1. in the Age of the Photovoltaic
Energy Meter
in the Age of the Photovoltaic

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

3. DC to AC Converter and the Meter
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. Harmonics Impacts on the Meter
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. Power measurement using 1 Element
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.
Wattmeter
Power (P) = Voltage (V) * Current (I)
Single Phase Meter needs
1 Element

7. Power measurement using 1.5 Element
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. 1 Element – Fraud cannot be detected
Energy Meter in the Age of the Photovoltaic
1 Element – Fraud cannot be detected

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

10. How it looks like?

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

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

13. Reactive energy due to phase shift
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. The meaning of Active and Reactive Energy
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. Analogy to Active and Reactive Energy
Energy Meter in the Age of the Photovoltaic
Analogy to Active and Reactive Energy

16. What is Power Factor (PF)?
Energy Meter in the Age of the Photovoltaic
What is Power Factor (PF)?
for pure Sine wave PF calculated as follows
PF = Ratio of Active Power to Apparent Power (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. Harmonics from large number of Photovoltaic converters cause
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. Effects of harmonics on wave
Energy Meter in the Age of the Photovoltaic
Effects of harmonics on wave
3rd Harmonic
anti-phase 3rd Harmonic

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

20. PF for Distorted wave for distorted Sine wave PF calculated as follows
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. No Harmonics, Balanced 3 phase 4 wire system
Energy Meter in the Age of the Photovoltaic
No Harmonics, Balanced 3 phase 4 wire system

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

23. Current Sensors are strongly affected by Harmonics
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. DC Component Impact on the Current Sensors
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. DC Component Impact on the Current Sensors (cont.)
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. Harmonics Impact on Meter’s Power Supply
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. Harmonics Impact on Meter’s Power Supply
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 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 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. Accuracy Stability Over Years
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