Dissertation Announcement for Roshan Sharma — 02/24/2021 at 10:00 AM

January 28, 2021

Dear Faculty, Graduate and Undergraduate Students,

You are cordially invited to my Ph.D. dissertation defense.

Dissertation Title: Applications of Battery Energy Storage to Mitigate Disturbances and Uncertainties in Energy Systems with High Penetration of Renewable Resources
Date and time: Wednesday, February 24, 2021, 10:00 AM
Venue: Simrall-228 (Conference Room)
Candidate: Roshan Sharma
Degree: Doctor of Philosophy, Electrical and Computer Engineering


Dr. Masoud Karimi-Ghartemani
Associate Professor of Electrical and Computer Engineering
(Major Professor)

Dr. Randolph F. Follett
Associate Professor of Electrical and Computer Engineering
(Committee Member)

Dr. Yong Fu
Professor of Electrical and Computer Engineering
(Committee Member)

Dr. Seungdeog Choi
Associate Professor of Electrical and Computer Engineering
(Committee Member)


Solar photovoltaic (PV) is the fastest growing energy resource. The price of energy generation from residential PV has dropped from $0.50 to $0.10 per kWh in the past decade. One challenge with this resource is that the amount of power available depends on the solar irradiance and temperature at the PV site. As a result, the abrupt changes in solar irradiance due to fast moving clouds cause disturbances to the hosting electricity network and lead to voltage and frequency oscillations. The impact is more severe in a weak grid with high penetration of such resources. Evolving grid interconnection standards are imposing requirements to limit the impact of these disturbances on the grid.

The battery energy storage (BES) technology has also experienced a significant price drop (e.g., from $1100 to $156 per kWh for lithium-ion batteries) in the past decade. As a result, the complementary PV+BES solutions have been considered. A sufficient BES capacity equipped with appropriate control systems can respond to both abrupt and long-term PV power variations. Properly formulating the problem and developing efficient control systems is crucial to achieving the best performance with the least size of BES. This defines the scope and objective of the research presented in this dissertation.

This research develops two distinct BES operating solutions. In the first one, the BES is co-located with the PV and connects to its dc output terminals, i.e. the dc-coupling scenario. The BES controller ensures that the PV+BES system exhibits a desirable power ramp rate set by the user. The proposed BES does not alter the PV converter or its controls. Neither does it alter the inverter settings that interfaces to the ac grid.

In the second solution, the BES is not co-located with the PV. It detects the PV disturbances from their signatures on its locally measured signals and takes the proper action to respond. An approach based on capacitor emulation combined with droop mechanism is developed and optimally designed to provide dynamic and static voltage support. The BES of this solution can respond to more than one PV systems. Moreover, it responds to disturbances originated from non-PV sources, such as load disturbances.

The dissertation presents the detailed modeling and control of the BES system. Optimal control techniques are developed to ensure robust and instantaneous responses. For the simulation study, the proposed BES systems are implemented in a hybrid dc/ac study system and the effect of the solutions on both dc and ac subsystems is investigated. The real-time results obtained by implementing the proposed controllers on laboratory scale hardware prototypes are also presented.

Thank you,

Roshan Sharma