STUDY OF DIRECT CURRENT POWER TOPOLOGIES AND TECHNOLOGY APPLIED ON HIGH VOLTAGE CHARGING SYSTEMS

ABSTRACT This article describes the actual state of art of the current battery charging systems, with a special focused on its technical, technological features and its operation modes. The most important factors considered for this functional and theoretical study are from the following points of view: State of the art: This article reviews the technological division between lithium batteries and the most suitable power topology for each one. Technological factor: The article reviews the technological state from the point of view of the power components as: MOSFET transistors, diodes, with special focused in the power ranges, technological limits and costs. Theoretical factor: This factor is focused in the description of the power topologies and its preferred selection depending on the voltage and the current range of its potential application. This chapter also shows the basic theoretical approach and the key differences between uni-directional and bi-directional power architectures. Control Theory: The current control systems have a lot of similarities between each other, either in alternating current or direct current. However The operation of battery charging systems has common and functional drifts in its behaviours with standard direct current converters. This article describes and analyses their similarities and their differences.

Power quality metrics for DC grids with pulsed power loads

<span lang="EN-GB">DC grids can effectively feed pulsed power loads (PPLs), integrating local energy storage to minimize the impact on other connected loads and implementing buffered sub-grids to isolate susceptible loads even more. The identification of regulatory limits for PPL integration and DC grid response and the assessment of PPL impact necessitate suitable Power Quality (PQ) metrics. Existing indexes and limits (e.g. ripple and distortion, voltage fluctuation) are compared to other metrics, derived from control methods and knowledge of the peculiar characteristics of PPL and interaction with DC grids in some examples. The objective is a unified approach for PQ metrics suitable for a wide range of DC grids and in particular to the behavior of PPLs.</span>

Origins and Effects of Education System Transplantation: A Literature Review

This article reviews the literature on educational transplantation, which discussed three related issues: what is the definition of educational system transplantation, what are the typical models of educational system transplantation and what are the effects of educational system transplantation associated with exporting and receiving countries. The literature suggests that educational system transplantation expands the choices for education reforms and promotes the internal regime innovation for the receiving countries. Empirical cases reflect the educational system transplantation encountered the issues on cultural adaptability and compatibility among different education regimes and highly relied on the cultural context differences and suitable power operations.

Research regarding the common problems of design of the bunkers – A review

Understanding the behavior of granular material in a bunker not only helps to design properly and achieve the correct granular flow, but also needs the engineer to ensure that the bunker is properly designed and conducted to withstand the tasks and demands exercised during its operation. Small and shallow bunkers are commonly used in industry when free space is limited. Shallow bunkers induce the flow of the funnel, which can cause problems such as segregation and agglomeration of the material inside it, which leads to considerable damage to the final product. The design and location of a suitable power supply and an appropriate outlet is still critical and is perceived rather as a science. The paper presents some innovative solutions related to the design, modeling and construction of solid material storage and unloading bunkers.

Real-Time Minimization Power Losses by Driven Primary Regulation in Islanded Microgrids

Islanded microgrids are small networks that work independently from the main grid. The frequency and voltage in islanded microgrids are affected directly by the output power of distributed generators and power demand variations. In this work, a real-time driven primary regulation, which relies on optimized P-f droop coefficients, is proposed. In all operating conditions, it minimizes the power losses for islanded microgrids. The proposed configuration will allow the optimization modules to interact with each other and adjust parameters producing a suitable power sharing among generators. The methodology is tested based on a hardware-in-the-loop experimental set-up where distributed generators are connected to a group of loads. A parametric analysis is implemented for verification of the effectiveness of the proposed configuration as well as the improvement of the system reliability.

Economic Analysis of 4MW Distributed Photovoltaic Power Generation Project Based on PVsyst Software Simulation

We use PVsyst software to simulate and calculate the first year electricity generation of 4 MW distributed photovoltaic power generation project. In order to analyze and select the suitable power plant operation mode, the total generating capacity of photovoltaic power station in 25 years has been estimated by using component attenuation of 25 years. This research reports on the findings shown by PVsyst software that evaluates the economy aspects brought by two kinds of operation modes which are full grid access mode and spontaneous use of residual power grid access mode. The research content has reference value for the construction of roof distributed photovoltaic power station in China.

A Centralized Smart Decision-Making Hierarchical Interactive Architecture for Multiple Home Microgrids in Retail Electricity Market

The principal aim of this study is to devise a combined market operator and a distribution network operator structure for multiple home-microgrids (MH-MGs) connected to an upstream grid. Here, there are three distinct types of players with opposite intentions that can participate as a consumer and/or prosumer (as a buyer or seller) in the market. All players that are price makers can compete with each other to obtain much more possible profitability while consumers aim to minimize the market-clearing price. For modeling the interactions among partakers and implementing this comprehensive structure, a multi-objective function problem is solved by using a static, non-cooperative game theory. The propounded structure is a hierarchical bi-level controller, and its accomplishment in the optimal control of MH-MGs with distributed energy resources has been evaluated. The outcome of this algorithm provides the best and most suitable power allocation among different players in the market while satisfying each player’s goals. Furthermore, the amount of profit gained by each player is ascertained. Simulation results demonstrate 169% increase in the total payoff compared to the imperialist competition algorithm. This percentage proves the effectiveness, extensibility and flexibility of the presented approach in encouraging participants to join the market and boost their profits.