Pavol Bauer

Bio: Pavol Bauer is an academic researcher from Delft University of Technology. The author has contributed to research in topics: Photovoltaic system & Power electronics. The author has an hindex of 43, co-authored 466 publications receiving 7015 citations. Previous affiliations of Pavol Bauer include United States Department of Energy.

Operation of Grid-Connected DFIG Under Unbalanced Grid Voltage Condition

Abstract: Doubly fed induction generator (DFIG) still shares a large part in today's wind power market. It provides the benefits of variable speed operation cost-effectively, and can control its active and reactive power independently. Crowbar protection is often adopted to protect the rotor-side voltage source converter (VSC) from transient overcurrent during grid voltage dip. But under unbalanced grid voltage condition, the severe problems are not the transient overcurrent, but the electric torque pulsation and dc voltage ripple in the back-to-back VSCs. This paper develops dynamic models in MATLAB/Simulink, validates it through experiments, investigates the behavior of DFIG during unbalanced grid voltage condition, and proposes new controllers in separated positive and negative sequence. Methods to separate positive and negative sequence components in real time are also developed, and their responses to unsymmetrical voltage dip are compared. Simulation results prove that the separated positive and negative sequence controllers limit the torque pulsation and dc voltage ripple effectively.

A Novel Distributed Direct-Voltage Control Strategy for Grid Integration of Offshore Wind Energy Systems Through MTDC Network

Abstract: Although HVDC transmission systems have been available since mid-1950s, almost all installations worldwide are point-to-point systems. In the past, the lower reliability and higher costs of power electronic converters, together with complex controls and need for fast telecommunication links, may have prevented the construction of multiterminal DC (MTDC) networks. The introduction of voltage-source converters for transmission purposes has renewed the interest in the development of supergrids for integration of remote renewable sources, such as offshore wind. The main focus of the present work is on the control and operation of MTDC networks for integration of offshore wind energy systems. After a brief introduction, this paper proposes a classification of MTDC networks. The most utilized control structures for VSC-HVDC are presented, since it is currently recognized as the best candidate for the development of supergrids, followed by a discussion of the merits and shortcomings of available DC voltage control methods. Subsequently, a novel control strategy-with distributed slack nodes-is proposed by means of a DC optimal power flow. The distributed voltage control (DVC) strategy is numerically illustrated by loss minimization in an MTDC network. Finally, dynamic simulations are performed to demonstrate the benefits of the DVC strategy.

Practical Capacity Fading Model for Li-Ion Battery Cells in Electric Vehicles

Abstract: This paper proposes a practical capacity fading model for Li-ion cells based on real operating conditions in electric vehicles (EVs). Numerous LiFePO4 cells have been cycled with a current profile containing regenerative braking to determine the capacity fading rate. The cells have been cycled at different temperatures with different initial state of charges, depth of discharges, or C-rates. From the experiments, an empirical model is constructed, which is capable of modeling the capacity fading in EV battery cells under most operating conditions. The capacity fading model can be used to estimate the state of health of EV battery cells, and simple ways to optimize the battery lifetime are proposed.

Driving Range Extension of EV With On-Road Contactless Power Transfer—A Case Study

Abstract: As future electric vehicles (EVs) emerge, achievable driving range by these vehicles remains a major bottleneck. A battery EV has a fairly limited driving range per charging and takes a long time to charge. Moreover, the existing technology only enables stationary charging, which means that an EV has to be parked during the duration of its charge replenishment. Contactless power transfer (CPT) system presents the opportunity of on-road charge replenishment of EVs. This paper presents case studies which illustrate the effect of on-road charge replenishment on driving range of an EV for varying levels of power transfer by the CPT system in urban and highway driving scenarios.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

World energy outlook

Abstract: This chapter discusses leading problems linked to energy that the world is now confronting and to propose some ideas concerning possible solutions. Oil deserves special attention among all energy sources. Since the beginning of 1981, it has merely been continuing and enhancing the downward movement in consumption and prices caused by excessive rises, especially for light crudes such as those from Africa, and the slowing down of worldwide economic growth. Densely-populated oil-producing countries need to produce to live, to pay for their food and their equipment. If the economic growth of the industrialized countries were to be 4%, even if investment in the rational use of energy were pushed to the limit and the development of nonpetroleum energy sources were also pursued actively, it would be extremely difficult to prevent a sharp rise in prices. It is evident that it is absolutely necessary to pursue actively the development of coal, natural gas, and nuclear power if a physical shortage of energy is not to block economic growth.

Multiobjective evolutionary algorithms: A survey of the state of the art

Abstract: A multiobjective optimization problem involves several conflicting objectives and has a set of Pareto optimal solutions. By evolving a population of solutions, multiobjective evolutionary algorithms (MOEAs) are able to approximate the Pareto optimal set in a single run. MOEAs have attracted a lot of research effort during the last 20 years, and they are still one of the hottest research areas in the field of evolutionary computation. This paper surveys the development of MOEAs primarily during the last eight years. It covers algorithmic frameworks such as decomposition-based MOEAs (MOEA/Ds), memetic MOEAs, coevolutionary MOEAs, selection and offspring reproduction operators, MOEAs with specific search methods, MOEAs for multimodal problems, constraint handling and MOEAs, computationally expensive multiobjective optimization problems (MOPs), dynamic MOPs, noisy MOPs, combinatorial and discrete MOPs, benchmark problems, performance indicators, and applications. In addition, some future research issues are also presented.

Wireless Power Transfer for Electric Vehicle Applications

Abstract: Wireless power transfer (WPT) using magnetic resonance is the technology which could set human free from the annoying wires. In fact, the WPT adopts the same basic theory which has already been developed for at least 30 years with the term inductive power transfer. WPT technology is developing rapidly in recent years. At kilowatts power level, the transfer distance increases from several millimeters to several hundred millimeters with a grid to load efficiency above 90%. The advances make the WPT very attractive to the electric vehicle (EV) charging applications in both stationary and dynamic charging scenarios. This paper reviewed the technologies in the WPT area applicable to EV wireless charging. By introducing WPT in EVs, the obstacles of charging time, range, and cost can be easily mitigated. Battery technology is no longer relevant in the mass market penetration of EVs. It is hoped that researchers could be encouraged by the state-of-the-art achievements, and push forward the further development of WPT as well as the expansion of EV.