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Energy Meter in the Age of the Photovoltaic

Energy Meter in the Age of the Photovoltaic . Energy Meter in the Age of the Photovoltaic . Grid connected Solar PV system configuration. Energy Meter in the Age of the Photovoltaic . DC to AC Converter and the Meter.

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Energy Meter in the Age of the Photovoltaic

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  1. Energy Meter in the Age of the Photovoltaic

  2. Energy Meter in the Age of the Photovoltaic Grid connected Solar PV system configuration

  3. Energy Meter in the Age of the Photovoltaic DC to AC Converter and the Meter Converts DC to AC, the result is not a pure Sine wave and therefore contains Harmonics

  4. Harmonics in electrical Grid

  5. Energy Meter in the Age of the Photovoltaic Harmonics Impacts on the Meter • Displacement of Power Factor (PF) • Current in the Neutral wire (for 4 wire system) • DC-Component in the Current flow • Impact on Current & Voltage Sensors • Impact on Power Supply

  6. Energy Meter in the Age of the Photovoltaic Power measurement using 1 Element Blondel's theorem (named after André Blondel), states that: In a system of N wires, needs (N-1) wattmeter to measure the electrical Power. • For example: 3 phase meter , 3 wire needs 2 wattmeters, but a 3 phase meter, 4 wire (with a neutral) needs 3 wattmeters. Power (P) = Voltage (V) * Current (I) Wattmeter Single Phase Meter needs 1 Element

  7. Energy Meter in the Age of the Photovoltaic Power measurement using 1.5 Element Current in the Neutral wire, we need to add Current-Meter 1.5 Element

  8. Energy Meter in the Age of the Photovoltaic 1 Element – Fraud cannot be detected

  9. Energy Meter in the Age of the Photovoltaic 1.5 Element - Fraud Detection

  10. How it looks like?

  11. Energy Meter in the Age of the Photovoltaic Power measurement - Voltage/Current some phase in this case Pave is Maximum MAX

  12. Energy Meter in the Age of the Photovoltaic Phase shift between Voltage and Current

  13. Energy Meter in the Age of the Photovoltaic Reactive energy due to phase shift (1) (2) Reactive Energy • (1)ø = 00 , only Active Power • (2)ø ≠ 00 , phase shift between Voltage and Current, portion of the Power curve going negative Reactive Energy • (2) Pav is decreased

  14. Energy Meter in the Age of the Photovoltaic The meaning of Active and Reactive Energy • Active Power (W) produces real work • Reactive Power (var) is the power required to produce the magnetic fields to enable the real work to be done • Apparent Power (VA) is considered the Total Power that the Electric company supplies to produce the required amount of Active Power • √ Active Power ? Reactive Power ?? Apparent Power

  15. Energy Meter in the Age of the Photovoltaic Analogy to Active and Reactive Energy

  16. Energy Meter in the Age of the Photovoltaic What is Power Factor (PF)? for pure Sine wave PF calculated as follows • PF = Ratio of ActivePower to ApparentPower (W/VA) Power Space Vectors • PF depends on the phase angle between Voltage and Current waves • A low PF indicates a low energy efficiency (losses)

  17. Energy Meter in the Age of the Photovoltaic Harmonics from large number of Photovoltaic converters cause Displacement of Power Factor (PF) hence increase Reactive Energy

  18. Energy Meter in the Age of the Photovoltaic Effects of harmonics on wave 3rd Harmonic anti-phase 3rd Harmonic

  19. Energy Meter in the Age of the Photovoltaic Effects of harmonics on Power PAV2 = VRMS2 * IRMS12 > PAV1 = VRMS1 * IRMS1 P(W) S(VA) Q(var) S(VA) Displacement of PF PF produces Reactive Energy

  20. Energy Meter in the Age of the Photovoltaic PF for Distorted wave Fourier Transform for distorted Sine wave PF calculated as follows Energy of the harmonics is mainly Reactive energy

  21. Energy Meter in the Age of the Photovoltaic No Harmonics, Balanced 3 phase 4 wire system

  22. Energy Meter in the Age of the Photovoltaic The special about the 3rd Harmonics Harmonics can cause current on the Neutral Wire in3Phase 4 wire system

  23. Energy Meter in the Age of the Photovoltaic Current Sensors are strongly affected by Harmonics • Toroid for CT meters up to 15A (no DC-Tolerance) • Toroid for Direct Connection up to 200A • No DC tolerance (needs strong shielding), problem with DC-Component • DC-Tolerance (large Core, needs strong shielding – Expensive) • Shunt current up to 120A • No problem with DC component

  24. Energy Meter in the Age of the Photovoltaic DC Component Impact on the Current Sensors • Distorted wave: “Fourier Transform” shows DC component • DC Component impact on the Energy measurement Shunt

  25. Energy Meter in the Age of the Photovoltaic DC Component Impact on the Current Sensors (cont.) Magnetic Hysteresis DC component DC component impact on CT Linearity

  26. Energy Meter in the Age of the Photovoltaic Harmonics Impact on Meter’s Power Supply • "Linear-Power-Supply" and “Switched-Mode-Power Supply”, using a step-down transformer. Usually when correctly designed using high quality capacitors, these types do not “suffer” much from harmonic distortion

  27. Energy Meter in the Age of the Photovoltaic Harmonics Impact on Meter’s Power Supply • “Capacitor-Power-Supply” using a Voltage Dropping Capacitor. The capacitor can be damaged significantly by harmonics • The problem is more difficult when the Meter is installed outside under a burning sun

  28. Energy Meter in the Age of the Photovoltaic Energy Meter in the Age of the Photovoltaic Summary 1/2 • Meter cannot resolve the problems caused to the Voltage and Current waveforms, the meter will use those waves to measure energy quantities (P, Q, S) • Voltage and mainly Current Sensors are affected by Harmonic distortion • Photovoltaic Energy supplier’s billing should be based on three electrical quantities: Active power (P), Reactive power (Q) and Apparent power (S) • Meter should be with measurement of P, Q and S. The difference in kVA meter measurement can be as large as 30% when the waveform is distorted • For PF displacement, it is necessary to install “PF-Correction -Capacitors”

  29. Energy Meter in the Age of the Photovoltaic Energy Meter in the Age of the Photovoltaic Summary 2/2 • Energy of the harmonics is mainly Reactive energy, even though there are no requirements in the IEC standards for testing Reactive Energy under the effects of harmonics?? • 3 phase 4-wire system, Meter should be of type “1.5 Element”, (measurement of the Neutral wire current) • CT current sensor cannot detect DC-Component, and also affected by DC-Component. So it is a question if a meter uses CT as a current sensor can be used? • Shunt current sensor can detect DC component . Can be used, provided that the Meter can measure DC-Component (“All-Pass”) • Capacitor-Power-Supply: only with high quality capacitors, that can withstand harmonic distortion

  30. Energy Meter in the Age of the Photovoltaic Accuracy Stability Over Years

  31. Thank you for your attention! SEEEI 2012 By: Avi Lugassi Energy Meter in the Age of the Photovoltaic

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