On the equivalent ZIP parameter extraction of desktop computer cases and LCD monitors connected in parallel

Constant-impedance, constant-current and constant-power ZIP models of electrical loads arecommonly used in smart grid and residential load applications. Some of residential loads are ofnonlinear nature such as LCD monitors and computers. In this study, first, equivalent ZIP modelformulas of parallel-connected electrical loads are derived. Then, the ZIP models of an LCDmonitor, a computer case and the computer case and the monitor connected in parallel have beenobtained using experimental data and least-squares curve fitting method. Finally, the equivalentZIP model formulas are tested with the experimental data. It has been found that for the rectifiernonlinear loads with different ZIP parameters, the formulas do not give acceptable errors.Therefore, for rectifier nonlinear loads, the measurement-based approach for load modeling mustbe performed

Quantifying flexibility in EV charging as DR potential : analysis of two real-world data sets

The increasing adoption of electric vehicles (EVs) presents both challenges and opportunities for the power grid, especially for distribution system operators (DSOs). The demand represented by EVs can be significant, but on the other hand, sojourn times of EVs could be longer than the time required to charge their batteries to the desired level (e.g., to cover the next trip). The latter observation means that the electrical load from EVs is characterized by a certain level of flexibility, which could be exploited for example in demand response (DR) approaches (e.g., to balance generation from renewable energy sources). This paper analyzes two data sets, one from a charging-at-home field trial in Flanders (about 8.5k charging sessions) and another from a large-scale EV public charging pole deployment in The Netherlands (more than 1M sessions). We rigorously analyze the collected data and quantify aforementioned flexibility: (1) we characterize the EV charging behavior by clustering the arrival and departure time combinations, identifying three behaviors (charging near home, charging near work, and park to charge), (2) we fit statistical models for the sojourn time, and flexibility (i.e., non-charging idle time) for each type of observed behavior, and (3) quantify the the potential of DR exploitation as the maximal load that could be achieved by coordinating EV charging for a given time of day t, continuously until t vertical bar Delt

Determining the Ability of Distributed Generation to Relieve Stress Placed on the Grid by Electric Vehicle Charging

The increased penetration of Electric Vehicles (EVs) within the market presents the challenge of how to best integrate and charge these vehicles without causing undue stress to the grid. Public charging, in particular, fast DC charging technologies can cause stress to the grid, including voltage deviations, increased loading, and power losses, leading municipal utilities to hesitate on approval. Distributed Generation (DG) provides a generation source closer to the load, which can offset these stresses. These DG units can be coupled with the installation of charging stations, providing on-site electricity supply; multiple DGs can be used in situations where on-site DG is not feasible. While the goal of EVs is to obtain a more environmentally friendly way of transportation, the electricity used to charge them must have a quick ramp up speed and, thus, is generated by coal plants. However, DG, generating locally, from renewable sources and with cleaner technology, has great potential to relieve stress to the grid as an alternative to conventional power plants, while also helping reach the goal of “green” transportation. The purpose of this project is to determine DG’s capability of relieving EV induced stress onto the grid and to investigate strategies maximizing this benefit. Through the use of Ladder Iterative Power flow techniques, an accepted methodology, and simulations of a standard IEEE-37 bus system via MATLAB and GridLAB-D, DG units are proven to reduce voltage deviations and power losses and counter increased loading caused by EV charging stations in a way that is more beneficial that simply increasing the capacity generated on the generation side of the grid. Though many have studied the effects of both DG installation and EV charging station installation, no studies have paired these losses with EV charging station installation, DG’s ability to alleviate issues, or the correlation between decreased losses and a reduction in pollution. Pollution calculations based upon the power losses within various cases of a distribution system also prove that DG can reduce losses and other stresses, while also reducing the pollution caused by increasing the capacity of the grid to meet the demand of EV charging. Through optimizing generating capacity and location of various DG units, a helpful model is provided for utilities to more readily accept the increased demand for EV charging facilities by utilizing DG. These findings can help increase the adoption rate of EVs, thus reducing non-renewable fuel consumption, while also ensuring minimal stress to the electric grid and adding more renewable generation to the electric generation portfolio.No embargoAcademic Major: Electrical and Computer Engineerin

Parameter-independent battery control based on series and parallel impedance emulation

Appropriate voltage control is essential in order to extend the useful life of a battery. However, when universal chargers are used, the design of this control becomes more complicated, given the fact that the battery impedance value may vary considerably, depending not only on the operating point but also on the type, size and aging level of the battery. This paper firstly shows how the voltage regulation can become extremely variable or even unstable when the controller is designed according to the proposals in the literature. We then go on to propose the emulation of a series and parallel impedance with the battery, which is easy to implement and achieves a control that is completely independent of the battery connected. The simulation results obtained for batteries with resistances ranging from 10 mO to 1 O, show the problems with existing controls and confirm that the proposed control response is similar for all the possible range of battery resistances.Peer ReviewedPostprint (published version

