Electronics and Electric Drives
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Advanced Control Methods for High Performance Dual Two-Level Inverter for Traction Application
(2021)
The topology of the dual two-level inverter in combination with an electrical machine with open-end winding is an optimal
solution for the realization of high requirements from the automotive sector for high-performance traction drives. In this
publication, methods for extending the operating range and improving output voltage and current quality are presented
for synchronous as well as asynchronous PWM methods for the entire operating range for this system configuration.
Emphasis is placed on symmetrical power sharing between the inverters to maximize the power range. Optimal integration
of the system is achieved by the topology-related possibility of DC fast charging of the energy storages from a DC grid
without an additional charging unit.
Increasing data transmission rates and bandwidth both belong to the challenges of the development of high-performance wireless communication systems. Multi-channel communication systems commonly use several narrowband power amplifiers each one for a single communication channel. Lossy couplers are needed both to separate the different channels from each other at the amplifiers input and to combine the amplified signals on each channel at the output. This approach depicts a poor efficiency and is limited to a few number of channels since each channel duplication involves 3 dB losses due to couplers.
Alternatively, broadband radio frequency power amplifiers ensuring the simultaneous transmission of several carriers on a wide frequency range contribute to increase the cost and resource efficiency of transceivers in wireless communication systems. Gain flatness, a high output power, and low power levels of second and third order harmonics are required on the whole operating frequency range of the power amplifier in multi-carrier communication systems since overtones will degrade the quality of the communication.
The present work investigates the performances of a broadband push-pull power amplifier based on LDMOS transistors, the input matching network using a 8:1 transmission line transformer. For the first time investigations on harmonic distortions of the amplified signal when using a transformer with 8:1 impedance transformation ratio are presented. Characterisation of the power amplifiers performances is focused on gain flatness, output power, harmonic distortions and efficiency at 110 W.
The European Union-funded Advanced Superconducting Motor Experimental Demonstrator (ASuMED) project started in May 2017 with the purpose of demonstrating the benefits of a new, fully superconducting motor for reaching the targets established by the Flightpath 2050 plan. The project aims at a motor power density of 20 kW kg−1 using
a high-temperature superconducting (HTS) stator. The rotor will use HTS stacks operating like permanent magnets. A highly efficient cryostat for the motor combined with an integrated cryogenic cooling system and associated power converter will be used. This article provides a general overview of the prototype that is currently being assembled and that will be tested soon.
Im vorliegenden Beitrag wird die Topologie des Doppelzweipunktwechselrichters für die Anwendung in Elektrofahrzeugen vorgestellt. Dazu werden zunächst der Schaltungsaufbau und die spezifischen Schaltungseigenschaften näher erläutert. Anschließend werden relevante Vorteile dieser Topologie für die Anwendung in Elektrofahrzeugen dargestellt. Für die Kombination unterschiedlicher Energiequellen mit Hilfe des Doppelzweipunktwechselrichters werden geeignete Steuerungsstrategien präsentiert und anhand von realen Messungen am Systemprüfstand verifiziert. Mit dem Vorgestellten Verfahren kann die Leistungsaufteilung auf die beiden Energiespeicher und deren Energieaustausch untereinander mit hohem Freiheitsgrad gesteuert werden.
Electric drives in road vehicles with a battery as energy storage are about to be introduced to the mass market. In order to guarantee the quality and operational safety of battery-powered vehicles, considerable efforts must be made by car manufacturers and their suppliers. Since the properties of the batteries significantly determine the performance of the vehicles, special test benches with precise measuring systems are required for the accurate determination of the battery properties. The safety devices of the traction batteries must also be tested on high-performance test benches. In this paper the necessary test benches and the corresponding measuring systems are presented. Estimations of the measurement uncertainty and possibilities to increase measurement accuracy are presented.
High Dynamic Power Balancing for Dual Two-Level Inverters during High-Speed Machine Operation
(2020)
This paper aims to present optimized square-wave modulation strategies for the dual two-level inverter, fed by two separate and galvanically isolated energy sources, to balance and control the energy distribution of both inverter systems. Especially for high-speed operation, the methods keep the machine in the required state while decreasing the switching operations to a minimum. Method one aims to compensate voltage fluctuations of variable DC-link voltages, while the second method ensures a symmetrical power distribution for the two inverter systems. In addition, both methods offer the possibility of adapting the amplitude of the usually fixed fundamental load voltage during square-wave modulation.
This paper aims to present an optimized inverter topology, based on the dual two-level inverter, for feeding an open-end winding electrical machine with superconductive stator windings and a superconductive rotor. In order to achieve a high torque density, the stator windings are built of several superconducting tapes being in parallel. One inverter of the dual two-level inverter is equipped with powerful IGBT semiconductors and supplies the machine with energy. The second inverter is a low voltage MOSFET inverter that monitors the superconductor resistance (quench detection) and balances the current on the parallel superconductive tapes for guaranteeing an optimum operation with respect to the superconductive losses.
In this contribution, a highly dynamic calculation method of power quantities and additional electrical quantities, such as RMS values and fundamental waveforms, is presented. Typically, these quantities are calculated periodically based on the fundamental cycle of the electrical voltages and currents. Hence, they are well defined during steady state conditions for ideal periodical waveforms. During dynamic balancing processes, electrical signals are non-periodic. In a strict sense, the fundamental cycle-based definitions, which are well known from the literature, are not valid for these transient signals. However, this paper presents a novel definition for the calculation of cycle-based quantities based on the switching cycle of the inverter output voltages. This definition delivers instantaneous results during transient balancing processes, whereby it approximates the conventional fundamental cycle-based definitions during the steady state.
This contribution presents an innovative approximation method for the estimation of power quantities, fundamental waveforms, and RMS values of inverter-fed electrical machines. Typically, all these parameters are calculated as cyclically linked to the fundamental cycle of the voltages and currents of the inverter output or machine input. In order to increase the dynamic of this calculation, a suitable evaluation method based on the inverter switching cycle has been presented in previous publications. The present paper extends this switching frequency-based analysis by introducing additional quantities such as apparent and reactive power. Moreover, the paper describes the utilization of this analysis method for a power control of a dual two-level inverter-fed application.
This paper reveals that the standard test procedures for the qualification and verification of traction battery systems are not sufficient in certain cases. In fact, realistic and application-oriented tests on the interaction among the complex battery subsystems are inevitable. To achieve these objectives, a high-performance test bench with the unique selling features of a high voltage/- and current range, extremely low ripple currents, and high dynamics is presented. For the operation of the applied multiphase current-sharing inverter for charging/discharging the device under test (DUT), special control algorithms, especially a current balancing control method, is introduced.