Study On Voltage Control Of Active Distribution Network

Large-scale access of distributed generators to distribution network being brought under actively control of the active distribution network(ADN), could effectively solve the traditional distribution network's problems of weak grid, insufficient ability of renewable energy absorption, low level of interacting, et al. For the reasons above, active distribution network has gained more and more attention in the field of distribution network technology at home and abroad.This paper is mainly to study the voltage control of ADN. It firstly summarized relevant concepts, research status of ADN, as well as the current research results of the distributed generators(DG) ' influence to ADN, after studying current techniques and literature about DG and ADN.Then this paper narrated the power flow calculation method of the network after the access of DG makes it changing from single power system to multi-power system, namely classified the nodes firstly based on DG's interface model, then transformed the nodes to PQ nodes or PV nodes which could be tackled by traditional power flow calculation methods, lastly simulated and verified in an ADN example with the tool of Matlab programming, to lay foundation for studying the influence of DG to the voltage level of ADN.In order to study the influence of DG to network voltage, a triangular distributed load model was used to calculate the voltage profile based on the linear superposition law. Then the principle how the DG influencing the voltage profile and stability was deduced and analyzed from the aspects of installation site and capacity of DG. In addition, an auxiliary verification was made by adapting optimal location based on voltage sensitivity index and optimal capacity based on minimizing the network losses. Simulation and verification were done with the IEEE 33 nodes distribution network in Matlab/Simulink as well at last.Lastly, a new method of voltage control combining the on-load tap changer(OLTC) with distribution static synchronous compensator(D-STATCOM), aimed to improve the quality of voltage and decrease the network losses, was applied after studying and comparing the current techniques of voltage control for distribution network which contains DG. This method has the merit of OLTC's automation voltage control as well as the merit of D-STATCOM's rapid response. Finally, combined with previous study results of the influence of DG location and capacity to voltage profile of ADN, simulation was done in the IEEE 33 nodes distribution network modeled in Simulink to verify the feasibility and validity of the developed voltage control method.