Synchronized Measurements Processing Methodology as a Tool for Monitoring Power System Oscillations

Monitoring, protection and control of the electrical power system require the design and implementation of specific applications that are based on analytical methods for the processing of synchronized measurements. Therefore, it is necessary to select the adequate type of mathematical analysis that best suits the requirements of a particular application. This paper describes analytical methods used for the processing of synchronized measured electrical quantities for detection and analysis of the variety of oscillations. The oscillatory phenomena of active power and frequency as a case study of one disturbance in the power system are analyzed. The results of processing the actual synchronized measurements for that case study are presented afterwards. Different data processing methods (spectral analysis methods) are compared, and finally, a recommendation for appropriate methods for processing synchronized measurements in application for recognition, processing and alarming of oscillations of active power is given

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

Accurate Damping Factor and Frequency Estimation for Damped Real-Valued Sinusoidal Signals

The interpolated discrete Fourier transform (IpDFT) is one of the most popular techniques to estimate the parameters of a damped real-valued sinusoidal signal (DRSS). However, its accuracy is affected by strong noise presence and short observation windows. To this end, this letter proposes a novel two-point IpDFT method, called I2pZDFT, for the parameter estimation of a DRSS. The proposed I2pZDFT uses the zero-padding technique to increase the sampling rate in the frequency domain. The conjugate symmetry and the parity of the zero-padded signal are utilized to eliminate the influence of the spectral leakage. Simulation results highlight that the proposed I2pZDFT outperforms the existing IpDFT-based methods in terms of noise immunity, especially in the case of observation windows as short as 0.5-1 cycles

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

Phasor Parameter Modeling and Time-Synchronized Calculation for Representation of Power System Dynamics

The electric power grid is undergoing sustained disturbances. In particular, the extreme dynamic events disrupt normal electric power transfer, degrade power system operating conditions, and may lead to catastrophic large-scale blackouts. Accordingly, control applications are deployed to detect the inception of extreme dynamic events, and mitigate their causes appropriately, so that normal power system operating conditions can be restored. In order to achieve this, the operating conditions of the power system should be accurately characterized in terms of the electrical quantities that are crucial to control applications. Currently, the power system operating conditions are obtained through SCADA system and the synchrophasor system. Because of GPS time-synchronized waveform sampling capability and higher measurement reporting rate, synchrophasor system is more advantageous in tracking the extreme dynamic operating conditions of the power system. In this Dissertation, a phasor parameter calculation approach is proposed to accurately characterize the power system operating conditions during the extreme electromagnetic and electromechanical dynamic events in the electric power grid. First, a framework for phasor parameter calculation during both electromagnetic and electromechanical dynamic events is proposed. The framework aims to satisfy both P-class and M-class PMU algorithm design accuracy requirements with a single algorithm. This is achieved by incorporating an adaptive event classification and algorithm model switching mechanism, followed by the phasor parameter definition and calculation tailored to each identified event. Then, a phasor estimation technique is designed for electromagnetic transient events. An ambient fundamental frequency estimator based on UKF is introduced, which is leveraged to adaptively tune the DFT-based algorithm to alleviate frequency leakage. A hybridization algorithm framework is also proposed, which further reduces the negative impact caused by decaying DC components in electromagnetic transient waveforms. Then, a phasor estimation technique for electromechanical dynamics is introduced. A novel wavelet is designed to effectively extract time-frequency features from electromechanical dynamic waveforms. These features are then used to classify input signal types, so that the PMU algorithm modeling can be thereafter tailored specifically to match the underlying signal features for the identified event. This adaptability of the proposed algorithm results in higher phasor parameter estimation accuracy. Finally, the Dissertation hypothesis is validated through experimental testing under design and application test use cases. The associated test procedures, test use cases, and test methodologies and metrics are defined and implemented. The impact of algorithm inaccuracy and communication network distortion on application performance is also demonstrated. Test results performance is then evaluated. Conclusions, Dissertation contributions, and future steps are outlined at the end

Roles of dynamic state estimation in power system modeling, monitoring and operation

