• Title, Summary, Keyword: Converters

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Modified Ac-Dc Single-Stage Converters

  • Moschopoulos, Gerry;Liu, Yan;Bassan, Sondeep
    • Journal of Power Electronics
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    • v.7 no.1
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    • pp.44-54
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    • 2007
  • Ac-dc power conversion can either be done with two separate converter stages or with a single converter stage. Two-stage ac-dc converters, however, can be costly and complex, while the performance of single-stage converters is compromised due to a reduced number of components. Several researchers have therefore proposed adding some sort of auxiliary circuit consisting of a second switch and some passive elements to single-stage converters to improve their performance. Although these modified single-stage converters may have two converters, they are not two-stage converters as they do not have two separate and independently controlled converters that are always operating to convert power from one form to another. In this paper, the operation of ac-dc single-stage converters is first reviewed and their strengths and weaknesses are noted. The operation of several modified single-stage converters, including one proposed by the authors, is then discussed, and the paper concludes by presenting experimental results that confirm the feasibility of the proposed converter.

A Comparative Study of Simple Ac-Dc PWM Full-Bridge Current-Fed and Voltage-Fed Converters

  • Moschopoulos Gerry;Shah Jayesh
    • Journal of Power Electronics
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    • v.4 no.4
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    • pp.246-255
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    • 2004
  • Ac-dc PWM single-stage converters that integrate the PFC and dc-dc conversion functions in a single switching converter have been proposed to try to minimize the cost and complexity associated with implementing two separate and independent switch-mode converters. In this paper, two simple ac-dc single-stage PWM full-bridge converters are considered - one current-fed, the other voltage-fed. The operation of both converters is explained and their properties are noted. Experimental results obtained from simple lab prototypes of both converters are presented, then compared and discussed.

A New Approach to Reduced-Order Modeling of Multi-Module Converters

  • Park, Byung-Cho
    • Journal of Electrical Engineering and information Science
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    • v.2 no.4
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    • pp.92-98
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    • 1997
  • This paper presents a new approach to obtaining a reduced-order model for multi-module converters. The proposed approach can be used to derive the reduced-order model for a wide class of multi-module converters including pulse-width-modulated (PWM) converters, soft-switched PWM converters, and resonant converters. The reduced-order model has the structure of a conventional single-module converter while preserving the dynamics of the original multi-module converter. Derivation procedures and the use of the reduced-order model is demonstrated using a three-module boost converter.

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Circuit Properties of Zero-Voltage-Transition PWM Converters

  • Ostadi, Amir;Gao, Xing;Moschopoulos, Gerry
    • Journal of Power Electronics
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    • v.8 no.1
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    • pp.35-50
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    • 2008
  • A zero-voltage-transition (ZVT) pulse width modulated (PWM) converter is a PWM converter with a single main power switch that has an auxiliary circuit to help it turn on with zero-voltage switching (ZVS). There have been many ZVT-PWM converters proposed in the literature as they are the most popular type of ZVS-PWM converters. In this paper, the properties and characteristics of several types of ZVT-PWM converters are reviewed. A new type of ZVT-PWM converter is then introduced, and the operation of a sample converter of this type is explained and analyzed in detail. A procedure for the design of the converter is presented and demonstrated experimentally. The feasibility of the new converter is confirmed with results obtained from an experimental prototype. Conclusions on the performance of ZVT-PWM converters in general are made based on the efficiency results obtained from the experimental prototypes of various ZVT-PWM converters of different types.

Input Impedances of PWM DC-DC Converters: Unified Analysis and Application Example

  • Pidaparthy, Syam Kumar;Choi, Byungcho
    • Journal of Power Electronics
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    • v.16 no.6
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    • pp.2045-2056
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    • 2016
  • The input impedances of pulse width modulated (PWM) dc-to-dc converters, which dictate the outcomes of the dynamic interaction between dc-to-dc converters and their source subsystem, are analyzed in a general and unified manner. The input impedances of three basic PWM dc-to-dc converters are derived with both voltage mode control and current mode control. This paper presents the analytical expressions of the 24 input impedances of three basic PWM dc-to-dc converters with the two different control schemes in a factorized time-constant form. It also provides a comprehensive reference for future dynamic interaction analyses requiring knowledge of the converters' input impedances. The theoretical predictions of the paper are all supported by measurements on prototype dc-to-dc converters. The use of the presented results is demonstrated via a practical application example, which analyzes the small-signal dynamics of an input-filter coupled current-mode controlled buck converter. This elucidates the theoretical background for the previously-reported eccentric behavior of the converter.

