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Regulated Peak Power Tracking (RPPT) System Using Parallel Converter Topologies
Muhammad Saqib Ali,Hyun-Su Bae,Seong-Jun Lee,Bo-Hyung Cho 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.6
Regulated peak power tracking (RPPT) systems such as the series structure and the series-parallel structures are commonly used in satellite space power systems. However, these structures process the solar array power or the battery power to the load through two cascaded regulators during one orbit cycle, which reduces the energy transfer efficiency. Also the battery charging time is increased due to placement of converter between the battery and the solar array. In this paper a parallel structure has been proposed which can improve the energy transfer efficiency and the battery charging time for satellite space power RPPT systems. An analogue controller is used to control all of the required functions, such as load voltage regulation and solar array stabilization with maximum power point tracking (MPPT). In order to compare the system efficiency and the battery charging efficiency of the proposed structure with those of a series (conventional) structure and a simplified series-parallel structure, simulations are performed and the results are analyzed using a loss analysis model. The proposed structure charges the battery more quickly when compared to the other two structures. Also the efficiency of the proposed structure has been improved under different modes of solar array operation when compared with the other two structures. To verify the system, experiments are carried out under different modes of solar array operation, including PPT charge, battery discharge, and eclipse and trickle charge.
Regulated Peak Power Tracking (RPPT) System Using Parallel Converter Topologies
Ali, Muhammad Saqib,Bae, Hyun-Su,Lee, Seong-Jun,Cho, Bo-Hyung The Korean Institute of Power Electronics 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.6
Regulated peak power tracking (RPPT) systems such as the series structure and the series-parallel structures are commonly used in satellite space power systems. However, these structures process the solar array power or the battery power to the load through two cascaded regulators during one orbit cycle, which reduces the energy transfer efficiency. Also the battery charging time is increased due to placement of converter between the battery and the solar array. In this paper a parallel structure has been proposed which can improve the energy transfer efficiency and the battery charging time for satellite space power RPPT systems. An analogue controller is used to control all of the required functions, such as load voltage regulation and solar array stabilization with maximum power point tracking (MPPT). In order to compare the system efficiency and the battery charging efficiency of the proposed structure with those of a series (conventional) structure and a simplified series-parallel structure, simulations are performed and the results are analyzed using a loss analysis model. The proposed structure charges the battery more quickly when compared to the other two structures. Also the efficiency of the proposed structure has been improved under different modes of solar array operation when compared with the other two structures. To verify the system, experiments are carried out under different modes of solar array operation, including PPT charge, battery discharge, and eclipse and trickle charge.
Ali Saqib,Haq Muhammad Abdul,Naz Shahina,Faheem Akbar Muhammad 한국응용곤충학회 2022 Journal of Asia-Pacific Entomology Vol.25 No.2
The efficiency of pesticides is greatly affected by their ability to adhere and retain on foliage surface. Neem oil, though a very well-known source of many biologically active pesticidal compounds, is very sensitive to envi ronmental parameters, such as UV light. Also, due to volatilization, it is lost in environment and hence fail to reach target and show activity. In this study we attempted to stabilize neem oil emulsion and increase its retention on foliage surface by adding varying concentration of gum cordia. Gum cordia is an anionic poly saccharide derived from Cordia myxa fruits with strong adhesion and emulsification properties. The lethal concentration (LC 50 ) of the final formulations were also determined against aphid species Myzus persicae and Schizaphis graminum. Adhesion was found to be dependent on the concentration of gum cordia as well as type of crop. Increasing gum cordia in neem oil formulations resulted in increase in adhesion of the spray on the leaf surfaces and up to 6 times higher adhesion was observed with 0.5% gum cordia on mustard leaf compared to control. The LC 50 decreased with increasing gum cordia concentration. The LC 50 values of neem oil sprayed on mustard, spinach, and wheat leaves with 0.5% gum cordia were 0.205, 0.715, and 2.074% respectively while for neem oil control spray (with no gum cordia) LC 50 values were 1.833, 2.112, and 4.992% respectively for the above tested leaves. Presence of greater than 0.125% gum cordia in neem formulations provided the barrier against UV irradiation.
자체전원공급 가능한 시스템을 위한 유연한 저전력 저항 메모리 소자
Muhammad Muqeet Rehman,Hafiz Mohammad Mutee ur Rehman,Shenawer Ali Khan,Muhammad Saqib,Woo Young Kim 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
최근 유기 비휘발성 메모리 장치는 주목받고 있다 1, 2. 본 연구에서, 두 고분자 물질(오렌지 염료, 폴리 3-헥실티오핀)의 합성물로 제작된 비휘발성 메모리 소자를 보고한다. 이 메모리 소자는 유연기판 상에 은(Ag)/유기복합체/은(Ag)의 샌드위치 구조를 가지도록 제조되었다. 제작된 메모리 소자는 -1.5V에서 +1.5V 까지의 동작전압 범위에서 전류 상한선을 1mA를 가지도록 작동하였고, 그 결과 저전력소모 동작이 가능하게 되었다. 또한 100 번 이상의 반복 측정에서도 고저항 상태와 저저항 상태가 서로 간섭하지 않고 일정한 동작을 유지하였으며, 4시간 이상 연속 동작에서도 정상 동작하였음을 확인하였다. 이 메모리 소자의 동작 메커니즘은 공간전하제한 전류(SCLC) 메커니즘으로 작동함을 이중로그 곡선으로부터 확인할 수 있었고, 오렌지 염료를 추가할수록 메모리동작을 위한 문턱전압의 크기가 감소함을 확인하였다. 폴리 3-헥실티오핀 기반의 기존 연구결과에 비해 굽힘반경 5cm 범위까지 25 번의 굽힘측정에서도 안정적인 결과를 나타내었다. 본 연구 성과는 유기물질을 기반으로 하는 고신뢰성 저전력 메모리 소자를 위한 중요한 진전으로 평가되며, 나노발전소자와도 호환가능한 자체전력공급 가능한 시스템의 중요한 요소로서 기여할 것으로 기대된다. Organic nonvolatile memory devices are of significant interest these days<sup>1,2</sup>. In this study we have reported the non-volatile memory behavior of an organic composite based on two polymers i.e. orange dye (OD) and poly(3-hexylthiophene-2,5-diyl) (P3HT). This memory device was fabricated on flexible substrate for the possible application of wearable electronics with a sandwiched structure of silver (Ag)/P3HT-OD/Ag. This device exhibited its memory behavior by applying a small voltage sweep of – 1.5 V to 1.5 V with a current compliance (CC) of 10<sup>-3</sup> A hence, resulting in low power consumption. The obtained electrical results were highly stable as the values of both high resistance state (HRS) and low resistance state (LRS) were not deteriorated for more than 100 voltage sweeps. The device was tested for nearly 4 h without any considerable deterioration in its electrical characteristics. The conduction mechanism of this device was based on space charge limited current (SCLC) model as depicted form the double logarithmic I-V curve. Addition of OD resulted in the reduction of threshold voltage (V<sub>th</sub>) value due to its lower value of work function which provided an easy path for the charge carriers to move from one electrode to another electrode. Significant achievement of this work is that no other P3HT based RRAM device has been characterized for its mechanical robustness, but our memory device showed stable electrical results against 25 bending cycles in the bending diameter range of 15 cm to 5 cm. This device is a significant step forward towards achieving a next generation low power memory device based on organic materials. Also, this low-power device will be expected to combine with nanogenerator for self-powered system in future.