2017 Research Portfolio

Power Delivery and Utilization - Transmission

Program 39 - Grid Operations

Last Updated: 14-Jun-2016
Program Description

In many ways, today's power system must be operated to meet objectives for which it was not explicitly designed. The transmission system is operated to transfer larger amounts of energy over greater distances utilizing an increasingly higher percentage of non-traditional resources than were considered when it was built. Generation resources are more constrained and increasingly more variable and uncertain. Demand resources are now increasingly used for resource adequacy and providing ancillary services in many regions. All of these changes are occurring at a rate that is outpacing corresponding growth in transmission infrastructure. As a result, new methods and tools will be required to operate tomorrow’s grid reliably and efficiently.

Under these circumstances, it is imperative that operators be provided with actionable information based on real-time data regarding the status of the system, as well as decision-making support to respond to rapid changes that might occur in the near future. New sources of real-time data from synchrophasor measurements and forecasts of future load and variable renewable output levels, along with improved visibility of alarms and protection system implications, enable the possibility of providing operators with increased situational awareness and advanced decision-support tools. System operators need such tools to continue to reliably and economically operate the system in the face of emerging challenges.

EPRI’s Grid Operations research program is addressing these needs by improving real-time situational awareness, developing tools that use synchrophasor and other measurements to assess the present system operating point relative to thermal, transient, and voltage stability operating limits, evaluating methods for more intelligently managing alarms, and developing tools to manage the grid through extreme events and restore the system in the event of an outage.

Research Value

The mission of EPRI's Grid Operations research program is to support the development of next-generation situational awareness, analysis, and control capabilities that will be required to operate the transmission grid in the most reliable and economic manner as the grid continues to evolve at an unprecedented rate. In 2017, this will be accomplished through a collaborative process in which EPRI works with its utility and independent system operator (ISO) members and other stakeholders to identify existing research gaps and associated project needs that would provide value to EPRI members. Once identified, the EPRI Grid Operations team of technical and project management experts work with members and the world’s foremost experts in related research areas to structure and conduct specific projects that provide value in the near-term, mid-term, and long-term. Finally, this value is transferred to members through collaborative advisory and task force interactions, workshops and webcasts, and specific applications and demonstrations of the developed methods and tools.

 

Approach

EPRI's Grid Operations research program delivers value using the shared experiences and understanding of its utility and ISO members in conjunction with the expertise of EPRI's staff and network of worldwide contractors. The program conducts research projects that lead to prototype methods and tools that are applied and validated by system operators before being transferred to commercial vendors that supply and support member applications. EPRI also engages with external industry standards, regulatory, and research efforts to ensure that the EPRI research program is taking advantage of broader industry efforts and advancing the state of the art.

This research program also strives to provide near-term, mid-term, and long-term value from each research project each year. For example, in 2016 the System Voltage and Reactive Power Management project (39.012) will deliver: (1) an updated version of a reference guide on Industry Practices and Tools for Voltage/VAR Planning and Management that can be used immediately to inform member planning and operating practices and to educate new staff in this area; (2) a new prototype software tool to determine improved load models for real-time power flow studies from synchrophasor measurements that can be evaluated by members for further refinement; and (3) preliminary research results to develop an improved method to calculate the voltage collapse point for stability analysis that can be implemented in new assessment tools in the future.

Accomplishments

EPRI's Grid Operations program has provided critically needed technologies and information for its members over many years. Examples include:

