Multiphase Topologies Research Articles

Comparative analysis of three‐phase dual active bridge converter with different transformer topology and modern universal control for DC microgrids

AbstractThe presented work discusses issues related to the use of modern multiphase topologies of Dual Active Bridge (DAB)‐type converters. Converters of this type are widely used in most DC microgrid applications. The introduction emphasizes a comparative analysis between single‐phase and multi‐phase DAB topologies within high‐power DC microgrids, delving into their respective advantages, drawbacks, design procedures, and considerations based on the latest knowledge. The publication explores the comparison and selection of viable topologies for deployment in high‐power and high‐efficiency DC microgrids. The unified method of controlling 1‐phase and multi‐phase DAB converters was proposed in this design, simplifying the issues of DC microgrid control. All topologies were tested on the same controller concept. The study performs laboratory investigation of DAB 1‐phase and 3‐phase: Star–Star, and Star–Delta topologies. Attention was paid to maintaining uniform operating conditions of the system, contrary to studies known from the literature, all tests were carried out on the same laboratory stand and the same magnetic components in different configurations. Analytical and laboratory analyses of the Zero Voltage Switching (ZVS) region were performed, accounting for non‐linear phenomena. Based on these findings, an assessment of the system's performance in soft switching was carried out. The presented results were implemented in a simulation model and subsequently validated through tests on a constructed laboratory setup to ensure the proper operation of the system. This work meticulously presents and discusses variations in efficiency, dynamic response, phase current harmonic distribution, phase shift distribution, ZVS switching region, and more among the examined topologies. To ensure a fair comparison, the converter configuration for both simulation and laboratory models utilized identical components across all configurations.

Hegazkinen elektrifikazioa: aktuatzaile elektromekanikoak eta propultsio elektrikoa

Gaur egun, elektrifikazio-maila altuak dituzten hegazkinak (MEA, More Electric Aircraft, ingelesez) kontuan hartzen dira aireko garraio ekologikoagoa, jasangarriagoa eta eraginkorragoa lortzeko. Alde horretatik, tradizionalak diren sistema pneumatikoak, hidraulikoak, eta mekanikoak sistema elektrikoengatik ordezkatu nahi dira, denborarekin, MEA kontzeptuaren helburuak lortzeko. Bi aplikazio elektriko nabarmentzen dira MEA motako hegazkinetan: aktuadore elektromekanikoak (EMA, Electro Mechanical Actuator, ingelesez) eta propultsio elektrikoa/hibridoa. Teknologia horien teknologiaren egoera garatzen da lan honetan, eta egileek EMA prototipo erreal batean lortutako emaitzak azaltzen dira. Horrez gain, sistema horien elementu nagusi diren potentzia-sistemak eta motor elektrikoak aztertzen dira, industria aeronautikoaren beharrizan zorrotzak direla-eta egokienak izan daitezkeen fase anitzeko topologietan zentratuz.

Magnetic Design and Experimental Evaluation of a Commercially Available Single Integrated Transformer in Three-Phase <italic>LLC</italic> Resonant Converter

Multiphase topologies are preferably employed in power conversion systems to lessen the per-phase circuit current, conduction losses, devices thermal stresses, and to reduce the output current ripples. A multiphase LLC resonant dc/dc converter usually possesses a number of magnetic cores equal to the number of phases. These magnetic cores are the major contributors to supply volume, weight, and size. For these reasons, circuit designers tend to select the topologies that have a minimal number of magnetic cores. In this paper, the authors aim to promote the industrial applications of the three-phase LLC resonant converter by integrating three transformers into a single commercially available magnetic core to reduce the volume, weight, and cost of the power converter. A comprehensive magnetic analysis for the three-phase-integrated transformer is conducted. Finite element method (FEM) simulation and experimental tests are carried out to validate the proper operation of the integrated transformer utilized in a 390-/12-V to 500-W prototype. Furthermore, the power losses distribution has been presented. The proposed integrated transformer has been proven effective, and it realized a uniform thermal distribution along the core compared to the three-discrete transformers.

A Current Sharing Method Utilizing Single Balancing Transformer for a Multiphase LLC Resonant Converter With Integrated Magnetics

Integrated magnetics is applied to replace the three-discrete transformers by a single core transformer in a three-phase LLC resonant converter. The magnetic circuit of the integrated transformer is analyzed to derive coupling factors between the phases; these coupling factors are intentionally minimized to realize the magnetic behavior of the three-discrete transformers, with the benefit of eliminating the dead space between them. However, in a practical design, the transformer parameters in a multiphase LLC resonant converter are never exactly identical among the phases, leading to unbalanced current sharing between the paralleled modules. In this regard, a current balancing method is proposed in this paper. The proposed method can improve the current sharing between the paralleled phases relying on a single balancing transformer, and its theory is based on Ampere’s law, by forcing the sum of the three resonant currents to zero. Theoretically, if an ideal balancing transformer has been utilized, it would impose the same effect of connecting the integrated transformer in a solid star connection. However, as the core permeability of the balancing transformer is finite, the unbalanced current cannot be completely suppressed. Nonetheless, utilizing a single balancing transformer has an advantage over the star connection, as it keeps the interleaving structure simple which allows for traditional phase-shedding techniques, and it can be a solution for the other multiphase topologies where realizing a star connection is not feasible. Along with the theoretical discussion, simulation and experimental results are also presented to evaluate the proposed method considering various sources of the unbalance such as a mismatch in: 1) resonant and magnetizing inductances; 2) resonant capacitors; 3) transistor on-resistances of the MOSFETS; and 4) propagation delay of the gate drivers.

