• Proceedings of the KIEE Conference
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• 2011.07a
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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.

• Proceedings of the KIPE Conference
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• 2017.07a
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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.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1167-1168
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• 2011

두 대의 동일한 H-bridge 모듈로 구성되는 Cascaded H-bridge 멀티레벨인버터는 출력전압에 5-레벨을 형성할 수 있으며 출력전압의 THD를 개선시키기 위해 PWM 스위칭을 적용할 수 있다. 출력필터 사이즈를 줄이기 위해 PWM 스위칭 주파수를 높일 수 있지만 스위칭 손실이 증가하게 된다. 본 논문에서는 이러한 경우 스위칭 손실을 저감시킬 수 있는 변형된 스위칭 패턴을 제안한다. Cascaded H-bridge 멀티레벨인버터의 특성을 고려하여 하단 H-bridge 모듈의 스위치는 기본 출력전압 레벨을 형성하도록 동작시키며, 상단 H-bridge 모듈 스위칭에 의한 출력값이 기본 전압레벨에 가감되어 PWM 출력전압 형성하도록 동작시킨다. 제안된 스위칭 패턴을 Cascaded H-bridge 멀티레벨인버터에 적용하여 기존 스위칭 방법과 비교 분석한다.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1504-1512
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• 2016

This paper presents a new single-phase asymmetrical cascaded multilevel DC-link inverter. The proposed inverter comprises two stages. The main stage of the inverter consists of multiple similar cells, each of which is a half-bridge inverter consisting of two switches and a single DC source. All cells are connected in a cascaded manner with a fixed neutral point. The DC source values are not made equal to increase the performance of the inverter. The second circuit is a folded cascaded H-bridge circuit operating at a line frequency. One of the main advantages of this proposed topology is that it is a modular type and can thus be extended to high stages without changing the configuration of the main stage circuit. Two control schemes, namely, low switching with selective harmonic elimination and sinusoidal pulse width modulation, are employed to validate the proposed topology. The detailed approach of each control scheme and switching pulses are discussed in detail. A 150W prototype of the proposed system is implemented in the laboratory to verify the validity of the proposed topology.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.29-35
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• 2013

For the purpose of designing and applying optimum surge protection, one of the essential points is to take into account the energy coordination between cascaded surge protective devices(SPDs) and it is important to obtain an acceptable sharing of the energy stress between two cascaded SPDs. In this paper, in case of two voltage-limiting SPDs connected in parallel, the amount of splitting impulse current and energy that flow through each SPDs is investigated as a function of the protective distance. As a result, the energetic coordination between cascaded SPDs is strongly dependent on the voltage protection level of SPDs and the protective distance. It was confirmed that the sharing of the energy between two cascaded SPDs and the limited voltage levels are appropriate when the voltage protection levels of both upstream and downstream SPDs are the same.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1096-1097
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• 2015

Cascaded DC-DC컨버터 방식은 전체 모듈을 하나의 인버터로 제어하는 중압집중방식에 비하여 일사량 변화 및 부분 음영에 대하여 최대전력발전에 유리하다. 태양광발전시스템에서 똑같은 조건의 부분 음영이 발생하였을 때 중앙집중 인버터 방식에서는 부분 음영의 영향을 받는 모듈이 부하로 작용하여 최대전력점을 제대로 추정하지 못하는 반면 Cascaded DC-DC컨버터 방식은 일사량의 변화에도 최대전력추종을 하여 비교적 높은 효율로 발전을 할 수 있다. 본 논문에서는 태양광발전시스템에서 중앙집중 인버터 방식과 Cascaded DC-DC컨버터 방식에 부분 음영이 발생하지 않았을 때와 발생하였을 때의 발전량의 차이를 PSCAD/EMTDC를 통해 모의 분석하고, 실제 태양광발전시스템에 적용하여 비교 분석한다.

• Journal of Power Electronics
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• v.16 no.1
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• pp.340-350
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• 2016

A cascaded hybrid multilevel inverter including a reconfiguration technique for low voltage dc distribution applications is proposed in this paper. A PWM generation fault detection and reconfiguration paradigm after an inverter cell fault are developed by using only a single-chip controller. The proposed PWM technique is also modified to reduce switching losses. In addition, the proposed topology can reduce the number of required power switches compared to the conventional cascaded multilevel inverter. The proposed technique is validated by using a 3-kVA prototype. The switching losses of the proposed multilevel inverter are also investigated. The experimental results show that the proposed hybrid inverter can improve system efficiency, reliability and cost effectiveness. The efficiency of proposed system is 97.45% under the tested conditions. The proposed hybrid inverter topology is a promising method for low voltage dc distribution and can be applied for the multiple loads which are required in a data center or telecommunication building.

• Journal of Power Electronics
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• v.15 no.4
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• pp.951-963
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• 2015

In this paper, a new symmetric multilevel inverter is proposed. A simple structure for the cascaded multilevel inverter topology is also proposed, which produces a high number of levels with the application of few power electronic devices. The symmetric multilevel inverter can generate 2n+1 levels with a reduced number of power switches. The basic unit is composed of a single and double source unit (SDS-unit). The application of this SDS-unit is for reducing the number of power electronic components like insulated gate bipolar transistors, freewheeling diodes, gate driver circuits, dc voltage sources, and blocked voltages by switches. Various new algorithms are recommended to determine the magnitude of dc sources in a cascaded structure. Furthermore, the proposed topology is optimized for different goals. The proposed cascaded structure is compared with other similar topologies. For verifying the performance of the proposed basic symmetric and cascaded structure, results from a computer-based MATLAB/Simulink simulation and from experimental hardware are also discussed.

• Current Optics and Photonics
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• v.2 no.5
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• pp.407-412
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• 2018

An optimal matching approach is proposed to maximally ensure the output power uniformity of the cascaded encoder in the passive optical network (PON) monitoring system based on a remote coding scheme. The calculation results show that the optimum arrangement can effectively reduce the difference of the total insertion loss in comparison to the random arrangement (i.e., 0.07 dB vs 2.67 dB in the cascaded encoder with 16 output ports). The proposed approach realizes the optimum configuration for the $1{\times}2$ optical splitters used without adding any extra components. The test results of the fabricated cascaded encoder with 32 output ports prove the feasibility of the proposed approach.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.7
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• pp.625-633
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• 2004

In this paper, position control of a car-like mobile robot using a neural network is presented. positional information of the mobile robot is given by a laser range finder located remotely through wireless communication. The heading angle is measured by a gyro sensor. Considering these two sensor information as a reference, the robot posture is corrected by a cascaded controller. To improve the tracking performance, a neural network with a cascaded controller is used to compensate for any uncertainty in the robot. The neural network functions as a compensator to minimize the positional errors in on-line fashion. A car-like mobile robot is built as a test-bed and experimental studies of several controllers are conducted and compared. Experimental results show that the best position control performance can be achieved by a cascaded controller with a neural network.