• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1841-1846
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• 2003

The mobile platform-manipulator discussed in this paper is a three link manipulator mounted on a mobile platform. This mobile manipulator is used for welding operation and it is able to operate in a narrow space. The task of the torch, which is mounted at the end effector of the manipulator, is to track along the seam line and the task of the mobile platform is to move the origin point of the manipulator in order to go away from the singularity of the manipulator’s configuration. In this paper, the path planning for the motion of two subsystems (i.e., the manipulator and the mobile platform) was presented by the decentralized control method. Two controllers for the mobile platform and the manipulator were designed, and the relationship between the independent controllers is its state information. The simulation results are also presented to demonstrate the effectiveness of the control method.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1355-1359
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• 2004

In this paper, We elicit the necessity of the Autonomous Decentralized Traffic Control System by analyzing problems of the Centralized Traffic Control System and present operation system. The automatic traffic control system using in large and high-density railway stations is designed and implemented on the basis of the elicited necessity in this paper. It is proposed to use broadcasting protocol for interface of stations in order to ensure autonomy. The result is that advantages of the Autonomous Decentralized Traffic Control System makes on-line expansion and maintenance available. step-by-step construction available. and reduce the area of the influences of system fault when any system fault happens.

• 전력전자학회논문지
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• 제24권3호
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• pp.191-200
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• 2019

This study proposes a hardware-in-the-loop simulation (HILS) system based on National Instruments' PXI platform to test power management and operation strategies for DC microgrids (MGs). The HILS system is developed based on the controller HIL prototype, which involves testing the controller board in hardware with a real-time simulation model of the plant in a real-time digital simulator. The system provides an economical and effective testing function for research on MG systems. The decentralized power management strategy based on the DC bus signaling method for DC MGs has been developed and implemented on the HILS platform. HILS results are determined to be similar to those of the off-line simulation in PSIM software.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.452-464
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• 2015

This paper proposes a DC microgrid operational strategy and control method for improved service reliability. The objective is to supply power to as many non-critical loads as possible, while providing an uninterrupted power supply to critical loads. The DC bus signaling method, in which DC voltage is an information carrier, is employed to implement the operational strategy in a decentralized manner. During grid-connected operation, a grid-tied converter balances the power of the microgrid by controlling the DC voltage. All loads are connected to the microgrid, and operate normally. During islanded operation, distributed generators (DGs), a backup generator, or an energy storage system balances the power. However, some non-critical loads may be disconnected from the microgrid to ensure the uninterrupted power supply to critical loads. For enhanced service reliability, disconnected loads can be automatically reconnected if certain conditions are satisfied. Control rules are proposed for all devices, and detailed microgrid operational modes and transition conditions are then discussed. Additionally, methods to determine control parameter settings are proposed. PSCAD/EMTDC simulation results demonstrate the performance and effectiveness of the proposed operational strategy and control method.

• Journal of Power Electronics
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• 제9권3호
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• pp.507-515
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• 2009

This paper proposes an autonomous decentralized control for a parallel connected uninterruptible power supply (UPS) system based on a fast power detection method using a FPGA based hardware controller for a single phase system. Each UPS unit detects only its output voltage and current without communications signal exchange and a quasi dq transformation method is applied to detect the phase and amplitude of the output voltage and the output current for the single phase system. Fast power detection can be achieved based on a quasi dq transformation, which results in a realization of very fast transient response under rapid load change. In the proposed method, the entire control system is implemented in one FPGA chip. Complicated calculations are assigned to hardware calculation logic, and the parallel processing circuit makes it possible to realize minimized calculation time. Also, an Nios II CPU core is implemented in the same FPGA chip, and the software can be applied for non-time critical calculations. Applying this control system, an autonomous decentralized UPS system with very fast transient response is realized. Feasibility and stable operation are confirmed by means of an experimental setup with three UPSs connected in parallel. Also, rapid load change is applied and excellent performance of the system is confirmed in terms of transient response and stability.

• Journal of Power Electronics
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• 제16권6호
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• pp.2315-2326
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• 2016

This paper discusses the elimination of DC voltage deviation and the enhancement of load current sharing accuracy in multi-terminal high voltage direct current (MT-HVDC) systems. In order to minimize the power line losses in different parallel network topologies and to insure the stable operation of systems, a decentralized control method based on a modified droop control is presented in this paper. Averaging the DC output voltage and averaging the output current of two neighboring converters are employed to reduce the congestion of the communication network in a control system, and the decentralized control method is implemented. By minimizing the power loss of the cable, the optimal load current sharing proportion is derived in order to achieve rational current sharing among different converters. The validity of the proposed method using a low bandwidth communication (LBC) network for different topologies is verified. The influence of the parameters of the power cable on the control system stability is analyzed in detail. Finally, transient response simulations and experiments are performed to demonstrate the feasibility of the proposed control strategy for a MT-HVDC system.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.810-819
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• 2016

Uncoordinated charging of large-scale electric vehicles (EVs) will have a negative impact on the secure and economic operation of the power system, especially at the distribution level. Given that the charging load of EVs can be controlled to some extent, research on the optimal charging control of EVs has been extensively carried out. In this paper, two possible smart charging scenarios in China are studied: centralized optimal charging operated by an aggregator and decentralized optimal charging managed by individual users. Under the assumption that the aggregators and individual users only concern the economic benefits, new load peaks will arise under time of use (TOU) pricing which is extensively employed in China. To solve this problem, a simple incentive mechanism is proposed for centralized optimal charging while a rolling-update pricing scheme is devised for decentralized optimal charging. The original optimal charging models are modified to account for the developed schemes. Simulated tests corroborate the efficacy of optimal scheduling for charging EVs in various scenarios.

