abstract: This dissertation develops advanced controls for distributed energy systems and evaluates performance on technical and economic benefits. Microgrids and thermal systems are of primary focus with applications shown for residential, commercial, and military applications that have differing equipment, rate structures, and objectives. Controls development for residential energy heating and cooling systems implement adaptive precooling strategies and thermal energy storage, with comparisons made of each approach separately and then together with precooling and thermal energy storage. Case studies show on-peak demand and annual energy related expenses can be reduced by up to 75.6% and 23.5%, respectively, for a Building America B10 Benchmark home in Phoenix Arizona, Los Angeles California, and Kona Hawaii. Microgrids for commercial applications follow after with increased complexity. Three control methods are developed and compared including a baseline logic-based control, model predictive control, and model predictive control with ancillary service control algorithms. Case studies show that a microgrid consisting of 326 kW solar PV, 634 kW/ 634 kWh battery, and a 350 kW diesel generator can reduce on-peak demand and annual energy related expenses by 82.2% and 44.1%, respectively. Findings also show that employing a model predictive control algorithm with ancillary services can reduce operating expenses by 23.5% when compared to a logic-based algorithm. Microgrid evaluation continues with an investigation of off-grid operation and resilience for military applications. A statistical model is developed to evaluate the survivability (i.e. probability to meet critical load during an islanding event) to serve critical load out to 7 days of grid outage. Case studies compare the resilience of a generator-only microgrid consisting of 5,250 kW in generators and hybrid microgrid consisting of 2,250 kW generators, 3,450 kW / 13,800 kWh storage, and 16,479 kW solar photovoltaics. Findings show that the hybrid microgrid improves survivability by 10.0% and decreases fuel consumption by 47.8% over a 168-hour islanding event when compared to a generator-only microgrid under nominal conditions. Findings in this dissertation can increase the adoption of reliable, low cost, and low carbon distributed energy systems by improving the operational capabilities and economic benefits to a variety of customers and utilities. / Dissertation/Thesis / Doctoral Dissertation Engineering 2019

abstract: In recent years, many school districts, community colleges, and universities in California have implemented energy management-as-a-service (EMaaS). The purpose of this study was to analyzes how EMaaS has been realized in California schools, including how performance expectations and service guarantees have been met, how value is created and captured, and which trends are emerging in the pay-for-performance models. This study used a qualitative research design to identify patterns in the collected data and allow theories to be drawn from the emergent categories and themes. Ten in-depth interviews were conducted with a diverse pool of facility managers, energy practitioners, superintendents, and associate superintendents working with EMaaS. Four themes emerged (1) peak shaving overperformance, (2) low risk/reward, (3) performance exactly as expected, and (4) hope in future flexibility. This study reveals medium to high levels of performance satisfaction from the customers of cloud-enabled and battery-based EMaaS in California schools. Value has been captured primarily through peak shaving and intelligent bill management. Large campuses with higher peaks are especially good at delivering energy savings, and in some instances without pairing batteries and solar. Where demand response participation is permitted by the utility companies, the quality of demand response performance is mixed, with performance being exactly as expected to slightly less than expected. The EMaaS business model is positioned to help California schools implement and achieve many of their future sustainability goals in a cost-effective way. / Dissertation/Thesis / Masters Thesis Construction Management 2020

The size and composition of the Swedish electricity generation are changing. This, in combination with new legal requirements from regulatory entities including the EU Directive 2019/944, creates several challenges for the design of the future system. Among other things, the directive suggests that flexibility solutions are to be integrated into grids to increase the degree of utilization and avoid congestions, when socio-economically profitable. This thesis evaluates what this could mean in a Swedish context, in combination with providing a basic understanding of the contradictions that can arise between a desired efficient grid use in an energy system that goes towards more distributed and intermittent energy generation sources. The work is carried out in collaboration with Vattenfall Eldistribution AB, focusing on the geographical area of Uppsala and Stockholm, the Swedish region hit hardest by local congestions. The work assumes that the economic value of a flexibility solution is at most equivalent to the cost of a conventional new construction aimed at capacity strengthening, or the Value of Lost Load (VoLL). The report’s most important deliverable is a model based on this view. The model is used to evaluate the economic value of flexibility per kWh, in three regional grid construction projects within the mentioned region.  The results show that there is a great potential for using flexibility resources to increase utilization in grids and also to optimize the costs that society pays for this infrastructure by such methods. However, the work concludes that the usage of flexible technologies primarily is to adapt electric consumption with intermittent energy generation, rather than being used to solve local grid capacity shortages.

