Matthias Gerlich

A bidirectional battery charger for electric vehicles with V2G and V2H capability and active and reactive power control

A bidirectional battery charger using a three-phase voltage source inverter (VSI) is presented to be employed in plug-in electric vehicle applications enabling Vehicle-to-Grid (V2G) and Vehicle-to-Home (V2H) functionality with simultaneous active and reactive power control. The charger is controlled by a grid supervising unit with voltage droop control, providing it with P (active) and Q (reactive) power requests, and is responsible of reporting back its available power reserves (apparent power). In V2G mode the grid voltage is observed and a current controller on the d-q coordinate system together with the three phase inverter can transfer energy in both directions. Also reactive power compensation, inductive or capacitive, is possible. Asymmetries on the grid load can also be compensated by slight modifications of the control regime. Further, in V2H mode, the charger system can be seen as the master grid-forming generator responsible to provide a stable voltage at the network frequency. A proper synchronization strategy is presented as well, to guarantee smooth reconnection with the power grid. The proposed architecture is modeled in Simulink and aims the realization in existing electric vehicle and smart grid prototypes of the Siemens AG.

Modelling and identification of a piezoelectrically driven fuel injection control valve

In this article, the modelling and identification of a piezoelectrically driven control valve of a common-rail diesel fuel injector in an experimental setup is presented. The piezoelectric actuator of the control valve exhibits a strong temperature dependence. Furthermore, an unknown mechanical parameter in the control valve mechanics, the idle stroke value, has to be determined. An optimization-based method is used for temperature adaptation as well as for the identification of the unknown idle stroke value. Both the suppression of the temperature dependence and the exact knowledge of the idle stroke value are essential for the opening width and opening point of time of the control valve and thus for the accuracy of the fuel injection. The identification task becomes even more challenging because only the electrical signals of the actuator, namely voltage and current, are measurable. The method is successfully validated in an experimental setup.

In-Cylinder Pressure Measurement with a Gasoline Injector

Abstract The paper describes a model based concept for measuring the combustion pressure with a piezo gasoline injector. For this purpose, the integrated piezo actuator is also used as sensor to avoid additional components and costs. In order to reconstruct the exact pressure signal, the time-varying piezo parameters are identified using a minimization approach. The potential of the concept is shown by experiments on a single cylinder test station.

Self-sensing-Aktoren am Beispiel eines piezoelektrischen Einspritzventils mit sensorischen Fähigkeiten

Zusammenfassung Piezoelektrische Einspritzventile werden im Automobilbereich bisher als reine Aktoren verwendet, obwohl die darin enthaltenen Piezoaktoren als sogenannte Self-sensing-Aktoren in der Lage sind, auch sensorische Aufgaben zu übernehmen. Dadurch könnten verbrennungsspezifische Größen bestimmt werden, ohne die Kosten- und Bauraumanforderungen wesentlich zu erhöhen. Im folgenden Artikel wird ein piezoelektrisches Einspritzventil mit sensorischen Fähigkeiten vorgestellt. Es wird gezeigt, dass dieses Bauteil die Überwachung des Zylinderdrucks erlaubt.

DI-CNG injector characterization at small energizing times by means of numerical simulation

In the last few years, a significant research effort has been made for developing and enhancing Direct Injection (DI) for compressed natural gas (CNG) engines. Several research projects have been promoted by the European Community (EC) in this field with the objective of finding new solutions for the automotive market and also of encouraging a fruitful knowledge exchange among car manufacturers, suppliers and technical universities.This paper concerns part of the research activity that has been carried out by the Politecnico di Torino, AVL List GmbH and Siemens AG within the EC VII Framework Program (FP) InGAS Collaborative Project (CP), aimed at optimizing the control phase of a new injector for CNG direct injection, paying specific attention to its behavior at small injected-fuel amounts, i.e., small energizing times. The CNG injector which was developed within the research project proved to be suitable to be used in a DI SI engine, featuring a pent-roof combustion chamber head and a bowl in piston, with reference to both homogeneous and stratified charge formation. Fuel flow measurements made by AVL on the four-cylinder engine revealed a good linearity between injection duration and fuel mass-flow rate for injection durations above a reference value.In order to improve the injector characterization at short injection durations, an experimental and numerical activity was designed. More specifically, a multidimensional CFD model of the actual injector geometry was built by Politecnico di Torino, and purposely-designed simulation cases were carried out, in which the needle-lift time-history was defined on the basis of experimental measurements made by Siemens. The numerical model was validated on the basis of experimental data concerning the total injected-fuel amount under different conditions. Then, the model was applied in order to evaluate the dynamic flow characteristic by taking also the inner geometry of the injector valve group into account, so as to establish a correlation to the needle lift measurements done by Siemens for injector characterization.In the paper this dynamic behavior of the injector is analyzed, under actual operating conditions, and its impact on the nozzle injection capability is discussed. The simulation results did not show significant oscillations of the stagnation pressure upstream of the nozzle throat section, and thus the resultant mass-flow rate profile is almost proportional to the needle-lift one. As a consequence, in order to characterize the injector flow behavior in the nonlinear region (short injection duration), the measurement of needle lift is sufficient.Copyright

Idle Stroke Detection for a Fuel Injection Control Valve

Abstract In this paper, a method for detecting the idle stroke of a piezoelectrically driven fuel injection control valve is presented. The idle stroke constitutes a small gap in the range of a few micrometers between the piezoelectric actuator and the control valve which has to be usually adjusted in the assembling process. The identification approach only relies on the analysis of the electric signals of the piezoelectric stack actuator. Neither a mathematical model of the piezoelectric actuator with its inherent nonlinear hysteresis behavior nor a model of the hybrid structure of the control valve mechanics is required. Measurement results prove the feasibility of the proposed concept.