PMU performance requirements and validation for closed loop applications

Abstract

Wide Area Measurement Systems (WAMS) are increasingly used to observe the static and dynamic performance of power systems. Synchronised phasor measurements are also a valuable wide-area input to control and protection schemes. It is important that PMUs perform correctly for the various purposes that the data is used for. Standard and type testing is valuable, but it is also necessary to have the capability to perform specific tests for the monitoring and control applications. In particular, where phasor measurements are applied to control schemes, it is important to assess the requirements and impact of the PMU data quality on the control scheme. This paper details the findings of the authors in the field of practical design and implementation of PMU's (Phasor measurement Units) in a system. The required response of PMU's under various types of system disturbances is examined through simulation of disturbances in a large power system. The response of the PMU required for power system stability applications is examined and tested for frequency variations and presence of harmonics in the system. The paper presents the simulation setup and the thought process behind creating a virtual setup for developing and testing PMU applications. This simulation environment allows testing of the system response with closed loop control involving phasor measurements. This approach can be used to prove the control scheme, and also to develop the requirements for the PMU speed, accuracy and communications latency for correct operation of the schemes under test.

Exploring the Relative Performance of Frequency-Tracking and Fixed-Filter Phasor Measurement Unit Algorithms Under C37.118 Test Procedures, the Effects of Interharmonics, and Initial Attempts at Merging P-Class Response With M-Class Filtering

“…These are sensible and useful values in a dynamic power system context. When these thresholds are used, the maximum allowable interharmonic levels which can be applied without causing triggering can be calculated by back-calculation of (2) and (3). This leads to the highest dotted line on Fig.…”

“…This lays down strict requirements for the required response to dynamic events, and harmonic signal content. The required TVE (Total Vector Error) accuracy is still 1%, although 0.4% is desirable [3]. It also specifies accuracy requirements for frequency and ROCOF (rate of change of frequency) measurements.…”

P and M Class Phasor Measurement Unit Algorithms Using Adaptive Cascaded Filters

“…During normal operation, the phase angles of the V a , V b , and V c phasors are separated by approximately 120°. The overall positive-sequence phasor can be calculated by: (5) Assuming that the single-phase sections are effective at filtering out noise, harmonics, etc. from V a, V b and V c , then V p will also rotate at a steady rate of 2π(f-f 0 ), for steady state inputs.…”

“…HASOR measurement units (PMUs) are being deployed in ever increasing numbers. They can be used to determine system instability [1,2], detect disconnected lines and islanded sections [3], aid in power system restoration [4], and to enable state estimator algorithms to converge with higher accuracy [5][6][7]. However, testing of early PMUs showed a large disparity between the reported values from PMUs provided by different manufacturers, particularly when frequency was off-nominal, during dynamic events, and when harmonic/inter-harmonic content was present [8,9].…”

“…This lays down strict requirements for the required response to dynamic events, and harmonic/inter-harmonic signal content. The required TVE (Total Vector Error) accuracy is still 1%, although 0.4% is desirable [5]. It also specifies accuracy requirements for frequency and ROCOF (rate of change of frequency) measurements.…”