PROGRAM | Electrical & Computer Engineering

By: Thunchanok Kaewnukultorn Chair: Steven Hegedus

ABSTRACT

The penetration of renewable energy systems into the centralized electric grid has been significantly increasing during the last decade. Due to technological advancements in photovoltaics (PV) that allow manufacturer costs to be relatively lower with shorter overall payback period, PV is seen to be the most ever-growing renewable energy resource and a variety of innovative approaches have been introduced to utility-scale systems to promote higher deployment of distributed energy resources (DERs). A decrease in technology cost, strong government incentives, and technological advancements such as higher PV module efficiency and innovative fabrication technologies have resulted in an exponential growth in worldwide PV installed capacity. One of the most promising PV technologies is bifacial PV modules which allow light reflecting from the ground below the modules to be absorbed at the rear surface and converted into electrical energy. According to the International Roadmap of Photovoltaic (ITRPV), the global installations of bifacial PV modules have been increasing beyond expectation and will reach 60% of total global PV integration by 2029. With an appropriate system configuration, bifacial modules can provide substantial benefits and outweigh additional costs. Although solar electricity can deliver clean and cost-effective energy, the intermittent nature of solar energy can lead to challenges with electric grid stability as the percentage of solar increases. High penetration of PV generation can cause over-voltages due to active power injection when load demand is low. Other problems associated with large fractions of PV in distribution networks include negative impacts on protection, power flow, and frequency stability.

Smart inverter-based resources (IBRs) and battery energy storage systems (BESS) have been introduced to mitigate the impact of such high penetration of renewable energy, as well as to support grid functionality by improving voltage and frequency stability and serving residential loads during grid failures. Network communications for the smart devices in the power grid offer substantial benefits to users and system operators by enabling real-time monitoring, control, and dispatch remotely. Nevertheless, synchronization control protocols utilized by smart inverters exchange local information with edge devices in the same network, causing them to be vulnerable to infiltration and cyberattacks. To support and stabilize the utility grid, modern smart inverters are embedded with modes of grid-supporting operation where the control settings are commanded by a centralized grid controller, rendering these functions vulnerable to cyberattacks as their smart functionalities provide direct access to their internal control settings and external data. Without an awareness of malicious attacks from the control side, the grid system could continuously respond to false inputs and the adversaries can generate system abnormalities which lead to both technical and economic disadvantages.  To deploy smart PV inverters to the field, main performance and grid-supporting control functionalities are crucial to be evaluated with the IEEE Standard for Interconnection and Interoperability of Distributed Energy Resources with Associated Electric Power Systems Interfaces (IEEE 1547-2018). Additionally, to ensure the security of the electric grid, the ability to withstand cyberattacks on the smart inverters needs to be assessed to have a better long-term preparation for more DER integration. The dissertation will be divided into two focuses: validation and implementation of smart inverter grid controls and analysis of the bifacial module’s performance.

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