LLC DC-DC Converter Performances Improvement for Bidirectional Electric Vehicle Charger Application

Electric Vehicle (EV) bidirectional charger technology is growing in importance. It defines the fact of returning the electricity stored in the batteries of EV to Grid (V2G), to Home (V2H), to Load (V2L), or in one word V2X mode. The EV onboard charger is divided into two parts: AC-DC and DC-DC converters. The isolated bidirectional DC-DC LLC resonant converter is used to improve the charger efficiency within both battery power and voltage ranges. It is controlled by varying the switching frequency based on a small signal modeling approach using the gain transfer function inversion method. The dimensions of the DC-DC LLC converter directly affect the charger cost. Moreover, they cause an important control frequency saturation zone, especially in V2X mode, where the switching frequency is out of the feasibility zone. The new challenge in this paper is to design an optimization strategy to minimize the LLC converter cost and improve the control frequency feasibility zone, for a wide variation of battery voltage and converter power, in the charging (G2V) and discharging (V2X) modes simultaneously. For our best knowledge, this optimization problem, in the case of a bidirectional (G2V and V2X) charger, is not yet considered in the literature. An optimal design that considers the control stability equations in the optimization algorithm is elaborated. The obtained results show a significant converter cost decrease and important expansion of control frequency feasibility zones. A comparative study between initial and optimized values, in G2V and V2X modes, is generated according to the converter efficiency.

Bone Remodeling Model Integrating the Biological Function and Damage Influences for the Cortical-Trabecular Interface

Bone remodeling process has been widely investigated in literature from an experimental and theoretical viewpoint. Indeed, the biological process of bone remodeling allows a continuous renewal of the microstructure over time and thus, it contributes to decrease the bone damage by repairing it. This research work aims to study the biological function’s (fbio) effects on the bone remodeling process trough bone density evolution. Parameter fbio is one of the important parameters that controls bone volume variation. The biological bone remodeling process is modeled in terms of equations describing the activity of the Basic Multi-cellular Units (BMU). We use a mathematical model to simulate damage repair, based on Garcia Aznar’s model. The results of simulation show a good match with experimental and clinical data: bone porosity decreases over time and decreases also as the biological factors increase. In the same view, the apparent density (ρa) decreases with bone volume fraction increases. We note that the governance of the evolution of bone density leads to consider the evolution of bone volume during youthful and the maturation phase with their saturation zone for adult in terms of growth.

Real-Time EM Look-Ahead Resistivity for Mapping of Oil/Water Contact While Drilling at Low Deviated Well, New Perspective for Mature Oil Fields Development: A Case Study Of Umm Gudair Field, Kuwait

The Umm Gudair (UG) Field is a carbonate reservoir of West Kuwait with more than 57 years of production history. The average water cut of the field reached closed to 60 percent due to a long history of production and regulating drawdown in a different part of the field, consequentially undulating the current oil/water contact (COWC). As a result, there is high uncertainty of the current oil/water contact (COWC) that impacts the drilling strategy in the field. The typical approach used to develop the field in the lower part of carbonate is to drill deviated wells to original oil/water contact (OOWC) to know the saturation profile and later cement back up to above the high-water saturation zone and then perforate with standoff. This method has not shown encouraging results, and a high water cut presence remains. An innovative solution is required with a technology that can give a proactive approach while drilling to indicate approaching current oil/water contact and geo-stop drilling to give optimal standoff between the bit and the detected water contact (COWC). Recent development of electromagnetic (EM) look-ahead resistivity technology was considered and first implemented in the Umm Gudair (UG) Field. It is an electromagnetic-based signal that can detect the resistivity features ahead of the bit while drilling and enables proactive decisions to reduce drilling and geological or reservoir risks related to the well placement challenges.

Characterization of aquifer system using electrical resistivity tomography (ERT) and induced polarisation (IP) techniques

Groundwater plays a major role as an alternative freshwater resource for irrigation and industrial purposes. This study aimed to characterize the subsurface of aquifer systems in TelukIntan district, Perak, Malaysia using Electrical Resistivity Tomography (ERT) and Induced Polarization (IP) methods. The horizontal profiling (TL1 and TL2) was conducted at length of 400 m. The estimated depth is 150 m below ground level (b.g.l.). An ABEM SAS 4000 Terrameter and ABEM LUND ES464 Imaging System were applied to create a resistivity pseudo-section using polar-dipole configuration. The collected geo-electrical data was interpreted using RESIST software with partial curve matching and computer iteration. ERT and IP survey profile results were validated with in-situ borehole data from borehole 2 (B2). Eleven samples of soil profile were collected at depth from 5.6 m to 61.2 m, with average percentage of sand, silt and clay are 93.77 %, 5.78 % and 0.02 %, respectively. The geology of subsurface settings is the key factor in determining the aquifer system characterized by interlayer sand-silt sequence indicating the saturation zone of aquifer underlain by shale at the bottom. Further study on hydraulics perspective is important to understand the overall capacity of the aquifer.

