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Congratulations to Yao Xu

Yao Xu, a PhD Student in CURENT under Professor Fangxing (Fran) Li, defended her dissertation titled “Adaptive Control for Power System Voltage and Frequency Regulation” on November 4th.  Faculty committee members were Dr. Leon Tolbert, Dr. Kevin Tomsovic and Dr. Mingzhou Jin (ISE). Yao received her BS and MS from Changsha University of Science & Technology, China. In addition, Yao recieved the UT Chancellor's Citation Award in Extraordinary Professional Practice on April 23rd of this year.   

Her abstract is below.  

Title: Adaptive control for power system voltage and frequency regulation

Abstract:
Variable and uncertain wind power output introduces new challenges to power system voltage and frequency stability. To ensure the safe and stable operation of a power system, the control for voltage and frequency regulation is studied in this work.

Static Synchronous Compensator (STATCOM) can provide fast and efficient reactive power support to regulate power system voltage. In the literature, various STATCOM control methods have been discussed including many applications of proportional–integral (PI) controllers. However, these previous works obtain the PI gains via a trial and error approach or extensive studies with a tradeoff between performance and applicability. Hence, control parameters for the optimal performance at a given operating point may not be effective at a different operating point. To improve, this work proposes a new control model based on adaptive PI control, which can self-adjust the control gains during disturbance such that the performance always matches a desired response, regardless of the change of operating condition. Moreover, a new method, called the flatness-based adaptive control (FBAC), for STATCOM voltage regulation is also proposed. By this method, the nonlinear STATCOM variables can be easily and exactly controlled by controlling flat output without solving differential equations. Further, the control gains can be dynamically tuned to satisfy the time-varying operation condition requirement.
Besides the voltage control, frequency control is also discussed in this work. Automatic generation control (AGC) is used to regulate power system frequency. Various control methods have been discussed in order to design control gains and obtain a good frequency response performance. However, the control gains obtained by existing control methods are usually fixed and designed for specific scenarios in the studied power system. The desired response may not be obtained when variable wind power is integrated into power systems. To address these challenges, an adaptive gain-tuning control (AGTC) for AGC with effects of wind resources is presented in this work. By AGTC, the PI control parameters can be automatically and dynamically calculated during the disturbance to make AGC consistently provide excellent performance under variable wind power.