DESl-LCA2 workshop - PMU presentation.pptx
Transcript of DESl-LCA2 workshop - PMU presentation.pptx
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Advanced Phasor Measurement Units for the Real-Time Monitoring of Transmission and Distribution Networks
Paolo Romano
Distributed Electrical Systems LaboratoryÉcole Polytechnique Fédérale de Lausanne - EPFL
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Outline
Introduction PMU requirements Proposed synchrophasor estimation algorithm Algorithm implementation Experimental validation Conclusion
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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.C37.118-2011):“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.”
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Introduction (2)What is a Phasor Measurement Unit (PMU)?
PMU timeline:1988
1st PMU prototype
1992
1st commercial PMU
1995
1st PMU Standard
(IEEE 1344)
2005
New PMU Standard
(IEEE C37.118-2005)
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Introduction of “Phasor” concept
1980s
GPStechnology
2011
Latest version ofIEEE Std.
C37.118-2011
2012
1st PMU prototype at EPFL
PMU typical configuration:
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Introduction (3)PMU applications within transmission networks
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Introduction (4)PMU applications within active distrib. networks
= Phasor Measurement Unit
RT Power System State Estimator
Phasor Data Concentrator - PDC
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
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PMU requirements (1)IEEE Std. C37.118-2011 - Definitions
Synchrophasor definition:
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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:
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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
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synchrophasor #1
111 ,, QPI
1E 2E synchrophasor #2
222 ,, QPIjX
PMU requirements (4)Active Distribution Networks applications
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Proposed synchrophasor est. algorithm (1)State of the Art of DFT based algorithms
Considered error sources:1. Aliasing 2. Long range leakage
3. Short range leakage 4 Harmonic interference
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Proposed synchrophasor est. algorithm (2)State of the Art of DFT based algorithms
1. Aliasing 2. Long range leakage
3. Short range leakage 4 Harmonic interference
Correction approaches:
Introduction of adequate anti-aliasing filters
Increasing of the sampling frequency
Interpolated DFT methods
Use of appropriate windowing functions
Iterative compensation of the self-interaction
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Proposed synchrophasor est. algorithm (3)Structure of the proposed algorithm
I. 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 50-100 kHz.
II. DFT analysis of the input signal, opportunely weighted with a proper window function.
III. First estimate of the synchrophasor by means of an interpolated-DFT approach.
IV. Iterative correction of the self-interaction between the positive and negative image of the DFT main tone.
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Proposed synchrophasor est. algorithm (4)Flow chart
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Proposed synchrophasor est. algorithm (4)Flow chart
3-4 periods of the fundamental frequency tone
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Proposed synchrophasor est. algorithm (4)Flow chart
Hanning window:
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Proposed synchrophasor est. algorithm (4)Flow chart
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Proposed synchrophasor est. algorithm (4)Flow chart
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Proposed synchrophasor est. algorithm (5)Flow chart
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Proposed synchrophasor est. algorithm (5)Flow chart
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Proposed synchrophasor est. algorithm (5)Flow chart
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Proposed synchrophasor est. algorithm (5)Flow chart
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Proposed synchrophasor est. algorithm (5)Flow chart
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Algorithm implementation (1)FPGA-optimized software implementation
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Process 1
Algorithm implementation (2)FPGA-optimized software implementation
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
Process 2
Process 3
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Algorithm implementation (3)Phase correction
-0.001 0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.011-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
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1.0
1.2
s(k)PPS
Time [s]
k0 1 2
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Algorithm implementation (4)FPGA clock error compensation
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Experimental validation (1)Compliance verification platforms
Time-Sync accuracy ±100 nswith 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%)
Control and synchronization of the other PXI boards
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.
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Experimental validation (2)Static tests – Signal frequency range
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Experimental validation (3)Static tests – Harmonic distortion
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Experimental validation (4)Dynamic tests – Amplitude-phase modulation
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Experimental validation (5)Dynamic tests – Frequency sweep
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Experimental validation (6)Dynamic tests – Amplitude step
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Conclusions (1)Future improvements
1. 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)
2. Adaptation of the algorithm to specific hardware platform:• NI-9076 (SIL-nanotera)• Zynq
3. Integration of GPS-independent synchronization systems: • Autonomous clocks (e.g. Rubidium-Oscilloquartz) • External synchronization signals provided by telecom protocols (Alcatel)
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The end
THANK YOU VERY MUCH FOR YOU
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