Statistical Behavior of PMU Measurement Errors: An Experimental Characterization

Different power system applications based on synchrophasors measured in different nodes of the electric grid require information about the statistical distribution of the errors introduced by the phasor measurement units (PMUs). The performance of these applications can be significantly affected by possible incorrect assumptions. The Gaussian distribution has been historically assumed in most of the approaches, but some more recent studies suggest the possibility of considering different distributions for more accurate modeling of the actual situation. In this article, proper statistical tools applied to the results achieved through a high-performance experimental test system are proposed to assess the statistical distribution of PMU errors under controlled steady-state conditions, thus providing a basis for defining suitable models to be used in specific applications

Traffic Modeling of a Cooperative Charge While Driving System in a Freight Transport Scenario

The aim of this paper is to present a research study on a traffic model developed for analysing the performance of the wireless inductive systems for charging while driving (CWD) fully electric vehicles (FEVs) from both traffic and energy points of view. The design assumptions of the developed traffic model are aimed to simulate in particular a freight distribution service in a fully cooperative traffic environment. In this case, the CWD service could be used to guarantee the minimum state of charge (SOC) of the batteries at the arrival to the depot that allows the vehicles to shortly start with further activities. In this way, the fleet manager could avoid wasting time for the stationary recharge, thus increasing the level of service of the freight distribution. The CWD system is applied to a multilane ring road with several intermediate on-ramp entrances, where the slowest lane is reserved for the charging activities, when authorized vehicles are present. A specific traffic model has been developed and implemented adopting a mesoscopic approach, where vehicle energy needs and charging opportunities affect drivers’ behavior. Overtaking maneuvers, as well as new entries in the CWD lane of vehicles which need to charge, have been modeled by taking into account a fully cooperative driving system among vehicles which manages an adequate gap between consecutive vehicles. Finally, a speed control strategy in which vehicles can be delayed to create an empty time-space slot in the CWD lane, is simulated at a defined node. This type of control, though is simulated to allow extraordinary maintenance operations, which may require a free charging zone for a given time slot, could also be applied to support merging maneuvers for on ramp vehicles

Space Vector Taylor–Fourier Models for Synchrophasor, Frequency, and ROCOF Measurements in Three-Phase Systems

Taylor-Fourier (TF) filters represent a powerful tool to design phasor measurement unit (PMU) algorithms able to estimate synchrophasor, frequency, and rate of change of frequency (ROCOF). The resulting techniques are based on dynamic representations of the synchrophasor, and hence, they are particularly suitable to track the evolution of its parameters during time-varying conditions. Electrical quantities in power systems are typically three-phase and weakly unbalanced, but most PMU measurement techniques are developed by considering them as a set of three single-phase signals; on the contrary, this peculiarity can be favorably exploited to improve accuracy and reduce the computational cost. In this respect, this paper proposes to directly perform the TF expansion of the space vector (SV) samples obtained from three-phase measurements. A new paradigm allows to independently estimate positive and negative sequence synchrophasors along with system frequency and ROCOF, leveraging the three-phase characteristics. The performance of the proposed technique is assessed by using test signals inspired by the standard IEEE C37.118.1-2011, including noise as well as magnitude and phase unbalance. Achieved results highlight the flexibility of the enhanced SV-based approach, which is capable to combine excellent dynamic performance together with an accurate estimation of both positive and negative sequence components

Measurement Platform for Latency Characterization of Wide Area Monitoring, Protection and Control Systems

Wide area monitoring, protection and control (WAMPAC) systems have emerged as a critical technology to improve the reliability, resilience, and stability of modern power grids. They are based on phasor measurement unit (PMU) technology and synchronized monitoring on a wide area. Since these systems are required to make rapid decisions and control actions on the grid, they are characterized by stringent time constraints. For this reason, the latency of WAMPAC systems needs to be appropriately assessed. Following this necessity, this article presents the design and implementation of a measurement platform that allows latency characterization of different types of WAMPAC systems in several operating conditions. The proposed WAMPAC Characterizer has been metrologically characterized through a WAMPAC Emulator and then used to measure the latency of a WAMPAC system based on an open-source platform frequently used by transmission system operators (TSOs) for the implementation of their PMU-based wide area systems

"Charge while driving" for electric vehicles: road traffic modeling and energy assessment

The aim of this research study is to present a method for analyzing the performance of the wireless inductive charge-while-driving (CWD) electric vehicles, from both traffic and energy points of view. To accurately quantify the electric power required from an energy supplier for the proper management of the charging system, a traffic simulation model is implemented. This model is based on a mesoscopic approach, and it is applied to a freight distribution scenario. Lane changing and positioning are managed according to a cooperative system among vehicles and supported by advanced driver assistance systems (ADAS). From the energy point of view, the analyses indicate that the traffic may have the following effects on the energy of the system: in a low traffic level scenario, the maximum power that should be supplied for the entire road is simulated at approximately 9 MW; and in a high level traffic scenario with lower average speeds, the maximum power required by the vehicles in the charging lane increases by more than 50 %

