Impact of Acquisition Wideband Noise on Synchrophasor Measurements: A Design Perspective

Abstract

Next-generation Phasor Measurement Units (PMU) are expected to be more accurate than existing ones, especially to address the stricter requirements of future active distribution grids. From this perspective, the influence of acquisition wideband noise (which includes multiple contributions both in amplitude and in phase) has to be carefully evaluated. In this context, the contribution of this paper is twofold. First, it provides a general framework to evaluate the effect of wideband noise on synchrophasor amplitude, phase, frequency and rate of change of frequency (ROCOF) estimation. The results of this analysis show that the influence of wideband noise can become critical for compliance with the requirements reported in the IEEE Standards C37.118.1-2011 and C37.118.1a-2014, especially for frequency and ROCOF estimation. In addition, the paper reports general guidelines to choose the PMU effective resolution and sampling rate for which the impact of wideband noise on both P Class and M Class PMUs is negligible.

Iterative-Interpolated DFT for Synchrophasor Estimation: A Single Algorithm for P- and M-Class Compliant PMUs

“…5 shows the accuracy in estimating the IpDFT correction term δ as a function of P , when analyzing a signal at 47.5 Hz with a sampling rate of 50 kHz and a window length of 60 ms. In order to emulate more realistic conditions, the signal is characterized by an 80 dB Signal-to-Noise Ratio (SNR) [23]. As it can be noted, in this specific case, the effect of the compensation becomes negligible after P = 2 iterations both for the Hanning and the cosine windows.…”

“…In particular, the case of a signal characterized by a main tone at 47.5 Hz and an interharmonic tone at 20 Hz is presented (similar results hold for all combinations of f 0 and f i in the OOBI range). Again, an 80 dB SNR is considered [23]. Fig.…”

“…Moreover, two tables summarize the maximum obtained TVE, FE and RFE and the maximum limit allowed by [1] in all tests (Tables II and III). Although [1] does not provide any guidelines regarding the noise, additive white Gaussian noise with zero mean and variance corresponding to an SNR in the range [60, 80] dB is added to the various reference signals, in order to simulate more realistic conditions [23]. For the sake of clarity, since the trend of errors is similar for any value of SNR, the graphs refer to an SNR of 80 dB, whereas the tables include the maximum obtained errors for both 60 and 80 dB.…”

Phasor Measurement Unit Test Under Interference Conditions

“…Adjustments such as a longer observation window (number of cycles used by the PMU for estimation), an increased sampling rate, and a larger effective number of bits of the A/D sampling could improve the accuracy under noise conditions. Reference [46] describes details on how these adjustments affect the accuracy of the PMU, and advantages and possible disadvantages of such adjustments. A number of guidelines are also provided in [46] to help PMU designers make a balanced choice of these parameters.…”

“…Reference [46] describes details on how these adjustments affect the accuracy of the PMU, and advantages and possible disadvantages of such adjustments. A number of guidelines are also provided in [46] to help PMU designers make a balanced choice of these parameters.…”