• Journal of international Conference on Electrical Machines and Systems
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• 제2권3호
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• pp.321-329
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• 2013

A multilevel inverter employing a cascade transformer is proposed for a silent-discharge-tube ozone generating system. The proposed inverter consists of four full-bridge inverters and fourteen transformers which have a series-connected secondary. It can accurately control the amplitude of the output voltage; hereby, it improves a linear characteristic of the rate of ozone yielding. The power regulation characteristics and operational principle of the proposed system are explained from a practical point of view. High precision ozone generating performance of the proposed multilevel inverter is verified by computer-aided simulations and experiment results.

• Journal of Power Electronics
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• 제10권2호
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• pp.155-164
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• 2010

This paper presents a voltage control algorithm for a hybrid multilevel inverter based on a staged-perception of the inverter voltage vector diagram. The algorithm is applied to control a three-stage eighteen-level hybrid inverter, which has been designed with a maximum number of symmetrical levels. The inverter has a two-level main stage built using a conventional six-switch inverter and medium- and low- voltage three-level stages constructed using cascaded H-bridge cells. The distinctive feature of the proposed algorithm is its ability to avoid the undesirable high switching frequency for high- and medium- voltage stages despite the fact that the inverter's dc sources voltages are selected to maximize the number of levels by state redundancy elimination. The high- and medium- voltage stages switching algorithms have been developed to assure fundamental switching frequency operation of the high voltage stage and not more than few times this frequency for the medium voltage stage. The low voltage stage is controlled using a SVPWM to achieve the reference voltage vector exactly and to set the order of the dominant harmonics. The inverter has been constructed and the control algorithm has been implemented. Test results show that the proposed algorithm achieves the desired features and all of the major hypotheses have been verified.

• 전력전자학회논문지
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• 제9권6호
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• pp.620-627
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• 2004

H-브릿지 멀티레벨 인버터는 여러 개의 단상 Power Cell을 직렬로 연결함으로써 저전압 전력용 반도체를 사용하여 고전압을 얻을 수 있고, 정현파에 가까운 출력전압 파형을 얻을 수 있는 멀티레벨 인버터 토폴로지이다. 본 논문은 산업현장에서 신뢰성을 인정받아 많이 사용되고 있는 직렬통신 방식의 일종인 CAN통신 인터럽터를 이용한 H-브릿지 멀티레벨 인버터 Power Cell의 PU 동기화 및 위상전이 방법에 관한 것이다. 제안된 방법의 주요 장점은 주제어기와 셀 제어기 사이에 직렬통신(CAN)을 사용함으로써 주제어기와 셀 제어기의 신호선의 단순화, 주제어기의 부담 감소, Power Cell의 모듈화, 셀 단위의 보호동작 용이, 확장성 향상 그리고 제어 신호 및 Power Cell의 신뢰성을 향상에 있다. 13레벨로 구성된 H-브릿지 멀티레벨 인버터 시험을 통해 제안된 방법의 타당성과 신뢰성을 입증하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.70-71
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• 2017

This paper presents a new cascaded boost multilevel converter topology for distributed generation (DG) systems. Most of DG systems, such as photovoltaic (PV), wind turbine and fuel cells, normally require the complex structure power converters, which makes the system expensive, complex and hard to control. However, the proposed converter topology can generate a much higher output voltage just by using the standard low-voltage switch devices and low voltage DC-sources in a simplified structure, also enhancing the reliability of the switch devices. Simulation and experimental results with a 1.2kW system are presented to validate the proposed topology and control method.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 추계종합학술대회
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• pp.681-684
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• 2005

본 논문은 (3$^{n-1}$+2) 레벨 형성법에 기반한 멀티레벨 인버터를 제안한다. PWM 인버터, LEVEL 인버터와 다단 변압기로 구성되는 이 회로는 양질의 출력전압을 형성하기 위해서 이차측이 직렬로 결합된 다단 변압기를 이용하게 된다. 변압기 권선비의 적절한 선택을 통해 입력전압의 정수비 형태로 주어지는 출력전압레벨을 형성할 수 있다. 제안된 방식으로 11레벨, 29레벨 시작품을 제작하여 실험을 통해 타당성을 검증한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1163-1164
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• 2011

