Methodology and Tools for Field Testing of Synchrophasor Systems

The electrical power grid, as one of today’s most critical infrastructures, requires constant monitoring by operators to be aware of and react to any threats to the system’s condition. With control centers typically located far away from substations and other physical grid equipment, field measurement data forms the basis for a vast majority of control decisions in power system operation. For that reason, it is imperative to ensure the highest level of data integrity as erroneous data may lead to inappropriate control actions with potentially devastating consequences. Performance of one of the most advanced monitoring systems, the synchrophasor system, is the focus of this thesis. This research will look at testing techniques used for performance assessment of synchrophasor system performance in the field. Existing methods will be reviewed and evaluated for deficiencies in capturing system performance regarding data quality. The focus of this work will be on improving synchrophasor data quality, by introducing new testing methodology that utilizes a nested testing approach for end-to-end testing in the field using a portable test set and associated software tools. The capability of such methods and these tools to fully characterize and evaluate the performance of synchrophasor systems in the field will be validated through implementation in a large-scale testbed. The purpose of this research is to specify, develop and implement a methodology and associated tools for field-testing of synchrophasor systems. To this day, there is no dedicated standard for field-testing of synchrophasor systems. This resulted in an inability to define widely accepted procedures to detect deterioration of system performance due to poor data quality and caused communication failures, unacceptable device and subsystem accuracy, or loss of calibration. This work will demonstrate how the new approach addresses the mentioned performance assessment gap. The feasibility of implementation of the proposed test procedures will be demonstrated using different test system configurations available in a large-scale testbed. The proposed method is fully leveraging the benefits of a portable device specifically developed for field-testing, which may be used for improvement of commissioning, maintenance and troubleshooting tests for existing installations. Use Cases resulting from this work will illustrate the practical benefits of the proposed methodology and associated tools

Performance Improvement of Wide-Area-Monitoring-System (WAMS) and Applications Development

Wide area monitoring system (WAMS), as an application of situation awareness, provides essential information for power system monitoring, planning, operation, and control. To fully utilize WAMS in smart grid, it is important to investigate and improve its performance, and develop advanced applications based on the data from WAMS. In this dissertation, the work on improving the WAMS performance and developing advanced applications are introduced.To improve the performance of WAMS, the work includes investigation of the impacts of measurement error and the requirements of system based on WAMS, and the solutions. PMU is one of the main sensors for WAMS. The phasor and frequency estimation algorithms implemented highly influence the performance of PMUs, and therefore the WAMS. The algorithms of PMUs are reviewed in Chapter 2. To understand how the errors impact WAMS application, different applications are investigated in Chapter 3, and their requirements of accuracy are given. In chapter 4, the error model of PMUs are developed, regarding different parameters of input signals and PMU operation conditions. The factors influence of accuracy of PMUs are analyzed in Chapter 5, including both internal and external error sources. Specifically, the impacts of increase renewables are analyzed. Based on the analysis above, a novel PMU is developed in Chapter 6, including algorithm and realization. This PMU is able to provide high accurate and fast responding measurements during both steady and dynamic state. It is potential to improve the performance of WAMS. To improve the interoperability, the C37.118.2 based data communication protocol is curtailed and realized for single-phase distribution-level PMUs, which are presented in Chapter 7.WAMS-based applications are developed and introduced in Chapter 8-10. The first application is to use the spatial and temporal characterization of power system frequency for data authentication, location estimation and the detection of cyber-attack. The second application is to detect the GPS attack on the synchronized time interval. The third application is to detect the geomagnetically induced currents (GIC) resulted from GMD and EMP-E3. These applications, benefited from the novel PMU proposed in Chapter 6, can be used to enhance the security and robust of power system

Integration of conventional and unconventional Instrument Transformers in Smart Grids

In this thesis the reader will be guided towards the role of Instrument Transformers inside the always evolving Smart Grid scenario. In particular, even non-experts or non-metrologists will have the chance to follow the main concepts presented; this, because the basic principles are always presented before moving to in-deep discussions. The chapter including the results of the work is preceded by three introductive chapters. These, contain the basic principles and the state of the art necessary to provide the reader the tools to approach the results chapter. The first three chapters describe: Instrument Transformers, Standards, and Metrology. In the first chapter, the studied Instrument Transformers are described and compared with particular attention to their accuracy parameters. In the second chapter instead, two fundamental international documents, concerning Instrument Transformers, are analysed: the IEC 61869 series and the EN 50160. This has been done to be completely aware of how transformers are standardized and regulated. Finally, the last introductive chapter presents one of the pillars of this work: metrology and the role of uncertainty. In the core of the work Instrument Transformers integration in Smart Grid is distinguished in two main topics. The first assesses the transformers behaviour, in terms of accuracy, when their normal operation is affected by external quantities. The second exploits the current and voltage measurements obtained from the transformers to develop new algorithm and techniques to face typical and new issue affecting Smart Grids. In the overall, this thesis has a bifold aim. On one hand it provides a quite-detailed overview on Instrument Transformers technology and state of the art. On the other hand, it describes issues and novelties concerning the use of the transformers among Smart Grids, focusing on the role of uncertainty when their measurements are used for common and critical applications

