• 전기학회논문지P
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• 제63권4호
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• pp.361-367
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• 2014

This paper is related to a new solar power conditioner for a built-in step-up chopper function. In the first step-up chopper proposed solar PV power conditioner for mutually connected in series with the input voltage of the bypass diodes are respectively connected to the positive terminal should install the mutual boosting chopper diode connected in series with the boost chopper switching element between the two power supply and at the same time the first and the second was connected to a second diode and a resonance inductor and a snubber capacitor in series with each other. And the common connection point between the bypass diode and the step-up chopper and the step-up chopper diode common connection point of the switching elements of the input voltage was set to the boost inductor for storing energy. In addition, between the step-up chopper and the step-up chopper diode and a switching element of a joint connection point of the first auxiliary diode and the second common connection point of the auxiliary diode was provided, the resonance capacitor. Between the step-up chopper and the step-up chopper diode and a switching element of a joint connection point and the common connection point of the resonance inductor snubber capacitor and connecting the third secondary diode, between two power supply lines is characterized by configuring the DC link capacitor bus lines in parallel. Therefore, it is possible to suppress the switching loss through, DC link bus lines, as well as there could seek miniaturization and weight reduction of the power conditioner itself by using a common capacitor of the non-polar non-polar electrolytic capacitor having a capacitor, the service life of the circuit can be extended and it is possible to greatly reduce the loss can be greatly improve the reliability of the product and the operation of the product itself.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.105-106
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• 2016

In low-power grid-connected photovoltaic(PV) system, Single-phase transformerless full-bridge inverter is commonly used. However in transformerless photovoltaic application, the ground parasitic capacitance created by grounding between PV panels and ground. This ground parasitic capacitance inject additional current into the inverter, these currents cause electromagnetic interference problem, safety problem and harmonics problem in PV applications. In order to eliminate the ground current, This paper propose various inverter topologies in PV applications. These proposed inverter topologies are verified through simulation using PSIM.

• Journal of Power Electronics
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• 제13권2호
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• pp.313-321
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• 2013

This paper describes the operation analysis results of a communication-based DC micro-grid using a hardware simulator developed in the lab. The developed hardware simulator is composed of distributed generation devices such as wind power, photovoltaic power and fuel cells, and energy storage devices such as super-capacitors and batteries. Whole system monitoring and control was implemented using a personal computer. The power management scheme was implemented in a main controller based on a TMS320F28335 chip. The main controller is connected with the local controller in each of the distributed generator and energy storage devices through the communication link based on a CAN or an IEC61850. The operation analysis results using the developed hardware simulator confirm the ability of the DC micro-grid to supply the electric power to end users.

• 조명전기설비학회논문지
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• 제26권7호
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• pp.70-76
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• 2012

In general, the unidirectional power flow is normal in distribution feeders before activation of distributed power source such as PV. However, the interactive power flow is likely to occur in case of the power system under distributed generation. This interactive power flow can cause an unexpected effect on convectional protection coordination systems designed based only on the unidirectional power flow system. When the power line system encounters a problem, the interactive power flow can be a contributed current source and this makes the fault current bigger or smaller compared to the unidirectional case. The effect of interactive power flow is varied depending on the location of the point to ground fault, relative location of the PV, and connection method. Therefore it is important to analyse characteristics of fault current and interactive flow for various transformer connection and location of the PV. This paper proposes a method of improved protection coordination which can be adopted in the protective device for customers in distribution feeders interconnected with the PV. The proposed method is simulated and analysed using PSCAD/EMTDC under various conditions.

• 한국태양에너지학회 논문집
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• 제33권6호
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• pp.92-97
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• 2013

This paper proposes DC offset current compensation method of transformerless fuel cell/PV PCS. DC offset current is generated by the unbalanced internal resistance of the switching devices in full bridge topology. The other cause is the sensitivity of the current sensor, which is lower than DSP in resolution. If power converter system has these causes, the AC output current in the inverter will generate the DC offset. In case of transformerless grid-connected inverter system, DC offset current is fatal to grid-side, which results in saturating grid side transformer. Several simulation results show the difficulties of detecting DC offset current. Detecting DC offset current method consists of the differential amplifiers and PWM is compensated by the output of the Op amp circuit with integrator controller. PSIM simulation verifies that the proposed method is simpler and more effective than using low resolution current sensor alone.

