Micah J. Till

Design and Implementation of a Real-Time Off-Grid Operation Detection Tool from a Wide-Area Measurements Perspective

Real-time situational awareness tools are of critical importance to power system operators, especially during emergencies. The availability of electric power has become a linchpin of most post-disaster response efforts, because public and private sector services depend upon it. Knowledge of the scope and extent of facilities impacted, as well as the duration of their dependence on backup power, enables emergency response officials to plan for contingencies and provide a better overall response. Based on the measurement data acquired by the frequency disturbance recorders deployed in the North American power grids, an off-grid detection method is proposed and implemented. This method monitors the critical electrical loads and detects the transition of these loads from an on-grid operation to an off-grid operation, during which the loads are fed by an uninterrupted power supply or a backup generation system. The details of the detection algorithm are presented, and some case studies and off-grid detection scenarios are also provided to verify the effectiveness and robustness. This paper also presents the real-time implementation of this method and several effectively detected off-grid situations. Moreover, two visualization tools are developed to display the real-time system operation condition in an intuitive manor.

Impact of GPS Signal Loss and Its Mitigation in Power System Synchronized Measurement Devices

With the aid of global positioning system (GPS), synchronized measurement devices (SMDs) are increasingly deployed across power systems to monitor the status of electric grids by providing accurate measurement data along with unified time stamps. Unfortunately, GPS receivers tend to lose signal lock when certain uncontrollable and unpredictable factors arise. In order to investigate the presence of GPS signal loss (GSL) issues on measurement devices, analysis is performed on historical data from both phasor data concentrators and FNET/GridEye servers. Meanwhile, the impact of GSL on field measurement accuracy has not been previously explored in depth. Through analysis and experimental tests, this paper discovers angle drift caused by GSL, which consequently leads to the total vector error exceeding the IEEE standard C37.118.1-2011. Furthermore, a compensation method is proposed to rectify the angle drift and laboratory experiments demonstrate that the proposed method does effectively reduce angle drift and mitigate the impact of GSL in SMDs.

A Novel Method for Phasor Measurement Unit Sampling Time Error Compensation

This paper focuses on a novel method for successive approximation register analog to digital converter control in synchronized phasor measurement units (PMUs). 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 real-time using the pulse per second (PPS) timing reference from global positioning system. The sampling control is adaptively adjusted each second according to the latest estimated oscillator frequency. The “saw tooth” in phasor angle error and DC offset and spikes in frequency error can be effectively eliminated by applying the proposed method. The simulation and experiment results validate the effectiveness and accuracy of the proposed method, which is believed to be able to greatly improve the performance of PPS-disciplined synchronous sampling methods in PMUs.

Impact of High PV Penetration on the Inter-Area Oscillations in the U.S. Eastern Interconnection

This study explores the impact of high-photovoltaic (PV) penetration on the inter-area oscillation modes of large-scale power grids. A series of dynamic models with various PV penetration levels are developed based on a detailed model representing the U.S. Eastern Interconnection (EI). Transient simulations are performed to investigate the change of inter-area oscillation modes with PV penetration. The impact of PV control strategies and parameter settings on inter-area oscillations is studied. This paper finds that as PV increases, the damping of the dominant oscillation mode decreases monotonically. It is also observed that the mode shape varies with the PV control strategy and new oscillation modes may emerge under inappropriate parameter settings in PV plant controls.

Frequency response of the Eastern Interconnection due to increased wind generation

Wind powered electricity generation is gaining ground in the Eastern Interconnection (EI). Wind turbines create electricity from what is widely hailed as zero-cost, emission-free fuel. However, the technology does present engineering challenges. Compared to traditional synchronous machines, wind turbines contribute almost no inertia to the power system. Since most turbines do not have governor or exciter units either, their ability to regulate frequency disturbances, or potential lack thereof, is a concern for utilities. This study takes the Multiregional Modeling Working Group (MMWG) EI model as a base case and removes governor units, modifies generator inertia values, and disables exciter controls to simulate the frequency response of the EI with different levels of wind penetration.

