VFDs and Harmonics in HVAC Applications

Transcription

1 VFDs and Harmonics in HVAC Applications Larry Gardner Product Marketing Manager Yaskawa America, Inc. Jeff Grant Senior Sales Engineer LONG Building Technologies October 20, Yaskawa America, Inc.

2 Presentation Bounds This presentation will cover VFDs in HVAC VFD design differences Harmonics mitigation IEEE 519 basics We won t cover In-depth power system design System specifics Brand preferences Pricing 2

3 Agenda Typical HVAC VFD applications Ratings and certifications Reasons to use VFDs VFD performance factors Topology and theory of operation Harmonic performance and mitigation Multi-pulse Active front end Matrix design IEEE vs. IEEE

4 Typical HVAC VFD Applications Supply and return fans Cooling tower fans Chilled water pumps Chiller compressors 4

5 Typical VFD Ratings and Certifications Power range V: HP V: HP Ambient operating temperature Open Type IP00: -10 C to 50 C (14 F to 122 F) Certifications UL, CSA, CE, RoHS Motor types supported Induction, Surface Permanent Magnet, Interior Permanent Magnet 5

6 Reasons to Use VFDs Energy efficiency Power consumed varies with the cube of the speed Mechanical life Ramp up to speed, ramp to stop Controls to match the job PI controls, real-time clock, many others Connectivity BACnet, Metasys, Apogee, Modbus, others Former problems solved Harmonics mitigation 6

7 VFD Performance Factors Efficiency Power Factor Size Motor Control Harmonics 7

8 Conventional Drive Topology Operation Convert AC to DC Convert DC to variable frequency AC Advantages Process control and energy savings Good displacement power factor Compact size Disadvantages Poor input harmonics Poor distortion power factor Wasted braking energy L1 L2 L3 Input Rectifiers Conventional Drive DC Bus Insulated Gate Bi-Polar Transistor (IGBT) Output IGBTs T1 T2 T3 IM 8

9 Conventional Drive Output Phase Generation Pulse width modulation approximates a sinusoidal wave Comparison of carrier value to sine value turns pulses on and off 1 PWM Output Frequency Voltage 0-1 9

10 Power Quality Concerns Power factor Reactive loads Induction motors Transformers Generators Arc lamps Electric furnaces Harmonics Non-linear loads Battery chargers Electronic ballasts Variable frequency drives Switching mode power supplies 10

11 Power Factor Why it Matters Power factor Quantifies how efficiently a load utilizes the current it draws Low power factor = Inefficient current utilization Requires increased power system capacity and higher utility bills 11

12 True Power Factor Formula True Power Factor is the product of the Distortion Power Factor multiplied by the Displacement Power Factor. pf true = pf dist pf disp Where: pf true pf dist pf disp = True Power Factor = Distortion Power Factor = Displacement Power Factor 12

13 Harmonics Why it Matters IEEE 519 Current distortion Conductor heating Transformer sizing, heating Financial impact Utility billing, fines Source: 13

14 Reducing VFD Harmonics VFD harmonics mitigation DC reactor (DC link choke) High impedance to harmonic frequencies Passive harmonic filters LC circuit used to filter current harmonics Multi-pulse rectifiers Phase shifts in series to lessen current pulses Active front end Dual-rectifier to cancel harmonics Low-harmonics VFD design AC-to-AC design creates sinusoidal current All these cost money and reduce efficiency! 14

15 Harmonics Performance Comparison Details VFD VFD ithd ithd 100% 50% 100% Current Harmonics 50% 0% Variable Frequency Drive without reactor88% % Fundamental Wave Variable Frequency Drive with DC reactor33% Current Waveform Current Distortion True Power Factor* VFD AC-to-AC ithd ithd 100% 50% 0% 100% 50% 0% Variable Frequency Drive with multi-pulse 6 to 12% HVAC Matrix Variable Frequency Drive to 5% 0.98 *60Hz at full load 15

16 Matrix IGBT Bi-directional Switch Circuit of Insulated Gate Bi- Polar Transistors (IGBT) and diodes Enables bi-directional switching between input phases Switching produces simulated sine wave output Enables regenerative power back to the supply 16

17 AC-to-AC Drive Topology AC input to variable frequency AC output Nine bi-directional switches No DC bus Advantages Ultra-low input harmonics Near-unity true power factor ~ Regenerative energy savings Smaller than other harmonic solutions Price Comparable to other low-harmonic solutions Higher than conventional drives L1 L2 L3 T1 T2 T3 M 17

18 AC-to-AC Theory of Operation Phase voltage differences Available at all times for Matrix operation Nine IGBTs can switch any input phase to any output phase at any time AC-to-AC design knows What voltages to use when for pulse width modulation for generation of three output phases Input Phase Voltages Vr Vs Vt Phase Voltage Differences Vrs Vrt Vst -Vrs -Vrt -Vst

19 IEEE 519 IEEE Recommended Practice and Requirements for Harmonic Control in Electric Power Systems IEEE vs. IEEE Point of Common Coupling (PCC) The point of measurement to determine compliance Measurements Conclusions 19

20 IEEE vs. IEEE IEEE page teaching document PCC vaguely defined Device-focused Short-term measurements IEEE page-document with no attempt to educate 12 pages of intro, TOC, disclaimers, and participants 10 pages of content 7 pages of Annexes A-D PCC clearly defined System-focused Long-term measurements 20

21 PCC in IEEE Within an industrial plant, the PCC is the point between the nonlinear load and other loads. 21

22 PCC Excerpt from IEEE The recommended limits in this clause apply only at the point of common coupling and should not be applied to either individual pieces of equipment or at locations within a user s facility. 22

23 IEEE PCC for Industrial Users High voltage side of the transformer 23

24 IEEE PCC for Commercial Users Low voltage side of the service transformer 24

25 IEEE and VFDs Variable frequency drives Neither compliant nor non-compliant with IEEE Not the only producers of harmonics Part of a larger user s system Compliance measured at the prescribed point of common coupling Harmonics estimation software available From IEEE , 1.2 Purpose This recommended practice is to be used for guidance in the design of power systems with non-linear loads. 25

26 IEEE Harmonics Mitigation The limits in this recommended practice represent a shared responsibility for harmonic control between system owners or operators and users. At the system level Phase-shifted buses at the service entrance If necessary At the device level Conventional VFDs Any of the mitigation methods mentioned earlier AC-to-AC VFDs Harmonic levels (<5%) need no additional mitigation 26

27 Contact Information Larry Gardner Product Marketing Manager Yaskawa America, Inc. Jeff Grant Senior Sales Engineer LONG Building Technologies 27

28 2016 Yaskawa America, Inc.