• 한국산학기술학회논문지
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• 제15권7호
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• pp.4692-4697
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• 2014

태양광 전원은 태양광 패널이 설치된 지역의 위치와 날씨 그리고 기후 등에 매우 큰 영향을 받으며, 전원으로서의 사용시간의 제한과 출력의 불확실성이라는 특성을 갖는다. 이러한 태양광 전원의 불확실성을 가능한 줄이기 위해, 태양광 전원의 출력에 대한 오랜 기간 동안의 데이터를 분석하여 출력의 평균값을 산출해 내었다. 태양광 전원의 출력의 평균값은 태양광 전원에 직접 연결되어 그리드에 안정적인 전력을 공급하기 위한 Li 에너지 저장장치의 적정 용량산정과 운용방식에 꼭 필요한 데이터이며, 이로부터 Li 배터리의 충방전모드에 의해 그리드에 일정한 출력의 전력을 공급하는 것이 가능하도록 하였다. 태양광 전원과 Li 배터리를 포함하는 시스템이 악조건의 그리드 운전상태에서의 동작특성을 관찰하기 위해 Li 배터리의 충전율이 100%에서 10%로 단시간에 감소될 정도의 과부하 상태에 대해 태양광 전원과 Li 배터리의 운용특성을 분석하고 Li 배터리 셀 단위의 출력 및 온도특성을 해석하였다.

• 한국정보통신학회논문지
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• 제17권5호
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• pp.1187-1195
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• 2013

태양광 인버터는 항상 태양전지 어레이의 최대 전력을 추종하며 동작해야 한다. 또한 태양광 인버터는 폭넓은 태양전지의 최대 전력점 전압과 관계없이 최대 전력점을 추종해야 한다. 태양전지의 전류리플이 발생한다면 최대 전력점 추종 기능이 저하되고 일사량 변동이나 최대 전력점 변동 시 정상적으로 추종하기 어려워진다. 이러한 문제점을 해결하기 위해 본 논문에서는 고효율의 새로운 최대 전력점 추종 알고리즘과 태양전지의 전류리플 감소 알고리즘을 제안하였다. 4KW급 계통연계형 태양광 인버터에 적용하여 실험한 결과 최대 전력점 추종 효율이 99.97%, 인버터 출력 효율은 97.5%, 인버터 전류의 고조파 총 왜곡률은 1.05%로 우수한 성능을 보였다. 또한 0.5초 동안 일사량을 100% -> 10%, 10% -> 100%로 급격히 변동하였을 때에도 안정된 최대 전력점 추종이 가능함을 알 수 있었다.

• 반도체디스플레이기술학회지
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• 제13권4호
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• pp.43-48
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• 2014

Two-level inverter has some disadvantages like high harmonics contained in the output current, efficiency limit and stress to switching device as IGBT and FET. Many researches have reported multi-level inverter to complement two-level inverter of problems. In this paper, we suggest MPPT algorithm of multi-string three-level solar inverter that considered nowadays. We added midpoint controller in order to implement the MPPT algorithm because the three-level inverter has to need midpoint controller and procured the stability of direct current link. We verify the superiority of multi-string T-Type inverter and the algorithm we suggested with solar irradiance variation experiment and MPPT efficiency measurement. The MPPT efficiency was confirmed with a high efficiency more than 99.97%.

• 전력전자학회논문지
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• 제20권1호
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• pp.11-18
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• 2015

This paper proposes a high-efficiency 3-kW hybrid ESS with emergency power supply. The proposed system enables efficient use of power from photovoltaic (PV) cells and energy storage system (ESS). The proposed system can operate as an uninterruptible power supply (UPS) when grid fault occurs, providing seamless transfer from grid-connected mode to stand-alone mode. The LLC converter for PV achieves ZVS turn-on of switches and ZCS turn-off of diodes, and the isolated bidirectional DC-DC converter for ESS achieves ZCS turn-off regardless of load condition, resulting in high efficiency. The efficiency and performance of the proposed hybrid ESS has been verified by a 3-kW prototype.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.117-122
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• 2005

This paper proposes an inverter for the grid-connected photovoltaic system based on the transformer-less inverter. This system consists of a high frequency converter bridge, high frequency transformer, diode bridge rectifiers, a DC filter, a low frequency inverter bridge, and an AC filter. The high frequency converter bridge switching at 20kHz is used to generate bipolar PWM pulse, and the high frequency transformer raise its voltage twice, which is subsequently rectified by diode bridge rectifiers to result in a full-wave rectified sine wave. Finally, it is unfolded by a low frequency inverter bridge to result in a 60Hz sine wave power output. Even though the high frequency link system needs more power semiconductors, a reduced size, light weight, and saved parts cost make this system more comparative than the other systems due to elimination of 60Hz transformer.