Research on the Nonlinear Characteristic of Flow in the Electro-Hydraulic Servo Pump Control System

In an electro-hydraulic servo system, the system flow is used as an intermediate variable to control the output displacement/force/speed of the actuator, and it plays the role of a medium for energy transmission and conversion. Therefore, the control of the system flow is the essence of state control for the system actuator. The purpose of this paper is to study the non-linear characteristics of pump control system flow and pave the way for high-performance control of the system. Based on the flow partition idea, the system output flow is divided into the dead zone, load zone, and saturation zone. We establish a mathematical model of the hydraulic system to analyze and study the effect of the nonlinear characteristics of the servo motor and the positive displacement pump on the system flow partition characteristics. We focus on the effects of the positive displacement pump shear flow internal leakage, pressure difference flow internal leakage, oil compression, servo motor rotation friction, and servo motor torque reserve rate on the system flow output, and analyze the partition characteristics of the system flow under different working conditions. We provide a theoretical basis for a high-precision control strategy for a hydraulic system.

Influence of cement slurry heat release on physical properties of marine hydrate reservoirs during well cementing

Natural gas hydrates gradually become the focus of new energy resources, and the study of hydrate exploitation is growing vigorously during recent years. Well cementing is an important process during energy exploitation, especially when encounters hydrate bearing sediments in deep-water oil and gas drilling, showing great research significance and becoming a research hotspot. In this study, the exploratory well of SH2 of GMGS-1 project is chosen as the object of study, a cementing model of two dimensions based on this exploratory well is build, the invasion process of cement slurry is reappeared by TOUGH+HYDRATE, and the physical properties response of hydrate reservoirs during the cementing process is analyzed based on the numerical simulation data. In which, a view of “continuous stage simulation” to solve the problem of dynamic heat release of cement slurry is created and used for the first time. Result illustrated that the invasion behavior of cement slurry almost only occurred during the stage of holding pressure, the temperature has significantly increased in the area of reservoir which is invaded by cement slurry. At the same time, a large amount of decomposed hydrate have generated gas and water, which form high pressure region and transfer toward the deeper of reservoir. However, the variation in the temperature is not significant and the hydrate barely no longer decomposed in those area which outside or even though close to this area. There also have generated secondary hydrate closed to the area of decomposition and formed high saturation zone of hydrate. The results also proved the feasibility of “continuous stage simulation”, and played a guiding significance for the field well cementing.

Performance Evaluation of Enhanced Bioretention Systems in Removing Dissolved Nutrients in Stormwater Runoff

Bioretention has great potential in managing and purifying urban stormwater runoff. However, information regarding the removal of nutrients in bioretention systems with the use of media, plants, and saturated areas is still limited. In this study, three devices of control, conventional bioretention (DS), and strengthened bioretention (SZ) were investigated to enhance the simultaneous removal of nitrogen and phosphorus. The experimental column SZ showed the best performance for total phosphorus (TP), ammonia (NH4+-N) and total nitrogen (TN) removal (85.6–92.4%, 83.1–92.7%, 57.1–74.1%, respectively), whereas DS columns performed poorly for NH4+-N removal (43.6–81.2%) under different conditions. For the removal of nitrate, the columns of Control and DS exhibited negative performance (−14.3% and −8.2%) in a typical event. Further evaluation of water quality revealed that in the early stages of rainfall, the effluent of the SZ column was able to reach quality standards of Grade IV for surface water in China. Moreover, although the ion-exchange and phosphate precipitation occurred on the surface of the media, which were placed in the saturation zone, it did not change the surface crystal structure.

INCORPORATION OF HYBRID BIOFILTERS IN WATER-SENSITIVE URBAN DESIGN

This paper presents a research study aimed at the development of a hybrid biofilter that can serve for two different applications. This is a unique approach due to the prolonged dry period in Israel covering 7-8 months of the year. The tactic suggested herein is to use the same system for stormwater harvesting/treatment during winter, and for bioremediation of nitrate-contaminated groundwater during summer. Crude cotton and Eucalyptus wood-chips served as alternative carbon sources for denitrification, and both proved to support efficient reduction of nitrate with minimal release of nitrite and organic matter. During the stage of stormwater treatment, two types of biofilter-columns (120 & 70 cm long) were tested, with a minimal saturation zone and no addition of organic carbon. Complete nitrification could be achieved, even under high instantaneous hydraulic loads for both column types. Vegetation on top of the biofilters contributed to improved removal of the nitrate formed, by plant assimilation.