Slides for the PSERC Webinar on January 20, 2015

This webinar deals with the development of a new electromagnetic transient (EMT)-transient stability (TS) hybrid simulation platform and its application to fault-induced delay voltage recovery (FIDVR) study on the WECC system. The webinar focuses on the development of the EMT-TS hybrid simulation platform, which integrates PSCAD/EMTDC and the open source power system simulation software InterPSS. The developed platform features a decoupled architecture and flexible switch of interaction protocols. A combined interaction protocol with a corresponding protocol switching algorithm is also proposed. A multi-port three-phase Thé venin equivalent is proposed for representing an external network in an EMT simulator. Correspondingly, the external network is represented in three-sequence and a three-sequence TS simulation algorithm is proposed. These techniques allow simulation of unsymmetrical faults within the internal network without the constraint of balanced voltages at the boundary. The numerical example deals with detailed simulation of residential air conditioner (A/C) compressor motor stalling and the corresponding fault induced delayed voltage recovery (FIDVR) event in a region within the WECC system, using the EMT-TS hybrid simulation developed in PSERC Project S-58. A fault voltage magnitude-based criterion is proposed for internal network boundary identification. Modeling of the internal network with multi-port three-phase Thé venin equivalents in PSCAD is discussed. A special two-step initialization approach is introduced to initialize internal networks with a large percentage of induction motor loads. Detailed simulation of residential air conditioner (A/C) compressor motor stalling and FIDVR phenomenon within a large power system under symmetrical faults is realized for the first time. The phenomenon of A/C motor stalling spreading to A/C units on the unfaulted phase is observed and analyzed. In addition, the sensitivity of simulation results with respect to load composition is studied. Finally, the point-on-wave effects of the A/C stalling are also analyzed.

PSERC Webinar on February 3, 2015

The continuously increasing demand for electric power and the need for efficient grid integration and transmission of remote large-scale renewable energy resources have revived the interest in High-Voltage Direct Current (HVDC) systems. The HVDC systems based on the Voltage-Sourced Converter (VSC) are a promising technology for (i) expansion of the power networks for large cities, (ii) grid integration of renewable energy resources, i.e., hydropower and offshore wind farms, (iii) long-distance bulk power transmission, (iv) interconnection of asynchronous power grids, and (v) electrification of isolated loads, islands, and oil and gas stations.The key enabling technology for VSC-HVDC systems is efficient, scalable, and fault-tolerant high-power VSCs. The Modular Multilevel Converter (MMC) topology is a newly introduced VSC which, conceptually, does not have the drawbacks of the existing high-power VSCs. The emergence of the MMC has opened up a new avenue for research and development of not only the VSC-HVDC systems but also for other emerging applications including interfacing energy storage devices to the utility grid, collection systems of offshore wind farms, and medium-voltage high-power adjustable speed drives. This presentation deals with control and operational challenges of the MMC-HVDC systems.

Slides for the PSERC Webinar on February 17, 2015

In recent years, the Software Defined Networking (SDN) has gained significant popularity among network operators and equipment manufacturers. By providing an efficient way to separate the forwarding decisions from packet processing, the SDN approach is able to address many challenges in design and operation of complex networks, including the high cost of developing and deployment of new applications, poor utilization of network resources, inadequate support of real-time applications, and many others. We will begin the presentation by surveying the fundamentals of the SDN approach. We will provide a detailed explanation of the network abstractions and protocols, including a core data model, as well as primitives including instructions, actions, meters, groups, and queues. Then, we will discuss the benefits and advantage of using SDN for improving the performance and availability of power systems networks. We will emphasize meeting specific requirements of transmission and distribution systems as well as handling faults and outages. Finally, we will discuss research efforts, the technology outlook for OpenFlow and SDN technologies, and open research problems.

Slides for the PSERC Webinar on March 3, 2015 

This presentation will describe ongoing research that uses in situ microclimate and tower-based measurement, remote sensing, ensemble weather forecasts, and visualization of turbine SCADA data to understand wind farm interactions with crops, turbine-layer flow fields, and the overlying free atmosphere. Diurnally and seasonally changing meteorological conditions indigenous to the U.S. Midwest and Great Plains have a high impact on power production and environmental interactions in wind farms. The nocturnal low-level jet and its accompanying high thermal stratification and high shear of wind speed and wind direction across the rotor layer can lead to inaccurate wind condition forecasts and stress on turbine components. High-resolution (in time) animation of power production by individual turbines in a wind farm provides insight on how turbine-flow interactions change under changing meteorological conditions.

Slides for the PSERC Webinar on March 17, 2015

An ongoing power system challenge is how best to utilize and ultimately present information to a human user derived from time-varying power system data. In operations this data might come from measurement systems such as SCADA or PMUs, while in a study context it might be generated by a time-domain simulation such as transient stability. Much of the previous visualization research has focused the display of information from a single snapshot in time. Traditionally, the time-variation in system information has been shown using eithers trip-chart recorders or 2D graphs. While certainly useful, these techniques have some significant disadvantages. This presentation will show some newer techniques, including leveraging machine learning, to help effectively extract the information contained in power system time-varying data. The application of these techniques to intelligent alarm processing will also be covered.

