PQ01. Harmonic Solutions for VFD s. Review of Power Control Harmonics, Power Factor, Distortion & Displacement

PQ01 Harmonic Solutions for VFD s Review of Power Control Harmonics, Power Factor, Distortion & Displacement

Related Content at the Expo PQ02 Power Quality and Monitoring.. PQ03 Using Test Eqipment to Detect and Measure PQ Issues PQ04 Understanding Power Monitoring PD02 Power Quality and Monitoring MC04 Installation Considerations for VFD s

What Are Harmonics?

What Are Harmonics? Ideal Often seen

What Are Harmonics?

What Are Harmonics? What Are Waveforms? 0 10.00 20.00 50.0 A sinusoidal waveform has no harmonics 30.00 40.00 Rfund.V =.. 00.0 100 0.0 50. 0 0 50.0-50 00.0-100 50.0-150 0 10.00 20.00 30.00 40.00

What Are Harmonics and Waveforms? 0 10.00 20.00 30.00 50.0 This non-sinusoidal waveform contains harmonics 40.00 Rtotal.V =.. 00.0 100 0.0 50. 0 0 50.0-50 00.0-100 50.0-150 0 10.00 20.00 30.00 40.00

Let s Create a Distorted Waveform Fundamental (1st harmonic) Only fundamental at 60Hz

Fundamental and 5th Harmonic Some 5th harmonic, 153deg

1st, 5th and 7th Harmonics A little of 7th harmonic, 282deg

1st, 5th, 7th and 11th Harmonics A bit of 11th harmonic, 0deg

1st and Sum of the 5th, 7th and 11th Sum the 5th, 7th and 11th harmonic currents

Fundamental, Harmonics, Total Sum the harmonics with the fundamental

FFT and How Are Harmonics Measured? Power Source Harmonic Power Meter Performing FFT 100 80 60 40 20 0 A1 Waveform 178.67 Arms, 34.40 %THD 1 5 10 15 20 25 30 35 40 45 50 10/28/2010-1:46:18.297 PM M AC Drive Motor

FFT, RSS, THD I harm = 30.83A I fund = 70.71A I total = 77.14A I THD = 43.6% = I harm / I fund Harmonic Number Frequency Hz Amplitude RMS Amplitude RMS^2 Phase Angle 0 DC 0.00 0.00 0 1 60 70.71 5000.00 357 3 180 0.00 0.00 0 5 300 27.97 782.50 153 7 420 10.85 117.67 282 9 540 0.00 0.00 0 11 660 5.54 30.74 0 13 780 2.79 7.79 81 15 900 0.00 0.00 0 17 1020 2.54 6.44 189 19 1140 1.45 2.09 246 21 1260 0.00 0.00 0 23 1380 1.37 1.88 10 25 1500 0.91 0.84 58 27 1620 0.00 0.00 0 29 1740 0.78 0.61 185 Sum of 3rd to 29th 950.56 Square Root of Sum 30.83 Iharm Sum of 1st to 29th 5950.56 Square Root of Sum 77.14 Itotal

What Is I(THD)? I THD = I harm / I fund So, I harm = I THD * I fund I THD is a ratio between two numbers, it does not stand alone! We can decrease I THD by either decreasing Iharm or increasing Ifund

Frequency, Amplitude, Phase Angle Harmonics are simply integer multiples of the fundamental frequency for example, if 60Hz is the fundamental (sometimes referred to as the 1st harmonic), then the 2nd harmonic is 120Hz, the 3rd harmonic is 180Hz, etc. Any non-sinusoidal waveform can be created by the addition of harmonics at various amplitudes and phase angles

Electrical Loads and Current Harmonics Power Source Load Type? Line Current Harmonics?

