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Dissertation Defense

Using Distributed Energy Resources to Improve Power System Stability and Voltage Unbalance

Mengqi Yao


The increasing penetration of renewables has driven power systems to operate closer to their stability boundaries and makes maintaining power quality in distribution systems more difficult. The objective of this work is to develop methods for controlling distributed energy resources to improve stability and voltage unbalance.

First, we develop a new demand response strategy to improve system stability.  We propose to improve voltage and small-signal stability by increasing and decreasing loads while keeping the total loading constant so as not to affect system frequency.  Multiple optimization problems and solution algorithms are developed for determining the optimal loading pattern to improve different voltage or small-signal stability margins. Second, we apply Steinmetz design to control the reactive power injections of distributed solar photovoltaic systems to mitigate voltage unbalance. The benefit of using Steinmetz design is that our controllers do not need to solve any optimization problem so the computation is fast. To apply the Steinmetz controller to real systems, we propose different approaches to cope with inverter reactive power limits and communication delays. We also propose strategies to reduce the adverse of the Steinmetz controller on the feeder voltage profile and unbalance at noncritical nodes.

Chair: Professor Johanna Mathieu

Remote Access: https://bluejeans.com/676970619