• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1182-1187
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• 2014

This paper proposes an energy management strategy and adaptive control for superconducting magnetic energy storage (SMES) in a distribution power system with a grid-connected photovoltaic (PV) farm. Application of the SMES system can decrease the output power fluctuations of PV system effectively. Also, it can control the real and reactive powers corresponding to the scheduled reference values with adequate converter capacity, which are required at a steady-state operating point. Therefore, the adaptive control strategy for SMES plays a key role in improving the system stability when the PV generation causes uncertain variations due to weather conditions. The performance of proposed energy management strategy and control method for the SMES is then evaluated with several case studies based on the PSCAD/EMTDC$^{(R)}$ simulation.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.515-517
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• 2007

본 논문에서는 고 kW가치를 갖는 계통연계형 PV 시스템을 제안한다. 기존의 낮은 시스템 이용율을 향상 시킬수 있으며, 고kW 가치 시스템을 통한 전력 예비율 확보에 도움을 줄 수 있다. 전력저장 장치 및 에너지 충 방전용 전력 변환 장치로 구성되는 전력 조절기를 추가 함으로써 기존 시스템에 비해 PV-array 용량을 작게 설치하여도 peak-cut 효과를 크게 할수 있으며, PV시스템 설비 이용율을 높일 수 있다. 이를 시뮬레이션을 통하여 그 타당성을 검증하였다.

• Advances in Energy Research
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• v.4 no.1
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• pp.1-28
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• 2016

A grid-connected photovoltaic (PV) system comprised of multicrystalline silicon (mc-Si) modules was installed in a cold climate region in the U.S. This roof-mounted stationary PV system is a real-world application of PV for building energy generation in International Energy Conservation Code (IECC) Climate Zone 5 (and possibly similar climate zones such as 6, 7 and 8), and it served the purposes of research, demonstration, and education. The importance of this work is highlighted by the fact that there has been less emphasis on solar PV system in this region of the U.S. because of climate and latitude challenges. The system is equipped with an extensive data acquisition system capable of collecting performance and meteorological data while visually displaying real-time and historical data through an interactive online interface. Experimental data was collected and analyzed for the system over a one-year period with the focus of the study being on measurements of power production, energy generation, and efficiency. The annual average daily solar insolation incident upon the array was found to be $4.37kWh/m^2$. During the first year of operation, the PV system provided 5,801 kWh (1,264 kWh/kWp) of usable AC electrical energy, and it was found to operate at an annual average conversion efficiency and PR of 10.6 percent and 0.79, respectively. The annual average DC to AC conversion efficiency of the inverter was found to be 94 percent.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1081-1082
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• 2008

Photovoltaic (PV) power generation system has been widely studied as a clean and renewable power source. The purpose of this study is to keep the output power of photovoltaic cells maximum under any weather conditions. There are so many MPPT (Maximum Power Point Tracking) methods. P&O method has been used as a key MPPT method, both voltage and current coming out from PV array have to be feedback in the method. Thus, the system has a complex structure, and may fail to track MPP of PV array when unexpected weather conditions happen. In order to reduce the feedback components, POS MPPT control method was proposed by the authors. In this paper, the authors apply the POS MPPT control method to three phase PCS system. And the effectiveness of the proposed control scheme is demonstrated through PSCAD/EMTDC simulation.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.45-48
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• 2002

This paper proposes a grid-connected inverter using the negative conductance of PV power system, which has four IGBTs and simple controller. Most of modern electric loads generate the current harmonics and the line voltage distortion. The new solar-to-ac converter(STAC) provides by emulating a negative conductance load to the line voltage, so the current harmonics from STAC is canceled the effect of the harmonics from other loads. As a result, the line voltage distortion is decreased. The proposed system have low cost, small size, and light weight compared to conventional photovoltaic converter

• Journal of Climate Change Research
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• v.5 no.1
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• pp.1-12
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• 2014