  • Power Flow Optimization Version (PFOpt) 1.0 (3002005857): The PFOPT package implements robust AC (nonlinear) power flow algorithms that are more robust to bad initial points and stressed (near singular Jacobians) cases as compared to the traditional AC power flow technique, the Newton-Raphson method. The new algorithms can be used to test difficult to solve cases from non-convergent state estimator cases or from challenging planning power flows cases.  While the goal of the research is to engage commercial tool vendors to incorporate the new algorithms, the PFOpt tool can be used for evaluating existing cases and provide insights for adjusting the cases to allow them to converge.
  • 24 Hour Day-Ahead Reactive Power Forecasting and Optimal Scheduling (3002002171) and Short-Term Reactive Power Forecasting and Scheduling (STRPFS) Version 1.0 (3002002842): This report describes algorithms and an associated prototype software tool to forecast day-ahead reactive power needs at a substation level and optimally schedule reactive power resources to meet those needs. The methods and tools developed as part of this project optimize the power system to produce a security-constrained case, reduce losses, increase reactive reserve, and securely maintain voltage stability. The control variables available to the operators include generator bus voltages, transformer voltage/phase angle tap set points, and switched shunt statuses.
  • System Restoration Tools: System Restoration Navigator Integrated into EPRI Operator Training Simulator (SRN/OTS) and Optimal Blackstart Capability (OBC) (3002002840): This report describes new algorithms for developing system restoration plans and supporting operator decision support as to the next step during an actual restoration event. Supporting research and case study results were provided for the OBC research in technical report #1024262 and for the SRN in technical report #1020055. The associated algorithms are incorporated into the following prototype tool sets:
    • Optimal Blackstart Capability (OBC) Tool 1.0 (1025089): This software tool was delivered in 2012 and incorporates a new algorithm to identify the optimal location and size of blackstart units with the objective function of maximizing total generation output within a given restoration time frame. An updated version of this tool incorporating needed changes identified during initial applications of the prototype tool is being developed and expected to be delivered in 2015.
    • System Restoration Navigator (SRN) Version 2.0 (1021715): This software tool, delivered in 2011, incorporates algorithms to determine successive restoration actions to optimally achieve specified restoration objectives at identified priority levels. This stand-alone version of the tool can be utilized in developing restoration plans and protocols. An updated version of this tool is also being developed and expected to be delivered in 2015
    • System Restoration Navigator (SRN) Integrated with EPRI Operator Training Simulator (OTS) Version 1.0 (3002002807): The stand-alone version of the SRN was integrated into the EPRI OTS for demonstrating and evaluating real-time application of the SRN algorithms to support an operator’s next decision during a restoration event. The integrated SRN was developed as a stand-alone component with an API that provides the capability for the EPRI OTS, or any other commercial dispatch training simulator, to interact with the SRN to obtain guidance for the operator on subsequent restoration outages.
    • Reactive Power Management to Address Long-Term Voltage Stability Using Voltage Control Area (VCA) Technique (1024258): This software tool investigates voltage security problems and identifies the voltage control areas to address steady-state stability problems and effective deployment and utilization of reactive power resources.
    • Online Measurement-Based Voltage Stability Assessment Tool (MBVSA) Version 2.0 (1024990): The MBVSA software calculates voltage stability indices at the substation and load center levels for a power transmission system using measurement data at key substations. The tool can be used offline to analyze historical data or integrated into the control room of a transmission system if fed with online measurement data from phasor measurement units (PMUs) or the Entergy Management System (EMS).

 

Key Activities

In 2017, EPRI's Grid Operations research program will offer its members a focused research portfolio with the following objectives:

  • Improve system reliability and reduce operational risks through the improved situational awareness of operators, including incorporating equipment health and protection system information into the control center, streamlining alarm management methods through identification of root causes and grouping of alarms, and identifying multiple operating boundaries and margins into aggregated visualizations.
  • Support operators in identifying potential voltage stability concerns in real time by more accurately modeling the voltage sensitivity of loads and more accurately determining the actual voltage collapse point when evaluating transfers across an interface. The project will also accomplish this task by providing a (1) reference guide to ensure that steady-state and post-contingency system voltage performance is maintained  and (2) a new method/tool for identifying voltage control areas across which the optimal mix of available reactive resources can be identified.
  • Improve restoration time and reduce outage costs through identifying optimal blackstart capability requirements and developing restoration decision-support applications that take into account the impacts of emerging resources such as HVDC and renewables.
  • Support operator situational awareness and decision making by developing advanced analysis algorithms that use emerging hardware and software-enabled approaches to increase computational efficiency and improve the performance of control room applications, and increase the resolution of calculations to take advantage of new inputs such as synchrophasor data.
  • Investigate tools and techniques that validate and correct synchrophasor data which can then be used to assess power system stability and predict unstable system behavior in a forecasted time window and to develop associated control methods to mitigate potential stability issues.
Estimated 2017 Program Funding
$4.7M
Program Manager
Daniel Brooks, 865-218-8040, dbrooks@epri.com
Non-EPRI Members: Contact Program Manager - Daniel Brooks; 865-218-8040; dbrooks@epri.com
Last Updated
  • 39.011: Situational Awareness Using Comprehensive Information
    15-Jun-2017

    Situational awareness is critical for grid operators to maintain system reliability and reduce the risk of wide-scale power outages. System operators are increasingly challenged with interpreting more data and more uncertainties impacting daily grid operations.

