• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2007년도 춘계학술대회
• /
• pp.153-156
• /
• 2007

This paper presents the design, development and performance of a power conditioning system (PCS) for application to a 250kW Molten Carbonate Fuel Cell (MCFC) generation system. A DSP controller was used to control the dc-dc and dc-ac converter operation for grid connection and power injection to the grid. The controller must also supervise the total PCS operation while communicating with the fuel cell system controller. A control method for parallel operation of dc-dc converters was proposed and verified. A 250kW prototype was successfully built and tested. Experimental performances are compared to minimum target requirements of the PCS for MCFC.

• 한국자동차공학회논문집
• /
• 제19권5호
• /
• pp.14-21
• /
• 2011

In diesel engines, accurate EGR control is important due to its effect on nitrogen oxide and particulate matter emissions. Conventional EGR control system comprises a PI feedback controller for tracking target air mass flow and a feedforward controller for fast response. Physically, the EGR flow is affected by EGR valve lift and thermodynamic properties of the EGR path, such as pressures and temperatures. However, the conventional feedforward control output is indirectly derived from engine operating conditions, such as engine rotational speed and fuel injection quantity. Accordingly, the conventional feedforward control action counteracts the feedback controller in certain operating conditions. In order to improve this disadvantage, in this study, we proposed feedforward EGR control algorithm based on a physical model of the EGR system. The proposed EGR control strategy was validated with a 3.0 liter common rail direct injection diesel engine equipped with a DC motor type EGR valve.

• 전력전자학회논문지
• /
• 제22권4호
• /
• pp.369-372
• /
• 2017

This paper presents a control scheme for three-level NPC inverters using small DC-link capacitors. To reduce the inverter system volume, the film capacitor with small capacitance is a promising candidate for the DC-link. When small capacitors are applied in a three level inverter, however, the AC ripple component increases in the DC-link NPV (neutral point voltage). In addition, the three-phase input grid currents are distorted when the DC-link capacitors are fed by diode rectifier. In this paper, the additional circuit is applied to compensate for small capacitor systems defect, and the offset voltage injection method is presented for the stabilization in NPV. These two proposed processes evidently ensure the quality improvement of the input grid currents and output load currents. The feasibility of the proposed method is verified by experimental results.

• 전력전자학회논문지
• /
• 제20권4호
• /
• pp.321-329
• /
• 2015

The static synchronous compensator (STATCOM) of cascaded H-bridge configuration accompanying multiple separate DC sides is inherently subject to the problem of uneven DC voltages. These DC voltages in one leg can be controlled by adjusting the AC-side output voltage of each cell inverter, which is proportional to the active power. However, when the phase current is extremely small, large AC-side voltage is required to generate the active power to balance the cell voltages. In this study, an alternative zero-sequence current injection method is proposed, which facilitates effective cell balancing controllers at no load, and has no effect on the power grid because the injected zero sequence current only flows within the STATCOM delta circuit. The performance of the proposed method is verified through simulation and experiments.

• 한국식품영양학회지
• /
• 제30권4호
• /
• pp.665-672
• /
• 2017

The anti-diabetic effect of dried-silkworm Dongchunghacho water extracts was investigated in streptozotocin (STZ)-induced diabetic rats. Seven-week-old SD rats were randomly assigned to six groups: normal control (NC) group, diabetic control (DC) group, water extracts of Paecilomyces japonica grown on a dried-silkworm (PJ-DS, 50 mg/kg) group, PJ-DS (250 mg/kg) group, water extracts of Cordyceps militaris grown on a dried-silkworm (CM-DS, 250 mg/kg) group, and water extracts of dried-silkworm (DS, 250 mg/kg) group. These groups were orally provided with sample dissolved in water respectively for four weeks after an injection of STZ (60 mg/kg, ip) followed by identification of diabetic control (DC) group. After four weeks, body weight of all diabetic groups was significantly lower than that of the normal control (NC) group, but among diabetic groups there were no significant differences. Blood glucose levels of the PJ-DS (50 mg/kg), PJ-DS (250 mg/kg), CM-DS (250 mg/kg) and DS (250 mg/kg) groups were reduced compared to the DC group by 3.0 percent, 18.5 percent, 6.9 percent and 13.1 percent, respectively. Concentration of total cholesterol and triglyceride in blood plasma were to some degree decreased in PJ-DS (250 mg/kg) and DS (250 mg/kg) groups compared to the DC group. According to these results dried-silkworm Dongchunghacho water extracts (PJ-DS) boost protection against STZ-induced toxicity.

• Journal of Power Electronics
• /
• 제3권4호
• /
• pp.249-258
• /
• 2003

This paper presents a high-efficient and cost effective three-phase AC/DC-DC/AC power conversion system with a single two-switch type active Auxiliary Resonant DC Link (ARDCL) snubber circuit, which can minimize the total power dissipation. The active ARDCL snubber circuit is proposed in this paper and its unique features are described. Its operation principle in steady-state is discussed for the three phase AC/DC-DC/AC converter, which is composed of PWM rectifier as power factor correction (PFC) converter, sinewave PWM inverter. In the presented power converter system not only three-phase AC/DC PWM rectifier but also three-phase DC/AC inverter can achieve the stable ZVS commutation for all the power semiconductor devices. It is proved that the proposed three-phase AC/DC-DC/AC converter system is more effective and acceptable than the previous from the cost viewpoint and high efficient consideration. In addition, the proposed two-switch type active auxiliary ARDCL snubber circuit can reduce the peak value of the resonant inductor injection current in order to maximize total system actual efficiency by using the improved DSP based control scheme. Moreover the proposed active auxiliary two-switch ARDCL snubber circuit has the merit so that there is no need to use any sensing devices to detect the voltage and current in the ARDCL sunbber circuit for realizing soft-switching operation. This three-phase AC/DC-DC/AC converter system developed for UPS can achieve the 1.8% higher efficiency and 20dB lower conduction noise than those of the conventional three-phase hard-switching PWM AC/DC-DC/AC converter system. It is proved that actual efficiency of the proposed three-phase AC/DC-DC/AC converter system operating under a condition of soft switching is 88.7% under 10kw output power.

