Reseach On Three-Phase Power Flow Analysis And State Estimation For Distribution Network With Multiple Generations

The Distributed Generation accessing to the grid is getting at a higher rate with the large-scale development of renewable energy in recent years,and changes the traditional distribution network single power supply mode,multiple genetations accessing to the distribution network will become the future distribution system trends.The distributed generation accessing to distribution network changes the network structure,voltage distribution and power loss,which has a great impact on the safe and stable operation of distribution system.The distribution network power flow analysis and state estimation is the basis of distribution network analysis,and provides a quantitative analysis basis for distribution generation better accessing to the grid,and the higher requirements of accuracy and efficiency of power flow calculation and state estimation are put forward.Based on the above research background,this paper mainly does the following research:1.In order to solve the problem that the phase component method can not be decoupled three-phase,and the sequential component method can not deal with the non-phase line effectively,this paper presents a hybrid modeling method,and uses symmetrical component method and unbalanced three-order decoupling compensation model to build three-order decoupling model for three-phase unbalanced distribution network,and also deduces the distribution regulator model with different connection modes,moreover analyzes the operation mode and control characteristics of wind turbine,PV power system,fuel cell and micro-turbine in detail,and establishes the node types of various distributed generation flow calculation.2.The hybrid algorithm of the path matrix method and BIBC?BCBV matrix are used to calculate the power flow of distribution network.The three-phase unbalanced distribution network is divided into two parts:a main radiation network with only three-phase lines and a sub-network with non-all-phase or weak-ring networks.The equivalent node injection current between the sub-network and the main network is calculated by using the rated voltage of the whole network.When the main network power flow converges,the contact point is taken as the balance node of the sub-network,and the weak loop and non-phase line are calculated by BIBC and BCBV matrix method.Finally,the accuracy and computational efficiency of the algorithm are verified by several IEEE bus systems,and analyzes the influence of the distribution generation on the distribution network voltage.3.This paper proposes a three-phase state estimation method based on the Extreme Learning Machine(ELM)pseudo-measurement model aiming at the shortcoming of the real-time measurement information.Firstly,the real-time and partial branch power measurements are inputted to the ELM for pseudo-measurement modeling.Then,the corresponding measurement error is generated by the Gaussian mixture model.The measurement equations of different node types distributed generations are established by the measurement transformation technique,and deduce the Jacobian iterative matrix.Finally,the three-phase state estimation of the distribution network based on weighted least squares is carried out.Finally,the IEEE 13-node test proves that the proposed method has good convergence.Compared with other pseudo-measurement modeling methods,the estimation results are relatively small error and high accuracy,and can effectively deal with the distributed generation.