Marcos Lafoz

Evaluation of the Magnetic Field Generated by the Inverter of an Electric Vehicle

In hybrid and electric vehicles, passengers sit very close to an electric system of significant power, which means that they may be subjected to high electromagnetic fields. The hazards of long-term exposure to these fields must be taken into account when designing electric vehicles and their components. Among all the electric devices present in the power train, the electronic converter is the most difficult to analyze, given that it works with different frequencies. In this paper, a methodology to evaluate the magnetic field created by a power electronics converter is proposed. After a brief overview of the recommendations of electromagnetic fields exposure, the magnetic field produced by an inverter is analyzed using finite element techniques. The results obtained are compared to laboratory measurements, taken from a real inverter, in order to validate the model. Finally, results are used to draw some conclusions regarding vehicle design criteria and magnetic shielding efficiency.

Fast Response Energy Storage Systems

Fast Response Energy Storage describes several technologies characterized by the ability to provide or to absorb a high amount of electrical energy in a short period of time without diminishing the life time of the storage device. Major technologies discussed in this chapter are: Electric Double Layer Capacitors (EDLC) that store energy in the electrical field of a capacitor; Flywheels that do it as kinetic energy and Superconducting Magnets (SME) where energy is kept in the magnetic field of a lossless inductor. All these technologies can develop a wide range of different applications. In this way, they can support an increasing level of renewable energy sources penetration in the conventional grid by providing the necessary features. The most important are: Power quality issues, including grid frequency regulation and grid voltage stability; Smart grids development, including hybrid energy storage systems, like EDLC plus batteries, that support short-term and long-term necessities of the grid and electrical and hybrid vehicles as distributed energy storage systems. In this chapter, the basics for these technologies are presented, addressing information about the power converters needed to manage the energy of these devices. Besides, the most important applications regarding renewable energy integration are described, providing information about implemented real systems.

Wave energy converter dimensioning constrained by location, power take-off and control strategy

The paper analyses the performance of a wave energy converter (WEC) employing a direct-drive linear switched-reluctance machine, providing a detailed method for optimal dimensioning of a WEC. The method derives the dimensions of a particular point absorber to reach objectives such as the maximization of energy extracted, or the minimization of volume. The characteristics of a particular location, the chosen power take-off (PTO) and the control strategy chosen define the restrictions of an optimization problem whose solutions are the dimensions of the most suitable WEC. The given generator parameters (maximum stroke, velocity and force) determine an optimal WEC design. Laboratory testing of the generator will validate the force and calculate efficiency, to be used as inputs for the optimization process. Aside from the preliminary WEC dimensions design, this method can be used for an energetic analysis of a particular PTO on various locations.

Passenger Exposure to Magnetic Fields in Electric Vehicles

In electric vehicles, passengers sit very close to an electric system of significant power, usually for a considerable amount of time. The relatively high currents achieved in these systems and the short distances between the power devices and the passengers mean that the latter could be exposed to relevant magnetic fields. This implies that it becomes necessary to evaluate the electromagnetic environment in the interior of these vehicles before releasing them in the market. Moreover, the hazards of magnetic field exposure must be taken into account when designing electric vehicles and their components. For this purpose, estimation tools based on finite element simulations can prove to be very useful. With appropriate design guidelines, it might be possible to make electric vehicles safe from the electromagnetic radiation point of view.

Power smoothing system for wave energy converters by means of a supercapacitor-based energy storage system

One of the main issues of wave energy nowadays is the oscillation of the generated power, which is due to the oscillating nature of the waves. These power fluctuations may have an important undesired impact on the electrical grid. This paper proposes a system that compensates power oscillations in wave energy applications by means of a supercapacitor-based energy storage system. A laboratory test bench is used to emulate wave power oscillations and to partially suppress them. The paper describes the control strategy implemented in the test bench and includes experimental results for regular waves.

