Hans Ertl

Bio: Hans Ertl is an academic researcher from Vienna University of Technology. The author has contributed to research in topics: Three-phase & Rectifier. The author has an hindex of 20, co-authored 53 publications receiving 2547 citations. Previous affiliations of Hans Ertl include University of Vienna.

Analysis and practical relevance of CM/DM EMI noise separator characteristics

Abstract: This Paper details two different contributions related to practical CM/DM EMI measurements. A first part investigates sources and implications of measurement errors that result for CM/DM separators in a practical measurement environment with a particular focus on the recently presented input impedance criterion for CM/DM separators. Furthermore, the realization of an active CM/DM separator, which features competitive separation capabilities (DMTR/CMRR > 51 dB and CMTR/DMRR > 47 dB for frequencies up to 10MHz), is presented.

Design and experimental evaluation of the loss-free braking resistor concept for applications in integrated converter machine systems

Abstract: If the braking resistor of a conventional dissipative braking system (braking chopper) of a three-phase AC motor drive is replaced by a thyristor bridge (loss-free braking resistor) controlled in the full inverter operation, the braking energy of the drive can be fed back into the mains. This means that the current flowing into the mains via always two phases from the DC link is controlled by the power transistor of the braking chopper. In this paper, this regenerative braking system is discussed based on a 10 kW laboratory model.

Performance of a Two-Stage Actively Damped LC Filter for GaN/SiC Motor Inverters

Abstract: In this paper, the filter performance of a wide-bandgap (WBG) three phase motor inverter with integrated sinusoidal output voltage LC filter is analyzed. To ensure a well damped system behaviour at low losses, an active damping scheme based on filter capacitor feedback is used. Unfortunately, the nonlinear DC-Bias dependent capacitance of the used ceramic capacitors (X7R is used to minimize filter volume) significantly affects the active damping. A symmetrical filter structure sufficiently reduces the capacitors voltage dependency. However, the paper shows that the symmetrical structure also causes negative effects in respective to the filters noise suppression performance. Modifications in the filter topology are reported and analyzed for reducing the impaired noise suppression. The proposed filter scheme finally results in a well damped system behaviour fulfilling established EMC standards according output noise demonstrated by experimental results of a 2 kW/400 V laboratory prototype.

Output Impedance Compensation of a Cascaded Advanced AC-Simulator

Abstract: For testing grid connected components usually an AC power source and external passive components such as inductors and resistors are used. In order to improve the power density of such a system a concept of a cascaded advanced AC-simulator with virtual output impedance has been proposed. Such a system consists of a large signal and a small signal inverter, which are connected in series to emulate arbitrary grid characteristics, like voltage dips, frequency profiles, harmonics and grid impedance. This concept shows some advantages in terms of small signal bandwidth and measurement accuracy. While the large signal inverter merely has to provide the fundamental voltages, the small signal inverter emulates the voltage drop of the virtual impedance as well as harmonics with higher dynamic. Since the expected output voltage of the small signal inverter is much lower compared to the fundamental signals, fast switching MOSFETs with lower Drain-Source voltage can be implemented. However, for small virtual impedance values the output impedance of the large signal generator cannot be neglected and has to considered or compensated. One approach is to compensate the output impedance of the large signal inverter within the control system of the small signal inverter. The implementation and verification of such a compensation concept for a cascaded AC-Simulator with virtual output impedance is presented in this work.

Design and Performance Evaluation of a Three Phase AC Power Source with Virtual Impedance for Validation of Grid Connected Components

Abstract: The paper reports design and performance evaluation of a three-phase AC power source which is mainly used for the development, validation and testing of grid connected converter system and components. The main objective of the designed AC power source is the controllability of the output (grid) voltage amplitude and frequency, harmonic components as well as of the grid impedance characteristic. The small signal bandwidth of the proposed system is specified up to 2 kHz. To fulfill this requirement at very low output noise voltage levels, the target switching frequency has to be in the region of 200 kHz. For achieving acceptable efficiency 1200V silicon carbide (SiC) MOSFETs are used. The paper presents a comparison of estimated and measured semiconductor losses for discrete as well as module packaging and discusses the implementation of the gate driver stage, of the DC link and of the EMI output filter.

Reliability of Capacitors for DC-Link Applications in Power Electronic Converters—An Overview

Abstract: DC-link capacitors are an important part in the majority of power electronic converters which contribute to cost, size and failure rate on a considerable scale. From capacitor users' viewpoint, this paper presents a review on the improvement of reliability of dc link in power electronic converters from two aspects: 1) reliability-oriented dc-link design solutions; 2) conditioning monitoring of dc-link capacitors during operation. Failure mechanisms, failure modes and lifetime models of capacitors suitable for the applications are also discussed as a basis to understand the physics-of-failure. This review serves to provide a clear picture of the state-of-the-art research in this area and to identify the corresponding challenges and future research directions for capacitors and their dc-link applications.

Control of a Single-Phase Cascaded H-Bridge Multilevel Inverter for Grid-Connected Photovoltaic Systems

Abstract: This paper presents a single-phase cascaded H-bridge converter for a grid-connected photovoltaic (PV) application The multilevel topology consists of several H-bridge cells connected in series, each one connected to a string of PV modules The adopted control scheme permits the independent control of each dc-link voltage, enabling, in this way, the tracking of the maximum power point for each string of PV panels Additionally, low-ripple sinusoidal-current waveforms are generated with almost unity power factor The topology offers other advantages such as the operation at lower switching frequency or lower current ripple compared to standard two-level topologies Simulation and experimental results are presented for different operating conditions

The Essence of Three-Phase PFC Rectifier Systems—Part II

Abstract: In the first part of this paper, three-phase power factor correction (PFC) rectifier topologies with sinusoidal input currents and controlled output voltage are derived from known single-phase PFC rectifier systems and/or passive three-phase diode rectifiers. The systems are classified into hybrid and fully active pulsewidth modulation boost-type or buck-type rectifiers, and their functionality and basic control concepts are briefly described. This facilitates the understanding of the operating principle of three-phase PFC rectifiers starting from single-phase systems, and organizes and completes the knowledge base with a new hybrid three-phase buck-type PFC rectifier topology denominated as Swiss Rectifier. Finally, core topics of future research on three-phase PFC rectifier systems are discussed, such as the analysis of novel hybrid buck-type PFC rectifier topologies, the direct input current control of buck-type systems, and the multi-objective optimization of PFC rectifier systems. The second part of this paper is dedicated to a comparative evaluation of four rectifier systems offering a high potential for industrial applications based on simple and demonstrative performance metrics concerning the semiconductor stresses, the loading and volume of the main passive components, the differential mode and common mode electromagnetic interference noise level, and ultimately the achievable converter efficiency and power density. The results are substantiated with selected examples of hardware prototypes that are optimized for efficiency and/or power density.

Multilevel Inverter Topologies for Stand-Alone PV Systems

Abstract: This paper shows that versatile stand-alone photovoltaic (PV) systems still demand on at least one battery inverter with improved characteristics of robustness and efficiency, which can be achieved using multilevel topologies. A compilation of the most common topologies of multilevel converters is presented, and it shows which ones are best suitable to implement inverters for stand-alone applications in the range of a few kilowatts. As an example, a prototype of 3 kVA was implemented, and peak efficiency of 96.0% was achieved.