• 제목/요약/키워드: transformerless

검색결과 62건 처리시간 0.036초

변압기 없는 고승압 직류 컨버터용 대칭형 Cockcroft-Walton 회로 (Symmetrical Cockcroft-Walton circuit for Transformerless High Step-Up DC-DC Converter)

  • 차대중;백지은;고광철
    • 조명전기설비학회논문지
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    • 제29권8호
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    • pp.70-75
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    • 2015
  • High Step-up DC-DC Converters have been demanded for renewable energy applications. Transformer or coupled inductor is generally used to boost output voltage of converters. This methods can relatively obtain high voltage than others, whereas have heavy weight and high cost. To complement these disadvantages, we studied transformerless high step-up DC-DC converter. In various transformerless topologies, Boost converters combined with Cockcroft-Walton have studied. In this paper, we proposed a symmetrical Cockcroft-Walton circuit for transformerless high step-up DC-DC converter. Finally, we simulated proposed converter to compare with existing converter. As a result, proposed converter has higher duty ratio or lower cost than existing transformerless converters which are discussed in this paper.

VPI-based Control Strategy for a Transformerless MMC-HVDC System Under Unbalanced Grid Conditions

  • Kim, Si-Hwan;Kim, June-Sung;Kim, Rae-Young;Cho, Jin-Tae;Kim, Seok-Woong
    • Journal of Electrical Engineering and Technology
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    • 제13권6호
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    • pp.2319-2328
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    • 2018
  • This paper introduces a control method for a transformerless MMC-HVDC system. The proposed method can effectively control the grid currents of the MMC-HVDC system under unbalanced grid conditions such as a single line-to-ground fault. The proposed method controls the currents of the positive sequence component and the negative sequence component without separating algorithms. Therefore, complicated calculations for extracting the positive sequence and the negative sequence component are not required. In addition, a control method to regulate a zero sequence component current under unbalanced grid conditions in the transformerless MMC-HVDC system is also proposed. The validity of the proposed method is verified through PSCAD/EMTDC simulation.

A Modified Single-Phase Transformerless Z-Source Photovoltaic Grid-Connected Inverter

  • Liu, Hongpeng;Liu, Guihua;Ran, Yan;Wang, Gaolin;Wang, Wei;Xu, Dianguo
    • Journal of Power Electronics
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    • 제15권5호
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    • pp.1217-1226
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    • 2015
  • In a grid-connected photovoltaic (PV) system, the traditional Z-source inverter uses a low frequency transformer to ensure galvanic isolation between the grid and the PV system. In order to combine the advantages of both Z-source inverters and transformerless PV inverters, this paper presents a modified single-phase transformerless Z-source PV grid-connected inverter and a corresponding PWM strategy to eliminate the ground leakage current. By utilizing two reversed-biased diodes, the path for the leakage current is blocked during the shoot-through state. Meanwhile, by turning off an additional switch, the PV array is decoupled from the grid during the freewheeling state. In this paper, the operation principle, PWM strategy and common-mode (CM) characteristic of the modified transformerless Z-source inverter are illustrated. Furthermore, the influence of the junction capacitances of the power switches is analyzed in detail. The total losses of the main electrical components are evaluated and compared. Finally, a theoretical analysis is presented and corroborated by experimental results from a 1-kW laboratory prototype.

Transformerless Cascaded AC-DC-AC Converter for Multiphase Propulsion Drive Application

  • Tao, Xing-Hua;Xu, Lie;Song, Yi-Chao;Sun, Min
    • Journal of international Conference on Electrical Machines and Systems
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    • 제1권3호
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    • pp.354-359
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    • 2012
  • A transformerless converter suitable for multiphase drive application is presented in this paper. The topology employs a cascaded H-bridge rectifier as the interface between the grid and multi inverters which drive the multiphase motor. Compared with the conventional structure, the new topology eliminates the input transformer and also has the advantages such as four quadrant operation, simple configuration, low cost, high efficiency, and so on. The control strategies for the grid-side cascade H-bridge rectifier and the motor-side inverter are studied accordingly. Based on the multi-rotational reference frame, modular control scheme is developed to regulate the multiphase drive system. Simulation results show the proper operation of the proposed topology and the corresponding control strategy.

