• Title/Summary/Keyword: Multilevel converter

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Robust Circulating Current Control in MMC Under the Unbalanced Voltage Condition (불평형 전압 조건에 강인한 모듈형 멀티레벨 컨버터의 순환전류 억제기법)

  • Moon, Ji-Woo;Park, Jung-Woo;Kang, Dae-Wook;Kim, Jang-Mok
    • Proceedings of the KIEE Conference
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    • 2015.07a
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    • pp.996-997
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    • 2015
  • This paper proposes parameter design principle of the sub-module capacitance, Arm inductance and a control method to reduced the circulating currents in modular multilevel converter(MMC) under unbalanced voltage conditions. Under balanced voltage conditions, only negative-sequence circulating currents exist. Consequently, the conventional method has considered only negative-sequence circulating currents in MMC. However, under unbalanced voltage conditions, there are positive-sequence, zero-sequence and negative-sequence circulating currents in MMC. Thus, under unbalanced voltage conditions, a control method should consider these all components. This study proposes the control method to reduced the circulating currents under the unbalanced voltage.

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A Modular Bi-Directional Power Electronic Transformer

  • Gao, Zhigang;Fan, Hui
    • Journal of Power Electronics
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    • v.16 no.2
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    • pp.399-413
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    • 2016
  • This paper presents a topology for a modular power electronic transformer (PET) and a control scheme. The proposed PET consists of a cascaded H-Bridge rectifier on the primary side, a high-frequency DC/DC conversion cell in the center, and a cascaded H-Bridge inverter on the secondary side. It is practical to use PETs in power systems to reduce the cost, weight and size. A detailed analysis of the structure is carried out by using equivalent circuit. An algorithm to control the voltages of each capacitor and to maintain the power flow in the PET is established. The merits are analyzed and verified in theory, including the bi-directional power flow, variable voltage/frequency and high power factor on the primary side. The experimental results validated the propose structure and algorithm.

A Dynamic Power Distribution Strategy for Large-scale Cascaded Photovoltaic Systems

  • Wang, Kangan;Wu, Xiaojie;Deng, Fujin;Liu, Feng
    • Journal of Power Electronics
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    • v.17 no.5
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    • pp.1317-1326
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    • 2017
  • The cascaded H-bridge (CHB) multilevel converter is a promising topology for large-scale photovoltaic (PV) systems. The output voltage over-modulation derived by the inter-module active power imbalance is one of the key issues for CHB PV systems. This paper proposed a dynamic power distribution strategy to eliminate the over-modulation in a CHB PV system by suitably redistributing the reactive power among the inverter modules of the CHB PV system. The proposed strategy can effectively extend the operating region of the CHB PV system with a simple control algorithm and easy implementation. Simulation and experimental results carried out on a seven-level CHB grid-connected PV system are shown to validate the proposed strategy.

Capacitance Value Analysis of Valve Test Circuit for HVDC MMC (HVDC MMC용 Valve 시험회로의 커패시터 용량 분석)

  • Seo, Byuong-Jun;Jo, Gwang-Rae;Nho, Eui-Cheol;Kim, Heung-Geun;Chun, Tae-Won
    • Proceedings of the KIPE Conference
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    • 2018.07a
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    • pp.456-457
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    • 2018
  • 본 논문에서는 MMC(Modular Multilevel Converter)용 Valve 시험회로의 설계를 위한 커패시터 값 선정에 대한 분석을 하고자 한다. 기존의 HVDC MMC용 Valve 시험회로는 전류를 선형적으로 증가시키고 감소시키기 때문에 적절한 전압과 전류를 공급할 커패시터와 인덕터의 설계가 중요하다. Valve 시험회로의 동작을 분석하고, 최적의 커패시터와 인덕터를 선정하여 각 서브모듈의 전압과 입력 전류의 오차를 낮추었으며 시뮬레이션을 통해 타당성을 검증하였다.

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Development of simulation model for offshore wind power generation with MMC for HILS application (HILS 적용을 위한 해상풍력 계통 연계 MMC 모델 개발)

  • Shin, Dong-Cheol;Yoon, Jin-Woo;Lee, Dong-Myung
    • Proceedings of the KIPE Conference
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    • 2018.07a
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    • pp.372-373
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    • 2018
  • HVDC(High Voltage Direct Current)전력망은 발전소에서 생산한 교류를 직류로 변환한 이후 송전하여 부하에 가까운 전력변환기를 이용하여 교류로 변환한 후에 사용하는 방식이며, 전압형 HVDC에 MMC(Modular Multilevel Converter)가 널리 사용되고 있다. 본 논문에서는 MMC가 적용된 HVDC를 이용한 해상 풍력 계통 제어 성능을 테스트하기 위해 실시간 시뮬레이션 툴인 RT-Lab에 적용한 모델에 대해 설명하고자 한다.

