• Journal of Power Electronics
• /
• v.16 no.6
• /
• pp.2243-2257
• /
• 2016

This paper presents a two stage three-phase proton exchange membrane fuel cell (PEMFC) generation system. When the system is connected to a three-phase load, it is very sensitive to the characteristics and type of the load. Especially unbalanced three-phase loads, which result in a pulsating power that is twice the output frequency at the inverter output, and cause the dc-link to generate low frequency ripples. This penetrates to the fuel cell side through the front-end dc-dc converter, which makes the fuel cell work in an unsafe condition and degrades its lifespan. In this paper, the generation and propagation mechanism of low frequency ripple is analyzed and its impact on fuel cells is presented based on the PEMFC output characteristics model. Then a novel method to evaluate low frequency current ripple control capability is investigated. Moreover, a control scheme with bandpass filter inserted into the current feed-forward path, and ripple duty ratio compensation based on current mode control with notch filter is also proposed to achieve low frequency ripple suppression and dynamic characteristics improvement during load transients. Finally, different control methods are verified and compared by simulation and experimental results.

• Journal of Power Electronics
• /
• v.16 no.3
• /
• pp.1176-1189
• /
• 2016

In this paper, a novel quasi-direct power control (Q-DPC) scheme based on a resonant frequency adaptive proportional-resonant (PR) current controller with a variable frequency resonant phase locked loop (RPLL) is proposed, which can achieve a fast power response with a unity power factor. It can also adapt to variations of the generator frequency in T-type Three-level shaft synchronous generator (SSG) converters. The PR controller under the static α-β frame is designed to track ac signals and to avert the strong cross coupling under the rotating d-q frame. The fundamental frequency can be precisely acquired by a RPLL from the generator terminal voltage which is distorted by harmonics. Thus, the resonant frequency of the PR controller can be confirmed exactly with optimized performance. Based on an instantaneous power balance, the load power feed-forward is added to the power command to improve the anti-disturbance performance of the dc-link. Simulations based on MATLAB/Simulink and experimental results obtained from a 75kW prototype validate the correctness and effectiveness of the proposed control scheme.

• Proceedings of the KIPE Conference
• /
• 2016.11a
• /
• pp.73-74
• /
• 2016

본 논문은 포워드-플라이백 컨버터와 태양광 단일 전원 비대칭 다단식 H-bridge 다중 레벨 인버터를 적용한 태양광 전력 조절 시스템에 관한 논문이다. 이는 기존에 연구되었던 대칭형 다단식 H-Brdige 다중 레벨 인버터나 플라이백 컨버터를 사용한 태양광 전력 조절 시스템의 단점을 보완 한 것이다. 대칭형 다단식 멀티 레벨 인버터는 각 H-Bridge 구조 마다 독립된 전원이 필요하지만, 포워드-플라이백(Foward-Flyback) 컨버터를 접목시켜 단일 태양광 전원으로 하나의 다단식 H-Brdige 인버터를 구성 할 수 있고, 또한 기존의 플라이백 컨버터를 포워드-플라이백 컨버터로 대체 하면서 기존 대비 대용량 설비가 용이하고 효율적인 태양광 전력 조절 시스템을 설계 할 수 있다. 제안한 시스템의 가능성을 확인하기 위하여, PSIM 시뮬레이션을 통해 계통 연계형 1kW급 태양광 시스템의 최대 전력 추종 제어(Maximum Power Point Tracking)와 인버터의 $V_{dc}$ 전압 제어를 확인하였다.

• Journal of the Korea Computer Industry Society
• /
• v.8 no.1
• /
• pp.49-56
• /
• 2007

Various kind of laser had been used on addition to endoscope for obstetrics and gynecology, gas laser such as CO2 laser had been used mainly much in laparoscope surgical operation mainly Thermal effect of beam displays other result different component parts of cellular tissue and different close of a marketplace of laser beam and priority solidification of temperature increase consists in cellular tissue, and cutting or carbonization process happens and evaporation by breakdown of cellular tissue happens more than $300^{\circ}$. <중략> Ostabilization of pulse transformer by high tension output module of CO2analog laser for obstetrics and gynecology that accomplish marks of honor kind switching and accuracy is required, and stabilize with laser output applying Turn-off in existent hard switching forward converter, on city happened switching damage, damage increase of output diode station recovery special quality, parasitism shock, design and result that manufacture, brought result that improve than existing product. Will be bought to get into superior result if supplement as systematic late.

• The KIPS Transactions:PartB
• /
• v.12B no.1 s.97
• /
• pp.91-100
• /
• 2005

It has been proposed diverse methods to use web information efficiently as the size of information is increasing. Most of search systems use a keyword-based method that mostly relies on syntactic information. They cannot utilize semantic information of documents and thus they could generate to users. To solve shortcoming in searching documents, a technique using the Semantic Web is suggested. A semantic web can find relevant information to users by employing metadata which are represented using standard ontologies. Each document is annotated with a metadata which can be reasoned by agents. In this paper, we propose a search system using semantic web technologies. Our semantic search system analyzes semantically questions that user input, and get resolution information that user want. To improve efficiency and accuracy of semantic search systems, this paper proposes DQL(DAML Query Language) engine that employs inference engine to execute reasoning and DQL converter that changes keyword form question of the user to DQL.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.45 no.1
• /
• pp.28-36
• /
• 2008

This paper discusses theimplementation of the low-voltage, low-power, third-order, 1-bit switched capacitor delta-sigma modulator of the implantable cardiac pacemaker. The distributed, feed-forward structure and bulk-driven OTA were used in order to achieve an efficient operation under a supply voltage of 1V or lower. The designed modulator has a dynamic range of 49dB at 0.9V supply voltage and consumes 816nW of power. Such a significant reduction in power consumption allows diverse applications, not only in pacemakers, but also in implantable biomedical devices that operate with limited battery power. The core chip size of the modulator is $1000{\mu}m*500{\mu}m$ manufactured, with the $0.18{\mu}m$ CMOS standard process.

• Journal of Power Electronics
• /
• v.16 no.3
• /
• pp.1110-1121
• /
• 2016

The mathematical model of a three phase PWM converter under the stationary αβ reference frame is deduced and constructed based on a Proportional-Resonant (PR) regulator, which can replace trigonometric function calculation, Park transformation, real-time detection of a Phase Locked Loop and feed-forward decoupling with the proposed accurate calculation of the inductance voltage vector. To avoid the parallel resonance of the LCL topology, the active damping method of the proportional capacitor-current feedback is employed. As to current vector error elimination, an optimized PR controller of the inner current loop is proposed with the zero-pole matching (ZPM) and cancellation method to configure the regulator. The impacts on system's characteristics and stability margin caused by the PR controller and control parameter variations in the inner-current loop are analyzed, and the correlations among active damping feedback coefficient, sampling and transport delay, and system robustness have been established. An equivalent model of the inner current loop is studied via the pole-zero locus along with the pole placement method and frequency response characteristics. Then, the parameter values of the control system are chosen according to their decisive roles and performance indicators. Finally, simulation and experimental results obtained while adopting the proposed method illustrated its feasibility and effectiveness, and the inner current loop achieved zero static error tracking with a good dynamic response and steady-state performance.