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

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

2 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

3 What Are Harmonics?

4 What Are Harmonics? Ideal Often seen

5 What Are Harmonics?

6 What Are Harmonics? What Are Waveforms? A sinusoidal waveform has no harmonics Rfund.V =

7 What Are Harmonics and Waveforms? This non-sinusoidal waveform contains harmonics Rtotal.V =

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

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

10 1st, 5th and 7th Harmonics A little of 7th harmonic, 282deg

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

12 1st and Sum of the 5th, 7th and 11th Sum the 5th, 7th and 11th harmonic currents

13 Fundamental, Harmonics, Total Sum the harmonics with the fundamental

14 FFT and How Are Harmonics Measured? Power Source Harmonic Power Meter Performing FFT A1 Waveform Arms, %THD /28/2010-1:46: PM M AC Drive Motor

15 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 Sum of 3rd to 29th Square Root of Sum Iharm Sum of 1st to 29th Square Root of Sum Itotal

16 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

17 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

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

19 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

20 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

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

22 What are Loads That Have Current Harmonics? A non-sinusoidal waveform contains harmonics Rfund.V =.. Rtotal.V = This is an example of a non - linear load

23 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

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

25 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

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

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

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

29 Typical Current Waveform for 6 Diode (Pulse) Rtotal.V =

31 Why 5 th and 7 th? Why do the line currents contain 5 th and 7 th harmonics? Harmonic Number

Harmonics 2 4 6 8 10 12 14 16 18 1 3 5 7 9 11 13 15 17 19 0 50.

00 40.00 Rtotal.V =.. harmonics because each half cycle is identical 30.00 00.

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

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

36 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

37 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%

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

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

40 Excessive Harmonic Current Causing Voltage Flat-Topping

41 Volts Excessive Harmonic Current Causing Voltages with High Peaks Ev ent Details/Waveforms VAC RMS 720 volts peak D V A-B V B-C V C-A V 22:19: /23/2009 Wednesday 22:19: :19: :19:59.89 Event #397 at 12/23/ :19: Timed

IEEE Std 519-2014 * Provides harmonic current limits for a facility *

42 IEEE Std * Provides harmonic current limits for a facility * Provides harmonic voltage limits for the utility connected to facility

43 What Are the IEEE 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.

44 What Are the IEEE 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%

45 What Are the IEEE 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 (%) < < < < > 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

46 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

47 THD, Fund current, and Harmonic current % How Does Motor Load Affect I THD? Pulse Buffered Drive Currents I harm I fund I THD % 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.

48 Vthd vs Load I TDD Ithd, % Iharm, A Vthd, % Max V thd 100hp drive on 250kVA xfmr, 6% % Load

49 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

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

51 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

52 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

53 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

54 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

55 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

56 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

57 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

58 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

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

60 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

61 How can we reduce (mitigate) the harmonic current?

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

63 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 Transformer xfmr % Z 187 Line Reactor Typical values are 3% and 5% impedance 200 La.I = f(t AC DC Drive DC M hp AC Motor Load 0 0 NOTE: shown is 3% LR

64 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 La.I = f(t hp Motor Load 0 0 NOTE: Ipk about 1.5x Irms

65 Typical I THD of 20 to 35% Big help for drives w/o DC link choke 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 La.I = f(t Motor Load NOTE: shown is 3% LR

66 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 m m m m 20.00m 24.90m Ia = f( S,... Motor Load m m m m 20.00m 24.90m

67 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 PF Current from Transformer AC DC Active Filter M hp m m m m 20.00m 24.90m Ia = f( S, Motor Load m m m m 20.00m 24.90m

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

72 Active Front-End Typical I THD of 3 to 5% Transformer xfmr % Z AC Drive DC DC AC Regen PF Notch Filter M hp Lx1.I = Motor Load

73 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

74 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

75 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 You can find these products in the Solution Area SA01

Electric Drives, Motors, and PowerMonitor Product

76 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

Harmonic Mitigation for Variable Frequency Drives. HWEA Conference February 15, Kelvin J. Hurdle Rockwell Bus. Dev. Mgr.

Harmonic Mitigation for Variable Frequency Drives HWEA Conference February 15, 2011 Kelvin J. Hurdle Rockwell Bus. Dev. Mgr. 1 OVERVIEW Linear vs. Non- Linear Load Definitions AC Drive Input Current Harmonics