Comparative study of digital control schemes for interleaved multi-phase buck converters

The increasing amount of required functionality in today’s electronic devices demands for more advanced power supply concepts. A possible solution to increase the performance and efficiency of DC-DC converters is to use multi-phase topologies. These converters employ multiple parallel power stages, hence sharing the total load current. In order to provide a regulated output voltage and equal sharing of the total current, a control loop is an essential part of such a converter. This paper presents three digital control schemes for multi-phase buck converters, namely, a linear voltage mode controller, a combined Ton/Toff control and a non-linear sliding mode control (SMC) law. Experimental results of a two-phase buck converter highlight the effectiveness of more sophisticated controllers and the benefits of multi-phase over single-phase converters.

A New Modeling and Analysis Approach Based on State-Space Averaging for Converters

4-quadrant converters (4QCs) have been widely applied in power active VAR and harmonic compensators, FACTS, electric drive systems, and a variety of other applications. The state-space averaging model is usually quite facile and suitable for converter topologies with only two switch states, like half-bridge 4QC units. When directly used in topologies with multiple switch states, however, the modeling method becomes overly complicated. Due to this, plus the fact that multi-phase PWM 4QCs and even other varieties of converters are mostly multi-unit-symmetrical, a novel method is necessary. By researching the inner link between multi-phase topologies and half-bridge units, including inter-phase symmetry configurations, and control relations, this paper proposes a general unified modeling approach for application to multi-phase 4QCs. A series of conclusions are derived, alongside theoretical analysis of the model. The validity of the model and its theory is confirmed using single-phase and three-phase 4QCs and their numerical simulating waveforms as special cases. The proposed method may also extend to the modeling, analysis, and general research of other varieties of converter topologies.

A New Method for Determining the Leakage Inductances of a Nine-Phase Synchronous Machine From No-Load and Short-Circuit Tests

The accurate determination of stator leakage inductances is presently an open issue in the analysis and testing of multiphase electric machines. Calculation methods are available, which involve complicated and often poorly precise three-dimensional (3-D) analyses. Experimental determination techniques, using measurements on the wound stator with the rotor removed, are also possible, but quite impractical, as they need to be performed during machine manufacturing or require rotor withdrawal. In this paper, a new approach is proposed to determine all the stator self- and mutual leakage inductances of a nine-phase synchronous machine based on a minimal set (a couple) of magnetostatic finite-element (FE) simulations, and on the measurements taken during no-load and short-circuit routine tests. The procedure is applied to a wound-field salient pole nine-phase synchronous generator for validation, showing good accordance with the results obtained from measurements on the machine with the rotor removed. A discussion is also proposed on the possibility to extend the presented procedure to other multiphase topologies.

Analysis of Output Current-Ripple RMS in Multiphase Drives Using Polygon Approach

Multiphase variable-speed drives, supplied from two-level voltage-source inverters (VSIs), are currently considered for a number of industrial applications. Although various multiphase pulsewidth-modulated (PWM) schemes had been recently developed, very little has been reported with regard to the impact of these schemes on harmonic losses (current ripple). This paper presents a general analytical analysis and comparison of harmonic losses of two basic continuous PWM (CPWM) schemes aimed at sinusoidal output-voltage generation. The analysis utilizes the concept of multiple polygon connections, which exist for multiphase systems, and covers all multiphase topologies with an odd phase number and single neutral connection. General harmonic distortion factors (HDFs) of sinusoidal PWM (SPWM) and harmonic injection PWM (HIPWM) are determined and compared for various phase numbers. Theoretical findings are verified by means of simulations and experimentally using a five-phase induction motor drive.

Output Power of Switched Reluctance Generator with regard to the Phase Number and Number of Stator and Rotor Poles

This paper deals with comparison of the SRG output power with regard to the phase number and number of stator and rotor poles. An optimal topology of SRG magnetic circuit from the point of view of achieved output power is investigated by means of FE analysis. On the base of presented mathematical model the output power is simulated for two kinds of single phase and five kinds of multiphase topologies. Some measurements are carried out in motoring mode and compared with FEM investigations and simulations to verify mathematical model of SR machine. Ill. 12, bibl. 12, tabl. 2 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.109.3.164