Research On Islanding Detection Of Distributed Photovoltaic Power Generation System

At present, the energy crisis and environmental destruction have become the focus of the world.And the development and utilization of renewable energy can solve the problems above. As a renewable energy, solar energy is utilized increasingly year by year. Grid-connected photovoltaic generation is one of the main utilization of solar energy, in which distributed photovoltaic power generation is considered to be able to save investment, reduce the power loss and improve the distribution network reliability. As an essential function of grid-connected photovoltaic generation inverter, the realization of islanding detection is divided into two parts: Passive islanding detection has the large none detection zone and low harmonic wave, while active islanding detection has the large harmonic wave and fast detection speed. Therefore, this article proposes an improved slip mode frequency shift islanding detection technology to solve the compatibility of current harmonic and response speed in islanding detection.The major works done in this paper include:1. A distributed photovoltaic power generation system is designed and the PV model,including the mathematic model and the engineering model, is built. The former BOOST circuit of the PV system uses conductance increment method to realize MPPT. The control strategy of grid-connected photovoltaic generation inverter consists of double loop and PI control.2. The principle of the islanding detection and its standard are analyzed.Passive islanding detection is analyzed by using OVP/UVP etc, active islanding detection is analyzed by using SMS etc, and None Detection Zone of islanding detection is analyzed by using f0 Q ×f coordinate method etc.3. Excellent islanding detection should satisfy low current harmonic before system islanding and fast detection speed after system islanding, but traditional islanding detection can’t meet both the demands. Thus, this article proposes an improved slip mode frequency shift islanding detection technology, which has the low disturbance before system islanding and the high disturbance after system islanding and satisfys low current harmonic before system islanding and fast detection speed after system islanding.4. Contrast to traditional slip mode frequency shift islanding detection technology, the principle of the improved slip mode frequency shift islanding detection technology and its None Detection Zone are analyzed. By using the Matlab/simulink to design a distributed photovoltaic power generation model, the truth that the improved islanding detection has the characteristics of the low disturbance before system islanding and the high disturbance after system islanding is proved.