Power system dynamic state estimation (DSE) remains an active research area. This is driven by the absence of accurate models, the increasing availability of fast-sampled, time-synchronized measurements, and the advances in the capability, scalability, and affordability of computing and communications. This paper discusses the advantages of DSE as compared to static state estimation, and the implementation differences between the two, including the measurement configuration, modeling framework and support software features. The important roles of DSE are discussed from modeling, monitoring and operation aspects for today's synchronous machine dominated systems and the future power electronics-interfaced generation systems. Several examples are presented to demonstrate the benefits of DSE on enhancing the operational robustness and resilience of 21st century power system through time critical applications. Future research directions are identified and discussed, paving the way for developing the next generation of energy management systems and novel system monitoring, control and protection tools to achieve better reliability and resiliency.Departamento de Energía de EE. UU TPWRS-00771-202

Directions of Application of Phasor Measurement Units for Control and Monitoring of Modern Power Systems: A State-of-the-Art Review

The development of modern power systems is directly related to changes in the traditional principles of management, planning, and monitoring of electrical modes. The mass introduction of renewable energy sources and control devices based on power electronics components contributes to changing the nature of the flow of transient and quasi-established electrical modes. In this area, the problem arises of conducting a more accurate and rapid assessment of the parameters of the electrical regime using synchronized vector measurement devices. The paper presents an extensive meta-analysis of the modern applications of phasor measurement units (PMUs) for monitoring, emergency management and protection of power systems. As a result, promising research directions, the advantages and disadvantages of the existing approaches to emergency management, condition assessment, and relay protection based on PMUs are identified. © 2023 by the authors.National Science Foundation, NSF; U.S. Department of Energy, USDOE; Electric Power Research Institute, EPRI; Russian Science Foundation, RSF: 23-79-01024The reported study was supported by Russian Science Foundation, research project № 23-79-01024.A major system accident in 1965 in the USA [] led to the active development of research aimed at increasing the observability and controllability of EPSs []. A separate class of studies was aimed at improving the accuracy of the procedure for assessing the state of the EPS mode by increasing the accuracy and sampling frequency of measuring instantaneous values of currents and voltages. These requirements were considered in the phasor measurement concept, which was formulated at the Virginia Institute of Technology with the financial support of the US Department of Energy, the US Electric Power Research Institute, and the US National Science Foundation

Impact of prominent synchrophasor estimation algorithms on power system stability assessment