Design methodology of a high speed switched reluctance generator drive for aircrafts

The paper proposes a high speed switched reluctance (SR) drive for aircraft applications, covering the demand of more electric aircrafts (MEA) and defending the particular benefits of this machine technology against others, such as permanent magnet synchronous generators. An appropriate topology of electrical machine and power converter for a high speed DC distribution grid is selected. Firstly, the electromagnetic design of the generator, by means of FEM, is described in detail, paying attention to the problem of the torque ripple and pointing out some solutions to improve it, based on an iterative optimisation of both stator and rotor geometries and phases activation and deactivation angles. Then, the design of power electronics is also analysed, obtaining the required modules and cooling system from a simulation model, using the maximum and average current levels as well as the duty cycles. The model has been developed from the generator electromagnetic design and integrates the control strategy, in charge of controlling the DC-link voltage. An iterative procedure using FEM analysis and the simulation model is also used to validate the thermal and mechanical behaviour of the system. Finally, the integration of the complete electric drive is discussed with the criteria of maintaining the system within the available room and keeping the temperature under the maximum limits. The application of aircraft equipment is specially demanding in terms of robustness, low maintenance, fault tolerance, high temperature and harsh environment, and those are the reasons why the SR generator is a reliable alternative.

Multifunctional test bench for the emulation and testing of electric vehicle fast-charging from urban railway power lines

This paper describes the development and operation of a laboratory test bench specifically designed to emulate an electric vehicle charging platform in which the energy is supplied from an urban railway power line. This platform was developed in order to prove the technical feasibility of the proposed charging method and to assess its performance. Further research includes the development and comparison of control strategies from the energy management point of view.

Technology description and characterization of a low-cost flywheel for energy management in microgrids

This paper describes a modular, integrated and low-cost kinetic energy storage system (KESS), its electrical characterization as well as its future integration and operation in a microgrid within the scope of a project called MIRED-CON (Microgeneration with Renewable Sources and its control). This project aims to develop, using the power microgrid installed in the CEDER (Soria, Spain), an advanced metering and control infrastructure to improve the operation performance and efficiency of the distribution grid. Metallic flywheel and switched reluctance machine are chosen as energy storage device to provide stability to the microgrid, frequency regulation and power peak limitation, achieving a high performance in the grid operation. The KEES is integrated with a grid side converter (GSC) to connect to the A mains, providing extra functionality to the system. The combined operation of the proposed KESS together with photovoltaic (PV) panels, wind power generation and micro-pumped hydro energy storage (PHES) in the real application is analyzed by means of different simulations using MATLAB/Simulink software. Two operation modes are considered regarding the KESS: grid-connected mode (smoothing the power generation with renewables) and islanded mode (controlling the frequency and the voltage of the microgrid). Electrical characterization from experimental results are used by the central control unit to have information about the available power and energy in the device, thus improving the energy management in the real facility.

Minimum losses point tracking and minimum current point tracking in interior PMSMs

Advanced control strategies for efficiency optimization in interior PMSMs are usually model-based, potentially providing very accurate results and good performance at the cost of parameter dependency and the associated drawbacks. Search-based methods, on the contrary, perform more modestly but depend neither on models nor on parameters. This paper compares both approaches in terms of steady-state efficiency.

Switched Reluctance Drives with Degraded Mode for Electric Vehicles

There are many types of electrical machines suitable for electric vehicles. Nowadays, most manufacturers and researchers tend towards two major alternatives: permanent magnet synchronous machines and induction machines. However, these are not the only competitive candidates. Reluctance machines, which have been well-known for some decades already, present some interesting advantages. For instance, switched reluctance machines are intrinsically redundant and fault-tolerant, which makes them attractive for applications in which robustness is compulsory. In this sense, switched reluctance drives can keep working even when one of their phases loses its functional‐ ity for any reason. In an electric vehicle, this would mean being able to keep driving the vehicle even after some failures, although with reduced performance (in degraded mode). In this chapter, switched reluctance drives for traction applications are analyzed, focusing on their capability to operate in degraded mode (with m-1 phases available).