Towards a Zero Inertia Grid thanks to Synchrophasor Measurements

Date: Wednesday, May 25                              Time: 5:00 pm – 6:30 pm (CEST)

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Name of the organizer: Panayiotis (Panos) Moutis

Organization: Carnegie Mellon University, USA


Short biography of the chair: Panayiotis (Panos) Moutis, PhD, has been Special Faculty with the Scott Institute for Energy Innovation at Carnegie Mellon University (CMU) since August 2018 (postdoc at Electrical & Computer Engineering, CMU, 2016-18). His recent grants include one from the national system operator of Portugal, REN, for the development of a transmission expansion planning platform, and another from the moonshot factory of Google, X, for the digital twin of the electrical grid. Between 2018-20 he served as a Marie Curie Research Fellow with DEPsys, Switzerland, on distribution grid synchronized measurements and state estimation. In 2014 he was awarded a fellowship by Arup UK (through the University of Greenwich), on the “Research Challenge of Balancing Urban Microgrids in Future Planned Communities”. In 2013 he won the “IEEE Sustainability 360o Contest” on the topic of Power. Throughout 2007-15, as part of Prof. Nikos Hatziargyriou’s research group he contributed to over a dozen R&D projects funded by the European Commission. Panos received both his diploma (2007) and his PhD (2015) degrees in Electrical & Computer Engineering at the National Technical University of Athens, Greece, and has published more than 30 papers and contributed to 5 book chapters. He has accumulated over 10 years of industry experience on projects of Renewable Energy Sources and Energy Efficiency, and serves in energy start-ups as advisor and executive. He is a senior member of multiple IEEE societies, member of the IEEE-USA Energy Policy Committee and NASPI, associate editor of IEEE & IET scientific journals, active contributor to IEEE standards working groups, chair of the IEEE Smart Grid Publications Committee and editor-in-chief of the “IEEE Smart Grid Newsletter”. Personal Website for more information:

Panel Abstract: Renewables and battery storage systems gradually displace conventional generators with large rotating inertias. Rotating inertias have allowed system operators to respond to critical grid events in times of a few seconds, while the severity of the grid events themselves has been dampened by the collective grid inertia. As the energy portfolios change in the pursuit of the decarbonization of the electricity sector, the reduction of rotating inertia will limit the system operators’ response time to milliseconds and the grid criticalities will gradually become more severe. Clearly, we need faster and more granular grid status monitoring, to enable faster remedial responses. This means that we will require from synchrophasor measurements (at the timescales of sub-period detail) to detect the rigidness of the grid and inform the controllers of fast acting inverter-interfaced resources. This panel will review the current stage of research in estimating grid inertia and enabling inverter control action thanks to synchrophasor measurements. We will also attempt to draw a roadmap towards a zero-inertia grid and what are the expectations from phasor measurement units, the supporting IT set-ups and their interactions with the most crucial grid components and stakeholders.

Panelist 1:

Name: Panayiotis (Panos) Moutis

Organization: Carnegie Mellon University, USA


Short bio and photo: included above in the Panel Chair section

Title of presentation: What is the Zero Inertia Grid and what affects its stability

Abstract: As an introduction to the panel and the ensuing discussions, several studies on the instability concerns introduced by high amounts of inverter-interfaced resources are reviewed. The studies focus on the contribution of two factors: the frequency control droop on the active power setpoint of the inverter and the size of the grid impedance at the inverter output. Both of these concerns are in turn functions of the grid operating status and characteristics. System inertia in a low-inertia grid may vary considerably under very typical system operation, while grid impedance may change as faults occur or system reconfiguration actions are performed. Given the fact that the time constants of grid phenomena will be shifting to those of electrical time scale (a few ms), the value of synchrophasor measurements and the applications they enable is particularly crucial.

