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전압sag-swell과 고조파 보상기능을 갖는 Z-소스 전력품질보상시스템
박희재(Hee-Jae Park),오승열(Seung-Yeol Oh),정영국(Young-Gook Jung),임영철(Young-Cheol Lim) 전력전자학회 2009 전력전자학술대회 논문집 Vol.2009 No.2
본 연구에서는 배전계통의 전압 및 전류 품질을 통합적으로 개선할 수 있는 수동필터 연계형 Zㅡ소스 전력품질 보상 시스템을 제안한다. 제안된 시스템의 주안점은 전압의 변동을 보상하는 직렬형 인버터와 고조파를 보상하는 병렬형 인버터에 각각 Z-소스 토폴로지를 적용하는 것이다. 전압 sag와 swell이 발생하는 과도상태에서 제안된 시스템의 성능을 검증하기 위하여 PSIM시뮬레이션을 하여 타당성을 입증하였다.
연료전지 전원의 3상 하이브리드 Z-소스 동적 전압 보상기(Z-HDVR)
박희재(Hee-Jae Park),정영국(Young-Gook Jung),임영철(Young-Cheol Lim) 전력전자학회 2007 전력전자학술대회 논문집 Vol.- No.-
본 연구에서는 전압품질에 민감한 설비를 위한 3상 하이브리드 Z-소스 동적 전압 보상기(Z-HDVR : Hybrid Z-Source Dynamic Voltage Restorer)을 제시하였다. 제안된 시스템은 수동필터와 Z-소스 토폴로지의 직렬형 능동필터로 구성된다. Z-HDVR의 ESS(Energy Storage System)로는 친환경적인 고분자 전해질 연료전지(PEMFC : Proton Exchange Membrane Fuel Cells)를 사용하였다. 고조파 검출 알고리즘은 동기좌표계의 id-iq 이론에 의하였으며, 부하전압 보상을 위하여 PI제어를 사용하였다. 전압swell 및 sag등 다양한 전원 조건하에서 제안된 시스템의 보상 성능을 검토하였다.
오재홍 ( Jae Hong Oh ),박희재 ( Hee Jae Park ),최미라 ( Mira Choi ),박혜진 ( Hai-jin Park ) 대한피부과학회 2019 대한피부과학회지 Vol.57 No.7
Dermatomyositis (DM) is an idiopathic inflammatory myopathy characterized by typical cutaneous manifestation and inflammation of the skeletal muscles. However, this progressive symmetric proximal muscle weakness may be minimal or absent in clinically amyopathic DM (CADM). Importantly, DM has been associated with malignancy, which is related to poor prognosis. Therefore, every newly diagnosed patient with DM should undergo thorough screening investigations for hidden internal malignancy. We report a case of CADM, with severe intractable itching, which was finally diagnosed as paraneoplastic dermatomyositis associated with gastric cancer in a 77-year-old woman. The patient had typical cutaneous features of DM and mild elevation of muscle enzymes without muscle weakness. (Korean J Dermatol 2019;57(7):395∼398)
오재홍 ( Jae Hong Oh ),고병창 ( Byeong Chang Ko ),박희재 ( Hee Jae Park ),함승필 ( Seung Pil Ham ),박혜진 ( Hai-jin Park ) 대한피부과학회 2020 대한피부과학회지 Vol.58 No.10
Ectopic nails are rare and characterized by the growth of nail-like structures in a location other than the typical nail unit. Diagnosis of the ectopic nail is based on histologic examination consistent with a fully developed nail plate and matrix structure. Surgical resection of the entire matrix of ectopic nails is the gold standard for management. Cases of acquired ectopic nails without traumatic events have rarely been reported. A 25-year-old woman presented with a 15-year nail-like structure below the 4th fingernail of the left hand. She denied any history of trauma. Histologically, the keratinous structure was consistent with the nail plate. Plain radiography revealed an osteolytic lesion on the distal phalanx. However, she refused further evaluation and surgical excision. Herein, we report a unique case of an acquired ectopic nail without trauma. (Korean J Dermatol 2020;58(10):694∼696)
회전체의 진동 측정과 분석을 통한 이상 진단 시스템 개발
문준희(Jun Hee Moon),강성범(Sung Bum Kang),박희재(Heui Jae Park) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Rotating machinery's faults such as unbalanced mass, eccentricity, and bearing fracture make the characteristic features of vibration different from that of normal operating condition. Fault diagnosis of the rotating machinery is achieved by the following ways: Firstly, identify the system in normal condition with a linear model. Secondly, assess the stochastic characteristic of the system in order to define the threshold of abnormal condition and to design a digital filter appropriate for the system. Finally, diagnose the system fault by error difference evaluation and by STFT analysis. The developed algorithm is experimentally verified for a CD-ROM drive.
액터-크리틱 알고리즘을 이용한 리액션 휠 진자의 스윙업 제어
김대원(Dae-Won Kim),박희재(Hee Jae Park) 제어로봇시스템학회 2021 제어·로봇·시스템학회 논문지 Vol.27 No.10
In this study, we verified the performance of the swing-up control method for a reaction wheel pendulum using the actor-critic algorithm in both simulation and experiment and suggested the possibility that reinforcement learning, using shallow neural networks, can be applied to studying intelligent robots that act in real-world environments, such as a robot that teaches itself to walk through trial and error. The actor of the proposed actor-critic algorithm used the policy network to determine the rotational direction of the reaction wheel based on the angular position and velocity of the pendulum and the angular velocity of the reaction wheel. The critic used the value network to estimate the expected reward based on the same factors as the actor’s. In both simulation and in the real-world environment, through trial and error, the proposed algorithm successfully learned how to swing up and stabilize the pendulum by choosing the rotational direction ‒ between the clockwise and counter-clockwise directions ‒ of the reaction wheel.