Cascaded H-bridge 멀티레벨인버터의 구동을 위해서는 독립된 입력전압원의 확보가 필요하다. 본 논문에서는 이러한 Cascaded H-bridge 멀티레벨 인버터의 구조적 제약을 극복하기 위해 Buck-boost 컨버터와 Flyback 컨버터의 결합을 이용한 단일입력전원 구동 방법을 제안한다. 제안된 회로의 이론적 분석을 수행하고 시뮬레이션을 통하여 타당성을 검증한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.387-388
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• 2017

Cascaded H-bridge 멀리레벨인버터는 출력전압 레벨 수를 증가시켜 고전압 응용이 가능하도록 하는 전력변환장치로 모듈화 특성이 우수하여 그 활용 범위를 넓혀가고 있다. 출력 전압레벨 수를 증가시켜 보다 정현파에 가까운 양질의 출력전압을 생성하기 위해서는 스위칭 소자와 입력 전압원 개수의 증가로 인해 회로구조와 제어방법이 복잡해지는 문제가 발생한다. 하지만 스위칭 여유율(Redundancy)에 따른 대체 스위칭 패턴의 적용으로 전체 시스템의 신뢰성을 개선시킬 수도 있다. 본 논문에서는 고장나무 분석을 통해 Cascaded H-bridge 멀티레벨 인버터의 위험도를 계산하고 스위칭 여유율과의 관련성을 분석하고자 한다.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1674-1683
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• 2016

In this paper, a Finite Control Set Model Predictive Control (FCS-MPC) for a five level cascaded multilevel inverter (CMLI) with reduced switch topology is proposed. Five switches are used here instead of conventionally used eight switches. The main contribution of this paper is to make the MPC controller work for the reduced switch topology using only 19 voltage vectors in place of conventional 61 voltage vectors for a five level CMLI. This simplifies the execution of the MPC algorithm, paving a way for the significant reduction in the computational time. The controller makes use of the excellent ability of MPC to multitask, by adding one more objective which is to reduce the average switching frequency in addition to controlling the load current. This is especially important, since switching losses and therefore switching frequency is significant for high-power applications. The trade-off of this MPC is that the current is not as smooth as the 61 vector scheme, but well within the limits of IEEE standards. The results shown prove that this MPC works well in steady state and dynamic conditions too.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권1호
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• pp.77-83
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• 2012

In this paper, an optimal solution to the harmonic reduction problem in a cascaded multilevel inverter with non-equal DC sources using a genetic algorithm (GA) is presented. Switching angles are generated for different values of modulation index by the proposed algorithm, considering minimum voltage total harmonic distortion (THD) whereas selected harmonics are controlled within the allowable limits at all desired modulation indices including the point of discontinuity. Results are stored as a look-up table to be used to control the inverter for a certain operating point. The computed angles are used in a simulated circuit in Matlab\Simulink to validate the results.

• Journal of Power Electronics
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• 제10권4호
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• pp.365-373
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• 2010

This paper proposes a hybrid single carrier sinusoidal modulation suitable for multiphase multilevel inverters. Multiphase multilevel inverters are controlled by hybrid modulation to provide multiphase variable voltage and a variable frequency supply. The proposed modulation combines the benefits of fundamental frequency modulation and single carrier sinusoidal modulation (SC-SPWM) strategies. The main characteristics of hybrid modulation are a reduction in switching losses and improved harmonic performance. The proposed algorithm can be applied to cascaded multilevel inverter topologies. It has low computational complexity and it is suitable for hardware implementations. SC-SPWM and its base modulation design are implemented on a TMS320F2407 digital signal processor (DSP). A Complex Programmable Logic Device realizes the hybrid PWM algorithm and it is integrated with a DSP processor for hybrid SC-SPWM generation. The feasibility of this hybrid modulation is verified by spectral analysis, power loss analysis, simulation and experimental results.