Design and Optimization of a High-Frequency GaN-Based ANPC Three-Level Converter as an Arbitrary PWL Voltage Generator
2020 IEEE Applied Power Electronics Conference and Exposition (APEC)
Recent advances in technology of GaN power devices and high-frequency magnetic materials are key ... more Recent advances in technology of GaN power devices and high-frequency magnetic materials are key enablers of small, compact designs of power converters in MHz range and the power range up to several hundreds of watts. However, impact of the devices and magnetic materials must be carefully characterized in order to fully understand the boundaries of current technology and to be able to exploit it fully. This is usually performed through a holistic, automated design procedure based on multi-objective optimization which focuses on the converter efficiency and power density for the given electrical parameters. In this paper, an optimized 100W, 1.75MHz-switching frequency, four-quadrant, voltage-source PWL arbitrary generator based on ANPC Three-Level converter is presented. The generator is capable of providing ±100V, ±1A at the output, with the tracking speeds up to 2V/µs, and the steady state efficiency beyond 95% and with a size below 12cm2. Thermal management of the system is successfully resolved using advanced cooling plates based on pyrolytic graphite sheets and forced air convection. Having these characteristics, the presented generator outperforms existing linear and hybrid power amplifiers from the literature.
Ultra-Versatile Power Converter based on a Multi-Winding Flyback Transformer for EV Application
2021 IEEE Vehicle Power and Propulsion Conference (VPPC), 2021
In this paper, an ultra-versatile power converter based on a multi-winding flyback transformer is... more In this paper, an ultra-versatile power converter based on a multi-winding flyback transformer is presented for EV application. Although the power converter concept, presented as Multi-cell Multi-port Bidirectional Flyback (M2BF), was initially proposed to interconnect several DC loads and/or sources, this paper proposes different configurations based on M2BF to interconnect and isolate different ports of an Electric Vehicle (EV), such as AC grid, High Voltage (HV) battery or Low Voltage (LV) battery. Numerous configurations are presented for each EV functionality, remarking the main differences and advantages respect to other configurations or SoA solutions. The main idea is to create a single power converter that performs the main functionalities of the EV, integrating several converters in a single circuit.
Methodology for multi-die package semiconductor Thermal Model in a Dynamic Environment
2021 28th International Workshop on Electric Drives: Improving Reliability of Electric Drives (IWED), 2021
This paper provides a detailed methodology for the development of a dynamic thermal model based o... more This paper provides a detailed methodology for the development of a dynamic thermal model based on the finite element method and statistical modelling. Finite element method based thermal modelling, consisting of a nonphysical model, is improved by means of statistical correlations to obtain accurate temperature estimates in response to dynamic boundary conditions, in contrast to the classical thermal models which are very dependent on the boundary conditions such as Cauer and Foster network, thus allowing it application for digital twinning and device failure reporting. The dynamic thermal model has been developed for a TO-247 IGBT device and, later, benchmarked and verified against measurements obtained from an experimental platform, composed of three IGBT half-bridge mounted on a single heatsink with forced air cooling.
In modern telecommunication systems, the requirements for amount of transmitted data are increasi... more In modern telecommunication systems, the requirements for amount of transmitted data are increasing. In order to transmit as much information as possible for a given spectral band, both amplitude and phase modulation are applied. The main power consumers in transmitters are power amplifiers(PA), placed in the output stage. During the last decade, a lot of efforts have been invested in optimization of the efficiency of RF power amplifiers. One of notable techniques is Kahn’s envelope and restoration (EER) principle, where highly efficient envelope tracker and non-linear RF amplifier (e.g. class E, F) are combined. In this paper, two different approaches in envelope tracking are presented. The first approach is based on an analog multiplexer and a linear regulator in series, while the second tracker consists of PWM controlled switches and the fourth order output filter. Both trackers are supplied with highly efficient (96%) switch-capacitor based multilevel power converter, which acts...
2017 IEEE Energy Conversion Congress and Exposition (ECCE), 2017
In modern aircraft designs, there is a need for new high power isolated DC/DC converters. Full br... more In modern aircraft designs, there is a need for new high power isolated DC/DC converters. Full bridge derived topologies are appropriate for these specifications. Aircraft specifications are demanding and a high power density is needed. In order to decrease volume, reactive component, such as the transformer have to be optimized in volume, weight and loses. High frequency is needed to decrease inductive component core size and magnetic integration is a key factor. With the use of high frequency, topologies that take advantage of both ZVS and q-ZCS can offer the best results. Resonant topologies have a lot of benefits for this kind of requirement in this application. In this paper, a comparison of different state of the art full-bridge based topologies is made. A detailed explanation of the benefits of the Series-Parallel solution is provided. Experimental result of the prototype are also shown to prove the concept.
