Study On Islanding Detection Of Grid-Connected System

Nowadays, with the situation of energy resource crisis and the demand of circumstance protection, solar energy are developed actively by all countries of the world. With the applications of the grid-connected equipment in generation systems,the probability of islanding in utility networks increases and the risk associated with unintentional islanding must be taken into account, therefore it is crucial to solve the problem of islanding. In order to prevent the occurrence of islanding, an effective anti-islanding detection should be emploied.The main research contents of this paper include:1. The mechanism of islanding is analyzed, the probability and the risk associated with unintentional islanding is discussed.2. The active methods and the passive methods in local detection schemes are described in detail, and a model is set up with Matlab/simulink.3. The NDZ is regarded as performance index to evaluate anti-islanding methods' effectiveness in this paper, and is described quantificationally by using phase criterion and Matlab simulation.4. Based on freescale 56F8036 the main control circuit of the 6KVA three-phase grid connected inverter has been designed, control software's flow charts included.