What are Loads That Do Not Have Current Harmonics? A sinusoidal waveform has no harmonics Voltage Current This is an example of a linear load

Examples of Linear Loads Induction motors Incandescent lights Resistance heaters Power Factor Correction Caps Electromagnetic devices Transformers non-linear During energization Over-voltage

What are Loads That Have Current Harmonics? 0 50.0 10.00 20.00 30.00 A non-sinusoidal waveform contains harmonics 40.00 Rfund.V =.. Rtotal.V =.. 00.0 100 0.0 50. 0 0 50.0-50 00.0-100 This is an example of a non - linear load 50.0-150 0 10.00 20.00 30.00 40.00

Examples of Non-Linear Loads Single Phase Fluorescent lights (ballast) Incandescent lights with light dimmers Anything with an ac-dc power supply Computers (ac-dc PS) Monitors (ac-dc PS) TVs (ac-dc PS) LED lighting Three Phase Welders Arc furnaces UPS DC power supplies DC Drives Phase control PWM AC Drives 6-Step PWM

A Typical AC Drive How Do Drives Create Harmonics? M Power Source AC Drive Motor Line Current Harmonics

AC Line Input Copyright 2011 Rockwell Automation, Inc. All rights reserved. What Does it Do? Bus = Fixed Vdc Input AC Drive Output 480Vac 60Hz AC Motor Output 0-460Vac 0-60Hz Converter AC to DC DC Bus Filter 650Vdc Inverter DC to AC

Let s Look at Some Voltages and Current Ia Vac Vab AC Power Line Load Vbus

First Current Pulse Into A Out of B AC Power Line Load 1

Second Current Pulse Into A Out of C AC Power Line Load 2

Typical Current Waveform for 6 Diode (Pulse) 0 50.0 10.00 20.00 30.00 40.00 Rtotal.V =.. 00.0 100 0.0 50. 0 0 50.0-50 00.0-100 50.0-150 0 10.00 20.00 30.00 40.00

Why 5 th and 7 th? Why do the line currents contain 5 th and 7 th harmonics? 100 90 80 70 60 50 40 30 20 10 0 1 3 5 7 9 11 13 15 17 19 21 23 25 Harmonic Number

Harmonics 2 4 6 8 10 12 14 16 18 1 3 5 7 9 11 13 15 17 19 0 50.0 20 NOTE: No even 10.00 20.00 40.00 Rfund.V =.. 50.0-150 0 10.00 20.00 30.00 40.00 Rtotal.V =.. harmonics because each half cycle is identical 30.00 00.0 100 0.0 50. 0 0 50.0-50 00.0-100 Copyright 2011 Rockwell Automation, Inc. All rights reserved. 32

SO WHAT what do I care if adjustable speed drives draw current harmonics on a power distribution system?

Issues with Excessive Harmonic Current PLC EQUIPMENT Current Harmonics PCC TELEPHONE EQUIPMENT DATA PROCESSING CENTER create I H HARMONIC SOURCE Voltage Distortion

Summary of Excessive Harmonic Current Concerns Increased Utility current requirement Inability to expand or utilize equipment Larger wire size needed = increased installation costs Component overheating Distribution transformers, generators & wires Reduced Utility power factor Increase in utility costs Equipment malfunction Due to voltage distortion with multiple or loss of zero crossing Due to voltage distortion such as flat topping Excitation of Power System Resonance's creating over-voltage s If PFCC in system PCC PFC I H PLC EQUIPMENT TELEPHONE EQUIPMENT DATA PROCESSING CENTER PFC HARMONIC SOURCE

When Should You Be Concerned About Harmonics? If service Transformer is Loaded near rating 60% 20 % of total Load is Non-Linear electronic load When PF correction capacitors Used or Planned When Voltage Distortion exceeds 8%

Example of High I thd with Low V thd - 1500kVA, 75hp I thd = 37% V thd = 0.9%

Example of High I thd with High V thd - 75kVA, 75hp I thd = 29% V thd = 9.3%

Excessive Harmonic Current Causing Voltage Flat-Topping

Volts Excessive Harmonic Current Causing Voltages with High Peaks Ev ent Details/Waveforms 750 477VAC RMS 720 volts peak 500 250 0-250 -500-750 D V A-B V B-C V C-A V 22:19:59.86 12/23/2009 Wednesday 22:19:59.87 22:19:59.88 22:19:59.89 Event #397 at 12/23/2009 22:19:59.800 Timed

