Increasing penetration of stochastic photovoltaic (PV) generation into the electric power system poses significant challenges to system operators. In the thesis, we evaluate the spatial and temporal correlations of stochastic PV generation at multiple sites. Given the unique spatial and temporal correlation of PV generation, an optimal data-driven forecast model for short-term PV power is proposed. This model leverages both spatial and temporal correlations among neighboring solar sites, and is shown to have improved performance compared with conventional persistent model. The tradeoff between communication cost and improved forecast quality is studied using realistic data sets collected from California and Colorado. n IEEE 14 bus system test case is used to quantify the value of improved forecast quality through the reduction of system dispatch cost. The Modified spatio-temporal forecast model which has the least forecast PV overestimate percentage shows the best performance in the dispatch cost reduction.

abstract: This thesis examines using thermal energy storage as a demand side management tool for air-conditioning loads with the goal of increasing photovoltaic penetration. It uses Arizona State University (ASU) as a case study. The analysis is completed with a modeling approach using typical meteorological year (TMY) data, along with ASU’s historical load data. Sustainability, greenhouse gas emissions, carbon neutrality, and photovoltaic (PV) penetration are all considered along with potential economic impacts. By extrapolating the air-conditioning load profile from the existing data sets, it can be ensured that cooling demands can be met at all times under the new management method. Using this cooling demand data, it is possible to determine how much energy is required to meet these needs. Then, modeling the PV arrays, the thermal energy storage (TES), and the chillers, the maximum PV penetration in the future state can be determined. Using this approach, it has been determined that ASU can increase their solar PV resources by a factor of 3.460, which would amount to a PV penetration of approximately 48%. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2016

The variable nature of photovoltaic (PV) generation can cause voltage fluctuations in power distribution systems. Feedback control can be used to minimize the voltage fluctuations. This thesis presents the results obtained from comparing the control performance of two types of PV generation feedback control, namely Volt-VAR control and constant power factor control. A three minute PV generation transient is used to evaluate controller performance, where the transient data used originated from one second measurements taken on an actual PV generator. Using the three minute transient, a set of parametric studies are performed on both feedback control strategies. The performance of the control strategies are compared as to voltage control on the distribution feeder and also to the effect that the control may have on transmission system voltage. In considering transmission system voltage, the reactive power drawn from the substation during the transient is evaluated. Simulation results suggest that the choice of control to be implemented should be based on both transmission and distribution system operational concerns. / Master of Science

Time-series power flow simulations are consecutive power flow calculations on each time step of a set of load and generation profiles that represent the time horizon under which a network needs to be analyzed. These simulations are one of the fundamental tools to carry out cost-benefit analyses of grid planing and operation strategies in the presence of distributed energy resources, unfortunately, their execution time is quite substantial. In the specific case of cost-benefit analyses the execution time of time-series power flow simulations can easily become excessive, as typical time horizons are in the order of a year and different scenarios need to be compared, which results in time-series simulations that require a rather large number of individual power flow calculations. It is often the case that only a set of aggregated simulation outputs is required for assessing grid operation costs, examples of which are total network losses, power exchange through MV/LV substation transformers, and total power provision from PV generators. Exploring alternatives to running time-series power flow simulations with complete input data that can produce approximations of the required results with a level of accuracy that is suitable for cost-benefit analyses but that require less time to compute can thus be beneficial. This thesis explores and compares different methods for shortening time-series power flow simulations based on reducing the amount of input data and thus the required number of individual power flow calculations, and focuses its attention on two of them: one consists in reducing the time resolution of the input profiles through downsampling while the other consists in finding similar time steps in the input profiles through vector quantization and simulating them only once. The results show that considerable execution time reductions and sufficiently accurate results can be obtained with both methods, but vector quantization requires much less data to produce the same level of accuracy as downsampling. Vector quantization delivers a far superior trade-off between data reduction, time savings, and accuracy when the simulations consider voltage control or when more than one simulation with the same input data is required, as in such cases the data reduction process can be carried out only once. One disadvantage of this method is that it does not reproduce peak values in the result profiles with accuracy, which is due to the way downsampling disregards certain time steps in the input profiles and to the averaging effect vector quantization has on the them. This disadvantage makes the simulations shortened through these methods less precise, for example, for detecting voltage violations.

A microgrid is a subnetwork of power system that consists of a group of distributed energy sources and loads. It is designed to integrate distributed generation, loads, energy storage devices, converters, and monitoring and protection devices. Generally, a successful microgrid could run both in island mode (off-grid) and in grid-connected mode (on-grid), being able to convert between two modes at any time. With continuous development of the power system, distributed renewable generation unit accounts for an increasing proportion, since microgrid could effectively connect these generation units to the main grid, thereby improving the energy efficiency and the energy structure. Microgrid is increasingly playing an important role in the power system. This thesis focuses on reducing the cost of microgrids through economic operation, including both static and dynamic economic operations. Three cases are tested based on these two methods. Also, each case will include four situations including one without ESS and three situations with 2MWh ESS, 3MWh ESS, 4MWh ESS, respectively.

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. Abrupt changes in solar irradiance can 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 impacts of these disturbances on the grid. 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. Therefore, complementary PV+BES solutions are increasingly considered. A BES of sufficient capacity equipped with appropriate controls can respond to both abrupt and long-term PV power variations. Properly formulating the problem and developing efficient control systems is crucial. These define the scope and objective of this research. This research develops two BES solutions. In the first one, the BES is co-located with the PV and connects to its dc output terminals. The BES controller ensures that the PV+BES system exhibits a desirable power ramp rate set by the user. In the second solution, the BES is not co-located with the PV. It detects the disturbances from their signatures on its locally measured signals and takes proper actions. An approach based on capacitor emulation combined with a droop mechanism is developed and optimally designed to provide dynamic and static supports. The BES can respond to the disturbances from more than one PV system and non-PV sources, such as load disturbances. The dissertation presents detailed modeling and control of the BES system. Optimal control techniques are developed to ensure robust and fast responses. For the simulation study, the proposed BES systems are implemented in a hybrid dc/ac study system and the effect on both dc and ac subsystems are investigated. The real-time results obtained by implementing the proposed controllers on laboratory-scale hardware prototypes are also presented.