Pioneer Design of Non-contact Synchronized Measurement Devices Using Electric and Magnetic Field Sensors

Traditional synchrophasors rely on current transformers and potential transformers physically connected to transmission lines or buses to acquire input signals for phasor measurement. However, it is challenging to install and maintain traditional phasor measurement units in some remote areas due to lack of facilities. Since transmission lines naturally generate alternating electrical and magnetic fields in the surrounding atmosphere, this paper presents two innovative designs for non-contact synchronized measurement devices (NCSMDs), including an electric field sensor-based non-contact SMD (E-NCSMD) and a magnetic field sensor-based non-contact SMD (M-NCSMD). Compared with conventional synchrophasors, E-NCSMD and M-NCSMD are much more flexible to be deployed and have much lower costs, making E-NCSMDs and M-NCSMD highly accessible and useful for a wide array of phasor measurement applications. Laboratory and field experiment results verified the effectiveness of the designs of both E-NCSMD and M-NCSMD.

Source Location Identification of Distribution-Level Electric Network Frequency Signals at Multiple Geographic Scales

The distribution-level electric network frequency (ENF) extracted from an electric power signal is a promising forensic tool for multimedia recording authentication. Local characteristics in ENF signals recorded in different locations act as environmental signatures, which can be potentially used as a fingerprint for location identification. In this paper, a reference database is established for distribution-level ENF using FNET/GridEye system. An ENF identification method that combines a wavelet-based signature extraction and feedforward artificial neural network-based machine learning is presented to identify the location of unsourced ENF signals without relying on the availability of concurrent signals. Experiments are performed to validate the effectiveness of the proposed method using ambient frequency measurements at multiple geographic scales. Identification accuracy is presented, and the factors that affect identification performance are discussed.

Rotor angle stability and inter-area oscillation damping studies on the U.S. Eastern Interconnection (EI) under high wind conditions

This paper studies the impact of wind generation on generator rotor angle and inter-area oscillation stability. A comparative simulation study is conducted based on a U.S. Eastern Interconnection (EI) planning model for year 2030. The wind penetration level is 17% of the total generation. Generator critical clearing time (CCT) and inter-area oscillation damping ratio are evaluated. It is observed that rotor angle stability is barely affected while inter-area oscillation damping shows discernible improvement due to wind generation. Possible explanations are then explored.

Primary Frequency Response Adequacy Study on the U.S. Eastern Interconnection Under High-Wind Penetration Conditions

This paper investigates the primary frequency response adequacy of the U.S. Eastern Interconnection with high-wind penetration in the year 2030. This paper starts with the creation of a realistic baseline dynamic model by validating against synchrophasor measurements. A dynamic simulation is performed to evaluate the impact of high-wind generation on a primary frequency response. Mitigation measures are then investigated.

Synchronized Wireless Measurement of High-Voltage Power System Frequency Using Mobile Embedded Systems

This paper focuses on synchronized wireless measurement of high-voltage (HV) power system frequency using mobile embedded systems (MESs) integrated with a wireless electric field sensor (WEFS). Unlike traditional synchronized frequency measurement devices, which rely on potential transformers and current transformers physically connected to system elements, a WEFS is used to realize wireless signal acquisition in the vicinity of any HV apparatus. The MES performs real-time frequency estimation using a recursive discrete Fourier transform based algorithm. Network time protocol (NTP) is used for time synchronization, increasing the system flexibility by eliminating global positioning system reliance. An NTP-based synchronized sampling control method is proposed and implemented in MES to compensate the sampling time error caused by local time drift and division residue. The proposed system has the advantages of portability and lower cost, making it highly accessible and useful for a wide array of synchronized frequency measurement applications. Experiment results verify the accuracy and effectiveness of the proposed system.