Panelist 2:

Name: Evangelos Farantatos

Organization: Electric Power Research Institute, USA


Short biography: Evangelos Farantatos received the Diploma in Electrical and Computer Engineering from the National Technical University of Athens, Greece, in 2006 and the M.S. and Ph.D. degrees from the Georgia Institute of Technology, Atlanta, GA, USA, in 2009 and 2012, respectively. He is a Senior Project Manager with the Grid Operations and Planning R&D Group at EPRI, Palo Alto, CA. He is managing and leading the technical work of various R&D projects related to synchrophasor technology, power systems monitoring and control, power systems stability and dynamics, renewable energy resources modeling, grid operation and protection with high levels of inverter-based resources. He is a Senior Member of IEEE. In summer 2009, he was an intern at MISO.

Title of presentation: Online Inertia Estimation & Monitoring – Needs, Challenges, Industry Practices and R&D

Abstract: As power systems are transitioning towards decarbonization, there are increased concerns around system reliability and especially frequency security. With increasing penetration of inverter based renewable energy resources that continue to displace conventional synchronous machines, the overall system inertia is reducing and this directly impacts the rate of change of frequency (RoCoF) that the power system is exposed to immediately following a disturbance. Higher RoCoFs allow less time for frequency responsive services to act and hence threaten under frequency load shedding (UFLS) or in more severe cases, system separation. Utilities around the world have established planning procedures and operational constraints in the form of RoCoF constraints or critical inertia floors to accommodate existing equipment withstand and available reserve capabilities. In this context, system operators are monitoring system inertia in their control rooms in real time and also looking at forecasts. The ability to estimate or measure inertia accurately in real time allows system operators to manage the grid and procure frequency response services in an efficient manner. However, most of the control room inertia monitoring at this time is based on online EMS telemetered generating stations. Estimates from EMS monitored generation does not account for the demand side inertia contribution from large industrial loads and demand side generation (e.g. embedded synchronous generation). To address this challenge, measurement based techniques for system inertia estimation are emerging. This presentation will summarize state-of-the-art methods and industry practices for system inertia estimation, as well as R&D activities that investigate the use of synchronized measurements provided by phasor measurement units (PMUs) for system inertia estimation.

Panelist 3:

Name: Deepak Ramasubramanian

Organization: Electric Power Research Institute, USA

Short biography: He received the M.Tech. degree from the Indian Institute of Technology Delhi, New Delhi, India, in 2013, and the Ph.D. degree from Arizona State University, Tempe, AZ, USA, in 2017. He is currently a Senior Engineer Scientist in the Grid Operations and Planning Group, Electric Power Research Institute, Knoxville, TN, USA. He is a recipient of the North American SynchroPhasor Initiative Outstanding Graduate Student Award and the POSOCO Power System Award. His research interests include modeling, control, and stability analysis of the bulk power systems with recent focus on the associated impacts of large-scale integration of converter interfaced generation.

Title of presentation: Modeling and analysis of systems with newer forms of inverter control

Abstract: The growth of inverter-based resources (mostly based on renewable energy) are changing the electrical grid physics. Even though inverter-based resources (IBRs) have already been operating harmoniously with with conventional units, in some cases, IBRs approach a 100% contribution to the local power demand. Grid-forming inverters are a category of controls and coordination strategies for systems with the aforementioned characteristics and could enable renewable integration at scale with added security, resilience, efficiency, and affordability. Over the next five years, the UNIFI consortium will develop the methods and assess the challenges in ensuring interoperability and meeting functional requirements for these technologies, by integrating research capabilities and project objectives. The UNIFI consortium will demonstrate how the next-generation power systems will operate using federated hardware test beds. The value of accurate, synchronized and highly granular system measurements is key to enabling the stable, secure and efficient control of grid forming inverters in a low or zero inertia grid. Some preliminary yet fundamental aspects of this consideration will be discussed.

Panelist 4:

Name: Qiteng Hong

Organization: University of Strathclyde, Glasgow

Short biography: He received the B.Eng. (Hons.) and Ph.D. degrees in electronic and electrical engineering from the University of Strathclyde, Glasgow, U.K., in 2011 and 2015, respectively. He is currently a Lecturer (Strathclyde’s Chancellor’s Fellow) with the University of Strathclyde. His main research interest includes power system protection and control of future networks with high penetration of renewable generation. Dr. Hong is a Regular Member CIGRE Working Group B5.50 and IEEE Working Group P2004. He was the Technical Lead at the CIGRE UK Next Generation Network (2014-2019) and the Secretary of IET Scotland Southwest Committee (2015-2018).

