Distributed Voltage Optimization Control Of Distribution Networks With High Penetration Of PVs

With the increasing penetration of distributed photovoltaics(PVs)in distribution networks(DNs),the operation security and stability of DNs face great challenges,especially the voltage violation problem.Using optimization methods to actively control the distributed PVs and other voltage regulation devices is of great significance to eliminate voltage violation and improve the economic efficiency of DNs.This thesis focuses on the distributed voltage optimization control of DNs with high penetration of PVs.The main work and contributions are summarized as follows:1)With the PV installation node as the basic control unit,a distributed multi-agent voltage control method is proposed for DNs.Based on the in-depth analysis of voltage regulation capability of PVs,the proposed distributed multi-agent voltage control strategy can realize low-cost and high-speed voltage control for DNs through four stages.They are local prevention,distributed reactive power coordination,active power optimal curtailment and power recovery control of PVs.Besides,the proposed strategy has adaptive capability for the dynamic changes of network topology.2)With the PV generation cluster as the basic control unit,a network partition and double-layer cluster voltage optimization method are proposed.A novel cluster performance index based on the electrical distance and regional voltage autonomy is presented to partition a DN into several clusters using Tabu search algorithm.The proposed double-layer cluster voltage optimization strategy includes the cluster autonomous optimization and distributed intercluster optimization,aimed at minimizing the PV active power curtailment and network active power losses.The cluster autonomous optimization realizes fast and optimal voltage control within cluster by alternately updating the intra-cluster optimal solution and the virtual slack bus voltage.The distributed intercluster optimization uses the alternating direction method of multipliers to realize global optimal control of all clusters.3)Considering the incomplete measurement data in DNs,a coordinated voltage optimization method is proposed for PV generation clusters.Using network simplification method,an equivalent simplified network with complete measurement is obtained to replace the original DN.Through evaluating voltage regulation capability of reactive power resources and implementing cluster autonomous optimization,the proposed coordinated cluster voltage optimization strategy can fully utilize the reactive power resources of different clusters and realize fast and optimal voltage control of clusters.The cluster autonomous optimization is aimed at the weighted minimization of intra-cluster network losses,PV generation losses and voltage violation amounts of downstream clusters,which improves the calculation speed by redefining the virtual slack bus.4)With the substation as the basic control unit,two hierarchical distributed optimization methods are proposed for high voltage(HV)and medium voltage(MV)DNs.Based on the practical operation requirements of HV and MV DNs,two hierarchical distributed control architectures are constructed.The mixed-integer global optimization model of HV and MV DNs is formulated and decomposed,which optimizes the operation of continuous and discrete voltage regulation devices.Then,an improved generalized Benders decomposition algorithm and a hybrid distributed algorithm based on the generalized Benders decomposition and branch-and-bound method are proposed for two hierarchical control architectures.Two hierarchical distributed optimization methods both can exert the mutual voltage support capability of HV and MV DNs and achieve globally optimal control of HV and MV DNs.