Investigation on the development of a sliding mode controller for constant power loads in microgrids

Abstract: To implement renewable energy resources, microgrid systems have been adopted and developed into the technology of choice to assure mass electrification in the next decade. Microgrid systems have a number of advantages over conventional utility grid systems, however, they face severe instability issues due to the continually increasing constant power loads. To improve the stability of the entire system, the load side compensation technique is chosen because of its robustness and cost effectiveness. In this particular occasion, a sliding mode controller is developed for a microgrid system in the presence of constant power loads to assure a certain control objective of keeping the output voltage constant at 480 V. After that, a robustness analysis of the sliding mode controller against parametric uncertainties was performed and the sliding mode controller’s robustness against parametric uncertainties, frequency variations, and additive white Gaussian noise (AWGN) are presented. Later, the performance of the proportional integral derivative (PID) and sliding mode controller are compared in the case of nonlinearity, parameter uncertainties, and noise rejection to justify the selection of the sliding mode controller over the PID controller. All the necessary calculations are reckoned mathematically and results are verified in a virtual platform such as MATLAB/Simulink with a positive outcome

A Comprehensive Review on Constant Power Loads Compensation Techniques

Microgrid, because of its advantages over conventional utility grids, is a prudent approach to implement renewable resource-based electricity generation. Despite its advantages, microgrid has to operate with a significant proportion of constant power loads that exhibit negative incremental impedance and thus cause serious instability in the system. In this paper, a comprehensive review is presented on accomplished research work on stabilization of dc and ac microgrid. After reviewing these, microgrid system stabilization techniques are classified with required discussions. As found out in this paper, the stabilization techniques can basically be classified as compensation done: 1) at feeder side; 2) by adding intermediate circuitry; and 3) at load side. Finally, after analyzing the merits and drawbacks of each generalized technique, several infographics are presented to highlight the key findings of this paper

Design of a three-axis micro-scale metrology system for the characterization of cylindrical flexures

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 57).The objective of this thesis was to develop a laser metrology system in order to measure the movement in two of the rotation axes of a cylindrical flexure. The building and characterization of this system was achieved in an effort to measure cylindrical flexures such that rules for modeling them might be developed. The system developed measures translations of the flexure normal to the circular surface of the cylinder as well as rotations about the axes within this plane. While numerous metrology systems capable of achieving these functionalities exist, this system has inherent benefits in cost, range, and resolution. Using three lasers reflected off of mirrors mounted on a cylindrical flexure and captured by photodiodes, we are able to characterize micro-scale movements of the system with a resolution of 134 pm and a range of 5.04[mu]m of translation.by Ron M. Perez.S.B

The Hitchin Image in Type-D

Motivated by their appearance as Coulomb branch geometries of Class S theories, we study the image of the local Hitchin map in tame Hitchin systems of type-D with residue in a special nilpotent orbit $\mathcal{O}_H$. We describe two important features which distinguish it from the type A case studied in arXiv:2008.01020. The first feature, which we term even type constraints, arise iff the partition label $[\mathcal{O}_H]$ has even parts. In this case, our Hitchin image is non-singular and thus different from the one studied by Baraglia and Kamgarpour. We argue that our Hitchin image always globalizes to being the Hitchin base of an integrable system. The second feature, which we term odd type constraints, is related to a particular finite group $\overline{A}_b(\mathcal{O}_H)$ being non-trivial. When this finite group is non-trivial, we have $\mid \overline{A}_b \mid$ choices for the local Hitchin base. Additionally, we also show that the finite group $\overline{A}_b(\mathcal{O}_H)$ encodes the size of the dual special piece.Comment: 37 pages + references, 3 figure

Preliminary Evaluation of the Effectiveness of the GAVAC® Immunogen and the Rational Use of Acaricides as an Alternative for an Integrated Tick Control Program in Ecuador

