1. Advanced Phasor Measurement Units for the Real-Time Monitoring
of Transmission and Distribution Networks
Paolo Romano
Distributed Electrical Systems Laboratory
École Polytechnique Fédérale de Lausanne - EPFL
Good morning everyboy, most of you know me already. My name is Paolo Romano and I am here for presenting my research plan proposal for my candidacy exam.
As you can see form the title I am going to talk about PMU and I hope to do it in the most clear and easy way.

2. Outline Introduction PMU requirements
Proposed synchrophasor estimation algorithm
Algorithm implementation
Experimental validation
Conclusion

3. Introduction (1) Power networks new paradigms
Evolution of distribution networks passive  active
major changes in their operational procedures;
need of advanced and smarter tools to manage the increasing complexity of the grid;
main involved aspect is the network monitoring by means of Phasor Measurement Units (PMUs);
PMU definition (as stated in IEEE Std.C ):
“A device that produces synchronized measurements of phasor (i.e. its amplitude and phase), frequency, ROCOF (Rate of Change Of Frequency) from voltage and/or current signals based on a common time source that typically is the one provided by the Global Positioning System UTC-GPS.”

4. Introduction (2) What is a Phasor Measurement Unit (PMU)?
PMU timeline:
1988
1st PMU
prototype
1992
1st commercial
PMU
1995
Standard
(IEEE 1344)
2005
New PMU
(IEEE C37.118
-2005)
1893
Introduction of
“Phasor” concept
1980s
GPS
technology
2011
Latest version of
IEEE Std. C
2012
1st PMU prototype
at EPFL
PMU typical configuration:

5. Introduction (3) PMU applications within transmission networks

6. Introduction (4) PMU applications within active distrib. networks
Phasor Data Concentrator - PDC
RT Power System State Estimator
Network in normal operation:
Voltage sensitivities computation
Power flows sensitivities computation
V/P real time optimal control
Real time congestion management
Network in emergency conditions:
Islanding detection
Fault identification
Fault location
The main focus of this activity together with several other project from our lab is concentrated on the development of a new infrastructure where the protection and control functionalities are concentrated and unified in a single object
Within this context the PMU plays a very relevant role since it’s the device the support the whole infrastructure.
In particular…
= Phasor Measurement Unit

7. PMU requirements (1) IEEE Std. C37.118-2011 - Definitions
Synchrophasor definition:

8. PMU requirements (2) IEEE Std. C37.118-2011 – Measurement compliance
Reporting rates:
Performance classes:
P-class: faster response time but less accurate
M-class: slower response time but greater precision
Measurement evaluation:

9. PMU requirements (3) Active Distribution Networks applications
Peculiar characteristics of distribution networks:
reduced line lengths;
limited power flows values;
high harmonic distortion levels;
dynamic behaviors
Improved accuracy
of synchrophasors
measurements

10. PMU requirements (4) Active Distribution Networks applications
 synchrophasor #1
 synchrophasor #2

11. 4 Harmonic interference
Proposed synchrophasor est. algorithm (1) State of the Art of DFT based algorithms
Considered error sources:
4 Harmonic interference
3. Short range leakage
1. Aliasing
2. Long range leakage

12. 4 Harmonic interference
Proposed synchrophasor est. algorithm (2) State of the Art of DFT based algorithms
Correction approaches:
Iterative compensation of the self-interaction
Use of appropriate windowing functions
Introduction of adequate anti-aliasing filters
Increasing of the sampling frequency
1. Aliasing
2. Long range leakage
3. Short range leakage
4 Harmonic interference
Interpolated DFT methods

13. Proposed synchrophasor est
Proposed synchrophasor est. algorithm (3) Structure of the proposed algorithm
Signal acquisition (voltage/current), within a GPS-PPS tagged window T (e.g. 80 ms, i.e. 4 cycles at 50 Hz) with a sampling frequency in the order of kHz.
DFT analysis of the input signal, opportunely weighted with a proper window function.
First estimate of the synchrophasor by means of an interpolated-DFT approach.
Iterative correction of the self-interaction between the positive and negative image of the DFT main tone.

14. Proposed synchrophasor est. algorithm (4) Flow chart

15. Proposed synchrophasor est. algorithm (4) Flow chart
3-4 periods of the fundamental frequency tone

16. Proposed synchrophasor est. algorithm (4) Flow chart
Hanning window:

17. Proposed synchrophasor est. algorithm (4) Flow chart

18. Proposed synchrophasor est. algorithm (4) Flow chart

19. Proposed synchrophasor est. algorithm (5) Flow chart

20. Proposed synchrophasor est. algorithm (5) Flow chart

21. Proposed synchrophasor est. algorithm (5) Flow chart

22. Proposed synchrophasor est. algorithm (5) Flow chart

23. Proposed synchrophasor est. algorithm (5) Flow chart

24. Algorithm implementation (1) FPGA-optimized software implementation

25. Algorithm implementation (2) FPGA-optimized software implementation
Process 1
Process 2
Process 3
GPS-synchronization process:
Time uncertainty of ± 100 ns
Compensation of the FPGA clock drift
Pipelined signal acquisition:
6 parallel channels (3 voltages 3 currents)
Phase correction
Synchrophasor estimation algorithm:
Optimized DFT computation for power systems typical frequencies
32-bits fixed-point implementation

26. Algorithm implementation (3) Phase correction

27. Algorithm implementation (4) FPGA clock error compensation

28. Experimental validation (1) Compliance verification platforms
HW - PXI based platform:
SW - Desktop based platform:
Generate the test signal in host according to each test item in IEEE C37.118, 2011 then run the FPGA algorithm in desktop.
Control and synchronization
of the other PXI boards
Time-Sync accuracy ±100 ns
with 13 ns standard deviation
18-bit resolution inputs at
500 kS/s, analog input accuracy
980 μV over ±10 V input range
(accuracy of 0.01%)

29. Experimental validation (2) Static tests – Signal frequency range

30. Experimental validation (3) Static tests – Harmonic distortion

31. Experimental validation (4) Dynamic tests – Amplitude-phase modulation

32. Experimental validation (5) Dynamic tests – Frequency sweep

33. Experimental validation (6) Dynamic tests – Amplitude step

34. Conclusions (1) Future improvements
Design of a iDFT algorithm satisfying both class P and M requirements:
Sensitivity to algorithm parameters (Fs, N, w(n), interpolation scheme, no. of iteration)
Out of band interference test compliance (signal pre-filtering)
Adaptation of the algorithm to specific hardware platform:
NI-9076 (SIL-nanotera)
Zynq
Integration of GPS-independent synchronization systems:
Autonomous clocks (e.g. Rubidium-Oscilloquartz)
External synchronization signals provided by telecom protocols (Alcatel)

35. THANK YOU VERY MUCH FOR YOU ATTENTION
The end
THANK YOU VERY
MUCH FOR YOU
ATTENTION