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RISS 인기검색어
- 검색키워드
- 저자 : Pham Van Nho (검색결과 3 건)
- 무료
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Pham, Khoa-Dang,Nguyen, Nho-Van The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.3
This paper presents a pulse-width modulation strategy to eliminate the common mode voltage (CMV) with reduced CMV spikes in multilevel inverters since a high CMV magnitude and its fast variations dv/dt result in bearing failure of motors, overvoltage at motor terminals, and electromagnetic interference (EMI). The proposed method only utilizes the zero CMV states in a space vector diagram and it is implemented by a carrier-based pulse-width modulation (CBPWM) method. This method is generalized for odd number levels of inverters including neutral-point-clamped (NPC) and cascaded H-bridge inverters. Then it is extended to the over-modulation mode. The over-modulation mode is implemented by using the two-limit trajectory principle to maintain linear control and to avoid look-up tables. Even though the CMV is eliminated, CMV spikes that can cause EMI and bearing current problems still exist due to the deadtime effect. As a result, the deadtime effect is analyzed. By taking the deadtime effect into consideration, the proposed method is capable of reducing CMV spikes. Simulation and experimental results verify the effectiveness of the proposed strategy.
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Preparation of the Transparent Conductive ZnO Nano Material by Means of Pulsed Spray Pyrolysis
Pham Hoang Ngan,Nguyen Quang Tien,Do Thanh Dat,Pham Van Nho 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Transparent conductive ZnO lms play an important role in nano science and nanotechnology. Many methods have had various successes in preparing ZnO. In this contribution, we present some results from using a pulsed spray method and subsequent annealing in a hydrogen atmosphere for the preparation of transparent conductive ZnO films. The performances of ZnO produced by using various precursors and in various technology conditions were investigated. We attained ZnO films with sheet resistances below 100 and an average transparency of about 80 % in the visible region of the light spectrum. Those values are of the same magnitude as ones prepared by using other methods. The mechanism of annealing effect in a hydrogen environment is discussed. Transparent conductive ZnO lms play an important role in nano science and nanotechnology. Many methods have had various successes in preparing ZnO. In this contribution, we present some results from using a pulsed spray method and subsequent annealing in a hydrogen atmosphere for the preparation of transparent conductive ZnO films. The performances of ZnO produced by using various precursors and in various technology conditions were investigated. We attained ZnO films with sheet resistances below 100 and an average transparency of about 80 % in the visible region of the light spectrum. Those values are of the same magnitude as ones prepared by using other methods. The mechanism of annealing effect in a hydrogen environment is discussed.
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Khoa-Dang Pham,Nho-Van Nguyen 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.3
This paper presents a pulse-width modulation strategy to eliminate the common mode voltage (CMV) with reduced CMV spikes in multilevel inverters since a high CMV magnitude and its fast variations dv/dt result in bearing failure of motors, overvoltage at motor terminals, and electromagnetic interference (EMI). The proposed method only utilizes the zero CMV states in a space vector diagram and it is implemented by a carrier-based pulse-width modulation (CBPWM) method. This method is generalized for odd number levels of inverters including neutral-point-clamped (NPC) and cascaded H-bridge inverters. Then it is extended to the over-modulation mode. The over-modulation mode is implemented by using the two-limit trajectory principle to maintain linear control and to avoid look-up tables. Even though the CMV is eliminated, CMV spikes that can cause EMI and bearing current problems still exist due to the deadtime effect. As a result, the deadtime effect is analyzed. By taking the deadtime effect into consideration, the proposed method is capable of reducing CMV spikes. Simulation and experimental results verify the effectiveness of the proposed strategy.
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