    Generally, this project aims to utilize new sources of data and develop new methods and tools to improve operators' situational awareness and decision support. In 2017, the R&D efforts in this project will continue to focus on new the following specific efforts which are detailed in the subsequent project descriptions:

    1. Methods and tools for operators to visualize the present operating point relative to multiple operating limits and to assess the most critical, or “nearest” operating limit to the present operating point
    2. Methods and tools to better integrate and assimilate alarms, equipment and protection system status data into the control center including methods to aggregate and prioritize alarms and visualize the implications of protection system changes

     

    • P39.011A: Situational Awareness Using Comprehensive Information: Visualization of Operating Boundaries
      13-Jun-2016

      Situational awareness is critical for grid operators to maintain system reliability and minimize major power outages. At present, the combination of rapid growth of regional electricity markets, increasing integration of variable generation resources, and lack of corresponding growth in transmission infrastructure is introducing more data and more uncertainties into daily grid operations. These changes could result in the transmission system operating closer to its limits and could increase the likelihood of stability issues during disturbances or equipment failures.

      This project aims to develop new methods and tools to improve operators' situational awareness of the operating limits relative to the current operating point and associated operating decision support. In 2017, the R&D efforts will focus on the following research questions:

      • Computing Critical Operating Boundaries: What definition of critical operating boundaries is most appropriate to operators in different situations?  Can the identification of critical operating boundaries be conducted automatically and dynamically for diverse operating conditions? How can we identify operator actions that can mitigate or avoid system violations?
      • Visualization of Operating Boundaries: How can we identify and visualize dynamically the most critical operating information, while still allowing the operator to drill efficiently into multiple layers of analytical data? How can we visualize effective operator actions?
    • P39.011B: Situational Awareness Using Comprehensive Information: Alarm, Equipment Condition, and Protection Information in Control Rooms
      13-Jun-2016

      Situational awareness is critical for grid operators to maintain reliability and minimize major system disruptions. Although there is an increasing availability of sensor data related to power system equipment health, system operators generally have little visibility of information or decision support that can be derived from this data. Information as to the condition of critical equipment and protection systems in the power system can help operators recognize potential increased risks associated with changes to the state of the system.

      Managing alarms associated with equipment conditions and system changes has become increasingly important in recent years.  An EPRI survey found that the volume and complexity of the alarms received in control centers are increasing.  Operators need better processes and tools to derive and prioritize actionable information from alarms and to better visualize the potential implications of alarms.

      Additionally, other sources of information are becoming available within the control room. This project looks at how these new sources, along with new techniques for traditional information, can be combined to improve the overall operator awareness of the system.

  • 39.012: System Voltage and Reactive Power Management
    15-Jun-2017

    Per the IEEE/CIGRE Joint Task Force on Stability Terms and Definitions, voltage stability refers to the ability of a power system to maintain steady voltages at all buses in the system after being subjected to a disturbance from a given initial operating condition.  Whether steady voltages can be maintained following a disturbance depends upon the balance between reactive power demand and resources.  A disturbance may upset the balance such that the available reactive power resources may not meet the demand.  The resulting reactive power shortage can be due to factors such as high reactive power demand associated with power flows and associated reactive power losses across highly inductive transmission lines, tripping of area generators due to over-excitation condition, etc.  Excessive shortage can result in progressively lower voltages across an area of a power system.  This voltage instability phenomenon can cause loss of load as well as cascading outages involving area transmission lines and generators.  If this leads to a blackout or abnormally low voltages in a significant portion of a power system, it is termed as voltage collapse.

    Voltage stability is a major concern in system operations and a leading factor that limits power transfers. The changing generation mix and the changing dynamic characteristics of loads bring more challenges to maintain voltage stability in the operating environment.  Identifying potential voltage instability areas and determining the required reactive power requirements in real time are technical challenges that need to be solved. There are also increasing research needs regarding techniques for optimally managing dynamic reactive resources to ensure fast voltage recovery, as well as techniques for sensing voltage recovery following disturbances.  The long term goal of project P39.012 (Voltage and Reactive Power Management) is to develop improved tools and techniques for real-time voltage stability assessment and reactive power management.