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Interconnection of DERs into the transmission lines is starting to take a substantial share of the total power capacity. Although the largest share of power generation attributes to coal and gas power plants, renewable energy is gradually increasing. However, in the past, the size of DERs was relatively smaller, and rooftop PV was the dominant renewable energy source. As a result, the studies for interconnection focused on those rooftop PVs on the distribution side. Since the scenario is slowly changing as more utilities increase the share of clean energy by building large-scale solar farms and wind farms, it is necessary to study the effect of those DERs in the transmission system. Among the various issues, this work focuses on the impact on a transmission system's voltage stability. When the voltage stability at a point in the system is compromised, it can affect the entire power system's overall security, quality, and reliability. Therefore, this work aims to assess the system's stress due to increased loading conditions and increased growth of DERs integration. A steady-state voltage stability index is used to generate a heat-map that identifies the areas where the system can go unstable in events like the loss of the renewable generation under a bus. The steady-state simulation is performed on the IEEE 14 bus system in Distributed Engineering Workstation (DEW) to find the system's weak links using the stability heat-map. DERs are added to the corresponding weak buses, and the improvement in the stability margin for various penetration levels are studied. The results obtained from the steady-state analysis are also verified using the dynamic simulation of the model using OpenModelica. / Master of Science / Transmission networks are going through some of the fundamental changes in how they are planned and operated as more and more renewable energy sources are connected to the grid. Unlike the traditional setup where the transmission line transfers bulk power from a large generator to the load center at a different location, the advent of renewable energy resources enables the power to be generated in distributed form. It allows electrical power to be generated closer to the demand. In the long run, the transmission system's stress reduces as a significant portion of demand is supplied locally. Thus, the distributed energy resources (DERs) in the power grid have the potential for substantial economic and environmental benefits. However, it can also bring about a range of challenges to the power system. Among the various issues, this work focuses on the effects on a transmission system's voltage stability. When the voltage stability at a point in the system is compromised, it can affect the entire power system. Therefore, this work aims to assess the stress on the system due to increased loading conditions and increased growth of DERs integration, utilizing a voltage stability index to identify the areas where the system can go unstable in events like the loss of renewable generation under a bus. The steady-state simulation is performed on the IEEE 14 bus system to find the weak links in the system where DERs can improve the system's stability. The results obtained from the steady-state analysis are verified using the dynamic simulation of the model.

Power systems constitute a pillar of the critical infrastructure and, as a result, their cybersecurity is paramount. Traditional power system architectures are moving from their original centralized nature to a distributed paradigm. This transition has been propelled by the rapid penetration of distributed energy resources (DERs) such as rooftop solar panels, battery storage, etc. However, with the introduction of new DER devices, technologies, and operation models, the threat surface of power systems is inadvertently expanding. This dissertation provides a comprehensive overview of the cybersecurity landscape of DER-enabled power systems outlining potential attack entry points, system vulnerabilities, and the corresponding cyberattack impacts. Cyber-physical energy systems (CPES) testbeds are crucial tools to study power systems and perform vulnerability analyses, test security defenses, and evaluate the impact of cyberattacks in a controlled manner without impacting the actual electric grid. This work also attempts to provide bottom-up security solutions to secure power systems from their lowest abstraction layer, i.e., hardware. Specifically, custom-built hardware performance counters (HPCs) are proposed for the detection of malicious firmware, e.g., malware, within DER inverter controllers. The experimental results prove that HPCs are an effective host-based defense and can accurately identify malicious firmware with minimum performance overheads. Also, methodologies to secure communication protocols and ensure the nominal operation of DER devices using physics-informed schemes are presented. First, DERauth, a battery-based secure authentication primitive that can be used to enhance the security of DER communication, is proposed and evaluated in a CPES testbed. Then, a physics-based attack detection scheme that leverages system measurements to construct models of autonomous DER agents is presented. These measurement-based models are then used to discern between nominal and malicious DER behavior. The dissertation concludes by discussing how the proposed defense mechanisms can be used synergistically in an automated framework for grid islanding to improve power system security and resilience, before it provides prospective directions for future research.

