Event Location


Dr. Johanna Mathieu

Assistant Professor

University of Michigan

Electrical and Computer Engineering

Thursday, October 11, 2018

3:00 p.m. - 4:00 p.m.

2250 EB

“An Optimal Power Flow Approach to Improve Power System Voltage Stability Using Demand Response”


The increasing penetration of renewables has driven power systems to operate closer to their stability boundaries, increasing the risk of instability. We propose a multiperiod optimal power flow approach that uses demand responsive loads to improve steady-state voltage stability, which is measured by the smallest singular value (SSV) of the power flow Jacobian matrix. In contrast to past work that employs load shedding to improve stability, our approach improves the SSV by decreasing and increasing individual loads while keeping the total loading constant to avoid fluctuation of the system frequency. Additionally, an energy payback period maintains the total energy consumption of each load at its nominal value. The objective function balances SSV improvements against generation costs in the energy payback period. We develop an iterative linear programming algorithm using singular value sensitivities to obtain an AC-feasible solution. We demonstrate its performance on two IEEE test systems. The results show that demand response actions can improve static voltage stability, in some cases more cost-effectively than generation actions. We also compare our algorithm's performance to that of an iterative nonlinear programming algorithm from the literature. We find that our approach is approximately 6 times faster when applied to the IEEE 9-bus system, allowing us to demonstrate its performance on the IEEE 118-bus system. This work is in collaboration with Mengqi Yao (UM) and Daniel Molzahn (Argonne National Laboratory).


Johanna Mathieu is an assistant professor in the Department of Electrical Engineering and Computer Science at the University of Michigan, Ann Arbor. She received her PhD in mechanical engineering from the University of California, Berkeley in 2012 and was a postdoctoral researcher in the Power Systems Laboratory at ETH Zurich, Switzerland from 2012 to 2103 before starting at UM in January 2014. Her research focuses on ways to reduce the environmental impact, cost, and inefficiency of electric power systems via new operational and control strategies. She is particularly interested in developing new methods to actively engage distributed flexible resources such as energy storage, electric loads, and distributed renewable resources in power system operation.

Faculty Host:  Dr. Joydeep Mitra (

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