Abstract:With the penetration of distributed generation ( DG) ,distribution network planning is faced with the uncertainties coming from both sides of power supply and load. Firstly,according to the probability density function,the multi - state model of distribution system is established,which represents the uncertainties by means of multi - state power flow calculation. Secondly,a comprehensive planning model of distribution network with DG and network structure adjustment based on the chance constrained programming is proposed,which is optimized by an improved genetic algorithm. By calculating and analyzing practical examples of distribution network in an area,it is demonstrated that the proposed algorithm has a good efficiency and convergence performance. The results show that the economic benefits are effectively improved by comprehensive planning of DG and the network reconfiguration.