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As inverter-based distributed energy resources (DERs) such as photovoltaic (PV) and battery energy storage system (BESS) penetrate within the distribution system. New challenges regarding how to utilize these devices to improve power quality arises. Before, PV systems were required to disconnect from the grid during a large disturbance, but now smart inverters are required to have dynamically controlled functions that allows them to remain connected to the grid. Monitoring power flow at the point of common coupling is one of the many functions the controller should perform. Smart inverters can inject active power to pick up critical load or inject reactive power to regulate voltage within the electric grid. In this context, this thesis focuses on a high level and local control design that incorporates DERs. Different controllers are implemented to stabilize the microgrid in an Islanding and resiliency mode. The microgrid can be used as a resiliency source when the distribution is unavailable. An average model in the D-Q frame is calculated to analyze the inherent dynamics of the current controller for the point of common coupling (PCC). The space vector approach is applied to design the voltage and frequency controller. Secondly, using inverters for Volt/VAR control (VVC) can provide a faster response for voltage regulation than traditional voltage regulation devices. Another objective of this research is to demonstrate how smart inverters and capacitor banks in the system can be used to eliminate the voltage deviation. A mixed-integer quadratic problem (MIQP) is formulated to determine the amount of reactive power that should be injected or absorbed at the appropriate nodes by inverter. The Big M method is used to address the nonconvex problem. This contribution can be used by distribution operators to minimize the voltage deviation in the system. / Master of Science / Reliable power supply from the electric grid is an essential part of modern life. This critical infrastructure can be vulnerable to cascading failures or natural disasters. A solution to improve power systems resilience can be through microgrids. A microgrid is a small network of interconnected loads and distributed energy resources (DERs) such as microturbines, wind power, solar power, or traditional internal combustion engines. A microgrid can operate being connected or disconnected from the grid. This research emphases on the potentially use of a Microgrid as a resiliency source during grid restoration to pick up critical load. In this research, controllers are designed to pick up critical loads (i.e hospitals, street lights and military bases) from the distribution system in case the electric grid is unavailable. This case study includes the design of a Microgrid and it is being tested for its feasibility in an actual integration with the electric grid. Once the grid is restored the synchronization between the microgrid and electric must be conducted. Synchronization is a crucial task. An abnormal synchronization can cause a disturbance in the system, damage equipment, and overall lead to additional system outages. This thesis develops various controllers to conduct proper synchronization. Interconnecting inverter-based distributed energy resources (DERs) such as photovoltaic and battery storage within the distribution system can use the electronic devices to improve power quality. This research focuses on using these devices to improve the voltage profile within the distribution system and the frequency within the Microgrid.

Residential solar Photovoltaic (PV) installations are increasing at a very high pace in the United States. In 2017 there are approximately one million residential solar PV installations in the US. A significant share of these installations are downstream of distribution transformers and thus connected to the secondary. To precisely analyze voltage variations induced by PV systems into distribution systems, accurate models of load and PV systems connected to the secondary side of distribution transformers are required. In the work here we consider two secondary circuit modeling approaches, simple secondary and detailed secondary models. In simple secondary models all loads and all PV generators below a distribution transformer are modeled as an aggregate load and an aggregate PV generator. In the detailed secondary models all loads and PV systems below the distribution transformers are modeled individually and secondary conductors and service drops are also modeled. Using a cloud motion simulator, it is observed that employing the simple secondary models can lead to inaccurate and conservative results. Moreover, the locations with the greatest voltage changes are different in the two modeling approaches. This paper highlights the importance of utilizing detailed secondary models over simple secondary models in analyzing PV generation. / Master of Science / Power system planners and operators rely on computer-based modeling and analysis of the electric grid to ensure that electricity is delivered to consumers in a reliable manner. The current modeling is done either to simulate the high voltage transmission networks, or the primary distribution networks. Till now these modeling approaches have worked well as the electricity flow in the electric grid is largely unidirectional, i.e. power flows from the transmission network to the distribution network. Neglecting the secondary distribution network topology in such a structure of the electric grid does not introduce significant calculation errors. However, the rapid growth of residential solar PV based distributed generation over the last few years, which is expected to continue into the foreseeable future, has motivated the need to rethink this modeling and analysis paradigm. As the penetration levels of distributed generation increase, there will be bi-directional flow of electricity between the transmission and distribution networks. Accurate analysis of such a decentralized electric grid cannot be performed if secondary distribution network topology is neglected in the models. So, to precisely analyze voltage variations induced by PV systems into distribution systems, accurate models of load and PV systems connected to the secondary side of distribution transformers are required. This thesis highlights the importance of using detailed models of secondary distribution.