Graduate Seminar: Amar Ramapuram

When

March 21, 2018    
1:10 pm - 2:00 pm

Where

3043 ECpE Building Addition
Coover Hall, Ames, Iowa, 50011

Event Type

Speaker: Amar Ramapuram, ECpE Graduate Student

Advisor: Venkataramana Ajjarapu

Title: Online Monitoring & Mitigation of Voltage Instability using Synchrophasors

Abstract: With the increasing need for economic operation of the power grid, the system is being operated closer to their limits and so there is a need to address the increasing risk of voltage instability in the power grid. In this work, we have proposed methods that can monitor and mitigate the both short-term (in this case FIDVR) and long-term voltage instability by utilizing the increasing penetration of Phasor Measurement Units in the power grid and utilizing smart thermostats for control. In the first part of our work, we look at the FIDVR phenomenon where the voltage recovery is delayed due to the stalling of 1-phase motors. We propose to use the susceptance of the load to monitor FIDVR and show that the sudden rise in susceptance indicates that an FIDVR event has taken place at the substation and the rise in the susceptance provides the PMU with a reasonable estimate of the proportion of the load that is stalled. This information can be used to estimate the time to recovery and also to determine the proportion of the air conditioners to disconnect for recovering within a set amount of time. To verify that this method indeed works as expected, multiple simulations in PSSE on the IEEE 162 Bus system are done with the results showing the expected behavior. To test the real-time nature of the method, the FIDVR phenomenon is simulated in a real-time test-bed and is shown to be able to determine the control amount in an online manner. In the second part of our work, we look at the long term voltage stability phenomenon. To improve the understanding of the Thevenin index for long term voltage stability, we have derived an analytical relation between the local index and the system Jacobain, and thus we provided a mathematical justification for the use of the local index as an indicator for global stability. Exploiting this relation, we define a sensitivity based index and have verified that this index at the control center can validate the local Thevenin index on large systems. This sensitivity based index can be modified to account for various what-if scenarios (reactive limit reached, line outage, etc.) in an intuitive and computationally efficient manner. This enables the operator to assess the true state of the system with the ability by considering the generator reactive limits and to also predict the limit induced bifurcations which is not possible using present Thevenin indices.

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