A comparative analysis of two approaches in EER based envelope tracking power supplies
2017 IEEE Applied Power Electronics Conference and Exposition (APEC), 2017
In modern telecommunication systems, the requirements for amount of transmitted data are increasi... more In modern telecommunication systems, the requirements for amount of transmitted data are increasing rapidly. For a better spectral efficiency complex type modulations (QaM, OFDM) are used, resulting in high PAPR signals. As a consequence, if conventional linear amplifiers (classes A, B) are used in transmitters, prominent linearity, but poor efficiency are assured. The efficiency of the transmitters can be significantly improved using some of the popular techniques: Kahn EER technique, ET technique, Doherty amplifier, Chireix's amplifier. In this paper, two different approaches in supplying power amplifier based on EER technique are presented. The same part of both envelope amplifiers (EA) is switched-capacitor based voltage divider combined with switching structure, analog multiplexer. The analog multiplexer is assisted with series linear regulator, in the first system, and with a fourth order LC filter, in the second system. Two prototypes for 10 W average output power with about 40 W peak output power are fabricated and the experimental results are compared in terms of efficiency and signal quality.
In this paper, implementation and testing of non- commercial GaN HEMT in a simple buck converter ... more In this paper, implementation and testing of non- commercial GaN HEMT in a simple buck converter for envelope amplifier in ET and EER transmission techn iques has been done. Comparing to the prototypes with commercially available EPC1014 and 1015 GaN HEMTs, experimentally demonstrated power supply provided better thermal management and increased the switching frequency up to 25MHz. 64QAM signal with 1MHz of large signal bandw idth and 10.5dB of Peak to Average Power Ratio was gener ated, using the switching frequency of 20MHz. The obtaine defficiency was 38% including the driving circuit an d the total losses breakdown showed that switching power losses in the HEMT are the dominant ones. In addition to this, some basic physical modeling has been done, in order to provide an insight on the correlation between the electrical characteristics of the GaN HEMT and physical design parameters. This is the first step in the optimization of the HEMT design for this particular application.
This paper illustrates the impact of including a flying capacitor in a Boost converter. Both topo... more This paper illustrates the impact of including a flying capacitor in a Boost converter. Both topologies, Boost and Boost with Flying Capacitor, are compared in terms of efficiency and volume. Results obtained from an optimization algorithm are validated through simulations and a hardware prototype.
Valley Current Control for the Flying Capacitor Voltage Balancing in the Three-Level Boost Converter with Variable Switching Frequency
2021 IEEE Energy Conversion Congress and Exposition (ECCE), 2021
Valley current control (V-CMC) in the three-level flying capacitor (FC) boost converter in case o... more Valley current control (V-CMC) in the three-level flying capacitor (FC) boost converter in case of triangular conduction mode (TCM) operation under variable switching frequency $\left(f_{\mathrm{SW}}\right)$ and $T_{\mathrm{ON}}$ control is discussed in this paper. Main differences of this operating mode with the results previously presented in the literature for the constant switching frequency operation in terms of static instability of the inductor current and FC voltage are discussed. It is shown that the issue of subhamronic oscillations that exists in case of constant $f_{\mathrm{SW}}$ operation and demands inclusion of the compensation ramp, does not exist in case of variable switching frequency operation. Detailed theoretical analysis is conducted on the subject of the FC voltage imbalance and it is concluded that under equal magnetizing times in both halfs of the period, and balanced corresponding dead-times, FC voltage is perfectly balanced. On the other side, in case of no consumption at the output, it is discovered that, even under theoretically ideal conditions, charge balance of the flying capacitor for boosting factor higher than 2 can be achieved for any value of $V_{C \mathrm{fly}}$ voltage. This leads to the static imbalance of the flying capacitor voltage for $V_{\mathrm{IN}}\lt V_{\mathrm{OUT}} / 2$ and no-load conditions. In order to solve the problem of the previously described FC voltage imbalance, a very simple correction in the control loop is proposed that does not require any additional hardware and it is based on a very simple manipulation of the data that is already available in the FPGA. All the theoretical analysis presented is verified by the comprehensive prototype measurements under all theoretically analyzed conditions.