    The 2017 P39.012 project consists of 3 sub-projects as follows:

    1. P39.012A – Reference Guide - Industry Practices and Tools for Voltage/Reactive Power Planning and Management (VVPM)
    2. P39.012B – Improved Static Load Modeling from Synchrophasor Data for Real-Time Contingency Analysis and Voltage Stability Assessment Studies
    3. P39.012C – Tools for defining Voltage Control Areas and computation of available Reactive Power Reserves
    • P39.012A: Reference Guide - Industry Practices and Tools for Voltage/Reactive Power Planning and Management (VVPM)
      13-Jun-2016

      Voltage and Reactive Power (VAR) Planning and Management (VVPM) refers to maintaining satisfactory voltage performance across the power system of interest. Excessively low or high voltages have negative impact on power system stability performance and equipment.  Maintaining voltages to within satisfactory range requires proper planning and managing reactive power resources of the system.  Reactive power deficiency can lead to voltage instability or voltage collapse, while excessive reactive power can lead to high voltages that can damage equipment.  Therefore, transmission planners and operators work closely to identify reactive power resource requirements and means to control voltages.  VVPM plays an extremely critical role in maintaining power system reliability, as evident from many of the wide-area blackouts that have occurred in recent decades due to insufficient reactive power resources.  Also, there are increasing cases where voltage-constrained flowgates force operators to curtail transactions across these interfaces due to VVPM problems. 

    • P39.012B: Improved Static Load Modeling from Synchrophasor Data for Real-Time Contingency Analysis and Voltage Stability Assessment Studies
      02-Mar-2017

      Reliability Coordinators and Transmission Operators perform power flow studies in real-time operations environment to identify potential operating scenarios (e.g. power transfers, generation dispatch, contingencies, etc.) that could jeopardize the bulk power system’s Operating Reliability.  These power flow studies typically assume constant P/constant Q load modeling to represent the loads connected at transmission substation levels.  The constant P/constant Q load model does not capture the sensitivity of load to voltage, especially a portion of load that may be directly proportional to the voltage.  Therefore, this model is considered to be conservative for power flow study scenarios (e.g. increased power transfers, contingencies, etc.) that result in reduced system voltages.  The use of such conservative load model can result in undue operating restrictions such as power transfer across a voltage stability constrained interface.

      To capture load sensitivity to voltage, these power flow studies can employ the ZIP --- constant impedance/constant current/constant power --- load model.  It has been observed that use of ZIP load model to represent the load within a voltage stability constrained interface can support increased power transfer across the interface.  However, a reasonably accurate ZIP load model for such locations is necessary so that Operating Reliability is not compromised.  If synchrophasor data are available at such locations, it is possible to investigate load sensitivity to voltage, which can be utilized to develop the corresponding ZIP model.

    • P39.012C: Tools for Defining Voltage Control Areas and Computation of Available Reactive Power Reserves
      25-Jul-2017

      Reactive power resources are extremely important for maintaining adequate voltages as well as system voltage stability. However, reactive power cannot be transferred over long distances in the Grid. Defining zones of the network for voltage control over which the available reactive resources within the zone are effective is important to monitor and maintain adequate voltage control capabilities and maintain system reliability.

  • 39.013: Decision Support Tools for System Emergency and Restoration
    • P39.013A: Decision Support Tools for System Emergency and Restoration-- Decision Support System Restoration
      14-Jun-2016

      Ensuring that the power system is resilient to outages due to terrestrial and solar weather, cyber-attacks, malicious actors and other events has received increased attention in recent years. Federal and state governments are working jointly with the power industry to address resiliency by focusing on approaches such as hardening of assets and availability of spare equipment. Additional efforts are needed to make prudent planning decisions as to grid investments and provide operators support in making decisions during resiliency events. Similarly, planners and operators need improved tools to expedite system restoration following major outages or blackouts.  EPRI's research in this area is focused on:

      1. New methods and tools for developing restoration plans as the resource mix changes.
      2. Visualization and decision support tools for managing restoration and resiliency events by real-time operations.
      3. Methods and tools for planners to make prudent investments in designing the system to operate reliably during extreme resiliency events.
  • 39.014: Application of New Computing Technologies and Solution Methodologies in Grid Operations
    • P39.014A: Application of New Computing Technologies and Solution Methodologies in Grid Operations
      13-Jun-2016