A PI-based Control Scheme for Primary Cascaded H-Bridge Rectifier in Transformerless Traction Converters

  • Tao, Xing-Hua;Li, Yong-Dong;Sun, Min
    • Journal of international Conference on Electrical Machines and Systems
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    • 제1권3호
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    • pp.360-365
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    • 2012
  • Cascaded H-Bridge rectifier (CHBR) is a more attractive solution in traction application for its transformerless structure. Because of the currents of different cells are exactly the same one, it is a challenge job to regulate the voltages of cells with only one current controller. In this paper, a PI-based control scheme is presented to deal with the voltages balance issue in CHBR. To satisfy the demand of rectifier such as unity power factor and regulated output DC voltages, the proposed control scheme consists of two parts. One is for shaping the grid current waveform and regulating the sum of DC-link voltages of all the cells; the other one is for balancing DC-link voltages. The latter is more concerned in this paper and is discussed in detail especially. Simulations and experiments are carried on. The results verified the feasibility and effectiveness of the proposed scheme.

변압기 없는 계통연계형 PV PCS에서의 MPPT 제어기법 비교 분석 (Comparison and analysis of the MPPT algorithms in transformerless grid-connected PV PCS)

  • 이경수;정영석;소정훈;유권종;최재호
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2004년도 하계학술대회 논문집 B
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    • pp.1471-1473
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    • 2004
  • Maximum power point tracking(MPPT) is used in photovoltaic(PV) systems to maximize the photovoltaic array output power, irrespective of the temperature and irradiation conditions. The object of this paper is to compare and analyze MPPT efficiency for different MPPT techniques by changing irradiance. Also, this paper introduces transformerless grid-connected inverter. Simple flow charts and characteristics of each MPPT algorithm are shown. The implementation of transformerless grid-connected inveter system was based on a digital signal processor(DSP). Simulation was carried out for each MPPT method.

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무변압기형 태양광 시스템에서 누설전류를 제거하기 위한 3레벨 인버터의 단순 SVPWM (A Simplified SVPWM for Three Level Inverters to Eliminate Leakage Currents in Transformeless Photovoltaic Systems)

  • 아르살란 안살리;김희준
    • 전기학회논문지
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    • 제65권2호
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    • pp.319-328
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    • 2016
  • This paper proposes a simplified SVPWM for three level inverters in transformerless photovoltaic (PV) systems. With the proposed SVPWM the three level space vector (SV) diagram is divided into only six sectors as in conventional two level SV diagram in such a way that only seven SVs are used among all the available SVs of three level inverter. The main features of the proposed SVPWM are that it is simple to implement, less switching losses as compared to conventional SVPWM and most importantly it eliminates the leakage currents in transformerless PV systems. Detailed theoretical analysis of the proposed SVPWM are presented and verified by numerical simulations and experimental results.

절연형 단상 태양광 PCS의 직류링크 커패시터 저감 (Reduction of DC-link Capacitance for Single-Phase Transformerless Photovoltaic Power Converters)

  • 누옌황부;이동춘
    • 전력전자학회:학술대회논문집
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    • 전력전자학회 2016년도 전력전자학술대회 논문집
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    • pp.365-366
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    • 2016
  • This paper presents a single-phase transformerless photovoltaic (PV) power converter systems based on the AC/DC boost inverter, which is capable of solving the leakage current and second-order ripple power issues. By eliminating the inherent ripple power in single-phase inverter, the bulky electrolytic capacitor can be replaced by a small film capacitor. The validity of the proposed scheme has been verified by the simulation results.

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변압기 없는 태양광 발전용 인버터의 제작 및 성능 특성 (The design and performance characteristic of transformerless inverter for the photovoltaic system)

  • 안교상;임회천;김신섭
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2003년도 하계학술대회 논문집 B
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    • pp.1368-1370
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    • 2003
  • In this paper, the design and performance characteristics of a 3 kW class transformerless photovoltaic inverter was introduced. The field test results of the photovoltaic power inverter showed that the excellence of power quality, the characteristic of starting waveform, the stability and reliability of operation.

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