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Simulation of Grid-Forming Inverters Dynamic Models using a Power Hardware-in-the-Loop Testbed

Conference Record of the IEEE Photovoltaic Specialists Conference

Hernandez-Alvidrez, Javier; Summers, Adam; Reno, Matthew J.; Flicker, Jack D.; Pragallapati, Nataraj

Modern power grids include a variety of renewable Distributed Energy Resources (DERs) as a strategy to comply with new environmental and renewable portfolio standards (RPSs) imposed by state and federal agencies. Typically, DERs include the use of power electronic (PE) interfaces to interactwith the power grid. Recently this interaction has not only been focused on supplying maximum available energy, but also on supporting the power grid under abnormal conditions such as low voltage/frequency conditions or non-unity power factor. Over the last few years, grid-following inverters (GFLIs) have proven their value while providing these ancillary grid-support services either at residential or utility scale. However, the use of grid-forming inverters (GFMIs) is gaining momentum as the penetration-level of DERs increases and system inertia decreases. Under abnormal operating conditions, GFMIs tend to better preserve grid stability due to their intrinsic ability to balance loadswithout the aid of coordination controls. In order to gain and propose fundamental insights into the interfacing of GFMIs to real time simulation, this paper analyzes the dynamics of two different GFMI simulation models in terms of stability and load changes using a Power Hardware-in-the-Loop (PHIL) simulation testbed.

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TYPE Conference Poster YEAR 2019
OSTIScopus

Grid-forming Inverter Experimental Testing of Fault Current Contributions

Conference Record of the IEEE Photovoltaic Specialists Conference

Gurule, Nicholas S.; Hernandez-Alvidrez, Javier; Reno, Matthew J.; Summers, Adam; Gonzalez, Sigifredo; Flicker, Jack D.

Historically, photovoltaic inverters have been grid-following controlled, but with increasing penetrations of inverter-based generation on the grid, grid-forming inverters (GFMI) are gaining interest. GFMIs can also be used in microgrids that require the ability to interact and operate with the grid (grid-tied), or to operate autonomously (islanded) while supplying their corresponding loads. This approach can substantially improve the response of the grid to severe contingencies such as hurricanes, or to high load demands. During islanded conditions, GFMIs play an important role on dictating the system's voltage and frequency the same way as synchronous generators do in large interconnected systems. For this reason, it is important to understand the behavior of such grid-forming inverters under fault scenarios. This paper focuses on testing different commercially available grid-forming inverters under fault conditions.

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TYPE Conference Poster YEAR 2019
DOIOSTIScopus

Fault Current Correction Strategies for Effective Fault Location in Inverter-Based Systems

Conference Record of the IEEE Photovoltaic Specialists Conference

Matthews, Ronald C.; Hossain-McKenzie, Shamina S.; Reno, Matthew J.

The grid of the future will integrate various distributed energy resources (DERs), microgrids, and other new technologies that will revolutionize our energy delivery systems. These technologies, as well as proposed grid-support functions, require inverter-based systems to achieve incorporation into the overall system(s). However, the presence of inverters and other power electronics changes the behavior of the grid and renders many traditional tools and algorithms less effective. An inverter is typically designed to limit its own current output to avoid overloading. This can result in both voltage collapse at the inverter output and limited energy being delivered during a fault so that protective relays cannot respond properly. To avoid sustained faults and unnecessary loss of service, it is proposed that either supercapacitor or flywheel energy storage be utilized to energize faults upon overload of the inverter to achieve fault current correction. This paper will discuss these challenges for inverter-based system fault detection, explore fault current correction strategies, and provide MATLAB/Simulink simulation results comparing the effectiveness of each strategy.

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TYPE Conference Poster YEAR 2019
DOIOSTIScopus

Cygnus System Timing

IEEE International Pulsed Power Conference

Ormond, Eugene C.; Garcia, Michael R.; Parrales, Martin F.; Smith, John R.; Amos, Percy H.; Hogge, Keith W.; Misch, Michael K.; Mohammed, Mohammed; Truong, Hoai T.V.

The Cygnus Dual Beam Radiographic Facility consists of two identical radiographic sources each with a dose rating of 4-rad at 1 m, and a 1-mm diameter spot size. The development of the rod pinch diode was responsible for the ability to meet these criteria1. The rod pinch diode in a Cygnus machine uses a 0.75-mm diameter, tapered tip, tungsten anode rod extended through a 9-mm diameter, aluminum cathode aperture. When properly configured, the electron beam born off the aperture edge can self-insulate and pinch onto the tip of the rod creating an intense, small x-ray source. The Cygnus sources are utilized as the primary diagnostic on Subcritical Experiments that are single-shot, high-value events. The system timing on Cygnus will be evaluated as related to the following system elements: HV trigger generator, Marx, pulse forming line and rod pinch diode. Spare trigger generators will also be included in this evaluation.

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TYPE Conference Poster YEAR 2019
DOIOSTIScopus

Three-Dimensional Model of the Saturn Accelerator Water Tri-Plate Transmission Line Connection to the Vacuum Insulator Stack

IEEE International Pulsed Power Conference

Struve, Kenneth; Ulmen, Ben

Calculation of the power flow from the 36 pulse forming lines to the vacuum region of Saturn has always been complicated by the three-dimensional structure of the rod and bottle connections to the vacuum insulator stack. Recently we have completed a 3-D calculation of the bottle configuration and found a large error in previous impedance estimates. We have used this calculation to determine impedance and to construct a 2-D model of each of the 36 bottles of each level of the insulator using the Transmission Line Matrix (TLM) technique. These TLM models are then used in a 2-D model for each of the three levels of the insulator. Each model starts at a measured forward-going pulse in the water tri-plate and ends at the Brehmstrahlung load at the center of the machine. Because of long transmission line lengths and short pulse lengths, each level can be considered independent of the others. A combination of the three models then represents a quasi-3-D model of the load region of the machine. The results of these calculations agree well with measurement and thereby provide confidence in simulation predictions for those areas where measurements are not possible. Details of the 3-D bottle calculation, the TLM model, and results of the load region simulations using this model are given.

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TYPE Conference Poster YEAR 2019
DOIOSTIScopus

Determining interface structures in vertically aligned nanocomposite films

APL Materials

Lu, Ping

Vertically aligned nanocomposite (VAN) films have self-assembled pillar-matrix nanostructures. Owing to their large area-to-volume ratios, interfaces in VAN films are expected to play key roles in inducing functional properties, but our understanding is hindered by limited knowledge about their structures. Motivated by the lack of definitive explanation for the experimentally found enhanced ionic conductivity in Sm-doped-CeO2/SrTiO3 VAN films, we determine the structure at vertical interfaces using random structure searching and explore how it can affect ionic conduction. Interatomic potentials are used to perform the initial searching, followed by first-principles calculations for refinement. Previously unknown structures are found, with lower energy than that of an optimized hand-built model. We find a strongly distorted oxygen sublattice which gives a complex landscape of vacancy energies. The cation lattice remains similar to the bulk phase, but has a localized strain field. The excess energy of the interface is similar to that of high angle grain boundaries in SrTiO3.

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TYPE Journal Article YEAR 2019
DOIOSTIScopus
Results 23201–23300 of 99,299
Results 23201–23300 of 99,299