Traditional engineering instruction is deductive, beginning with theories and progressing to the applications of those theories Alternative teaching approaches are more inductive Topics are introduced by presenting specific observations, case studies or problems, and theories are taught or the students are helped to discover them only after the need to know them has been established This study reviews several of the most commonly used inductive teaching methods, including inquiry learning, problem-based learning, project-based learning, case-based teaching, discovery learning, and just-in-time teaching The paper defines each method, highlights commonalities and specific differences, and reviews research on the effectiveness of the methods While the strength of the evidence varies from one method to another, inductive methods are consistently found to be at least equal to, and in general more effective than, traditional deductive methods for achieving a broad range of learning outcomes

Inductive Teaching and Learning Methods: Definitions, Comparisons, and Research Bases

This paper presents the latest comprehensive literature review of AC and DC microgrid (MG) systems in connection with distributed generation (DG) units using renewable energy sources (RESs), energy storage systems (ESS) and loads. A survey on the alternative DG units' configurations in the low voltage AC (LVAC) and DC (LVDC) distribution networks with several applications of microgrid systems in the viewpoint of the current and the future consumer equipments energy market is extensively discussed. Based on the economical, technical and environmental benefits of the renewable energy related DG units, a thorough comparison between the two types of microgrid systems is provided. The paper also investigates the feasibility, control and energy management strategies of the two microgrid systems relying on the most current research works. Finally, the generalized relay tripping currents are derived and the protection strategies in microgrid systems are addressed in detail. From this literature survey, it can be revealed that the AC and DC microgrid systems with multiconverter devices are intrinsically potential for the future energy systems to achieve reliability, efficiency and quality power supply.

AC-microgrids versus DC-microgrids with distributed energy resources: A review

The significant benefits associated with microgrids have led to vast efforts to expand their penetration in electric power systems. Although their deployment is rapidly growing, there are still many challenges to efficiently design, control, and operate microgrids when connected to the grid, and also when in islanded mode, where extensive research activities are underway to tackle these issues. It is necessary to have an across-the-board view of the microgrid integration in power systems. This paper presents a review of issues concerning microgrids and provides an account of research in areas related to microgrids, including distributed generation, microgrid value propositions, applications of power electronics, economic issues, microgrid operation and control, microgrid clusters, and protection and communications issues.

State of the Art in Research on Microgrids: A Review

The electric vehicle (EV) technology addresses the issue of the reduction of carbon and greenhouse gas emissions. The concept of EVs focuses on the utilization of alternative energy resources. However, EV systems currently face challenges in energy storage systems (ESSs) with regard to their safety, size, cost, and overall management issues. In addition, hybridization of ESSs with advanced power electronic technologies has a significant influence on optimal power utilization to lead advanced EV technologies. This paper comprehensively reviews technologies of ESSs, its classifications, characteristics, constructions, electricity conversion, and evaluation processes with advantages and disadvantages for EV applications. Moreover, this paper discusses various classifications of ESS according to their energy formations, composition materials, and techniques on average power delivery over its capacity and overall efficiencies exhibited within their life expectancies. The rigorous review indicates that existing technologies for ESS can be used for EVs, but the optimum use of ESSs for efficient EV energy storage applications has not yet been achieved. This review highlights many factors, challenges, and problems for sustainable development of ESS technologies in next-generation EV applications. Thus, this review will widen the effort toward the development of economic and efficient ESSs with a longer lifetime for future EV uses.

Review of energy storage systems for electric vehicle applications: Issues and challenges

A variety of rechargeable batteries are now available in world markets for powering electric vehicles (EVs). The lithium-ion (Li-ion) battery is considered the best among all battery types and cells because of its superior characteristics and performance. The positive environmental impacts and recycling potential of lithium batteries have influenced the development of new research for improving Li-ion battery technologies. However, the cost reduction, safe operation, and mitigation of negative ecological impacts are now a common concern for advancement. This paper provides a comprehensive study on the state of the art of Li-ion batteries including the fundamentals, structures, and overall performance evaluations of different types of lithium batteries. A study on a battery management system for Li-ion battery storage in EV applications is demonstrated, which includes a cell condition monitoring, charge, and discharge control, states estimation, protection and equalization, temperature control and heat management, battery fault diagnosis, and assessment aimed at enhancing the overall performance of the system. It is observed that the Li-ion batteries are becoming very popular in vehicle applications due to price reductions and lightweight with high power density. However, the management of the charging and discharging processes, CO2 and greenhouse gases emissions, health effects, and recycling and refurbishing processes have still not been resolved satisfactorily. Consequently, this review focuses on the many factors, challenges, and problems and provides recommendations for sustainable battery manufacturing for future EVs. This review will hopefully lead to increasing efforts toward the development of an advanced Li-ion battery in terms of economics, longevity, specific power, energy density, safety, and performance in vehicle applications.

State-of-the-Art and Energy Management System of Lithium-Ion Batteries in Electric Vehicle Applications: Issues and Recommendations

Direct power control (DPC) has increasingly gained attention in the last years as a robust and simple control scheme. Yet, the implications of some of the assumptions made by the original table-based DPC are not well explained in the literature. Here, a new formulation of DPC is presented, that allows to analyze the shortcomings of this kind of algorithms, mainly regarding the power limits in which table-based algorithms are valid. This is a key aspect for microgrid applications, as they require a wide range of possible active and reactive power setpoints in order to be able to control the system's voltage and frequency. A new table is then presented that allows to overcome those limitations. The proposed table is valid at any point of the inverter's power limits.

Table-Based Direct Power Control: A Critical Review for Microgrid Applications

The use of wind energy is now an established fact, and many educational institutions are introducing this topic into their engineering studies. Problem-based learning (PBL), as a student-centered instructional approach, has contributed to important developments in engineering education over the last few years. This paper presents the experience of a problem-based learning approach within the context of teaching wind energy conversion systems for electricity generation at an Electrical and Electronic Master's degree level. Students were given the problem of finding the response of a wind turbine to a grid fault. Groups of three students worked on a cooperative learning project for 15 weeks, with the instructor providing resource assistance and information at all stages of the work. Two tools were designed to help the students: a virtual wind turbine simulator and a real wind turbine setup. Both experimental tools are described, and the results obtained by the students are discussed. The results show that the students valued both tools and were able to address problems at a high cognitive level.

Problem-Based Learning in Wind Energy Using Virtual and Real Setups

A Ni–Cd battery model considering state of charge and hysteresis effects

Testing Low Voltage Ride Through capabilities of solar inverters

This paper presents a new formulation for direct power control (DPC) with several improvements over previous DPC formulations such as an exact discrete-time expression for the predicted power variations yielded by a given inverter switching state and the inclusion of the computing delay time in the model. Based on this formulation, a variable-frequency optimal DPC algorithm is presented that selects the inverter switching state that minimizes the power error. This algorithm shows an excellent precision in estimating power variations, therefore reducing power ripple and unwanted current harmonics, while retaining the fast dynamics inherent to variable-frequency DPC. This makes this algorithm suitable for interfacing distributed generation to microgrids, where a fast and accurate power control is desirable in order to perform voltage and frequency regulation. Additionally, studies are carried out regarding the average switching frequency and the influence of the model parameters on the algorithm robustness.

J. Alonso-Martinez

Papers

Table-Based Direct Power Control: A Critical Review for Microgrid Applications

Problem-Based Learning in Wind Energy Using Virtual and Real Setups

A Ni–Cd battery model considering state of charge and hysteresis effects

Testing Low Voltage Ride Through capabilities of solar inverters

A New Variable-Frequency Optimal Direct Power Control Algorithm