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- 발행기관 : 포항공과대학교 전자컴퓨터공학부 (검색결과 3 건)
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김성영 포항공과대학교 전자컴퓨터공학부 2012 국내박사
배터리 충전기와 DC-DC 컨버터는 전기자동차에 장착된다. 배터리 충전기는 AC 그리드(AC grid)로부터 파워를 공급받아 메인 배터리를 충전한다. DC-DC 컨버터는 14V 시스템(라이트, 팬, 파워 윈도우 등)에 파워를 공급하는 역할을 한다. 하지만 전기자동차에서 부피 및 비용은 엄격하고 중요한 요건이므로 배터리 충전기와 DC-DC 컨버터를 하나로 통합하는 것이 좋다. 배터리 충전기와 DC-DC 컨버터는 3-포트 컨버터를 이용하여 하나의 토폴로지로 통합 될 수 있다. 3-포트 컨버터는 3개의 H-브릿지와 3개의 와인딩을 가진 하나의 트랜스포머로 구성된다. 메인 배터리, AC grid 그리고 14V 파워 시스템은 각각의 H-브릿지에 연결된다. 본 논문은 3-포트 컨버터가 배터리 충전기 모드 혹은 DC-DC 컨버터 모드일 경우 H-브릿지들 사이의 파워 제어 방법에 관한 것을 논한다. 각각의 모드에서 3개의 H-브릿지 중 2개의 H-브릿지만 파워전달에 이용되기 때문에, 남은 하나의 포트의 파워출입은 허용되지 않는다. 여기서 파워출입이 허용되지 않는 포트를 본 논문에서 idling port라고 불린다. Idling port로의 파워 전달을 막기 위해서, 본 논문에서는 가상 분리 기법(virtual isolation scheme)을 제안한다. 가상 분리 기법의 기본 아이디어는 idling port로 흐르는 전류를 0A로 제어해서 idling port로 출입하는 파워를 막는 것이다. 페이서 분석(phasor analysis)을 이용하면, idling port로 흐르는 전류를 0A으로 제어 할 수 있는 idling port의 전압조건을 구할 수 있다. 즉 이 전압 조건을 idling port의 dc-link 전압이 유지하는 동안 idling port로 흐르는 파워를 막을 수 있다. 이러한 가상 분리 기법 조건에서는 idling port의 전압은 다른 2개의 포드들의 전압의 끝점을 연결한 선분 위에 놓이게 된다. 동시에 모든 인덕터 전류들은 평행한 상태에 놓이게 되면서, idling port로 흐르는 전류가 0A가 된다. 이러한 가상 분리 기법의 유효성은 시뮬레이션과 실험 결과로 증명된다. The EV needs to be equipped with an on-board battery charger and a DC-DC converter. The main battery is charged from the AC grid via the battery charger. The DC-DC converter supplies power to the 14V auxiliary power systems such as lights, fans, wipers, power windows, radio, etc. However, in EVs the volume and cost requirements are so strict that it is better to combine the battery charger with the DC-DC converter. The battery charger and the DC-DC converter can be combined in a single unit with the three-port converter topology. It consists of three H-bridges and a three-winding transformer. The main battery, AC grid, and 14V auxiliary power systems are connected to each H-bridge. The control goal is to operate the battery charger and the DC-DC converter exclusively. Since two ports are engaged in each operation, there remains one idling port. To block power flowing into an idling port, a virtual isolation scheme is proposed. According to the phasor diagram, the isolation condition requires that an end point of the voltage vector of the idling port should lie on the line that connects the end points of the other two vectors. In such a case, all the inductor current vectors of the Δ-equivalent circuit are parallel and no inductor current flows into the idling port. Therefore, the net power from/to the idling port is equal to zero. Effectiveness of the proposed isolation scheme is verified by simulation and experimental results.
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A Study on Highly Efficient Multimode/Multiband Power Amplifiers for Reconfigurable RF Transmitters
강대현 포항공과대학교 전자컴퓨터공학부 2011 국내박사
Flexible and reconfigurable radio frequency (RF) transmitters with multimode and multiband capability are indispensable to handle the various evolving wireless communication systems. This thesis focuses on advanced power amplifier (PA) architectures for multimode multiband operation. Four major works toward flexible transmitters are explored in this thesis. First, a class-AB/F PAs is introduced for multimode operation. The class-F operation of the PA is highly efficient and comparable to the class-F PA. The class-AB operation is also highly efficient and linear. Second, Doherty PAs for handset applications are analyzed and implemented with the simplified circuit structure. Proper input power division and output combination assist the PA’s load modulation and result in great performance of efficiency and linearity. Third, a bandwidth (BW)-enhanced Doherty PA is proposed. The BW limiting factors are addressed and the PA utilize a lower Q of quarter-wavelength transformer and eliminates the phase compensation circuit and the additional offset line to enhance the overall BW of the Doherty PA. Finally, a multimode/multiband PAs with a boosted supply modulator is developed for handset applications. A linear broadband class-F amplifier is designed for multiband operation. The efficiency and bandwidth are enhanced by the boosted supply modulator. Multimode operation for various wireless application is accomplished thanks to programmable hysteresis control and automatic switching current adaptation from the hybrid switching amplifier. All the works are implemented for demonstration using CMOS and HBT technologies. The efforts could result in multimode multiband operation of the RF transmitter for the future intelligent radio terminals.
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Estimation Points Assignment와 Power Control을 이용한 RFID Tag Floor Localization의 성능향상
이제원 포항공과대학교 전자컴퓨터공학부 2010 국내석사
RFID Tag Floor Localization consists of a tag floor and an RFID reader with its antenna and localization algorithm. Tag Floor is a set of passive transponders which are placed on floor in grid with their ID and positions. Mobile robot carries an RFID reader with its antenna, which can recognize around passive transponders. And localization algorithm estimates the position of the mobile robot by using positions of recognized transponders. However, this system has low accuracy problem, so it cannot be used for real localization problems. Therefore, this paper proposes an efficient method to improve accuracy of RFID Tag Floor Localization with analysis of RFID Tag Floor Localization. In tag floor, tag recognition cases are limited and finite. Also, there exist recognition faces. In each face, same tag recognition pattern is shown. It means that only finite estimation points of RFID reader can exist in RFID Tag Floor Localization. So, if recognition ranges are known, Estimation Points Assignment (EPA) is possible. Estimation Points Assignment means that estimation points are assigned artificially for each recognition case to minimize error variance. So, it shows better performance than that of medium value method or mean method. Moreover, power control is an efficient method to improve accuracy of RFID Tag Floor Localization. It can be analyzed as like analysis of RFID Tag Floor Localization. By the analysis, it is easily to verify that power control can make various recognition cases and power control can divide the recognition faces. Also, a number of estimation points increases. In result, the variance of errors decreases in regardless of mean method or EPA. However, EPA can be used in power control and make better performance. Therefore, proposed algorithms, based on the analysis, can raise the accuracy of RFID Tag Floor Localization without additional costs. It can be verified in the results of the simulations and experiments.
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