Spasoje Miric

Last Name

Miric

First Name

Spasoje

ORCID

0000-0001-7885-6093

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Publications1 - 10 of 35

Enhanced Complex Space Vector Modeling and Control System Design of Multiphase Magnetically Levitated Rotary–Linear Machines
Miric, Spasoje; Giuffrida, Rosario V.; Bortis, Dominik; et al. (2020)
IEEE Journal of Emerging and Selected Topics in Power Electronics
Automatic Time-Division Multiplexing for Inductive Power Transfer to Multiple Stainless-Steel-Enclosed Receivers
Xu, Junzhong; Miric, Spasoje; Bortis, Dominik; et al. (2024)
IEEE Journal of Emerging and Selected Topics in Power Electronics
Linear actuators employed in the food-processing or pharmaceutical industry must be enclosed in stainless steel (SS) for hygienic reasons. Therefore, cables and cable carriers should be avoided and wireless, i.e., inductive power transfer (IPT) should be employed. To achieve high efficiencies, the magnetic field components of the IPT system should be oriented parallel to the SS enclosures, which can be achieved with a coaxial arrangement of closed magnetic cores mounted on the moving part/slider and a stationary primary winding. As an alternative to the typically employed current-impressed operating modes of IPT systems with a constant primary-winding current that limits part-load efficiency, the high magnetic coupling of this arrangement facilitates operation as an isolated constant-voltage-transfer-ratio series-resonant dc-dc converter, i.e., a dc transformer (DCX). However, then, only a single receiver can receive power at any given time, and a time-division multiplexing (TDM) method is needed to supply multiple receivers with power in a cyclic manner. This article proposes a novel automatic TDM (A-TDM) method that, unlike previous TDM methods, does not require any communication link nor a central controller. The new method is verified during startup, steady-state operation, and under load transients using an exemplary SS-enclosed IPT system with two 100 W receivers.
Double Stator Linear-Rotary Actuator with a Single Set of Mover Magnets
Miric, Spasoje; Schuck, Marcel; Tüysüz, Arda; et al. (2018)
2018 IEEE Energy Conversion Congress and Exposition (ECCE)
Dual-Inverter Topology for Single-Phase Supplied Drive Systems without Electrolytic Capacitor
Haider, Michael; Bortis, Dominik; Miric, Spasoje; et al. (2021)
2021 24th International Conference on Electrical Machines and Systems (ICEMS)
Single-phase supplied variable speed drive (VSD) systems are widely used in industrial applications and typically feature a two-stage design with a power factor corrected (PFC) boost rectifier and a three-phase voltage source inverter (VSI). However, the electrolytic DC-link capacitor, which is needed to cope with the twice grid frequency power pulsation, and the required boost inductor are unfavourable in terms of reliability, volume, cost, and complexity. Therefore, the proposed concept employs a dual-inverter topology with a three-phase open-end winding (OEW) machine, avoiding high-frequency inductors, and controls the system such that the power pulsation is buffered in the inertia of the drive train. Accordingly, the DC-link capacitance can be reduced drastically, enabling an electrolytic capacitor-less system, featuring a higher power density and an increased lifetime. This paper presents the operating principle and the corresponding closed-loop control structure, to achieve PFC operation, DC-link voltage balancing and average speed control. Detailed analysis reveals that the machine voltage can be selected independently of the grid peak voltage in contrast to existing concepts. The converter performance is evaluated based on simple performance indices with respect to the machine voltage. In the context of a 7.5kW compressor application for railway brakes with a wide input voltage range, a semiconductor loss reduction of 30% can be obtained compared to a state-of-the-art approach, further reducing the converter volume. Finally, the proper operation is verified with a closed-loop circuit simulation.
Three Levels Are Not Enough: Scaling Laws for Multilevel Converters in AC/DC Applications
Azurza Anderson, Jon; Zulauf, Grayson; Papamanolis, Panteleimon; et al. (2021)
IEEE Transactions on Power Electronics
Single-phase inverters and rectifiers in 230 V $_{\text{rms}}$ applications, with a dc-side voltage of 400 V, achieve ultrahigh efficiency with a simple two-level topology. These single-phase designs typically utilize a line-frequency unfolder stage, which has very low losses and essentially doubles the peak-to-peak voltage that can be generated on the ac side for a given dc-link voltage. For certain applications, however, such as higher power grid-connected photovoltaic inverters, electric vehicle chargers, and machine drives, three-phase converters are needed. Because of the three-phase characteristic of the system, unfolders cannot be similarly used, leading to a higher minimum dc-link voltage of the three-phase line-to-line voltage amplitude, which is typically set to 800 V for 230 V $_{\text{rms}}$ phase voltage systems. Previous demonstrations indicate that significantly more levels—and the associated higher cost and complexity—are required for ultrahigh-efficiency three-phase converters relative to their single-phase counterparts. In this article, we seek to determine the fundamental reason for the performance difference between three-phase 800 V dc-link converters and single-phase 400 V converters. First, we build a 2.2 kW dc/ac hardware demonstrator to confirm the necessity of higher complexity converters, showing a simultaneous reduction in efficiency and power density between a two-level 400 V benchmark (99.2% peak efficiency at 18.0 kW/L) and a three-level 800 V inverter phase-leg (98.8%, 9.1 kW/L). With the motivation confirmed, we derive general scaling laws for bridge-leg losses across the number of levels and dc-link voltage, finding the efficiency-optimal chip area and the minimum semiconductor losses. With commercially available Si or GaN power semiconductors, the scaling laws indicate that six or more levels would be required for an 800 V three-phase ac/dc converter to meet or exceed the bridge-leg efficiency of a two-level 400 V GaN benchmark for a fixed output filter. With a complete Pareto optimization, we find that at least seven levels are necessary to recover the efficiency of the two-level 400 V benchmark, and we validate this theory with a seven-level 800 V 2.2 kW hardware prototype with a power density of 15.8 kW/L and a peak efficiency of 99.03%. Finally, two practical solutions that make use of the benefits of unfolder bridges familiar in single-phase systems are identified for three-phase systems. © 2020 IEEE.
