Harmonics and Their Impact on Power Quality. Wayne Walcott Application Engineering Manager June, 2017

Transcription

1 Harmonics and Their Impact on Power Quality Wayne Walcott Application Engineering Manager June, 2017

2 Presentation Overview A little about harmonics What are harmonics What are NOT harmonics What creates harmonics IEEE STD 519 Harmonic solutions General types The good, the bad and ugly Tools and resources Harmonics calculator and selection tools MTE technical experts When your customer calls 2

3 Terms IEEE Institute of Electrical and Electronic Engineers (IEEE) - A non profit, global association working for the development, implementation and maintenance of technology-centered products and services. IEEE-STD 519 IEEE standard to provide recommendations for clean source of electrical energy. Harmonic Distortion Steady State electrical noise THiD Total harmonic current distortion THvD Total harmonic voltage distortion TDD Total demand distortion Additional terms can be found at 3

4 Where Harmonics Come From Variable speed drives The leading source of harmonic distortion. Fluorescent lighting, battery chargers, servers, UPS and dimmers. Induction arc furnaces, welders and induction heat treating place an added financial burden on utilities and stress the grid. Utilities make VA power and typically bill for watts, but that is changing. 4

5 Harmonics and Linear Loads Linear loads do not cause harmonic distortion. They operate with a smooth pure sinewave. Linear loads reduce the overall percentage of harmonic distortion in a system. 60%* of motors sold today are designed for non VFD operation. 40%* are designed for VFD use. VFD use is steadily increasing globally due to regulations and the desire for increased energy efficiency. Therefore the need for harmonic solutions is also steadily increasing. * According to Regal Beloit 5

6 Harmonics What they are and are not Voltage dip Power interruption Voltage rise Transient over-voltage Harmonic distortion Commutation dips/notches Voltage fluctuation Harmonic distortion: Steady state Repetitive Continuous Deformations Voltage waveforms Current waveforms Many other types of power disturbances exist and cause distortions on the line but are not steady state. All distortions result in deviations from the ideal sinusoidal waveform. Frequency fluctuation 6

7 Harmonics Where they are Input harmonics Passive solutions Active solutions VFD Output harmonics dv/dt filters Sinewave filters Common mode filters dv/dt combined filters 0 o Rectifier 1 Inverter M Not covered in this Presentation 7

8 Harmonics The Parts and Pieces + = Fig 1 : Fundamental 60Hz sine wave Figure 2 : 5th harmonic 300 Hz frequency = 5 times fundamental Figure 3 : Combination of the waveforms results in distortion 5th harmonic 7th harmonic 11th harmonic Harmonic current waveform 13th harmonic 8

9 Harmonic Mitigation The Goals The goal in harmonic mitigation: Remove all harmonic frequencies above the fundamental frequency (60 Hz for USA) There are many ways to accomplish this goal. Each method has strengths and weaknesses The key is to find the right balance. 100% 80% 60% 40% 20% 0%

10 Electrical Power Triangle Y Pure sine wave THiD=0% THvD=0% Phase shifted THiD=0% THvD=0% Total amps Reactive amps = Power factor Real amps = Work X 10

11 Harmonics - The Third Dimension Y Z Distorted sine wave Total amps THiD>30% THvD=system dependent Harmonic amps = distortion Real amps = work Reactive amps = power factor X 11

12 Harmonics Trouble, Trouble, Trouble Voltage Distortion THvD V = Z * I Impedance Current Distortion THiD Multiple zero crossings Malfunction of electronic equipment Damage to electronic equipment Transient generation Increased EMI Increased losses in machine windings Torque ripples in motors Resonance generation Erratic equipment operation Transformer overload (heat) Increased hysteresis losses Overload (heat) Increased winding stray loads Nuisance tripping of relays and circuit breakers Stressing of PF correction capacitor Premature equipment aging Cable overload/heating Neutral conductor overload Skin and proximity effects of conductors Dielectric failure 12

13 IEEE-519 Utility driven IEEE-519 is written to control the quality of power utilities deliver to users. The utility provides a voltage to the consumer. The users draws current based on the loads. The user equipment effects the quality of power delivered by the utility. Only together can there be a quality product for all users. 13