Influence of DC/DC Stage on the Design of the Output Filter of the Inverter Stage in Two-Stage Grid-Connected PV Systems
2021 IEEE Energy Conversion Congress and Exposition (ECCE), 2021
One-stage and two-stage grid connected PV systems are compared in terms of compactness for both, ... more One-stage and two-stage grid connected PV systems are compared in terms of compactness for both, 1000-V and 1500-V PV string voltage levels. Design space of the inverter’s output filter is investigated for case when dc bus voltage is very well controlled to its minimum value and when it varies in the full operating range. Full multivariable optimization is conducted for the analyzed design spaces in order to investigate possible compensation of the increase of the total system volume caused by the addition of a dc/dc stage by achieving more compact inverter stage for better controlled dc bus voltage. It is concluded that for the same efficiency, filter designs with lower dc bus voltage can occupy $\approx$ 50% less volume compared to the case when dc bus varies in the full operating range. Hybrid, multilevel, partial power processing topologies that employ new classes of 650-V and 900-V WBG devices, that are already reported in the literature and that occupy $\approx$ 0.8 -0.9dm 3 for the design rated for 1500-V PV system and 20kW of the output power are very good candidates for a dc/dc stage that can control dc bus voltage at the input of the inverter stage and that can improve significantly compactness of the inverter stage and of the whole system. All the analysis and estimations are justified by comprehensive simulations of the 1500-V grid-connected PV inverter in PSIM package.
2018 IEEE Applied Power Electronics Conference and Exposition (APEC), Mar 1, 2018
Switch-mode technology is the common choice for high efficiency audio power amplifiers. The dynam... more Switch-mode technology is the common choice for high efficiency audio power amplifiers. The dynamic nature of real audio reduces efficiency as less continuous output power can be achieved. Based on methods used for RF amplifiers this paper proposes to employ envelope tracking techniques to the power supply in order to improve efficiency. A 100 W prototype system was designed. Measured results show that systems employing envelope tracking can improve system efficiency from 2% to 12%, i.e. a factor of 6. The temperature rise is strongly reduced, especially for the switching power MOSFETs where it is halved from 100 • C to 50 • C.
System Linearity-Based Characterization of High-Frequency Multilevel DC–DC Converters for S-Band EER Transmitters
IEEE Journal of Emerging and Selected Topics in Power Electronics, 2019
In modern telecommunications systems, the requirements for the amount and speed of transmitted da... more In modern telecommunications systems, the requirements for the amount and speed of transmitted data are increasing rapidly. For better spectral efficiency, complex-type modulations [quadrature amplitude modulation (QAM) and orthogonal frequency-division multiplexing (OFDM)] are used, resulting in high peak-to-average power ratio (PAPR) signals. As a consequence, when conventional linear amplifiers (classes A and AB) are used in transmitters, both prominent linearity and poor efficiency are assured. The efficiency of the transmitters can be significantly improved using some of the popular techniques: Kahn envelope elimination and restoration (EER) principle, envelope tracking (ET) technique, Doherty amplifier, and Chireix’s amplifier. In this article, two different approaches in supplying a 2.4-GHz class-E power amplifier (PA) ( ${S}$ -band) based on the EER technique are analyzed and compared. The consistent part of the EER transmitters is a switched-capacitor-based voltage divider combined with a switching structure—analog multiplexer, in the envelope amplifiers (EAs) and a class-E PA. The analog multiplexer is assisted with a series linear regulator in the first system and a fourth-order ${LC}$ filter in the second system, providing supply modulation for the PA. The systems are compared in terms of efficiency and system linearity using the standard metrics [error vector magnitude (EVM) and adjacent channel power ratio (ACPR)]. Special consideration is devoted to the characterization of how the EAs affect the quality of the RF output signal. It is shown that the tested EER transmitters can reproduce 16-QAM and 64-QAM signals up to 2.5 MHz, manifesting an average efficiency of about 32% with the first transmitter, and 16-QAM signals up to 660 kHz RF bandwidth and average efficiency of 44% with the second transmitter. A software tool that accurately estimates the EA linearity is utilized and successfully tested on both EER transmitters.
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Papers by Miroslav Vasic