Research On Distribution Power Flow Algorithm With Distributed Generation

Distribution network power flow calculation is an important tool for analyzing and planning distribution system.With the development and utilization of renewable green energy,distributed generation has transformed the distribution network from a single power supply structure to a multi-power supply structure,which not only has significant impact on power flow,network loss,voltage distribution and protection of the power distribution system,but also increases the complexity of distribution network power flow calculation methods.Therefore,in this thesis,with the background of the integration of distributed photovoltaic(PV)sources into distribution networks,the steady-state model and power flow calculations after accessing distribution systems are studied.The main work is as follows:By studying the working principle and physical characteristics of the PV cell,active power output model of PV array is obtained,and combined with the maximum power point tracking control model to obtain the active power output model of PV power generation system.By studying the working principle and control method of the inverter,the reactive power output model of PV power generation system was established using the state-space average method.Finally,PV power generation system integrated model is obtained.The PV power generation system is incorporated into the distribution network to obtain a distribution network load calculation model containing distributed PV sources.Based on the basic principle of the BX-type fast decomposition method,the generalized Tellegen’s theorem is applied to the BX-type method for power flow calculations.Based on the generalized Tellegen’s theorem,a method of calculating power flow is proposed.The method uses the small perturbation theorem of the general Tellegen’s theorem to derive the power flow correction equation,and iterative equations are used to solve the two subproblems P-θ and Q-U alternately.Based on the detailed analysis of distributed power generation characteristics,discusses the processing methods of node types when distributed power supply is applied to distribution network load flow calculation.Combining the power flow calculation model of distribution network containing distributed PV sources,a method for calculating power flow of distribution network with distributed PV sources is given.Through the simulation calculation of IEEE-14 node power distribution system and IEEE-33 node distribution system with distributed generation,and compared with the traditional BX fast decomposition method,which shows that the proposed method is accuracy and rapidity.At the same time,analyze the influence of the distribution network with distributed PV sources on each node of voltage,transmission power and network loss.