• International Journal of Internet, Broadcasting and Communication
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• 제13권2호
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• pp.60-66
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• 2021

Blockchain is a technology that enables trust-based consensus and verification based on a decentralized network. Distributed ID (DID) is based on a decentralized structure, and users have the right to manage their own ID. Recently, interest in self-sovereign identity authentication is increasing. In this paper, as a method for transparent and safe sovereignty management of data, among data pseudonymization techniques for blockchain use, various methods for data encryption processing are examined. The public key technique (homomorphic encryption) has high flexibility and security because different algorithms are applied to the entire sentence for encryption and decryption. As a result, the computational efficiency decreases. The hash function method (MD5) can maintain flexibility and is higher than the security-related two-way encryption method, but there is a threat of collision. Zero-knowledge proof is based on public key encryption based on a mutual proof method, and complex formulas are applied to processes such as personal identification, key distribution, and digital signature. It requires consensus and verification process, so the operation efficiency is lowered to the level of O (log_eN) ~ O(N²). In this paper, data encryption processing for blockchain DID, based on zero-knowledge proof, was proposed and a one-way encryption method considering data use range and frequency of use was proposed. Based on the content presented in the thesis, it is possible to process corrected zero-knowledge proof and to process data efficiently.

• 한국컴퓨터정보학회논문지
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• 제26권3호
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• pp.59-67
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• 2021

블록체인 기술은 2008년 나카모토 사토시라는 신원미상의 인물이 비트코인이라는 암호화폐를 제안하면서 시작되었다. 나카모토 사토시는 기존의 금융 시스템에 대한 불신을 가지고 있었고 은행과 같은 중개자 없이도 해킹이나 변조에 견고한 금융시스템을 블록체인 기술을 통해 구현하고자 했다. 사토시는 비트코인의 생성과, 거래의 위조를 방지하기 위한 기술로 블록체인을 제안하였고 이를 통해 화폐의 발행과 거래, 그리고 검증의 기능을 구현하였다. 이후 스마트 계약을 블록체인 상에서 구현할 수 있는 암호화폐인 이더리움이 개발되면서 예금, 대출, 보험, 파생상품 등 복잡한 계약이 필요한 금융상품을 암호화폐의 영역으로 끌어들일 수 있게 되었다. 또한 실물자산과 결합을 통해 금융 기관이 제공했던 상품을 대체할 수 있는 가능성도 확대해 나가고 있다. 이러한 애플리케이션들을 Decentralized Finance(DeFi)라고 정의한다. 본 논문은 전반적인 DeFi의 기술적 이해와 현재 운영되고 있는 어플리케이션의 소개를 위하여 작성되었다. 먼저 전반적인 DeFi를 구현하는 기술들과 생태계에 대해서 설명한 후 대표적인 DeFi 애플리케이션들을 특징별로 분류하여 설명한다.

• 한국컴퓨터정보학회논문지
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• 제26권4호
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• pp.75-84
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• 2021

본 논문에서는 사용자 정보를 신뢰성 있게 관리하는 DID 기반의 견고한 사용자 정보 관리 서비스인 InfoDID를 소개한다. 블록체인 기술은 탈중앙화 기반으로 데이터를 투명하게 다룰 수 있는 환경을 제공하여 현재 블록체인을 활용한 다양한 서비스들이 개발되고 있다. 최근 사용자의 개인 정보에 대한 중요성이 부각되면서 사용자가 자신의 정보를 통제할 수 있는 분산 식별자를 지원하는 DID 기술이 주목받고 있으며, 이를 기반으로 다양한 정보를 관리하는 서비스들이 시도되고 있다. InfoDID는 블록체인 기반의 DID 기술을 활용하여 빈번히 요청되는 개인 정보를 신뢰성 있게 제어하고, 사용자가 자신의 정보를 보다 편리하게 다른 서비스들에게 제공하도록 지원한다. 또한 서비스의 연속성을 지원하기 위하여, InfoDID는 블록체인 응용서비스의 견고한 실행을 제공하는 BR2K 기법을 채택하여 부분적인 서비스 실패의 경우에도 체계적으로 복구될 수 있다. 이러한 작업을 용이하게 수행하기 위하여, InfoDID와 같이 BR2K 기법을 적용한 블록체인 응용서비스의 복제 상태를 지속적으로 확인할 수 있으며 결함 복구를 지원하는 복제 상태 모니터링 도구가 제시된다.