      Control center operation is becoming more complex as new reliability, economics, and public policy issues emerge.  Computer simulations and system measurement data are used to analyze present system status and what-if-scenarios to derive succinct information for operators to make better informed decisions.  The complexities of the system models upon which these decisions are made are increasing with high penetrations of distributed resources pushing the need to include distribution level details into grid models.  Additionally, the availability of new sources of data, such as synchrophasor data at much higher resolutions than traditional control room data provides the basis for conducting analyses on much higher time resolutions than in the past.  The purpose of this project is to explore leveraging advancements in data processing, computing technologies and numerical methods to enable efficient processing, simulation and analysis of more complex system models and higher time resolutions to provide timelier, more complete, and more accurate information to operators and engineers.

       

  • 39.015: Synchrophasor Applications for Next Generation Monitoring and Control
    15-Jun-2017

    39.015: Synchrophasor Applications:  Stability Analysis and Prediction Using Synchrophasors (2017)

    Along with the increasing deployment in the power system grids of Phasor Measurement Units (PMUs) and other devices that provide high-resolution, synchronized measurements, numerous synchrophasor-based applications have been and continue to be developed, both for offline and online environment that target to enhance grid operations and planning and are expected to contribute to the improvement of grid reliability. To leverage synchrophasor technology, the research subject of this work is twofold.

    The first goal is to develop advanced synchrophasor applications that enable and improve real-time stability assessment and control. The availability of high-resolution, synchronized measurements from PMUs presents an opportunity to develop advanced analytical techniques that can evaluate stability performance in the immediate time window, identify a potential instability condition, and activate a remedial, automated control action to address the instability condition. Such techniques, if implemented in a real-time online environment, can increase the reliability of the system and can also obviate the need for an anticipatory action, thus potentially eliminating the associated economic penalties.

    The second goal is to develop advanced algorithms, techniques and tools to improve the robustness of synchrophasor applications towards successful integration of those into real-time operations. Although it is widely recognized that synchrophasor-based applications could significantly improve power system operations, there are several challenges that remain to be solved to achieve high levels of accuracy and robustness of the applications, especially if they are targeted to be implemented in a real-time production environment.  

    • P39.015A: Synchrophasor Applications for Next Generation Monitoring and Control
      14-Jun-2016

      Along with the increasing deployment in the power system grids of Phasor Measurement Units (PMUs) and other devices that provide high-resolution, synchronized measurements, numerous synchrophasor-based applications have been and continue to be developed, both for offline and online environment that target to enhance grid operations and planning and are expected to contribute to the improvement of grid reliability and security.

      One of the applications that has attracted the interest of the industry is utilizing synchronized measurements for real-time oscillations control. In today’s interconnected power grids, small signal stability and low-frequency oscillations are a significant issue limiting the power transfer capability and even deteriorating power system security. Typically local controllers (such as generator power system stabilizers) have been used to suppress these low-frequency oscillations, and they are conventionally designed and tuned based on the system circuit model around a particular operating point and for hypothetical critical contingency scenarios. Synchronized measurements enable the development and design of wide-area and adaptive controllers that adapt to the grid changing conditions, thus overcoming the limitations of traditional controllers, resulting in improved oscillations damping control.

      Although it is widely recognized that synchrophasor-based applications could significantly improve power system operations, there are several challenges that remain to be solved to achieve high levels of accuracy and robustness of the applications, especially if they are targeted to be implemented in a real-time production environment. One of the challenges is the data quality of the streaming data and their impact on the robustness of the applications. There are several drivers of bad synchrophasor data, such as PMU hardware failure, poor communications network performance, etc. A data conditioning tool that will continuously monitor the quality of the streaming data and accurately differentiate bad data from abnormal measurement values due to a system contingency is necessary. 

      Another factor that can increase the robustness of synchrophasor applications is accurate offline testing. Typically the offline design and testing of synchrophasor based applications is performed using unfiltered and clean simulation data, without taking into account the PMUs filtering effect. The same typically holds when performing offline component and/or system model validation using recorded measurement data. It is important to analyze and consider the filtering effects of PMUs when comparing between actual synchrophasors provided by PMUs and simulation results generated by electromechanical dynamics simulation tools.