A grid connected photovoltaic system design and analysis under different grid conditions

In grid-connected PV systems particularly, the connection of PV array and balance of system to the utility grid has to fulfill the technical requirement of interconnection from the utility grid. This is to ensure high power quality; substantial safety interaction and reliability of the utility are achieved. Therefore, abnormal operating conditions that could affect the grid connected PV systems have to be prevented. One of the major safety issues related is the challenge to avoid unintentional island mode of operation. Islanding is the situation in which a distribution system becomes electrically isolated from the remainder of the power system, yet continues to be energized by distributed generation (DG) connected to it. Unintentional islanding can create a severe impact to the power system stability due to the loss of grid synchronization. Consequently, this causes the DG to be out of the voltage and frequency references. This may damage the electrical devices and systems equipment and also technical workers may be placed under safety hazards in the islanded section. In this study, design and construction of a real time controller for islanding detection in grid connected PV systems was proposed. 1 kWp grid connected PV system was developed for this aim. Proposed control method eliminates drawbacks of present methods used in islanding detection and islanding can be detected with developed real time controller by measuring circuit parameters like change of voltage, current and frequency between PV system-load and utility grid. Electronic development boards were designed for this purpose and data was obtained from the PV system and evaluated with designed real time controller. Thanks to this method, more reliable and having fast response time control structure was developed according to the present methods. The proposed real time controller in this thesis was developed with Labview unit and its useful tools. Labview development board has the advantage of flexibility, and rapid system prototyping capability. There are not any islanding detection studies according to the IEEE standards for grid connected PV systems in our country. Proposed study will have also an important role about determining the required criterions for islanding detection in our utility grid. Keywords: Grid Connected Photovoltaic System, Islanding Detection, Labview.