Slides for the PSERC Webinar on April 7, 2015

One of the U.S. grand energy challenges is to enable integration of at least 80% renewable energy resources at a competitive cost in the power grid by 2050. While it is technically feasible to run the U.S. economy on renewable technologies that are available today, what is missing is a flexible power system infrastructure to accommodate the unique characteristics of renewable energy resources, such as susceptibility to violation of operational limits. This problem is exacerbated in small-scale power systems (e.g., microgrids) which have relatively limited resources. In this talk, I will discuss strategies to address these challenges using an add-on control for transient response shaping of controllable devices. This strategy augments an existing controller and enhances its performance by monitoring the response and temporarily modulating the set point. The salient features of this strategy are (i) robustness with respect to system parameters, (ii) independence from the system model, (iii) reliance merely on local signals, and (iv) absence of a need to adjust existing controllers. I will also present case studies to evaluate the performance of this strategy and demonstrate its feasibility.

Slides for April 21, 2015, PSERC Webinar

Flexible Transmission Decision Support is an open-source software solution for power flow control. With advanced operational optimization software, we are able to identify correction actions to redirect power around transmission bottlenecks to enhance reliability and lower operational costs by making better use of existing transmission hardware (e.g., circuit breakers). Funded by the US DOE Advanced Research Projects Agency – Energy (ARPA-E) Green Electricity Network Integration (GENI) program, we have developed a message passage interface (MPI) based, high performance computing real-time contingency analysis (RTCA) package that incorporates post-contingency corrective transmission switching. This RTCA tool is envisioned to work seamlessly alongside existing energy management systems (EMS) to identify corrective actions that are passed on to the operator. By incorporating corrective control within RTCA, we are able to substantially reduce post-contingency violations, thereby reducing the need to implement expensive preventive actions.

Slides for the PSERC Webinar on September 15, 2015

In this talk we will first give an overview of the voltage control problem in distribution systems with high penetration of distributed energy resources DERS, and describe various decentralized solutions to the problem, such as using on-load tap changer (OLTC) transformers, capacitor banks, and distributed generations (DGs). Then we will focus on the fast voltage control problem using the VAR-capable inverters of DGs and batteries that are dependent on the availability and quality of communication links. With no communication capability, inverters can perform local voltage control by measuring bus voltage, such as in droop control design. We will present a distributed voltage control approach that is resilient to random failures of communication links using only bus-to-bus communications. Compared to existing distributed solutions, our proposed approach uses only local voltage measurements and thus has minimal requirements for sensing hardware. We will present numerical results from realistic three-phase distribution test cases. The results demonstrate the effectiveness of the proposed methods under imperfect communication scenarios.

Slides for the PSERC Webinar on October 6, 2015

Advanced Metering Infrastructure (AMI) initiatives provide popular tools to incorporate changes to modernize the electricity grid, reduce peak loads, and meet energy efficiency targets. There is the looming issue of how to communicate and handle consumer data collected by electric utilities, and to manage limited communication network resources. This webinar will describe the data volume challenges arising from AMI for electric utility communications networks and present techniques for scalable meter data management that also preserve application quality within tolerable limits. Some of the techniques and results discussed in this webinar were obtained through the PSERC industry funded project “ Towards a Privacy-Aware Information-Sharing Framework for Advanced Metering Infrastructures.”

Slides for the PSERC Webinar on October 20, 2015

The electricity grid is transforming itself from a hierarchical, passive, and sparsely-sensed engineering system towards a flat, active, and ubiquitously-sensed cyber-physical system. The emerging data from synchrophasors, renewables, and smart meters offers opportunities as well as scientific challenges to dynamically learn and adaptively control the grid. This talk offers two case studies that leverage the spatio-temporal correlations of the streaming data to improve the decision-making in bulk power systems.

The first case study uses local and neighboring renewable generation data to improve the renewable forecast in the near term (i.e., hours-ahead). Compared with conventional temporal-only statistical forecast models, spatio-temporal models allow the system operator to have more accurate near-term forecasts of wind and photovoltaic generation, which, in turn, reduce the cost of real-time economic dispatch. The second case study presents the spatio-temporal analytics of synchrophasor data. High-dimensional synchrophasor data could be reduced to a much lower-dimensional subspace. The change of the subspace is leveraged for early detection of anomalies such as inter-area oscillations. This talk concludes with several open research questions on data analytics that would benefit from industry-academia collaboration.

Slides for the PSERC Webinar on November 3, 2015

In this talk we summarize the objectives of our PSERC project on standards for dynamics in electric energy systems. As part of this project, we have introduced a unifying modeling for changing electric energy systems. The proposed standards are effectively performance criteria that different stakeholders must meet for the system to remain reliable as new technologies, in particular, are deployed. Illustrations are provided for transient stability performance criteria.

Slides for the PSERC Webinar on November 17, 2015

Phasor Measurement Units (PMU’ s) provide synchronized measurements at high rates for wide area situational awareness and decision support for mission critical applications. High quality PMU data is vital for these applications, especially for real-time wide area control. PMU data quality can be impacted by filtering and estimation algorithms within the PMU, settings and firmware issues, time error, and errors caused by the communication system, data concentrator, and data historian. PMU performance testing before installation and remote in-field testing can ensure the data quality at the device level. Data cleansing efforts for streaming data need to be embedded locally, in a decentralized manner, and also at centralized control centers to support different possible applications using PMU data. Statistical and data mining approaches supported by physics can be adopted locally at the substation level while system level approaches are needed for decentralized and control center state estimation. This talk will present (1) research activities related to development of a PMU performance analyzer (PPA) tool for in-lab and remote, in-field testing; and (2) data mining approaches for data cleansing and for analyzing impacts of data quality on PMU applications. The talk will include a discussion of a real-time wide area monitoring and control test bed that will support the testing and validation of PMU’ s and PMU-based applications.