Francis K. Tuffner

Evaluation of Conservation Voltage Reduction (CVR) on a National Level

Conservation Voltage Reduction (CVR) is a reduction of energy consumption resulting from a reduction of feeder voltage. While there have been numerous CVR systems deployed in North America there has been little substantive analytic analysis of the effect; the majority of the published results are based on empirical field measurements. Since these results are based on empirical measurements it is difficult to extrapolate how this technology will behave on the various types of distribution feeders found throughout the nation. This report has utilized the Taxonomy of Prototypical feeder developed under the Modern Grid Initiative (MGI), now the Modern Grid Strategy (MGS), in order to estimate the benefits of CVR on multiple distribution feeder types. This information will then be used to determine an estimate of the national benefits of a wide scale deployment of CVR.

Energy Storage for Power Systems Applications: A Regional Assessment for the Northwest Power Pool (NWPP)

Wind production, which has expanded rapidly in recent years, could be an important element in the future efficient management of the electric power system; however, wind energy generation is uncontrollable and intermittent in nature. Thus, while wind power represents a significant opportunity to the Bonneville Power Administration (BPA), integrating high levels of wind resources into the power system will bring great challenges to generation scheduling and in the provision of ancillary services. This report addresses several key questions in the broader discussion on the integration of renewable energy resources in the Pacific Northwest power grid. More specifically, it addresses the following questions: a) how much total reserve or balancing requirements are necessary to accommodate the simulated expansion of intermittent renewable energy resources during the 2019 time horizon, and b) what are the most cost effective technological solutions for meeting load balancing requirements in the Northwest Power Pool (NWPP).

Effects of distributed energy resources on conservation voltage reduction (CVR)

Conservation voltage reduction (CVR) is one of the cheapest technologies that can be intelligently leveraged to provide considerable energy savings. The addition of renewables in the form of distributed resources can affect the entire power system, but more importantly, affects the traditional substation control schemes at the distribution level. This paper looks at the effect on energy consumption, peak load reduction, and voltage profile changes caused bu the addition of distributed generation in a distribution feeder using a volt-var control (VVC) technique for CVR with different end-of-line (EOL) measurements. An IEEE 13-node system is used to simulate the various cases. Energy savings and peak load reduction for different simulation scenarios are compared.

Using electric vehicles to mitigate imbalance requirements associated with an increased penetration of wind generation

The integration of variable renewable generation sources continues to be a significant area of focus for power system planning. Renewable portfolio standards and initiatives to reduce the dependency on foreign energy sources drive much of the deployment. Unfortunately, renewable energy generation sources like wind and solar tend to be highly variable in nature. To counter the energy imbalance caused by this variability, wind generation often requires additional balancing resources to compensate for the variability in the electricity production. With the expected electrification of transportation, electric vehicles may offer a new load resource for meeting all, or part, of the imbalance created by the renewable generation. This paper investigates a regulation-services-based battery charging method on a population of plug-in hybrid electric vehicles to meet the power imbalance requirements associated with the introduction of 11 GW of additional wind generation into the Northwest Power Pool. It quantifies the number of vehicles required to meet the imbalance requirements under various charging assumptions.

Probing Signal Design for Power System Identification

This paper investigates the design of effective input signals for low-level probing of power systems. In 2005, 2006, and 2008 the Western Electricity Coordinating Council (WECC) conducted four large-scale system-wide tests of the western interconnected power system where probing signals were injected by modulating the control signal at the Celilo end of the Pacific DC intertie. A major objective of these tests is the accurate estimation of the inter-area electromechanical modes. A key aspect of any such test is the design of an effective probing signal that leads to measured outputs rich in information about the modes. This paper specifically studies low-level probing signal design for power-system identification. The paper describes the design methodology and the advantages of this new probing signal which was successfully applied during these tests. This probing input is a multi-sine signal with its frequency content focused in the range of the inter-area modes. The period of the signal is over 2 min providing high-frequency resolution. Up to 15 cycles of the signal are injected resulting in a processing gain of 15. The resulting system response is studied in the time and frequency domains. Because of the new probing signal characteristics, these results show significant improvement in the output SNR compared to previous tests.

Improving small signal stability through operating point adjustment

ModeMeter techniques for real-time small-signal stability monitoring continue to mature, and more and more phasor measurements are available in power systems. It has come to the stage to bring modal information into real-time power system operation. This paper proposes to establish a procedure for Modal Analysis for Grid Operations (MANGO). Complementary to PSS and other traditional modulation-based control, MANGO aims to provide suggestions such as redispatching generation for operators to mitigate low-frequency oscillations. Load would normally not be reduced except as a last resort. Different from modulation-based control, the MANGO procedure proactively maintains adequate damping at all times, rather than reacting to disturbances when they occur. The effect of operating points on small-signal stability is presented in this paper. Implementation with existing operating procedures is discussed. Several approaches for modal sensitivity estimation are investigated to associate modal damping and operating parameters. The effectiveness of the MANGO procedure is confirmed through simulation studies of several test systems.