Title of presentation: Enhanced Frequency Control for Future Power Network with Low Inertia Using Synchrophasor Measurements

Abstract: The clean energy shift in power systems has led to a massive decrease of system inertia, which makes frequency control challenging, due to the small response times before frequency drops to unacceptable levels. Network operators must, thus, procure increased power reserves representing higher operational costs. Moreover, since renewable generation is arbitrarily dispersed in a power system, there are differences in the inertia across interconnected regions and, as a result, to their frequency behavior. Novel wide-area monitoring and control topologies that are capable of dispatching fast and coordinated response from a variety of distributed resources are necessary. A novel system, termed “Enhanced Frequency Control Capability (EFCC)”, considers the regional impact of frequency disturbances and is capable of deploying much faster response compared with conventional primary response schemes (from a few seconds to within one second), thus enhancing the frequency control in future power systems with low inertia. The overall architecture of the EFCC system and the design of the key components within it to realise the enhanced frequency control objectives will be discussed, including case studies on distinguishing frequency events from pure electrical faults to avoid unnecessary operation.

Panelist 5:

Name: Krish Narendra

Organization: Electric Power Group LLC, USA

Short biography: Krish Narendra, Ph.D, is the COO and Technology Lead of Electric Power Group LLC (EPG). Krish joined EPG in September 2017 and has over 30 years of experience and is a prominent expert in power system protection, monitoring, control and analysis. Krish works on real time grid monitoring, visualization and analytics to address industry needs for asset health monitoring, digital solutions for power grid automation, and control. Krish’s expertise spans innovative design, commercialization of protective relays and disturbance monitoring recorders, and use of advanced digital signal processing technologies on embedded systems to enable real time grid security, analytics, asset health and automation. Krish has published over 40 papers in various IEEE/IEC journals and conferences, and holds several patents. He is a member of the IEEE PRSC working groups, the PRTT of NASPI, the CIGRE C4-B5 working group and NERC SMS committee.

Title of presentation: Real-Time Inertia Monitoring Using Synchrophasors

Abstract: With the increasing penetrations of renewable generation in the North American power grid the “low inertial response” of the power grid is becoming a growing concern. In such types of grids it is difficult to estimate the time varying inertia constant during major infeed loss or disturbances because of the complexities of identifying the number of machines participating including the load (which may also contribute to the rotational inertia). The overall inertia constant and hence the rotational kinetic energy, if available for each of the balancing authorities (Operators) in near real time (online), would help them in accessing the next course of action to recover the system faster avoiding stability issues. Planners can also use the estimated inertia constant and do the system model validation for better evaluation of the planned contingencies. The presentation aims at the conceptual aspects of the “inertial response of electrical grid” with growing renewables.

Panelist 6:

Name: Dr. Yilu Liu

Organization: University of Tennessee Knoxville and Oak Ridge National Lab, USA


Short biography: Yilu Liu received her M.S. and Ph.D. degrees from the Ohio State University, Columbus, in 1986 and 1989. She received the B.S. degree from Xian Jiaotong University, China. Dr. Liu is currently the UT-ORNL Governor’s Chair at the University of Tennessee and Oak Ridge National Laboratory. She is also the deputy director of the DOE/NSF engineering research center CURENT ( She led the effort to create the North American power grid Frequency Monitoring Network FNET/GridEye (, Dr. Liu is an expert in large grid dynamic modeling, simulations, and monitoring. Dr. Liu is a member of National Academy of Engineering, a member of the National Academy of inventors, a fellow of IEEE. She can be reached at

Title of presentation: Benefit of Grid Edge Synchronized Measurements

Abstract: The talk will provide an overview on the effort of power grid wide-area monitoring and observations that were made possible from the grid edge synchronized data. The critical roles of wide-area phasor measurement in situation awareness, operation, and control will be discussed. The concept of electromechanical wave propagation in power grid will be demonstrated using measurement data collected from the actual grids. Applications of time synchronized data in event location, oscillation location detection, model validation, and high renewable grids will be discussed.