Rahel Herzog


Last Name

Herzog

First Name

Rahel

ORCID

0009-0001-2860-5592

Organisational unit

02294 - Mechatronische Systeme / Mechatronic Systems

Filters

2024 - 20253
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Publications 1 - 3 of 3
  • Novel Bidirectional Three-Switch Single-Stage Single-Phase AC-DC Buck-Boost Converter With Ground-Referenced Output
    Item type: Journal Article
    Herzog, Rahel; Menzi, David; Leibl, Michael; et al. (2025)
    IEEE Journal of Emerging and Selected Topics in Power Electronics
    DC loads or sources like motor drives, batteries, and strings of photovoltaic (PV) panels with power levels up to the lower single-digit kilowatt range are typically connected to the single-phase mains using bidirectional ac-dc converters providing power factor correction (PFC) functionality. Often, a dc output voltage range spanning from values lower than to values greater than the grid voltage amplitude is required, and hence, the ac-dc converter must provide buck-boost capability. As an alternative to conventionally used two-stage systems, single-stage converters promise lower realization effort and, in particular, fewer active components like power transistors. This article, therefore, analyzes a new bidirectional single-stage single-phase ac-dc buck-boost converter with only three power transistors, whose topology is identified using a systematic approach that is briefly summarized. Advantageously, the new ac-dc converter's negative dc output terminal is connected to the mains neutral, i.e., there is no common-mode (CM) voltage at the dc output. The operating principle is explained in detail, and a new advanced modulation method is proposed, which reduces the switching losses by more than 33% and lowers the component stresses. A 3.3-kW proof-of-concept (non-optimized) demonstrator is developed, which connects to the single-phase European ac mains (230 V rms, line-to-neutral) and provides a wide dc output voltage range of 300-450 V. Both the conventional and the proposed advanced modulation method are experimentally verified, confirming an improvement of the peak efficiency from 95.9% to 96.7% (300 V dc output, 2.5 kW output power) for the advanced modulation method.
  • Novel Single-Stage High-Frequency-Isolated Four-Switch Bidirectional Single-Phase PFC Rectifier
    Item type: Conference Paper
    Herzog, Rahel; Menzi, David; Leibl, Michael; et al. (2024)
    2024 IEEE Workshop on Control and Modeling for Power Electronics (COMPEL)
    Power Factor Correction (PFC) rectifiers supplying a dc bus common for several variable speed motor drives should provide galvanic isolation and bidirectional power flow capability. State-of-the-art topologies often suffer from two-stage power conversion and/or high active component count. Therefore, this paper investigates a novel single-phase single-stage high-frequency-isolated PFC rectifier with non-pulsating input current and low active component count, i.e., only four standard power transistors with well-defined blocking voltages. The paper systematically explains the operating principle, and derives the main power component voltage and current stresses resulting in design guidelines for the realization of a 2.5kW prototype system interfacing the European 230V (rms) single-phase ac grid and an isolated 400V dc output, which achieves an estimated nominal efficiency close to 96%. Further, the paper details the closed-loop control strategy and proposes a start-up procedure, which are both verified by means of circuit simulations.
  • Active Low-Voltage Half-Bridge-Based CM EMI Filter for Three-Phase Motor Inverters
    Item type: Conference Paper
    Herzog, Rahel; Huber, Jonas (2025)
    2025 Energy Conversion Congress & Expo Europe (ECCE Europe)
    Voltage-source inverters (VSIs) provide dc-ac conversion in three-phase motor drives, e.g., operating from a common dc-bus in industry or from a battery in electric vehicles. To comply with electromagnetic interference (EMI) regulations, dc-side passive filters are needed, which can contribute up to 30% of the total converter weight/volume. Consequently, active filters (AFs) are of interest: Even though the AF effectiveness becomes limited at higher frequencies, the cutoff frequency of the remaining passive filter can be increased and its size thus substantially reduced. This paper proposes a common-mode (CM) AF for six-switch three-phase VSIs operated with standard SPWM or SVM. The AF only requires two low-voltage half bridges and a capacitive injection network. The operating principle, sensitivities, and design aspects are presented, and detailed circuit simulations of an industrial motor drive (400 V dc, 2.5 kW, IEC 61800−3 EMI limits, 24 V AF supply) and an EV traction inverter (800 V dc, 125 kW, CISPR 25 EMI limits, 48 V AF supply) verify the concept, indicating a reduction of the required CM filter inductance by a factor of 2 (EV) to 6 (industrial) compared to a passive filter.
Publications 1 - 3 of 3