Manes Recheis

Fast and accurate battery model applicable for EV and HEV simulation

The need to reduce fuel consumption, minimize emissions, and improve levels of safety, comfort, and reliability is expected to result in a much higher demand for electric power in future cars. In order to develop the needed control algorithms and to optimize the required components some kind of virtual prototype environment is needed. Even so for most components good models already exist, an adequate model for the battery is still missing. However, this is needed since the battery has a large impact on the efficiency of the total system. Therefore this work presents a battery model applicable for EV and HEV simulations.

Selection of Magnetic Materials for Bearingless High-Speed Mobile Flywheel Energy Storage Systems

Beside a higher amount of reactive power and a lower power to weight ratio compared with other machine types, the switched reluctance motor (SRM) features robustness, low cost, failure tolerance, and a wide operation temperature range. With additional power electronics and construction effort, the SRM can be operated as a bearingless drive. This is important to increase the lifetime of bearings in vacuum since their lubrication is difficult. In this paper, the technical potential of this particular motor topology to produce torque and radial force is evaluated based on finite element simulations. Additionally, the estimated hysteresis and eddy current losses during the normal and bearingless drive operation depending on the selected soft magnetic materials are evaluated.

Improving kinetic energy storage for vehicles through the combination of rolling element and active magnetic bearings

The demand for short term energy storage providing high power for electric and hybrid-electric vehicles is increasing dramatically. Stationary flywheel energy storage systems (FESS) are established as uninterruptible power supply (UPS) and represent an emerging market. In contrast, mobile FESS are currently only used in few applications such as motor sports. To enable a wider use in personal and public transportation the lifespan of the flywheels bearings needs to be increased significantly. This paper presents an alternative approach to extend the lifespan of the flywheels bearings by using a combination of rolling element and active magnetic bearings (CREAMB).

Fast and accurate battery model including temperature dependency

The need to reduce fuel consumption, minimize emissions, and improve levels of safety, comfort, and reliability is expected to result in a much higher demand for electric power in future cars. In order to develop the needed control algorithms and to optimize the required components adequate simulation models are needed. In this paper, the authors present a battery model based on an equivalent electrical circuit able to describe the current-voltage behavior depending on the state of charge and temperature. Due to the simple structure of the model only a small computational effort is required. Nevertheless a good agreement between measurement and simulation is achieved.

Low distortion power amplifier for battery measurement systems

Typically a battery is the best choice as electrical energy storage for mobile applications. Design and optimization of the system components are based on simulation of the whole system needing an adequate battery model. For the parameter identification measurement data is needed. This work presents a prototype of a measurement system that is capable of testing and obtaining the required measurements from batteries with capacities from a few mAh for embedded devices to several hundred Ah for hybrid electric vehicles and electric vehicles.

Evaluation of inductive displacement sensors for a basic active magnetic bearing test rig

In order to fulfill the requirements of an active magnetic bearing used for automotive application, two different inductive displacement sensor principles are evaluated. A basic test system is constructed in order to evaluate the sensor hardware. The results of the displacement measurement tested in a closed loop control operation are presented. Furthermore the test rigs performance is evaluated using two different control structures. A PID control and a state space control, by means of a Kalman Filter, are used

Mobile Flywheel Energy Storage Systems: Determining Rolling Element Bearing Loads to Expand Possibilities

Efficient energy storage is the key to modern hybrid or zero emission vehicles and low carbon mobility in general. Compared to conventional storage technologies like batteries, flywheel energy storage systems (FESSs) offer various theoretical advantages, such as high cycle life, no capacity fade over time, temperature independence, easy determination of state of charge, and complete recyclability. However, the special operating conditions of FESSs-such as vacuum, high rotational speeds, and high gyroscopic reactions, etc.-make bearing design a complex and crucial endeavor. This article describes methods of determining loads for rolling element bearings in automotive FESSs. An overview of FESS technology is given, followed by the discussion of an analytic, numeric, and empiric approach, including a detailed comparison of the different methods. Furthermore, the concept of a test bench investigating flywheel behavior in a resilient mount is described, and its results regarding the design of an FESS-tovehicle mount are discussed in depth.

State of charge determination of LiFePO 4 batteries using an external applied magnetic field

In recent years, lithium ion (Li-ion) batteries have become ubiquitous energy sources for various battery-powered applications. Due to the good availability, the moderate raw material costs and the thermal stability, lithium iron phosphate (LiFePO4) has become a common cathode active material for secondary cells. Batteries of this cell chemistry are further characterized by a high power density and are therefore often used in automotive applications. Unfortunately these cells show nonlinear and very flat open circuit voltage (OCV) characteristics, therefore the state of charge (SOC) can not be estimated accurately by means of model based estimation algorithms. This paper investigates an alternative way to determine the cells SOC, whereas instead of the OCV in combination with Coulomb counting, the variation of the inductance of an external sense coil is used to quantify the SOC.

Impedance measurements of ferrite core displacement sensors for flywheel energy storage systems

For active magnetically suspended rotors in flywheel energy storage systems (FESSs), an inexpensive, robust and reliable contactless displacement measurement is needed. This paper evaluates five different ferrite cores of different size and geometry for a possible use as a displacement sensor. The measurement method and procedure which was built to compare the different cores is described in details. Further the measurement results are discussed.