14 IEEE-519 Point of Common Coupling Point of Common Coupling In specifications, the point of common coupling (PCC) is often vaguely defined and is open to multiple interpretations. In IEEE , PCC is very well defined. PCC is not at the equipment but is a point on a public power supply system. This serves the utility more than the consumer. The point of common coupling (PCC) can also defined as follows. Within an industrial plant, the PCC is the point between the nonlinear load and other loads. This is where the most value is to the consumer. Keep the harmonics away from system components. In most cases the mitigation goal is in the industrial plant which assures the operation of the plant is not negatively affected by the harmonics. The last resort is at the point on a public power supply system. This is where the utility can step in a influence the consumer to do harmonic cleanup. 14

15 Harmonics Prevention is the Best Medicine Harmonic solutions don t do any real work, they simply prevent work stoppages. Some solutions can reduce energy costs. Passive harmonic filters improve system power factor. Companies typically choose to use harmonic solutions to reduce the probability of having a problem. 15

16 Harmonic Solutions There is no single solution that: There is no Single Perfect Harmonic Solution Provides the best performance At the lowest cost With the highest efficiency Satisfies all requirements Applicable to all size of drives Useable in new and retrofit In all applications In every environment BEST BETTER GOOD Harmonic performance levels used in this presentation Meets IEEE-519 Does not meet IEEE-519 Does not meet IEEE

17 Harmonic Solution Categories Passive solutions Solutions that use passive devices together to reduce harmonics: Inductors Capacitors Resistors Passive devices make no interactive response to a system. Active Solutions One way Solutions that use active devices together to reduce harmonics: Active devices require the use of a microprocessor control Two way interactive 17

18 Passive Reactors and Filters GOOD GOOD BEST DC reactors (chokes) Standard in most AC VFDs DC reactor only Offers good performance Practicable / easy / low cost Does not meet IEEE-519 AC Reactors Three phase line side AC reactor only Offers good performance Offers AC transient protection Practicable / easy / low cost Does not meet IEEE-519 Harmonic Filters Offers best harmonic performance AC reactor and capacitor combination Good load and grid stability Meets IEEE

19 Passive Reactor and Filter- Comparison DC Reactors AC Reactors Filters Meets IEEE 519 No No Yes Retrofit No Yes Yes THiD Level 35% 40% 35% 40% < 5% Cost Low Low Medium Transient Protect No Yes Yes Increases THvD No Yes No High Efficiency Yes Yes Yes 19

20 Passive Multipulse Solutions GOOD 0 o Rectifier 1 Inverter 6 Pulse Standard VFD No Mitigation Does not Meet IEEE o 0 o Rectifier 1 Rectifier 2 BETTER Inverter 12 Pulse Requires an input transformer Offers medium mitigation performance High load and grid stability Optimal for step-down/up solutions Cost effective on large loads Does not Meet IEEE o 0 o 0 o +20 o Rectifier 1 Rectifier 2 Rectifier 3 BEST Inverter 18 Pulse Requires special input transformer Well-known technology Offers high mitigation Cost effective on medium loads Robust and Simple Meet IEEE

21 Reactors and Filters - Comparison 20 o 30 o 0 o 0 o 0 o +20 o 6 Pulse 12 Pulse 18 Pulse Meets IEEE 519 No No Yes Retrofit Yes Yes No THiD Level 30% 40% 12% 15% < 5% Cost Low Medium High Transient Protect No Yes Yes Increases THvD No Yes No High Efficiency Yes Yes Yes 21

22 Active Solutions Active Filter BEST Active Filter Rectifier Inverter Active Filter Filter Only (No VFD) Offers high performance Complicated / high cost Required special commissioning Meets IEEE-519 Low Harmonic Drive BEST Active Filter Rectifier Inverter Low Harmonic VFD Filter and VFD combined Offers high performance Required special commissioning Complicated / high cost Meets IEEE-519 Active Front End BEST Passive Filter Active Rectifier Inverter Active Front End VFD Filter and VFD combined Offers high performance Required special commissioning Complicated / high cost Meets IEEE

23 Active Solutions Comparison Active Filter Low Harmonic Drive Active Front End AFE Meets IEEE 519 Yes Yes Yes Retrofit Yes No No THiD Level < 5% < 5% < 5% Cost Medium High Very High Transient Protect No No Yes Increases THvD No No No High Efficiency No No No 23

24 Harmonic Solutions Efficiency Goal is the Highest Efficiency VFD Only DC Reactor AC Reactor Passive Filters 12 Pulse Percent Efficiency 18 Pulse Active front end Low harmonic drive