Transmission Line Parameter Estimation using Synchrophasor Data

abstract: Transmission line parameters play an important role in state estimation, dynamic line rating, and fault analysis. Because of this, several methods have been proposed in the literature for line parameter estimation, especially using synchrophasor data. However, success of most prior research has been demonstrated using purely synthetic data. A synthetic dataset does not have the problems encountered with real data, such as invariance of measurements and realistic field noise. Therefore, the algorithms developed using synthetic datasets may not be as effective when used in practice. On the other hand, the true values of the line parameters are unknown and therefore the algorithms cannot be directly implemented on real data. A multi-stage test procedure is developed in this work to circumvent this problem. In this thesis, two popular algorithms, namely, moving-window total least squares (MWTLS) and recursive Kalman filter (RKF) are applied on real data in multiple stages. In the first stage, the algorithms are tested on a purely synthetic dataset. This is followed by testing done on pseudo-synthetic datasets generated using real PMU data. In the final stage, the algorithms are implemented on the real PMU data obtained from a local utility. The results show that in the context of the given problem, RKF has better performance than MWTLS. Furthermore, to improve the performance of RKF on real data, ASPEN data are used to calculate the initial estimates. The estimation results show that the RKF algorithm can reliably estimate the sequence impedances, using ASPEN data as a starting condition. The estimation procedure is repeated over different time periods and the corresponding results are presented. Finally, the significance of data drop-outs and its impact on the use of parameter estimates for real-time power system applications, such as state estimation and dynamic line rating, is discussed. To address the problem (of data drop-outs), an auto regressive integrated moving average (ARIMA) model is implemented. The ability of this model to predict the variations in sequence impedances is demonstrated.Dissertation/ThesisMasters Thesis Electrical Engineering 201

Measurement of dynamic voltage variation effect on instrument transformers for power grid applications

Within the framework of distribution and transmission grids, the knowledge of Instrument Transformers (ITs) behavior in distorted conditions is a topic of great interest. Its relevance stems from the ITs wide use in metering, protection, monitoring and control applications, where their role is to reduce voltage and current to levels compatible with measuring instrument inputs. In force standards require that the performance of measuring instruments is assessed under realistic conditions. On the contrary, performance tests of ITs are generally carried out only at rated conditions, so that their behavior under actual waveforms is not fully known. To cover this gap, a suitable setup for the traceable test of Voltage instrument Transformers (VTs) under a quite large set of static and time-varying test waveforms is developed. The paper, after a short description of the setup, shows the performance of two commercial VTs under some power quality events, that are amplitude and phase modulations and voltage dips

Development and application of synchronized wide-area power grid measurement

Phasor measurement units (PMUs) provide an innovative technology for real-time monitoring of the operational state of entire power systems and significantly improve power grid dynamic observability. This dissertation focuses on development and application of synchronized power grid measurements. The contributions of this dissertation are as followed:First, a novel method for successive approximation register analog to digital converter control in PMUs is developed to compensate for the sampling time error caused by the division remainder between the desirable sampling rate and the oscillator frequency. A variable sampling interval control method is presented by interlacing two integers under a proposed criterion. The frequency of the onboard oscillator is monitored in using the PPS from GPS.Second, the prevalence of GPS signal loss (GSL) on PMUs is first investigated using real PMU data. The correlation between GSL and time, spatial location, solar activity are explored via comprehensive statistical analysis. Furthermore, the impact of GSL on phasor measurement accuracy has been studied via experiments. Several potential solutions to mitigate the impact of GSL on PMUs are discussed and compared.Third, PMU integrated the novel sensors are presented. First, two innovative designs for non-contact PMUs presented. Compared with conventional synchrophasors, non-contact PMUs are more flexible and have lower costs. Moreover, to address nonlinear issues in conventional CT and PT, an optical sensor is used for signal acquisition in PMU. This is the first time the utilization of an optical sensor in PMUs has ever been reported.Fourth, the development of power grid phasor measurement function on an Android based mobile device is developed. The proposed device has the advantages of flexibility, easy installation, lower cost, data visualization and built-in communication channels, compared with conventional PMUs.Fifth, an identification method combining a wavelet-based signature extraction and artificial neural network based machine learning, is presented to identify the location of unsourced measurements. Experiments at multiple geographic scales are performed to validate the effectiveness of the proposed method using ambient frequency measurements. Identification accuracy is presented and the factors that affect identification performance are discussed

On the importance of characterizing virtual pmus for hardware‐in‐the‐loop and digital twin applications

open5noThis research was funded by EdgeFLEX, grant number 883710. This project received funding from the European Union’s Horizon 2020 research and innovation program.In recent years, the introduction of real‐time simulators (RTS) has changed the way of researching the power network. In particular, researchers and system operators (SOs) are now ca-pable of simulating the complete network and of making it interact with the real world thanks to the hardware‐in‐the‐loop (HIL) and digital twin (DT) concepts. Such tools create infinite scenarios in which the network can be tested and virtually monitored to, for example, predict and avoid faults or energy shortages. Furthermore, the real‐time monitoring of the network allows estimating the status of the electrical assets and consequently undertake their predictive maintenance. The success of the HIL and DT application relies on the fact that the simulated network elements (cables, gener-ation, accessories, converters, etc.) are correctly modeled and characterized. This is particularly true if the RTS acquisition capabilities are used to enable the HIL and the DT. To this purpose, this work aims at emphasizing the role of a preliminary characterization of the virtual elements inside the RTS system, experimentally verifying how the overall performance is significantly affected by them. To this purpose, a virtual phasor measurement unit (PMU) is tested and characterized to understand its uncertainty contribution. To achieve that, firstly, the characterization of a virtual PMU calibrator is described. Afterward, the virtual PMU calibration is performed, and the results clearly highlight its key role in the overall uncertainty. It is then possible to conclude that the characterization of the virtual elements, or models, inside RTS systems (omitted most of the time) is fundamental to avoid wrong results. The same concepts can be extended to all those fields that exploit HIL and DT capa-bilities.openMingotti A.; Costa F.; Cavaliere D.; Peretto L.; Tinarelli R.Mingotti A.; Costa F.; Cavaliere D.; Peretto L.; Tinarelli R