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Currently, many countries in the world are finding the suitable solutions to reduce the dependence on fossil fuels such as coal, oil and natural gas because these traditional energy sources have been limited and they cause environmental pollution in the process of usage. Renewable energy is considered as an important solution that can improve energy security, protects the environment, and develops economy. At the present, the solar power which is a semiconductor technology that converts sunlight directly into electricity is the most promising as a future renewable energy technology, but solar power generation is dependent on sunlight to effectively collect solar energy. Thus, the utilization rate of the power conditioner system (PCS) including DC/DC converter and DC/AC inverter in the photovoltaic (PV) system is very low in the case where the solar array cannot receive the sunlight, especially the night time. The maximum power point tracking (MPPT) is performed by the boost-type DC/DC converter while the power at the output terminals of the solar array is supplied into the utility grid by the grid-tied DC/AC inverter. We can add the small scale wind power system to the existing solar power generation system to improve the utilization rate of the PCS because the small scale wind turbine utilizes possibly the PCS at night and also can use the remaining capacity of the PCS during the daytime. The grid-connected hybrid power system with the wind generator and the PV array can provide the continuous maximum power from the wind and solar energy sources by studying the maximum power point (MPP) control technique. On the other hand, the PCS of the PV system cannot control optimally the small wind turbine in the grid-tied solar-wind hybrid power systems since the output characteristics of the small wind turbine and the PV array are not the same. Therefore, the novel design is proposed in this study by which the small scale wind turbine could be connected to the grid-tied power conditioner of the solar power system by emulating characteristic of the solar panel. The topology of the PV cell emulating system comprises the small scale wind turbine, a battery, and the power converter circuit. The small scale wind turbine charges the battery in the first stage. After that, the power converter circuit detects the current flowing into the PCS and operates it with the help of the control system. The novel design is composed of technical solutions of the PV cell cooperating system as below:-The grid-tied PV cell emulating system in stand-alone mode: When the solar array cannot receive sunlight, only the small scale wind turbine operates the PCS and this operation mode is called in stand-alone mode. In this mode, the solar array is bypassed in order to avoid the situation that it becomes the load. The PV cell emulating system can connect to the DC/DC converter to perform the MPPT control because the power converter circuit emulates the technical characteristic of the actual solar panel and the technical chatechnical of the solar panel is modeled by two and three linear equations. -The grid-tied PV cell cooperating system in connection mode: When sunlight appears, both the small scale wind power generating system and PV cell can operate the PCS. In this mode, the solar array can be connected to the PV cell cooperating system in series and parallel to generate the power into the utility grid with the support of the PCS. In this thesis, the simulation and experimental results show that PV cell emulating system in the stand alone mode can connect and transmit the power to the utility grid by the grid-tied power conditioner in case of the PV array cannot receive sunlight and the PV cell cooperating system also can connect to the solar array in the series/parallel connection mode in the case of the solar irradiation becomes weakly in the cloudy and rainy weather.Therefore, the utilization rate of the grid-tied PCS of the solar power system is enhanced.
本文 / Department of Electrical and Electronic Engineering, Graduate School of Engineering, Mie University
102p
Collection (particular)国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文
Date Accepted (W3CDTF)2018-06-04T01:14:06+09:00
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