Rhipicephalus microplus one of the ectoparasites with the most significant impact on livestock health and the economy in Ecuador and globally. Controlling ticks through chemical means has been demonstrated to be ineffective, resulting in acaricide resistance and increasing costs and health problems in tropical and subtropical livestock. Several tick control alternatives have been investigated to date, showing promising results under laboratory conditions but not in field applications. The use of multiple control alternatives in a comprehensive management plan for tick control has proven to be effective in reducing tick infestation. The objective of this study was to determine the effectiveness of immunization with the Gavac® vaccine and its effect on the rational use of acaricides. The study aimed to establish the impact of immunization on the biotic potential of Rhipicephalus microplus, the level of infestation, and the frequency of acaricidal baths. In a pilot farm, 176 bovines were vaccinated, and 30 animals were observed every 15 days for eight months, resulting in 18 observations. Observationally, a significant reduction in tick load on animals was identified, as well as a reduction in the use of acaricides by less than 10% (1 bath) compared to the farm’s estimated use. On average, acaricidal baths were administered 23 days after vaccination. The study found a statistically significant decrease in the number of ticks on the animals, the weight of the eggs, and their hatching percentage after the inclusion of the vaccination program on the farm. However, no statistically significant effect on the weight of engorged ticks was observed. In conclusion, the Gavac® vaccine has a positive observational effect on controlling the presence of ticks in animals and a negative effect on their reproductive aspects. Keywords: Rhipicephalus microplus; vaccine; bovines; acaricide control; integrated tick control program. Resumen Rhipicephalus microplus es considerado como uno de los ectoparásitos de mayor impacto sanitario y económico en las ganaderías del Ecuador y del mundo. En la actualidad, se ha demostrado que los métodos de control químico son poco eficientes y generan resistencias a los acaricidas en las garrapatas; aumentando los costos y los problemas sanitarios en las ganaderías tropicales y subtropicales. Hasta la presente fecha se han investigado varias alternativas de control para las garrapatas con buenos resultados en condiciones de laboratorio; no así, en su aplicación en el campo. El uso combinado y técnico de dos o más alternativas de control ha mostrado buenos resultados en la disminución de las garrapatas dentro de un “plan de manejo integral para el control de las garrapatas”. El objetivo de este estudio fue determinar la efectividad de la inmunización con la vacuna Gavac® y su efecto en el uso racional de acaricidas; estableciendo el impacto de la inmunización sobre el potencial biótico de Rh. microplus, el nivel de infestación y la frecuencia de los baños acaricidas. En una finca piloto se vacunaron a 176 bovinos; de los cuales, 30 animales fueron observados cada 15 días por 8 meses (18 observaciones). Observacionalmente, se identificó una reducción significativa de la carga de garrapatas en los animales; así como, una reducción del uso de acaricidas menor al 10% (1 baño) en comparación con lo estimado por la finca. El promedio por baño acaricida fue de 23 días tras la vacunación. Se obtuvo una disminución estadísticamente significativa en el número de garrapatas sobre los animales, el peso de los huevos y su porcentaje de eclosión tras la inclusión del programa en el predio. No se observó un efecto estadísticamente significativo en el peso de las garrapatas ingurgitadas. En conclusión, la vacuna tiene un efecto positivo observacional sobre el control de la presencia de las garrapatas en los animales y un efecto negativo en los aspectos reproductivos de las mismas. Palabras Clave: Rhipicephalus microplus; vacuna; bovinos; control acaricida; plan de manejo integrado

How the Emitted Size Distribution and Mixing State of Feldspar Affect Ice Nucleating Particles in a Global Model

The effect of aerosol particles on ice nucleation and, in turn, the formation of ice and mixed phase clouds is recognized as one of the largest sources of uncertainty in climate prediction. We apply an improved dust mineral specific aerosol module in the NASA GISS Earth System ModelE, which takes into account soil aggregates and their fragmentation at emission as well as the emission of large particles. We calculate ice nucleating particle concentrations from K-feldspar abundance for an active site parameterization for a range of activation temperatures and external and internal mixing assumption. We find that the globally averaged INP concentration is reduced by a factor of two to three, compared to a simple assumption on the size distribution of emitted dust minerals. The decrease can amount to a factor of five in some geographical regions. The results vary little between external and internal mixing and different activation temperatures, except for the coldest temperatures. In the sectional size distribution, the size range 24 micrometer contributes the largest INP number

How the Assumed Size Distribution of Dust Minerals Affects the Predicted Ice Forming Nuclei

The formation of ice in clouds depends on the availability of ice forming nuclei (IFN). Dust aerosol particles are considered the most important source of IFN at a global scale. Recent laboratory studies have demonstrated that the mineral feldspar provides the most efficient dust IFN for immersion freezing and together with kaolinite for deposition ice nucleation, and that the phyllosilicates illite and montmorillonite (a member of the smectite group) are of secondary importance.A few studies have applied global models that simulate mineral specific dust to predict the number and geographical distribution of IFN. These studies have been based on the simple assumption that the mineral composition of soil as provided in data sets from the literature translates directly into the mineral composition of the dust aerosols. However, these tables are based on measurements of wet-sieved soil where dust aggregates are destroyed to a large degree. In consequence, the size distribution of dust is shifted to smaller sizes, and phyllosilicates like illite, kaolinite, and smectite are only found in the size range 2 m. In contrast, in measurements of the mineral composition of dust aerosols, the largest mass fraction of these phyllosilicates is found in the size range 2 m as part of dust aggregates. Conversely, the mass fraction of feldspar is smaller in this size range, varying with the geographical location. This may have a significant effect on the predicted IFN number and its geographical distribution.An improved mineral specific dust aerosol module has been recently implemented in the NASA GISS Earth System ModelE2. The dust module takes into consideration the disaggregated state of wet-sieved soil, on which the tables of soil mineral fractions are based. To simulate the atmospheric cycle of the minerals, the mass size distribution of each mineral in aggregates that are emitted from undispersed parent soil is reconstructed. In the current study, we test the null-hypothesis that simulating the presence of a large mass fraction of phyllosilicates in dust aerosols in the size range 2 m, in comparison to a simple model assumption where this is neglected, does not yield a significant effect on the magnitude and geographical distribution of the predicted IFN number. Results from sensitivity experiments are presented as well