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Carrier Based Common Mode Voltage Reduction Techniques in Neutral Point Clamped Inverter Based AC-DC-AC Drive System

  • Ojha, Amit;Chaturvedi, Pradyumn;Mittal, Arvind;Jain, Shailendra
    • Journal of Power Electronics
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    • v.16 no.1
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    • pp.142-152
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    • 2016
  • Common mode voltage (CMV) generation is a major problem in switching power converter fed induction motor drive systems. CMV is the zero sequence voltage generated due to the switching action of power converters. Even a small magnitude of CMV with a high rate of change may circulate large bearing currents which may damage a machine's bearings and shorten its life. There are several methods of controlling CMV. This paper presents 3-level sinusoidal pulse width modulation based techniques to control the magnitude and rate of change of CMV in multilevel AC-DC-AC drive systems. Simulation and experimental investigations have been presented to validate the performance of proposed technique to control CMV in 3-level neutral point clamped inverter based AC-DC-AC system.

Modified Unipolar Carrier-Based PWM Strategy for Three-Level Neutral-Point-Clamped Voltage Source Inverters

  • Srirattanawichaikul, Watcharin;Premrudeepreechacharn, Suttichai;Kumsuwan, Yuttana
    • Journal of Electrical Engineering and Technology
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    • v.9 no.2
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    • pp.489-500
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    • 2014
  • This paper presents a simple modified unipolar carrier-based pulsewidth modulation (CB-PWM) strategy for the three-level neutral-point-clamped (NPC) voltage source inverter (VSI). Analytical expressions for the relationship between modulation reference signals and output voltages are derived. The proposed modulation technique for the three-level NPC VSI includes the maximum and minimum of the three-phase sinusoidal reference voltages with zero-sequence voltage injection concept. The proposed modified CB-PWM strategy incorporates a novel method that requires only of one triangular carrier wave for generate the gating pulses in three-level NPC VSI. It has the advantages of being simplifying the algorithm with no need of complex two/multi-carrier pulsewidth modulation or space vector modulation (SVM) and it's also simple to implement. The possibility of the proposed CB-PWM technique has been verified though computer simulation and experimental results.

A Novel Pulse-Width and Amplitude Modulation (PWAM) Control Strategy for Power Converters

  • Ghoreishy, Hoda;Varjani, Ali Yazdian;Farhangi, Shahrokh;Mohamadian, Mustafa
    • Journal of Power Electronics
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    • v.10 no.4
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    • pp.374-381
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    • 2010
  • Typical power electronic converters employ only pulse width modulation (PWM) to generate specific switching patterns. In this paper, a novel control strategy combining both pulse-width and amplitude modulation strategies (PWAM) has been proposed for power converters. The Pulse Amplitude Modulation (PAM), used in communication systems, has been applied to power electronic converters. This increases the degrees of freedom in eliminating or mitigating harmonics when compared to the conventional PWM strategies. The role of PAM in the novel PWAM strategy is based on the control of the converter's dc sources values. Software implementation of the conventional PWM and the PWAM control strategies has been applied to a five-level inverter for mitigating selective harmonics. Results show the superiority of the proposed strategy from the THD point of view along with a reduction in the inverter power dissipation.

A Novel Multilevel AC-AC Converter Without Commutation Problem (커뮤테이션 문제가 없는 멀티레벨 AC-AC 컨버터)

  • Kim, Sanghoon;Kim, Heung-Geun;Cha, Honnyong;Chun, Tae-Won;Nho, Eui-Cheol
    • Proceedings of the KIPE Conference
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    • 2014.07a
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    • pp.293-294
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    • 2014
  • 본 논문에서 커뮤테이션 문제가 없는 새로운 직접형 PWM 멀티레벨 AC-AC 컨버터를 제안한다. 스위칭셀 구조와 결합인덕터를 사용한 단상 PWM AC-AC 컨버터를 다단으로 결합한 구조로써 제안한 컨버터는 커뮤테이션 문제를 해결하기 위해 입력전압의 극성을 검출할 필요가 없다. 다단구조로 갈 경우 제안된 컨버터는 멀티레벨 출력이 가능하고 작은 전압내압을 가진 스위치 소자를 이용해서 높은 AC 전압을 얻을 수 있다. 그리고 Phase Shift PWM 기법을 적용하여서 인터리브드 효과로 인해 출력 필터의 크기를 획기적으로 줄일 수 있다. 400W급 2단 구조의 컨버터를 제작하여서 성능을 검증하였다.

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multilevel DC/DC converter (다중레벨 DC/DC 컨버터)

  • Lee, Seung-yul;Lee, Sang-Hyeok;Kang, Sung-gu;Song, Gwang-suk;Park, Sung-Jun
    • Proceedings of the KIPE Conference
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    • 2012.07a
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    • pp.516-517
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    • 2012
  • 최근 신재생 에너지 발전과 더불어 고효율, 고품질의 대용량 계통 연계형 발전에 대한 수요는 증가하고 있는 추세이다. 또한 스위치 소자값이 저렴해짐에 따라 새로운 멀티레벨 인버터에 대한 토폴로지 연구가 활발히 진행되고 있다. 멀티레벨 인버터는 레벨을 증가시킴으로서 THD 감소와 고효율을 이룰 수 있는 반면, 다수의 DC 전원이 필요한 단점을 갖고 있다. 따라서 본 논문에서는 하나의 DC 전원을 입력하면 독립적인 3개의 DC 전원을 출력하는 멀티레벨용 DC/DC 컨버터를 제안한다.

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