A Study on the Performance Analysis for Power Converters of Electric Propulsion Ship (전기 추진선박의 전력변환장치 성능 분석에 관한 연구)

  • Kim, Jong-Su;Oh, Sae-Gin;Kim, Sung-Hwan;Kim, Hyun-Soo;Kim, Deok-Ki;Yoon, Kyoung-Kuk
    • Journal of the Korean Society of Marine Engineering
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    • v.32 no.8
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    • pp.1278-1284
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    • 2008
  • Electric propulsion motors are operated from a variable frequency drive, which supplies power to motors at a frequency appropriate to the desired speed. The objective of this study was to evaluate power converters for shipboard applications and to recommend converters that meet lower harmonic distortion levels and torque ripples. Two systems were studied in detail : Cyclo-converters and PWM-converters. Cyclo-converters are the obvious choice where size, weight and efficiency are the most critical issues. However they have a disadvantage in power factor and they produce severe torque ripples in the motor which makes them unacceptable without special systems. PWM-converters produces better motor current waveform and eliminates common mode voltage issues at the motor, but suffers a multiple stages of power conversion and the isolating transformer. Results of this case study show that PWM-converters are more advanced and efficient drives for induction motor of electric propulsion ship.

Average Current Control for Parallel Connected Converters

  • Jassim, Bassim M.H.;Zahawi, Bashar;Atkinson, David J.
    • Journal of Power Electronics
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    • v.19 no.5
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    • pp.1153-1161
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    • 2019
  • A current sharing controller is proposed in this paper for parallel-connected converters. The proposed controller is based on the calculation of the magnitudes of system current space vectors. Good current distribution between parallel converters is achieved with only one Proportional-Integral (PI) compensator. The proposed controller is analyzed and the circulating current impedance is derived for paralleled systems. The performance of the new control strategy is experimentally verified using two parallel connected converters employing Space Vector Pulse Width Modulation (SVPWM) feeding a passive RL load and a 2.2 kW three-phase induction motor load. The obtained test results show a reduction in the current imbalance ratio between the converters in the experimental setup from 53.9% to only 0.2% with the induction motor load.

Design Assessment and Certification Scheme of Tidal Energy Converters (조류발전설비 설계 평가 및 인증시스템)

  • Kim, Mikum;Kim, Manneung
    • 한국신재생에너지학회:학술대회논문집
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    • pp.238.1-238.1
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    • 2010
  • Researches and developments of tidal energy converters are close to commercialization stage. But, commercialization of tidal energy converters is not ready in korea. In Europe, many experts of company, laboratory and public institution involved in marine energy are active for commercialization of marine energy converters in European Marine Energy Centre. Furthermore, in IEC/TC114, standardization of technical standards for assessment and certification of tidal energy converters of each country is under discussion. Therefore, We have to prepare for commercialization, standardization and entry into the overseas market. In this study, trends of commercialization and standardization of international markets of marine energy converters are investigated and certification schemes of overseas are analyzed. We expect that this study will make contribution to establish the foundation of commercialization of tidal energy converters.

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Thyristor-Based Resonant Current Controlled Switched Reluctance Generator for Distributed Generation

  • Emadi Ali;Patel Yogesh P.;Fahimi Babak
    • Journal of Electrical Engineering and Technology
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    • v.2 no.1
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    • pp.68-80
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    • 2007
  • This paper covers switched reluctance generator (SRG) and its comparison with induction and synchronous machines for distributed generation. The SRG is simple in design, robust in construction, and fault tolerant in operation; it can also withstand very high temperatures. However, the performance and cost of the SRG power electronics driver are highly affected by the topology and design of the converter. IGBT and MOSFET based converters are not suitable for very high power applications. This paper presents thyristor-based resonant converters which are superior candidates for very high power applications. Operations of the converters are analyzed and their characteristics and dynamics are determined in terms of the system parameters. The resonant converters are capable of handling high currents and voltages; these converters are highly efficient and reliable as well. Therefore, they are suitable for high power applications in the range of 1MW or larger for distributed generation.

Research on High Efficiency Non-Isolated Push-Pull Converters with Continuous Current in Solar-Battery Systems

  • Li, Yan;Zheng, Trillion Q.;Chen, Qian
    • Journal of Power Electronics
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    • v.14 no.3
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    • pp.432-443
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    • 2014
  • In order to improve the output efficiency of solar cells and to extend the life span of batteries, the input currents of converters are required to be continuous. If low output voltage ripple is required at the same time, it is obvious that the application of basic two-order converters (such as Buck and Boost derived converters) will not be good enough. In this paper, a lot of non-isolated push-pull converters (NIPPCs) with continuous current will be introduced due to their lower current stress, higher efficiency and better EMC performance. By decomposing the converters into push-pull cells, inductor and free-wheeling diodes, two families of NIPPCs based on single inductor and coupled inductor separately are systematically generated. Furthermore, characteristics analyses for some of the generated converters are also shown in this paper. Finally, two prototypes based on the corresponding typical topologies are built in the lab to verify the theoretical outcomes.