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조병극 대한환경위생공학회 1992 대한환경위생공학회지 Vol.7 No.2
Since 1960's along with industrialization and urbanization, economic growth has been . achieved, however, at the same time, environmental condition has been seriously deteriorated. . Currently, volume of wastewater has been increasing at annual rate of 7% in sewage and 20% in industrial wastewater. However, the nation's sewage treatment serves only 33% of the municipal wastewater as of 1991. Major portion of air pollutants comes from combustion of oil and coal which comprise 81% of total energy use and emission gases from motor vehicles increasing at an accelerated rate. It is known that Korea generates the highest amount of waste per capta. Nevertheless, it is not sufficient to reduce the volume of waste by means of resources recovery and recycling. Recognizing the importance of global environmental problems such as ozone layer depletion, global warming and acid rain, international society has been making various efforts since the 1972 Stockholm conference. In particular, it is expected that the Rio conference which has adopted the Rio declaration and Agenda 21 will form a crucial turning point of the emerging new world order after the Cold War confrontation. To cope with such issues as domestic pollution and global environmental problems, the fundamental national policy aims at harmonizing "environmental protection and sustainable development". The Ministry of Environment has recently set up a mid-term comprehensive plan which includes annual targets for environmental protection. According to the government plan, gradual improvement of various environmental conditions and specific measures to achieve them is planned in time frame. Additional sewage treatment plants will be constructed in urban areas with the target to treat 65% of the nation's municipal sewage by 1996. Supply of clean fuels such as LNG will also be expanded starting from large cities as a cleaner substitute energy for coal and oil. In parallel with expansion of LNG, emphasis will be placed on installation of stack monitoring system. Due to the relatively limited land, government's basic policy for solid waste treatment is to develop large scale landfill facilities rather than small sized ones. Thirty three regional areas have been designated for the purpose of waste management. For each of these regions, big scale landfill site is going to be developed. To increase the rate of waste recycling the government is planning to reinforce separate collection system and to provide industries with economic incentives. As a part of meeting the changing situation on global environmental problems after UNCED, and accommodation regulatory measures stipulated in the global environmental conventions and protocols, national policy will try to alter industrial and economic structure so as to mitigate the increasing trends of energy consumption, by encouraging energy conservation and efficiency. In this regard, more attention will be given to the policy on the development of the cleaner technology. Ultimately, these policies and programs will contribute greatly to improving the current state of national public health.
PWM 컨버터의 교류 전원 인터페이스를 위한 LCL 필터 설계
조병극(Byung-Geuk Cho),이학준(Hak-Jun Lee),설승기(Seung-Ki Sul) 전력전자학회 2010 전력전자학술대회 논문집 Vol.2010 No.11
본 논문에서는, PWM 컨버터의 교류 전원 인터페이스를 위한 LCL 필터 설계에 대해 기술한다. 새로운 형태의 LCL 필터 전류 제어기를 소개하고 기존의 전류 제어 방식을 통한 필터 설계 값에 제안된 제어 기법을 적용 시켜 전류 제어 결과를 분석한 후, 제안된 제어기를 통한 필터 설계 측면에서의 유연성 및 용이함에 대해 언급한다. 분석의 타당성을 입증하기 위해 모의 실험 결과를 첨부하였다.
독립 구동에 의한 다상 BLDC 전동기 토크 맥동 저감
조병극(Byung-Geuk Cho),유현재(Hyunjae Yoo),설승기(Seung-Ki Sul),빈재구(Jae-Ku Bin),송종환(Jong-Hwan Song) 전력전자학회 2009 전력전자학술대회 논문집 Vol.2009 No.1
본 논문에서는, 일부 상의 고장 상태에서도 정상 운전이 가능한, 독립 구동에 의한 다상 BLDC 전동기 토크 맥동 저감 방식에 대해 기술한다. 제안된 방식에서는 상절환(Commutation) 구간이 없는 전(全) 상(phase) 도통 방식을 이용하여 맥동 토크 성분의 크기를 저감 시킬 수 있으며 고장 시에도 새로운 지령을 도출할 필요 없이 정상 운전 시의 지령을 그대로 사용하여 허용 가능한 전류 범위 내에서 최대 토크로 운전 할 수 있다. 따라서 제안된 방식은 전동기의 상(phase) 수에 관계없이 임의의 다상 BLDC 전동기 구동에 적용될 수 있으며 손쉽게 고장 허용(fault tolerant) 운전을 적용할 수 있다. 제안된 방식의 타당성을 입증하기 위해 12상 BLDC 전동기 독립 구동 시스템을 컴퓨터로 모의하고 이를 통하여 제안된 방식이 맥동 토크 성분을 저감 시키고 다상 BLDC 독립 구동 시스템에도 일반화 시킬 수 있음을 확인하였다.
조병극,하정익,설승기 전력전자학회 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.2
To obtain phase currents information in AC drives, shunt sensing technology is known to show great performance in cost-effectiveness and therefore it is widely used in low cost applications. However, shunt sensing methods are unable to acquire phase currents in certain operation conditions. This paper deals with the derivation of the boundary conditions for phase current reconstruction in three-shunt sensing inverters and proposes a voltage injection method to expand the measurable areas. As the boundary conditions are deeply dependent on the switching patterns, they are typically analyzed on the voltage vector plane for space vector pulse width modulation (SVPWM) and discontinuous pulse width modulation (DPWM). In the proposed method,the voltage injection and its compensation are conducted within one sampling period. This guarantees fast current reconstruction and the injected voltage is decided so as to minimize the current ripple. In addition to the voltage injection method, a sampling point shifting method is also introduced to improve the boundary conditions. Simulation and experimental results are presented to verify the boundary condition derivation and the effectiveness of the proposed voltage injection method.
Comparison of Phase Lock Loops of PWM Converters under Voltage Disturbance
Ravi Mohan Lal,조병극,설승기 대한전기학회 2011 대한전기학회 학술대회 논문집 Vol.2011 No.4
This paper reviews state of the art algorithms for determining phase angle information of utility grid voltage under non-ideal grid conditions. An accurate estimate of phase angle is essential in power conversion systems for reference sinusoidal signal generation in order to meet power quality standards in grid connected converters. In practice, various fault conditions leads to different grid conditions and the acquisition of accurate phase angle becomes important for the control of power factor, active/reactive power control and for harmonic compensation. This paper provides brief description of synchronization techniques, together with comparative analysis of modern synchronization methods using simulations to show their capability to track the phase angle information and extraction of their positive sequence components.