IEEE Std 519-2014 * Provides harmonic current limits for a facility * Provides harmonic voltage limits for the utility connected to facility

What Are the IEEE 519-2014 Standards? Harmonic Voltage Limits Low-Voltage Systems Table 10.2 Application Maximum THD (%) Special Applications - hospitals and airports 3.0% General System 5.0% Dedicated System - exclusively converter load 10.0% Harmonic Voltage Limits Low-Voltage Systems Application Max Notch Depth Special Applications - hospitals and airports 10% General System 20% Dedicated System - exclusively converter load 50% Rule of Thumb Keep notch depth less than 10% if any other equipment will be connected to that same point of common coupling.

What Are the IEEE 519-2014 Standards? Harmonic Voltage Limits Low-Voltage Systems Table 10.2 Application Max Notch Depth Special Applications - hospitals and airports 10% General System 20% Dedicated System - exclusively converter load 50%

What Are the IEEE 519-2014 Standards? Current distortion Limits for General Distribution Systems (120V through 69,000V) Maximum Harmonic Current Distortion in Percent of Iload Isc/Iload <11 11<=h<17 17<=h<23 23<=h<35 35<=h TDD (%) <20 4.0 2.0 1.5 0.6 0.3 5.0 20<50 7.0 3.5 2.5 1.0 0.5 8.0 50<100 10.0 4.5 4.0 1.5 0.7 12.0 100<1000 12.0 5.5 5.0 2.0 1.0 15.0 >1000 15.0 7.0 6.0 2.5 1.4 20.0 Even harmonics are limited to 25% of the odd harmonic limits above Isc=maximum short circuit current at PCC Iload=maximum demand load current (fundamental frequency component) at PCC Current harmonics create voltage harmonics so there are current harmonic limits Table 10.3 Table 10.3

What Is Ithd vs Itdd? I thd = I harm / I fund at any speed or load level I tdd (IEEE519) = I harm / I fund at max load I tdd (xfmr) = I harm / I fund at rated transformer current

THD, Fund current, and Harmonic current % How Does Motor Load Affect I THD? 100 90 80 70 60 50 40 30 20 10 0 6-Pulse Buffered Drive Currents I harm I fund I THD 0 20 40 60 80 100 % Load I TDD NOTES: I THD = I harm / I fund I THD increases as load decreases I fund decreases as load decreases I harm decreases as load decreases (drive is at full speed) Copyright 2011 Rockwell Automation, Inc. All rights reserved.

Vthd vs Load 50 45 40 35 30 I TDD 25 20 15 10 5 0 Ithd, % Iharm, A Vthd, % 0 10 20 30 40 50 60 70 80 90 100 Max V thd 100hp drive on 250kVA xfmr, 6% % Load

Why Itdd on Table 10.3? I tdd is called for because that is a worst case condition. Please note: This is not where I thd is maximum But, it is where V thd is maximum because I harm is maximum When V thd is a maximum, then greatest likelihood of problems exist

The Goal of IEEE 519 Thou Shalt Not Thou Shalt Not Mess Up Up Thy Thy Neighbor s Line Voltage Neighbor s Line Voltage

Who Is Your Neighbor? utility transformer Iharm Ifund PCC1 I(TDD) is measured at each metering point Iharm A Ifund A Customer Other Customer A 2500kVA 5.75%Z 480Vsec Goal is to keep the V(THD) at PCC1 <= 5%, Iharm B Ifund B Iharm C Ifund C Customer Other Customer B Customer Other Customer C

Example utility transformer 241Arms 2960Arms PCC1 I(TDD) limits are met at each metering point 113Arms 981Arms Customer Other Customer A 300hp 6-p drives 600hp linear load 2500kVA 5.75%Z 480Vsec 101Arms 926Arms Customer Other Customer B 80hp unbuf drives 700kW linear load at PCC1: V(THD) = 3.6% 72Arms 1053Arms Customer Other Customer C 1000hp 12-p drives

What About Within Customer A or B or C? Customer A V(THD) <= 10% 300hp 6-P drives 600hp linear loads PCC1 113Arms 981Arms Isc/Iload = 53.3 V(THD) = 2.0% I(TDD) = 11.5% V(THD) <= 8% V(THD) <= 8% Meets IEEE 519 at PCC1 and within plant