MANGO – Modal Analysis for Grid Operation: A Method for Damping Improvement through Operating Point Adjustment

Small signal stability problems are one of the major threats to grid stability and reliability in the U.S. power grid. An undamped mode can cause large-amplitude oscillations and may result in system breakups and large-scale blackouts. There have been several incidents of system-wide oscillations. Of those incidents, the most notable is the August 10, 1996 western system breakup, a result of undamped system-wide oscillations. Significant efforts have been devoted to monitoring system oscillatory behaviors from measurements in the past 20 years. The deployment of phasor measurement units (PMU) provides high-precision, time-synchronized data needed for detecting oscillation modes. Measurement-based modal analysis, also known as ModeMeter, uses real-time phasor measurements to identify system oscillation modes and their damping. Low damping indicates potential system stability issues. Modal analysis has been demonstrated with phasor measurements to have the capability of estimating system modes from both oscillation signals and ambient data. With more and more phasor measurements available and ModeMeter techniques maturing, there is yet a need for methods to bring modal analysis from monitoring to actions. The methods should be able to associate low damping with grid operating conditions, so operators or automated operation schemes can respond when low damping is observed. The work presented in this report aims to develop such a method and establish a Modal Analysis for Grid Operation (MANGO) procedure to aid grid operation decision making to increase inter-area modal damping. The procedure can provide operation suggestions (such as increasing generation or decreasing load) for mitigating inter-area oscillations.

Evaluating the Feasibility to Use Microgrids as a Resiliency Resource

Regulated electricity utilities are required to provide safe and reliable service to their customers at a reasonable cost. To balance the objectives of reliable service and reasonable cost, utilities build and operate their systems to operate under typical historic conditions. As a result, when abnormal events such as major storms or disasters occur, it is not uncommon to have extensive interruptions in service to the end-use customers. Because it is not cost effective to make the existing electrical infrastructure 100% reliable, society has come to expect disruptions during abnormal events. However, with the increasing number of abnormal weather events, the public is becoming less tolerant of these disruptions. One possible solution is to deploy microgrids as part of a coordinated resiliency plan to minimize the interruption of power to essential loads. This paper evaluates the feasibility of using microgrids as a resiliency resource, including their possible benefits and the associated technical challenges. A use-case of an operational microgrid is included.

Energy storage for variable renewable energy resource integration — A regional assessment for the Northwest Power Pool (NWPP)

This paper addresses the following key questions in the discussion on the integration of renewable energy resources in the Pacific Northwest power grid: a) what will be the future balancing requirement to accommodate a simulated expansion of wind energy resources from 3.3 GW in 2008 to 14.4 GW in 2019 in the Northwest Power Pool (NWPP), and b) what are the most cost effective technological solutions for meeting the balancing requirements in the Northwest Power Pool (NWPP). A life-cycle analysis was performed to assess the least-cost technology option for meeting the new balancing requirement. The technologies considered in this study include conventional turbines (CT), sodium sulfur (NaS) batteries, lithium ion (Li-ion) batteries, pumped hydro energy storage (PH), and demand response (DR). Hybrid concepts that combine 2 or more of the technologies above are also evaluated. This analysis was performed with collaboration by the Bonneville Power Administration and funded by the Energy Storage Systems Program of the U.S. Department of Energy.

Modern Grid Strategy: Enhanced GridLAB-D Capabilities Final Report

GridLAB-D is a software simulation environment that was initially developed by the US Department of Energy (DOE) Office of Electricity (OE) for the purpose of enabling the effective analysis of emerging smart grid technologies. In order to achieve this goal GridLAB-D was developed using an open source approach with the intent that numerous people and organizations would contribute to the ongoing development. Because of the breadth and complexity of the emerging smart grid technologies the inclusion of multiple groups of developers is essential in order to address the many aspects of the smart grid. As part of the continuing Modern Grid Strategy (MGS) the Pacific Northwest National Laboratory (PNNL) has been tasked with developing an advanced set of GridLAB-D capabilities. These capabilities were developed to enable the analysis of complex use case studies which will allow for multi-disciplinary analysis of smart grid operations. The advanced capabilities which were developed include the implementation of an unbalanced networked power flow algorithm, the implementation of an integrated transmission and distribution system solver, and a set of use cases demonstrating the capabilities of the new solvers.