Evaluation of Steady-State and Dynamic Performance of a Synchronized Phasor Measurement Unit

Transcription

1 Electrical Power and Energy Conference 2012 Resilient Green Energy Systems for a Sustainable Society Evaluation of Steady-State and Dynamic Performance of a Synchronized Phasor Measurement Unit Dinesh Rangana Gurusinghe Athula D. Rajapakse University of Manitoba, Canada Krish Narendra ERLPhase Power Technologies Ltd, Canada October 30, 2012 Power Systems Group

2 Outline Introduction Phasor Measurement Technology PMU Test Setup Sources of Errors Results and Discussion Steady-state Signal Frequency Steady-state Out-of-Band Interference Measurement Bandwidth Linear Ramp of System Frequency Step Response Conclusion

3 Introduction Synchrophasor is a phasor value obtained from a waveform with respect to a time synchronized reference signal Phasor measurement unit (PMU) is a device, which can extract phasor values as well as the frequency and the rate of change of frequency (ROCOF) PMU can be a stand-alone unit as well as a functional unit within another physical unit such as a protective relay or a power system data recorder PMUs when combined with communication infrastructure enable online observation of the dynamics of a power system spread over a large geographical area Today, utilities deploy PMUs to solve a variety of power system protection, automation and control problems

4 Why PMUs Need to be Evaluated? A number of vendors producing PMUs while hardware and algorithms from different vendors resulting in inconsistency Novel PMU applications demand high accuracy and consistency to ensure precise reflection of power system behaviour specially under dynamics The latest IEEE PMU standard C provides, necessary guidelines and performance tests to ensure dynamic compliances Introduces two performance class filters (P class and M class) P class applications requiring narrow operating range and fast response M class applications requiring full operating range and greater precision equations for frequency and ROCOF measurements and defines their error limits expansion to the concept of total vector error (TVE)

5 Phasor Measurement Technology A general dynamic phasor can be represented as, The frequency of the reference signal is 50 or 60 Hz and a cosine function with zero phase offset As X m (t)and Δf(t)are functions of time, by replacing them with suitable mathematical functions different dynamic test cases can be produced

6 PMU Test Setup Power system electromagnetic transient simulation (PSCAD/EMTDC) software precisely produces playback (COMTRADE) files with signals from mathematical models The Doble F6150 real-time playback device that supplies real voltage and current signals at their appropriate levels (69 V voltage and 5 A current inputs) The PMU extract phasors using discrete Fourier transform (DFT) and other interested analogue measurements such as frequency, ROCOF and power The PMU measurements are evaluated against the actual test signals generated from the mathematical models, which were already used to produce COMTRADE files

7 Sources of Errors Sources of errors include both measurement and op-erational errors of COMTRADE file, playback device ampli-fier, GPS receiver, and so on COMTRADE file error occurs due to conversion of analogue into integervaluesanditcanbeminimizedby selectingascalewithproper precision(16-bit) and suit-able time step(50 µs) The accuracy of the GPS receiver used is ±1 µs (a ±26 µs timing error causes1%tvein60hzsystem) The influence of these errors can be minimized by properly calibrating the instrumentation using the known voltage and/or current signal It is important to calibrate both magnitudes and time errors

8 Results and Discussion Tests need to be accomplished over the entire range of interest and include a range of operating conditions The M class operating range is considered as it is the full range operation of PMU Test results illustrate performances of the highest reporting rate of 60 frames per second (fps) Steady-state compliances include, Signal Frequency, Magnitude (Voltage and Current), Phase Angle, Harmonic Distortion, Out-of-Band Interference Dynamic compliances include, Measurement bandwidth, Linear system frequency ramp, Step response

9 Steady-state Signal Frequency Frequency of test signals are varied from 55 Hz to 65 Hz while all other quantities are kept constant Total Vector Error (%) Max Min Mean Signal Frequency (Hz) It is important to note that the phasor rotates with time as the signal frequency deviates from the nominal frequency.

10 SS Out-of-Band Interference A 10% out-of-band interference is introduced into the test signal The interference signal should be in phase with the fundamental component The frequency of an interference signal is varied from 10 Hz to second harmonic (120 Hz in 60 Hz system) Total Vector Error (%) Max Min Mean Frequency of Interference (Hz)

11 Measurement Bandwidth Test signals for measurement bandwidth are primarily 50 or 60 Hz waveforms that are amplitude or/and phase angle modulated with a sinusoidal waveform The test signal is represented as, Total Vector Error (%) Max Min Mean Mdoulation Frequency (Hz)

12 Linear Ramp of System Frequency The input signal frequency is linearly ramped to test performances during power system frequency changes The test signal is represented as, Total Vector Error (%) Max Min Mean Ramp Rate (Hz/s)

13 Step Response Step response provide a simple and easily observed method of comparing the PMU response to a sudden input change Step responses include, The latest IEEE PMU standard C provides, Magnitude step (positive and negative) Phase angle step (positive and negative) The test signal is represented as,

14 Magnitude (+)ve Step Response Current Input (A) Magnitude (A) Total Vector Error (%) Time (s) Actual Measured

15 Phase Angle (+)ve Step Response Current Input (A) Phase angle (deg) Total Vector Error (%) Time (s) Actual Measured

16 Conclusion The PMU steady-state and dynamic performance tests specified in the IEEE C standard are reviewed Simple and repeatable PMU dynamic performance evaluation method is proposed As TVE combines error from magnitude, phase angle and timing it is important to minimize all these error components The PMU tested did not satisfy some dynamic requirements as it has been designed according to the previous standard (C ) But the performances of the PMU can be enhanced if the new performance class (low-pass finite impulse response) filters will be implemented

17 Electrical Power and Energy Conference 2012 Resilient Green Energy Systems for a Sustainable Society Thank You?