A Software-based Low-Jitter Servo Clock for Inexpensive Phasor Measurement Units

This paper presents the design and the implementation of a servo-clock (SC) for low-cost Phasor Measurement Units (PMUs). The SC relies on a classic Proportional Integral (PI) controller, which has been properly tuned to minimize the synchronization error due to the local oscillator triggering the on-board timer. The SC has been implemented into a PMU prototype developed within the OpenPMU project using a BeagleBone Black (BBB) board. The distinctive feature of the proposed solution is its ability to track an input Pulse-Per-Second (PPS) reference with good long-term stability and with no need for specific on-board synchronization circuitry. Indeed, the SC implementation relies only on one co-processor for real-time application and requires just an input PPS signal that could be distributed from a single substation clock

Accuracy and Reliability Improvement of Wide-Area Power Grid Monitoring

Phasor Measurement Unit (PMU) is one of the key elements of wide area measurement systems (WAMS) in advanced power system monitoring, protection, and control applications. Frequency Disturbance Recorder (FDR) developed by the Power IT Laboratory at the University of Tennessee, is a low-cost and single-phase PMU used at the distribution level. Traditional PMUs use GPS as the only timing source. They will stop working when GPS signal is lost or unstable. Two alternative GPS independent timing sources including eLoran and Chip Scale Atomic Clock were tested for long-term reliability and short-term accuracy to study the application of the two methods in synchrophasor measurement area. Phasor measurement accuracy is of great concern for power grid researchers and operators. The hardware and software measurement algorithm of the FDRs were analyzed to study the error sources. The hardware of the FDRs was upgraded based on the analysis to improve measurement accuracy. Further, two different phasor measurement algorithms that are based on discrete Fourier Transform (DFT) and signal model will be introduced, respectively. The aim is to improve the phasor measurement accuracy under different steady-state and dynamic conditions as well as in a real power grid environment at the distribution level. Moreover, to better evaluate the measurement accuracy of PMUs, a PMU testing system was built. A calibration method that can compensate the time delay of the PMU testing system was proposed, and the testing results were compared to NIST to verify the accuracy of the PMU testing system after calibration. At last, a concept of “Universal Grid Analyzer” (UGA) was proposed and a prototype was built. The UGA has improved phasor measurement accuracy thanks to the proposed adaptive high-accuracy synchronous sampling algorithm and high-precision ADC. Meanwhile, the UGA can also function as a synchronized power quality analyzer that has harmonics measurement, voltage sag and swell detection functions. Moreover, the noise analysis function of the UGA that can help the analysis of phasor measurement accuracy in a real power grid environment was developed

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

Development and Hardware Implementation of a Phasor Measurement Unit using Microcontroller

As the world continues to move towards a Smarter Grid day by day, it has become the necessity to incorporate real-time monitoring of the grid wherein the instantaneous snapshot of the health of the grid can be made available. No other parameters than the Instantaneous Phasors, considered to be the heart-beats of the Electrical Grid, can represent the complete health status of the grid. This paper discusses how an Open Hardware Platform (Arduino Due with ARM Cortex M3 Micro-controller) can be used to estimate the phasors of a three phase system in real-time. The Pulse Per Second(PPS) signal from a GPS module is used to generate the sampling pulses. These pulses synchronise the sampling process by the Analog to Digital Converters(ADC), used by the PMU throughout the globe because of the high accuracy of the atomic clocks in the GPS satellites. The microcontroller uses a 64-Point DFT algorithm to estimate the phasors. The reference time is obtained from the GPS module which is the UTC time, with which the phasors are time stamped and displayed in a real-time Graphical User Interface(GUI) designed using Python(another open source programming language

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

Design and implementation of a low-cost phasor measurement unit: a comprehensive review

The complexity of the contemporary electrical power systems imposes challenges in aspect of monitoring, protection and control. In order to obtain high speed of response, wide area effect and prices synchronization, the grid control functions can be benefited by the implementation of Phasor Measurement Units (PMU). The paper is aimed to make a review of the commercial implementation of Phasor Measurement Units and then open source based implementations (open architecture hardware and software). This paper focuses on standard implementations; as a consequence the concept of virtual PMU is not discussed here

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

The GPS-Linked Transponder - A Command, Telemetry, and Positioning System for Small Spacecraft

A proposed GPS-Linked Transponder (GLT) Command, Telemetry, and Positioning System is described that offers significant advantages over present systems. The new system would replace the standard coherent transponder and modify existing ground-based systems to provide the U.S. space industry with significantly smaller and lighter-weight flight systems in addition to simplified ground stations with reduced operating costs. The GLT comprises a NASA STDN/ DSN-compatible or AFSCN/SGLS-compatible command receiver/detector, a 20-Mbps-capable PCM/PSK telemetry transmitter with a selectable-rate FEC encoder and optional encryptor, and a dual-mode spacecraft positioning subsystem including a full GPS receiver/navigator and/or GPS trans digitizer. The GLT design is based on similar hardware developed by APL for SDlO. The system will recover high accuracy spacecraft position and time data-either in real time autonomously or in near-real time on the ground-using advanced GPS positioning techniques. A simplified command receiver option is also available when compatibility with existing standards is not required and improved capability is desired. In the transdigitizer-only mode, mass and size are reduced to nearly one-tenth of existing transponder systems. Other advantages include reduced complexity and significantly higher uplink and downlink data rate communications than presently supported. Five ground-station configurations are defined, each providing varying levels of spacecraft positioning accuracies to the user