What About Back-up Generator? Customer A V(THD) <= 10% 300hp 6-P drives 600hp linear loads PCC1 V(THD) <=8% Isc/Iload = 53.3 V(THD) = 2.0% I(TDD) = 11.5% G V(THD) <8% Meets IEEE 519 within the plant if the generator is sized properly

Information Needed for Generator Applications Generator Issue Information Required kw Rating Prime Mover / Engine Specifications Generator Reactive Capability Curve kvar Lagging Generator Reactive Capability Curve kvar Leading Generator Reactive Capability Curve Voltage Distortion Generator Impedance, X d Voltage Notching Generator Impedance, X d Harmonic Current Regulator Control Drive Precharge Regulator Control Table 3 Generator Issues and Information Required to Understand and Resolve those Issues. General Guidelines For 6 pulse drives Generator sized 250% of Drive HP For 18 pulse drives Generator sized 125% of Drive HP

What About the Power Factor? What is the Power Factor of a Non-Linear load? PF = Watts/VA or phase angle between voltage and current REACTIVE Current y-axis Itotal S S Iharm D P 2 Q Ireact Q 2 D 2 Ifund z-axis HARMONIC Current S 1 Ireal P x-axis REAL Current (in phase with line-to-neutral voltage, VLN) Linear Load Power Factor No Current Distortion Copyright 2011 Rockwell Automation, Inc. All rights reserved. Non-Linear Load Power Factor Includes the Effect of Current Distortion

Power Factor Total PF = PF(disp) * PF(dist) Displacement power factor - PF(disp) PF(disp) = Ireal / Ifund = a number between.01 and 1.0 involves only the fundamental quantities includes the real and reactive currents Distortion power factor - PF(dist) PF(dist) = Ifund / Itotal = a number between.01 and 1.0 includes the fundamental and harmonic (distorted) currents Itotal = fundamental and harmonic currents

Current Amplitudes I total = 105.6Arms Iharm = 33.1Arms I 5 = 29.3Arms I 7 = 10.9Arms I 11 = 7.9Arms I 13 = 4.5Arms. Ifund = 100.3Arms Ireal = 98.6Arms Ireact = 18.0Arms

Current Amplitudes I total = 105.6 Arms I harm = 33.1 Arms I fund = 100.3 Arms I real = 98.6 Arms I react = 18.0 Arms

Current Relationships I total = 105.6Arms I harm = 33.1Arms I fund = 100.3Arms I real = 98.6Arms PF disp = I real /I fund = 0.98 PF dist = I fund /I total = 0.95 PF total = PF disp *PF dist PF total = 0.93 I react = 18.0Arms

How can we reduce (mitigate) the harmonic current?

Typical I THD of 80 to 120% Sensitive to line voltage 150 162 0.0transients High peak line currents Drive Without DC Link Choke 175 Transformer xfmr % Z Common configuration for drives < 5hp 187 0 0 200 La.I = f( 0.0 200 AC DC Drive DC M hp AC Motor Load NOTE: Ipk about 3x Irms 00.0-20 00.0-40 150 162 175 187 200

Line Reactor, Drive w/o DC Link Choke Copyright 2008 Rockwell Automation, Inc. All rights reserved. Typical I THD of 30 to 45% Big help for drives without DC link choke 150 0.0 162 175 Transformer xfmr % Z 187 Line Reactor Typical values are 3% and 5% impedance 200 La.I = f(t 0.0 200 AC DC Drive DC M hp AC Motor Load 0 0 NOTE: shown is 3% LR 00.0-20 00.0-40 150 162 175 187 200

Copyright 2008 Rockwell Automation, Inc. All rights reserved. Drive With DC Link Choke Typical I THD of 30 to 40% Transformer xfmr % Z AC Drive DC Link Choke DC Less sensitive to line transients DC M AC 150 0.0 162 175 187 200 La.I = f(t hp 0.0 200 Motor Load 0 0 NOTE: Ipk about 1.5x Irms 00.0-20 00.0-40 150 162 175 187 200