Algorithms for the synchrophasor measurement in steady-state and dynamic conditions

Phasor measurement units (PMUs) are becoming one of the key issues of power network monitoring. They have to be able to perform accurate estimations of current and voltage signals either under steady-state or dynamic conditions. The first part of this PhD thesis analyses the impact of the phasor models on the estimation accuracy, focuses on algorithms proposed in the literature for the estimation of phasors and studies their performance under several different conditions. On the basis of the results of this analysis, in the second part of this thesis an innovative approach to improve the performance of synchrophasor estimation is presented. The method proposes a modified version of the synchrophasor estimation algorithm which uses the non-orthogonal transform defined as Taylor-Fourier Transform (TFT) and which is based on a Weighted Least Squares (WLS) estimation of the parameters of a second order Taylor model of the phasor. The aim of the proposed enhancements is to improve the performance of the algorithm in presence of fast transient events and to achieve a Phasor Measurement Unit that is simultaneously compliant with both M and P compliance classes, suggested by the synchrophasor standard IEEE C37.118.1. In particular, while the TFT based adaptive algorithm is used for synchrophasor estimation, frequency and Rate of Change of Frequency (ROCOF) are estimated using the higher derivatives outputs of the adaptive TFT. Frequency estimation feedback is used to tune the algorithm and achieve better performance in off-nominal conditions. The proposed approaches are validated by means of simulations in all the static and dynamic conditions defined in the standard. In the last chapter, the algorithm proposed above is used in a novel architecture, compliant to IEC 61850, for a distributed IED-based PMU, to be used in electrical substations. In particular, a measurement architecture based on process bus and sampled values synchronized with IEEE 1588-2008 is proposed, so that voltage and current signals are acquired by a Merging Unit device, while the PMU signal processing is performed on a IED (Intelligent Electronic Device), in compliance with IEEE C37.118.1-2011

PMU-based distribution system state estimation with adaptive accuracy exploiting local decision metrics and IoT paradigm

A novel adaptive distribution system state estimation (DSSE) solution is presented and discussed, which relies on distributed decision points and exploits the Cloud-based Internet of Things (IoT) paradigm. Up to now, DSSE procedures have been using fixed settings regardless of the actual values of measurement accuracy, which is instead affected by the actual operating conditions of the network. The proposed DSSE is innovative with respect to previous literature, because it is adaptive in the use of updated accuracies for the measurement devices. The information used in the estimation process along with the rate of the execution are updated, depending on the indications of appropriate local metrics aimed at detecting possible variations in the operating conditions of the distribution network. Specifically, the variations and the trend of variation of the rms voltage values obtained by phasor measurement units (PMUs) are used to trigger changes in the DSSE. In case dynamics are detected, the measurement data are sent to the DSSE at higher rates and the estimation process runs consequently, updating the accuracy values to be considered in the estimation. The proposed system relies on a Cloud-based IoT platform, which has been designed to incorporate heterogeneous measurement devices, such as PMUs and smart meters. The results obtained on a 13-bus system demonstrate the validity of the proposed methodology that is efficient both in the estimation process and in the use of the communication resources

Knowledge Management for Policy

The Communication C(2016)6626 on Data, Information and Knowledge Management sets the objective to improve knowledge management and collaborative working in the European Commission, modernising the Institution by overcoming silos mentalities and connecting synergies between portfolios. The European Commission’s science and knowledge service, the Joint Research Centre (JRC) has taken up this challenge in its 2030 Strategy, striving to become more efficient in mobilising scientific competences around the Commission’s policy goals and to transform from a traditional research-producing organisation into a world-leading manager of knowledge for EU policy-making.JRC.H-Knowledge Management (Ispra

Line Impedance Estimation Based on Synchrophasor Measurements for Power Distribution Systems

Effective monitoring and management applications on modern distribution networks (DNs) require a sound network model and the knowledge of line parameters. Network line impedances are used, among other things, for state estimation and protection relay setting. Phasor measurement units (PMUs) give synchronized voltage and current phasor measurements, referred to a common time reference (coordinated universal time). All synchrophasor measurements can thus be temporally aligned and coordinated across the network. This feature, along with high accuracy and reporting rates, could make PMUs useful for the evaluation of network parameters. However, instrument transformer behavior strongly affects the parameter estimation accuracy. In this paper, a new PMU-based iterative line parameter estimation algorithm for DNs, which includes in the estimation model systematic measurement errors, is presented. This method exploits the simultaneous measurements given by PMUs on different nodes and branches of the network. A complete analysis of uncertainty sources is also performed, allowing the evaluation of estimation uncertainty. Issues related to operating conditions, topology, and measurement uncertainty are thoroughly discussed and referenced to a realistic model of a DN to show how a full network estimator is possible