The electricity network is a critical infrastructure and its reliability is of paramount importance for the functionality of many critical systems in the modern society. Power system stability is one of the imperative aspects that impacts the reliability of electrical networks, hence power system stability needs to be observed in real-time for secure and reliable operation of the power grids. Conventionally, supervisory control and data acquisition (SCADA) based wide-area monitoring systems (WAMS) have been used for this purpose, however, they are predominantly designed to detect static changes in steady-state stability. In contrast, modern wide-area power networks pose significant challenges such as presence of power electronic switching loads and inductive motor loads, asynchronous distributed generation and dynamic fluctuations in demand and supply. Synchrophasor based WAMS is the next generation WAMS technology and offers great advantages over traditional SCADA systems such as precise time synchronisation, universally accepted standardisation and extremely fast and robust phasor estimation. A strategically placed network of phasor measurement units (PMUs) enables full visibility of the entire power network. Time synchronised PMU data can then be transferred to a phasor data centre (PDC) using efficient communication algorithms where multi facet analysis, including realtime stability assessment, could be performed. Despite significant benefits of the synchrophasor technology, several factors have hindered the widespread adoption ofthe synchrophasor technology. This research addresses such contemporary issues. The first phase of this research details an empirical study of existing synchrophasor estimation algorithms (SEAs) and considers the need for a benchmark in terms of robustness. Synchrophasor research is heavily populated with studies presenting diverse SEAs. Interestingly, not many studies have attempted to develop a robust SEA based on the mathematical technique proposed in the original Institute of Electrical and Electronics Engineers (IEEE) standardisation (i.e. IEEE std. C37.118.1-2011), the quadrature demodulation (QD) technique. Therefore, a verifiable benchmark algorithm is not currently available. This research presents comprehensive synchrophasor estimation models developed based on the QD technique and is then presented as the benchmark SEA. Proposed models are tested against all compliance requirements stipulated in the latest IEEE standardisation. Furthermore, a detailed comparison of prominent synchrophasor models is conducted against the proposed benchmark models, to understand the impact of the SEAs on the overall phasor estimation. Results establish a clear link between the accuracy/latency of the phasor estimation and the accompanying synchrophasor algorithm. The second phase of this research involves testing and comparison of synchrophasor models on hardware platforms. Even though development of SEA has been a prominent research area, only a few of these studies have been verified and validated with field tested results. This is a significant barrier to the advent of improved SEAs beyond academic literature, especially in industrial applications. A laboratory scale, hardware based synchrophasor test platform is proposed where any synchrophasor algorithm can be tested for any test condition or fault signal. Key highlights of this section include; global position system (GPS) time synchronisation of synchrophasors and a sinusoidal pulse width modulation (SPWM) technique based scalable input system capable of generating measurement conditions emulating any fault condition. Results establish the superiority of the proposed benchmark algorithm and identify key implementation issues in hardware implementation of some of the prominent synchrophasor models. The final phase of this research develops a synchrophasor based WAMS by using a bottom-up approach to evaluate real-time stability of wide-area networks under practical power network fault conditions. As part of this research the analyses and the impact of SEAs on the overall stability assessment has been evaluated. Development and testing of PMUs, and stability studies are historically conducted in two disjointed silos. As a result, stability analysis is often conducted based on the assumption that the PMU data delivered to the PDC are accurate and instantaneous. On the other hand, SEAs are tested against the compliance criteria listed in the IEEE standardisation which do not involve any practical power network faults. This study attempts to dive into this unexplored territory. Performance in realtime voltage and frequency stability of prominent SEAs is evaluated by employing a strategically placed PMU network on two standard power networks simulation models. The IEEE 9-bus system and New England 39-bus system are considered and consists synchronous generation sources, dynamic load centres and transmission links. By modelling practical transient fault conditions such as short circuit faults, loss of generation and addition of load centres, the real-time voltage and frequency stability have been studied. A modified highest Lyapunov exponent (HLE) based real-time stability assessment algorithm (RSAA) is proposed to suit implementation in practical power networks. Despite the full compliance against the IEEE standardisation, tested algorithms produce significantly different outcomes in the stability assessment that may directly impact on the subsequent activation of protection systems and overall network stability. Results of this study point to interesting findings and establishes a clear link between the reliability and the performance of the underlining SEA. In conclusion, key findings of this research contribute to two prominent areas within the synchrophasor research; SEA development and testing, and real-time stability assessment. This research has established a strong link between these disjointed research fields, thereby enabling future advancements synchrophasor based stability monitoring and control systems

Wide-Area Measurement-Based Applications for Power System Monitoring and Dynamic Modeling

Due to the increasingly complex behavior exhibited by large-scale power systems with more uncertain renewables introduced to the grid, wide-area measurement system (WAMS) has been utilized to complement the traditional supervisory control and data acquisition (SCADA) system to improve operators’ situational awareness. By providing wide-area GPS-time-synchronized measurements of grid status at high time-resolution, it is able to reveal power system dynamics which cannot be captured before and has become an essential tool to deal with current and future power grid challenges. According to the time requirements of different power system applications, the applications can be roughly divided into online applications (e.g., data visualization, fast disturbance and oscillation detection, and system response prediction and reduction) and offline applications (e.g., measurement-driven dynamic modeling and validation, post-event analysis, and statistical analysis of historical data). In this dissertation, various wide-area measurement-based applications are presented. Firstly a pioneering WAMS deployed at the distribution level, the frequency monitoring network (FNET/GridEye) is introduced. For conventional large-scale power grid dynamic simulation, two major challenges are 1) accuracy of detailed dynamic models, and 2) computation burden for online dynamic assessment. To overcome the restrictions of the traditional approach, a measurement-based system response prediction tool using a Multivariate AutoRegressive (MAR) model is developed. It is followed by a measurement-based power system dynamic reduction tool using an autoregressive model vi to represent the external system. In addition, phasor measurement unit (PMU) data are employed to perform the generator dynamic model validation study. It utilizes both simulation data and measurement data to explore the potentials and limitations of the proposed approach. As an innovative application of using wide-area power system measurement, digital recordings could be authenticated by comparing the extracted frequency and phase angle from recordings with power system measurement database. It includes four research studies, i.e., oscillator error removal, ENF phenomenology, tampering detection, and frequency localization. Finally, several preliminary data analytics studies including inertia estimation and analysis, fault-induced delayed voltage recovery (FIDVR) detection, and statistical analysis of oscillation database, are presented