With continued economic growth, Korea has seen an increase in the nighttime activities of its citizens as hours of activity have extended into night. There is an increasing trend in energy consumption related to citizens' nighttime activities. In order to analyze ideas for an efficient replacement of the power consumption of streetlights and for profit generation by applying grid-type solar systems, this study used an RETScreen model. Through energy analysis and cost analysis, the application benefit and viability of grid-type solar street light systems were analyzed. With analysis result of a total weekly power generation of 114 kWh via a grid-connected solar streetlight system, it was shown that the net present value of a grid-connected solar street light system is 155,362 KRW, which would mean a payback period of about 5.2 years, and as such, it was shown that profit could be generated after about 6 years. In addition, if the grid-connected solar power generation system proposed by this study is to be applied, it was shown that 401,935 KRW in profit could be generated after the 20-year useful life set for the solar system. In addition, the sensitivity analysis was performed taking into account the price fluctuations of SMP, maintenance. As a result, a payback period has increased by 1~2 years, and there were no significant differences. Because the most important factor that affect the economic analysis is the cost of supply certification of renewable energy, a stable sales and acquisition of this certification are very important. the Seoul-type Feed in Tariff(FIT) connected to other institutions will enable steady sales by confirming to purchase the certification for 12 years. Therefore, if those issues mentioned above are properly reflected, Central-grid PV system project will be able to perform well in the face of unfavorable condition of solar PV installation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.8
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• pp.2968-2974
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• 2010

Nowadays, the PV systems have been focused on the grid connection between the power source and the grid. The PV inverter can be considered as the core of the whole system because of an important role in the grid-interfacing operation. An important issue in the inverter control is the load current regulation. In the literature, Proportional Integral (PI) controller, which is normally used in the current-controlled Voltage Source Inverter (VSI), cannot be a satisfactory controller for an AC system because of the steady-sate error and the poor disturbance rejection, especially in high-frequency range. Compared with conventional PI controller, Proportional Resonant (PR) controller can introduce an infinite gain at the fundamental frequency of the AC source; hence it can achieve the zero steady-state error without requiring the complex transformation and the de-coupling technique. Theoretical analyses of both PI and PR controller are presented and verified by simulation and experiment. Both controller are implemented in a 32-bit fixed-point TMS320F2812 DSP processor and evaluated on a 3kW experimental prototype PV Power Conditioning System (PCS). Simulation and experimental results are shown to verify the controller performances.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.9
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• pp.444-453
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• 2017

This paper proposes an operational algorithm for a Photovoltaic Power-Hardware-In-Loop Simulator that is designed to improve the control algorithm and reliability of the PV Inverter. There was an instability problem in the PV PHILS with the conventional algorithm when it was connected tothe PV inverter. Initially, a real-time based computing unit with mathematical modeling of the PV array is implemented and a DC amplifier and an isolated device for DC power measurement are integrated. Several experiments were performed based on theabove concept undercertain conditions, which showed that the proposed algorithm is more effective for the PV characteristic test and grid evaluation test than the conventional method.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.309-316
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• 2011

A PLL system has widely used for synchronizing the grid voltage at the grid-connected inverter for supplying power from the PV generation systems. In this paper, a PLL algorithm without both the loop filter and PI controller is suggested for improving the performance of synchronization at the single-phase and three-phase grid connected inverters. In order that the output voltage of a phase detector in the PLL has only a dc voltage, and it approaches to 0 when the synchronization signal is locked to the grid voltage, the feedback signals are determined by using two-phase voltages. After the PLL system with a proportional controller is modelled with the small signal analysis, the stability and steady-state error are investigated. Through the simulation studies and experimental results, the performances of the proposed PLL algorithm are verified.

• Proceedings of the KAIS Fall Conference
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• 2012.05b
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• pp.512-516
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• 2012

Recently the Korean government's green energy growth policy has been taken at the national level due to the sufficient supply of renewable energy. Some specific technique should be taken in consideration for the operation of the grid voltage and power quality management. In this case, there may have some chance of operational problems. Typical problems arise when grid-connected solar power produced by Pacific sunshine. The power flow in the reverse direction can create overvoltage on the distribution line and gives value of malfunction on the system. Line voltage and overvoltage adjustment practice can stop these symptoms occurred. Under these circumstances, this paper presents an interconnection test devices for photovoltaic(PV) systems composed of distribution system simulator, PV system simulator and control and monitoring systems using the LabVIEW S/W, and simulates the customer voltage characteristics considering the 3 parameters on the introduction capacity for PV systems, system configuration and Power factor. This paper also proposes a new calculation algorithm for voltage profile to make comparison between calculation values and test device values. The results show that the simulation results for the normal operation characteristics of PV systems which are very practical and effective.