The Combined Effect of Photovoltaic and Electric Vehicle Penetration on Conservation Voltage Reduction in Distribution System

Global conditions over the past dozen years have led to an expanded appetite for renewable energy sources: The diminishing fossil fuel supply, the political instability of countries producing these fossil fuels, the ever-more destructive effects of global warming, and the lowering of costs for renewable energy technologies have made countries around the world reconsider their sources of energy. The proliferation of photovoltaic (PV) systems especially has surged dramatically with the decreasing initial costs for installation, and increasing government support in the form of renewable energy portfolios, feed-in-tariffs, tax incentives, etc. Furthermore, electric vehicles (EV) are also becoming widespread due to recent advances in battery and electric drive technologies, and the desperate need to reduce air pollution in urban areas. Meanwhile, electric utilities are always making an effort to run their system more efficiently by encouraging the use of energy-efficient appliances and customer participation in demand-side management programs. In an attempt to further reduce load demand; many utilities regulate the voltage along their distribution feeders in a particular way that is referred to as conservation voltage reduction (CVR). The key principle of CVR operation is that the ANSI standard voltage band between 114 and 126 volts can be compressed via regulation to the lower half (114–120) instead of the upper half (120–126), producing measurable energy savings at low cost and without harm to consumer appliances. As the penetration of distributed PV and EV charging station increases, this can dramatically change the conventional demand profile as PV system act as negative loads during the daylight hours, and EVs significantly increase load demand during charging. Consequently, traditional means of controlling the voltage by capacitor switching and voltage regulators can be improved in this “smart” grid era by adding a fleet of enabling devices including the smart PV inverter functionalities, such as Volt/VAR control, and intelligent EV charging schemes. This thesis explores how better energy conservation is achieved by CVR in a modern distribution system with advanced distributed PV systems inverters and EV loads. Then it summarizes computer simulations that are conducted on the IEEE 37 and IEEE 123 node test feeders using OpenDSS interfaced with MATLAB

Behavioral characterization of electric vehicle charging loads in a distribution power grid through modeling of battery chargers

The plug-in electric vehicle (PEV) is a new atypical load in power systems. In future, PEV load will play a significant role in the distribution grids. This integrated load into the power grid may overload the system components, increase power losses, and affect the voltage profile in the distribution systems. Currently, the constant power load model is most commonly used for the modeling of the electric vehicle (EV) load that considers the EV loads as constant power elements without considering the voltage dependence of the EV charging system. EV load demand cannot be considered as a constant power due to the fact that modeling as a constant power load will not provide accurate information about the behavior of the charging system during the charging process. In this paper, an accurate model representing the realistic behavior of EV load is developed which is based on the ZIP load model with the ZIP parameters established through the realistic EV load data. The proposed model can be used to analyze the true behavior of the EV charger integrated to an electricity grid and determine the impacts of EV charging load on the grid. A realistic charging system was used to test and capture the EV load behavior and extract the coefficients of the EV ZIP load model, which have been verified using computer simulations and laboratory experiments. Additionally, a comparative study between the proposed ZIP load model and the constant power load model was carried out, and the results were verified with the practical EV load data. The results confirm that EV represented using constant power load will not provide the true reflection of the EV load behavior and the EV impacts on the power grid

Behavioral Characterization of Electric Vehicle Charging Loads in a Distribution Power Grid through Modeling of Battery Chargers

Plug-in Electric Vehicle (PEV) is a new atypical load in power systems. In future, PEV load will play a significant role in the distribution grids. This integrated load into the power grid may overload the system components, increase power losses and may violate system constraints. Currently, the most common method of Electric Vehicle (EV) modeling is to consider the EV loads as constant power elements without considering the voltage dependency of EV charging system during state of charges (SOC). EV load demand cannot be considered as a constant power, as modeling as a constant power load will not provide accurate information about the behavior of charging system during charging process. As several research projects on smart grids are now looking into realistic models representing the realistic behavior of an EV loads, this paper proposes a methodology for modeling of EV charger integrated to an electricity grid in order to understand the impacts of EV charging load. A charging system was designed to capture the EV load behavior and extract the coefficients of the EV ZIP load model. A comparative study was carried out with different types of load models. The results indicate that the assumptions of load demand as a constant power to analysis the effect of PEVs on power grid would not be effective in real time application of PEVs

Propuesta metodológica para la estimación de modelos de carga de vehículos eléctricos y sistemas de almacenamiento de energía

La presente tesis de maestría aborda la problemática del modelado de carga basado en mediciones, cuando se consideran nuevos elementos de carga, tales como vehículos eléctricos y sistemas de almacenamiento de energía, en sistemas de potencia modernos. De acuerdo a lo anterior, se plantea una metodología sistemática que permite definir los modelos que logran ajustarse al comportamiento de las cargas antes mencionadas, mediante la aplicación conjunta de técnicas meta heurísticas de optimización y la definición de indicadores del error, que forman parte de un proceso iterativo