Kurt S. Myers

A Comparison of Real-Time Thermal Rating Systems in the U.S. and the U.K.

Real-time thermal rating is a smart-grid technology that allows the rating of electrical conductors to be increased based on local weather conditions. Overhead lines are conventionally given a conservative, constant seasonal rating based on seasonal and regional worst case scenarios rather than actual, say, local hourly weather predictions. This paper provides a report of two pioneering schemes-one in the U.S. and one in the U.K.-where real-time thermal ratings have been applied. Thereby, we demonstrate that observing the local weather conditions in real time leads to additional capacity and safer operation. Second, we critically compare both approaches and discuss their limitations. In doing so, we arrive at novel insights which will inform and improve future real-time thermal rating projects.

Smart Grid Constraint Violation Management for Balancing and Regulating Purposes

The gradual active load penetration in low-voltage distribution grids is expected to challenge their network capacity in the near future. Distribution system operators should for this reason resort to either costly grid reinforcements, use of low-voltage boosters, or demand response (DR) mechanisms. Since DR implementation is usually more cost effective, it is the favorable solution to avoid or delay the need for grid reinforcement. To this end, this paper presents a framework for handling grid limit violations, both voltage and current, to ensure a secure and qualitative operation of the distribution grid. This framework consists of two steps, namely a proactive centralized, and subsequently, a reactive decentralized control scheme. The former is employed to balance the 1-h-ahead load, while the latter aims at regulating the consumption in real time. In both schemes, fairness in terms of utilization of demand flexibility among the customers is incorporated. It is demonstrated that the proposed methodology aids in keeping the grid status within preset limits while utilizing flexibility from all flexibility participants.

Dynamic Line Rating systems: Research and policy evaluation

Dynamic Line Rating (DLR) is a smart grid technology that allows the rating of electrical conductors to be increased based on local weather conditions. Overhead lines are conventionally given a conservative rating based on worst case scenarios. We demonstrate that observing the conditions in real time leads to additional capacity and safer operation. This paper provides a report of a pioneering scheme in the United States of America in which DLR has been applied. Thereby, we demonstrate that observing the local weather conditions in real time leads to additional capacity and safer operation. Secondly, we discuss limitations involved. In doing so, we arrive at novel insights which will inform and improve future DLR projects. Third, we provide a policy background and discussion to clarify the technologys potential and identifies barriers to the imminent adoption of dynamic line rating systems. We provide suggestions for regulatory bodies about possible improvements in policy to encourage adoption of this beneficial technology.

Optimum Aggregation and Control of Spatially Distributed Flexible Resources in Smart Grid

This paper presents an algorithm to optimally aggregate spatially distributed flexible resources at strategic microgrid/smart-grid locations. The aggregation reduces a distribution network having thousands of nodes to an equivalent network with a few aggregated nodes, thereby enabling distribution system operators (DSOs) to make faster operational decisions. Moreover, the aggregation enables flexibility from small distributed flexible resources to be traded to different power and energy markets. A hierarchical control architecture comprising a combination of centralized and decentralized control approaches is proposed to practically deploy the aggregated flexibility. The proposed method serves as a great operational tool for DSOs to decide the exact amount of required flexibilities from different network section(s) for solving grid constraint violations. The effectiveness of the proposed method is demonstrated through simulation of three operational scenarios in a real low voltage distribution system having high penetrations of electric vehicles and heat pumps. The simulation results demonstrated that the aggregation helps DSOs not only in taking faster operational decisions, but also in effectively utilizing the available flexibility.

Active control of thermostatic loads for economic and technical support to distribution grids

Active control of electric water heaters (EWHs) is presented in this paper as a means of exploiting demand flexibility for supporting low-voltage (LV) distribution grids. A single-node model of an EWH is implemented in DIgSILENT PowerFactory using a thermal energy balancing equation and three decentralized control schemes are designed to ensure consumer comfort, economic benefit to the consumer, and technical support to LV grids. First, a price-based control that adaptively adjusts an allowable energy band per electricity price is implemented to ensure economic benefit. Next, an adaptive update of the energy band is done based on feeder loading to respect thermal grid constraints. Finally, a voltage-based control is implemented to provide real-time voltage support to the LV grids. Simulation results demonstrate the capability of the presented method to realize both economic and technical advantages. For the given configuration and pricing scheme, EWH owners are able to decrease their electricity cost by 29.33%, along with simultaneous assurance of consumer comfort and grid constraints.

INVESTIGATION OF A DYNAMIC POWER LINE RATING CONCEPT FOR IMPROVED WIND ENERGY INTEGRATION OVER COMPLEX TERRAIN

Dynamic Line Rating (DLR) is a smart grid technology that allows the rating of power line to be based on real-time conductor temperature dependent on local weather conditions. In current practice overhead power lines are generally given a conservative rating based on worst case weather conditions. Using historical weather data collected over a test bed area, we demonstrate there is often additional transmission capacity not being utilized with the current static rating practice. We investigate a new dynamic line rating methodology using computational fluid dynamics (CFD) to determine wind conditions along transmission lines at dense intervals. Simulated results are used to determine conductor temperature by calculating the transient thermal response of the conductor under variable environmental conditions. In calculating the conductor temperature, we use both a calculation with steady-state assumption and a transient calculation. Under low wind conditions, steady-state assumption predicts higher conductor temperatures that could lead to curtailments, whereas transient calculations produce conductor temperatures that are significantly lower, implying the availability of additional transmission capacity.

Simulation of Vertical Axis Wind Turbines With Variable Pitch Foils

A dynamic computer model of a turbine was developed in MATLAB in order to study the behavior of vertical axis wind turbines (VAWTs) with variable pitch (articulating) foils. The simulation results corroborated the findings of several empirical studies on VAWTs. The model was used to analyze theories of pitch articulation and to inform the discussion on turbine design. Simulations of various models showed that pitch articulation allowed Darrieus-style vertical axis wind turbines to start from rest. Once in motion, the rotor was found to accelerate rapidly to very high rotational velocities. The simulations revealed a plateau region of high efficiency for small-scale Darrieus-style VAWTs with symmetric airfoils at tip speed ratios in the range of 3 to 4 and demonstrated the advantages of using a dynamic generator load.Copyright

Technical Assessment for the CPC FD-7x-1500 Wind Turbine located at Tooele Army Base, Tooele Utah

The CPC FD-7x-1500 Wind Turbine was installed with funding from the Energy Conservation Investment Program (ECIP). Since its installation, the turbine has been plagued with multiple operational upsets causing unacceptable down time. In an effort to reduce down time, the Army Corps of Engineers requested the Idaho National Laboratory conduct an assessment of the turbine to determine its viability as an operational turbine.