:

///

PWM-rectifier

Active Front End

/// /

/ /

Active filter

Dd

y

D

-20%

+20%

0%

12 & 18-pulse

• Built-in as Standard

• Practical / Easy

• Low cost

• Robust

• Low cost

• Robust

• Efficient

• Sizable

• High mitigation

• Retrofit-able

• Efficient (sleep mode)

• Compact

• Easy to spec.

• High mitigation

• 100% Regenerative

Harmonic Mitigation Summary


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Other Mitigation Techniques

Oversize hardware components, still abidingto regulations, and allow harmonics to flow.

Oversize distribution transformers.

Oversize switchgear and distribution cabling toreduce risk of insulation breakdown.

Use “K-factor” system transformers toincrease heat tolerance.


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Hardware for over-sizing is expensive.

Harmonic energy is dissipated in the form ofheat which is also expensive.


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Hardware for over-sizing is expensive.

Harmonic energy is dissipated in the form ofheat which is also expensive.

Harmonics can also be reduced by:

Balancing loads on phases.

Improving Displacement Power Factor


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Learning Objectives




Calculation of THiD




Software Tools


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1.1

Calculation Software The Danfoss freeware MCT31 calculates a

reasonable estimate of the harmonic contentwithin specified installation.

Advanced calculations require lots of inputs toreach a reliable result not just on the lowvoltage side but also at medium voltage level.


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1.1




Most calculation tools are only including lowvoltage grid data (some with back grounddistortion) and are thus calculating with anaccuracy of ±10 - 20%.


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1.1





Other background distortion levels are notincluded.


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1.1





Other background distortion levels are notincluded.

More accuracy can be achieved when using theDanfoss HCS software which requires additionalgrid data.

HCS includes Pspice simulation from systemlevel medium voltage interaction to low voltage.


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Summary

Harmonics are signals contained in distorted periodic signals.


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Summary


Time Domain / Frequency Domain Graphs are required when analyzing harmonicamplitudes.


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Summary



Loads that draw non-sinusoidal currents produce harmonics.


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Summary




Standards and Recommendations exist to advise to what level harmonics areacceptable.


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Summary





Harmonic Mitigation Techniques are many and are dealt between passive andactive solutions.


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Summary





Harmonic Mitigation Techniques are many and are dealt between passive andactive solutions.

Software Tools such as MCT31 and HCS are available to simulate harmonics topredict potential problems.

Documents

Basic Harmonics Training