Application of WBG Power Devices in Future 3-Φ Variable Speed Drive Inverter Systems "How to Handle a Double-Edged Sword"
Kolar, Johann W.; Azurza Anderson, Jon; Miric, Spasoje; et al. (2020)
2020 IEEE International Electron Devices Meeting (IEDM)
Latest research results on three-phase wide-bandgap (WBG) inverter systems with full-sinewave output voltage filtering are reported. A new soft-switching modulation scheme for two-level 1200 V SiC inverters is described. Furthermore, a new Figure-of-Merit for determining maximum multi-level (ML) bridge-leg efficiency is defined and low-voltage GaN devices are evaluated considering ML flying capacitor (FC) and multi-cell inverter structures. Finally, new integrated-filter buck-boost current DC-link inverter topologies are discussed.
Three-Dimensional Analytical Modeling of an Eddy-Current-Based Non-Contact Speed Sensor
Tüysüz, Arda; Stolz, Tibor; Muetze, Annette; et al. (2021)
IEEE Open Journal of Industry Applications
This paper presents a computationally efficient, three-dimensional electromagnetic model for eddy-current-based speed sensors featuring an injection coil, two or more pick-up coils and a magnetic yoke. The superposition of incident and reflected fields, which was adopted in previous works, is replaced by a direct formulation; and Maxwell's equations are solved for the magnetic flux density vector, rather than involving a higher-order vector potential. The injected current is accounted for in the boundary conditions, and special attention is given to the modeling of the in-plane spreading of the coils by deriving coil-linkage functions. The magnetic field and eddy current distributions in the whole problem space is obtained by algebraically solving a 12-by-12 linear equation system. Results of the model are compared to experimental results from earlier publications for verifying the validity of the models. Even though derived primarily with the eddy-current-based speed sensing application in mind, the analysis presented in this paper can potentially contribute to various other eddy-current-based applications such as non-destructive testing, where probes with a magnetic yoke are utilized.
Comparative Evaluation of Overload Capability and Rated Power Efficiency of 200V Si/GaN 7-Level FC 3-Φ Variable Speed Drive Inverter Systems
Rohner, Gwendolin; Miric, Spasoje; Bortis, Dominik; et al. (2021)
2021 IEEE Applied Power Electronics Conference and Exposition (APEC)
Variable speed drive systems in e.g. robotics applications are challenged with discontinuous operation cycles and short-time overload current requirements of 2-3 times nominal load. As the motor itself constitutes a large thermal time constant compared to the semiconductor devices in the inverter, latter create a bottleneck for the increased losses during overload operation. Hence, special focus has to be laid on the inverter overload capability, preferably without overdimensioning the system. In this paper a transient thermal model of optimized cooling approaches for 200V GaN and Si packages is empirically deduced. The model is then used to design a 7-Level Flying Capacitor inverter (7L FCi) aiming for 99% efficiency at nominal load for facilitated motor integration and 3 times overload capability. Consequently, the number of parallel switches, switching frequencies and the volume of passive components such as the flying capacitors and the output filter inductor is considered. In order to omit oversizing the inverter and the output inductor for overload operation, an unorthodox way of increasing the switching frequency during overload is proposed. It is concluded, that the small chip size of the 200V GaN devices compared the 200V Si devices poses additional challenges when dealing with overload operation.
Dynamic Analysis of the Hydrodynamic Bearing of a Two-Stage Pediatric Left Ventricular Assist Device
Linnemeier, Sarah; Giuffrida, Rosario V.; Miric, Spasoje; et al. (2024)
The International Journal of Artificial Organs
Design and Experimental Analysis of a Selfbearing Double-Stator Linear-Rotary Actuator
Miric, Spasoje; Giuffrida, Rosario; Rohner, Gwendolin; et al. (2021)
2021 IEEE International Electric Machines and Drives Conference (IEMDC)
Linear-rotary actuators (LiRAs) are today used in industry applications where a controlled linear and rotary motion is necessary such as pick-and-place robots, servo actuation of gearboxes or tooling machines. However, in special industry applications that require high purity and/or high precision positioning, the usage of conventional LiRAs with mechanical bearings is limited. Therefore, in this paper a LiRA with integrated magnetic bearings, i.e. a selfbearing/bearingless LiRA, is analyzed. The actuator employs concentrically arranged linear and rotary stators placed inside and outside a cylindrically shaped mover, which results in a so-called selfbearing double-stator (SBDS) LiRA. A FEM geometry optimization of the SBDS LiRA is performed and Pareto performance plots concerning linear force and torque generation are obtained. A SBDS LiRA hardware demonstrator and an 18-phase inverter power supply hardware prototype are built and their operation is experimentally verified by rotary and linear position step response measurements.

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Spasoje Miric

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