• 한국식품영양과학회지
• /
• 제28권4호
• /
• pp.912-916
• /
• 1999

The purpose of this study was to investigate the effect of saponin in the shoot of Aralia elata on serum lipid level and glucose in streptozotocin(STZ) induced diabetic rats. Sprague Dawley normal male rats weighing 70$\pm$5g were randomly assigned to normal(control group), crude saponin(S group), and shoot of Aralia elata(D group). Experimental diets have been fed for 6 weeks. STZ induced diabetic rats were classified to diabetic control(DC group) and crude saponin(DS group). Diabetic rats were experimentally induced by intravenous injection of STZ(65mg/kg of body weight) dissolved in citrate buffer(pH 4.5). DS group has been i.p. injected with crude saponin solved in phosphate buffer(pH 7.0, 10mg/100g body weight) and DC group fed for 10 days. Body weight decreased significantly in crude saponin group. Feed intakes and feed efficiency ratio were not significantly different among C, S, and D group. The crude saponin group has indicated the lowest values of serum total cholesterol, glucose, and triglyceride. However, the values of serum glucose and triglyceride were not significant. Insulin levels among the crude saponin group, the shoot powder group, and the control group were not significantly different. When STZ induced diabetic rats have i.p. injection of crude saponin, the crude saponin has reduced the serum glucose but it is not been significant.

• Journal of Power Electronics
• /
• 제19권2호
• /
• pp.560-568
• /
• 2019

This paper studies the inherent relationship between currents and zero-sequence components. Then a precise algorithm is proposed to calculate the injected zero-sequence component to control the DC-Link neutral-point voltage balance, which can result in a more efficient and flexible neutral point voltage balance with a desirable performance. In addition, it is shown that carried-based PWM with the calculated zero-sequence component scheme can be equivalent to space-vector pulse-width modulation (SVPWM). Based on the proposed method, the optimal zero-sequence component of the feasible modulation indices is analyzed. In addition, the unbalanced load limitation of the DC-Link neutral-point voltage balance control is also revealed. Simulation and experimental results are shown to verify the validity and practicality of the proposed algorithm.

• 지구물리와물리탐사
• /
• 제10권4호
• /
• pp.353-360
• /
• 2007

본 연구에서는 담수 주입에 의한 해수침투 개선 가능성을 확인하기 위해 담수주입 현장 실증시험을 수행하였으며, 담수 주입 효과 및 거동 평가를 위해 시추공에서의 다채널 전기전도도 모니터링과 물리검층, 지표에서의 전기비저항 및 자연전위 모니터링을 수행하고 그 적용성을 평가하였다. 담수주입 전후 및 주입 기간 중 수행된 물리검층과 다채널 전기전도도 모니터링 결과 담수 주입에 따른 공내수 및 대수층의 전기전도도의 감소 양상과, 이러한 주입효과가 수개월 이상 지속됨을 확인할 수 있었다. 담수주입에 따른 지하수의 유동 탐지를 목적으로 한 자연전위 모니터링의 경우, 현장 기상 여건 및 비분극 전극의 장기간 활용에 따른 문제로 인해 의미 있는 결과를 얻지 못하였으나 전기비저항탐사 모니터링의 경우에는 주입 담수에 의한 영향이 주입정 주위의 전기비저항 증가 양상으로 관측되어 담수체 거동과 영향 반경을 확인할 수 있었다. 이로부터 담수주입에 의한 담수체의 거동 평가와 개선효과를 판단하는 방법으로서 지구물리 기법들이 효과적으로 적용될 수 있으며, 이러한 평가기술에 기반 한 최적설계가 이루어질 경우 담수주입기술이 해수침투 피해 개선을 위해 효과적으로 적용될 수 있을 것으로 판단된다.

• Journal of Power Electronics
• /
• 제14권5호
• /
• pp.957-966
• /
• 2014

Some of DC actuators used in home automation, office automation, medical equipment and automotive systems require a position sensor. In low power applications, the introduction of such a transducer remarkably increases the whole system cost, which justifies the development of sensorless position estimation techniques. The well-known AC motor drive sensorless techniques exploiting the fundamental component of the back electromotive force cannot be used on DC motor drives. In addition, the sophisticated approaches based on current or voltage signal injection cannot be used. Therefore, an effective and inexpensive sensorless position estimation technique suitable for DC motors is presented in this paper. This technique exploits the periodic pulses of the armature current caused by commutation. It is based on a simple pulse counting algorithm, suitable for coping with the rather large variability of the pulse frequency and it leads to the realization of a sensorless position control system for low cost, medium performance systems, like those in the field of automotive applications.