Typical I THD of 20 to 35% Big help for drives w/o DC link choke 0.75-0.95 PF Line Reactor in Addition to a DC Link Choke Transformer xfmr % Z Line Reactor Typical values are 3% and 5% impedance AC DC Drive DC Link Choke DC M hp AC 150 0.0 162 175 187 200 La.I = f(t Motor Load 0.0 200 0 0 NOTE: shown is 3% LR 00.0-20 00.0-40 150 162 175 187 200

Passive Harmonic Filter Typical I THD of 4 to 7% Transformer xfmr % Z AC Drive DC Link Choke DC DC AC 0.3 to 1.0 PF M Passive Filter hp -25.00m 150.0-20.00m -10.00m 0 10.00m 20.00m 24.90m Ia = f( S,... Motor Load 100.0 100.0 50.0 50.0 0 0-50.0-50.0-100.0-100.0-150.0-150.0-25.00m -20.00m -10.00m 0 10.00m 20.00m 24.90m

Active Harmonic Filter Typical I THD of 3 to 6% Transformer xfmr % Z Ifund Ifund + Iharm AC Drive DC Link Choke DC Iharm DC AC 0.9-0.99 PF Current from Transformer AC DC Active Filter M hp -25.00m -20.00m -10.00m 0 10.00m 20.00m 24.90m 150.0 Ia = f( S,... 100.0 100.0 Motor Load 50.0 50.0 0 0-50.0-50.0-100.0-100.0-150.0-150.0-25.00m -20.00m -10.00m 0 10.00m 20.00m 24.90m

Multi-Pulse VFD 12-Pulse Typical I THD of 9 to 12% 18-Pulse Typical I THD of 4 to 5% 0.90-25.00m -20.00m - 0.99-10.00m 200.0 PF Transformer 0 xfmr % Z 10.00m 3 9 Multi-Phase Transformer 20.00m 24.90m Ia = f( S,... 100.0 100.0 AC DC Drive DC Link Choke Multi-Set 6 pulse bridge DC M hp AC Motor Load 0 0-100.0-100.0-200.0-200.0-25.00m -20.00m -10.00m 0 10.00m 20.00m 24.90m

Active Front-End Typical I THD of 3 to 5% Transformer xfmr % Z AC Drive DC DC AC Regen 0.8 1.0 PF Notch Filter M hp 145 150 0.0 162 175 187 195 Lx1.I = Motor Load 0.0 100 0 0 00.0-10 00.0-20 145 150 162 175 187 195

Popular Harmonic Mitigation Choices 18-Pulse - widely accepted Works well Has become more expensive Passive Filters Suited to lower power ratings <100 hp Numerous suppliers Active Filters Versatile used for single drives or multiple drives AFE Increasing in interest and use Feature of line regeneration capability makes it attractive

What Did We Learn? What are harmonics? Distorted waveform, sine wave element that make up distorted waveform How are they measured? FFT RSS THD TDD PCC Why do drives produce line current harmonics? Non Linear Load, 6 pulse rectifiers How much is too much? Voltage distortion greater than 5% How do we apply IEEE-519? Limits guidelines How do harmonics vary with load? Voltage distortion increase as Iharm increases as a % of maximum available current How can the drive harmonics be reduced? DC link choke, Line reactor, Passive filter, active filter, xfmr config, multipulse converter, active front end What about Power Factor? Disp pf high, total pf is dist pf * disp pf ( lower than disp pf) Total pf proportional to Ithd Be careful with passive filters and leading pf What about gensets ( Generators )? Increase in Vthd due to greater impedances, Voltage regulation issues when applied to drives PCC I H PLC EQUIPMENT TELEPHONE EQUIPMENT DATA PROCESSING CENTER HARMONIC SOURCE

PQ01 - Harmonic Solutions for VFD s Thank You! Dave Dahl Rockwell Automation Randy Keranen Werner Electric Drives, Motors, and PowerMonitor Product Manager rkeranen@wernerelec.com Matrix AP Harmonic Filter 76