Browsing by Author "Vasquez, Diana C."

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    ANGLE STABILITY PREDICTIONS
    (Office of the Vice Chancellor for Research, 2012-04-13) Nilchi, Maryam N.; Longbottom, Daniel W.; Vasquez, Diana C.; Rovnyak, Steven M.
    The variance of phase angle changes over the network is a good display of total stress and angle stability. The integral square generator angle (ISGA) changes had been recommended earlier to evaluate how severe the stable and unstable transient contingencies in simulation are. This project offers its addition to bus voltage angles (ISBA) which could be measured with synchronized phasor measurement units (PMUs) over a wide-ranging area. By restructuring continuous paths that go outside the boundary be-tween positive and negative 180 degrees before calculating the ISBA, the cutoff of bus angles at positive and negative 180 degrees is recovered. The project also directs the matter of obtaining the best angle stability index as the threshold between stable and unstable classes with use of simulation da-ta. This issue becomes more difficult by the fact that large databases might include a few events for which loss of synchronism happens toward the end of the simulation sequence.
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    EXPANSION OF DYNAMIC SIMULATION MODEL FOR A DISTRIBUTED GENERATOR UNINTENTIONAL ISLANDING DETECTION SCHEME
    (2010) Vasquez, Diana C.; Rovnyak, Steven; Rizkalla, Maher; Chen, Yaobin
    The interconnection of distributed resources requires specific voltage regulation, monitoring, protective relaying, power quality, and islanding detection. For this reason IEEE established standard IEEE 1547 that ensures the compliance with such requirements and it will help formulate technical specifications for grid interconnection with Distributed Generator (DG) resources. In search of meeting the IEEE 1547 standard requirement of detecting unintentional islanded operation, there has been ongoing research to develop anti-islanding methods that can detect the different changes that can occur when the grid is disconnected. A team of Electrical Engineering faculty at Indiana University Purdue University Indianapolis has worked previously on testing a DG unintentional Islanding Detection Scheme. This scheme uses an active anti-islanding method in which a small 1 Hz perturbation signal is added into the DG system and it helps detect when the grid is disconnected. The scheme uses the premise that a frequency deviation caused by perturbation to the system is smaller when the grid is connected than when it is in an island. In an initial dynamic simulation model for the islanding detection scheme, a two-machine microgrid system is used to explore frequency and voltage responses when the grid is disconnected. In this thesis, the two-machine microgrid is expanded to a ten-machine system so it can be shown that the frequency deviation caused by a perturbation signal is much smaller when the grid is connected even for a larger DG network. The 1 Hz component of the DG electrical frequency in a multiple machine microgrid system is also calculated in this thesis. This project was conducted in different stages. First, it was necessary to calculate the steady state power flow and electric power of a three-machine system and update the two-machine MATLAB program with the necessary changes. After making the changes, it was necessary to simulate the system and adjust the inertia of the machine that represents the grid to ensure that the simulation output was close in magnitude to previous testing results. When the three-machine system was successfully generated, a brand new program was created so a multiple machine system could be simulated. Then the multiple machine program was used to simulate and experiment with up to a ten-machine system. Finally a program to calculate the 1 Hz component of the DG electrical frequency was generated and used to show that the magnitude squared of the 1 Hz component is inversely proportional to the number of machines connected to the system. These last findings will later help set the threshold for islanding detection appropriately for different numbers of DG.